JP3048491B2 - Fixing device temperature controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for a fixing device which is applied to a fixing device of an image forming apparatus such as an electrostatic copying machine or a facsimile and controls ON / OFF of a heater for heating the fixing device.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine, an electrostatic latent image formed on a photosensitive drum is visualized as a toner image, and the toner image is transferred onto a sheet of paper. I try to fix it. The fixing device includes a pressure roller and a heat roller heated by a heater, and heats and fixes toner on a sheet passing between the rollers.

In order to perform heat fixing, it is necessary that the fixing device has reached a predetermined high temperature. For this reason, in a copying machine or the like, a predetermined waiting time is required from when the power is turned on until copying becomes possible, which is inconvenient for the user. Therefore, there is a demand for reducing the waiting time and, if possible, eliminating the waiting time. For that purpose, it is necessary to heat the fixing device to a predetermined high temperature in a short time.

[0004]

On the other hand, from the viewpoint of energy saving, it is preferable to heat the fixing device only when required.
Also in this case, it is necessary to heat the fixing device to a predetermined high temperature within a very short time from the start of copying until the sheet is conveyed to the fixing device. Therefore, in order to enable rapid heating of the fixing device, the inventor of the present application increased the heating capacity of the heater, reduced the diameter of the heat roller and the pressure roller, and set the heat capacity relatively to the heating capacity of the heater. I tried to make it smaller.

[0005] However, in some copies up to several times from the start of copying, a fixing failure may occur. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and can heat a fixing device only when image formation is required, and can also prevent a fixing defect occurring at an early stage of image formation thereafter. An object of the present invention is to provide a temperature control device for a fixing device.

[0006]

According to a first aspect of the present invention, there is provided an image forming apparatus including a pressure roller and a heat roller heated by a heater, and heat-fixing toner to a sheet passing between the two rollers. A temperature control device of a fixing device that is applied to a fixing device of an image forming apparatus and that turns on and off the power supply to the heater based on a signal from a heat roller temperature detection unit that detects a temperature of the heat roller; In response to the input, the process is started with energization of the heater turned on, and the warm-up control unit that turns off energization of the heater when the required first off-temperature is reached, and the warm-up control unit Starts processing to target the required control temperature in response to turning off the power to the heater, and processes in the state where the power to the heater is turned off in response to the input of the image formation end signal. A normal control unit for ending the processing, wherein the normal control unit adds an initial correction amount determined in accordance with an amount related to the cumulative energization time to the heater after the input of the image formation start signal in an initial stage of the process. and sets the control temperature, the initial correction unit that stores an amount related to the cumulative energization time during the image forming ends at the end of image formation seen including, the initial correction unit, the warm-up control unit
Before turning on the power to the heater by
According to the initial detected temperature detected by the output means,
Adjust the initial correction amount, and adjust the
The amount of the initial correction is reduced in accordance with the increase of the amount .

According to a second aspect of the present invention, in the temperature control device for a fixing device according to the first aspect, the initial correction section turns on power supply to the heater by a warm-up control section.
Before the heat roller temperature detection means
If the period detection temperature is higher than the predetermined temperature,
At the end of the previous image formation stored at the end of image formation
Related to the cumulative energizing time and the current image formation start
The amount related to the accumulated energization time after the signal input
The initial correction amount gradually decreases as the amount of
It is characterized by having it done .

[0008]

[0009]

[0010]

According to the first aspect of the invention, when image formation is started, the warm-up control section starts energizing the heater to perform warm-up, and when the first off-temperature is reached. Then, the processing shifts to the processing by the normal control unit, and thereafter, the sheet passes through the fixing device. In the early stage of the process of the normal control unit, even if the heat roller heated by the heater has reached a predetermined temperature, the pressure roller tends not to be sufficiently heated yet, and this is a cause of the fixing failure. Was thought to cause. Therefore, the control temperature in the initial stage of the process of the normal control unit is corrected to be high, so that the occurrence of the fixing failure is prevented.

On the other hand, when the temperature of the pressure roller is high, if the initial correction unit performs the same correction as when the temperature is low, the control temperature may be too high. Therefore, when the detected temperature of the heat roller before the processing by the warm-up control unit is high, it is assumed that the temperature of the pressure roller is also high, and the initial correction amount is corrected. The temperature of the pressure roller,
It is considered that the temperature tends to increase as the cumulative energization time to the heater increases. Therefore, to prevent that with the increase of the quantity associated with the cumulative energization time of the heater by <br/> going to reduce the initial amount of correction, the control temperature becomes too high.

According to the second aspect of the invention, the following effects can be obtained. That is, the image formation may be started again only a short time after the end of the previous image formation, and in this case, when the current image formation is performed, the temperature of the pressure roller is still high. It is considered to be in a state. Therefore, when the temperature of the pressure roller is assumed to be high, and the initial detection temperature of the heat roller is high, the amount related to the cumulative energization time to the heater at the end of the previous image formation and the heater in the current image formation And an amount related to the cumulative energization time to the motor, and the initial correction amount is reduced in accordance with the increase of the added amount. As a result, the control temperature is prevented from becoming too high.

[0013]

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a schematic diagram showing an internal configuration of a copying machine as an image forming apparatus including a temperature control device of a fixing device according to an embodiment of the present invention. Referring to FIG. 1, the copying machine is arranged along the upper surface of copying machine main body 1 in a state in which a document placed on a transparent document mounting plate is pressed by a document holder inside copying machine main body 1. An optical system 3 for illuminating the original table 2 to be moved, the original moved by the original table 2 and guiding the reflected light from the original to the photosensitive drum 42, and developing the electrostatic latent image formed on the photosensitive drum 42 The image forming unit 4 includes a fixing unit 54 that heats and fixes the toner image transferred to the sheet after being visualized by the device 41 and a toner image transferred to the sheet. And a paper transport section 5 for discharging the paper to the discharge tray 56 of the printer.

Although not shown, an operation section on which a copy start switch and other switches are arranged is provided on the upper surface of the copying machine main body 1. The optical system 3 includes a fluorescent lamp 31 as a light source for illuminating a document moved on the document table, a plurality of light sources arranged in a direction orthogonal to the document moving direction, and forming a reflected light from the document on a photosensitive drum 42. Is formed.

The image forming section 4 has a charging charger 43, a developing device 41, a transfer charger 44 and a cleaning device 45 arranged around a photosensitive drum 42 in this order. The image forming unit 4 includes a charging charger 43
On the outer peripheral surface of the photosensitive drum 42 uniformly charged by
After forming an electrostatic latent image by forming an original image, the electrostatic latent image is visualized into a toner image by a developing device 41, the toner image is transferred to a sheet by a transfer charger 44, and a residual toner is removed by a cleaning device. 45 for recovery.

The sheet transport section 5 pulls out sheets one by one from a sheet feed tray 61, and abuts the leading edge of a sheet from a manual sheet feed section 60 or a sheet feed tray 61 with a sheet feed roller 51 having a half-moon cross section. Registration rollers 53a and 53b for temporarily holding the sheet, and a heat roller 54a included in a fixing device 54 for fixing the toner image transferred to the sheet.
And a pressure roller 54b, and a pair of discharge rollers 55a, 55
5b.

The paper transport section 5 further includes a paper feed detection switch 57, a paper discharge detection switch 58, a heat roller temperature detection sensor SH, and an ambient temperature detection sensor SA. The paper feed detection switch 57 is a limit switch disposed upstream of the registration rollers 53a and 53b in the paper transport direction. The paper discharge detection switch 58 is a limit switch disposed upstream of the discharge rollers 55a and 55b in the paper transport direction. Consists of switches. Further, the heat roller temperature detection sensor SH is composed of a thermistor arranged at a predetermined portion of the heat roller 54a, and detects the temperature of the heat roller 54a.
The ambient temperature detection sensor SA is composed of a thermistor arranged at a predetermined position in the copying machine main body 1 that is not affected by heat, and detects the ambient temperature of the environment where the fixing device 54 is placed .

The fixing device 54 heats and fixes the toner on the sheet passing between the pressure roller 54b and the heat roller 54a heated by the heater 59. Heat roller 5
Reference numeral 4a denotes a metal roller, in which the heater 59 including a cartridge heater is housed, and heated by the heater 59. The pressure roller 54b is made of a rubber roller, is supported movably in the radial direction, and is urged by a spring member (not shown) toward the heat roller 54a with a predetermined urging force.

FIG. 2 is a block diagram showing an electric configuration of the copying machine. The control unit 7 for controlling the operation of each unit of the copying machine includes a CPU 71, a ROM 72 storing a program to be executed by the CPU 71, a RAM 73 used as a work area of the CPU, and the number of energizations to the heater 59 at the end of image formation. And the like are stored. The CPU 71 is provided on the upper surface of the copying machine main body 1 and is connected with the operation unit 10 including the copy start switch 10a, the image forming unit 4, the sheet transporting unit 5, the motor drive circuit MC, and the document table moving mechanism 20. . The motor drive circuit MC drives a motor M as a drive source for driving the document table 2, the image forming unit 4, the sheet conveying unit 5, and the like. Original table moving mechanism 2 by motor M
0, the image forming unit 4 and the paper transport mechanism PDM are driven in synchronization.

The paper transport unit 5 includes a paper feed detection switch 57, a paper discharge detection switch 58, a heat roller temperature detection sensor SH, an ambient temperature detection sensor SA, and an on / off switch for energizing a heater 59. A relay drive circuit RDC for driving the relay R and a paper transport mechanism PDM for transporting the paper by the driving force of the motor M are included, and are each connected to the CPU 71.

The CPU 71 controls ON / OFF of the heater 59 of the fixing device 54 based on a program read from the ROM 72. The concept of the control at this time is to continuously energize the heater 59 in accordance with a copy start signal, A warm-up control unit (not shown) for raising the temperature to a temperature (first off-temperature T ₂ ) described later, and intermittently energizing the heater 59 based on the elapsed time and the like after the warm-up is completed. And a normal control unit (not shown) for maintaining a predetermined control temperature.

In setting the control temperature,
As described later, the reference temperature T ₃ that is initially set, (not shown) initial correction unit for adding the initial correction amount D ₁ (n) in the initial process, when fed only during sheet passing correction amount D ₂ corrected by the sheet passing time correcting unit for adding the environmental correction unit (not shown), and in accordance with the ambient temperature t ₀ adds the environmental correction amount D ₃ (not shown), are set control temperature T _C is . As will be described later in detail, the initial correction unit adjusts the initial correction amount according to the initial detection temperature of the heat roller 54a and the number of energizations n to the heater 59 before the warm-up control unit starts processing. Thus, the initial correction amount is gradually reduced with the passage of time. This is considered to be because the temperature of the pressure roller 54b tends to increase in accordance with the increase in the cumulative energizing time to the heater 59. Therefore, the heater that performs the intermittent operation as an amount directly related to the cumulative energizing time is used. The initial correction amount is reduced in accordance with an increase in the number of times of energization of the capacitor 59.

The operation for performing such control will be described with reference to flowcharts shown in FIGS. 3 to 6 and FIGS. 7 to 9 showing temporal changes in the temperatures of the heat roller 54a and the pressure roller 54b. explain. Step S
Steps 1 to S13 show the flow of processing by the warm-up control unit. When the warm-up control unit starts processing in response to the input of a copy start signal by pressing down the copy start switch 10a, first, initial settings for clearing the previous data such as the detected temperatures t ₀ , t _{1 to} t _3, etc. Is performed (step S1), and the heat roller temperature detection sensor S
The initial temperature t ₁ of the heat roller is read based on the signal from H (step S2).

Next, in step S3, the number n of times of power supply to the heater is determined. Referring to FIG. 6, step S
3 will be described. If the initial temperature t ₁ is lower than the predetermined temperature T ₁ in step S301, the initial value of the energization frequency n is set to 1 (step S302). This is because when initial temperature t ₁ of the heat roller 54a is low, the temperature of the pressure roller 54b is also projected to be low, it is intended to attempting to normal correction.

On the other hand, if the initial temperature t ₁ is equal to or higher than the predetermined temperature T ₁ in step S301, the number of energization times n at the end of the previous copy stored in the nonvolatile memory 74
The value of 1 is read (step S303), the ambient temperature t ₀ is read (step S304), and the initial control temperature T _{3 is set} to an initial correction amount D ₁ (n1) and an environmental correction amount D ₃ (t ₀ ). adding the control temperature T _C of the temporary is determined (step S305). Next, step S306
In the above, the initial temperature t ₁ is equal to the control temperature T _c determined above.
In the above case, the value of the number of times of energization n1 to the heater at the end of the previous copy is set as the initial value of the number of times of energization n to be integrated this time (step S308). This is because when the initial temperature t ₁ is equal to or higher than the control temperature T _c after the last copy, the temperature of the pressure roller 54b is assumed to little down, line correction as a continuation of the previous initial correction The purpose is to try.

On the other hand, when the initial temperature t ₁ is lower than the control temperature T _c at the time of previous image formation ends at step S306, the value of the current number n1 to the heater at the previous copying ends, the initial temperature t Value N according to ₁
The smaller value of (t ₁ ) is adopted as the initial value of the current-carrying number n to be integrated this time (step S307). N (t ₁ ) is set to increase as t ₁ increases. At the start of the second copy shown in FIG. 9, the number n1 of times of power supply to the heater at the end of the previous copy is n1.
Is adopted as an initial value.

Next, in step S4, the control temperature T _C was determined based on the initial value of the current number n determined in step S3, a predetermined amount D ₀ the predetermined (e.g., 2
By subtracting 0 ° C.), the first off-temperature T ₂ is determined. That is, the first off-temperature T ₂ is given by the equation T
₂ = T ₃ + D ₁ (n) + D ₃ (t ₀ ) −D ₀

Next, the power supply to the heater 59 is turned on.
After step S5), reset the timer and start counting
(Steps S6 and S7). Next, from step S8 to step
In Step S12, the detected temperature t of the heat roller 54a _TwoBut
The monitored temperature t of the heat roller 54a is monitored._TwoIs the first one
Temperature T_TwoWhen the temperature reaches the limit, the power supply to the heater 59 is turned off (s
Steps S12 and S13. 8 and 9).
The processing by the upgrade controller ends. Meanwhile, the heater
A predetermined time has elapsed since the power was supplied to
Event value C is a predetermined value C₁Judgment whether it becomes above)
However, the detected temperature of the heat roller t_TwoIs the first off temperature
If not, it is determined to be abnormal (steps S9, S1).
0), for example, a table indicating that the operation unit 10 of the copying machine is abnormal.
An indication is made.

Since the first-time OFF temperature T ₂ is set to be lower than the control temperature T _c by a predetermined amount D ₀ according to the control temperature T _c , as shown in FIG. 8 and FIG. The amount of overshoot can be reduced. As a result, after the first round of off power supply to the heater 59, it is possible to suppress the overshoot of the temperature descending side, moreover, as described later, an intermittent control based on the elapsed time and the control temperature T _C Therefore, at the time of copying the first sheet, it is possible to control the temperature while avoiding the high-temperature offset area and the fixing failure area.

In particular, it is possible to avoid both high-temperature offset at the leading end of the sheet and poor fixing at the trailing end of the sheet, in copying at the transition from warm-up to normal control, in which the temperature change is likely to be severe. . Also in the second copy start time as shown in FIG. 9, since the first round off temperature T ₂ is set according to control temperature T _c to be now controlled, repeated a plurality of times of copying Even in such a case, it is possible to more reliably prevent the occurrence of high-temperature offset and fixing failure. In FIG. 8, for the sake of comparison, the temperature change in the case where the first off-temperature is not lowered is shown by a dashed line, but the overshoot amounts on the temperature rising side and the falling side are both large.

Next, steps S14 to S38
Indicates a process by the normal control unit. First, the timer is reset to start counting (step S1).
4, 15). In step S16, the presence or absence of a copy end signal is determined. When the copy end signal is input, after the energization of the heater 59 is confirmed to be off, the current energization frequency n is set as the previous energization frequency n1, and the non-volatile operation is performed. Is stored in the memory 74, and then the process ends (steps S17 to S17).
9). The copy end signal is output when the number of copies set in the operation unit 10 has been completed.
The case where the apparatus is stopped due to an abnormality of the copying machine is also included.

If the copy end signal has not been input in step S16, the processing by the normal control unit is continued. The correction value D ₁ (n) is added to the initially set control temperature T ₃ , and this is set as the control temperature _Tc (step S20). This is because the control temperature _Tc is increased in the initial stage of the process of the normal control section, in which the temperature of the pressure roller 54b tends to be insufficiently heated, to prevent occurrence of a fixing failure.

The correction amount D ₁ (n) is determined by the heater 59
The function is set so as to decrease to zero in accordance with the number n of times of current supply to the motor. This is because the temperature of the pressure roller 54b gradually increases and converges to a predetermined temperature as time elapses from the start of the process by the normal control unit. Thereby, it is possible to prevent the pressure roller 54b from becoming an unnecessary high temperature.

Next, in steps S21 and S22, on the condition that the paper is being passed (the paper is present in the fixing device 54), the paper feed correction amount D which is more constant at the control temperature T _C is set.
₂ is added. It is determined that the sheet passes through a time region from when the discharge detection switch 58 is turned on until a predetermined time (for example, 3 seconds) elapses after the paper feed detection switch 57 is turned off. By increasing the control temperature T _C only during paper passing, there are the following advantages. That is, when the heat capacity of the heat roller 54a is set small, the pressure roller 54b
, The fixing heat may be generated at the rear end of the sheet. Therefore, it is conceivable to always increase the control temperature T _{C. In} such a case, a high-temperature offset occurs at the leading end of the sheet. On the other hand, as shown in FIGS. 7 and 9, the control temperature T _C is set high only during paper passing, so that a high-temperature offset occurs at the leading edge of the paper and
It is possible to prevent both of the occurrence of the fixing failure at the rear end of the sheet. In other words, when the leading edge of the sheet passes, the control temperature T _C is set low until the end of the sheet, so that the temperature of the heat roller 54a decreases, and the occurrence of high-temperature offset can be prevented. On the other hand, the temperature of the heat roller 54a becomes high when the sheet passes through the rear end of the sheet, so that the occurrence of fixing failure can be prevented.

On the other hand, the above-mentioned constant paper feed correction amount D ₂ is
₂ (x), and a function can be set so as to increase in accordance with the elapsed time x from the start of sheet passing (turn on of the sheet ejection detection switch). Thereby, more accurate temperature control during paper passing becomes possible, and the occurrence of the high-temperature offset and the fixing failure can be reliably prevented. Next, in steps S23 and S24, the ring on which the fixing device is placed is set.
Ambient temperature t ₀ of the border is read, the ambient temperature t ₀
Further enjoined to the control temperature Tc environmental correction amount D ₃ (t ₀₎ in accordance with. This has the following advantages. That is,
When the ambient temperature t ₀ low, large quantity of heat to take the sheet from the pressure roller 54b and the temperature is low in the paper, since it is considered to hinder the stable temperature control, in accordance with the ambient temperature t _0, the control temperature Tc , Stable temperature control is performed.

Next, after it is confirmed that the power supply to the heater 59 has been turned off (step S25), steps S26 to S26 are performed.
In step 29, the first time of turning off (or the previous
(E.g., when the power supply to the power supply is turned off) is longer than a predetermined time (for example, 2 seconds) (the count value C by the timer is more than a predetermined value C _OFF ), and the temperature detected by the heat roller 54a Two conditions are monitored that t ₃ is lower than the control temperature T _C. Only when both conditions are satisfied, the power supply to the heater 59 is turned on (step S30). The off state of energization of the heater 59 continues for at least 2 seconds. Thereafter, the timer is reset (step S31), and the process returns to step S16 to repeat the processing.

In step S25, the communication with the heater 59 is performed.
When the power is on, the steps S32 to S32 are executed.
In step S35, the power supply to the heater 59 was turned on last time.
The elapsed time from the start reaches a predetermined time (for example, 1 second)
That the count value C by the timer is a predetermined value C_ONthat's all
And the detected temperature t of the heat roller 54a. _Three
Is the control temperature T_CAre higher than
Is seen. When one of the two conditions is met
To turn off the power to the heater 59 (step S3).
6). Therefore, the ON state of energization to the heater 59 is
It will last for up to one second. Then, the initial correction amount D
₁(n) is not zero (the initial correction has not been completed).
As a matter, the number of times of energization of the heater 59 is replaced with n + 1
(Steps S37 and S38), the timer is reset.
After (Step S31), the process returns to Step S16 to execute the process.
repeat.

[0039] In the normal control of repeating the steps of step S16 and subsequent as described above, power supply to the heater 59 is intermittently controlled by combining the on-time or off-time and the control temperature T _C, the temperature variation is suppressed . Further, in the initial stage of the normal control process, the control temperature T _C is corrected to be high, and the control temperature T _C is further corrected only at the time of sheet feeding, and further, correction is performed according to the ambient temperature t ₀ .
Thereby, more stable temperature control can be performed. When the copying is completed, if the power supply to the heater 59 is turned off, the heater 59 is left as it is.
If the power supply to is turned on, it is turned off, and the process ends. As a result, the apparatus enters a state of waiting for the start of the next copy.

As described above, according to the present embodiment, the power supply to the heater 59 is controlled only at the time of copying, thereby achieving energy saving. Further, after the warm-up, the control temperature T _C considering the initial correction amount D ₁ (n) should be used in the initial stage of the process of the normal control unit in which the temperature of the pressure roller 54b tends to be insufficiently heated. Accordingly, occurrence of fixing failure can be prevented.

Further, the initial correction amount D ₁ (n) is gradually reduced in accordance with the increase in the number n of times of power supply to the heater 59. Thereby, it is possible to prevent the pressure roller 54b from becoming an unnecessary high temperature. Therefore, occurrence of a high-temperature offset can be prevented. Moreover, in the above initial correction, when the initial temperature t ₁ of the heat roller 54a is low before turning on the power to the first heater 59, a normal initial correction amount is added, and when the initial temperature t ₁ is high, By adding a relatively small initial correction amount,
And to set the control temperature T _C. As a result, it is possible to prevent the fixing temperature from becoming too high, so that it is possible to prevent the occurrence of a high-temperature offset or the like.

It should be noted that the present invention is not limited to the above-described embodiment, and that the gist of the present invention is not changed, for example, by adopting the cumulative energizing time instead of the energizing frequency in the correction of the initial correcting section. And various changes can be made.

[0043]

According to the first aspect of the present invention, when image formation is started, the warm-up control section starts energizing the heater to perform warm-up.
When the first OFF temperature is reached, the process proceeds to the normal control section, and thereafter, the sheet passes through the fixing device. Since the control temperature is initially corrected so as to increase the control temperature in the initial stage of the process of the normal control unit in which the temperature of the pressure roller tends to be not sufficiently warmed, it is possible to prevent the occurrence of a fixing defect. Furthermore, since the initial correction amount is adjusted in accordance with the initial detection temperature of the heat roller, it is possible to prevent the control temperature from becoming too high due to the correction, thereby preventing the occurrence of a high-temperature offset or the like.

[0044] The temperature of the pressure roller is considered to tend to increase with the increase of the cumulative energization time of the heater. Therefore, the initial correction amount is reduced in accordance with the increase in the amount related to the cumulative energization time to the heater. Thereby, it is possible to prevent the occurrence of a high-temperature offset or the like due to the control temperature becoming too high.

According to the second aspect of the invention, the following effects can be obtained. That is, the image formation may be started again only a short time after the end of the previous image formation, and in this case, when the current image formation is performed, the temperature of the pressure roller is still high. It is considered to be in a state. Therefore, when the temperature of the pressure roller is assumed to be high, and the initial detection temperature of the heat roller is high, the amount related to the cumulative energization time to the heater at the end of the previous image formation and the heater in the current image formation And an amount related to the cumulative energization time to the motor, and the initial correction amount is reduced in accordance with the increase of the added amount. As a result, the control temperature is prevented from becoming too high.

[0046]

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an internal configuration of a copying machine including a temperature control device of a fixing device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the copying machine.

FIG. 3 is a flowchart showing an operation at the time of warm-up in the operation of temperature control of the fixing device.

FIG. 4 is a flowchart illustrating an operation during normal control among operations of temperature control of the fixing device.

FIG. 5 is a flowchart showing an operation during normal control of the temperature control operation of the fixing device, and is a continuation of the flowchart of FIG. 4;

FIG. 6 is a flowchart showing a flow for determining the number of times of energization n of the heater.

FIG. 7 is a schematic diagram showing a temporal change in the temperature of the heat roller and the pressure roller.

FIG. 8 is a diagram showing a temporal change in the temperature of the heat roller and the pressure roller in a transition stage from the warm-up control to the normal control.

FIG. 9 is a diagram showing in detail a temporal change of the temperature of the heat roller and the pressure roller.

[Explanation of symbols]

1 copier body 54 fixing device 54a heat roller 54b pressure roller 59 heater SH heat roller temperature detection sensor SA ambient temperature detection sensor 7 control unit 71 CPU 72 ROM T _C control temperature D ₁ (n) during the initial correction amount D ₂ copies Paper Correction amount D ₃ (t ₀ ) Environmental correction amount t ₀ Ambient temperature t ₁ Initial detection temperature of heat roller t _2, t ₃ Current detection temperature of heat roller T ₁ Predetermined initial detection temperature T ₂ First off-temperature n, n1 Number of energization (amount related to cumulative energization time)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsukasa Sugaya 1-2-28 Tamazo, Chuo-ku, Osaka-shi, Osaka Inside Mita Kogyo Co., Ltd. (72) Inventor Junichi Hirobe 1-2-2 Tamazo, Chuo-ku, Osaka-shi, Osaka No. 28, Mita Kogyo Co., Ltd. (56) References JP-A-64-4784 (JP, A) JP-A-2-208684 (JP, A) JP-A-3-145683 (JP, A) JP-A-3 −209492 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/20 G03G 15/20 G05D 23/19

Claims (2)

(57) [Claims] An image forming apparatus includes a pressure roller and a heat roller heated by a heater, and heats and fixes toner on a sheet passing between the two rollers. In the temperature control device of the fixing device that turns on and off the power supply to the heater based on a signal from the roller temperature detection unit, the process starts with the power supply to the heater turned on in response to the input of the image formation start signal, A warm-up control unit for turning off the power supply to the heater when the required first off-temperature is reached, and a process for targeting the required control temperature in response to the power off to the heater by the warm-up control unit. A normal control unit that starts and terminates the process in a state where the power to the heater is turned off in response to the input of the image formation end signal. The control temperature is set by adding an initial correction amount determined according to an amount related to the cumulative energization time to the heater after the input of the image formation start signal, and at the end of image formation, An initial correction unit configured to store an amount related to the cumulative energization time, wherein the initial correction unit includes a heater that is controlled by a warm-up control unit;
Before turning on the power to the
The initial correction amount is set according to the detected initial temperature.
Adjust and increase the amount related to the cumulative energization time.
A temperature control device for a fixing device, wherein the initial correction amount is reduced accordingly . 2. The temperature control device for a fixing device according to claim 1, wherein the initial correction unit detects the initial temperature detected by the heat roller temperature detection unit before turning on the power supply to the heater by the warm-up control unit. When the temperature is equal to or higher than a predetermined temperature, the amount related to the accumulated energization time at the end of the previous image formation stored at the end of the previous image formation and the accumulated energization time after the input of the current image formation start signal A temperature control device for a fixing device, wherein the initial correction amount is gradually reduced in accordance with an increase in an amount obtained by adding an amount related to the temperature of the fixing device.