JP2001331058A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device to detect the temperature unevenness of a heating roller in a peripheral direction. SOLUTION: This fixing device possesses fixing temperature detecting means 330 and 340 to detect the temperature of the heating roller 91 and a controlling part 500 to fetch temperature information from the fixing temperature detecting means 330 and 340 while rotating the heating roller 91 and to detect the temperature of at least three or more points per one rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a heating roller in which a heating means is disposed at a position deviated from the center of rotation, and a pressure roller which is in pressure contact with the heating roller. The present invention relates to a fixing device for causing a transfer material having a toner image transferred thereon to pass therethrough and thermally fixing the toner image to the transfer material.

[0002]

2. Description of the Related Art As a fixing device of a heat roller type currently used in an image forming apparatus such as a copying machine and a laser beam printer, there is one as shown in FIG. FIG.
2 (a) is a front view in which a part of the fixing device is broken, FIG. 12 (b)
13 is a right side view of FIG.

[0003] In the figure, a core 1 of a heating roller 1001 is shown.
On the surface of No. 003, a coat layer 1005 for improving the releasability from the toner is provided. Inside the cored bar 1003, a halogen heater lamp as a heat source, a first halogen heater lamp 1007 and a second halogen heater lamp 1009 in the conventional example are provided.

Reference numeral 1011 denotes a pressure roller whose surface is formed of a rubber layer. In recent years, to reduce warm-up time,
The thickness of the core metal 1003 of the heating roller 1001 is reduced.

However, when the thickness of the heating roller 1001 is reduced, the temperature of the non-sheet passing portion (end portion) of the heating roller 1001 rises when the transfer material having a small width is continuously fixed to the central portion of the heating roller 1001. Is remarkable.

In order to solve this, a heating roller 100 is used.
1st first and second halogen heater lamps 1007,
The heat distribution ratio of 1009 has been changed. For example, the first halogen heater lamp 1007 has a heat distribution ratio that mainly heats the end portion of the heating roller 1001, and the second halogen heater lamp 1009 has a heat distribution ratio that mainly heats the central portion of the heating roller 1001. A first temperature detecting means 1011 for detecting the temperature at the end of the heating roller 1001 and a second temperature detecting means 1013 for detecting the temperature at the center of the heating roller 1001 are provided. When fixing the transfer material continuously, the second halogen heater lamp 9 is mainly driven, and when fixing the transfer paper having a wide width, the first and second halogen heater lamps 1007 and 1009 are set. If driven, the surface temperature of the heating roller 1001 can be kept substantially constant.

[0007]

SUMMARY OF THE INVENTION In a fixing device,
During idling before fixing, the heating roller 10
1 is stationary.

[0008] Even at the time of idling, the temperature control of the heating roller is performed. On the other hand, in the fixing device having the above-described configuration, two halogen heater lamps 1 having different heat values are used.
Reference numerals 007 and 1009 deviate from the center of rotation of the heating roller 1001.

Therefore, when the heating roller 1001 is stationary, the temperature unevenness in the circumferential direction of the heating roller 1001 in the cross section taken along the cutting line AA in FIG. 12 has a mountain shape as shown in FIG.

When the heating roller 1001 having such temperature unevenness in the circumferential direction is rotated, as shown in FIG.
There is a problem that the temperature unevenness appears periodically, and the fixing unevenness occurs periodically in the transfer material.

On the other hand, when the heating roller having no such temperature unevenness in the circumferential direction is rotated at a standstill, as shown in FIG. 14B, no periodic temperature unevenness occurs and no fixing unevenness occurs. do not do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to provide a fixing device for detecting uneven temperature in a circumferential direction of a heating roller. A second object is to provide a fixing device that does not cause periodic fixing unevenness on a transfer material.

[0013]

According to a first aspect of the present invention, there is provided a heating roller in which a heating means is disposed at a position deviated from the center of rotation, and a pressure roller which presses against the heating roller. A fixing device for passing a transfer material onto which a toner image has been transferred between the heating roller and the pressure roller, and thermally fixing the toner image to the transfer material, wherein a fixing temperature for detecting a temperature of the heating roller is provided. A fixing unit that captures temperature information from the fixing temperature detecting unit and detects at least three or more temperatures per rotation in the circumferential direction of the heating roller. is there.

If the heating means is arranged at a position deviated from the center of rotation of the heating roller, temperature irregularities occur in the circumferential direction of the heating roller during idling. The change in the temperature unevenness in the circumferential direction of the heating roller is 1 per rotation of the heating roller.
It is a change that forms two peaks.

In order to detect such a change, it is necessary to detect three or more different temperatures per rotation of the heating roller. The control unit can detect a change in temperature unevenness by detecting at least three or more temperatures in one rotation in the circumferential direction of the heating roller.

According to a second aspect of the present invention, the control unit according to the first aspect of the present invention is arranged such that the temperature information from the fixing temperature detecting means is provided at an interval of one of the following formulas (1) and (2). 2. The fixing device according to claim 1, wherein sampling is performed.

When the time for one rotation of the heating roller is an integral multiple of the sampling interval, (heating roller circumference / heating roller linear speed) / (sampling interval of fixing temperature detecting means) ≧ 3 (1) If the time for one rotation of the roller is not an integral multiple of the sampling interval, (heating roller circumference / heating roller linear speed) / (sampling interval of fixing temperature detecting means) ≧ 1 (1) The heating roller makes one rotation If the time is an integral multiple of the sampling interval, no matter how many times the heating roller rotates, the temperature at the same location in the circumferential direction of the heating roller will be detected. Temperature must be detected.

(Time for one rotation of the heating roller) / (Sampling interval of fixing temperature detecting means) ≧ 3 That is, (Circumferential length of heating roller / Linear speed of heating roller) / (Sampling interval of fixing temperature detecting means) ≧ 3 ... (1)

If the time for one rotation of the heating roller is not an integral multiple of the sampling interval, three or more temperatures can be detected per rotation in the circumferential direction of the heating roller by continuously sampling.

(Time for one rotation of heating roller) / (Sampling interval of fixing temperature detecting means) ≧ 1 That is, (peripheral length of heating roller / linear speed of heating roller) / (sampling interval of fixing temperature detecting means) ≧ 1 ... (2) According to a third aspect of the present invention, when the heating roller starts rotating, the control unit of the first or second aspect of the present invention fetches temperature information from the temperature detecting means and changes the temperature information. If the cycle substantially coincides with the time during which the heating roller makes one rotation, and the fluctuation width is larger than a predetermined value, the fixing operation is temporarily stopped, and the heating roller is stopped until the fluctuation width becomes smaller than the predetermined value. This is a fixing device that performs preliminary rotation.

When the heating roller starts rotating, the control unit takes in temperature information from the temperature detecting means, and a fluctuation cycle of the temperature information substantially coincides with a time of one rotation of the heating roller. If the width is larger than the predetermined value, it is determined that the heating roller has a temperature unevenness that causes periodic fixing unevenness in the circumferential direction, and the fixing operation is temporarily stopped, and until the fluctuation width becomes smaller than the predetermined value. In other words, by performing the preliminary rotation of the heating roller until the temperature unevenness in the circumferential direction of the heating roller becomes smaller than a predetermined value and then performing the fixing, the periodic fixing unevenness does not occur in the transfer material.

As an example of the heating roller in which the heating means is disposed offset from the center of rotation, there is a plurality of heating means in the heating roller as in the invention according to claim 4. Further, as in the invention according to claim 5,
Some heating units have different heat distributions in the axial direction.

According to a sixth aspect of the present invention, there is provided a fixing device according to any one of the first to fifth aspects, wherein the temperature detecting means is an infrared sensor. Since the temperature detecting means is an infrared sensor, it can detect the temperature without contacting the heating roller.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the drawings. (Overall Configuration) First, the overall configuration of a copying apparatus provided with the fixing device of the present embodiment will be described with reference to FIG.

In FIG. 1, an image forming apparatus 1 includes an automatic document feeder (ADF) A and a document image reading unit B for reading an image of a document conveyed by the automatic document feeder A.
An image control unit C for processing the read document image; a writing unit D including a writing unit 12 for writing on an image carrier 10 formed of a photosensitive drum in accordance with the data after the image processing; Around the charging electrode 14,
An image forming section E including image forming means such as a developing means 16 comprising a magnetic brush type developing device, a charging electrode 18, a separation electrode 20, and a cleaning means 21, and a tray for accommodating a transfer material (hereinafter, referred to as recording paper) P Paper storage means (hereinafter, referred to as
Storage section for 22, 24 (referred to as a paper feed tray or tray)
F etc.

The automatic document feeder A includes a document table 26,
The main components are a roller group including the roller R1 and a document transport processing unit 28 including a switching unit for appropriately switching the movement path of the document.

The original image reading section B is located below the original glass G and has two mirror units 30 and 31 which can reciprocate while maintaining the optical path length, and a fixed imaging lens (hereinafter, referred to as a lens).
33, a linear image sensor (hereinafter, referred to as CCD) 35, etc.
(Polarizer) 42 and the like. The automatic document feeder A has a configuration different from that of the conventional automatic document feeder, but its principle is well known.
D. An image forming apparatus and an image forming process provided with image processing means (means for forming a toner image on the image carrier 10 and transferring the toner image onto a sheet) are well known, and a description thereof will be given. Is simply done.

Note that R10 shown on the front side of the transfer electrode 19 is a registration roller, H shown on the downstream side of the separation electrode is a fixing device (details will be described later), and the heating roller 91 is pressed against the heating roller 91. The recording paper P on which the toner image has been transferred is fixed between the heating roller 91 and the pressure roller 92, so that the toner image is thermally fixed on the recording paper P. You.

In the above configuration, the process of forming a toner image on the image carrier 10, transferring the toner image on a sheet, and then discharging the toner image to a discharge tray is as follows. In this specification, a transfer area where a transfer electrode is located may be referred to as an image recording unit.

An original (not shown) placed on the original placing table 26 is transported in the original transport processor 28, and slit exposure is performed by the exposure means L while passing under the roller R1. It is.

The reflected light from the original passes through mirror units 30 and 31 and a lens 33 at fixed positions, is coupled onto a CCD, and is read. The image information read by the document image reading unit B is processed by the image processing means, encoded, and stored in a memory on the image control board C.

The image data is called in accordance with the image formation, the laser light source 40 in the writing section D is driven in accordance with the image data, and the image carrier 10 is exposed. Prior to this exposure, a predetermined surface potential is applied to the image carrier 10 rotating in the direction of the arrow (counterclockwise) by corona discharge of the charging electrode 14. As a result, an electrostatic latent image corresponding to the image data is formed on the image carrier 10.

The electrostatic latent image is reversal-developed by the developing means 16 to become a visible image (toner image). On the other hand, the image carrier 10
Before the leading end of the upper toner image reaches the transfer area, for example, one sheet of recording paper P in the feed tray 22 is fed and conveyed, reaches the registration roller R10, and is regulated at the leading end.

The recording paper P is a toner image, that is, the image carrier 10
The sheet is conveyed toward the transfer area by a registration roller R10 that starts rotating in synchronization so as to overlap the upper image area.

In the transfer area, the toner image on the image carrier 10 is transferred onto the recording paper P by the urging of the transfer electrode, and then the recording paper P is separated from the image carrier 10 by the urging of the separation electrode 20. Separated.

Thereafter, the toner powder forming the toner image is melted and fixed on the recording paper P by heating and pressing of the fixing device H, and the recording paper P is discharged through a paper discharge passage 78 and a paper discharge roller 79. The sheet is discharged onto the tray T.

(Fixing Device) The configuration of the fixing device H will be described in detail with reference to FIGS. FIG. 3 is a side view of the fixing device H, and FIG. 4 is a view in the direction of the arrow X in FIG.

In the heating roller 91, reference numeral 191 denotes a cylindrical metal core (roller base) having both end faces opened. A release layer 194 is formed on the outer peripheral surface of the metal core 191.

In the present embodiment, the material of the core metal 191 is either aluminum or iron, and the material of the release layer 194 is PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), A resin having good releasability such as ethylene fluoride was used.

Further, the thickness of the core metal 191 was 2.0 mm or less, and the thickness of the release layer 194 was about 20 μm. Heating roller 91
Inside the first area, a first halogen heater lamp as a first heating means for mainly heating an area (L1) outside the passing area of the predetermined size recording paper P within the passing area of the predetermined size recording paper P. 210, and a second halogen heater lamp 220 as a second heating means for mainly heating the passage area (L2) of the recording paper P of a predetermined size.

The pressure roller 92 has a structure in which a PFA tube is covered on the circumferential surface of foamed silicone rubber, and has a surface hardness (Asker C hardness) of 35 to 75. Then, the pressure roller 92
Presses the heating roller 91 with a total load of 5 to 25 kgf by the urging force of the spring 90, sets the nip pressure between the pressing roller 92 and the heating roller 91 to 0.2 to 2.0 kgf / square cm, and sets the nip passing time to 20 to 40 msec.

As shown in FIG. 4, the fixing device H of this embodiment is provided with two temperature detecting means 330 and 340. One is a first temperature detecting means 330 for detecting the temperature of the heating roller 91 in the area L1, and a second temperature detecting means 340 for detecting the temperature of the heating roller 91 in the area L2. In this embodiment, an infrared sensor is used as the first and second temperature detecting means.

Reference numeral 350 denotes a fan as cooling means for cooling the end of the area L2. The cleaning mechanism 100 includes a main winding roller 103 around which a web 101 made of an aromatic polyamide nonwoven fabric is wound, a winding roller 105 for winding the web 101, and a web backup roller 107 for pressing the web 101 against a heating roller 91. ing.

The take-up roller 105 is driven to rotate by a predetermined amount when an image is formed on a predetermined number of recording sheets P, so that an unused portion of the web 101 is pressed against the heating roller 91.

Next, the electrical configuration of the fixing device of this embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating an electrical configuration of the fixing device shown in FIG. In the figure, reference numeral 310 denotes a first heating driving unit including a circuit for driving the first halogen heater lamp 210, and reference numeral 320 denotes a second driving heating unit including a circuit for driving the halogen heater lamp 220.

Reference numeral 500 denotes a control unit, which is a first temperature detecting means 3
30 and the second temperature detecting means 340.
When the power switch of the image forming apparatus main body is turned on, a start command sent from the image forming apparatus main body, and when the copy button of the image forming apparatus main body is turned on, the temperature information (t2) from the image forming apparatus main body is turned on. , The recording paper size information (W) and the set copy number information (I), and the first and second halogen heaters via the first and second heating driving means 310 and 320. Lamp 210, 220
In addition, the fan 350 is driven via the cooling driving means 360 and a counter 501 is provided.

Next, the operation of the fixing device having the above configuration will be described with reference to FIGS.
This will be described with reference to FIG. First, the overall operation of the fixing device will be described with reference to FIG. 5, which is a flowchart illustrating the overall operation of the control unit 500. When the power switch is turned on, warm-up control (step 1) is performed. When the warm-up is completed, idling control (step 2) is performed until a copy command is issued, and the apparatus stands by.

If there is a copy command during idling control (step 3), preliminary rotation control (step 4) is performed, fixing control (step 4) is performed, and when copying is completed, the process returns to idling control (step 2).

Next, warm-up control, idling control, preliminary rotation control, and fixing control will be described. (Warm-Up Control) A description will be given with reference to FIGS. 6 and 7, which are flowcharts for explaining the warm-up control of the fixing device shown in FIG.

FIG. 6A is a flowchart showing warm-up control of the first halogen heater lamp, and FIG.
FIG. 7 is a flowchart showing warm-up control of the second halogen heater lamp, and FIG. 7 is a flowchart showing an operation of judging termination of warm-up control.

The control section 500 performs the three flows shown in FIGS. 6A, 6B and 7 every 200 msec as warm-up control. In the flow shown in FIG. 6A, the temperature information (t1) from the first temperature detecting means 330 is fetched,
The temperature (t1) of the region L1 of the heating roller 91 is compared with a predetermined temperature (T1) (Step 1).

The temperature (t1) of the heating roller 91 is equal to a predetermined temperature (T1).
If lower, the first halogen heater lamp 210 is driven (step 2). If the temperature (t1) of the heating roller 91 is equal to or higher than the predetermined temperature (T1), the first halogen heater lamp 21
0 drive is stopped (step 3) and warm-up (W
U) The end flag 1 is turned on (step 4).

Similarly, in the routine shown in FIG. 6B, the temperature information (t2) from the second temperature detecting means 340 is taken in, and the temperature (t2) of the area L2 of the heating roller 91 and the predetermined temperature (T2 ) (Step 1).

When the temperature (t2) of the heating roller 91 reaches a predetermined temperature (T2)
If lower, the second halogen heater lamp 220 is driven (step 2). If the temperature (t2) of the heating roller 91 is equal to or higher than the predetermined temperature (T2), the second halogen heater lamp 22
0 drive is stopped (step 3) and warm-up (W
U) The end flag 2 is turned on (step 4).

In the flow shown in FIG. 7, the WU end flag
It is checked whether both 1 and WU end flag 2 are on (step 1). If both are on, the WU end flag is turned on (step 2).

(Idling Control) The idling control of the fixing device shown in FIG. 3 will be described with reference to FIG. 8 which is a flowchart for explaining the idling control.

FIG. 8A is a flowchart showing idling control of the first halogen heater lamp, and FIG. 8B is a flowchart showing idling control of the second halogen heater lamp.

The controller 500 performs idling control as follows:
The two flows shown in FIGS. 8A and 8B are performed every 200 msec. In the flow shown in FIG. 8A, the temperature information (t1) from the first temperature detecting means 330 is fetched, and the temperature (t1) of the area L1 of the heating roller 91 is compared with a predetermined temperature (T1 ′). Perform (Step 1).

The temperature (t1) of the heating roller 91 reaches a predetermined temperature (T
1 '), the first halogen heater lamp 210
(Step 2). If the temperature (t1) of the heating roller 91 is equal to or higher than the predetermined temperature (T1 '), the driving of the first halogen heater lamp 210 is stopped (step 3).

Similarly, in the flow shown in FIG.
The temperature information (t2) from the second temperature detecting means 340 is fetched, and the temperature (t2) of the area L2 of the heating roller 91 and the predetermined temperature (T2) are taken.
2 ′) is compared (step 1).

The temperature (t2) of the heating roller 91 reaches a predetermined temperature (T
2 '), the second halogen heater lamp 220
(Step 2). If the temperature (t2) of the heating roller 91 is equal to or higher than the predetermined temperature (T2 '), the driving of the second halogen heater lamp 220 is stopped (step 3).

(Preliminary Rotation Control) A description will be given with reference to FIG. 9 which is a flowchart illustrating the preliminary rotation control of the fixing device shown in FIG.

Upon receiving the copy start command, the control section 500 drives the heating roller 91 (step 1), and uses the second temperature detecting means 340 to acquire the temperature information of the heating roller 91 at the following sampling intervals. Read more than once (step
2).

That is, as in the present embodiment, the first and second halogen heater lamps 21 as heating means are used.
0,220 is displaced from the center of rotation of the heating roller 91, the idling of the heating roller 91
Temperature unevenness occurs in the circumferential direction.

The change in the temperature unevenness in the circumferential direction of the heating roller 91 is a change in which one peak is formed per one rotation of the heating roller 91. In order to detect such a change, it is necessary to detect three or more different temperatures per rotation of the heating roller 91.

When the time for one rotation of the heating roller 91 is an integral multiple of the sampling interval, the temperature at the same location in the circumferential direction of the heating roller 91 is detected no matter how many times the heating roller 91 rotates. It is necessary to detect three or more different temperatures during one rotation of the heating roller 91.

(Time for one rotation of the heating roller) / (Sampling interval of fixing temperature detecting means) ≧ 3 That is, (peripheral length of heating roller / linear speed of heating roller) / (sampling interval of fixing temperature detecting means) ≧ 3 ... (1)

If the time for one rotation of the heating roller 91 is not an integral multiple of the sampling interval, three or more temperatures per rotation in the circumferential direction of the heating roller 91 can be detected by continuously sampling.

(Time for one rotation of heating roller) / (Sampling interval of fixing temperature detecting means) ≧ 1 That is, (circumferential length of heating roller / heating roller linear velocity) / (sampling interval of fixing temperature detecting means) ≧ 1 (2) Next, the fluctuation period (t) of the temperature in the circumferential direction of the heating roller 91 is calculated (Step 3).

When the fluctuation period (t) is substantially equal to the rotation period of the heating roller 91, the temperature fluctuation width of the heating roller 91
(ΔT) is calculated (steps 4 and 5), and when the temperature fluctuation width (ΔT) is equal to or smaller than a predetermined value (temperature fluctuation unevenness causing periodic fixing unevenness) (step 6), the process proceeds to the next fixing control. I do.

If the temperature fluctuation width (ΔT) is larger than the predetermined value (step 6), it is determined that there is temperature unevenness that causes periodic fixing unevenness in the circumferential direction of the heating roller 91, and the temperature fluctuation width (ΔT) is determined. The preliminary rotation is continued until) becomes equal to or less than the predetermined value.

Further, when the fluctuation period (t) of the temperature in the circumferential direction of the heating roller 91 is different from the rotation period of the heating roller 91 in step 4, the temperature fluctuation is caused by the on / off of the halogen heater lamps 210 and 220. Therefore, it is determined that the temperature is not uneven in the circumferential direction, and the process proceeds to the next fixing control.

(Fixing Control) The fixing control of the fixing device shown in FIG. 3 will be described with reference to FIGS.

In FIG. 10, (a) is a flowchart showing copy control of the first halogen heater lamp, and (b) is a flowchart showing copy control of the second halogen heater lamp. In addition, in FIG. 11, (a) is a flowchart showing the drive control of the cooling fan, and (b) is a flowchart showing the stop control of the cooling fan.

The control unit 500 performs copy control as shown in FIG.
The two flows 0 (a) and (b) are performed every 200 msec. In the flow shown in FIG. 10A, the temperature information (t1) from the first temperature detecting means 330 is fetched, and the temperature (t1) of the area L1 of the heating roller 91 is compared with a predetermined temperature (T1 ″). Perform (Step 1).

The temperature (t1) of the heating roller 91 reaches a predetermined temperature (T
1 ″), the first halogen heater lamp 210
(Step 2). If the temperature (t1) of the heating roller 91 is equal to or higher than the predetermined temperature (T1 ″), the driving of the first halogen heater lamp 210 is stopped (step 3).

Similarly, in the flow shown in FIG. 10B, the temperature information (t2) from the second temperature detecting means 340 is taken in, and the temperature (t2) of the region L2 of the heating roller 91 and the predetermined temperature (T2 )) (Step 1).

The temperature (t2) of the heating roller 91 reaches a predetermined temperature (T
2 ″), the second halogen heater lamp 220
(Step 2). If the temperature (t2) of the heating roller 91 is equal to or higher than the predetermined temperature (T2 ″), the driving of the second halogen heater lamp 220 is stopped (step 3).

Further, when there is a copy command, the control unit 500
Executes the flow of FIG. 11A once. In the flow shown in FIG. 11A, when there is a copy command, the control unit 500 reads the size information (w) of the recording paper P (Step 1),
The size (w) of the recording paper P to be passed is compared with a predetermined size (W: for example, B5R) (step 2), and the size (w) of the recording paper P to be passed is determined in advance. Given size (W)
In the following cases, the fan 350 is driven (step
3).

When a copy end command is issued, the control unit 5
00 executes the flow of FIG. 11B once. In the flow shown in FIG. 11B, when there is a copy end command, if the fan 350 is being driven (step 1), the control unit 500 stops driving the fan 350 (step 2).

According to the above configuration, the following effects can be obtained. (1) The controller 500 controls the heating roller 91 before fixing.
By detecting at least three or more temperatures during one rotation in the circumferential direction, a change in temperature unevenness in the circumferential direction of the heating roller 91 can be detected.

(2) When the heating roller 91 starts rotating, the control section 500 takes in the temperature information from the second temperature detecting means 340, and the fluctuation period of the temperature information is changed.
When the fluctuation width is larger than a predetermined value, the start of the fixing operation is temporarily stopped, and the preliminary rotation of the heating roller 91 is performed until the fluctuation width becomes smaller than the predetermined value. In addition, temperature unevenness in the circumferential direction of the heating roller 91 is eliminated, and periodic fixing unevenness does not occur on the transfer material P.

(3) First and second temperature detecting means 33
Reference numeral 0,340 denotes an infrared sensor, which can detect the temperature of the heating roller 91 without contact.

[0084]

As described above, according to the first aspect of the present invention, when the heating means is disposed at a position deviated from the rotation center of the heating roller, the temperature in the circumferential direction of the heating roller during idling is reduced. Unevenness occurs.

The change in the temperature unevenness in the circumferential direction of the heating roller is a change in which one peak is formed per rotation of the heating roller. To detect such a change, use heating roller 1
It is necessary to detect three or more different temperatures per rotation.

The control unit can detect a change in temperature unevenness by detecting at least three or more temperatures during one rotation in the circumferential direction of the heating roller. According to the invention described in claim 2, when the time for one rotation of the heating roller is an integral multiple of the sampling interval, the temperature at the same location in the circumferential direction of the heating roller is detected regardless of the number of rotations of the heating roller. Therefore, it is necessary to detect three or more different temperatures during one rotation of the heating roller.

(Time for one rotation of heating roller) / (Sampling interval of fixing temperature detecting means) ≧ 3 That is, (circumferential length of heating roller / heating roller linear speed) / (sampling interval of fixing temperature detecting means) ≧ 3 (1)

If the time for one rotation of the heating roller is not an integral multiple of the sampling interval, three or more temperatures per rotation in the circumferential direction of the heating roller can be detected by performing continuous sampling.

(Time for one rotation of heating roller) / (Sampling interval of fixing temperature detecting means) ≧ 1 That is, (circumferential length of heating roller / heating roller linear velocity) / (sampling interval of fixing temperature detecting means) ≧ 1 (2) According to the third aspect of the present invention, when the heating roller starts rotating, the control unit takes in the temperature information from the temperature detecting means, and the fluctuation period of the temperature information is one when the heating roller is rotated. If the fluctuation time is substantially equal to the rotation time and the fluctuation width is larger than a predetermined value, the fixing operation is temporarily stopped, and the preliminary rotation of the heating roller is performed until the fluctuation width becomes smaller than a predetermined value. There is no temperature unevenness in the circumferential direction of the heating roller, and no periodic fixing unevenness occurs on the transfer material.

According to the sixth aspect of the present invention, since the temperature detecting means is an infrared sensor, it is possible to detect the temperature without contacting the heating roller.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an electrical configuration of a fixing device according to an embodiment.

FIG. 2 is a diagram illustrating an overall configuration of an image forming apparatus provided with a fixing device according to the exemplary embodiment.

FIG. 3 is a side view of the fixing device according to the embodiment.

FIG. 4 is a view in the direction of the arrow X in FIG. 3;

FIG. 5 is a flowchart illustrating overall control of the image forming apparatus provided with the fixing device according to the embodiment.

6 is a flowchart illustrating warm-up control of the fixing device shown in FIG. 3, wherein FIG. 6 (a) is a flowchart illustrating warm-up control of a first halogen heater lamp, and FIG. FIG. 5 is a flowchart showing warm-up control of the halogen heater lamp of FIG.

FIG. 7 is a flowchart illustrating idling control of the fixing device shown in FIG. 3 in the fixing device shown in FIG. 3;

FIGS. 8A and 8B are flow charts for explaining idling control of the fixing device shown in FIG. 3; FIG. 8A is a flow chart showing idling control of a first halogen heater lamp, and FIG. It is a flowchart which shows idling control of a heater lamp.

FIG. 9 is a flowchart illustrating a preliminary rotation control of the fixing device illustrated in FIG. 3;

FIGS. 10A and 10B are flowcharts illustrating copy control of the fixing device shown in FIG. 3, wherein FIG. 10A is a flowchart illustrating copy control of a first halogen heater lamp, and FIG. It is a flowchart which shows the copy control of a heater lamp.

11 is a flowchart illustrating copy control of the fixing device illustrated in FIG. 3, wherein FIG. 11A is a flowchart illustrating driving control of a cooling fan, and FIG. 11B is a flowchart illustrating stop control of the cooling fan; FIG.

FIG. 12 is a diagram illustrating an example of a conventional fixing device.

FIG. 13 is a view for explaining temperature unevenness in the circumferential direction of the heating roller shown in FIG.

FIG. 14 is a diagram illustrating a problem.

[Explanation of symbols]

 91 heating roller 92 pressure roller 191 core metal 210 first halogen heater lamp (heating means) 220 second halogen heater lamp (heating means) 330 first temperature detecting means (fixing temperature detecting means) 340 second temperature Detecting means (fixing temperature detecting means) 500 control unit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H033 AA03 BA25 BA27 BA31 BA32 BB18 BB28 BB37 CA07 CA28 CA30 CA40 CA48 3K058 AA86 BA18 CA23 CA70 CA92 CB27 CE17 CE23 CE28 CE29 CE32 DA02 DA26 GA06 5H323 AA36 BB20 CA08 CB04 CB04 GG16 HH09 KK05 LL17 MM02

Claims (6)

[Claims] 1. A heating roller in which heating means is disposed offset from the center of rotation, and a pressure roller which presses against the heating roller, wherein a toner image is transferred between the heating roller and the pressure roller. A fixing temperature detecting means for detecting a temperature of a heating roller, and a fixing temperature detecting means for rotating the heating roller. And a control unit that takes in temperature information from the controller and detects at least three or more temperatures per rotation in the circumferential direction of the heating roller. 2. The fixing unit according to claim 1, wherein the control unit samples the temperature information from the fixing temperature detecting unit at any one of the following formulas (1) and (2). apparatus. When the time for one rotation of the heating roller is an integer multiple of the sampling interval, (heating roller circumference / heating roller linear speed) / (sampling interval of fixing temperature detecting means) ≧ 3 (1) If the rotation time is not an integral multiple of the sampling interval, (heating roller circumference / heating roller linear speed) / (fixing temperature detecting means sampling interval) ≧ 1… (2) 3. The control unit, when the heating roller starts rotating, takes in temperature information from the temperature detecting means, and a fluctuation cycle of the temperature information substantially coincides with a time of one rotation of the heating roller. 3. The method according to claim 1, wherein when the fluctuation width is larger than a predetermined value, the fixing operation is temporarily stopped, and the preliminary rotation of the heating roller is performed until the fluctuation width becomes smaller than the predetermined value. Fixing device. 4. The fixing device according to claim 1, wherein a plurality of the heating units in the heating roller are provided. 5. The fixing device according to claim 4, wherein heat distribution in the axial direction of the heating unit is different. 6. The fixing device according to claim 1, wherein said temperature detecting means is an infrared sensor.