JP2018096932A - Temperature measuring device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature measuring device that can accurately measure the ambient temperature of an object with a thermistor, even in a situation where the thermistor is mounted on the same substrate with an electronic component generating a large amount of heat when power is supplied thereto, and stop of supply of power and start of supply of power to the electronic component are performed in a short time, and an image forming apparatus.SOLUTION: A temperature measuring device comprises a substrate, a driving circuit 61, a thermistor 63, a timing processing part 83 and a temperature calculation part 86. The driving circuit 61 is formed on the substrate and drives a developing device 23. The thermistor 63 is mounted on the substrate and outputs a detection signal according to the ambient temperature of the developing device 23. The timing processing part 83 acquires a power supply stopping time during which supply of power to the developing device 23 is stopped. The temperature calculation part 86 calculates the ambient temperature of the developing device 23 on the basis of the detection signal output from the thermistor 63 and the power supply stopping time acquired from the timing processing part 83.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a temperature measuring device and an image forming apparatus.

  An image forming apparatus that forms an image on a sheet by an electrophotographic method includes a developing device that forms a toner image on an image carrier such as a photosensitive drum, and a transfer that transfers the toner image on the image carrier to a transfer material such as a sheet. Equipment. As this type of image forming apparatus, it is known that the temperature or ambient temperature of a developing device, a transfer device, or the like is detected by a temperature measurement sensor, and development processing and transfer processing are controlled based on the detected temperature of the temperature measurement sensor. (For example, see Patent Documents 1 and 2).

  Incidentally, the measurement of the ambient temperature of an object such as a developing device or a transfer device may be performed by a thermistor mounted on a drive circuit board, for example. In addition to the thermistor, the drive circuit board may be mounted with an electronic component that generates a large amount of heat during power feeding, such as a magnetic permeability sensor for measuring the toner concentration of the developing device. When an electronic component having a large calorific value is mounted on the drive circuit board together with the thermistor, the temperature of the drive circuit board rises, so that the temperature detected by the thermistor becomes higher than the actual ambient temperature. For this reason, it is considered that the ambient temperature is calculated by performing offset correction by subtracting a constant value in consideration of the temperature rise of the drive circuit board from the temperature detected by the thermistor.

JP 9-211963 A JP 2004-221968 A

  The offset correction is performed on the assumption that the temperature of the drive circuit board is cooled to the same level as the ambient temperature. On the other hand, when the time from when power supply is stopped to when power supply is resumed is short for an electronic component that generates a large amount of heat during power supply, for example, when the image forming process is executed immediately after shifting to the sleep mode, the drive is performed. The temperature of the circuit board may remain higher than the ambient temperature. In this case, the temperature detected by the thermistor is higher than the actual ambient temperature due to the drive circuit board being hotter than the ambient temperature. For this reason, it is difficult to accurately measure the ambient temperature even by performing the offset correction under a situation where power supply stop and power supply of an electronic component that generates a large amount of heat during power supply are performed in a short time.

  In the present invention, the thermistor is mounted on the same substrate as the electronic component that generates a large amount of heat during power feeding, and the thermistor surrounds the object even when power feeding is stopped and power feeding is performed in a short time. It is an object of the present invention to provide a temperature measuring device and an image forming apparatus capable of accurately measuring temperature.

  A temperature measurement device according to one aspect of the present invention includes a substrate, a drive circuit, a thermistor, a time measurement processing unit, and a temperature calculation unit. The drive circuit is formed on the substrate, drives a predetermined object, and has an electronic component. The thermistor is mounted on the substrate and outputs a detection signal corresponding to the ambient temperature of the object. The time measurement processing unit acquires a power supply stop time during which power supply to the electronic component is stopped. The temperature calculation unit calculates an ambient temperature of the object based on a detection signal output from the thermistor and the power supply stop time acquired by the time measurement processing unit.

  An image forming apparatus according to another aspect of the present invention includes the temperature measuring device and an image forming unit that forms an image on a sheet.

  According to the present invention, even if the thermistor is mounted on the same substrate as the electronic component that generates a large amount of heat during power feeding, and the power supply is stopped and started in a short time, the thermistor can perform the object inspection. It is possible to provide a temperature measuring device and an image forming apparatus that can accurately measure the ambient temperature.

FIG. 1 is a schematic diagram illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram showing a schematic configuration of a main part of the image forming apparatus of FIG. FIG. 3 is a time chart showing an example of a change with time of a detection signal from the thermistor in the image forming apparatus of FIG. FIG. 4 is a time chart showing another example of the change over time of the detection signal from the thermistor in the image forming apparatus of FIG. FIG. 5 is a table showing an example of a first correction data table stored in the storage unit of the control unit shown in FIG. FIG. 6 is a time chart showing another example of the change over time of the detection signal from the thermistor in the image forming apparatus of FIG. FIG. 7 is a table showing an example of the second correction data table stored in the storage unit of the control unit shown in FIG. FIG. 8 is a flowchart showing the procedure of the temperature calculation process executed by the CPU of the control unit shown in FIG. FIG. 9 is a flowchart showing a procedure of temperature calculation processing executed by the CPU of the control unit shown in FIG. FIG. 10 is a block diagram showing a schematic configuration of a main part of the image forming apparatus according to the second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below is merely an example embodying the present invention, and the embodiment of the present invention can be changed as appropriate without departing from the scope of the present invention.

[First Embodiment]
First, an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

  An image forming apparatus 10 shown in FIG. 1 is a printer capable of forming a color image on a sheet using toner. The present invention can be applied to, for example, a monochrome printer, a copying machine, a facsimile machine, and a multifunction machine in addition to a color printer.

  The image forming apparatus 10 includes an image display unit 11, a paper feed tray 17, a paper discharge tray 18, and an operation display unit 19 having a touch panel, a liquid crystal display unit, and the like.

  The image forming unit 11 forms an image on a sheet. The image forming unit 11 includes a plurality of image forming units 1 to 4, an intermediate transfer unit 5, an optical scanning device 14, a secondary transfer device 15, and a fixing device 16.

  Each of the image forming units 1 to 4 includes a photosensitive drum 21 that carries a toner image (an example of the image carrier of the present invention), a charging device 22, and a developing device 23 that contains a developer including toner and a carrier (of the present invention). An example of a developing unit as an object), a primary transfer device 24, and a drum cleaning device 25 are provided. The developing device 23 forms a toner image on the photosensitive drum 21.

  The intermediate transfer unit 5 includes an intermediate transfer belt 51, a driving roller 52, and a driven roller 53. A toner image carried on the photosensitive drum 21 is transferred to the intermediate transfer belt 51, and a toner image composed of a plurality of color toner images (four colors in the present embodiment) is formed. The intermediate transfer belt 51 is supported by a driving roller 52 and a driven roller 53 so as to be rotationally driven.

  The secondary transfer device 15 transfers the toner image transferred to the intermediate transfer belt 51 onto the sheet conveyed from the paper feed tray 17. The sheet on which the toner image is transferred is conveyed to the fixing device 16 by a conveyance unit (not shown). The fixing device 16 includes a heating roller 161 and a pressure roller 162. The fixing device 16 conveys the sheet on which the toner image is transferred while applying heat and pressure. As a result, the toner image is melted and fixed on the sheet. The sheet on which the toner image is fixed is further conveyed downstream, and is discharged and held on a discharge tray 18 disposed above the intermediate transfer unit 5.

  As shown in FIG. 2, the image forming apparatus 10 further includes a drive circuit board 6, a real time clock (RTC) 7, and a control unit 8. The drive circuit board 6, the RTC 7, and the control unit 8 constitute a temperature measuring device of the present invention.

  The drive circuit board 6 includes a board (not shown) and a drive circuit 61 that is formed on the board and drives a predetermined object. The object includes, for example, components of the image forming units 1 to 4, and is the photosensitive drum 21, the charging device 22, the developing device 23, the primary transfer device 24, and the drum cleaning device 25. The drive circuit 61 includes a magnetic permeability sensor 62 (an example of the electronic component of the present invention).

  The magnetic permeability sensor 62 outputs a signal corresponding to the carrier concentration in the developer accommodated in the developing device 23. Here, since the carrier concentration has a correlation with the toner concentration, the toner concentration can be detected by detecting the carrier concentration, and the remaining amount of toner can be detected. The magnetic permeability sensor 62 is not particularly limited as long as it can detect a change in the magnetic permeability of the developer, and a known magnetic permeability sensor can be used. Examples of the magnetic permeability sensor 62 include a sensor that detects the amount of change in magnetic permeability based on the carrier concentration of the waste developer based on a phase difference generated when a periodic signal having a predetermined frequency is input to a transformer, a coil, or the like. It is done.

  A thermistor 63 is mounted on a substrate (not shown) of the drive circuit substrate 6. The thermistor 63 is a chip thermistor, for example, and outputs a detection signal having an output value Y corresponding to the ambient temperature of the developing device 23. The thermistor 63 is connected to a CPU 82 of the control unit 8 described later. Therefore, the detection signal output from the thermistor 63 is input to the CPU 82.

  The RTC 7 is an IC dedicated to timing, and is mounted on, for example, a main board (not shown). The RTC 7 provides information related to time. The RTC 7 is connected to a CPU 82 of the control unit 8 described later. And CPU82 acquires the information regarding time from RTC7. Note that the RTC 7 may be mounted on another board such as an engine board constituting the control unit 8 instead of the main board.

  The control unit 8 includes a storage unit 81 and a CPU 82. The control unit 8 executes various programs stored in the storage unit 81 by the CPU 82, thereby comprehensively controlling the image forming operation.

  In addition to various programs, the storage unit 81 stores, for example, information necessary for program execution, a first correction data table 811 and a second correction data table 812. The first correction data table 811 is a table of first correction data in which the power supply stop time X1 during which power supply to the magnetic permeability sensor 62 is stopped and the first correction amount A1 are associated with each other. The first correction amount A1 is for correcting the calculated value of the ambient temperature based on the detection signal output from the thermistor 63. On the other hand, the second correction data table 812 is a table of second correction data in which the power supply continuation time X2 in which power supply to the magnetic permeability sensor 62 is continued is associated with the second correction amount A2. The second correction amount A2 is for correcting the calculated value of the ambient temperature based on the detection signal output from the thermistor 63.

  Here, FIG. 3 is a time chart showing an example of a change with time of the detection signal from the thermistor 63.

  The solid line in FIG. 3 indicates the output value Y of the detection signal. In the example shown in FIG. 3, power supply to the magnetic permeability sensor 62 is started in a state where the drive circuit board 6 sufficiently dissipates heat and the temperature of the thermistor 63 is the ambient temperature of the developing device 23. The output value Y1 of the detection signal output from the thermistor 63 when the temperature of the thermistor 63 is the ambient temperature of the developing device 23 is referred to as a first saturation output value Y1.

  When power supply to the magnetic permeability sensor 62 is started, the output value Y of the detection signal monotonously increases with time from the first saturated output value Y1 corresponding to the ambient temperature. In addition, when a certain time X2m elapses after power supply to the magnetic permeability sensor 62 is started, the output value Y of the detection signal becomes the constant value Y2. Hereinafter, the constant time X2m is referred to as a second saturation time X2m, and the constant value Y2 is referred to as a second saturation output value Y2.

  On the other hand, when power supply to the magnetic permeability sensor 62 is stopped in a state where the output value Y of the detection signal is the second saturation output value Y2, the output value Y of the detection signal is monotonically with time from the second saturation output value Y2. Decrease. In addition, when a certain time X1m has elapsed since the power supply to the magnetic permeability sensor 62 is stopped, the output value Y of the detection signal becomes a constant value at the first saturation output value Y1. Hereinafter, the fixed time X1m is referred to as a first saturation time X1m.

  By the way, the thermistor 63 is mounted on the same substrate as the magnetic permeability sensor 62 that generates a large amount of heat, and thus is affected by the heat generated by the magnetic permeability sensor 62. Therefore, the thermistor 63 outputs a detection signal of an output value Y corresponding to a temperature higher than the ambient temperature of the actual developing device 23 indicated by a two-dot chain line in FIG. Therefore, in this embodiment, when the ambient temperature of the developing device 23 is detected based on the detection signal from the thermistor 63, the output value Y of the detection signal is offset to the lower value side by a predetermined fixed amount ΔY. Calculate the ambient temperature.

  Hereinafter, the constant amount ΔY is referred to as an offset amount ΔY. The offset amount ΔY is a difference value between the second saturation output value Y2 and the output value Y3 of the detection signal from the thermistor 63 corresponding to the ambient temperature of the developing device 23 in the second saturation time X2m.

  Further, when the power supply stop time X1 from when the power supply to the magnetic permeability sensor 62 is stopped to when the power supply is started is shorter than the first saturation time X1m, the thermistor when the power supply to the magnetic permeability sensor 62 is started. The output value Y from 63 becomes higher than the first saturation output value Y1. For example, as shown in FIG. 4, after the power supply to the magnetic permeability sensor 62 is stopped in a state where the output value Y is at the second saturation output value Y2, the power supply to the magnetic permeability sensor 62 is reached before the first saturation time X1m is reached. When is restarted, the output value Y of the detection signal from the thermistor 63 becomes higher by ΔY1 than the first saturation output value Y1. Therefore, in the present embodiment, when the power supply stop time X1 is shorter than the first saturation time X1m, the output value Y of the detection signal from the thermistor 63 is corrected.

  Specifically, as shown in FIG. 5, the correction of the output value Y is performed based on the first correction data table 811 stored in the storage unit 81. In FIG. 5, the power supply stop time X1 is shown as a ratio to the first saturation time X1m, and the first correction amount A1 is shown as a ratio to the difference Ym between the second saturation output value Y2 and the first saturation output value Y1. Has been.

  The first correction data table 811 is a table of the first correction data in which the power supply stop time X1 and the first correction amount A1 are associated as described above. The first correction amount A1 is set to a value corresponding to ΔY1, for example. The first correction amount A1 is calculated, for example, from a change over time in the output value Y when power supply to the magnetic permeability sensor 62 is stopped in a state where the output value Y is at the second saturated output value Y2.

  Conversely, when the power supply duration X2 from when the power supply to the magnetic permeability sensor 62 is started until the power supply is stopped is shorter than the second saturation time X2m, when the power supply to the magnetic permeability sensor 62 is started next. The output value Y from the thermistor 63 may be lower than the second saturation output value Y2. For example, as shown in FIG. 6, after the power supply to the magnetic permeability sensor 62 is started in a state where the output value Y is at the first saturated output value Y1, the power supply to the magnetic permeability sensor 62 is reached before the second saturation time X2m is reached. Is stopped, the output value Y of the detection signal from the thermistor 63 is lower by ΔY2 than the second saturation output value Y2. Therefore, in the present embodiment, the correction of the output value Y of the detection signal from the thermistor 63 is performed when the power supply continuation time X2 is shorter than the second saturation time X2m.

  Specifically, as illustrated in FIG. 7, the correction of the output value Y is performed based on the second correction data table 812 stored in the storage unit 81. In FIG. 7, the power supply duration time X2 is shown as a ratio to the second saturation time X2m, and the second correction amount A2 is shown as a ratio to the difference Ym between the second saturation output value Y2 and the first saturation output value Y1. Has been.

  As described above, the second correction data table 812 is a table of the second correction data in which the power supply duration time X2 is associated with the second correction amount A2. The second correction amount A2 is set to a value corresponding to ΔY2, for example. The second correction amount A2 is calculated, for example, from a change over time in the output value Y when power supply to the magnetic permeability sensor 62 is started in a state where the output value Y is at the first saturated output value Y1.

  The first correction data and the second correction data may be stored in the storage unit 81 as a function without being tabulated.

  The CPU 82 shown in FIG. 2 includes a time measurement processing unit 83, a first correction amount determination unit 84, a second correction amount determination unit 85, and a temperature calculation unit 86.

  The time measurement processing unit 83 acquires the power supply stop time X1 and the power supply duration time X2. Specifically, the time measurement processing unit 83 first acquires first time information related to the power supply start time from the RTC when power supply to the magnetic permeability sensor 62 is started, and stores the first time information in the storage unit 81, for example. The time measuring unit 83 acquires second time information related to time from the RTC when power supply to the magnetic permeability sensor 62 is stopped, and stores the second time information in the storage unit 81, for example. The time measuring unit 83 updates the first time information stored in the storage unit 81 to the latest information every time power supply to the magnetic permeability sensor 62 is started, and power supply to the magnetic permeability sensor 62 is stopped. Each time the second time information stored in the storage unit 81 is updated to the latest information. Then, the time measuring unit 83 calculates the power supply stop time X1 at the start of power supply to the magnetic permeability sensor 62 based on the program stored in the storage unit 81, the first time information, and the second time information, and the magnetic permeability When the power supply to the sensor 62 is stopped, the power supply duration time X2 is calculated.

  Based on the first correction data stored in the storage unit 81, the first correction amount determination unit 84 determines the first correction amount A1 corresponding to the power supply stop time X <b> 1 calculated by the time measurement processing unit 83. In the present embodiment, the first correction amount determination unit 84 determines the first correction amount A1 corresponding to the power supply stop time X1 based on the first correction data table 811 (see FIG. 5).

  Based on the second correction data stored in the storage unit 81, the second correction amount determination unit 85 determines the second correction amount A2 corresponding to the power supply duration time X2 calculated by the time measurement processing unit 83. In the present embodiment, the second correction amount determination unit 85 determines the second correction amount A2 corresponding to the power supply duration time X2 based on the second correction data table 812 (see FIG. 7).

  The temperature calculation unit 86 calculates the ambient temperature of the developing device 23 based on the detection signal output from the thermistor 63 and the power supply stop time X1 and power supply continuation time X2 calculated by the time measuring unit 83. Specifically, the temperature calculation unit 86 is determined by the detection signal output from the thermistor 63, the first correction amount A1 determined by the first correction amount determination unit 84, and the second correction amount determination unit 85. Based on the second correction amount A2, the ambient temperature of the developing device 23 is calculated.

  Conventionally, offset correction is performed on the assumption that the temperature of the drive circuit board is cooled to the same level as the environmental temperature. Therefore, the time from when power supply to an electronic component such as the magnetic permeability sensor 62 that generates a large amount of heat during power supply is stopped until power supply is resumed is short, and the temperature of the drive circuit board is the ambient temperature of the object such as the developing device. It is difficult to accurately measure the ambient temperature if it is not cooled to the same degree. On the other hand, in the image forming apparatus 10 of the present invention, when the power supply stop time X1 of the magnetic permeability sensor 62 is short, the correction considering the power supply stop time X1 is performed based on the first correction data. Therefore, in the image forming apparatus 10, the thermistor 63 is mounted on the same substrate as the electronic component such as the magnetic permeability sensor 62 that generates a large amount of heat during power supply, and the power supply stop and power supply start of the electronic component such as the magnetic permeability sensor 62 are short. Even in a situation where time is required, the ambient temperature of an object such as the developing device 23 can be accurately measured by the thermistor 63.

  Further, in the image forming apparatus 10, even when the power supply duration X2 of the magnetic permeability sensor 62 is short, the correction considering the power supply duration X2 is performed based on the second correction data. Therefore, in the image forming apparatus 10, the thermistor 63 can measure the ambient temperature of an object such as the developing device 23 more accurately.

  Next, the ambient temperature calculation process executed by the control unit 8 will be described with reference to the flowcharts of FIGS. 8 and 9. In the figure, S1, S2,... Represent processing procedure (step) numbers. The processing in each step is executed by the time measurement processing unit 83, the first correction amount determination unit 84, the second correction amount determination unit 85, the temperature calculation unit 86, and the like of the control unit 8.

<Steps S1 and S2>
As shown in FIG. 8, the control unit 8 determines whether or not the power supply to the magnetic permeability sensor 62 is started on the condition that the main power source is in an on state (step S1: Yes) (step S2). . When power supply to the magnetic permeability sensor 62 is started (step S2: Yes), the control unit 8 shifts the process to step S3. On the other hand, when the power supply to the magnetic permeability sensor 62 is not started (step S2: No), the control unit 8 shifts the process to step S7.

<Step S3>
In step S <b> 3, the time measurement processing unit 83 of the control unit 8 acquires first time information related to the power supply start time when power supply to the magnetic permeability sensor 62 is started from the RTC 7, and uses the first time information stored in the storage unit 81. Update.

<Step S4>
In step S4, the time measuring unit 83 of the control unit 8 calculates the power supply stop time X1 based on the second time information stored in the storage unit 81 and the first time information updated in step S3. . The second time information is information regarding the power supply stop time updated by the time measuring unit 83 of the control unit 8 in step S8 (see FIG. 9) described later.

<Step S5>
In step S5, the first correction amount determination unit 84 of the control unit 8 responds to the power supply stop time X1 calculated in step S4 based on the first correction data table 811 (see FIG. 5) stored in the storage unit 81. The first correction amount A1 is determined and the first correction amount A1 stored in the storage unit 81 is updated.

<Step S6>
In step S <b> 6, the temperature calculation unit 86 of the control unit 8 calculates the ambient temperature of the developing device 23. Specifically, first, the control unit 8 is output from the thermistor 63 based on the first correction amount A1 determined in step S5 and the second correction amount A2 stored in the storage unit 81 in step S10 described later. The output value Y of the detected signal is corrected. Next, the control unit 8 calculates the ambient temperature based on the relationship between the corrected output value Y and the ambient temperature of the developing device 23.

<Step S7>
In step S <b> 7, the control unit 8 determines whether power supply to the magnetic permeability sensor 62 is stopped. When power supply to the magnetic permeability sensor 62 is stopped (step S7: Yes), the control unit 8 shifts the process to step S8 in FIG. On the other hand, when the power supply to the magnetic permeability sensor 62 is not stopped (step S7: No), the control unit 8 shifts the process to step S2 and calculates the ambient temperature of the developing device 23 again. That is, in the image forming apparatus 10, the calculation of the ambient temperature of the developing device 23 is repeatedly performed while the power supply to the magnetic permeability sensor 62 is continued.

<Steps S8 and S9>
As shown in FIG. 9, the timekeeping processing unit 83 of the control unit 8 acquires the second time information regarding the power supply start time when the power supply to the magnetic permeability sensor 62 is stopped from the RTC 7 and stores the second time information stored in the storage unit 81. The 2-hour information is updated (step S8). Further, the time measurement processing unit 83 of the control unit 8 calculates the power supply duration time X2 based on the first time information updated in step S3 and the second time information updated in step S8 (step S9). .

<Step S10>
In step S10, the second correction amount determination unit 85 of the control unit 8 sets the second correction amount A2 corresponding to the power supply duration time X2 calculated in step S9 based on the second correction data table 812 (see FIG. 7). The second correction amount A2 determined and stored in the storage unit 81 is updated.

<Step S11>
In step S11, the control unit 8 determines whether or not the main power source is turned off. When the main power supply is not turned off (step S11: No), the control unit 8 shifts the process to step S2 (see FIG. 8) and continues the ambient temperature calculation process. On the other hand, when the main power supply is turned off (step S11: Yes), the control unit 8 ends the ambient temperature calculation process.

[Second Embodiment]
Next, an image forming apparatus according to a second embodiment of the present invention will be described with reference to FIG. This image forming apparatus includes a timing information providing unit 9. The time information provider 9 includes a capacitor 91 and a detector 92.

  The capacitor 91 is charged when power is supplied to the magnetic permeability sensor 62, and is discharged when power supply to the magnetic permeability sensor 62 is stopped. The capacitor 91 preferably has a discharge time longer than the first saturation time X1m (see FIG. 3) when power supply to the magnetic permeability sensor 62 is stopped. For example, the capacitor 91 has a capacity of 10 seconds or more. If it is.

  The detection unit 92 detects the discharge amount of the capacitor 91 when power supply to the magnetic permeability sensor 62 is stopped. A signal from the detection unit 92 is input to the time measurement processing unit 83. The detection unit 92 includes, for example, a load such as a resistor on the capacitor 91 and a voltage measurement unit that measures the terminal voltage of the capacitor 91. The voltage measurement unit is configured as a voltage detection circuit that outputs a signal having a level corresponding to the terminal voltage, for example. However, the configuration of the voltage measuring unit is not particularly limited.

  The time measurement processing unit 83 acquires the power supply stop time X1 based on the detection result of the detection unit 92. For example, the time measuring unit 83 calculates the power supply stop time X1 based on a predetermined relationship between the discharge amount of the capacitor 91 (for example, the terminal voltage) and the power supply stop time X1. The power supply stop time X1 is used for determination of the first correction amount A1 by the first correction amount determination unit 84.

  For example, when the load resistance (discharge resistance) is constant, the power supply stop time X1 can be calculated by the following equation. In the following formula, C is a capacitor capacity (F), R is a discharge resistance (Ω), V0 is a capacitor terminal voltage (V) at the start of discharge, V is a capacitor terminal voltage (V) detected after the start of discharge. is there.

            X1 = −C × R × ln (V / V0)

  In the above-described embodiment, the object in the image forming apparatus 10 is the developing device 23. However, the object may be a transfer unit such as the primary transfer device 24 and the secondary transfer device 15.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Image forming part 23 Developing device 62 Magnetic permeability sensor 63 Thermistor 7 RTC
8 Control Unit 81 Storage Unit 811 First Correction Data Table 812 Second Correction Data Table 82 CPU
83 Timekeeping Processing Unit 84 First Correction Amount Determination Unit 85 Second Correction Amount Determination Unit 86 Temperature Calculation Unit 91 Condenser 92 Detection Unit

Claims (8)

A substrate,
A drive circuit formed on the substrate and driving a predetermined object and having an electronic component;
A thermistor mounted on the substrate and outputting a detection signal according to the ambient temperature of the object;
A timing processing unit for acquiring a power supply stop time during which power supply to the electronic component is stopped;
Based on the detection signal output from the thermistor and the power supply stop time acquired by the time measuring unit, a temperature calculation unit that calculates the ambient temperature of the object;
A temperature measuring device comprising: A storage unit that stores first correction data in which the power supply stop time is associated with a first correction amount for correcting the ambient temperature calculated based on the detection signal;
Based on the first correction data stored in the storage unit, a first correction amount determination unit that determines a first correction amount according to the power supply stop time acquired by the time measuring unit;
Further comprising
The temperature calculation unit calculates an ambient temperature of the object based on a detection signal output from the thermistor and a first correction amount determined by the first correction amount determination unit;
The temperature measuring device according to claim 1. The timekeeping processing unit acquires a power supply duration time during which power supply to the electronic component is continued,
The storage unit stores second correction data in which the power supply duration time is associated with a second correction amount for correcting an ambient temperature calculated based on the detection signal,
A second correction amount determination unit that determines a second correction amount according to the power supply duration acquired by the time measurement unit based on the second correction data stored in the storage unit;
The temperature calculation unit includes a detection signal output from the thermistor, a first correction amount determined by the first correction amount determination unit, and a second correction amount determined by the second correction amount determination unit. Calculating the ambient temperature of the object based on
The temperature measuring device according to claim 2. With a real time clock,
The time measuring unit acquires the power supply stop time based on time information acquired from the real-time clock,
The temperature measuring device according to claim 1. A capacitor that is charged when power is supplied to the electronic component; and a detection unit that detects a discharge amount of the capacitor after power supply to the electronic component is stopped.
The time measuring unit acquires the power supply stop time based on a detection result by the detection unit,
The temperature measuring device according to claim 1 or 2. The temperature measuring device according to any one of claims 1 to 5,
An image forming unit for forming an image on a sheet;
An image forming apparatus comprising: The object is a developing unit that forms a toner image on an image carrier.
The image forming apparatus according to claim 6. The developing unit has a developer containing toner and carrier,
The electronic component is a magnetic permeability sensor that detects a carrier concentration in the developer.
The image forming apparatus according to claim 7.

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