JP2001305906A - Thermal fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a trouble in a thermal fixing device adaptable to ZESM. SOLUTION: In this thermal fixing device provided with a fixing roller and two heat sources incorporated in the fixing roller, a heating range by a 1st heat source for heating a main paper passing range in the longitudinal direction of the roller is divided into an end area near to the heating range by the 2nd heat source for heating the subordinate paper passing range and other central heating area, and heating intensity in an end heating area is limited to 30 to 50% of the heating intensity of the central heating area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device mounted on an image forming apparatus such as a printer, a facsimile, a copying machine, and the like.

[0002]

2. Description of the Related Art In an image forming apparatus, various types of sheets, such as A-row, B-row and letter-row, as well as irregular-size sheets, are to be recorded as image information. Any of these can be used to pass paper. Correspondingly, even in the thermal fixing device, even if the paper of all the sizes is continuously passed, the surface temperature of the fixing roller is controlled so as to be kept efficient and uniform. Is required. Therefore, it has been proposed and realized to provide a plurality of heaters to be built in the fixing roller.

[0003] In recent years, the demand for energy saving has been increasing daily, and the fixing unit of an image forming apparatus has reached a zero energy standby state when the apparatus is not operated. Mode (ZESM) is being adopted. In this ZESM, as in the conventional standby mode, the image forming apparatus can copy or copy instantly or almost instantly upon receiving an operation instruction. That is, in the ZESM state, only a minimal amount of energy is consumed to maintain electronic functions such as timers, counters and memory functions. In an apparatus called a so-called “future copier”, the ZE
SM is equivalent to sleep mode

[0004]

In such a ZESM-compliant thermal fixing device, the thickness of the fixing roller is extremely thin in order to shorten the start-up time. For example, φ40mm
The roller has a heat conduction of about 0.3 mm when made of an iron material and about 0.4 mm when made of an aluminum material. Also, as for the heater (heat source), since other parts are not operating in the stationary state at the time of start-up, a heater having the maximum effective output (eg, 1200 W) allowed by the apparatus is used. In such a case, it is performed to use the maximum effective output (for example, 860 W) that is allowed in the operating state by thinning out the lighting rate.

[0005] However, a configuration in which two different built-in heaters are used to heat different areas of the fixing roller and light distribution is divided by each heater (the first and second heaters have the same output per unit length) In this case, when small-size sheets such as A5 length and B5 length are continuously passed, the temperature of the roller portion in the outer area of the paper size area immediately rises, The temperature rising state is transmitted to the range of the temperature detecting means on the end side, and an abnormal temperature may be detected on the end side, or a problem such as welding of the roller due to an abnormal temperature rise may occur,
On the other hand, when a large-size sheet is continuously passed over the entire roller width, the temperature drop in the sheet area is large, and the temperature may be lower than the temperature required for fixing. This tends to be more remarkable as the ability of the heat fixing device to pass paper increases (for example, in an experiment, it was remarkable from a paper that can pass A4 width at a speed of 40 sheets / min or more). In addition, a temperature difference occurs in the roller inner peripheral surface portion, which is shaded with respect to each heater, as compared with the other portions. From the characteristic surface of both heaters, the temperature increase gradient of the end portion heater is lower, In the area where the roller is shaded on the roller end side by the center area heating heater, a difference of about 60 ° C. occurs, for example, as compared with the high area on the opposite side. The detection becomes slow and dull, so that the ZESM cannot be achieved, and of course, there is a danger that the member will melt on the opposite side.
Further, in performing the heater control based on the detection of the roller surface temperature, a delay (time lag) in response from the surface temperature detection to the heater control is present even in the case of a thin fixing roller. At startup, if the system is kept on standby until the target detection temperature is detected, the startup time until paper can pass will be outside the target time (designed startup time) or the heater off timing Due to the delay, the roller surface may be melted due to overshoot.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the ZESM-compatible thermal fixing device.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a heat fixing apparatus comprising a fixing roller and two heat sources built in the roller, wherein one of the heat sources is provided in a longitudinal direction of the roller. The first heat source for heating the main paper passing area in the direction, and the other heat source is the second heat source for heating the subordinate paper passing area. In a heat fixing device in which the driving of each heat source is individually controlled based on the detection result of the detecting means, the heating range of the first heat source is changed to an end region close to the heating range of the second heat source and another central heating region. This can be solved by limiting the heating intensity in the end heating zone to 30 to 50% of the heating intensity in the central heating zone.

The output of the first heat source and the output of the second heat source are divided into the first heat source: the second heat source = 6.25 in the full lighting state.
A ratio of 3.75 to 5: 5 is preferred. In addition, the heating range by the first heat source and the heating range by the second heat source have an overlapping portion, and the heating range by the second heat source is
It is more effective if it can be divided into an end area near the heating range by the first heat source and another central heating area, and the heating intensity at the overlapping portion can be adjusted to 30 to 50% of the maximum heating intensity. .

The output control of each heat source is made variable between the start-up and the sheet passing, and the sheet size at the time of sheet passing is only the heating target area of the first heat source. It is more preferable that the output of each heat source is changed depending on the size of the target area. In the case where the paper size is a size relating to the heating target areas of both heat sources, after a certain time of paper passing, the output of each heat source is further changed, or the paper size is applied only to the heating target area of the first heat source, and If the full width of the heating target area is not reached, the fixing control temperature is lowered from the initial state immediately or after a certain period of paper passing, or the fixing control temperature is gradually lowered during continuous paper passing. Good to do.

Each heat source and each temperature detecting means are arranged such that the distance between the second heat source and the temperature detecting means therewith is shorter than, ie, close to, the distance between the first heat source and the temperature detecting means therewith. If so, it is preferable. In order to ensure such an arrangement, the fitting holes of the support for fitting and holding the heat source ends are formed with different diameters in accordance with the end diameters of the respective heat sources. In addition, the overheat prevention device attached to each heat source is adjusted so that the interval between the first heat source and the overheating prevention device therewith is equal to the interval between the second heat source and the overheating prevention device therefor. It is good to arrange.

At the time of start-up, based on the temperature rise gradient during temperature rise, if the gradient is not less than a certain value, it is preferable that paper can be passed after a certain period of time. If the temperature rise gradient does not reach a certain value, the sheet is not allowed to pass, or the roller temperature after a certain period of time is detected. Until the heat source is reached, the paper can be passed by driving the heat source. It is more preferable that the heat source is turned off for a predetermined time when the fixing roller switches from the rotating state to the stopped state, and then the temperature is controlled again after that.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an example shown in the drawings. First, an image forming apparatus according to the present invention will be described. The configuration of the entire image forming apparatus is basically the same as that of the conventional image forming apparatus. In FIG. 1, around the photosensitive drum 21 which is an electrostatic latent image carrier, a charging device for charging the surface of the drum is provided. Charger 22, writing unit for forming latent image on uniformly charged surface (multi-beam writing)
23, a developing device 24 for forming a toner image by attaching a charged toner to the latent image on the drum surface, a transfer device (transfer conveyance belt unit) 25 for transferring the formed toner image on the drum to a recording sheet, A cleaning device 27 for removing residual toner on the drum and a charge removing device 28 for removing residual potential on the drum are sequentially arranged. In such a configuration, when image formation is performed in N / P (negative / positive), the photosensitive member 21 whose surface is uniformly negatively charged by the charging charger 22 is replaced with the writing unit 23.
To form an electrostatic latent image, and the developing device 24 forms a toner image. The toner image is transferred to the transfer belt 29.
The transfer device 25 includes a paper feed bank 26 formed by combining a tandem tray, a universal tray, a fixed tray, and the like at the lower part of the apparatus from the surface of the photosensitive drum 21.
Alternatively, the image is transferred onto the recording sheet conveyed from the horizontal paper feed tray. The recording sheet electrostatically attached to the photosensitive drum 21 at the time of this transfer is separated from the photosensitive drum 2 by a separation claw.
Separated from 1. The unfixed toner image on the recording sheet is fixed on the recording sheet by the fixing device 30.
On the other hand, the toner remaining on the photosensitive drum 21 without being transferred is removed and collected by the cleaning device 27.
The photosensitive drum 21 from which the residual toner has been removed is initialized by the charge removing lamp 28, and is used for the next image forming process.

Next, a fixing device 30 according to the present invention will be described with reference to FIG.
Will be described. Although the following description will be made on the assumption that the paper passing reference is at the center in the longitudinal direction of the roller, the present invention can be easily applied to the reference based on the end. As shown, two heaters 2a and 2a are attached to the fixing roller 1 against which the pressure roller 4 is pressed.
b is built in. On the surface of the fixing roller 1, there are provided two thermistors 3a and 3b corresponding to the above-mentioned two heaters, in addition to the separation claw 5 for preventing the paper from being wound around at the time of discharging the paper. Further, thermostats 6a and 6b, which are devices for preventing excessive temperature rise, are also arranged in contact with the surface of the fixing roller 1 so as to correspond to the two heaters. A thermal fuse may be used instead of the thermostat.

As can be understood from FIG. 3, the two heaters are provided for the first area for the central area corresponding to the main sheet passing area.
A second heater 2b for the heater 2a and an end area corresponding to a sub-sheet passing area. The two thermistors are a central area thermistor 3a and an end area thermistor 3b. The thermostat also has a thermostat 6 for the central area.
a and the end region thermostat 6b. Each solid state relay (SS
Power supply to each heater is controlled as is well known via R). In FIG. 4, which clarifies the positional relationship of each heater, thermistor, and thermostat in the roller circumferential direction,
Central area thermistor 3a and end area thermistor 3b
Are located at the same position in the circumferential direction of the roller and overlap each other. That is, for the heater built in the fixing roller 1 and arranged in a fixed state irrespective of the rotation of the roller, the end region thermistor 3b is longer than the center region thermistor 3a by a distance from the first heater 2a. The two heaters 2b are located so as to have a contact point with the fixing roller. As for the thermostat, the distance between the first heater 2a and the central region thermostat 6a is equal to the distance between the second heater 2b and the end region thermostat 6b.
By placing each of the two heaters in parallel and each thermostat at an equal distance, the thermostat is arranged at a position where the original radiant heat is not hindered by the presence of a heater other than the heater to be sensed. .

In order to properly hold the plurality of heaters in the fixing roller, as shown in FIG. 5, the diameters of the insulator portions at the ends of the first heater 2a for the center and the second heater 2b for the end are each φd. ₁ , φd ₂ (φd ₁ ≠ φd ₂ ; in the illustrated example, φd ₂
d ₁ <φd ₂ ). The diameters of the fitting holes of the heater bracket 8 for fitting and holding these insulator portions are also φD ₁ , φD ₂ (φD ₁ ≠ φ) corresponding to φd ₁ and φd ₂ , respectively.
D _2, in the illustrated case φD ₁ <φD _2). For this reason, each fitting hole can be fitted and installed only by the corresponding heater at 1 to 1 without fail. In order to properly maintain the positional relationship between the fixing roller 1 and each of the heaters 2a and 2b, the heater bracket 8 is, of course, directly or indirectly attached to the roller bearing.

The first heater 2a and the second heater 2b are arranged as shown in FIG.
, And the second heater 2b
Has a light-emitting portion (that is, a heating portion) only in a length range of 55 mm at both ends, and the first heater 2a has a center 210 m excluding both ends.
Although the light-emitting portion has a light-emitting portion in the length range of m, as shown in FIG. 30m each at both ends of the light emitting part of the length range
In the length range of m, the emission intensity is suppressed to about 30% to 50%. By performing such light distribution, it is possible to avoid an excessive rise in temperature at both end regions of the light emitting section of the first heater 2a even when continuous small-size paper is passed.

The first heater 2a and the second heater
With the heater 2b, the output distribution of each heater is set to 6.25: 3.
By setting the ratio to 75: 5: 5, the temperature distribution can be made more uniform. For example, when the lighting rate is 1.0 (at the time of startup) and the total output of both heaters is 1200 W, the first heater is allocated to 750 W and the second heater is allocated to 450 W.
Both heaters are set so that the temperature distribution becomes uniform within a range of 600 W each. As an example, the first heater for the center area is 650 W, and the second heater for the end area is 55 W.
As shown in FIG. 7, at the time of sheet passing, first, the sheet width is detected at the start, and the sheet is supplied to the first heater 2a.
If the size applies to both the second heater 2b and the second heater 2b, for example, A3 or A4 size, the lighting rate is 0.72, that is, the first heater 468W and the second heater 396W, and the detected paper size is the first heater. 2a, the lighting rate of the first heater is 553 W of 0.85,
Control is performed so that the lighting ratio of the heater can be switched to a combination of output ratios of 0.56 and 308 W.

Further, by setting the lighting rate to 0.72, which is the same, and performing the sheet passing with the first heater 468W and the second heater 396W, the time from when the sheet is started to when the temperature returns to a suitable temperature can be reduced. When the temperature returns to that level and stabilizes, the fixing temperature does not become uniform if the same ratio is maintained.
out 2) is the first to correct it.
By switching the lighting ratio of the heater to a combination of the output ratio of 553 W of 0.85 and the lighting ratio of the second heater to 308 W of 0.56, it is possible to stabilize the fixing temperature distribution during continuous operation of the ZESM fixing device. Become.

When the detected sheet size is applied only to the first heater, as described above, the first heater 553W,
When the output ratio is switched to the output ratio of the second heater 308W, but the paper continues for a certain period of time thereafter (Time out in FIG. 7).
5), and further detects the sheet size. If the sheet is narrower than the width of the first heater 2a, the fixing set temperature is set to
Control is performed so that both the center and the end are lowered by 10 degrees. With such control, it is possible to suppress a rise in the temperature outside the paper area at the time of a small size (postcard, A6, B5T, etc.), to detect an abnormal temperature at the end side, or to prevent the rollers from being welded due to the actual abnormal temperature. To prevent.

Further, if the paper continues to be passed for a certain period of time (corresponding to Time out 3 and 4 in FIG. 7) for any paper type, control is performed so that the fixing set temperature is further lowered at both the center and the end. I do. With such control, the temperature rise outside the paper area during continuous paper passing is suppressed,
Prevents problems such as meltdown and bearing lock.

On the other hand, temperature control for avoiding delay in response to temperature detection in the above configuration will be described below. In the flowchart of FIG. 8, when the power is turned on, t = 0 (S1), the surface temperature T1 after t1 seconds is detected (S2), and the temperature T2 after t2 seconds is detected (S3).
T2-T1 is determined and this temperature gradient is constant (for example, 20
Degrees) or more (S4), after a certain time (Time out, S
In 5), copying is permitted (S6) to avoid a response delay.
If the temperature gradient is not equal to or higher than the predetermined value in the determination of T2-T1, it is notified that the temperature is abnormal and that copying is not allowed (S7), and a defect such as disconnection of the heater can be found at an early stage.

In order to avoid malfunctions in the event of abnormal detection when the heater is in short supply due to voltage fluctuations in the supply power source or when the room temperature is extremely low, it is difficult to start up in the ZESM mode in advance. In the flowchart of FIG. 9, the temperatures T1 and t2 after t1 seconds from the time when the power is turned on.
If the temperature gradient of the temperature T2 after 2 seconds is not equal to or more than the predetermined value, the temperature T3 after t3 seconds is further detected (S7), and if the temperature reaches a predetermined temperature (eg, 160 ° C.) (S8), copying is permitted. (S9). If the temperature has not reached the certain temperature, it is notified as an abnormality and copying is disabled (S10).

Further, when the fixing operation is terminated and the rotation of the roller is stopped from the rotation state of the fixing roller when the copying operation is started and the paper is passed, the pressure roller and the heat loss at the time of the paper passing are considered at the time of the paper passing. Since a large amount of heat is supplied to the roller, if the roller is stopped as it is and the OFF timing of the heater is delayed, a sharp rise in temperature will occur.
Therefore, as shown in FIG. 10, after the fixing is completed, the fixing control temperature value is temporarily lowered to a normal temperature (for example, 20 ° C.) so that the heater does not need to be turned on, and a fixed time (for example, 0.
After 5 seconds), control is performed again to return the fixing control temperature to the original state. Thus, it is possible to avoid problems such as surface melting due to overshoot due to a rise in temperature when the rotation of the fixing roller is stopped after the completion of paper feeding.

In addition to the suppression of the light emission intensity at the end of the first heater for the central region, the light emission intensity of the second heater for the end region at the boundary side end region with the first heater is also reduced. In addition, the emission intensity suppression region overlaps with the first heater end emission region while suppressing the temperature, so that the temperature at the boundary between the two heaters can be complemented, and the temperature can be easily maintained in that range. At this time, as shown in FIG. 11, the emission intensity in the overlapping range (oblique grid line portion) is set to 30% of the maximum emission intensity.
It is preferable to adjust to about 50% to obtain an improved type of the example shown in FIG. In order to form an overlapping range, the light emitting portion of the second heater is extended from 55 mm of the first example to, for example, 70 mm, and the extended range is set as a light emission intensity suppression region. In particular, such a configuration is, for example, 35 A4 size paper per minute.
It is preferable to apply the present invention to an apparatus that forms an image on about a sheet or less. Experiments show that with such a configuration, it is easier to keep the temperature on the roller surface uniform even when various paper sheets are passed continuously.
A more favorable result was obtained than the configuration of the first example. And
In such a configuration, output distribution, lighting rate change, and fixing temperature control of each heater are performed as described above.

[0025]

According to the present invention, the heating range by the first heat source for heating the main sheet passing area in the longitudinal direction of the roller is close to the heating area by the second heat source for heating the sub-sheet passing area. Divided into end area and other central heating area,
The heating intensity in the end heating zone is 30 times the heating intensity in the central heating zone.
Therefore, the surface temperature of the fixing roller can be kept uniform even when the paper of various sizes is continuously fed, even if the thermal fixing device is ZESM compliant, In this case, the temperature rises up to the temperature detecting means for the second heat source and the temperature rises to an abnormal temperature, and problems such as roller welding for abnormal temperature rise can be solved.

When the output of the first heat source and the output of the second heat source are fully lit, the first heat source: the second heat source = 6.25: 3.75 or more
The ratio of 5: 5 is an ideal heat source output distribution for keeping the temperature distribution of the roller uniform. Also the first
The heating range of the heating source and the heating range of the second heating source have an overlapping portion, and the heating range of the second heating source is divided into an end region close to the heating range of the first heating source and another central heating region. The heating intensity at 30 to the maximum heating intensity
When adjusted to 50%, for example, in the case of an image forming apparatus having a thin fixing roller compatible with ZESM and having a sheet passing speed of 35 sheets or less per minute,
In particular, it effectively acts on the temperature drop at the boundary when the roller width is full size.

The output control of each heat source is made variable between start-up and paper passing, and the paper size at the time of paper passing is only the heating target area of the first heat source. By configuring so that the output of each heat source is changed depending on the size of the target area, it is possible to avoid a problem due to the paper passing size while realizing the ZESM. In the case where the paper size is a size relating to the heating target areas of both heat sources, after a certain time of paper passing, the output of each heat source is further changed, or the paper size is applied only to the heating target area of the first heat source, and If the full width of the heating target area is not reached, the fixing control temperature is lowered from the initial state immediately or after a certain period of paper passing, or the fixing control temperature is gradually lowered during continuous paper passing. By doing so, it is possible to keep the surface temperature of the fixing roller uniform even when the paper is continuously fed.

If each heat source and each temperature detecting means are arranged such that the distance between the second heat source and the temperature detecting means for the second heat source is shorter than the distance between the first heat source and the temperature detecting means for the first heat source, the standing state can be achieved. It is possible to avoid a meltdown due to a rise in temperature more than expected due to a delay in raising time or a response delay. In addition, if the overheat prevention device attached to each heat source has the same interval between the first heat source and the overheating prevention device for the first heat source and the interval between the second heat source and the overheating prevention device for the same, Variations in operating time can be minimized, and smoke and ignition can be avoided in abnormal situations.

At the time of startup, based on the temperature rise gradient during the temperature rise, if the gradient is equal to or more than a certain value, if the paper can be passed after a certain period of time, the start-up time is over, and the surface of the fixing roller due to overshoot is caused. In addition, it is possible to provide a safer and more stable ZESM-compatible machine that can prevent problems such as melting of the steel. When the temperature rise gradient does not reach a certain value, it is possible to detect a defect such as disconnection of a heat source at an early stage by disabling the paper passing, and further detect a roller temperature after a certain time, and detect the detected temperature. If the value is equal to or greater than a fixed value, the heat source is driven until the fixing set temperature is reached so that paper can be passed. It is possible to avoid malfunction or the like of abnormality detection even under conditions where startup is difficult. When the fixing roller is switched from the rotation state to the stop state, the heat source is turned off for a predetermined time, and then the temperature is controlled again. Problems can be resolved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus according to the present invention.

FIG. 2 is a schematic sectional view showing a configuration of a heat fixing device according to the present invention.

FIG. 3 is a schematic diagram for explaining a heating area of a first heater and a second heater.

FIG. 4 is a diagram showing a positional relationship of each thermistor and each heater in a cross section of a fixing roller.

FIG. 5 is a partial schematic perspective view showing an example of mounting a heater end;

FIG. 6 is a graph showing a light emission distribution as a first example.

FIG. 7 is a flowchart illustrating a configuration in which the output of each heat source and the fixing control temperature are variable between startup and continuous paper feeding.

FIG. 8 is a flowchart illustrating control for permitting copying based on a temperature rise gradient at the time of startup.

FIG. 9 is a flowchart illustrating control for safely bringing out a copy-enabled state while avoiding a malfunction in abnormality detection even when the temperature rise gradient at the time of startup is not at a constant value.

FIG. 10 is a flowchart illustrating a control for avoiding a problem when the rotation of the roller stops after the end of the sheet passing.

FIG. 11 is a graph showing a light emission distribution as a second example.

[Explanation of symbols]

 Reference Signs List 1 fixing roller 2a first heater 2b second heater 3a, 3b thermistor 4 heating roller 5 separation claw

Continued on the front page F term (reference) 2H033 AA32 AA42 BA25 BA26 BA27 BA30 BA38 BB18 BB21 CA03 CA04 CA05 CA07 CA17 CA28 CA30 CA32 CA48 3K058 AA04 BA18 CA23 CA61 CA71 CB02 CE16 DA02 GA06

Claims (15)

[Claims] 1. A fixing roller and a fixing roller built in the roller.
A heat fixing device including one heat source, wherein one heat source is a first heat source for heating a main sheet passing area in a longitudinal direction of the roller, and the other heat source heats a subordinate sheet passing area. A heat fixing device, wherein a temperature detecting means is provided for each heat source, and the driving of each heat source is individually controlled based on a detection result by the detecting means. Is divided into an end region close to the heating range by the second heat source and the other central heating region, and the heating intensity in the end heating region is 30 to 5 of the heating intensity in the central heating region.
A heat fixing device characterized by being limited to 0%. 2. The distribution of the outputs of the first heat source and the second heat source is determined as follows: first heat source: second heat source = 6.25: 3.75 to 5: 5.
The heat fixing device according to claim 1, wherein the ratio is adjusted to: 3. The heating range of the first heat source and the heating range of the second heat source are overlapped with each other, and the heating range of the second heat source is changed to an end area near the heating range of the first heat source and other central heating. 3. The heat fixing device according to claim 1, wherein the heating intensity at the overlapping portion is adjusted to 30 to 50% of the maximum heating intensity. 4. The output control of each heat source is made variable between startup and paper passing, and the paper size at the time of paper passing is only the size of the first heat source to be heated. The heat fixing device according to any one of claims 1 to 3, wherein an output of each heat source is changed depending on the size of the heating target area. 5. The thermal fixing device according to claim 4, wherein when the paper size is a size corresponding to the heating target areas of both heat sources, the output of each heat source is further changed after a fixed time of paper passing. apparatus. 6. The fixing control temperature is reduced from an initial state immediately or after a certain period of paper passing when the paper size covers only the heating target area of the first heat source and does not cover the entire width of the heating target area. 5. The method according to claim 4, wherein
3. The heat fixing device according to claim 1. 7. The heat fixing device according to claim 4, wherein the fixing control temperature is reduced stepwise during continuous paper passing. 8. Each heat source and each temperature detecting means are arranged such that an interval between the second heat source and the temperature detecting means therewith is shorter than an interval between the first heat source and the temperature detecting means therewith. The heat fixing device according to any one of claims 1 to 3, wherein: 9. The heat source according to claim 8, wherein the fitting holes of the support for fitting and holding the heat source ends are formed to have different diameters in accordance with the end diameters of the respective heat sources. Fixing device. 10. The overheat prevention device attached to each heat source, wherein an interval between the first heat source and the overheat prevention device therefor and a distance between the second heat source and the overheat prevention device therefor are set. 9. The heat fixing device according to claim 8, wherein the heat fixing devices are arranged so as to be equal. 11. The apparatus according to claim 1, wherein, at the time of startup, based on a temperature rise gradient during temperature rise, if the gradient is equal to or more than a predetermined value, paper can be passed after a predetermined time. The heat fixing device according to claim 1. 12. The heat fixing device according to claim 11, wherein if the temperature rise gradient does not reach a predetermined value, paper passing is disabled. 13. When the temperature rise gradient does not reach a predetermined value, a roller temperature after a certain period of time is further detected, and if the detected temperature is equal to or higher than a predetermined value, a heat source is used until the fixing temperature is reached. The heat fixing device according to claim 11, wherein the heat fixing device is driven to enable paper passing. 14. The apparatus according to claim 1, wherein when the fixing roller is switched from the rotating state to the stopped state, the heat source is turned off for a predetermined time and then the temperature is controlled again. 3. The heat fixing device according to claim 1. 15. An image forming apparatus comprising the heat fixing device according to claim 1. Description: