JP4667255B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus provided with a detection device for detecting moisture content information of a laminate of planar objects such as paper using electromagnetic waves. In particular, an electromagnetic wave including at least a part of a frequency region of 30 GHz to 30 THz (an electromagnetic wave in a frequency region called millimeter wave to terahertz wave, and also referred to as terahertz wave in this specification) The present invention relates to an image forming apparatus provided with an apparatus for detecting information on the water content of a laminate of shaped objects.

Conventionally, an image forming apparatus such as a printer is easily affected by environmental changes such as temperature and humidity. Therefore, in order to obtain stable image quality in various environments, a sensor such as a thermohygrometer is installed around the image forming system, and the information detected by this sensor is fed back to the image forming conditions to control the image forming system. It is carried out.

However, in a method in which a sensor for detecting temperature and humidity is provided around the image forming system and the image forming system is controlled based on information detected by the sensor, the temperature and humidity of an object to be detected by the sensor is detected. It is hard to say that is accurately detected. For this reason, the control of the image forming system is not optimal.

Therefore, the following method has been proposed (see Patent Document 1). That is, here, a detection device having a plurality of light emitting units having different emission wavelengths and a light receiving unit that receives the light output is used. Then, the light-receiving unit receives the reflected light reflected by the detection object such as paper by sequentially emitting light from the plurality of light-emitting units, and the moisture content of the detection object is based on a preset value from the comparison result of these light reception signals. The amount is judged and the image forming conditions are controlled.

However, the distribution of the moisture content of the paper set in the tray is not uniform in the paper stacking direction, and there is a difference in the moisture content between the upper, middle, and lower portions of the stacked paper. Therefore, the water content detected by the above method is the water content of the upper part of the paper laminated. Therefore, especially when printing with a high-speed printer or the like, there may be a difference between the moisture content of the detected paper and the moisture content of the actually printed paper.
JP-A-8-137145

The present invention has been made in view of the above situation, and detects moisture content information (for example, the average moisture content of the entire paper set in a tray) of a laminate of planar objects. The technology to do is provided.

In view of the above problems, the image forming apparatus of the present invention configured to include a storage unit configured to be able to store a stacked body in which planar objects are stacked,
An irradiation unit for irradiating an electromagnetic wave including at least a part of a frequency region of 30 GHz or more and 30 THz or less to a predetermined position of the stacked body in an in-plane direction of the planar object stored in the storage unit ;
Among the electromagnetic waves irradiated by the irradiation unit, the detection unit for detecting the intensity of the electromagnetic wave transmitted through the laminate , or the electromagnetic wave transmitted through the laminate and reflected from the bottom of the storage unit ;
A counting unit for counting planar objects included in the stacked body stored in the storage unit;
A storage unit for storing information on attenuation of electromagnetic waves due to water content contained in the planar object;
Using the number of stacks counted by the counting unit and the information on the attenuation, a processing unit for obtaining the moisture content contained in the stacked body stored in the storage unit;
It is characterized by having.

According to the present invention, the information on the detected electromagnetic wave and the information on the attenuation of the electromagnetic wave due to the moisture of the planar object are compared, and the information on the moisture content of the laminate is detected. Therefore, information on the moisture content of the entire laminate (for example, the average moisture content of the entire paper set in the tray) can be detected in a non-contact manner, that is, irradiation of an electromagnetic wave detection object. . Therefore, for example, by feeding back the moisture content information to the image forming conditions, it is possible to control the image forming system more suited to the paper state.

Specific examples will be described below in order to clarify an embodiment of a detection apparatus or method for detecting information of a laminated body in which planar objects such as paper are laminated according to the present invention.

Here, an apparatus or method for detecting the water content of paper using electromagnetic waves including frequencies in the millimeter to terahertz range will be described. A typical embodiment of the present invention is used in a printer that prints a large amount of paper at a high speed, such as a Print On Demand (POD) machine. This is more suitable for detecting the moisture content of the entire paper set in the printer tray than detecting the moisture content of each sheet of paper.

(Example 1)
FIG. 1 is a schematic diagram showing the configuration of the first embodiment of the present invention. In Example 1, as shown in FIG. 1, an electromagnetic wave generator 1 is installed above a tray 3 in which a sheet 4 that is a planar object that is a detection object is placed, and an electromagnetic wave including a frequency from the millimeter wave to the terahertz region (terahertz). Wave) 8 is irradiated perpendicularly to the surface of paper 4. The electromagnetic wave may be a continuous wave or a pulse wave. Since the terahertz wave 8 passes through the paper 4, the transmitted electromagnetic wave 9 is detected by the electromagnetic wave detector 2 installed below the tray 3. At this time, holes for allowing electromagnetic waves to pass through are provided in the upper and lower portions of the tray 3.

In the first embodiment, the arithmetic processing unit 5 calculates the maximum amplitude value from the transmitted electromagnetic wave 9 detected by the electromagnetic wave detector 2. Here, the maximum amplitude value is information on the electromagnetic wave detected by the electromagnetic wave detector 2. Between the maximum amplitude value, the number of sheets of paper, and the moisture content contained in the paper, for example, there is a relationship as shown in FIG. 2, so it is possible to prepare and store this in advance and use it as a calibration curve. it can. That is, when the number of sheets of paper is known, the water content contained in the paper (for example, the ratio of the water content to the total weight of the paper) can be detected from the maximum amplitude value calculated by the arithmetic processing unit 5. Here, when the point to be obtained is not on the straight line shown in FIG. 2, the water content may be obtained by using an interpolation method or an extrapolation method. Note that the horizontal axis in FIG. 2 is linear, but the vertical axis is displayed using logarithm. The reason for calculating the maximum amplitude value is to improve the SN ratio.

The relationship shown in FIG. 2 is obtained because terahertz waves are easily absorbed by water. Therefore, the frequency of the terahertz wave to be used is preferably a frequency that is particularly absorbed by moisture. For example, a frequency in the vicinity of 1 THz may be used. As for the number of sheets, if the operator inputs to the device when setting the sheets in the tray, the number of sheets taken out from the tray and printed is counted by the counter mounted on the printer. You can always know the number of sheets in tray 3 after the start. Alternatively, as another method, the number of sheets of paper 4 may be detected from a scale or the like installed at the bottom of the tray 3.

Regarding the calibration curve, which is information regarding the attenuation of electromagnetic waves due to moisture of the paper, which is a planar object, each calibration curve is used for each paper type, and the operator inputs the paper type to the apparatus during printing. If such calibration curve data is stored in the apparatus as the database 6, the maximum amplitude value, which is the information of the electromagnetic wave detected by the detector 2 calculated by the arithmetic processing unit 5, is compared and the paper 4 Information on the moisture content (here, the average moisture content of the laminated paper) can be detected.

As another method, the moisture content of the paper laminate may be detected using the slope of the calibration curve. In this case, the moisture content of the paper can be detected even if the operator does not input the number of papers when the paper 4 is set in the tray 3. Specifically, if the slope of the calibration curve is registered in the database 6 as a database, the arithmetic processing unit 5 detects the water content of the paper 4 by calculating the change in the maximum amplitude value with respect to the change in the number of papers. can do. That is, it is assumed that the maximum amplitude value calculated by the arithmetic processing unit 5 at a certain time is V1. Since the number of printed papers can be known by a counter mounted on the printer, if the maximum amplitude value calculated by the arithmetic processing unit 5 from a certain point in time, for example, after printing 100 sheets, is V2. The change of the maximum amplitude value due to the number of sheets is obtained as (V2−V1) / 100. From this value, the moisture content of the paper laminate can be detected by comparing this value with the value of the change in the maximum amplitude value with respect to the change in the number of papers registered in the database 6 (the slope of the calibration curve). In this method, this change is information on the electromagnetic wave detected by the electromagnetic wave detector 2.

Image formation that controls the image forming conditions such as fixing temperature control on the photosensitive drum of the image forming apparatus, the average moisture content of the entire paper laminate reflecting the moisture content inside the paper detected in this way. Feedback is applied to the control unit 7 for reflection. This makes it possible to control the image forming system more suited to the paper state. That is, since the image forming control unit 7 is feedback-controlled based on the average moisture content information of the entire paper laminate, even if there is some variation in the moisture content of the laminated paper, the paper laminate As a result, an image can be formed relatively well on each paper. In this case, since the paper printed in the process of obtaining the change in the maximum amplitude value depending on the number of papers is printed before the image forming system is controlled, the printing state may not be so good. There is also. If the print state is within the allowable range, it can be used as it is, or if it is not acceptable, it can be discarded.

(Example 2)
FIG. 3 is a schematic diagram showing the configuration of the second embodiment of the present invention. In the second embodiment, as shown in FIG. 3, the electromagnetic wave generator 1 is installed in an obliquely upward direction of the tray 3 in which the paper 4 that is a detection object enters, and an electromagnetic wave (terahertz wave) 8 including a frequency in the millimeter wave to terahertz region is generated. Irradiate the surface of paper 4 from an angle. At this time, the electromagnetic wave 8 is applied to the substantially center of the bottom of the tray 3 with the paper 4 not in the tray 3. The bottom of the tray 3 is made of a material that reflects the electromagnetic wave 8, for example, aluminum, so that the electromagnetic wave 8 is reflected at the bottom of the tray 3. The reflected electromagnetic wave 10 that has been reflected is detected by the electromagnetic wave detector 2 installed above the tray 3 in the same manner as the electromagnetic wave generator 1. A hole for allowing the electromagnetic wave 8 and the reflected electromagnetic wave 10 to pass through is provided in the upper part of the tray 3. Since the electromagnetic wave 8 including the millimeter wave to terahertz frequency passes through the paper 4, the reflected electromagnetic wave 10 can be detected by the electromagnetic wave detector 2 even when the paper 4 is on the tray 3.

Also in the present embodiment, the arithmetic processing unit 5 calculates the maximum amplitude value from the reflected electromagnetic wave 10 obtained by the electromagnetic wave detector 2. At this time, the reflected electromagnetic wave 10 includes reflected electromagnetic waves from various surfaces in the paper laminate, but the electromagnetic waves transmitted to the bottom of the laminated body and reflected there can be identified from the phase and the like, What is necessary is just to identify and to calculate the maximum amplitude value. Then, by using the relationship between the maximum amplitude value, the number of sheets of paper, and the moisture content contained in the sheet as a calibration curve, when the number of sheets of paper 4 is known, the maximum amplitude value calculated by the arithmetic processing unit 5 is used. The average water content contained in the laminate of paper 4 can be detected.

Regarding the detection method of the number of paper, the calibration curve, the role of the database 6 and the like, the same as described in the first embodiment can be applied to this embodiment.

Also in this embodiment, the moisture content of the entire paper reflecting the moisture content inside the paper detected in this way is reflected in the image formation control unit 7 that controls the image formation conditions in the photosensitive drum, thereby making the paper more It is possible to control the image forming system in accordance with the state.

(Example 3)
FIG. 4 is a schematic diagram showing the configuration of the third embodiment of the present invention. In this embodiment, the moisture content of the paper laminate is detected using two transmitted electromagnetic waves. As shown in Fig. 4, two electromagnetic wave generators 1 are installed above a tray 3 containing paper 4 as a detection object, one of which emits 0.1 THz electromagnetic waves and the other receives 1 THz electromagnetic waves 8 on the paper surface of paper 4. Irradiate vertically. Since the electromagnetic wave 8 including frequencies from the millimeter wave to the terahertz region passes through the paper 4, the two transmitted electromagnetic waves 9 are detected by the two electromagnetic wave detectors 2 installed below the tray 3, respectively. At this time, holes for passing electromagnetic waves are provided in the upper and lower portions of the tray 3, respectively.

Also in the present embodiment, the arithmetic processing unit 5 calculates the maximum amplitude value from the transmitted electromagnetic waves obtained by the two electromagnetic wave detectors 2, respectively. Again, since there is a relationship as shown in FIG. 2 between these maximum amplitude values, the number of sheets of paper, and the water content contained in the paper, it can be used as a calibration curve. In this way, when the number of papers is known, the water content contained in the paper can be detected from the maximum amplitude value calculated by the arithmetic processing unit 5.

In the present embodiment, the same method as described in the first embodiment can be applied to the method for detecting the number of paper sheets, the calibration curve, the role of the database 6, and the like.

In this embodiment, two electromagnetic wave generators 1 of 0.1 THz and 1 THz are used. FIG. 5 is a diagram showing the difference in the change in the maximum amplitude value with respect to the change in the number of papers when the two electromagnetic wave generators 1 of 0.1 THz and 1 THz are used. Note that the moisture content of the paper used at this time is the same, and the two maximum amplitude values are standardized when the number of paper sheets is zero. In addition, the horizontal axis in FIG. 5 is linearly displayed, but the vertical axis is displayed using logarithm.

As shown in FIG. 5, an electromagnetic wave with a frequency of 0.1 THz has a property of permeating the paper relatively well even if the paper is thick. Therefore, when the number of papers to be detected is thick, the moisture content of the paper is detected with an electromagnetic wave of 0.1 THz, and when the number of papers is not thick, the moisture content of the paper is detected with an electromagnetic wave of 1 THz. The electromagnetic wave to be used is automatically switched depending on the number of sheets. Further, when the thickness of the paper is not thick, the detection accuracy of the water content of the paper can be increased by using the two electromagnetic wave generators 1 in combination. That is, when the paper is not thick, the arithmetic processing unit 5 obtains two maximum amplitude values, and therefore the moisture content of the two papers is calculated using the calibration curve for each used electromagnetic wave. This makes it possible to improve the detection accuracy of the moisture content of the paper laminate by, for example, averaging the moisture content of these two papers.

The two electromagnetic wave generators 1 may emit electromagnetic waves having the same frequency. In this case, always use two electromagnetic wave detectors 2 regardless of the thickness of the paper, and average the moisture content of the two papers obtained using these detection values. What is necessary is just to detect the water content of.

Also in this embodiment, by reflecting the moisture content of the entire paper detected in this way in the image formation control unit 7, it is possible to control the image forming system more suited to the state of the paper.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a configuration of a detection device according to a first embodiment of the present invention that detects moisture content of paper using transmitted electromagnetic waves. It is a figure which shows the example of the calibration curve which consists of water content (water content), the number of sheets of paper, and a maximum amplitude value. FIG. 5 is a schematic diagram showing a configuration of a detection apparatus according to a second embodiment of the present invention that detects the moisture content of paper using reflected electromagnetic waves. FIG. 5 is a schematic diagram showing a configuration of a detection apparatus according to a third embodiment of the present invention that detects the water content of paper using a plurality of transmitted electromagnetic waves. FIG. 9 is a diagram illustrating a difference in change in maximum amplitude value with respect to a change in the number of papers of two electromagnetic waves in Example 3.

Explanation of symbols

1… Irradiation part (electromagnetic wave generator)
2… Detection unit (electromagnetic wave detector)
4… A planar object (detected object, paper)
5 ... Calculation processor
6 ... Database
7 ... Image formation controller
8 ... electromagnetic wave
9 ... Transmitted electromagnetic wave
10 ... Reflected electromagnetic wave

Claims (9)

An image forming apparatus configured to include a storage unit configured to store a stacked body in which planar objects are stacked,
An irradiation unit for irradiating an electromagnetic wave including at least a part of a frequency region of 30 GHz or more and 30 THz or less to a predetermined position of the stacked body in an in-plane direction of the planar object stored in the storage unit ;
Among the electromagnetic waves irradiated by the irradiation unit, a detection unit for detecting the intensity of the electromagnetic wave transmitted through the laminate , or the intensity of the electromagnetic wave transmitted through the laminate and reflected from the bottom of the storage unit ;
A counting unit for counting planar objects included in the stacked body stored in the storage unit;
A storage unit for storing information on attenuation of electromagnetic waves due to water content contained in the planar object;
Using the number of stacks counted by the counting unit and the information on the attenuation, a processing unit for obtaining the water content contained in the stacked body stored in the storage unit;
An image forming apparatus characterized by have a. The image forming apparatus according to claim 1, wherein the storage unit is a tray. The counting unit includes a counter that counts the used planar object,
3. The image forming apparatus according to claim 1, wherein the number of uses counted by the counter is subtracted from the number of stacked layers input when the stacked body is stored in the storage unit. The said counting part is comprised including the weigh scale which measures the weight of the said laminated body accommodated in the said accommodating part, and acquires the said lamination | stacking number using the said weight. Image forming apparatus. The information on the attenuation stored in the storage unit includes the thickness of the laminate, the maximum amplitude value of the transmitted or reflected electromagnetic wave detected by the detector, and the water content contained in the laminate. The image forming apparatus according to claim 1, wherein the image forming apparatus is a calibration curve constituted by two parameters. The change of the maximum amplitude value with respect to the used number of the stored planar objects is calculated, and the stored stack of layers is calculated from the calculated change and the slope of the calibration curve stored in the storage unit. The image forming apparatus according to claim 5, wherein the moisture content contained in the body is acquired. A plurality of the irradiation unit, a plurality of the irradiation unit irradiates the electromagnetic waves respectively different frequencies, the calibration curve to claim 5 or 6, characterized in that stored in advance in correspondence to the plurality of frequency The image forming apparatus described. The image forming apparatus according to claim 1, wherein an image forming condition is controlled based on the acquired water content. The image forming apparatus according to claim 8, wherein the control of the image forming condition is control of a fixing temperature.

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