JP2007086473A - Belt type fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt type fixing device which always controls the temperature of a fixing belt of a fixation part to specified temperature. <P>SOLUTION: A CPU 64 controls heat generation of a halogen heat generating device 57 in a heat roller 51 so that its temperature becomes the set temperature corresponding to the detected temperature by referring to a correspondence table of detected temperature and set temperature previously stored in a ROM 65 to obtain set temperature corresponding to detected temperature while monitoring the temperature of the heat roller part detected by a second temperature sensor 56 all the times so that the temperature of the heat roller rises when the temperature of a pressure roller part detected by a first temperature sensor 55 is low and the temperature of the heat roller part becomes lower than the previous temperature as the temperature of the pressure roller part rises. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a belt-type fixing device that sequentially controls the temperature of a heating roller in a belt-type fixing device in an electrophotographic image forming apparatus so as to always maintain the temperature of the fixing belt in a fixing unit at a predetermined temperature.

  2. Description of the Related Art Conventionally, there is an image recording apparatus that prints a color image (hereinafter also referred to as “printing”) using toner with an electrophotographic method. Color printing using toner is dedicated to the three subtractive colors of yellow (yellow), magenta (red), and cyan (blue), and the black portion of characters and images, etc., for one page of paper. A total of four toner images of black (black) are transferred onto a sheet, and the superimposed image is fixed on the sheet by applying heat and pressure in a fixing device to form a color image.

  Conventionally, as a fixing device in such an image forming apparatus, a pressure-heat roller pair system mainly including a heat roller and a pressure roller has been used. However, the fixing by the pressure roller pair method has a problem that the rising of the fixing temperature is slow, and in order to solve this problem, a belt type fixing device has been proposed and put into practical use.

  The belt-type fixing device can exhibit a fixing function that is extremely quick to rise by making the fixing belt thin and reducing the outer peripheral wall thickness of the heating roller. However, since the heat capacities of the fixing belt and the heating roller are small, the temperature of the fixing belt changes drastically depending on how heat is deprived in the fixing unit. As a result, fixing failure may occur under conditions that require a large amount of heat.

  FIG. 5 is a diagram showing a temperature change characteristic when attention is paid to a certain point on the fixing belt in the conventional belt-type fixing device. In the figure, the horizontal axis represents time, and the vertical axis represents a temperature at a certain point on the fixing belt.

In FIG. 5, when the fixing belt rotates, a certain point (correctly one line) of the fixing belt leaves the fixing roller and reaches immediately before the heating roller. This point is point A.
Thereafter, the fixing belt starts to be heated rapidly by the heating roller while passing over the heating roller, and rapidly rises to a predetermined temperature (160 ° C.). This point is point B.

  When the fixing belt continues to rotate and reaches a predetermined temperature (160 ° C.), a certain point of the fixing belt is separated from the heating roller, and the fixing roller and the pressure roller face each other through the fixing belt while slightly radiating heat. To the fixing unit. This point is point C.

While passing through the fixing unit, the fixing belt rapidly loses heat due to heat absorption from the fixing roller, the pressure roller, and the sheet, and the temperature is lowered. This point is point D.
In this state, a certain point of the fixing belt arrives again immediately before the heating roller. This point is point E. In this way, the fixing process proceeds while repeating points A to E (A≈E).

The temperature at which the fixing belt is lowered at point D varies depending on the temperature of the fixing roller, the temperature of the pressure roller, and the type of paper used.
In general, in an image forming apparatus, driving of a fixing device is stopped when not operating from the viewpoint of energy saving. While the operation is stopped, the fixing roller and the pressure roller are left in a state where heat cannot be absorbed from the fixing belt. Therefore, this standing time is also the heat radiation time of the fixing roller and the pressure roller.

If the operation is stopped for a long time, the fixing roller and the pressure roller are left standing for a long time, and the temperature further decreases. That is, the temperature of the fixing belt portion in contact with the fixing roller is lowered.
This temperature drop is heated so as to be recovered by raising it to a predetermined temperature by contact with the heating roller. If the degree of temperature decrease is too large, a certain point of the fixing belt is reached before the predetermined temperature is reached. Leaves the heating roller and causes a fixing failure in the fixing unit.

  In order to avoid this problem, increasing the heat capacity of the heating roller is one of the countermeasures. However, increasing the heat capacity of the heating roller means that the start-up is delayed. It is not preferable because it goes against the intended function.

In addition, as described above, the temperature of the fixing belt varies greatly depending on the type of paper used. However, since a large amount of heat is required particularly when a toner image is fixed on OHP paper, the amount of heat generated by the heating roller is normally set. In order to properly use paper and OHP paper, a method of controlling the amount of heat generated by the heating roller by measuring the temperature of the fixing belt in contact with the heating roller has been proposed. (For example, refer to Patent Document 1.)
FIG. 6A is a side sectional view schematically showing the structure of such a belt-type fixing device, and FIG. 6B is a temperature change of the fixing belt which has been clarified as a result of an experiment with this belt-type fixing device. It is a figure which shows a characteristic.

  First, as shown in FIG. 6 (a), in the belt type fixing device 1, the fixing belt 2 is stretched over the heating roller 3 and the fixing roller 4, and the fixing roller 4 is added via the fixing belt 2. The pressure roller 5 is in pressure contact. Further, a temperature sensor 6 is arranged on the outer periphery of the heating roller 3 and detects the temperature of the surface of the fixing belt 2.

  The heat generation of the heating roller 3 is controlled so as to reach a predetermined temperature based on the temperature detected by the temperature sensor 6. In this way, the temperature of the fixing belt 2 is directly monitored to control the heat generation of the heating roller 3, so that the temperature of the fixing belt 2 after passing through the heating roller 3 is stable.

The sheet 8 guided to the guide unit 7 and conveyed to the belt-type fixing device 1 is passed by the fixing roller 4 and the pressure roller 5 while passing through the fixing unit where the fixing roller 4 and the pressure roller 5 face each other. A pressure is applied and heat is applied from the fixing belt 2 to fix the toner image 9 transferred on the paper surface to the paper surface.
Japanese Patent Laid-Open No. 2001-282034

  However, in the configuration of the belt-type fixing device disclosed in Patent Document 1, the temperature up to the initial set temperature of the fixing belt is set when a large temperature drop occurs in the fixing roller and the pressure roller as described above. Even when the temperature sensor 6 detects the temperature, the temperature drops below the fixing temperature until the heated portion reaches the opposing portion (fixing portion) between the fixing roller and the pressure roller, which causes problems such as fixing failure. May occur.

  The temperature change characteristic of the fixing belt shown in FIG. 6B specifically shows the above problem. FIG. 4 (b) shows the temperature change of the fixing belt when the temperature of the fixing roller is raised to 80 ° C. and the heating roller is temperature controlled near 160 ° C. which is a predetermined fixing temperature. It is a figure which shows a characteristic.

  As shown in FIG. 6B, at the first and second rotations of the fixing belt, even if the temperature up to the initial set temperature of the fixing belt is detected by the temperature sensor 6, the fixing belt itself has a sufficient amount of heat. When the temperature reaches the fixing portion, the fixing belt temperature cannot maintain the predetermined fixing temperature of 160 ° C.

However, by continuing further rotation, the temperature at the time of reaching the fixing portion gradually increases and stabilizes at a predetermined fixing temperature of around 160 ° C.
The above shows the temperature change after restarting the process after a certain stop period of the image forming process. However, when heat is absorbed by a sheet having a large amount of heat absorption, the fixing process for the subsequent sheet is continuously performed. As a result, the fixing operation from the first rotation in FIG. Therefore, fixing failure is caused.

  An object of the present invention is to provide a belt-type fixing device that controls the temperature of a fixing belt in a fixing unit so as to always maintain a predetermined temperature in view of the above-described conventional situation.

The configuration of the belt type fixing device of the present invention will be described below.
The belt-type fixing device according to the present invention includes a heating roller, a fixing roller, an endless fixing belt stretched between the heating roller and the fixing roller, and opposed to the fixing roller via the fixing belt. In a belt-type fixing device including the fixing roller and a pressure roller that presses the fixing belt, an opposing portion between the fixing roller and the pressure roller is used to detect a surface temperature immediately after fixing of the fixing belt. A first temperature sensor disposed in the vicinity of the downstream side in the rotation direction, and a portion of the fixing belt in contact with the heating roller to detect the surface temperature of the fixing belt heated to recover the fixing temperature by the heating roller. A second temperature sensor arranged in the vicinity of the downstream side in the rotation direction, a surface temperature detection result immediately after fixing of the fixing belt output from the first temperature sensor, and the first temperature sensor. A temperature control device that controls the heat generation of the heating roller so as to reach a set temperature determined based on the detection result of the surface temperature of the fixing belt immediately after being heated by the heating roller. Configured.

  According to the present invention, it is possible to provide a belt-type fixing device that controls to always maintain the temperature of the fixing belt in the fixing unit at a predetermined temperature.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 is a cross-sectional view illustrating an internal configuration of a color image forming apparatus (hereinafter simply referred to as a printer) provided with a belt-type fixing device according to Embodiment 1 of the present invention.

  The printer 10 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 12, an intermediate transfer belt unit 13, a paper feeding unit 14, and a duplex printing transport unit 15. It consists of

The image forming unit 12 has a configuration in which four image forming units 16 (16M, 16C, 16Y, and 16K) are arranged in a multistage manner from right to left in FIG.
Of the four image forming units 16, the three upstream image forming units 16M, 16C, and 16Y are magenta (M), cyan (C), and yellow (subtractive three primary colors). A monocolor image is formed with the color toner of Y), and the image forming unit 16K forms a monochrome image with the black (K) toner mainly used for characters and dark portions of the image.

  Each of the image forming units 16 has the same configuration except for the color of toner stored in a toner container (toner cartridge). Accordingly, the configuration of the black (K) image forming unit 16K will be described below as an example.

  The image forming unit 16 includes a photosensitive drum 17 at the bottom. The peripheral surface of the photosensitive drum 17 is made of, for example, an organic photoconductive material. A cleaner 18, a charging roller 19, an optical writing head 21, and a developing roller 23 of the developing device 22 are arranged around the periphery of the photosensitive drum 17.

  The developing unit 22 applies magenta (M), cyan (C), yellow (Y), or black (K) toner to the upper toner container as indicated by M, C, Y, and K in FIG. An intermediate portion is provided with a toner replenishing mechanism for the lower portion.

  The developing unit 22 is provided with the developing roller 23 in the side opening at the lower portion thereof, a toner stirring member, a toner supply roller for supplying toner to the developing roller 23, and a toner layer on the developing roller 23 as a fixed layer. It has a doctor blade that regulates the thickness.

  The intermediate transfer belt unit 13 has an endless transfer belt 24 extending in a flat loop shape from substantially the left and right sides of the figure at the center of the main body, and the transfer belt 24 is stretched over the transfer belt 24. A driving roller 25 and a driven roller 26 are provided to circulate and move the belt 24 counterclockwise in the figure.

  The transfer belt 24 transfers the toner image directly to the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The whole is called an intermediate transfer belt unit.

  The intermediate transfer belt unit 13 includes a belt position control mechanism 27 in the loop of the flat loop-shaped transfer belt 24. The belt position control mechanism 27 includes a primary transfer roller 28 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 17 via the transfer belt 24.

  The belt position control mechanism 27 includes three primary transfer rollers 28 corresponding to the three image forming units 16M, 16C, and 16Y of magenta (M), cyan (C), and yellow (Y) as vertical support shafts. Rotate to the center with the same period.

  Then, the belt position control mechanism 27 performs transfer by rotating one primary transfer roller 28 corresponding to the black (K) image forming unit 16K at a rotational movement period different from the period of the three primary transfer rollers 28. The belt 24 is separated from the photosensitive drum 17.

  That is, the belt position control mechanism 27 sets the position of the transfer belt 24 of the intermediate transfer belt unit 13 in the full color mode (all four primary transfer rollers 28 are in contact with the transfer belt 24) and the monochrome mode (in the image forming unit 16K). Only the corresponding primary transfer roller 28 is in contact with the transfer belt 24) and all non-transfer modes (all four primary transfer rollers 28 are separated from the transfer belt 24).

  In the intermediate transfer belt unit 13, a belt cleaner unit is disposed further upstream of the image forming unit 16M on the uppermost stream side in the belt movement direction on the upper surface, and is flat and thin so as to be almost along the entire lower surface. The waste toner collecting container 29 is detachably disposed.

  The paper feed unit 14 includes two paper feed cassettes 31 arranged in two upper and lower stages, and in the vicinity of the paper feed opening (right side in the drawing) of the two paper feed cassettes 31, respectively, A feeding roller 33, a separating roller 34, and a standby conveyance roller pair 35 are disposed.

  In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 35, a secondary transfer roller 36 that is in pressure contact with the driven roller 26 via the transfer belt 24 is disposed, and a secondary transfer portion to the paper is arranged. Forming.

  A belt-type fixing device 37 is disposed downstream (upward in the drawing) of the secondary transfer portion, and the fixed sheet is carried out of the belt-type fixing device 37 further downstream of the belt-type fixing device 37. A pair of carry-out rollers 38 and a pair of paper discharge rollers 41 that discharge the discharged paper to a paper discharge tray 39 formed on the upper surface of the apparatus are provided.

  The duplex printing conveyance unit 15 includes a start return path 42a branched from the intermediate conveyance path between the carry-out roller pair 38 and the paper discharge roller pair 41 in the right lateral direction in the figure, and then an intermediate return path 42b bent downward. A terminal return path 42c that bends in the left lateral direction opposite to the above and eventually reverses the return sheet, and four return roller pairs 43a, 43b, 43c, 43d arranged in the middle of these return paths. ing.

The exit of the end return path 42 c communicates with a conveyance path to the pair of standby conveyance rollers 35 corresponding to the sheet feeding cassette 31 below the sheet feeding section 14.
In this example, a cleaning unit 45 and a take-in roller 46 are disposed on the upper surface of the intermediate transfer belt unit 13.

  The cleaning unit 45 comes into contact with the upper surface of the transfer belt 24 to scrape and remove the waste toner, and the take-in roller 46 takes over the waste toner removed by the cleaning unit 45 and is not shown in the drawing, and is temporarily stored in the belt cleaner unit. The accumulated waste toner is conveyed to the upper part in the dropping cylinder by a conveying screw and sent to the waste toner collecting container 29 through the dropping cylinder.

  Further, in order to bring the cleaning unit 45 into pressure contact with the transfer belt 24 with an appropriate pressure, a pressure roller 47 is provided on the intermediate transfer belt unit 13 side to press the transfer belt 24 toward the cleaning unit 45 from below. ing.

  As shown in FIG. 1, the printer 10 does not directly transfer a toner image onto a conventional sheet, but passes a transfer belt 24 to a sheet that is vertically conveyed to a secondary transfer unit by a standby conveyance roller pair 35. Thus, the toner image is transferred.

Therefore, it is possible to cope with a maintenance process for recovering from a problem such as a paper jam occurring in the paper transport path by simply opening the right side of FIG.
In addition, since troubles such as paper jams do not occur in the arrangement section of the kits, the operation for attaching and detaching consumables such as kits concentrated on the left side of FIG. 1 may be a small space that can be replaced in the longitudinal direction. It is configured as follows.

  Thereby, the dimension between kits is reduced as much as possible, and size reduction of the whole apparatus main body is achieved. Further, the optical writing head itself is also miniaturized and is configured closer to the photosensitive drum.

  FIG. 2 is an enlarged view of the belt-type fixing device 37 disposed in the printer having the above configuration. In the drawing, a secondary transfer portion including the transfer belt 24, the driven roller 26 and the secondary transfer roller 36 is partially shown below the belt type fixing device 37.

  As shown in the figure, the belt-type fixing device 37 includes a heat roller 51, a pressure roller 52, an endless fixing belt 53 stretched between the heat roller 51 and the pressure roller 52, and the fixing belt 53. The pressure roller 52 and the pressure roller 54 that presses the fixing belt 53 are disposed opposite to the pressure roller 52.

  The fixing belt 53 is formed by forming a silicon sponge layer having a thickness of 300 μm on a nickel base material having a thickness of about 35 μm, and further forming a PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether, universal) having a thickness of 30 μm on the surface thereof. It is an endless belt having a configuration in which a kind of fluororesin called resin) is attached.

The heat roller 51 is an aluminum hollow roller having a thickness of 1 mm, and a halogen heat generating device 57 is built therein.
The pressure roller 52 is configured by adhering a silicon sponge 59 around the metal core 58, and the pressure roller 54 facing the pressure roller 52 is also configured by adhering the silicon sponge 62 around the metal core 61. ing.

  As a result, the sheet onto which the toner image is secondarily transferred and carried upward into the belt-type fixing device 37 can be well gripped by the facing portion (fixing portion) between the pressure roller 52 and the pressure roller 54. It has become.

  Further, the belt-type fixing device 37 includes a first temperature sensor 55 disposed in the vicinity of the downstream side in the rotation direction indicated by arrows a and b in the drawing with respect to the opposing portion (fixing portion) between the pressure roller 52 and the pressure roller 54. The second temperature sensor 56 is provided in the vicinity of the downstream side in the rotation direction indicated by the arrow c in the drawing of the fixing belt 53 at the portion in contact with the heat roller 51.

  The first temperature sensor 55 is arranged to detect the surface temperature immediately after the fixing of the fixing belt 53, and the second temperature sensor 56 uses the reduced temperature after fixing as a predetermined fixing temperature. It is arranged to directly measure the surface temperature of the fixing belt 53 in the portion in contact with the surface of the heat roller 51 heated by the heat roller 51 to recover the heat.

  FIG. 3 is a block diagram of a fixing temperature control circuit in the printer 10 configured as described above. As shown in FIG. 3, the fixing temperature control circuit includes a print controller (hereinafter referred to as PR_CONT) 63, a CPU (central processing unit) 64, a ROM (read only memory) 65, a fixing SW (switch) power supply 66, and a belt type fixing. The apparatus 37 is comprised.

The belt-type fixing device 37 is supplied with heat roller power from a fixing SW power source 66, whereby the halogen heat generating device 57 shown in FIG. 2 of the heat roller 51 is driven to generate heat.
The surface temperature immediately after fixing of the fixing belt 53 is sent from the first temperature sensor 55 shown in FIG. 2 to the PR_CONT 63 as a pressure roller temperature signal 67 (actually, a surface temperature signal immediately after fixing of the fixing belt 53).

  Further, the surface temperature of the fixing belt 53 in contact with the surface of the heat roller 51 is also determined from the second temperature sensor 56 shown in FIG. Temperature signal) to PR_CONT63.

The PR_CONT 63 performs analog / digital conversion processing on each signal and outputs it to the CPU 64.
The CPU 64 compares the converted signal input from the PR_CONT 63 with a value set in advance in the ROM 65, and outputs a fixing control command to the PR_CONT side according to a program stored in the ROM 65 in advance.

  The PR_CONT 63 outputs a fixing temperature control signal to the fixing SW power supply 66 in accordance with the fixing control command input from the CPU 64. The fixing SW power supply 66 supplies heat roller power to the belt-type fixing device 37 based on the temperature control signal input from the PR_CONT 63.

  FIG. 4A is a diagram showing a correspondence table 69 between the detected temperature and the set temperature set in advance in the ROM 65, which is used for the above-described fixing control command. FIG. FIG. 6 is a diagram illustrating a temperature change characteristic of the fixing belt 53 that changes.

  3 and 4 (a) and 4 (b), the first temperature sensor 55 detects the temperature of the portion of the fixing belt 53 where the temperature has decreased after fixing, and the detection result is expressed as a pressure roller temperature signal 67 as PR. -The CPU 64 is notified via the CONT 63, and the surface temperature of the fixing belt 53 in the portion in contact with the surface of the heat roller 51 is notified as the heat roller temperature signal 68 to the CPU 64 via the PR-CONT 63 by the second temperature sensor 56. The

  The CPU 64 refers to the detected temperature / set temperature correspondence table 69 stored in advance in the ROM 65, so that the surface of the heat roller 51 has a set temperature corresponding to the detected temperature in a range matching the pressure roller temperature signal 67. The fixing SW power supply 66 is controlled via the PR-CONT 63 so as to change the set temperature of the heat roller 51 while sequentially detecting the surface temperature of the fixing belt 53 in the part in contact with the second temperature sensor 56, thereby The temperature of the heat roller 51 is controlled.

  According to the experiment, by changing the set temperature sequentially according to the reference of the correspondence table 69 of the detected temperature and the set temperature shown in FIG. 4 (a), the process shown in the temperature change characteristic of FIG. It has been found that the fixing temperature of the fixing device 37 is maintained in a stable state while changing upward and downward around a predetermined rated fixing temperature of 160 ° C.

  Here, the process shown in the temperature change characteristic of FIG. 4B will be further described with reference to the correspondence table 69 of the detected temperature and the set temperature of FIG. In the temperature change characteristic diagram of FIG. 4B, the pressure roller temperature signal 67 from the first temperature sensor 55 indicates that the temperature of the pressure roller portion is 80 ° C. at the start of the rotation operation of the fixing belt 53. The heat roller 51 is heated to 190 ° C. based on the pointer of the correspondence table 69 between the detected temperature and the set temperature.

  As a result, the fixing belt 53 enters the fixing portion in a state where the temperature is increased to around 180 ° C. Therefore, the fixing heat is deprived and the temperature is lowered to around 110 ° C., but it is not lowered to 90 ° C. as shown in the conventional example of FIG. This is because the initial heating is set large based on the temperature detection of the pressure roller portion.

  As described above, since the lowered temperature after the first fixing is around 110 ° C., the heat roller 51 is then heated to 185 ° C. again based on the pointer of the correspondence table 69 between the detected temperature and the set temperature. . Although this heating is 5 ° C. lower than the previous time, since the temperature after fixing has increased to around 110 ° C. as described above, the fixing belt 53 is kept in the fixing portion with the temperature rising to about 180 ° C. as in the previous time. storm in.

  Then, the temperature is lowered due to the loss of fixing heat, but this time the temperature of the pressure roller 52 is higher than the previous time, so the temperature drop is improved to around 120 ° C. Again, the heat roller 51 is heated to 180 ° C. based on the pointer of the correspondence table 69 of the detected temperature and the set temperature. Although this heating is also 5 ° C. lower than the previous time, since the temperature after fixing has increased to around 120 ° C. as described above, the fixing belt 53 is slightly lower than the previous time but sufficiently above 160 ° C. Rush into.

  While repeating this, as the temperature of the pressure roller portion after fixing rises, the temperature of the heat roller portion is decreased by 5 ° C., and the temperature of the pressure roller portion after fixing and the heating temperature of the heat roller portion eventually become the predetermined fixing temperature. Thus, a stable state can be maintained with a slight vertical fluctuation around 160 ° C.

  In this way, the heating temperature of the heating roller portion is controlled according to the temperature of the pressure roller portion, and the heating temperature of the heating roller is set high before the fixing belt portion whose temperature has decreased after fixing reaches the heating roller. Since the fixing temperature of the fixing belt is prevented from lowering to a predetermined temperature or less, there is no possibility of causing a fixing defect even immediately after the start-up or even when a sheet having a large heat capacity is continuously fixed.

FIG. 2 is a cross-sectional view illustrating an internal configuration of a printer including the belt-type fixing device according to the first exemplary embodiment. 2 is an enlarged view of a belt-type fixing device provided in the printer according to Embodiment 1. FIG. 3 is a block diagram of a fixing temperature control circuit of the printer in Embodiment 1. FIG. (a) is a diagram showing a correspondence table between detected temperatures and preset temperatures set in advance in the ROM used for the fixing control command of the fixing temperature control circuit, and (b) is a temperature change characteristic of the fixing belt that changes according to the fixing control command. FIG. It is a figure which shows the temperature change characteristic when paying attention to one certain point on the fixing belt in the conventional belt type fixing device. (a) is a side sectional view schematically showing the structure of a belt-type fixing device in another conventional example, and (b) is a diagram showing the temperature change characteristics of the fixing belt found as a result of experiments with the belt-type fixing device. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Belt type fixing device 2 Fixing belt 3 Heating roller 4 Fixing roller 5 Pressure roller 6 Temperature sensor 7 Guide part 8 Paper 9 Toner image 10 Printer 12 Image forming part 13 Intermediate transfer belt unit 14 Paper feeding part 15 Duplex printing transport unit 16 (16M, 16C, 16Y, 16K) Image forming unit 17 (17m, 17c, 17y, 17k) Photosensitive drum 18 Cleaner 19 Charging roller 21 Optical writing head 22 Developer 23 Developing roller 24 Transfer belt 25 Drive roller 26 Driven Roller 27 Belt position control mechanism 28 Primary transfer roller 29 Waste toner collection container 31 Paper cassette 32 Paper take-out roller 33 Feed roller 34 Rolling roller 35 Standby conveyance roller pair 36 Secondary transfer roller 37 Belt type fixing device 38 Unloading roller pair 39 Output tray 41 Paper discharge roller pair 42a Start return path 42b Intermediate return path 42c End return path 43a, 43b, 43c, 43d Return roller pair 45 Cleaning unit 46 Capture roller 47 Press roller 51 Heat roller 52 Pressure roller 53 Fixing belt 54 Pressure roller 55 First Temperature sensor 56 Second temperature sensor 57 Halogen heating device 58, 61 Core metal 59, 62 Silicon sponge 63 Print controller (PR_CONT)
64 CPU (central processing unit)
65 ROM (read only memory)
66 Fixing SW (switch) power supply 67 Pressure roller temperature signal 68 Heat roller temperature signal 69 Correspondence table between detected temperature and set temperature

Claims (1)

A heating roller, a fixing roller, an endless fixing belt stretched between the heating roller and the fixing roller, and the fixing roller and the fixing belt disposed opposite to the fixing roller via the fixing belt; In a belt-type fixing device provided with a pressure roller for pressing,
A first temperature sensor disposed in the vicinity of the downstream side in the rotational direction of the fixing roller and the pressure roller in order to detect the surface temperature immediately after fixing of the fixing belt;
A second temperature sensor disposed in the vicinity of the downstream side of the fixing belt in the rotation direction of the fixing belt in order to detect the surface temperature of the fixing belt heated to recover the fixing temperature by the heating roller;
The surface temperature detection result immediately after fixing of the fixing belt output from the first temperature sensor and the surface temperature detection result of the fixing belt immediately after being heated by the heating roller output from the second temperature sensor A temperature control device for controlling the heat generation of the heating roller so as to have a set temperature determined based on
A belt-type fixing device.

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