JP2019035920A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can reduce power consumption of a heat source.SOLUTION: A fixing device 9 comprises: a rotatable endless fixing member 21; a pressure member 23 that forms, with the fixing member 21, a pressure area N for sandwiching and conveying a sheet; a pressing member 25 that presses the fixing member 21 against the pressure member 23 in the pressure area N, while in contact with an inner peripheral surface of the fixing member 21 with lubricant Lu therebetween; a heat source 43 that has heating areas divided into plurality in a width direction intersecting the conveyance direction of the sheet and each individually capable of generating heat, and heats the fixing member 21; and detection means 55 that detects the temperature of the heat source 43 or the fixing member 21. The image forming apparatus causes all the heating areas to generate heat until the detection means 55 detects a predetermined temperature, and causes only the heating areas corresponding to the size of the sheet to generate heat after the detection means detects the predetermined temperature.SELECTED DRAWING: Figure 2

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.

  In the fixing device, a pressure region is formed between a heating member such as a fixing belt or a fixing roller and a pressure member such as a pressure roller, and the paper on which the toner image is transferred passes through the pressure region. Thus, the toner image is fixed on the paper by heating and pressing.

  Patent Documents 1 and 2 describe a fixing device in which a heat source for heating a heating member can be adjusted according to the width of a sheet. The fixing device described in Patent Document 1 forms a pressure region by pressing a plurality of heater elements arranged in the width direction of a recording paper (paper) against a pressure roller (pressure member) through a film. ing. A heater element to be heated is set based on the width of the recording paper, and the operation timing of the heater element is controlled. The fixing device described in Patent Document 2 includes a heating body that is disposed in the longitudinal direction of a heating rotator (heating member) and has a plurality of heating elements that can generate heat individually. Then, the amount of electric power supplied to the heating element corresponding to the passing portion of the recording material (paper) and the heating element corresponding to the non-passing portion is controlled.

JP-A-8-152807 JP 2015-28531 A

  However, the fixing device described in Patent Document 1 has a problem that when only the heater element corresponding to the width of a small size recording paper is operated, the torque of the driving source that drives the pressure member increases. The torque of the drive source will be described. The film is driven to rotate as the pressure roller is driven by a driving source to rotate. In this case, the heater element slides against the rotating film. In order to reduce the load on the film due to the sliding, a lubricant is generally interposed between the film and the heater element. In many cases, the lubricant is semi-solid when the temperature is low, and the fluidity increases as the temperature increases.

  Accordingly, when only the heater element corresponding to the width of the small size recording paper is operated, the temperature outside the paper passing area does not rise. Then, since the temperature of the lubricant remains low and the fluidity is low outside the paper passing area, the load when the film slides on the heater element increases. As a result, the torque of the driving source of the pressure roller that rotates the film is increased. When the torque of the drive source increases in this way, the rotation of the pressure roller and the film may become unstable.

  Further, in the fixing device described in Patent Document 2, during the warm-up, the entire heating element is energized and heated regardless of the width of the sheet, so that more power is consumed than necessary.

  In view of the above circumstances, an object of the present invention is to provide a fixing device capable of suppressing power consumption of a heat source and an image forming apparatus including the fixing device.

  In order to solve the above-described problems, a fixing device of the present invention includes a rotatable endless fixing member, a pressure member that forms a pressure region in which a sheet is sandwiched and conveyed between the fixing member, In the pressure region, a pressing member that contacts the inner peripheral surface of the fixing member via a lubricant and presses the fixing member against the pressing member, and a plurality of portions in the width direction that intersects the paper conveyance direction A heat source that heats the fixing member independently, and a detection unit that detects a temperature of the heat source or the fixing member, wherein the detection unit has a predetermined temperature. Until all the heat generating areas are heated, and after the detection means detects the predetermined temperature, only the heat generating areas corresponding to the size of the paper are heated.

  In the present invention, the detection means includes the heat source at a non-sheet passing area outside the width direction of the sheet passing area of the previously conveyed sheet, or an end portion in the width direction of the sheet passing area of the maximum size sheet. Alternatively, the temperature of the fixing member may be detected.

  In the fixing device of the present invention, a driving source that rotates the pressure member to rotate the fixing member is provided, and the predetermined temperature is the driving torque of the driving source after the fixing member is heated by the heat source. The temperature may be the temperature of the heat source or the fixing member when the temperature is stabilized.

  An image forming apparatus according to the present invention includes an image forming unit that forms a toner image on a sheet, and the fixing device described above that fixes the toner image on the sheet.

  According to the present invention, in the case of small-size paper, only the area corresponding to the small-size paper is heated, so that the heater can save power. At this time, since the outside of the area of the small size paper is also heated to a predetermined temperature, the driving of the fixing member and the pressure member can be stabilized.

1 is a front view schematically showing an internal configuration of a printer according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. FIG. 3 is a plan view showing a heater of the fixing device according to the embodiment of the present invention. FIG. 3 is a block diagram of a control unit of a fixing device according to an embodiment of the present invention. 6 is a flowchart illustrating a fixing operation of the fixing device according to the embodiment of the present invention. 6 is a graph showing a relationship between a heater temperature and a driving torque in the fixing device according to the embodiment of the present invention.

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

  First, the overall configuration of a printer as an image forming apparatus will be described with reference to FIG. FIG. 1 is a front view schematically showing the internal configuration of the printer 1. Hereinafter, the front side of the paper in FIG. 1 is the front side (front side) of the printer 1, and the left and right directions will be described with reference to the direction when the printer 1 is viewed from the front. L and R of each figure show the left direction and the right direction, respectively.

  The apparatus main body 2 of the printer 1 includes a paper feed cassette 3 that accommodates the paper S, a paper feed device 5 that feeds the paper S from the paper feed cassette 3, an image forming unit 7 that forms a toner image on the paper S, A fixing device 9 that fixes the toner image onto the paper S, a paper discharge device 11 that discharges the paper S, and a paper discharge tray 13 that receives the discharged paper S are provided. Further, a conveyance path 15 for the sheet S from the sheet feeding device 5 to the sheet discharge device 11 through the image forming unit 7 and the fixing device 9 is formed in the apparatus main body 2.

  The printer 1 includes a control unit 17 that controls the paper feed cassette 3, the paper feed device 5, the image forming unit 7, the fixing device 9, and the paper discharge device 11 to execute an image forming operation for forming an image on the paper S. ing.

  Next, the fixing device 9 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the fixing device.

  As shown in FIG. 2, the fixing device 9 includes a fixing belt 21 as a fixing member, a pressure roller 23 as a pressure member that forms a pressure region N between the fixing belt, and a pressure region N. And a pressure assembly 25 as a pressing member that presses the fixing belt 21 against the pressure roller 23. Further, the fixing device 9 includes a fixing housing (not shown) in which these are supported.

  The fixing belt 21 is an endless belt having a predetermined inner diameter and a width longer than the width of the paper. The fixing belt 21 is formed of a flexible material, and includes a base material layer, an elastic layer provided on the outer peripheral surface of the base material layer, and a release layer provided on the outer peripheral surface of the elastic layer. Yes. The base material layer is formed of a metal such as SUS or Ni. The elastic layer is formed of silicon rubber or the like. The release layer is formed of a PFA tube or the like. Moreover, a sliding layer may be formed on the inner peripheral surface of the base material layer. The sliding layer is formed of polyimide amide or PTFE.

  The fixing belt 21 is rotatably supported by a fixing housing by a belt guide 31. The belt guide 31 has an arcuate cross-sectional shape along the inner peripheral surface of the fixing belt 21 and is formed of a material having a spring property. The belt guide 31 applies tension to the fixing belt 21 and stabilizes the rotation path of the fixing belt 21.

  The pressure roller 23 includes a metal core, an elastic layer provided on the outer peripheral surface of the metal core, and a release layer provided on the outer peripheral surface of the elastic layer. The elastic layer is formed of silicon rubber or the like. The release layer is formed of a PFA tube or the like.

  The pressure roller 23 is disposed in the fixing housing so as to come into contact with the fixing belt 21 from below the fixing belt 21, and forms a pressure region N between the pressure roller 23 and the fixing belt 21. The pressure roller 23 is connected to a motor 35 as a drive source and is driven to rotate. When the pressure roller 23 is rotated counterclockwise in FIG. 2 by the motor 35, the fixing belt 21 is driven by the pressure roller 23 to rotate in the clockwise direction opposite to the rotation direction of the pressure roller 23. . As a result, the conveyed paper S passes through the pressure area N.

  The pressure assembly 25 includes a stay 41 disposed in a hollow portion of the fixing belt 21, a heater 43 as a heat source supported by the stay 41, and a heater holder 51 that holds the heater 43.

  The stay 41 is a rectangular tubular member that is longer than the length of the fixing belt 21 in the width direction. The stay 41 passes through the hollow portion of the fixing belt 21 and is fixed to the fixing housing at both ends.

  Next, the heater 43 will be described with reference to FIG. FIG. 3 is a plan view of the heater.

  The heater 43 is a ceramic heater having a length equivalent to the length along the width direction X of the fixing belt 21. The ceramic heater includes a thin plate-like ceramic substrate 45 and a heating element 47 built in the ceramic substrate 45. The heating element 47 is disposed so as to meander in the ceramic substrate 45. When the heating element 47 is energized, the ceramic substrate 45 generates heat.

  The heater 43 includes heat generation regions R1, R2, and R3 obtained by dividing a sheet passing region of a maximum width sheet (for example, A4 landscape size) into three in the width direction X. The heat generating regions R1, R2, and R3 can generate heat independently. The central heat generation region R1 in the width direction X is a small heat generation region R1 corresponding to the width of a small size paper (for example, envelope size, postcard size, A5 vertical size, etc.). The small size heat generation region R1 and the small size heat generation regions R2 and R3 on both outer sides in the width direction X of the small size heat generation region R1 are heat generation regions corresponding to the width of the maximum width sheet S. One heating element 47 is built in each of the small-sized heat generating region R1 and the small-sized heat generating regions R2 and R3. As a result, the small-size heat generation region R1 and the small-size heat generation regions R2 and R3 can be independently heated. Note that the small-size outside heat generation regions R2 and R3 may be integrally heated. Each heating element 47 is electrically connected to the control unit 17.

  Referring to FIG. 2 again, the heater holder 51 supports the heater 43. The heater holder 51 is a flat, substantially rectangular parallelepiped member having a length equivalent to the length along the width direction X of the fixing belt 21. A recess is formed along the width direction X on the lower surface of the heater holder 51. A heater 43 is accommodated in the recess. In the concave portion, a center as a detection means is provided at a position corresponding to at least one of the small-size heat generation area R1 of the heater 43 and the small-size outside heat generation areas R2 and R3 (small-size outside heat generation area R2 in this embodiment). A thermistor 53 and an end thermistor 55 are accommodated. The central thermistor 53 detects the temperature of the small-size heat generation region R1 of the heater 43, and the end thermistor 55 detects the temperature of the small-size heat generation region R2. Both thermistors 53 and 55 are electrically connected to the control unit 17.

  The heater holder 51 is fixed to the lower surface of the stay 41 with the heater 43 facing downward. As a result, in the pressurizing region N, the lower surface of the heater holder 51 (including the heater 43) contacts the inner peripheral surface of the fixing belt 21 and presses the fixing belt 21 toward the pressing roller 23. As described above, when the fixing belt 21 is driven to rotate, the lower surface of the heater holder 51 including the heater 43 slides with respect to the inner peripheral surface of the fixing belt 21. In order to reduce the load caused by the sliding, a lubricant Lu is interposed between the lower surface of the heater holder 51 including the heater 43 and the inner peripheral surface of the fixing belt 21.

  The belt guide 32 described above is fixed to the upper portion of the stay 41.

  Next, the control unit 17 will be described with reference to FIG. FIG. 4 is a block diagram of the control unit. The control unit 17 includes a temperature determination unit 61 and a heater selection unit 63.

  Detection results of the central thermistor 53 that detects the temperature of the small-size heat generation region R1 of the heater 43 and the end thermistor 55 that detects the temperature of the small-size heat generation region R2 are input to the temperature determination unit 61. Based on the input detection result, the temperature distribution of the heater 43 in the width direction X is obtained.

  The heater selection unit 63 can energize the heating element 47 in the small-size heating region R1 of the heater 43 and the heating elements 47 in the small-size heating regions R2 and R3 independently. The heater selection unit 63 selects a heat generation region to be energized based on the temperature distribution of the heater 43 obtained by the temperature determination unit 61.

  The fixing operation of the fixing device 9 having the above configuration will be described with reference to the flowchart of FIG.

  When the image forming operation is started, in step S <b> 1, the heater selection unit 63 starts energizing the heating elements 47 of all the heating regions R <b> 1, R <b> 2, R <b> 3 of the heater 43, and covers the entire sheet passing region of the fixing belt 21. Heat. The temperature of the small-sized heat generating region R1 and the temperature of the small-sized heat generating region R2 of the heater 43 are detected by the central thermistor 53 and the end thermistor 55, respectively.

  In step S2, the control unit 17 determines whether or not the sheet S on which an image is formed is a small size. As a result, if it is determined that the size is small, the process proceeds to step S3.

  In step S3, the temperature determination unit 61 determines whether or not the end thermistor 55 of the small-size outside heat generation region R2 has detected a predetermined temperature T1.

  Here, the predetermined temperature T1 will be described with reference to FIG. FIG. 6 is a graph showing an example of the relationship between the heater temperature and the drive torque, where the horizontal axis shows the heater temperature and the vertical axis shows the drive torque. The drive torque indicates the drive torque of the motor 35. The driving torque can be measured with a torque meter, for example.

  As described above, the lubricant Lu is interposed between the inner peripheral surface of the fixing belt 21 and the lower surface of the heater holder 51 including the heater 43. Lubricant Lu is semi-solid when the temperature is low, and has a property of increasing fluidity as the temperature increases. Therefore, when the temperature of the heater 43 is low, the temperature of the lubricant Lu is low and the fluidity is low, so that the load when the fixing belt 21 slides on the heater holder 51 increases. Thereby, as shown in the graph of FIG. 6, the driving torque of the motor 35 that rotates the pressure roller 23 that rotates the fixing belt 21 to follow is high. As the temperature of the heater 43 increases, the fluidity of the lubricant Lu increases, so the load when the fixing belt 21 slides with respect to the heater holder 51 decreases, and the driving torque of the motor 35 also decreases.

  The predetermined temperature T1 indicates a temperature at which the driving torque of the motor 35 is fully reduced and stabilized. That is, by causing all the heat generating regions R1, R2, and R3 of the heater 43 to generate heat up to this temperature T1, the sliding load on the heater holder 51 of the fixing belt 21, that is, the driving torque of the motor 35 can be reduced. The predetermined temperature T1 depends on the type of the lubricant Lu and the like, but is 100 degrees as an example.

  Referring to FIG. 5 again, when the temperature determination unit 61 determines in step S3 that the end thermistor 55 in the small-size outside heat generation region R2 has detected the predetermined temperature T1, the process proceeds to step S4.

  In step S4, the heater selection unit 63 stops energizing the heating element 47 in the small-size outside heat generation region R2, energizes only the heating element 47 in the small-size heating region R1, and proceeds to step S5.

  In step S5, the temperature determination unit 61 determines whether or not the central thermistor 53 of the small size heat generation region R1 has detected a fixing temperature T2 higher than a predetermined temperature T1. The fixing temperature T2 is a temperature at which the toner can be melted, and is 160 degrees as an example. When it is determined that the central thermistor 53 of the small size heat generating region R1 has detected the fixing temperature T2, the process proceeds to step S6 and the fixing operation is started. In other words, the sheet S on which the toner image has been transferred by the image forming unit 7 is conveyed to the pressurizing region N, and the toner image is heated and pressed to be fixed to the sheet S. During this fixing operation, the fixing belt 21 is driven and rotated, but the temperatures of the small-size outside heat generation regions R2 and R3 are maintained near the predetermined temperature T1, and the sliding load on the heater holder 51 of the fixing belt 21 is maintained. Is small, the driving torque of the motor 35 does not increase.

  If it is determined in step S2 that the paper S is not a small size, the process proceeds to step S5. In this case, since all the heat generation regions R1, R2, and R3 of the heater 43 are equally heated, if the temperature detected by the central thermistor 53 of the small size heat generation region R1 reaches the fixing temperature T2, the total heat generation. It can be considered that the regions R1, R2, and R3, that is, the paper passing regions of the maximum width paper S are heated to the same temperature.

  As described above, according to the fixing device 9 of the present invention, in the case of the small size paper S, only the small size heat generation region R1 corresponding to the width of the paper is heated, so that the heater 43 can save power. At this time, since the small-size outside heat generation regions R2 and R3 are also heated to a temperature at which the driving torque of the motor 35 is stabilized, the driving torque of the motor 35 does not increase. Accordingly, the driving of the fixing belt 21 and the pressure roller 23 can be stabilized.

  In the present embodiment, when the end thermistor 55 of the small-size outside heat generation region R2 detects the predetermined temperature T1 (step S3 in FIG. 5), the energization to the heating elements 47 in the small-size outside heat generation regions R2 and R3 is performed. Was stopped (step S4 in FIG. 5). However, when the temperature of the heater 43 is uniform in the width direction X, such as in the morning, when one of the thermistors 53, 55 detects the predetermined temperature T1, the heat generation in the small-size outside heat generation regions R2, R3 You may control to stop the electricity supply to the body 47. FIG. However, after the small size paper S is continuously printed, the temperature of the small size heat generating region R1 is higher than the temperature of the small size heat generating regions R2 and R3, so that the end thermistor 55 has a predetermined temperature. When T1 is detected, it is preferable to stop energization of the heat generating elements 47 in the small-size outside heat generating regions R2 and R3.

  As described above, by detecting the temperature at the lowest temperature in the width direction X, the entire area of the sheet passing region in the width direction X can be reliably heated to a predetermined temperature T1 or higher. A portion having the lowest temperature in the width direction X is a non-sheet passing area outside the sheet passing area of the previously conveyed sheet S or a width direction end of the sheet passing area of the maximum width sheet S.

  Note that after the energization of the heat generating element 47 in the small-size outside heat generation regions R2 and R3 is stopped (step S4 in FIG. 5), the temperature of the small-size outside heat generation regions R2 and R3 decreases. Therefore, when the end thermistor 55 detects a temperature lower than the predetermined temperature T1 (for example, 80 degrees), control is performed so that energization to the heating elements 47 in the small-size outside heating regions R2 and R3 is started again. Also good. As a result, the temperature of the entire heat generation region can be set to about the predetermined temperature T1, and the lubricant Lu can be maintained in a highly fluid state.

  In the present embodiment, all the heat generating regions R1, R2, and R3 are caused to generate heat until the end thermistor 55 detects the predetermined temperature T1, but one of the thermistors 53 and 55 has a predetermined temperature. When a temperature lower than T1 is detected, only the corresponding heat generation region may generate heat up to a predetermined temperature T1.

  In the present embodiment, the paper S is divided into two sizes, a small size and a maximum width size, but may be divided into three or more sizes. For example, it can be divided into three sizes: small size (for example, envelope size), medium size (for example, postcard size), and maximum width size (for example, A4 horizontal size). In this case, the heat generating area of the heater 43 is divided so as to correspond to each size, and the temperature of each heat generating area is detected by a thermistor. Thereby, since the heat generating area outside the paper passing area can be narrowed, the heat generating efficiency of the heater 43 can be improved.

  In the present embodiment, the thermistors 53 and 55 detect the temperature of the heater 43, but the temperature of the fixing belt 21 may be detected. In this case, a non-contact type temperature sensor can be used.

  Moreover, although the planar ceramic heater was used as a heat source, a halogen heater can also be used. In this case, a halogen heater having a heating element in the small-size heat generation region R1 and a halogen heater having a heating element in the regions corresponding to the small-size heat generation regions R2 and R3 may be used.

  Further, in the pressurizing region N, the lower surface of the heater holder 51 of the pressurizing assembly 25 is brought into contact with the inner peripheral surface of the fixing belt 21, but the pressurizing assembly 25 has an inner peripheral surface of the fixing belt 21. You may provide the press pad which contacts. In this case, the lubricant Lu is interposed between the pressing pad and the fixing belt 21. In this case, the above-described halogen heater can be used as a heat source.

  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, and thus may have various technically preferable limitations. 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 Printer (image forming device)
9 Fixing device 21 Fixing belt (fixing member)
23 Pressure roller (pressure member)
25 Pressure assembly (pressing member)
35 Motor (drive source)
43 Heater (heat source)
53, 55 Thermistor (detection means)

Claims (4)

A rotatable endless fixing member;
A pressurizing member that forms a pressurizing region for conveying the paper while sandwiching the paper between the fixing member;
In the pressure region, a pressing member that contacts the inner peripheral surface of the fixing member via a lubricant and presses the fixing member against the pressure member;
A heat source that heats the fixing member, and has a heat generating region that is divided into a plurality of portions in the width direction intersecting the paper transport direction and that can independently generate heat;
Detecting means for detecting the temperature of the heat source or the fixing member,
Until the detection means detects a predetermined temperature, all the heat generating regions are heated,
After the detecting means detects the predetermined temperature, only the heat generating area corresponding to the size of the paper conveyed through the pressure area is heated.   The detection means includes the heat source or the fixing member at a non-sheet passing area outside the width direction of the sheet passing area of the previously conveyed sheet or an end portion in the width direction of the sheet passing area of the maximum size sheet. The fixing device according to claim 1, wherein the temperature of the fixing device is detected. A driving source for rotating the pressure member to follow the fixing member;
The fixing according to claim 1, wherein the predetermined temperature is a temperature of the heat source or the fixing member when a driving torque of the driving source is stabilized after the fixing member is heated by the heat source. apparatus. An image forming unit that forms a toner image on paper;
An image forming apparatus comprising: the fixing device according to claim 1, wherein the toner image is fixed on the sheet.

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