JPH11109781A - Image forming device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a partial failure in fixing, paper wrinkles, or the like, by providing for instance a stopping means for stopping the conveyance of an image-formed medium to a fixing means with a carrying means, when the temperature difference between temperatures detected with first and second detecting means becomes a prescribed value or above. SOLUTION: A temperature sensor 41 for detecting the temp., attached in a contact state with the surface of a heating roller 35a is provided in its longitudinal central part and a temperature sensor 42 for detecting the temp., attached in the contact state with the surface of the heating roller 35a similarly is provided in its longitudinal end part. Then, a microcomputer interrupts a copying operation, when the temperature difference between the central part and end part of the heating roller 35a becomes a prescribed one or above, based on the temperatures detected by the sensors 41 and 42. Thus, the distribution of the temp. is suppressed within a fixed range, so that the partial failure in fixing on a copying paper, the paper wrinkles, or the like, can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electronic copying machine using a fixing device and an image forming method.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus is provided with a fixing device having a heat roller for fixing a sheet on which a toner image is formed by pressing and heating the sheet on the sheet. As the temperature control of the fixing device, a first temperature control method includes providing one or more temperature sensors in the fixing device, and performing an image forming operation when the detected temperature of the temperature sensors becomes equal to or lower than a predetermined temperature T1. Is interrupted, and control is performed to restart the image forming operation when the temperature detected by the temperature sensor returns to the predetermined temperature T2. This is because the paper loses heat,
This is to prevent fixing defects caused by a decrease in fixing temperature.

[0003] A second temperature control method is a method in which a fixing device is used.
In some cases, at least one temperature sensor is provided, and when the temperature detected by the temperature sensor becomes equal to or higher than a predetermined (determinable as abnormal) temperature T3, the image forming operation is stopped and the heater is turned off. This prevents destruction of the device due to high temperatures.

FIG. 10 shows an example in which the copy operation is not interrupted.
Only the temperature control of the heater indicates a temperature change when a narrow sheet having a width such as A4-R is passed in a low temperature environment. In such a case, the heat of the center portion is taken away by the paper and the temperature is lowered, and the heat is not taken away at the end portion of the paper. Therefore, when the heat is distributed by the heater to increase the temperature of the center portion, The temperature rises.

FIG. 11 is a diagram showing a change in the temperature of the heat roller at the time of continuous copying of A4-R sheets by conventional control based on the first temperature control method. In this case, the temperature in the central portion decreases, but if the temperature T1 or less is detected at the time of X1, the copy operation is interrupted while the heat roller is idly rotated. When the copying operation is interrupted, the central portion of the heat roller loses heat,
The temperature starts to rise as shown in FIG. As a result, since the temperature drop in the central portion stops, the lighting time of the heater by the temperature comparison circuit is shortened, and the end portion is deprived of heat by the central portion,
The temperature decreases as shown by Y1. When the temperature of the central portion is restored at the time of X2, the copying operation is restarted, so that the temperature of the central portion starts decreasing again and the temperature of the end increases.

FIG. 12 is a diagram showing a temperature change of a heat roller at the time of continuous copying of B5-R sheets by conventional control. In this case, since the paper of B5-R is smaller than A4-R, less heat is taken, so that the temperature at the center does not fall below T1 and only the temperature at the end increases without interruption of copying. .

FIG. 13 is a diagram showing a change in temperature of the heat roller at the time of continuous copying of A4 paper by conventional control. In this case, since the width of the A4 paper is large, heat is taken off at both the center and the end, but the heat supply amount is smaller at the end where the heat roller cannot be directly heated as compared with the center. Therefore, especially at the start of the copy operation, the temperature is temporarily lowered because the temperature is not sufficiently warmed. afterwards,
If the copying operation is continued as it is, those who cannot directly warm up the heat roller can warm up.

As described above, the first temperature control and the second temperature control for the fixing device are defensive against the temperature abnormality of the fixing device, such as preventing the fixing failure at a low temperature and preventing the destruction of the device at a high temperature. However, it does not make the fixability uniform. Therefore, an image forming apparatus having a fixing unit capable of preventing the occurrence of partial fixing failure due to non-uniformity of the temperature distribution and the occurrence of paper wrinkles due to a temperature difference by keeping the temperature distribution of the fixing unit within a certain range. There is a need for a device.

[0009]

As described above, the temperature distribution of the fixing unit is kept within a certain range to prevent the occurrence of partial fixing failure due to non-uniform temperature distribution or paper wrinkles due to temperature difference. It is desired that the temperature distribution of the fixing device be kept within a certain range to prevent a partial fixing failure due to non-uniform temperature distribution or a paper wrinkle due to a temperature difference. It is an object of the present invention to provide an image forming apparatus and an image forming method that can perform the above-described operations.

[0010]

An image forming apparatus according to the present invention comprises: an applying unit for applying a developer image corresponding to image information on an image forming medium; and a conveying unit for conveying the image forming medium by the applying unit. Fixing means for fixing the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying means, having a fixing roller having a built-in heating element, First and second sensors for detecting the surface temperatures of different portions of the fixing roller, respectively.
Control means for controlling the surface temperature of the fixing roller by controlling power supply to the heating element based on at least the temperature detected by the first detection means;
And stopping means for stopping the conveyance of the image forming medium by the conveying means to the fixing means when the temperature difference between the temperatures detected by the first and second detecting means becomes equal to or more than a predetermined value. I have.

An image forming apparatus according to the present invention comprises: an applying unit for applying a developer image corresponding to image information on a medium on which an image is to be formed;
The image forming apparatus includes a conveying unit that conveys the image forming medium by the applying unit and a fixing roller that includes a heating element. A fixing unit for fixing the developer onto the image forming medium, first and second detecting units for detecting surface temperatures of different portions of the fixing roller, and a temperature detected by at least the first detecting unit. Control means for controlling the surface temperature of the fixing roller by controlling the power supply to the heating element, and when the temperature difference between the detected temperatures by the first and second detecting means is equal to or greater than the first temperature difference. Stopping means for stopping the conveyance of the image forming medium to the fixing means by the conveying means; and after the stop by the stopping means, the temperature difference between the temperatures detected by the first and second detection means is reduced to the second. When equal to or less than the temperature difference, and a resume resuming means the conveyance of the image forming medium to said fixing means by the conveying means.

[0012] The image forming apparatus of the present invention comprises: an applying unit for applying a developer image corresponding to the image information on the image forming medium;
The image forming apparatus includes a conveying unit that conveys the image forming medium by the applying unit and a fixing roller that includes a heating element. A fixing unit for fixing the developer onto the image forming medium, first and second detecting units for detecting surface temperatures of different portions of the fixing roller, and a temperature detected by at least the first detecting unit. Control means for controlling the surface temperature of the fixing roller by controlling power supply to the heating element; the width of the image forming medium conveyed by the conveying means is smaller than the width of the fixing roller; Determining means for determining whether the width is equal to or less than a width, and a temperature difference between temperatures detected by the first and second detecting means is equal to or more than a predetermined value, and the image forming medium is determined by the determining means. When it is determined that more than the predetermined width,
The image forming apparatus includes stop means for stopping the conveyance of the image forming medium to the fixing means by the conveyance means.

[0013] The image forming apparatus of the present invention includes: an applying unit for applying a developer image corresponding to image information on a medium on which an image is to be formed;
The image forming apparatus includes a conveying unit that conveys the image forming medium by the applying unit and a fixing roller that includes a heating element. A fixing unit for fixing the developer onto the image forming medium, first and second detecting units for detecting surface temperatures of different portions of the fixing roller, and a temperature detected by at least the first detecting unit. Control means for controlling the surface temperature of the fixing roller by controlling power supply to the heating element; the width of the image forming medium conveyed by the conveying means is smaller than the width of the fixing roller; Determining means for determining whether or not the width is equal to or less than a width; a temperature difference between the temperatures detected by the first and second detecting means is equal to or greater than the first temperature difference; When it is determined that more than the predetermined width,
Stop means for stopping the conveyance of the image forming medium to the fixing means by the conveyance means, and after the stop by the stop means, the temperature difference between the temperatures detected by the first and second detection means is a second temperature difference. When the following conditions are satisfied, the image forming apparatus includes a restart unit that restarts the conveyance of the image forming medium to the fixing unit by the conveyance unit.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an internal configuration of a main body 11 of an electronic copying machine 1 as an image forming apparatus according to the present invention. A photosensitive drum 12 is rotatably provided at a substantially central portion of the main body 11.

Around the photosensitive drum 12, a charging charger 13, an LED array 31, an exposing unit 14, a developing unit 15, a transfer charger (transfer means) 17, a peeling charger 18, and a cleaner 19 are sequentially arranged along the rotation direction. And a static eliminator 20.

An exposure system 21 is provided at an upper portion in the main body 11. The exposure system 21 includes an exposure lamp 22, first to third reflecting mirrors 23, 24, 25, a variable magnification lens block 26, fourth to sixth reflecting mirrors 27,
8, 29.

On one side of the main body 11, there are provided paper cassettes 30a, 30b, 30c and a large-capacity paper cassette (LCF) 30d, which is a large-capacity supply means of 1000 sheets or more.

A sheet (image forming medium) P fed from the sheet cassettes 30a, 30b, 30c or the large-capacity cassette 30d is fed to a sheet transport path 32 provided in the main body 11.
Is transported along.

A registration roller 33, a transfer / separation charger 17, 18, a conveyance belt 34, a fixing device 35, and a pair of paper discharge rollers 36 are sequentially provided in the paper conveyance path 32 along the conveyance direction of the paper P. I have.

A document table 38 is provided on the upper surface of the main body 11. During normal copying, the exposure system 21 scans the original O placed on the original placing table 38 with light, and reflects the reflected light to the charging charger 13.
Thus, an image is formed on the photosensitive drum 12 whose surface is charged to form an electrostatic latent image. The electrostatic latent image is visualized by supplying the developer from the developing device 15. At this time, when the sheet P is supplied from the sheet cassettes 30a, 30b, 30c or the large-capacity cassette 30d, the sheet P is sent to the image transfer unit 12a between the photosensitive drum 12 and the transfer charger 17, and the sheet P is exposed. The visible image on the drum 12 is transferred to the paper P. Paper P on which this image has been transferred
Is peeled off from the photosensitive drum 12 by the action of the peeling charger 18, sent to the fixing device 35 as fixing means by the transport belt 34, and the image is fixed. The sheet P on which the image has been fixed is discharged via the pair of discharge rollers 36.

In the case of double-sided copying, the gate P is switched to the reversing sheet feeding section 39 so that the sheet P
Is guided to the reversing sheet feeding section 39, and after being turned over, the sheet is conveyed again along the sheet conveying path 32, the image is transferred to the back side, fixed, and discharged.

FIG. 3 shows a schematic configuration of the fixing device 35. The fixing device 35 includes a cylindrical heat roller 35a,
The heat roller 3 is positioned below and in parallel
5a, a press roller 35b for fixing the toner on the paper P by heat and pressure, and a heater lamp 35c such as a halogen lamp as a heating means inside the heat roller 35a and supplying heat to the surface thereof. Have been.

At the center of the heat roller 35a in the longitudinal direction, a temperature sensor (first detecting means) 41 for temperature detection, which is attached in contact with the surface of the heat roller 35a, is provided. At a longitudinal end of the heat roller 35a, a temperature sensor (second detecting means) 42 for temperature detection, which is also mounted in contact with the surface of the heat roller 35a, is provided.

FIG. 2 is a block diagram showing a configuration of a main part of a control system of the image forming apparatus. That is, a microcomputer 40 for controlling the entire apparatus, a temperature sensor 41 provided at an end of the heat roller 35a, a temperature sensor 42 provided at a central portion of the heat roller 35a, various settings such as a copy start instruction and the number of copies. Operating unit 43, a RAM 44 storing various data, a ROM 45 storing a control program, etc., a temperature comparing unit 46 for comparing the temperatures detected by the temperature sensor 41 and the temperature sensor 42, and a heater lamp 35c. (Heater lamp driver) 4 for turning on / off the power
7 and a heater lamp 35c.

The temperature comparing section 46 includes a temperature sensor 41,
Alternatively, the surface temperature of the heat roller 35a is controlled by turning the heater lamp 35c on and off by the driver 47 based on the temperature detected by the temperature sensor 42.

FIG. 4 shows the distribution of heat supplied to the heat roller 35a by the heater lamp 35c. As shown in FIG.
In the end portion, since the heat is supplied only from one side as compared with the heat supplied to the central portion, the amount of supplied heat is increased.

Next, control when the interruption of the copy operation is determined will be described with reference to the flowchart shown in FIG. That is, when the user inputs conditions such as the number of copies and the like by using the operation unit 43 and instructs to start copying, the operation unit 43 sends a signal indicating the copy conditions and the copy start to the microcomputer 40. Thereby, the microcomputer 40 determines that the copy start has been instructed (step S1). Then, the microcomputer 40 performs a copy operation under a plurality of process controls (not shown) (step S2). Further, each time one copy is completed, the microcomputer 40 determines whether or not to interrupt the copy operation based on the temperatures detected by the temperature sensor 41 and the temperature sensor 42 (step S3). When it is determined that the copy operation is not interrupted, the process returns to step S2 to continue the copy operation. Further, when it is determined that copying has been interrupted,
The copy operation is interrupted (step S5), and when it is determined that the copy operation is to be resumed, the process returns to step S2 to resume the copy operation.

Next, the heat roller 35 shown in FIGS.
The temperature change of a will be described. FIG. 6 shows a temperature change of the heat roller 35a during the continuous copying of the A4-R size. After the start of copying, at the time X3 before the temperature of the central portion falls below the limit temperature value T1 at which normal fixing is possible, the temperature difference between the temperature of the central portion and the temperature of the end portion (end portion temperature) is the temperature difference A. (First temperature difference). This X
When the copying operation is interrupted at the time point 3, the heat roller 35
In the central part of a, the temperature starts to rise because the heat is not taken away by the copy sheet. At this time, heat roller 3
Conversely, the end of 5a is deprived of heat at the center and its temperature drops.
Then, after the interruption of the copying operation, the temperature difference between the central portion and the end portion becomes smaller than the temperature difference B (second temperature difference) at the time point of X4. When the copy operation is restarted at the time of X4, the temperature of the central portion decreases again, and the temperature of the end portion increases.

FIG. 7 shows the temperature change of the heat roller during continuous copying of B5-R size copy paper. As shown in FIG. 7, since the B5-R size sheet is smaller than the A4-R size continuous copy, the amount of heat taken by the sheet is smaller, and the temperature difference between the center and the end of the heater roller 35a is the temperature difference A. It takes a long time to reach X5 at which the temperature difference between the central portion and the end portion reaches the temperature difference B after the copying operation is interrupted at the time point of X5.

FIG. 8 shows the temperature change of the heat roller 35a during continuous copying of A4 size copy paper. In this case, A4 size paper is A4-R or B
Since the portion in contact with the heat roller 35a is wider than that of 5-R, the heat is similarly taken at both the center and the end. Therefore, the heat roller 35a cannot be directly warmed compared with the central temperature (heat is supplied from only one side).
The temperature at the end portion is greatly reduced particularly at the start of the copy operation because the heat supply amount is small and the heat roller is not sufficiently warmed up. As shown in FIG.
At the start of copying, the temperature of the end portion drops greatly at the start of copying in the four size continuous copy, and the temperature difference between the end portion temperature and the central portion temperature becomes X.
At time point 7, the temperature difference becomes C (first temperature difference). This X7
When the copying operation is interrupted at the point
The heat of “a” is not taken away, and the temperature difference between the center portion temperature and the end portion temperature becomes the temperature difference D (second temperature difference) at the time point of X8. When the copying operation is restarted at the time point of X8, the heat roller 35a is sufficiently warmed up and the heat of the heat distribution is supplied as shown in FIG. And the end temperature change.

Next, the fixing temperature control based on the temperature difference between the temperature sensor 41 and the temperature sensor 42 will be described with reference to the flowchart shown in FIG. That is, when the copy is started, the microcomputer 40 operates the driver 4
7 turns on the heater lamp 35c. This allows
The surface temperature of the heat roller 35a is
The heater lamp 35c is controlled to be on and off by the temperature comparison circuit 46 so as to reach a predetermined temperature. The ON / OFF control of the heater lamp 35c by the temperature comparison circuit 46 is performed until the microcomputer 40 instructs the end of the copy. In this state, the microcomputer 40 determines whether or not the temperature at the central portion of the heater roller 35a is equal to or lower than the limit value T1 at which normal fixing is possible, based on the detection result of the temperature sensor 41 (step S10). If it is determined that the temperature at the center of the heat roller 35a is equal to or lower than T1, the copying operation is interrupted (standby) (step S11), and the heat roller 3
5a is rotated idle (step S12). Here, it is determined whether or not the temperature at the center is equal to or lower than T3 indicating an abnormal operation of the fixing device (step S13).
That is, if it is determined that the temperature is T3 or more, it is determined that the fixing device is in an abnormal operation, and the apparatus is stopped in order to avoid a meltdown of the device due to an abnormally high temperature. If the temperature is equal to or lower than T3, it is determined whether or not the temperature of the central portion is equal to or higher than T2 (step S14). If it is determined that the temperature of the central portion is not equal to or higher than T2, the above steps S12 to S12 are performed. The processing up to S14 is repeated, and when it is determined that the temperature of the central portion is equal to or higher than T2, it is determined that the copy operation is possible, and the restart (start) of the copy operation is determined, and the process returns to step S10.

If it is determined in step S10 that the temperature at the center is not lower than T1 (not lower than T1), the microcomputer 40 sets the temperature sensor 41 and the temperature sensor 4
Then, it is determined whether or not the center temperature is lower than the end temperature (step S20). When it is determined that the center temperature is lower than the end temperature,
A temperature difference C indicating the interruption of the copy operation when the temperature difference between the center temperature and the end temperature is higher than the end temperature.
It is determined whether or not this is the case (step S21). By this judgment. If the temperature difference between the central portion and the end portion is not more than the temperature difference C, it is determined that the fixing temperature is normal, the process returns to step 10, and the copying operation is continued.

When it is determined in step S21 that the temperature difference between the central portion and the end portion is equal to or less than the temperature difference C, the microcomputer 40 sets the copy paper width to a predetermined paper width (here, B5-B5). It is determined whether the paper is narrower than (R size) (step S22). When the copying operation is continued with a sheet having a width smaller than the predetermined sheet width, the heat at the end of the heat roller 35a is not taken away due to the narrow sheet width, and the temperature at the end increases. Therefore, when it is determined in step S22 that the copy sheet is narrower than the predetermined sheet width, the heat roller 3
Without performing the temperature control of 5a, the process returns to step S10 to continue the copy operation. The size of the predetermined sheet width in step S22 may be an A4-R size or the like.

If it is determined in step S22 that the size is larger than the predetermined sheet width, the copying operation is interrupted (step S23), and the heat roller 35a is rotated idle (step S24). Then, it is determined whether or not the temperature difference between the central portion and the end portion is equal to or more than a temperature difference E indicating an abnormal operation of the fixing device (step S25). It is determined whether or not the difference is equal to or less than D (step 26). When it is determined that the temperature difference is not less than or equal to the predetermined value D (D or more), the process returns to step S24. When it is determined in step S26 that the temperature difference is less than or equal to the temperature difference D (step S26), the copying operation is performed. Is resumed, and the process returns to step S10. When it is determined in step S20 that the center temperature is lower than the end temperature, it is determined whether or not the temperature difference is equal to or higher than the temperature difference A at which the copying operation when the end temperature is high is interrupted (step S20). S3
0). If it is determined that the temperature difference between the central portion and the end portion is not more than the temperature difference A, the process returns to step 10 and the copying operation is continued. When it is determined that the temperature difference is equal to or larger than the temperature difference A, the copying operation is interrupted (step S31), and the heat roller 35a is caused to idle (step S32). Further, the microcomputer 40 determines whether or not the temperature difference is equal to or higher than the temperature difference F indicating the abnormality of the fixing device (step S33), and is determined to be equal to or lower than the temperature difference B at which the copying operation is restarted (step S34). As a result, when it is determined that the temperature difference is not smaller than the predetermined temperature difference B, the process returns to step 32, and the interruption of the copy operation is continued. When it is determined that the temperature difference is equal to or less than B, the copying operation is restarted (step S35),
Returning to step S10, the temperature control is repeated until the copying operation is completed.

As described above, the temperature detected by the temperature sensors provided at the center and the end of the heat roller is not less than the normal operating temperature T1 and not more than T3, and the temperature difference between the center and the end is: The copying operation is interrupted when the temperature difference exceeds a predetermined value.

Thus, the temperature distribution of the heat roller can be kept within a certain range, and the occurrence of partial fixing failure on the copy paper and the occurrence of paper wrinkles can be prevented. Further, the temperature detected by the temperature sensors provided at the center and the end of the heat roller is not less than the normal operating temperature T1 and not more than T3, and the temperature difference between the center and the end is a predetermined temperature difference A (or When the temperature difference becomes equal to or more than the temperature difference C), the copying operation is interrupted. When the temperature difference between the central portion and the end portion becomes equal to or less than the predetermined temperature difference B (or the temperature difference D), the copying operation is stopped. It is intended to resume. As a result, the temperature distribution of the heat roller is kept within a certain range, and it is possible to prevent the occurrence of a partial fixing failure on the copy paper and the occurrence of paper wrinkles.

[0037]

As described above in detail, according to the present invention, the temperature distribution of the fixing device is kept within a certain range, and the fixing is partially uneven due to uneven temperature distribution, or the paper is wrinkled due to the temperature difference. An image forming apparatus and an image forming method capable of preventing the occurrence of image formation can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an internal configuration of a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a main part of a control system of the digital copying machine.

FIG. 3 is an external view illustrating a configuration of a fixing device.

FIG. 4 is a view showing a heat distribution of heat supplied to a heat roller.

FIG. 5 is a flowchart for explaining copy operation control.

FIG. 6 is a diagram showing a temperature change of a heat roller for holding a continuous copy of A4-R size paper.

FIG. 7 is a diagram illustrating a temperature change of a heat roller during continuous copying of B5-R size paper.

FIG. 8 is a diagram illustrating a temperature change of a heat roller during continuous copying of A4 size paper.

FIG. 9 is a flowchart for explaining temperature control of the fixing device.

FIG. 10 is a diagram showing a temperature change of a heat roller at the time of continuous copying of A4-R size paper by only conventional temperature control.

FIG. 11 is a diagram showing a temperature change of a heat roller during continuous copying of A4-R size paper by conventional control.

FIG. 12 is a diagram showing a temperature change of a heat roller during continuous copying of B5-R size paper by conventional control.

FIG. 13 is a diagram showing a temperature change of a heat roller during continuous copying of A4 size paper by conventional control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 35 ... Fixing device 35a ... Heat roller 35c ... Heater lamps 41 and 42 ... Temperature sensor 40 ... Microcomputer 46 ... Temperature comparison part 47 ... Heater lamp driver

Claims (8)

[Claims] An image forming apparatus includes: an application unit configured to apply a developer image corresponding to image information onto an image forming medium; a conveying unit configured to convey the image forming medium by the applying unit; and a fixing roller including a heating element. A fixing unit that fixes the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying unit; and a surface of a separate portion of the fixing roller. First and second detecting means for respectively detecting the temperature, and at least a temperature detected by the first detecting means,
Control means for controlling the surface temperature of the fixing roller by controlling the power supply to the heating element; and when a temperature difference between the temperature detected by the first and second detection means becomes a predetermined value or more. An image forming apparatus, comprising: a stopping unit configured to stop conveyance of the image forming medium by the conveyance unit to the fixing unit. 2. An image forming apparatus comprising: an application unit configured to apply a developer image according to image information onto an image forming medium; a conveying unit configured to convey the image forming medium by the applying unit; and a fixing roller including a heating element. A fixing unit that fixes the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying unit; and a surface of a separate portion of the fixing roller. First and second detecting means for respectively detecting the temperature, and at least a temperature detected by the first detecting means,
Control means for controlling the surface temperature of the fixing roller by controlling power supply to the heating element; and a temperature difference between the temperatures detected by the first and second detection means being equal to or greater than the first temperature difference. A stopping means for stopping the conveyance of the image forming medium to the fixing means by the conveying means; and a temperature difference between the temperatures detected by the first and second detecting means after the stop by the stopping means. An image forming apparatus comprising: a resuming unit for resuming the conveyance of the image forming medium to the fixing unit by the conveying unit when the temperature difference becomes equal to or less than 2. 3. An image forming apparatus comprising: an application unit configured to apply a developer image according to image information onto an image forming medium; a conveying unit configured to convey the image forming medium by the applying unit; and a fixing roller including a heating element. A fixing unit that fixes the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying unit; and a surface of a separate portion of the fixing roller. First and second detecting means for respectively detecting the temperature, and at least a temperature detected by the first detecting means,
Control means for controlling the surface temperature of the fixing roller by controlling power supply to the heating element; and a width of the image forming medium conveyed by the conveying means is smaller than a width of the fixing roller, and Determining means for determining whether or not the width is equal to or less than a predetermined width; and a temperature difference between the temperatures detected by the first and second detecting means is equal to or more than a predetermined value, and the image forming medium has a predetermined width by the determining means. An image forming apparatus comprising: a stopping unit configured to stop the conveyance of the image forming medium to the fixing unit by the conveying unit when the determination is made. 4. An image forming apparatus comprising: an application unit configured to apply a developer image according to image information onto an image forming medium; a conveying unit configured to convey the image forming medium by the application unit; and a fixing roller including a heating element. A fixing unit that fixes the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying unit; and a surface of a separate portion of the fixing roller. First and second detecting means for respectively detecting the temperature, and at least a temperature detected by the first detecting means,
Control means for controlling the surface temperature of the fixing roller by controlling power supply to the heating element; and a width of the image forming medium conveyed by the conveying means is smaller than a width of the fixing roller, and Determining means for determining whether the width is equal to or less than a predetermined width; and a temperature difference between the temperatures detected by the first and second detecting means is equal to or greater than the first temperature difference, and the image forming medium is determined by the determining means. Stopping means for stopping the conveyance of the image forming medium to the fixing means by the conveying means when it is determined that the width is equal to or more than a predetermined width; and after the stop by the stopping means, the first and second detecting means An image forming apparatus comprising: a resuming unit for resuming the conveyance of the image forming medium to the fixing unit by the conveying unit when the detected temperature difference becomes equal to or less than the second temperature difference. . 5. An image forming apparatus comprising: an application unit configured to apply a developer image corresponding to image information onto an image forming medium; a conveying unit configured to convey the image forming medium by the applying unit; and a fixing roller including a heating element. A fixing unit that fixes the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying unit; and a surface of a separate portion of the fixing roller. An image forming apparatus comprising: first and second detecting means for detecting temperature, respectively, based on at least a temperature detected by the first detecting means.
By controlling the power supply to the heating element, the surface temperature of the fixing roller is controlled, and when the temperature difference between the temperatures detected by the first and second detecting means becomes a predetermined value or more, the fixing is performed. Stopping the conveyance of the image forming medium by the conveyance means to the means. 6. An application device for applying a developer image according to image information on an image forming medium, a conveying device for conveying the image forming medium by the applying device, and a fixing roller having a built-in heating element. A fixing unit that fixes the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying unit; and a surface of a separate portion of the fixing roller. An image forming apparatus comprising: first and second detecting means for detecting a temperature, respectively, based on at least a temperature detected by the first detecting means;
By controlling the power supply to the heating element, the surface temperature of the fixing roller is controlled, and when the temperature difference between the temperatures detected by the first and second detecting means is equal to or greater than the first temperature difference, Stopping the conveyance of the image formation medium to the fixing unit by the conveyance unit, and stopping the conveyance of the image formation medium to the fixing unit by the conveyance unit, and then detecting the first and second detection units. When the temperature difference between the temperatures becomes equal to or less than the second temperature difference, the conveyance of the image forming medium to the fixing unit by the conveyance unit is restarted. 7. An image forming apparatus comprising: an application unit configured to apply a developer image according to image information on an image forming medium; a conveying unit configured to convey the image forming medium by the applying unit; and a fixing roller including a heating element. A fixing unit that fixes the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying unit; and a surface of a separate portion of the fixing roller. An image forming apparatus comprising: first and second detecting means for detecting temperature, respectively, based on at least a temperature detected by the first detecting means.
By controlling the power supply to the heating element, the surface temperature of the fixing roller is controlled, and the width of the image forming medium conveyed by the conveying means is smaller than the width of the fixing roller, and has a predetermined width. And determining whether the temperature difference between the temperatures detected by the first and second detecting means is equal to or greater than a predetermined value and the image forming medium is equal to or greater than a predetermined width. Stopping the conveyance of the image forming medium to the fixing means by the means. 8. An image forming apparatus comprising: an applying unit configured to apply a developer image according to image information onto an image forming medium; a conveying unit configured to convey the image forming medium by the applying unit; and a fixing roller including a heating element. A fixing unit that fixes the developer on the image forming medium to the image forming medium by heating the image forming medium conveyed by the conveying unit; and a surface of a separate portion of the fixing roller. An image forming apparatus comprising: first and second detecting means for detecting temperature, respectively, based on at least a temperature detected by the first detecting means.
By controlling the power supply to the heating element, the surface temperature of the fixing roller is controlled, and the width of the image forming medium conveyed by the conveying means is smaller than the width of the fixing roller, and has a predetermined width. And determining whether the temperature difference between the temperatures detected by the first and second detecting means is equal to or greater than the first temperature difference and the image forming medium is equal to or greater than a predetermined width. Stopping the conveyance of the image formation medium to the fixing unit by the conveyance unit, stopping the conveyance of the image formation medium to the fixing unit by the conveyance unit, and then stopping the conveyance by the first and second detection units. When the temperature difference of the detected temperature becomes equal to or less than the second temperature difference, the conveyance of the image forming medium to the fixing unit by the conveyance unit is restarted.