JP2020079880A - Fixing device and image forming apparatus including the fixing device - Google Patents

Abstract

To make it possible to reduce the occurrence of a twist of a fixing member due to a temperature difference of lubricant.SOLUTION: A heater 212 is a heat source in which a plurality of heating areas HA1 to HA3 are arranged side by side in a direction orthogonal to the direction of movement of a fixing member 211. Heater temperature sensors 213a to 213c respectively detect the temperature of the plurality of heating areas HA1 to HA3. A power control unit 101, when a sheet P is inserted into a nip part N, supplies, to a paper feed heating area located at a position through which the sheet P passes among the plurality of heating areas HA1 to HA3, a maintaining power for maintaining the temperature of the paper feed heating area to a predetermined control temperature, and supplies, to non-paper feed heating areas located at positions through which the sheet P does not pass among the plurality of heating areas HA1 to HA3, a power to maintain the temperature of the non-paper feed heating areas to a temperature lower than the temperature of the paper feed heating area, and to the temperature having a constant temperature difference kept from the temperature of the paper feed heating area.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device that fixes a toner image transferred onto a recording medium onto the recording medium by thermocompression bonding, and an image forming apparatus including the fixing device.

  An electrophotographic image forming apparatus includes a fixing device that fixes a toner image transferred onto a recording medium such as paper. The fixing device generally includes a belt-shaped fixing member heated by a heat source, and a pressure member arranged to face the fixing member, and a toner is formed in a nip portion formed between the fixing member and the pressure member. The image is fixed on the recording medium by heating and pressing (thermocompression).

  The following Patent Document 1 discloses a direct heating type fixing device in which a heat source comes into contact with an inner peripheral surface of a fixing member to directly heat the fixing member. In this direct heating type fixing device, grease is applied to the inner peripheral surface of the fixing member in order to enhance slidability of the fixing member with respect to the heat source. The heat source has a flat plate elongated shape, and the longitudinal direction thereof is arranged parallel to the width direction of the fixing member. The heat source has a plurality of heating regions formed in the longitudinal direction, and selectively heats a heating region in a position where the recording medium passes among the plurality of heating regions to heat only a necessary heating region. Is possible. This suppresses power consumption and prevents excessive temperature rise at the end of the fixing member.

Japanese Patent No. 5241144

  However, in the above fixing device, when the selective heating by the heat source is performed, temperature unevenness occurs in the surface of the fixing member, and the lubricant such as grease has a property that the viscosity becomes high when the temperature is low. There is a difference in the viscosity of the lubricant applied to the. This causes unevenness of the sliding torque within the surface of the fixing member. As a result, the fixing member may be twisted.

  The present invention has been made in view of the above circumstances, and an object thereof is to make it possible to reduce the occurrence of twist of the fixing member due to the temperature difference of the lubricant.

  A fixing device according to an aspect of the present invention includes a belt-shaped fixing member having an inner peripheral surface coated with a lubricant, and a fixing target recording medium inserted between the fixing member and the fixing member. And a heat source for contacting the inner peripheral surface of the fixing member to heat the fixing member, wherein a plurality of heating regions are provided in a direction orthogonal to the moving direction of the fixing member. A plurality of heat sources arranged in parallel, a temperature detection unit that detects the temperature of each of the plurality of heating regions, and a plurality of the plurality of temperature detection units that are detected by the temperature detection unit when the recording medium is inserted into the nip portion. While maintaining the temperature of the paper passing heating area at the position where the recording medium passes in the heating area at a predetermined control temperature, the maintenance power is supplied to the paper passing heating area, and the temperature detecting unit The detected temperature of the non-paper-passage heating area in the position where the recording medium does not pass among the plurality of heating areas is lower than the temperature of the paper-passing heating area and with respect to the temperature of the paper-passing heating area. And a power control unit that supplies power for maintaining a temperature that maintains a constant temperature difference to the non-paper passing heating region.

  An image forming apparatus according to another aspect of the present invention includes an image forming unit that forms a toner image, and the fixing device that fixes the toner image formed by the image forming unit onto the surface of the recording medium. And an image forming apparatus including.

  According to the present invention, it is possible to reduce the occurrence of twist of the fixing member due to the temperature difference of the lubricant.

FIG. 1 is a cross-sectional view showing structures of a fixing device and an image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a functional block diagram showing an electrical configuration of the fixing device and the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view showing the configuration of the fixing device according to the first exemplary embodiment of the present invention. (A) is a schematic plan view showing the structure of a heating element portion of the heater, and (B) is a schematic sectional view of the heater. It is a figure showing each heater heat generation pattern according to paper size, and a heater temperature sensor arrangement example. FIG. 6 is a diagram showing a transition of a temperature detected by each temperature sensor when fixing a small-sized sheet. FIG. 6 is a diagram showing a relationship between a heater heat generation pattern and a temperature distribution of the heater when fixing a small size sheet. 3 is a flowchart illustrating an example of temperature control processing of the fixing device according to the first exemplary embodiment of the present invention. It is a figure which shows an example of the characteristic data which shows the relationship between the temperature difference between each heating area of a heat source, and a torque difference. It is a functional block diagram which shows the electric constitution of the fixing device and image forming apparatus concerning 2nd Embodiment of this invention. It is a figure which shows an example of the characteristic data which shows the relationship between the temperature of a lubricant, and a viscosity. 8 is a flowchart illustrating an example of temperature control processing of the fixing device according to the second exemplary embodiment of the present invention. It is a functional block diagram which shows the electric constitution of the fixing device and image forming apparatus concerning 3rd Embodiment of this invention. It is a figure which shows the relationship between the heater heat generation pattern and the temperature distribution of a heater concerning the modification of this invention.

  A fixing device and an image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a sectional view showing the structures of a fixing device and an image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a functional block diagram showing the electrical configurations of the fixing device and the image forming apparatus according to the first embodiment of the present invention.

  The image forming apparatus 1 is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 is configured to include a document reading unit 5, a document feeding unit 6, a control unit 10, an image forming unit 12, a paper feeding unit 14, a fixing unit 20, and the like in a device body 11. The image forming apparatus 1 includes a fixing device 200. The fixing device 200 includes a fixing unit 20 and an operation control unit 100 described later (particularly, a component that controls the fixing unit 20 in the operation control unit 100).

  The operation unit 47 (see FIG. 1) is, for example, a start key for instructing execution of a function that can be performed by the image forming apparatus 1, a determination key (enter key) for confirming the operation of the operator, and further numerical input. It is equipped with a numeric input key and the like.

  In addition, the operation unit 47 includes a display unit 473 that displays operation guidance and the like for the operator. The display unit 473 is a touch panel, and the operator can operate the image forming apparatus 1 by touching an image or an icon displayed on the display unit 473.

  The control unit 10 includes a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. The processor is a CPU (Central Processing Unit), an MPU (Micro-Processing Unit), an ASIC (Application Specific Integrated Circuit), or the like.

  In the control unit 10, the control program stored in the ROM or the built-in HDD is executed by the CPU, so that the document reading unit 5, the document feeding unit 6, the image forming unit 12, the paper feeding unit 14, and It functions as the operation control unit 100 that controls the operation of the fixing unit 20 and the like.

  The operation control unit 100 includes a power control unit 101, a paper timing determination unit 102, and a storage unit 103. The storage unit 103 stores at least various data used by the power control unit 101 and the paper timing determination unit 102, information such as a storage table in which the types of the paper P and the heat generation pattern of the heater 212, which will be described later, are associated with each other. Remembered.

  When the image forming apparatus 1 performs a document reading operation, the document reading unit 5 is placed on the document fed by the document feeding unit 6 or the document placing glass 161 under the control of the operation control unit 100. The image of the original document is optically read to generate image data. The image data generated by the document reading unit 5 is stored in a built-in HDD (Hard Disk Drive), a computer connected to a network, or the like.

  When the image forming apparatus 1 performs an image forming operation, under the control of the operation control unit 100, the image forming unit 12 converts the image data generated by the above document reading operation or the image data stored in the built-in HDD. Based on this, a toner image is formed on the sheet P as a recording medium fed from the sheet feeding unit 14.

  When performing color printing, the image forming unit 12M for magenta, the image forming unit 12C for cyan, the image forming unit 12Y for yellow, and the image forming unit 12Bk for black of the image forming unit 12 are charged, exposed, and developed. By the above process, toner images of respective colors are formed on the photosensitive drum 121. The formed toner images of the respective colors are superimposed on the intermediate transfer belt 125 by the primary transfer roller 126 to form a color toner image. The superimposed color toner images are transferred by the secondary transfer roller 210 to the paper P that has been transported in the transport path 190. After the toner image is transferred onto the paper P in this manner, the fixing unit 20 performs the fixing process, and the paper P on which the fixing process is completed is discharged to the discharge tray 151.

  FIG. 3 is a cross-sectional view showing the configuration of the fixing unit 20. The fixing unit 20 includes a fixing roller 21 and a pressure roller 22 as main components. The fixing roller 21 and the pressure roller 22 are housed in a resin housing 24.

  The pressure roller 22 is configured by forming an elastic layer of silicon rubber on an iron cored bar, and coating the outer surface of the elastic layer with a PFA resin film having a thickness of 50 μm. The pressure roller 22 is rotatably supported in the housing 24 so as to be rotatable counterclockwise in FIG. During the fixing process, the rotary shaft 23 of the pressure roller 22 is rotationally driven by the rotary drive unit 95 (see FIG. 2) including a motor or the like under the control of the operation control unit 100. The pressure roller 22 and the fixing roller 21 form a nip portion N through which the sheet P to be fixed is inserted. The pressure roller 22 is an example of the pressure member in the claims.

  The fixing roller 21 includes a belt-shaped fixing member 211, a heater 212, three heater temperature sensors 213a to 213c, a holding member 214, and a pressing member 215.

  The fixing member 211 is configured by coating the inner surface and the outer surface of a stainless steel belt having an outer diameter of 30 mm and a thickness of 0.03 mm with fluororesin. The fixing member 211 is axially supported in the housing 24 so as to be rotatable clockwise in the plane of FIG. The fixing member 211 has an inner peripheral surface coated with a lubricant such as grease. The fixing member 211 is pressed against the pressure roller 22 by a pressing member 215 made of a heat-resistant resin pad, and is driven to rotate as the pressure roller 22 rotates. The fixing member 211 forms a nip portion N between the fixing member 211 and the pressure roller 22 arranged to face it, and fixes the toner image on the sheet P inserted in the nip portion N.

  The heater 212 is, for example, a ceramic heater, is a heater that contacts the inner peripheral surface of the fixing member 211 and heats the fixing member 211, and is a direction orthogonal to the moving direction of the fixing member 211 (Z shown in FIG. 3). This is a heater in which a plurality (for example, three) of heating regions HA1 to HA3 are arranged in parallel in the longitudinal direction which is the (direction).

  Here, the structure of the heater 212 will be described with reference to FIGS. 4 and 5. FIG. 4A is a schematic plan view showing the structure of the heating element portion of the heater, and FIG. 4B is a schematic sectional view of the heater. FIG. 5 is a diagram showing each heater heat generation pattern according to the paper size and an example of heater temperature sensor arrangement.

  As shown in FIG. 4(A), the heater 212 has a plurality of resistance heating elements forming the heating regions HA1 to HA3 arranged in the longitudinal direction (Z direction shown in FIG. 4), and both ends of these resistance heating elements are arranged. An electrode electrically connected to each of the electrodes is arranged. As shown in FIG. 4B, the heater 212 includes a heater base material 212a, a glaze layer 212b, a resistance heating element 212c and an electrode 212d, and an overcoat layer 212e in the thickness direction (X direction shown in FIG. 4). It has a laminated structure.

  The heater base 212a is, for example, an insulating ceramic substrate such as alumina or aluminum nitride, and has a plate shape with a low heat capacity. The glaze layer 212b serves, for example, as a heat storage layer.

  The resistance heating element 212c is a resistance heating element such as Ag/Pd (silver palladium), RuO2 (ruthenium oxide), Ta2N (tantalum nitride), and the like, and the longitudinal direction of the heater substrate (Z direction shown in FIGS. 3 and 4). Are formed along the line. The electrode 212d includes a common electrode 212d1 connected to one end side of the resistance heating elements 212c and a selection electrode 212d2 connected to the other end side of the resistance heating elements. As shown in FIG. 5, the selection electrode 212d2 includes an electrode 212d21 for supplying power to the heating area HA1, an electrode 212d22 for supplying power to the heating area HA2, and a power for supplying power to the heating area HA3. And electrodes 212d23.

  As shown in FIG. 5, when power is supplied to the electrode 212d21 of the selection electrode 212d1 by the power control unit 101, the heating area HA1 generates heat. When power is supplied to the electrode 212d22 of the selection electrode 212d1 by the power control unit 101, the heating area HA2 generates heat. When power is supplied to the electrode 212d23 of the selection electrode 212d1 by the power control unit 101, the heating area HA3 generates heat.

  When performing full-size heating of the heater 212 (that is, heating in all the heating regions HA1 to HA3), the power control unit 101 supplies power to all the electrodes 212d21 to 212d23 of the selection electrode 212d1. Further, when heating the heater 212 in a small size (that is, in the heating area HA1), the power control unit 101 supplies power to the electrode 212d21 of the selection electrode 212d1 and also described later on the electrodes 212d22 and 212d23. As described above, electric power is supplied to keep the temperature difference between the heating area HA1 and the heating areas HA2 and HA3 constant. In addition, the power control unit 101 supplies power to the electrodes 212d21 and 212d22 of the selection electrode 212d1 and also to the electrode 212d23 when performing medium-sized heating of the heater 212 (that is, heating in the heating areas HA1 and HA2). Supplies electric power that makes the temperature difference between the heating areas HA1 and HA2 and the heating area HA3 constant, as will be described later.

  The overcoat 212e layer is, for example, a protective layer that is formed on the surface of the heater 212 that is in contact with the fixing member 211 and that protects the resistance heating element and the electrodes within a range that does not impair the thermal efficiency. The thickness of the overcoat layer 212e is sufficiently thin, and it is desirable that the overcoat layer 212e has good surface properties, and is coated with glass or a fluororesin.

  Under the control of the operation controller 100, the heater 212 performs a heating operation during the fixing process and stops the heating operation after the fixing process is completed. The heater 212 is an example of the heat source in the claims. The heater 212 may be a heat source such as an IH heater.

  The heater temperature sensors 213a to 213c are contact-type temperature sensors that contact the heater 212 and detect the temperatures of the heating regions HA1 to HA3 of the heater 212, respectively. As shown in FIG. 5, the heater temperature sensor 213a is arranged in the heating area HA1 and detects the temperature of the heating area HA1. The heater temperature sensor 213b is arranged in the heating area HA2 and detects the temperature of the heating area HA2. The heater temperature sensor 213c is arranged in the heating area HA3 and detects the temperature of the heating area HA3. The heater temperature sensors 213a to 213c output detection signals indicating the temperature values of the heating areas HA1 to HA3 of the heater 212 to the power control unit 101, respectively. The heater temperature sensors 213a to 213c are an example of the temperature detecting unit in the claims.

  The holding member 214 holds the heater 212. For example, the holding member 214 holds the heater 212 in a state in which the heater 212 in a state in which the heater temperature sensors 213a to 213c are in contact with the housing recess having a size capable of housing the heater 212.

  The fixing device 200 also includes a paper transport guide 191 and a paper position detection sensor 193. The paper transport guide 191 is a guide member that guides the paper P, which is directed from the transport path 190 toward the fixing unit 20, to the nip portion N.

  The paper position detection sensor 193 is a non-contact type position detection sensor that detects the position of the paper P toward the fixing unit 20. The sheet position detection sensor 193 is arranged, for example, at a position separated from the nip portion N on the upstream side of the conveyance of the sheet P by a predetermined distance (for example, one rotation of the fixing member 211). The paper position detection sensor 193 outputs a detection signal indicating the detection of the paper P to the power control unit 101.

  The paper timing determination unit 102 determines the arrival timing at which the leading edge of the paper P reaches the nip portion N based on the detection signal from the paper position detection sensor 193. For example, in the paper timing determination unit 102, the peripheral length L2 of the fixing member 211 is 80 [mm], the predetermined distance is also 80 [mm], and the linear velocity V of the fixing member 211 is 100 [mm/ s], the timing when 0.8 seconds (80 [mm]/100 [mm/s]=0.8 seconds) has elapsed from the timing when the paper position detection sensor 193 detects the leading edge of the paper P is detected. , It is determined that it is the arrival timing when the leading edge of the paper P reaches the nip portion N. Further, the paper timing determination unit 102 determines the end timing when the trailing edge of the paper P reaches the nip portion N based on the detection signal from the paper position detection sensor 193. For example, in the paper timing determination unit 102, the peripheral length L2 of the fixing member 211 is 80 [mm], the predetermined distance is also 80 [mm], and the linear velocity V of the fixing member 211 is 100 [mm/ If it is s], the timing when 0.8 seconds (80 [mm]/100 [mm/s]=0.8 seconds) has elapsed from the timing when the paper position detection sensor 193 detected the trailing edge of the paper P However, it is determined that it is the end timing when the trailing edge of the paper P reaches the nip portion N.

  The electric power control unit 101 maintains power to maintain the temperature of the heater 212 detected by the heater temperature sensors 213a to 213c at a predetermined control temperature (that is, the fixing temperature) (that is, the temperature of the heater 212 is predetermined). The power required to maintain the fixing temperature) is calculated and the maintenance power is supplied to the heater 212. The control temperature is determined depending on the type of toner used and the like, but is, for example, a temperature of 100° C. or higher and 200° C. or lower and a temperature suitable for fixing (for example, 170° C.).

  Specifically, as shown in FIG. 5, the power control unit 101 determines the heat generation pattern of the heater 212 during the fixing process according to the type of the paper P. The power control unit 101 can specify the type of the paper P based on the input of the paper type to the operation unit 47 by the operator or the detection signal from a known paper width detection sensor (not shown). Then, the power control unit 101 determines the heat generation pattern of the heater 212 corresponding to the type of the paper P based on the storage table stored in the storage unit 103.

  Subsequently, for example, when the type of the paper P is the small size shown in FIG. 5, the power control unit 101 is detected by the heater temperature sensors 213a to 213c when the paper P is inserted into the nip portion N. In addition, the maintenance power for maintaining the temperature of the sheet passing heating area (that is, the heating area HA1) at the position where the paper P passes among the plurality of heating areas HA1 to HA3 at a predetermined control temperature (for example, 170° C.) is provided. The sheet P is supplied to the sheet passing heating area (here, heating area HA1), and the sheet P is not passed among the plurality of heating areas HA1 to HA3 detected by the heater temperature sensors 213a to 213c. The temperature of the paper heating area (that is, the heating areas HA2 and HA3) is lower than the temperature of the paper heating area (here, heating area HA1) and with respect to the temperature of the paper heating area (here, heating area HA1). Electric power for maintaining a temperature (for example, 60° C.) that maintains a constant temperature difference (for example, 110° C.) is supplied to the non-sheet-passing heating regions (here, heating regions HA2 and HA3).

  As shown in FIGS. 6 and 7, the power control unit 101 controls the temperature of the heating area HA1 detected by the heater temperature sensor 213a and the heating areas HA2, HA3 detected by the heater temperature sensors 213b, 213c. The electric power to the plurality of heating regions HA1 to HA3 is controlled so that the temperature difference from the temperature is kept constant (for example, 110° C.).

  Here, the temperature control process of the fixing device 200 according to the first embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing an example of temperature control processing of the fixing device according to the first embodiment.

  When the image forming apparatus 1 receives a print instruction from the user, for example, the power control unit 101 receives an input of the paper type into the operation unit 47 by the operator or a detection signal from a known paper width detection sensor (not shown). Then, the type of paper P is specified (S1). The power control unit 101 specifies, for example, whether the type of the paper P is full size, medium size, or small size.

  The power control unit 101 determines a heat generation pattern of the heater 212 corresponding to the type of the paper P based on the storage table stored in the storage unit 103 (S2). For example, when the type of paper P is a small size, the power control unit 101 determines the small-sized heat generation pattern shown in FIG.

  The sheet timing determination unit 102 determines, based on the detection signal from the sheet position detection sensor 193, whether it is the arrival timing at which the leading edge of the sheet P reaches the nip portion N (S3). Specifically, the sheet timing determination unit 102 determines that the timing at which 0.8 seconds has elapsed from the timing at which the sheet position detection sensor 193 detects the leading edge of the sheet P is the arrival timing at which the nip portion N is reached.

  When it is determined that the arrival timing is not reached (NO in S3), the sheet timing determination unit 102 returns to S3 and waits for the arrival timing.

  On the other hand, when the paper timing determination unit 102 determines that the arrival timing is reached (YES in S3), the power control unit 101 determines whether or not the heater 212 has passed based on the heat generation pattern of the heater 212 determined in S2. The maintenance power for maintaining the temperature of the paper heating region at a predetermined control temperature (for example, 170° C.) is calculated, and the maintenance power is supplied to the paper heating region of the heater 212, and the non-paper heating is performed. Electric power for maintaining the temperature of the area lower than the temperature of the sheet heating area and maintaining a constant temperature difference with respect to the temperature of the sheet heating area is supplied to the non-sheet heating area (S4). ).

  For example, when the type of the paper P is a small size, the power control unit 101 determines the heating pattern of the small-sized heater 212 shown in FIG. 5 in S2, and the paper P is inserted into the nip portion N in S4. In this case, the temperature of the paper-passage heating area (that is, the heating area HA1) at the position where the paper P passes among the plurality of heating areas HA1 to HA3 detected by the heater temperature sensors 213a to 213c is predetermined. The plurality of heating areas HA1 detected by the heater temperature sensors 213a to 213c are supplied with the maintenance power for maintaining the controlled temperature (for example, 170° C.) to the sheet passing heating area (here, the heating area HA1). The temperature of the non-paper passing heating area (that is, the heating areas HA2 and HA3) in the position where the paper P does not pass among HA3 to HA3 is lower than the temperature of the paper passing heating area (here, heating area HA1) and the paper passing is performed. Electric power for maintaining the temperature (for example, 60° C.) that maintains a constant temperature difference (for example, 110° C.) with respect to the temperature of the heating region (here, heating region HA1) is the non-sheet-passing heating region (here, heating region HA2, Supply to HA3).

  The power control unit 101 determines, based on the detection signal from the paper position detection sensor 193, whether or not it is the timing when the trailing edge of the paper P reaches the nip portion N (S5). Specifically, the power control unit 101 determines that the timing at which 0.8 seconds has elapsed from the timing at which the sheet position detection sensor 193 detected the trailing edge of the sheet P is the timing at which the nip portion N is reached.

  When the power control unit 101 determines that the trailing edge of the paper P does not reach the nip portion N (NO in S5), the process returns to S5 and it is the timing when the trailing edge of the paper P reaches the nip portion N. When the determination is made (YES in S5), the supply of the maintenance power for maintaining the temperature of the sheet-passage heating region (here, heating region HA1) at the control temperature (for example, 170° C.) by the heating pattern of the heater 212 and the non-sheet-passing heating region (Here, heating regions HA2 and HA3) are supplied with electric power to maintain a temperature (for example, 110° C.) that maintains a constant temperature difference (for example, 110° C.) with respect to the temperature of the paper heating region (heating region HA1). , Are simultaneously ended (S6).

  Here, the relationship between the temperature difference and the torque difference between the heating regions of the heater 212 (heat source) (that is, between the heating regions HA2, HA3 and the heating region HA1) will be described with reference to FIG. FIG. 9: is a figure which shows an example of the characteristic data which shows the relationship between the temperature difference and torque difference between each heating area of a heat source. As shown in FIG. 9, the temperature T1 of the heating passage area of the heater 212 (that is, the heating area HA1) is 170° C., and the temperature T2 of the non-sheet passing heating area of the heater 212 (that is, the heating areas HA2 and HA3) is The temperature is lower than the temperature of the sheet-passage heating area (heating area HA1) and is a temperature (for example, 60° C.) that maintains a constant temperature difference (for example, 110° C.) with respect to the temperature of the sheet-passing heating area (heating area HA1). Therefore, from the difference between the torque value Tor1 at the temperature T1 and the torque value Tor2 at the temperature T2, the torque difference Tor12 (=Tor1-Tor2) is obtained. On the other hand, when the electric power is not supplied to the non-sheet passing heating area of the heater 212, the temperature of the non-sheet passing heating area (that is, the heating areas HA2 and HA3) is the temperature T3 (for example, 20° C.), The temperature difference is, for example, 150° C., and from the difference between the torque value Tor1 at the temperature T1 and the torque value Tor3 at the temperature T3, the torque difference Tor13 (=Tor1−Tor3)>the torque difference Tor12. .. As described above, according to the first embodiment, it is possible to make the torque difference Tor12 smaller than the torque difference Tor13.

  After S6, the operation control unit 100 determines whether or not the printing is completed (S7). The operation control unit 100 determines that the printing is not finished when there is the next printing (NO in S7), proceeds to S1, and executes the above S1 to S6. On the other hand, when there is no next print, the operation control unit 100 determines that the print is finished (YES in S7), and finishes this process.

  According to the fixing unit 20 and the image forming apparatus 1 according to the above-described first embodiment, the belt-shaped fixing member 211 has the inner peripheral surface coated with the lubricant. The pressure roller 22 is disposed so as to face the fixing member 211, and forms a nip portion N between the pressure roller 22 and the fixing member 211, through which the sheet P to be fixed is inserted. The heater 212 is a heat source that heats the fixing member 211 by coming into contact with the inner peripheral surface of the fixing member 211, and has a plurality of heating regions HA1 to HA3 arranged in parallel in a direction orthogonal to the moving direction of the fixing member 211. Is. The heater temperature sensors 213a to 213c detect the temperatures of the plurality of heating areas HA1 to HA3, respectively. When the paper P is inserted into the nip portion N, the power control unit 101 detects the heater temperature sensors 213a to 213c and detects the heater temperature sensors HA1 to HA3. Of the plurality of heating areas HA1 to HA3 detected by the heater temperature sensors 213a to 213c, while supplying the maintenance power for maintaining the temperature of the heating area to a predetermined control temperature to the sheet passing heating area. The power for maintaining the temperature of the non-paper passing heating area at a position where the paper P does not pass is lower than the temperature of the paper passing heating area and maintains a constant temperature difference with respect to the temperature of the paper passing heating area. Supply to the sheet heating area. Therefore, it is possible to suppress the temperature unevenness in the surface of the fixing member 211 during the selective heating by the heater 212 to a constant temperature difference, and to suppress the viscosity difference of the lubricant applied to the fixing member 211. can do. As a result, it is possible to suppress the occurrence of uneven sliding torque within the surface of the fixing member 211. Therefore, the occurrence of twist of the fixing member 211 due to the temperature difference of the lubricant can be reduced. In addition, compared with the case where the temperature of the non-paper feed heating area is the same as the temperature of the paper feed heating area, the temperature of the non-paper feed heating area is lower than the temperature of the paper feed heating area. Can be suppressed.

  Next, the fixing device and the image forming apparatus according to the second embodiment will be described with reference to FIGS. FIG. 10 is a functional block diagram showing the electrical configurations of the fixing device and the image forming apparatus according to the second embodiment of the present invention. FIG. 11 is a diagram showing an example of characteristic data showing the relationship between the temperature and the viscosity of the lubricant.

  In the first embodiment described above, the power control unit 101 sets the temperature difference between the temperature of the sheet-passage heating region and the temperature of the non-sheet-passage heating region as a constant temperature difference. This is different from the first embodiment in that the temperature difference is controlled such that the difference in viscosity between the lubricants in the paper passing portion and the non-paper passing portion is within a specified value.

  As shown in FIG. 10, the operation control unit 100 of the second embodiment includes a storage unit 103, a specifying unit 104, a determining unit 105, and a setting unit 106. The storage unit 103 stores in advance characteristic data (see FIG. 11) indicating the relationship between the temperature and the viscosity of the lubricant.

  The identifying unit 104 uses the characteristic data shown in FIG. 11 stored in the storage unit 103, and the lubricant when the temperature of the sheet passing heating region is the temperature detected by the temperature detecting unit (for example, the heater temperature sensor 213a). And the second viscosity of the lubricant when the non-paper-passage heating region is at the temperature detected by the temperature detection unit (for example, the heater temperature sensors 213b and 213c). Specifically, as shown in FIG. 11, the specifying unit 104 determines the first viscosity Vi1 of the lubricant when the sheet heating area (that is, the heating area HA1) of the heater 212 is the temperature Temp1, and the non-existence of the heater 212. The second viscosity Vi2 of the lubricant when the sheet passing heating area (that is, the heating areas HA2 and HA3) is at the temperature Temp2 is specified.

  The determination unit 105 determines whether or not the viscosity difference between the first viscosity and the second viscosity of the lubricant identified by the identification unit 104 is equal to or less than a predetermined specified value. Specifically, as shown in FIG. 11, the determination unit 105 determines whether or not the viscosity difference between the first viscosity Vi1 and the second viscosity Vi2 of the lubricant is less than or equal to a predetermined specified value Viref. To do. For example, in FIG. 11, the viscosity difference between the first viscosity Vi1 and the second viscosity Vi2 of the lubricant is a value that exceeds the specified value Viref.

  When the determination unit 105 determines that the difference in the viscosity of the lubricant is not less than or equal to a predetermined value, the setting unit 106 uses the characteristic data stored in the storage unit 103 to calculate the difference from the first viscosity. The temperature indicated by the viscosity within the specified value is specified as the target temperature of the non-paper feed heating area, and the temperature difference between the temperature of the paper feed heating area and the target temperature of the non-paper feed heating area is set as a constant temperature difference. To do. Specifically, as shown in FIG. 11, in the setting unit 106, the determination unit 105 determines that the viscosity difference Vi12 between the first viscosity Vi1 and the second viscosity Vi2 is not less than or equal to a predetermined specified value Viref. In this case, using the characteristic data stored in the storage unit 103, the temperature Temp3 indicated by the viscosity Vi3 within the specified value Viref from the first viscosity Vi1 is specified as the target temperature of the non-sheet passing heating area, and the sheet passing heating area is determined. And the target temperature of the non-sheet-passage heating area (that is, the temperature Temp3) are set as a constant temperature difference.

  The electric power control unit 101 supplies electric power for maintaining the temperature of the non-sheet-penetrating heating region to the target temperature (that is, the temperature Temp3) having the constant temperature difference set by the setting unit 106 to the non-sheet-penetrating heating region. To do. That is, as shown in FIG. 11, the power control unit 101 raises the temperature of the non-sheet-passage heating region to the target temperature (that is, the temperature Temp3) and maintains the power that is maintained at the target temperature (that is, the temperature Temp3). Supply to the sheet heating area. As a result, it is possible to control the temperature difference such that the difference in viscosity of the lubricant between the paper passing portion and the non-paper passing portion of the fixing member 211 is within a specified value.

  Here, the temperature control process of the fixing device 200 according to the second embodiment will be described with reference to FIG. FIG. 12 is a flowchart showing an example of temperature control processing of the fixing device according to the second embodiment. Since S1 to S7 are the same as those in the first embodiment, S11 to S14 according to the second embodiment will be described.

  After S4, the identifying unit 104 uses the characteristic data shown in FIG. 11 to determine the first viscosity Vi1 of the lubricant when the sheet heating area (that is, the heating area HA1) of the heater 212 is the temperature Temp1, and the heater 212. The second viscosity Vi2 of the lubricant when the non-sheet-passing heating area (that is, the heating areas HA2 and HA3) is temperature Temp2 is specified (S11).

  The determination unit 105 determines whether or not the difference in viscosity between the first viscosity Vi1 and the second viscosity Vi2 of the lubricant is equal to or less than a predetermined specified value Viref using the characteristic data shown in FIG. 11 ( S12). For example, in FIG. 11, the viscosity difference between the first viscosity Vi1 and the second viscosity Vi2 of the lubricant is a value that exceeds the specified value Viref.

  When the determination unit 105 determines that the viscosity difference between the first viscosity Vi1 and the second viscosity Vi2 is not less than or equal to a predetermined specified value (NO in S12), the setting unit 106 determines the characteristic data shown in FIG. The temperature Temp3 indicated by the viscosity in which the viscosity difference from the first viscosity Vi1 is within the specified value Viref is specified as the target temperature of the non-paper-passage heating area by using The temperature difference from the temperature (that is, the temperature Temp3) is set as a constant temperature difference (S13).

  The electric power control unit 101 supplies electric power for maintaining the temperature of the non-sheet-penetrating heating region to the target temperature (that is, the temperature Temp3) having the constant temperature difference set by the setting unit 106 to the non-sheet-penetrating heating region. Yes (S14). That is, as shown in FIG. 11, the power control unit 101 raises the temperature of the non-sheet-passage heating region to the target temperature (that is, the temperature Temp3) and maintains the power that is maintained at the target temperature (that is, the temperature Temp3). Supply to the sheet heating area.

  According to the second embodiment described above, the storage unit 103 stores in advance characteristic data (see FIG. 11) indicating the relationship between the temperature and the viscosity of the lubricant. By using the characteristic data shown in FIG. 11 stored in the storage unit 103, the first viscosity of the lubricant when the temperature of the sheet passing heating region is the temperature detected by the temperature detecting unit (for example, the heater temperature sensor 213a) and , The second viscosity of the lubricant when the non-paper-passage heating region is at the temperature detected by the temperature detecting unit (for example, the heater temperature sensors 213b and 213c). The determination unit 105 determines whether or not the difference in viscosity between the first viscosity Vi1 and the second viscosity Vi2 of the lubricant is less than or equal to a predetermined specified value Viref. When the determination unit 105 determines that the difference in the viscosity of the lubricant is not less than or equal to a predetermined value, the setting unit 106 uses the characteristic data stored in the storage unit 103 to calculate the difference from the first viscosity. The temperature indicated by the viscosity within the specified value is specified as the target temperature of the non-paper feed heating area, and the temperature difference between the temperature of the paper feed heating area and the target temperature of the non-paper feed heating area is set as a constant temperature difference. To do. The electric power control unit 101 supplies electric power for maintaining the temperature of the non-sheet-penetrating heating region to the target temperature (that is, the temperature Temp3) having the constant temperature difference set by the setting unit 106 to the non-sheet-penetrating heating region. To do. As a result, the in-plane viscosity difference of the fixing member 211 when the heater 212 performs the selective heating can be reliably made equal to or less than the specified value. Thereby, it is possible to further suppress the occurrence of unevenness of the sliding torque within the surface of the fixing member 211. Therefore, the occurrence of twist of the fixing member 211 due to the temperature difference of the lubricant can be further reduced.

  Next, the fixing device and the image forming apparatus according to the third embodiment will be described with reference to FIG. FIG. 13 is a functional block diagram showing the electrical configurations of the fixing device and the image forming apparatus according to the third embodiment of the present invention.

  In the third embodiment, when the torque value of the pressure roller 22 exceeds a predetermined threshold value, the constant temperature difference is changed to a predetermined smaller temperature difference, and the temperature of the sheet passing heating region is changed to The difference from the second embodiment is that the temperature is further raised to the temperature difference after the change.

  As shown in FIG. 13, the fixing device 200 according to the third exemplary embodiment includes a current measuring unit 221 that measures a current value supplied to a drive source (for example, a motor) that drives the pressure roller 22. The current measuring unit 221 is, for example, an ammeter.

  As shown in FIG. 13, the operation control unit 100 of the third embodiment includes a torque calculation unit 107 and a torque determination unit 108. The storage unit 103 stores in advance characteristic data (see FIG. 11) indicating the relationship between the temperature and the viscosity of the lubricant.

The torque calculation unit 107 calculates a torque value based on the current value measured by the current measurement unit 221 using a conversion formula stored in the storage unit 103 in advance. For example, the torque value T is proportional to the current value I measured by the current measuring unit 221, and is represented by the following equation (1).
T = Kt x I (1)
However, I: current [A], Kt: torque constant [Nm/A]

  The torque determination unit 108 determines whether or not the torque value calculated by the torque calculation unit 107 exceeds a predetermined threshold value. The storage unit 103 stores in advance a predetermined threshold value.

  When the torque determination unit 108 determines that the torque value exceeds the threshold value, the setting unit 106 changes the constant temperature difference to a predetermined smaller temperature difference and changes the temperature of the non-sheet passing heating region from the temperature. The temperature that becomes the temperature difference after the change is specified as the target temperature of the non-sheet passing heating area.

  The power control unit 101 supplies electric power for maintaining the temperature of the non-sheet-penetrating heating region to the target temperature which is the changed temperature difference set by the setting unit 106, to the non-paper-penetrating heating region.

  According to the third embodiment, it is possible to confirm whether or not the torque value of the drive source (for example, motor) of the pressure roller 22 exceeds the threshold value. Further, when the torque value of the drive source (for example, motor) of the pressure roller 22 exceeds the threshold value, the sheet passing portion of the fixing member 211 (that is, the sheet passing heating area of the heater 212 in the fixing member 211 is heated. The viscosity of the lubricant in the non-sheet passing portion of the fixing member 211 (that is, the portion heated by the non-sheet passing heating region of the heater 212 in the fixing member 211) becomes higher than the viscosity of the lubricant in the portion. Since the slidability of the non-sheet passing portion of the fixing member 211 may deteriorate due to the presence of the fixing member 211, the temperature of the non-sheet passing heating area of the heater 212 is increased to increase the sheet passing heating area and the non sheet passing heating. By changing the constant temperature difference from the area to a smaller temperature difference, the torque difference between the paper passing portion and the non-paper passing portion of the fixing member 211 can be reduced, and the torque of the fixing device 200 as a whole can be improved. it can. Therefore, the occurrence of twist of the fixing member 211 due to the temperature difference of the lubricant can be further reduced.

  Note that when a driving source (for example, a motor) that drives the fixing member 211 is provided instead of driving the pressure roller 22, the current measuring unit 221 uses the driving source (for example, a motor) that drives the fixing member 211. The supplied current value may be measured.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made.

<Modification>
In the above embodiment, as shown in FIG. 7, the temperature of the non-sheet-passing heating area (that is, the heating areas HA2, HA3) at the position where the paper P does not pass among the plurality of heating areas HA1 to HA3 is the sheet heating. Electric power is maintained at a temperature lower than the temperature of the region (heating region HA1) and at a temperature (for example, 60° C.) that maintains a constant temperature difference (for example, 110° C.) with respect to the temperature of the sheet heating region (heating region HA1). Although it is supplied to the non-sheet passing heating area (heating areas HA2 and HA3), the present invention is not limited to this.

  As shown in FIG. 14, the electric power control unit 101 has a temperature lower than the temperature of the sheet heating area (heating area HA1) in the heating area HA3 in the non-sheet passing heating area and the sheet heating area (heating area HA1). ) Is supplied to the heating area HA3 with a temperature (for example, 60° C.) that maintains a constant temperature difference (for example, 110° C.), and power is supplied to the heating area HA2 in the non-sheet feeding heating area. It may not be supplied.

  Specifically, as shown in FIG. 14, the non-paper-passage heating area is connected to an adjacent area (here, heating area HA2) adjacent to the paper-passing heating area in a direction orthogonal to the moving direction of the fixing member 211. It is configured by being divided into an end area (here, heating area HA3) separated from the paper heating area.

  The electric power control unit 101 detects the temperature of the end area (heating area HA3) of the non-paper-passage heating area detected by the heater temperature sensor 213c at a temperature lower than the temperature of the paper-passage heating area, and heats the paper-passage. Electric power for maintaining a temperature that maintains a constant temperature difference with respect to the temperature of the area is supplied to the end area (heating area HA3) of the non-paper feeding heating area, and an adjacent area ( No power is supplied to the heating area HA2).

  According to the above modification, electric power is supplied to the adjacent area (heating area HA2) as compared with the case where electric power is supplied to the adjacent area (heating area HA2) and the end area (heating area HA3) of the non-sheet passing heating area. It is possible to save power only by not doing so. Furthermore, since the adjacent area (heating area HA2) of the non-paper passing heating area is located between the paper passing heating area (heating area HA1) and the end area (heating area HA3) of the non-paper passing heating area. By the paper passing portion of the fixing member 211 (the portion heated by the paper passing heating area) and the end portion of the non-paper passing portion of the fixing member 211 (the end area of the non-paper passing heating area (heating area HA3)). The heat from the (heated portion) is transmitted to a portion of the fixing member 211 sandwiched between the sheet passing portion and the end portion of the non-sheet passing portion, and the viscosity of the sandwiched portion of the fixing member 211 can be reduced. it can. Therefore, it is possible to suppress the difference in viscosity within the surface of the fixing member 211.

1 Image Forming Apparatus 10 Control Unit 12 Image Forming Section 20 Fixing Section 21 Fixing Roller 22 Pressure Roller (Pressure Member)
100 operation control unit 101 power control unit 103 storage unit 104 specifying unit 105 determination unit 106 setting unit 107 torque calculation unit 108 torque determination unit 200 fixing device 211 fixing member 212 heater (heat source)
213a to 213c Heater temperature sensor (temperature detector)
221 Current measuring unit

Claims (5)

A belt-shaped fixing member having an inner peripheral surface coated with a lubricant,
A pressure member that is arranged to face the fixing member and that forms a nip portion between the fixing member and a recording medium to be fixed is inserted;
A heat source for heating the fixing member by contacting the inner peripheral surface of the fixing member, wherein a plurality of heating regions are arranged in parallel in a direction orthogonal to the moving direction of the fixing member,
A temperature detection unit that detects the temperature of each of the plurality of heating regions,
When the recording medium is inserted into the nip portion, the temperature of the paper-passage heating area at the position where the recording medium passes among the plurality of heating areas detected by the temperature detecting unit is predetermined. A non-sheet passing sheet at a position where the recording medium does not pass among the plurality of heating zones detected by the temperature detecting section while supplying the maintenance power for maintaining the controlled temperature to the sheet passing heating zone. Electric power is supplied to the non-paper-passage heating area so as to maintain the temperature of the heating area at a temperature lower than the temperature of the paper-passing heating area and maintaining a constant temperature difference from the temperature of the paper-passing heating area. And a power control section for controlling the fixing device. A storage unit that stores in advance characteristic data indicating the relationship between the temperature and viscosity of the lubricant,
By using the characteristic data stored in the storage unit, the first viscosity of the lubricant when the paper passing heating region is at the temperature detected by the temperature detecting unit, and the non-paper passing heating region is A specifying unit that specifies the second viscosity of the lubricant when the temperature is detected by the temperature detecting unit;
A determination unit that determines whether or not the viscosity difference between the first viscosity and the second viscosity specified by the specifying unit is equal to or less than a predetermined specified value;
When the determination unit determines that the viscosity difference is not equal to or less than the specified value, the characteristic data stored in the storage unit is used to determine that the viscosity difference from the first viscosity is within the specified value. The temperature shown is specified as the target temperature of the non-paper-passage heating area, and a setting unit that sets the temperature difference between the temperature of the paper-passage heating area and the target temperature of the non-paper-passage heating area as the constant temperature difference, Equipped with
The power control unit supplies electric power for maintaining the temperature of the non-paper feed heating region to the target temperature that is the constant temperature difference set by the setting unit, to the non-paper feed heating region. Item 2. The fixing device according to item 1. A current measuring unit that measures a current value supplied to a drive source that drives the pressure member or the fixing member;
A torque calculation unit that calculates a torque value based on the current value measured by the current measurement unit,
A torque determination unit that determines whether or not the torque value calculated by the torque calculation unit exceeds a predetermined threshold value,
When the torque determination unit determines that the torque value exceeds the threshold, the setting unit changes the constant temperature difference to a predetermined smaller temperature difference, and the The temperature that is the temperature difference after the change from the temperature is specified as the target temperature of the non-paper passing heating area,
The electric power control unit supplies electric power for maintaining the temperature of the non-sheet passing heating region to the target temperature which is the changed temperature difference set by the setting unit, to the non-sheet passing heating region. The fixing device according to claim 2. In the direction orthogonal to the moving direction of the fixing member, it is divided into the paper passing heating region and the non-paper passing heating region,
The non-paper passing heating region is configured by being divided into an adjacent region adjacent to the paper passing heating region and an end region distant from the paper passing heating region in a direction orthogonal to the moving direction of the fixing member. ,
The power control unit has a temperature of the end region of the non-paper passing heating region detected by the temperature detecting unit lower than a temperature of the paper passing heating region and the paper passing heating region. To the end region of the non-paper feed heating region, and does not supply power to the adjacent region of the non-paper feed heating region. The fixing device according to any one of claims 1 to 3. An image forming unit that forms a toner image,
An image forming apparatus comprising: the fixing device according to claim 1, which fixes the toner image formed by the image forming unit onto the surface of the recording medium.