JP6866766B2 - Fixing device, image forming device and fixing operation control method - Google Patents

Description

The present invention relates to a fixing device, an image forming device, and a fixing operation control method.

Conventionally, there is an image forming apparatus that performs an operation of heating and fixing the toner after adhering a coloring material such as toner on a recording medium such as paper. As such heating, a method that is indirectly performed by heating a roller, a belt, or the like that comes into contact with the recording medium with a heater is widely used. By appropriately controlling the on / off of the heater based on the temperature measurement result of the heating surface, the recording medium and toner are kept within the appropriate temperature range, and fixing failure occurs due to insufficient temperature, and even when the recording medium is discharged due to overheating. It is possible to prevent the occurrence of tacking in which the recording media stacked on top of each other stick to each other without completing the fixing of the toner.

However, when the image forming apparatus corresponds to the sizes of a plurality of recording media, if the heating surface becomes longer in the width direction perpendicular to the transport direction of the recording medium, a temperature difference is likely to occur in the width direction, resulting in uneven fixing. There is a problem that the occurrence of tacking and the like is not effectively suppressed. On the other hand, in Patent Document 1, a plurality of heaters are provided so as to heat different ranges in the width direction, and the heating range and each heater are provided according to the detection temperature of the plurality of temperature sensors and the size of the recording medium to be heated. A technique for controlling the on / off of heating of the above is disclosed.

Japanese Unexamined Patent Publication No. 2005-62331

However, in the conventional heating configuration that causes the temperature distribution in the width direction, the temperature is not always properly controlled at a position deviating from the measurement position of the temperature sensor, and the coloring material on the recording medium is uniformly applied in the width direction. There is a problem that it may be difficult to fix.

An object of the present invention is to provide a fixing device, an image forming device, and a fixing operation control method capable of easily and more appropriately fixing a color material on a recording medium without increasing the configuration related to temperature control.

In order to achieve the above object, the invention according to claim 1 is
A fixing operation unit that fixes the color material on the recording medium by a heating operation over a predetermined fixing width,
A temperature measuring unit that measures the temperature related to the heating operation by the fixing operation unit, and
A control unit that controls the operation of the fixing operation unit,
With
The fixing operation unit includes a first heat source unit that generates heat in a first heating range within a predetermined range from both end positions of the fixing width in the width direction along the fixing width direction, and a part of the first heating unit. It has a second heat source unit that generates heat in a second heating range that overlaps at least a part of the range, and has a heat source unit that generates heat in different heating ranges.
The temperature measuring unit includes a first temperature measuring unit that measures the temperature at a predetermined first measuring position within the first heating range, and both ends of the temperature measuring unit that are within the second heating range and are more than the first measuring position. It has a second temperature measuring unit that measures the temperature at a position close to the center of the position.
The control unit controls the heat generation operation of the first heat source unit based on the measured temperature by the first temperature measuring unit and the first heating set temperature, and the measured temperature and the second heating set temperature by the second temperature measuring unit. When the heat generation operation of the second heat source unit is controlled based on the above and the temperature related to the heating operation is lowered, the lowering of the first heating set temperature is started after the lowering of the second heating set temperature is started. It is a fixing device characterized by being allowed to operate.

Further, the invention according to claim 2 is the fixing device according to claim 1.
The control unit is characterized in that when the temperature related to the heating operation is lowered, the first heating set temperature and the second heating set temperature are each lowered in a plurality of steps.

Further, the invention according to claim 3 is the fixing device according to claim 1 or 2.
The control unit is characterized in that the heat generation operation is controlled by changing the duty ratio of the heat generation time for at least one of the first heat source unit and the second heat source unit.

Further, the invention according to claim 4 is the fixing device according to claim 3.
The control unit controls the heat generation operation of the second heat source unit at the duty ratio set by PI control based on the second heating set temperature and the measurement temperature measured by the second temperature measurement unit. When lowering the temperature related to the heating operation, after lowering the second heating set temperature, the duty ratio of the second heat source unit becomes equal to or less than a predetermined reference value, and then the first heating set temperature is set. It is characterized by lowering.

The invention according to claim 5 is the fixing device according to any one of claims 1 to 4.
When the control unit continuously fixes the coloring material to a plurality of recording media, the temperature measured by the second temperature measuring unit is within a predetermined range from the second heating set temperature. It is characterized in that the decrease of the second heating set temperature is started after the rate of change becomes equal to or less than a predetermined reference value, and the decrease of the first heating set temperature is started after the start.

The invention according to claim 6 is the fixing device according to any one of claims 1 to 5.
The heat source unit includes a third heat source unit that generates heat in a third heating range complementary to the first heating range in the width direction.
The control unit is characterized in that the third heat source unit generates heat with priority over the second heat source unit based on the measured temperature of the second temperature measurement unit.

The invention according to claim 7 is the fixing device according to any one of claims 1 to 6.
The first measurement position is characterized in that the first heating range and the second heating range are defined at overlapping positions.

The invention according to claim 8 is the fixing device according to any one of claims 1 to 7.
The second heat source unit is characterized in that heat is generated with the entire fixing width as the second heating range.

Further, the invention according to claim 9 is the fixing device according to claim 8.
The calorific value per unit length of the second heat source unit in the width direction is the smallest of the calorific values per unit length of the heat source unit.

The invention according to claim 10 is the fixing device according to any one of claims 1 to 9.
Equipped with a detector that acquires a predetermined index value related to the surrounding environment
The control unit is characterized in that the temperature related to the heating operation is changed based on the predetermined index value.

The invention according to claim 11 is the fixing device according to any one of claims 1 to 10.
The control unit determines the speed at which the color material is fixed, the area ratio of the color material on the recording medium to the recording medium, the presence or absence of a predetermined post-processing operation after the color material is fixed, and the color material on both sides of each recording medium. It is characterized in that the temperature related to the heating operation is changed based on at least one of whether or not fixing is performed.

Further, the invention according to claim 12
A forming motion unit that forms an image by adhering a coloring material on a recording medium,
The fixing device according to any one of claims 1 to 11.
It is an image forming apparatus characterized by being provided with.

Further, the invention according to claim 13 is
The fixing operation unit includes a fixing operation unit that fixes the color material on the recording medium by a heating operation over a predetermined fixing width, and a temperature measuring unit that measures the temperature related to the heating operation by the fixing operation unit. In the width direction along the direction of the fixing width, a first heat source portion that generates heat in a first heating range within a predetermined range from both end positions of the fixing width, and a part thereof is at least a part of the first heating range. A second heat source unit that generates heat in an overlapping second heating range and a heat source unit that generates heat in different heating ranges are included, and the temperature measuring unit is a predetermined first measuring position within the first heating range. A first temperature measuring unit that measures the temperature in the above, and a second temperature measuring unit that measures the temperature at a position within the second heating range that is closer to the center of the both end positions than the first measuring position. It is a fixing operation control method of the fixing device to have.
A first heat generation control step that controls the heat generation operation of the first heat source unit based on the temperature measured by the first temperature measuring unit and the first heating set temperature.
A second heat generation control step that controls the heat generation operation of the second heat source unit based on the temperature measured by the second temperature measurement unit and the second heating set temperature.
When the temperature related to the heating operation is lowered, the set temperature control step of starting the lowering of the first heating set temperature after starting the lowering of the second heating set temperature.
It is characterized by including.

According to the present invention, there is an effect that the color material on the recording medium can be easily and more appropriately fixed in the fixing device without increasing the configuration related to temperature control.

It is a schematic block diagram of the Embodiment of the image forming apparatus which has the fixing apparatus of this invention. It is a block diagram which shows the functional structure of an image forming apparatus. It is a schematic diagram which shows the structure of the image fixing part and the temperature measuring part. It is a figure explaining the heating range of the fixing heater inside the fixing roller, and the temperature measurement position by a temperature measuring part. It is a schematic diagram which shows the temperature distribution about the extending direction of a fixing roller. It is a figure explaining the temperature setting, the temperature measurement value, and the operation setting of a fixing heater in an image forming apparatus. It is a flowchart which shows the control procedure of the set temperature control process which is executed in an image forming apparatus. It is a figure which shows the flowchart which shows the control procedure of the tacking adjustment processing. It is a figure which shows the modification of the image fixing part. It is a figure which shows the modification of the structure which concerns on fixing in an image forming apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 which is an embodiment of an image forming apparatus having the fixing apparatus of the present invention.

The image forming apparatus 1 includes an image forming unit 16 (forming operation unit), an image fixing unit 17 (fixing operation unit), a temperature measuring unit 18, a conveying unit 19, an image reading unit 21, and an operation receiving unit 22. , Display unit 23 and the like.

The image forming unit 16 forms an image on a recording medium (paper) based on the image data of the image forming target. The image forming unit 16 includes four sets of exposure units 161, photoconductors 162, and developing units 163 corresponding to the color components of C (cyan), M (magenta), Y (yellow), and K (black), respectively. .. Further, the image forming unit 16 has a transfer body 164 and a secondary transfer roller 165. The image forming unit 16 is not particularly limited, but can form an image in a range of up to 297 mm in, for example, A4 length or A3 width, that is, a width direction perpendicular to the transport direction of the recording medium.

The exposure unit 161 includes a laser diode (LD). The exposure unit 161 makes the LD emit light based on the image data, irradiates the surface of the charged photoconductor 162 with a laser beam, exposes the surface, and forms an electrostatic latent image on the photoconductor 162.
The developing unit 163 supplies toners (coloring materials) of each color of C, M, Y, and K to the exposed photoconductor 162 by a developing roller, respectively, to generate an electrostatic latent image formed on the photoconductor 162. develop.

Images (monochromatic images) developed with C, M, Y, and K toners (coloring materials) on the four photoconductors 162 are sequentially transferred from each photoconductor 162 onto the transfer body 164. As a result, a color image in which the C, M, Y, and K color toners are superimposed on the transfer body 164 is formed. The transfer body 164 has an endless belt wound around a plurality of transfer body transfer rollers, and the endless belt rotates according to the rotation of each transfer body transfer roller.

The secondary transfer roller 165 transfers the color image on the transfer body 164 to the supplied recording medium. Here, by applying a predetermined transfer voltage to the secondary transfer roller 165 with the color image recording medium and the transfer body 164 sandwiched between them, the toner on the transfer body 164 is attracted to the recording medium for recording. Transferred to the medium and adhered.

The image fixing unit 17 heats and pressurizes the recording medium on which the toner is transferred to perform a fixing process for fixing the toner on the recording medium.
The temperature measuring unit 18 measures the heating temperature (temperature) related to the fixing (heating operation) of the image fixing unit 17, and outputs the measurement result to the control unit 11. The detailed configuration and operation of the image fixing unit 17 and the temperature measuring unit 18 (see FIG. 2) will be described in detail later.

The transport unit 19 includes a plurality of paper transport rollers, and transports the recording medium along a predetermined transport path according to the rotation operation. At least a part of the paper transport rollers is arranged in pairs so as to hold the recording medium, and the recording medium is moved by rotating in opposite directions while holding the recording medium. The recording medium is supplied from a selection of the plurality of supply trays 195 and is guided to the secondary transfer roller 165 by the paper transport roller.

The transport unit 19 includes a reversing mechanism 191 that reverses the front and back of the recording medium that has been fixed by the image fixing unit 17 and retransmits it to the secondary transfer roller 165. In the image forming apparatus 1, when an image is formed on both sides of the recording medium, the front and back sides of the recording medium are inverted by the reversing mechanism 191 and the recording medium is discharged to the discharge tray 196 after the images are formed on both sides. .. When the image is formed on only one side of the recording medium, the recording medium on which the image is formed on one side is discharged to the discharge tray 196 without the front and back sides of the recording medium being reversed by the reversing mechanism 191.

The image reading unit 21 is a scanner that reads an image on a reading medium and generates and outputs image data including monochromatic image data for each color component of R (red), G (green), and B (blue).

The operation reception unit 22 includes input devices such as a touch panel arranged so as to be superimposed on the operation keys and the screen of the display unit 23, and converts the input operations for these input devices into operation signals to control the control unit 11 (see FIG. 2). ).

The display unit 23 includes a display screen such as an LCD (Liquid crystal display), and displays the status of the image forming apparatus 1 and an operation screen related to an input operation on the touch panel.

FIG. 2 is a block diagram showing a functional configuration of the image forming apparatus 1.
In addition to the above-mentioned image reading unit 21, operation receiving unit 22, display unit 23, image forming unit 16, image fixing unit 17, temperature measuring unit 18, and conveying unit 19, the image forming apparatus 1 includes a control unit 11 and a storage unit. A unit 12, an image processing unit 13, a communication unit 24, an environment detection unit 25 (detection unit), and the like are provided.

The control unit 11 has a storage unit 12, an image processing unit 13, an image forming unit 16, an image fixing unit 17, a temperature measuring unit 18, a transport unit 19, an image reading unit 21, an operation receiving unit 22, and a display unit via a bus 30. It is connected to the 23 and the communication unit 24, and controls the overall operation of the image forming apparatus 1 in an integrated manner. For example, the control unit 11 causes the image processing unit 13 to perform predetermined image processing on the acquired image data, and stores the processed image data in the storage unit 12. Further, the control unit 11 causes the image forming unit 16 to form an image on the recording medium based on the image data stored in the storage unit 12 while conveying the recording medium to the conveying unit 19, and also causes the image fixing unit 17 to form an image on the recording medium. To fix the toner on the recording medium by controlling the operation of.

The control unit 11 has a CPU 111 (Central Processing Unit), a RAM 112 (Random Access Memory), and a ROM 113 (Read Only Memory).
The CPU 111 reads and executes a control program stored in the ROM 113 or the storage unit 12 to perform various arithmetic processes.
The RAM 112 provides the CPU 111 with a working memory space and stores temporary data.

The ROM 113 stores various control programs and setting data executed by the CPU 111. The ROM 113 may be a mask ROM, or may be a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory.

The storage unit 12 has a DRAM (Dynamic Random Access Memory), an HDD (Hard Disk Drive), or the like, and includes image data read by the image reading unit 21 and image data input from the outside via the communication unit 24. Processed data and the like are stored by these image processing units 13. The storage of these data may be appropriately shared with the RAM 112.

The image processing unit 13 performs various image processing on the image data stored in the storage unit 12, the RAM 112, or the like, and stores the image data in the storage unit 12 as processed data. The image processing unit 13 includes, for example, a rasterization processing unit, a color conversion unit, a gradation correction unit, a halftone processing unit, and the like as a hardware configuration for performing image processing. Alternatively, a part or all of these processes may be executed by software by a dedicated CPU or the like.

The communication unit 24 is an input / output interface that controls transmission / reception of data to / from an external computer, a print server, another image forming apparatus, or the like. Examples of the communication unit 24 include a network card and drivers related to various serial interfaces.

The environment detection unit 25 is a sensor that measures and acquires a predetermined index value related to the surrounding environment of the image forming apparatus 1, and here, at least the ambient temperature is measured and output to the control unit 11. Further, the environment detection unit 25 may be able to detect ambient humidity and the like.

The image fixing unit 17 includes a central heater 176 (third heat source unit), an overall heater 177 (second heat source unit), an end heater 178 (first heat source unit), and an external heating heater 179 (collectively, fixing heaters 176 to 179). Also referred to as; a heat source unit), the toner on the recording medium is heated and fixed.
The temperature measuring unit 18 includes a central measuring unit 181 (second temperature measuring unit), an end measuring unit 182 (first temperature measuring unit), and the like. Each measurement result is output to the control unit 11.
Of these, the fixing device according to the present embodiment is configured by the control unit 11, the image fixing unit 17, and the temperature measuring unit 18.

Next, the image fixing unit 17 and the temperature measuring unit 18 of the present embodiment will be described.
FIG. 3 is a schematic view of the configurations of the image fixing unit 17 and the temperature measuring unit 18 when viewed from the same direction as in FIG.

The image fixing portion 17 includes a fixing roller 172, a pressure roller 173, an external heating roller 174, and the like.

The fixing roller 172 holds the recording medium P together with the pressurizing roller 173, and is rotated by a motor or the like (not shown) based on the control by the control unit 11. The fixing heaters 176 to 178 are provided inside the fixing roller 172 so as to extend in the direction of the rotation axis. Each of the fixing heaters 176 to 178 generates heat when energized based on the control by the control unit 11. As the fixing heaters 176 to 178, halogen lamp heaters are used here.

The pressure roller 173 is urged in the direction of the fixing roller 172 by an elastic member (not shown), forms a fixing nip with the fixing roller 172, and holds the recording medium P between the fixing roller 172 and the fixing roller 172. To do. The pressurizing roller 173 rotates with the rotation of the fixing roller 172 (movement of the recording medium P when the recording medium P is narrowly held). The pressurizing roller 173 may be rotated at a rotation speed synchronized with the fixing roller 172 by a motor or the like based on the control by the control unit 11.

The fixing roller 172 and the pressurizing roller 173 heat the recording medium P while holding the recording medium P between the fixing nips and conveying the pressure in the conveying direction R (arrow direction). As a result, the toner on the recording medium P is melted and fixed. The set temperature of the fixing roller 172 during contact with the recording medium P is appropriately determined according to the type of toner, the maximum amount, and the like. Here, for example, an image is continuously displayed on a plurality of recording media at about 200 ° C. When it is formed, the temperature is slightly lower than this. The heat generation state of the fixing heaters 176 to 178 is controlled so that the fixing roller 172 is in this temperature range.

The external heating roller 174 is arranged in a state where the surface is in contact with the surface of the pressure roller 173, and rotates with the rotation of the pressure roller 173. Inside the external heating roller 174, an external heating heater 179 extending in the direction of the rotation axis is provided. The external heater 179 generates heat when it is energized based on the control by the control unit 11. The heat of the external heating roller 174 heated by the external heating heater 179 is transmitted to the pressure roller 173 to heat the pressure roller 173.

FIG. 4 is a diagram for explaining the heating range of the fixing heaters 176 to 178 inside the fixing roller 172 and the temperature measurement position by the temperature measuring unit 18.
The central heater 176 is provided with a tungsten filament 176b in a tubular portion 176a extending in the width direction. The overall heater 177 is provided with a tungsten filament 177b in a tubular portion 177a extending in the width direction. Further, the end heater 178 is provided with a tungsten filament 178b in a tubular portion 178a extending in the width direction. Halogen gas having a predetermined concentration is sealed in each of the cylinder portions 176a to 178a. The reference voltage related to the heat generation operation of the fixing heaters 176 to 178 is set based on the concentration of the halogen gas enclosed in the tubular portions 176a to 178a. Here, the calorific value per unit length of the overall heater 177 is smaller than the calorific value per unit length of the central heater 176 and the end heater 178 (the smallest among the heat source portions), and the fixing roller 172 Used for basic heating of the entire surface.

The central heater 176 generates heat only in a predetermined range (third heating range) near the central portion with respect to the maximum transferable recording medium width (here, 210 mm in A4 length; predetermined fixing width) in the width direction. The filament 176b is provided as described above. The overall heater 177 overlaps at least a portion of the maximum recording medium width in the width direction (ie, along the anchorage width) (the entire space between both ends of the anchorage width; the second heating range, the heating range of the end heater 178). ) Is provided so that the filament 177b generates heat. The end heater 178 generates heat in both ends in the width direction (first heating range; within a predetermined range from both ends of the fixing width) in the heat generation range of the entire heater 177 so that the central heater 176 does not generate heat (that is, the fixing width). A filament 178b is provided (in a range complementary to the heat generation range of the central heater 176). That is, these fixing heaters 176 to 178 are arranged so as to generate heat in different heating ranges from each other.

The central measurement unit 181 is a heating range (within the second heating range) of the central heater 176 and the entire heater 177, and the fixing roller is located substantially near the center in the width direction (a position closer to the center than the first measurement position below). The surface temperature of 172 is measured. The end measurement unit 182 is a heating range (position where the first heating range and the second heating range overlap; the first measurement position) of the entire heater 177 and the end heater 178, and is a position closer to one end. Measure the surface temperature of the fixing roller 172 with. Here, the end measuring unit 182 is arranged so as to measure the temperature at a position close to the boundary of the heating range of the central heater 176 and the end heater 178, and is smaller than the above-mentioned maximum recording medium width (width). It facilitates proper temperature control when forming an image on a (narrow) recording medium.

Next, the heating operation control of the fixing heaters 176 to 178 in the image fixing unit 17 will be described.
In the image forming apparatus 1 of the present embodiment, the control unit 11 controls the on / off of the fixing heaters 176 to 178 based on the set temperature and the measured temperature. Here, the central heater 176 and the overall heater 177 are on / off controlled by PI control based on the history of the measured temperature by the central measuring unit 181 (second heat generation control step). The end heater 178 is on / off controlled according to the magnitude relationship between the measured temperature and the set temperature by the end measuring unit 182 (first heat generation control step).

Further, here, the control unit 11 can perform a control operation in which the on / off state of the central heater 176 and the overall heater 177 is periodically switched in a short time by a set duty ratio (ratio of heat generation time). The on / off switching cycle (frequency) is appropriately determined, but here, the phase of the sine wave is set to 0 degrees and 180 degrees (zero cross point) in units of the power frequency half cycle of the AC power supplied to the fixing heaters 176 to 178. Half-cycle duty control (HCD control) can be performed by synchronizing and switching to change the ratio between the number of half cycles in the on period and the number of half cycles in the off period.
In this image forming apparatus 1, the heating operation (heat generation) by the central heater 176 is prioritized, and the history of the measured temperature by the central measuring unit 181 is higher than the set temperature in a state where the heating by the overall heater 177 is completely turned off. If it passes, the central heater 176 is switched off.

As described above, by heating the temperature of the toner (recording medium) to an appropriate temperature range, the toner is fixed on the recording medium. If the temperature of the toner is too low, fixing failure occurs, and if the temperature of the toner is too high, tacking occurs in which the recording media discharged to the discharge tray 196 and stacked are adhered to each other before the toner solidifies. This tacking is caused not only by the temperature of the toner (recording medium) at the time of fixing, but also by other factors such as the ambient temperature (environmental temperature; a predetermined index value related to the ambient environment) and the image formation speed at the time of continuous image formation. (Discharge rate of recording medium per hour, that is, rate of heating and fixing toner), amount of toner applied on recording medium (area ratio), presence or absence of double-sided printing (heat fixing of toner on both sides), and predetermined The susceptibility to tacking also differs depending on the post-processing operation, for example, the presence or absence of other processing such as cutting before being discharged to the discharge tray 196. That is, if the environmental temperature is low, the image formation speed is low, the amount of toner applied is small, single-sided printing is performed, and the product is discharged to the discharge tray 196 after being post-processed, the temperature at the time of fixing is slightly higher. It doesn't matter if it is high, but the opposite of these factors, the more likely it is that tacking will occur.

In the fixing roller 172, due to the heat capacity of the fixing roller 172 itself and the recording medium in contact with the fixing roller 172, the measured temperature actually rises and falls as compared with the on and off timings of the fixing heaters 176 to 178. There is a time lag. Further, the fixing roller 172 is provided with a rotating shaft and fixing heaters 176 to 178 along the width direction inside the fixing roller 172, so that heat is easily generated from the roller boss and the like at both ends, that is, on the side surface, and therefore, the whole. When the heater 177 and the end heater 178 are turned off, particularly when the end heater 178 is turned off, the temperature drops faster in the portion closer to both ends than in the portion closer to the center.

FIG. 5 is a schematic view showing the temperature distribution of the fixing roller 172 in the extending direction.
When the end heater 178 is off and heating is performed only by the overall heater 177, heat radiation from both ends creates a temperature gradient from the center to both ends of the fixing roller 172 (FIG. 5 (a)). ). Therefore, even if an appropriate temperature is maintained at the measurement position Pse of the end measurement unit 182, the temperature drop on the end side is even greater than this. If the image is formed in such a state, the toner is not sufficiently fixed near the end portion, resulting in poor fixing.

This temperature gradient is suppressed when the high-power end heater 178 is intermittently turned on together with the overall heater 177 (FIG. 5 (b)). As a result, the temperature becomes appropriate at both the measurement position Psc of the central measurement unit 181 and the measurement position Pse of the end measurement unit 182.

Moreover, the temperature does not drop significantly even on the end side. When the end heater 178 is continuously turned on, the heating range of the end heater 178 becomes overheated, and the heating range of the end heater 178 is particularly high as compared with the heating situation near the center by the overall heater 177. A temperature peak occurs near the center (Fig. 5 (c)).

FIG. 6 is a diagram illustrating a temperature setting, a temperature measurement value, and an operation setting of the fixing heaters 177 and 178 in the image forming apparatus 1 of the present embodiment. FIG. 6A is a diagram illustrating the measured temperature Tsc and the set temperature Ttc (second heating set temperature) of the central measuring unit 181 and the operating state (duty ratio Hc) of the overall heater 177. FIG. 6B shows the measurement temperature Tse (first heating set temperature) of the end measurement unit 182, the temperature Tme and the set temperature Tte at a position closer to the end than the measurement position of the end measurement unit 182, and It is a figure explaining the operation state (on-off state He) of the end heater 178.

As shown in FIG. 6A, before the start of the image forming operation (about 30 seconds), the fixing roller 172 is heated (preheated) at a set temperature Ttc higher than that during image formation, and the fixing roller 172 is set. When the temperature stabilizes, the entire heater 177 is turned off once (about 10 to 30 seconds; Hc = 0). When the image forming operation is started (about 30 seconds) and the recording medium is supplied, the heat of the fixing roller 172 is taken away by the recording medium, the measurement temperature Tsc is lowered, the overall heater 177 is turned on, and the duty ratio is reduced. It operates continuously at 100% (Hc = 100) (about 30 to 50 seconds).

At the time of image formation, the set temperature Ttc of the measurement temperature Tsc by the central measurement unit 181 is lower than the temperature at the time of preheating, and is changed to the original heating temperature of the recording medium (about 50 seconds). Further, when image formation is continuously performed, the set temperature Ttc is further lowered (about 160 to 250 seconds) in order to prevent tacking. The set temperature Ttc is not particularly limited, but it is preferable that the set temperature Ttc is not lowered all at once, but is gradually lowered (in a plurality of steps). At this time, the measured temperature Tsc of the central measuring unit 181, that is, the surface temperature near the central portion of the fixing roller 172 gradually rises according to the heat capacity and thermal conductivity of the fixing roller 172, and after a while, the set temperature. Higher than Ttc (about 150 seconds). However, since the measured temperature Tsc of the central measuring unit 181 has been lower than the set temperature Ttc for a long time (about 30 to 150 seconds), in PI control, the overall heater 177 operates even if the set temperature Ttc is lowered. Is not turned off for a while (Hc = 100 until about 210 seconds, Hc = 60 in about 230 seconds). As a result, this time, the measured temperature Tsc of the central measuring unit 181 continues to be slightly higher than the set temperature Ttc for a while (~ about 340 seconds).

As shown in FIG. 6B, the measured temperature Tse by the end measuring unit 182 initially changes in the same manner as the measured temperature Tsc by the central measuring unit 181 due to preheating and endothermic heat from the recording medium after the start of image formation. Show (~ about 60 seconds). However, after that, the measured temperature Tse rapidly increased due to the continuous operation of the end heater 178 and the overall heater 177, and as shown in FIG. 5 (c), the heating range of the end heater 178 and the central heater 176. The temperature Tse measured by the end measuring unit 182 near the boundary with the heating range becomes higher than the temperature Tsc measured by the central measuring unit 181, and the end heater 178 is turned off (about 100 seconds; He = 0).

After that, in the image forming apparatus 1 of the present embodiment, the lowering timing of the set temperature Tte of the end measuring unit 182 is delayed from the lowering timing of the set temperature Ttc of the central measuring unit 181 (here, about 230 seconds or more). .. It is preferable that the set temperature Tte is also gradually lowered in a plurality of steps in the same manner as the set temperature Ttc. Here, the lowering timing is set at the timing when the duty ratio of the overall heater 177 becomes a predetermined reference value, for example, 60% or less. As a result, the end heater 178 is turned on twice (about 150 seconds, about 220 seconds) for a short time before the lowering timing. If the end heater 178 does not have an on period, as shown in FIG. 5 (a) above, the temperature gradient in the heating range by the end heater 178 appears remarkably by the operation of only the overall heater 177, that is, , The actual temperature Tme becomes lower than the set temperature Tte near the end of the heating range. After the operating duty ratio of the overall heater 177 is sufficiently lowered, the overall heater 177 and the end heater 178 are intermittently balanced according to the hierarchical relationship between the set temperatures Ttc and Tte and the measured temperatures Tsc and Tse. As shown in FIG. 5B as a whole, the temperature unevenness can be reduced, that is, the deviation between the measured temperatures Tsc, Tse, and the temperature Tme can be reduced. When the overall heater 177 and the end heater 178 are intermittently operated in the state of FIG. 5 (a), the temperature unevenness is gradually eliminated, but by the time the state of FIG. 5 (b) is reached. It takes time, and poor fixing will continue.

FIG. 7 is a flowchart showing a control procedure by the control unit 11 of the set temperature control process executed in the image forming apparatus 1 of the present embodiment.
This set temperature control process is started when the image formation process is started from the preheat set state.

When the set temperature control process is started, the control unit 11 (CPU111) sets the set temperature Ttc of the central measurement unit 181 and the set temperature Tte of the end measurement unit 182 at the time of image formation, respectively, after the continuous image recording operation is started. The temperature is lowered to the set temperature of (step S101).

The control unit 11 acquires the measured temperature Tsc from the temperature measuring unit 18 at a predetermined sampling rate, the measured temperature Tsc becomes equal to or higher than the set temperature Ttc, and the rate of change of the measured temperature Tsc | dTsc / dt | is the predetermined reference value D. It is determined whether or not the result is as follows (step S102). If it is determined that at least one of them is not satisfied (“NO” in step S102), the control unit 11 repeats the process of step S102.

When it is determined in the determination process of step S102 that all the conditions are satisfied (“YES” in step S102), the control unit 11 sets the set temperature Ttc of the central measurement unit 181 stepwise at the time of forming a continuous image. The operation of lowering the temperature to the set temperature of (step S103) is started.

The control unit 11 determines whether or not the duty ratio Hc related to the operation of the overall heater 177 is equal to or less than a predetermined reference value (step S104). If it is determined that the value is not equal to or less than the reference value (“NO” in step S104), the control unit 11 repeats the process of step S104.

When it is determined that the duty ratio Hc is equal to or less than a predetermined reference value (“YES” in step S104), the control unit 11 sets the set temperature Tte of the end measurement unit 182 stepwise at the time of continuous image formation. The operation of lowering the temperature to the set temperature is started (step S105). Then, the control unit 11 ends the set temperature control process.
Each process of this set temperature control process constitutes a set temperature control step in the fixing operation control method of the embodiment of the present invention.

This set temperature control process is a control related to prevention of tacking and prevention of fixing failure when the tacking is prevented, but as described above, other factors also affect the susceptibility to tacking. Therefore, the set temperature control process may not be performed according to these other factors.

FIG. 8 is a diagram showing two types of flowcharts showing a control procedure by the control unit 11 of the tacking adjustment process.
As shown in FIG. 8A, when the tacking adjustment process is started, the control unit 11 determines whether or not the ambient temperature measured by the environment detection unit 25 is equal to or higher than the reference value (step S201). .. If it is determined that the value is not equal to or higher than the reference value (“NO” in step S201), the control unit 11 ends the tacking adjustment process.

When it is determined that the value is equal to or higher than the reference value (“YES” in step S201), the control unit 11 analyzes the data of the image to be formed and determines that the area of the toner applied on the recording medium is the area of the recording medium. It is determined whether or not the ratio (coverage) to the area is equal to or greater than a predetermined value (step S202). If it is determined that the value is not equal to or higher than the predetermined value (“NO” in step S202), the control unit 11 ends the tacking adjustment process.

If it is determined that the value is equal to or higher than the predetermined value (“YES” in step S202), the control unit 11 determines whether or not the image forming speed is equal to or higher than the reference value (step S203). If it is determined that the value is not equal to or higher than the reference value (“NO” in step S203), the control unit 11 ends the tacking adjustment process.

If it is determined that the value is equal to or greater than the reference value (“YES” in step S203), the control unit 11 determines whether or not the aftertreatment device is connected (step S204). If it is determined that the device is not connected (connected) (“NO” in step S204), the control unit 11 ends the tacking adjustment process.

If it is determined that the aftertreatment device is not connected (“YES” in step S204), the control unit 11 determines whether or not the double-sided printing is performed (step S205). If it is determined that the printing is not double-sided printing (“NO” in step S205), the control unit 11 ends the tacking adjustment process. If it is determined that the print is double-sided (“YES” in step S205), the control unit 11 calls and executes the set temperature control process described above (step S206). When the set temperature control process is completed, the control unit 11 returns the process to the tacking adjustment process (RETURN), and then ends the tacking adjustment process as it is.

In this way, it is possible to control so that the set temperature control process is executed only when all the factors are satisfied. Alternatively, as shown in FIG. 8B, when the branch is replaced with “YES” and “NO” in the processing of steps S201 to S204 and the branch is branched to “YES” in any of the processing of steps S201 to S205. , It is also possible to control to shift to the process of step S206.
In addition, some of these five factors may be temporarily or completely excluded from the determination conditions. Further, here, only the presence / absence of the set temperature control process is switched, but the set temperature may be switched (changed).

[Modification example]
FIG. 9 is a diagram showing a modified example of the image fixing portion in the image forming apparatus 1 of the present embodiment.
In the image fixing portion 17a of the modified example, a fixing belt 175 is bridged between the fixing roller 172 and another roller 171. The fixing belt 175 is heated by the fixing heaters 176 to 178 on the way, and then comes into contact with the recording medium P to fix the toner on the recording medium P.
The temperature measuring unit 18 measures the surface temperature of the fixing belt 175 between the time when the fixing belt 175 is heated by the fixing heaters 176 to 178 and the time when the fixing belt 175 comes into contact with the recording medium P.

As described above, the configuration related to fixing may be performed by the fixing belt 175 instead of the fixing roller 172.

FIG. 10 is a diagram showing a modified example of the configuration related to fixing in the image forming apparatus 1. In the above embodiment, the fixing heating operation is performed by the three heaters of the central heater 176, the whole heater 177, and the end heater 178. However, in the fixing roller 172a of the modified example shown in FIG. 10A, the central heater 176 is used. I don't have it. Even with such a configuration, the same temperature control can be applied. In this case, the overall heater 177 has an output capable of sufficiently heating the central portion by itself. However, since there is no central heater 176, the temperature change according to the operation of the entire heater 177 in the central portion in the width direction becomes large, and the change in power consumption (load) at the time of turning on / off tends to be large. It is necessary to have a margin in the power supply capacity of the power supply, which tends to lead to an increase in cost.

Further, in the fixing roller 172b of the modified example shown in FIG. 10B, in addition to the central heater 176 and the overall heater 177, an intermediate heater 1781 and an end heater 1782 are provided, and the outside of the heating range of the central heater 176 is from both ends. The heating range is further divided by the two heaters according to the distance between the two heaters. The temperature of each heating range is measured by the intermediate measuring unit 183 and the end measuring unit 182.

As described above, the image forming apparatus 1 of the present embodiment measures the temperature of the image fixing unit 17 for fixing the toner on the recording medium by the heating operation over a predetermined fixing width and the temperature related to the heating operation by the image fixing unit 17. The temperature measuring unit 18 and the control unit 11 for controlling the operation of the image fixing unit 17 are provided.
The image fixing portion 17 generates heat in the first heating range within a predetermined range from the positions of both ends of the fixing width (the positions of both ends of the fixing roller 172, that is, the fixing heaters 176 to 178) in the width direction along the direction of the fixing width. Includes an end heater 178 to generate heat in a second heating range that partially overlaps at least a part of the first heating range, and a fixing heater 176 to 178 that generates heat in different heating ranges. The temperature measuring unit 18 is an end measuring unit 182 that measures the temperature at a predetermined first measuring position within the first heating range, and an end measuring unit 182 that is within the second heating range and is located at both ends of the first measuring position. It has a central measuring unit 181 that measures the temperature at a position close to the center.
The control unit 11 controls the heat generation operation of the end heater 178 based on the measured temperature and the set temperature Tte by the end measuring unit 182, and generates heat of the entire heater 177 based on the measured temperature and the set temperature Ttc by the central measuring unit 181. When the operation is controlled and the temperature related to the heating operation is lowered, the set temperature Ttc is started to be lowered after the set temperature Ttc is started to be lowered.
In this way, when lowering the heating temperature, it is easier to stop the heat generation of the entire heater 177 by first lowering the set temperature Ttc in the center, while the set temperature Tte on the end side is not lowered thereafter. By providing, the end heater 178 is easily controlled to generate heat. As a result, it is possible to prevent the operation of the end heater 178 from being stopped for a long time due to the operation of the overall heater 177, heat dissipation from the vicinity of the end of the fixing roller 172, and the temperature being lowered to prevent fixing failure. .. Therefore, in this fixing device, the toner on the recording medium can be fixed easily and more appropriately without increasing the configuration related to temperature control.

Further, when the temperature related to the heating operation is lowered, the control unit 11 lowers the set temperature Tte and the set temperature Ttc in a plurality of steps, respectively.
In this way, by not lowering the set temperature all at once, the difference between the set temperature and the actual temperature can be suppressed to a small size, and the set temperature can be finely followed by heater control. Therefore, the temperature gradient near the end of the fixing roller 172 can be effectively suppressed.

Further, the control unit 11 controls the heat generation operation of at least one of the end heater 178 and the overall heater 177 by changing the duty ratio of the heat generation time.
By adjusting the calorific value according to the duty ratio, not just the on / off control, the calorific value can be controlled more finely, and the temperature followability of the fixing roller 172 can be improved. The temperature gradient near the end of 172 can be suppressed more effectively. Moreover, since the power load does not change significantly at one time, the load on the power supply can be reduced.

Further, the control unit 11 controls the heat generation operation of the entire heater 177 with a duty ratio set by PI control based on the set temperature Ttc and the measurement temperature measured by the central measurement unit 181 to lower the temperature related to the heating operation. In this case, after lowering the set temperature Ttc, the set temperature Tte is lowered after the duty ratio of the overall heater 177 becomes equal to or less than a predetermined reference value (60% or the like).
In this way, when the response of the overall heater 177 according to the measurement temperature Tsc is significantly delayed, the end measurement unit 182 starts responding after the overall heater 177 starts responding and the heat generation operation is stopped more than the standard. By lowering the set temperature Tte, the continuous operation of the overall heater 177 and the lowering of the set temperature Tte do not prolong the continuation of the off state of the end heater 178, whereby the temperature gradient in the heating range of the end heater 178. In particular, it is possible to prevent fixing defects due to a temperature drop near both ends, and to continue appropriate image formation while preventing tacking.

Further, when the control unit 11 continuously fixes the toner to a plurality of recording media, the temperature measured by the central measurement unit 181 is within a predetermined range from the set temperature Ttc, and the rate of change of the measurement temperature Tsc | dTsc. After / dt | becomes a predetermined reference value D or less, the set temperature Tsc is started to decrease, and after the start, the set temperature Tse is started to decrease.
In this way, the timing for lowering the set temperature Ttc of the central measurement unit 181 is measured after the measurement temperature Tsc of the central measurement unit 181 actually reaches the set temperature Ttc and the change is settled (saturated). It is possible to suppress a situation in which the change tendency of the temperature Tsc and the set temperature Ttc are in opposite directions and the state in which the response is poor continues.

Further, the fixing heaters 176 to 178 include a central heater 176 that generates heat in a third heating range complementary to the first heating range of the end heater 178 in the width direction, and the control unit 11 is a measurement temperature of the central measurement unit 181. The central heater 176 is heated in preference to the overall heater 177.
In this way, by heating with the central heater 176 in addition to the overall heater 177 even near the center in the width direction of the fixing roller 172, a large change in power consumption can be seen as compared with the combination of the overall heater 177 and the end heater 178 only. It can suppress frequent occurrence. As a result, the load on the power supply can be reduced, and in particular, the occurrence of flicker and the like can be prevented and stable operation can be performed.

Further, the measurement position by the end measuring unit 182 is set to a position where the first heating range by the end heater 178 and the second heating range by the overall heater 177 overlap.
In such a case, even when the end heater 178 is off, the temperature of the end measuring unit 182 can be within an appropriate range by continuously operating the overall heater 177, but the temperature is further higher than the measurement position of the end measuring unit 182. On the end side, the effect of heat dissipation tends to be noticeable and the temperature gradient tends to be large. In such a case, by performing the temperature control of the present invention, it is possible to effectively reduce the temperature gradient near the end of the fixing roller 172 and suppress fixing defects.

Further, the overall heater 177 generates heat with the entire fixing width as the second heating range.
In this way, by performing additional heating with the end heater 178 at the end of the fixing roller 172 that dissipates a large amount of heat with respect to the overall heater 177, it is usually possible to appropriately control the fixing temperature, but it is related to fixing. If the operation of the overall heater 177 continues when the set temperature is lowered, heat is dissipated from the end of the fixing roller 172 without additional heating at the end, and the temperature gradient becomes large. In such a case, by applying the control of the set temperature according to the present invention, it is possible to easily and appropriately maintain the temperature of the entire fixing roller 172 and prevent tacking while suppressing fixing defects.

Further, the calorific value per unit length by the overall heater 177 in the width direction is the smallest among the calorific values per unit length of the fixing heaters 176 to 178.
Even if the entire heater 177, which generates a small amount of heat, is used to heat the end of the fixing roller 172, more heat is dissipated and the temperature gradient in the width direction becomes large, so that fixing failure at the end is likely to occur. Therefore, by applying the present invention to the image fixing portion 17 having such a configuration, it is possible to prevent tacking while suppressing fixing defects particularly effectively.

Further, a predetermined index value relating to the surrounding environment, here, an environment detection unit 25 for measuring and acquiring the ambient temperature is provided, and the control unit 11 changes the temperature related to the heating operation based on the ambient temperature.
The likelihood of tacking varies not only with the heating temperature of the recording medium but also with other factors such as these, but tacking is particularly high when the ambient temperature is low and the temperature of the recording medium drops rapidly. Is unlikely to occur, so it is possible to reduce the time and effort required for control operation by not performing fine control of the fixing temperature. On the contrary, by controlling the fixing temperature more finely according to such surrounding environmental factors, it is possible to more stably and surely prevent both fixing failure and tacking.

Further, the control unit 11 determines the speed at which the color material is fixed, the area ratio of the toner on the recording medium to the recording medium, the presence or absence of a predetermined post-processing operation after the toner is fixed, and the fixing of the toner on both sides of each recording medium. The temperature related to the heating operation is changed based on at least one of whether or not the above is performed. Similar to the above, if it is not necessary to consider the factors that affect the presence or absence of tacking, fine control of the fixing temperature can be omitted, or finer control can be performed to achieve more stable fixing failure. And the occurrence of tacking can be prevented.

Further, the image forming apparatus 1 of the present embodiment includes an image forming unit 16 that forms an image by adhering toner on a recording medium, and the above-mentioned fixing device (image fixing unit 17, temperature measuring unit 18, and control unit 11). And. In such an image forming apparatus 1, the fixing operation is surely performed after the image is formed, and the tacking of the recording medium discharged after the fixing can be effectively prevented.

Further, in the fixing operation control method of the present embodiment, the first heat generation control step for controlling the heat generation operation of the end heater 178 based on the measurement temperature Tse and the set temperature Tte by the end measurement unit 182, and the measurement by the central measurement unit 181. The second heat generation control step that controls the heat generation operation of the overall heater 177 based on the temperature Tsc and the set temperature Ttc, when the temperature related to the heating operation is lowered, the set temperature Ttc is lowered after the set temperature Ttc is started to be lowered. Includes a set temperature control step, which initiates.
In this way, when lowering the heating temperature, it is easier to stop the heat generation of the entire heater 177 by first lowering the set temperature Ttc in the center, while the set temperature Tte on the end side is not lowered thereafter. By providing, the end heater 178 is easily controlled to generate heat. As a result, it is possible to prevent the operation of the end heater 178 from being stopped for a long time due to the operation of the overall heater 177, heat dissipation from the vicinity of the end of the fixing roller 172, and the temperature being lowered to cause fixing failure. .. Therefore, in this fixing device, the toner on the recording medium can be fixed easily and more appropriately without increasing the configuration related to temperature control.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above embodiment, the operation control of the entire heater 177 is set to PI control, and the operation control of the end heater 178 is set to control based on a simple comparison of the magnitude relationship between the measured temperature and the set temperature by the end measuring unit 182. However, it is not limited to this. Even if the operation control of the end heater 178 is PI control, the temperature quickly recovers and rises further near the boundary between the heating range of the end heater 178 and the central heater 176. Correspondingly, the period during which the end heater 178 is not turned on tends to continue, and the same problem may occur. Therefore, by applying the present invention, the temperature gradient in the heating range of the end heater 178 can be effectively reduced.

On the other hand, even when the operation of the overall heater 177 is not PI control, for example, the overall heater 177 is turned off when the temperature is higher than the set temperature and turned on when the temperature is lower than the set temperature. ) A similar situation can occur when performing motion control.

Further, when PID control is used for the operation control of these heaters, the duration of the on state of the entire heater 177 during this period can be slightly shortened. However, in the original heating control, the time lag between the on / off of the heater and the fluctuation of the measured temperature is very large, and if the influence of the D control is too large, the temperature required for the fixing operation during normal image formation is reached. Problems such as the heater being turned off before can occur. Therefore, even when PID control is used within a range in which there is no problem in normal operation, the present invention can be applied and a considerable effect can be obtained.

Further, the same situation occurs even when the end heater 178 is duty-driven or the overall heater 177 is simply driven on and off. In this case, the start timing for lowering the set temperature Tte of the end heater 178 can be determined by switching to the off state instead of the duty ratio of the overall heater 177, or by a predetermined time after the switch.

Further, in the above embodiment, as a case where the on state of the overall heater 177 continues to be a problem for a long time even though the set temperature Ttc is lowered, the start of the continuous image forming operation after preheating is taken as an example. As described above, the present invention is not limited to such cases. The present invention can be applied because the same situation can occur even when the material, thickness or size of the recording medium is changed, the image forming speed is changed, or the image to be formed is changed. ..

Further, in the above embodiment, control by a combination of the overall heater 177 and the end heater 178 is premised, but the configuration is not limited to the configuration in which the overall heater 177 heats over the entire width (fixing width) of the fixing roller 172. .. It suffices that the end heater 178 and the heating range are arranged so as to partially overlap.
In addition, specific details such as the specific configuration, structure, arrangement, control content, and control procedure shown in the above embodiment can be appropriately changed without departing from the spirit of the present invention.

1 Image forming device 11 Control unit 12 Storage unit 13 Image processing unit 16 Image forming unit 161 Exposure unit 162 Photoreceptor 163 Developing unit 164 Transfer unit 165 Secondary transfer roller 17, 17a Image fixing unit 171 Roller 172, 172a, 172b Fixing roller 173 Pressurizing roller 174 External heating roller 175 Fixing belt 176 Central heater 176a to 178a Cylinder part 176b to 178b Filament 177 Overall heater 178 End heater 1781 Intermediate heater 1782 End heater 179 External heating heater 18 Temperature measuring unit 181 Central measuring unit 182 End measurement unit 183 Intermediate measurement unit 19 Transport unit 191 Reversing mechanism 195 Supply tray 196 Discharge tray 21 Image reading unit 22 Operation reception unit 23 Display unit 24 Communication unit 25 Environment detection unit 30 Bus Hc Duty ratio He on / off state P Recording medium

Claims (13)

A fixing operation unit that fixes the color material on the recording medium by a heating operation over a predetermined fixing width,
A temperature measuring unit that measures the temperature related to the heating operation by the fixing operation unit, and
A control unit that controls the operation of the fixing operation unit,
With
The fixing operation unit includes a first heat source unit that generates heat in a first heating range within a predetermined range from both end positions of the fixing width in the width direction along the fixing width direction, and a part of the first heating unit. It has a second heat source unit that generates heat in a second heating range that overlaps at least a part of the range, and has a heat source unit that generates heat in different heating ranges.
The temperature measuring unit includes a first temperature measuring unit that measures the temperature at a predetermined first measuring position within the first heating range, and both ends of the temperature measuring unit that are within the second heating range and are more than the first measuring position. It has a second temperature measuring unit that measures the temperature at a position close to the center of the position.
The control unit controls the heat generation operation of the first heat source unit based on the measured temperature by the first temperature measuring unit and the first heating set temperature, and the measured temperature and the second heating set temperature by the second temperature measuring unit. When the heat generation operation of the second heat source unit is controlled based on the above and the temperature related to the heating operation is lowered, the lowering of the first heating set temperature is started after the lowering of the second heating set temperature is started. A fixing device characterized by being allowed to operate. The fixing device according to claim 1, wherein the control unit lowers the first heating set temperature and the second heating set temperature in a plurality of steps when the temperature related to the heating operation is lowered. Claim 1 or 2 is characterized in that the control unit controls the heat generation operation by changing the duty ratio of the heat generation time for at least one of the first heat source unit and the second heat source unit. The fixing device described. The control unit controls the heat generation operation of the second heat source unit at the duty ratio set by PI control based on the second heating set temperature and the measurement temperature measured by the second temperature measurement unit. When lowering the temperature related to the heating operation, after lowering the second heating set temperature, the duty ratio of the second heat source unit becomes equal to or less than a predetermined reference value, and then the first heating set temperature is set. The fixing device according to claim 3, wherein the fixing device is lowered. When the control unit continuously fixes the coloring material to a plurality of recording media, the temperature measured by the second temperature measuring unit is within a predetermined range from the second heating set temperature. Claims 1 to 4, wherein the lowering of the second heating set temperature is started after the rate of change becomes equal to or less than a predetermined reference value, and the lowering of the first heating set temperature is started after the start. The fixing device according to any one of the above. The heat source unit includes a third heat source unit that generates heat in a third heating range complementary to the first heating range in the width direction.
Any one of claims 1 to 5, wherein the control unit causes the third heat source unit to generate heat with priority over the second heat source unit based on the measured temperature of the second temperature measurement unit. The fixing device according to the section. The fixing device according to any one of claims 1 to 6, wherein the first measurement position is defined at a position where the first heating range and the second heating range overlap. The fixing device according to any one of claims 1 to 7, wherein the second heat source unit generates heat with the entire fixing width as the second heating range. The fixing device according to claim 8, wherein the calorific value per unit length in the width direction by the second heat source unit is the smallest among the calorific values per unit length in the heat source unit. Equipped with a detector that acquires a predetermined index value related to the surrounding environment
The fixing device according to any one of claims 1 to 9, wherein the control unit changes the temperature related to the heating operation based on the predetermined index value. The control unit determines the speed at which the color material is fixed, the area ratio of the color material on the recording medium to the recording medium, the presence or absence of a predetermined post-processing operation after the color material is fixed, and the color material on both sides of each recording medium. The fixing device according to any one of claims 1 to 10, wherein the temperature related to the heating operation is changed based on at least one of whether or not fixing is performed. A forming motion unit that forms an image by adhering a coloring material on a recording medium,
The fixing device according to any one of claims 1 to 11.
An image forming apparatus comprising. The fixing operation unit includes a fixing operation unit that fixes the color material on the recording medium by a heating operation over a predetermined fixing width, and a temperature measuring unit that measures the temperature related to the heating operation by the fixing operation unit. In the width direction along the direction of the fixing width, a first heat source portion that generates heat in a first heating range within a predetermined range from both end positions of the fixing width, and a part thereof is at least a part of the first heating range. A second heat source unit that generates heat in an overlapping second heating range and a heat source unit that generates heat in different heating ranges are included, and the temperature measuring unit is a predetermined first measuring position within the first heating range. A first temperature measuring unit that measures the temperature in the above, and a second temperature measuring unit that measures the temperature at a position within the second heating range that is closer to the center of the both end positions than the first measuring position. It is a fixing operation control method of the fixing device to have.
A first heat generation control step that controls the heat generation operation of the first heat source unit based on the temperature measured by the first temperature measuring unit and the first heating set temperature.
A second heat generation control step that controls the heat generation operation of the second heat source unit based on the temperature measured by the second temperature measurement unit and the second heating set temperature.
When the temperature related to the heating operation is lowered, the set temperature control step of starting the lowering of the first heating set temperature after starting the lowering of the second heating set temperature.
A fixing operation control method comprising.

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