JP3931192B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device temperature control method and a fixing device used in an electrophotographic recording apparatus such as an electrophotographic printer, a copying machine, and a facsimile machine.

  Conventionally, a fixing device used in an electrophotographic recording apparatus passes a recording paper in which unfixed toner is attached to a roller pressure contact portion between a heating roller as a first roller and a pressure roller as a second roller. In this way, the toner is a pressure roller type in which the toner is pressure-fused and fixed on the recording paper.

  The heating roller has a heat source (for example, a halogen lamp) inside the cored bar, and has an elastic body (for example, silicone rubber) in which a release layer having high water and oil repellency is formed on the outer periphery of the cored bar.

  Since the pressure roller is in pressure contact with the elastic body, an elastic body deforming portion (hereinafter, the length of the deforming portion is referred to as a nip amount) is formed, and the recording paper to which unfixed toner is attached passes through the elastic body deforming portion. By doing so, fixing is performed.

Further, in order to control the surface temperature of the heating roller, a temperature sensor (for example, a thermistor) is disposed in contact with the surface of the heating roller.
Japanese Patent Laid-Open No. 10-171293

  When recording paper having a narrow width is continuously passed through the fixing device, there is a problem that a temperature difference between the inside and outside of the sheet passing width occurs.

Oite the fixing equipment of the present invention includes a heat source for heating the first roller, a first temperature sensor in contact with the roller surface of the first roller while being placed to the maximum width outside of the recording paper, the recording A second temperature sensor disposed outside the maximum paper width of the paper and in contact with the roller surface of the second roller; and a second temperature sensor disposed within the maximum paper width of the recording paper and in contact with the roller surface of the second roller. 3 temperature sensors and temperature control means for controlling energization to the heat source. The temperature control means obtains a difference between the detected temperature of the second temperature sensor and the detected temperature of the third temperature sensor, and is preset to the difference. The control target temperature is calculated by multiplying the calculated coefficient and adding to the detected temperature of the first temperature sensor, and the energization to the heat source is controlled based on the control target temperature.

In the fixing device of the present invention, the plurality of rollers include a heating roller that heats the fixing belt and a second fixing roller that is in pressure contact with the fixing roller. A first heat source that uniformly heats over the second, a second heat source that generates a larger amount of heat at the center than the end, and a first temperature sensor that is in contact with the inner surface of the fixing belt outside the sheet passing range A second temperature sensor that is in contact with the center of the inner surface of the fixing belt, a third temperature sensor that is in contact with the outer surface of the fixing belt and outside the sheet passing range, and energization of the first and second heat sources. And a control unit for determining a coefficient K for multiplying the temperature difference Δt between the first temperature sensor and the second temperature sensor from the output t of the third temperature sensor, and calculating the coefficient K by Δt To obtain a temperature difference T within and outside the recording paper passing range on the outer surface of the fixing belt. By subtracting the temperature difference T from the output t of the temperature sensor, the temperature within the recording paper passing range on the outer surface of the fixing belt is calculated.

  With the above configuration, by calculating the temperature of the center surface of the heating roller and controlling energization to the heat source of the heating roller, it is possible to prevent the occurrence of low temperature offset due to insufficient heat quantity.

  Embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element common to each drawing.

First Embodiment FIG. 1 is an external perspective view of a fixing device according to a first embodiment, and FIG. 2 is an AA cross-sectional view of the fixing device shown in FIG. The fixing device 1 includes a pair of heating rollers 3 and 4 having a length C extending in the width direction of the recording paper 2 conveyed in the arrow B direction. The recording paper 2 to which the unfixed toner 5 is adhered passes through the pressure contact portions 6 of the heating rollers 3 and 4 that form the nip amount N, and the unfixed toner 5 is fused to the recording paper 2.

  The heating roller 3 is formed on the outer periphery of a cored bar 7 extending in the width direction of the recording paper 2 by a heat-resistant elastic body 8 having a low thermal conductivity, such as silicone rubber or fluorine rubber. A metal foil 10 having a small heat capacity (for example, nickel, stainless steel, etc. having a thickness of 0.01 to 0.1 mm) having a water release and oil repellency, for example, a fluorine-based release layer 9 on the outer peripheral surface of the elastic body 8. Are closely formed. The length of the metal foil 10 is equal to the length C of the heating roller 3.

  A heat source 11 and a foreign matter removing blade 12 extending in the direction of the cored bar are in contact with the release layer 9. Further, a temperature sensor 13 (for example, a thermistor) for detecting the surface temperature of the heating roller 3 is in contact with an end of the release layer 9 (outside the maximum paper width L of the recording paper).

  The heating roller 4 has substantially the same configuration as the heating roller 3 except that the release layer 9 is not provided on the outer surface of the metal foil 10 and the foreign matter removing blade 12 and the temperature sensor 13 are not provided. is there.

  Here, the manufacturing method of a heating roller is demonstrated. FIG. 18 is an explanatory view showing a manufacturing method of the heating roller. First, as shown in FIG. 18A, a cylindrical electrode 63 (for example, stainless steel) in which a plating solution 60, for example, a nickel sulfonate solution is filled in a container 61 and an insulating layer 62 is provided on the outer periphery, and an electrode 64 made of nickel. Soak and face each other.

  By connecting the cylindrical electrode 63 to the negative electrode and the electrode 64 to the positive electrode, the metal foil 10 made of nickel metal is formed on the inner surface of the cylindrical electrode 63 by electroplating.

  Next, an adhesive is applied to the inner surface of the metal foil 10, and as shown in FIG. 18B, the column 65 is illustrated with the cylindrical electrode 63, the cored bar 7 and the column 65 sandwiched between the lids 66 and 67. It is fixed by a nut and mounted on a material container 69 provided with a piston 68 into which silicone serving as the elastic body 8 pressurizes and flows and is held in the material container 69. The lid 67 is provided with an injection port 70, and the lid 66 is provided with an overflow port 71.

  When the piston 68 is pressed, liquid silicone is injected into the metal foil 10 from the injection port 70 and solidifies in a roller shape while cross-linking with the adhesive. When the silicone is solidified, it is taken out from the cylindrical electrode 63 as shown in FIG. In this state, the heating roller 4 is formed.

  Next, in order to form the heating roller 3, a release layer 9 is provided by applying a fluorine-based material to the outer surface of the roller taken out from the cylindrical electrode 63.

  As described above, when the metal foil 10 is deposited on the inner surface of the cylindrical electrode 63 by the electroplating method, if the fluorine powder is uniformly dispersed in the plating solution 60 by the surfactant, the fluorine on the inner surface of the cylindrical electrode 63 is obtained. A composite plating foil made of nickel metal containing powder is deposited.

  The cylindrical electrode 63 is heat-treated at a temperature around the melting point of fluorine (for example, a processing temperature of 320 ° C. to 380 ° C., a processing time of 0.5 H to 1.5 H), whereby a fluorine thin film is formed on the surface of the metal foil. Thus, it is not necessary to newly provide the release layer 9.

  Further, the metal foil 10 may be formed by extrusion or the like without depending on the electroplating method. In this case, the release layer 9 is first provided on the outer periphery of the metal foil 10 to increase the rigidity, and then liquid silicone is injected into the inside to form a roller.

  Alternatively, the thickness of the metal foil 10 may be increased, and liquid silicone may be injected into the inside to form a roller, and then the outer periphery of the metal foil 10 may be ground.

  In addition, a silicone elastic body 8 is injected into the outer circumference of the core metal 7 to form a roller shape, and then immersed in a palladium chloride solution to precipitate palladium on the surface of the elastic body 8. After washing with water, for example, in a NiP solution It is immersed and nickel as the metal foil 10 is deposited on the surface of the elastic body 8 by electroless plating. Thereafter, the metal foil 10 deposited on the end of the roller is removed by cutting.

  In addition, when nickel as the metal foil 10 is deposited on the surface of the elastic body 8 by electroless plating, a composite plating foil made of nickel metal containing fluorine powder is deposited by dispersing fluorine powder in a NiP solution. It can also serve as the release layer 9.

  In addition, when a silicone elastic body 8 is injected into the outer periphery of the core metal 7 to form a roller by injecting palladium into the silicone, it is immersed in a palladium chloride solution to deposit palladium on the surface of the elastic body 8. No palladium treatment is required.

  The heat source 11 is installed on the upstream side of the roller pressure contact portion 6 with respect to the roller rotation directions E and F, a halogen lamp 14 is provided in a housing having a reflection surface inside, and the length D of the heat source 11 is the recording paper. It exceeds the maximum paper width L of 2 and is shorter than the length C of the heating roller 3.

  FIG. 3 is a control block diagram of the fixing device shown in FIG. The control unit 20 includes a central processing unit (hereinafter referred to as a CPU 21), a memory 22, and an I / O port 23. The memory 22 stores data in the data storage unit 22a and the surface temperature of the heating roller 3 is a predetermined temperature. A threshold storage unit 22b for storing a threshold to be controlled is provided.

  A driver circuit 24, 25, a temperature sensor 13, and a recording paper sensor 26 are connected to the CPU 21 via an I / O 23 port, and a halogen lamp 14 and a heating roller drive motor 27 are connected to the driver circuits 24, 25, respectively. It is.

  Next, the operation will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the fixing device shown in FIG. When an operator turns on a power switch (not shown), power is supplied to an apparatus, for example, an electrophotographic printer, and at the same time, the CPU 21 is reset to initialize the electrophotographic printer.

  After initialization, in step S1, the CPU 21 energizes the halogen lamp 14 and the heating roller drive motor 27 via the driver circuits 24 and 25, and passively rotates the heating rollers 3 and 4 in the directions of arrows E and F, respectively. Heat.

  In step S <b> 2, the CPU 21 detects the surface temperature of the heating roller 3 through the temperature sensor 13 and compares it with the threshold value stored in the threshold value storage unit 22 b of the memory 22. If the surface temperature of the heating roller 3 reaches the threshold value, the process branches to step S3. If not, the process branches to step S1.

  In step S3, the CPU 21 stops energizing the halogen lamp 14, and in step S4, the CPU 21 feeds the recording paper 2 from a cassette (not shown) and feeds it to an image forming unit (not shown). The toner image formed by the image forming unit is transferred to the recording paper 2, and the recording paper 2 to which the toner image has been transferred is conveyed toward the fixing device 1.

  In step S5, the CPU 21 detects the recording sheet 2 through the recording sheet sensor 13. If the trailing edge of the recording sheet is detected, the processing for one recording sheet is terminated, and if not, the process branches to step S6.

  In step S6, the CPU 21 detects whether or not the surface temperature of the heating roller 3 is equal to or lower than the predetermined temperature through the temperature sensor 13. If the surface temperature of the heating roller 3 is equal to or lower than the predetermined temperature, the process branches to step S7. Branches to step S8.

  In step S7, the CPU 21 energizes the halogen lamp 14 and branches to step S4.

  In step S8, the CPU 21 stops energization of the halogen lamp 14, and branches to step S4.

  In the present embodiment, the metal foil 10 having a small heat capacity and having the release layer 9 on the outer peripheral surface of the elastic body 8 is formed in close contact. However, as shown in FIG. An elastic body layer 15 having high heat conductivity and heat resistance may be provided between the release layer 9 and the release layer 9. In this case, distortion to the metal foil 10 at the roller pressure contact portion 6 can be reduced, and peeling of the metal foil 10 from the elastic body 8 can be prevented.

  The elastic body layer 15 is formed by applying silicone having a high thermal conductivity and heat resistance to the outer peripheral surface of the metal foil 10 and further applying the release layer 9 and performing cross-linking baking.

  Further, when an elastic body layer 15 having high thermal conductivity and heat resistance is provided between the metal foil 10 and the release layer 9, as shown in FIG. If the relationship between the width G and the maximum width L of the recording paper that can be fixed is C> G> L, the elastic body layer 15 wraps the metal foil 10 and both ends thereof are tightly formed on the elastic body 8. 8. The adhesion and adhesion between the metal foil 10 and the elastic body layer 15 are improved, and the problem that the metal foil 10 peels can be prevented.

  Also, as shown in FIG. 7, a plurality of openings 16 are provided at the end of the metal foil 10 outside the range of the maximum paper width L of the recording paper 2, and the elastic body 8 and the elastic body layer 15 are coupled through the openings 16. It is possible to improve the adhesion and adhesion between the elastic body 8, the metal foil 10, and the elastic body layer 15.

  Further, in order to improve the adhesion and adhesion between the elastic body 8 and the metal foil 10, as shown in FIGS. 8 and 9, a resin inside the metal foil 10 outside the maximum paper width L of the recording paper 2, Or the sleeve member 17 which has the unevenness | corrugation which consists of metals is joined. In this case, the adhesion between the metal foil 10 and the elastic body 8 can be improved without affecting the distortion of the elastic body 8 that forms the nip amount N of the roller pressure contact portion 6 necessary for fixing.

  Further, in this embodiment, the temperature sensor 13 is provided so as to contact the end surface of the heating roller 3 (outside the maximum paper width L of the recording paper). However, as shown in FIG. The temperature sensors 18 and 19 may be provided in contact with the center surface and the end surface of the heating roller 4 that is not.

  FIG. 11 is an explanatory diagram of temperature control of the modification shown in FIG. The horizontal axis represents the heating roller position, and the vertical axis represents the surface temperature of the heating roller. Curves A and B indicate the surface temperatures of the heating rollers 3 and 4 when the recording paper 2 to which the unfixed toner 5 is adhered respectively pass through the roller pressure contact portion 6.

  In the temperature control, the temperature t4 on the surface of the central portion of the heating roller 3 is set as the control temperature and compared with the predetermined temperature t0. When the temperature t4 exceeds the predetermined temperature t0, the energization to the heat source of the heating roller 3 is stopped, When t4 is equal to or lower than the predetermined temperature t0, the heat source of the heating roller 3 is energized.

  Here, when the recording paper 2 to which the unfixed toner 5 is adhered passes through the roller pressure contact portion 6, the surface temperature of the heating rollers 3 and 4 is lower than the set temperature t0 because heat is transferred to the recording paper 2.

  The amount of temperature change at that time is not uniform because the heat conductivities and heat capacities of the heating rollers 3 and 4 are different.

  During the warming up before the start of printing, the surface temperature of the heating rollers 3 and 4 is controlled based on the predetermined temperature t0.

  When printing is started and the recording paper 2 passes through the roller pressure contact portion 6, the temperature gradient Δ of the heating roller 4 is calculated through the temperature sensors 18 and 19.

Δ = t2-t1 (1)
At this time, the temperature t4 of the surface of the central portion of the heating roller 3 is calculated from the temperature t3 of the end surface of the heating roller 3 obtained through the temperature sensor 13 and the temperature gradient Δ by the following equation.

t4 = t3−K × Δ (2)
Here, the coefficient K is a value obtained experimentally. When the calculated surface temperature t4 is equal to or lower than the predetermined temperature t0, the temperature t3 of the end surface of the heating roller 3 detected through the temperature sensor 13 at that time is heated so as to increase by the temperature difference tx = (t0−t4). Energize the heat source of the roller 3.

  Thus, by calculating the temperature t4 of the surface of the central portion of the heating roller 3 and controlling the energization to the heat source of the heating roller 3, it is possible to prevent the occurrence of low temperature offset due to insufficient heat quantity.

  In this embodiment, the coefficient K obtained experimentally is multiplied by the temperature gradient Δ and subtracted from the temperature t3 of the end surface of the heating roller 3 to obtain the control temperature t4. However, the temperature gradient Δ and the temperature t3 are A table for obtaining the control temperature t4 by using as a reference element may be obtained by experiment, and the table may be referred to.

  This temperature control method can be applied not only to a fixing device that heats a metal pipe in contact with a heat source, but also to a type in which a heat source is provided inside a heating roller.

  According to the first embodiment, since the metal foil having a small heat capacity is directly heated by the halogen lamp, the heating roller is quickly heated.

  In addition, since the metal foil with a small heat capacity is directly heated by the halogen lamp, to increase the printing speed, the roller outer diameter of the elastic body having a low thermal conductivity is increased to increase the nip amount of the roller pressure contact portion. The required amount of heat can be supplied without increasing the size, and the apparatus can be downsized.

Second Embodiment FIG. 12 is a partial cross-sectional view of a heating roller according to a second embodiment. The difference from the first embodiment is that when the temperature sensor 13 is installed in the center of the heating roller 3, it is in the vicinity of the metal foil 10 within a radius r that does not affect the distortion that forms the nip of the heating roller 3. The temperature sensor 13 is embedded and installed, and the liquid silicone that becomes the elastic body 8 when solidified is inserted and crosslinked in a roller shape and held.

  When the temperature sensor installed at the center of the heating roller 3 is placed in contact with the surface of the heating roller 3, the foreign matter removing blade 12 out of a small amount of toner that cannot be fixed on the recording paper 2 and adheres to the surface of the heating roller. The toner that has passed through the toner accumulates in the temperature sensor, and the accumulated toner is detached at a certain time and adheres to the recording paper 2 to contaminate the recording paper surface.

  The above-mentioned problems can be solved by installing the temperature sensor embedded in the heating roller.

  Since the operation is the same as that of the first embodiment, the description thereof is omitted.

  According to the second embodiment, since the temperature sensor installed in the center of the heating roller is embedded in the heating roller, a small amount of toner that cannot be fixed on the recording paper and adheres to the surface of the heating roller is Before it grows large enough to adhere to the recording paper and contaminate the recording paper surface, it is removed by the blade.

Third Embodiment FIG. 13 is a sectional view of a fixing device according to a third embodiment. The difference from the first embodiment is that the casings 30 and 31 of the heat sources 11 and 11 that are installed in contact with the surfaces of the heating rollers 3 and 4 are formed of a heat insulating heat reflecting member and Notched portions 32 and 33 are provided, and the recording paper 2 onto which the toner image has been transferred by the image forming apparatus 34 is preheated and then passed through the roller pressing portion 6.

  Since the operation is the same as that of the first embodiment, the description thereof is omitted.

  According to the third embodiment, the heat source housing is shielded by the heat insulating heat reflecting member to block the thermal influence on the device arranged near the fixing device, for example, the image device that forms the toner image to be transferred onto the recording paper. To do.

  Further, since the recording paper before passing through the roller pressure contact portion is preheated from the notch portion provided in the housing, the recording paper can be preheated before entering the roller pressure contact portion, and the efficiency of toner fixing can be improved. .

  In the present embodiment, the heat sources 11 and 11 installed in contact with the surfaces of the heating rollers 3 and 4 are installed on the upstream side of the roller pressing portion 6 with respect to the roller rotation directions E and F. As shown in FIG. 4, the heat source 11 installed in contact with the surface of the heating roller 3 may be installed downstream of the roller pressure contact portion 6 with respect to the roller rotation direction E. In this case, the casing 31 of the heat source 11 installed in contact with the surface of the heating roller 4 is provided with a notch 33 for preheating the recording paper 2 and installed in contact with the surface of the heating roller 3. The housing 30 of the heat source 11 is not provided with a notch.

  By doing so, the thermal influence on the device arranged near the fixing device, for example, the image device for forming the toner image to be transferred onto the recording paper is further reduced.

Fourth Embodiment FIG. 15 is a configuration diagram of a heat source according to a fourth embodiment, in which FIG. 15 (A) shows a side view, and FIG. 15 (B) is a cross-sectional view taken along line AA in FIG. An arrow view is shown. The difference from the first embodiment is that a ceramic heater 40 is provided in place of the halogen lamp as the heat source 11 installed in contact with the surfaces of the heating rollers 3 and 4.

  In the fixing device according to the first embodiment, the heat source 11 uniformly heats the maximum paper width L of the recording paper 2. When the surface temperature of the heating rollers 3 and 4 reaches a predetermined temperature and the toner is fixed on the narrow recording paper, the heat moves to the recording paper 2 at the center of the heating rollers 3 and 4, and the heating rollers 3 and 4. However, the temperature at the end of the heating roller that does not directly contact the recording paper 2 does not drop as much as the central portion.

  When the surface temperature of the heating roller 3 becomes a predetermined temperature or lower, the heat source 11 is automatically energized. When the center of the heating roller 3 reaches a predetermined temperature, the temperature of the end of the heating roller where the heat has not moved so much to the recording paper is too high, and then wider than the previous recording paper 2. When the recording paper 2 reaches the roller pressure contact portion 6, the toner fused by the heating roller 3 that has become too high adheres to the end of the heating roller 3 and winds the recording paper 2 around the heating roller 3. The phenomenon occurs.

  The fixing device according to the fourth embodiment has a structure that prevents such a high temperature offset phenomenon.

  That is, the ceramic heater 40 is provided on a heater substrate 41 made of ceramic, for example, heaters 40 a to 40 e such as tantalum oxide and ruthenium oxide, which are divided into a plurality of pieces in the paper width direction of the recording paper 2. One end of the heaters 40a to 40e is connected to the common line 42, and the other end is connected to the drive lines 43a to 43e. A protective layer 44 having both insulation and wear resistance is provided on the surface of the heaters 40a to 40e. The maximum width of the ceramic heater 40 is equal to the maximum paper width L of the recording paper 2, and the recording paper indicated by a two-dot chain line represents the recording paper 2 having a paper width narrower than the maximum width L of the heat source.

  FIG. 16 is a control block diagram of the fixing device according to the fourth embodiment. The control unit 50 includes a central processing unit 51 (hereinafter referred to as CPU 51), a memory 52, and an I / O port 53. The data storage unit 52a for storing data and the temperature of the heat source 11 are set to a predetermined temperature in the memory 52. A threshold storage unit 52b that stores a threshold to be controlled is provided.

  A recording paper size setting key 54, a driver circuit 55, a temperature sensor 13, and a recording paper sensor 26 are connected to the CPU 51 via an I / O port 53, and a heater 40 is connected to the driver circuit 55.

  Next, the operation will be described with reference to FIG. FIG. 17 is a flowchart showing the operation of the fixing device shown in FIG. When an operator turns on a power switch (not shown), power is supplied to an apparatus, for example, an electrophotographic printer, and at the same time, the CPU is reset to initialize the electrophotographic printer.

  After initialization, in step S1, the CPU 51 checks whether or not the recording paper size is input from the recording paper size setting key 54. If the recording paper size is input, the process branches to step S2.

  In step S2, the CPU 51 energizes the number of heaters corresponding to the recording paper size via the driver circuit 55.

  In step S <b> 3, the CPU 51 detects the surface temperature of the heating roller 3 through the temperature sensor 13 and compares it with the threshold value stored in the memory 52. If the surface temperature of the heating roller 3 reaches the threshold value, the process branches to step S4. If not, the process branches to step S2.

  In step S4, the CPU 51 stops energization of the heat source 11, and in step S5, the recording paper 2 is unwound from a cassette (not shown) and fed to an image forming unit (not shown). The toner image formed by the image forming unit is transferred to the recording paper 2, and the recording paper 2 to which the toner image is transferred is conveyed toward the fixing device 1.

  In step S6, the CPU 51 detects the trailing edge of the recording sheet through the recording sheet sensor 26. If the trailing edge of the recording sheet is detected, the process for one recording sheet is terminated, and if not, the process branches to step S7.

  In step S7, the CPU 51 detects whether or not the surface temperature of the heating roller 3 is equal to or lower than a predetermined temperature through the temperature sensor 13. If the surface temperature of the heating roller 3 is equal to or lower than the predetermined temperature, the process branches to step S8. Branches to step S9.

  In step S8, the CPU 51 energizes the heat source via the driver circuit 55, and branches to step S5.

  In step S9, the CPU 51 stops energization of the heat source 11, and branches to step S5.

  In this embodiment, the size of the recording paper is set by the recording paper size setting key. However, the CPU detects it by a paper width sensor arranged in the traveling path of the recording paper so that the necessary number of heaters are energized. It may be.

  According to the fourth embodiment, since the metal foil having a small heat capacity is directly heated by the ceramic heater, the heating roller starts up quickly.

  In addition, the ceramic heater is divided into a plurality of heaters and can be heated freely. The surface temperature of the heating roller is detected by temperature sensors installed at the center and end, so the surface temperature at both ends of the heating roller is at the center. This prevents an offset phenomenon in which the toner heated to be higher than the area and welded toner adheres to the surface of the heating roller and winds the recording paper around the heating roller.

  In the first to fourth embodiments, both the first and second rollers are heating rollers. However, only the first roller may be a heating roller, and the second roller may be a simple pressure roller without a heat source. Good.

  In addition, the release layer is provided on the first roller and not on the second roller. However, since the residual toner may move from the first roller to the second roller and contaminate the recording paper, It is also preferable to provide the roller.

  Further, although the elastic layer is provided on the first roller and not on the second roller, it is preferably provided on the second roller in order to improve the adhesion between the metal foil and the elastic body.

Fifth Embodiment In the first to fourth embodiments, a roller type fixing device using a pair of heating rollers has been described. However, the fixing device includes a pair of fusers for fixing unfixed toner to recording paper. There is a belt system in which a belt is hung between one fixing roller and a heating roller.

  Each of the pair of fixing rollers, the heating roller, and the fixing belt has an elastic body having high heat resistance, and the recording paper passes through a pressure contact portion formed by the pair of fixing rollers via the fixing belt to record unfixed toner. Fusing to paper.

  Also in the belt-type fixing device, when the printing speed is increased as in the roller-type fixing device, the heat capacity of the fixing belt that heats and fixes the unfixed toner is small. Therefore, as shown in FIG. The heat was lost to the recording paper during the passage of the belt, and the belt temperature was greatly lowered.

  In addition, if a narrow width of recording paper is continuously passed through the fixing device, a belt temperature difference between the inside and outside of the sheet passing width occurs, and if the belt temperature within the sheet passing width is secured at the optimum fixing temperature, the temperature difference increases. However, there is also a problem that the heat alarm temperature has been reached and printing has to be interrupted.

  FIG. 19 is a schematic view of a fixing device according to the fifth embodiment. Each of the pair of fixing rollers 81 and 82, the heating roller 83, and the fixing belt 84 has an elastic body having high heat resistance and a large heat capacity, and the pair of fixing rollers 81 and 82 via the fixing belt 84 has a nip amount. The recording paper 86 passes through the press contact portion 85 that forms N, and the unfixed toner 87 is fused to the recording paper 86.

  The heating roller 83 has a first heat source (for example, a halogen lamp) 88 and a second heat source (for example, a halogen lamp) 89 inside, and is in pressure contact with the fixing belt 84 to pass the temperature sensors 90a to 90c to the recording paper passage range. It is installed inside and outside.

  The first temperature sensor 90a is in contact with the inner surface of the fixing belt 84 outside the sheet passing range, the second temperature sensor 90b is in contact with the center of the inner surface of the fixing belt 84, and the third temperature sensor 90c is in the fixing belt 85. Is in contact with the outside surface of the recording paper.

  FIG. 20 is an explanatory diagram of the heat generation amount of the heat source inside the heating roller shown in FIG. 19, where the vertical axis indicates the heat generation amount, and the horizontal axis indicates the position in the heat source longitudinal direction. The first heat source 88 generates a uniform heat generation amount W1 everywhere regardless of the position in the longitudinal direction, whereas the second heat source 89 has a heat generation amount W2 lower than the heat generation amount W1 in the center portion. A heat value W3 lower than that at the center is generated at the end.

  FIG. 21 is a control block diagram of the fixing device shown in FIG. The control unit 91 includes a central processing unit 92 (hereinafter referred to as a CPU 92), a memory 93, and an I / O port 94. A recording paper size setting key 95, a driver circuit 96, a first temperature sensor 90a, a second temperature sensor 90b, a third temperature sensor 90c, and a recording paper sensor 97 are connected to the CPU 92 via an I / O port 94. The driver circuit 96 is connected with a first heat source 88 and a second heat source 89.

  The memory 93 is provided with a data storage unit 93a for storing data, an energization stop temperature t1 for controlling the temperatures of the first heat source 88 and the second heat source 89 to a predetermined temperature, and a threshold storage unit 93b for storing an energization start temperature t2. It is.

  The data storage unit 93a stores the size of the recording sheet set from the recording sheet size setting key 95, and the threshold storage unit 93b stores the energization stop temperature t1, the energization start temperature t2, the energization stop temperature t1, and the energization. The coefficient K used when calculating the start temperature t2 is stored.

  The CPU 92 calculates the temperature at the center of the outer surface of the fixing belt from the temperature t of the third temperature sensor 90c installed outside the recording paper passage range, and determines the energization stop temperature t1 and the energization start temperature t2.

  The energization stop temperature t1 and the energization start temperature t2 are calculated by obtaining a coefficient K by which the temperature difference Δt between the first temperature sensor 90a and the second temperature sensor 90b is multiplied from the temperature t of the third temperature sensor 90c. , The coefficient K is multiplied by Δt to obtain a temperature difference T inside and outside the recording paper passing area on the outer surface of the fixing belt, and the temperature difference T is subtracted from the temperature t of the third temperature sensor 90c to stop the energization stop temperature t1 and the energization start temperature. t2 is calculated.

  Next, the operation will be described with reference to FIG. FIG. 23 is a flowchart showing the operation of the fixing device shown in FIG. When an operator turns on a power switch (not shown), power is supplied to an apparatus, for example, an electrophotographic printer, and at the same time, the CPU 92 is reset to initialize the electrophotographic printer.

  In step S 1, the CPU 92 energizes the first heat source 88 via the driver circuit 96, and in step S 2, the surface temperature of the center portion of the outer surface of the fixing belt is calculated from the temperature t of the third temperature sensor 90 c and stored in the memory 93. A comparison check is made with the energization stop temperature t1. If the surface temperature of the central portion of the outer surface of the fixing belt 84 has reached the energization stop temperature t1, the process branches to step S3.

  In step S3, the CPU 92 stops energizing the heat source. In step S4, the CPU 92 detects the presence or absence of recording paper through the recording paper sensor 97. If there is recording paper, the process branches to step S6, and if there is no recording paper, the process branches to step S5.

  In step S <b> 5, the CPU 92 calculates the surface temperature at the center of the outer surface of the fixing belt from the temperature t of the third temperature sensor 90 c and compares it with the energization start temperature t <b> 2 stored in the memory 93. If the surface temperature of the central portion of the outer surface of the fixing belt 84 has reached the energization start temperature t2, the process branches to step S1, and if not, the process branches to step S4.

  In step S6, the CPU 92 refers to the data storage section 93a to check whether the recording sheet is a narrow recording sheet. If the recording sheet is a narrow recording sheet, the CPU 92 branches to step S7. Branch to

  In step S <b> 7, the CPU 92 calculates the surface temperature at the center of the outer surface of the fixing belt from the temperature t of the third temperature sensor 90 c and compares it with the energization start temperature t <b> 2 stored in the memory 93. If the surface temperature at the center of the outer surface of the fixing belt 84 has reached the energization start temperature t2, the process branches to step S8.

  In step S <b> 8, the CPU 92 energizes the first heat source 88 and the second heat source 89 via the driver circuit 96.

  In step S <b> 9, the CPU 92 calculates the surface temperature of the center portion of the outer surface of the fixing belt from the temperature t of the third temperature sensor 90 c and compares it with the energization stop temperature t <b> 1 stored in the memory 93. If the surface temperature at the center of the outer surface of the fixing belt 84 has reached the energization stop temperature t1, the process branches to step S4.

  When narrow recording sheets are continuous, Steps S4 to S9 are repeated, and when the surface temperature of the central portion of the outer surface of the fixing belt 84 reaches the energization start temperature t2, the first heat source 88 and the second heat source 88 are processed. Since the heat source 89 is energized, the belt temperature difference within and outside the sheet passing width range is quickly secured at the optimum fixing temperature.

  The recording paper size set from the recording paper size setting key 95 is interrupted when the setting key 95 is pressed and stored in the data storage section 93a. The recording paper is conveyed after the fixing belt reaches the energization stop temperature t1.

  In the present embodiment, the first heat source 88 and the second heat source 89 are provided inside the heating roller 83. However, the first heat source 88 is provided inside the heating roller 83, and the fixing roller 81 or the fixing roller 82 is provided. A second heat source 89 may be provided in the interior. In this case, variations in the belt temperature can be suppressed by compensating for the temperature drop in the central portion of the belt due to the passage of each recording sheet by the fixing roller having a large heat capacity.

  Further, the first heat source 88 may be provided inside the heating roller 83 and the fixing rollers 81 and 82. In this case, the fixing belt 84 is heated by the heat source 88 of the heating roller 83, and the fixing rollers having a large heat capacity are heated by the respective heat sources 88. By compensating for the roller, variations in belt temperature can be suppressed.

  According to the fifth embodiment, the temperature decrease in the center of the belt is obtained from the temperature detected by the temperature sensor installed outside the recording paper passage range, and the fixing belt is attached by a heat source that generates a larger amount of heat in the center than at the end. By heating, even if heat is taken away by the recording paper while passing the recording paper, the belt temperature difference inside and outside the paper passing width range can be reduced, and the belt temperature within the paper passing width range can be reduced. Can be secured at the optimum fixing temperature regardless of the width of the recording paper.

1 is an external perspective view of a fixing device according to a first embodiment. FIG. 2 is an AA cross-sectional arrow view of the fixing device illustrated in FIG. 1. FIG. 2 is a control block diagram of the fixing device shown in FIG. 1. 2 is a flowchart illustrating an operation of the fixing device illustrated in FIG. 1. It is a modification (1) of a heating roller. It is a modification (2) of a heating roller. It is a modification (3) of a heating roller. It is a modification (4) of a heating roller. It is an AA cross-sectional arrow view of FIG. It is a modification of temperature sensor arrangement. It is explanatory drawing of the temperature control of the modification shown in FIG. It is a fragmentary sectional view of the heating roller by a 2nd embodiment. FIG. 9 is a cross-sectional view of a fixing device according to a third embodiment. It is a modification of the fixing device according to the third embodiment. It is a block diagram of the heat source by 4th Embodiment. FIG. 10 is a control block diagram of a fixing device according to a fourth embodiment. 17 is a flowchart illustrating an operation of the fixing device illustrated in FIG. 16. It is explanatory drawing which shows the manufacturing method of a heating roller. It is the schematic of the fixing device by 5th Embodiment. It is explanatory drawing of the emitted-heat amount of the heating roller shown in FIG. FIG. 20 is a control block diagram of the fixing device shown in FIG. 19. It is explanatory drawing of the belt temperature fall by recording paper passage. 20 is a flowchart showing an operation of the fixing device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 3, 4 Heating roller 8 Elastic body 10 Metal foil 15 Elastic body layer 16 Opening part 17 Sleeve part 84 Fixing belt

Claims (3)

The recording paper to which the unfixed toner is attached is passed through the roller pressure contact portion between the first roller and the second roller rotating in opposite directions, whereby the toner is pressed and fused to the recording paper for fixing. Oite to the fixing equipment,
A heat source for heating the first roller;
A first temperature sensor in contact with the roller surface of the first roller while being placed to the maximum width outside of the recording paper,
A second temperature sensor disposed outside the maximum paper width of the recording paper and in contact with a roller surface of the second roller;
A third temperature sensor disposed within the maximum paper width of the recording paper and in contact with the roller surface of the second roller;
Temperature control means for controlling energization to the heat source,
The temperature control means obtains a difference between the detected temperature of the second temperature sensor and the detected temperature of the third temperature sensor, and multiplies the difference by a preset coefficient to obtain the detected temperature of the first temperature sensor. A fixing device that calculates a control target temperature by adding, and controls energization to the heat source based on the control target temperature. The fixing roller is pressed against a fixing belt supported by a plurality of rollers, and the recording paper on which unfixed toner is adhered to one surface is passed through the pressing portion between the fixing belt and the fixing roller, whereby the toner is recorded on the recording paper. In a fixing device for fixing by pressure fusion to
The plurality of rollers include a heating roller that heats the fixing belt and a second fixing roller that presses against the fixing roller,
Inside the heating roller, a first heat source that uniformly heats the fixing belt over the belt width, a second heat source that generates a larger amount of heat at the center than at the end,
A first temperature sensor in contact with the inner surface of the fixing belt that is outside the recording paper passing range;
A second temperature sensor in contact with the center of the inner surface of the fixing belt;
A third temperature sensor in contact with the outer surface of the fixing belt that is outside the recording paper passing range;
A controller for controlling energization of the first and second heat sources,
The control unit obtains a coefficient K by which the temperature difference Δt between the first temperature sensor and the second temperature sensor is multiplied from the output t of the third temperature sensor, and multiplies the coefficient K by Δt to multiply the outer surface of the fixing belt. The temperature difference T within and outside the recording paper passing range is obtained, and the temperature within the recording paper passing range on the outer surface of the fixing belt is calculated by subtracting the temperature difference T from the output t of the third temperature sensor. apparatus.   The fixing device according to claim 2, wherein the second heat source is provided inside the fixing roller instead of the heating roller.

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