JPH0756402A - Image forming device with humidity detecting function - Google Patents

Abstract

PURPOSE:To provide an image forming device provided with a humidity detecting function, measuring directly the moisture contents at present of a recording paper, a developer, a transfer belt, etc., being easily affected by an environmental change in temperature, humidity, etc., and executing the correction control of image forming conditions based on the result of the measurement. CONSTITUTION:The electrophotographic, image forming device provided with an image forming part forming a copying image and humidity detecting devices 13, 16, 30 and 31 measuring the moisture contents of the objects to be measured arranged in the right places in a device, a control part for comparing the result of the measurement from respective humidity detecting devices 13, 16, 30 and 31 with the stored reference value, to execute the correcting control of the image forming conditions is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention accurately measures the humidity of recording paper, developer and transfer belt in an electrophotographic image forming apparatus, which is adversely affected by atmospheric humidity and causes deterioration of image quality. The present invention relates to an image forming apparatus having a humidity detecting function that performs correction processing on image forming conditions according to measured values.

[0002]

2. Description of the Related Art In an image forming apparatus utilizing an electrophotographic process such as a copying machine, a printer, a facsimile machine, etc., the amount of water (water content) such as recording paper stored in a tray, a developer in a developing section, a transfer belt, etc. If the ratio is increased, these become one of the factors that make the image forming conditions unstable, and the image quality is degraded. In order to maintain stable image quality without being affected by environmental changes such as humidity, sensors that detect temperature and humidity are provided around the photoconductor and outside the device to detect the atmosphere around the equipment and By comparing the result with a preset reference value, the correction control of the image forming condition is performed. However, in the conventional device, the position of the sensor is not always appropriate and the object to be measured cannot be detected correctly, so that the above control cannot be performed accurately.

As a method for controlling the correction of the above-mentioned image forming conditions, for recording paper which is most susceptible to environmental changes, 10 to 30 W provided at the bottom of the recording paper tray when the image forming apparatus is powered on. The heating device is operated to dry (dehumidify) the recording paper and prevent moisture absorption, but since the heating device is always on, the heat accumulated in the recording paper is fed to the photoconductor side by the paper feed conveyance. As a result, the photoconductor is abnormally heated. Moreover, since the heating device is always in the operating state, waste of electric power is considerable. As for the water content of the recording paper for the copying machine, 4 to 8% is considered to be the optimum condition for transferring the image, and if the water content exceeds 10%, the transfer and separation efficiency of the image will be decreased and the feeding efficiency will decrease. This may cause a paper feed error during paper conveyance, or cause wrinkles and unfixing in the fixing device. And
The recording paper in the tray is generally fed from the top, and when replenishing the recording paper in the tray, it is also replenished from the top, but it is not always said that the fed recording paper is in the state of the optimum water content. Not limited to this, when an image is formed on such a recording sheet in an over-humid state, it may cause image quality defects and the like.

Further, the humidity detecting device is composed of a light emitting element and a light receiving element, and a filter for passing different wavelengths is provided on either the light emitting side or the light receiving side, and a method of replacing the filter for each measurement is adopted. Therefore, when measuring a moving detection object, the measurement position is different each time, which is not suitable for measuring a moving object. In addition, since it takes time and effort to replace the filter, operability is poor. A technique for controlling the charging potential of the photoconductor by providing a humidity sensor for measuring the water content of the developer inside the developing device is disclosed in JP-A-5-19579, but the water content of the developer is measured. It is impossible to prevent the deterioration of the image quality due to the absorbed recording paper or the charging belt only by controlling the charging potential of the photoconductor based on the above.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and directly measures the moisture content of a recording paper, a developer, a transfer belt, etc., which is easily affected by environmental changes such as temperature and humidity. Since the image forming condition is corrected and controlled based on the result, it is possible to obtain the optimum control condition corresponding to the change in the environment.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention is an electrophotographic apparatus provided with an image forming section for producing a copied image and a humidity detecting apparatus arranged in a proper place inside the apparatus for measuring the water content of an object to be measured. In the image forming apparatus, a control unit that corrects and controls the image forming condition by comparing the measurement result from each of the humidity detecting devices and the stored reference value is provided. A light emitting unit for irradiating the object to be measured, a plurality of light receiving units for receiving reflected light from the object to be measured at a predetermined angle, and a filter arranged on the front surface of each light receiving unit and having different transmission wavelengths, respectively. The control section compares the outputs from the respective light receiving sections, and controls the image forming conditions based on the comparison result and a preset reference value. Recording from paper equipment to photoconductor The humidity detecting device is arranged in the transport path, and the humidity detecting device includes a light emitting unit that irradiates the measurement target with projection light, a plurality of light receiving units that receive reflected light from the measurement target at a predetermined angle, and each light receiving unit. Each of which has a filter having a different transmission wavelength from the front surface of the recording medium, and a reference plate which is disposed at a position opposite to the light emitting portion with the recording paper conveying path interposed therebetween, and the control portion includes the measurement target. The presence or absence of the measurement target is determined based on the reflection output from the reference plate and the reflection output from the reference plate, and if there is the measurement target, the reflection output of the measurement target and the reflection of the reference plate again after a predetermined time. The output is compared, and the image forming condition is corrected and controlled by comparing the comparison result with a prestored reference value. One of the humidity detecting devices is installed in a paper feeding cassette constituting the paper feeding device. Moisture content of recording paper placed and stored The paper feed cassette is provided with a heating device for heating the stored recording paper to remove moisture, and the control unit obtains data on the moisture content of the stored recording paper obtained from the humidity detection device. Controlling the operation of the heating device based on the above, one of the humidity detecting devices is arranged in the developing device to detect the water content of the developer in the developing device, and the control unit is It stores control information for correcting the charging potential of the photoconductor in accordance with the water content of the developer.
The controller controls the charging potential based on the value of the water content of the developer detected when the copying operation is started,
The image forming unit of the image forming apparatus is provided with a transfer belt and a humidity detector for detecting the water content of the transfer belt,
The control unit performs correction control of the potential for transfer and separation based on the reference value stored in advance, the moisture content of the belt obtained from the humidity detection device, and the moisture content of the recording paper to be fed. What to do, the humidity detection device, a light emitting unit for irradiating the measured object with projection light, a plurality of light receiving units for receiving the reflected light from the measured object at a predetermined angle, on the front surface of each light receiving unit. Each of the filters is provided with a filter having a different transmission wavelength, and the control unit determines the presence or absence of the measurement target by comparing the output from each light receiving unit with a predetermined reference value. To do.

The present invention will be described in detail below with reference to the accompanying drawings. 1A and 1B are a schematic configuration diagram of an image reading unit and an image configuration unit of an image forming apparatus to which the present invention is applied. In the image reading unit 1,
When the original 4 is set on the contact glass 3 exposed by opening the original pressing plate 2, the original detection sensor 5 arranged immediately below the contact glass detects the original 4 on the contact glass. Reference numeral 6 is a closing switch, and the closing switch 6 is turned on during the closing operation of the document pressure plate 2.
Then, by outputting a close signal to a control unit (not shown), the control unit samples the output signal of the document detection sensor 5 and compares it with a reference value to determine the document size and select the corresponding recording paper. To do.

In FIG. 1B, the paper feed cassette 10 stores the recording papers 11 in a stacked manner, the heating device 12 is arranged at the bottom of the cassette, and the recording paper 11 is placed at a position facing the upper surface of the uppermost recording paper. Humidity detector 13 for measuring the humidity of recording paper
To place. A humidity detecting device 16 for recording paper is also arranged on the conveyance path between the paper feed cassette 10 and the photoconductor 15. A charger 20, a developing device 21, a transfer belt 22, a cleaning unit 23, and the like are sequentially arranged on the outer periphery of the photosensitive drum 15. Reference numeral 24 is a fixing device. Developing device 2
A developer humidity detector 30 and a transfer belt humidity detector 31 are disposed inside the transfer belt 22 and the transfer belt 22, respectively.

The above-mentioned humidity detecting devices 13, 16, 30, 3
No. 1 is placed at a suitable place where the influence of ambient light (particularly near infrared light) is small, or at a position protected by a cover or the like. Each detecting device is composed of a light emitting part and a light receiving part, and light receiving output sampling of the detecting device is performed based on a predetermined time during standby of the image forming apparatus and a document size determination signal. Judgment of detection results output from each detection device (amount of water content)
Is performed by comparison with a reference value stored in the control unit, and when it is detected that the moisture content of the recording paper stored in the storage unit exceeds the reference value by the detection device 13 provided in the paper feeding unit. The control unit turns on the heating device 12 to perform heating necessary for removing excess water. When the water content of the recording paper and the transfer belt being conveyed is detected by the detection devices 16 and 31 provided on the conveyance path and the transfer belt, respectively, and it is determined that the water content exceeds the reference value, By controlling the transfer and separation potentials, deterioration of image quality due to overhumidity is prevented. In addition, the detection device 3 in the developing device 21
When the detection result of the water content of the developer by 0 is excessive, the control unit controls the charging potential of the photoconductor to adjust the toner adhesion amount. When the water content detected by each of the detection devices is excessive and cannot be controlled, an abnormal state is displayed on the display unit in the operation unit.

Next, FIG. 2 is a schematic diagram showing a concrete example of the configuration of each of the above-mentioned detecting devices. This detecting device is a conveying recording paper detecting device 16, which measures the water content of the recording paper and detects the leading edge of the recording paper. Is for doing. The detection device 16 includes a light emitting source 35 for irradiating the detection target with detection light, and a light emitting section 37 including an optical fiber 36 for guiding the light source light to the measurement target.
It is composed of a plurality of light receiving parts 38, a filter 39, a reference plate 40 and the like. The projection light from the light source 35 passes through the optical fiber 36 and is applied to the object to be measured (the recording paper 11 being conveyed in this figure). Each light receiving section 38 is arranged on a line having a predetermined angle θ (5 to 20 degrees) with respect to the normal line of the reflected light from the surface of the object to be measured 11, and the sensitivity of each light receiving section is, for example, 0.6 to. 1.
Set to 8 μm. Filters 39 for allowing different wavelengths to pass through are arranged on the light-receiving surfaces of the respective light-receiving units 38, one filter 39 transmits the wavelength in the 1.45 μm wavelength band, and the other filter 39 has a wavelength of 1.4 μm or less. It is configured to transmit the wavelength band of. The 1.45 μm wavelength band is the wavelength most easily absorbed by the measured object when the water content is high. The reflected light output that is input to each light receiving unit via the filter is input as data to the control unit 42 via each amplification circuit 41, and the two reflected light outputs are compared in the control unit 42. Specifically, the output of 1.4 μm or less obtained from one light receiving unit and the output of the 1.45 μm wavelength band obtained from the other light receiving unit are compared, and the comparison result of both and the control unit Is compared with a reference value stored in advance to determine the water content.

Although the light source 35 dedicated to the detection device is provided in the above embodiment, the end portion of the optical fiber is disposed close to the light source used for other parts, not the light source dedicated to the detection device.
The light projected from the optical fiber onto the object to be measured may be guided to the light receiving section. In this embodiment, since the reflected light from the object to be measured is received by each light receiving section at the same time, the reflected output from the same position when the object to be detected is moving as well as being stopped. Since it can receive light, it is possible to measure a moving object. The above configuration is common to the detection devices 13, 30, 31 other than the detection device 16 for conveyed recording paper. However, some differences may occur in the setting of the reference value for determining the water content, etc., depending on the difference in the measurement target.

Further, in FIG. 2, as a method of detecting the water content of the object to be measured, a detector having a sensitivity of 1.45 μm wavelength band and a reference plate 40 are provided. According to this method, the reference plate 40 is used. By comparing the output of the reflected light and the output of the reflected light from the measured object with the output of the reference plate and the output of /1.45 μm, for example, even with one detection device, the moisture content of the measured object can be detected. It becomes possible to judge. Control unit 4
2 shows an example of the input signal for the signal 2 and the output signal from the control unit
The output of the reflected light from the reference plate 40 is measured by the detection device based on the copy start signal input by turning on the copy start key or some signal thereafter, and then, as shown in FIG. The passage of the leading edge of the conveyed recording paper is detected by detecting and determining the change in the output of the detection device at predetermined time intervals. Then, after a lapse of a predetermined time from the detection of the leading edge of the recording paper, the reflection output of the other surface of the same recording paper is measured. The control unit 42 compares the reflection output from the reference plate 40 and the reflection output from the recording paper, and controls the image forming conditions based on the reference value relating to the water content of the conveyed recording paper stored in advance in the control unit. To do. In other words, the control unit 40 determines the presence / absence of the measurement target based on the reflection output from the measurement target and the reflection output from the reference plate, and, if the measurement target is present, after a predetermined time. The image forming condition is corrected and controlled by comparing again the reflection output of the object to be measured and the reflection output of the reference plate and comparing the comparison result with a reference value stored in advance. Specific contents regarding the control of each image forming condition will be described later.

According to this method, since the reference plate is included in the detection device, it is possible to reduce the cost by reducing the component structure of the light receiving circuit, and it is also possible to detect the presence or absence of conveyance of the recording paper. It is also possible to reduce the cost by reducing the number of sensors and the number of signals. It is necessary to detect the conveyed recording paper while the copier is operating, but the measurement of the water content of the recording paper in the paper feed cassette and the developer in the developing device is mainly performed while the copier is in standby. To do. That is, when the copying machine is on standby, the output of the detection device 13 arranged in the developing device 21 and the detection device 13 for detecting the recording paper in the paper feed cassette is output every predetermined time set by the control unit. Is sampled.

The received light output of the reflected light obtained by projecting the light source light onto the recording paper 11 containing the light source by the detection device 13 in the paper feed cassette 10 is compared with the reference value in the control unit, and the reference value is set. When it is determined that the excess water content is included, the heating means 12 at the bottom of the paper feed cassette is operated to generate heat, and excess water in the recording paper (bundle) is exhausted to the outside. When the received light output is smaller than the reference value, it is determined that the water content of the recording paper is an ideal value of 4 to 7%, and the heating device is turned off. In this way, by turning the heating device on and off according to the detected light receiving output (water content), it is possible to maintain the optimum state as copy paper without heating the recording paper unnecessarily. Of course, this detection operation may be performed during the operation of the copying machine.

Next, the detecting device 30 arranged in the developing device 21 detects the water content of the developer in the developing device by the same method as described above. However, the detection target in this case is not the recording paper but the developer, but the detection determination method is performed according to the case of the recording paper. Along with the start of the document exposure scanning by the image reading apparatus 1 shown in FIG. 1A, a potential for forming a latent image is charged and formed on the photoconductor 15 by the charging charger 20. An electrostatic latent image is formed on the photoconductor 15 by exposure scanning, and the toner on the developing sleeve in the developing device moves onto the photoconductor to develop the latent image. The transfer amount of the developer fluctuates depending on the relationship between the charge potential on the surface of the photoconductor and the developing bias voltage. However, when the water content in the developer is high, the transfer amount (charge amount) of the developer decreases and the concentration decreases. Therefore, if the charge potential on the surface of the photoconductor is corrected and controlled based on the previously measured water content during development, it is possible to always secure a fixed amount of movement and prevent deterioration of image quality. In general, when the water content in the developer is high, control may be performed so that the potential is corrected to the plus side with respect to the standard value of the charging potential.

Next, the transfer belt 22 is a means for once receiving and holding the developed image on the photosensitive member, transferring it to the recording paper, and further separating the recording paper. (Electrical resistance) Image holding power is greatly affected by changes in humidity conditions, and as humidity increases, the electrical resistance of the transfer belt decreases. Therefore, transfer is performed based on the data regarding the water content of the transfer belt obtained by the detection device 31. It is necessary to control the charging potential of the belt. At this time, a more appropriate transfer ability can be maintained by considering the water content of the recording paper as the transfer medium. That is, when the original size is selected and detected by the key operation of the operation unit or the original size detection function at the start of the copying operation, the control unit selects the size in the paper feed cassette selected based on the detection signal. The respective outputs of the detection device 13 and the detection device 31 of the transfer belt unit are sampled. The light receiving outputs from the plurality of light receiving units 38 constituting the detection device are compared and determined by the control unit, and the transfer and separation potential correction control is performed based on the value stored in the control unit. Only the transfer potential of the transfer belt may be controlled. Generally, when the water content of the recording paper and the transfer belt is higher than a preset reference value, the charging potential of the transfer belt is controlled to the positive side.

Incidentally, the above-mentioned detection devices 13, 16, 30,
Reference numeral 31 also has a function of detecting the presence or absence of the recording paper or the developer which is the measurement target. For example, the light receiving units 39, 39
When comparing the output of 1.4 μm or less, which is the output of 1., with each output of the 1.45 μm wavelength band, the absorption wavelength band of water does not change with the reflected output of 1.4 μm or less, so it is irrelevant to the determination of the water content. Can determine the presence or absence of the measured object,
When the reflected output of 1.4 μm or less shows a low value and when both outputs show a low value, it can be determined that there is no recording paper or developer. As a result, it is possible to detect the absence of the recording paper or the developer without providing a special detecting means, and display the paper replenishment display, the developer replenishment display, etc. on the display unit of the operation unit to prompt the replenishment. Therefore, the cost can be reduced by reducing the number of detecting means. Further, regarding the transfer belt, it is possible to detect the presence or absence of the recording paper and the presence or absence of breakage of the belt in addition to the detection of the leading edge.

Next, FIG. 3 is a diagram showing a control flow for detecting the amount of water and the presence / absence of an object to be measured when the detecting device of FIG. 2 is applied to the image forming device of FIG. By turning on the power source, the initial setting process, the sheet moisture detection by the detection device 13, the agent moisture detection by the detection device 30, and the document size detection by the sensor 5 are sequentially performed (steps S1 to 5). When the start key is turned on and the paper size is selected, the recording paper is fed from the paper feed cassette accommodating the selected recording paper toward the image forming unit (transfer position) (steps S6 and S7). Then, the detection device 16
The sheet conveyance detection is performed and the transfer belt detection is performed by the detection device 31 (steps S8 and 9). Then, when the copy scan is started, each of the detection devices 13, 30, 16, 3 described above is started.
The charging output control, the transfer output control and the like are sequentially performed based on the image forming condition corrected based on the detection result of 1 (steps 10, 11, 12).

Next, FIG. 4 shows a subroutine of the paper moisture detection in the above step 3, in which the control unit is the detection device 13.
By comparing the detection signal from each of the light receiving sections 38 constituting the above with the reference value in the control section, the presence or absence of recording paper in the paper feed cassette and the water content value are determined, and the water content is within the controllable range. And if it exceeds the reference value, the heating device 12 is operated in accordance with a specific value of the water content, and heating for removing excess water is performed (steps S20 to 24, 27).
If it does not exceed the reference value, the heating device is not operated or the heating device is turned off (step S25). If the amount of water exceeds the controllable range, an abnormal processing display is displayed (step S26).

FIG. 5 (a) shows the agent moisture detection subroutine of step 4 of FIG. 3, in which the control unit compares the detection signal from each light receiving unit 38 constituting the detection device 30 with the reference value in the control unit. By doing so, the presence or absence of the recording paper of the developer in the developing device and the value of the water content are determined, and the charging output control is performed as necessary. FIG. 5B shows a charging output control subroutine. When the water content is determined to be within the controllable range by comparing the data obtained from the detection device 30 with the reference value, the correction control is performed. Whether or not there is a need (step 34
~ 36), and if it exceeds the reference value, the charging potential of the photoconductor is controlled according to the specific value of the water content (step S3).
7) If it does not exceed the reference value, it is charged to the standard value (step S38). In step 61, if the water content is too high to be controlled, step 39
The abnormal processing display is performed at.

Next, FIG. 6 is a subroutine for detecting the sheet conveyance in step 8 of FIG. 3, in which the detecting device 16 starts the reading of the reference plate 40 based on the sheet feeding signal, and when the output changes, the recording is performed. Since the leading edge of is detected, the data on the recording paper is read and both data are compared (steps 40 to 46).

Next, FIG. 7A is a subroutine of step 9 of FIG. 3, in which the reflected light output from the belt is detected by the detecting device 3.
The water content, the presence or absence of damage to the belt, and the presence or absence of the recording paper are determined by detecting the value in 1 and comparing it with a reference value in the control unit. FIG. 7 (b) is a subroutine of step 12 of FIG. 3, comparing the moisture detection result of the conveyed paper in FIG. 6 and the moisture detection result of the transfer belt in FIG. From the results obtained by comparing the results, if the water content of the transfer belt is within a controllable range from the relationship with the water content of the recording paper on the belt, it is determined whether correction is necessary ( Steps S53-5
7). If the water content exceeds the standard value, step 5
Correction control of the value selected in 8 (belt transfer potential control)
If no correction is necessary, transfer with a standard value.
If the amount of water is uncontrollable, an error processing display is made in step 60.

FIG. 8 shows a procedure for determining the presence / absence of a recording paper, a developer, and a transfer belt as an object to be measured, and the wavelength of the output of the reflected light from the light receiving portion is 1.4 or less <1.45.
If it is, it is determined that there is no. The present invention is shown in FIG.
An image forming apparatus other than the image forming apparatus configured as shown in FIG.
For example, without the image reading unit shown in FIG.
It is also applicable to an apparatus including only the image forming section shown in (b).

[0024]

As described above, according to the present invention, recording paper,
By directly detecting and measuring the water content of the measurement target such as the developer and transfer belt, it is possible to automatically adjust the image forming conditions and always obtain a stable image even when the environment such as humidity changes. Further, it is possible to detect the presence or absence of the measurement target.

[Brief description of drawings]

1A and 1B are a schematic configuration explanatory diagram of an image reading unit and an schematic configuration explanatory diagram of an image forming unit of an image forming apparatus to which the present invention is applied.

FIG. 2 is a specific configuration explanatory view of an example of a detection device according to the present invention.

FIG. 3 is a flowchart showing a procedure of control including water content detection by the image forming apparatus to which the present invention is applied.

FIG. 4 is a flowchart of a subroutine showing a procedure for detecting paper moisture.

5A and 5B are flowcharts showing a procedure for detecting moisture in a developer and controlling a charging output.

FIG. 6 is a flowchart showing a control procedure of sheet conveyance detection.

7A and 7B are flowcharts showing a procedure of moisture detection and transfer output control of the transfer belt.

FIG. 8 is a flowchart showing a control procedure for detecting the presence / absence of an object to be measured.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 image reading part, 2 document pressure plate, 3 contact glass, 4 document, 5 document detection sensor, 6 close switch, 10 paper feed cassette, 11 recording paper, 12 heating device, 13 humidity detection device for stored recording paper, 15 photoconductor ,
16 Transport Recording Paper Humidity Detecting Device, 20 Charging Charger, 21 Developing Device, 22 Transfer Belt, 23 Cleaning Section, 24 Fixing Device, 30 Developer Humidity Detecting Device, 31 Transfer Belt Humidity Detecting Device, 35 Emission Light Source, 36 Optical fiber, 37 light emitting part, 38 light receiving part, 39 filter, 40 reference plate,

Claims (7)

[Claims] 1. An electrophotographic image forming apparatus, comprising: an image forming unit for producing a copied image; and a humidity detecting device arranged in a proper place inside the device for measuring a moisture content of an object to be measured. An image forming apparatus having a humidity detecting function, comprising: a control unit for correcting and controlling an image forming condition by comparing a measurement result from the apparatus with a stored reference value. 2. The humidity detecting device comprises a light emitting section for irradiating the object to be measured with projection light, a plurality of light receiving sections for receiving reflected light from the object to be measured at a predetermined angle, and each of the light receiving sections. The control section compares the outputs from the respective light receiving sections with each other, and the image forming conditions are controlled based on the comparison result and a preset reference value. An image forming apparatus having a humidity detecting function according to claim 1. 3. One of the humidity detecting devices is arranged in a recording paper transporting path from a paper feeding device to a photoconductor, and the humidity detecting device includes a light emitting part for irradiating the object to be measured with projection light. , A plurality of light receiving portions that receive the reflected light from the object to be measured at a predetermined angle, filters that are respectively disposed on the front surface of each light receiving portion and have different transmission wavelengths, and the recording paper conveyance path is sandwiched between the plurality of light receiving portions. A reference plate disposed at a position opposite to the light emitting unit, and the control unit determines the presence or absence of the measurement target based on the reflection output from the measurement target and the reflection output from the reference plate. , If there is an object to be measured, after a predetermined time, the reflected output of the object to be measured is again compared with the reflected output of the reference plate, and the image forming condition is corrected by comparing the comparison result with a previously stored reference value. The humidity according to claim 1, which is controlled. An image forming apparatus having a detection function. 4. One of the humidity detecting devices is for detecting the moisture content of a recording paper which is arranged and housed in a paper feeding cassette which constitutes the paper feeding device. Is equipped with a heating device that heats the stored recording paper to remove moisture, and the controller controls the operation of the heating device based on the data regarding the moisture content of the stored recording paper obtained from the humidity detection device. An image forming apparatus having a humidity detecting function according to claim 1. 5. One of the humidity detecting devices is arranged in the developing device to detect the water content of the developer in the developing device, and the controller controls the water content of the developer to a large extent. Accordingly, control information for correcting the charging potential of the photoconductor is stored, and the control unit controls the charging potential based on the value of the water content of the developer detected when the copying operation is started. An image forming apparatus having a humidity detecting function according to claim 1. 6. An image forming unit of the image forming apparatus is provided with a transfer belt and a humidity detecting device for detecting a water content of the transfer belt, and the control unit obtains a reference value stored in advance and the humidity detecting device. 2. The humidity detection function according to claim 1, wherein correction control of the potential for transfer and separation is performed based on the data regarding the water content of the transfer belt and the data regarding the water content of the recording paper to be fed. Image forming apparatus equipped. 7. The humidity detecting device includes a light emitting section for irradiating the object to be measured with projection light, a plurality of light receiving sections for receiving reflected light from the object to be measured at a predetermined angle, and each of the light receiving sections. The control unit is provided with filters having different transmission wavelengths, respectively, and the control unit compares the output from each light receiving unit with a predetermined reference value to determine the presence or absence of the measured object. An image forming apparatus having a humidity detecting function according to claim 1.