JPH0990810A - Control method for thermal fixing unit in image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a device from being burned caused by the trouble of a fixing unit by monitoring a power source voltage supplied to the fixing unit and detecting the abnormality of the fixing unit based on temperature rise per prescribed time. SOLUTION: When a power source switch is turned on, the temperature rising rate of a fixing roller 6 corresponding to the value of the power source voltage impressed on a heater is obtained by looking up a voltage/temperature table. Besides, difference between the value of a temperature detection signal which is outputted from a thermistor 8 and shows the present temperature of the roller 6 and the prescribed temperature of the roller 6 is calculated. Based on the temperature difference and the temperature rising rate, time until the temperature of the roller 6 arrives at the prescribed temperature after the power source voltage is started and supplied to the heater is calculated. After the calculated time elapses, it is decided whether the temperature of the roller 6 arrives at the prescribed temperature or not so as to decide whether the fixing unit 7 is abnormal or not. Thus, even when the power source voltage supplied to the fixing unit 7 is fluctuated, the abnormality of the fixing unit 7 can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a heat fixing device in an image forming apparatus used in a copying machine, a printer device, a facsimile device or the like.

[0002]

2. Description of the Related Art As a control method of a fixing device provided in an image forming apparatus for forming a toner image on a sheet and thermally fixing the toner image, such as a copying machine, a printer apparatus, a facsimile apparatus, etc. Japanese Patent Laid-Open No. 1-293379, "Method for Preventing Abnormality of Fixing Device", JP-A-60-217
"Heater control device" disclosed in Japanese Patent No. 280,280,
A "copying machine" and the like disclosed in Japanese Patent Application Laid-Open No. 0-123880 are known. In this case, according to the "method for preventing abnormality of fixing device" disclosed in Japanese Patent Laid-Open No. 1-293379, the temperature of the fixing roller is set after a timer sets a time from power-on to a predetermined temperature according to the power supply voltage. Monitoring is performed, and when the time set in the timer has elapsed, it is determined whether or not the temperature of the fixing roller has reached a predetermined temperature, and when this has not reached the predetermined temperature, an abnormality has occurred in the fixing device. By making a determination, accidents such as burning due to the fixing device do not occur.

Further, the "heater control device" disclosed in Japanese Patent Laid-Open No. 60-217280 detects the temperature at a predetermined time cycle, and detects the difference between the detected temperatures obtained by the respective detecting operations. By comparing with a preset reference temperature difference, and if there is a difference between them, it is determined that an abnormality has occurred in the fixing device, so that accidents such as burnout due to the fixing device do not occur. . In addition, JP-A-60-
The "copying machine" disclosed in Japanese Patent No. 123880 discloses a fixing device in which the fixing roller of the fixing device is activated when printing is enabled before the fixing device reaches a predetermined temperature and a sheet is conveyed to a place where the fixing device is located. By setting the temperature to a predetermined value, the waiting time after the power is turned on until printing is possible is shortened.

[0004]

However, the above-mentioned method of controlling the heat fixing device has the following problems. First, in a normal image forming apparatus, a failure occurs in an element that controls on / off of a heater that heats a fixing roller, a failure in a thermistor itself that detects the temperature of the fixing roller, and the thermistor moves away from the surface of the fixing roller. Therefore, the temperature of the fixing roller may be monitored, and if the temperature of the fixing roller falls below a specified temperature, the toner may not melt sufficiently or the fixing roller may overheat and burn out. I try not to. However, in the conventional control method of the heat fixing device, as a method for monitoring whether the temperature of the fixing roller is abnormal, the heating time when the fixing roller is heated and the temperature of the fixing roller are Is checked, and based on the check result, it is determined whether or not an abnormality has occurred in the fixing device.
At this time, if the power supply voltage is low, the time from when the power is turned on until the temperature of the fixing roller reaches a predetermined temperature becomes long, and conversely, when the power supply voltage is high, the monitoring time is shortened. When the power supply voltage is low, the monitoring time elapses before the temperature of the fixing roller reaches the predetermined temperature, and it is determined that the temperature of the fixing roller is abnormal. Therefore, there is a problem that the monitoring time needs to be long in consideration of the low power supply voltage, and the waiting time from the power being turned on to the time when printing becomes possible becomes long accordingly. .

However, if the monitoring time is lengthened, when the power supply voltage becomes high, the temperature of the fixing roller becomes too high before the monitoring time elapses, and the fixing roller overheats and is burned. Occurs. For these reasons, there is a problem that it is difficult to set an optimum monitoring time that can cope with the low power supply voltage and the high power supply voltage. Therefore, as a method for solving such a problem, the above-mentioned Japanese Patent Laid-Open No. 1-
In the "fixing device abnormality prevention method" disclosed in Japanese Patent No. 293379, an optimum monitoring time can be set by adjusting the monitoring time in accordance with the power supply voltage, whereby the power supply voltage is high. Even when the temperature is low, it is possible to detect whether the temperature of the fixing roller is abnormal. However, in such a method, when the power is turned on, the value of the power supply voltage is detected, and the monitoring time is set based on the detection result. Therefore, in order to monitor the temperature of the fixing roller, the fluctuation of the power supply voltage is detected. The monitoring time must have a certain margin so that it is not affected by. For this reason, when the power supply voltage fluctuates and the power supply voltage rises, the temperature of the fixing roller rises quickly, and the margin of the fixing roller causes the temperature of the fixing roller to become too high and burn out. I was afraid.

Further, in the "heater control device" disclosed in Japanese Patent Laid-Open No. 60-217280, the temperature of the fixing roller is repeatedly detected in a time cycle shorter than the time required for the temperature of the fixing roller to reach a predetermined temperature. The temperature of the fixing roller can be detected whether the power source voltage is high or low. However, in such a method, when the power supply voltage fluctuates, the difference in the detected temperature obtained by each detection operation is out of the range of the reference temperature difference, and even when the fixing roller side is operating normally, an abnormality occurs. There is a risk that it may be determined that

Further, in the "copying machine" disclosed in Japanese Patent Laid-Open No. 60-123880, printing is enabled before the fixing device reaches a predetermined temperature so that printing can be performed quickly when the power is turned on. However, in such a method, in consideration of the voltage fluctuation of the power supply voltage, even when the power supply voltage is low and the temperature rise rate of the fixing roller is small, before the printed paper reaches the fixing device portion, the fixing roller The time from turning on the power until printing is enabled is set so that the temperature can be raised to a predetermined temperature.Therefore, when the power supply voltage is high, the temperature of the fixing roller becomes the predetermined temperature. However, since there is a case where printing is not possible in some cases, there is a problem that useless waiting time occurs correspondingly.

In view of the above circumstances, the present invention can detect the abnormality of the fixing device by monitoring the power supply voltage supplied to the fixing device based on the temperature rise per predetermined time. It is therefore an object of the present invention to provide a method of controlling a thermal fixing device in an image forming apparatus, which can prevent burnout of the device due to a failure of the fixing device. Further, according to the second aspect, the power supply voltage supplied to the fixing device can be monitored, and the abnormality of the fixing device can be detected based on the time taken for a predetermined temperature rise, which results in the failure of the fixing device. It is an object of the present invention to provide a method for controlling a heat fixing device in an image forming apparatus, which can prevent the apparatus from being burnt out. According to the third aspect of the present invention, when the power is turned on, the power supply voltage supplied to the fixing device is monitored, and the optimum temperature is set before the surface temperature of the fixing roller in the fixing device reaches a predetermined temperature. At the timing
Providing a method for controlling a thermal fixing device in an image forming apparatus that can shorten the waiting time from power-on to first printing by feeding paper and can obtain an image with good fixing properties The purpose is to do.

[0009]

In order to achieve the above object, the present invention provides, in claim 1, a fixing roller controlled to reach a predetermined temperature after a toner image is formed on a sheet by a printing mechanism. In a method of controlling a thermal fixing device in an image forming apparatus that melts and fixes a toner image formed on the sheet, a voltage value when a power supply voltage is applied to a heater that heats the fixing roller, and the fixing roller. Based on the contents of the voltage / temperature table showing the relationship with the temperature rise rate per unit time, after obtaining the temperature rise rate corresponding to the power supply voltage, this temperature rise rate and the current temperature of the fixing roller, Based on the predetermined temperature, after applying a power supply voltage to the heater,
The time until the temperature of the fixing roller reaches a predetermined temperature is obtained, and this time is compared with the actual time until the temperature of the fixing roller reaches the predetermined temperature to determine whether there is an abnormality in the fixing device. It is characterized by doing.

According to a second aspect of the present invention, after the toner image is formed on the paper by the printing mechanism, the toner image formed on the paper is melted and fixed by the fixing roller controlled to a predetermined temperature. In a method of controlling a heat fixing device in an apparatus, a relationship between a voltage value when a power supply voltage is applied to a heater that heats the fixing roller and a time required to raise the fixing roller by a unit temperature. After the required time corresponding to the power supply voltage is obtained based on the contents of the voltage / time table indicating, the temperature difference between the current temperature of the fixing roller and the predetermined temperature, the unit temperature, and the required time. Based on
The time from the application of the power supply voltage to the heater until the temperature of the fixing roller reaches the predetermined temperature is calculated, and this time and the actual time until the temperature of the fixing roller reaches the predetermined temperature are calculated. Is compared to determine whether or not there is an abnormality in the fixing device.

According to a third aspect of the present invention, after the toner image is formed on the paper by the printing mechanism, the toner image formed on the paper is melted and fixed by the fixing roller controlled to a predetermined temperature. In a method of controlling a heat fixing device in an apparatus, a voltage value when a power supply voltage is applied to a heater that heats the fixing roller and a temperature of the fixing roller that may start feeding to a printing mechanism. Based on the contents of the voltage / temperature table indicating the relationship, the temperature of the fixing roller that may start feeding is determined, and the current temperature of the fixing roller reaches the temperature of the fixing roller that may start feeding. Then, the printing is enabled and the paper feeding is started.

In the above structure, in the first aspect, after the toner image is formed on the sheet by the printing mechanism, the toner image formed on the sheet is melted and fixed by the fixing roller controlled to have a predetermined temperature. In a method of controlling a thermal fixing device in an image forming apparatus, a relationship between a voltage value when a power supply voltage is applied to a heater that heats the fixing roller and a temperature increase rate of the fixing roller per unit time is shown. After the temperature rise rate corresponding to the power supply voltage is obtained based on the contents of the voltage / temperature table, the heater is powered based on the temperature rise rate, the current temperature of the fixing roller, and the predetermined temperature. The time from when the voltage is applied until the temperature of the fixing roller reaches a predetermined temperature is obtained, and this time and the temperature of the fixing roller are the predetermined value. The power supply voltage supplied to the fixing device is monitored by comparing the actual time until the fixing temperature is reached to determine whether or not there is an abnormality in the fixing device, and fixing is performed based on the temperature rise per predetermined time. To detect abnormalities in the vessel,
This prevents burnout of the device due to failure of the fixing device.

According to a second aspect of the present invention, after the toner image is formed on the paper by the printing mechanism, the toner image formed on the paper is melted and fixed by the fixing roller controlled to a predetermined temperature. In a method of controlling a heat fixing device in an apparatus, a relationship between a voltage value when a power supply voltage is applied to a heater that heats the fixing roller and a time required to raise the fixing roller by a unit temperature. After the required time corresponding to the power supply voltage is obtained based on the contents of the voltage / time table indicating, the temperature difference between the current temperature of the fixing roller and the predetermined temperature, the unit temperature, and the required time. Based on
The time from the application of the power supply voltage to the heater until the temperature of the fixing roller reaches the predetermined temperature is calculated, and this time and the actual time until the temperature of the fixing roller reaches the predetermined temperature are calculated. The power supply voltage supplied to the fixing device is monitored by determining whether the fixing device is abnormal or not, and the fixing device is detected as abnormal based on the time required for a predetermined temperature rise. In order to prevent the device from being burned out due to the failure of the fixing device, the third aspect of the present invention is to fix the toner image on the sheet by a printing mechanism and then to fix the toner image on the sheet by a fixing roller controlled to a predetermined temperature. In a method of controlling a heat fixing device in an image forming apparatus that melts and fixes a toner image formed on a roller, when a power supply voltage is applied to a heater that heats the fixing roller, The temperature of the fixing roller that may start feeding based on the contents of the voltage / temperature table that indicates the relationship between the voltage value for the printing mechanism and the temperature of the fixing roller that may start feeding for the print mechanism. When the current temperature of the fixing roller reaches the temperature of the fixing roller at which the sheet feeding may be started, printing is enabled and sheet feeding is started to fix the sheet when the power is turned on. The power supply voltage supplied to the container is monitored, and before the surface temperature of the fixing roller in the fixing device reaches a predetermined temperature, the paper is fed at the most optimal timing and after the power is turned on. The waiting time until the first print is shortened and an image with good fixing property is obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a block diagram showing an example of a laser printer device to which an embodiment of a method of controlling a heat fixing device in an image forming apparatus according to the present invention is applied. The laser printer device 1 shown in this figure has a casing 2 formed in a rectangular shape, and a commercial power supply voltage which is arranged in the casing 2 and is supplied through a power cord 3 to take in an AC power supply voltage. , A power supply unit 4 for generating a stabilized DC voltage and the like, and a sheet provided with a toner image, which is disposed in the casing 2 and is discharged from a printing mechanism (not shown), and pressurizes the sheet. A fixing device 7 that heats the fixing roller 6 while pressing it with the roller 5, a thermistor 8 that is mounted on the fixing roller 6 and that detects the temperature of the fixing roller 6 and outputs a temperature detection signal, and the casing. 2, the process for controlling the operation of each part of the apparatus as shown in FIG. 2, the power supply voltage output from the power supply unit 4 and the temperature detection signal output from the thermistor 8 are fetched to the fixing roller. An engine board 9 which performs processing such as control of the temperature of the La 7, attached to the fixing roller 6, and a heater 10 which generates heat by receiving a power supply voltage output from the engine board 9.

When the power switch is turned on, a power supply voltage, a stabilization voltage, etc. are generated based on the commercial power supply voltage supplied via the power cord 3, and the power supply voltage, the stabilization voltage, etc. are generated. While supplying each part of the apparatus, the heat generation amount of the heater 10 is controlled according to the value of the power supply voltage and the value of the temperature detection signal output from the thermistor 8 to bring the fixing roller 6 of the fixing device 7 to a predetermined temperature. When the image data to be printed and the print instruction are input before the temperature is increased to a predetermined temperature and the printable state is achieved by the print mechanism.
After a toner image corresponding to the image data is formed on the sheet, the fixing device 7 melts and fixes the toner on the sheet, and the sheet is discharged to the outside of the apparatus.

In this case, the engine board 9 is shown in FIG.
As shown in FIG. 3, the DC voltage output from the rectification bridge circuit 11 is composed of a rectification bridge circuit 11 that rectifies the power supply voltage output from the power supply unit 4 and two resistors 12a and 12b connected in series. A voltage dividing circuit 13 for dividing the voltage, a capacitor 14 for smoothing the DC voltage output from the voltage dividing circuit 13 to generate a voltage value signal indicating the voltage value of the power supply voltage, and one end of the power supply line 1
5 is connected to the other end of the thermistor 8 connected to 5, and receives a temperature detection signal in the form of a current signal output from the thermistor 8 according to the resistance value of the thermistor 8 and outputs a temperature detection signal in the form of a voltage signal. The resistor 16 for charging, the voltage value signal output from the capacitor 14 by the first analog port and the second analog port, and the temperature detection signal output from the resistor 16 are captured and A / D-converted, and Based on the converted voltage value signal and the temperature detection signal, a preset process is performed to turn on / off the fixing roller 6 to a predetermined temperature.
Processing for generating an off signal, processing for generating various control signals necessary for controlling the operation of each part of the apparatus, and the like C
And PU17.

Further, the engine board 9 has the C
A diode 18 that receives an ON / OFF signal output from the output terminal of the PU 17, and an ON state and an OFF state according to the ON / OFF signal that has passed through the diode 18,
A triac 19 that supplies the power supply voltage supplied from the power supply unit 4 to the heater 10 to generate heat when the heater 10 is in the on state.

Then, when the power switch is turned on, a voltage value signal obtained by rectifying and smoothing the power supply voltage supplied from the power supply unit 4 and a temperature detection signal output from the thermistor 8. Based on the above, a preset process is performed to heat the heater 10 and raise the temperature of the fixing roller 6 to a predetermined temperature.

At this time, since the temperature rising rate of the fixing roller 6 changes according to the value of the power supply voltage supplied to the heater 10, as shown in FIG. 4, the value of the power supply voltage supplied to the heater 10 is changed. And a value of the temperature rise rate of the fixing roller 6 are measured in advance, and as shown in FIG. 4, each time the power supply voltage changes by 2 V, a voltage / temperature table showing how many times it rises in 10 seconds. 20 is created and this is the CP
It is stored in the memory in U17.

If the current value (current voltage value) of the power supply voltage output from the power supply unit 4 is 90V, the temperature rise rate is "0" when the contents of the voltage / temperature table 20 are looked up. 30 ", the temperature (environmental temperature) before supplying the power supply voltage to the heater 10 is 30 ° C, and the predetermined temperature of the fixing roller 6 is 18 ° C.
If it is 0 ° C., the calculation shown in the following equation is performed, and {(180 [° C.] − 30 [° C.]) / 30 [° C./S]}.
10 = 50 [S] When the temperature of the fixing roller 6 does not reach the predetermined temperature in 50 seconds after the supply of the power supply voltage to the heater 10 is started, it is determined that some abnormality has occurred in the fixing device 7, The function of the printer mechanism is stopped, and a message indicating that an error has occurred is displayed on the operation panel.

If the current value of the power supply voltage output from the power supply unit 4 is 104V, the voltage /
When the contents of the temperature table 20 are looked up, it is determined that the temperature rise rate is "44". At this time, the heater 10
Temperature (environmental temperature) before supplying power voltage to the
Then, if the predetermined temperature of the fixing roller 6 is 180 ° C.,
The calculation shown in the following equation is performed to obtain {(180 [° C.]-30 [° C.]) / 44 [° C./S]}.
10 = 34 [S] When the temperature of the fixing roller 6 does not reach the predetermined temperature in 34 seconds after the supply of the power supply voltage to the heater 10 is started, it is determined that some abnormality has occurred in the fixing device 7, The function of the printer mechanism is stopped, and a message indicating that an error has occurred is displayed on the operation panel.

In parallel with the above-described operation, before the temperature of the fixing roller 6 reaches a predetermined temperature, the value of the power supply voltage shown in FIG. 6 and the printing mechanism are based on the value of the voltage value signal. On the other hand, the fixing roller 6 that may start feeding
The voltage / temperature table 21 showing the relationship with the temperature is accessed to read the temperature corresponding to the power supply voltage.

At this time, if the power supply voltage is 90 V,
When the contents of the voltage / temperature table 21 are looked up, it is determined that the optimum temperature for starting sheet feeding is 170 ° C., and the fixing roller 6 indicated by the temperature detection signal output from the thermistor 8 is detected. When the value reaches 170 ° C., a print enable signal is generated and each part of the apparatus is set in a print enable state.

If the power supply voltage is 104V,
When the contents of the voltage / temperature table 21 are looked up, it is determined that the optimum temperature for starting sheet feeding is 156 ° C., and the fixing roller 6 indicated by the temperature detection signal output from the thermistor 8 is detected. When the value reaches 156 ° C., a print enable signal is generated and each part of the apparatus is set in a print enable state.

In this state, when the image data to be printed and the print instruction are input, the printing mechanism is controlled to form a toner image corresponding to the image data on the sheet, and then the fixing device 7 is formed. Then, the toner on the paper is fused and fixed, and the paper is ejected out of the apparatus.

Thus, in this embodiment, when the power switch is turned on, the voltage / temperature table 20 is looked up and the temperature of the fixing roller 6 corresponding to the value of the power voltage applied to the heater 10 is looked up. The difference (temperature) between the value (environmental temperature) of the temperature detection signal indicating the current temperature of the fixing roller 6 output from the thermistor 8 and the predetermined temperature (target temperature) of the fixing roller 6 while obtaining the rate of increase Difference), and based on these temperature differences and the temperature rise rate, the time from the start of the supply of the power supply voltage to the heater 10 until the temperature of the fixing roller 6 reaches a predetermined temperature is calculated. When this time has elapsed, it is determined whether the temperature of the fixing roller 6 has reached a predetermined temperature, and whether the fixing device 7 is abnormal is determined. Even when the power supply voltage supplied to the destination device 7 varies, it is possible to detect the abnormality of the fixing device 7, whereby it is possible to prevent a beforehand burnout of the device due to failure of the fixing device 7.

Further, in this embodiment, the fixing roller 6 is
Before the temperature of the fixing roller 6 reaches a predetermined temperature, the voltage / temperature table 21 shown in FIG. 6 is accessed based on the value of the voltage value signal, the temperature corresponding to the power supply voltage is read, and the temperature of the fixing roller 6 is When the temperature corresponding to the value of the power supply voltage is reached, a print enable signal is generated so that each part of the apparatus is ready for printing.
Even if the value of the power supply voltage supplied to the sheet fluctuates, the sheet can be fed at the optimum timing before the surface temperature of the fixing roller 6 in the fixing device 7 reaches a predetermined temperature.
As a result, it is possible to shorten the waiting time from power-on to the first print, and it is possible to obtain an image with good fixability.

Further, in the above-mentioned embodiment, the temperature rise rate of the fixing roller 6 corresponding to the value of the power supply voltage is calculated based on the voltage / temperature table 20 shown in FIG.
The time from when the power supply voltage is supplied to 0 until the temperature of the fixing roller 6 reaches a predetermined temperature is calculated.
As shown in FIG. 7, a voltage / time table 22 is created which shows the relationship between the value of the power supply voltage and the time required for the temperature of the fixing roller 6 to rise by 40 ° C. after supplying the power supply voltage to the heater 10. The voltage / time table 22 may be used to determine whether or not the fixing device 7 is abnormal.

In this case, when the power switch is turned on, the voltage / time table 22 is accessed,
After obtaining the time corresponding to the current value of the power supply voltage supplied to the heater 10, this time and the unit temperature (in this case, 40
C) and the difference (temperature difference) between the current temperature (environmental temperature) of the fixing roller 6 and a predetermined temperature (target temperature), the temperature of the fixing roller 6 is kept at the predetermined temperature after the power supply voltage is supplied. Until the time corresponding to the value of the power supply voltage elapses after the power supply voltage is supplied to the heater 10, it is determined whether or not the temperature of the fixing roller 6 has reached a predetermined temperature. Based on this determination result, it is determined whether the fixing device 7 is abnormal.

By doing so, if the value of the power supply voltage is 90 V, the temperature rises by 40 ° C. in 15 seconds.
When the environmental temperature is 30 ° C., it takes 56 seconds until the temperature of the fixing roller 6 reaches the predetermined temperature (180 ° C.). Therefore, 5 seconds after the supply of the power supply voltage to the heater 10 is started.
When 6 seconds have elapsed, it is possible to determine whether or not the temperature of the fixing roller 6 has reached a predetermined temperature, and based on the determination result, it can be determined whether or not the fixing device 7 is abnormal.

Similarly, if the value of the power supply voltage is 104 V, the temperature rises by 40 ° C. in 8 seconds, so that the environmental temperature is 30 ° C.
At this time, it takes 30 seconds for the temperature of the fixing roller 6 to reach a predetermined temperature (180 ° C.). Therefore, when 30 seconds have elapsed since the supply of the power supply voltage to the heater 10 was started, It is possible to determine whether or not the temperature of 6 has reached a predetermined temperature, and based on the determination result, it can be determined whether or not the fixing device 7 is abnormal.

Even in this case, similarly to the above-described embodiment, the power source voltage supplied to the fixing device 7 is monitored and the abnormality of the fixing device 7 is detected based on the time per unit temperature rise. As a result, it is possible to prevent the device from being burned due to the failure of the fixing device 7. Further, in each of the above-described embodiments, the rectifying bridge circuit 11, the voltage dividing circuit 13, and the capacitor 14 are provided in the engine board 9 to rectify and smooth the power supply voltage supplied from the power supply unit 4. The voltage value signal is generated by the CPU 17 and processed by the CPU 17. However, the DC voltage corresponding to the value of the power voltage supplied to the heater 10 in a one-to-one relationship is output from the power supply unit 4. Sometimes
The DC voltage may be taken in the engine board 9 as a voltage value signal and processed by the CPU 17.

[0033]

As described above, according to the present invention, in claim 1, the power supply voltage supplied to the fixing device is monitored,
The abnormality of the fixing device can be detected based on the temperature rise per predetermined time, and thus the device can be prevented from being burned due to the failure of the fixing device. Further, according to the second aspect, the power supply voltage supplied to the fixing device can be monitored, and the abnormality of the fixing device can be detected based on the time taken for a predetermined temperature rise, which results in the failure of the fixing device. It is possible to prevent burnout of the device. According to the third aspect of the present invention, when the power is turned on, the power supply voltage supplied to the fixing device is monitored, and the optimum temperature is set before the surface temperature of the fixing roller in the fixing device reaches a predetermined temperature. By feeding the paper at the timing, it is possible to shorten the waiting time from the power-on to the first printing, and it is possible to obtain an image with good fixability.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a laser printer device to which an embodiment of a method of controlling a heat fixing device in an image forming apparatus according to the present invention is applied.

FIG. 2 is a block diagram showing an example of a connection relationship between the power supply unit shown in FIG. 1 and an engine board.

FIG. 3 is a circuit diagram showing a detailed configuration example of the engine board shown in FIG.

FIG. 4 is a graph showing an example of a relationship between a value of a power supply voltage applied to the fixing roller shown in FIG. 1 and temperature.

5 is a schematic diagram showing an example of a voltage / temperature table used when determining whether or not the fixing device is abnormal by the engine board shown in FIG. 1. FIG.

6 is a schematic diagram showing an example of a voltage / temperature table used when determining whether printing is possible by the engine board shown in FIG. 1. FIG.

FIG. 7 is a schematic diagram showing an example of a voltage / time table used when determining whether or not the fixing device is abnormal in another example of the method of controlling the thermal fixing device in the image forming apparatus according to the present invention. .

[Explanation of symbols]

1 laser printer device, 2 housing, 3 power cord,
4 power supply unit, 5 pressure roller, 6 fixing roller, 7 fixing device, 8 thermistor, 9 engine board, 10 heater, 11 rectifying bridge circuit, 12a,
12b resistor, 13 voltage divider, 14 capacitor, 1
5 power lines, 16 resistors, 17 CPU, 18 diodes, 19 triacs, 20 voltage / temperature table, 21 voltage / temperature table, 22 voltage / time table

Claims (3)

[Claims] 1. A thermal fixing device in an image forming apparatus for fusing and fixing a toner image formed on a sheet by a fixing roller controlled to a predetermined temperature after forming a toner image on the sheet by a printing mechanism. In the control method of No. 3, based on the contents of a voltage / temperature table showing the relationship between the voltage value when a power supply voltage is applied to the heater for heating the fixing roller and the temperature increase rate of the fixing roller per unit time. After the temperature rise rate corresponding to the power supply voltage is obtained, the power supply voltage is applied to the heater based on the temperature rise rate, the current temperature of the fixing roller, and the predetermined temperature, and then the The time until the temperature of the fixing roller reaches the predetermined temperature is obtained, and this time and the actual time until the temperature of the fixing roller reaches the predetermined temperature are calculated. A method for controlling a heat fixing device in an image forming apparatus, wherein the presence or absence of abnormality of the fixing device is determined by comparison. 2. A thermal fixing device in an image forming apparatus for fusing and fixing a toner image formed on a sheet by a fixing roller controlled to a predetermined temperature after forming a toner image on the sheet by a printing mechanism. In the control method, the voltage / time indicating the relationship between the voltage value when a power supply voltage is applied to the heater that heats the fixing roller and the time required to raise the fixing roller by a unit temperature. After determining the required time corresponding to the power supply voltage based on the contents of the table, the heater is determined based on the temperature difference between the current temperature of the fixing roller and the predetermined temperature, the unit temperature, and the required time. Then, the time from when the power supply voltage is applied to when the temperature of the fixing roller reaches a predetermined temperature is calculated. A method of controlling a thermal fixing device in an image forming apparatus, which comprises determining whether or not there is an abnormality in the fixing device by comparing the actual time until the temperature reaches a predetermined temperature. 3. A thermal fixing device in an image forming apparatus for fusing and fixing a toner image formed on a sheet by a fixing roller controlled to have a predetermined temperature after forming a toner image on the sheet by a printing mechanism. In the control method, the voltage / voltage indicating the relationship between the voltage value when a power supply voltage is applied to the heater that heats the fixing roller and the temperature of the fixing roller that may start feeding to the printing mechanism. Based on the contents of the temperature table, determine the temperature of the fixing roller that may start feeding, and when the current temperature of the fixing roller reaches the temperature of the fixing roller that may start feeding, printing is possible. Then, the method for controlling the thermal fixing device in the image forming apparatus is characterized in that the sheet feeding is started.