JP2002268421A - Fixing device, method for controlling temperature of fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device in which all the problems of the prior technology such as fixing unevenness, wrinkles, and also a hot offset are solved by almost uniformizing temperature distribution in the longitudinal direction of a fixing roller. SOLUTION: In a fixing device 9 provided with a fixing roller 9A provided with a plurality of heating means 10 and 11 having different light distribution characteristics, the heating means 10 and 11 have flat regions and inclined regions adjacent to the flat regions as light distribution regions, and inclined regions in light distribution are provided at the same positions in the heating means 10 and 11, and the inclinations of the inclined regions at the same positions are almost equalized in the heating means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a fixing device and an image forming apparatus using the same, and more particularly to temperature control during fixing.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, a developed toner image transferred from a photosensitive member forming a latent image carrier is prevented from peeling off from a transfer medium. For this purpose, a fixing step is performed. In the fixing step, for example, an operation of permeating and fusing the toner to a sheet or the like as an image carrier in a state where the toner used for the developing process is melted by heating and pressing is adopted.

The fixing system includes a contact fixing system in which the heat source side member and the toner to be fixed are in direct contact, and a non-contact system using ambient heating. A typical example of the contact fixing method is a heat roller fixing method. The heat roller fixing method includes a pair of rollers that contact each other, one of which is used as a heating roller that directly contacts the toner, and the other is used as a pressure roller. A nip portion capable of pinching and conveying the sheet is formed at a position where the two rollers come into contact with each other. When the sheet passes through the nip portion, heat and pressure are applied to melt and permeate the toner into the sheet.

[0004] The heating roller has a heat source such as a halogen lamp or a nichrome wire inside, and is capable of fixing by directly contacting the toner. As a configuration of the fixing roller, besides a configuration in which a heat source is built in, there is also a configuration in which a heating element having a heating layer on a surface and capable of self-heating is used. The fixing roller maintains the heat source so that the surface temperature becomes a predetermined temperature by a temperature sensor provided on the peripheral surface, thereby stabilizing the amount of heat supplied to the sheet passing through the nip portion. Let me. The amount of heat is set in accordance with the heating time based on the moving speed of the sheet in the nip portion, and power control for the heat source is performed so as to obtain a heat source temperature corresponding to the amount of heat.

In recent years, energy saving has been advocated, and a fixing device which consumes power is no exception. For this reason, in the fixing device, a method has been adopted in which the power consumed during standby is reduced by lowering the temperature during standby.

However, if the temperature during standby is lowered, the time required for the fixing device to rise to a temperature at which the fixing device can be fixed, that is, a so-called warm-up time, becomes longer, and the efficiency in copying, printing out, or printing becomes poor. . In order to shorten the warm-up time, there is a method of reducing the heat capacity by reducing the thickness of the fixing roller. When the heat capacity of the fixing roller is reduced, the temperature on the surface of the fixing roller reacts sensitively.
In other words, in a place where heat radiation is easy due to a low heat capacity, heat dissipation proceeds, causing a temperature drop, and a temperature difference from a place where heat dissipation does not progress so much becomes remarkable. Therefore, the temperature tends to be non-uniform in the axial direction of the fixing roller, that is, in the sheet width direction. As a result, depending on the size and conveyance state of the heated member including the sheet passing through the nip portion, the fixing property may be deteriorated due to a change in the temperature distribution in the longitudinal direction.

The heated member includes not only the sheet but also the toner carried on the sheet, and the size of the sheet carrying the toner is, for example, when the image forming apparatus using the fixing device is a copying machine. A3 portrait, A4 portrait,
There are A4 width, B4 length, B4 width, B5 length, B5 width, and the like.
Of these sizes, setting the short axis direction of the sheet (corresponding to the width direction which is a direction perpendicular to the length direction of the sheet) in a state parallel to the axial direction of the fixing roller is a vertically long state, that is, In the state where the conveyance direction coincides with the longitudinal direction of the sheet, the longitudinal direction of the sheet (the length direction of the sheet) is set parallel to the axial direction of the fixing roller. This is a state where the width direction of the sheet matches.

When the heated member passes through the nip portion, the following problems occur due to the difference in the area facing the longitudinal direction of the fixing roller. When a small-sized heated member is passed through the nip portion, heat is consumed in a region where the heated member is opposed, but the fixing roller and the pressure roller are in a region where the heated member is not opposed. Due to the direct contact, heat is stored due to no consumption of heat to the member to be heated, and the temperature rises.

In the area where the temperature has risen, the temperature rise becomes more remarkable than the case where the temperature is controlled to the predetermined temperature, and as a result, the temperature may reach the predetermined temperature or more. For this reason, for example, after fixing an A4 size sheet, as in the case of fixing an A3 size sheet, passing a large size heated member after passing a small size heated member,
The temperature distribution in the longitudinal direction of the fixing roller in a large-sized heated member is not uniform, and there is a possibility that uneven fixing and wrinkles may occur in the heated member. In addition, in the region of an abnormally high temperature, the toner carried on the large-sized heated member newly passing through is excessively melted, and the viscoelasticity causes the toner to reversely transfer to the surface of the fixing roller, thereby causing a so-called hot offset phenomenon. It can happen.

Conventionally, as a method of solving such a problem, two or more heaters having different light distribution characteristics are used as a heating source, and the lighting ratio of the heater is changed between startup and passage of a heated member. There has been proposed a method in which the lighting ratio of the heater is changed according to the size of the member to be heated or the number of times of continuous fixing (for example, JP-A-5-165372 and JP-A-5-281877). JP, JP-A-6-11999, JP-A-6-193
62, JP-A-6-19363, JP-A-8-193
No. 220932, JP-A-11-167307).

[0011]

In general, when a plurality of heaters are used, there is a problem that if the light distributions of the heaters overlap, the light distribution at those portions becomes too strong. That is, when the light emitting regions corresponding to the light distribution are overlapped with each other, the temperature increases due to the overlapping of the light emission amounts at those portions. For this reason, in the method disclosed in the above-mentioned publication in which a plurality of heaters are used, the lighting ratio of the heater only switches between the rising time and the normal fixing operation as a reference. As a result, no measures have been taken against non-uniform temperature distribution in the longitudinal direction of the fixing roller.

In the method disclosed in the above publication,
When switching the lighting state of a plurality of heaters, it is necessary to provide a temperature sensor used for detecting the temperature distribution on the surface of the fixing roller by each heater at a position where the light distribution of each heater is the largest. However, the above publication does not disclose any light distribution characteristics in such a temperature sensor and a heater. Therefore, if the peak position in the light distribution of the heater is different from the position of the temperature sensor, the peak position of the light distribution cannot be detected.
As a result, the temperature of the heater at a position where the peak position cannot be detected abnormally rises, and the temperature distribution in the longitudinal direction of the fixing roller cannot be uniformly controlled.

If the temperature distribution in the longitudinal direction of the fixing roller is not uniform, as described above, fixing unevenness and wrinkles are generated on the member to be heated, and further, an abnormal image is obtained due to hot offset. The problem remains.

An object of the present invention is to substantially uniform the temperature distribution in the longitudinal direction of a fixing roller, which causes fixing unevenness, wrinkles, and hot offset in view of the above-mentioned problems in the conventional fixing device and image forming apparatus. Accordingly, an object of the present invention is to provide a fixing device and an image forming apparatus that can solve all of the above problems.

[0015]

According to the first aspect of the present invention,
A fixing roller provided with a plurality of heating means having different light distribution characteristics; and a pressing member provided in contact with the fixing roller, wherein the fixing roller and the pressing member sandwich a heated member containing toner. In a fixing device that fixes toner contained in a member to be heated by heat and pressure by conveying, the heating means has a flat area as a light distribution area and an inclined area adjacent to the flat area. An inclined region in the light distribution is set at the same position between the heating means, and the inclination of the inclined region at the same position is substantially equal between the heating means.

According to a second aspect of the present invention, there is provided a fixing roller provided with a plurality of heating means having different light distribution characteristics, and a pressing member provided in contact with the fixing roller. In a fixing device that fixes the toner contained in the heated member by heat and pressure by nipping and conveying the heated member including the toner by the pressure member, the heating unit includes a flat region as a light distribution region and a flat region as a light distribution region. An adjacent inclined region can be set, and the inclined region in the light distribution is located at the same position between the heating units, and each heating unit is related to a time average value that is a temporal average value of the amount of light emitted by each heating unit. It is characterized in that the sum of them is calculated so that they are set to be equal over the entire light emitting region of each heating means, and that the slopes of the inclined regions at the same position are substantially equal between the heating means.

According to a third aspect of the present invention, there is provided a first heating means having a high light distribution area at a central portion in the longitudinal direction, a second heating means having a high light distribution area at a position other than the center in the longitudinal direction, and a second heating means. A fixing roller that includes a temperature detecting unit that can detect a heating state from the heating unit, and that can control power supplied to the second heating unit based on a temperature detected by the temperature detecting unit; A fixing member provided in contact with the fixing member, and fixing the toner contained in the heated member by heat and pressure by nipping and conveying the heated member including toner by the fixing roller and the pressing member. In the above, the difference between the maximum value in the temperature distribution in the longitudinal direction on the surface of the fixing roller and the temperature in the center in the longitudinal direction on the surface of the fixing roller is such that hot offset occurs in the toner immediately after startup, and the longitudinal direction of the surface of the fixing roller The difference between the maximum value of the temperature distribution and the temperature at the center in the longitudinal direction of the surface of the fixing roller falls within a range that does not cause a hot offset at the time of the immediately following sheet passing, and the temperature of the surface of the fixing roller within the width of the recording medium of the maximum size is reduced. A temperature at which the power supplied to the second heating means is set to a temperature lower than the temperature detected by the temperature detection means at the time of start-up at which the temperature becomes higher than the temperature causing the fixing failure, and It is characterized by starting up.

According to a fourth aspect of the present invention, there is provided a first heating means having a high light distribution area at a central portion in the longitudinal direction, a second heating means having a high light distribution area at a position other than the center in the longitudinal direction, and a second heating means. A fixing roller that includes a temperature detecting unit that can detect a heating state from the heating unit, and that can control power supplied to the second heating unit based on a temperature detected by the temperature detecting unit; A fixing member provided in contact with the fixing member, and fixing the toner contained in the heated member by heat and pressure by nipping and conveying the heated member including toner by the fixing roller and the pressing member. In the above, the difference between the maximum value in the temperature distribution in the longitudinal direction on the surface of the fixing roller and the temperature in the center in the longitudinal direction on the surface of the fixing roller is such that hot offset occurs in the toner immediately after startup, and the longitudinal direction of the surface of the fixing roller The difference between the maximum value of the temperature distribution and the temperature at the center in the longitudinal direction of the surface of the fixing roller falls within a range that does not cause hot offset at the time of immediately following sheet passing, and the temperature of the surface of the fixing roller within the width of the largest size recording medium. At a time (second temperature) lower than the temperature (first temperature) detected by the temperature detecting means at the time of start-up of the heating means, which is now at a temperature higher than the temperature causing the fixing failure. The temperature is set to a value at which the electric power supplied to the second heating means is cut off, and the apparatus is started up.

According to a fifth aspect of the present invention, there is provided a first heating means having a high light distribution area at a central portion in the longitudinal direction, a second heating means having a high light distribution area at a position other than the center in the longitudinal direction, and a second heating means. A fixing roller that includes a temperature detecting unit that can detect a heating state from the heating unit, and that can control power supplied to the second heating unit based on a temperature detected by the temperature detecting unit; A fixing member provided in contact with the fixing member, and fixing the toner contained in the heated member by heat and pressure by nipping and conveying the heated member including toner by the fixing roller and the pressing member. In, the difference between the maximum value of the temperature distribution in the longitudinal direction of the fixing roller surface and the temperature in the longitudinal center of the fixing roller surface falls within a range that does not cause hot offset at the time of passing the paper immediately after, and the maximum size The temperature of the surface of the fixing roller within the width of the recording medium becomes higher than the temperature causing the fixing failure.At the time of the start-up, the temperature of the fixing roller becomes lower than the temperature detected by the temperature detecting means. 2 is characterized in that temperature control for setting a temperature at which power supplied to the heating means is cut off is executed.

According to a sixth aspect of the present invention, there is provided a first heating means having a high light distribution region at a central portion in the longitudinal direction, and a second heating means having a high light distribution region at a position other than the central portion in the longitudinal direction. A fixing roller that controls the power supplied to the heating unit based on the temperature of a temperature detecting unit installed near the end of the fixing roller, and a pressing member provided opposite to the fixing roller to form toner and toner. The maximum value of the temperature distribution in the longitudinal direction of the surface of the fixing roller and the length of the surface of the fixing roller in a fixing device that fixes the unfixed toner image to the toe image support by applying heat and pressure to the recording material composed of the toner image support The difference from the temperature at the center in the direction falls within a range that does not cause hot offset at the time of the immediately following sheet passing, and the temperature of the surface of the fixing roller is higher than the temperature that causes the fixing failure within the width of the recording medium of the maximum size. The temperature at which the power supplied to the second heating means is reduced to a temperature (second temperature) lower than the temperature (first temperature) detected by the temperature detection means at the time of start-up as described above. And start the launch,
After the temperature detected by the temperature detecting means reaches the second temperature, temperature control is performed to change the temperature at which power supplied to the second heating means is cut off to the first temperature.

A seventh aspect of the present invention is characterized in that the fixing device according to any one of the first to sixth aspects is used in an image forming apparatus.

[0022]

Embodiments of the present invention will be described below. Note that, in the embodiment described below, the case where the center in the width direction of the sheet conveyed to the fixing device is set as the sheet conveyance reference is intended, but the same applies to the case where the one-side reference is set as the target. Keep it.

FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus using a fixing device according to the present invention. The image forming apparatus shown in FIG. 1 is a laser printer, but is not limited thereto. It may be a facsimile machine or a printing machine. In FIG. 1, a laser printer 1 includes a highly conductive photoconductor 2 formed in a cylindrical shape as a latent image carrier.
It has.

Around the photosensitive member 2, a charging device 3, a writing device 4, a developing device 5, a transfer device 6, and a cleaning device for executing an image forming process along a clockwise rotation in FIG. 7 and a static eliminator 8 are arranged.

The photosensitive member 2 is charged by a charging device 3 during the rotation process.
When the writing device 4 forms an electrostatic latent image corresponding to image information, the developing device 5 subjects the electrostatic latent image to visible image processing using toner. The toner image subjected to the visible image processing is transferred to a sheet S fed at a registration timing from a sheet feeding device (not shown) at a transfer position constituted by the photoconductor 2 and the transfer device 6. .

The sheet S that has passed the transfer position is the sheet S
The toner image carried by the fixing device 9 fixed in the transport path is fixed and discharged. The photoreceptor 2 after the transfer removes the residual toner and residual charge by the cleaning device 7 and the charge removing device 8 and is uniformly charged by the charging device 3 to prepare for the next image formation.

FIG. 2 is a schematic diagram showing the structure of the fixing device 9. In FIG.
A, 9B. The roller 9A on the side facing the face drawing of the sheet S is a fixing roller having heating sources 10 and 11 therein, and the roller 9B facing this is configured as a pressing roller.

Heating source 1 built in fixing roller 9A
0 and 11 use a halogen lamp, respectively,
Heating regions are set for the heater 10 serving as a heating source for the central portion in the axial direction, and for the heater 11 serving as the second heating source for both ends in the axial direction other than the center in the axial direction. The heating temperature in each of these areas depends on the fixing roller 1
0 corresponding to each area on the peripheral surface
Is managed by the temperature sensor 12 and the second temperature sensor 13.

The rollers 9A and 9B in the fixing device 9 can rotate while being pressed against each other by a pressing means and a rotation driving means (not shown), and a nip capable of nipping and conveying the sheet S at a position where both rollers come into contact with each other. The toner image is fixed by applying heat and pressure to the toner image on the sheet S. Although not shown, the fixing device 9 includes means for applying a release agent to the surface of the fixing roller,
A separating claw for separating sheets, an excessive temperature rise prevention mechanism, a cleaning mechanism, a cover, and the like are provided.

First heater 10 and second heater 11
Is characterized in that the light emission distribution characteristics in the axial direction of the fixing roller 9A are different, the first heater 10 has a high light emission amount at the axial center portion and is low at the axial end portion, and the second heater 11 has an axial direction. The amount of light emission is low at the center and the flag is hidden at the axial end.
In FIG. 2, the corresponding portions of the first and second heaters 10 and 11 are intentionally emphasized by the resistance lines in order to emphasize the portions having high light emission amounts. FIG. 3 shows the light emission distribution of the first heater 10 in the axial direction, and FIG. 4 shows the light emission distribution of the second heater 11 in the axial direction. In FIGS. 3 and 4, the light emission distribution characteristics of each of the heaters 10 and 11 are shown by straight lines. In practice, however, a curve which is not a straight line but is approximately a straight line is shown. . As a method of making the emission distribution characteristics different, a method is employed in which the winding density of a halogen lamp is made different from place to place, and the heater is incident on the inner surface of a cylinder having a constant radius centered on the heater per unit length in a longitudinal direction thereof. Can be made different for each location.

The light distribution of the heater has a flat area and an inclined area. FIG. 5 shows the light distribution characteristics of the second heater 11 for explaining the flat area and the inclined area. In FIG. 5, a region indicated by a solid line with arrows at both ends is a flat region,
The other area is an inclined area. The flat area is an area where the light emission amount is substantially uniform in the longitudinal direction. Even if it is somewhat uneven, if the uniformity is relatively high compared to the surroundings,
The area is regarded as a flat area. The inclined area is outside the high light distribution flat area, and is caused by the effect that light emitted in the high light distribution flat area obliquely reaches the low light distribution area.

The first temperature sensor 12 shown in FIG. 2 is installed near the center of the fixing roller in the longitudinal direction (axial direction) so as to be in non-contact with the fixing roller 10. Measure the surface temperature. The reason why the fixing roller 10 is installed in a non-contact manner is to prevent the surface of the fixing roller 10 from being damaged. The second temperature sensor 12 shown in FIG. 2 is installed close to the axial end of the fixing roller 10 and measures the temperature of the surface of the axial end of the fixing roller 10. Second temperature sensor 1
Reference numeral 2 denotes a fixing roller 10 when the recording medium (sheet) having the maximum size that can be fixed is installed outside a region through which the recording medium passes.
The fixing roller 10 may be installed in a non-contact state.

Next, a method for controlling the temperature of the fixing device will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of a control unit for executing temperature control.
The main part of the control unit 14 is configured by a microcomputer. The input side is connected to first and second temperature sensors 12 and 13 via an I / O interface (not shown), and the first and second temperature sensors are connected to the output side. Two heaters 10 and 11 are connected.

In the control section 14 shown in FIG. 6, when output signals from the first and second temperature sensors 12 and 13 are inputted, the temperature information and other information such as the size of the recording medium are obtained. On / off control of the first and second heaters 10, 11 is executed based on the above.

When warming up the fixing device 9,
While both the first and second temperature sensors 12 and 13 have not reached the target temperatures, the ratio of the time during which the first heater 10 is turned on to the time during which the second heater 11 is turned on While maintaining the first and second values
Of the heaters 10 and 11 are turned on. While the first temperature sensor is over the target temperature, turn off the first heater 10,
While the second temperature sensor 13 is over the target temperature, the second
Heater 11 is turned off. The same applies to the case where the fixing device 9 is maintained at the temperature during standby.

When the sheet S is passed through the fixing device 9, the first heater 10 is turned on while the first and second temperature sensors 12 and 13 do not reach the target temperatures. While maintaining the ratio of the time during which the second heater 11 is turned on to the time during which the second heater 11 is turned on, both the first and second heaters 10, 11 or Power is supplied to only one of the two heaters 10 and 11. The first heater 10 is turned off while the first temperature sensor 12 exceeds the target temperature, and the second heater 11 is turned off while the second temperature sensor 13 exceeds the target temperature. Instead of such control, more complicated control may be performed in consideration of the temperature change speed detected by the temperature sensor and the past number of sheets passed.

Next, the configuration of a heater for generating an appropriate temperature distribution when a recording medium (hereinafter, referred to as a recording medium) such as a large-sized sheet S1 is passed will be described. In order to avoid fixing unevenness, it is desirable that the temperature is uniform in a region where the recording medium S1 passes.
To do this, you need to
The sum of the time averages of the light emission amounts of the two heaters needs to be uniform over the entire width of the large-sized recording medium S1 in the width direction. For example, a large-size recording medium S1
Is the size indicated by the solid line S1 with double-ended arrows in FIG. 7, the time average value of the light emission amount of the first heater 10 has the distribution indicated by the broken line P1 in FIG.
If the time average value of the light emission amount of the second heater 11 has the distribution shown by the solid line P2 in FIG.
The value obtained by adding the time average values of the light emission amounts of 0 and 11 has a distribution indicated by a solid line (P1 + P2) in FIG. Since the temperature distribution on the surface of the fixing roller 10 is similar to the light emission amount distribution, in the case of such a light emission amount distribution, heat shortage near both ends of the large-sized recording medium S1 is insufficient, and the large amount of heat is insufficient. Fixing failure occurs near both ends of the recording medium S1 of the size.

In the present invention, the light emission amounts of the heaters 10 and 11 are adjusted so that the temperature is uniform in the area where the recording medium S1 passes when the large-size recording medium S1 is passed. (Embodiment 1) The time average value of the light emission amount in the high light distribution region of the two heaters 10 and 11 whose high light distribution regions do not overlap each other is made equal, and the time average value of the light emission amount in the inclined region at that time. Were made equal by two heaters, and the position of the slope area was made equal by two heaters. FIG. 9 is a diagram for explaining the embodiment in this case, in which a solid line S1 with double-ended arrows is a line indicating the width of a large-size recording medium, and a dotted line P3 is , And the solid line P4 is the time average of the light emission amount of the second heater 11. Solid lines P5 and P6 with double-ended arrows indicate the inclined area of the heater. The inclined areas of the two heaters 10 and 11 are both in the range indicated by solid lines P5 and P6 with arrows at both ends. In this case, the value obtained by adding the temporal average values of the light emission amounts of the two heaters is as shown by the solid line (P3 + P4) in FIG. 10, and is uniform over the entire width of the large-sized recording medium S1. However, in the above description, it is necessary that the inclinations of the inclined regions of the two heaters located at the same position are opposite to each other. The condition is automatically satisfied if the high light distribution areas of the two heaters do not overlap each other. Therefore, in the following description, it is assumed that the inclinations of the inclined areas of the two heaters at the same position are opposite to each other. The word "gradient" is used without regard to the direction of the slope, without specifying it. That is, the expression that the gradients are equal does not imply that the directions of the gradients are equal, but simply means that the absolute values of the gradients are equal. If the magnitude of the time average value of the light emission amount in the high light distribution region is different, the gradient of the inclined region is different. Assuming that the light emission ratio of the second heater 11 is reduced and the time average value of the light emission amount in the high light distribution region of the second heater 11 is reduced, the distribution of the time average value of the light emission amount is as shown in FIG. The gradient of the time average value of the light emission amount in the inclined area of the second heater 11 (solid lines P5, P6, P5 ', and P6' in FIG. 11) is the same as that in the inclined area of the second heater 11 in FIG. It becomes gentler than the gradient. In FIG. 11, a solid line P3 indicates a time average value of the light emission amount of the first heater 10, and a solid line P4 'indicates a time average value of the light emission amount of the second heater 11. Therefore, equalizing the gradients of the above-described inclined regions by the two heaters 10 and 11 is based on the premise that the two heaters are compared with the same time average of the light emission amount in the high light distribution region.

When the light distribution in each of the heaters 10 and 11 is graphed by assuming that the light emission rate in the high light distribution area is 100%, each heater is prepared so that the gradient of the light emission rate in the inclined area becomes equal. By doing so, when the time average value of the light emission amount in the high light distribution region in the two heaters 10 and 11 is made equal, the gradient of the time average value of the light emission amount in the inclined region of the two heaters can be made equal. it can. (Embodiment 2) FIG. 22 is a diagram for explaining Embodiment 2, which is different from Embodiment 1 in that three heaters having different light emitting regions are provided. . Other configurations are the same as in the first embodiment. FIG.
In the above, the time average value of the light emission amount in the high light distribution region of the three heaters in which the high light distribution regions do not overlap each other is equal, the position of the inclined region is equalized by the two heaters, and the time of the light emission amount in the inclined region is equal. The gradient of the average value was made equal between the two heaters having the slope region at the same position. In FIG. 22, a solid line S1 with arrows at both ends is a line indicating the width of a large-sized recording medium, a two-dot chain line P3 is a time average value of the light emission amount of the first heater 10, and a solid line P4 is a second heater. 11 is the time average of the light emission amount, and the dashed line P5 is the time average of the light emission amount of the third heater. A solid line P7 with arrows at both ends is an inclined area of the first heater 10 and the second heater 11, and a solid line P8 with arrows at both ends is an inclined area of the first heater 10 and the third heater. Also in this case, the value obtained by adding the time average values of the light emission amounts of the three heaters is the same as that shown in (P3 + P4) in FIG. 10, and becomes uniform over the entire width of the large-size recording medium S1. . (Embodiment 3) First and second heaters 1 shown in Embodiment 1
Although 0 and 11 have only a high light distribution flat area and an inclined area, this embodiment is intended for a heater having a low light distribution flat area. In such a case, if the temporal average values of the light emission amounts in the high light distribution region of the two heaters are equalized, the high light distribution region of one heater and the flat region of the low light distribution of the other heater overlap each other. The light emission amount becomes larger than the other portions, and the total light distribution of the two heaters is not uniform. In this embodiment, in the high light distribution range of each heater, the sum of the time averages of the light emission amounts of the two heaters is made substantially equal, and the gradient of the time average value of the light emission amount in the inclined region is made almost equal between the two heaters. In addition, the positions of the inclined areas of the heaters were made substantially equal between the two heaters.

In FIG. 12, a solid line S1 with double-ended arrows is a line indicating the width of a large-size recording medium, and a dashed line P9 is
This is the average value of the light emission amount of the heater 10 over time, and the solid line P1
0 is a time average value of the light emission amount of the second heater 11. Solid lines P11 and P12 with double-ended arrows are the inclined areas of the first heater 10, and solid lines P13 and P14 with double-ended arrows are the inclined areas of the second heater 11. In the high light distribution region of the first heater 10 and the high light distribution region of the second heater 11, the light emission of the two heaters is adjusted so that the sum of the temporal average values of the light emission amounts of the two heaters becomes equal. In FIG. 12, a broken line P15 is a value obtained by adding the temporal average values of the light emission amounts of the two heaters. FIG. 13 shows a broken line P15, that is, a value obtained by adding the time average values of the light emission amounts of the two heaters.
Is a solid line (P9 + P10). As described above, the sum of the temporal average values of the light emission amounts of the two heaters becomes uniform over the entire area of the large-sized recording medium S1 in the width direction.

Here, the result of comparing the temperature control method described in the above embodiment with the temperature distribution when this method is not used will be described below. (Comparative Example 1) FIG. 14 shows a case where the position of the inclined region is different between the two heaters, unlike the present embodiment. The broken line L1 in FIG. The solid lines L2 and L3 with double-ended arrows are
Is the slope of the light distribution of the heater. Further, a solid line L4 is a time average value of the light emission mat of the second heater 11, and solid lines L5 and L6 with double-ended arrows are inclined regions of the light distribution of the second heater 11. The slopes (L2, L3) of the light distribution of the first heater 10 and the slopes (L5, L6) of the light distribution of the second heater 11 have the same width and slope but different positions. In this case, a value obtained by adding the time average values of the light emission amounts of the two heaters becomes a state shown by a solid line (L1 + L4) in FIG. 15 and has a peak at a position where the inclination regions of the light distribution of the two heaters overlap. It becomes uneven. (Comparative Example 2) FIG. 16 shows a case where the gradient in the inclined area is different between the two heaters unlike the case of the present embodiment, and a broken line L1 ′ in FIG. It is a time average value of the light emission amount, and solid lines L2 'and L3' with arrows at both ends are shown.
Is an inclined region of the light distribution of the first heater 10. In FIG. 16, a solid line L4 ′ is a time average value of the light emission amount of the second heater 11, and solid lines L5 ′ and L
6 ′ is an inclined region of the light distribution of the second heater 11. The slope (and thus the width) of the slope of the light distribution of the first heater 10 and the slope of the light distribution of the second heater 11
Are different. In this case, the value obtained by adding the temporal average values of the light emission amounts of the two heaters is a solid line (L1 ′ +
L4 '), the light distribution of the two heaters becomes non-uniform with a peak at the position where the slopes overlap.

Next, a description will be given of the structure and light distribution method of the heater so that an appropriate temperature distribution is obtained when the fixing roller is started. The light distribution of the two heaters 10 and 11 and the light distribution of the two heaters 10 and 11 are so set that the sum of the time averages of the light emission amounts of the two heaters 10 and 11 is uniform over the entire width direction of the large-sized recording medium S1. Even when the ratio of the time during which the power supply 11 is turned on is adjusted, a uniform temperature distribution cannot be obtained over the entire width direction of the large-sized recording medium S1 at the time of startup, and the temperature distribution is close to the high light distribution range of the second heater 11. The temperature distribution has a mountain. The reason is as follows.

In FIG. 18, when the first temperature sensor 12 reaches a target temperature at which the first heater 10 is turned off,
The temperature distribution in the axial direction of the fixing roller 9A is as shown by the solid line Q1 in FIG. 18, and the temperature at the position X1 where the second temperature sensor 13 is installed is the target temperature at which the second heater 11 is turned off. Since the temperature T1 is lower than T2,
This is because the second heater 11 continues to emit light until the temperature of the second temperature sensor 13 reaches the target temperature T2.
FIG. 18 shows only a half range in the axial direction of the fixing roller 9A.

The temperature of the second temperature sensor 13 is the target temperature T
2, the temperature distribution in the axial direction of the fixing roller 9A becomes as shown by a broken line Q2 in FIG. 18, and thereafter, the heat conduction in the longitudinal direction of the fixing roller and the heat radiation into the air cause the fixing roller 9A to emit heat. The temperature distribution in the axial direction of 9A becomes gentle, and after several minutes, the state shown by a broken line Q3 in FIG. 18 is obtained. In FIG. 18, the temperature T3 is the highest temperature in the temperature distribution indicated by the broken line Q3. If the sheet is passed while having a high peak and a temperature distribution as shown by a broken line Q2 in FIG. 18, a hot offset is caused.

In this embodiment, the target temperature for controlling the second heater 11 is adjusted so as to reduce the height of the peak of the temperature distribution in the axial direction of the fixing roller 9A when the fixing roller 10 is started. . Embodiment 4 Hereinafter, a control method for the target temperature will be described. The fixing device is started up by temporarily setting the target temperature T2 of the second temperature sensor 13, and the surface of the fixing roller 9A at the time when the time change of the surface temperature of the fixing roller 9A becomes small (about 5 minutes after the start of the start-up). By repeatedly measuring the peak value of the temperature in the axial direction (the temperature indicated by the symbol T3 in FIG. 18), the maximum value of the temperature distribution in the axial direction on the surface of the fixing roller 9A and the fixing roller 9A
The difference between the temperature at the center in the axial direction of the surface and the temperature of the surface of the fixing roller 9A within the range of causing no hot offset when the sheet is passed immediately after startup and within the range of the width of the sheet as the recording medium of the maximum size. The second temperature sensor 1 is set so that the temperature becomes higher than the temperature causing the fixing failure.
3 is determined.

Next, the temperature T2 is set to a predetermined temperature higher than the temperature T2 set as the target temperature of the second temperature sensor 13, in this embodiment, 60 ° C.
When the fixing device 9 was started up after resetting to a value lower by
The maximum value of the temperature of the surface of the fixing roller 9A at the time of start-up (the temperature indicated by T4 in FIG. 19: Q2) is the second value.
As shown in FIG. 20, the temperature decreased by about 10 ° C. as compared with the case where the target temperature of the temperature sensor 13 was T2. In FIG. 20, a chain line F1 indicates an axial direction of the surface of the fixing roller 9A when the temperature of the surface of the fixing roller 9A at the start-up when the target temperature of the second temperature sensor 13 is T2 indicates the maximum value. The solid line F2 indicates the temperature distribution, and the solid line F2 indicates the maximum value of the surface of the fixing roller 9A when the temperature of the surface of the fixing roller 9A is the highest when the fixing device is started up at a temperature 60 ° C. lower than the target temperature T2. It is an axial temperature distribution.
Ta was the highest temperature in the temperature distribution indicated by the dashed-dotted line F1, and Tb was the highest temperature in the temperature distribution indicated by the solid line F2. The difference between the two was about 10 ° C. as described above.

In this embodiment, the control section 14 shown in FIG. 6 executes temperature control according to the procedure shown in FIG.
In FIG. 23, a fixing roller is used as an expression of the fixing roller 9A. In FIG. 23, when the control is started, a tentative target temperature is set (ST1), and the fixing roller 9 is set.
A is started (ST2).

Next, the difference between the maximum value in the axial temperature distribution of the fixing roller 9A and the temperature at the axial center of the fixing roller 9A falls within a range where hot offset is not caused when the sheet is passed immediately after startup. Is determined (ST3). In FIG. 23, step S
In T3, the maximum value in the temperature distribution of the fixing roller 9A and T _M, the temperature at the axial center of the fixing roller 9A and T _CM, the difference between the temperature of a predetermined temperature difference T _H,
It is shown that it is determined whether or not the temperature difference (T _M −T _CM ) between the two is equal to or smaller than a predetermined temperature difference (T _H ).

When the temperature difference (T _M -T _CM ) is within the predetermined range, the surface temperature (T _MA ) of the fixing roller 9A is within the range of the width of the recording medium S1 of the maximum size, and the fixing failure is caused. whether or not higher than the temperature _{(T F)} to produce a _{(T MA}
> T _F ) is determined (ST4), and if the temperature is high, a temporary target value is set as the target temperature during operation (ST4).
5) After setting the target temperature at startup to a value lower than the target temperature during operation (ST6), the fixing roller 9A is started (ST7). (Embodiment 5) Next, another embodiment relating to temperature control will be described. In the fourth embodiment, the temperature about 5 minutes after the start of the start-up is determined when the target temperature of the second temperature sensor 13 is T2, and when the target temperature of the second temperature sensor 13 is T2.
21 is obtained when the fixing device 9 is set up at a value 60 ° C. lower than when the fixing device 9 is started. FIG.
In FIG. 1, a dashed-dotted line G1 indicates a temperature distribution in the axial direction of the surface of the fixing roller 9A about 5 minutes after the start of startup when the target temperature of the second temperature sensor 13 is T2, and a solid line G1.
2 indicates that the target temperature of the second temperature sensor 13 is 60 times higher than T2.
This is a temperature distribution in the axial direction of the surface of the fixing roller 9A about 5 minutes after the start of the start-up of the fixing device 9 when the fixing device 9 is started with the value set to a low value of ° C. In FIG. 21, a solid line S1 with double-ended arrows is a line for indicating half the length in the width direction of a large-sized recording medium.

When the fixing device 9 is started with the target temperature of the second temperature sensor 13 set to a value lower than T2, the temperature decreases at the position where the end of the large-size recording medium S1 passes, and With respect to a recording medium having a size, a fixing failure may be caused at the end.

In the present embodiment, when the fixing device is started up with the target temperature of the second temperature sensor 13 set to a value 60 ° C. lower than T2, the second temperature sensor 13 After a minute, the target temperature of the second temperature sensor 13 is returned to T2. As a result, the maximum value of the temperature of the fixing roller surface at the time of startup is lower by about 7 ° C. than when the target temperature of the second temperature sensor 13 is T2, and the fixing is performed about 3 minutes after the start of startup. The temperature distribution in the longitudinal direction of the roller surface is set to obtain substantially the same result as when the target temperature of the second temperature sensor 13 is T2.

In this embodiment, the above control is executed by the control unit 14 based on the flowchart shown in FIG. In FIG. 24, when the processing shown in FIG. 23 is executed and the target temperature for the fixing roller 9A is set and started, a predetermined time has elapsed from the time when the temperature detected by the second temperature sensor 13 has reached the target temperature. It is determined whether or not (ST8). In step ST8, if the predetermined time has elapsed from the time when the second temperature sensor 13 detects the target temperature, the target temperature of the second temperature sensor 13 is lowered and the start-up of the fixing roller 9A is continued. (T9, ST10).

[0053]

According to the first aspect of the present invention, the temperature distribution in the longitudinal direction corresponding to the axial direction of the fixing roller has a light distribution including a flat area and an inclined area, and the position of the high light flat area is high. In a plurality of different heating means, the time average value of the light emission amount in the high light distribution region is made equal between the heating means,
At least one heating unit has a slope region in the light distribution at substantially the same position, and the gradient of the slope region at the same position is made substantially equal between the heating units, so that the fixing roller is heated using a plurality of heating units. In this case, the energy input to the fixing roller can be made uniform in the longitudinal direction of the fixing roller. This makes it possible to make the temperature distribution in the longitudinal direction of the fixing roller uniform over the entire width of the large-sized recording medium.

According to the second aspect of the present invention, the temperature distribution in the longitudinal direction corresponding to the axial direction of the fixing roller has a light distribution including a flat area and an inclined area, and the position of the high light distribution flat area is different. In the fixing device which heats by the heating means, a slope region in the light distribution is provided at substantially the same position of two or more heating means, and the time average value of the light emission amount of each heating means is applied to all the heating means. Since the sum was made substantially equal at all high light distribution area positions, and the gradient of the inclined area at the same position was made substantially equal between the heating means, when the fixing roller was heated using a plurality of heating means, the high light distribution was obtained. Even if a heating unit having both a flat area of low light distribution and a flat area of low light distribution is included, the energy input to the fixing roller can be made uniform in the longitudinal direction of the fixing roller. Thereby, the temperature distribution in the longitudinal direction of the fixing roller can be made uniform over the entire width direction of the large-sized recording medium, thereby making it possible to prevent the occurrence of defective fixing and wrinkles.

According to the third and fifth aspects of the present invention, the first heating means having a high light distribution area at the center in the longitudinal direction corresponding to the axial direction of the fixing roller and the high light distribution area other than the center in the longitudinal direction. And a second heating unit having a second heating unit, wherein the power supplied to the second heating unit is controlled based on the temperature of a temperature detection unit installed at a position near an end of the fixing roller.
The difference between the maximum value of the temperature distribution in the longitudinal direction of the fixing roller surface and the temperature at the center in the longitudinal direction of the fixing roller surface falls within a range that does not cause a hot offset at the time of the immediately following sheet passing, and within the width of the recording medium of the maximum size. The power supplied to the second heating means is lowered to a temperature lower than the temperature detected by the temperature detection means at the time of start-up when the temperature of the surface of the fixing roller becomes higher than the temperature causing the fixing failure. Since the temperature is set at a temperature at which the fixing roller is turned off, the maximum value of the temperature of the surface of the fixing roller at the time of startup can be reduced. This makes it possible to reduce the risk of occurrence of hot offset.

According to the fourth and sixth aspects of the present invention, the first heating means having a high light distribution area in the central portion in the longitudinal direction corresponding to the axial direction of the fixing roller and the high light distribution area in addition to the central portion in the longitudinal direction. And a second heating unit having a second heating unit, wherein the power supplied to the second heating unit is controlled based on the temperature of a temperature detection unit installed at a position near an end of the fixing roller.
The difference between the maximum value of the temperature distribution in the longitudinal direction of the surface of the fixing roller and the temperature in the center of the surface of the fixing roller in the longitudinal direction is within a range in which hot offset is not caused at the time of paper passing immediately after startup, and the recording medium of the maximum size. The temperature of the fixing roller surface becomes higher than the temperature at which the fixing failure occurs within the width of the fixing roller.
The temperature at which the input power to the second heating means is set to a temperature at which the input power to the second heating means is turned off after the temperature detected by the temperature detection means reaches a second temperature. Is changed to the first temperature, so that in addition to the effect of the third aspect, it is possible to prevent a situation in which the temperature near the end of the fixing roller does not become sufficiently high. As a result, it is possible to reduce the possibility of causing a fixing failure at the end of a large-size recording medium.

According to the seventh aspect of the present invention, the temperature distribution in the entire longitudinal direction corresponding to the axial direction of the fixing roller is represented by:
Since it is possible to uniformize the entire size of the recording medium including the entire area in the width direction, fixing defects do not occur,
Furthermore, since a temperature at which a hot offset occurs within the range of the width of the recording medium is not set, occurrence of an abnormal image due to improper fixing or offset, and prevention of wrinkles on the recording medium can be prevented. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus using a fixing device according to an embodiment of the present disclosure.

FIG. 2 is a schematic diagram for explaining a configuration of a fixing device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a temperature distribution in a first heater which is one of the heating sources used in the fixing device shown in FIG. 2;

FIG. 4 is a diagram showing a temperature distribution in a second heater which is another one of the heating sources used in the fixing device shown in FIG.

FIG. 5 is a diagram for explaining a method of expressing a temperature distribution in the fixing roller shown in FIG. 2;

FIG. 6 is a block diagram illustrating a configuration of a control unit used in the fixing device illustrated in FIG. 2;

FIG. 7 is a diagram for explaining a relationship between a temperature distribution in first and second heaters used in the fixing device and a width direction area of a large-sized recording medium.

FIG. 8 is a diagram for explaining a relationship in which the temperature distribution shown in FIG. 7 acts in the width direction of the recording medium.

FIG. 9 is a diagram for explaining the relationship between the temperature distribution in the first and second heaters and the operation in the width direction of the recording medium in one example according to the embodiment of the present invention.

FIG. 10 is a diagram for explaining an operational relationship between a sum in a gradient region in the temperature distribution shown in FIG. 9 and a recording medium.

FIG. 11 is a diagram for explaining an operational relationship between a temperature distribution and a recording medium when the light emission ratio between the first and second heaters shown in FIG. 9 is changed.

FIG. 12 is a diagram for explaining an operational relationship between a temperature distribution in first and second heaters and a recording medium in another example according to the embodiment of the present invention.

13 is a diagram for explaining an operational relationship between a sum in a gradient region in the temperature distribution shown in FIG. 12 and a recording medium.

FIG. 14 is a diagram for explaining an operational relationship between a temperature distribution in first and second heaters and a recording medium for explaining a comparative example with respect to the embodiment shown in FIGS. 9 and 12;

FIG. 15 is a diagram for explaining the operational relationship between the sum of the gradient regions in the temperature distribution shown in FIG. 14 and the recording medium.

FIG. 16 is a view similar to FIG. 14 for explaining a comparative example with respect to the embodiment shown in FIG. 9 and FIG. 12 for explaining the operational relationship between the temperature distribution in the first and second heaters and the recording medium. FIG.

FIG. 17 is a diagram for explaining an operational relationship between the sum of the gradient areas in the temperature distribution shown in FIG. 16 and a recording medium.

FIG. 18 is a diagram for explaining detection temperatures of first and second temperature sensors in still another example according to the embodiment of the present invention.

FIG. 19 is a diagram for explaining the maximum temperature at the detected temperature shown in FIG. 18;

FIG. 20 is a diagram showing a temperature relationship for explaining an operation of still another example according to the embodiment of the present invention.

FIG. 21 is a diagram showing a temperature relationship for explaining an operation of still another example according to the embodiment of the present invention.

FIG. 22 is a diagram for explaining an operational relationship between a temperature distribution of each heater and a recording medium when another heater is added in the embodiment shown in FIG. 9;

FIG. 23 is a flowchart illustrating an operation of the control unit according to the embodiment described in FIG. 18;

FIG. 24 is a flowchart for explaining the operation of the control unit according to the embodiment described in FIG. 21;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser printer which is one of the image forming apparatuses 2 Photoconductor which is a latent image carrier 9 Fixing device 9A Fixing roller which forms a fixing roller 9B Pressure roller 10 Heater which is the first heating means 11 Second heating means Certain heater 12 First temperature sensor 13 Second temperature sensor 14 Control unit S Sheet forming a recording medium serving as a toner image support S1 Sheet forming a large-sized recording medium P5, P5'P6, P6 'Slant area T3 Fixing Maximum temperature in the axial direction of the roller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 3/00 335 H05B 3/00 335 F term (Reference) 2H033 AA03 AA09 AA15 BA25 BA27 BA32 BB18 CA03 CA07 CA28 CA45 CA48 3K058 AA86 BA18 CA12 CA61 DA02 DA06 5H323 AA36 CA06 CB04 CB42 DA01 EE01 FF01 KK05 MM02

Claims (7)

[Claims] A fixing roller provided with a plurality of heating means having different light distribution characteristics; and a pressing member provided in contact with the fixing roller, wherein the fixing roller and the pressing member include toner. In a fixing device that fixes the toner contained in the heated member by heat and pressure by nipping and conveying the heated member, the heating unit includes a flat area as a light distribution area and an inclined area adjacent to the flat area. A fixing device, wherein an inclined region in the light distribution is set at the same position between the heating units, and the inclination of the inclined region at the same position is made substantially equal between the heating units. 2. A fixing roller having a plurality of heating means having different light distribution characteristics, and a pressing member provided in contact with the fixing roller, wherein the fixing roller and the pressing member contain toner. In a fixing device that fixes the toner contained in the heated member by heat and pressure by nipping and conveying the heated member, the heating unit includes a flat area as a light distribution area and an inclined area adjacent to the flat area. The slope region in the light distribution is located at the same position between the heating means, and the sum of the heating means is calculated with respect to the time average value, which is the average value of the amount of light emitted by each heating means over time. A fixing device wherein the heating means are set so as to be equal over the entire light emitting area, and the inclination of the inclined area at the same position is substantially equal between the heating means. 3. A first heating means having a high light distribution area at the center in the longitudinal direction, a second heating means having a high light distribution area at a position other than the center in the longitudinal direction, and a heating state from the second heating means. A fixing roller capable of controlling the input power to the second heating means based on a temperature detected by the temperature detecting means, and provided in contact with the fixing roller. A fixing member, comprising: a pressing member; and fixing the toner contained in the heated member by heat and pressure by nipping and conveying the heated member including toner by the fixing roller and the pressing member. The difference between the maximum value in the temperature distribution in the longitudinal direction on the surface and the temperature in the center in the longitudinal direction on the surface of the fixing roller falls within a range that does not cause a hot offset at the time of passing the paper immediately after, and the recording medium of the maximum size. The temperature of the surface of the fixing roller within the width becomes higher than the temperature causing the fixing failure.
2. A fixing device characterized in that the fixing device is started by setting a temperature at which power supplied to the heating means is cut off. 4. A first heating means having a high light distribution area at the center in the longitudinal direction, a second heating means having a high light distribution area at a position other than the center in the longitudinal direction, and a heating state from the second heating means. A fixing roller capable of controlling the input power to the second heating means based on a temperature detected by the temperature detecting means, and provided in contact with the fixing roller. A fixing member, comprising: a pressing member; and fixing the toner contained in the heated member by heat and pressure by nipping and conveying the heated member including toner by the fixing roller and the pressing member. The difference between the maximum value in the temperature distribution in the longitudinal direction on the surface and the temperature in the center in the longitudinal direction on the fixing roller surface causes a hot offset in the toner immediately after startup, and the maximum value in the temperature distribution in the longitudinal direction on the fixing roller surface. The difference from the temperature at the center in the longitudinal direction of the fixing roller surface falls within a range that does not cause hot offset at the time of passing the paper immediately after,
In addition, the temperature of the fixing roller surface within the width of the recording medium of the maximum size is higher than the temperature causing the fixing failure. A temperature at which power supplied to the second heating means is cut off to a temperature (second temperature) lower than the first temperature) and start-up is started, and the temperature detected by the temperature detection means becomes the second temperature. A temperature at which the power supplied to the second heating means is cut off after the temperature reaches the first temperature. 5. A first heating means having a high light distribution area at the center in the longitudinal direction, a second heating means having a high light distribution area at a position other than the center in the longitudinal direction, and a heating state from the second heating means. A fixing roller capable of controlling the input power to the second heating means based on a temperature detected by the temperature detecting means, and provided in contact with the fixing roller. A temperature control method of a fixing device, comprising: a pressing member; and fixing and conveying the toner contained in the heated member by heat and pressure by nipping and conveying the heated member including toner by the fixing roller and the pressing member. The difference between the maximum value of the temperature distribution in the longitudinal direction of the fixing roller surface and the temperature at the center in the longitudinal direction of the fixing roller surface is within a range that does not cause a hot offset at the time of passing the paper immediately after, and the recording medium of the maximum size. The temperature of the surface of the fixing roller within the width of the body becomes higher than the temperature causing the fixing failure. At the time of start-up, the temperature becomes lower than the temperature detected by the temperature detecting means. A temperature control method for setting a temperature at which power supplied to the heating means is cut off. 6. A power supply to the second heating means, comprising: a first heating means having a high light distribution area at a central portion in the longitudinal direction; and a second heating means having a high light distribution area at a portion other than the central portion in the longitudinal direction. A toner and a toner image support with a fixing roller that controls the temperature based on the temperature of a temperature detecting unit installed near the end of the fixing roller and a pressing member provided opposite to the fixing roller. In a temperature control method of a fixing device for fixing an unfixed toner image to a toe image support by applying heat and pressure across a recording material, the maximum value of the temperature distribution in the longitudinal direction of the surface of the fixing roller and the center in the longitudinal direction of the surface of the fixing roller Is within a range that does not cause hot offset at the time of passing the paper immediately after, and the temperature of the fixing roller surface is higher than the temperature that causes the fixing failure within the width of the maximum size recording medium. The temperature at which the power supplied to the second heating means is turned off is set to a temperature (second temperature) lower than the temperature (first temperature) detected by the temperature detection means at the time of start-up. Then, after the temperature detected by the temperature detecting means reaches the second temperature, temperature control is performed to change the temperature at which power supplied to the second heating means is cut off to the first temperature. A temperature control method for a fixing device. 7. An image forming apparatus using the fixing device according to any one of claims 1 to 6.