JP2003050518A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of performing fixation on an optimum fixing condition. SOLUTION: This fixing device 7 is equipped with a fixing roller 25, a pressure roller 27, thermistors 29 and 30 detecting the temperature of the rollers 25 and 27, a strain gage 43 detecting the pressuring force of the roller 27 to the roller 25, and a CPU 33 controlling the temperature of the roller 25 and the pressuring force of the roller 27. Temperature distribution data, that is, the measured temperature at the specified parts of the rollers 25 and 27 and a fixing condition data are previously inputted in the CPU 33, and the CPU 33 selects the measured temperature coincident or the most approximate to the detected temperature by the thermistors 29 and 30 and the detected pressure by the gage 43 from the temperature distribution data, and obtains set temperature and set pressuring force corresponding to the selected measured temperature from the fixing condition data and performs fixing processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus using an electrophotographic process such as a facsimile, a printer and a copying machine.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a facsimile, a printer or a copying machine, an image forming section for forming a toner image on a transfer material and a toner image formed by the image forming section are fixed on the transfer material. A fixing device is provided, and the fixing device fixes the toner image on the transfer material by a fixing roller that applies heat to the toner image and a pressure roller that is in pressure contact with the fixing roller. During driving, the temperature of the fixing roller is deprived of heat by the pressure roller and the transfer material and decreases, and the temperature of the pressure roller deprives heat of the fixing roller and rises. In order to sufficiently fix the toner image on the transfer material, it is necessary to maintain the temperature of the fixing roller at a predetermined temperature. Therefore, the temperature of the fixing roller is detected by the temperature detection sensor, and the temperature of the fixing roller is controlled according to the detection result.

An example of such a fixing device is Japanese Patent Laid-Open No. 200
Japanese Unexamined Patent Publication No. 0-19886 discloses a technique of controlling the fixing temperature of the fixing roller and the pressing force of the pressure roller based on the detected temperature detected by the temperature detecting sensor.

Further, Japanese Patent Laid-Open No. 9-79432 discloses that
Temperature detecting sensors are arranged at two positions in the longitudinal direction of the fixing roller and the pressure roller, and the temperature detected by these temperature detecting sensors is compared with a reference temperature to control the temperature of the fixing roller to a predetermined temperature. The technology is disclosed.

[0005]

However, in the former technique, the fixing temperature of the fixing roller and the pressure of the pressure roller are set only on the basis of the temperature detected by the temperature detection sensor, so that the pressure roller is pressed. The temperature distribution in the longitudinal direction of the fixing roller and pressure roller that changes with pressure cannot be accommodated,
There is a problem that fixing cannot be performed under the optimum fixing conditions.

Also in the latter technique, the fixing temperature of the fixing roller is only set according to the difference between the temperatures of the fixing roller and the pressure roller and the reference temperature, and like the former technique, There is a problem that the temperature distribution in the longitudinal direction of the fixing roller and the pressure roller, which changes with the pressure of the pressure roller, cannot be dealt with, and fixing cannot be performed under optimum fixing conditions.

Therefore, it is an object of the present invention to provide a fixing device capable of fixing under optimum fixing conditions.

[0008]

According to a first aspect of the present invention, there is provided a fixing roller, a pressure roller, a temperature detecting means for detecting the temperature of at least one of the fixing roller and the pressure roller, and an application to the fixing roller. A fixing device comprising a pressure detection means for detecting the pressure of a pressure roller and a control means for controlling the temperature of the fixing roller and the pressure of the pressure roller, wherein the control means includes the fixing roller and the pressure roller. Of at least one of the temperature distribution data and the fixing condition data are input in advance, and the temperature distribution data indicates that the fixing roller and the pressure roller change depending on the type of transfer material under a predetermined set temperature and set pressure. The fixing temperature data is the measured temperature of at least one predetermined portion, the fixing condition data is the optimum set temperature and the set pressure force for fixing obtained for each of the measured temperatures, and the control unit controls the temperature From the data, select the above-mentioned measured temperature that matches or is closest to the detected temperature of the temperature detecting means and the detected pressure of the pressure detecting means, obtain the set temperature and the set pressurizing force corresponding to the selected measured temperature from the fixing condition data, and fix. It is characterized by performing processing.

According to the first aspect of the present invention, at least the fixing roller and the pressure roller that change depending on the type of the transfer material (size, thickness, material, etc. of the transfer material) under a predetermined set temperature and set pressure. The temperature of one predetermined portion is measured, and the predetermined set temperature and the measured temperature for each set pressure are input to the control means as temperature distribution data. Further, the optimum set temperature and set pressure for fixing are obtained by a test for each measured temperature, and these are input to the control means as fixing condition data.

During driving, the temperature detecting means detects the temperature of at least one of the fixing roller and the pressure roller, and the pressing force detecting means detects the pressing force of the pressing roller with respect to the fixing roller. The measurement temperature is selected from the temperature distribution data by. As a result, the optimum set temperature and set pressure for fixing are selected from the fixing condition data, and the fixing process is performed.

The measured temperature of a predetermined portion of the fixing roller and the pressure roller, which changes depending on the type of the transfer material under a predetermined set temperature and set pressure, and the set temperature and set pressure optimum for fixing are measured for each measurement temperature. Since it is input in advance to the control means, it is possible to perform fixing under optimum fixing conditions,
It is possible to improve the reliability of the fixing device and prevent the occurrence of abnormal images due to defective fixing.

According to a second aspect of the present invention, in the first aspect of the invention, at least one of the temperature of the fixing roller and the pressure roller after a predetermined period of time is determined by the temperature gradient detected by the temperature detecting means at each time. It is characterized in that the measured temperature is calculated and the measured temperature is selected from the temperature distribution data based on the calculated value and the pressure detected by the pressure detecting means.

In the invention described in claim 2, claim 1
In addition to the same effect as the invention described in (1), the control means changes the detected temperature in the temperature detecting means with time, that is, a temporal gradient of the detected temperature (the detected temperature of the temperature detecting means is 10 ° C. in 5 seconds). The temperature of at least one of the fixing roller and pressure roller after a predetermined time is calculated based on the temperature rise, etc., and the measured temperature is selected from the temperature distribution data based on the calculated value and the detected pressure, and the selected measured temperature is supported. The fixing process is performed by selecting the fixing condition to be set from the fixing condition data.

The control means calculates the temperature of at least one of the fixing roller and the pressure roller after a predetermined time, so that the temperature difference between the detected temperature and the actual temperature, that is, the temperature detection means detects the temperature. Since it is possible to correct the temperature difference caused by the time required from the fixing to the fixing, the fixing can be performed under more optimum fixing conditions.

The invention according to claim 3 is the same as claim 1 or 2.
In the invention described in (1), the temperature detecting means includes a thermistor or a thermocouple.

According to the invention described in claim 3, claim 1
Alternatively, the temperature detection can be accurately performed by using the thermistor or the thermocouple as the temperature detection means, as well as the same effects as those of the invention described in 2, so that the device is destroyed due to excessive temperature rise, the load is increased, and the fixing failure is caused. Can be prevented.

The invention according to a fourth aspect is the first to the third aspects.
In the invention described in any one of above, the control means is provided with a limiter for restricting an upper limit of the pressing force of the pressure roller against the fixing roller.

According to the invention described in claim 4, claim 1
In addition to the same effect as the invention described in any one of 1 to 3, a limiter for restricting the upper limit of the pressing force of the pressure roller with respect to the fixing roller is provided, so that the device is destroyed due to excessive pressing force, the load is increased, and Fixing failure can be prevented.

The invention described in claim 5 is the invention according to claims 1 to 4.
In the invention described in any one of above, the control means maximizes the pressing force of the pressure roller when the temperature detected by the temperature detection means is equal to or lower than a predetermined value.

According to the invention of claim 5, claim 1
When the temperature detected by the temperature detecting means is equal to or lower than a predetermined value, the pressure applied to the pressure roller is maximized to achieve the same effect as that of the invention described in any one of the items 1 to 4 above. Since it is difficult for heat to escape from between the roller and the roller, it is possible to obtain a fixing ratio above a certain level even if the fixing temperature is low, and the control pattern by the control unit is reduced, so that the control load of the control unit can be reduced.

The invention according to claim 6 is the same as claims 1 to 5.
In the invention described in any one of 1,
A piezoelectric element or a strain gauge is provided.

According to the invention of claim 6, claim 1
Through the use of a piezoelectric element or strain gauge that is inexpensive and compact as the pressing force detection means, the pressure detection can be performed accurately and the cost can be reduced. Space saving can be achieved.

[0023]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a copying machine according to the present invention, FIG. 2 is an enlarged sectional view showing a fixing device, and FIG. 3 is a front view showing a fixing roller and a pressure roller. . As shown in FIG. 1, the copier 1 generally includes a sheet feeding device 3 that feeds a transfer material P such as a sheet, an image forming unit 5 that forms an untransferred image (toner image) on the transfer material P, and an image forming unit 5. The fixing device 7 fixes the transferred image on the transfer material P by heat and pressure. The sheet feeding device 3 feeds the sheets stacked on the bottom plate 11 in the sheet feeding tray 9 toward the image forming unit 5 by the sheet feeding roller 13.

The image forming section 5 includes a photoconductor 1 which is an image carrier.
4, a charging device 15 that charges the photoconductor 14, a writing device 17 that forms an electrostatic latent image on the surface of the charged photoconductor 14 by optical writing, and toner is supplied to the electrostatic latent image of the photoconductor 14. As a result, a developing device 19 that visualizes a toner image, a transfer device 21 that transfers the toner image of the photoconductor 14 onto the transfer material P from the paper feeding device 3, and the photoconductor 1 after transfer.
And a cleaning device 23 for cleaning 3.

As shown in FIGS. 2 and 3, the fixing device 7 includes a fixing roller 25 that fixes an image on the transfer material P, a pressure roller 27 that is in pressure contact with the fixing roller 25, and the fixing roller 2.
Fixing thermistor that detects the temperature of 5 (temperature detection means)
29, a pressure thermistor (temperature detecting means) 30 that detects the temperature of the pressure roller 25, a pressure unit 31 that presses the pressure roller 27 toward the fixing roller 25, and the fixing roller 2.
5, a discharge roller pair 28 for discharging the transfer material P on which the toner image has been transferred by the pressure roller 27, and a central arithmetic processing for controlling the temperature of the fixing roller 25 and the pressure of the pressure roller 27 on the fixing roller 25. CPU that is a device (control means)
And 33.

The transfer material P from the image forming section 5 is conveyed toward the paper discharge roller pair 28 while being sandwiched between the fixing roller 27 and the pressure roller 27. The toner image on the transfer material P is transferred to the transfer material P by heat from a heat source 36 such as a heater built in the fixing roller 27 and pressure of the pressure roller 27 against the fixing roller 25 by driving of the pressure unit 31. To be done.

The fixing thermistor 29 is a fixing roller 25.
Are arranged at both end portions and the central portion in the longitudinal direction, respectively, and detect the temperature at the central portion and the end portion on the surface of the fixing roller 25. The pressurizing thermistor 30 is
The pressure rollers 27 are arranged at both ends in the longitudinal direction of the pressure roller 27 and detect the temperatures of both ends on the surface of the pressure roller 27. These fixing and pressurizing thermistors 29, 30
The detected temperature detected by is transmitted to the CPU 33 via the temperature control unit 35 that controls the temperature of the fixing roller 25.

The pressure unit 31 is swingable about a fulcrum 37 and supports a pressure roller 27, a swing member 39, a laminated piezoelectric ceramic 41 that expands and contracts by energization, and a support of the laminated piezoelectric ceramic 41. A strain gauge (pressure detecting means) 43 fixed to the body 41a and detecting the pressure of the pressure roller 27 against the fixing roller 25, and a pressure control unit 45 controlling the pressure of the pressure roller 27 against the fixing roller 25.
A reference pressure value output unit (limiter) 47 for holding the pressure of the pressure roller 27 by the pressure control unit 45 at a preset reference pressure is provided. As the pressure unit 31, for example, a cam may be brought into contact with the shaft of the pressure roller 27, and the pressure of the pressure roller 27 with respect to the fixing roller 25 may be adjusted by the rotation of the cam. Not limited.

In the present embodiment, the reference pressure value output unit 47
Has an upper limit of the pressing force of the pressure roller 27 against the fixing roller 25. In the present embodiment, the upper limit value of the pressing force of the pressure roller 27 is set to 6.0 kgf so that the pressing force of the pressure roller 27 does not exceed the upper limit value. Pressure roller 27 for fixing roller 25
By providing the reference pressure value output unit 47 that regulates the upper limit of the pressing force, it is possible to prevent device breakdown, load increase, and fixing failure due to excessive pressing force.

Multilayer piezoelectric ceramic 4 of pressure control unit 45
The energization of 1 causes the laminated piezoelectric ceramic 41 to expand and contract, and this expanding and contracting motion causes the rocking member 39 to rock through the spring 49. As a result, the swing member 3
The pressure roller 27 supported by 9 moves up and down to change the distance to the fixing roller 25. That is, by changing the distance between the fixing roller 25 and the pressure roller 27, the pressure applied by the pressure roller 27 to the fixing roller 25 (the pressure between the fixing roller 25 and the pressure roller 27) is adjusted. . At this time, the strain gauge 43 receives the load from the spring 49 to detect the pressure applied to the pressure roller 27, and the detected pressure detected by the strain gauge 43 is transmitted to the CPU 33 via the pressure control unit 45. It

The CPU 33 controls the driving of the fixing device 7 and also controls each part of the copying machine 1. In the present embodiment, when the temperature detected by the fixing and pressurizing thermistors 29, 30 is equal to or lower than a predetermined value (160 ° C. in the present embodiment), the CPU 33 maximizes the pressing force of the pressure roller 27 (the present embodiment). In the form of 6.0 kgf),
The pressurizing unit 31 is controlled via the pressurizing controller 45. As described above, when the detected temperature of the thermistors 29 and 30 is equal to or lower than the predetermined value, by maximizing the pressure applied to the pressure roller 27, it becomes difficult for heat to escape from between the fixing roller 25 and the pressure roller 27. Even if the fixing temperature is low, a fixing ratio above a certain level can be obtained, and the control pattern by the CPU 33 is reduced, so that the control load of the control means can be reduced.

Further, in the CPU 33, the fixing roller 25 that changes depending on the type of the transfer material P (size, thickness, material, etc. of the transfer material P) under a predetermined set temperature and set pressure.
The temperature distribution data, which is the measured temperature at both ends and the center of the pressure roller 27, and the fixing condition data, which is the set temperature and the set pressurizing force, which are optimum for fixing, are input in advance for each measured temperature of the temperature distribution data. There is.

In the present embodiment, changes in the temperature distribution of the fixing roller 25 and the pressure roller 27 when the transfer materials P of different sizes are passed under a predetermined set temperature and set pressure are obtained by a test, and these changes are obtained. CP for each temperature distribution data
It is input to U27. Table 1 shows an example of this temperature distribution data.

[0034]

[Table 1]

Table 1 shows that the pressure of the pressure roller 27 is 5.0.
This is temperature distribution data showing the temperatures of the central portion and the end portion of the fixing roller 25 when the pressure is kgf, and the measured temperature A is A3.
The measured temperature of both ends and the central portion of the fixing roller 25 when the transfer material P of size A is passed, and the measured temperature B is the measured temperature of the fixing roller 25 when the transfer material P of A4 size is passed. The measured temperature C is the measured temperature of the fixing roller 25 when a small-sized transfer material P such as a postcard is passed.

In addition to the data shown in Table 1, the temperature distribution data input to the CPU 33 has a pressure of 4.5 kg.
At f, 5.5 kgf, etc., the measured temperature (temperature distribution) of each portion of the fixing roller 25 corresponding to each pressing force and the temperature distribution of the pressure roller 27 corresponding to each pressing force are input. Further, the CPU 33 is also preliminarily input with temperature distribution data showing the relationship between the time when the fixing roller 25 is started up and the temperature of each part of the fixing roller 25. Furthermore,
The temperature distribution data when the transfer materials P having different thicknesses or the transfer papers P having different materials are used are also input to the CPU 33 in advance.

Further, the CPU 33 has the fixing roller 25 corresponding to each of the measured temperatures A, B and C of the above-mentioned temperature distribution data.
The fixing condition data which is the set temperature and the pressurizing force of the pressure roller 27 are input in advance. In this embodiment,
For each of the measured temperatures A, B, and C of the above-mentioned temperature distribution data, the optimum setting temperature and setting or pressure for fixing are obtained by a test, and these fixing condition data are input to the CPU 33. Table 2 shows an example of this fixing condition data.

[0038]

[Table 2]

Table 2 shows the set temperature of the fixing roller 25 and the set pressing force of the pressure roller 27 corresponding to the above-mentioned temperature distribution data. When the measured temperature A is the fixing condition A,
The fixing process of the transfer material P is performed under the fixing condition B at the measurement temperature B and the fixing condition C at the measurement temperature C.

Next, the operation of the present embodiment will be described based on the above-mentioned configuration and the flowchart of FIG. 4. FIG. 4 is a flow chart for explaining the operation of the fixing device.

When the start key of the operation unit of the copying machine 1 is pressed to enter the driving state (step S
1) The fixing and pressure thermistors 29 and 30 detect the temperature of each part of the fixing roller 25 and the pressure roller 27 in the longitudinal direction, and transmit the detected temperature to the CPU 33 (step S2).

The CPU 33 receives the detected temperature signals from the fixing and pressurizing thermistors 29 and 30, and changes the detected temperature in the thermistors 29 and 30 with time, that is, a time gradient of the detected temperature for x seconds. The expected temperatures of the subsequent fixing roller 25 and pressure roller 27 are calculated (step S3). Then, the strain gauge 43 detects the pressure applied by the pressure roller 27 to the fixing roller 25, and transmits the detected pressure detected to the CPU 33 (step S4).

The CPU 33 compares the pressure value detected by the strain gauge 43, the calculated value (temperature value) calculated in step S3, and the temperature distribution data input in advance (step S5), and makes a match or the closest approximation. The measurement temperature is selected from the temperature distribution data (step S6). Then, the set temperature and the set pressure corresponding to the selected measured temperature are selected from the fixing condition data (step S7), and the fixing process is performed by the selected set temperature and the set pressure (step S).
8).

In steps S3 to S6, for example, when the A3 size transfer material P is being fed, the temperature detected by the thermistor 29 at the end of the fixing roller 27 is 166.
C., the temperature detected by the thermistor 29 in the central portion is 157.degree. C., and if the temperature of the fixing roller 25 is increased by 2.degree. C. per second (temperature gradient is 2) at this time, the fixing roller after 3 seconds The temperature at the end and the center of 25 increases by 6 ° C. That is, the CPU 33 causes the fixing roller 25 after 3 seconds.
It is calculated (predicted) that the temperature of the end portion is 172 ° C and the temperature of the central portion is 163 ° C.

At this time, the pressure value of the strain gauge 43 is 5.0.
If it is kgf, the most approximate measured temperature A is selected from the temperature distribution data shown in Table 1. As a result, the fixing condition A corresponding to the measured temperature A is selected from the fixing condition data shown in Table 2. That is, the set temperature of the fixing roller 25 (fixing temperature) is set to 180 ° C., and the set pressure of the pressure roller 27 to the fixing roller 25 is set to 5.0 kgf.
In this case, the CPU 33 controls the amount of electricity supplied to the heat source 36 of the fixing roller 25 so that the temperature of the fixing roller 25 rises by approximately 10 ° C.

In the above example, the CPU 33 controls to raise the temperature of the fixing roller 25. However, depending on the fixing condition selected from the correlation data, the CPU 33 lowers the temperature of the fixing roller 25 or performs fixing. It goes without saying that control is performed to increase or decrease the pressure applied by the pressure roller 27 to the roller 25.

As described above, based on the temperature distributions of the fixing roller 25 and the pressure roller 27 obtained by the temperature detected by the thermistors 29 and 30 and the pressure applied by the strain gauge 43, the temperature of the fixing roller 25 and the pressure roller 27 are detected. By setting the pressure force of the transfer roller P and the pressure force of the pressure roller 27,
Since it is possible to sufficiently cope with the temperature distribution in each part of the fixing roller 25 and the pressure roller 27, which changes depending on the type, it is possible to perform fixing under optimum fixing conditions, and the reliability of the fixing device 11 is improved. It is possible to prevent the occurrence of abnormal images due to poor fixing.

Further, the CPU 33 calculates the temperatures of the fixing roller 25 and the pressure roller 27 after x seconds,
The temperature difference between the detected temperature and the actual temperature, that is, the thermistor 2
Since it is possible to correct the temperature difference caused by the time required from the temperature detection by 9, 30 to the fixing, it is possible to perform the fixing under the more optimum fixing condition.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

For example, in the present embodiment, the fixing roller 2
5 and the temperature of both the pressure roller 27 were detected,
Only the temperature of either the fixing roller 25 or the pressure roller 27 may be detected, and the temperature distribution may be selected based on the calculated value based on the detected temperature and the detected pressure detected by the strain gauge 43. Further, the calculated value based on the temperature gradient is not calculated, and the detected temperature of the thermistors 29 and 30 and the strain gauge 43
The temperature distribution may be selected depending on the pressure.

In the present embodiment, the temperature distributions of the fixing roller 25 and the pressure roller 27 are only the temperatures at both ends and the central portion thereof, but in the longitudinal direction of the fixing roller 25 and the pressure roller 27, for example, It may be temperature distribution data showing the temperature of the portion every 5 cm.

Further, the fixing and pressurizing thermistor 29,
Although 30 is arranged in the longitudinal direction of the fixing roller 25 and the pressure roller 27, it may be arranged at different angles in the circumferential direction of the fixing roller 25 and the pressure roller 27. In this case, the temperature distributions in the circumferential direction of the fixing roller 25 and the pressure roller 27 can also be detected, and the temperature distribution data and the fixing condition data based on the temperature distributions are input to the CPU 33, and the above-described embodiment is used. The same operation may be performed. Thus, the set temperature of the fixing roller 25 and the set pressure of the pressure roller 27 can be obtained according to changing conditions such as when the sheet enters, when the sheet is conveyed, and when there is no sheet.

In the present embodiment, the strain gauge 43 is used as the pressure detecting means, but the present invention is not limited to this, and as shown by the chain double-dashed line in FIG.
1, the piezoelectric element 51 may detect the pressure of the pressure roller 27 against the fixing roller 25. In this case, the end of the spring 49 is directly attached to the support member 41a of the laminated piezoelectric ceramic 41.

In the present embodiment, the thermistors 29 and 30 are used as the temperature detecting means, but the present invention is not limited to this, and for example, a thermocouple or the like may be used. Further, the number of fixing thermistors 29 is not limited to three, and for example, two or four may be provided.
There may be one or more or one, and similarly the number of pressurizing thermistors 30 arranged is not limited to two. Even if the number of thermistors 29 and 30 is single, the temperature distribution of the fixing roller 25 can be grasped by comparing the detected temperature of the thermistors 29 and 30 with the temperature distribution data.

In the present embodiment, the reference pressure value output unit 47
Although the reference pressure value output unit 47 was used as a limiter by setting the upper limit value of the pressing force to
For example, it may be a stopper that restricts the swing of the swing member 39, and is not particularly limited.

The fixing device 1 according to the present invention is applied to the copying machine 1. However, the fixing device 1 is not limited to this, and is applied to an image forming apparatus such as a facsimile, a printer, or a composite machine of these, in addition to the copying machine 1. However, the same effect is obtained.

[0057]

According to the first aspect of the present invention, the measured temperature of the predetermined portion of the fixing roller and the pressure roller which changes depending on the type of the transfer material under the predetermined set temperature and set pressure, and the fixing for each measured temperature. Since the optimum setting temperature and setting pressure have been input to the control means in advance, fixing can be performed under the optimum fixing conditions, the reliability of the fixing device is improved, and abnormal images due to defective fixing are generated. Occurrence can be prevented.

The invention described in claim 2 has the same effect as that of the invention described in claim 1, and the control means is:
By calculating the temperature of at least one of the fixing roller and the pressure roller after a predetermined time, the temperature difference between the detected temperature and the actual temperature, that is, it is required from the time when the temperature detecting means detects the temperature until the fixing is performed. Since the temperature difference caused by the time can be corrected, the fixing can be performed under more optimal fixing conditions.

According to the third aspect of the invention, the same effect as that of the first or second aspect of the invention can be obtained, and the temperature can be accurately detected by using the thermistor or the thermocouple as the temperature detecting means. It is possible to prevent device damage, load increase, and fixing failure due to excessive temperature rise.

According to the invention described in claim 4, the same effect as the invention described in any one of claims 1 to 3 is obtained, and a limiter for limiting the upper limit of the pressing force of the pressure roller against the fixing roller is provided. As a result, it is possible to prevent device destruction, load increase, and fixing failure due to excessive pressure.

The invention described in claim 5 has the same effect as that of the invention described in any one of claims 1 to 4, and when the temperature detected by the temperature detecting means is below a predetermined value, By maximizing the pressing force, it becomes difficult for heat to escape from between the fixing roller and the pressure roller, so that it is possible to obtain a fixing ratio above a certain level even when the fixing temperature is low, and the control pattern by the control means is also used. Because it will be less
The control load of the control means can be reduced.

In the invention described in claim 6 or 7, the same effect as the invention described in any one of claims 1 to 5 is obtained, and an inexpensive and compact piezoelectric element or strain gauge is used as the pressing force detecting means. By using it, pressure detection can be accurately performed, and cost reduction and space saving can be achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a printer according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a fixing device.

FIG. 3 is a front view showing a fixing roller and a pressure roller.

FIG. 4 is a flowchart illustrating an operation of the fixing device.

[Explanation of symbols]

7 Fixing device 24 CPU (control means) 25 fixing roller 27 Pressure roller 29 Fixing thermistor (temperature detection means) 30 Pressurizing thermistor (temperature detection means) 33 CPU (control unit) 43 Strain gauge (pressure detection means) 47 Reference pressure value output section (limiter) 51 Piezoelectric element (pressure detection means)

Claims (6)

[Claims] 1. A fixing roller, a pressure roller, a temperature detecting means for detecting the temperature of at least one of the fixing roller and the pressure roller, and a pressure detecting means for detecting the pressure of the pressure roller against the fixing roller. A fixing device for controlling the temperature of the fixing roller and the pressing force of the pressure roller, wherein the control means includes temperature distribution data of at least one of the fixing roller and the pressure roller, and fixing condition data. The temperature distribution data is the measured temperature of at least one predetermined part of the fixing roller and the pressure roller that changes depending on the type of transfer material under the predetermined set temperature and set pressure. The data is the optimum set temperature and set pressure for fixing determined for each of the above measured temperatures, and the control means uses the temperature distribution data to detect the temperature detected by the temperature detecting means. And the pressure detected by the pressure detection means, or the above-mentioned measured temperature that is closest to the detected pressure is selected, and the set temperature and the set pressure corresponding to the selected measured temperature are obtained from the fixing condition data, and the fixing process is performed. apparatus. 2. The temperature of at least one of the fixing roller and the pressure roller after a predetermined time is calculated based on the temperature gradient detected by the temperature detecting means at each time, and the calculated value and the pressure detected by the pressure detecting means. The fixing device according to claim 1, wherein the measured temperature is selected from the temperature distribution data according to. 3. The fixing device according to claim 1, wherein the temperature detecting means includes a thermistor or a thermocouple. 4. The fixing device according to claim 1, wherein the control unit includes a limiter that regulates an upper limit of the pressing force of the pressure roller with respect to the fixing roller. 5. The fixing unit according to claim 1, wherein the control unit maximizes the pressure applied by the pressure roller when the temperature detected by the temperature detection unit is equal to or lower than a predetermined value. apparatus. 6. The fixing device according to claim 1, wherein the pressing force detecting unit includes a piezoelectric element or a strain gauge.