JP2002372892A - Fixing device, malfunction detection method therefor, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of improving safety and detecting the temperature of a fixing body without contact, a malfunction detection method for the fixing device, and an image forming device. SOLUTION: A difference between the detected temperature value of an infrared detection thermister 1 and the detected temperature value of a temperature compensation thermister 2 is computed and the computed value is outputted. Based on a time change in the output computed value, it is detected whether the temperature of a fixing roller is increasing or not. Based on the result of the detection, it is determined whether the rise in the temperature of the fixing roller has continued for a predetermined time period or not. Based upon the result of the determination, it is determined whether the fixing device is in an abnormal state or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device, a method for detecting an abnormality thereof, and an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a fixing device provided in an image forming apparatus adopting an electrophotographic system or the like includes a thermosensitive element such as a thermistor as a temperature detecting method of a fixing roller as a fixing member. A contact temperature detecting method is generally used in which a sensor is brought into contact with the surface of a fixing roller to be heated, and the surface temperature of the sensor is detected based on the output state of the sensor.

In a fixing device using the above-mentioned contact temperature detecting method, when a problem occurs in temperature control due to some event, the output of the sensor is compared with a predetermined value, and the output of the sensor is determined. A safety device is used in which when the predetermined value is reached, the fixing device is determined to be abnormal and stops heating the fixing roller. Since the safety device in this case is simply constituted by a hardware circuit such as a comparator, unlike a control in which software such as a CPU is interposed, the safety device has high safety in which an uncontrollable state such as runaway cannot occur.

On the other hand, in the contact temperature detecting method, since the sensor is brought into direct contact with the fixing roller, the fixing roller is damaged, and the dirt accumulated in the flaw sticks to the transfer paper as a recording material or remains on the fixing roller. There is also a problem that the toner accumulates on the above-mentioned sensor and collapses when a large amount of toner is collected, thereby contaminating the transfer paper.

In view of the above, the use of a non-contact temperature sensor for detecting the temperature of the fixing roller without contacting the fixing roller has been studied in recent years. As one of the non-contact temperature sensors, an infrared absorbing film serving as an infrared absorbing member is used, and the temperature of the infrared absorbing film and the temperature of a holder serving as a holding member for holding the infrared absorbing film are measured by main temperature detecting means and sub temperature detecting means, respectively. There is a thermistor-type non-contact temperature sensor that measures the temperature of a fixing roller, which is an object to be measured, based on the relationship between the detection results of both thermistors by observing with a thermistor. The non-contact temperature sensor of this system has a merit that the structure is simple and the cost is low, and the problem that occurs in the contact type sensor by the above-described contact temperature detection method can be solved.

FIG. 9 is a block diagram showing an example of the configuration of a non-contact temperature sensor.

As shown in FIG. 9, the non-contact temperature sensor includes an infrared absorbing film (not shown) as an infrared absorbing member, an infrared detecting thermistor 1 as main temperature detecting means attached to the infrared absorbing film, and Holder (not shown) as a holding member for holding the infrared absorbing film
A temperature compensating thermistor 2, which is a sub-temperature detecting means, and resistors R1, R2 for pulling up the outputs of the infrared detecting thermistor 1 and the temperature compensating thermistor 2, respectively.
The system includes buffers 3 and 4, A / D converters 5 and 6, a CPU 7 serving as temperature estimating means, and a memory 8.

In the structure shown in FIG. 9, the infrared absorbing film is installed so as to be close to and opposed to the object to be measured, and the infrared absorbing film absorbs infrared rays emitted in accordance with the temperature of the object to be measured and raises the temperature. Is generated.

Since the thermistor changes its electric resistance depending on the temperature, the output of the infrared detecting thermistor 1 is
The divided voltage constituted by the pull-up resistor R1 is output according to the temperature of the infrared absorbing film. on the other hand,
Similarly, the temperature compensation thermistor 2 generates a voltage corresponding to the temperature of the holder at its output.

Further, the outputs of the infrared detecting thermistor 1 and the temperature compensating thermistor 2 are input to A / D converters 5 and 6 via buffers 3 and 4 respectively connected thereto. Is entered. The CPU 7 selects from the memory 8 temperature data corresponding to each combination from the input output data of the infrared detection thermistor 1 and the output data of the temperature compensation thermistor 2 and outputs the selected data as the detected temperature of the object to be measured.

[0011]

However, in the above-mentioned non-contact temperature sensor of the thermistor type, the temperature must be calculated via the CPU. There was a problem that safety could not be ensured.

Therefore, the present invention aims to improve safety,
It is an object of the present invention to provide a fixing device capable of detecting the temperature of a fixing member in a non-contact manner, a method for detecting an abnormality thereof, and an image forming apparatus.

[0013]

According to the present invention, the object is to fix a recording material carrying an unfixed image on the recording material by heating the recording material while contacting the recording material with the fixing member. An apparatus, comprising: an infrared absorbing member that absorbs infrared radiation emitted from a fixing member; a holding member that holds the infrared absorbing member; a main temperature detecting unit that detects a temperature of the infrared absorbing member; A sub-temperature detecting unit for detecting a temperature; and a temperature estimating unit for estimating and detecting the temperature of the fixing body based on a main detected temperature value of the main temperature detecting unit and a sub-detected temperature value of the sub-temperature detecting unit. A fixing device for calculating a difference between the main detected temperature value and the sub-temperature detected value and outputting the calculated value; Detect if it is Temperature rise detecting means, a duration determining means for determining whether or not the temperature rise state of the fixing body has continued for a predetermined time based on the detection result by the temperature rise detecting means; and This is achieved by the first invention including an abnormality determining unit that determines whether the fixing device is abnormal.

Further, according to the present invention, the above object is achieved in the first aspect, wherein the temperature rise detection means has a signal delay means for delaying and outputting a signal of an output operation value of the operation means,
The present invention is also achieved by the second invention in which it is configured to determine whether or not the fixing body is in a temperature rising state based on a difference between the output operation value and the output value of the signal delay unit and determine whether the fixing body is in a temperature rising state.

Further, according to the present application, the above object is achieved according to the first aspect, wherein the temperature rise detecting means has a signal differentiating means for differentiating and outputting a signal of an output calculated value of the calculating means,
The present invention is also attained by the third invention in which the apparatus is configured to determine whether or not the fixing body is in a temperature rising state based on the output value of the signal differentiating means and to detect the temperature.

According to the present application, the above object is achieved in the first aspect of the present invention in that the duration determining means integrates an output signal of the temperature rise detecting means and outputs the integrated signal. An integration value comparison unit that compares the output value with a preset integration reference value, and determines whether the temperature rise state of the fixing body has continued for a predetermined time based on a comparison result of the integration value comparison unit. The present invention is also achieved by the fourth invention.

Further, according to the present application, the above object is to provide a fixing device for fixing an unfixed image to the recording material by heating the recording material carrying the unfixed image while contacting the fixing material with the fixing member. An infrared absorbing member that absorbs infrared radiation emitted from the fixing member, a holding member that holds the infrared absorbing member, a main temperature detecting unit that detects a temperature of the infrared absorbing member, and detects a temperature of the holding member. Sub temperature detecting means;
The fixing device includes a temperature estimating unit that estimates and detects the temperature of the fixing body based on a main detection temperature value of the main temperature detection unit and a sub detection temperature value of the sub temperature detection unit. A fifth aspect of the invention includes a sub-temperature comparing unit that compares the set sub-temperature reference value with the set sub-temperature reference value, and a sub-abnormality determining unit that determines whether the fixing body is abnormal based on the comparison result of the sub-temperature comparing unit. It is also achieved by the invention.

Further, according to the present application, the above object is to provide a fixing device for fixing the unfixed image to the recording material by heating the recording material carrying the unfixed image while making contact with the fixing member. An infrared absorbing member that absorbs infrared radiation emitted from the fixing member, a holding member that holds the infrared absorbing member, a main temperature detecting unit that detects a temperature of the infrared absorbing member, and detects a temperature of the holding member. A fixing device comprising: a sub-temperature detecting unit; and a temperature estimating unit configured to estimate and detect the temperature of the fixing body based on a main detected temperature value of the main temperature detecting unit and a sub-detected temperature value of the sub-temperature detecting unit. Temperature range determining means for determining whether the main detected temperature value and the sub detected temperature value are outside a predetermined temperature value range, and the fixing member is abnormal based on the determination result of the temperature range determining means. Whether or not Also achieved by a sixth invention of and a temperature range abnormality determining means for.

Further, according to the present application, the above object is achieved according to the sixth aspect, in which the temperature range determining means includes a main level shifting means for shifting the level of the main detected temperature value, and an output of the main level shifting means. A main comparing unit that compares the sub-detected temperature value with the sub-detected temperature value, and determines whether the main detected temperature value and the sub-detected temperature value are outside a predetermined temperature value range based on the comparison result by the main comparing unit. This is also achieved by the seventh invention in which the determination is made.

According to the present application, the above object is achieved in the sixth or seventh aspect of the present invention in that the temperature range judging means comprises: a sub-level shift means for shifting the level of the sub-detected temperature value; A sub-comparison means for comparing the output of the shift means with the main detection temperature value, wherein the main detection temperature value and the sub-detection temperature value are outside a predetermined temperature value range based on the comparison result by the sub-comparison means. It is also attained by the eighth invention in which it is configured to determine whether or not.

Further, according to the present application, the above object is to provide a fixing device for fixing the unfixed image to the recording material by heating the recording material carrying the unfixed image while contacting the fixing material. An infrared absorbing member that absorbs infrared radiation emitted from the fixing member, a holding member that holds the infrared absorbing member, a main temperature detecting unit that detects a temperature of the infrared absorbing member, and detects a temperature of the holding member. A fixing device comprising: a sub-temperature detecting unit; and a temperature estimating unit configured to estimate and detect the temperature of the fixing body based on a main detected temperature value of the main temperature detecting unit and a sub-detected temperature value of the sub-temperature detecting unit. Calculating means for calculating the difference between the main detected temperature value and the sub-detected temperature value and outputting the calculated value; calculating comparing means for comparing an output calculated value of the calculating means with a predetermined calculation reference value; The operation comparing means Fixing body on the basis of the calculation results are also achieved by the ninth invention of and a temperature difference abnormality determining means that determines whether an abnormality.

Further, according to the present application, the above object is to provide a fixing device for fixing the unfixed image to the recording material by heating the recording material carrying the unfixed image while contacting the recording material with the fixing member. An infrared absorbing member that absorbs infrared radiation emitted from the fixing member, a holding member that holds the infrared absorbing member, a main temperature detecting unit that detects a temperature of the infrared absorbing member, and detects a temperature of the holding member. Sub temperature detecting means;
An abnormality detection method for a fixing device, comprising: a temperature estimating unit that estimates and detects a temperature of the fixing body based on a main detection temperature value of the main temperature detection unit and a sub detection temperature value of the sub temperature detection unit. A calculation step of repeatedly calculating the difference between the temperature value and the sub-detection temperature value at predetermined time intervals; and a comparison step of comparing a previous calculation result of the calculation step with a current calculation result. Based on the comparison result, the length of time during which the current comparison result is larger than the previous comparison result is counted, and when the count result reaches a preset count value, the fixing device is abnormal. This is also achieved by the tenth aspect of determining that there is.

Further, according to the present application, the above object is to provide a fixing device for fixing the unfixed image on the recording material by heating the recording material carrying the unfixed image while contacting the recording material with the fixing member. An infrared absorbing member that absorbs infrared radiation emitted from the fixing member, a holding member that holds the infrared absorbing member, a main temperature detecting unit that detects a temperature of the infrared absorbing member, and detects a temperature of the holding member. An abnormality of the fixing device, comprising: a sub-temperature detecting unit; and a temperature estimating unit that estimates and detects the temperature of the fixing body based on a main detected temperature value of the main temperature detecting unit and a sub-detected temperature value of the sub-temperature detecting unit. The detection method includes a calculation step of calculating a difference between a main detection temperature value and a sub detection temperature value, and a calculation result comparison step of comparing a calculation result of the calculation step with a preset value. Results based on the comparison result of the comparing step, fixing member is also achieved by the eleventh invention of determining whether an abnormality.

According to the present application, the object is to provide an image forming apparatus for recording an image formed by a series of image forming processes on a recording material. The present invention is also attained by a twelfth invention that includes the fixing device described above.

[0025]

Embodiments of the present invention will be described with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described.

FIG. 1 shows an example of an electrophotographic laser beam printer 101 suitably showing the image forming apparatus of the present embodiment.
FIG. 1 is a schematic cross-sectional view illustrating a schematic configuration of a printer (hereinafter, abbreviated as a printer 101).

The printer 101 forms an image on a sheet-like recording material P in accordance with image information provided from an image information providing device (not shown) such as a host computer provided outside the main body of the printer 101. This is an image forming apparatus in which a series of image forming processes of recording is performed according to a known electrophotographic method.

As shown in FIG. 1, the printer 101 includes a drum-shaped rotatable photosensitive member 102 serving as a latent image carrier, a developing device 103, and an exposure process corresponding to image information from an image information providing device. A laser scanner unit 105 (hereinafter, abbreviated as a scanner 105) for forming an electrostatic latent image corresponding to the image information on the outer peripheral surface of the photoconductor 102, and a roll for performing a transfer process on the recording material P A rotatable transfer member 106 and a fixing device 107 adapted to apply a fixing process to the recording material P after the transfer process by applying heat and pressure.

Next, a series of image forming processes in the printer 101 will be described.

First, the photosensitive member 102 is moved in the direction of arrow K1 by pressing a start button or the like (not shown) provided on the main body of the printer 101 to instruct the printer 101 to start a series of image forming processes. Rotational drive is started at a specified peripheral speed, and the outer peripheral surface of the photoconductor 102 is charged to a specified potential distribution by the charging roller 108 and the photoconductor 102, to which a specified bias is applied, slidingly contacting each other.

Next, the charged portion on the outer peripheral surface of the photosensitive member 102 is scanned and exposed by the scanner 105 in accordance with the image information from the image information providing device, so that an electrostatic latent image corresponding to the image information is obtained. Is formed in the above-described region, the electrostatic latent image is visualized as a developer image by the developer of the developing device 103, and a predetermined number of recording materials P can be stored and the main body of the printer 101 The image is transferred from the detachably supported cassette 111 to the recording material P conveyed at a predetermined timing or the like to a space formed between the photosensitive member 102 and the transfer member 106 by a rotatable paper feed roller 112 or the like. The developer image is transferred by the body 106.

Then, the recording material P on which the transfer processing has been performed is subjected to fixing processing by the fixing
The sheet is discharged to the outside of the apparatus by a discharge roller 113 rotatably supported by the main body 1 and is stacked on a tray 114 attached to one side of the main body, thereby completing a series of image forming processes. It will be.

Next, the fixing device 107 will be described in detail.

As shown in FIG. 1, the fixing device 107 includes a fixing roller 107a as a fixing body, a pressure roller 107b disposed in pressure contact with the fixing roller 107a, and a non-contact temperature sensor 107c. .

FIG. 2 is a diagram showing a schematic configuration of the non-contact temperature sensor 107c, and FIG. 3 is a configuration diagram of an abnormality detection circuit of the non-contact temperature sensor 107c according to the present invention in the present embodiment.

Non-contact temperature sensor 107c of this embodiment
As shown in FIG. 2 and FIG. 3, an infrared absorbing film 1a as an infrared absorbing member, a holder 2a as a holding member,
An infrared detecting thermistor 1 serving as a main temperature detecting means and a temperature compensating thermistor 2 serving as a sub-temperature detecting means are provided.

The non-contact temperature sensor 107c is
Pull-up resistors R1 and R2, buffers 3 and 4, differential amplifier 9 as arithmetic means, comparator 10, resistor Ra
To Rd, a duration determining means including a capacitor Cb, a resistor Re, and a comparator 11, a comparator 12 serving as a sub-temperature comparing means, and an abnormality determining means (see FIG. (Not shown), an auxiliary temperature abnormality determination means (not shown), and an abnormality detection circuit including resistors Rf to Rg, a capacitor Ca, diodes Da and Db, and the like. In FIG. 3, Vref
1 and Vref2 each indicate a preset reference voltage.

The infrared absorbing film 1a absorbs infrared rays emitted from the fixing roller 107a, which is an object to be measured, according to the temperature thereof, and raises the temperature according to the amount of the absorbed infrared rays.

The infrared detecting thermistor 1 is attached to the infrared absorbing film 1a and detects the temperature of the infrared absorbing film 1a.

The temperature compensation thermistor 2 is attached to a holder 2a for holding the infrared absorbing film 1a, and detects the temperature of the holder 2a.

The pull-up resistor R1 pulls up one end of the infrared detecting thermistor 1, and the pull-up resistor R2
One end of the temperature compensating thermistor 2 is pulled up.

The buffer 3 performs impedance conversion of a divided voltage signal composed of the pull-up resistor R 1 and the electric resistance of the infrared detecting thermistor 1, and the buffer 4 uses the pull-up resistor R 2 and the electric resistance of the temperature compensation thermistor 2. The configured divided voltage signal is subjected to impedance conversion.

The differential amplifier 9 calculates the difference between the output voltage from the buffer 3 and the output voltage from the buffer 4.

FIG. 4 is a diagram showing the change characteristics of the outputs of the infrared detecting thermistor 1 and the temperature compensating thermistor 2 when the temperature of the fixing roller 107a, which is the object to be measured, is increased in the above configuration.

As shown in FIG. 4, when the temperature of the object to be measured (fixing roller 107a) is rising, the output signal of the infrared detecting thermistor 1 falls relatively sharply, and the output of the temperature compensating thermistor 2 decreases. The signal is slightly delayed, and the signal is degraded in a manner following the signal. Therefore, while the difference between the two output signals tends to increase, the state where the temperature of the device under test rises continues.

Here, the operation of the non-contact temperature sensor 107c in the configuration shown in FIG. 3 will be described.

In the present embodiment, when the temperature of the object to be measured rises, the infrared absorbing film 1a absorbs infrared rays emitted from the object to be measured and causes a rise in temperature. The electric resistance of the thermistor 1 decreases. As a result, the infrared detection voltage input to the buffer 3 decreases and is input to the differential amplifier 9.

On the other hand, the holder 2a for holding the infrared absorbing film 1a itself rises in temperature due to the temperature rise of the object to be measured, and the electrical resistance of the temperature compensating thermistor 2 decreases in response to the temperature rise. . As a result, the temperature compensation signal input to the buffer 4 also decreases, and is input to a different end of the differential amplifier 9 from the above.

The differential amplifier 9 receives the operation of the input signal and calculates the difference between the signal based on the infrared detection voltage and the temperature compensation signal as follows. ΔV = (temperature compensation signal) − (infrared detection signal) However, the actual output needs to be biased.

The result of this operation is input to the (+) terminal of the comparator 10 via the resistors Ra and Rb, and the signal ΔV obtained by delaying the output ΔV of the differential amplifier 9 by signal delay means including the resistor Rc and the capacitor Ca. Is input to the (−) end of the comparator via the resistor Rd. Therefore, the output of the comparator 10 maintains the high impedance because the delayed signal input to the (-) terminal always has a lower value while the difference voltage ΔV is rising, and maintains the high impedance. A voltage level signal having a charging characteristic is input to the (+) terminal of the comparator 11, which is a means, by a signal integrating means including a pull-up resistor Re and a capacitor Cb.

Further, the output of the comparator 11 changes from a ground short-circuit state to a high impedance state until the signal input to the (+) terminal reaches the reference voltage Vref1, which is the integration reference value input to the (-) terminal. Switch to state. As a result, the operation of the comparator 11 is an operation of outputting a high level by the pull-up resistor Rf when the increasing tendency of ΔV is continued for a predetermined period.

Incidentally, the pull-down resistor R connected to the intermediate point between the resistors Ra and Rb is used to divide the output ΔV from the differential amplifier 9 to decrease it, thereby causing the comparator 10 to malfunction. To prevent That is, when the increasing tendency of ΔV exceeds a predetermined level determined by the resistances Ra and R, and furthermore, the resistance Rc and the capacitor Ca, the output of the comparator 10 becomes a high impedance state, and if it becomes lower than this, it becomes a ground short state.

On the other hand, the output of the comparator 12 for comparing the temperature compensation signal output from the buffer 4 with a predetermined reference voltage Vref2 is connected to a pull-up resistor Rg, and the output of the comparator 11 is Da. And an OR connection by a diode Db. Thereby, the holder 2a to which the temperature compensation thermistor 2 is attached
When the temperature exceeds a predetermined temperature defined by the Vref2, the diode-ORed output operates to output a high level regardless of the output state of the comparator 11.

Therefore, as described above, according to the configuration of the embodiment shown in FIG. 3, the temperature difference between the temperature of the infrared absorbing film and the temperature of the holder holding the infrared absorbing film is calculated. While an operation of outputting an error signal is performed when the rising tendency (that is, the temperature difference is increasing) continues for a predetermined period, the reference voltage Vre is output during this predetermined period.
Since it can be adjusted by the setting of f1, if this setting is set longer than the maximum time until the temperature of the fixing unit reaches the predetermined fixing temperature, depending on the output state of the error signal,
It is possible to detect a control abnormality of the fixing device.

Further, in addition to the above operation, a temperature compensation voltage from the temperature compensation thermistor and a predetermined reference voltage V
By comparing with the ref2, an error signal indicating that the temperature of the film holder has exceeded the predetermined temperature can be output. Therefore, the reference voltage Vref2 is set to a value at which the temperature of the fixing device exceeds the steady value. With this arrangement, it is possible to detect an abnormality in the temperature control of the fixing device in the same manner as described above.

By using the error signal described above,
If a circuit for interrupting the power supply to the fixing heater, which has been used conventionally, is configured, the safety circuit of the fixing device can be configured without using a control unit including software such as a CPU, so that it is difficult to avoid such a runaway of the CPU. It is possible to configure a safety device that operates reliably even in an abnormal state.

(Second Embodiment) Next, a second embodiment of the present invention will be described. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 5 is a diagram showing an example of the configuration of the abnormality detection circuit according to the present embodiment.

In the present embodiment, in the configuration of the first embodiment, the output of the differential amplifier 9 for calculating ΔV is passed through a differentiating circuit 13 as a signal differentiating means, and the increase duration of ΔV is determined from the result. Thus, an error signal is generated.

As shown in FIG. 5, the abnormality detecting circuit compares the output of the differentiating circuit 13 with a preset reference voltage Vref3, and outputs the output to ground short or high impedance according to the result. Is provided.

In FIG. 5, the operation up to the differential amplifier 9 is the same as in the first embodiment, and calculates and outputs the difference (ΔV) between the temperature compensation voltage and the infrared detection voltage. The output is input to the differentiating circuit 13, and the differentiating circuit 13 superimposes a bias on a voltage corresponding to the calculated slope of the rise and fall of ΔV and outputs the resulting signal as a differentiated signal. This output is input to the comparator 14 and compared with the reference voltage Vref3. This Vref3 is set to a voltage value at which the increasing tendency of ΔV can be reliably determined, whereby the increasing tendency of ΔV is determined. Switch the output to high impedance. As a result, the output signal of the comparator 14 gradually increases its level based on the characteristics of the time constant circuit formed by the pull-up resistor Re and the capacitor Cb, and the output signal of the comparator 14 is pulled as long as the high impedance of the output of the comparator 14 continues. It rises to the up voltage Vc.

In the subsequent operation, as in the first embodiment, when the signal based on the time constant characteristic exceeds the reference voltage Vref1, the output of the comparator 11 switches and outputs an error signal.

(Third Embodiment) Next, a third embodiment of the present invention will be described. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 6 is a block diagram showing the configuration of the temperature range determining means and the temperature range abnormality determining means of the fixing device of this embodiment.

This embodiment shows a configuration in which an error signal is output on the assumption that an abnormality has occurred in each thermistor.

In this embodiment, as shown in FIG. 6, the temperature range judging means and the temperature range abnormality judging means are constituted by the comparators 15, 16 and the resistors Rh to Rm.

As shown in FIG. 6, the infrared detection voltage from the buffer 3 is applied to the (-) input terminal of the comparator 15 as the main comparing means, as the main level shifting means constituted by the resistors Rh and Ri. The input is biased by the circuit, and the temperature compensation voltage from the buffer 4 is input to the (+) terminal.

In this configuration, when the temperature of the device under test is equivalent to the ambient temperature, the buffer 3 and the buffer 4
Are almost the same, so that the comparator 15
Is higher than that of the signal input to the (-) terminal by the amount of bias by the above-described level shift circuit. Therefore, the output of the comparator 15 in this state is a ground short state.

On the other hand, when the object to be measured is heated and the temperature starts to rise, the voltages of both the buffer 3 and the buffer 4 decrease. In this operation, the signal (infrared ray detection signal) of the buffer 3 is normally steeper, but the output of the comparator 15 is inverted in the range where both thermistors output normally under the above-mentioned adjustment of the bias amount. Not configured.

When the temperature compensating thermistor 2 fails in the open mode or when the infrared detecting thermistor 1 fails in the short mode, the (+) of the comparator 15
Since the signal input to the terminal has an extremely high value compared to the signal input to the (-) terminal, the output of the comparator 15 has a high impedance, and outputs a high-level error signal by the pull-up resistor R1. Becomes

Similarly, the temperature compensation voltage from the buffer 4 is biased by a level shift circuit as a sub-level shift means composed of a resistor Rj and a resistor Rk and input to the (-) terminal of a comparator 16 as a sub-comparison means. The infrared detection voltage from the buffer 3 is connected so as to be directly input to the (+) terminal of the comparator 16, and the resistances Rj, Rj and Rj of the level shift circuit are set so that the output of the comparator 16 does not become high impedance in the normal operation range. By setting Rk, for example, it is possible to detect an abnormal state such as when the infrared detection thermistor 1 fails in the open mode or when the temperature compensation thermistor 2 fails in the short mode, and output it as an error signal. .

FIG. 7 shows another configuration of the present embodiment.

In the configuration shown in FIG. 7, a differential amplifier circuit as a calculating means for calculating the difference between the infrared detection voltage and the temperature compensation voltage, and the output of the circuit is connected to two reference voltages set under the respective conditions. It comprises a comparator as two operation comparing means for comparing, and a pull-up resistor as a temperature highest judging means for pulling up the output of the comparator.

In this configuration, when the infrared detection voltage is extremely large with respect to the temperature compensation voltage, or conversely, when the temperature compensation voltage is extremely large with respect to the infrared detection voltage, one of the comparators inverts the output. , And an error signal. Therefore, in the same manner as described above, it is possible to determine a failure in the open / short mode of the infrared detection thermistor 1 and the temperature compensation thermistor 2 and output the abnormal state as an error signal.

Therefore, according to the above-described embodiment, since the abnormality of the temperature sensor itself can be reliably detected by a simple hardware circuit, the execution of the heater control based on the sensor signal in the abnormal state can be avoided, and the safety is high. The effect that the image forming apparatus can be provided is obtained.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the present embodiment, a case will be described in which the present invention similar to the above-described first to third embodiments is implemented by software control with a conventional hardware configuration.

FIG. 8 shows an example of a control flow according to this embodiment. Note that the flow shown in FIG. 8 is a subroutine executed by a timer interrupt set every second, for example.

When a timer interrupt occurs as described above,
First, the COUNTER is checked in S1, and if this is less than 1, it is determined that the operation is the first operation, and the process proceeds to S2.

At S2, the difference (ΔV1) between the temperature compensation voltage (V2) and the infrared detection voltage (V1) is calculated, and at S3, COUNTE is calculated.
Set R to 1 and once go through this routine.

In the second and subsequent timer interrupts, S1
In step S4, it is determined that the interrupt is the second or later interrupt by checking the COUNTER. In step S4, a new temperature compensation voltage (V
The difference (ΔV2) between 2) and the infrared detection voltage (V1) is calculated.

At S5, the magnitude relationship between ΔV1 and ΔV2 is confirmed. If ΔV2 is greater, the temperature compensation voltage (V
It is determined that the difference between 2) and the infrared detection voltage (V1) continues to increase, and the process proceeds to S6.

At S6, the COUNTER value is confirmed again, and it is determined whether or not the above-described tendency of the temperature difference to spread continues for a predetermined period. Here, if the predetermined period has been reached, it is determined that the heating by the heater has been continued for a predetermined time or longer, and it is determined that there is an abnormality. Execute If it is determined in S6 that the predetermined period has not been reached, in S8, .DELTA.V2 is replaced with .DELTA.V1, and in S9, the COUNTER is incremented, and the routine once exits. Further, when it is determined in S5 that the difference between the temperature compensation voltage (V2) and the infrared detection voltage (V1) is not wide, in S10, ΔV
After replacing 2 with ΔV1, COUNTER is set to 1 in S11, and the routine exits.

Therefore, according to the above-described control, the abnormality control of the heater operation can be detected only by installing the control software in the same circuit configuration for performing the temperature measurement, so that the safety function of the heater can be added simply and at low cost. There is. However, as described in other embodiments, when the CPU goes out of control, this control may not function properly, so that it is necessary to separately provide a safety device. That is, the present embodiment has the greatest advantage that the safety function can be added at low cost when the safety function is doubled or tripled.

[0086]

As described above, according to the first aspect of the present invention, the calculating means calculates the difference between the main detected temperature value and the sub detected temperature value and outputs the calculated value. The temperature rise detecting means detects whether or not the fixing member is in a temperature rising state based on a temporal change in the output calculation value of the calculating means, and the duration determining means determines whether the fixing member is in a temperature rising state. It is determined whether the temperature rise state of the fixing member has continued for a predetermined time based on the predetermined time, and the abnormality determination unit determines whether the fixing device is abnormal based on the determination result by the duration determination unit. Therefore, safety can be improved, and the temperature of the fixing member can be detected in a non-contact manner.

According to the second aspect of the present invention,
The calculating means calculates the difference between the main detected temperature value and the sub-temperature detected value and outputs the calculated value. The temperature rise detecting means calculates the difference between the output calculated value of the calculating means and the output value of the signal delay means. And determines whether the fixing member is in a temperature rising state based on the detection result.The duration determining means determines whether the temperature rising state of the fixing member has continued for a predetermined time based on the detection result by the temperature rising detecting means. And the abnormality determining means determines whether or not the fixing device is abnormal based on the result of the determination by the duration determining means. Temperature can be detected.

Further, according to the third invention of the present application, the calculating means calculates the difference between the main detected temperature value and the sub-temperature detected value and outputs the calculated value, and the temperature rise detecting means calculates Based on the output value of the signal differentiating means, it is determined whether or not the fixing body is in a temperature rising state, and the temperature is determined by the duration determining means. It is determined whether or not the fixing time has continued, and the abnormality determining means determines whether or not the fixing device is abnormal based on the result of the determination by the continuous time determining means. The temperature of the fixing member can be detected in a non-contact manner.

According to the fourth invention of the present application,
The calculating means calculates the difference between the main detected temperature value and the sub-temperature detected value and outputs the calculated value, and the temperature rise detecting means sets the fixing member based on a temporal change in the output calculated value of the calculating means. Detects whether or not the temperature is rising, and the duration determining means
Abnormality determining means for determining whether or not the temperature rising state of the fixing member has continued for a predetermined time based on a result of comparison between the output value of the signal integrating means by the integrated value comparing means and a preset integration reference value; Since it is determined whether or not the fixing device is abnormal based on the determination result by the time determination unit, safety can be improved and the temperature of the fixing body can be detected in a non-contact manner.

Further, according to the fifth invention of the present application, the sub-temperature comparing means compares the sub-detected temperature value with a preset sub-temperature reference value, and Since it is determined whether or not the fixing member is abnormal based on the comparison result of the comparing means, safety can be improved and the temperature of the fixing member can be detected in a non-contact manner.

Further, according to the sixth invention of the present application,
The temperature range determining means determines whether the main detection temperature value and the sub-detection temperature value are outside a predetermined temperature value range set in advance, and the temperature range abnormality determining means determines whether the temperature Therefore, it is possible to improve the safety and detect the temperature of the fixing member in a non-contact manner.

Further, according to the seventh aspect of the present invention, the temperature range judging means determines the main detected temperature value and the sub detected temperature value based on the comparison result between the output of the main level shift means by the main comparing means and the sub detected temperature value. It is determined whether the detected temperature value is outside a predetermined temperature range.The main detection temperature value and the sub-detection temperature value are outside a predetermined temperature range. The temperature range abnormality determining means determines whether or not the fixing body is abnormal based on the determination result of the temperature range determining means. Temperature can be detected.

According to the eighth invention of the present application,
The temperature range determination means determines whether the main detection temperature value and the sub detection temperature value are outside a predetermined temperature value range based on the comparison result between the output of the sub level shift means and the main detection temperature value by the sub comparison means. Whether the temperature range abnormality determination means,
Since it is determined whether or not the fixing body is abnormal based on the result of the determination by the temperature range determining means, it is possible to improve safety and detect the temperature of the fixing body without contact.

Further, according to the ninth aspect of the present invention, the calculating means calculates the difference between the main detected temperature value and the sub-detected temperature value and outputs the calculated value, and the calculating and comparing means calculates the difference. The output calculation value of the calculation means is compared with a predetermined calculation reference value, and the temperature difference abnormality determination means determines whether or not the fixing member is abnormal based on the calculation result of the calculation comparison means. Therefore, the safety can be improved, and the temperature of the fixing member can be detected in a non-contact manner.

According to the tenth aspect of the present invention,
In a calculation step, a difference between the main detection temperature value and the sub detection temperature value is repeatedly calculated at predetermined time intervals, and in a comparison step, a previous calculation result of the calculation step is compared with a current calculation result, and the comparison step is performed. Counting the length of time during which the current comparison result is greater than the previous comparison result based on the comparison result, and if the count result reaches a preset count value, the fixing device malfunctions. Therefore, it is possible to improve the safety and detect the temperature of the fixing member without contact.

Further, according to the eleventh aspect of the present invention, the difference between the main detection temperature value and the sub detection temperature value is calculated in the calculation step, and the calculation result in the calculation step is calculated in the calculation result comparison step. Is compared with a preset value, and it is determined whether or not the fixing member is abnormal based on the comparison result in the above calculation result comparing step. Can be detected.

Further, according to the twelfth aspect of the present invention, it is determined whether or not the fixing device is abnormal based on the main detected temperature value and the sub temperature detected value.
It is possible to improve the safety and detect the temperature of the fixing member without contact.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of a non-contact temperature sensor section of a fixing device provided in the image forming apparatus of FIG. 1;

FIG. 3 is a diagram illustrating a configuration for detecting an abnormality of the fixing device according to the first embodiment of the present invention.

FIG. 4 is a diagram for explaining a relationship between a detection output value of a main temperature detection unit and a detection output value of a sub-temperature detection unit according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration for detecting an abnormality of a fixing device according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of a configuration for detecting an abnormality of a fixing device according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating another example of a configuration for detecting an abnormality of a fixing device according to a third embodiment of the present invention.

FIG. 8 is a flowchart for explaining abnormality detection of a fixing device according to a fourth embodiment of the present invention.

FIG. 9 is a diagram illustrating a configuration for detecting an abnormality of a conventional fixing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Infrared detection thermistor (main temperature detection sensor) 1a Infrared absorption film (infrared absorption film) 2 Temperature compensation thermistor (sub temperature detection sensor) 2a Holder (holding member) 9 Differential amplifier (calculation means) 13 Differentiation circuit (signal differentiation means) 101 Electrophotographic laser beam printer (image forming apparatus) 107 Fixing device 107a Fixing roller (fixing device) P Recording material

Claims (12)

[Claims] 1. A fixing device for fixing an unfixed image on a recording material by heating a recording material carrying the unfixed image while contacting the recording material with the fixing member, wherein the fixing device absorbs infrared rays radiated from the fixing member. An infrared absorbing member, a holding member for holding the infrared absorbing member, a main temperature detecting means for detecting the temperature of the infrared absorbing member, a sub temperature detecting means for detecting the temperature of the holding member, and the main temperature detecting And a temperature estimating means for estimating and detecting the temperature of the fixing body based on the main detected temperature value of the means and the sub detected temperature value of the sub temperature detecting means. Calculating means for calculating the difference between the two, and outputting the calculated value; temperature rise detecting means for detecting whether the fixing member is in a temperature rise state based on a temporal change in the output calculated value of the calculation means; The temperature rise detection means Duration determining means for determining whether the temperature rise state of the fixing body has continued for a predetermined time based on the detection result, and determining whether the fixing device is abnormal based on the determination result by the duration determining means. A fixing device comprising: an abnormality determining unit. 2. The temperature rise detecting means has signal delay means for delaying and outputting a signal of an output operation value of the operation means,
2. The fixing device according to claim 1, wherein the fixing device is configured to determine whether or not the temperature of the fixing body is in an elevated state based on a difference between the output calculation value and the output value of the signal delay unit. . 3. The temperature rise detecting means has a signal differentiating means for differentiating and outputting a signal of an output calculation value of the calculating means, and based on an output value of the signal differentiating means, whether the fixing body is in a temperature rising state. The fixing device according to claim 1, wherein the fixing device is configured to determine whether or not to perform the detection. 4. A continuation time discriminating means, comprising: a signal integrating means for integrating and outputting an output signal of the temperature rise detecting means; and an integrated value comparing means for comparing an output value of the signal integrating means with a preset integration reference value. Means for judging whether or not the temperature rise state of the fixing member has continued for a predetermined time based on a comparison result of the integral value comparing means.
3. The fixing device according to claim 1. 5. A fixing device for fixing an unfixed image to the recording material by heating a recording material carrying the unfixed image while contacting the recording material with the fixing member, wherein the fixing device absorbs infrared rays radiated from the fixing member. An infrared absorbing member, a holding member for holding the infrared absorbing member, a main temperature detecting means for detecting the temperature of the infrared absorbing member, a sub temperature detecting means for detecting the temperature of the holding member, and the main temperature detecting The fixing device includes a temperature estimating means for estimating and detecting the temperature of the fixing body based on a main detection temperature value of the means and a sub detection temperature value of the sub temperature detection means. A fixing device comprising: a sub-temperature comparing unit that compares a temperature reference value; and a sub-abnormality determining unit that determines whether the fixing body is abnormal based on a comparison result of the sub-temperature comparing unit. 6. A fixing device for fixing an unfixed image on a recording material by heating a recording material carrying the unfixed image while contacting the recording material with the fixing member, wherein the fixing device absorbs infrared rays radiated from the fixing member. An infrared absorbing member, a holding member for holding the infrared absorbing member, a main temperature detecting means for detecting the temperature of the infrared absorbing member, a sub temperature detecting means for detecting the temperature of the holding member, and the main temperature detecting A fixing device provided with a temperature estimating means for estimating and detecting the temperature of the fixing member based on a main detected temperature value of the means and a sub detected temperature value of the sub temperature detecting means; Temperature range judging means for judging whether the temperature is outside a predetermined temperature value range set in advance, and temperature range abnormality judging for judging whether the fixing member is abnormal based on the judgment result of the temperature range judging means. With means A fixing device. 7. The temperature range judging means has main level shifting means for shifting the level of the main detected temperature value, and main comparing means for comparing the output of the main level shifting means with the sub detected temperature value, 7. The apparatus according to claim 6, wherein the main detection means is configured to determine whether the main detection temperature value and the sub detection temperature value are outside a predetermined temperature value range based on a comparison result. Fixing device. 8. The temperature range judging means has a sub-level shift means for shifting the level of the sub-detection temperature value, and a sub-comparison means for comparing the output of the sub-level shift means with the main detection temperature value, 7. The system according to claim 6, wherein the main detection temperature value and the sub detection temperature value are determined to be out of a predetermined temperature value range based on a comparison result by the sub comparison means. Item 8. The fixing device according to Item 7. 9. A fixing device for fixing an unfixed image to the recording material by heating a recording material carrying the unfixed image while contacting the recording material with the fixing member, wherein the fixing device absorbs infrared rays radiated from the fixing member. An infrared absorbing member, a holding member for holding the infrared absorbing member, a main temperature detecting means for detecting the temperature of the infrared absorbing member, a sub temperature detecting means for detecting the temperature of the holding member, and the main temperature detecting A fixing device provided with a temperature estimating means for estimating and detecting the temperature of the fixing member based on a main detected temperature value of the means and a sub detected temperature value of the sub temperature detecting means; Computing means for computing the difference between the two, and outputting the computed value; computing means for comparing the computed value output from the computing means with a preset computation reference value; and fixing based on the computation result of the computation comparing means. Abnormal body A fixing device for determining whether or not the temperature difference is abnormal. 10. A fixing device for fixing an unfixed image to the recording material by heating a recording material carrying the unfixed image while contacting the recording material with the fixing member, wherein the fixing device absorbs infrared rays radiated from the fixing member. An infrared absorbing member, a holding member for holding the infrared absorbing member, a main temperature detecting means for detecting the temperature of the infrared absorbing member, a sub temperature detecting means for detecting the temperature of the holding member, and the main temperature detecting A fixing device having a temperature estimating means for estimating and detecting the temperature of the fixing member based on a main detected temperature value of the fixing means and a sub detected temperature value of the sub temperature detecting means. A calculating step of repeatedly calculating a difference from the detected temperature value at predetermined time intervals; and a comparing step of comparing a previous calculation result of the calculation step with a current calculation result. Based on the comparison result, the length of time during which the current comparison result is greater than the previous comparison result is counted, and when the count result reaches a preset count value, the fixing device is abnormal. A method for detecting an abnormality of a fixing device, characterized by determining that there is a fixing device. 11. A fixing device for fixing an unfixed image to the recording material by heating a recording material carrying the unfixed image while making contact with the fixing member, wherein the fixing device absorbs infrared rays emitted from the fixing member. An infrared absorbing member, a holding member for holding the infrared absorbing member, a main temperature detecting means for detecting the temperature of the infrared absorbing member, a sub temperature detecting means for detecting the temperature of the holding member, and the main temperature detecting A fixing device having a temperature estimating means for estimating and detecting the temperature of the fixing member based on a main detected temperature value of the fixing means and a sub detected temperature value of the sub temperature detecting means. A calculating step of calculating a difference from the detected temperature value; and a calculating result comparing step of comparing a calculating result of the calculating step with a preset value. A method for detecting an abnormality in a fixing device, comprising: determining whether an abnormality has occurred in a fixing body based on the following. 12. An image forming apparatus for recording an image formed by a series of image forming processes on a recording material,
An image forming apparatus comprising the fixing device according to claim 1.