JP2002031980A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease power consumption of a fixing device by making energy (power) required for heating of a heating roll to the necessary minimum in an image forming device utilizing an electrophotographic system. SOLUTION: In the device, the temperature of the surfaces of an upper heating roll 31 and a lower heating roll 32 is detected by an upper temperature sensor 35 and a lower temperature sensor 36, respectively, the time for the surface temperature of each heating roll 31 and 32 to reach a given temperature is predicted from the rate of variation of the surface temperature and a carrying mechanism 21 is controlled so that the fixing device 3 is reached by the paper P to be transferred on the predicted point of time.

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 a full-color printer using an electrophotographic system, and more particularly to a fixing apparatus for fixing a toner image transferred on a transfer sheet onto the transfer sheet. Related to temperature control.

[0002]

2. Description of the Related Art As is conventionally known, a fixing device of a monochrome image forming apparatus using an electrophotographic system is provided with a heater inside, a heating roller having a metal surface, and
An elastic layer such as silicon rubber is formed on the surface, and is configured with a pressure roller that abuts on a heating roller at a predetermined pressure.
The transfer paper having a single-color toner image transferred on its surface is passed between a heating roller and a pressure roller, the heat of the heating roller softens the toner, and the softened toner is transferred by the pressure of the pressure roller. It is fixed on the paper surface.

However, in a full-color image forming apparatus, for example, toner images of each color of Y (yellow), M (magenta), C (cyan) and B (black) are laminated on the surface of a transfer sheet. Therefore, when the toner image is fixed on the transfer receiving paper by using the fixing device for the single-color image forming apparatus, the toner image is fixed because the surface of the heating roller is hard or the pressure of the pressure roller is too strong. There is a problem that the toner is crushed and the colors are mixed, and the image quality of the image formed on the transfer receiving paper is deteriorated.

Therefore, in a full-color image forming apparatus, an elastic layer made of a heat-resistant resin such as silicon rubber is also formed on the surface of the heating roller in order to reduce the contact pressure between the heating roller and the pressing roller. A heater is also provided inside the pressure roller to compensate for a decrease in thermal conductivity due to the layer. In other words, a pair of heating rollers having an elastic layer on the surface are used instead of the heating roller and the pressure roller,
The pair of heating rollers are brought into contact with each other with a pressure smaller than the pressure at which the pressure roller comes into contact with the heating roller, and the transfer paper on which the toner images of a plurality of colors are transferred by lamination is passed between the pair of heating rollers. Further, the toner is softened by the heat of the heating roller, and the softened toner is fixed to the surface of the transfer receiving paper by a pressure acting between the heating rollers.

When the print start switch is turned on, the heater inside the heating roller is turned on, and the temperature of the heating roller surface rises relatively quickly from a predetermined standby temperature to a target control temperature. Then, when the temperature of the surface of the heating roller reaches the target control temperature, conveyance of the transfer-receiving sheet, exposure of the surface of the photosensitive drum, and the like are started.

When the number of prints is as small as about 1 to 3, the printing operation ends before the temperature of the surface of the heating roller is controlled. However, as the number of prints increases, it is necessary to control the temperature of the heating roller. In the conventional heating roller temperature control, regardless of whether for single color or full color, the temperature of the surface of the heating roller is generally detected by a temperature sensor, and the temperature of the surface of the heating roller reaches the upper limit of the target control temperature range. It is controlled so that the heater is turned off at a point in time, and turned on again when it drops to the lower limit of the target control temperature range.

[0007]

In the fixing device of the conventional image forming apparatus, the transfer of the transfer sheet is started when the temperature of the surface of the heating roller reaches the target control temperature, and the exposure of the photosensitive drum is performed. However, there is a problem in that there is a large time loss between when the user gives an instruction to start printing by turning on a switch of the image forming apparatus and when the printing operation is actually started. Was.

Further, since the heater is provided inside the heating roller, a temperature gradient is formed from the heater to the surface of the heating roller. In particular, in a full-color image forming apparatus, since an elastic layer such as silicon rubber is formed on the surface of the heating roller, the temperature gradient is steep.
Therefore, when the temperature of the surface of the heating roller is detected by the temperature sensor and the heater is turned off when the surface temperature reaches the target control temperature, the inside of the heating roller is at a higher temperature. Due to the heat capacity of the core part, the surface temperature increases even after the heater is turned off. When the number of prints is small, a rise in temperature after printing is a waste of energy, which causes an increase in power consumption of the image forming apparatus.

On the other hand, when the number of prints is large and it is necessary to control the temperature of the heating roller, even if the heater is turned on again when the temperature of the surface of the heating roller drops to the lower limit of the target control temperature range, the heating roller is not affected. It takes time for the surface temperature to rise, and during this time, there is a possibility that prints that have passed through the fixing device may have defective fixing.

The present invention has been made in order to solve the above-mentioned problems of the prior art. First, the time from when the user instructs the start of the printing operation to when the printing operation is actually started is described. It is an object of the present invention to provide an image forming apparatus capable of shortening the time. Secondly, it is another object of the present invention to provide an image forming apparatus that reduces power consumption by a fixing device and reduces causes of image quality deterioration such as defective fixing.

[0011]

In order to achieve the above object, a first image forming apparatus of the present invention has a heating means,
A fixing device including a heating roller whose surface temperature is controlled by turning on / off a heating unit, a temperature sensor for measuring the temperature of the surface of the heating roller, and a temperature of the surface of the heating roller detected by the temperature sensor Calculating means for predicting the time when the temperature of the surface of the heating roller reaches a predetermined temperature, and the toner image is transferred to the surface when the temperature of the surface of the heating roller reaches the predetermined temperature. As the leading end of the transfer receiving paper reaches the fixing device,
And a transfer sheet transfer control means for controlling timing of starting transfer of the transfer sheet.

Further, a second image forming apparatus of the present invention includes a fixing device including a heating roller having a heating unit, the surface temperature of which is controlled by turning on / off the heating unit, and a surface of the heating roller. A temperature sensor for measuring the temperature of the heating roller, a calculating means for predicting a time when the temperature of the surface of the heating roller reaches a predetermined temperature from a change in the temperature of the surface of the heating roller detected by the temperature sensor, and Temperature control means for predicting a change in the temperature of the surface of the heating roller according to the size and the number of prints, and controlling on / off of the heating means.

In each of the above structures, the heating roller is
It is preferable that the heating means is provided inside the core body, having a metal-made cylindrical core body and an elastic layer provided on the surface of the core body.

It is preferable that the heating roller is a pair of rollers provided vertically above and below the transporting path of the sheet to be transferred and contacting each other at a predetermined pressure.

Further, it is preferable that the upper and lower heating rollers are individually controlled.

Further, it is preferable that the heating means is a heating element.

Alternatively, it is preferable that the heating means is an induction heating device including a coil and a high-frequency circuit for applying a high-frequency voltage to the coil.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the image forming apparatus of the present invention will be described. FIG. 1 is a diagram showing a configuration of a color printer which is an embodiment of the image forming apparatus of the present invention. As shown in FIG. 1, in this color printer, for example, Y (yellow), M (magenta), C (cyan),
Four image forming units 10 corresponding to the four colors (black)
Y, 10M, 10C, and 10B are arranged in parallel.
Each image forming unit 10Y, 10M, 10C, 10B
Are substantially the same, and differ only in the color of the toner. Therefore, only the image forming unit 10Y will be described in detail.

The image forming unit 10Y includes a photosensitive drum (image carrier) 11 which rotates about an axis perpendicular to the paper surface.
A charger 12 for charging a predetermined range of the surface of the photoconductor drum 11 substantially uniformly, an exposure device 13 for forming a latent image by selectively exposing the surface of the photoconductor drum 11, A developing device 14 for developing a latent image formed on the photosensitive drum 11 by attaching toner to the latent image to form a toner image, and transferring the toner image on the photosensitive drum 11 onto a transfer paper Transfer device 1 for performing
5 and a cleaning device 16 for removing toner remaining on the photosensitive drum 11.

Each of the image forming units 10Y, 10M, 10M
Below the transfer belts C and 10B, an endless transfer belt 20 for transporting the transfer sheet P in order from right to left in the figure and a drive mechanism 21 thereof are provided. Each image forming unit 1
The transfer devices 15 of 0Y, 10M, 10C, and 10B are provided inside the transfer belt 20, respectively. The image forming units 10Y, 10M,
The toner images of each color are sequentially transferred by 10C and 10B. The toner image transferred onto the transfer sheet P is fixed by a fixing device 30 provided on the downstream side of the transfer belt 20 in the transport direction of the transfer sheet P, and then the transfer sheet P is discharged outside the apparatus. Is done.

The fixing device 30 includes an upper heating roller 31 which rotates about a direction perpendicular to the transport direction of the transfer sheet P as an axis.
A lower heating roller 32 that contacts the upper heating roller 31 at a predetermined pressure, an upper heating device 33 provided inside the upper heating roller 31, and a lower heating device 34 provided inside the lower heating roller 32, Upper heating roller 31 and lower heating roller 3
Upper temperature sensor 35 and lower temperature sensor 36 for detecting the temperature of the surface of
Control device 100 for controlling ON / OFF of the control unit 4 (see FIG. 6)
It is composed of Further, in the vicinity of the fixing device 30, for example, on the downstream side in the transport direction of the transfer sheet P, a paper discharge switch 37 for detecting the transfer of the transfer sheet P is provided.

As shown in FIG. 2, the upper heating roller 31 and the lower heating roller 32 are formed of a hollow cylindrical metal core 3.
00 and an elastic layer 301 such as silicon rubber provided on the outer peripheral surface of the core 300, and an upper heating device 33 and a lower heating device 34 such as a segment heater inside the core 300.
Is provided.

Although the upper heating roller 31 and the lower heating roller 32 have substantially the same configuration, since the toner image is transferred to the upper side of the transfer sheet P, the upper heating roller 31 is provided on the upper heating roller 31 which is in direct contact with the toner image. The power and target control temperature of the upper heating device 33 are set to be higher and higher than the power and target control temperature of the lower heating device 34 provided on the lower heating roller 32, respectively.

Next, the upper heating device 33 in the present embodiment
The timing of the temperature control of the lower heating device 34 and the start of the transfer of the transfer sheet P will be described.

FIG. 3 shows a case where the number of prints is three or less, and (a) shows an upper heating roller 31 and a lower heating roller 32.
(B) is a timing chart showing the on / off timing of the upper heating device 33 inside the upper heating roller 31 and the lower heating device 34 inside the lower heating roller 32; 3) is a timing chart showing the timing of discharging the transfer sheet P on which the toner image has been fixed from the fixing device.

In FIG. 3A, the solid line is a graph showing a change in the temperature of the surface of the upper heating roller 31. As an example, the target control temperature is set to 160 ° C. A broken line is a graph showing a change in the temperature of the surface of the lower heating roller 32, and the target control temperature is set to 140 ° C.

In FIG. 3B, the vertical axis represents the upper heating device 33 of the upper heating roller 31 and the lower heating device 34 of the lower heating roller 32.
Represents the voltage (unit: V) applied to.

Similarly, in FIG. 3C, the vertical axis represents the output (unit: V) of the discharge switch 37 provided near the fixing device.
The output is set so that the output when the transfer sheet is not passing is 5 V and the output when the transfer sheet is passing is 0 V. Also in this case, the voltage value itself does not have much meaning and may be taken as the timing of turning on / off the discharge switch 37.

As can be seen by comparing FIGS. 3A and 3B, the surface temperature of the upper heating roller 31 is set to the target control temperature (1).
When the temperature reaches about 150 ° C. slightly lower than 60 ° C.), the upper heating device 33 and the lower heating device 34 of the lower heating roller 32 are turned off almost simultaneously. However, the temperature inside the upper heating roller 31 and the lower heating roller 32 is higher than the surface, and the internal heat is gradually transmitted to the surface. The temperature continues to rise and has reached the target control temperature respectively.

On the other hand, as can be seen by comparing FIGS. 3A and 3C, when the temperature of the surface of the upper heating roller 31 reaches about 150 ° C., the first transfer of the transfer sheet P is started. are doing. In this case, since the number of prints is small, when the surface temperatures of the upper heating roller 31 and the lower heating roller 32 reach the target control temperatures, the printing is completed. Therefore, the upper heating device 33 of the upper heating roller 31
It is not necessary to turn on the lower heating device 34 of the lower heating roller 32 again.

FIG. 4 shows the case where the number of prints is 4 or more and 8 or less, and (a), (b) and (c) are the same as those in FIG. As can be seen by comparing FIG. 4B and FIG. 3B, the upper heating device 33 and the lower heating device 34 of the lower heating roller 32 are turned off almost at the same time. In the case shown in FIG. 4B, the timing of turning off is larger than that in FIG.
It is slower than the case shown in (b).

FIG. 5 shows a case where the number of prints is nine or more, and (a), (b) and (c) are the same as those in FIG. In this case, since the number of prints is large,
It is necessary to maintain the temperature of each surface of the upper heating roller 31 and the lower heating roller 32 at the target control temperature for a certain time. Therefore, as shown in FIG. 5B, the upper heating device 33 of the upper heating roller 31 and the lower heating device 34 of the lower heating roller 32 are
Temperature control is performed so as to be turned on / off at different timings.

Specifically, in FIG. 5A, in order to reduce the overshoot in which the temperature of the surface of the upper heating roller 31 becomes 160 ° C. or more, as shown in FIG.
The upper heating device 33 of the upper heating roller 31 having a large power is turned off first. Even when the upper heating device 33 of the upper heating roller 31 is turned off, the heat transmitted from the inside of the upper heating roller 31 and the heat of the lower heating device 34 of the lower heating roller 32 cause the upper heating roller 31 and the lower heating roller The surface temperature of 32 is maintained at approximately the target control temperature.

Further, from the change in the surface temperature of the upper heating roller 31, the mode is returned to the normal mode at the timing of the undershoot in which the surface temperature of the upper heating roller 31 becomes 160 ° C. or less. Turn on again. Thereafter, while measuring changes in the surface temperature of the upper heating roller 31 and the temperature of the surface of the lower heating roller 32, the timings of overshoot and undershoot are predicted, and the upper heating device 33 is adjusted in accordance with the timing.
On / off of the lower heating device 34 is controlled. Therefore,
When the number of prints is nine or more, the upper heating device 33 of the upper heating roller 31 and the lower heating device 34 of the lower heating roller 32
Are controlled independently of each other.

Next, the control device 100 in the present embodiment
6 is shown in FIG. The overall control unit 101 includes, for example, a CPU that performs arithmetic processing and a ROM that stores a control program and the like, and controls the entire image forming apparatus. The temperature estimating unit 102 includes a CPU, a ROM storing a temperature estimating program, a RAM temporarily storing measured data, and the like.
5 and a time required for the surface temperatures of the upper heating roller 31 and the lower heating roller 32 to reach a predetermined target control temperature from changes in the surface temperatures of the upper heating roller 31 and the lower heating roller 32 detected by the lower temperature sensor 36. , The timing of overshoot and undershoot, etc. are predicted from the target control temperature. The temperature control unit 103 includes, for example, a CPU, R
OM and a switching element such as a transistor. Based on the prediction result of the temperature prediction unit 102 and the number of prints by the print number calculation unit 104 described later,
On / off of the upper heating device 33 and the lower heating device 34 is controlled.

The number-of-prints calculation unit 104 includes a CPU, a ROM, and the like, and has an interface (I / F) 3.
The print size and the number of prints are predicted from image data transmitted from a personal computer or the like via the printer 8. The transmitted image data is R
The information is temporarily stored in the storage unit 105 such as an AM. The paper transport control unit 106 includes, for example, a CPU, a ROM, a switching element, and the like. The paper transport control unit 106 is configured to take out the paper P to be transferred from the paper cassette or transport the paper P based on the prediction result of the temperature prediction unit 102. On / off of the drive mechanism 21 is controlled. The exposure control unit 107 includes a CPU,
Each of the image forming units 10 </ b> Y, 10 </ b> M, and 10 </ b> M is configured by a ROM or the like, using image data stored in the storage
10C and 10B are controlled. Also, the discharge switch 37
Is also input to the overall control unit 101 and is used by the sheet conveyance control unit 106 to control the conveyance timing of the transfer target sheet P.

FIG. 7 shows a control flow of the control circuit 100 immediately after the main switch of the image forming apparatus is turned on. First, when the main switch of the image forming apparatus is turned on, the temperature control unit 103 controls the switching element and the like, and the upper heating device 33 and the lower heating device 3 of the fixing device 30.
4, the heating of the upper heating roller 31 and the lower heating roller 32 is started (step # 1). In parallel with this, the temperature prediction unit 102 uses the output signals from the upper temperature sensor 35 and the lower
The measurement of the surface temperature of the first and lower heating rollers 32 is started (step # 3).

Immediately after the main switch of the image forming apparatus is turned on, the surface temperature of the upper heating roller 31 and the lower heating roller 32 is generally room temperature, so that the warm-up is performed to a predetermined standby temperature. Therefore, the temperature prediction unit 102 monitors the change in the temperature of the surface of the upper heating roller 31 and the lower heating roller 32 while monitoring the temperature of the surface of the upper heating roller 31 and the lower heating roller 32 until the temperature of the surface reaches the predetermined standby temperature. Is calculated (step # 5).

Next, the overall control unit 101 determines whether or not to perform the printing operation following the warm-up from the output of the print number calculation unit 104 and the like (step # 7). When the print operation is not performed (Step # 7)
NO), the temperature control unit 103 waits for the warm-up time W1 to elapse (step # 9), and stops the power supply to the upper heating device 33 and the lower heating device 34 with the elapse of the warm-up time W1. The heating of the lower heating roller 32 and the lower heating roller 32 is terminated (step # 1).
1).

On the other hand, when an image signal is output from a personal computer or the like via the interface 38 (YES in step # 7), the number-of-printed-sheets calculating section 1
In step # 13, data relating to the time required from the start of printing to the end of printing, such as the print size and the number of prints, is calculated using the image signal (step # 13).

When the number of prints is calculated, the temperature controller 103 determines whether the number of prints is three or less (step # 15) or eight or less (step # 17). When the number of prints is 3 or less (step #
15 (YES at 15), the temperature control unit 103
And the timing S for turning off the lower heating device 34 almost simultaneously
1 (see FIG. 3B) is calculated (step # 19).
In parallel with this, when the temperature of the surface of the upper heating roller 31 reaches a predetermined temperature, the paper transport control unit 106 determines from the prediction result of the temperature The transfer start timing T1 of the sheet P to be transferred so that the leading end of the sheet P just reaches the fixing device 30.
(See FIG. 3C) (step # 21).

Similarly, when the number of prints is 4 or more and 8 or less (YES in step # 17), the temperature control unit 103
Calculates the timing S2 (see FIG. 4B) for turning off the upper heating device 33 and the lower heating device 34 almost simultaneously (step # 23). Also, the paper transport control unit 106
From the prediction result of the temperature predicting unit 102, a timing T1 (see FIG. 4C) of the start of the transfer of the transfer sheet P is calculated (step # 25).

If the number of prints is nine or more (NO in step # 17), the temperature control unit 103
And the timing S for turning off the lower heating device 34 almost simultaneously
3 (see FIG. 5B) is calculated (step # 27).
Further, the sheet conveyance control unit 106 determines, based on the prediction result of the temperature prediction unit 102, that the transfer start timing T1
(See FIG. 5C) is calculated (step # 29). When the number of prints is nine or more, the upper heating device 33 and the lower heating device 34 are controlled to be on / off as described above, and the upper heating roller 31 and the lower heating roller 32 are turned on until the printing operation is completed. Are controlled so that the temperature of each of them is maintained within a certain temperature range with respect to the target control temperatures (for example, 160 ° C. and 140 ° C.) (Step #)
31, # 33). Upon completion of the printing operation, the flow returns to step # 3 to prepare for the next printing. This flow is forcibly terminated by turning off the main switch of the image forming apparatus.

In the above embodiment, the upper heating device 33 provided inside the upper heating roller 31 and the lower heating device 34 provided inside the lower heating roller 32
Although each heating element such as a segment heater was used, the present invention is not limited to this. The heating element is composed of a coil and a high-frequency circuit for applying a high-frequency voltage to the coil.
An induction heating device or the like that directly generates heat in the core body 300 by using an eddy current flowing through zero may be used. Although a full-color printer has been described as an example of the image forming apparatus, the present invention is not limited to this, and uses heating as a fixing device, such as a color or monochromatic printer, a copying machine, and a facsimile machine. It goes without saying that it can be applied to all things. Further, the heating device is not limited to the device provided inside the heating roller, but may be provided outside the heating roller.

[0045]

As described above, according to the first image forming apparatus of the present invention, a fixing device including a heating roller having a heating means, the surface temperature of which is controlled by turning on / off the heating means. An apparatus, a temperature sensor for measuring the temperature of the surface of the heating roller, and arithmetic means for predicting a point in time at which the temperature of the surface of the heating roller reaches a predetermined temperature from a change in the temperature of the surface of the heating roller detected by the temperature sensor. When the surface temperature of the heating roller reaches the predetermined temperature, the transfer start timing of the transfer sheet is controlled so that the leading end of the transfer sheet on which the toner image has been transferred reaches the fixing device. Since the transfer sheet transfer control means is provided, the time required for the transfer sheet to reach the fixing device after the surface of the heating roller reaches a predetermined temperature can be reduced as compared with the conventional example. The time required to print is shortened.

Further, according to the second image forming apparatus of the present invention, there is provided a fixing device including a heating roller having a heating means, the surface temperature of which is controlled by turning on / off the heating means.
A temperature sensor for measuring the temperature of the surface of the heating roller, calculating means for predicting a point in time at which the temperature of the surface of the heating roller reaches a predetermined temperature based on a change in the temperature of the surface of the heating roller detected by the temperature sensor; A temperature control unit for predicting a change in the temperature of the surface of the heating roller according to the size of the paper and the number of prints and controlling ON / OFF of the heating unit is provided. By turning off the heating means in anticipation of the time point when the temperature reaches the temperature, the energy (electric power) required for heating the heating roller can be minimized, and the power consumption by the fixing device can be reduced. is there. Also, instead of controlling the on / off of the heating means when the temperature actually changes as in the conventional example, the on / off of the heating means is controlled by predicting a change in the temperature of the surface of the heating roller. Therefore, the width of the change in the temperature of the surface of the heating roller can be reduced, and even when a plurality of sheets are printed, the fixing conditions are stabilized, and it is possible to prevent image quality deterioration such as defective fixing.

As a heating roller, a metal roller having a cylindrical core and an elastic layer provided on the surface of the core is used, and the transfer means is provided by providing a heating means inside the core. Even when a plurality of color toner images are stacked on a sheet, the toner image can be satisfactorily fixed on the sheet to be transferred, and the heating device itself can be made compact. In particular, when an elastic layer such as a heat-resistant resin is provided on the surface of the heating roller, the present invention is effective because heat conductivity is low and a certain time is required until the surface is heated to a predetermined temperature. It is.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a color printer that is an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a cross-sectional view showing a detailed configuration of an upper heating roller 31 and a lower heating roller 32 in the embodiment.

3A is a graph showing a change in surface temperature of an upper heating roller 31 and a lower heating roller 32 when the number of prints is three or less, and FIG. FIG. 4C is a timing chart showing ON / OFF timing, and FIG. 5C is a timing chart showing timing of discharging the transfer sheet P on which the toner image is fixed from the fixing device.

4A is a graph showing a change in surface temperature of an upper heating roller 31 and a lower heating roller 32 when the number of prints is 4 or more and 8 or less, and FIG.
3 is a timing chart showing ON / OFF timing of the lower heating device 34, and FIG. 3C is a timing chart showing timing of discharging the transfer sheet P on which the toner image is fixed from the fixing device.

5A is a graph showing a change in the temperature of the surface of the upper heating roller 31 and the lower heating roller 32 when the number of prints is nine or more, and FIG. FIG. 4C is a timing chart showing ON / OFF timing, and FIG. 5C is a timing chart showing timing of discharging the transfer sheet P on which the toner image is fixed from the fixing device.

FIG. 6 is a block diagram illustrating a configuration of a control device 100 according to the embodiment.

FIG. 7 is a flowchart illustrating an operation of the image forming apparatus according to the exemplary embodiment.

[Explanation of symbols]

 10Y, 10M, 10C, 10B: Image forming unit 20: Transfer belt 21: Transport mechanism 30: Fixing device 31: Upper heating roller 32: Lower heating roller 33: Upper heating device 34: Lower heating device 35: Upper temperature sensor 36: Lower temperature sensor 37: Ejection switch 38: Interface 100: Control device 101: Overall control unit 102: Temperature prediction unit 103: Temperature control unit 104: Print number calculation unit 105: Storage unit 106: Paper transport control unit 107: Exposure control unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 3/00 310 H05B 3/00 335 335 6/06 393 6/06 393 6/14 6/14 G03G 21 / 00 372 (72) Inventor Shokane Dobashi 1-2-28 Tamazo, Chuo-ku, Osaka-shi F-term in Kyocera Mita Corporation (Reference) 2H027 DA12 DA38 DA46 DC10 DC19 EA12 EC02 EC20 ED17 ED25 EE02 EE07 EF06 2H033 AA32 BA07 BA25 BA25 BA32 BB03 BB13 BB15 BB18 BB28 BE06 CA03 CA07 CA17 CA19 CA28 CA30 CA32. LL13 MM02

Claims (7)

[Claims] A fixing device that includes a heating roller that has a heating unit and whose surface temperature is controlled by turning on / off the heating unit; a temperature sensor that measures a temperature of a surface of the heating roller; Arrival time estimating means for estimating when the temperature of the surface of the heating roller reaches a predetermined temperature from a change in the temperature of the surface of the heating roller detected by a sensor; and Transfer paper transport control means for controlling the timing of starting the transport of the transfer paper so that the leading end of the transfer paper having the toner image transferred to the surface thereof reaches the fixing device when the paper reaches the fixing device. An image forming apparatus comprising: 2. A fixing device including a heating roller having a heating unit, the surface temperature of which is controlled by turning on / off the heating unit, a temperature sensor for measuring the surface temperature of the heating roller, and the temperature sensor. An arrival time estimating means for estimating a time point at which the temperature of the surface of the heating roller reaches a predetermined temperature from a change in the temperature of the surface of the heating roller detected by a sensor; and The image forming apparatus further includes a temperature control unit that predicts a change in the temperature of the surface of the heating roller and controls on / off of the heating unit. 3. The heating roller has a metal tubular core and an elastic layer provided on the surface of the core, and the heating means is provided inside the core. The image forming apparatus according to claim 1, wherein: 4. The image forming apparatus according to claim 3, wherein the heating roller is a pair of rollers provided vertically above and below the conveyance path of the sheet to be transferred and abutting on each other at a predetermined pressure. 5. The image forming apparatus according to claim 4, wherein the upper and lower heating rollers are individually controlled. 6. The image forming apparatus according to claim 3, wherein the heating unit is a heating element. 7. The image forming apparatus according to claim 3, wherein the heating unit is an induction heating device including a coil and a high-frequency circuit for applying a high-frequency voltage to the coil. .