JP6528577B2 - Image forming apparatus, control method, and control program - Google Patents

Description

  The present disclosure relates to control of an image forming apparatus, and more particularly to control of a fixing device provided in the image forming apparatus.

  Electrophotographic image forming apparatuses are in widespread use. An electrophotographic image forming apparatus includes a fixing device. The fixing device includes a heating unit (heating rotating body) and a pressure unit (pressure rotating body) pressed against the heating unit. The heating unit has a heating roller, a fixing roller, and a fixing belt. The fixing belt is stretched around the heating roller and the fixing roller. The fixing roller is in pressure contact with the pressure unit via the fixing belt. The pressure unit includes a pressure roller. Heaters are respectively provided inside the heating roller and the pressure roller. The image forming apparatus adjusts the contact pressure between the heating roller and the pressure roller and heats the heater to melt the toner image on the printed matter passing between the heating roller and the pressure roller, thereby toning the toner image. Fix in printed matter.

  Regarding a fixing device, Japanese Patent Application Laid-Open No. 2009-139778 (Patent Document 1) discloses a “fixing device capable of improving productivity by shortening printing time and reducing power consumption of recording materials of large and small sizes”. doing. Japanese Patent Application Laid-Open No. 2011-191508 (Patent Document 2) discloses an image forming apparatus capable of quickly recovering from the standby state while reducing the overshoot amount of the fixing belt temperature. Japanese Patent Laid-Open No. 2011-013309 (Patent Document 3) discloses a fixing device that "stabilizes the fixing performance of an image".

JP, 2009-139778, A JP, 2011-191508, A JP, 2011-013309, A

  In recent fixing devices, it is required to reduce the time required for warm-up to heat the fixing device to a printable temperature and to save power. In order to realize this, a member such as a belt or a thin film is used instead of the heating roller. Thereby, the heat capacity of the fixing device can be reduced, and the heat transfer efficiency to the printed matter is improved. As a result, the time required for warm-up is reduced and power consumption is reduced.

  In addition, cost reduction of the fixing device is desired. In order to realize this, the pressing and separating mechanism for adjusting the contact pressure of the heating roller and the pressing roller may be omitted. Therefore, in a normal use state, the pressure roller is always in pressure contact with the heating roller. Further, in order to reduce the cost, the heater may be omitted from the inside of the pressure roller and may be provided only in the inside of the heating roller. Such a fixing device transmits heat to the fixing belt by rotating the heating roller, and transfers the heat to a contact portion between the fixing belt and the pressure roller (hereinafter, also referred to as a “nip portion”).

  The fixing device is provided with a sensor (for example, a thermistor or the like) for detecting the temperature of the surface of the heating roller, and the power supplied to the heating roller is determined according to the detected temperature. Thermistor must be located near the heat source (e.g., heater, etc.) of the heating roller due to safety issues. As described above, since the heat source is provided at a position distant from the nip portion, when the rotation of the heating roller is stopped, there is a difference between the temperature detected by the thermistor and the temperature of the nip portion It occurs.

  Because of this, the fixing devices disclosed in Patent Documents 1 to 3 can not accurately detect the temperature of the nip portion, and can not accurately control the amount of power supplied to the fixing device. When the amount of power supplied to the fixing device is small, the print quality is degraded. When the amount of power supplied to the fixing device is large, the amount of heat supplied to the printed matter increases, so-called curling that the printed matter deforms in an arc shape occurs, and noise occurs such as the toner image being disturbed and the gloss decreasing. Do. Thus, when the temperature of the nip portion becomes unstable, desired printing accuracy can not be obtained.

  The present disclosure has been made to solve the problems as described above, and an object in one aspect is to provide an image forming apparatus capable of improving the printing accuracy of a fixing device. An object in another aspect is to provide a control method capable of improving the printing accuracy of a fixing device. Another object of the present invention is to provide a control program capable of improving the printing accuracy of a fixing device.

According to an aspect, an image forming apparatus includes a fixing device. The fixing device includes a rotatable heating unit having a heat source, and a rotatable pressing unit pressed against the heating unit, and heating the heat source causes the printed matter to pass between the heating unit and the pressing unit. Fix the toner image. In the image forming apparatus, the number of contact portions between the heating unit and the pressing unit is set based on the rotation time after the rotation of the heating unit is started and the stop time at which the heating unit is stopped before the rotation . A first estimation unit for estimating one temperature and a determination unit for determining the power to be supplied to the heat source according to the estimated first temperature.

  Preferably, the image forming apparatus further includes a first measurement unit for measuring the rotation time. The image forming apparatus stores the measured rotation time as a history.

Preferably, the first measurement unit measures all or part of until completed since the start of rotation of the heating unit as a rotation time.

  Preferably, in the image forming apparatus, when the rotation time reaches a predetermined value, when printing is started, when printing is completed, or when power supply to the image forming apparatus is completed, the rotation time is Remember.

  Preferably, the image forming apparatus stores the stop time of the rotation of the heating unit. The stop time is calculated based on the start time of the rotation and the stored stop time when the rotation of the heating unit is started.

  Preferably, the first estimation unit estimates the first temperature based on predetermined information defining the relationship between the rotation time and the stop time, and the temperature of the contact portion.

  Preferably, the image forming apparatus further includes a second estimation unit for estimating a second temperature of a portion of the heating unit different from the contact portion based on the information on the operation of the image forming apparatus. The determination unit determines the power according to the first temperature and the second temperature.

  Preferably, the information related to the operation of the image forming apparatus includes an operation time indicating a time since the power of the image forming apparatus is turned on.

  Preferably, the image forming apparatus further includes a second measurement unit for measuring the operation time. The image forming apparatus stores the operation time as a history.

  Preferably, the second measurement unit measures, as the operation time, all or part of the time from the start of supply of power to the heating unit to the present time.

  Preferably, the second measurement unit clears the operation time when the temperature of the heating unit is equal to or lower than a predetermined temperature when starting measurement of the operation time.

Preferably, the operation time as the history is equal to or more than the rotation time as the history.
Preferably, when an operation time reaches a predetermined time, printing is started, or when printing is completed, the image forming apparatus operates at any time when power supply to the image forming apparatus is completed. Remember.

  Preferably, the second estimation unit estimates the second temperature based on predetermined information defining the relationship between the operation time and the second temperature when warm-up of the fixing device is started.

  Preferably, the image forming apparatus further includes a sensor for detecting the temperature of the heating unit. The second estimation unit estimates the second temperature from the temperature detected by the sensor.

Preferably, the heat source is provided at a position separated from the contact portion by a predetermined distance or more.
Preferably, no heat source is provided in the vicinity of the contact portion.

  Preferably, the heating unit includes a heating roller having a heat source therein, a fixing roller disposed opposite to the heating roller, and a fixing belt stretched around the heating roller and the fixing roller. The contact portion is an area on the fixing roller between the fixing roller and the pressing unit. The area on the fixing roller heated by the heating roller is an area other than the contact portion.

  Preferably, the temperature of the heating unit is controlled by adjusting the duty ratio of the voltage applied to the heat source or adjusting the power value applied to the heat source.

Preferably, the heating unit and the pressing unit are always in contact with each other.
According to another aspect, a control method of an image forming apparatus is provided. The image forming apparatus includes a fixing device. The fixing device includes a rotatable heating unit having a heat source, and a rotatable pressing unit pressed against the heating unit, and heating the heat source causes the printed matter to pass between the heating unit and the pressing unit. Fix the toner image. The control method is based on the rotation time from the start of the rotation of the heating unit and the stop time information in which the heating unit is stopped before the rotation , the first of the contact portions between the heating unit and the pressing unit Estimating the temperature and determining the power to be supplied to the heat source according to the estimated first temperature.

According to still another aspect, a control program of an image forming apparatus is provided. The image forming apparatus includes a fixing device. The fixing device includes a rotatable heating unit having a heat source, and a rotatable pressing unit pressed against the heating unit, and heating the heat source causes the printed matter to pass between the heating unit and the pressing unit. Fix the toner image. The control program causes the image forming apparatus to set the heating unit and the pressing unit on the basis of a rotation time after the rotation of the heating unit is started and a stop time at which the heating unit has stopped before the rotation . The steps of estimating the first temperature of the contact portion and determining the power to be supplied to the heat source according to the estimated first temperature are performed.

In one aspect, the printing accuracy of the fixing device can be improved.
The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention taken in conjunction with the accompanying drawings.

FIG. 1 shows an example of a device configuration of an image forming apparatus according to an embodiment. FIG. 2 is a plan view of the fixing device. It is sectional drawing along the III-III line in FIG. It is sectional drawing along the IV-IV line in FIG. It is a figure for demonstrating the method to measure the rotation time of a heating part. It is a figure showing the relationship between the rotation time of a heating part, and the temperature of a nip part. It is a figure showing the relationship of the detection temperature of a thermistor, and the correction value of duty ratio. It is a figure showing the relationship of the average detection temperature of the thermistor in the past predetermined time, and the correction value of duty ratio. FIG. 7 is a diagram showing a change in surface temperature of the heating unit when duty control according to the embodiment is performed and a change in surface temperature of the heating unit when duty control according to the embodiment is not performed. FIG. 2 is a block diagram showing an example of a functional configuration of the image forming apparatus according to the embodiment. 6 is a flowchart showing a part of processing executed by the image forming apparatus according to the embodiment. FIG. 1 is a block diagram showing a main hardware configuration of an image forming apparatus according to an embodiment. FIG. 8 is a view showing the configuration of a fixing device according to a modification.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description of these will not be repeated. In addition, each embodiment and each modification which are explained below may be combined suitably suitably.

First Embodiment
[Image forming apparatus 100]
An image forming apparatus 100 according to the embodiment will be described with reference to FIG. FIG. 1 is a view showing an example of the apparatus configuration of the image forming apparatus 100. As shown in FIG.

  FIG. 1 shows an image forming apparatus 100 as a color printer. Although the image forming apparatus 100 as a color printer will be described below, the image forming apparatus 100 is not limited to a color printer. For example, the image forming apparatus 100 may be a monochrome printer, or may be a monochrome printer, a color printer, and a multifunction peripheral of a facsimile (so-called MFP: Multi-Functional Peripheral).

  The image forming apparatus 100 includes image forming units 1A to 1D, an intermediate transfer belt 11, a primary transfer unit 12, a secondary transfer unit 13, a cleaning unit 15, a tray 16, a cassette 17, a control device 18, and And an exposure control unit 19 and a fixing device 20.

  The image forming unit 1A forms a black (BK) toner image. The image forming unit 1B forms a yellow (Y) toner image. The image forming unit 1C forms a toner image of magenta (M). The image forming unit 1D forms a cyan (C) toner image. The intermediate transfer belt 11 rotates in the direction of the arrow 21, and the image forming units 1A to 1D are arranged in order along the rotation direction of the intermediate transfer belt 11, respectively.

  The image forming units 1A to 1D each include a photosensitive member 2, a charging unit 3, a developing unit 4, a cleaning unit 5, and an exposure unit 9.

  The photosensitive member 2 is an image carrier that carries a toner image. As an example, for the photosensitive member 2, a photosensitive drum having a photosensitive layer formed on the surface thereof is used. The photosensitive member 2 rotates along the rotation direction of the intermediate transfer belt 11.

  The charging unit 3 uniformly charges the surface of the photosensitive member 2. The exposure unit 9 applies a laser to the photosensitive member 2 in accordance with the control signal from the exposure control unit 19 and exposes the surface of the photosensitive member 2 in accordance with the designated image pattern. Thereby, an electrostatic latent image corresponding to the input image is formed on the photosensitive member 2.

  The developing unit 4 develops the electrostatic latent image formed on the photosensitive member 2 as a toner image. As an example, the developing unit 4 develops the electrostatic latent image using a developer including toner and carrier.

  The photosensitive member 2 and the intermediate transfer belt 11 are in contact with each other at a portion where the primary transfer portion 12 is provided. A predetermined transfer bias is applied to the contact portion, and the toner image on the photosensitive member 2 is transferred to the intermediate transfer belt 11 by the transfer bias. At this time, a toner image of black (BK), a toner image of yellow (Y), a toner image of magenta (M), and a toner image of cyan (C) are sequentially superimposed and transferred to the intermediate transfer belt 11. Thus, a color toner image is formed on the intermediate transfer belt 11.

  The cleaning unit 5 includes a cleaning blade. The cleaning blade is in pressure contact with the photosensitive member 2 and collects toner remaining on the surface of the photosensitive member 2 after the transfer of the toner image.

  The cassette 17 is provided at the lower part of the image forming apparatus 100. Printed matter 14 such as paper is set in the cassette 17. The printed matter 14 is sent to the secondary transfer unit 13 one by one from the cassette 17. By synchronizing the timing of delivery and conveyance of the printed matter 14 with the position of the toner image on the intermediate transfer belt 11, the toner image is transferred to an appropriate position of the printed matter 14. Thereafter, the printed matter 14 is sent to the fixing device 20.

  The fixing device 20 includes a rotatable heating unit 30 and a pressure roller 32 (pressure unit) pressed against the heating unit 30. The fixing device 20 heats the heating unit 30 to melt the toner on the printed matter 14 passing between the heating unit 30 and the pressure roller 32, and fixes the toner image on the printed matter 14. Thereafter, the printed matter 14 is discharged to the tray 16.

  The cleaning unit 15 includes a cleaning blade. The cleaning blade is in pressure contact with the intermediate transfer belt 11 and collects toner remaining on the intermediate transfer belt 11 after the transfer of the toner image. The toner is transported by a transport screw (not shown) and collected in a waste toner container (not shown).

  The control device 18 controls the image forming apparatus 100. The control device 18 controls, for example, the exposure control unit 19 and the fixing device 20. Regarding control of the fixing device 20, the control device 18 controls a motor (not shown) provided in the heating unit 30 to adjust the rotation speed, rotation time, and the like of the heating unit 30. As a control method of the said motor, PWM (Pulse Width Modulation) control is mentioned, for example.

[Structure of fixing device 20]
The structure of the fixing device 20 shown in FIG. 1 will be described in more detail with reference to FIGS. FIG. 2 is a plan view of the fixing device 20. As shown in FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG.

  As shown in FIGS. 2 to 4, the fixing device 20 includes a heating unit 30, a pressure roller 32, and thermistors 36 </ b> A and 36 </ b> B. The heating unit 30 includes a heating roller 31, a fixing belt 33, and a fixing roller 34. The heating roller 31 has therein a heating long heater 35A and a heating short heater 35B.

  The heating roller 31 is formed of, for example, a cylindrical core metal made of aluminum or the like. The thickness of the cored bar is, for example, 0.6 mm. A resin layer made of PTFE (polytetrafluoroethylene) or the like is formed on the outer peripheral surface of the cored bar. The thickness of PTFE is, for example, 15 μm. The outer diameter of the heating unit 30 is, for example, 25 mm. The length in the longitudinal direction of the heating unit 30 is, for example, 330 mm.

  The pressure roller 32 is disposed to face the heating roller 31. The pressure roller 32 is formed of, for example, a cylindrical core metal made of aluminum or the like. The outer diameter of the pressure roller 32 is, for example, 35 mm. The thickness of the core metal is, for example, 2 mm. A rubber layer and a resin layer made of PFA (perfluoroalkoxyalkane) or the like are formed on the outer peripheral surface of the core metal. The thickness of the rubber layer is, for example, 2 mm. The thickness of PFA is, for example, 30 μm.

  The fixing belt 33 is stretched by the heating roller 31 and the fixing roller 34, and rotates in conjunction with the heating roller 31 and the fixing roller 34. The fixing belt 33 is made of polyimide, a rubber layer, PFA or the like. The outer diameter of fixing belt 33 is, for example, 60 mm. The thickness of the polyimide is, for example, 70 mm. The thickness of the rubber layer is, for example, 200 μm.

  The fixing roller 34 is in pressure contact with the fixing belt 33 of the heating unit 30. Fixing roller 34 is formed of, for example, a cylindrical cored bar made of iron or the like. The outer diameter of the fixing roller 34 is, for example, 30 mm. The outer diameter of the cored bar is, for example, 18 mm. A rubber layer and a sponge layer are formed on the outer peripheral surface of the cored bar. The thickness of the rubber layer is, for example, 4 mm. The thickness of the sponge layer is, for example, 2 mm. An area on the fixing roller 34 between the fixing roller 34 and the pressure roller 32 corresponds to a nip portion.

  The heating long heater 35A is provided inside the heating roller 31. The heating long heater 35A is, for example, a halogen lamp heater. The wattage of the heating long heater 35A is, for example, 999 W. The heating long heater 35A has a heat source 38A inside. The length of the portion generating heat in the heat source 38A is, for example, 290 mm. The amount of heating is changed according to the power supplied to the heat source 38A. A resistance heating element or an induction heating device may be provided instead of the heating long heater 35A.

  The heating short heater 35 B is disposed to face the heating long heater 35 A, and is provided inside the heating roller 31. The heating short heater 35B is, for example, a halogen lamp heater. The wattage of the heating short heater 35B is, for example, 790 W. The heating short heater 35B has a heat source 38B inside. The length of the portion generating heat in the heat source 38B is, for example, 180 mm. The amount of heating can be changed according to the power supplied to the heat source 38B. A resistance heating element or an induction heating device may be provided instead of the heating short heater 35B.

  The heat sources 38A and 38B are provided at positions separated from a contact portion (that is, a nip portion) between the heating unit 30 and the pressure roller 32 by a predetermined distance or more. That is, the heat sources 38A and 38B are not provided in the vicinity of the nip portion. Therefore, the area on the fixing roller 34 heated by the heating roller 31 is only the contact portion with the heating roller 31 on the fixing belt 33. That is, the area on the fixing roller 34 heated by the heating roller 31 is an area other than the nip portion.

  The thermistors 36A and 36B are temperature sensors for detecting the temperature of the fixing belt 33. The thermistors 36A and 36B are disposed to face the fixing belt 33, and are disposed in non-contact with the fixing belt 33. The thermistor 36A is disposed, for example, at a position 70 mm away from the center sheet passing reference of the fixing belt 33 in the longitudinal direction. The thermistor 36 B is disposed, for example, at a position 135 mm apart from the center sheet passing reference of the fixing belt 33 in the longitudinal direction.

[Nip temperature estimation method]
A method of estimating the temperature of the contact portion (that is, the nip portion) between the heating unit 30 and the pressure roller 32 will be described with reference to FIGS. 5 and 6. FIG. 5 is a diagram for explaining a method of measuring the rotation time of the heating unit 30. As shown in FIG. FIG. 6 is a diagram showing the relationship between the rotation time of the heating unit 30 and the temperature of the nip portion.

  As described above, the rotation of the heating unit 30 transfers heat to the nip. On the other hand, if the rotation of the heating unit 30 is stopped, the temperature of the nip does not rise. That is, the temperature of the nip portion changes according to the rotation of the heating unit 30.

  Focusing on this point, the image forming apparatus 100 estimates the temperature (first temperature) of the nip portion based on the information on the rotation operation of the heating unit 30, and the heat source of the heating unit 30 according to the estimated temperature. Determine the power supplied to the Thus, even if the thermistor is provided at a position away from the nip portion, the temperature of the nip portion can be accurately estimated.

  As an example, the information related to the rotation operation includes a rotation time after the rotation of the heating unit 30 is started, and a stop time when the heating unit 30 is stopped before the rotation. The image forming apparatus 100 estimates the temperature of the nip portion according to the rotation time and the stop time of the heating unit 30.

  As shown in the graph (A) of FIG. 5, measurement of the rotation time of the heating unit 30 is started, for example, based on the transition of the image forming apparatus 100 from the non-operation state to the operation state. The “operation state” refers to a state in which the heating roller 31 of the heating unit 30 is rotating in response to a print instruction or the like. The “non-operating state” refers to a state in which the image forming apparatus 100 is operating with less power consumption than the operating state. The inactive state includes, for example, a sleep state in which the image forming apparatus 100 is maintained in the low power state.

  When the measurement of the rotation time is started, the nip portion may be warmed to some extent by the rotation of the heating portion 30 immediately before. Therefore, the image forming apparatus 100 adds the count at the start of measurement of the rotation time according to at least one of the rotation time of the heating unit 30 immediately before and the stop time of the heating unit 30 immediately before. That is, the image forming apparatus 100 determines an initial value of the rotation time according to at least one of the rotation time and the stop time of the heating unit 30 immediately before, and counts the rotation time from the initial value.

  The initial value is, for example, a time during which the heating unit 30 has been rotated from the present to a past predetermined time (hereinafter, also referred to as “past rotation time”). The past rotation time may be calculated by totaling the rotation time in the past predetermined time, or may be calculated by subtracting the total stop time of the heating unit 30 from the past predetermined time.

  The graph (B) of FIG. 5 shows the relationship between the state of the image forming apparatus 100 and the past rotation time. It is assumed that the past rotation time is time t1 when the image forming apparatus 100 shifts from the non-operation state to the operation state. At this time, the image forming apparatus 100 starts measurement of the rotation time with the time t1 as an initial value.

  When the past rotation time is calculated from the stop time, when the rotation of the heating unit 30 is started, the image forming apparatus 100 determines the difference between the start time of the rotation and the stop time immediately before the rotation. Calculated as The stop time is stored as a history when the rotation of the heating unit 30 is stopped. The history is read out when calculating the stop time.

In one aspect, the image forming apparatus 100 measures the whole until the ends from being rotated in the heating section 30 is started. In another aspect, the image forming apparatus 100 measures a part of the period from when the rotation of the heating unit 30 starts to when the rotation ends. For example, the image forming apparatus 100 measures only the time when the rotational speed is equal to or higher than the predetermined speed as the rotational time.

  The image forming apparatus 100 stores the measured rotation time as a history. The history is stored, for example, in a storage device 120 described later at a predetermined timing. As an example, when the rotation time reaches a predetermined value, the printing of the image forming apparatus 100 is started, and when the printing of the image forming apparatus 100 is completed, the power supply to the image forming apparatus 100 is ended. It is one of the times when

  The image forming apparatus 100 estimates the temperature of the nip portion based on predetermined information defining the relationship between the rotation time of the heating unit 30 and the temperature of the nip portion. As an example, the predetermined information is a table, an equation, or the like that defines the relationship between the rotation time and the temperature of the nip portion. Since the rotation time of the heating unit 30 can be calculated even from the stop time of the heating unit 30, the predetermined information indicates the heating unit instead of the relationship between the rotation time of the heating unit 30 and the temperature of the nip unit. The relationship between the stop time of 30 and the temperature of the nip may be defined.

  The graph (A) of FIG. 6 shows the relationship between the rotation time of the heating unit 30 and the temperature of the nip portion. As shown in graph (A), the temperature of the nip increases as the rotation time increases, and the temperature of the nip decreases as the rotation time decreases. Based on this relationship, the image forming apparatus 100 estimates the temperature corresponding to the measured rotation time as the temperature of the nip portion.

  The image forming apparatus 100 determines the power to be supplied to the heating unit 30 according to the estimated temperature of the nip portion. More specifically, if the estimated temperature of the nip portion is higher than the target temperature, the power supplied to the heating unit 30 is reduced. At this time, the larger the difference between the estimated temperature of the nip portion and the target temperature, the larger the reduction range of the supplied power. On the other hand, if the estimated temperature of the nip portion is lower than the target temperature, the power supplied to the heating unit 30 is increased. At this time, the larger the difference between the estimated temperature of the nip portion and the target temperature, the larger the increase in supplied power.

  In one aspect, the image forming apparatus 100 controls the temperature of the heating unit 30 by adjusting the duty ratio of the voltage applied to the heat sources 38A and 38B (see FIG. 4) of the heating unit 30. The duty ratio is a ratio of time during which the heat source is energized for a predetermined time. For example, assuming that the duty ratio is 50% and the on / off cycle of energization to the heat source is 2 seconds, the image forming apparatus 100 alternately repeats one second of energization and one second of non-energization. . In another aspect, the image forming apparatus 100 is controlled by adjusting a constant power value applied to the heat source of the heating unit 30.

  The width of the nip (hereinafter, also referred to as “nip width”) along the rotational direction of the heating unit 30 and the pressure roller 32 changes according to the degree of thermal expansion of the nip, so the nip width is It correlates with the temperature of the nip. Focusing on this point, the image forming apparatus 100 may adjust the power supplied to the heating unit 30 according to the nip width instead of the temperature of the nip portion.

(Modification 1)
The temperature inside the image forming apparatus 100 becomes higher as the time after the power is turned on (hereinafter, also referred to as “operating time”) elapses. Therefore, the temperature of the heating unit 30 is also easily heated as the operation time of the image forming apparatus 100 becomes longer.

  In the present modification, the image forming apparatus 100 further uses the operation time of the image forming apparatus 100 in addition to the rotation time of the heating unit 30 to determine the power supplied to the heating unit 30. More specifically, the image forming apparatus 100 estimates the temperature (degree of warming) of the portion of the heating unit 30 different from the nip portion based on the past operation information, and determines the temperature and the temperature of the nip portion. Based on the power supplied to the heating unit 30 is determined. The operation information includes, for example, a time (i.e., an operation time) since the power of the image forming apparatus 100 is turned on.

  The measurement of the operation time is started based on the power of the image forming apparatus 100 being turned on. The image forming apparatus 100 counts all or part of the operation time during measurement as the operation time. As an example, the image forming apparatus 100 may count the operation time only when the temperature of the heating unit 30 is equal to or higher than a predetermined level.

  The image forming apparatus 100 stores the measured operation time as a history. The history is stored, for example, in a storage device 120 described later at a predetermined timing. As an example, when the operation time reaches a predetermined time, the printing of the image forming apparatus 100 is started, and when the printing of the image forming apparatus 100 is finished, the power supply to the image forming apparatus 100 is ended. It is one of the times when

  The image forming apparatus 100 uses predetermined information defining the relationship between the temperature of the portion of the heating unit 30 different from the nip (hereinafter, also referred to as “the temperature of the heating unit 30”) and the operation time. Based on the above, the temperature of the heating unit 30 is estimated. The predetermined information is, for example, a table, a formula, or the like that defines the relationship between the rotation time and the temperature of the heating unit 30.

  The image forming apparatus 100 determines the power supply to the heating unit 30 according to the estimated temperature of the heating unit 30 and the estimated temperature of the nip unit. As an example, when the estimated temperature of the heating unit 30 is higher than the target temperature, the image forming apparatus 100 reduces the power supplied to the heating unit 30. As the estimated temperature of the heating unit 30 is lower than the target temperature, the image forming apparatus 100 increases the power supplied to the heating unit 30.

  When image forming apparatus 100 is in operation, heating unit 30 is rotating, so the operation time stored as a history is equal to or more than the rotation time of heating unit 30 described above stored as a history. . Therefore, if the rotation time is longer than the operation time for some reason, the image forming apparatus 100 replaces the rotation time with the operation time.

  Although the method of estimating the temperature of the heating unit 30 from the operation time of the image forming apparatus 100 has been described above, the image forming apparatus 100 uses the temperature detected by the thermistors 36A and 36B to determine the temperature of the heating unit 30 You may estimate Alternatively, the image forming apparatus 100 may use the temperature detected by the thermistors 36A and 36B as the estimated temperature of the heating unit 30 as it is.

(Modification 2)
In the second modification, the image forming apparatus 100 estimates the temperature of the nip portion and the temperature of the heating unit 30, and determines the power supplied to the heating unit 30 according to these temperatures. In the present modification, the image forming apparatus 100 determines the power supply to the heating unit 30 using other information in addition to the temperature of the nip and the temperature of the heating unit 30.

  In the present modification, the image forming apparatus 100 determines the duty ratio of the heating unit 30 using the following equation (1).

Duty ratio = (A + B) / C (1)
“A” shown in the equation (1) represents the amount of heat per unit time required to fix the toner on a predetermined number of printing particles. In one aspect, as the size of the printed matter is larger, the image forming apparatus 100 increases the value of “A”. The size of the printed matter is obtained, for example, from setting information at the time of printing. In another aspect, the image forming apparatus 100 increases the value of “A” as the number of printed matter passing the fixing device 20 in a predetermined time increases. The number of sheets may be previously set at the time of design or the like, or may be obtained from setting information at the time of printing. In yet another aspect, as the heat capacity of the toner is larger, the image forming apparatus 100 increases the value of “A”.

  "B" shown in the equation (1) represents the amount of heat consumed in the nip portion. "B" is represented by the following formula (2).

B = D (temperature) × E × F (t _rot + δ _rot ) (2)
“D (temperature)” shown in the equation (2) is a function with the temperature of the heating unit 30 as an input, and represents the amount of heat released from the heating unit 30. As the temperature of the heating unit 30 is higher, “D (temperature)” is higher. That is, as the temperature of the heating unit 30 is higher, the amount of heat released from the heating unit 30 is larger.

  "E" shown in Formula (2) is a constant. “E” is preset, for example, at the time of design.

“F (t _rot + δ _rot )” shown in the equation (2) is a function having a correlation with the estimated temperature of the nip portion, and is a function having “t _rot + δ _rot ” as an input. “T _rot ” represents the time after the rotation of the heating unit 30 is started. “Δ _rot ” represents a past rotation time (see FIG. 5) within a predetermined past time when the rotation of the heating unit 30 is started. The temperature of the nip is estimated from "t _rot " and "δ _rot " by the estimation method described above. As the temperature of the nip portion is higher, “F (t _rot + δ _rot )” is smaller, and as the temperature of the nip portion is lower, “F (t _rot + δ _rot )” is larger. As a result, when the temperature of the nip is high, the duty ratio of the heating unit 30 is lowered, and when the temperature of the nip is low, the duty ratio of the heating unit 30 is increased.

  The value C shown in the equation (1) is a value determined by the power supplied to the heat source of the heating unit 30 and the temperature (the degree of warming) of the heating unit 30. The value C is expressed by the following equation (3).

C = supplied power × G (t + δ) (3)
“G (t + δ)” shown in the equation (3) is a function having a correlation with the temperature of the heating unit 30 (see “Modification 1”), and is a function having “t + δ” as an input. The output value of “G (t + δ)” is determined by “t + δ” representing the operation time of the image forming apparatus 100 regardless of the presence or absence of the rotation of the heating unit 30. “T” represents an operation time after the power of the image forming apparatus 100 is turned on. That is, "t" represents a tone time (for example, from morning 1) after the power is turned on. “Δ” represents an operation time within a predetermined time in the past since the power of the image forming apparatus 100 was turned on.

  The temperature inside the image forming apparatus 100 increases as the operation time increases, so the temperature of the heating unit 30 also increases as the operation time of the image forming apparatus 100 increases. That is, as the operation time becomes longer, the heating unit 30 warms even with less power. Focusing on this point, “G (t + δ)” decreases as “t + δ” increases, and “G (t + δ)” increases as “t + δ” decreases. Thereby, the duty ratio of the heating unit 30 is lowered as the operation time becomes longer.

(Modification 3)
Although the image forming apparatus 100 can stabilize the temperature of the nip portion by determining the duty ratio by the above-described method and controlling the fixing device 20, the power situation of the fixing device 20 or the power situation of the fixing device 20 can not be assumed in advance. Depending on the attributes of the sheet, the temperature of the nip may deviate from the target temperature (set temperature) of the fixing device 20. Therefore, the image forming apparatus 100 corrects the duty ratio when the detected temperature of at least one of the thermistor 36A and the thermistor 36B deviates from the target temperature. Hereinafter, the thermistors 36A and 36B are collectively referred to as the thermistor 36.

  The method of correcting the duty ratio will be described with reference to FIGS. 7 and 8. FIG. 7 is a diagram showing the relationship between the detected temperature of the thermistor 36 and the correction value of the duty ratio. FIG. 8 is a diagram showing the relationship between the average detected temperature of the thermistor 36 and the correction value of the duty ratio within a predetermined time in the past.

The corrected duty ratio is expressed by the following equation (4).
Duty ratio after correction = duty ratio before correction + correction value by detection temperature + correction value by average detection temperature (4)
The “correction value by the detected temperature” shown in the equation (4) is determined based on, for example, the table 41 shown in FIG.

  More specifically, image forming apparatus 100 determines which of the “temperature regions” shown in table 41 the detected temperature belongs to, in accordance with the degree to which the detected temperature of thermistor 36 deviates from the target temperature. .

  For example, when the detected temperature is "target temperature + 10 ° C" or more, the temperature range "0" is selected. When the detected temperature is equal to or higher than “target temperature + 6 ° C.” and lower than “target temperature + 10 ° C.”, the temperature range “1” is selected. If the detected temperature is "target temperature + 2 ° C" or more and less than "target temperature + 6 ° C", the temperature range "2" is selected. When the detected temperature is "target temperature-2 ° C" or more and less than "target temperature + 2 ° C", the temperature range "3" is selected. When the detected temperature is "target temperature-6 ° C" or more and less than "target temperature-2 ° C", the temperature range "4" is selected. When the detected temperature is "target temperature-10 ° C" or more and less than "target temperature-6 ° C", the temperature range "5" is selected. When the detected temperature is less than "target temperature-10 ° C", the temperature range "6" is selected.

  Next, the image forming apparatus 100 determines whether the current detected temperature is rising or falling. As an example, when the image forming apparatus 100 determines that the current detected temperature is lower than the previous detected temperature, the image forming apparatus 100 determines “at the time of temperature decrease”. If not, the image forming apparatus 100 determines that the temperature has risen.

  The image forming apparatus 100 determines the correction value of the duty ratio based on the selected temperature region and the determination result of whether the temperature is decreasing or increasing with reference to the table 41. For example, when the temperature range “0” is selected and the determination result is “temperature drop”, the image forming apparatus 100 reduces the current duty ratio by 15%. When the temperature region “0” is selected and the determination result is “at temperature rise”, the image forming apparatus 100 reduces the current duty ratio by 17.50%.

  The “correction value by the average detected temperature” shown in the equation (4) is determined based on the table 42 shown in FIG. More specifically, the image forming apparatus 100 calculates the average detected temperature in the past predetermined time, and the average detected temperature is shown in the table 42 according to the degree to which the average detected temperature deviates from the target temperature. Determine which of the temperature regions it belongs to.

  For example, when the average detected temperature is "target temperature + 10 ° C" or more, the temperature range "0" is selected. When the average detected temperature is equal to or higher than “target temperature + 6 ° C.” and lower than “target temperature + 10 ° C.”, the temperature range “1” is selected. If the average detected temperature is equal to or higher than “target temperature + 2 ° C.” and lower than “target temperature + 6 ° C.”, the temperature range “2” is selected. When the average detection temperature is "target temperature-2 ° C" or more and less than "target temperature + 2 ° C", the temperature range "3" is selected. When the average detection temperature is "target temperature-6 ° C" or more and less than "target temperature-2 ° C", the temperature range "4" is selected. When the average detection temperature is "target temperature-10 ° C" or more and less than "target temperature-6 ° C", the temperature range "5" is selected. If the average detected temperature is less than "target temperature-10 ° C", the temperature range "6" is selected.

  The image forming apparatus 100 refers to the table 42 and determines the correction value of the duty ratio based on the selected temperature region. For example, when the temperature range “0” is selected, the image forming apparatus 100 reduces the current duty ratio by 5%.

[Comparison result]
The effectiveness of controlling the duty ratio of the heating unit 30 in accordance with the estimated temperature of the nip portion will be described with reference to FIG. FIG. 9 shows a change in surface temperature of heating unit 30 when duty control according to the present embodiment is performed, and a change in surface temperature of heating unit 30 when duty control according to the present embodiment is not performed. FIG.

  The surface temperature of the heating unit 30 shown in the graph (A) stably changes with respect to the target temperature as compared with the graph (B). Thus, the image forming apparatus 100 can stably control the surface temperature of the heating unit by determining the duty ratio of the heating unit 30 in accordance with the estimated temperature of the nip unit. As a result, the image forming apparatus 100 can improve the printing accuracy.

[Functional Configuration of Image Forming Apparatus 100]
The functions of the image forming apparatus 100 will be described with reference to FIG. FIG. 10 is a block diagram showing an example of a functional configuration of the image forming apparatus 100. As shown in FIG.

  As shown in FIG. 10, the image forming apparatus 100 includes a control device 18 and a fixing device 20. Control device 18 includes, as functional components, measurement unit 150, estimation unit 152, measurement unit 154, estimation unit 156, and determination unit 158.

  Measurement unit 150 starts measuring the rotation time of heating unit 30 based on the transition of image forming apparatus 100 from the non-operation state to the operation state. That is, the measurement is started based on the fact that the image forming apparatus 100 receives the print instruction and the rotation of the heating unit 30 is started. For example, measurement unit 150 stops measurement of rotation time based on the transition of image forming apparatus 100 from the non-operation state to the operation state, and stores the measured rotation time in storage device 120 described later.

  The estimation unit 152 estimates the temperature of the nip portion based on the information on the rotational operation of the heating unit 30. The information on the rotation operation includes the rotation time of the heating unit 30, the stop time, the past rotation time, the past stop time, and the like. Since the method of estimating the temperature of the nip portion is as described above, the description will not be repeated. The estimation unit 152 outputs the estimated temperature of the nip portion to the determination unit 158.

  The measurement unit 154 starts measuring the operation time of the image forming apparatus 100 based on the fact that the power of the image forming apparatus 100 is turned on. When the measurement of the operation time is started, the measurement unit 154 clears the operation time when the temperature of the heating unit 30 is equal to or less than the predetermined temperature.

  The estimation unit 156 estimates the temperature of the heating unit 30 (that is, the temperature of the heating unit 30) of a portion different from the nip unit based on the information on the operation of the image forming apparatus 100. The information regarding the operation of the image forming apparatus 100 includes, for example, an operation time measured by the measurement unit 154. Since the method of estimating the temperature of heating unit 30 is as described above, the description will not be repeated.

  The determination unit 158 determines the duty ratio of the voltage applied to the heating unit 30 according to the estimated temperature of the nip unit and the estimated temperature of the heating unit 30. More specifically, the determination unit 158 lowers the duty ratio as the estimated temperature of the nip portion and the estimated temperature of the heating portion 30 are higher than the target temperature, and the estimated temperature of the nip portion and the estimated temperature of the heating portion 30 are targeted The lower the temperature, the higher the duty ratio.

Control Structure of Image Forming Apparatus 100
The control structure of the image forming apparatus 100 will be described with reference to FIG. FIG. 11 is a flowchart showing a part of the process performed by the image forming apparatus 100. The process of FIG. 11 is implemented, for example, by the control device 18 as a CPU (Central Processing Unit) executing a program. In another aspect, part or all of the processing of FIG. 11 may be performed by circuit elements or other hardware.

  In step S10, the control device 18 determines whether the power of the image forming apparatus 100 is turned on. When the control device 18 determines that the power of the image forming apparatus 100 is turned on (YES in step S10), the control device 18 switches the control to step S12. If not (NO in step S10), control device 18 executes the process of step S10 again.

  In step S12, the control device 18 starts measurement of the operation time of the image forming apparatus 100 as the measurement unit 154 (see FIG. 10) described above. At the start of the measurement, when the temperature of the heating unit 30 is equal to or lower than the predetermined temperature, the control device 18 clears the operation time.

  In step S20, control device 18 determines whether image forming apparatus 100 has shifted from the non-operation state to the operation state. As an example, image forming apparatus 100 transitions from the non-operating state to the operating state based on the reception of the print instruction when the non-operating state is received. When control device 18 determines that image forming apparatus 100 has shifted from the non-operation state to the operation state (YES in step S20), control is switched to step S22. If not (NO in step S20), control device 18 executes the process of step S20 again.

  In step S22, the control device 18 starts measurement of the rotation time of the heating unit 30 as the measurement unit 150 (see FIG. 10) described above.

  In step S24, the control device 18 estimates the temperature of the nip portion based on the rotation time of the heating unit 30, as the above-described estimation unit 152 (see FIG. 10). As an example, the control device 18 estimates the temperature of the nip portion based on a table or equation in which the correlation between the rotation time and the temperature of the nip portion is previously defined.

  In step S26, the control device 18 estimates the temperature of the heating unit 30 according to the operation time of the image forming apparatus 100 as the above-described estimation unit 156 (see FIG. 10). As an example, the control device 18 estimates the temperature of the heating unit 30 based on a table or an equation in which the correlation between the operation time and the temperature of the heating unit 30 is defined in advance.

  In step S28, the control device 18 determines the duty ratio of the voltage applied to the heating unit 30 based on the estimated temperature of the nip unit and the estimated temperature of the heating unit 30 as the above-described determination unit 158 (see FIG. 10). Do.

  In step S30, the control device 18 controls the heating unit 30 with the duty ratio determined in step S28.

  In step S40, control device 18 determines whether image forming apparatus 100 has shifted from the operating state to the non-operating state. As an example, the image forming apparatus 100 transitions from the operating state to the non-operating state when the state in which the print instruction is not received continues for a predetermined time or more. When control device 18 determines that image forming apparatus 100 has shifted from the operating state to the non-operating state (YES in step S40), the control shown in FIG. 11 is ended. If not (NO in step S40), control device 18 returns the control to step S24. The duty ratio is periodically updated by repeating the processes of steps S24 to S40.

[Hardware Configuration of Image Forming Apparatus 100]
An example of the hardware configuration of the image forming apparatus 100 will be described with reference to FIG. FIG. 12 is a block diagram showing the main hardware configuration of the image forming apparatus 100. As shown in FIG. As illustrated in FIG. 12, the image forming apparatus 100 includes a read only memory (ROM) 101, a CPU 102, a random access memory (RAM) 103, a network I / F (interface) 104, a scanner 106, and a printer. 107, an operation panel 108, and a storage device 120.

  The ROM 101 stores control programs and the like executed by the image forming apparatus 100. The CPU 102 is the control device 18 described above. The CPU 102 controls the operation of the image forming apparatus 100 by executing various programs such as a control program of the image forming apparatus 100. The RAM 103 functions as a working memory and temporarily stores various data necessary for the execution of the control program.

  An antenna (not shown) or the like is connected to the network I / F 104. The image forming apparatus 100 exchanges data with other communication devices via the antenna. Other communication devices include, for example, mobile communication terminals such as smart phones, servers, and the like. Image forming apparatus 100 may be configured to be able to download control program 122 according to the present embodiment from a server via an antenna.

  The scanner 106 optically reads an original set in the image forming apparatus 100 to generate image data of the original.

  The printer 107 converts, for example, image data read by the scanner 106 or print data transmitted from another communication device into data for printing by an electrophotographic method, and a document etc. based on the converted data. Is an apparatus for printing an image of

  Operation panel 108 is configured as a touch panel, and receives a touch operation on image forming apparatus 100. As an example, the operation panel 108 includes a display panel and a touch sensor provided so as to overlap the display panel. Operation panel 108 receives, for example, a setting operation regarding control program 122, a print instruction, and the like.

  The power supply 109 supplies power to various devices of the image forming apparatus 100 based on pressing of a power button (not shown) of the image forming apparatus 100.

  The storage device 120 is, for example, a storage medium such as a hard disk or an external storage device. Storage device 120 stores, as an example, control program 122 for implementing the process according to the present embodiment.

  The control program 122 according to the present embodiment may not be provided as a single program but may be provided by being incorporated into a part of an arbitrary program. In this case, the process according to the present embodiment is realized in cooperation with an arbitrary program. Even a program that does not include such a part of modules does not deviate from the spirit of the program according to the present embodiment. Furthermore, some or all of the functions provided by the control program 122 according to the present embodiment may be realized by dedicated hardware. Furthermore, the image forming apparatus 100 may be configured as a so-called cloud service in which at least one server implements the process according to the present embodiment.

[Operation of fixing device 20]
The operation of the fixing device 20 at the time of printing will be described with reference to FIGS. 2 to 4 again.

  Assuming that the detected temperature of the thermistor 36A is T1, the correction coefficient for temperature adjustment is A, and the corrected temperature for temperature adjustment is TA1, the following equation (5) is satisfied. The temperature after correction TA1 is adjusted by turning on and off the heat sources 38A and 38B. The post-correction temperature TA1 corresponds to the “detected temperature” shown in the table 41 (see FIG. 7) and the table 42 (see FIG. 8).

TA1 = A × T1 (5)
The operation of bringing the surface of the fixing belt 33 and the pressure roller 32 to a printable temperature after the power of the image forming apparatus 100 is turned on is called warm-up, and the time taken for warm-up is called warm-up time. Warm-up is performed, for example, when the power is turned on again, when the jam handling is restored, when the cover is closed, when returning from the sleep mode, or the like.

  At the time of warm-up, the fixing device 20 drives the heating unit 30 to raise the temperature of the heating unit 30 to a printable temperature (that is, a target temperature). The target temperature is, for example, 155 ° C. The fixing device 20 receives the corrected temperature TA1 and controls the heating long heater 35A and the heating short heater 35B.

  The image forming apparatus 100 rotates the pressure roller 32 by transmitting the driving force to a driving gear (not shown), and rotates the heating unit 30, the fixing belt 33, and the fixing roller 34. Thus, the heat of the heating unit 30 is transferred to the surfaces of the fixing belt 33 and the pressure roller 32. The linear velocity of the fixing device 20 at this time (the speed at which the printed material passes the fixing device 20) is, for example, 135 mm / s. By the heating by the heating unit 30 and the rotation of the heating unit 30, the surfaces of the fixing belt 33 and the pressure roller 32 rise to the printable temperature.

  When the temperature T1 detected by the thermistor 36A is multiplied by the correction coefficient A and the corrected temperature TA1 becomes a printable temperature, the fixing device 20 outputs a signal (ready) indicating that the printing is possible to the image forming apparatus 100. . The signal is output based on, for example, that the corrected temperature TA1 has reached 135.degree. The image forming apparatus 100 is in a standby state when the print signal is not received, and starts printing when the print signal is received. The target temperature in the standby state is, for example, 155 ° C. to 150 ° C. The target temperature is controlled by turning on and off the heating long heater 35A and the heating short heater 35B.

  When printing a plain paper in full color, the linear velocity of the fixing device is, for example, 135 mm / s. The target temperature at this time is, for example, 155 ° C. to 170 ° C. With the corrected temperature TA1 as an input, the on / off of the heating long heater 35A or the heating short heater 35B is controlled.

  More specifically, the image forming apparatus 100 determines that the temperature of the end portion of the fixing belt 33 is high if the value obtained by subtracting the after-correction temperature TB1 for heat source selection from the detection temperature T2 by the thermistor 36B is equal to or greater than a predetermined value. The heating short heater 35B located at the end is determined as the target of on / off control. If the value obtained by subtracting the after-correction temperature TB1 for heat source selection from the detected temperature T2 by the thermistor 36B is less than a predetermined value, the image forming apparatus 100 sets the heating long heater 35A as a target of on / off control.

  The temperature control of the fixing device 20 will be further described by taking a printing process of B4 size paper as an example.

  Before the paper passes through the fixing device 20, the temperature of the thermistor 36B at the end is not high. Therefore, the image forming apparatus 100 controls the heating long heater 35A, and receives the corrected temperature TA1 as an input. Turn 35A on and off. For example, if the length of the heating long heater 35A is 290 mm and the width of the B4 paper is 257 mm, the heating width becomes wider than the sheet passing width, so the sheet passing area and the non-sheet passing area in the heating range An area is generated. In this case, since the heat is not absorbed by the sheet in the non-sheet-passing region, the temperature of the non-sheet-passing region gradually increases with each passing of the paper as compared with the temperature of the sheet-passing region.

  Thermistor 36B is arranged, for example, at a position 135 mm apart from the central sheet passing reference of fixing belt 33 in the longitudinal direction, and the end of the sheet passing area is 128.5 mm from the central sheet passing reference in the same direction. Do. The image forming apparatus 100 determines that the temperature of the end of the fixing belt 33 is high if the value obtained by subtracting the after-correction temperature TB1 from the detected temperature T2 by the thermistor 36B is equal to or higher than a predetermined value. The heater 35A is switched to the heating short heater 35B.

Modification of Fixing Device 20
A modification of the configuration of the fixing device 20 will be described with reference to FIG. FIG. 13 is a view showing the configuration of a fixing device 20 according to a modification.

  In this modification, in the fixing device 20, the thermistors 40A and 40B are provided instead of the thermistors 36A and 36B (see FIG. 3). The thermistors 40A and 40B are provided between the heating roller 31 and the fixing roller 34, and are provided in contact with the surface of the fixing roller 34.

  Further, in the fixing device 20 according to the present modification, a heater 47 is provided in addition to the heating long heater 35A and the heating short heater 35B. The heater 47 is provided inside the pressure roller 32.

[Summary]
As described above, the image forming apparatus 100 estimates the temperature of the nip portion based on the operation information of the heating portion 30 such as rotation time and stop time, and the heat source of the heating portion 30 according to the estimated temperature of the nip portion. Determine the power supplied to the As a result, since the image forming apparatus 100 can stably control the temperature of the nip portion, print quality can be improved.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

  1A to 1D image forming unit, 2 photoconductor, 3 charging unit, 4 developing unit, 5, 15 cleaning unit, 9 exposure unit, 11 intermediate transfer belt, 12 primary transfer unit, 13 secondary transfer unit, 14 printed matter, 16 tray 17 cassettes 18 control devices 19 exposure control units 20 fixing devices 21 arrows 30 heating units 31 heating rollers 32 pressure rollers 33 fixing belts 34 fixing rollers 35A long heating heater 35B short heating heater , 36A, 36B, 40A, 40B Thermistor, 38A, 38B Heat source, 41, 42 table, 47 heater, 100 image forming apparatus, 101 ROM, 102 CPU, 103 RAM, 104 network I / F, 106 scanner, 107 printer, 108 Operation panel, 109 power, 120 memory Location, 122 control program, 150, 154 measurement section, 152, 156 estimation unit, 158 determination unit.

Claims (22)

An image forming apparatus,
Equipped with a fixing device,
The fixing device is
A rotatable heating unit having a heat source;
And a rotatable pressure unit pressed against the heating unit;
By heating the heat source, a toner image is fixed to the printed matter passing between the heating unit and the pressing unit,
The first of the contact portion between the heating unit and the pressing unit is based on the rotation time from the start of the rotation of the heating unit and the stop time at which the heating unit is stopped before the rotation . A first estimator for estimating the temperature;
An image forming apparatus, comprising: a determination unit configured to determine power to be supplied to the heat source according to the estimated first temperature. The image forming apparatus further includes a first measurement unit for measuring the rotation time,
The image forming apparatus according to claim 1 , wherein the image forming apparatus stores the measured rotation time as a history. The first measurement unit measures all or part of until the completion of the started rotation of the heating portion as the rotation time, the image forming apparatus according to claim 2. In the image forming apparatus, when the rotation time reaches a predetermined value, when printing is started, when printing is finished, or when the power supply to the image forming apparatus is finished, the rotation time is storage to the image forming apparatus according to claim 2 or 3. The image forming apparatus stores stop time of rotation of the heating unit,
The stop time, when the rotation of the heating unit is started, and the start time of the rotation, the stored is calculated based on the stop time, to any one of claims 1 to 4, Image forming apparatus as described. The first estimation unit estimates the first temperature based on the rotation time and the and stop time, predetermined information that defines the relationship between the temperature of the contact portion, the first to fifth aspects The image forming apparatus according to any one of the above. The image forming apparatus further includes a second estimation unit for estimating a second temperature of a portion of the heating unit different from the contact portion based on information on the operation of the image forming apparatus.
The determination unit determines the power according to the first temperature and the second temperature, the image forming apparatus according to any one of claims 1 to 6. The image forming apparatus according to claim 7 , wherein the information related to the operation of the image forming apparatus includes an operation time representing a time since the power of the image forming apparatus is turned on. The image forming apparatus further includes a second measurement unit for measuring the operation time,
The image forming apparatus according to claim 8 , wherein the image forming apparatus stores the operation time as a history. The image forming apparatus according to claim 9 , wherein the second measurement unit measures, as the operation time, all or part of the time from the start of supply of power to the heating unit to the present time. The second measurement unit, when starting the measurement of the operating time, when the temperature of the heating unit is a predetermined temperature or lower, clearing the operation time, the image forming apparatus according to claim 9 or 10 . The image forming apparatus according to any one of claims 9 to 11 , wherein the operation time as a history is equal to or longer than the rotation time as a history. The image forming apparatus may perform the operation time any of when the printing is started when the operation time reaches a predetermined time, when the printing is completed, or when the power supply to the image forming apparatus is finished. The image forming apparatus according to any one of claims 9 to 12 , which stores the image. The second estimation unit estimates the second temperature based on predetermined information defining the relationship between the operation time and the second temperature when warm-up of the fixing device is started. The image forming apparatus according to any one of claims 9 to 13 . The image forming apparatus further includes a sensor for detecting the temperature of the heating unit.
The image forming apparatus according to any one of claims 7 to 14 , wherein the second estimation unit estimates the second temperature from the temperature detected by the sensor. Said heat source, said has a contact portion provided at a predetermined distance or more away, the image forming apparatus according to any one of claims 1 to 15. The image forming apparatus according to any one of claims 1 to 16 , wherein the heat source is not provided in the vicinity of the contact portion. The heating unit is
A heating roller having the heat source inside;
A fixing roller disposed opposite to the heating roller;
A fixing belt stretched around the heating roller and the fixing roller;
The contact portion is an area on the fixing roller between the fixing roller and the pressing unit,
Area on the fixing roller that is heated by the heating roller, said a region other than the contact portion, an image forming apparatus according to any one of claims 1 to 17. The temperature of the heating section, by adjusting the duty ratio of the voltage applied to the heat source, or may be controlled by adjusting the power value applied to the heat source, any one of claims 1 to 18 The image forming apparatus according to claim 1. The image forming apparatus according to any one of claims 1 to 19 , wherein the heating unit and the pressing unit are always in contact with each other. A control method of the image forming apparatus,
The image forming apparatus includes a fixing device.
The fixing device is
A rotatable heating unit having a heat source;
And a rotatable pressure unit pressed against the heating unit;
By heating the heat source, a toner image is fixed to the printed matter passing between the heating unit and the pressing unit,
The control method is
The first of the contact portion between the heating unit and the pressing unit is based on the rotation time from the start of the rotation of the heating unit and the stop time at which the heating unit is stopped before the rotation . Estimating the temperature,
Determining the power to be supplied to the heat source according to the estimated first temperature. A control program of the image forming apparatus,
The image forming apparatus includes a fixing device.
The fixing device is
A rotatable heating unit having a heat source;
And a rotatable pressure unit pressed against the heating unit;
By heating the heat source, a toner image is fixed to the printed matter passing between the heating unit and the pressing unit,
The control program causes the image forming apparatus to
The first of the contact portion between the heating unit and the pressing unit is based on the rotation time from the start of the rotation of the heating unit and the stop time at which the heating unit is stopped before the rotation . Estimating the temperature,
Determining the power to be supplied to the heat source according to the estimated first temperature.