JP2013025188A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of effectively resolving fixing irregularity while saving energy.SOLUTION: When the number of small-size print sheets relating to a print job is more than a predetermined number of sheets, a control unit supplies a power from a power supply circuit to a thermoelectric transducer to cool a rotation axis-directional both ends of a fixing roller 200. After that, the control unit calculates a temperature difference ΔT between a temperature of the ends in the rotation axis direction of the fixing roller 200 and a temperature of a central part, using temperature sensors 230 and 231 and, as the temperature difference ΔT is greater, increases the power supplying amount to the thermoelectric transducer 220. When the print job is finished, the thermoelectric transducer 220 is connected to a charging circuit to accumulate an electric power in a storage battery.

Description

  The present invention relates to an image forming apparatus, and more particularly, to a technique for preventing uneven fixing due to heating of a non-sheet passing area.

  In an image forming apparatus that uses a fixing roller to thermally fix toner images on recording sheets of various sizes, if small size paper that is less than the fixing roller width is continuously fed, the recording sheet of the fixing roller does not contact. The temperature of the paper area is higher than the temperature of the paper passing area where the recording sheet comes into contact. In this state, when a recording sheet having a larger size is passed, fixing unevenness in which the fixing state is different between the passing area and the non-passing area of the small size paper occurs.

  For such problems, for example, using the Seebeck effect, a technique for driving a cooling fan with an electromotive force due to a temperature difference between a paper passing area and a non-paper passing area or switching a cooling duct fin has been proposed. ing. According to this technique, it is possible to cool the non-sheet passing region while saving energy with a simple configuration (see Patent Document 1).

JP 2008-040235 A

However, in the above prior art, cooling cannot be performed unless a sufficient temperature difference occurs between the paper passing area and the non-paper passing area. That is, since the cooling cannot be performed unless the non-sheet passing region is heated to some extent, the non-sheet passing region cannot be prevented from being overheated.
Specifically, in order to obtain power sufficient to drive a fan that cools the non-sheet passing area, the temperature difference between the sheet passing area and the non-sheet passing area needs to be 50 ° C. or more. However, the fixing unevenness to be eliminated can occur even when the temperature difference between the paper passing area and the non-paper passing area is less than 50 ° C. Therefore, in order to prevent fixing unevenness, it is necessary to cool the non-sheet passing area even if the temperature difference from the sheet passing area is less than 50 ° C.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can effectively eliminate uneven fixing while saving energy.

  In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus that uses a fixing rotator to thermally fix a toner image on a recording sheet having a plurality of paper-passing widths. Thermoelectric conversion element disposed near the end in the direction, power supply means for supplying power to the thermoelectric conversion element, and the temperature of the thermoelectric conversion element is lowered by power supply before the fixing rotator is overheated. And a power supply control means for cooling the battery.

In this way, the temperature of the thermoelectric conversion element is lowered prior to overheating of the fixing rotator and the end of the fixing rotator is cooled, so that fixing unevenness can be effectively prevented while saving energy.
In this case, the fixing rotator is provided with end temperature detecting means for detecting the temperature of the end portion in the rotation axis direction of the fixing rotator, and the power feeding control means is configured to detect the fixing rotator when the detected end temperature is higher than a predetermined temperature. You may cool the edge of. In this way, the non-sheet passing area can be cooled even if the temperature difference between the sheet passing area and the non-sheet passing area is not large as in the above-described prior art. It can be effectively prevented.

In addition, a central part temperature detecting means for detecting the temperature of the central part in the rotation axis direction of the fixing rotator is provided, and the power supply control means increases the amount of power supplied to the thermoelectric conversion element as the temperature difference between the end part and the central part increases. May be increased. In this way, overheating of the non-sheet passing area can be prevented more quickly.
In this case, the end temperature detecting means may detect the end temperature from the amount of power generated by the thermoelectric conversion element in the non-powered state. In this way, since the thermoelectric conversion element also serves as the temperature sensor, the number of parts constituting the image forming apparatus can be reduced.

The image forming apparatus according to the present invention further includes a size detecting unit that detects the sheet passing width of the recording sheet prior to fixing, and the power feeding control unit has the detected sheet passing width smaller than the effective heating length of the fixing rotator. In this case, the end of the fixing rotator is cooled. Even in this case, fixing unevenness can be effectively prevented while saving energy.
In this case, when the detected sheet passing width is smaller than the effective heating length of the fixing rotator and the number of continuously passing recording sheets is smaller than a predetermined number, a cooling prohibiting unit for prohibiting cooling by the power supply control unit is provided. Is preferable.

  In addition, a speed detection unit that detects the rotation speed of the fixing rotator may be provided, and the power supply control unit may increase the amount of power supplied to the thermoelectric conversion element as the rotation speed increases. Since the heat capacity of thick paper is larger than that of plain paper, it is necessary to make the fixing speed lower than that of plain paper. In the case of thick paper, if the cooling power of the thermoelectric conversion element is weakened, the temperature of the non-sheet passing area will be reduced. It can prevent falling too much.

  In the above case, the thermoelectric conversion element is preferably a Peltier element.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a cross-sectional view illustrating a main configuration of a fixing device 115. FIG. It is a block diagram which shows the main structures of a control system. It is a flowchart which shows operation | movement of the control part 112 for preventing the overheating of a non-sheet passing area | region. It is a flowchart which shows operation | movement of the control part 112 which concerns on the modification of this invention. It is a block diagram which shows the main structures of the control system which concerns on the modification of this invention. It is a flowchart which shows operation | movement of the control part 112 which concerns on the modification of this invention. It is a flowchart which shows operation | movement of the control part 112 which concerns on the modification of this invention.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 is a so-called tandem type multi-function peripheral (MFP), and includes a document reading unit 100, an image forming unit 110, and a paper feeding unit 130. . The document reading unit 100 optically reads a document placed on the document table tray 101 and conveys it by an automatic document feeder (ADF) 102 to generate image data. The image data is stored in the control unit 112 described later.

  The image forming unit 110 includes image forming units 111Y to 111K, a control unit 112, an intermediate transfer belt 113, a secondary transfer roller pair 114, a fixing device 115, a discharge roller pair 116, a discharge tray 117, a cleaner 118, and a timing roller pair 119. It has. The image forming unit 110 is equipped with toner cartridges 120Y to 120K that supply toners of Y (yellow), M (magenta), C (cyan), and K (black) colors.

  The image forming units 111Y to 111K receive toner supply from the toner cartridges 120Y to 120K, respectively, and form toner images of each color of YMCK under the control of the control unit 112. For example, the image forming unit 111Y includes a photosensitive drum 121, a charging device 122, an exposure device 123, a developing device 124, and a cleaning device 125. Under the control of the control unit 112, the charging device 122 uniformly charges the outer peripheral surface of the photosensitive drum 121. The exposure device 123 image-exposes the outer peripheral surface of the photosensitive drum according to the image data to form an electrostatic latent image.

  The developing device 123 supplies toner to the outer peripheral surface of the photosensitive drum 121 to develop (visualize) the electrostatic latent image. A transfer voltage is applied to the primary transfer roller 126, and the toner image on the outer peripheral surface of the photosensitive drum 121 is electrostatically transferred (primary transfer) to the intermediate transfer belt 113 by electrostatic adsorption. Thereafter, the cleaning device 125 neutralizes the outer peripheral surface of the photosensitive drum 121 with a neutralizing lamp, and then scrapes off residual toner with a cleaning blade.

Similarly, the image forming units 111M to 111K also form toner images of each color of MCK, and these toner images are primarily transferred onto the intermediate transfer belt 113 so as to overlap each other. The intermediate transfer belt 113 is an endless rotator, and rotates in the direction of arrow A to convey the primary transferred toner image to the secondary transfer roller pair 114.
The paper feeding unit 130 includes a paper feeding cassette 131 that stores the recording sheets S for each paper size, and supplies the recording sheets S to the image forming unit 110. The supplied recording sheet S is unloaded one by one in parallel with the intermediate transfer belt 113 conveying the toner image, and is conveyed to the secondary transfer roller pair 114 via the timing roller pair 119. The timing roller pair 119 includes a pair of rollers, and adjusts the timing at which the recording sheet S reaches the secondary transfer roller pair 114.

  The secondary transfer roller pair 114 is composed of a pair of rollers having a potential difference, and the roller pairs are pressed against each other to form a transfer nip portion. The toner image on the intermediate transfer belt 113 is electrostatically transferred (secondary transfer) onto the recording sheet S at the transfer nip portion. The recording sheet S to which the toner image is transferred is conveyed to the fixing device 115. Further, after the secondary transfer, the residual toner remaining on the intermediate transfer belt 113 is further conveyed in the direction of arrow A, then scraped off by the cleaning blade 118 and discarded.

  The fixing device 115 heats and melts the toner image and presses the toner image on the recording sheet S. The recording sheet S to which the toner image has been fused is discharged onto the discharge tray 117 by the discharge roller pair 116. The control unit 112 controls the operation of the image forming apparatus 1 including the above-described operation panel (not shown). The control unit 112 also transmits / receives image data to / from other devices such as a personal computer (PC) and accepts jobs.

In transferring the toner image, a transfer charger or a transfer belt may be used instead of the transfer roller. Further, when the residual toner on the intermediate transfer belt 113 is removed, a cleaning brush or a cleaning roller may be used instead of the cleaning blade 118.
[2] Configuration of Fixing Device 115 Next, the configuration of the fixing device 115 will be described.

  FIG. 2 is a cross-sectional view illustrating a main configuration of the fixing device 115. As shown in FIG. 2, the fixing device 115 includes a fixing roller 200, a pressure roller 210, a thermoelectric conversion element 220, and temperature sensors 230 and 231. The pressure roller 210 is biased by a biasing means such as a spring (not shown), so that the pressure roller 210 is pressed against the fixing roller 200 with a load of 300 N to 500 N, for example, and a fixing nip having a nip length of about 5 mm to 15 mm is formed. Form.

  The fixing roller 200 is rotationally driven in the direction of arrow B by a rotation driving unit (not shown). The pressure roller 210 is driven to rotate in the direction of the arrow D by the pressure frictional force with the fixing roller 200. Of course, the pressure roller 210 may be driven to rotate, and the fixing roller 200 may be driven to rotate. The recording sheet S is conveyed in the direction of arrow C and enters the fixing nip, whereby the toner T is heat-fixed.

  The fixing roller 200 is obtained by forming a release layer 202 on the outer peripheral surface of a hollow cylindrical cored bar 201. The cored bar 201 is made of a metal material such as aluminum (Al) or iron (Fe), and a halogen heater 203 is disposed therein. The thickness of the core bar 201 is preferably within a range of 0.1 mm to 5 mm, and more preferably within a range of 0.2 mm to 1.5 mm in consideration of weight reduction and shortening of warm-up time.

  The release layer 202 may be formed by attaching a tube made of a fluorine-based material such as PFA (Perfluorotetrafluoroethylene), PTFE (Polytetrafluoroethylene), ETFE (Ethylenetetrafluoroethylene), or the like. A material coated with a fluorine-based material may be used. The thickness of the release layer 202 is preferably in the range of 5 μm to 100 μm. Further, the contact angle with water is preferably 90 degrees or more, more preferably 110 degrees. Furthermore, the surface roughness is preferably in the range of 0.01 μm to 50 μm.

  As the fluorine-based tube, it is preferable to use commercially available PFA350-J, 451HP-J, and 951HPPlus (all manufactured by Mitsui DuPont Chemical). In order to increase the fixing nip width, an elastic layer may be provided between the metal core 201 and the release layer 202. The material of the elastic layer is preferably a material having elasticity and heat resistance, and examples thereof include silicone rubber and fluorine rubber. Although there is no limitation in particular in the thickness of an elastic layer, Usually, the inside of the range of 0.05 mm-2 mm is preferable.

The pressure roller 210 is obtained by sequentially laminating an elastic layer 212 and a release layer 213 on the outer peripheral surface of a hollow cylindrical cored bar 211. As a material of the cored bar 211, a heat resistant resin such as polyphenylene sulfide (PPS) may be used in addition to a metal material such as aluminum or iron.
The elastic layer 212 is formed from a member having heat resistance and elasticity. For example, a silicon sponge body is suitable as such a member. If a sponge body is used as the elastic layer 212, the heat insulation of the pressure roller 210 can be improved and the thermal efficiency of the fixing device 115 can be improved. When a silicon sponge material is used for the elastic layer 212, the thickness is preferably in the range of 2 mm to 15 mm, more preferably in the range of 3 mm to 10 mm. The hardness of the elastic layer 212 is preferably in the range of 10 degrees to 60 degrees, more preferably in the range of 15 degrees to 20 degrees with an Asker rubber hardness meter.

  The release layer 213 is a layer for enhancing the surface release property of the pressure roller 210, and a material that can withstand use at the fixing temperature is used. For example, a fluororesin such as silicone rubber, fluororubber, PFA, PTFE, FEP, or PFEP may be used. The thickness of the release layer 213 is preferably in the range of 5 μm to 100 μm, more preferably in the range of 10 μm to 50 μm. In addition, you may add a electrically conductive material, an abrasion-resistant material, a good heat conductive material etc. in the mold release layer 213 as a filler as needed. Further, in order to improve the interlayer adhesion, an adhesion treatment with a primer or the like may be performed.

  The thermoelectric conversion element 220 is a so-called Peltier element (for example, a thermo module manufactured by Ferrotec Co., Ltd. may be used), and both end portions in the rotation axis direction of the fixing roller 200, that is, small size paper is passed. In the case of the non-sheet passing area. Further, a temperature sensor 230 is disposed at a position different from the thermoelectric conversion element 220 in the circumferential direction, which is an end portion of the fixing roller 200 in the rotation axis direction.

The temperature sensor 230 detects the temperature of the end portion in the rotation axis direction of the fixing roller 200 (non-sheet passing region when a small size sheet is passed) in the outer peripheral surface of the fixing roller 200. The fixing device 115 is also provided with a temperature sensor 231 that detects the temperature of the central portion of the outer peripheral surface of the fixing roller 200 in the rotation axis direction of the fixing roller 200.
[3] Configuration of Control System The fixing device 115 that thermally fixes toner images on recording sheets of various sizes uses a thermoelectric conversion element 220 to cool a non-sheet passing area when continuously passing small size paper. To do. The configuration of the control system used for this purpose will be described.

  FIG. 3 is a block diagram showing the main configuration of the control system. As shown in FIG. 3, the control system 3 includes a control unit 112, a thermoelectric conversion element interface board (hereinafter referred to as “I / F board”) 310, a power supply device 320, a storage battery 330, and the like. The control unit 112 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, and a RAM (Random Access Memory) 303. The CPU 301 reads a program from the ROM 302 when the image forming apparatus 1 is turned on, and executes the program using the RAM 303 as a working storage area.

  The I / F board 310 includes a charging circuit 311, a power supply circuit 312, and a relay contact 313. The charging circuit 311 is a circuit for charging the storage battery 330 with the power generated by the thermoelectric conversion element 220 using the heat in the non-sheet passing region. In the present embodiment, power charged in storage battery 330 is used as a power source for operation panel 350. The image forming apparatus 1 displays information and accepts user instruction input via the operation panel 350.

  The power supply circuit 312 supplies DC power (for example, DC 24 V) from the power supply device 320 to the thermoelectric conversion element 220 to cool the fixing roller 200 by lowering the temperature of the thermoelectric conversion element 220. The power supply device 320 includes an SSR (Solid State Relay) 321, and the fixing roller 200 is maintained at a predetermined temperature by the CPU 301 performing on / off control.

The power supply circuit 312 is connected to a commercial power supply 342. When the main power switch 341 of the image forming apparatus 1 is turned on, power is supplied to each unit in the apparatus. The relay contact 313 connects the thermoelectric conversion element 220 to either the charging circuit 311 or the power supply circuit 312 by the CPU 301 turning on and off the transistor 352 and controlling the relay 351.
The CPU 301 controls the SSR 321 and the transistor 352 with reference to the temperature detected by the temperature sensors 230 and 231.

[4] Cooling Operation of Non-Paper Passing Area Next, an operation performed by the control unit 112 for preventing overheating of the non-paper passing area will be described.
FIG. 4 is a flowchart showing the operation of the control unit 112 for preventing overheating of the non-sheet passing area. As shown in FIG. 4, when the main power switch 341 of the image forming apparatus 1 is turned on, the control unit 112 turns on the transistor 352 and connects the thermoelectric conversion element 220 to the storage battery 330 (S401). As a result, the electric power generated by the thermoelectric conversion element 220 is stored in the storage battery 330.

  When the control unit 112 receives a print job (S402: YES), the control unit 112 checks whether or not the sheet passing width of the recording sheet related to the print job is smaller than the maximum effective heating length of the fixing roller 200. This is because it is determined whether or not there is a possibility that the non-sheet passing area is overheated by checking the presence or absence of the non-sheet passing area. Note that the maximum effective heating length of the fixing roller 200 refers to the maximum sheet passing width that the fixing roller 200 can fix.

  When the sheet passing width is smaller than the maximum effective heating length (S403: YES), the number of printed sheets related to the print job is confirmed. When the number of printed sheets is larger than the number (N) stored in advance in the ROM 302 (S404: YES), the thermoelectric conversion element 220 is connected to the power supply circuit 312 (S405). As a result, a DC voltage is applied to the thermoelectric conversion element 220, so that the thermoelectric conversion element 220 cools down and both ends of the fixing roller 200 in the rotation axis direction are cooled.

Thereafter, the control unit 112 calculates a temperature difference ΔT between the end portion temperature and the central portion temperature in the rotation axis direction of the fixing roller 200 detected using the temperature sensors 230 and 231 (S406), and the temperature difference ΔT is calculated. If it is equal to or greater than the predetermined value T1 (S407: YES), the control unit 112 controls the power supply circuit 312 to set the amount of power supplied to the thermoelectric conversion element 220 to the predetermined value W1 (S408).
If the temperature difference ΔT is less than the predetermined value T1 (S407: NO) and is equal to or greater than the predetermined value T2 (S409: YES), the amount of power supplied to the thermoelectric conversion element 220 is set to the predetermined value W2 (S410). If the temperature difference ΔT is less than the predetermined value T2 (S409: NO), the power supply amount is set to the predetermined value W3. The predetermined values T1, T2 and the predetermined values W1, W2, and W3 are stored in the ROM 302, and there is the following relationship between them.

T1> T2,
W1>W2> W3
Thereafter, if the print job is not completed (S412: NO), the process proceeds to step S406, and the above processing is repeated. When the print job is completed (S412: YES), the thermoelectric conversion element 220 is connected to the charging circuit 311 (S413), the process proceeds to step S402, and the above process is repeated.

In this way, before the non-sheet passing area of the fixing roller 200 is overheated, the thermoelectric conversion element 220 is cooled by supplying power and the cool air is supplied to the fixing roller 200. Can be prevented.
Further, as the temperature difference between the end portion and the center portion of the fixing roller 200 in the rotation axis direction, that is, the temperature difference between the non-sheet passing region and the sheet passing region is larger, a higher voltage is applied to the thermoelectric conversion element 220. As a result, the temperature is lowered to a lower temperature, so that the temperature of the non-sheet passing region of the fixing roller 200 can be quickly maintained at an appropriate temperature.

[5] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) In the above embodiment, the amount of power supplied to the thermoelectric conversion element 220 is controlled using two predetermined values T1 and T2 for the temperature difference ΔT between the paper passing area and the non-paper passing area. However, it goes without saying that the present invention is not limited to this, and control may be performed using one predetermined value or three or more predetermined values instead.

  Further, the necessity of cooling may be determined based on only the sheet passing width of the recording sheet without monitoring the temperature difference ΔT and without considering the number of printed sheets. FIG. 5 is a flowchart showing the operation of the control unit 112 according to this modification. As shown in FIG. 5, also in this modification, when the main power switch 341 is turned on, the control unit 112 connects the thermoelectric conversion element 220 to the storage battery 330 (S501).

  Thereafter, when a print job is received (S502: YES), if the sheet passing width of the recording sheet related to the print job is smaller than the maximum effective heating length of the fixing roller 200 (S503: YES), the thermoelectric conversion element 220 is turned on. The circuit 312 is connected (S504). When the print job is executed in this state and the print job is completed (S505: YES), the thermoelectric conversion element 220 is connected to the charging circuit 311 (S506), the process proceeds to step S502, and the above processing is repeated.

In this way, overheating of the non-sheet passing area of the fixing roller 200 can be prevented with a simpler configuration.
(2) In the above embodiment, the case where the necessity of cooling the non-sheet passing area of the fixing roller 200 is determined based on the sheet passing width of the recording sheet has been described, but it goes without saying that the present invention is not limited to this. Alternatively, the following may be used instead.

  FIG. 6 is a block diagram showing a main configuration of a control system according to this modification. As shown in FIG. 6, the control system 6 according to the present modification has substantially the same configuration as the control system 3 according to the above embodiment, while the control unit 112 includes a timer 304 and the I / F board 310 includes The difference is that an ammeter 601 is provided and the temperature sensor 230 that detects the end temperature of the fixing roller 200 is eliminated. This is because the amount of power generated by the thermoelectric conversion element 220 increases as the end temperature of the fixing roller 200 increases, and the amount of current generated by the thermoelectric conversion element 220 is detected instead of eliminating the temperature sensor 230. An ammeter 601 is placed.

  FIG. 7 is a flowchart showing the operation of the control unit 112 according to this modification. As shown in FIG. 7, when power is turned on, the control unit 112 connects the thermoelectric conversion element 220 to the storage battery 330 (S 701) and accepts a print job (S 702: YES). The amount of current I generated by the thermoelectric conversion element 220 is detected (S703). Then, when the predetermined value Ith is read from the ROM 302 and the current amount I is larger than the predetermined value Ith (704: YES), it is determined that the temperature of the non-sheet passing area of the fixing roller 200 is high. Then, the thermoelectric conversion element 220 is connected to the power supply circuit 312 to cool the non-sheet passing area of the fixing roller 200 (S705).

  Further, when the current amount I is equal to or less than the predetermined value Ith (704: NO), it is determined that the temperature of the non-sheet passing region of the fixing roller 200 is not so high, so the thermoelectric conversion element 220 is connected to the charging circuit 311. Connected and stored in the storage battery 330 (S706). After the processes in steps S705 and S706, a predetermined time is read from the ROM 302 and set in the timer 304 (S707).

  When the timer 304 times out (S708: YES), the thermoelectric conversion element 220 is connected to the charging circuit 311 (S709). If the print job is not completed (S710: NO), the process proceeds to step 703, and the current amount A series of processes, such as detecting I, is repeated. If the print job is completed (S710: YES), the process proceeds to step S702, and the above processing is repeated.

  (3) Although not particularly mentioned in the above embodiment, when thick paper is passed as a recording sheet in addition to plain paper, the heat capacity is larger than that of plain paper, and it is necessary to supply a sufficient amount of heat. Therefore, it is necessary to reduce the fixing speed (number of sheets passed per unit time). When the fixing speed is decreased, the same portion of the fixing roller 200 is cooled by the thermoelectric conversion element 220 over a longer time. In such a case, if the paper is cooled in the same way as plain paper, the temperature of the fixing roller 200 may be excessively lowered. For such a problem, for example, the following may be performed.

FIG. 8 is a flowchart showing the operation of the control unit 112 according to this modification. As shown in FIG. 8, also in this modification, the control unit 112 connects the thermoelectric conversion element 220 to the charging circuit 311 when the power is turned on (S801).
Thereafter, when a print job is received (S802: YES), if the sheet passing width of the recording sheet related to the print job is smaller than the maximum effective heating length of the fixing roller 200 (S803: YES), the thermoelectric conversion element 220 is turned on. The circuit 312 is connected (S804). When the fixing speed (paper passing speed) is low for reasons such as passing thick paper (S805: YES), the amount of power supplied to the thermoelectric conversion element 220 is reduced. Accordingly, since the fixing speed is low, it is possible to prevent the same portion on the outer peripheral surface of the fixing roller 200 from being overcooled.

When the fixing speed is high (S805: NO), the power supply amount is increased so that a sufficient amount of heat can be supplied (S807). Then, when the print job is executed in this state and the print job is completed (S808: YES), the thermoelectric conversion element 220 is connected to the charging circuit 311 (S809), the process proceeds to step S802, and the above process is repeated.
In this way, overheating of the non-sheet passing area can be prevented regardless of the fixing speed.

  (4) In the above embodiment, the case where the non-sheet passing region is cooled using the pair of thermoelectric conversion elements 220 has been described, but it is needless to say that the present invention is not limited to this. When passing the recording sheet, a plurality of pairs of thermoelectric conversion elements may be used in accordance with the width of each sheet. In this way, a more appropriate range of the fixing roller 200 can be effectively cooled.

  (5) In the above embodiment, the case where the electric power generated using the thermoelectric conversion element 220 is supplied to the operation panel 350 via the storage battery 330 has been described. However, the present invention is not limited to this. Needless to say, power may be supplied to devices other than the operation panel 350. For example, if power is supplied to the thermoelectric conversion element 220 during cooling of the non-sheet passing area, unlike the conventional technique, it is not necessary to match the power generation period and the cooling period in time. It can be cooled effectively prior to overheating.

(6) In the above-described embodiment, the case of so-called center sheet passing, in which the central portion of the fixing roller 200 is the sheet passing area, has been described as an example. However, it goes without saying that the present invention is not limited to this. The same effect can be obtained by applying the present invention to a so-called single-sided sheet passing region including an end on one side of the fixing roller 200.
(7) Although the halogen lamp type fixing device has been described as an example in the above embodiment, it is needless to say that the present invention is not limited to this, and other methods such as an electromagnetic induction heat generation method and a resistance heating element method can be used. Even if the present invention is applied to the fixing device, the same effect can be obtained.

  (8) In the above embodiment, the tandem type color multifunction peripheral has been described as an example. However, it is needless to say that the present invention is not limited to this, and the present invention may be applied to color machines other than the tandem type. . Further, the same effect as above can be obtained even if the present invention is applied to a single function machine such as a printer, a copying machine, or a facsimile machine.

  The image forming apparatus according to the present invention is useful as an apparatus for preventing uneven fixing due to heating of a non-sheet passing area.

1 ……………… Image forming device 110 ………… Image forming unit 115 ………… Fusing device 200 ………… Fusing roller 210 ………… Pressing roller 220 ………… ... thermoelectric conversion element 230, 231 ... temperature sensor 304 ......... timer 310 ......... thermoelectric conversion element interface board 311 ......... charge circuit 312 ......... power supply circuit 330 ............... Storage battery 601 ……………… Ammeter

Claims (8)

An image forming apparatus that uses a fixing rotator to thermally fix a toner image on a recording sheet having a plurality of sheet passing widths,
A thermoelectric conversion element disposed in the vicinity of the end in the rotation axis direction of the fixing rotating body;
A power supply means for supplying power to the thermoelectric conversion element;
An image forming apparatus comprising: a power supply control unit configured to cool the end portion of the fixing rotator by lowering the temperature of the thermoelectric conversion element by power supply before the fixing rotator is overheated. An end temperature detecting means for detecting the temperature of the end in the rotation axis direction of the fixing rotator,
The image forming apparatus according to claim 1, wherein the power supply control unit cools the end of the fixing rotating body when the detected end temperature is higher than a predetermined temperature. A central temperature detecting means for detecting the temperature of the central portion in the rotation axis direction of the fixing rotating body;
The image forming apparatus according to claim 2, wherein the power supply control unit increases the amount of power supplied to the thermoelectric conversion element as the temperature difference between the end portion and the central portion increases. The image forming apparatus according to claim 2, wherein the end temperature detecting unit detects the end temperature from the amount of electric power generated by the thermoelectric conversion element in a non-powered state. Provided with a size detection means for detecting the sheet passing width of the recording sheet prior to fixing,
The image forming apparatus according to claim 1, wherein the power supply control unit cools an end of the fixing rotator when the detected sheet passing width is smaller than an effective heating length of the fixing rotator. A cooling prohibiting unit that prohibits cooling by the power supply control unit when the continuous sheet passing number of the recording sheets whose detected sheet passing width is smaller than the effective heating length of the fixing rotator is smaller than a predetermined number; The image forming apparatus according to claim 5. A speed detecting means for detecting the rotational speed of the fixing rotating body;
The image forming apparatus according to claim 1, wherein the power supply control unit increases the amount of power supplied to the thermoelectric conversion element as the rotational speed increases. The image forming apparatus according to claim 1, wherein the thermoelectric conversion element is a Peltier element.

Images