JP2023183799A - Non-contact type temperature measurement device and image formation apparatus having the same - Google Patents

Abstract

To provide a non-contact type temperature measurement device which can effectively prevent erroneous offset correction from being performed by false recognition in a case where offset correction should not be performed like a case where a measurement object is heated for a short time at correction timing at which a prescribed offset correction condition may be established, and provide an image formation apparatus having the same.SOLUTION: A non-contact type temperature measurement device 300 is configured to perform offset correction under a prescribed offset correction condition for performing offset correction, uses a detection temperature Ts detected by using a detection temperature detection element 75s as the offset correction condition, and performs offset correction when the detection temperature Ts detected by using the detection temperature detection element 75s is equal to or less than a prescribed threshold Th.SELECTED DRAWING: Figure 7A

Description

The present disclosure relates to a non-contact temperature measurement device that measures the temperature of a measurement target without contact, and an image forming device such as a copying machine, a multifunction device, a printer, and a facsimile device equipped with the same.

A non-contact temperature measuring device that measures the temperature of an object while being separated from the object includes, for example, a temperature sensing element (such as a sensor) that detects the temperature of the object without contact. Some devices have a non-contact temperature sensor that includes a compensating temperature sensing element (for example, a compensating thermistor) that detects the environmental temperature (the temperature of the surrounding atmosphere that is not affected by heat from the object to be measured).

Such a non-contact temperature measuring device detects the object to be measured based on the change in the output of the temperature sensing element for detection according to the measured temperature of the object to be measured and the change in the output of the temperature sensing element for compensation according to the environmental temperature. It is possible to measure temperature without contact and is widely used.

FIG. 8A is a three-sided view showing an example of a non-contact temperature sensor 75 including a detection temperature detection element 75s and a compensation temperature detection element 75c. FIG. 8B is a cross-sectional view showing the detection temperature sensing element 75s and the compensation temperature sensing element 75c in the non-contact temperature sensor 75 shown in FIG. 8A.

As shown in FIGS. 8A and 8B, in the non-contact temperature sensor 75, the temperature detection element 75s detects radiant heat from the measurement target 400 due to infrared IR, and the temperature sensor 75 detects the radiant heat by infrared IR from the measurement target 400, and The environmental temperature (surrounding atmospheric temperature) is detected by the provided compensation temperature sensing element 75c.

The measured temperature T of the object to be measured 400 requires various temperature corrections depending on the environmental temperature around the temperature sensing element 75s at the time of measurement of the detected temperature Ts detected using the temperature sensing element 75s. be. Specifically, the measured temperature T is calculated based on the physical law of radiant heat and the actual measurement based on the detected temperature Ts detected using the detection temperature detection element 75s and the environmental temperature (compensation temperature Tc) detected using the compensation temperature detection element 75c. It can be determined by converting using a conversion formula and/or conversion table or other conversion means according to the value. For example, in a non-contact type temperature measuring device, the measurement temperature T of the measurement target 400 is measured as follows. That is, first, the detection output (detection voltage converted from the resistance value of the thermistor) from the temperature detection element 75s corresponding to the measured temperature T of the measurement object 400 and the compensation corresponding to the compensation temperature Tc of the measurement object 400 are determined. The compensation output (compensation voltage converted from the resistance value of the thermistor) from the temperature sensing element 75c is obtained, and the difference between these outputs (voltage difference) is determined. Next, the obtained output difference and compensation output analog signals are converted into digital data by an AD converter (not shown). Next, the measured temperature T of the measurement object 400 is measured by performing predetermined arithmetic processing using the output difference and the compensation output converted into digital data.

Regarding this, in an image forming apparatus equipped with a fixing device that has a fixing member (for example, a fixing member such as a fixing belt, a heating roller, or a fixing roller) for heating and fixing an unfixed toner image on a sheet, a non-contact temperature Further explanation will be given by taking as an example a case where the measurement temperature T of the fixing member is measured by a measuring device.

In recent image forming apparatuses, the speed at which the temperature of the fixing member is increased has increased due to the ability to heat up quickly due to a shortened warm-up time, and a high-speed response of a non-contact temperature measuring device is required. High-speed response of a non-contact temperature measuring device is achieved mainly by downsizing the sensing element. In particular, the output difference (voltage difference) tends to become smaller. Therefore, in order to accurately measure the measured temperature T of the measurement target 400 from a small output difference, an operational amplifier is usually used that increases the number of AD conversion bits and amplifies the output difference.

By the way, operational amplifiers have their own offset value (offset voltage), which has been a cause of errors in the differential output obtained by amplifying the output difference in the operational amplifier.

<Relationship between operational amplifier differential input and output>
FIG. 9A is a graph showing an example of the relationship between the differential input (input voltage), ideal output (ideal voltage), and actual output (output voltage) of the operational amplifier. In FIG. 9A, the gain of the operational amplifier is 5 (5 times amplification), and the offset voltage is 100 mV (offset voltage is 20 mV when the gain is 1).

As shown in FIG. 9A, operational amplifiers have an inherent offset voltage. For example, if the voltage difference is amplified by a gain of 5 (5 times), the offset voltage will also be amplified by 5 times. In this example, when the offset voltage is 20 mV, the output voltage=(input voltage+offset voltage 20 mV)×5, and the offset voltage of 100 mV is added to the output voltage.

Here, although the designer can confirm the rated value (maximum value) of the offset value (offset voltage) from the data sheet of the operational amplifier, etc., the offset value differs for each operational amplifier. Furthermore, since the offset value of the operational amplifier may change due to environmental changes or changes over time, it is preferable to repeatedly perform offset correction at correction times when predetermined offset correction conditions for performing offset correction can be satisfied.

<Relationship between operational amplifier differential input and output>
FIG. 9B is a chart showing an example of the relationship between the compensation output (compensation voltage), the differential output (differential voltage), and the measured temperature when the compensation temperature Tc is 25° C. Figure 9B shows the differential voltage of an ideal operational amplifier (offset voltage is 0 mV) and the differential voltage of an actual operational amplifier (offset voltage before amplification is 20 mV) with an offset voltage of 100 mV (20 mV x gain = 5) added. ing. It also shows a temperature error between the measured temperature of the object 400 measured using the ideal operational amplifier and the measured temperature of the object 400 measured using the actual operational amplifier.

Note that although FIG. 9B shows an example when the compensation temperature Tc is 25° C., the offset value (offset voltage) does not change even if the compensation temperature Tc changes.

In this way, in the operational amplifier, the offset value (offset voltage) needs to be offset corrected when measuring the measured temperature T of the measurement target 400.

In this regard, the offset correction can be performed as follows, using the differential output in the heat source non-operating state where the heat source (not shown) that heats the measurement target 400 is not operating as the offset correction value. .

That is, the detection temperature sensing element 75s and the compensation temperature sensing element 75c are mounted in close positions on the board, or those with similar element characteristics are selected, so that they have the same temperature characteristics. ing. Therefore, originally, when the detection temperature detection element 75s and the compensation temperature detection element 75c detect the same temperature of the measurement object 400, the differential output becomes 0.

Generally, the offset voltage is constantly added to the output voltage regardless of the input voltage. The differential voltage (see * in FIG. 9B) when the environmental temperature (compensation temperature Tc) and the measured temperature T are the same indicates the offset voltage itself.

From this point of view, the correction timing at which the predetermined offset correction conditions can be satisfied is the initial state when the detection temperature sensing element 75s and the compensation temperature sensing element 75c can detect the same temperature with respect to the measurement target 400. In other words, when the heat source is not operating (specifically, when the power switch is turned on and power is supplied but the heat source is not operating), the differential output is measured as the offset correction value. The acquired measurement offset correction value is considered as the offset correction value of the operational amplifier, and the offset correction value when the heat source is not in operation is subtracted from the differential output during measurement of the measurement object 400 to cancel the influence of the offset value. (For example, see Patent Document 1).

The predetermined offset correction condition, that is, the condition necessary to obtain the offset correction value, is that the measurement target 400 (for example, a fixing member such as a fixing belt, a heating roller, and a fixing roller) and the non-contact temperature sensor 75 must have the same temperature. Therefore, it is necessary that the heat source (for example, a heater lamp) is in a non-operating state.

Conventionally, when the heat source is inactive, for example, an edge temperature sensor (sheet non-conveyance area) provided at the edge of the measurement target 400 (sheet non-conveyance area in a fixing member such as a fixing belt, heating roller, fixing roller, etc.) has been used. The edge temperature detected by the edge temperature sensor 74 is set as the offset correction condition, and the offset correction is performed when the edge temperature detected by the edge temperature sensor 74 is below a predetermined threshold (specifically, 30°C). I was going.

Japanese Patent Application Publication No. 2015-4758

However, when the heat source (heater lamp) generates heat (after the image forming device's power switch is turned on and the heat source is turned on), the heat source immediately stops generating heat (the image forming device's power switch is turned off), etc. When the object 400 is heated for only a short period of time, the temperature in the heating region of the object 400 increases because the object 400 to be measured is heated only for a short period of time, but the temperature near the boundary of the heating region is not heated. Because the amount is small and the temperature becomes difficult to rise due to heat transfer to the edge of the object to be measured 400, the temperature at the edge of the object to be measured 400 does not rise, and as a result, the edge temperature sensor Offset correction is performed when the edge temperature detected by the (temperature sensor for detecting sheet non-conveying area) is below the threshold of the offset correction condition (specifically 30 degrees Celsius) and when the heat source is inactive, which is the correction time. It ends up. That is, the compensation temperature Tc detected using the compensation temperature detection element 75c hardly rises due to the short heating time; 75s, and an output difference (voltage difference) occurs between the compensation output from the compensation temperature detection element 75c and the detection output from the detection temperature detection element 75s due to heating. A problem with non-contact temperature measurement devices is that they mistakenly recognize this output difference as an offset value (offset voltage), and incorrectly perform offset correction even though offset correction should not be performed. .

Therefore, the present disclosure prevents incorrect offset correction from being performed due to erroneous recognition when offset correction should not be performed, such as when the measurement target is heated for a short time at a correction time when predetermined offset correction conditions can be satisfied. An object of the present invention is to provide a non-contact temperature measuring device that can effectively prevent the above-mentioned problems, and an image forming apparatus equipped with the same.

In order to solve the above problems, a temperature measuring device according to the present disclosure includes a temperature sensing element for sensing the measured temperature of a measurement object in a non-contact manner and a temperature sensing element for compensation that senses the environmental temperature. The offset included in the differential output obtained by amplifying the output difference by the operational amplifier includes a temperature sensor and an operational amplifier that amplifies the output difference between the output of the temperature sensing element for detection and the output of the temperature sensing element for compensation. A non-contact temperature measuring device that measures a value and performs offset correction to remove the offset from the differential output based on the measured offset value, the device comprising: a predetermined offset correction for performing the offset correction; The offset correction is performed when the offset correction condition is set to the offset correction condition, and the detected temperature detected using the temperature sensing element is set as the offset correction condition. It is characterized in that the offset correction is performed when is below a predetermined threshold value.

Further, an image forming apparatus according to the present disclosure includes the temperature measuring device according to the present disclosure, and a fixing device having a fixing member for heating and fixing an unfixed toner image to a sheet, and the measurement target is a temperature measuring device according to the present disclosure. It is characterized by being a member.

According to the present disclosure, it is possible to prevent erroneously performing offset correction due to misrecognition when offset correction should not be performed, such as when the object to be measured is heated for a short time at a correction time when predetermined offset correction conditions can be satisfied. This makes it possible to effectively prevent this.

1 is a schematic cross-sectional view of an image forming apparatus including a non-contact temperature measuring device according to an embodiment of the present disclosure, viewed from the front. 2 is a schematic cross-sectional view showing a fixing device in the image forming apparatus shown in FIG. 1. FIG. A perspective view of a pressure roller, a fixing belt, a heat source, an edge temperature sensor, a first non-contact temperature sensor and a second non-contact temperature sensor in a non-contact temperature sensor, a fixing roller, and a heating roller in a fixing device, viewed diagonally from above. It is a diagram. FIG. 2 is a schematic block diagram showing a control configuration for measuring an object to be measured. It is a schematic diagram which shows the positional relationship of the edge temperature sensor, the 1st non-contact temperature sensor, and the 2nd non-contact temperature sensor in a non-contact temperature sensor with respect to a measurement target. FIG. 2 is a circuit diagram illustrating a temperature measurement circuit showing a non-contact temperature sensor electrically connected to an operational amplifier. 7 is a flowchart showing the first half of an example of control operation for offset correction according to the present embodiment. 7 is a flowchart illustrating an example of an intermediate portion of an example of control operation for offset correction according to the present embodiment. 7 is a flowchart showing another example of the intermediate portion of the example of the control operation for offset correction according to the present embodiment. 7 is a flowchart showing the second half of an example of control operation for offset correction according to the present embodiment. FIG. 3 is a three-sided view showing an example of a non-contact temperature sensor including a temperature sensing element for detection and a temperature sensing element for compensation. 8A is a cross-sectional view showing a detection temperature sensing element and a compensation temperature sensing element portion in the non-contact temperature sensor shown in FIG. 8A. FIG. It is a graph which shows an example of the relationship between the differential input of an operational amplifier, an ideal output, and an actual output. It is a chart showing an example of the relationship between compensation output and differential output and measured temperature when compensation temperature is 25°C.

Embodiments according to the present disclosure will be described below with reference to the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 including a non-contact temperature measuring device 300 according to an embodiment of the present disclosure, viewed from the front. In addition, in the figure, the code|symbol X has shown the width direction (depth direction), the code|symbol Y has shown the left-right direction Y orthogonal to the width direction X, and the code|symbol Z has shown the up-down direction.

The image forming apparatus 100 shown in FIG. 1 prints a monochrome image on a sheet P such as recording paper using an electrophotographic method according to image data read by an image reading device 10 or image data transmitted from the outside. This is an image forming apparatus that forms images. Note that the image forming apparatus 100 may be a color image forming apparatus that forms multicolor and monochrome images.

The image forming apparatus 100 includes an image reading apparatus 10 and an image forming apparatus main body 110, and the image forming apparatus main body 110 is provided with an image forming section 101 and a sheet conveying system 102.

The image forming section 101 includes an exposure device 1 (exposure unit), a development device 2 (development unit), a photoconductor drum 3, a photoconductor cleaning device 4, a charging device 5, a transfer device 6 (transfer unit), and a fixing device 7 (fixing unit). unit). Further, the sheet conveyance system 102 includes a paper feed tray 8 and a discharge tray 9.

A document placement glass 11 and a document reading glass 12 are provided at the top of the image forming apparatus main body 110, and an image for reading an image of a document (not shown) is provided at the bottom of the document placement glass 11 and document reading glass 12. A reading device 10 is provided. The document placement glass 11 is a document placement table on which a document is placed. Further, a document conveying device 13 is arranged above the document placing glass 11 and the document reading glass 12. The document reading glass 12 is provided at a position to read the document conveyed by the document conveyance device 13. The image of the document read by the image reading device 10 is sent as image data to the image forming device main body 110, and an image formed based on the image data is formed (printed) on the sheet P in the image forming device main body 110. .

In the image forming apparatus 100, when performing image formation (printing), a sheet P is supplied from the paper feed tray 8, and the sheet P is conveyed to the registration rollers 15 by the conveyance roller 14a provided along the sheet conveyance path S. Next, the sheet P is conveyed at a timing to align the sheet P and the toner image on the photoreceptor drum 3, and the toner image on the photoreceptor drum 3 is transferred onto the sheet P by the transfer device 6. Thereafter, the unfixed toner on the sheet P is melted and fixed by heat by the fixing device 7, and is discharged onto the discharge tray 9 via the conveyance rollers 14b to 14b and the discharge roller 16a. In addition, in the image forming apparatus 100, when performing image formation (printing) not only on the front side of the sheet P but also on the back side, the sheet P is conveyed in the opposite direction from the discharge roller 16b to the reversing path Sr, and the front and back sides of the sheet P are conveyed in the opposite direction. The toner image is reversed and guided to the registration rollers 15 again, a toner image is fixed on the back side of the sheet P in the same manner as on the front side of the sheet P, and the toner image is ejected to the ejection tray 9. In this way, image forming apparatus 100 completes a series of printing operations. Note that the sheet P is conveyed along the sheet conveyance path S in the rotational axis direction (width direction X) of the photoreceptor drum 3 with the center of the image forming apparatus body 110 as a reference (center reference).

<Fixing device>
FIG. 2 is a schematic cross-sectional view showing the fixing device 7 in the image forming apparatus 100 shown in FIG. FIG. 3 shows a pressure roller 71, a fixing belt 72, a heat source 73, an edge temperature sensor 74, a first non-contact temperature sensor 751 and a second non-contact temperature sensor 752 in a non-contact temperature sensor 75, in the fixing device 7, FIG. 7 is a perspective view of a fixing roller 76 and a heating roller 77 viewed diagonally from above. FIG. 4 is a schematic block diagram showing a control configuration for measuring the measurement object 400 (72). FIG. 5 is a schematic diagram showing the positional relationship of the end temperature sensor 74, the first non-contact temperature sensor 751, and the second non-contact temperature sensor 752 in the non-contact temperature sensor 75 with respect to the measurement target 400 (72). . Further, FIG. 6 is a circuit diagram showing a temperature measurement circuit showing a non-contact temperature sensor 75 (751, 752) electrically connected to the operational amplifier 310.

Next, an example in which the non-contact temperature measuring device 300 according to the present embodiment is applied to a belt fixing type fixing device 7 will be described below.

Note that the display unit 51 is provided with an operation panel 50 on the front side (the front side in the width direction X) of the image reading device 10 of the image forming apparatus main body 110 shown in FIG.

(First embodiment)
The fixing device 7 includes a pressure roller 71 , a fixing belt 72 that is an example of the object to be measured 400 , a heat source 73 , an edge temperature sensor 74 , and a non-contact temperature sensor 75 . The image forming apparatus 100 further includes a control section 60 (see FIGS. 2 and 4). The pressure roller 71 is supported by a main body frame 70 (see FIG. 2) of the fixing device 7 so as to be rotatable around a rotation axis δ. The fixing belt 72 faces the pressure roller 71 and, together with the pressure roller 71, pinches and conveys the sheet P.

In this example, the fixing device 7 is of a belt fixing type, and a fixing belt 72 is wound around a plurality of rollers (in this example, a fixing roller 76 and a heating roller 77). The fixing belt 72 is configured to transfer heat from the heating roller 77 to the fixing roller 76 . The fixing belt 72 and the pressure roller 71 are rotated by the fixing roller 76 being rotationally driven. In the fixing device 7, the pressure roller 71 is pressed against the fixing roller 76 via the fixing belt 72, and the sheet P on which the unfixed toner image is formed is sandwiched between the fixing belt 72 and the pressure roller 71 and conveyed. It is supposed to be done.

As shown in FIG. 4, the control unit 60 includes a processing unit 60a consisting of a computer such as a CPU (Central Processing Unit), a non-volatile memory such as a ROM (Read Only Memory), and a volatile memory such as a RAM (Random Access Memory). The storage unit 60b includes a memory. The control unit 60 controls the operation of various components by having the processing unit 60a load a control program previously stored in the ROM of the storage unit 60b onto the RAM of the storage unit 60b and execute it. .

The display unit 51 displays predetermined display information. The display section 51 is electrically connected to the output system of the control section 60. Thereby, the control section 60 can display a message to be described later on the display section 51 by transmitting the display control data processed by the processing section 60a to the display section 51.

The non-contact temperature measuring device 300 includes a non-contact temperature sensor 75, an operational amplifier (310, 320), and a control section 60, and performs offset correction.

In the image forming apparatus 100, power to the control unit 60 is supplied from a power source E via a power switch 80. That is, when the power switch 80 is turned on, the control unit 60 is activated, and when the offset correction conditions described below are satisfied, offset correction is performed, and then the heat source 73 is activated and the measurement target 400 (in this example, The fixing belt 72) is heated, and the measurement temperature T of the measurement object 400 (72) is measured. On the other hand, if the offset correction conditions are not satisfied, the heat source 73 is activated without performing offset correction, the measurement object 400 (72) is heated, and the measured temperature T of the measurement object 400 (72) is measured. be done.

As shown in FIG. 5, the edge temperature sensor 74 is provided so as to be in contact with an edge region in the width direction The end temperature of the end region (α2) in the width direction X of the object to be measured 400 (72) is detected. The end temperature sensor 74 is electrically connected to the input system of the control unit 60 (see FIG. 4). Thereby, the end temperature sensor 74 can transmit a signal regarding the end temperature of the end region (α2) of the measurement object 400 (72) to the control unit 60.

The non-contact temperature sensor 75 (751, 752) is provided apart from the central region in the width direction , detects the temperature of the central region (α1) in the width direction X of the object to be measured 400 (72). The non-contact temperature sensor 75 (751, 752) is electrically connected to the input system of the control unit 60 (see FIG. 4). Thereby, the non-contact temperature sensor 75 (751, 752) can transmit a signal regarding the temperature of the central region (α1) of the measurement object 400 (72) to the control unit 60.

Specifically, the first non-contact temperature sensor 751 and the second non-contact temperature sensor 752 are provided apart from the center and one end of the sheet conveying area α1 of the object 400 (72) to be measured. The temperature at the center and one end of the object 400 (72) in the sheet conveyance area α1 is detected.

The non-contact temperature sensor 75 (751, 752) includes a detection temperature detection element 75s (detection temperature detection thermistor) and a compensation temperature detection element 75c (compensation temperature detection thermistor). Electrically connected to the input system. The temperature detection element 75s detects the measured temperature T of the measurement object 400 (72) in a non-contact manner. In this example, the compensation temperature detection element 75c detects the environmental temperature (compensation temperature Tc) in a non-contact manner. Note that the compensating temperature sensing element 75c may detect the environmental temperature while in contact with a member such as a housing that can measure the environmental temperature. Further, the configuration of the non-contact temperature sensor 75 is similar to the configuration shown in FIG. 8B described above, and the description thereof will be omitted here.

The operational amplifier 310 amplifies the output difference (voltage difference Vd) between the output of the detection temperature detection element 75s (detection voltage Vs) and the output of the compensation temperature detection element 75c (compensation voltage Vc) with a gain G1 (5 times). A differential output (differential voltage AVd) is output. The operational amplifier 320 outputs the compensation output (compensation voltage Vc) of the compensation temperature detection element 75c with a gain G2 (1x).

In offset correction, the non-contact temperature measuring device 300 measures the offset value F (see FIG. 4) included in the differential voltage AVd obtained by amplifying the voltage difference Vd with the operational amplifier 310, and calculates the offset value based on the measured offset value F. Then, offset correction is performed to remove the offset from the differential output AVd.

The non-contact temperature measuring device 300 further includes a DC power supply D, a detection resistor Rs, and a compensation resistor Rc.

In the temperature measurement circuit shown in FIG. 6, a detection temperature detection element 75s and a detection resistor Rs connected in series are connected to a DC power supply D, and a compensation temperature detection element 75c and a compensation temperature detection element 75c connected in series are similarly connected to a DC power supply D. A resistor Rc is connected to a DC power supply D. The differential operational amplifier 310 has a gain G1 of 5 (5 times amplification), and the compensation operational amplifier 320 has a gain G2 of 1 (1 times amplification). The connection C1 between the detection temperature detection element 75s and the detection resistor Rs is connected to one input terminal 311 of the differential operational amplifier 310, and the connection between the compensation temperature detection element 75c and the compensation resistor Rc. A connecting portion C2 between them is connected to the other input terminal 312 of the differential operational amplifier 310 and the input terminal 321 of the compensation operational amplifier 320.

In the non-contact temperature measuring device 300 according to the present embodiment, the measurement temperature T of the measurement object 400 (72) is first measured at a detection temperature corresponding to the measurement temperature T of the measurement object 400 (72). The detection voltage Vs from the sensing element 75s (voltage converted from the resistance value of the thermistor) and the compensation voltage Vc from the compensation temperature sensing element 75c (thermistor resistance value) corresponding to the compensation temperature Tc of the measurement object 400 (72) (voltage converted from ) and find the voltage difference between them Vd (=Vc-Vs). Specifically, since the detection temperature detection element 75s and the compensation temperature detection element 75c are elements whose resistance values change according to temperature changes, they are respectively a known detection resistor Rs and a known compensation resistor Rc. A detected voltage Vs and a compensation voltage Vc obtained by dividing the voltage are obtained.

Here, the voltage difference Vd between the compensation voltage Vc and the detection voltage Vs tends to become smaller as the response speed of the non-contact temperature sensor 75 becomes faster (see description of background art).

Therefore, in order to accurately detect the voltage difference Vd, the differential operational amplifier 310 is used to amplify the voltage difference Vd between the compensation voltage Vc and the detection voltage Vs to obtain the differential voltage AVd. Further, the compensation voltage Vc is inputted to the compensation operational amplifier 320 to obtain the compensation voltage Vc. The obtained differential voltage AVd and compensation voltage Vc are input to the control section 60. Here, the compensation operational amplifier 320 also has an offset voltage, but since the gain G2 of the compensation operational amplifier 320 is 1, the offset voltage of the compensation operational amplifier 320 is at a level that can be ignored.

Next, the control unit 60 takes in the compensation voltage Vc and the differential voltage AVd as analog values, and converts the analog signals of the compensation voltage Vc and the differential voltage AVd into digital data using an AD converter (not shown). Note that the detection voltage Vs can be determined from the compensation voltage Vc and the voltage difference Vd (Vs=Vc−AVd/gain G1 of the operational amplifier 310).

Next, by performing predetermined calculation processing using the differential output (differential voltage AVd) and compensation output (compensation voltage Vc) converted into digital data, the measured temperature T of the measurement object 400 (72) is measured. do. Specifically, since the sensor characteristics of the relationship between temperature and voltage are unique to each non-contact temperature sensor 75, the detection temperature Ts is determined from the detection voltage Vs, and the compensation temperature Tc is determined from the compensation voltage Vc, depending on the individual sensor characteristics. be able to. Then, the measured temperature T can be determined from the detected temperature Ts and the compensation temperature Tc using a predetermined conversion means H (see FIG. 4) stored in advance in the storage section 60b. For example, the measured temperature T may be determined from the compensation voltage Vc and the differential voltage AVd using an approximate expression. Furthermore, the measured temperature T may be determined from the compensation voltage Vc and the differential voltage AVd using a predetermined two-dimensional table.

By the way, in the operational amplifier 310, the offset voltage needs to be offset-corrected in order to measure the measured temperature T of the object to be measured 400 (72).

In this regard, the non-contact temperature measuring device 300 is configured to perform a heat source non-operation state in which the heat source 73 that heats the measurement object 400 (72) is not in operation at a correction time when a predetermined offset correction condition can be satisfied. Offset correction is performed using the differential voltage AVd of AVd as the offset correction value F. Here, the correction timing is at an initial state in which the detection temperature sensing element 75s and the compensation temperature sensing element 75c can detect the same temperature with respect to the measurement target 400 (72), that is, when the heat source 73 is activated. This is when the heat source is not operating (specifically, when the heat source 73 is not operating even if the power switch 80 is turned on and power is supplied). The differential voltage AVd at this time is obtained as the measurement offset correction value Fm, and the obtained measurement offset correction value Fm is considered as the offset correction value F of the operational amplifier 310, and the differential voltage AVd when measuring the measurement object 400 (72) is The influence of the offset value is canceled by subtracting the offset correction value F during the heat source non-operation state from .

As a predetermined offset correction condition for performing offset correction, that is, a condition necessary for obtaining the offset correction value F, it is necessary that the measurement target 400 (72) and the non-contact temperature sensor 75 have the same temperature, and therefore, It is necessary that the heat source 73 (heater lamp in this example) is in a non-operating state.

Conventionally, when the heat source is inactive, for example, an edge temperature sensor 74 (temperature sensor for detecting sheet non-conveyance area) provided at the end of the measurement object 400 (72) (sheet non-conveyance area α2 in fixing belt 72) ) is used as an offset correction condition, and offset correction is performed when the end temperature detected by the end temperature sensor 74 is below a predetermined threshold (specifically, 30° C.).

However, the compensation temperature Tc detected using the compensation temperature detection element 75c hardly rises because the heating is for a short time, but the temperature in the heating area (sheet conveyance area α1) which has increased even though it is for a short time , is quickly detected by the temperature sensing element for detection 75s, and a voltage difference Vd is generated due to heating between the compensation output from the temperature sensing element for compensation 75c and the detection output from the temperature sensing element for sensing 75s. The non-contact temperature measuring device 300 has a problem in that it mistakenly recognizes this voltage difference Vd as an offset voltage and performs incorrect offset correction even though offset correction should not be performed.

In this regard, in this embodiment, the control section 60 includes a temperature detection control section 61, a first determination control section 62, and an offset correction control section 63. The temperature detection control unit 61 detects the detected temperature Ts of the measurement object 400 (72) using a signal related to the detected temperature Ts outputted from the detection temperature sensing element 75s. The first determination control unit 62 sets the detected temperature Ts detected by the temperature detection control unit 61 as an offset correction condition, and determines that the detected temperature Ts detected by the temperature detection control unit 61 is less than or equal to a predetermined threshold (for example, 30° C.). Determine whether or not. The offset correction control unit 63 performs offset correction when the first determination control unit 62 determines that the detected temperature Ts detected by the temperature detection control unit 61 is less than or equal to a threshold value (for example, 30° C.). The differential output (differential voltage AVd) at this time is stored as the offset correction value F in the storage section 60b. After that, the offset correction value F stored in the storage unit 60b is subtracted from the differential output (AVd) when the heat source 73 is activated and the measurement object 400 (72) heated by the heat source 73 is measured. , an ideal or near-ideal differential output (AVd) can be obtained. In this way, an accurate measured temperature can be obtained without the influence of the offset value.

According to this embodiment, the control unit 60 sets the detected temperature Ts detected using the detection temperature sensing element 75s as an offset correction condition, and when the detected temperature Ts is equal to or lower than a predetermined threshold (specifically, 30° C.). Since the offset correction is performed at a certain time, the temperature sensing element 75s can immediately respond to the temperature rise of the object to be measured 400 (72). For example, when the temperature of the measurement target 400 (72) that has been heated for a short period of time rises above the threshold value (specifically, 30°C) of the offset correction conditions, the measurement target 400 (72) is heated using the temperature sensing element 75s for detection. By detecting the detected temperature Ts that exceeds the threshold value of the offset correction condition for (72), it is possible to prevent offset correction from being performed.

Therefore, when offset correction should not be performed, such as when the object to be measured 400 (72) is heated for a short period of time at a correction time when predetermined offset correction conditions can be met, erroneous offset correction may be performed due to misrecognition. can be effectively prevented.

In the present embodiment, the first determination control unit 62 detects the central detected temperature Ts detected using the detection temperature sensing element 75s in the first non-contact temperature sensor 751 and the detected temperature Ts in the second non-contact temperature sensor 752. The offset correction control unit 63 determines whether at least one of the detected temperatures Ts at one end detected using the detection temperature sensing element 75s is below a predetermined threshold (for example, 30°C), and The offset correction may be performed when the first determination control unit 62 determines that at least one of the detected temperature Ts and the detected temperature Ts of the one end is equal to or less than a predetermined threshold value.

In this case, if there is temperature unevenness or temperature gradient in the heating region (sheet conveyance region α1), it may not be possible to accurately establish the offset correction condition based on the detection temperature Ts detected using the detection temperature sensing element 75s. .

Therefore, the following configuration may be used. That is, the temperature detection control unit 61 detects the detected temperature Ts at the center using the detection temperature sensing element 75s of the first non-contact temperature sensor 751 and the second non-contact temperature sensor in the sheet conveyance area α1. The temperature difference between the detected temperatures Ts at one end detected using the temperature sensing element 75s at 752 is calculated. The first determination control unit 62 determines whether the temperature difference between the detected temperature Ts at the center and the detected temperature Ts at one end is smaller than a predetermined temperature difference threshold (for example, 5° C.). The offset correction control unit 63 determines that at least one of the detected temperature Ts at the center and the detected temperature Ts at one end is equal to or lower than a predetermined threshold (for example, 30° C.), and the temperature at the center calculated by the temperature detection control unit 61 is Offset correction is performed when the first determination control unit 62 determines that the temperature difference between the detected temperature Ts at the end portion and the detected temperature Ts at one end portion is smaller than the temperature difference threshold value. As a result, even if at least one of the detected temperature Ts at the center and the detected temperature Ts at one end is below a predetermined threshold, the temperature difference between the detected temperature Ts at the center and the detected temperature Ts at one end is the temperature difference. If it is equal to or greater than the threshold value, it is possible to prevent offset correction from being performed. Therefore, the detection temperature Ts detected using the detection temperature detection element 75s (the detection temperature detection elements 75s, 75s in the first non-contact temperature sensor 751 and the second non-contact temperature sensor 752) The offset correction conditions can be established with high precision using the detected temperatures Ts, Ts).

Alternatively/in addition, the control unit 60 detects the on-time interval from the last time the power switch 80 was turned on to the current time, and determines that the detected temperature Ts is below the threshold and the on-time interval is Offset correction may be performed when it is determined that the on-time interval is larger than a predetermined reference on-time interval.

Alternatively/Furthermore, from the viewpoint that offset correction may not be performed accurately if the ambient temperature changes rapidly, the control unit 60 detects the temperature change rate per unit time of the ambient temperature (compensation temperature Tc). However, offset correction may be performed when it is determined that the detected temperature Ts is less than or equal to a threshold value and that the rate of change in temperature is less than or equal to a predetermined rate of change.

In the present embodiment, preferably, the threshold value of the offset correction condition can be set to the recommended upper limit temperature of the image forming apparatus 100 (rated upper limit usable temperature, for example, 30° C.) or lower. Here, if the threshold value of the offset correction condition exceeds the recommended upper limit temperature of the image forming apparatus 100, erroneous recognition may occur when offset correction should not be performed, such as when the object to be measured 400 (72) is heated for a short time. The risk of performing offset correction may increase. On the other hand, even if the threshold value of the offset correction condition is within the recommended temperature range (rated usable temperature range, for example, 10°C to 30°C) of the image forming apparatus 100, if it is too low, when offset correction should be performed, The chances that the detected temperature Ts detected using the temperature detecting element 75s continuously exceeds or exceeds the threshold value increases, and there is a possibility that the offset correction will not be performed.

(Second embodiment)
By the way, if the differential output (differential voltage AVd) is greater than or equal to a predetermined abnormal output threshold (abnormal voltage threshold), it is possible that some abnormality has occurred in the temperature measuring device 300. Here, as the abnormal output threshold value, a value of the differential output (AVd) at which some abnormality may occur in the temperature measuring device 300 can be exemplified. For example, in an abnormal state such as when the leakage current in the temperature measurement circuit of the temperature measurement device 300 increases and the potential changes, accurate temperature measurement cannot be performed.

In this regard, in the second embodiment, in the first embodiment, the control unit 60 includes a second determination control unit 64 that determines whether the differential output (AVd) is equal to or greater than a predetermined abnormal output threshold, and an offset When performing correction, if the second determination control unit 64 determines that the differential output (AVd) is equal to or higher than a predetermined abnormal output threshold, an alarm is issued indicating that there may be an abnormality in the temperature measuring device 300. and an alarm control section 65 that issues an alarm. For example, a warning or error message such as "There may be an abnormality in the temperature measurement circuit. Please call a service person." may be displayed on the display section 51 of the operation panel 50 or/and on the sound generating section (not shown). Display and/or sound may be emitted.

By doing so, the user can be made aware that accurate temperature measurement cannot be performed by measuring the temperature of the measurement target object 400 (72) in an abnormal state.

(Third embodiment)
By the way, there may be a situation where offset correction is never performed, such as when the environmental temperature (for example, 35 degrees Celsius) of the installation environment of the measurement object 400 (72) always exceeds the threshold value (for example, 30 degrees Celsius) of the offset correction condition. There is sex.

In this regard, in the third embodiment, in the first embodiment or the second embodiment, for example, the initial offset correction (before shipment from the factory) is performed in the production process of the factory, and the offset correction value of the offset correction performed in the production process is An initial offset correction value is stored in advance in the storage unit 60b. If the detected temperature Ts detected using the detection temperature sensing element 75s continuously exceeds a threshold value (for example, 30° C.) after the initial offset correction value is stored in the storage portion 60b, the offset correction control section 63 An initial offset correction value stored in advance in the storage unit 60b is used.

By doing this, even if the environmental temperature (for example, 35 degrees Celsius) of the environment in which the measurement target 400 (72) is installed after shipment from the factory continues to exceed the offset condition threshold (for example, 30 degrees Celsius), for example, the factory production Offset correction can be performed using the differential output (AVd) of offset correction performed during the process or factory shipment.

Here, once the detection temperature Ts detected using the detection temperature detection element 75s becomes equal to or lower than the threshold value, the detection temperature is The offset correction value F obtained by the offset correction performed when the detected temperature Ts detected using the element 75s becomes below the threshold value can be used, so that after the detected temperature Ts once becomes below the threshold value, the detected temperature Ts becomes lower than the threshold value. Even if the detected temperature Ts exceeds the threshold value, the offset correction value F obtained when the detected temperature Ts becomes equal to or less than the threshold value can be used. In this case, as in the present embodiment, the storage area of the storage unit 60b stores the initial offset correction value in the production process, and the storage area 60b stores the offset correction value F when the detected temperature Ts becomes below the threshold value. The initial offset correction value stored in the production process can be rewritten to the offset correction value F when the detected temperature Ts becomes equal to or less than the threshold value in the storage section 60b. By doing so, it is possible to omit the control configuration of the control unit 60 for determining whether or not the detected temperature Ts has once become equal to or less than the threshold value.

(Fourth embodiment)
By the way, the differential output (AVd) usually contains noise, but even if the differential output (AVd) contains noise, if it is below a predetermined lower limit threshold that can be considered not to be 0, the difference It is preferable to consider that the dynamic output (AVd) is zero.

In this regard, in the fourth embodiment, in any one of the first to third embodiments, the second determination control unit 64 determines whether the differential output (AVd) is below a predetermined lower limit threshold. Determine. When performing offset correction, the offset correction control unit 63 sets the measured offset correction value Fm to 0 when the second determination control unit 64 determines that the differential output (AVd) is below a predetermined lower limit threshold. The offset correction value F is rewritten into the measured offset correction value Fm(0) in the storage unit 60b. Here, the lower limit threshold can be set to a value on the order of a noise level.

By doing so, the differential output (AVd) below the lower limit threshold can be regarded as noise, and thereby offset correction can be performed with the offset value set to zero.

(Fifth embodiment)
In the fifth embodiment, in any one of the first to fourth embodiments, the offset correction control section 63 uses the second determination control section 64 to determine the differential output (AVd) when performing offset correction. If it is determined that the differential output (AVd) is below the abnormal output threshold, the differential output (AVd) is set as the measured offset correction value Fm, and the offset correction value F is set as the measured offset correction value Fm [differential output (AVd)] in the storage unit 60b. rewrite.

By doing so, it is possible to reliably update the offset correction value F to the newly acquired measured offset correction value Fm every time offset correction is performed in the storage unit 60b.

By the way, when the differential output (AVd) is equal to or greater than the lower limit threshold, it can be considered that the differential output (AVd) is not 0 even if it includes noise.

In this regard, in the present embodiment, the offset correction control unit 63 performs offset correction when the second determination control unit 64 determines that the differential output (AVd) is equal to or higher than the lower limit threshold. The dynamic output (AVd) is set as the measured offset correction value Fm, and the offset correction value F is rewritten into the measured offset correction value Fm [differential output (AVd)] in the storage section 60b.

In this case, the offset correction value F may be simply rewritten to the measurement offset correction value Fm [differential output (AVd)], but the lower limit threshold is regarded as noise, and the measurement offset correction value Fm is changed from the differential output (AVd) to the lower limit. A value obtained by subtracting a threshold value may also be used. By doing so, each time offset correction is performed in the storage unit 60b, the offset correction value F can be accurately updated to the measured offset correction value Fm obtained by subtracting the lower limit threshold value considered as noise from the differential output (AVd).

In this embodiment, the second determination control unit 64 determines whether the measured offset correction value Fm is different from the offset correction value F stored in the storage unit 60b. The offset correction control unit 63 performs offset correction when the second determination control unit 64 determines that the measured offset correction value Fm is different from the offset correction value F stored in the storage unit 60b. , the offset correction value F may be rewritten to the measured offset correction value Fm in the storage unit 60b.

By doing so, it is possible to omit the rewriting operation to the storage section 60b when the measured offset correction value Fm is equal to the offset correction value F stored in the storage section 60b.

In the present embodiment, the second determination control unit 64 determines whether the measured offset correction value Fm is less than the offset correction value F stored in the storage unit 60b. When performing offset correction, the offset correction control section 63 performs offset correction when the second judgment control section 64 determines that the measured offset correction value Fm is less than the offset correction value F stored in the storage section 60b. , the measured offset correction value Fm is set to the offset correction value F stored in the storage unit 60b, and the offset correction value F is set to the measured offset correction value Fm (the offset correction value F stored in the storage unit 60b) in the storage unit 60b. ) or leave it as is.

By doing so, even if the measured offset correction value Fm falls below the offset correction value F stored in the storage section 60b, it can be maintained at the offset correction value F stored in the storage section 60b. This is particularly effective when another offset factor that is not caused by the operational amplifier 310 is added to the offset value.

In the present embodiment, when performing offset correction, the offset correction control unit 63 determines that the measured offset correction value Fm in the second determination control unit 64 is equal to or greater than the offset correction value F stored in the storage unit 60b. If it is determined, the offset correction value F may be rewritten to the measured offset correction value Fm in the storage unit 60b.

By doing this, when the measured offset correction value Fm exceeds the offset correction value F stored in the storage unit 60b, the offset correction value F stored in the storage unit 60b is changed to the measured offset correction value Fm. Can be updated.

In the present embodiment, the second determination control unit 64 determines whether the differential output (AVd) is below a predetermined upper threshold that is larger than the lower threshold. The offset correction control unit 63 performs offset correction when the second determination control unit 64 determines that the differential output (AVd) is greater than or equal to a predetermined lower limit threshold and less than a predetermined upper limit threshold. , the offset correction value F may be rewritten to the measured offset correction value Fm in the storage unit 60b.

By doing so, it is possible to reliably update the offset correction value F to an appropriate measurement offset correction value Fm.

In this embodiment, when performing offset correction, the offset correction control unit 63 determines that the measured offset is The correction value Fm may be set as the upper limit threshold, and the offset correction value F may be rewritten to the measured offset correction value Fm (upper threshold) in the storage unit 60b. Here, the upper limit threshold can be set to a value that is lower than the abnormal output threshold and smaller by a predetermined amount than a value that may suddenly occur due to a leak or the like.

By doing so, it is possible to reliably update the offset correction value F to the measured offset correction value Fm suppressed to the upper limit threshold without making the offset correction value F larger than the upper limit threshold. This is particularly effective when the differential output (AVd) suddenly becomes larger than the upper limit threshold due to leakage or the like.

(Sixth embodiment)
By the way, the offset value of the operational amplifier 310 usually changes over time. Therefore, if the offset value changes over time after offset correction, the measured temperature of the measurement object 400 (72) cannot be measured with high accuracy. Therefore, it is preferable to repeatedly perform offset correction at correction times when predetermined offset correction conditions can be satisfied.

In this regard, in the sixth embodiment, in any one of the first to fifth embodiments, the offset correction control unit 63 determines that the heat source 73 that heats the measurement object 400 (72) is not operating. Offset correction is performed every time the heat source is inactive (in this example, every time the power switch 80 is turned on), when the detected temperature Ts detected using the detection temperature sensing element 75s is below the threshold value.

By doing this, it is possible to perform offset correction for the offset value of the operational amplifier 310 that has changed over time every time the heat source is not in operation. Measurements can be made with high precision.

(Seventh embodiment)
In the seventh embodiment, in any one of the first embodiment to the sixth embodiment, the control unit 60 controls the power switch 80 to It has an increasing tendency value calculation section 66 that stores the history of the differential output (AVd) in the storage section 60b and calculates an increasing tendency value indicating an increasing tendency of the differential output (AVd). The second determination control unit 64 determines whether the increasing tendency value calculated by the increasing tendency value calculating unit 66 is equal to or greater than a predetermined abnormal tendency value.

Here, as an example of the abnormal tendency value, an increasing tendency value with a high possibility that some kind of abnormality will occur in the temperature measuring device 300 can be exemplified. As an increasing tendency value indicating an increasing tendency of the differential output (AVd), for example, the history of the differential output (AVd) is calculated every time the heat source is not in operation (in this example, every time the power switch 80 is turned on). In the storage unit 60b, differential outputs (AVd) that have a positive difference from the previous differential output (AVd) and whose differential output ratio is equal to or higher than the reference ratio can be listed. The differential output ratio can be a ratio of the differential output (AVd) to a predetermined abnormal output threshold. The reference ratio is not limited thereto, but can be exemplified as a ratio of about 70% to 80% or more with respect to the abnormal output threshold.

When the second determination control unit 64 determines that the increasing trend value is greater than or equal to a predetermined abnormal trend value, the alarm control unit 65 issues an alarm indicating that it is necessary to check the operating state of the temperature measuring device 300. emanate. For example, the alarm control unit 65 may display a warning or error message on the display unit 51 of the operation panel 50 or/and a sound generator (not shown) such as “The temperature measurement circuit is likely to become abnormal.” A message may be displayed and/or a sound may be emitted.

In this way, the second determination control unit 64 determines that even if the differential output (AVd) does not exceed the abnormal output threshold, it increases from the previous differential output (AVd) and approaches the abnormal output threshold. The alarm controller 65 issues an alarm indicating that it is necessary to check the operating state of the temperature measuring device 300, so that the temperature measuring circuit can be checked in advance (for example, checking the output voltage, etc.). ), it is possible to prevent a failure of the temperature measuring device 300 from occurring by taking measures such as having a worker such as a service person perform the following steps.

(Eighth embodiment)
By the way, if the differential output (AVd) is equal to or greater than the abnormal output threshold, accurate temperature measurement cannot be performed, and there is a possibility that the image forming apparatus 100 will have a fixing failure. For this reason, it is desirable to stop the image forming operation.

In this regard, in the eighth embodiment, in any one of the first to seventh embodiments, the control unit 60 uses the second determination control unit 64 to perform the differential output (AVd ) is greater than or equal to a predetermined abnormal output threshold, the image forming apparatus includes an operation stop control section 67 that stops the image forming operation.

By doing so, it is possible to avoid fixing failure in the image forming apparatus 100. Then, a worker such as a service person takes measures such as repairing or replacing the temperature measurement circuit board, and after confirming that it is normal, can start the image forming operation.

<Example of offset correction control>
FIGS. 7A to 7D are flowcharts showing a first half, an example of a middle part, another example of the middle part, and a second half of an example of the control operation of offset correction according to the present embodiment, respectively.

Prior to performing the offset correction control operations shown in FIGS. 7A to 7D, the first offset correction is performed in the production process of the factory, and the initial offset correction value Fi of the offset correction performed in the production process is stored in the storage unit 60b. Memorize it in advance.

In the flowcharts shown in FIGS. 7A to 7D, first, as shown in FIG. 7A, when the power switch 80 is turned on (S1), the control unit 60 controls the measurement target object 400 detected using the end temperature sensor 74. The end temperature Te of the sheet non-conveyance area α2 in (72), the detected temperature Ts of the center of the sheet conveyance area α1 in the measurement target 400 (72) detected using the first non-contact temperature sensor 751, It is determined whether or not the detected temperature Ts at one end of the sheet conveyance area α1 of the object to be measured 400 (72) detected using the second non-contact temperature sensor 752 is equal to or lower than the threshold Th (30° C. in this example). S2). Next, if the control unit 60 determines that at least one of the end temperature Te, the detected temperature Ts of the center, and the detected temperature Ts of one end exceeds the threshold Th (S2: No), the control unit 60 sets the offset The initial offset correction value Fi previously stored in the storage unit 60b during the production process is substituted for the correction value F, and the process moves to S19 shown in FIG. 7D. On the other hand, if the end temperature Te, the detected temperature Ts at the center, and the detected temperature Ts at one end are all below the threshold Th (S2: Yes), the control unit 60 acquires the differential voltage AVd. Then, it is determined whether the differential voltage AVd is equal to or greater than the abnormal voltage threshold Va (S5). When the control unit 60 determines that the differential voltage AVd is lower than the abnormal voltage threshold Va (S5: No), it determines whether the differential voltage AVd is lower than the lower limit threshold Vmin (S6). When the control unit 60 determines that the differential voltage AVd is less than the lower limit threshold Vmin (S6: Yes), it substitutes 0 for the measurement offset correction value Fm (S7), and performs the process in S13 shown in FIG. 7B or in FIG. 7C. The process moves to S13a shown in FIG. Moreover, when the control unit 60 determines that the differential voltage AVd is greater than or equal to the lower limit threshold Vmin (S6: No), it determines whether the differential voltage AVd exceeds the upper limit threshold Vmax (S8). When the control unit 60 determines that the differential voltage AVd exceeds the upper limit threshold Vmax (S8: Yes), it substitutes the upper limit threshold Vmax for the measurement offset correction value Fm (S9), and performs S13 or the diagram shown in FIG. 7B. The process moves to S13a shown in 7C. Further, when the control unit 60 determines that the differential voltage AVd is equal to or lower than the upper limit threshold Vmax (S8: No), the control unit 60 substitutes (differential voltage AVd - lower limit threshold Vmin) for the measurement offset correction value Fm. S10), the process moves to S13 shown in FIG. 7B or S13a shown in FIG. 7C. Note that in S10, the differential voltage AVd may be substituted for the measured offset correction value Fm.

On the other hand, if the control unit 60 determines that the differential voltage AVd is equal to or higher than the abnormal voltage threshold Va (S5: Yes), the control unit 60 displays a message on the display unit indicating that there is a possibility that there is an abnormality in the temperature measuring device 300. 51 (S11), the image forming operation of the image forming apparatus 100 is stopped (S12), and the process ends.

Next, in the case of the example shown in FIG. 7B, the control unit 60 determines whether the measured offset correction value Fm is different from the offset correction value F stored in the storage unit 60b (S13), and determines that they are different. If it is determined that they are equal (S13: Yes), the measured offset correction value Fm is substituted for the offset correction value F (S14), and the process moves to S15 shown in FIG. The process moves to S15 shown in 7D.

Further, in the case of the example shown in FIG. 7C, the control unit 60 determines whether the measured offset correction value Fm is less than the offset correction value F stored in the storage unit 60b (S13a), and determines whether the measured offset correction value Fm is less than the offset correction value F stored in the storage unit 60b. (S13a: Yes), the offset correction value F stored in the storage unit 60b is substituted for the offset correction value F (S14a), and the process moves to S15 shown in FIG. 7D. If it is determined that it is equal to or greater than the correction value F (S13a: No), the measured offset correction value Fm is substituted for the offset correction value F (S14), and the process moves to S15 shown in FIG. 7D.

Next, as shown in FIG. 7D, the control unit 60 stores the offset correction value F in the storage unit 60b (S15) (updates the offset correction value F), and stores the history of the differential voltage AVd in the storage unit 60b. It is stored and an increasing tendency value K is calculated (S16).

Next, the control unit 60 determines whether the increasing tendency value K is greater than or equal to the abnormal tendency value Ka (S17), and if it is determined that the increasing tendency value K is less than the abnormal tendency value Ka (S17: No), the process proceeds to S19. On the other hand, if it is determined that the temperature is equal to or higher than the abnormal tendency value Ka (S17: Yes), a message indicating that it is necessary to check the operating state of the temperature measuring device 300 is displayed on the display unit 51 (S18), and S19 to move to.

Next, the control unit 60 operates the heat source 73 (S19), measures the measured temperature T of the measurement object 400 (72) (S20), and obtains the compensation voltage Vc and the differential voltage AVd (S21, S22). ).

Next, the control unit 60 substitutes (obtained differential voltage Vc - offset correction value F) for the proper differential voltage RAVd (S23), and sets the obtained compensation voltage Vc and the proper differential voltage RAVd. The measured temperature T is determined from (S24).

The present disclosure is not limited to the embodiments described above, and can be implemented in various other forms. Therefore, such embodiments are merely illustrative in all respects, and should not be interpreted in a limiting manner. The scope of the present disclosure is indicated by the claims, and is not restricted in any way by the main text of the specification. Furthermore, all modifications and changes that come within the scope of equivalents of the claims are intended to be within the scope of the present disclosure.

100 Image forming device 300 Temperature measuring device 310 Differential operational amplifier (an example of an operational amplifier)
320 Operational amplifier for compensation 400 Measurement object 51 Display section 60 Control section 60a Processing section 60b Storage section 61 Temperature detection control section 62 First judgment control section 63 Offset correction control section 64 Second judgment control section 65 Alarm control section 66 Increasing tendency Value calculation unit 67 Operation stop control unit 7 Fixing device 72 Fixing belt (an example of a measurement target)
73 Heat source 74 End temperature sensor 75 Non-contact temperature sensor 751 First non-contact temperature sensor 752 Second non-contact temperature sensor 75c Compensation temperature detection element 75s Detection temperature detection element 80 Power switch AVd Differential voltage D DC power supply E Power supply F Offset correction value Fi Initial offset correction value Fm Measurement offset correction value H Conversion means IR Infrared rays K Increasing tendency value Ka Abnormal tendency value P Sheet RAVd Appropriate differential voltage Rc Compensation resistor Rs Detection resistor T Measurement temperature Tc Compensation temperature Te End temperature Th Threshold Ts Detection temperature Va Abnormal voltage threshold Vc Compensation voltage Vd Voltage difference Vmax Upper threshold Vmin Lower threshold Vs Detection voltage X Width direction α1 Sheet conveyance area α2 Sheet non-conveyance area

Claims (8)

a non-contact temperature sensor including a detection temperature detection element that non-contactly detects the measured temperature of a measurement target and a compensation temperature detection element that detects environmental temperature;
an operational amplifier that amplifies the output difference between the output of the temperature detection element for detection and the output of the temperature detection element for compensation,
A non-contact type temperature sensor that measures an offset value included in a differential output obtained by amplifying the output difference using the operational amplifier, and performs offset correction to remove the offset from the differential output based on the measured offset value. A measuring device,
The offset correction is configured to be performed when a predetermined offset correction condition is met for performing the offset correction,
The offset correction is performed when the detected temperature detected using the temperature detecting element is equal to or less than a predetermined threshold value, and the detected temperature detected using the temperature detecting element is set as the offset correction condition. A temperature measuring device featuring: The temperature measuring device according to claim 1,
In performing the offset correction, if the differential output is equal to or greater than a predetermined abnormal output threshold, a temperature measuring device is characterized in that when the differential output is greater than or equal to a predetermined abnormal output threshold, an alarm is issued indicating that there is a possibility that there is an abnormality in the temperature measuring device. The temperature measuring device according to claim 1,
An initial offset correction value that is the offset correction value obtained by the offset correction is stored in a storage unit in advance,
If the detected temperature detected using the temperature sensing element for detection continuously exceeds the threshold value after the initial offset correction value is stored in the storage unit, the A temperature measuring device characterized by using an initial offset correction value. The temperature measuring device according to claim 1,
When performing the offset correction, if the differential output is less than a predetermined abnormal output threshold, the differential output is set as a measured offset correction value, and the offset correction value is rewritten in a storage unit as the measured offset correction value. A temperature measuring device featuring: The temperature measuring device according to claim 1,
performing the offset correction when the detected temperature detected using the temperature sensing element for detection is equal to or lower than the threshold value each time the heat source is inactive, in which the heat source for heating the measurement object is not activated; A temperature measuring device featuring: The temperature measuring device according to claim 1,
An increasing tendency value indicating an increasing tendency of the differential output is calculated each time the heat source is not operating, and the increasing tendency value is equal to or greater than a predetermined abnormal tendency value. 1. A temperature measuring device, characterized in that when the temperature measuring device is detected, an alarm is issued indicating that the operating state of the temperature measuring device needs to be confirmed. The temperature measuring device according to any one of claims 1 to 6,
a fixing device having a fixing member for heating and fixing the unfixed toner image on the sheet;
The image forming apparatus is characterized in that the object to be measured is the fixing member. The image forming apparatus according to claim 7,
When performing the offset correction, if the differential output is equal to or higher than a predetermined abnormal output threshold, an alarm indicating that there may be an abnormality in the temperature measuring device is issued, and the image forming operation is stopped. Features of the image forming device.

Images