JPH11143283A - Control method of thermal fixing device - Google Patents

Abstract

(57) Abstract: To provide a high quality print by judging heat absorption of a sheet to be heat-fixed and fixing the sheet by a heat roller controlled to a temperature suitable for the sheet. In a sheet passing area, heat absorption of a sheet is determined based on a difference (transient time) between a time when the temperature of the heat roller reaches one temperature and a time when the temperature of the heat roller reaches the other temperature. The temperature of the heat roller is corrected according to the difference. Or
The heat absorption of the sheet is determined based on the temperature difference between the paper feed side and the paper discharge side of the heat roller, and the temperature of the heat roller is corrected according to the temperature difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium (hereinafter, generally referred to as paper) for printing on a printer, a copying machine, or the like (hereinafter, generically referred to as "printer") to which electrophotographic recording or electrostatic recording technology is applied. ) Is a method for controlling an apparatus for thermally fixing a developing material (hereinafter, collectively referred to as toner) transferred to
In particular, this is a technique related to a method for controlling a fixing temperature.

[0002]

2. Description of the Related Art In a printer, toner is adhered to an electrostatic latent image formed on a photoreceptor, an insulator, or the like, the image is made visible, the toner is transferred to a sheet, and the toner is fixed on the sheet by heating. Printing of characters, images, etc. is performed.

In this fixing, a method is known in which a sheet is pressed against a heat roller and a pressure roller which is pressed and rotated by being pressed against the heat roller, and the sheet is passed between the rollers by rotation of both rollers. Heating of the fixing is performed by heating from both a heat roller and a pressure roller having a built-in heater.
7585), but in many cases only the heat roller is heated by a heater from the viewpoint of cost and the like.

As the heat roller, a roller made of aluminum, iron, or the like having a thickness of about 1 mm to several mm is used, and it is known that the surface of the roller is coated with Teflon or the like in order to prevent toner adhesion to the roller surface. I have.

In the heating of the heat roller, a conventional example in which a means for heating the surface of the heat roller with a heater or the like is added (Japanese Patent Laid-Open No.
55036), but in consideration of thermal efficiency, cost, and the like, a heater is often provided only inside the heat roller.

In many cases, the heater of the heat roller incorporates a single heater corresponding to the width of the heat roller. However, a method of incorporating a plurality of heaters can improve the uniformity of temperature distribution on the surface of the heat roller. Japanese Unexamined Patent Publication (Kokai) No. 2-262177) and improving the fixing and warming-up processes (Japanese Patent Application Laid-Open No. 8-286557).

When the surface of the heat roller heated by the heater reaches a predetermined temperature range, paper feeding is started and toner is fixed. The surface temperature of the heat roller is measured by bringing a temperature sensor into contact with the surface or measuring radiant heat in a non-contact manner. A temperature control based on heating the heater by turning off the heater when the measured temperature of the temperature sensor exceeds a predetermined temperature and turning on the heater when the measured temperature falls below the predetermined temperature is generally known. In this heater energization control, a main heater and an auxiliary heater are provided. The main heater is constantly energized, the energization of the auxiliary heater is controlled on / off, and the heat roller is maintained in a predetermined temperature range. A method has been used in which the amount of electricity is controlled in accordance with the difference between the temperature and the predetermined temperature to maintain the heat roller in a predetermined temperature range.

[0008] In addition to natural heat radiation, heat radiation from the heat roller
One is that a large amount of heat is transferred to the relatively low pressure roller when the fixing device is started. Because the heat radiation speed is fast,
The surface temperature of the heat roller immediately after the start of sheet feeding (hereinafter, referred to as the temperature of the heat roller) may be lower than a predetermined temperature range, and normal fixing may not be performed. As a countermeasure, there is disclosed a control method in which the temperature of the heat roller is set to a higher temperature at the time of start-up than at the time of steady state for fixing (Japanese Patent Laid-Open No. 5-15057).
6 etc.).

Further, the heat radiation condition of the heat roller also changes depending on the thickness, moisture absorption, surface roughness and the like of the paper passing therethrough. When the heat roller is controlled under a certain condition, fixing is insufficient on paper having large heat absorption, and curling is caused by excessive heating on paper having low heat absorption. On the other hand, a method of controlling a heat fixing device for securing a desired fixing state has been proposed,
It has been implemented.

In the simplest case, when the operator inputs the type of paper to be fixed or the like from the operation panel of the printer, the temperature of the heat roller is set to a predetermined temperature according to the type of paper. . However, since the operator determines the type of paper and operates the paper, there are problems such as an operation error and annoyance.

A conventional example in which the temperature of the heat roller is controlled by detecting the temperature change of the heat roller due to the paper passing will be described with reference to FIG.
This will be described below. In FIG. 7A), a temperature sensor 3 for measuring the temperature of the paper passing area of the heat roller 1 and a non-paper passing area (that is,
A temperature sensor 4 for measuring the temperature of the end portion of the heat roller 1 outside the maximum sheet passing width w is provided. In this example, the temperature sensor 3 is a non-contact type sensor, and the temperature sensor 4 is a contact type sensor.

A heater (not shown) is provided in the tube of the heat roller 1 to control the energization of the heater based on the temperatures measured by the temperature sensors 3 and 4 to bring the heat roller 1 to a reference temperature. The pressure roller 2 is pressed by the heat roller 1. When the heat roller 1 is rotated, the pressure roller 2 is driven to rotate, and the paper (not shown) pressed by both rollers is passed and conveyed, and the toner is fixed. Is done.

Before the sheet is passed, the same temperature is measured by the temperature sensor 3 and the temperature sensor 4. Heat roller 1 when paper is passed
From the heat roller 1, the temperature of the paper passing area of the heat roller 1 drops, and the temperature is detected by the temperature sensor 3.

A method is disclosed in which the heat radiation due to paper passing is recognized based on the difference between the measured temperatures of the temperature sensor 3 and the temperature sensor 4, and the heat roller 1 is fixed at a changed temperature obtained by correcting the initial reference temperature. (JP-A-2-259680).
Also disclosed is a method in which the temperature sensor 3 detects a temperature change of the heat roller 1 due to paper passing, and controls the heat generation of the heater based on the measured temperature of the temperature sensor 4 to correct the change temperature. (JP-A-4-296889).

FIG. 7B) shows a fixing unit 10 which detects the temperature of the paper passing area of the heat roller 1 by the temperature sensor 3, analyzes the change in the measured temperature, and controls the amount of heat generated by the heater 5 according to the analysis result. (JP-A-6-95549).

A pressure roller 2 is pressed against a heat roller 1 having a built-in heater 5. The paper 6 onto which the toner 7 has been transferred is passed, conveyed, and fixed from right to left in the drawing by rotation of both rollers. The temperature sensor 3 for measuring the temperature of the paper passing area of the heat roller 1 is connected to a temperature change analysis unit 8. The heater 5 is connected to the temperature controller 9 and controls the temperature of the heat roller 1.

The amount of heat generated by the heater 5 is controlled by the temperature control unit 9 so that the heat roller 1 has the reference temperature, and the paper 6 is started to pass. The temperature change of the heat roller 1 varies depending on the thickness of the paper 6 and the moisture absorption. The temperature is measured by the temperature sensor 3, and the temperature change is analyzed by the temperature change analysis unit 8 to obtain a temperature change rate. The optimum temperature of the heat roller corresponding to the rate of change is determined and controlled by the temperature control unit 9.

In these conventional examples, a change in the temperature of the heat roller due to the conditions of the sheet is detected, and fixing suitable for each sheet is performed, and unnecessary heating is also saved.

[0019]

In fixing a printer, the thickness, surface roughness, moisture absorption, and material (including OHP, etc.) of paper
Fixing under optimal conditions according to the conditions is important for ensuring the quality of printed matter. In addition, printer users and applications are diversified, and it is desired that the setting of fixing conditions be automated as much as possible. On the other hand, there are strong demands for low price, easy maintenance, and the like.

To cope with this, a method of recognizing a temperature change in the paper passing area of the heat roller and adapting the temperature of the heat roller from the information on the temperature change is effective. The conventional example of FIG.
The paper passing is recognized from the difference in the measured temperature between the paper passing area and the non-paper passing area of the heat roller 1. However, it is necessary to lengthen the heat roller 1 and the heater. It is necessary to find the correspondence between the measured temperatures of the temperature sensor 3 and the temperature sensor 4 and to adjust the position of the heat roller and the heater in the longitudinal direction. It takes.

In the conventional example shown in FIG. 7B), the sheet passing is recognized from the rate of change of the measured temperature in the sheet passing area of the heat roller 1, and the temperature change analyzing unit 8 analyzes the sheet passing to obtain the rate of change. Although the specific contents of the temperature change analysis unit 8 are not disclosed, a complicated temperature change analysis unit is required to directly obtain the temperature change rate from various temperature change profiles depending on the paper 6.

In view of the above situation, the present invention provides a technique of a heat fixing device that recognizes paper passing from a measured temperature of a heat roller, realizes temperature control according to the recognition by a simple method, and is easily adjusted. Is what you do.

[0023]

According to the present invention, the heater of the heat roller is turned on and off based on the temperature measurement of only the paper passing area of the heat roller. The basic concept will be described first.

On the other hand, at first, the heater is turned on / off at a reference temperature, a transition time from when the measured temperature reaches the predetermined temperature to the predetermined temperature is measured, and then a change temperature corrected according to the transition time is measured. The on / off control of the heater is performed.

On the other hand, at first, the heater is turned on / off at the reference temperature, the temperature difference between the paper feed side and the paper discharge side of the heat roller is measured, and then the heater is set at the changed temperature corrected in accordance with the temperature difference. The on / off control is performed.

The former is based on the measurement of the transient time, and the latter is a direct measurement of the temperature difference to judge the state of the sheet to be passed and correct the temperature of the heat roller, so that good fixing can be easily performed. . Further, instead of the correction of the temperature, the amount of energization may be corrected. The following is a detailed description.

The heat roller is heated by on / off control of energization of the heater, and the paper is pressed against the heat roller and the pressure roller.
The present invention relates to a method of controlling a heat fixing device using a principle of passing a sheet by rotating both rollers (generally, a pressure roller is driven to rotate by rotation of a heat roller) and fixing toner on the sheet.

The temperature of the paper passing area of the heat roller is measured, and when the measured temperature exceeds the reference temperature, the heater power is turned off, and when the measured temperature is lower than the reference temperature, the heater power is turned on (hereinafter, referred to as “heater”). This is called on / off control of energization of the heater). The on / off control of the energization of the heater and the heat radiation of the heat roller cause the measured temperature to fluctuate above and below the reference temperature within a certain range. After the measured temperature becomes equal to or higher than the reference temperature, paper feeding is started. This corresponds to starting the printer or starting heating of the heat roller from standby.

When the paper is passed, the heat radiation of the heat roller increases due to the heat absorption of the paper. The time difference between the time when the measured temperature reaches the reference temperature and the time until the next time the reference temperature is reached, that is, the transient time is obtained. This transition time depends on the difference in heat absorption due to the thickness of the sheet, moisture absorption, and the like. If the heat absorption is large,
The transition time above the reference temperature is short, and the transition time below the reference temperature is long, and vice versa when heat absorption is low. That is, the state of the sheet can be determined based on the transition time. This determination is made by the transient times between or above the reference temperature or their ratio.

If the heat absorption of the sheet is large, the average temperature of the heat roller becomes low, and the sheet having a large heat absorption requires a large amount of heat for a predetermined fixing, so that the fixing becomes insufficient. In the fixing for a certain period of time, it is necessary to increase the temperature of the heat roller by an amount corresponding to a large amount of heat to increase the speed of heat transfer to the sheet. On the other hand, if the heat absorption of the sheet is small, the average temperature of the heat roller becomes high, so that the sheet may curl depending on the reference temperature. Therefore, a change temperature for making the fixing temperature appropriate, that is, a change temperature for correcting the reference temperature corresponding to the transition time as the judgment information is set in advance. Based on the measured transition time, a change temperature to be set is selected, the heater is turned on / off at the changed temperature, and the heat roller is heated. This enables fixing at an appropriate temperature.

Instead of correcting the reference temperature described above, the average fixing temperature can be corrected by correcting the amount of current supplied to the heater in accordance with the transition time. That is, the heater on / off control is performed at the reference temperature, but the amount of power for causing the heater to generate heat may be set to a changed amount of power obtained by correcting the initial reference amount of power in accordance with the transition time. For example, if the amount of electric power is increased, the time period in which the heat roller exceeds the reference temperature is increased, so that the average fixing temperature is increased. Such a change in the amount of power may be achieved by changing the amount of current supplied to one heater, or by providing several heaters in the heat roller and changing the number of heaters that generate heat.

The transition time may be obtained from the time from the first reference temperature at which the heater is turned on / off to the second reference temperature separately determined. As described above, the first reference temperature or the reference electric energy is corrected in accordance with the measured transition time, and the heater is heated based on these changed values to control the temperature of the heat roller. The setting of the second reference temperature can be determined in consideration of the thermal characteristics of the heater, the heat roller and the like, so that the degree of freedom of design is increased and the temperature of the heat roller can be controlled with higher accuracy.

Further, the transition time may be obtained between the paper passing state and the paper non-passing state, and the accuracy may be improved by comparing these.
That is, when a plurality of sheets are intermittently passed, first, a first transition time from when the measured temperature in the sheet passing state becomes the first reference temperature to the second reference temperature, A second transition time from the first reference temperature in the paper state to the second reference temperature is determined. The difference between the first and second transition times gives more accurate information on the temperature drop of the heat roller due to heat absorption of the passed paper. A change temperature (or change power amount) for correcting the first reference temperature (or reference power amount) is determined in advance corresponding to the first and second transition times. Select a changed temperature (or changed power amount) that matches the difference between the measured first and second transition times, and change the temperature (or changed power amount).
On-off control based on the above, to optimize the temperature of the heat roller.

The measurement in the non-sheet-passing state may be performed at the time of starting the heat fixing device or at the time of starting from the stand-by state. Also, to measure the transient time,
Without setting the second reference temperature, the second reference temperature may be obtained from the difference between the time when the first reference temperature is reached and the time when the first reference temperature is next reached, but as described above, the second It is more convenient to set a reference temperature.

Next, based on the temperature difference between the paper feed side and the paper discharge side of the paper passing area of the heat roller, the temperature drop of the heat roller due to the heat absorption of the paper is recognized, and the reference temperature is set so as to perform appropriate fixing. Alternatively, a method of controlling the heater on / off by changing the electric energy will be described.

A first measured temperature on the paper supply side and a second measured temperature on the paper discharge side in the paper passing area of the heat roller are determined. That is, in the process in which the paper is pressed against a certain width in the circumferential direction of the heat roller, and the paper moves in accordance with the rotation of the heat roller, the first measured temperature at the position before the heat roller is pressed and the temperature after the pressure are pressed. And measuring a second measured temperature at the location. The temperature difference between the first and second measured temperatures corresponds to the temperature drop of the heat roller due to the heat absorption of the sheet at the press contact portion, and the temperature change of the heat roller due to the sheet passing can be recognized.

The on / off control of the heater is initially performed based on the comparison between the measured temperature and the reference temperature. After the temperature difference is measured, the corrected changed temperature and the measured The fixation is performed based on a comparison with the temperature, and the fixing is performed by a heat roller whose temperature is adjusted. This measured temperature may be either the first or second measured temperature, but the accuracy of temperature control is higher when the second measured temperature is used. Further, the reference temperature may be fixed, and the electric energy of the heater may be changed according to the temperature difference, as described above.

Further, the temperature difference between the paper feed side and the paper discharge side is obtained in a paper passing state and a paper non-passing state, and by comparing these temperature differences, the temperature change of the heat roller due to the paper passing can be reduced. It can measure with high accuracy. In this method, the influence of measurement errors of the two temperature sensors for measuring these temperatures can be easily avoided.

A first temperature difference between the first and second measured temperatures in the sheet passing state is obtained, and a second temperature difference between the first and second measured temperatures in the non-sheet passing state is obtained. . Since the second temperature difference does not include the temperature change of the heat roller due to paper passing, the difference between the first and second temperature differences is the net temperature change due to paper passing.

The first and second temperature sensors for detecting the first and second measured temperatures can reduce the second temperature difference to zero by adjusting their characteristics and the positional relationship with the surface of the heat roller.
If this adjustment is insufficient, it is determined as a second temperature difference and measured as an apparent temperature difference. In this case, the first temperature difference includes the apparent temperature difference and the temperature change due to paper passing. If the third temperature difference is obtained from the difference between the first and second temperature differences, the temperature change of the heat roller due to the sheet passing can be accurately recognized. As described above, if the on / off control is performed at the changed temperature or the changed power amount in which the power amount of the heater is corrected in accordance with the third temperature difference, the fixing can be further improved. Adjustment between the two temperature sensors is also facilitated.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is for explaining the principle of a heat fixing process according to the present invention. FIG. 1A) is a sectional view, and FIG. 1B) is a side view.

The heat roller 20 is heated by the heater 21 provided in the tube, and when the heat roller 20 rotates in the direction of the arrow r,
The pressed pressure roller 23 is also driven to rotate. The dotted paper 24 is guided by a mechanism (not shown) in the direction of arrow s (paper feed side), and is inserted and pressed between the heat roller 20 and the pressure roller 23 to fix the toner 25 on the solid paper 24. . The sheet 24 is moved and discharged in the direction of arrow s in synchronization with the rotation of both rollers (discharge side). At this time, a well-known technique for separating the paper 24 from the heat roller 20 by a separation claw (not shown) may be used.

Although an example is shown in which the temperature of the heat roller is measured by the temperature sensor 26 (paper discharge side) and the temperature sensor 27 (paper supply side), only one of them is used in some embodiments.
These sensors are disposed in a contact or non-contact state in a region (sheet passing region) of the heat roller 20 within a range of a width w where the sheet 24 shown in FIG. As the temperature sensor, a known sensor such as a thermistor, a thermocouple, or an infrared detecting element may be used.

FIG. 1A shows an example in which the paper sensor 22 detects paper passing. The paper sensor 22 is, for example, an optical sensor having a function of emitting light and receiving light.
4 is detected. The timing at which the paper 24 comes into contact with the heat roller 20 can be known from the moving speed of the paper 24 and the distance between the paper sensor 22 and the pressure contact position between the two rollers. Instead of using the paper sensor 22, the timing at which the paper 24 comes into contact with the heat roller 20 may be determined based on, for example, a drive signal of a paper feed cassette of a printer (not shown).

FIG. 2 shows an example of a circuit block diagram for controlling the principle configuration of FIG. FIG. 2A) shows an overall outline, and FIG. 2B) shows a circuit block diagram relating to temperature measurement and control when one temperature sensor 26 is used.

The configuration of FIG. 2A) will be described with reference to FIG. A terminal 21a of the heater 21 built in the heat roller 20 is connected to a heater control unit 29, and electric power for heat generation is supplied from a heater power supply. Terminal 26 of temperature sensor 26
a is connected to the temperature control unit 28 and measures the temperature. The temperature sensor 27 may be used.

When the temperature measured by the temperature sensor 26 reaches a predetermined temperature, the temperature control unit 28 sends a signal to the heater control unit 29 to turn on and off the power supply to the heater 21. Further, the temperature control unit 28 sends a signal to start time counting to the time measuring unit 30 when the temperature reaches a predetermined temperature, and sends a signal to stop counting when the temperature reaches the next predetermined temperature. Than this,
A transient time of the temperature that changes between the two temperatures can be determined. The transition time is sent to the main control unit 31 as information for determining the thermal condition of the sheet 24 as described later.

The main controller 31 determines an appropriate temperature of the heat roller 20 based on the measured transition time. That is,
The main control unit 31 stores in advance an appropriate change temperature of the heat roller 20 corresponding to the transition time, compares the measured transition time with the stored change temperature, and sets an appropriate change temperature. It is designed to be extracted.

The information on the changed temperature is sent from the main controller 31 to the temperature controller 28. The temperature control unit 28 is changed to perform on / off control of energization of the heater 21 based on the changed temperature, and the heat roller 20 corresponding to the measured transition time is changed.
Temperature control is performed.

The detection signal of the sheet 24 from the sheet sensor 22 is sent to the main control section 31 to determine whether the sheet is in the sheet passing state or the non-sheet passing state. Also, according to a command from the main control unit 31,
The mechanism control unit 32 controls the mechanism such as the rotation of the heat roller 20. A microcomputer or the like can be used for the main control unit 31, and the configuration is not limited to the configuration shown in the drawings as long as it achieves the gist of the present invention.

An example of the details of the temperature measurement and control of FIG. 2B will be described. The temperature control unit 28 includes a comparison unit 33, an A / D conversion unit 34, and a storage unit 35. Temperature sensor 26
Is converted into a digital signal by the A / D converter 34 and sent to the comparator 33.

The storage unit 35 initially stores a reference temperature. The reference temperature may be set to, for example, a temperature of a heat roller that can appropriately fix a sheet having a standard paper thickness and moisture absorption. The comparison unit 33 compares the reference temperature read from the storage unit 35 with the A / D-converted measurement temperature, and if the measured temperature is equal to or higher than the reference temperature, sends a signal to the heater control unit 29 to turn off the heater power. If the temperature is lower than the reference temperature, a signal for turning on the heater power is sent.

Further, the comparing section 33 sends a signal to the time measuring section 30 at the time when the measured temperature reaches the reference temperature, and starts counting the clock signal. When the measured temperature exceeds the reference temperature (or becomes lower than the reference temperature) and then returns to the reference temperature, the comparison unit 33 determines in the same manner as described above, and sends a signal to the time measurement unit 30 to stop counting at that time. Send.
If a second reference temperature is determined in addition to the reference temperature and stored in the storage unit 35, the comparison unit 33 determines that the measured temperature has reached the second reference temperature, and the time measurement unit 30 There is another way to send a signal to stop counting. Either way,
The transition time of the temperature change can be measured from the difference between these times. The measured transition time is sent to the main control unit 31.

On the other hand, the relationship between the transient time and the appropriate temperature of the heat roller enabling good fixing is determined by preliminary experiments and the like. The transition time and the appropriate temperature may correspond to continuous values, but quantization at a reasonable level is preferred. The main control unit 31 stores information on the correspondence between the transition time and the appropriate temperature.
Is stored in advance in the storage unit.

The main controller 31 compares the measured transient time with an appropriate temperature stored in advance and extracts a temperature suitable for the transient time. That is, a changed temperature obtained by correcting the reference temperature is extracted. Of course, if the transition time is a standard value, the changed temperature and the reference temperature match.

The information on the selected changed temperature is stored in the main controller 31.
Is sent to the storage unit 35 and stored. Temperature sensor 2
The temperature measured at 6 and subjected to A / D conversion is read from the storage unit 35 and compared with the changed temperature by the comparison unit 33. In response to the change in the measured temperature, a signal for turning on / off the energization of the heater is sent to the comparison unit 33 or the heater control unit 29 based on the changed temperature. The temperature of the heat roller conforms to the thermal conditions of the paper 24, and appropriate thermal fixing is possible. If the thermal conditions of the paper 24 or the temperature environment of the apparatus change, the measured transient time changes accordingly, so that the temperature control of the appropriate heat roller and the appropriate fixing are realized through the same process as above. it can.

FIG. 3 shows the profile of the measured temperature change of the heat roller 20 and the ON / OFF timing of energization of the heater 21. The profile of the temperature change depends on the heat capacity of the heat roller 20, the calorific value of the heater 21, and the like, and is shown as one model. However, the basic concept described below can be applied to all the profiles.

FIG. 3A) will be described. The area 1 corresponds to the temperature change of the heat roller 20 in the non-sheet passing state at the time of startup or startup from standby. The energization of the heater 21 may be performed by raising the temperature with a constant power. However, it is also possible to increase the power at the initial stage of the heating and heat the heater 21 with the reduced reference power as the temperature approaches the reference temperature Ts to shorten the startup time. Absent. Based on the reference temperature Ts, energization is turned on at time t1, turned off at t2, and turned on at t3. That is, t2-t1 = t12 is the transition time in the ON state, and t3-t2 = t23 is the transition time in the OFF state.

The area 2 is a temperature change in the sheet passing state.
The energization is turned on at time t4 based on the reference temperature Ts, and t
It is turned off at 5 and turned on at t6. t5-t4 = t
45 is a transition time of the ON state, and t6−t5 = t56
Is the transition time in the OFF state.

Comparing the transition time between the paper passing state and the paper non-passing state, the relationship between the ON state at t12 <t45 and t23>
There is a relation of the OFF state at t56. That is, the average temperature of the heat roller is lower in the sheet passing state than in the sheet non-passing state.

The area 3 shows the case where the sheet is passed by performing on / off control based on the changed temperature Tu obtained by correcting the reference temperature Ts in accordance with the flow of FIG. 4 described later. Power is turned on at time t7, turned off at t8, and turned on at t9. This is an example in which the average temperature of the heat roller is also increased to enable appropriate fixing. Although not shown, the average temperature of the heat roller can be increased by increasing the reference power.

An example of correcting the reference temperature Ts and performing on / off control at the changed temperature Tu will be described with reference to the flowchart of FIG. 4A). Start operation of the printer. Heater 2
The temperature of the heat roller 20 rises by the current supply of 1. The temperature T of the heat roller is measured to determine whether the temperature has reached the reference temperature Ts,
When the time reaches Ts, the paper feeding is started. The heater 21 is on / off controlled based on Ts. The difference [t] between the time when the temperature T reaches Ts and the next time when the temperature T reaches Ts is measured by the time measuring unit 30.
Ask for. [T] corresponds to t45 or t56 in FIG. 3A), and either t45 or t56 may be used. Furthermore,
The ratio between t45 and t56 may be used.

In the storage section of the main control section 31, a changed temperature Tu in which Ts is corrected corresponding to [t] is stored in advance. In the main control unit 31, Tu corresponding to the measured [t]
Is stored in the storage unit 35. The comparison unit 3 controls the heater control unit 29 to be turned on and off based on this Tu.
3 sends a signal as described above.

Referring to FIG. 3B). The area 1 is an example in which the standard paper 24 is passed, and the area 2 is an example in which the paper 24 having a large heat absorption is passed. The first reference temperature of the heat roller is T1, and the energization of the heater 21 is controlled to be on / off at T1. T2 is a second reference temperature, and the temperature set higher than T2 is indicated as T2H, and the temperature set lower than T2 is indicated as T2L.

In the region 1, the transition time from T1 to T2L is t2-t1 = t12, and the transition time from T1 to T2H is t4-t3 = t34. In the area of 1, t6−t5 = t56 and t8−t7 = t78, respectively.

Comparison of t12 and t56, or t34 and t7
From the comparison with No. 8, the paper 24 having the heat absorption characteristic (per unit area) deviated from the standard in the area 2 can be determined. That is,
In the illustrated example, since heat absorption is large, t12> t56, t12
34 <t78. Although not shown, the size relationship is reversed if the small heat absorbing paper 24 is passed. Of course,
It may be compared with the transition time in the non-sheet passing state.

Although the first reference temperature T1 is a temperature at which the energization of the heater 21 is controlled to be turned on and off, it goes without saying that the present invention can be substantially implemented even if another temperature is selected as T1.

Based on the above judgment, the temperature may be controlled according to the same flow as in FIG. 4A). For example, [t] is changed to t5
6 or t78, Tu adapted to t56 or t78
May be selected to perform on / off control based on Tu. Furthermore, it is also possible to control the difference between t12 (or t34) and t56 (or t78), which are standard transition times, as [t]. In any case, Tu is higher than T1 if the heat absorption of the paper 24 is larger than the standard value, and T is smaller if the heat absorption is smaller than the standard value.
u is controlled to be lower than T1 to fix.

Using the difference in the transition time of the temperature between the paper passing state and the non-paper passing state, the heat absorption of the paper is determined, and the heat roller 2
A flowchart for controlling the temperature of 0 is shown in FIG. 4B).

First, the printer is started, the heater 21 is heated, and the heat roller 20 is heated. Temperature sensor 26
Then, the temperature of the heat roller 20 is measured, and after the temperature reaches the first reference temperature T1, the sheet feeding is started. The paper sensor 22 determines whether the heat roller 20 is in a paper passing state or a paper non-passing state. This non-passing state indicates that a plurality of sheets 2
4, it is convenient to use the state of the paper gap when passing paper, but the state immediately before the start of paper passing may be used.

When the temperature T of the heat roller 20 in the sheet passing state is T1
The time measurement unit 30 calculates a difference [tY] between the time when the second reference temperature is reached and the time when the second reference temperature is reached. Even without paper,
Similarly, [tN] is obtained from the time difference. In the main controller 31, the difference [tD] between [tY] and [tN] = [tY] −
[TN] is obtained. Since this [tD] corresponds to the change in the temperature of the heat roller due to the passing of the paper, the thermal condition of the paper 24 can be determined.

On the other hand, the relationship between [tD] and the fixing temperature suitable for it is determined in advance by a preliminary experiment or the like, and based on this relationship, [tD] and the changed temperature Tu obtained by correcting T1 corresponding thereto are determined. This information is stored in the storage unit of the main control unit 31.

The main control section 31 selects Tu suitable for the measured [tD] and stores it in the storage section 35. The information of the temperature sensor 26 and Tu are compared by the comparing unit 33, and T
The process of turning on and off the heater control unit 29 based on u is the same as described above.

In FIG. 5, the temperature difference between the two positions of the heat roller 20, that is, the paper supply side a and the paper discharge side b is measured, and the heat absorption of the sheet 24 is determined based on the temperature difference. The method for controlling the temperature to the optimum was shown.

FIG. 5A) shows a graph at a certain time.
3 schematically shows a temperature distribution on the circumference of the heat roller 20 (the surface of the paper passing area). The heat roller 20 rotates in the r direction, and the paper 24 moves in the s direction following the rotation.

If the temperature of the heat roller 20 heated by a heater (not shown) near the center of the heat roller 20 is in a completely non-contact state with the sheet 24 (ie, a non-sheet passing state), the entire circumference is The temperature T becomes uniform above.

When heat is absorbed by the contact of the paper 24 by passing the paper, the portion of the heat roller 20 (c
The temperature of ~ d) decreases. c is the position where the contact starts,
d is a position to be separated. Immediately before this time, since the accumulation of the contact time of the sheet 24 increases from c to d, the temperature drop increases from c to d.

After d, the sheet 24 is separated, there is no heat absorption, and the surface temperature of the heat roller 20 is rapidly recovered mainly by heat conduction in the thickness direction of the heat roller. However, paper 2
4 causes a temperature drop ΔT corresponding to the heat capacity absorbed.

By measuring this ΔT, the heat absorption by the paper 24 can be determined. The actual measurement is performed while the heat roller 20 is rotating. In synchronization with the rotation, the heat absorption by the paper 24 (the temperature T of the heat roller 20 decreases by ΔT for each rotation) is also continued, and the heater Although heat itself is added, T itself changes every moment, but the temperature difference between the positions a and b of the heat roller 20 can always be measured as ΔT.

FIG. 5B) shows an example of a circuit block diagram for measuring the temperature difference between a and b of the heat roller 20. The temperature difference between the temperature sensor a27 and the temperature sensor b26 is obtained by the difference detection unit 36. This temperature difference and the temperature sensor b26
A / D conversion is performed by the A / D converter 34 with the measured temperature. As the absolute value of the temperature, the temperature measured by the temperature sensor a27 may be used, but the temperature sensor b26 is convenient in that information on heat absorption by the sheet 24 can be quickly recognized. The reference temperature of the temperature sensor b26 is stored in the storage unit 35 from the main control unit 31.

Further, the temperature of the temperature sensor b26 for realizing appropriate fixing (changed temperature obtained by correcting the reference temperature) is determined in advance in accordance with the temperature difference between the temperature sensor a27 and the temperature sensor b26 by a preliminary experiment or the like. . This information is stored in a storage unit in the main control unit 31 in advance.

In the comparison section 33, initially, the temperature sensor b2
The measured temperature of No. 6 is compared with the reference temperature of the storage unit 35. Based on the reference temperature, a signal for controlling on / off of energization of the heater is sent to the heater control unit 29 to control the temperature of the heat roller 20.

A temperature sensor a27 and a temperature sensor b26
Is sent to the main control unit 31. In the figure, an example via the comparison unit 33 is shown, but this is not a necessary condition of the present invention. The main control unit 31 compares the changed temperature corresponding to the temperature difference stored in advance with the measured temperature difference, and selects a changed temperature suitable for the temperature difference.

The selected changed temperature is recorded in the storage unit 35. The comparison unit 33 compares the changed temperature read from the storage unit 35 with the temperature measured by the temperature sensor b26. A signal for turning on / off the heater energization is sent to the heater control unit 29 based on the changed temperature to control the temperature of the heat roller 20, so that the fixing temperature can be optimized.

FIG. 6 shows a flowchart of two methods for correcting and controlling the temperature of the heat roller 20 in accordance with the above-mentioned temperature difference. 6A) determines the heat absorption of the sheet 24 from the difference in temperature between the sheet passing state and the non-sheet passing state, and FIG.
The temperature of 0 is corrected.

First, FIG. 6A) will be described. The heating of the heat roller 20 is started, and the temperature Ta of the temperature sensor a27 is detected.
And the temperature Tb of the temperature sensor b26. The comparing unit 33 compares Tb with the reference temperature Ts. When the temperature reaches Ts, the sheet feeding is started, and the heater control unit 29 is instructed to turn on / off the energization of the heater based on Ts.

The difference ΔT between Ta and Tb in the sheet passing state is obtained by the difference detecting section 36. In the storage unit of the main control unit 31, a changed temperature Tu in which Ts is corrected in accordance with ΔT is stored in advance. In the main control unit 31, the T that matches the measured ΔT
u is selected and stored in the storage unit 35. This Tu and Tb
Are compared by the comparison unit 33, and the on / off control of energization of the heater is performed based on Tu. The heat absorption of the paper 24 is determined from ΔT, and the temperature of the heat roller 20 that can appropriately cope with the heat absorption is controlled.

In FIG. 6B), similarly to FIG. 6A), start-up is started, and the temperature difference between Ta and Tb is obtained by the difference detection unit 36. The temperature difference in the paper passing state is ΔT1, and the temperature difference in the non-paper passing state is ΔT2.
And The discrimination between the paper passing state and the paper non-passing state is performed, for example, by referring to FIG.
The detection is performed based on the detection of the paper 24 by the paper sensor 22 in A). Since there is a time difference in measurement between ΔT1 and ΔT2, at least one of them is stored once in the storage unit of the main control unit 31,
When both information of 1 and ΔT2 are collected in the main control unit 31,
A difference ΔT3 between ΔT1 and ΔT2 is obtained.

On the other hand, ΔT3
The changed temperature Tu in which Ts is corrected in accordance with
1 is stored in advance in the first storage unit. To find ΔT3,
In order to compensate for the measurement error of Ta and Tb, the characteristic difference between the temperature sensors a and b, and the like, when Tu is obtained in advance by experiments or the like, ΔT1 in an ideal state where these errors can be ignored.
May be treated as ΔT3. Alternatively, it can be obtained by simulation.

The main controller 31 measures ΔT3
Is selected. This Tu is stored in the storage unit 35, and is compared with Tb measured by the comparison unit 33. T
Based on u, a signal for instructing ON / OFF control of the heater energization is sent to the heater control unit 29 to control the temperature of the heat roller 20.

According to this method, the influence between the two temperature sensors, for example, the influence of the arrangement, temperature characteristics, toner adhesion, and the like can be excluded, so that the assembly and maintenance of the heat fixing device can be facilitated. Further, the temperature of the heat roller suitable for the sheet may be controlled by correcting the amount of electric power supplied to the heater, for example, without being limited to the example described above.

[0092]

According to the first to fourth aspects, since the temperature change of the heat roller is determined based on the arrival time difference between the predetermined temperatures, it is possible to easily realize appropriate heat fixing to paper having different heat absorption.

Since the heat absorption of the sheet is determined based on the temperature difference between the sheet supply side and the sheet discharge side of the heat roller, the temperature control of the heat roller suitable for the sheet is quickly and simplified. Claim 6
Improves the accuracy of the temperature control of the fifth aspect, and facilitates the assembly and maintenance of the heat fixing device.

[Brief description of the drawings]

FIG. 1 is a view for explaining the principle of a heat fixing process according to the present invention.

FIG. 2 is a diagram showing an example of a circuit block for temperature control according to the present invention.

FIG. 3 is a diagram illustrating an example of a temperature change profile of a heat roller and an energization timing.

FIG. 4 is a diagram illustrating an example of a flowchart of temperature control.

FIG. 5 is a diagram showing an example of a circuit block for temperature distribution and temperature control of a heat roller.

FIG. 6 is a diagram showing another example of a flowchart of temperature control.

FIG. 7 illustrates a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heat roller 2 Pressure roller 3 Temperature sensor 4 Temperature sensor 5 Heater 6 Paper 7 Toner 8 Temperature change analysis unit 9 Temperature control unit 10 Fixing unit 20 Heat roller 21 Heater 22 Paper sensor 23 Pressure roller 24 Paper 25 Toner 26 Temperature sensor 27 temperature sensor 28 temperature control unit 29 heater control unit 30 time measurement unit 31 main control unit 32 mechanism control unit 33 comparison unit 34 A / D conversion unit 35 storage unit 36 difference detection unit

Claims (6)

[Claims] A heat roller is heated by on / off control of energization of a heater, a sheet is pressed against the heat roller and a pressure roller, and the rotation of both rollers causes the sheet to pass therethrough, thereby fixing toner on the sheet. A step of obtaining a measured temperature of a paper passing area of the heat roller; a step of performing on / off control of energization of the heater based on a comparison between the measured temperature and a reference temperature; After the measured temperature has become equal to or higher than the reference temperature, a step of starting paper feeding, and a transition time is determined from a difference between the time when the measured temperature reaches the reference temperature and the time until the next temperature reaches the reference temperature. Correcting the reference temperature, selecting the changed temperature suitable for the transient time from the predetermined changed temperatures corresponding to the transient time, and comparing the measured temperature with the changed temperature. On / off system for energizing the heater based on The was, the control method of the thermal fixing device, characterized in that heating the heat roller. 2. A heat roller is heated by on / off control of energization of a heater, a sheet is pressed against the heat roller and a pressure roller, and the rotation of both rollers causes the sheet to pass therethrough, thereby fixing toner on the sheet. Determining a measured temperature of a paper passing area of the heat roller; and controlling on / off of energization of the heater with a reference electric energy based on a comparison between the measured temperature and a reference temperature. Starting the sheet feeding after the measured temperature has become equal to or higher than the reference temperature; and transiently detecting the difference between the time when the measured temperature reaches the reference temperature and the time until the next time the reference temperature is reached. Determining the time, selecting the changed power amount that is suitable for the transient time from the predetermined changed power amount corresponding to the transient time, correcting the reference power amount, and selecting the measured temperature and Based on the comparison with the reference temperature, the heater And on-off control of the energization change power amount control method of the thermal fixing device, characterized in that heating the heat roller. 3. A heat roller is heated by on / off control of energization of a heater, a sheet is pressed against the heat roller and a pressure roller, and the rotation of both rollers causes the sheet to pass therethrough, thereby fixing toner on the sheet. A step of obtaining a measured temperature of a sheet passing area of the heat roller; and a step of controlling on / off of energization of the heater based on a comparison between the measured temperature and a first reference temperature. After the measured temperature has become equal to or higher than the first reference temperature, a step of starting paper passing, and from the time when the measured temperature has reached the first reference temperature until the second reference temperature has been reached. Determining a transition time from the time difference of the step (c), wherein the first reference temperature is corrected, and the change temperature suitable for the transition time is selected from the change temperatures predetermined for the transition time. Based on a comparison between the measured temperature and the changed temperature. A method for controlling a heat fixing device, comprising: controlling the energization of a heat roller to heat the heat roller. 4. A heat roller is heated by on / off control of energization of a heater, a sheet is pressed against the heat roller and a pressure roller, and a plurality of the sheets are intermittently passed by rotation of both rollers. A method of controlling a heat fixing device for fixing toner on the sheet, a step of obtaining a measured temperature of a sheet passing area of the heat roller, and energizing the heater based on a comparison between the measured temperature and a first reference temperature. Controlling the on / off control of the following; and starting the sheet passing after the measured temperature becomes equal to or higher than the first reference temperature; and setting the measured temperature in the sheet passing state to the first reference temperature. Calculating a first transient time from the difference between the time when the second reference temperature is reached and the time when the second reference temperature is reached; and Obtaining a second transition time from a difference in time until the second reference temperature is reached; Correcting the first reference temperature, from the predetermined change temperature corresponding to the difference between the first and second transition times, adapting the difference between the first and second transition times. A method for controlling a heat fixing device, comprising: selecting the changed temperature; and controlling on / off of energization of the heater based on a comparison between the measured temperature and the changed temperature to heat the heat roller. 5. A heating roller is heated by on / off control of energization of a heater, a sheet is pressed against the heating roller and a pressure roller, and the rotation of both rollers causes the sheet to pass therethrough, thereby fixing toner on the sheet. Determining a first measured temperature of a sheet passing area on the sheet feeding side of the heat roller and a second measured temperature of a sheet passing area on the sheet discharging side of the heat roller; A step of performing on / off control of energization of the heater based on a comparison between the measured temperature and a reference temperature; and a step of starting paper passing after the second measured temperature becomes equal to or higher than the reference temperature. A step of obtaining a temperature difference between the first and second measured temperatures; and a step of correcting the reference temperature and selecting the changed temperature that matches the temperature difference from a predetermined changed temperature corresponding to the temperature difference. Based on a comparison between the second measured temperature and the changed temperature,
A method for controlling a heat fixing device, wherein the heat roller is heated by performing on / off control of energization of the heater. 6. A heating roller is heated by on / off control of energization of a heater, a sheet is pressed against the heating roller and a pressing roller, and a plurality of the sheets are intermittently passed by rotation of both rollers. A method for controlling a heat fixing device for fixing toner on the sheet, wherein a first measured temperature of a sheet passing area on a sheet feeding side and a second measured temperature of a sheet passing area on a sheet discharging side of the heat roller are obtained. A step of performing on / off control of energization of the heater based on a comparison between the second measured temperature and a reference temperature; and, after the second measured temperature becomes equal to or higher than the reference temperature, A step of starting; a step of calculating a first temperature difference between the first and second measured temperatures in a sheet passing state; and a step of calculating a second temperature of the first and second measured temperatures in a non-sheet passing state. Determining a temperature difference between the first and second temperature differences, and determining a third temperature difference from the difference between the first and second temperature differences. Correcting the temperature, from the changed temperatures predetermined corresponding to the third temperature difference, select the changed temperature that matches the third temperature difference, and select the second measured temperature and the changed temperature. A method for controlling a heat fixing device, wherein the heat roller is heated by performing on / off control of energization of the heater on the basis of the comparison.