JP2005172911A - Fixing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing apparatus wherein a temperature control is performed so that a temperature difference between a plurality of heating means for a fixing roller may be always controlled within an allowable extent. <P>SOLUTION: An abnormality in temperature of the fixing apparatus 16H is detected based on the temperature detected by two non-contact type temperature sensors having the same responsiveness, that is, a 1st temperature sensor 19H for detecting the temperature of radiant heat from the center part of the fixing roller 31 and a 2nd temperature sensor 20H for detecting the temperature of radiant heat from the end part of the fixing roller 31. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, or a complex machine thereof, and more particularly to temperature control and abnormal temperature detection of a fixing device.

  In general, an electrophotographic image forming apparatus reads an image read by a scanner, forms a toner image of the image read on a recording material in the image forming apparatus, and sends the formed recording material to a fixing device. Therefore, the unfixed toner image on the recording material is heated and fixed to obtain a print image.

  The fixing device includes a fixing roller as a heating member having a heating source inside, and a pressure roller as a pressure member that forms a fixing nip in pressure contact with the fixing roller. The fixing roller is rotationally driven by a driving source, and the pressure roller is rotated following the fixing roller. The fixing roller and the pressure roller heat and press the recording material while nipping and conveying the recording material at the fixing nip to melt and fix the toner image on the recording material. The surface temperature of the fixing roller is detected by a temperature sensor, and the temperature of the fixing roller is controlled so as to always be an appropriate temperature.

With regard to this type of conventional temperature control device, there has been disclosed a temperature abnormality detection device that makes an abnormality when the temperature difference between the non-contact temperature sensor and the contact temperature sensor exceeds a predetermined temperature difference. (For example, see Patent Document 1)
Among the plurality of heating means, W.W. During UP (Warm-Up), even if the temperature of the heater heated later reaches the target temperature, the temperature that is detected as abnormal when the temperature of the previously heated heater does not reach the target temperature An anomaly detection device is disclosed. (For example, see Patent Document 2)
JP2002-372893 JP-A-9-106212

  As shown in Patent Document 1, in a fixing device including a contact-type temperature detection sensor and a non-contact-type temperature detection sensor, if the contact-type temperature sensor is attached to the sheet passing area of the fixing roller, the fixing roller may be damaged. Yes, this hinders image formation. Also, if the temperature difference is calculated using the detection temperatures of multiple temperature sensors with different temperature detection responsiveness to detect an abnormality in the fixing device, there will be a difference from the actual temperature difference on the fixing roller surface. Temperature control may not be possible.

  As shown in Patent Document 2, in a fixing device that heats a plurality of heating means with a time difference, at the time of warm-up, a heating means that allows one of the plurality of heating means to reach a target temperature earlier than the other heating means. And the other heating means is selected as a heating means that reaches the target temperature later. In a fixing device that detects an abnormality of the fixing device by using a temperature difference between detection temperatures of both heating units, if the temperature increase rate of both heating units is equal, the abnormality detection may not be possible. In addition, W.W. Anomaly detection during UP is possible. Unable to detect abnormality after UP completion.

  An object of the present invention is to provide a fixing device capable of performing temperature control so that a temperature difference between a plurality of heating units in a fixing roller is always within an allowable range.

The invention described in claim 1
A first heating unit that heats the central portion of the fixing roller in response to power supply from the driving power source, a second heating unit that heats both ends of the fixing roller, and a first temperature that detects the temperature of the central portion of the fixing roller. Temperature detection means, second temperature detection means for detecting the temperature of the end of the fixing roller, and the first and second detection temperatures according to the first and second detection temperatures detected by the first and second temperature detection means. A temperature control unit that controls the temperature of the fixing roller to a predetermined target value by independently controlling the two heating units;
The first and second temperature detecting means are arranged in different areas of the sheet passing area on the fixing roller that have equivalent responsiveness and are non-contact.
It is determined whether the difference between the first detected temperature detected by the first temperature detecting means and the second temperature detected temperature detected by the second temperature detecting means is greater than or equal to a predetermined temperature difference, and the predetermined temperature A first determination means for determining an abnormality when the difference is greater than or equal to,
Energization control means for stopping energization from the drive power source to the first and second heating means when it is determined that the first determination means is abnormal;
A fixing device.

The invention according to claim 2
A first heating unit that heats the central portion of the fixing roller in response to power supply from the driving power source, a second heating unit that heats both ends of the fixing roller, and a first temperature that detects the temperature of the central portion of the fixing roller. Temperature detection means, second temperature detection means for detecting the temperature of the end of the fixing roller, and the first and second detection temperatures according to the first and second detection temperatures detected by the first and second temperature detection means. A temperature control unit that controls the temperature of the fixing roller to a predetermined target value by independently controlling the two heating units;
The first and second temperature detecting means are arranged in different areas of the sheet passing area on the fixing roller that have equivalent responsiveness and are non-contact.
The first temperature detection means includes a first detection temperature sensor that detects heat radiated from a central portion of the fixing roller, and a first compensation temperature sensor that detects an ambient temperature of the central portion of the fixing roller. ,
The second temperature detection means includes a second detection temperature sensor that detects heat radiated from an end portion of the fixing roller, and a second compensation temperature sensor that detects an ambient temperature of the end portion of the fixing roller. ,
First calculating means for calculating a surface temperature of the center portion of the fixing roller based on a first detected temperature detected by the first detected temperature sensor and a first compensated temperature detected by the first compensated temperature sensor;
Second calculating means for calculating an end surface temperature of the fixing roller based on a second detected temperature detected by the second detected temperature sensor and a first compensated temperature detected by the second compensated temperature sensor;
First determination means for determining whether the first and second compensation temperatures detected by the first and second compensation temperature sensors are equal to or higher than a predetermined set temperature;
When it is determined by the first determination means that the temperature is equal to or higher than a predetermined set temperature, it is determined whether or not a difference between the center surface temperature and the end surface temperature is equal to or greater than a predetermined temperature difference. A second determination means for determining an abnormality,
Energization control means for stopping energization from the drive power source to the first and second heating means when it is determined as abnormal by the second determination means;
A fixing device.

The invention according to claim 3
Third determination means for determining whether the first and second compensation temperatures are equal to or lower than a predetermined set temperature, and when the first and second compensation temperatures are determined to be equal to or lower than the set temperature, the first A fourth determination means for determining whether or not a difference between the detected temperature and the second detected temperature is equal to or greater than a predetermined temperature difference;
3. The fixing device according to claim 2, wherein the energization control unit stops energization from the drive power source to the first and second heating units when the fourth determination unit determines that the abnormality is present. 4. is there.

The invention according to claim 4
It is further determined whether or not a difference between the first compensation temperature and the second compensation temperature is equal to or greater than a predetermined temperature difference.
3. The fixing device according to claim 2, wherein the energization control unit stops energization from the driving power source to the first and second heating units when the fifth determination unit determines that the abnormality is present. 4. is there.

The invention described in claim 5
The temperature control means controls the hysteresis temperature so that the first and second detection temperatures, or the center surface temperature and the end surface temperature are within a predetermined temperature range with respect to a preset target temperature. The fixing device according to claim 1, wherein the fixing device is a fixing device.

The invention described in claim 6
The fixing device according to claim 5, wherein the temperature control unit controls the first and second heating units within a temperature range of 1 ° C. to 5 ° C. in a temperature range of the hysteresis temperature control. It is.

The invention described in claim 7
The fixing device according to claim 5, wherein the temperature control unit can change a temperature range of the hysteresis temperature control depending on whether or not the fixing roller is operating.

The invention according to claim 8 provides:
The fixing device according to claim 5, wherein the temperature control unit alternately controls ON / OFF of the first and second heating units.

The invention according to claim 9 is:
The fixing device according to claim 1, wherein the first and second heating units are electromagnetic induction heaters.

  According to the first aspect of the present invention, it is possible to control energization of the fixing device so that the temperature difference between the plurality of heating units is within a predetermined range by detecting the temperatures of the plurality of heating units. It becomes.

  According to the invention described in claim 2, by calculating the surface temperature of each of the plurality of heating means based on the temperatures detected from two different temperature detection sensors, the temperature is detected more accurately, Each heating means can be appropriately energized.

  According to the third or fourth aspect of the invention, the same effect as that of the second aspect can be obtained, and various types of temperatures can be detected by detecting a plurality of different temperatures from two different temperature detection sensors. It becomes possible to control the energization of each of the plurality of heating means based on the abnormal temperature information.

  According to the invention described in claim 5 or 6, it is possible to accurately control the temperature of each of the plurality of heating means so that the temperature is within a predetermined temperature range with respect to the target temperature.

  According to the seventh aspect of the invention, the same effects as in the fifth aspect can be obtained, and the temperature of each of the plurality of heating means can be suitably controlled according to the operation state of the fixing roller. .

  According to the eighth aspect of the invention, the same effect as that of the fifth aspect can be obtained, and the power distribution to each of the plurality of heating means can be achieved by alternately turning on / off the plurality of heating means. Is no longer necessary.

  According to the ninth aspect of the present invention, the effect similar to that of any one of the first to seventh aspects can be obtained, and by using an electromagnetic induction heater as each of the plurality of heating means, fixing can be achieved. It becomes possible to heat the heating area of the roller quickly and evenly.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. The following description may include assertive expressions for terms and the like, but it shows preferred examples of the present invention and limits the meaning and technical scope of the terms of the present invention. Not what you want.

[First embodiment]
First, the configuration of the image forming apparatus will be described.

FIG. 1 shows an example of a temperature control circuit of an image forming apparatus including a fixing device using a halogen heater as a heating unit.
In FIG. 1, the image forming apparatus includes an operation unit 11, a document reading device 12, a motor driving high voltage circuit 13, a paper feeding unit 14, a system control unit 15H, a fixing device 16H, and a post-processing unit 17. Consists of.

  The operation unit 11 is for instructing various operations of the image forming apparatus, and includes, for example, operation input keys, a display screen, and the like. The operation input keys are configured to input settings of the image forming apparatus and driving operation instructions, and are, for example, operation buttons, a remote controller, and the like. The display screen is composed of, for example, an LCD (Liquid Crystal Display) or the like, and displays settings of the image forming apparatus, operating states, and the like. When the operation unit 11 is a touch panel, the display screen is configured to have operation input keys.

  The document reading device 12 is a functional unit that reads two-dimensional information of a document placed on a document table and converts it into digital data. That is, light is projected onto the document placed on the document table, the reflected light is read by the CCD, converted into linear digital data, and output to the system control unit 15H.

  The motor driving high voltage circuit 13 controls the rotation of the fixing roller 31 of the fixing device 16H and a pressure roller (not shown). When the operating condition is not satisfied, such as when a motor abnormality occurs, the interlock SW (SWitch) 18 is turned OFF, and the operation of the motor driving high voltage circuit 13 is stopped.

  The paper feed unit 14 feeds the paper placed on the paper feed table from the transfer paper tray to the transport mechanism.

  The system control unit 15H is configured by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and via the bus B by executing a system program stored in the storage unit. And overall control of the image forming apparatus.

  The system control unit 15H cooperates with the center detection temperature sensor temperature T1 and the end detection temperature T2 input from the first temperature sensor 21H and the second temperature sensor 22H, the temperature abnormality detection processing program, and the temperature control program. The first determination means, the temperature control means, and the energization control means can be realized.

  In the fixing device 16H, in order to detect the surface temperature of the fixing roller 31, first temperature detecting means (hereinafter referred to as a first temperature sensor 21H) for detecting the temperature of the radiant heat from the central portion of the fixing roller 31, Two non-contact sensors of second temperature detection means (hereinafter referred to as second temperature sensor 22H) for detecting the temperature of radiant heat from the end are provided.

  The fixing device 16H includes a fixing roller 31 as a heating member having a first heater 19 and a second heater 20 such as a halogen lamp heater inside, and a pressure member as a pressure member that presses against the fixing roller 31 to form a fixing nip. The fixing roller 31 is rotationally driven by a driving source (not shown), and the pressure roller is driven by the fixing roller 31 and rotated. The fixing roller 31 and the pressure roller heat and press the paper A while nipping and transporting the paper A at the fixing nip to melt and fix the toner image on the paper A.

  The post-processing device 17 is controlled by the system control unit 15H, and performs predetermined processing such as punching, stapling, and folding on the discharge tray and the copy supplied to the image forming unit in response to a post-processing request, and discharges it. Eject it into the tray.

  The interlock SW 18 is a switch that cuts off power to the motor when a motor abnormality occurs.

The first heater 19 </ b> H is a first heating unit that heats the central portion of the fixing roller 31.
The second heater 20 </ b> H is a second heating unit that heats the end portion of the fixing roller 31.
The first and second heaters 18H and 19H are controlled by the system control unit 15H based on the center detection temperature T1 detected by the first temperature sensor 21H and the end detection temperature T2 detected by the second temperature sensor. Is done.
In the first embodiment, the first and second heaters 19H and 20H use halogen heaters.

The first temperature sensor 21 </ b> H is a first temperature detection unit that is disposed above the fixing roller 31 and detects the temperature at the center of the fixing roller 31.
The second temperature sensor 22 </ b> H is a second temperature detection unit that is disposed above the fixing roller 31 and detects the temperature of the end of the fixing roller 31.
As the first and second temperature sensors 21H and 22H, resistance temperature detectors (eg, thermistors) are used.

  The DC power source 23 receives commercial AC power from the AC commercial power source 24, and based on the control signal of the system control unit 15H, the document reading device 12, the motor driving high voltage circuit 13, the paper feeding unit 14, the system control unit 15H, DC power is supplied to the fixing device 16H and the post-processing unit 17. The DC power supply 23 is turned on and off by the operator turning on and off the power supply SW25.

  The heater power supply unit 26 receives AC power from the AC commercial power supply 24 and supplies DC power to the first heater 19H and the second heater 20H based on a control signal from the system control unit 15H.

  The main relay 27 supplies AC power from the AC commercial power supply 24 to the heater power supply unit 26. When the temperature of the fixing device 16H is abnormal, the power supply to the heater power supply unit 26 is cut off by the main relay OFF signal from the system control unit 15H.

  In the above configuration, the operation of the temperature control device of the fixing device will be described.

The operation during warm-up will be described with reference to FIGS.
FIG. 3 shows the temperature characteristics of the fixing device 16H during normal operation.
During the warm-up, that is, until both the center detection temperature T1 and the end detection temperature T2 reach the target control temperature T0 (for example, T0 = 200 ° C.), the temperature difference between the center detection temperature T1 and the end detection temperature T2 If ΔT is within a predetermined range (for example, ΔT ≦ 40 ° C.), it is determined to be normal, and heating for maintaining energization of the first heater 19H and the second heater 20H is continuously performed.

  When the temperature difference ΔT is outside a predetermined range (for example, ΔT = 60 ° C.), as shown in FIG. 3, it is determined that the detected temperature is abnormal, and the system control unit 15H transmits a stop control signal to the heater power supply unit 26. In both cases, an OFF control signal is transmitted to the main relay 27 of the fixing device 16H to stop energization of the fixing device 16H.

[Second Embodiment]
First, the configuration of the fixing device according to the second embodiment will be described. In the configuration of the fixing device according to the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be made. Description is omitted and only different functional parts are described.

FIG. 4 shows an example of a temperature control circuit of an image forming apparatus including a fixing device 16I using an induction heater as a heating unit.
The fixing device 16I includes a system control unit 15I, a fixing roller 31, a first heater 19I, a second heater 20I, a first temperature sensor 21I, a second temperature sensor 22I, a heater power supply unit 26, and an AC commercial unit. A power supply 24 and a main relay 27 are included.

  The system control unit 15I includes a buffer / amplifier circuit 151 and a CPU 152.

The buffer amplifier circuit 151 receives the first detection temperature TD1 and the first compensation temperature TC1 from the first temperature sensor 21I as input voltage signals, and receives the second detection temperature TD2 and the second compensation temperature TC2 from the second temperature sensor 22I. Is input as an input voltage signal.
The first detection temperature TD1, which is an output signal of the first temperature sensor 21I at the center of the fixing roller 31, is input to the buffer circuit A1, and the first compensation temperature TC1 is input to the buffer circuit A2. When the output signals of the buffer circuit A1 and the buffer circuit A2 are input to the amplifier circuit A3, the center surface temperature TF1 is calculated.
Similarly, for the output signal of the second temperature sensor 22I at the end of the fixing roller 31, the second detected temperature TD2 is input to the buffer circuit A4, and the second compensation temperature TC2 is input to the buffer circuit A5. Output signals of the buffer circuit A4 and the buffer circuit A5 are input to the amplifier circuit A6, and the end surface temperature TF2 is calculated. The first detection temperature TD1, the first compensation temperature TC1, the center surface temperature TF1, the second detection temperature TD2, the second compensation temperature TC2, and the end surface temperature TF2 are respectively output voltage signals from the buffer amplifier circuit 151 as the CPU 152. Is input.

  The buffer amplifier circuit 151 is not limited to the illustrated circuit.

  The CPU 152 performs overall control of the fixing device 16I by executing a system program stored in the storage unit and various programs such as a temperature abnormality detection processing program and a temperature control program according to the present invention.

  The CPU 152 receives the first detection temperature TD1, the first compensation temperature TC1, the center surface temperature TF1, the second detection temperature TD2, the second compensation temperature TC2, the end surface temperature TF2, and the temperature input from the buffer amplifier circuit 151. By cooperating with the abnormality detection processing program and the temperature control program, the first and second calculation means, the first to fifth determination means, the temperature control means, and the energization control means can be realized.

  The first heater 19I is an induction heater that heats the central portion of the fixing roller 31 as a first heating unit, and the second heater 20I is a second heating unit that heats an end portion of the fixing roller 31. The induction heater is a heater that can perform uniform heating at a temperature of 200 ° C. or higher without contacting the fixing roller 31. It operates by receiving power supply from the heater power supply unit 26.

The first temperature sensor 21 </ b> I is a non-contact type temperature sensor that measures the temperature of the center portion of the fixing roller 31 as a first temperature detecting unit, and detects the heat radiated from the fixing roller 31. And a first compensation temperature sensor that detects the ambient temperature of the first detection temperature sensor.
The first detection temperature TD1 and the first compensation temperature TC1 detected by the first temperature sensor 301 are output to the buffer / amplifier circuit 151 as voltage signals.

  The second temperature sensor 22I is a non-contact temperature sensor that measures the temperature of the end portion of the fixing roller 31 as a second temperature detection unit, and a second detection temperature sensor that detects heat radiated from the fixing roller 31. And a second compensation temperature sensor that detects the ambient temperature of the second detection temperature sensor. The second detection temperature TD2 and the second compensation temperature TC2 detected by the second temperature sensor 22I are output to the buffer / amplifier circuit 151 as voltage signals.

  The heater power supply unit 26 is supplied with AC 100V or 200V AC power from the AC commercial power supply 24, and based on the first and second control signals from the CPU 152, independently the first heater 19I and the second heater 20I. Supply power to

  The AC commercial power supply 24 supplies AC power to the heater power supply unit 26, and its operation is ON / OFF controlled by a control signal output from the CPU 152 to the main relay 27.

  In the above configuration, the operation of the temperature control circuit of the image forming apparatus including the fixing device 16I will be described with reference to FIG.

The first detection temperature TD1, the first compensation temperature TC1, the center surface temperature TF1 output from the first temperature sensor 21I, the second detection temperature TD2, the second compensation temperature TC2, output from the second temperature sensor 22I, and the end The part surface temperature TF2 is input to the CPU 152 as a voltage signal subjected to buffer amplifier processing by the buffer amplifier circuit 151. The input first detection temperature TD1, first compensation temperature TC1, second detection temperature TD2, and second compensation temperature TC2 are converted from the voltage signal by the CPU 152 as temperature data (step S101).
Further, the center surface temperature TF1 and the end surface temperature TF2 are calculated as temperature data in the CPU 152 in step S101 as the first and second calculation means.

  In step S102 as the first determining means, it is determined whether or not the converted first compensation temperature TC1 and second compensation temperature TC2 are equal to or higher than a predetermined set temperature TC0 (for example, TC1 and TC2 ≧ TC0 = 60 ° C.). Is done.

  When it is determined that the first compensation temperature TC1 and the second compensation temperature TC2 are equal to or higher than a predetermined set temperature TC0 (step S102; YES), the center surface temperature TF1 and the fixing roller 31 that are calculated temperatures at the center of the fixing roller 31 are determined. Reference is made to the end surface temperature TF2, which is the calculated temperature of the end (step S103).

  Based on the reference result, in step S104 as the second determination means, the center surface temperature TF1 that is the calculated temperature of the fixing roller 31 and the end surface temperature TF2 that is the calculated temperature of the end of the fixing roller 31 are calculated. It is determined whether or not the temperature difference ΔTF is equal to or higher than a predetermined set temperature (for example, ΔTF ≧ 40 ° C.).

  When it is determined that the calculated temperature difference ΔTF is 40 ° C. or more (step S104; YES), it is determined that the temperature control of the fixing roller 31 is abnormal, and an error signal is output to the operation unit 11 (step S105).

  In step S106 as the energization control means, the CPU 152 outputs an OFF control signal to the first and second heater power supplies in the heater power supply unit 26, and interrupts the energization from the AC commercial power supply 24 to the heater power supply unit 26. At the same time, an OFF control signal is also output to the main relay 27 and the main relay 27 is turned OFF to cut off the energization to the fixing roller 31.

  Then, an error code indicating that a temperature abnormality has occurred is displayed on the operation unit 11 (step S107).

  When it is determined that the first compensation temperature TC1 and the second compensation temperature TC2 are not equal to or higher than the predetermined set temperature TC0 (step S102; NO), the first compensation temperature TC1 at the center of the fixing roller 31 and the first compensation temperature TC1 at the end of the fixing roller 31 are determined. 2 Refer to the compensation temperature TC2 (step S108).

  Based on the reference result, in step S109 as the third determining means, it is determined whether or not the first compensation temperature TC1 and the second compensation temperature TC2 are lower than a predetermined set temperature TC0.

When it is determined that the first compensation temperature TC1 and the second compensation temperature TC2 are lower than the predetermined set temperature TC0 (step S109: YES), the temperatures of the first detection temperature TD1 and the second detection temperature TD2 are referred to (step S110). ).
When it is determined that the first compensation temperature TC1 and the second compensation temperature TC2 are not lower than the predetermined set temperature TC0 (step S109: NO), the values of the first compensation temperature TC1 and the second compensation temperature TC2 are referred to again. (Step S108).

  Based on the reference result, in step S111 as the fourth determination means, it is determined whether or not the detected temperature difference ΔTD between the first detected temperature T1 and the second detected temperature T2 is equal to or higher than a predetermined temperature (for example, ΔTD = 40 ° C.). To do.

When it is determined that the detected temperature difference ΔTD is equal to or higher than the predetermined temperature (step S111; YES), it is determined that the temperature control of the fixing roller 31 is abnormal, and an error signal is output to the operation unit 11 (step S105).
When it is determined that the detected temperature difference ΔTD is equal to or higher than the predetermined temperature (step S111; NO), the first detected temperature TD1 and the second detected temperature TD2 are referred to again (step S110).

  When it is determined that the first compensation temperature TC1 and the second compensation temperature TC2 are lower than the predetermined set temperature TC0 (step S109: YES), the temperatures of the first detection temperature TD1 and the second detection temperature TD2 are referred to (step S110). ).

  Further, based on the reference result of the first compensation temperature TC1 at the center of the fixing roller 31 and the second compensation temperature TC2 at the end of the fixing roller 31 (step S108), the first compensation temperature TC1 is determined in step S112 as the fifth determining means. Whether or not the compensation temperature difference ΔTC between the second compensation temperature TC2 and the second compensation temperature TC2 is equal to or higher than a predetermined set temperature (for example, ΔTC ≧ 40 ° C.).

When it is determined that the compensation temperature difference ΔTC is equal to or higher than the predetermined set temperature (step S112; YES), it is determined that the temperature control of the fixing roller 31 is abnormal, and an error signal is output to the operation unit 11 (step S105). ).
When it is determined that the compensation temperature difference ΔTC is not equal to or higher than the predetermined set temperature (step S112; NO), the first and second compensation temperatures TC1 and TC2 are referred to again (step S108).

  FIG. 6 shows the first detection temperature TD1, the first compensation temperature TC1, the second detection temperature TD2, the second compensation temperature TC2 detected by the first temperature sensor 21I and the second temperature sensor 22I, and the center calculated by the CPU 152. 6 is a temperature characteristic of the fixing device 16I in a normal state showing the correspondence between the part surface temperature TF1 and the end part surface temperature TF2.

In a low temperature region where the first compensation temperature TC1 and the second compensation temperature TC2 have not reached the target set temperature TC0 (for example, TC0 = 60 ° C.), the detected temperature difference ΔTD between the first detected temperature TD1 and the second detected temperature TD2. Becomes a predetermined temperature difference (for example, ΔTD = 40 ° C.), the abnormal temperature T is detected, an abnormal signal is output from the CPU 152 as the energization control means, and the heating of the fixing roller 31 is stopped.
In the low temperature region, when the compensation temperature difference ΔTC, which is the temperature difference between the first compensation temperature TC1 and the second compensation temperature TC2, becomes a predetermined temperature difference (for example, ΔTC = 40 ° C.), The CPU 152 outputs an abnormal signal, and the heating of the fixing roller is stopped.

  In the high temperature region after the first compensation temperature TC1 and the second compensation temperature TC2 reach the target ambient set temperature TC0 (for example, TC0 = 60 ° C.), the temperatures of the center surface temperature TF1 and the end surface temperature TF2 When the difference ΔTF becomes a predetermined temperature difference (for example, ΔTF = 40 ° C.), it is detected as an abnormality, an abnormality signal is output from the CPU 152 as the energization control means, and the heating of the fixing roller 31 is stopped.

  FIG. 7 shows the temperature control of the fixing roller 31 during warm-up, standby operation, and copying.

  During warm-up, temperature abnormalities are detected in both the low temperature region and the high temperature region, and the temperature control of the first and second heaters is performed.

During standby operation, that is, when both the center surface temperature TF1 and the end surface temperature TF2 reach the target control temperature T0 and the fixing roller 31 is stopped, the temperature abnormality in the high temperature region is detected and the fixing is performed. An ON / OFF control signal is sent from the CPU 152 as the temperature control means to the heater power supply unit 26 so as to be within a predetermined temperature range ΔT _OFF (for example, ΔT _OFF = 3 ° C.) from the target control temperature T0 when the roller 31 is stopped. The first heater 21I and the second heater 22I are subjected to hysteresis temperature control.

During copying, that is, when both the center surface temperature TF1 and the end surface temperature TF2 reach the target control temperature T0 and the fixing roller 31 is rotating, the temperature abnormality in the high temperature region is detected and the fixing is performed. Taking the temperature change due to the rotation of the roller 31 into account, the _ON / _OFF control is performed so that the target control temperature T0 during the rotation of the fixing roller 31 is within a predetermined temperature range ΔT _ON > ΔT _OFF (for example, ΔT _ON = 4 ° C.). A signal is transmitted from the CPU 152 as the temperature control means to the heater power supply unit 26 to control the first heater 19H and the second heater 20H with hysteresis temperature.

  During standby operation and copying, the temperature abnormality in the high temperature region is detected, and the temperature control of the first and second heaters 21H and 22H is performed.

2 shows a temperature control circuit of an image forming apparatus including a fixing device 16H using a halogen heater. The temperature characteristic of the fixing device 16H at normal time is shown. The temperature characteristic of the fixing device 16H at the time of abnormality is shown. 2 shows a temperature control circuit of an image forming apparatus including a fixing device 16I using an induction heater. 6 shows an abnormality detection process flow of the fixing device 16I. The temperature characteristic of the fixing device 16I that calculates the surface temperature of the fixing roller 31 from the detected temperature and the compensation temperature is shown. The hysteresis temperature control of the fixing device 16I is shown.

Explanation of symbols

11 Operation Unit 12 Document Reading Device 13 Motor Drive High Voltage Circuit 14 Paper Feed Unit 15H System Control Unit 16H Fixing Device 17 Post-Processing Unit 18 Interlock SW
19H 1st heater 20H 2nd heater 21H 1st temperature sensor 22H 2nd temperature sensor 23 DC power supply 24 AC commercial power supply 25 Power supply SW
26 Heater power unit 27 Main relay 31 Fixing roller A Paper B Bus T0 Target control temperature T1 Center detection temperature T2 Edge detection temperature ΔT Temperature difference ΔTD Detection temperature difference ΔTC Compensation temperature difference ΔTF Surface temperature difference ΔT _{OFF When the} fixing roller stops temperature range [Delta] T _ON fixing roller temperature range during operation

Claims (9)

A first heating unit that heats the central portion of the fixing roller in response to power supply from the driving power source, a second heating unit that heats both ends of the fixing roller, and a first temperature that detects the temperature of the central portion of the fixing roller. Temperature detection means, second temperature detection means for detecting the temperature of the end of the fixing roller, and the first and second detection temperatures according to the first and second detection temperatures detected by the first and second temperature detection means. A temperature control unit that controls the temperature of the fixing roller to a predetermined target value by independently controlling the two heating units;
The first and second temperature detecting means are arranged in different areas of the sheet passing area on the fixing roller that have equivalent responsiveness and are non-contact.
It is determined whether the difference between the first detected temperature detected by the first temperature detecting means and the second temperature detected temperature detected by the second temperature detecting means is greater than or equal to a predetermined temperature difference, and the predetermined temperature A first determination means for determining an abnormality when the difference is greater than or equal to,
Energization control means for stopping energization from the drive power source to the first and second heating means when it is determined that the first determination means is abnormal;
A fixing device comprising: A first heating unit that heats the central portion of the fixing roller in response to power supply from the driving power source, a second heating unit that heats both ends of the fixing roller, and a first temperature that detects the temperature of the central portion of the fixing roller. Temperature detection means, second temperature detection means for detecting the temperature of the end of the fixing roller, and the first and second detection temperatures according to the first and second detection temperatures detected by the first and second temperature detection means. A temperature control unit that controls the temperature of the fixing roller to a predetermined target value by independently controlling the two heating units;
The first and second temperature detecting means are arranged in different areas of the sheet passing area on the fixing roller that have equivalent responsiveness and are non-contact.
The first temperature detection means includes a first detection temperature sensor that detects infrared rays radiated from a central portion of the fixing roller, and a first compensation temperature sensor that detects an ambient temperature of the central portion of the fixing roller. ,
The second temperature detection means includes a second detection temperature sensor that detects infrared rays emitted from the end of the fixing roller, and a second compensation temperature sensor that detects the ambient temperature of the end of the fixing roller. ,
First calculating means for calculating a surface temperature of the center portion of the fixing roller based on a first detected temperature detected by the first detected temperature sensor and a first compensated temperature detected by the first compensated temperature sensor;
Second calculating means for calculating an end surface temperature of the fixing roller based on a second detected temperature detected by the second detected temperature sensor and a first compensated temperature detected by the second compensated temperature sensor;
First determination means for determining whether the first and second compensation temperatures detected by the first and second compensation temperature sensors are equal to or higher than a predetermined set temperature;
When it is determined by the first determination means that the temperature is equal to or higher than a predetermined set temperature, it is determined whether a difference between the center surface temperature and the end surface temperature is equal to or greater than a predetermined temperature difference. A second determination means for determining an abnormality,
Energization control means for stopping energization from the drive power source to the first and second heating means when it is determined as abnormal by the second determination means;
A fixing device comprising: Third determination means for determining whether the first and second compensation temperatures are equal to or lower than a predetermined set temperature, and when the first and second compensation temperatures are determined to be equal to or lower than the set temperature, the first A fourth determination means for determining whether or not a difference between the detected temperature and the second detected temperature is equal to or greater than a predetermined temperature difference;
The fixing device according to claim 2, wherein the energization control unit stops energization from the drive power source to the first and second heating units when the fourth determination unit determines that the abnormality is present. It is further determined whether or not a difference between the first compensation temperature and the second compensation temperature is equal to or greater than a predetermined temperature difference.
3. The fixing device according to claim 2, wherein the energization control unit stops energization from the drive power source to the first and second heating units when the fifth determination unit determines that the abnormality is present.   The temperature control means controls the hysteresis temperature so that the first and second detection temperatures, or the center surface temperature and the end surface temperature are within a predetermined temperature range with respect to a preset target temperature. The fixing device according to claim 1, wherein   The fixing device according to claim 5, wherein the temperature control unit controls the first and second heating units within a temperature range of 1 ° C. to 5 ° C. in a temperature range of the hysteresis temperature control. .   The fixing device according to claim 5, wherein the temperature control unit can change a temperature range of the hysteresis temperature control depending on whether or not the fixing roller is operating.   The fixing device according to claim 5, wherein the temperature control unit alternately controls ON / OFF of the first and second heating units.   The fixing device according to claim 1, wherein the first and second heating units are electromagnetic induction heaters.

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