JP2018116145A - Toner density detection device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly correct a detection value of a toner density sensor regardless of a time change of a temperature.SOLUTION: A toner density detection device 13 of a printer includes: a toner density sensor 24 which outputs a detection value corresponding to toner density of developer by detecting the permeability of the developer containing toner; and a temperature sensor 25 which detects an ambient temperature of the toner density sensor 24. The toner density detection device 13 previously sets a correction value of correcting the detection value so as to suppress fluctuation of a transient response due to a time change of a temperature of the toner density sensor 24. The toner density detection device 13 measures a change rate of the detection temperature by the temperature sensor 25, identifies a correction value on the basis of the change rate of a measurement result, and performs correction processing for correcting the detection value of the toner density sensor 24 by using the identified correction value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a toner concentration detection device that detects the concentration of toner contained in a toner container or a developing device, and an image forming apparatus including the toner concentration detection device.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus such as a printer or a copying machine has a toner such as a developing unit that develops an image carrier such as a photosensitive drum with toner, or a toner container that contains toner supplied to the developing unit. A container. In the developing device and the toner container, for example, a two-component developer composed of a non-magnetic toner and a magnetic carrier is accommodated in a housing, and a toner concentration sensor is provided to detect the toner concentration (toner amount). . For example, the toner concentration sensor includes a magnetic permeability sensor that detects the magnetic permeability (magnetic flux density) of the developer in the housing, and outputs a detection value corresponding to the toner density based on the magnetic permeability. Such a magnetic permeability sensor has a temperature characteristic in which a detection value varies with a temperature change. For example, in the temperature characteristic of the magnetic permeability sensor, the detection value at a high temperature state (45 ° C.) is increased by 10% with respect to the detection value at normal temperature (20 ° C.). Therefore, the toner concentration detection device corrects the detected value of the magnetic permeability sensor based on the temperature characteristic.

  For example, a toner concentration detection device disclosed in Patent Document 1 includes an oscillation circuit that oscillates at a frequency corresponding to the magnetic permeability of a two-component developer, a frequency detection unit that detects an oscillation frequency, and a voltage that detects an oscillation start voltage. Based on the detected operating environment temperature and the oscillation start voltage by applying information indicating the relationship between the temperature characteristic of the oscillation start voltage and the oscillation frequency, the detection unit, the temperature detection unit for detecting the operating environment temperature of the oscillation circuit And a correction unit that corrects the detected oscillation frequency, and outputs the corrected oscillation frequency as toner density information.

JP 2013-160859 A

  The temperature characteristics of the magnetic permeability sensor as the toner concentration sensor as described above are observed when the magnetic permeability sensor is placed in the same temperature environment and the elements constituting the magnetic permeability sensor are sufficiently familiar. . However, in the magnetic permeability sensor, when the temperature changes, the transient response until the correct detection value corresponding to the temperature after the change is output differs depending on the degree of the temporal change of the temperature. The transient response speed until output has a transient response characteristic that varies depending on the degree of temperature change over time. Therefore, even if the detected value of the magnetic permeability sensor is corrected based on the temperature characteristic as described above, the correction result may vary due to a change in temperature with time.

  An object of the present invention is to appropriately correct a detection value of a toner density sensor regardless of a change in temperature with time.

  A toner concentration detection device according to the present invention detects a magnetic permeability of a developer containing toner, and outputs a detection value corresponding to the toner concentration of the developer, and an ambient temperature of the toner concentration sensor. A temperature sensor for detecting, a correction value for correcting the detection value is set in advance so as to suppress a change in transient response due to a temporal change in temperature of the toner density sensor, and a temperature detected by the temperature sensor is set. A change rate is measured, the correction value is specified based on the change rate of the measurement result, a correction process is performed to correct the detection value of the toner density sensor using the specified correction value, and further, the temperature sensor The detection value is corrected based on the detected current detected temperature so that a characteristic at a predetermined reference temperature of the toner density sensor can be obtained. To.

  The toner density detection device further includes a correction table that stores in advance one or more combinations of a temperature change rate range of the toner density sensor and the correction value of the toner density sensor. The correction value may be specified by referring to the correction table based on the change rate of the measurement result.

  The toner concentration detection apparatus includes a current current detection temperature detected by the temperature sensor, a first detection temperature that is a first time before the current time, and a second time that exceeds the first time from the current time. A storage unit that stores a previous second detected temperature is further included, and in the correction process, a first rate of change between the current detected temperature and the first detected temperature, the current detected temperature, and the second detected temperature. The second change rate with respect to the detected temperature is measured, the first correction value corresponding to the first change rate and the second change rate corresponding to the second change rate are referred to with reference to the correction table. And the current detection value of the toner density sensor may be corrected using the first correction value and the second correction value.

  An image forming apparatus of the present invention includes the above-described toner concentration detection device, and a developing unit that develops the electrostatic latent image formed on the image carrier using toner, and the toner concentration detection device includes: The toner density of the developer in the developing device is detected.

  Alternatively, an image forming apparatus of the present invention includes the above-described toner density detection device, a developing device that develops an electrostatic latent image formed on an image carrier using toner, and a toner that is applied to the developing device. A toner container to be replenished, wherein the toner concentration detection device is configured to detect a toner concentration of the developer in the toner container.

  According to the present invention, it is possible to appropriately correct the detection value of the toner density sensor regardless of the temperature change with time.

1 is a cross-sectional view illustrating a printer according to an embodiment of the present invention. 1 is a block diagram illustrating a toner density detection device for a printer and an electrical configuration around the printer according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating an electrical configuration of a magnetic permeability sensor in the toner concentration detection device for a printer according to an embodiment of the present invention. 6 is a graph illustrating an example of temperature characteristics of a magnetic permeability sensor in a toner concentration detection device for a printer according to an embodiment of the present invention. 6 is a graph illustrating an example of a transient response characteristic of a magnetic permeability sensor in a toner concentration detection device for a printer according to an embodiment of the present invention. 6 is a graph showing another example of the transient response characteristic of the magnetic permeability sensor in the toner concentration detection device of the printer according to the embodiment of the present invention. It is a graph which shows the further example of the transient response characteristic of the magnetic permeability sensor in the toner concentration detection apparatus of the printer which concerns on one Embodiment of this invention. 6 is a table showing an example of a correction value for a temperature change rate of a magnetic permeability sensor in a toner concentration detection device for a printer according to an embodiment of the present invention. 6 is a table showing another example of a correction value for a temperature change rate of a magnetic permeability sensor in a toner concentration detection device for a printer according to an embodiment of the present invention.

  First, the overall configuration of a printer 1 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIG. For convenience of explanation, the front side of the page in FIG. Arrows L, R, U, and Lo appropriately attached to the drawings indicate the left side, right side, upper side, and lower side of the printer 1, respectively.

  The printer 1 includes a box-shaped printer main body 2. A paper feed cassette for storing paper is mounted on the lower part of the printer main body 2, and a paper discharge tray is provided on the upper surface of the printer main body 2. An upper cover 3 is attached to the upper surface of the printer main body 2 so as to be openable and closable on the side of the paper discharge tray in order to attach and detach the following toner container 12 to the printer main body 2.

  An exposure unit composed of a laser scanning unit (LSU) is disposed below the paper discharge tray in the upper part inside the printer main body 2, and an image forming unit 5 is provided below the exposure unit. The image forming unit 5 is rotatably provided with a photosensitive drum 10 (image carrier) that is an image carrier. Around the photosensitive drum 10, a charger, a developing device 11, a transfer roller, A cleaning device is disposed along the rotation direction of the photosensitive drum 10.

  A toner container 12 (toner container) is disposed above the developing device 11, and the toner container 12 is a two-component developer composed of a non-magnetic toner and a magnetic carrier as a developer to be replenished to the developing device 11. Is accommodated in the container housing 12a. In addition, the printer main body 2 includes a toner concentration detection device 13 that detects the toner concentration of the nonmagnetic toner in the developing device 11.

  A paper transport path 15 is provided inside the printer main body 2. A paper feeding unit is provided in the vicinity of the paper feeding cassette at the upstream end of the conveyance path 15, and a transfer unit including the photosensitive drum 10 and the transfer roller is provided in the middle part of the conveyance path 15. A fixing device is provided in the downstream portion of the paper, and a paper discharge portion is provided in the vicinity of the paper discharge tray at the downstream end of the conveyance path 15.

  Next, an image forming operation of the printer 1 having such a configuration will be described. The printer 1 starts an image forming operation when image data is input from an external computer or the like and an instruction to start printing is given. First, after the surface of the photosensitive drum 10 is charged by the charger of the image forming unit 5, the photosensitive drum 10 is exposed in accordance with the image data by the laser beam from the exposure unit, and the photosensitive drum 10 is exposed. An electrostatic latent image is formed on the surface. Next, the developing device 11 of the image forming unit 5 develops the electrostatic latent image into a toner image using toner.

  On the other hand, the paper stored in the paper feed cassette is taken out by the paper feed unit and transported on the transport path 15. The sheet on the conveyance path 15 is conveyed to the transfer unit at a predetermined timing, and the toner image on the photosensitive drum 10 is transferred to the sheet by the transfer unit. The sheet on which the toner image is transferred is conveyed to a fixing device, and the toner image is fixed on the sheet by the fixing device. The paper on which the toner image is fixed is discharged from the paper discharge unit to the paper discharge tray.

  Next, the developing device 11 will be described. In the present embodiment, a configuration in which the developing device 11 applies a two-component developer including a non-magnetic toner and a magnetic carrier as a developer will be described. However, the developing device 11 uses a one-component developer composed only of magnetic toner. The structure applied as a developing agent may be sufficient. The developing device 11 includes a housing 20 that stores a developer containing toner. In the housing 20, a developing roller 21 that supplies toner to the photosensitive drum 10 and an agitating member 22 that agitates and conveys the toner. And a conveying member 23 are provided. Further, as shown in FIG. 2, the developing device 11 includes a toner concentration sensor 24 that detects the toner concentration in the housing 20, and a temperature sensor 25 such as a thermistor that detects the ambient temperature of the toner concentration sensor 24.

  The housing 20 is formed in a substantially box shape that is long in the front-rear direction, and has an opening that opens to the left so as to face the photosensitive drum 10 and a supply port 20a that opens to the top. The casing 20 communicates with the container casing 12a of the toner container 12 through the supply port 20a and the supply path. The developing roller 21 is formed in a columnar shape that is long in the front-rear direction, is disposed so as to face the photosensitive drum 10 through the opening, and is rotatably attached. The agitating member 22 and the conveying member 23 are formed in a columnar shape that is long in the front-rear direction, and are arranged with a long partition wall in the front-rear direction standing at the lower part in the housing 20 and are rotatably attached. In particular, the conveying member 23 is disposed below the supply port 20a.

  The toner concentration sensor 24 includes a magnetic permeability sensor that detects the magnetic permeability (magnetic flux density) of the developer in the housing 20, and outputs a voltage value (detected value) corresponding to the toner density based on the magnetic permeability.

  For example, as shown in FIG. 3, the toner density sensor 24 includes an oscillation circuit 30 that oscillates a clock signal having a predetermined frequency, and a resonance circuit 31 that has a coil 31a that resonates at the frequency of the clock signal. The resonance circuit 31 is configured such that the coil 31a resonates with the original clock signal output from the oscillation circuit 30, and outputs a resonance clock signal. The resonance clock 31 is affected by the influence of the magnetic permeability of the developer on the coil 31a. The frequency of the signal changes from the frequency of the original clock signal.

  Further, the toner density sensor 24 includes a phase comparison circuit 32, a smoothing circuit 33, and an amplification circuit 34. The phase comparison circuit 32 outputs a pulse signal indicating a phase difference in frequency between the original clock signal from the oscillation circuit 30 and the resonance clock signal from the resonance circuit 31. The smoothing circuit 33 smoothes the pulse signal output from the phase comparison circuit 32 and outputs a DC voltage, and the amplifier circuit 34 amplifies the DC voltage output from the smoothing circuit 33, and Output as detection value. The toner concentration sensor 24 composed of such a magnetic permeability sensor has a temperature characteristic in which the detection value fluctuates due to a temperature change. For example, as shown in FIG. Thus, the detection value at a high temperature (45 ° C.) increases by 10%.

  Further, the toner concentration sensor 24 constituted by a magnetic permeability sensor has a transient response characteristic in which the transient response speed until a correct detection value is output varies depending on the degree of temporal change in temperature. According to the transient response characteristic of the toner concentration sensor 24, for example, as shown in FIG. 5, the temperature of the toner concentration sensor 24 gradually increases from about 20 ° C. to about 40 ° C. (eg, over about 18 minutes). In this case, the output of the detection value by the toner density sensor 24 immediately follows the time change of the temperature and hardly delays. On the other hand, as shown in FIGS. 6 and 7, when the temperature of the toner concentration sensor 24 suddenly increases from about 20 ° C. to about 40 ° C. (eg, over about 10 minutes or about 5 minutes), the toner concentration The output of the detected value by the sensor 24 follows with a delay from the time change of the temperature, and it takes time to cope with the temperature after the change.

  Next, the toner concentration detection device 13 will be described. As shown in FIG. 2, the toner concentration detection device 13 includes the toner concentration sensor 24, the temperature sensor 25, and the control device 40. In the following, an example in which the toner density detection device 13 applies the control device 40 that controls the developing device 11 will be described. However, a main control device (not shown) that controls the printer 1 as a whole is applied as the control device 40. Also good.

  The control device 40 includes a control unit 41 configured with a CPU or the like, and a storage unit 42 configured with a ROM, a RAM, or the like. The control device 40 is connected to the toner density sensor 24 and the temperature sensor 25 of the developing device 11, and controls the toner density sensor 24 and the temperature sensor 25, respectively, and also uses the detected value from the toner density sensor 24 and the temperature sensor 25. Enter the detection temperature.

  Moreover, the control apparatus 40 is connected to each part, such as the drive part 43 of the developing device 11, and the drive part 43 is comprised with a motor etc., for example. The driving unit 43 is connected to the developing roller 21, the agitating member 22, and the conveying member 23 of the developing device 11 via a driving gear and the like, and is controlled by the control device 40 to the developing roller 21, the agitating member 22, and the conveying member 23. Rotates by transmitting rotational driving force.

  The storage unit 42 stores programs and data for realizing the developing function of the developing device 11, the toner density detecting function of the toner density detecting device 13, and other various functions. In the control device 40, the control unit 41 executes arithmetic processing according to each program stored in the storage unit 42 and controls each unit connected to the control device 40.

  In the storage unit 42, for example, a correction value for correcting the detection value of the toner density sensor 24 is set and stored in advance. This correction value is defined so as to suppress the fluctuation of the transient response due to the temporal change of the temperature of the toner concentration sensor 24 due to the transient response characteristic of the toner concentration sensor 24. The control device 40 predicts the transient response of the toner density sensor 24 based on the temperature detected by the temperature sensor 25, and corrects the detection value of the toner density sensor 24 with a correction value based on the prediction result. Specifically, the detection value of the toner density sensor 24 is corrected so as to increase as the rate of change of the temperature of the toner density sensor 24 per unit time increases. For example, the storage unit 42 stores a correction table 44 of one or more combinations of the temperature change rate range of the toner density sensor 24 and the correction value of the detection value of the toner density sensor 24.

  For example, the storage unit 42 stores, as the correction table 44, a first correction table 44a as shown in FIG. 8 for the temperature change rate of the toner density sensor 24 at a predetermined first time (for example, 1 minute). . In the first correction table 44a of FIG. 8, T (n) indicates the latest sampling temperature, and T (n-1) indicates the sampling temperature one minute before. In FIG. 8, for example, when the temperature rises by 20 ° C. per minute, the temperature change rate becomes 20. Further, the storage unit 42 uses the correction table 44 as the second change as shown in FIG. 9 for the temperature change rate of the toner density sensor 24 for a predetermined second time (for example, 30 minutes) exceeding the first time. The correction table 44b is stored. In the second correction table 44b of FIG. 9, T (n-30) indicates the sampling temperature 30 minutes before. In FIG. 9, for example, when the temperature rises by 20 ° C. in 30 minutes, the temperature change rate becomes 20.

  As a toner density detection function, the control device 40 stores the detection result (detected temperature) of the ambient temperature of the toner density sensor 24 detected by the temperature sensor 25 in the storage unit 42 in time series. For example, the storage unit 42 stores at least the current current detection temperature, the first detection temperature before a predetermined first time (for example, 1 minute), and the predetermined second time exceeding the first time. The detected temperature by the temperature sensor 25 is stored so that the second detected temperature before (for example, 30 minutes) can be grasped.

  Further, as a toner density detection function, the control device 40 detects a detection value (current detection value) corresponding to the current toner density of the developing device 11 with the toner density sensor 24, and detects the current density of the toner density sensor 24 with the temperature sensor 25. Detect the ambient temperature (current detection temperature). Then, the control device 40 measures the rate of change of the current detected temperature, for example, a first rate of change between the current detected temperature and the first detected temperature, and a second of the current detected temperature and the second detected temperature. Measure the rate of change.

  Next, the control device 40 specifies a correction value for correcting the current detection value of the toner density sensor 24 based on the change rate of the measurement result, and refers to the first correction table 44a, for example, to determine the first correction value. The first correction value corresponding to the change rate is specified, and the second correction value corresponding to the second change rate is specified with reference to the second correction table 44b. Further, the control device 40 performs a correction process for correcting the current detection value of the toner density sensor 24 using the specified correction value, and adds, for example, the first correction value and the second correction value to the current detection value. This corrects the current detection value. The control device 40 outputs the correction result as an output value of the toner concentration detection device 13 indicating an appropriate toner concentration of the developing device 11.

  In addition to the correction processing described above, the toner concentration detection device 13 uses the detection value at a predetermined temperature (reference temperature) as a reference, even when the temperature of the toner concentration sensor 24 is other than the predetermined temperature. Correction based on temperature is performed so that a value equivalent to the detected value is obtained. The toner concentration sensor 24 has a temperature characteristic such that the detected value increases as the temperature increases. For example, the detected value at a higher temperature (for example, 45 ° C.) than the detected value at a normal temperature (for example, 20 ° C.). May increase by 10% (see FIG. 4). Therefore, the toner concentration detection device 13 corrects the detection value so that the characteristic at the reference temperature of the toner concentration sensor 24 can be obtained based on the current detected temperature detected by the temperature sensor 25 by the control device 40 or the like. For example, when the normal temperature (for example, 20 ° C.) is set as the reference temperature and the toner concentration sensor 24 is in a high temperature state (for example, 45 ° C.), the detected value is 1.1 times that at the reference temperature. The detection value is corrected to 10/11.

  According to the present embodiment, as described above, the toner concentration detection device 13 of the printer 1 (image forming apparatus) detects the magnetic permeability of the developer containing toner, thereby detecting the toner concentration corresponding to the developer. A toner density sensor 24 that outputs a value and a temperature sensor 25 that detects the ambient temperature of the toner density sensor 24 are provided. In the toner concentration detection device 13, a correction value for correcting the detection value is set in advance so as to suppress the fluctuation of the transient response due to the time change of the temperature of the toner concentration sensor 24. The toner concentration detection device 13 measures the rate of change of the temperature detected by the temperature sensor 25, specifies a correction value based on the rate of change of the measurement result, and corrects the detection value of the toner concentration sensor 24 using the specified correction value. Correction processing is performed. Further, the toner concentration detection device 13 corrects the detection value based on the current detected temperature detected by the temperature sensor 25 so that the characteristic of the toner concentration sensor 24 at a predetermined reference temperature can be obtained.

  As a result, the toner concentration detection device 13 suppresses the fluctuation of the transient response speed due to the temporal change of the temperature of the toner concentration sensor 24 by the correction value in consideration of the transient response characteristic of the toner concentration sensor 24. The detection value of the toner density sensor 24 can be appropriately corrected regardless of the time change.

  Further, according to the present embodiment, the toner density detection device 13 further includes a correction table 44 that stores in advance one or more combinations of the temperature change rate range of the toner density sensor 24 and the correction value of the toner density sensor 24. Prepare. In the correction process of the toner concentration detection device 13, the correction value is specified with reference to the first correction table 44 a and the second correction table 44 b based on the measurement result of the change rate of the detected temperature by the temperature sensor 25. Thereby, the correction value considering the transient response characteristic of the toner density sensor 24 can be specified by a simple method.

  In addition, according to the present embodiment, the toner concentration detection device 13 has the current current detection temperature detected by the temperature sensor 25, the first detection temperature before the first time before the current time, and the first detection temperature before the current time. A storage unit 42 is further provided for storing the second detected temperature before the second time exceeding the first time. In the correction process of the toner density detection device 13, the first change rate between the current detection temperature and the first detection temperature and the second change rate between the current detection temperature and the second detection temperature are measured. Referring to the first correction table 44a and the second correction table 44b, the first correction value corresponding to the first change rate and the second correction value corresponding to the second change rate are specified, The current detection value of the toner density sensor 24 is corrected using the first correction value and the second correction value. Thus, the detection value of the toner density sensor 24 can be corrected more appropriately in order to more appropriately predict the transient response characteristic of the toner density sensor 24 and specify a more appropriate correction value. For example, when the temperature of the toner density sensor 24 has risen before the second time (30 minutes before), but the temperature has become steady before the first time (1 minute). There are various change patterns, such as when the temperature was steady before the second time (30 minutes before), but the temperature rose before the first time (1 minute). The transient response of the concentration sensor 24 varies widely. On the other hand, in the present embodiment, various transient responses of the toner concentration sensor 24 are taken into consideration by considering the first detection temperature before the first time and the second detection temperature before the second time. The detected value can be corrected corresponding to the above.

  In this embodiment, the printer 1 has a housing 20 and develops an electrostatic latent image formed on the photosensitive drum 10 (image carrier) using toner in the housing 20. The configuration in which the toner concentration detection device 13 is provided to detect the toner concentration in the housing 20 of the developing device 11 has been described. However, the toner concentration detection device 13 of the present invention is not limited to the configuration applied to the developing device 11. For example, in another embodiment, the printer 1 includes a container casing 12a, and includes a toner container 12 (toner container) that replenishes the toner in the container casing 12a with respect to the developing device 11, and has a toner concentration. The detection device 13 may be applied to detect the toner concentration in the container housing 12 a of the toner container 12.

  In the present embodiment, the toner concentration detection device 13 determines the correction value in consideration of the transient response characteristic of the toner concentration sensor 24 in advance by combining the range of the temperature change rate of the toner concentration sensor 24 and the correction value. Although the configuration including the stored correction table 44 has been described, the specification of the correction value of the toner density sensor 24 is not limited to this configuration. For example, in another embodiment, the toner density detection device 13 predefines and stores a mathematical formula in which a correction value is calculated based on the temperature change rate of the toner density sensor 24, and specifies the correction value based on this mathematical formula. It may be configured to.

  In the present embodiment, the case where the configuration of the present invention is applied to the monochrome printer 1 has been described. However, in another different embodiment, the present invention is applied to other image forming apparatuses such as a color printer, a copier, a facsimile machine, and a multifunction machine. It is also possible to apply this configuration.

1 Printer (image forming device)
2 Printer Main Body 5 Image Forming Unit 10 Photosensitive Drum 11 Developer 12 Toner Container (Toner Container)
24 toner density sensor 25 temperature sensor 40 control device 41 control unit 42 storage unit 44 correction table 44a first correction table 44b second correction table

Claims (5)

A toner concentration sensor that outputs a detection value corresponding to the toner concentration of the developer by detecting the magnetic permeability of the developer containing toner; and
A temperature sensor for detecting an ambient temperature of the toner concentration sensor,
A correction value for correcting the detection value is set in advance so as to suppress a change in transient response due to a temporal change in temperature of the toner concentration sensor,
A correction process for measuring a change rate of the temperature detected by the temperature sensor, specifying the correction value based on the change rate of the measurement result, and correcting the detection value of the toner density sensor using the specified correction value. And, further, correcting the detection value based on a current detected temperature detected by the temperature sensor so as to obtain a characteristic of the toner density sensor at a predetermined reference temperature. Detection device. A correction table that stores in advance one or more combinations of the temperature change rate range of the toner density sensor and the correction value of the toner density sensor;
2. The toner density detection apparatus according to claim 1, wherein in the correction process, the correction value is specified by referring to the correction table based on a change rate of the measurement result. A current detected temperature detected by the temperature sensor; a first detected temperature a first time before the present; a second detected temperature a second time before the first time greater than the present; A storage unit for storing
In the correction process, a first rate of change between the current detected temperature and the first detected temperature, and a second rate of change between the current detected temperature and the second detected temperature are measured,
With reference to the correction table, a first correction value corresponding to the first change rate and a second correction value corresponding to the second change rate are specified,
3. The toner density detection apparatus according to claim 2, wherein a current detection value of the toner density sensor is corrected using the first correction value and the second correction value. A toner concentration detection device according to any one of claims 1 to 3,
A developing unit that develops the electrostatic latent image formed on the image carrier using toner,
The image forming apparatus, wherein the toner concentration detection device is configured to detect a toner concentration of the developer in the developing device. A toner concentration detection device according to any one of claims 1 to 3,
A developing device for developing the electrostatic latent image formed on the image carrier using toner;
A toner container for supplying toner to the developing device,
The image forming apparatus, wherein the toner concentration detection device is configured to detect a toner concentration of the developer in the toner container.

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