JP4338474B2 - Fixing device, image forming apparatus, and fixing device control method - Google Patents

Description

  The present invention relates to a fixing device for fixing an image by pressing a sheet on which a non-fixed image is formed on a part of a peripheral surface of a heating roller that includes a plurality of heat sources that mainly heat each of a plurality of different areas and rotates. , An image forming apparatus including the same, and a control method of the fixing device.

In general, an electrophotographic image forming apparatus presses a recording paper (sheet) on which an unfixed toner image is formed with a pressure roller or the like against a rotating heating roller so that the unfixed toner image is recorded on a recording paper or the like. A fixing device that heats and fixes the sheet is provided.
In this fixing device, a plurality of heat sources (such as heaters) that mainly heat each of a plurality of areas corresponding to the size (pass width) of the sheet passing through the heating roller are included in the heating roller, and depending on the size of the sheet Some control multiple heat sources individually. For example, Patent Document 1 discloses a heating roller that includes a plurality of heat sources.
FIG. 6A is a schematic cross-sectional view of an example of such a conventional heating roller A. FIG.
The heating roller A includes a main heater 91 that is a heat source that mainly heats the first area W1 corresponding to the width of a small-sized sheet (for example, the sheet width during A4 longitudinal feeding or B5 longitudinal feeding) in the axial direction thereof. , And a sub-heater 92 that is a heat source for mainly heating the second region W2.
FIG. 6B is a graph showing a heat distribution (heat distribution characteristic) in the axial direction of the heating roller A of each of the main heater 91 and the sub heater 92.
As shown by the solid line in the figure, the main heater 91 generates heat (distribution) rated (100%) in the first region W1, and generates heat lower than the rating in the other second region W2. (For example, heat generation of a rated ratio of 30% to 40%) is performed. On the other hand, as indicated by a broken line, the sub-heater 92 generates heat of a rating (100%) in the second region W2, and heat generation lower than the rating (for example, a rating ratio of 5%) in the other first region W1. (~ 40% heat generation).
With such a configuration, at the time of fixing to a small size sheet, it is possible to save power by controlling not to perform unnecessary heating by the sub-heater 92, and there is no heat transfer to the sheet (heat is not taken away by the sheet). It is possible to prevent the second region W2 from becoming hot (a large temperature gap in the axial direction) and causing the heating roller to deteriorate or the fixing performance to become unbalanced.
In recent years, in particular, a thin-walled and low-heat-capacity (fast thermal response) heating roller is often used for weight reduction and power saving. In this case, the sheet-passing portion (the first region W1) and the non-sheet-passing are often used. Since the temperature gap of the portion (the second region W2) tends to increase, it is effective to use a plurality of heaters.

Further, in recent image forming apparatuses, when image formation is not performed (that is, fixing is not performed) due to a request for power saving, the image forming apparatus shifts to a so-called power saving mode, and a fixing apparatus with relatively large power consumption is also saved. Transition to power mode.
When the fixing device shifts to the power saving mode (standby state), the rotation of the heating roller A is stopped, and the set temperatures of the respective regions W1 and W2 (all regions) of the heating roller A are set to the fixing temperature (heating fixing). The temperature is set to a predetermined power saving set temperature lower than the temperature required for power saving, and is adjusted to the power saving set temperature by the heaters 91 and 92.

On the other hand, the heat roller A has a greater heat dissipation in the region closer to both ends thereof. Therefore, if the sub-heater 92 is not heated when fixing an image on a small size sheet, There is a case where the temperature does not rise sufficiently and causes fixing failure.
In order to cope with this, the conventional fixing device has a series of image fixing for a small-size sheet (that is, a series of sheets that pass only a part of the plurality of areas W1 and W2 among the areas W1 and W2). When the image fixing is performed), the set temperature of the first area W1 is set to the fixing temperature, the temperature is adjusted by the main heater 91, and the first fixing is performed according to the number of sheets on which image fixing is performed continuously. There is a configuration in which the temperature is adjusted by the sub heater 92 by sequentially lowering the set temperature of the two regions W2 (regions other than the first region) from the fixing temperature.

FIG. 7 shows the set temperatures of the areas W1 and W2 and the control states (ON / OFF) of the heaters 91 and 92 for a series of image fixing operations for a small-size sheet in such a conventional fixing device. It is a trend graph. In the graph, the set temperature of the first region W1 is represented by a thick solid line, and the set temperature of the second region W2 is represented by a thick broken line. The thin broken line represents the detected temperature.
When there is a print request (image formation request) from the state of the power saving mode, the set temperature of each of the areas W1 and W2 is changed from the set temperature T2 during power saving (displayed as standby temperature in the figure) to the fixing temperature T1 (in the figure, The setting is changed to (fixed set temperature and display), and the heaters 91 and 92 are controlled according to the set temperature. Printing (image formation) starts after the temperatures of the areas W1 and W2 follow the fixing temperature T1, and image fixing starts accordingly (range h1 in the figure).
Thereby, it is possible to prevent the vicinity of both end portions of the first region W1 from becoming insufficient in temperature.

Thereafter, until the end of printing (ie, at the end of image fixing), the set temperature of the first area W1 is maintained at the fixing temperature T1, while the set temperature of the second area W2 is set to a predetermined number of prints (image fixing). ), The temperature is sequentially set lower by a predetermined temperature range (range h2 in the figure).
Such control is performed because if the temperature of the second region W2 is maintained at the fixing temperature T1, the nip portion (contact portion) where the heating roller A is in pressure contact with the pressure roller becomes abnormally high due to overheating. This is to prevent this. That is, since it is difficult to detect the temperature at the nip portion, the temperature control of each of the regions W1 and W2 is performed by detecting the peripheral surface temperature of the heating roller A outside the nip portion. Even if the temperature is maintained at T1, the nip portion of the second region W2 where there is no heat transfer to the sheet is abnormally high above the fixing temperature T1 due to heat storage on the other side (pressure roller or the like) forming the nip portion. It becomes. In order to prevent this, the set temperature of the second region W2 is sequentially lowered according to the number of sheets to be continuously fixed.
When all of the series of printing (image fixing) are completed, the rotation of the heating roller A is stopped and the set temperature of each of the areas W1 and W2 is set to the set temperature at the time of power saving. T2 is set (range h3 in the figure).
JP 2000-242134 A

By the way, when the mode is shifted to the power saving mode after a series of printing (image fixing), the setting of the main heater 91 is changed to the temperature T2 lower than the set temperature (fixing temperature T1) so far. Stop (OFF).
On the other hand, for the sub-heater 92, as shown in the range of h3 in FIG. 7, the detected temperature of the second area W2 at the end of a series of image fixing is lower than the power-saving set temperature T2 (standby temperature). , The heating (ON) state is maintained until the detected temperature reaches the power-saving set temperature T2. In this case, the heat distribution in the first region W1 of the sub-heater 92 is not 0%, and the heat radiation amount at the nip portion of the stopped heating roller A is smaller than other peripheral surfaces (such as a pressure roller). Therefore, the temperature of the nip portion in the first region W1 of the heating roller A is higher than the temperature of the peripheral surface other than the nip portion (for example, +20 to 40 ° C.) (in the circumferential direction). Large temperature gap).
When a print request is generated with such a large temperature gap in the circumferential direction and the temperature is raised to the fixing temperature T1 by the heaters 91 and 92, the heating roller A and the pressure roller on the opposite side thereof. The portion (peripheral surface) that was the nip portion during the rotation of the rotation becomes an abnormally high temperature (for example, T1 + 20 to 40 ° C.) exceeding the fixing temperature T1.
FIG. 8 is a graph schematically showing the temperature distribution in the circumferential direction of the pressure roller when the heating from the power saving mode state in the conventional fixing device to the fixing temperature T1 is completed (the horizontal axis is the position in the circumferential direction). The vertical axis is the surface temperature).
As shown in FIG. 8, the temperature (for example, around 200 ° C.) at which the portion (N 0 range) that was the nip portion when the pressure roller stopped exceeds the toner melting temperature T 3 (fixing lower limit temperature, about 160 to 170 ° C.). )
Moreover, such a temperature gap in the circumferential direction remains even after the start of fixing (after the start of rotation). For example, it may take more than a dozen revolutions before the abnormally high temperature portion becomes lower than the toner melting temperature.
As described above, when the image is fixed by the pressure roller whose part in the circumferential direction is abnormally high, there is a problem that the image fixing performance is deteriorated. For example, partial “curl” occurs in one sheet, “uneven fixing performance”, and “wrinkle” occur.
Further, when the abnormally high temperature portion of the pressure roller exceeds the melting temperature of the toner, the toner adhering to the peeling claw that contacts the pressure roller is melted in order to peel the sheet after fixing, and the molten toner There is also a problem that the sheet adheres to the back surface of the sheet and soils the sheet. In addition, the pressure roller is deteriorated.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a nip portion of the heating roller when the heating roller is stopped after a series of image fixing by the heating roller including a plurality of heat sources. It is an object of the present invention to provide a fixing device capable of suppressing a temperature gap between the first portion and other portions, an image forming apparatus including the fixing device, and a fixing device control method.

In order to achieve the above object, the present invention presses a sheet on which an unfixed image is formed on a part of the peripheral surface of a heating roller that includes a plurality of heat sources that mainly heat a plurality of different regions. A fixing device for fixing an image in the heating roller, the rotation of which is stopped by the end of the image fixing during a period until each temperature of the plurality of regions falls to a predetermined base temperature after a series of image fixing ends. Power saving means for stopping all heating by a plurality of heat sources, and power saving that lowers each temperature of the plurality of areas by the plurality of heat sources below a fixing temperature necessary for image fixing after a heating stop period by the heating stop means And a power saving adjusting means for adjusting to the hourly setting temperature, wherein the base temperature is lower than the temperature of all of the plurality of regions at the end of the series of image fixing and the power saving time setting temperature. At low temperatures der shall be specified Chakusochi than the heating stop means, in the case after the end of the series of image fixing on the sheet which mainly passes only a partial area of the plurality of regions, By setting each set temperature of the plurality of regions to the base temperature and performing temperature adjustment by the plurality of heat sources, a period until each temperature of the plurality of regions falls to the base temperature is determined by the plurality of heat sources. The fixing device is configured to stop all the heating .

This reduces (suppresses) the temperature gap between the nip portion of the heating roller (pressure contact portion with the pressure roller, etc.) and other portions during the stop of heating after a series of image fixing. When the temperature is raised to the fixing temperature through the set temperature during power saving, it is possible to prevent the portion that was the nip portion during the stop from becoming an abnormally high temperature.

In the present invention, as described above, when the heating stop unit finishes the series of image fixing, the temperature of one of the plurality of regions and the temperature of the other region is equal to or lower than the power-saving set temperature. In this case, by setting each set temperature of the plurality of regions to the base temperature and performing temperature adjustment by the plurality of heat sources, a period until each temperature of the plurality of regions falls to the base temperature, It is configured to stop all heating by a plurality of heat sources.
Alternatively, when the temperature of one of the plurality of regions and the other region other than the plurality of regions at the end of the series of image fixing is equal to or lower than the power-saving set temperature, By setting each set temperature of the plurality of regions to the base temperature and performing temperature adjustment by the plurality of heat sources, a period until each temperature of the plurality of regions falls to the base temperature is determined by the plurality of heat sources. All heating is stopped.
In this way, there is proposed a system that controls the heating of the plurality of heat sources to be stopped based on the resulting temperature regardless of which region the sheet has passed through.

Also, as before Symbol plurality of regions, for example, a first region corresponding to a region in which a predetermined small-size sheet passes, is made of the other second region considered.
Of course, it may be provided with a heat source (such as a heater) that mainly heats three or more regions (for example, three regions corresponding to a small size, a medium size, and a large size).

The present invention may be an image forming apparatus characterized by including the fixing device.
On the other hand, the present invention may be understood as a method for controlling the fixing device. That is, control of a fixing device that fixes an image by pressing a sheet on which a non-fixed image is formed on a part of a peripheral surface of a heating roller that includes a plurality of heat sources that mainly heat different regions. A method in which heating by the plurality of heat sources is performed in the heating roller whose rotation has been stopped by the end of image fixing for a period until each temperature of the plurality of regions falls to a predetermined base temperature after a series of image fixing ends. After the heating stop process for stopping all, and the heating stop period in the heating stop process, the temperatures of the plurality of regions are adjusted to a power saving set temperature lower than the fixing temperature necessary for image fixing by the plurality of heat sources. A power saving temperature adjusting step, wherein the base temperature is lower than the temperature of all of the plurality of regions at the end of the series of image fixing and lower than the power saving set temperature. The control method for Fixing device Ru Ah, the heating stop step, if after the end of the series of image fixing on the sheet which mainly passes only a partial area of the plurality of regions, said plurality By setting each set temperature in the region to the base temperature and performing temperature adjustment by the plurality of heat sources, heating by the plurality of heat sources is performed for a period until each temperature in the plurality of regions falls to the base temperature. The fixing method is a control method for the fixing device, characterized in that all are stopped .

According to the present invention, after completion of a series of image fixing, the rotation is stopped by the end of the image fixing for a period until each temperature of the plurality of regions of the heating roller falls to a base temperature lower than a predetermined power saving set temperature. a heating stop means for all to stop locked heating by a plurality of heat sources that are included in the heating roller that, after a stop period of heating by the heating stopping means, the temperature image fixing of the plurality of areas by the plurality of heat sources since comprises a power-saving temperature adjusting means for adjusting a lower than the fixing temperature the power saving time set temperature required to, while stopping the series of post image fixing heating nip portion of the heating roller (pressure roller, etc. The temperature gap between the pressure contact part) and the other part is relaxed (suppressed), and when the temperature is raised to the fixing temperature, the part that was the nip part during the stoppage becomes abnormally high. Can be prevented.
As a result, it is possible to prevent deterioration in image fixing performance that causes partial “curling” in one sheet, “non-uniform fixing performance”, and “wrinkles”. Furthermore, it is possible to prevent the toner adhering to the peeling claw that comes into contact with the sheet pressure contact member such as the pressure roller from being melted, and to prevent the molten toner from adhering to the back surface of the sheet and soiling the sheet, thereby preventing the deterioration of the pressure roller and the like .

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a side sectional view showing the overall configuration of the image forming apparatus Z on which the fixing device X according to the embodiment of the present invention is mounted. FIG. 2 is a block diagram showing the schematic configuration of the main part of the image forming apparatus Z. 3 is a schematic cross-sectional view of a heating roller and a pressure roller of the fixing device X. FIG. 4 is a set temperature of each region of the heating roller and a control state of each heater with respect to that in the series of image fixing in the fixing device X. FIG. 5 is a flowchart showing the control procedure of the set temperature of the heating roller of the fixing device X, FIG. 6 is a schematic sectional view of the heating roller A provided in the conventional fixing device, and a graph showing the heat distribution characteristics of the heater, FIG. 7 is a trend graph showing the set temperature of each region of the heating roller and the control state of each heater for a series of image fixing in the conventional fixing device, and FIG. 8 is a power saving mode in the conventional fixing device. The temperature distribution in the circumferential direction of the pressure roller when the heating has been completed from the state to the fixing temperature is a graph schematically showing.

First, the configuration of the image forming apparatus Z on which the fixing device X according to the embodiment of the present invention is mounted will be described with reference to the side sectional view of FIG. 1 and the block diagram of FIG.
The image forming apparatus Z has a copier mode (copying mode), a printer mode, and a FAX mode as print modes. Operation input from an operation unit (not shown) and print job from an external host device such as a personal computer are performed. A print mode corresponding to reception (an example of an image formation request) is selected by a control unit described later.
As shown in FIG. 1, the image forming apparatus Z is roughly divided into a document reading unit 10, a paper feeding unit 20, a printing unit 30, and a paper discharge unit 40, and the document reading unit 10 is arranged above the paper feeding unit 20. A paper discharge unit 40 is provided at an intermediate position between the document reading unit 10 and the paper supply unit 20.
Hereinafter, the copier mode will be described from the above processing modes.
After the user places a document on the platen glass 11 of the document reading unit 10 (scanner unit), the sheet (recording paper) is placed on the sheet feeding cassette 21 of the sheet feeding unit 20 or the manual feed tray 23 provided on the side of the apparatus. After inputting the condition input key (number of printed sheets / printing magnification, etc.) on an operation panel (not shown) disposed on the front surface of the apparatus and operating the start key on the operation panel (an example of an image formation request) ) To start the copy operation.
When the start key is operated, a main drive motor (not shown) starts and each drive gear rotates. Thereafter, the paper feed roller 22 or 22a rotates to feed (feed) the paper into the apparatus, and the fed paper reaches the registration roller 31 (roller pair) and is captured. The registration roller 31 temporarily stops the paper so as to synchronize with the leading edge (image formation start portion) of the image formed on the photosensitive drum 32, and the leading edge of the paper is uniformly pressed against the registration roller 31. Thus, the leading edge position of the paper is corrected.

On the other hand, in the document reading unit 10, the copy lamp 12a (light source) is turned on, and the exposure starts when the copy lamp unit 12 moves in the direction of the arrow. Irradiation light applied to the document by the copy lamp 12a becomes reflected light (reflected light from the document) including image information of the document, and the reflected light is transmitted from the first mirror 12b provided in the copy lamp unit 12 to the second light. Reading is performed by inputting to the CCD 16 from the mirror 13, the third mirror 14, and the optical lens 15.
The image information read in this way is converted into an electrical signal by a CCD circuit (not shown), and the image information signal is subjected to image processing under a set condition, and the laser scanner unit. 33 as print data.

On the other hand, the entire photosensitive drum 32 is charged to a predetermined charging potential by the charging unit 34.
In the laser scanner unit 33, a polygon mirror 33b (rotating polygonal mirror) having a plurality of reflecting surfaces in the rotation direction is rotationally driven at a high speed by a polygon motor 33c, and laser light emitted from the semiconductor laser 33a is polygon mirror 33c. And the photosensitive drum 32 is irradiated while being deflected by various lenses. As a result, the laser beam is scanned on the photosensitive drum 32, and an electrostatic latent image is formed on the photosensitive drum 32. Thereafter, the toner on the MG roller 35a in the developing tank 35 is attracted onto the surface of the photosensitive drum 32, and the electrostatic latent image is visualized by the toner according to the potential gap on the photosensitive drum 32.
In addition, the paper (recording paper) to be imaged is conveyed in the direction of the photosensitive drum 32 by the registration roller 31 in time, and the toner on the photosensitive drum 32 is transferred to the paper by the transfer unit 36 (corona charger). Is done. The toner remaining on the photosensitive drum 32 is scraped off by the cleaning blade 37 a of the drum unit and collected by the cleaner unit 37.

On the other hand, the paper on which the toner has been transferred passes between the heating roller 71 and the pressure roller 72 of the fixing device X, and heat and pressure are applied, so that the unfixed toner on the paper melts and adheres to the paper. Then, the paper is discharged onto the paper discharge tray 42 by the paper discharge roller 41. The heating roller 38a is heated by a plurality of heaters 81 and 82 provided (enclosed) therein.
In addition, when it is detected by a predetermined sensor that a document is placed on the document tray 19 included in the document reading unit 10, the paper feed roller 51 rotates when a predetermined start key operation is performed. Then, the document placed on the document tray 19 is sent into the document reading unit 10 and is transported through a predetermined transport path Rt1. A registration roller 53 is provided on the conveyance path Rt1, and the original is captured by the registration roller 53 and positioned at the leading end of the original, and then conveyed to the original reading position at a predetermined timing.
On the other hand, the document being conveyed is exposed while the copy lamp unit 12 is stopped at a predetermined stop position (document reading position). The process of reading the document image by the reflected light from the document obtained by this exposure is as described above.
The document whose image has been read in this way is discharged to the document discharge unit 18.

  Further, as shown in FIG. 2, the image forming apparatus Z includes a communication unit 61 that performs communication control with a predetermined host device via a communication line, and an operation / display that is an input / output unit including a liquid crystal touch panel and the like. 62, an image memory 63 that is a storage means for print data received from the host device and image data read from a document, a setting memory 64 that is a storage means for various setting information, a CPU and its peripheral devices (ROM) A control unit 65 that controls the entire image forming apparatus Z by executing processing according to a predetermined program stored in the ROM, and shading correction and data format (data type) of the image data And an image processing unit 66 for performing various types of image processing such as conversion. The control unit 65 controls the image processing unit 66, the image reading unit 10, the printing unit 30, the paper feeding unit 20, and the like. The set temperature for the heating roller 81 is controlled.

Next, the configuration of the heating roller 71 and the pressure roller 72 provided in the fixing device X will be described with reference to FIG.
The heating roller 71 provided in the fixing device X has the same configuration as the above-described conventional heating roller A (see FIG. 6A). That is, the heating roller 71 is a main heat source that mainly heats the first area W1 corresponding to the width of a small size sheet (for example, the sheet width during A4 longitudinal feeding or B5 longitudinal feeding) in the axial direction. The heater 81 and the sub heater 82 which is a heat source which mainly heats the other 2nd area | region W2 are included. The heat distribution (heat distribution characteristic) in the axial direction of the heating roller 71 of each of the main heater 81 and the sub heater 82 is the same as the characteristic shown in FIG.
Further, the fixing device X includes the pressure roller 72 that presses against a part of the peripheral surface of the heating roller 71 that rotates a sheet (recording paper) on which an unfixed toner image is formed. The toner image is heat-fixed on the sheet.
The heating roller 71 has a rotating shaft connected to a driving source 73 such as a motor via a driving gear 74, and the rotating shaft of the pressure roller 72 meshes with the driving gear 74 to rotate the heating roller 71. A driven gear 75 that rotates the pressure roller 72 by being driven is provided.
The pressure roller 72 is elastically urged against the heating roller 71 by an urging means (not shown) and forms a nip portion N1 at the contact portion.
Furthermore, temperature sensors 81a and 82a are provided in the first area W1 and the second area W2 of the heating roller 71, respectively. The temperature sensors 81a and 82a detect the detected temperatures. Input to the controller 65. The controller 65 sets a set temperature as will be described later for each of the first area W1 and the second area W2, and the detected temperatures of the temperature sensors 81a and 82a corresponding to the areas W1 and W2 are set to the set temperatures. The main heater 81 and the sub heater 82 are controlled (energization ON / OFF) so as to follow.

Next, temperature control of the heaters 81 and 82 by the control unit 65 when performing image fixing will be described with reference to FIGS. 4 and 5.
Here, FIG. 4 shows a series of image fixing for a small-size sheet (that is, a sheet that mainly passes only one of the two areas W1 and W2 (a part of a plurality of areas)). 6 is a trend graph showing the set temperatures of the regions W1 and W2 and the control states (ON / OFF) of the heaters 81 and 82 corresponding to the set temperatures. In the graph, the set temperature of the first region W1 is represented by a thick solid line, and the set temperature of the second region W2 is represented by a thick broken line. The thin broken line represents the detected temperature.
FIG. 5 is a flowchart showing a control procedure of the set temperature of the heating roller 71 by the control unit 65. Hereinafter, STEP1, STEP2,... Represent processing procedure (step) numbers.
First, when a print request (image formation request) is detected from the standby state (power saving mode state) (STEP 1), it is checked whether the paper passing size (sheet size) of the print request is large or small. (STEP2).
Here, when it is determined that the sheet is a large size sheet (that is, a sheet that passes through both the first region W1 and the second region W2), the set temperatures of the first region W1 and the second region W2 are set to The fixing temperature T1 is set (STEP 3). As a result, both the main heater 81 and the sub-heater 82 are energized, and the temperature of both areas W1 and W2 is increased from the power-saving set temperature T2 (standby temperature) to the fixing temperature T1 ( (Step 4).
Next, when the temperatures of both the regions W1 and W2 reach the fixing temperature T1, the control unit 65 executes image processing by the image processing unit 66 and a series of printing processing by the printing unit 30 (STEP 5). While checking the presence or absence of the next printing process (STEP 6), the printing process (STEP 5) is repeated until all (a series of) printing processes are completed.
When a series of printing processes is completed (when there is no next printing), the set temperatures of both the regions W1 and W2 are changed to the power-saving set temperature T2 (standby temperature) (STEP 7).
As a result, the temperature adjustment operation of the control unit 65 turns off the energization of the heaters 81 and 82 (main and sub) (STEP 8), and the temperature of the regions W1 and W2 is set to the power saving time. When it is confirmed that the temperature has decreased to the set temperature T2 (standby temperature) (STEP 9), the state shifts to a standby state (power saving mode).

On the other hand, when it is determined in STEP2 that the sheet is a small size sheet (that is, when a series of image fixing is performed on a sheet that mainly passes only a part of the plurality of areas W1 and W2). First, the set temperature of the first area W1 and the second area W2 is set to the fixing temperature T1 (STEP 10).
As a result, both the main heater 81 and the sub-heater 82 are energized, and the temperature of both areas W1 and W2 is increased from the power-saving set temperature T2 (standby temperature) to the fixing temperature T1 ( (Step 11).
Next, when the temperatures of both the regions W1 and W2 reach the fixing temperature T1, the control unit 65 causes the image processing unit 66 to perform image processing and a series of printing processing by the printing unit 30 (STEP 12).
Here, the range of H1 in FIG. 4 represents a state of shifting from STEP 10 to STEP 12. That is, similarly to the conventional fixing device shown in FIG. 7, the set temperatures of the regions W1 and W2 are set from the power-saving set temperature T2 (shown as standby temperature in FIG. 4) to the fixing temperature T1 (in FIG. 4, The heater 81 and 82 are controlled by the controller 65 so that the detected temperatures of the areas W1 and W2 follow the set temperatures. Then, printing (image formation) starts after the temperatures of the areas W1 and W2 follow the fixing temperature T1, and image fixing starts accordingly.

Further, the control unit 65 repeats the printing process (STEP 12) until the completion of all (series) printing processes while checking the presence or absence of the next printing process (STEP 13). Each time fixing (printing) is executed, the set temperature of the second region W2 (that is, the set temperature of the sub heater 82) is sequentially lowered by one step (STEP 14 and STEP 15).
Here, the range of H2 in FIG. 4 represents a state in which the processing of STEP12 to STEP15 is repeated.
That is, the control unit 65 sets the set temperature of the first area W1 (an example of the partial area) to the fixing temperature T1 until the end of printing (end of image fixing), and the main heater 81 ( While adjusting the temperature by an example of a heat source corresponding to the partial area), in parallel with this, according to the number of sheets on which image fixing is performed continuously (every predetermined number of sheets), the second area W2 The set temperature in one example of another region other than a part of the region is sequentially decreased from the fixing temperature T1, and the temperature is adjusted by the sub heater 82 (an example of a heat source corresponding to the other region). Here, the control unit 65 is an example of the temperature adjusting means when passing through the other region. This is also the same as the conventional fixing device shown in FIG.

When a series of printing processes is completed (when there is no next printing), the control unit 65 (an example of the heating stop unit) sets the set temperatures in the areas W1 and W2 (an example of the plurality of areas). Is set to a predetermined base temperature Tx that is lower than the temperatures T3 and T4 of both the regions W1 and W2 at the end of a series of image fixing (Tx <T3 & Tx <T4) and lower than the power-saving set temperature T2 (standby temperature). (STEP 16), by adjusting the temperature by the heaters 81 and 82 (an example of the plurality of heat sources), the energization of the heaters 81 and 82 is turned off (heating stopped state) (STEP 17). At the same time, the rotation of the heating roller 71 is stopped (illustrated). Further, the controller 65 checks whether or not the temperatures of both the regions W1 and W2 have reached the base temperature Tx (STEP 18).
Here, the range of H3 in FIG. 4 represents a state in which the processing of STEP16 to STEP18 is being executed.
Next, when the temperature of both the regions W1 and W2 reaches the base temperature Tx (time Px in FIG. 4) (that is, after the heating by the control unit 65 is stopped), the control unit 65 The set temperatures W1 and W2 are set to the power-saving set temperature T2 (standby temperature) lower than the fixing temperature T1 required for image fixing (STEP 19).
Accordingly, the control unit 65 (an example of the power saving temperature adjusting means) adjusts the temperatures of the first region W1 and the second region W2 to the power saving set temperature T2 by the heaters 81 and 82. .
Then, when it is confirmed (STEP 20) that the temperature of each of the areas W1 and W2 has risen to the power-saving set temperature T2 (standby temperature), the process shifts to a standby state (power-saving mode).
Here, the range of H4 in FIG. 4 represents the state in which the processing of STEP19 and STEP20 is being executed.

  As described above, heating is stopped by stopping the heating by the plurality of heaters 81 and 82 (a plurality of heat sources) in the heating roller 71 that has stopped rotating after a series of image fixings (STEP 17). Since the temperature gap between the nip portion of the heating roller 71 (the pressure contact portion with the pressure roller 72) and the other portions is relaxed (suppressed), the power saving set temperature T2 is passed thereafter. When the temperature is raised to the fixing temperature T1 (STEP 19 and STEP 10), it is possible to prevent the portion that was the nip portion during the stop from becoming an abnormally high temperature.

In the above-described embodiment, after a series of image fixing for a small size sheet (mainly a sheet that passes through only the partial area), the set temperatures of the plurality of areas W1 and W2 are set in series. Is set to the base temperature Tx that is lower than the temperatures T3 and T4 of both the regions W1 and W2 at the end of image fixing and lower than the set temperature T2 during power saving, and accordingly, by the heaters 81 and 82 (a plurality of heat sources). All the heating by the heaters 81 and 82 is stopped by adjusting the temperature.
However, the method of stopping all the heaters 81 and 82 after the end of a series of image fixing is not limited to this.
For example, at the end of a series of image fixing, the control unit 65 (an example of the heating stop unit) causes the first area W1 (an example of the partial area) or the second area W2 (an example of the other area). It is checked whether one temperature (one of T3 and T4) is equal to or lower than the power-saving set temperature T2, and if one is equal to or lower than T2, both (all) areas W1 and W2 Each set temperature is set to the base temperature Tx that is lower than both the temperatures T3 and T4 of the first region W1 and the second region W2 at the end of a series of image fixing and lower than the power-saving set temperature T2. It is also conceivable that the heating by both heaters 81 and 82 is stopped by adjusting the temperature by the heaters 81 and 82.
Alternatively, at the end of a series of image fixing, it may be possible to forcibly stop (energize off) both the heaters 81 and 82 for a certain period of time sufficient to alleviate the temperature gap.

Further, the temperature difference (T2−T3) between the power-saving set temperature T2 and the base temperature T3 is a variation width (maximum) of the surface temperature of the heating roller 71 due to variations in the heat amount of the heaters 81 and 82. It is desirable to set larger than (temperature difference).
For example, when the variation width of the surface temperature of the heating roller 71 is about ± 2 ° C. to 5 ° C., (T2-T3) is set to about 5 ° C. to 10 ° C.
This makes it possible to easily detect the sheet size when paper is passed (passing through the sheet), and further, the temperature difference between the set temperature during power saving and the base temperature indicates that the device is in a standby state after printing is completed. As a result, it is possible to easily determine which heat source of the plurality of heat sources should be turned on and off with respect to the optimum temperature of the heating roller (the set temperature during power saving) when the energy saving mode is set.
In the above-described embodiment, the plurality of areas mainly heated by each of the plurality of heaters included in the heater 71 includes a first area W1 corresponding to an area through which a predetermined small-size sheet passes, and other areas. However, the present invention is not limited to this, and the heat source (heater or the like) mainly heats each of three or more regions (for example, three regions corresponding to a small size, a medium size, and a large size). ), The region corresponding to the region through which the sheet passes is regarded as the first region W1, and the other region is regarded as the second region W2, and the control is considered.

  The present invention can be used for a fixing device in an image forming apparatus.

1 is a side sectional view showing an overall configuration of an image forming apparatus Z on which a fixing device X according to an embodiment of the present invention is mounted. 2 is a block diagram illustrating a schematic configuration of a main part of the image forming apparatus Z. FIG. 3 is a schematic cross-sectional view of a heating roller and a pressure roller of the fixing device X. FIG. 6 is a trend graph showing a set temperature of each region of the heating roller and a control state of each heater with respect to the temperature in a series of image fixing in the fixing device X. FIG. 6 is a flowchart showing a control procedure for a set temperature of a heating roller of the fixing device X. 6 is a schematic cross-sectional view of a heating roller A provided in a conventional fixing device and a graph showing heat distribution characteristics of a heater. 6 is a trend graph showing a set temperature of each region of a heating roller and a control state of each heater with respect to the temperature when performing a series of image fixing in a conventional fixing device. 6 is a graph schematically showing the temperature distribution in the circumferential direction of the pressure roller when the temperature increase from the power saving mode state to the fixing temperature in the conventional fixing device is completed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image reading part 18 ... Document discharge part 20 ... Paper feed part 30 ... Printing part 31, 53 ... Registration roller 32 ... Photosensitive drum 33 ... Laser scanning unit 34 ... Charging unit 35 ... Developing tank 36 ... Transfer unit 40 ... Discharge Paper section 61 ... Communication section 62 ... Operation / display section 63 ... Image memory 64 ... Setting memory 65 ... Control section 66 ... Image processing section 71 ... Heating roller 72 ... Pressure roller 81 ... Main heater 81a ... Temperature sensor in the first area 82 ... Sub-heater 82a ... Second region temperature sensor W1 ... First region W2 ... Second region X ... Fixing device Z ... Image forming device T1 ... Fixing temperature T2 ... Power-saving set temperature (standby temperature)
Tx: Base temperature STEP1, STEP2, ... Processing procedure (step)

Claims (5)

A fixing device for fixing an image by pressing a sheet on which an unfixed image is formed on a part of the peripheral surface of a rotating heating roller including a plurality of heat sources that mainly heat each of a plurality of different regions,
Heating stop for stopping all heating by the plurality of heat sources in the heating roller that has stopped rotating due to the end of image fixing for a period until each temperature of the plurality of regions falls to a predetermined base temperature after a series of image fixing ends Means,
A power saving adjusting means for adjusting each temperature of the plurality of regions to a set temperature during power saving lower than a fixing temperature required for image fixing by the plurality of heat sources after a heating stop period by the heating stopping means; And
It said base temperature, in the series of the plurality of areas all constant Chakusochi Ru lower temperatures der than low and the power saving setting temperature than the temperature at the end of the image fixing,
In a case where the heating stop means is after the end of the series of image fixing for a sheet mainly passing only a part of the plurality of regions, the set temperature of the plurality of regions is set to the base temperature. And performing temperature adjustment with the plurality of heat sources to stop heating by the plurality of heat sources during a period until each temperature of the plurality of regions falls to the base temperature. Fixing device to do. A fixing device for fixing an image by pressing a sheet on which an unfixed image is formed on a part of the peripheral surface of a rotating heating roller including a plurality of heat sources that mainly heat each of a plurality of different regions,
Heating stop for stopping all heating by the plurality of heat sources in the heating roller that has stopped rotating due to the end of image fixing for a period until each temperature of the plurality of regions falls to a predetermined base temperature after a series of image fixing ends Means,
A power saving adjusting means for adjusting each temperature of the plurality of regions to a set temperature during power saving lower than a fixing temperature required for image fixing by the plurality of heat sources after a heating stop period by the heating stopping means; And
In the fixing device in which the base temperature is lower than the temperature of all of the plurality of regions at the end of the series of image fixing and lower than the set temperature during power saving,
When the temperature of one of the plurality of regions and the other region other than the plurality of regions is equal to or lower than the power-saving set temperature at the end of the series of image fixing, By setting each set temperature in the region to the base temperature and performing temperature adjustment by the plurality of heat sources, heating by the plurality of heat sources is performed for a period until each temperature in the plurality of regions falls to the base temperature. A fixing device characterized in that all are stopped. 3. The fixing device according to claim 1, wherein the plurality of areas includes a first area corresponding to an area through which a predetermined small-size sheet passes and another second area. An image forming apparatus characterized by being provided with a fixing device according to any one of claims 1-3. In the control method of the fixing device that performs pressing the sheet is unfixed image on a part of the peripheral surface is formed of a heat roller that rotates in containing a plurality of heat sources that mainly heats the plurality of different regions image fixing There ,
Heating stop for stopping all heating by the plurality of heat sources in the heating roller that has stopped rotating due to the end of image fixing for a period until each temperature of the plurality of regions falls to a predetermined base temperature after a series of image fixing ends Process,
A power saving temperature adjusting step of adjusting each temperature of the plurality of regions to a set temperature at power saving lower than a fixing temperature necessary for image fixing by the plurality of heat sources after the heating stop period by the heating stopping step; Have
It said base temperature, the control method of the series of image fixing of Ru lower temperatures der than said plurality of regions all low and the power saving setting temperature than the temperature at the end Fixing device,
In the case where the heating stop process is after the end of the series of image fixing for a sheet mainly passing through only a part of the plurality of regions, each set temperature of the plurality of regions is set to the base temperature. And performing temperature adjustment with the plurality of heat sources to stop heating by the plurality of heat sources during a period until each temperature of the plurality of regions falls to the base temperature. Control method for fixing device.

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