JP2003323074A - Image heating device, image forming apparatus, image copying machine and method for controlling temperature - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image heating device in which cost reduction is achieved, a difference in gloss among printed images on recording mediums is eliminated, and wrapping of a belt or the like at a high temperature is prevented. <P>SOLUTION: In the image heating device, a controlling means 79 estimates a temperature of a pressure roller 23 according to at least one of a temperature of a belt 20 detected by a temperature sensor 45 and a variation with time in the detected temperature from completion of the heating after application of electric power to a magnetization coil 25 by an exciting circuit 75 is stopped and the heating of the belt 20 by a heating roller 21 is stopped, so as to determine a set temperature for the belt in a subsequent image heating period. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image heating apparatus suitable for a fixing device for fixing an unfixed toner image by heating a conductive belt directly or indirectly through a metal roller by electromagnetic induction. And an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus using the image heating apparatus, an image copying apparatus using the image forming apparatus, and an image heating apparatus, an image forming apparatus and an image copying apparatus. Temperature control method.

[0002]

2. Description of the Related Art As an image heating apparatus represented by a fixing apparatus, a contact heating type image heating apparatus such as a roller heating type and a belt heating type has been generally used.

In recent years, an electromagnetic induction heating system, which has a possibility of rapid heating and high efficiency heating, has been attracting attention due to demands for shortening warm-up time and energy saving. In the belt heating method, a conductive belt having a smaller heat capacity is used in order to shorten the warm-up time. And
A high-frequency current is passed through the exciting coil, and a high-frequency magnetic field generated thereby generates an induced eddy current in the conductive belt, causing the conductive belt itself to generate Joule heat. By passing a recording medium (paper, OHP film, etc.) on which an unfixed toner image is formed, through a nip portion between a fixing roller and a pressure roller that are pressed against each other via the conductive belt that has generated heat,
An unfixed toner image can be fixed.

In the roller heating method, a metal roller having a thinner wall thickness is used in order to shorten the warm-up time. Then, a high-frequency current is passed through the exciting coil, an induced eddy current is generated in the metal roller by the high-frequency magnetic field generated by this, the Joule heat is generated in the metal roller, and the nip portion between the pressure roller and the metal roller is provided.
Alternatively, a recording medium (paper, OHP film, or the like) on which an unfixed toner image is formed in a nip portion between a fixing roller and a pressure roller facing the fixing roller via a heat-resistant resin belt that conveys heat conducted from a metal roller. ), An unfixed toner image can be fixed.

[0005]

[Patent Document 1] JP-A-6-149102

[0006]

In an image heating apparatus of belt type (a type using a conductive belt or a resin belt), a conductive belt having a low heat capacity is heated by electromagnetic induction (belt direct heating) or a metal roller. Conducts electromagnetic induction heating to heat transfer to a low heat capacity resin belt (belt indirect heating)
Therefore, although the temperature of the belt itself rises rapidly, the temperature of the pressure roller having a large heat capacity is low, so that the temperature of the pressure roller is low even when the belt reaches the fixing temperature in the initial stage. Further, if the intermittent printing is continuously performed, the temperature of the pressure roller rises, and as a result, the temperature fluctuation of the pressure roller becomes large, and the toner image fixed first and the toner image fixed later are If there is a difference in glossiness, or if the glossiness is bad, fixing failure will occur.

In order to solve such a problem, in the conventional image heating apparatus, the temperature of the pressure roller is taken into consideration when setting the fixing temperature. Therefore, in addition to the belt temperature sensor for detecting the belt temperature, A pressure roller temperature sensor for detecting the temperature of the pressure roller is provided, and the pressure contact portion between the belt and the pressure roller is based on the temperature detected by the temperature sensor and the temperature detected by the pressure roller. In the above, it is necessary to control the heating amount of the heat generating member so that the amount of heat applied to the recording medium maintains a predetermined reference value (for example, refer to Patent Document 1).

However, the original role of pressing the toner image onto the recording medium is not directly involved in the heating of the recording medium, but it is unnecessary to detect the temperature of the pressure roller that robs the heat of the belt. Providing a temperature sensor is not a preferable solution because it increases the cost.

Further, since the pressure roller has a large temperature variation due to sheet passing, when a temperature sensor is installed on the pressure roller,
Although it must be installed within the range of the paper width, if the surface of the pressure roller is damaged by the temperature sensor, the image on the back surface may be damaged during double-sided printing. When fixing a color toner image, this problem is particularly remarkable because the pressure roller is required to have the same releasability as the fixing roller, and many pressure rollers having a hard surface such as fluororesin are used.

Further, in the method of heating the metal roller to convey the heat by the resin belt, usually, in order to shorten the warm-up time, the metal roller is raised to a predetermined temperature and then the rotating operation of the metal roller is performed. Often starts. However, in the electromagnetic induction heating method, the temperature rises quickly, and when the metal roller is heated in a stationary state in the image heating device having a low heat capacity, a rapid temperature rise occurs partially, and the resin belt and the resin belt There is a risk that the elastic body or the like that has been damaged may deteriorate.

In particular, in the system in which the resin belt is wound around the metal roller and heated, if the metal roller is heated rapidly and becomes too high in temperature, the resin belt is wound according to the curvature of the metal roller and is permanently deformed. There is.
This is unlikely to occur in the conductive belt, and does not occur in the configuration in which the linear portion of the conductive belt is heated. That is, this problem is remarkable in the configuration in which the metal roller is heated and the heat is conveyed by the resin belt.

Further, from the viewpoint of energy saving, it is desirable that the heat generating member (conductive belt or metal roller) is heated only when the image heating device is used. Usually, in the case of the roller heating method, a heat generating member exists in the nip portion. However, in the case of a belt system in which the heat generating member and the nip portion are separated from each other, that is, the heat generating portion and the nip portion of the conductive belt or the metal roller around which the resin belt is wound and the nip portion are separated from each other, the conductivity is reduced. There is a time delay (temperature gradient) between the temperature change in the heat generating part of the belt or the heated part of the resin belt and the temperature change in the nip part.

Further, in order to instantly meet the printing request of the user, it is necessary to carry out the preheating even in the standby state.
However, it solves the problems such as winding and deterioration of the belt that occur when the temperature is too high when heated in a stationary state, and the temperature change at the heat generating part of the conductive belt or the heated part of the resin belt and the temperature at the nip part. In order to reduce the time delay with the change as much as possible, the rotating operation of the conductive belt or the metal roller must be continued even in the standby state. This is not preferable in terms of energy saving and noise accompanying the belt rotation operation.

The present invention has been made in view of the above problems, and an object thereof is to eliminate the temperature sensor for detecting the temperature of the pressure roller to reduce the cost, and therefore the temperature or temperature of the belt. By estimating the temperature of the pressure roller from the amount of change and setting the optimum fixing temperature during the next image heating, the difference in glossiness of the print image for each recording medium due to temperature fluctuations of the pressure roller is eliminated, Also, in order to prevent belt wrapping at high temperatures and to perform preheating that requires only a minimum belt rotation operation during standby until the start of the next image heating, noise reduction and energy saving are considered. Image heating device capable of shortening first print time, image forming apparatus using such image heating device, image copying device using such image forming device, and such image heating device, image forming device And to provide a temperature control method applied to an image copying apparatus.

[0015]

To achieve the above object, a first image heating apparatus according to the present invention comprises a movable heating member for directly heating a material to be heated (recording paper, OHP film, etc.). , A heating unit that directly or indirectly heats the heating member, a pressurizing unit that contacts the heating member, a temperature sensor that detects the temperature of the heating member, and the temperature of the heating member based on the temperature detected by the temperature sensor. And a change amount with respect to time of the detected temperature of the heating member after the heating of the heating member by the heating unit is stopped. It is characterized in that the temperature of the pressurizing means is estimated based on at least one of them, and the set temperature of the heating member at the time of the next image heating is determined.

According to the structure of the first image heating apparatus, the temperature sensor for detecting the temperature of the pressing means (pressing roller) is eliminated to reduce the cost and the heating means (belt).
The temperature of the pressure roller is estimated from the temperature or the amount of temperature change, and the optimum fixing temperature is set for the next image heating. It is possible to prevent the paper from being wrapped around.

In the first image heating apparatus, at least a part of the heating member is conductive (conductive belt), and the heat generating means includes an exciting means for directly heating the heating member using electromagnetic induction. Alternatively, the heat generating means is inscribed in the heating member,
A rotatable heat-generating member (for example, a metal roller) that at least partially has conductivity and indirectly heats a heating member (for example, a heat-resistant resin belt), and heats the heat-generating member using electromagnetic induction. Exciting means is included.

Further, in the first image heating apparatus, the heating member (belt) preferably has a heat capacity of 60 J / K or less, more preferably 40 J / K or less.

When the heat capacity of the belt is set to 60 J / K or less, when the belt is heated by the heat generating means with an input power of 1000 W, the portion actually heated is considered to be 1/10 or less of this in a stationary state. The belt temperature can be increased to 200 ° C. or higher in a short time of about 1 second.
When the heat capacity of the belt is set to 40 J / K or less, 9
When the belt is heated by the heating means with an input power of 00 W, the temperature of the belt can be raised to several hundreds of degrees Celsius or more in a short time of about 1 second.

Further, in the first image heating apparatus, the control means, when the detected temperature of the heating member (belt) is equal to or higher than a predetermined temperature (for example, 120 ° C.), the change amount of the detected temperature of the heating member with respect to time. Based on the above, the set temperature of the heating member at the time of the next image heating is determined, and when the detected temperature of the heating member is lower than the predetermined temperature, the heating member at the time of the next image heating is determined based on the detected temperature of the heating member. It is preferable to determine the set temperature of.

Further, the control means sets the reference value of the temperature of the heating member (the belt cooling curve with respect to the elapsed time) preset according to the elapsed time after the heating of the heating member by the heat generating means is stopped, and the temperature. It is preferable to determine the set temperature of the heating member at the time of the next image heating, based on the magnitude relationship with the actually measured value of the temperature of the heating member detected by the sensor. In this case, when the measured value is equal to or higher than the reference value, the control means selects the first reference table (reference table for high temperature) in which the first set temperature (for example, 163 ° C.) is stored, and the measured value Is less than the reference value, it is preferable to select a second reference table (medium temperature reference table) in which a second set temperature (for example, 167 ° C.) higher than the first set temperature is stored. Further, the reference value of the temperature of the heating member is expressed by a mathematical expression with the elapsed time from the end of image heating as a parameter.

The temperature of the pressure means (pressure roller) never becomes higher than the temperature of the belt. Therefore, if the detected temperature of the belt is lower than a predetermined temperature, for example, 120 ° C,
The temperature of the pressure roller is also considered to be low. However, when the detected temperature of the belt is a predetermined temperature, for example, 120 ° C. or higher, the temperature of the pressure roller may be high or low.

Therefore, when the detected temperature of the belt is 120 ° C. or lower with the above-mentioned predetermined temperature as the threshold value, based on the detected temperature of the belt immediately before starting the next image heating,
It is estimated that the temperature of the pressure roller is low, and the medium temperature (for example, 71
From a reference table (table B) for low temperature (for example, 70 ° C. or lower) to a set temperature (for example, 167 ° C. or 170).
C)).

On the other hand, when the detected temperature of the belt is higher than 120 ° C., the set temperature is determined as follows.

The change amount of the detected temperature of the belt with respect to the elapsed time (tp) from the end of the previous image heating to immediately before the start of the next image heating is small, that is, the detected temperature of the belt at the elapsed time tp is the elapsed time. The temperature of the pressure roller is estimated to be high when it is higher than a preset belt cooling curve (threshold temperature Tf), which is represented by a mathematical expression using tp as a parameter, and the first (for high temperature) reference table (table C) is used. ) Is selected, and the first preset temperature (for example, 163 ° C.) stored therein is determined as the preset temperature. On the contrary, when the change amount of the detected temperature of the belt with respect to the elapsed time tp is large, that is, the detected temperature of the belt at the elapsed time tp is lower than the cooling curve of the belt (threshold temperature Tf), the temperature of the pressure roller is low. Estimate and second (for medium temperature)
The reference table (table B) of No. 1 is selected, and the second set temperature (for example, 167 ° C.) higher than the first set temperature stored therein is determined as the set temperature.

As described above, by selecting the most suitable reference table according to the cooling state of the belt, the pressure roller can be obtained from the temperature of the belt or the change amount of the temperature without providing the temperature sensor for the pressure roller. The temperature can be estimated and the optimum fixing temperature can be set.

In the first image heating apparatus, the reference value of the temperature of the heating member and the measured value are large or small until a fixed time (for example, 2 seconds) after the heating of the heating member by the heating means is stopped. It is preferable not to judge. this is,
When the temperature sensor is composed of, for example, a thermistor from the end of printing to 2 seconds, the difference between the detected temperature (actual measurement value) of the belt and the threshold temperature (reference value) becomes less than the resolution of the thermistor, and the detected temperature and the threshold temperature are This is because it is not possible to accurately determine the magnitude relation of.

Further, in the first image heating apparatus, the control means controls the predetermined time (for example, 1
After the elapse of 80 seconds), it is preferable to determine the set temperature of the heating member during the next image heating, based on the detected temperature of the heating member.

When a predetermined time (for example, 180 seconds) has elapsed from the end of the previous image heating, the difference between the temperature of the belt and the temperature of the pressure roller is small, and when the temperature of the belt is high, the difference is high. When the temperature of the pressure roller is high and the temperature of the belt is low, it can be determined that the temperature of the pressure roller is also low. Therefore, the set temperature is simply determined by the detected temperature of the belt.

In the first image heating apparatus, in order to make the temperature detected by the temperature sensor for the heating member and the ambient temperature in the vicinity of the temperature sensor substantially coincide with each other, the heating material (paper, OHP film, etc.) is not passed through. Further, it is preferable to include a cover that covers at least a part of the heating member (belt), the temperature sensor, and the space occupied by the pressing unit (pressing roller).

According to this structure, the temperature of the pressure roller can be prevented from becoming higher than the temperature of the belt by making the detected temperature of the belt and the ambient temperature thereof coincide with each other. Can be estimated appropriately.

In order to achieve the above object, the second image heating apparatus according to the present invention is a movable heating member (belt) for directly heating a material to be heated (recording paper, OHP film, etc.).
A heating means for directly or indirectly heating the heating member, a pressing means for contacting the heating member, a temperature sensor for detecting the temperature of the heating member, and a temperature of the heating member based on the temperature detected by the temperature sensor. And a control means for controlling the heat generation amount of the heat generation means so that the temperature becomes a set temperature.
After stopping the heating of the heating member by the heat generating means,
The preheating mode for the heating member during the standby time until the start of the next image heating is determined based on at least one of the detected temperature of the heating member and the amount of change in the detected temperature with time.

According to the structure of the second image heating apparatus, the temperature sensor for detecting the temperature of the pressure roller is eliminated to reduce the cost, and at the time of waiting until the start of the next image heating,
By preheating the belt by selecting the optimum preheating mode for the belt, the first printing time can be shortened.

In the second image heating apparatus, at least a part of the heating member is electrically conductive (conductive belt), and the heat generating means includes an exciting means for directly heating the heating member using electromagnetic induction. Alternatively, the heat generating means is inscribed in the heating member,
A rotatable heat-generating member (for example, a metal roller) that at least partially has conductivity and indirectly heats a heating member (for example, a heat-resistant resin belt), and heats the heat-generating member using electromagnetic induction. Exciting means is included.

Further, in the second image heating apparatus, the heating member (belt) preferably has a heat capacity of 60 J / K or less, more preferably 40 J / K or less. As a result, the same effect as that of the first image heating apparatus can be obtained.

Further, in the second image heating apparatus, the control means causes the change amount of the detected temperature of the heating member (belt) with respect to time to be larger than a predetermined value (for example, from 150 ° C. to 120 ° C.).
When the cooling time tp to 0 ° C. is less than 10 seconds, that is, the amount of change in temperature is 3 deg / sec or more, the detected temperature from the temperature sensor is the first upper limit temperature (for example, while the heating member is moving). , 130 ° C.) and a first lower limit temperature (for example, 110 ° C.), a first preheating mode (mode 1) for controlling energization / de-energization of the heat generating means can be selected. preferable. In this case, the control means keeps the moving state of the heating member for a predetermined time (for example, 5
This is continued for 10 revolutions at 0 mm / sec), and the peak value of the input electric power when energizing the heat generating means is the maximum value (for example, 90
It is preferable to set it to 0 W).

According to this structure, when the belt temperature is rapidly decreasing from the end of the previous image heating, it is determined that the pressure roller is in the low temperature state, the input electric power is maximized, and the belt is rotated. Are rotated a predetermined number of times to generate a first upper limit temperature (for example, 130 ° C.) and a first lower limit temperature (for example, 1 ° C.).
By preheating the belt at 10 ° C.), it is possible to set the optimum preheating temperature in a short time with the minimum required belt driving.

Further, in the second image heating apparatus, the control means causes the amount of change of the detected temperature of the heating member (belt) with respect to time to be less than a predetermined value (for example, the cooling time tp from 150 ° C. to 120 ° C. is 10 seconds). Above, that is, when the amount of change in temperature is less than 3 deg / sec), the detected temperature from the temperature sensor is the second upper limit temperature (for example, 100 ° C. or 92 ° C.) with the heating member stopped. It is possible to select the second preheating mode (modes 2, 3, 4) for controlling energization / de-energization of the heat generating means so as to move back and forth between the lower limit temperature (for example, 97 ° C. or 87 ° C.). preferable. In this case, the control means changes the second upper limit temperature and the second lower limit temperature according to the environmental conditions (temperature, humidity), and controls the heat generating means according to the amount of change in the detected temperature of the heating member with respect to time. Each time the peak value of the input power during energization is changed and energization / de-energization of the heating means is repeated,
It is preferable to reduce the peak value of input electric power at the time of energizing the heat generating means by a constant factor.

According to this structure, when the amount of decrease in the belt temperature after the end of the previous image heating is small, it is determined that the pressure roller is still warm, and the applied power is reduced (for example, 130 W or less). Also, with the belt stopped, the second upper limit temperature (for example, 100 ° C. or 92 ° C.) and the second
By preheating the belt between the lower limit temperature (for example, 97 ° C. or 87 ° C.), the belt driving sound suddenly occurs, which saves power without causing unnecessary concern to the user. It is possible to reduce the first print time at the same time. In addition, the ambient environment is room temperature / normal humidity (NN
Environment), the second upper limit temperature is set to 100 ° C, the second lower limit temperature is set to 97 ° C, and in the case of low temperature / low humidity (LL environment), the second upper limit temperature is set to 92 ° C and the second lower limit temperature is set. 87 ℃
By setting it lower than that in the NN environment, optimal preheating can be performed according to the environmental conditions. Also,
The second preheating mode is further divided into modes 2, 3 and 4 in the order in which the amount of change in the detected temperature of the heating member with respect to time is large, and the input power (P0) initially set in modes 2 to 4 is made smaller, Further power saving can be realized by performing the preheating control so that the initially set input power P0 gradually decreases.

In the second image heating apparatus, the control means moves the heating member and stops the heating member when the amount of change in the temperature detected by the heating member with respect to time is within a predetermined range. It is preferable to select the third preheating mode in which energization / de-energization control for the heat generating means is alternately performed. In this case, the control means reduces the peak value of the input electric power at the time of energizing the heat generating means at a constant rate each time the heat generating means is repeatedly energized / de-energized, and the control means changes the peak value to the heat generating means according to the environmental conditions. It is preferable to change the peak value of the input power when the current is energized.

According to this structure, by setting the third preheating mode as an intermediate between the first preheating mode and the second preheating mode, more accurate preheating control can be performed. You can Further, by changing the setting of the second upper limit temperature and the second lower limit temperature depending on whether the ambient environment is the NN environment or the LL environment, optimal preheating according to the environmental conditions can be performed. . Also, by performing preheating control so that the input power gradually decreases,
Further power saving can be realized.

In the second image heating apparatus, in order to make the temperature detected by the temperature sensor by the temperature sensor and the ambient temperature in the vicinity of the temperature sensor substantially coincident with each other, at least one of the heating members excluding the passage portion of the material to be heated. It is preferable to provide a cover for covering the space occupied by the section, the temperature sensor, and the pressing means.

According to this structure, the temperature of the pressure roller is prevented from becoming higher than the temperature of the belt by matching the detected temperature of the belt and the ambient temperature thereof, as in the first image heating apparatus. The temperature of the pressure roller can be estimated appropriately.

In order to achieve the above object, the first image forming apparatus according to the present invention records an image forming means for forming and carrying an unfixed toner image on a recording medium which is a material to be heated. An image forming apparatus including a fixing device for thermally fixing to a medium, wherein the fixing device is a first or second image heating device.

According to the configuration of the first image forming apparatus,
It is possible to realize an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, which has the advantages of the first or second image heating apparatus. In this case, a cover for making the detected temperature of the heating member and the ambient temperature in the vicinity of the temperature sensor approximately match is provided on the first or second image heating device side.

In order to achieve the above object, the second image forming apparatus according to the present invention comprises an image forming means for forming and carrying an unfixed toner image on a recording medium which is a material to be heated, and the toner image. An image forming apparatus having a detachable fixing device for heat fixing to a recording medium, wherein the fixing device is a first or second image heating device without a cover, and the image forming device is mounted with the fixing device. At this time, in order to substantially match the temperature detected by the heating member by the temperature sensor and the ambient temperature in the vicinity of the temperature sensor, at least a part of the heating member, excluding the passage portion of the material to be heated, the temperature sensor, and It is characterized by comprising a cover for covering the space occupied by the pressurizing means.

According to the configuration of the second image forming apparatus,
It is possible to realize an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, which has the advantages of the first or second image heating apparatus. In this case, a cover for making the detected temperature of the heating member and the ambient temperature in the vicinity of the temperature sensor approximately match is provided on the image forming apparatus side with the image heating apparatus removed.

In order to achieve the above object, the image copying apparatus according to the present invention records an toner image according to an image reading device having an image reading means for reading an original image and an original image read by the image reading device. And a first or second image forming apparatus which is formed by heat fixing on a medium.

In order to achieve the above object, the first temperature control method according to the present invention comprises a movable heating member (belt) for directly heating a material to be heated (recording paper, OHP film, etc.), and a heating member. Based on the temperature detected by the temperature sensor and the temperature sensor that detects the temperature of the heating member, the heating unit that directly or indirectly heats the heating member, the pressing unit that contacts the heating member, and the temperature of the heating member reaches the set temperature. In order to substantially match the detection temperature of the heating member by the temperature sensor and the ambient temperature in the vicinity of the temperature sensor with the control unit that controls the heat generation amount of the heating unit, A temperature control method applied to an image heating apparatus having at least a part of a member, a temperature sensor, and a cover that covers a space occupied by a pressurizing unit, wherein heating of the heating member by a heat generating unit is performed. A heating member temperature measuring step of measuring at least one of a temperature of the heating member and a change amount of the temperature with time after stopping, and a temperature and temperature of the heating member measured in the heating member temperature measuring step. Based on at least one of the amounts of change with respect to time, the temperature of the pressurizing means is estimated, and it is determined in the set temperature determination step for determining the set temperature of the heating member during the next image heating, and the set temperature determination step. And a heat generation amount control step of controlling the heat generation amount of the heat generation means by the control means so that the set temperature is achieved.

According to the configuration of the first temperature control method,
A temperature control method suitable for the first image heating apparatus having the cover can be realized.

In order to achieve the above object, the second temperature control method according to the present invention comprises a movable heating member (belt) for directly heating a material to be heated (recording paper, OHP film, etc.), and a heating member. Based on the temperature detected by the temperature sensor and the temperature sensor that detects the temperature of the heating member, the heating unit that directly or indirectly heats the heating member, the pressing unit that contacts the heating member, and the temperature of the heating member reaches the set temperature. In order to substantially match the detection temperature of the heating member by the temperature sensor and the ambient temperature in the vicinity of the temperature sensor with the control unit that controls the heat generation amount of the heating unit, A temperature control method applied to an image heating apparatus having at least a part of a member, a temperature sensor, and a cover that covers a space occupied by a pressurizing unit, wherein heating of the heating member by a heat generating unit is performed. A heating member temperature measuring step of measuring at least one of a temperature of the heating member and a change amount of the temperature with time after stopping, and a temperature and temperature of the heating member measured in the heating member temperature measuring step. Based on at least one of the change amounts with respect to time, the preheating mode determination step for determining the preheating mode for the heating member and the preheating mode determination step for determining the preheating mode for the heating member during the standby until the start of the next image heating. A preheating step of preheating the heating member according to the preheating mode.

According to the configuration of this second temperature control method,
A temperature control method suitable for the second image heating apparatus having a cover can be realized.

In order to achieve the above-mentioned object, a third temperature control method according to the present invention comprises an image forming means for forming and carrying an unfixed toner image on a recording medium which is a material to be heated, and a recording medium (recording medium). Movable heating member (belt) for directly heating paper, OHP film, etc., heat generating means for directly or indirectly heating the heating member, pressurizing means for contacting the heating member, and temperature detection of the heating member And a control unit that controls the amount of heat generated by the heating unit so that the temperature of the heating member reaches the set temperature based on the temperature detected by the temperature sensor. Possible image heating device, and when the image heating device is installed,
At least a part of the heating member excluding the passage of the material to be heated, the temperature sensor, and the pressurizing means occupy the temperature of the heating member detected by the temperature sensor and the ambient temperature in the vicinity of the temperature sensor to substantially match. A temperature control method applied to an image forming apparatus including a cover for covering a space, wherein at least one of a temperature of the heating member and a change amount of the temperature with respect to time after the heating of the heating member by the heat generating means is stopped. The temperature of the pressurizing means based on at least one of the heating member temperature measuring step of measuring the temperature of the heating member and the temperature of the heating member measured in the heating member temperature measuring step and the amount of change of the temperature with time. It is estimated and set in the set temperature determination step that determines the set temperature of the heating member during the next image heating, and in the set temperature determination step. So that the set temperature, characterized in that it comprises a heating amount control step for controlling the heating value of the heating means by the control means.

According to the configuration of the third temperature control method,
A detachable first image heating device without a cover;
The fixing temperature control suitable for the image forming apparatus including the cover for the image heating apparatus can be realized.

In order to achieve the above-mentioned object, a fourth temperature control method according to the present invention comprises an image forming means for forming and carrying an unfixed toner image on a recording medium which is a material to be heated, and a recording medium (recording medium). Movable heating member (belt) for directly heating paper, OHP film, etc., heat generating means for directly or indirectly heating the heating member, pressurizing means for contacting the heating member, and temperature detection of the heating member And a control unit that controls the amount of heat generated by the heating unit so that the temperature of the heating member reaches the set temperature based on the temperature detected by the temperature sensor. Possible image heating device, and when the image heating device is installed,
At least a part of the heating member excluding the passage of the material to be heated, the temperature sensor, and the pressurizing means occupy the temperature of the heating member detected by the temperature sensor and the ambient temperature in the vicinity of the temperature sensor to substantially match. A temperature control method applied to an image forming apparatus including a cover for covering a space, wherein at least one of a temperature of the heating member and a change amount of the temperature with respect to time after the heating of the heating member by the heat generating means is stopped. Until the next image heating is started based on at least one of the heating member temperature measuring step of measuring one of the two with a temperature sensor and at least one of the temperature of the heating member measured in the heating member temperature measuring step and the change amount of the temperature with respect to time. And the preheating mode determination step for determining the preheating mode for the heating member during the standby of In accordance with the determined pre-heating mode in, characterized in that it comprises a preheating step of heating element to preheat.

According to the configuration of the fourth temperature control method,
A detachable second image heating device having no cover;
Preheating control suitable for the image forming apparatus including the image heating device cover can be realized.

[0057]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing the overall configuration of an image forming apparatus using the image heating device according to the embodiment as a fixing device. Less than,
The configuration and operation of this device will be described.

In FIG. 1, 17 is an exterior plate of the apparatus main body,
Reference numeral 1 is an electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum). The surface of the photosensitive drum 1 is uniformly charged to a predetermined negative dark potential V0 by the charger 2 while being rotationally driven in the direction of the arrow at a predetermined peripheral speed.

Reference numeral 3 denotes a laser beam scanner, which outputs a laser beam 4 modulated in accordance with a time series electric digital pixel signal of image information input from a host device such as an image reading device or a computer (not shown). The surface of the photosensitive drum 1 uniformly charged as described above is scanned and exposed by the laser beam 4. As a result, the absolute value of the potential of the exposed portion of the photosensitive drum 1 decreases to the bright potential VL, and an electrostatic latent image is formed on the surface of the photosensitive drum 1. This electrostatic latent image is reversely developed by the negatively charged toner of the developing device 5 to be visualized.

The developing device 5 includes a developing roller 6 which is rotationally driven.
Is equipped with. The developing roller 6 is arranged to face the photosensitive drum 1, and a thin layer of toner is formed on the outer peripheral surface thereof. The developing roller 6 has an absolute value of the photosensitive drum 1.
A developing bias voltage that is smaller than the dark potential V0 and larger than the bright potential VL is applied, whereby the toner on the developing roller 6 is transferred only to the portion of the photosensitive drum 1 at the bright potential VL, and electrostatic latent The image is visualized and the toner image 11 is formed.

On the other hand, the recording paper 8 is fed one by one from the paper feeding unit 7, passes through the registration roller pair 9, and is moved to the nip portion between the photosensitive drum 1 and the transfer roller 10 in synchronization with the rotation of the photosensitive drum 1. It will be sent at the right time. Then, the toner image 11 on the photosensitive drum 1 is transferred to the recording paper 8 by the transfer roller 10 to which a transfer bias is applied.

A fixing paper guide 13 guides the movement of the recording paper 8 after transfer to the fixing device 14 by the fixing paper guide 13. Recording paper 8 on which toner image 11 is transferred
After being separated from the photosensitive drum 1, the toner image 11 transferred to the fixing device 14 and transferred onto the recording paper 8 by this is
Is fixed. Further, 15 is a paper discharge guide, and the paper discharge guide 15 guides the recording paper 8 that has passed through the fixing device 14 to the outside of the apparatus. The recording paper 8 after the toner image 11 is fixed is discharged to the paper discharge tray 16. Reference numeral 18 denotes a fixing door for attaching / detaching the fixing device 14 and for processing a paper jam. The fixing door 18 rotates around a hinge 19 and is opened / closed together with the paper discharge tray 16. Then, by opening the fixing door 18, the fixing device 14 can be attached to and detached from the apparatus main body in a direction perpendicular to the axis of the heat generating roller 21 (see FIG. 2). The broken line in FIG. 1 shows the position of the fixing device 14 in the detached state, and the solid line shows the position when the fixing device 14 is mounted. As shown in FIG. 1, only the fixing device 14 is attached / detached while leaving an exciting means 24 such as an exciting coil 25 (see FIG. 2) described later in the apparatus main body.

Photosensitive drum 1 after recording paper 8 has been separated
The cleaning device 12 removes residuals such as transfer residual toner on the surface thereof, and is repeatedly used for the next image formation.

FIG. 13 is a schematic sectional view showing the overall construction of an image copying apparatus using the image forming apparatus shown in FIG. In FIG. 13, reference numeral 91 is a light source, which exposes the original 95. The light reflected from the non-image portion is reflected by the mirror 92, condensed by the lens 93, and the image information read by the photoelectric conversion element 94 such as CCD is time-series by an A / D converter (not shown) or the like. Is converted into a digital image signal. Then, the image signal is input to the laser beam scanner 3 of the image forming apparatus to form an image.

Next, regarding the image heating apparatus of this embodiment,
It will be described in more detail with a specific example.

FIG. 2 is a sectional view showing the structure of a fixing device as an image heating device used in the image forming apparatus.

In FIG. 2, reference numeral 25 is an exciting coil which constitutes a part of the exciting means 24. This exciting coil 25 is
It is formed by using a litz wire that is a bundle of thin wires, and has a cross-sectional shape that covers the fixing belt 20 wound around the heat roller 21. A core material 26 made of ferrite is provided at the center of the exciting coil 25 and a part of the back surface thereof. As the material of the core material 26, besides ferrite, a material having a high magnetic permeability such as permalloy can be used. The exciting coil 25 is provided outside the heat generating roller 21,
An exciting current of, for example, 23 kHz is applied from the exciting circuit 75. As a result, a part of the heat generating roller 21 is heated by electromagnetic induction.

Although the exciting coil 25 is provided outside the heat generating roller 21 in FIG. 2, the exciting coil may be arranged inside the heat generating roller 21.

A temperature sensor 45 is provided at a portion of the fixing belt 20 that has passed the contact portion with the heat generating roller 21 so as to come into contact with the back surface of the fixing belt 20, and thereby the temperature of the fixing belt 20 is detected. It

Reference numeral 79 is a control means, and the control means 79 is
Based on the temperature of the fixing belt detected by the temperature sensor 45 and the amount of change of the temperature with respect to time, the electric power supplied to the exciting coil 25 via the exciting circuit 75 is controlled so that the optimum fixing temperature is obtained, thereby generating heat. The heat generation amount of the roller 21 is controlled. This control method will be described in detail later.

Reference numeral 28 is a coil guide as a holding member. The coil guide 28 is made of a resin having a high heat resistance temperature such as PEEK material or PPS, and is integrated with the exciting coil 25 and the core material 26. In this way, the coil guide 2
By providing 8, the heat radiated from the heat generating roller 21 can be prevented from being trapped in the space between the heat generating roller 21 and the exciting coil 25 and damaging the exciting coil 25.

Although the core material 26 has a semicircular cross section in FIG. 2, the core material 26 does not necessarily have to have a shape corresponding to the shape of the exciting coil 25. For example, the shape may be approximately Π.

The thin fixing belt 20 has a base material made of a polyimide resin having a glass transition point of 360 ° C. and a diameter of 50 mm.
It is an endless belt having a thickness of 90 μm. The surface of the fixing belt 20 is coated with a release layer (not shown) made of fluororesin and having a thickness of 30 μm in order to impart releasability. As the material of the base material, in addition to the polyimide resin used in this example, a resin having heat resistance such as a fluororesin can be used. The glass transition point of the base material of the fixing belt 20 is preferably 200 ° C to 500 ° C.
Further, as the release layer on the surface of the fixing belt 20, PTF is used.
Resins and rubbers having good releasability such as E, PFA, FEP, silicone rubber, and fluororubber may be used alone or in combination. When the fixing belt 20 is used for fixing a monochrome image, only releasability is required to be secured, but when the fixing belt 20 is used for fixing a color image, it is desirable to impart elasticity, and in that case. Needs to form a thicker rubber layer. Also, the fixing belt 2
The heat capacity of 0 is preferably 60 J / K or less, more preferably 40 J / K or less.

The fixing belt 20 includes a fixing roller 22 having a diameter of 20 mm and a heat generating roller 21 having a diameter of 20 mm and made of a silicone rubber which is a foam having a low hardness (JIS A30 degrees) and elasticity. It is suspended with the tension of, and can rotate and move in the direction of arrow B.

The heating roller 21 has a diameter of 30 mm and a length of 3
It is made of a cylindrical SUS430 having a thickness of 20 mm and a thickness of 0.5 mm, and has a heat capacity of 54 J / K. The heat roller 21
As the material of SUS430, other magnetic metal such as iron can be used in addition to SUS430. The heat capacity of the heat generating roller 21 is preferably 60 J / K or less, more preferably 40 J / K or less.

The pressure roller 23 is made of silicone rubber having a hardness of JIS A65 degrees, and is pressed against the fixing roller 22 via the fixing belt 20 to form a nip portion. In this state, the pressure roller 23 is supported so as to rotate with the rotation of the fixing roller 22.
As the material of the pressure roller 23, other heat resistant resin such as fluororubber or fluororesin or rubber may be used. Further, in order to improve abrasion resistance and releasability, it is desirable that the surface of the pressure roller 23 is coated with a resin or rubber such as PFA, PTFE, FEP, etc., alone or in a mixture. Further, in order to prevent heat dissipation, the pressure roller 23 is preferably made of a material having low heat conductivity.

The pressure roller 23 is rotationally driven by a drive source (not shown) of the apparatus main body. In addition, the fixing roller 22
Rotates with the rotation of the pressure roller 23 via the fixing belt 20. Further, the heat generating roller 21 is used as the fixing belt 2.
It rotates with the rotation of the fixing roller 22 via 0.

Reference numeral 90 denotes a cover for covering a space occupied by the fixing belt 20, the heating roller 21 (apart from the portion facing the exciting coil 25), the fixing roller 22, the temperature sensor 45, and the pressure roller 23. , Fixing belt 2
By matching the temperature of 0 with the ambient temperature, the temperature of the pressure roller 23 can be prevented from becoming higher than the temperature of the fixing belt 20, and the temperature of the pressure roller can be properly estimated. it can.

Although the fixing belt 20 is suspended by the heat generating roller 21 and the fixing roller 22 in FIG. 2, a tube-shaped fixing belt may be provided on the fixing roller to form a uniaxial structure. Even in that case, it is driven by the pressure roller,
The fixing roller or the fixing pressing member may be fixed and only the tubular fixing belt may rotate, or the fixing roller and the fixing belt may rotate simultaneously. In that case, the exciting coil may be outside or inside the fixing belt.

An example of a uniaxial fixing device is shown in FIGS.
1 and FIG. 10 to 12, parts having the same configurations and functions as those in FIG. 2 are designated by the same reference numerals.

FIG. 10 is a sectional view showing a structural example of a uniaxial external coil type fixing device.

In FIG. 10, the fixing roller has a shaft center 20.
4, a magnetic shield layer 203 made of ferrite and a silicone rubber layer 202 of low-hardness (Asker-C40 degrees) elastic foam are provided, and a metallic fixing belt 201 is arranged on the outer side thereof. There is. Metal fixing belt 2
01 is the fixing belt 20 except that the base material of the fixing belt 20 is a very thin metal such as nickel produced by electroforming.
It has the same structure as.

With this structure, the apparent heat capacity is smaller than that of the biaxial structure, so the temperature rise time is shortened, but it is more susceptible to the pressure roller temperature, and the temperature control of the present invention is essential.

FIG. 11 is a sectional view showing a structural example of a uniaxial internal coil type fixing device.

In FIG. 11, the fixing roller 301 is made of a cylindrical SUS430 having a diameter of 30 mm, a length of 320 mm and a thickness of 0.8 mm. As the material of the fixing roller 301, other magnetic metal such as iron can be used instead of SUS430. The exciting coil 25 is wound on a coil holder 302 made of heat-resistant resin, and is fixed on the fixing roller 301.
The fixing roller 301 is heated from inside.

FIG. 12 is a sectional view showing an example of the structure of a uniaxial internal coil type belt fixing device.

In FIG. 12, a fixing belt 401 is a belt made of a very thin metal such as nickel whose base material is manufactured by electroforming, and having a release layer on the surface with an elastic silicone rubber layer sandwiched therebetween. As the release layer, PFA, PTF
Resins and rubbers having good releasability such as E, FEP, silicone rubber, and fluororubber may be used alone or in combination.

The fixing belt 401 is held between the pressing member 402 made of a heat resistant resin and the pressure roller 23, and is driven according to the rotation of the pressure roller.

In this structure, since the heat capacity of the fixing belt 401 is small, it is easily affected by the ambient temperature, and the fixing roller temperature also strongly depends on the fixing property. Therefore, the effect of improving the temperature control of the present invention is remarkably exhibited.

The fixing device having the above-described structure is shown in FIG.
Paper 8 on which the toner image 11 has been transferred by the image forming apparatus
With the surface on which the toner image 11 is transferred facing up
The toner image 11 on the recording paper 8 can be fixed by making it enter from the direction.

FIG. 3 shows the fixing belt 2 in this embodiment.
It is a figure which shows the cooling curve of the threshold temperature Tf of 0 with respect to the elapsed time tp from the printing completion time. This cooling curve will be described later with reference to the flowchart of FIG. 4, but when a print request is given by the user, it is detected by the temperature sensor 45 at the elapsed time tp from the end of the previous print to immediately before the start of the next print. Based on the magnitude relationship between the temperature Tb (measured value) of the fixing belt 20 and the threshold temperature Tf (reference value), one of a plurality of reference tables storing various fixing temperatures is selected to set the fixing temperature. Used for optimal control.

In FIG. 3, when printing is completed (tp = 0)
To tp = t _W (for example, 2 seconds), the temperature sensor 4
5 is composed of, for example, a thermistor, the difference between the detected temperature Tb of the fixing belt 20 and the threshold temperature Tf becomes less than the resolution of the thermistor, and the magnitude relationship between the detected temperature Tb and the threshold temperature Tf cannot be accurately determined. Wait without control.

From time t _W (2 seconds) to time t _F12 (for example,
In the time period up to 15 seconds), the threshold temperature Tf when the elapsed time tp is used as a parameter is represented by the following formula F1.

Tf = 0.00002tp ⁴ −0.0024tp ³ + 0.1017tp ² −2.5119tp + 167.68 (F1) From time t _F12 (15 seconds) to time t _F23 (for example, 60 seconds)
In the time period up to, the threshold temperature Tf when the elapsed time tp is used as a parameter is represented by the following formula F2.

Tf = 0.0000025tp ⁴ −0.0005tp ³ + 0.03901tp ² −1.5906tp + 162.53 (F2) From time t _F23 (60 seconds) to time t _F34 (for example, 90 seconds)
In the time period up to, the threshold temperature Tf when the elapsed time tp is used as a parameter is represented by the following formula F3.

Tf = −0.1313tp + 139.81 (F3) From time t _F34 (90 seconds) to time t _F45 (for example, 120
In the time period up to the second), the threshold temperature Tf when the elapsed time tp is used as a parameter is represented by the following formula F4.

Tf = −0.1tp + 136.99 (F4) From time t _F45 (120 seconds) to time t _E (for example, 180)
In the time period up to the second), the threshold temperature Tf when the elapsed time tp is used as a parameter is represented by the following formula F5.

Tf = −0.0831tp + 134.96 (F5) After the time t _E (180 seconds), the reference table is simply based on the temperature Tb of the fixing belt 20 without using the threshold temperature Tf. One of them is selected. this is,
When 180 seconds (t1) has elapsed from the end of the previous image heating, the temperature Tb of the fixing belt 20 is sufficiently low,
Therefore, it can be determined that the temperature of the pressure roller 23 is also low. Further, the temperature Tb of the fixing belt 20 is 120 ° C.
The same applies to the following cases.

Next, regarding the structure of the image heating apparatus and the method of controlling the fixing temperature by using the cooling curve of the fixing belt 20 as described above, in addition to FIGS. 2 and 3, FIGS.
A description will be given with reference to A, FIG. 5B, and FIG. 5C.

FIG. 4 is a flow chart showing the processing steps in the fixing temperature control routine applied to the image heating apparatus and the image forming apparatus according to this embodiment. FIG. 5A shows
5B is a diagram showing an example of contents of a low temperature reference table (table A), FIG. 5B is a diagram showing an example of contents of a medium temperature reference table (table B), and FIG. 5C is a diagram showing a high temperature reference table (table C). ) Is a diagram showing an example of contents.

In FIG. 4, first, when printing is completed (tp = 0), a timer (not shown) starts counting elapsed time tp (S401). After the printing is completed, if there is a print request from the user (S402), after waiting for the elapsed time tp to become t _W (= 2 seconds) or more (S402).
403), the temperature sensor 45 detects and measures the temperature Tb of the fixing belt 20 (S404).

Next, the temperature Tb of the fixing belt 20 (hereinafter referred to as "belt temperature") is used as a criterion for selecting the table B for medium temperature shown in FIG. 5B or the table C for high temperature shown in FIG. 5C. It is determined whether the temperature is higher than the temperature T _BC (= 120 ° C.) (S405). If the result of determination in step S405 is that the belt temperature Tb is 120 ° C. or lower (No), the process branches to step S406, and the belt temperature Tb is the low temperature table A and FIG. 5B shown in FIG. 5A.
It is determined whether or not the temperature is higher than the temperature T _AB (= 70 ° C.) which is a reference for selecting which one of the table B for medium temperature shown in FIG. If the result of determination in step S406 is that the belt temperature Tb is higher than 70 ° C. (Yes), table B is selected and the set temperature (160) stored in table B is selected.
C. or 167.degree. C.) to control the fixing temperature ("temperature control by table B": S407). vice versa,
As a result of the determination in step S406, the belt temperature Tb
Is 70 ° C. or lower (No), table A is selected and the set temperature stored in table A is higher than the set temperature in table B (165 ° C. or 170 ° C.).
The fixing temperature is controlled based on (° C) (see "Table A
Temperature control by ": S408).

On the other hand, if the result of determination in step S405 is that the belt temperature Tb is higher than 120 ° C. (Ye
s), proceeding to step S409, it is determined whether the elapsed time tp counted by the timer is t _E (= 180 seconds) or less. As a result of the determination in step S409, if the elapsed time tp exceeds 180 seconds (N
o), the process proceeds to step S413, the table C is selected, and the fixing temperature is controlled based on the set temperature (155 ° C. or 163 ° C.) lower than the set temperature in the table B (“temperature control by table C”). ).

On the other hand, if the result of determination in step S409 is that the elapsed time tp is within 180 seconds (Yes
s), proceeding to step S410, whether the elapsed time tp is within a time t _F12 (= 15 seconds) (two seconds or more) which is a reference for selecting one of the above formulas F1 and F2. To judge. As a result of the determination in step S410, when the elapsed time tp is within 15 seconds (Yes
s), the threshold temperature Tf is obtained by substituting the elapsed time tp immediately before the start of printing into the formula F1 (S411).

Next, the belt temperature Tb is determined in step S41.
It is determined whether the temperature is higher than the threshold temperature Tf obtained in 1 (S
412) If the belt temperature Tb is equal to or lower than the threshold temperature Tf (No), the process branches to step S407 to perform the temperature control by the table B for medium temperature. On the other hand, step S41
As a result of the determination in 2, the belt temperature Tb is the threshold temperature Tf.
If it is higher (Yes), the process proceeds to step S413 to perform temperature control by the high temperature table C.

On the other hand, if the result of determination in step S410 is that the elapsed time tp exceeds 15 seconds (No),
The process branches to step S414, and it is determined whether the elapsed time tp is within a time t _F23 (= 60 seconds) which is a reference for selecting one of the above formulas F2 and F3. As a result of the determination in step S414, the elapsed time tp is 60.
If it is within seconds (Yes), the elapsed time tp immediately before the start of printing is substituted into the formula F2 to obtain the threshold temperature Tf (S415).

Next, the belt temperature Tb is determined in step S41.
It is determined whether or not the temperature is higher than the threshold temperature Tf obtained in step 5 (S
416), if the belt temperature Tb is lower than or equal to the threshold temperature Tf (No), the process branches to step S407 to perform temperature control by the table B for medium temperature. On the other hand, step S41
As a result of the determination in 6, the belt temperature Tb is the threshold temperature Tf.
If it is higher (Yes), the process proceeds to step S413 to perform temperature control by the high temperature table C.

On the other hand, if the result of determination in step S414 is that the elapsed time tp exceeds 60 seconds (No),
The process branches to step S417, and it is determined whether the elapsed time tp is within a time t _F34 (= 90 seconds) which is a reference for selecting one of the above formulas F3 and F4. As a result of the determination in step S417, the elapsed time tp is 90.
If it is within seconds (Yes), the threshold temperature Tf is obtained by substituting the elapsed time tp until just before the start of printing into the formula F3 (S418).

Next, the belt temperature Tb is determined in step S41.
It is determined whether or not the temperature is higher than the threshold temperature Tf calculated in step 8 (S
419), if the belt temperature Tb is equal to or lower than the threshold temperature Tf (No), the process branches to step S407 to perform temperature control by the table B for medium temperature. On the other hand, step S41
As a result of the determination in 9, the belt temperature Tb is the threshold temperature Tf.
If it is higher (Yes), the process proceeds to step S413 to perform temperature control by the high temperature table C.

On the other hand, if the result of determination in step S417 is that the elapsed time tp exceeds 90 seconds (No),
The process branches to step S420, and it is determined whether the elapsed time tp is within a time t _F45 (= 120 seconds) that is a reference for selecting one of the above formulas F4 and F5. As a result of the determination in step S420, the elapsed time tp is 1
When it is within 20 seconds (Yes), the elapsed time tp immediately before the start of printing is substituted into the formula F4 to obtain the threshold temperature T.
f is calculated (S421).

Next, the belt temperature Tb is determined in step S42.
It is determined whether the temperature is higher than the threshold temperature Tf obtained in 1 (S
422), if the belt temperature Tb is equal to or lower than the threshold temperature Tf (No), the process branches to step S407 to perform temperature control by the table B for medium temperature. On the other hand, step S42
As a result of the determination in 2, the belt temperature Tb is the threshold temperature Tf.
If it is higher (Yes), the process proceeds to step S413 to perform temperature control by the high temperature table C.

On the other hand, if the result of determination in step S420 is that the elapsed time tp exceeds 120 seconds (N
o), the threshold temperature Tf is obtained by substituting the elapsed time tp until just before the start of printing into the formula F5 (S423).

Next, the belt temperature Tb is determined in step S42.
It is judged whether or not the temperature is higher than the threshold temperature Tf obtained in 3 (S
424), if the belt temperature Tb is equal to or lower than the threshold temperature Tf (No), the process branches to step S407 to perform temperature control by the table B for medium temperature. On the other hand, step S42
As a result of the determination in 4, the belt temperature Tb is the threshold temperature Tf.
If it is higher (Yes), the process proceeds to step S413 to perform temperature control by the high temperature table C.

By performing the fixing temperature control as described above, the temperature of the pressure roller 23 can be estimated from the temperature of the fixing belt 20 or the temperature change amount without providing a temperature sensor for detecting the temperature of the pressure roller 23. However, by setting the optimum fixing temperature at the time of heating the next image, cost reduction is achieved, and uneven gloss of the fixed image due to temperature fluctuation of the pressure roller 23 and winding of the fixing belt 20 at high temperature are prevented. can do.

(Second Embodiment) The configuration of the image heating apparatus according to the second embodiment of the present invention is the same as that of the first embodiment shown in FIG. 2, but in the first embodiment, While the fixing temperature control is performed using the cooling curve of the fixing belt 20, in the present embodiment, the preheating control for maintaining the temperature of the fixing belt 20 at about 100 ° C. during the standby from the end of the previous printing. It differs in that it does.

A method for controlling the preheating temperature will be described below with reference to FIGS. 6, 7, 8A and 8B.

FIG. 6 is a flow chart showing the processing steps in the preheating control routine applied to the image heating apparatus and the image forming apparatus according to this embodiment.

FIG. 7 shows the flow chart of FIG. 6 at 150 ° C.
To 120 ° C, the peak value P0 of the input power, the upper limit temperature Th, and the lower limit corresponding to the environmental conditions (NN environment, LL environment) in each preheating mode (mode 1 to mode 4) selected according to the cooling time tp It is a figure which shows the concrete value of temperature Tl.

FIG. 8A is a waveform diagram of the belt temperature and the applied power when the preheating temperature control is performed in the mode 1 of FIG. 7, and FIG. 8B is the preheating temperature control in the modes 2 and 3 of FIG. It is a waveform diagram of the belt temperature and the input power in the case of.

When the printing is completed, the preheating control routine of FIG. 6 is entered, and the temperature T _NL (= 15) is set as the reference for the environmental temperature Ta to select the NN environment or the LL environment.
(° C) or higher is determined (S601). As a result of the determination in step S601, if the environmental temperature Ta is equal to or higher than T _NL (Yes), the upper limit temperature Th and the lower limit temperature Tl of the NN environment shown in FIG. 7 are set (S602). On the other hand, as a result of the determination in step S601, the ambient temperature T
When a is lower than T _NL (No), the upper limit temperature Th and the lower limit temperature Tl of the LL environment shown in FIG. 7 are set (S60).
3).

Next, the cooling time tp required for the temperature of the fixing belt 20 to drop from 150 ° C. to 120 ° C. is measured (S604), and the cooling time tp is a criterion for selecting either mode 1 or mode 2. It is determined whether or not it is shorter than the cooling time t _M12 (for example, 10 seconds) (S60).
5). As a result of the determination in step 605, the cooling time t
When p is shorter than 10 seconds (Yes), preheating control by mode 1 is performed (S606).

As shown in FIG. 8A, when the cooling time tp from the time t0 when the temperature of the fixing belt 20 reaches 150 ° C. to the time t1 when it drops to 120 ° C. is less than 10 seconds, the mode 1 is entered. In mode 1, the fixing belt 20 is 50 mm
From the time t1 to the time t2, the exciting circuit 75 moves the exciting coil 25 from the exciting coil 75 while rotating and moving 10 revolutions per second.
As shown in FIG. 2, as shown in FIG. 7, energization is performed with electric power having a peak value of 900 W, and the operation of stopping energization is repeated from time t2 to time t3. As a result, the preheating control is performed so that the belt temperature moves back and forth between the upper limit temperature Th of 130 ° C. and the lower limit temperature Tl of 110 ° C.

Returning to FIG. 6 again, when the mode 1 is completed, the mode is shifted to the mode 2 and the preheating control by the mode 2 is performed (S608).

In the mode 2, the rotational movement of the fixing belt 20 is stopped, and as shown in FIGS. 7 and 8B, from the time t1 to the time t2, the exciting circuit 75 to the exciting coil 25 (FIG. 2). Then, energization is performed with electric power P0 having a peak value of 130 W, the energization is stopped from time t2 to time t3, and the peak value is 130 from time t3 to time t4.
Energization is performed with electric power P1 reduced to × 0.96W, and energization is stopped from time t4 to time t5, and time t5
Then, the power is supplied with the power P2 whose peak value is reduced to 130 × (0.96) ² W, and the operation of reducing the input power is repeatedly performed every power-on / power-off cycle.
As a result, if the belt temperature is NN, 100 ° C
Preheat control so as to move back and forth between the upper limit temperature Th of 97 ° C. and the lower limit temperature Tl of 97 ° C. In the case of the LL environment, preheating control so as to switch between the upper limit temperature Th of 92 ° C. and the lower limit temperature Tl of 87 ° C. Is done.

In the mode 2, when the peak value of the input power during energization becomes 100 W or less, the mode is shifted to the mode 3 and the preheating control by the mode 3 is performed (S610).

In the mode 3, the rotational movement of the fixing belt 20 is stopped, and as shown in FIGS. 7 and 8B, from the time t1 to the time t2, from the exciting circuit 75 to the exciting coil 25 (FIG. 2). Then, energization is performed with the electric power P0 having a peak value of 100 W, the energization is stopped from time t2 to time t3, and the peak value is 100 from time t3 to time t4.
Energization is performed with electric power P1 reduced to × 0.96W, and energization is stopped from time t4 to time t5, and time t5
Then, energization is performed with the electric power P2 whose peak value is reduced to 100 × (0.96) ² W, and in this manner, the operation of reducing the applied electric power is repeatedly performed in each energization / de-energization cycle.
As a result, if the belt temperature is NN, 100 ° C
Preheat control so as to move back and forth between the upper limit temperature Th of 97 ° C. and the lower limit temperature Tl of 97 ° C. In the case of the LL environment, preheating control so as to switch between the upper limit temperature Th of 92 ° C. and the lower limit temperature Tl of 87 ° C. Is done.

In mode 3, when the peak value of the input power during energization becomes 60 W or less, the mode shifts to mode 4,
Preheating control according to mode 4 is performed (S611).

In mode 4, the crest value is 60 W as shown in FIG. 7 in a state where the rotational movement of the fixing belt 20 is stopped.
Energize and de-energize with the power of. Accordingly, when the belt temperature is the NN environment, the upper limit temperature Th of 100 ° C.
And the lower limit temperature Tl of 97 ° C.
In the case of the L environment, the preheating control is performed so as to move back and forth between the upper limit temperature Th of 92 ° C. and the lower limit temperature Tl of 87 ° C.

Returning to FIG. 6 again, as a result of the determination in step S605, if the cooling time tp is 10 seconds or more (No), the process proceeds to step S607 to cool the cooling time tp.
Determines whether the cooling time is shorter than the cooling time t _M23 (for example, 20 seconds) which is a reference for selecting the mode 2 or the mode 3. When the cooling time tp is shorter than 20 seconds (Yes) as a result of the determination in step 607 (Yes), mode 2
Pre-heating control by is performed (S608).

On the other hand, if the result of determination in step 607 is that the cooling time tp is 20 seconds or more (No), the flow proceeds to step S609, and the cooling time tp is used as a criterion for selecting either mode 3 or mode 4. Cooling time t
_It is determined whether it is shorter than _M34 (for example, 30 seconds).
As a result of the determination in step 609, the cooling time tp is 3
If it is shorter than 0 second (Yes), the preheating control by the mode 3 is performed (S610).

On the other hand, if the result of determination in step 609 is that the cooling time tp is 30 seconds or longer (No), preheating control in mode 4 is performed (S611).

By performing the preheating control as described above, based on the temperature change amount of the fixing belt 20 (150 ° C.).
Depending on the cooling time from 1 to 120 ° C,
(3, 4 are selected), and during the standby until the start of the next image heating, the optimum preheating mode for the fixing belt 20 is selected to preheat the fixing belt 20 and the heat generating roller 21, thereby shortening the first print time. be able to.

In the present embodiment, mode 0 is shown in FIG. 7, which means that the user opens the door of the image forming apparatus and then closes the door again while waiting for preheating. This is the preheating mode for the case of returning to the original state. In such a case, when the door is opened, the energization of the fixing device is stopped for safety, and the ambient temperature lowers the internal temperature of the image forming apparatus and the belt temperature. When the belt temperature is less than 100 ° C., the preheating control by mode 0 is performed.

In mode 0, for example, in the case of the LL environment, a 4-second cycle (1
/ 8 duty ratio: input power equivalent to 63 W), and in the NN environment, 5 second cycle of 0.5 second energization and 4.5 second non-energization (1/10 duty ratio: input power equivalent to 50 W). Then, until the belt temperature reaches 100 ° C or higher,
The fixing belt 20 is gradually heated. Belt temperature is 10
When the temperature reaches 0 ° C., the mode is shifted to the mode 2 and the preheating temperature control as described above is performed.

(Third Embodiment) FIG. 9 shows a third embodiment of the present invention.
3 is a cross-sectional view showing the overall configuration of a color image forming apparatus using the image heating device according to the first or second embodiment as a fixing device.

In FIG. 9, the right end is the front surface of the color image forming apparatus, and the front door 67 is provided on the front surface. Reference numeral 68 denotes a transfer belt unit, which includes an intermediate transfer belt 69, three support shafts 70 suspending the intermediate transfer belt 69, and a cleaner 71, which are integrally attached to and detached from the color image forming apparatus. It is installed freely. In this case, as shown in FIG. 9, the front door 67 of the color image forming apparatus can be opened and the transfer belt unit 68 can be attached and detached.

A carriage 73 is provided adjacent to the transfer belt unit 68 on the left side inside the color image forming apparatus, and a black (B
K), cyan (C), magenta (M), yellow (Y)
Image forming units 72BK, 72 having a substantially fan-shaped cross section
C, 72M and 72Y are housed in a ring shape. Here, the carriage 73 is rotatable in the direction of the arrow.

The image forming unit 72 has process elements arranged around the photosensitive drum 1 and is integrated, and is constituted by the following parts.

Reference numeral 2 is a corona charger for uniformly charging the photosensitive drum 1 negatively, and 97 is black, cyan, and
This is a developing device that contains magenta and yellow toners and that forms a toner image for each color by adhering negatively chargeable toner from the developing roller 6 to the electrostatic latent image on the opposing photosensitive drum 1. In FIG. 20, 3 is a transfer belt unit 6
8 is a laser beam scanner provided below.

The image forming units 72BK to 72Y are opened by opening the upper door 74 on the upper surface of the color image forming apparatus.
It can be attached to and detached from the color image forming apparatus. When the carriage 73 rotates, the image forming unit 72
BK, 72C, 72M and 72Y do not rotate mirror 76
Rotate around. During image formation, the image forming units 72BK, 72C, 72M and 72Y are sequentially positioned at the image forming position P facing the intermediate transfer belt 69.

Next, the operation of the color image forming apparatus having the above structure will be described.

First, the carriage 73 is rotated to move the yellow image forming unit 72Y for the first color to the image forming position P.
To the position (state of FIG. 20). In this state, the laser beam 4 from the laser beam scanner 3 is applied to the image forming unit 72.
It passes between Y and the image forming unit 72M for magenta, is reflected by the mirror 76, enters the photosensitive drum 1 at the image forming position P, and an electrostatic latent image is formed on the photosensitive drum 1.
This electrostatic latent image is developed by the yellow toner conveyed to the developing roller 6 of the developing device 97 which faces the electrostatic latent image, and a toner image is formed on the photosensitive drum 1. Next, the yellow toner image formed on the photosensitive drum 1 is transferred to the intermediate transfer belt 6
9 is primarily transferred.

When the formation of the yellow toner image is completed,
The carriage 73 is rotated 90 ° in the direction of the arrow to move the magenta image forming unit 72M to the image forming position P. Then, the same operation as in the case of yellow is performed, and the magenta toner image is superimposed on the yellow toner image on the intermediate transfer belt 69. The same operation is further performed in the order of cyan and black to form a toner image in which four color toner images are superimposed on the intermediate transfer belt 69.

The transfer roller 10 is brought into contact with the intermediate transfer belt 69 in synchronism with the tip position of the black toner image of the fourth color on the intermediate transfer belt 69. And
The recording paper 8 is conveyed to the nip portion between the transfer roller 10 and the intermediate transfer belt 69, and the toner images of four colors are transferred (secondary transfer) to the recording paper 8. The recording paper 8 on which the toner image has been transferred passes through the fixing device 14 and is fixed, and then discharged to the outside of the apparatus. The toner remaining after the secondary transfer is removed by a cleaner 71 that comes in contact with and separates from the intermediate transfer belt 69 at the same timing.

After the formation of one image is completed, the yellow image forming unit 72Y is moved to the image forming position P to prepare for the next image formation.

In this embodiment, the fixing belt 20 is used.
Is formed by laminating a silicone rubber having a thickness of 150 μm on a base material made of a polyimide resin having a thickness of 90 μm. The fixing belt 20 is stretched in the fixing device 14
Aligns with the attachment / detachment direction.

As shown in FIG. 9, the fixing device 14 is attachable to and detachable from the main body of the apparatus as a unit in which the heat generating roller 21, the fixing roller 22 and the pressure roller 23 are integrated while leaving the exciting means 24 in the main body of the apparatus. . Here, the extending direction of the fixing belt 20 and the opening direction of the exciting means 24 having a substantially semicircular cross section are in agreement with the attaching and detaching direction of the fixing device 14. As a result, since the exciting means 24 and the heat generating roller 21 do not interfere with each other, the fixing device 1
4 can be easily attached and detached. The fixing device 14 is attached and detached by opening and closing the fixing door 18.

In each of the above embodiments, the heat generating roller 21 is caused to generate heat by electromagnetic induction, and the fixing belt 2 is heated.
Although 0 is indirectly heated, it is not necessarily limited to this configuration, and the fixing belt 20 having conductivity may be used and the fixing belt 20 may be directly heated by electromagnetic induction. In this case, the conductive fixing belt 20 has, for example, a thickness of 30 μm and a diameter of 60 m.
The surface of a nickel electroformed belt base material of m in thickness is coated with 150 μm of silicone rubber in order to fix a color image.

In each of the above embodiments, the cover 90 for making the temperature detected by the temperature sensor 45 of the fixing belt 20 and the ambient temperature in the vicinity of the temperature sensor 45 substantially coincide with each other is attached to the image heating device side. Although illustrated as an example, when the image heating apparatus is provided on the image forming apparatus side with the image heating apparatus removed, at least a part of the fixing belt 20, the temperature sensor 45, and the pressure roller 23 are provided when the image heating apparatus is mounted. It can also be configured to cover the occupied space.

[0151]

As described above, according to the present invention,
By removing the temperature sensor that detects the temperature of the pressure roller to reduce costs, the temperature of the pressure roller is estimated from the belt temperature or the amount of temperature change, and the optimum fixing temperature for the next image heating is determined. By setting it, it becomes possible to eliminate the difference in glossiness of the printed image for each recording medium due to the temperature fluctuation of the pressure roller, and to prevent belt wrapping at high temperature.

Further, at the time of waiting until the start of the next image heating, noise is reduced and energy is saved by performing optimum preheating that requires only a minimum belt rotation operation based on the temperature change amount of the belt. It is possible to shorten the first print time in consideration of the above.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the overall configuration of an image forming apparatus using an image heating apparatus according to a first embodiment of the present invention as a fixing device.

FIG. 2 is a cross-sectional view showing the configuration of the image heating apparatus according to the first embodiment.

FIG. 3 illustrates the fixing belt 20 according to the first embodiment,
Threshold temperature Tf with respect to elapsed time tp from the end of printing
Figure showing the cooling curve of

FIG. 4 is a flowchart showing processing steps in a fixing temperature control routine applied to the image heating apparatus and the image forming apparatus according to the first embodiment.

FIG. 5A is a diagram showing an example of contents of a low temperature reference table (table A).

FIG. 5B is a diagram showing an example of contents of a reference table for medium temperature (table B).

FIG. 5C is a diagram showing an example of contents of a high temperature reference table (table C).

FIG. 6 is a flowchart showing processing steps in a preheating control routine applied to the image heating apparatus and the image forming apparatus according to the second embodiment of the present invention.

FIG. 7 is a flow chart of FIG.
Environmental conditions (NN) in each preheating mode (mode 1 to mode 4) selected according to the cooling time tp to ℃
Diagram showing specific values of the peak value P0 of the input power, the upper limit temperature Th, and the lower limit temperature Tl corresponding to the environment, the LL environment)

8A is a waveform diagram of belt temperature and input power when preheating temperature control is performed in mode 1 of FIG.

FIG. 8B is a waveform diagram of belt temperature and input power when preheating temperature control is performed in modes 2 and 3 of FIG.

FIG. 9 is a cross-sectional view showing the overall configuration of a color image forming apparatus that uses the image heating apparatus according to the first or second embodiment as a fixing device as a third embodiment of the present invention.

FIG. 10 is a cross-sectional view showing another configuration example of the fixing device shown in FIG.

FIG. 11 is a cross-sectional view showing another configuration example of the fixing device shown in FIG.

FIG. 12 is a cross-sectional view showing another configuration example of the fixing device shown in FIG.

13 is a cross-sectional view showing the overall configuration of an image copying apparatus using the image forming apparatus shown in FIG.

[Explanation of symbols]

8 Recording medium (heated material) 11 Toner image 14 Fixing device (image heating device) 20 Fixing belt (heating member) 21 Heat generating roller (heat generating means) 22 Fixing roller 23 Pressure Roller (Pressure Means) 24 Excitation means 25 Excitation coil 45 Temperature sensor 75 Excitation circuit 79 control means 90 cover 91 Light source 92 mirror 93 lens 94 Photoelectric conversion element 95 manuscript 201 Metal fixing belt 202 Silicone rubber layer 203 Magnetic shield layer 204 axis 301 fixing roller 302 coil holder 401 fixing belt 402 pressing member

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 6/14 H05B 6/14 (72) Inventor Masaru Imai 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. Company (72) Inventor Tadafumi Shimizu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masahiro Sakai 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Matsuzaki Keiichi Osaka Prefecture Kadoma City 1006 Kadoma, Matsushita Electric Industrial Co., Ltd. (72) Inventor Kazunori Matsuo Osaka Kadoma City Kadoma 1006, Matsushita Electric Industrial Co., Ltd. (72) Inventor Ikuichi Kitagawa Osaka Kadoma City Kadoma Address 1006 Matsushita Electric Industrial Co., Ltd. F term (reference) 2H027 DA12 DA40 DE07 DE09 EA12 EA15 EB06 EC06 EC08 EC09 EC20 ED25 EE07 EE08 EF04 EF12 EF16 2H033 AA10 AA16 AA18 AA32 AA40 BA03 BA04 BA11 BA12 BA25 BA26 BA32 BB03 BB13 BB18 BB21 BB23 BE06 CA05 CA07 CA23 CA28 CA32 CA45 3K059 AB19 AB28 AC33 AD02 AD32 CD03 CD75 CD75

Claims (36)

[Claims] 1. A movable heating member that directly heats a material to be heated; a heat generating unit that directly or indirectly heats the heating member; a pressurizing unit that contacts the heating member; and a temperature of the heating member. A temperature sensor for detecting, and, based on the temperature detected by the temperature sensor, a control unit that controls the heat generation amount of the heat generation unit so that the temperature of the heating member reaches a set temperature, and the control unit is the After the heating of the heating member by the heat generating means is stopped, the temperature of the pressurizing means is estimated based on at least one of the detected temperature of the heating member and the amount of change with time of the detected temperature, and the next image An image heating apparatus, characterized in that the set temperature of the heating member during heating is determined. 2. The heating member is at least partially conductive, and the heat generating means includes an exciting means for directly heating the heating member using electromagnetic induction. Image heating device. 3. The heat generating means is inscribed in the heating member, at least a part of which has conductivity, and the rotatable heat generating member indirectly heats the heating member; and the heat generation using electromagnetic induction. An image heating apparatus according to claim 1, further comprising an exciting means for heating the member. 4. The image heating apparatus according to claim 1, wherein the heating member has a belt shape. 5. The image heating apparatus according to claim 1, wherein the heating member has a heat capacity of 60 J / K or less. 6. The image heating apparatus according to claim 1, wherein the heating member has a heat capacity of 40 J / K or less. 7. The control means, when the temperature detected by the heating member is equal to or higher than a predetermined temperature, based on the amount of change in the temperature detected by the heating member with respect to time, the control means changes the temperature of the heating member during the next image heating. When the set temperature is determined and the detected temperature of the heating member is lower than the predetermined temperature, the set temperature of the heating member during the next image heating is determined based on the detected temperature of the heating member. The image heating apparatus according to claim 1, wherein the image heating apparatus is an image heating apparatus. 8. The control means detects a reference value of the temperature of the heating member preset according to the elapsed time after the heating of the heating member by the heat generating means is stopped, and the temperature sensor detects the reference value. 7. The set temperature of the heating member at the time of the next image heating is determined based on the magnitude relationship with the actual measurement value of the temperature of the heating member according to claim 1. Image heating device. 9. The control unit selects a first reference table storing a first set temperature when the measured value is equal to or higher than the reference value, and the measured value is less than the reference value. 9. In this case, the image heating apparatus according to claim 8, wherein the second reference table storing a second set temperature higher than the first set temperature is selected. 10. The image heating apparatus according to claim 8, wherein the reference value of the temperature of the heating member is represented by a mathematical expression using a time elapsed from the end of image heating as a parameter. 11. The size relationship between the reference value and the actual measurement value is not determined until a fixed time after the heating of the heating member by the heat generating means is stopped. Image heating device. 12. The control unit sets the set temperature of the heating member at the time of the next image heating based on the detected temperature of the heating member after a predetermined time has elapsed from the end of the previous image heating. The method according to claim 1, wherein the determination is made.
The image heating device according to claim 1. 13. The image heating device, wherein the temperature of the heating member detected by the temperature sensor is substantially the same as the ambient temperature in the vicinity of the temperature sensor, the passage of the material to be heated is removed. At least part of the heating element,
The image heating apparatus according to claim 1, further comprising a cover that covers a space occupied by the temperature sensor and the pressing unit. 14. A movable heating member that directly heats a material to be heated; a heat generating unit that directly or indirectly heats the heating member; a pressurizing unit that contacts the heating member; and a temperature of the heating member. A temperature sensor for detecting, and, based on the temperature detected by the temperature sensor, a control unit that controls the heat generation amount of the heat generation unit so that the temperature of the heating member reaches a set temperature, and the control unit is the Based on at least one of the detected temperature of the heating member and the amount of change in the detected temperature with respect to time after the heating of the heating member by the heat generating means is stopped, the heating is performed in the standby state until the start of the next image heating. An image heating apparatus characterized by determining a preheating mode for a member. 15. The heating member according to claim 14, wherein at least a part of the heating member is electrically conductive, and the heat generating means includes an exciting means for directly heating the heating member using electromagnetic induction. Image heating device. 16. The heat generating means is inscribed in the heating member, at least a part of which has conductivity, and the rotatable heat generating member indirectly heats the heating member; and the heat generation using electromagnetic induction. 15. An image heating apparatus according to claim 14, further comprising an exciting means for heating the member. 17. The image heating apparatus according to claim 14, wherein the heating member has a belt shape. 18. The image heating apparatus according to claim 14, wherein the heating member has a heat capacity of 60 J / K or less. 19. The image heating apparatus according to claim 14, wherein the heating member has a heat capacity of 40 J / K or less. 20. When the amount of change in the temperature detected by the heating member with respect to time is larger than a predetermined value, the control means may:
Energization / non-energization control for the heat generating means is performed so that the temperature detected by the temperature sensor moves back and forth between a first upper limit temperature and a first lower limit temperature while the heating member is moving. 20. The image heating apparatus according to claim 14, wherein the first preheating mode is selected. 21. The image heating apparatus according to claim 20, wherein the control unit continues the moving state of the heating member for a predetermined time. 22. The image heating apparatus according to claim 20, wherein the control unit sets a peak value of input electric power when the heating unit is energized to a maximum value. 23. When the amount of change in the temperature detected by the heating member with respect to time is less than or equal to a predetermined value, the control unit keeps the heating member stopped and detects the second temperature detected by the temperature sensor. 20. The second preheating mode for controlling energization / de-energization of the heat generating means is selected so as to switch back and forth between an upper limit temperature and a second lower limit temperature. An image heating device according to one of the claims. 24. The image heating apparatus according to claim 23, wherein the control unit changes the second upper limit temperature and the second lower limit temperature according to environmental conditions. 25. The heating means is configured to move the heating member and stop the heating member when the amount of change in the temperature detected by the heating member with respect to time is within a predetermined range. 20. The image heating apparatus according to claim 14, wherein a third preheating mode for alternately performing energization / de-energization control for is selected. 26. The control unit changes the peak value of input electric power when the heating unit is energized in accordance with the amount of change in the temperature detected by the heating member with respect to time. The image heating device according to any one of 25. 27. The control means reduces the peak value of the input electric power at the time of energizing the heat generating means at a constant rate every time the energization / non-energization of the heat generating means is repeated. The image heating device according to claim 23. 28. The control means is responsive to environmental conditions to
26. The image heating device according to claim 23, wherein a peak value of input electric power when the heat generating means is energized is changed. 29. The image heating apparatus, wherein the temperature of the heating member detected by the temperature sensor is substantially the same as the ambient temperature in the vicinity of the temperature sensor, the passing member for the heated material is excluded. At least part of the heating element,
29. The image heating apparatus according to claim 14, further comprising a cover that covers a space occupied by the temperature sensor and the pressing unit. 30. An image forming apparatus comprising: an image forming unit that forms and carries an unfixed toner image on a recording medium that is a material to be heated; and a fixing device that thermally fixes the toner image on the recording medium. An image forming apparatus, wherein the fixing device is the image heating device according to any one of claims 1 to 29. 31. An image forming apparatus comprising: an image forming unit for forming and carrying an unfixed toner image on a recording medium, which is a material to be heated; and a detachable fixing device for thermally fixing the toner image on the recording medium. A device, wherein the fixing device is the image heating device according to any one of claims 1 to 12 and 14 to 28, and the image forming device, when the fixing device is mounted,
In order to substantially match the detected temperature of the heating member by the temperature sensor and the ambient temperature in the vicinity of the temperature sensor, at least a part of the heating member, excluding the passage portion of the material to be heated, the temperature sensor, An image forming apparatus comprising: a cover for covering a space occupied by the pressing unit. 32. An image reading apparatus having an image reading unit for reading an original image, and a toner image is heat-fixed and formed on a recording medium according to the original image read by the image reading apparatus. Image forming apparatus. 33. A movable heating member for directly heating a material to be heated, a heating means for directly or indirectly heating the heating member, a pressurizing means for contacting the heating member, and a temperature of the heating member. A temperature sensor that detects the temperature of the heating member, and a control unit that controls the amount of heat generated by the heating unit so that the temperature of the heating member reaches a set temperature based on the temperature detected by the temperature sensor; A space occupied by at least a part of the heating member, the temperature sensor, and the pressurizing means, excluding the passage portion of the material to be heated, in order to substantially match the detected temperature and the ambient temperature in the vicinity of the temperature sensor. A temperature control method applied to an image heating apparatus having a cover for covering the temperature of the heating member after the heating of the heating member by the heat generating means is stopped. And a temperature of the heating member measured in the heating member temperature measuring step for measuring at least one of the amounts of temperature and the amount of change with time of the heating member, and the amount of change of the temperature with time of the heating member. Based on at least one of them, the temperature of the pressurizing means is estimated, and a set temperature determination step of determining the set temperature of the heating member at the time of the next image heating; and the set temperature determined in the set temperature determination step. And a heat generation amount control step of controlling the heat generation amount of the heat generation means by the control means so as to reach a set temperature. 34. A movable heating member for directly heating a material to be heated, a heating means for directly or indirectly heating the heating member, a pressurizing means for contacting the heating member, and a temperature of the heating member. A temperature sensor that detects the temperature of the heating member, and a control unit that controls the amount of heat generated by the heating unit so that the temperature of the heating member reaches a set temperature based on the temperature detected by the temperature sensor; A space occupied by at least a part of the heating member, the temperature sensor, and the pressurizing means, excluding the passage portion of the material to be heated, in order to substantially match the detected temperature and the ambient temperature in the vicinity of the temperature sensor. A temperature control method applied to an image heating apparatus having a cover for covering the temperature of the heating member after the heating of the heating member by the heat generating means is stopped. And a temperature of the heating member measured in the heating member temperature measuring step for measuring at least one of the amounts of temperature and the amount of change with time of the heating member, and the amount of change of the temperature with time of the heating member. Based on at least one of them, in the standby time until the start of the next image heating, a preheating mode determination step of determining a preheating mode for the heating member, and a preheating mode determined in the preheating mode determination step are performed. Accordingly, a preheating step of preheating the heating member is included. 35. An image forming means for forming and carrying an unfixed toner image on a recording medium which is a material to be heated, a movable heating member for directly heating the recording medium, and the heating member directly or indirectly. Heating means for heating to
Based on the temperature detected by the temperature sensor and the temperature sensor that detects the temperature of the heating member, the pressurizing means that is in contact with the heating member, and the heat generation of the heat generating means such that the temperature of the heating member reaches the set temperature. A detachable image heating device for thermally fixing the toner image onto the recording medium; and a detection unit for detecting the heating member by the temperature sensor when the image heating device is mounted. In order to substantially match the temperature and the ambient temperature in the vicinity of the temperature sensor, a space occupied by at least a part of the heating member, the temperature sensor, and the pressurizing means, excluding the passage portion of the material to be heated, is provided. A temperature control method applied to an image forming apparatus having a covering cover, wherein the temperature of the heating member after stopping heating of the heating member by the heat generating means and Of the temperature of the heating member measured in the heating member temperature measuring step and at least one of the amounts of change of the temperature with time of the heating member, and Based on at least one, the temperature of the pressurizing unit is estimated, and a setting temperature determining step of determining the setting temperature of the heating member during the next image heating; and the setting determined in the setting temperature determining step And a heat generation amount control step of controlling the heat generation amount of the heat generation unit by the control unit so that the temperature becomes a temperature. 36. An image forming means for forming and carrying an unfixed toner image on a recording medium which is a material to be heated, a movable heating member for directly heating the recording medium, and the heating member directly or indirectly. Heating means for heating to
Based on the temperature detected by the temperature sensor and the temperature sensor that detects the temperature of the heating member, the pressurizing means that is in contact with the heating member, and the heat generation of the heat generating means such that the temperature of the heating member reaches the set temperature. A detachable image heating device for thermally fixing the toner image onto the recording medium; and a detection unit for detecting the heating member by the temperature sensor when the image heating device is mounted. In order to substantially match the temperature and the ambient temperature in the vicinity of the temperature sensor, a space occupied by at least a part of the heating member, the temperature sensor, and the pressurizing means, excluding the passage portion of the material to be heated, is provided. A temperature control method applied to an image forming apparatus having a covering cover, wherein the temperature of the heating member after stopping heating of the heating member by the heat generating means and Of the temperature of the heating member measured in the heating member temperature measuring step and at least one of the amounts of change of the temperature with time of the heating member, and A preliminary heating mode determining step of determining a preliminary heating mode for the heating member during standby until the start of the next image heating based on at least one; and a preliminary heating mode determined in the preliminary heating mode determining step. And a preheating step of preheating the heating member.