JP2006030623A - Heating device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating device and an image forming apparatus which stably control temperature of a film sliding surface of a heating element irrespective of a state of temperature control until an image forming operation is started and with which an image failure such as hot offset is not generated. <P>SOLUTION: In the heating device which has the heating element, a temperature detection element which detects temperature of the heating element, a film which slides and transfers to the heating element and a pressurizing body which is pressurized to the heating element via the film and forms a nip, conveys a recording material carrying an unfixed toner image to the nip, heats and fixes the toner image to the recording material by the nip, control temperature to control the heating element is determined according to time from power application (or stop of temperature control at the time of standby) of the heating device to start of the image forming operation of the heating device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heating device for heating a recording material, and more particularly to a heating device for melting and fixing a toner image to a recording material in an electrophotographic apparatus used in a copying machine or a printer. The present invention relates to a film heating type fixing device in which a recording material is closely attached.

  Conventionally, for example, as a recording material heating device in an electrophotographic image forming apparatus, a heating roller maintained at a predetermined temperature, and a pressure roller having an elastic layer and being in pressure contact with the heating roller, A hot roller heating system in which the toner image on the recording material is nipped and conveyed and heated by the two rollers is often used.

  And a heater that is a fixedly supported heating body, a heat-resistant film that is conveyed while being pressed against the heater, and a pressure member that causes the recording material to closely contact the heater via the film. A film heating and fixing apparatus having a system configuration in which an unfixed image formed and supported on a recording material surface is heated and fixed on the recording material surface by applying the heat to the recording material through a film has been put into practical use. In this film heat fixing apparatus, a low heat capacity heater can be used as a heater. Therefore, it is possible to reduce power consumption and shorten the wait time (quick start) as compared with the conventional heat roller heating method.

  FIG. 22 is a schematic sectional view of the film heating apparatus. Reference numeral 2 denotes an endless heat-resistant film which is externally fitted to a heating body support 1 (heater stay) which is a film guide member including a heating body. The inner peripheral length of the film 2 and the outer peripheral length of the heating body support 1 including the heating body are made larger by, for example, about 3 mm in the film, so that the film 2 has a larger peripheral length than the heating body support 1. Hold it loosely. The film 2 is a heat-resistant film having a film thickness of 100 μm or less in order to reduce the heat capacity and improve the quick start property. Reference numeral 3 denotes a heating body, in which an electric resistance material is applied to the surface of the substrate with a thickness of about 10 μm and a width of 1 to 3 mm, and a protective layer is coated thereon. Reference numeral 4 denotes a pressure roller as a pressure member that drives and rotates the film 2 between the heating body 3 and pressurizes the recording material to the heater through the film, and includes a core metal 4a and a heat-resistant rubber layer 4b. Then, it is driven and rotated by means (not shown) from the end of the cored bar 4a. In the temperature control in this apparatus, the output of the temperature detecting element 5 arranged on the heater 3 is A / D converted, taken into the CPU, and the electric power supplied to the heating body is controlled based on the information.

  FIG. 8 shows an example of temperature control in the conventional heating apparatus from when the apparatus is turned on until the image forming operation is performed. The solid line in the figure indicates the control temperature of the heating element.

  If the device is not operated for a long time, the heating device is at about room temperature. The output of the detected temperature of the temperature detecting element at that time indicates the room temperature. When the apparatus is turned on at the time point a in the figure, energization of the heating element is started, the temperature is controlled at a constant temperature so that the temperature detected by the temperature detection element becomes the standby temperature control Ts, and the apparatus enters a standby state. .

  When the apparatus receives an image formation start signal at time point b, the pressure roller rotates to start energization of the heating body and raise the temperature of the heating body to the print temperature Tp. The heating body is heated so as to maintain a print temperature Tp which is a heating temperature necessary for permanently fixing the unfixed toner image on the recording material before the leading end of the recording material carrying the unfixed toner image enters the nip. The body is temperature controlled.

  After the trailing edge of the recording material passes through the heating device at the time point c in the figure, the control temperature of the heating body is changed to the standby temperature, and the temperature of the heating body is lowered and adjusted to a constant temperature.

  FIG. 15 shows an example of temperature control in the conventional heating apparatus from standby temperature control Ts until the apparatus starts the image forming operation after receiving the standby temperature control stop signal.

  When the standby state temperature controlled by the standby temperature control Ts receives a standby temperature control stop signal at the time point d in the drawing, the energization of the heating body is stopped and the temperature of the heating body is lowered.

  When the apparatus receives a print start signal while the energization of the heating element is stopped at the time point b in the figure, the pressure roller rotates, the energization of the heating element is started, and the temperature of the heating element is increased to the print temperature Tp. Raise. The heating body is heated so as to maintain a print temperature Tp which is a heating temperature necessary for permanently fixing the unfixed toner image on the recording material before the leading end of the recording material carrying the unfixed toner image enters the nip. The body is temperature controlled.

  After the trailing edge of the recording material passes through the heating device at the time point c in the figure, the control temperature of the heating body is changed to the standby temperature Ts, and the temperature of the heating body is lowered and adjusted to a constant temperature.

FIG. 7 shows a table for determining the print temperature in the conventional heating apparatus. This method is a control method in which the temperature detection element detects the temperature of the heating body immediately before the start of the image forming operation, and determines the control temperature (printing temperature Tp) of the heating body based on the detected temperature (for example, Patent Documents). 1).
JP-A-8-36326

  However, in the conventional heating device, the temperature on the film sliding surface side of the heating body and the side opposite to the film sliding surface of the heating body are brought into contact with each other depending on the temperature control state performed until the image forming operation is started. There was a difference in the detected temperature of the temperature sensing element.

  For this reason, if the control temperature of the heating element is determined only by the temperature of the temperature detection element, an image problem may occur due to an excessive or insufficient amount of heat applied from the heating element to the recording material.

  For example, when the image forming operation is started after turning on the power supply of the heating device and leaving the temperature control during standby for a long time, the heating body is heated by the temperature control during standby, so that the heating shown in FIG. The temperature of point a in the film sliding surface side (A surface) of the body and the temperature of point b in the contact surface (B surface) of the temperature detecting element that is in contact with the opposite side of the heating body film sliding surface Are approximately the same temperature.

  However, if the image forming operation is started immediately after the heating device is turned on, the heating body starts heating from the low temperature of the installation environment of the device. The temperature of point a in the film sliding surface side (A surface) of the body and the temperature of point b in the contact surface (B surface) of the temperature detecting element that is in contact with the opposite side of the heating body film sliding surface There arises a problem that the temperature on the film sliding surface side of the heating body becomes higher than the print temperature Tp controlled by the temperature detection element. As a result, image defects such as hot offset may occur due to an excessive amount of heat applied from the heating body to the recording material.

  Therefore, the present invention has been made to solve the above-described problems of the prior art, and stably controls the temperature of the sliding surface of the heating body regardless of the temperature control state until the image forming operation is started. An object of the present invention is to provide a heating device and an image forming apparatus in which image defects such as hot offset and fixing failure do not occur.

  In order to solve the above problems, a first invention related to the present application includes a heating body, a temperature detection element that detects the temperature of the heating body, a film that slides on the heating body, a heating body via the film, In a heating device having a pressure member that forms a nip by pressure contact, transports a recording material carrying an unfixed toner image to the nip, and heat-fixes the toner image on the recording material at the nip. The control temperature for controlling the heating element is determined according to the time from when the heater is turned on until the image forming operation of the heating device is started.

  The second invention related to the present application is the first invention related to the present application. In the first invention related to the present application, when the time from when the power of the heating device is turned on until the image forming operation of the heating device is started is less than a certain time, The control temperature for controlling the heating element is lowered.

  A third invention relating to the present application includes a heating body, a temperature detection element that detects the temperature of the heating body, a film that slides on the heating body, and a pressure contact with the heating body through the film to form a nip. A heating and fixing device that transports a recording material carrying an unfixed toner image to a nip and heat-fixes the toner image on the recording material at the nip, and is heated while the heating device is on standby In a heating apparatus capable of controlling the body at a constant temperature and stopping the temperature control by stopping energization of the heating body that is on standby until the heating apparatus performs an image forming operation after the temperature control is stopped on standby The control temperature for controlling the heating body is determined in accordance with the time.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the heating element is controlled when the time from when the temperature control during standby is stopped until the heating device operates is less than a certain time. The temperature to perform is reduced.

  According to a fifth aspect of the present application, a heating body, a temperature detection element that detects the temperature of the heating body, a film that slides on the heating body, and a pressure contact with the heating body through the film form a nip. In a heating device having a heating body and transporting a recording material carrying an unfixed toner image to a nip and heating and fixing the toner image on the recording material in the nip, the image of the heating device is turned on after the heating device is turned on The control temperature for controlling the heating element is determined according to the time until the forming operation is started and the number of conveyed recording materials.

  The sixth invention related to the present application is the fifth invention related to the present application, in the case where the time from when the power of the heating device is turned on until the image forming operation of the heating device is started is less than a certain time, The control temperature for controlling the heating element is lowered.

  A seventh invention relating to the present application is characterized by including the heating device according to any one of claims 1 to 6 and performing image formation on a recording material.

  According to the invention, the time from when the heating device is turned on until the image forming operation of the heating device is started, and after the temperature control is stopped while the heating device is waiting, the image formation of the heating device is performed. The temperature of the back surface of the heating element according to the temperature state of the heating element substrate is changed by changing the control temperature of the temperature sensing element arranged on the film and non-sliding surface side of the heating element according to the time until the operation is started. Regardless of the temperature difference between the detection element contact portion and the film sliding surface of the heating element, the temperature can be controlled to the optimum temperature of the film sliding surface of the heating element.

  Therefore, it is possible to provide a heating apparatus and an image forming apparatus in which image defects such as fixing failure due to abnormal temperature drop of the heating body and hot offset due to abnormal temperature rise do not occur.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

(First embodiment)
FIG. 2 is a cross-sectional view showing a schematic configuration of a film-type heating apparatus as an embodiment of the present invention.

  In FIG. 2, reference numeral 1 denotes a horizontally long heater stay that is a heat-resistant resin as a heating material support, and serves as a guide member on the inner surface of the following endless film 2 (hereinafter referred to as film).

  Reference numeral 2 denotes a heat-resistant endless film which is externally fitted to the heater stay 1 including the heater 3 which is a heating body. The inner peripheral length of the film 2 and the outer peripheral length of the heater stay 1 including the heater 3 are about 3 mm larger than that of the film, so that the film 2 has a sufficient peripheral length with respect to the stay 1 including the heater 3. It fits loosely.

  The heater 3 as a heating body is screen-printed with an electric resistance material (heating element) such as Ag / Pd (silver palladium) in a thickness of 10 μm and a width of about 1 to 5 mm along substantially the center of the substrate made of alumina or the like. Etc., and coated with glass or fluororesin as a protective layer.

  A pressure body 4 is a pressure roller as a rotating body that drives the film 2 by forming a fixing nip N with the film 2 sandwiched between the heater 3 and a pressure roller core made of aluminum, iron, or the like. The motor M is composed of a gold 4a and a pressure roller elastic body 4b using heat-resistant rubber having good releasability such as silicone rubber which is externally mounted on the shaft, and the end of the pressure roller core 4a is a driving means. Is driven to rotate in the direction of the arrow. When the pressure roller 4 is rotated, the film 2 is also rotated in the direction of the arrow.

  When the film 2 is not driven, the remaining part of the film 2 except for the part sandwiched by the nip N between the heater 3 and the pressure roller 4 is substantially tension free.

  When the pressure roller 4 is rotationally driven, the film 2 is rotationally driven at the nip portion N while the film back surface slides on the surface of the heating body 3 at a speed substantially equal to the rotational peripheral speed of the pressure roller 4.

  In a state where the film drive and the heater 3 are energized, the recording material P carrying the unfixed image T is positioned upward between the film 2 and the pressure roller 4 in the nip portion N. When introduced, the recording material P passes through the nip portion N together with the film 2, and the heat energy of the heater 3 in contact with the back surface of the film in the nip portion N is applied to the recording material P through the film 2. As a result, the toner image T is thermally fixed.

  Here, in order to reduce the heat capacity and improve the quick start property, the film 2 preferably has a total thickness of 100 μm or less, and is a base layer such as polyimide, PEEK, PES, or PPS having heat resistance, strength, and durability. A composite layer film is used in which a conductive layer also serving as a primer is coated on the outer peripheral surface, and a release layer such as substantially insulating PTFE, PFA, FEP and the like having excellent release properties is further coated thereon.

  The temperature control is performed by A / D converting the output of the thermistor 5 as a temperature detection element provided on the opposite side (rear surface) of the resistance heating element 3a on the heating element 3, taking it into the CPU, and triac based on the information The AC voltage supplied to the resistance heating element 3a of the heating element 3 is controlled by controlling the electric power supplied to the heating element 3 by phase and wave number control.

  A schematic diagram of temperature control of the heating device is shown in FIG. Ts is a standby temperature controlled in a standby state when the apparatus is turned on, and Tp is a printing temperature controlled when the recording material is inserted into the heating apparatus. The horizontal axis represents time and the vertical axis represents temperature.

  The operation of FIG. 3 will be described. When the power is turned on at the time point “a” in the heating device in the room temperature state, energization control is performed so that energization of the heating body is started and the standby temperature Ts is reached. When a print signal is input to the heating device that has been in a standby state while being maintained at the standby temperature Ts and an image forming operation is started at a time point b, the print temperature Tp is set to match the recording material being conveyed to the heating device. The energization control is performed, and the recording material is conveyed to the heating device and fixed by heating. When the recording material passes through the heating device at time point c and the heat fixing is completed, the control temperature is changed to the standby temperature Ts again, and the heating device enters a standby state.

  FIG. 1 is a table for determining the print temperature Ts of the heating body in this embodiment. As shown in FIG. 1, it is determined according to the thermistor detection temperature at the start of the image forming operation and the time from when the power is turned on until the print signal is input and the image forming operation is started.

  Hereinafter, the temperature control of this embodiment will be described in detail with reference to FIGS. 3, 4, and 5.

  FIG. 6 is an enlarged configuration of the heater, where the B surface is the thermistor placement surface, the point b is the contact portion of the heater and the thermistor, the surface A is the film sliding surface side, and the point a is the thermistor placement of the film sliding surface. Position.

  3 to 5, the solid line indicates the control temperature controlled by the thermistor, and the broken line indicates the temperature at point a on the film sliding surface side (A surface in FIG. 6) opposite to the thermistor arrangement side of the heater.

  For example, as shown in FIG. 3, when the thermistor detection temperature at the start of the image forming operation is less than 100 ° C., the apparatus waits for 60 seconds or more in a standby state (between time a and time b) until the image forming operation is started after the power is turned on. In the state, the print temperature Ts of the first sheet at the start of the image forming operation is controlled at 200 ° C. The temperature at point a of the heater indicated by the broken line at that time is 200 ° C.

  As shown in FIG. 4, the thermistor detection temperature at the start of the image forming operation is less than 100 ° C., and the standby state (between time a and time b) until the image forming operation is started after the power is turned on is 30 seconds or more and less than 60 seconds. In the standby state, the temperature is controlled at 195 ° C. The temperature at point a of the heater indicated by the broken line at that time is 200 ° C.

  Further, as shown in FIG. 5, when the thermistor detection temperature at the start of the image forming operation is less than 100 ° C., the apparatus waits for less than 30 seconds in the standby state (between time a and time b) until the power is turned on and the image forming operation is started. In this state, the print temperature Ts of the first sheet at the start of printing is controlled at 190 ° C. The temperature at point a of the heater indicated by the broken line at that time is 200 ° C.

  As described above, in the heating device of the present embodiment, the temperature at the point a on the film sliding surface of the heater is controlled to a constant temperature regardless of the standby time until the image forming operation is started after the power is turned on. can do.

  As a comparative example, the temperature control of the conventional example will be described in detail with reference to FIG. 7, FIG. 8, and FIG.

  FIG. 7 is a table for determining the print temperature Ts of the heating element in the conventional example. The determination of the print temperature Ts of the heating element is determined according to the thermistor detection temperature at the start of the image forming operation as shown in FIG. .

  In the conventional example, when the thermistor detection temperature at the start of the image forming operation is less than 100 ° C., the print temperature Ts is the time in the standby state (between time a and time b) until the image forming operation is started after the power is turned on. Regardless, it is controlled at 200 ° C.

  For example, as shown in FIG. 8, when the thermistor detection temperature at the start of operation is less than 100 ° C., and in a standby state (between time a and time b) until the power is turned on and image formation is started, the standby state is 60 seconds or longer. The print temperature Ts of the first sheet at the start of image formation is controlled at 200 ° C. The temperature at point a of the heater indicated by the broken line at that time is 200 ° C.

  In addition, as shown in FIG. 9, the thermistor detection temperature at the start of operation is less than 100 ° C., and the standby state (between time a and time b) is waited for less than 30 seconds until the power is turned on and the image forming operation is started. In this case, the print temperature Ts of the first sheet at the start of image formation is controlled at 200 ° C. as in FIG. The temperature at point a of the heater indicated by the broken line at that time is 210 ° C.

  As described above, in the control of the conventional apparatus, the point a on the film sliding surface of the heater is determined depending on the time in the standby state (between point a and point b) until the image forming operation is started after the power is turned on. There was a difference in temperature.

  In the heating device of this example and the heating device of the conventional example, when the thermistor detection temperature at the start of operation is less than 100 ° C., the temperature of the film sliding surface of the heater is controlled to 200 ° C. The toner can be fixed satisfactorily.

  In this embodiment, the temperature of the film sliding surface of the heater can be controlled to 200 ° C. regardless of the standby time until the image forming operation is started after the power is turned on, and a recording material with a good image can be obtained. Can be fixed.

  In the example as a comparative example, the temperature of the film sliding surface of the heater can be controlled to 200 ° C. in a state where the time from when the power is turned on to when image formation is started waits for 60 seconds or more. A good image can be fixed on the recording material. However, if the time from when the power is turned on to when the image forming operation is started is as short as less than 30 seconds, the temperature of the film sliding surface of the heater becomes 210 ° C. An abnormal image such as an offset may occur.

(Second embodiment)
The configuration of the heat fixing apparatus is the same as that of the apparatus of the first embodiment shown in FIG. 2, and the same elements as those of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the present embodiment, when the previous image forming operation is completed and the print signal is not input to the apparatus for a certain time while the heating body is controlled at the standby temperature Ts, the energization to the heating body is stopped and the standby temperature is set. It has a function to stop control. In this embodiment, the standby stop time can be set to no stop, 15 minutes, 30 minutes, and 60 minutes. For example, when set to 30 minutes, 30 minutes after the previous image forming operation ends. When the image forming operation is not started, the standby temperature control is stopped.

  The operation of FIG. 11 showing the outline of the temperature control of this embodiment will be described. As shown in FIG. 11, in the heating apparatus controlled to the standby temperature Ts, when the apparatus receives a standby stop signal at time d, the energization of the heating body controlled to the standby temperature Ts is stopped. When an image forming operation is started at time b, the energization control is performed so that the printing temperature Tp is reached as the recording material is conveyed to the heating device when the image forming operation is started at time b. Then, the recording material is conveyed to the heating body and fixed by heating. When the image forming operation is completed at time point c, the control temperature is changed again to the standby temperature Ts, and the heating device enters a standby state.

  The print temperature Ts of the heating body in this embodiment is determined according to the thermistor detection temperature at the start of the image forming operation and the time from the stop of the standby temperature control to the start of the image forming operation as shown in FIG. Is done.

  Hereinafter, the temperature control of this embodiment will be described in detail with reference to FIGS. 11, 12, and 13.

  The solid line in FIGS. 11 to 13 indicates the temperature controlled by the thermistor, and the broken line indicates the temperature at point a on the film sliding surface side (A surface in FIG. 6) opposite to the thermistor arrangement side of the heater as the heating element.

  For example, as shown in FIG. 11, the thermistor detection temperature at the start of the image operation is less than 100 ° C., and the state (between the time point d and the time point b) until the standby temperature control is stopped and the image forming operation is started is less than 5 minutes. The printing temperature Ts of the first sheet at the start of printing is controlled at 200 ° C. The temperature at point a of the heater indicated by the broken line at that time is 200 ° C.

  In addition, as shown in FIG. 12, the thermistor detection temperature at the start of the image forming operation is less than 100 ° C., and the state (between time d and time b) until the standby temperature control is stopped and the image forming operation is started is 5 minutes or more. If it is less than 15 minutes, the printing temperature Ts for the first sheet at the start of image formation is controlled at 195 ° C. The temperature at point a of the heater indicated by the broken line at that time is 200 ° C.

  As shown in FIG. 13, when the thermistor detection temperature at the start of the image forming operation is less than 100 ° C., the state (between time d and time b) until the standby temperature control is stopped and the image forming operation is started is 15 minutes or more. Is controlled at 190 ° C. The temperature at point a of the heater indicated by the broken line at that time is 200 ° C.

  As a comparative example, the temperature control of the conventional example will be described in detail with reference to FIGS. 7, 14, and 15.

  FIG. 7 is a diagram showing the determination of the print temperature Tp of the conventional heating body. The determination of the print temperature Ts of the heating body is determined according to the thermistor detection temperature at the start of the image forming operation as shown in FIG. .

  For example, as shown in FIG. 14, the thermistor detection temperature at the start of the image forming operation is less than 100 ° C., and the state (between time d and time b) until the standby temperature control is stopped and the print signal is input is less than 5 minutes. The printing temperature Ts of the first sheet at the start of printing is controlled at 200 ° C. The temperature at point a of the heater indicated by the broken line at that time is 200 ° C.

  Further, as shown in FIG. 15, the thermistor detection temperature at the start of the image forming operation is less than 100 ° C., and the state (between time d and time b) until the standby temperature control is stopped and the print signal is input is 15 minutes or more. In this case, the printing temperature Ts of the first sheet at the start of printing is controlled at 200 ° C. as in FIG. The temperature at point a of the heater indicated by the broken line at that time is 210 ° C.

  As described above, in the control of the conventional apparatus, the temperature at the point a on the film sliding surface of the heater is changed according to the time (between time d and time b) until the standby temperature control is stopped and the image forming operation is started. A difference has occurred.

  In this embodiment, the time from when standby temperature control is stopped until the image forming operation is started (regardless of the time point d to the time point b, the temperature at the point a on the film sliding surface of the heater is controlled to a constant temperature. be able to.

  In the heating device of this example and the heating device of the conventional example, when the thermistor detection temperature at the start of operation is less than 100 ° C., the temperature of the film sliding surface of the heater is controlled to 200 ° C. The toner can be fixed satisfactorily.

  In this embodiment, the temperature of the film sliding surface of the heater can be controlled to 200 ° C. regardless of the time from when the standby temperature control is stopped and the image forming operation is started. It can be fixed.

  In the example as a comparative example, when the standby temperature control is stopped and the time until the image forming operation is started is less than 5 minutes, the temperature of the film sliding surface of the heater can be controlled to 200 ° C., A good image can be fixed on the recording material. However, if the standby temperature control is stopped and the time until the image forming operation is started is 15 minutes or longer, the temperature of the film sliding surface of the heater becomes 210 ° C., so that the amount of heat applied to the recording material becomes excessive. An image such as a hot offset may occur.

(Third embodiment)
The configuration of the heat fixing apparatus is the same as that of the apparatus of the first embodiment shown in FIG. 2, and the same elements as those of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In this embodiment, the print temperature Ts of the heating body is determined according to the thermistor detection temperature at the start of the image forming operation, the time from when the power is turned on until the image forming operation is started, and the number of sheets to be passed. It is determined.

  Hereinafter, the temperature control of the present embodiment will be described in detail with reference to FIGS. 17 and 18. The solid line in FIGS. 17 to 19 indicates the temperature controlled by the thermistor, and the broken line indicates the temperature at point a on the film sliding surface side (surface A in FIG. 6) opposite to the thermistor arrangement side of the heater as the heating element.

  For example, as shown in FIG. 17, when the thermistor detection temperature at the start of the image forming operation is less than 100 ° C. and the power is turned on and the image forming operation is started, it waits for less than 30 seconds. The third printing temperature Ts is controlled at 190 ° C., the fourth through sixth sheets are 195 ° C., and the fourth through sixth sheets are controlled at 190 ° C. The temperature at the point a of the heater at that time is maintained at about 200 ° C.

  Further, as shown in FIG. 18, when the thermistor detection temperature at the start of the image operation is less than 100 ° C. and in a standby state until the image forming operation is started after the power is turned on, the standby state is 30 seconds or more and less than 60 seconds. The printing temperature Ts of the first to third sheets is controlled at 195 ° C., and the fourth to tenth sheets are controlled at 200 ° C. The temperature at the point a of the heater indicated by the broken line at that time is maintained at about 200 ° C.

  As a comparative example, the temperature control of the conventional example will be described in detail with reference to FIGS.

  FIG. 19 is a diagram showing the determination of the print temperature Tp of the conventional heating body. The determination of the print temperature Ts of the heating body depends on the thermistor detection temperature at the start of the image forming operation and the number of sheets passed as shown in FIG. Determined.

  For example, as shown in FIG. 20, when the thermistor detection temperature at the start of the image forming operation is less than 100 ° C. and the apparatus is in a standby state until the image forming operation is started after the power is turned on, the first sheet The printing temperature Ts for the tenth sheet is controlled at 200 ° C. At that time, the temperature at the point a of the heater indicated by the broken line is 210 ° C. for the first sheet, which is higher than the control by the thermistor.

  As described above, in the control of the conventional apparatus, from the first sheet to the tenth sheet depending on the time in the standby state (between the time point a and the time point b) until the image forming operation is started after the power is turned on. There was a difference in the temperature at point a on the heater.

  In this embodiment, the film sliding surfaces of the first to tenth sheets of the heater regardless of the time of the standby state (between time a and time b) until the image forming operation is started after the power is turned on. The temperature at point a can be controlled to a constant temperature.

  In the heating device of this embodiment and the heating device of the conventional example, when the thermistor detection temperature at the start of operation is less than 100 ° C. and the number of sheets to be passed is from 1 to 10, the temperature of the film sliding surface of the heater By controlling the temperature at 200 ° C., the toner can be satisfactorily fixed on the recording material.

  In the present embodiment, the temperature of the film sliding surface of the heater is set when the number of sheets to be passed is from the first to the tenth regardless of the standby state time from when the power is turned on until the image forming operation is started. The temperature can be controlled to approximately 200 ° C., and a good image can be fixed on the recording material.

  In the conventional example as a comparative example, the temperature of the film sliding surface of the heater is 210 ° C. when the time of the standby state from when the power is turned on until the image forming operation is started is within 20 seconds. Since the amount of heat applied to the liquid becomes excessive, an image such as hot offset may be generated.

(Fourth embodiment)
FIG. 21 is a schematic diagram showing the configuration of the image forming apparatus of the present invention to which the heating apparatus described in the above-described embodiment is applied. In the figure, reference numeral 11 denotes a photosensitive drum having a diameter of, for example, 30 mm as an image carrier, and is rotated at a predetermined speed in the direction of arrow R1 by a drive source (not shown).

  Around the photosensitive drum 11, for example, a charging roller 12 having a diameter of 12 mm as a charging member that uniformly charges the surface of the photosensitive drum to a predetermined potential in order along the rotation direction, and image information on the photosensitive drum 11. In accordance with the exposure means 13 for forming an electrostatic latent image, developing means 14 for forming a toner image by attaching toner to the electrostatic latent image, and transfer for transferring the toner image on the photosensitive drum 11 to a recording material. For example, a transfer roller 15 having a diameter of 12 mm as a member and an image forming means such as a cleaner 16 for removing and collecting the residual toner adhering to the surface of the photosensitive drum 11 after transferring the toner image are arranged. Reference numeral 17 denotes a fixing device to which the heating device described in any of the first to third embodiments is applied.

  Next, the operation at the time of image formation by the image forming apparatus configured as described above will be described. The photosensitive drum 11 is rotationally driven at a predetermined speed in the arrow R1 direction. A voltage obtained by superimposing a DC voltage on an AC voltage is applied to the charging roller 12, and the surface of the photosensitive drum 11 is charged to a uniform potential of −600V.

  The charged photosensitive drum 11 receives an exposure La of image information by the exposure means 13 to form an electrostatic latent image. Next, a toner image is formed on the electrostatic latent image by the developing means 14.

  The transfer 15 transfers the toner image formed on the photosensitive drum 11 onto the recording material P and conveys it to the heating device 17 of the present invention to fix the toner image on the recording material P.

  On the other hand, the toner adhering to the surface of the photosensitive drum 11 after the transfer is cleaned and removed by the cleaner 16, and the next image forming operation is performed again.

Table for determining print temperature in Example 1 of the present invention The schematic block diagram of the heating apparatus in the Example of this invention The figure showing the temperature control in Example 1 of this invention The figure showing the temperature control in Example 1 of this invention The figure showing the temperature control in Example 1 of this invention Enlarged configuration diagram of a heater in an embodiment of the present invention Table for determining print temperature in conventional examples Diagram showing temperature control in conventional example Diagram showing temperature control in conventional example Table for determining print temperature in Example 2 of the present invention The figure showing the temperature control in Example 2 of this invention The figure showing the temperature control in Example 2 of this invention The figure showing the temperature control in Example 2 of this invention Diagram showing temperature control in conventional example Diagram showing temperature control in conventional example Table for determining print temperature in Example 3 of the present invention The figure showing the temperature control in Example 3 of this invention The figure showing the temperature control in Example 3 of this invention Table for determining print temperature in conventional examples Diagram showing temperature control in conventional example Schematic configuration diagram of an image forming apparatus in Embodiment 4 Schematic configuration diagram of heating device in conventional example

Explanation of symbols

3 Heating body (heater)
3a Heating element 5 Temperature sensing element (thermistor)
Tp Print temperature Ts Standby temperature

Claims (7)

A heating body, a temperature detection element that detects the temperature of the heating body, a film that slides on the heating body, and a pressure body that presses the heating body through the film to form a nip,
In a heating device that transports a recording material carrying an unfixed toner image to a nip and heat-fixes the toner image on the recording material at the nip.
A heating apparatus that determines a control temperature for controlling a heating body according to a time from when a power supply of the heating apparatus is turned on to when an image forming operation of the heating apparatus is started.   The control temperature for controlling the heating body is lowered when the time from when the power of the heating device is turned on to when the image forming operation of the heating device is started is less than a certain time. Heating device. A heating body, a temperature detection element that detects the temperature of the heating body, a film that slides on the heating body, and a pressure body that presses the heating body through the film to form a nip,
A heating and fixing device that conveys a recording material carrying an unfixed toner image to a nip and heat-fixes the toner image on the recording material at the nip;
While controlling the heating body at a constant temperature while the heating device is on standby, in the heating device that can stop the temperature control by stopping energization to the standby heating body,
A heating apparatus that determines a control temperature for controlling a heating body in accordance with a time from when temperature control is stopped during standby until the heating apparatus performs an image forming operation.   4. The heating device according to claim 3, wherein when the time from when the temperature control during standby is stopped to when the heating device operates is less than a certain time, the temperature for controlling the heating element is lowered. A heating body, a temperature detection element that detects the temperature of the heating body, a film that slides on the heating body, and a heating body that presses the heating body through the film to form a nip,
In a heating device that transports a recording material carrying an unfixed toner image to a nip and heat-fixes the toner image on the recording material at the nip.
Heating characterized in that the control temperature for controlling the heating element is determined according to the time from when the power of the heating device is turned on until the image forming operation of the heating device is started and the number of conveyed recording materials apparatus.   6. The control temperature for controlling the heating element is lowered when the time from when the power of the heating device is turned on until the image forming operation of the heating device is started is less than a certain time. Heating device.   An image forming apparatus comprising the heating device according to claim 1, wherein image formation is performed on a recording material.

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