JP2007304285A - Image forming apparatus, moisture content detector and sensor for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus closely identifying moisture contents on a surface layer of a recording medium to which an image is to be formed with high responsiveness and high accuracy and then feeding it back to processing condition. <P>SOLUTION: The moisture contents in sheet materials 1 being moved are detected by installing a sensor unit part 109 in a transporting path of the sheet materials 150 in the image forming apparatus. Air in the vicinity of the surface of the sheet materials 150 is stripped off by an air conducting duct 108 and guided to an air exhausting opening 104. A heat conduction type humidity sensor (heat conductivity sensor 101) with a heat sensitive resistor formed by MEMS (micro electromechanical system) technique is installed at the air exhausting opening 104 and the humidity is detected. The moisture contents on the surface layer of the sheet materials 150 is estimated from an output from the heat conductivity sensor 101 by a control part 120, and the processing condition corresponding to the moisture contents is set in an image forming process part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention relates to an image forming apparatus that automatically adjusts image forming conditions and the like by detecting the moisture content of a recording medium, and a moisture content detecting device that can be used for an image forming apparatus that detects the moisture content of a sheet material And an image forming apparatus sensor mounted on the image forming apparatus.

  In an image forming apparatus using an electrophotographic technique, the water content (water content, water content) of a sheet material on which an image is formed greatly affects image quality and processing stability. This is because the specific resistance of the sheet material decreases as the amount of moisture increases, so that an effective transfer voltage on the surface of the sheet material cannot be secured unless the transfer bias voltage applied to the transfer roller is increased. This is because the separation performance of the sheet material from the photosensitive drum is degraded unless the separation bias voltage of the separation charger is increased. In the fixing process using heat and pressure, the effective fixing temperature decreases due to the heat of vaporization of the moisture contained in the sheet material. Therefore, if the amount of moisture is high, the fixing roller temperature is increased to effectively fix the surface of the sheet material. It is necessary to ensure temperature.

  In view of this, it has been proposed that a moisture amount sensor is disposed in the sheet material stacking storage unit or the conveyance path to detect the moisture amount of the sheet material, and the detection result is fed back to the charging voltage, separation voltage, fixing temperature, and the like. .

  Patent Document 1 discloses an image forming apparatus in which a moisture amount sensor for detecting an infrared absorption peak is arranged in a sheet material stack storage unit and a reverse conveyance path for double-sided printing. The moisture content of the sheet material detected by the moisture sensor is fed back to the charging voltage and separation voltage of the image forming apparatus. The amount of moisture changed by the fixing process on one side is detected by a moisture amount sensor on the reverse conveyance path, and the charging voltage and separation voltage in image formation on the back side are also optimized.

  Patent Document 2 discloses an image forming apparatus that detects the humidity of a sheet material conveyance space to estimate the moisture content of the sheet material and adjusts processing conditions related to image formation based on the estimated moisture content. Here, the moisture in the sheet material is forcibly evaporated using the heat of the fixing roller, and the humidity of the sheet material conveyance space that changes according to the amount of water vapor generated is detected. The amount is estimated. Humidity detection is performed after a predetermined time since the sheet material passes through the fixing roller, so that the moisture content can be estimated individually for each sheet material, and the moisture content of the sheet material that varies from moment to moment can be tracked. Processing conditions can be adjusted.

  Patent Document 3 discloses a heat conduction type humidity sensor that is a humidity sensor having high output response to humidity change. The heat conduction type humidity sensor measures the humidity by utilizing the fact that the heat dissipation from the temperature sensitive resistor that self-heats by Joule heat changes according to the humidity. The heat conduction type humidity sensor can remarkably improve the output responsiveness by forming a temperature sensitive resistor having a very small heat capacity by using the MEMS technology (microfabrication technology applying the integrated circuit processing technology).

JP-A-7-234556 JP-A-11-202686 Japanese Patent Laid-Open No. 9-5284

  The moisture amount sensor disclosed in Patent Document 1 can detect the moisture amount from a remote position away from the surface of the sheet material, but requires a relatively large optical path space and device arrangement space at an upper position of the sheet material. Accordingly, the design of the sheet material conveyance path and the degree of freedom of component arrangement of the image forming apparatus are impaired, and the overall size and weight of the apparatus are hindered. The moisture sensor itself requires a large number of optical components, and the circuit configuration relating to signal detection and signal processing is also complicated.

  Furthermore, since the moisture content detection apparatus shown in Patent Document 1 detects the moisture content of the entire thickness of the sheet material, if the moisture content distribution is biased in the thickness direction, the moisture content of the essential sheet material surface layer is determined. There is a possibility of false detection. That is, moisture detection accuracy may be insufficient.

  Since the moisture content detection device for a sheet material disclosed in Patent Document 2 identifies the moisture content of a sheet material for which image formation has been completed (fixed), the identified moisture content is determined for the sheet material to be imaged from now on. It does not always coincide with the amount of water. If the moisture content is different between the first sheet material and the second sheet material, the processing conditions set according to the moisture content of the first sheet material are inappropriate for the second sheet material. There is a possibility.

  When the dried sheet material is stacked in a high humidity environment, the moisture content of the first sheet material protrudes and becomes high. Therefore, if a transfer bias voltage suitable for the first sheet material having a high water content is set, the transfer bias voltage is too high for the second and subsequent dried sheet materials, and the toner transfer position is upstream. Move to. As a result, there is a possibility that the transfer image is disturbed due to a so-called toner slippage defect.

  Also, if the fixing roller temperature suitable for the first sheet material having a high water content is set, the fixing roller temperature is too high for the dried second sheet material, and the first sheet is different from the image level. Tone, color and surface properties may vary. That is, it may not be possible to control the optimum image forming conditions.

  In addition, the moisture detection device for a sheet material disclosed in Patent Document 2 measures a change in humidity in the conveyance space by diffusing a very small amount of moisture contained in a small volume sheet material into a conveyance space for a vast sheet material. Therefore, even if a highly sensitive humidity sensor is used, a small difference in the moisture content of the sheet material cannot be identified. Therefore, the control of the transfer bias voltage and the fixing roller temperature becomes rough, and the result of image formation may vary.

  Since the moisture amount detection device disclosed in Patent Document 2 detects the moisture amount driven out of the sheet material by the humidity sensor, the moisture amount of the sheet material surface layer cannot be accurately detected. Since a blower fan is required and the duct volume is large, the number of parts of the image forming apparatus is increased, which hinders downsizing, noise reduction, and cost reduction of the image forming apparatus.

  An object of the present invention is to provide an image forming apparatus capable of finely identifying the moisture content of the surface layer of a recording medium to be imaged from now on with high responsiveness and high accuracy and feeding back to processing conditions. Another object of the present invention is to provide a moisture amount detection device capable of finely detecting the moisture content of the surface layer of the sheet material with high responsiveness and high accuracy.

  The image forming apparatus sensor of the present invention selectively collects air near the surface of the recording medium, accurately detects the humidity or heat transfer coefficient (also referred to as heat conductivity) of the gas, The purpose is to accurately estimate the moisture content of the sheet material.

  Another object of the image forming apparatus of the present invention is to control to the optimum image forming conditions according to the moisture content of the recording medium (sheet material or the like).

  The image forming apparatus of the present invention includes an image forming unit that forms an image on a recording medium, a detecting unit that detects a moisture content of the recording medium supplied to the image forming unit, and the detection unit based on the detected moisture content. And control means for adjusting processing conditions in the image forming means. The detection means includes humidity detection means for detecting the humidity of the air near the surface of the recording medium, and estimation means for estimating the moisture content based on the output of the humidity detection means.

  The moisture content detection device of the present invention detects the moisture content of a sheet material. An air guide means arranged in the sheet material conveyance path for separating the air near the surface of the conveyed sheet material from the sheet material and guiding it to a space away from the surface of the sheet material; and the space arranged in the space Humidity detecting means for detecting the humidity of the sheet, and estimation means for estimating the moisture content of the sheet material based on the detected humidity of the space.

  In the image forming apparatus of the present invention, the humidity of the air in the vicinity of the surface where the humidity changes sensitively in balance with the amount of moisture in the surface layer of the recording medium is detected at a position upstream of the image forming means, and the surface layer of the recording medium is detected. Estimate moisture content. Therefore, the moisture content of the surface layer of the recording medium on which an image is to be formed can be discriminated with high responsiveness and high precision and fed back to the image forming conditions.

  The moisture amount detection apparatus of the present invention selectively detects the humidity of air in the vicinity of the surface of a general sheet material that is not limited to a recording medium while the sheet material is moving on the sheet material conveyance path. A device that estimates the moisture content from the air by peeling off the air near the surface by the air guiding means from the surface of the conveyed sheet material without heating and pressurization as in the moisture content detection device shown in Patent Document 2. It is. At this time, air near the surface is selectively guided to a space away from the surface of the sheet material by using the movement of the air near the surface that moves together with the sheet material. Since the air near the surface continuously stripped from the surface of the sheet material is integrated and efficiently occupies the space, if high-sensitivity humidity detection means is provided in the space, it is precise and responsive that fully utilizes that high sensitivity High humidity detection and moisture amount estimation by humidity.

  Hereinafter, an image forming apparatus 300 according to an embodiment of the present invention will be described in detail with reference to the drawings. The image forming apparatus and the water content detection apparatus of the present invention are not limited to the limited configurations of the embodiments described below. As long as the humidity of the air in the vicinity of the surface of the sheet material before image formation is detected, another embodiment in which a part or all of the configuration of each embodiment is replaced with the alternative configuration can be realized.

  In the present embodiment, an example in which a moisture amount detection device 109 is mounted on an electrophotographic image forming apparatus 300 will be described. However, the moisture amount detection device 109 of the present embodiment can be mounted on an inkjet image forming apparatus, various printing apparatuses, a sheet material processing apparatus, a sheet material stacking apparatus, a sorter, and the like.

  Note that the configuration, operation, control, configuration of the humidity sensor, operation principle, signal processing, and the like of the image forming apparatus disclosed in Patent Documents 1 to 3 are not illustrated and are described in detail in order to avoid repeated complications. Is omitted.

<First Embodiment>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus of the first embodiment, FIG. 2 is an explanatory diagram of the configuration of the moisture amount detection device of the first embodiment, and FIG. 3 is an explanatory diagram of the configuration of the air duct.

  As shown in FIG. 1, the image forming apparatus 300 according to the first embodiment is a color copying machine that forms an image on a sheet material 150 by an image forming process unit 340. The reading unit 311 reads image information on the color original 312. The read information is converted into color-specific signals corresponding to four color toners of cyan, magenta, yellow, and black.

  On the other hand, the sheet material 150 accommodated in the cassette 321 is sent to the conveying belt 112 by the sending roller 322. A water content detection unit 109 is provided at a location close to the transport belt 112.

  Here, when the sheet material 150 is conveyed by the conveying belt 112, the air near the surface (air including information on the moisture content of the sheet material 150) that moves together with the sheet material 150 is selectively used as the moisture content detection unit. To 109. Based on the output of the water content detection unit 109, the control unit 120 estimates the water content of the sheet material 150 before image formation is performed by the image forming process unit 340.

  Next, the sheet material 150 is sent to the transfer device drum 330. A dielectric sheet is provided on the peripheral surface of the transfer device drum 330. The sheet material 150 is adsorbed and supported on the surface of the transfer drum 330 charged by the adsorption corona discharger 331. Thereafter, the toner image on the photosensitive drum 323 is transferred to the sheet material 150 by the action of the transfer corona discharger 332.

  The surface of the photosensitive drum 323 is cleaned by a blade cleaner 324. The pre-exposure lamp 325 and the pre-charger 326 remove the influence remaining on the surface layer of the photoreceptor due to the previous image formation. Next, the surface of the photosensitive drum 323 is uniformly charged by the primary charger 327. The charge amount at this time is determined based on the estimated moisture content of the sheet material 150.

  The laser beam scanner 328 scans the surface of the photosensitive drum 323 based on the color-specific signal of the read color original 312 to form an electrostatic latent image. The developing unit 329 includes four developing units of cyan, magenta, yellow, and black, and the developing unit corresponding to each color moves directly below the photosensitive drum 323 to convert the latent image on the photosensitive drum 323 into a toner image. Develop.

  The sheet material 150 is adsorbed and held until the four color toner images are sequentially transferred, and then separated from the transfer drum 330 by the operation of the separation claw 333. The separated sheet material 150 is sent to the heating roller fixing device 335 by the conveying belt 334, and is heated and pressurized to fix the toner image on the surface. The fixing temperature at this time is determined based on the estimated moisture content of the sheet material 150.

  The sheet material 150 after the completion of fixing is discharged to the tray 336. Further, the toner remaining on the surface of the photosensitive drum 323 after the transfer is completed is cleaned by the blade cleaner 324 and enters the next image forming cycle.

  As shown in FIG. 2, the sensor unit 109 of the first embodiment detects the humidity of the air in the vicinity of the surface of the sheet material 150 at a position away from the surface of the sheet material 150. The air guide duct 108 includes an air inlet 102, an air outlet 104, and an air flow path 103.

  The sheet material conveying device 113 includes belt driving rollers 110 and 111 and a conveying belt 112, and conveys the sheet material 150 from right to left in the drawing. The air introduction port 102 of the sensor unit 109 is disposed so as to face the direction in which the sheet material 150 is conveyed (the air introduction port 102 opens toward the upstream side in the conveyance direction).

  As shown in FIG. 3A, the heat transfer rate sensor 101 is disposed inside the air guide duct 108 via the heat transfer rate sensor support portion 106. The heat transfer rate sensor 101, the heat transfer rate sensor support portion 106, and the air guide duct 108 constitute a sensor unit portion 109 (FIG. 1).

In general, the humidity of the air in the vicinity of the sheet material 150 changes according to the moisture content of the sheet material 150. That is, if the moisture content of the sheet material 150 is large, the humidity of air in the vicinity thereof is high, and if it is low, the humidity is low. The rate of change in humidity is determined by the diffusion of water vapor in the air. That is, the air in the vicinity of the sheet material 150 has information regarding the moisture content of the sheet material 150. Here, when the diffusion coefficient of air-water vapor is D = 0.251E-4 [m ² / s], the water vapor diffusion time T to a place 1 mm away from the surface of the sheet material 150 is obtained from the following equation. It is done.

  That is, the humidity on the surface of the sheet material 150 before 40 ms can be measured at 1 mm from the surface of the sheet material 150.

  As shown in FIG. 2, when the sheet material 150 is conveyed by the sheet material conveying device 113, the air near the surface of the sheet material 150 moves so as to be dragged by the sheet material 150. Then, the direction of the moving air is changed by the air guide duct 108 and guided to the heat transfer coefficient sensor 101. As shown in Patent Document 3, the heat transfer rate sensor 101 is made by the MEMS technology, and can respond to a humidity change at a very high speed. Further, the control unit 120 controls the heat transfer rate sensor 101 and detects air humidity together with the detection result of the environmental temperature sensor 121.

  At this time, it is preferable to provide a distance control mechanism for adjusting the relative position between the air guide duct and the recording medium (sheet material 150) as necessary. By providing such a mechanism, the relative position between the air duct and the recording medium becomes constant, and the accuracy of collecting air near the surface of the recording medium (sheet material 150) is further increased.

  By measuring the humidity at the timing when the air near the surface of the sheet material 150 reaches the heat transfer coefficient sensor 101, the humidity of the air near the surface of the sheet material 150 can be measured. Further, the moisture content of the sheet material 150 can be estimated from the measured humidity of the air.

  Furthermore, if humidity sensing is performed a plurality of times while the air near the surface of the sheet material 150 reaches the heat transfer coefficient sensor 101, the humidity distribution in the conveying direction of the sheet material 150 can be estimated. In this case, the control unit 120 illustrated in FIG. 1 estimates the moisture content distribution in the conveyance direction of the sheet material 150. Then, optimized processing conditions that differ depending on the position of the sheet material 150 in the conveyance direction are set in the image forming process unit 340 and the heating roller fixing device 335.

  Moreover, the heat transfer rate sensor produced by the MEMS technology has a problem that it is very fragile by contact due to its delicate surface structure. However, in the first embodiment, since there is no fear that the sheet material 150 and the heat transfer rate sensor 101 are protected by the air guide duct 108, a highly reliable moisture amount detection device can be provided.

  As described above, the image forming apparatus 300 according to the first embodiment can measure the moisture content of the sheet material 150 such as paper before the start of image formation.

  According to the first embodiment, the air flow generated when the sheet material 150 is conveyed is actively used to selectively collect air near the surface of the sheet material 150 and perform humidity sensing. It is not necessary to heat the sheet material 150 at the time of detection. Therefore, it is possible to detect the moisture content of the sheet material 150 with very little energy consumption.

  Further, according to the first embodiment, since a heater and a wind guide fan for humidity measurement as in the image forming apparatus of Patent Document 2 are unnecessary, a simple and low-cost moisture amount detection device can be provided.

  Further, according to the first embodiment, by selectively sensing the humidity of the air in the vicinity of the surface, the amount of moisture that does not change the state of the sheet material 150 without heating, pressurization, light irradiation, or the like. A detection device can be provided.

  In addition, according to the first embodiment, a moisture amount detection device that can detect the moisture amount distribution in the conveyance direction of the sheet material 150 by one sensor unit 109 including one heat transfer coefficient sensor 101 is provided. it can.

  Further, according to the first embodiment, since the moisture content of the sheet material 150 can be accurately estimated before fixing, the optimum image forming conditions can be obtained and set for each sheet material 150 in real time. .

  Further, in the image forming apparatus 300 (color copying machine) according to the first embodiment, the charge amount and the fixing temperature are controlled based on the moisture content of the sheet material 150 before image formation, so that fine processing conditions can be obtained. Control becomes possible.

  In addition, it is possible to provide an image forming apparatus such as a copying machine or a printer that can optimally control the image forming conditions by accurately detecting the moisture content of the sheet material 150 and reflecting the detected results in the image forming conditions.

Second Embodiment
FIG. 4 is an explanatory diagram of the arrangement of sensor unit portions in the second embodiment. In the second embodiment, three sensor unit portions 109a, 109b, and 109c are arranged in a direction perpendicular to the conveying direction of the sheet material 150, and the moisture content distribution in the transverse direction of the sheet material 150 is estimated.

  As shown in FIG. 4, the sensor unit portions 109 a, 109 b, and 109 c are the same as the sensor unit portion 109 of the first embodiment shown in FIG. 1 and are arranged at the same conveyance direction position on the conveyance belt 112. The sensor unit portions 109a, 109b, and 109c are disposed apart from each other in the width direction of the sheet material 150 (displaced positions). Detect humidity. The sheet material 150 is conveyed in the arrow direction in the figure. The conveyance mechanism of the sheet material 150 is the same as that of the first embodiment.

  In the second embodiment, three sensor unit portions 109 a, 109 b, and 109 c are arranged at intervals in a direction substantially perpendicular to the conveying direction of the sheet material 150. By disposing a plurality of sensor unit parts in this way, it is possible to estimate the moisture content distribution in the transverse direction orthogonal to the conveying direction of the sheet material 150. The control unit 120 illustrated in FIG. 1 estimates the moisture content distribution in the transverse direction of the sheet material 150. Different optimized processing conditions for the positions of the center of the sheet material 150 and the left and right side edges are set in the image forming process unit 340 and the heating roller fixing device 335.

  Further, as described in the first embodiment, humidity sensing may be performed a plurality of times while the sheet material 150 passes under the sensor unit portions 109a, 109b, and 109c. Thereby, the humidity distribution in the conveying direction of the sheet material 150 can also be detected, and the two-dimensional distribution of the moisture content of the sheet material 150 can be estimated.

  According to the second embodiment, it is possible to easily estimate the moisture distribution in the conveyance direction and the width direction in one sheet material 150. It is possible to provide a moisture content detection device capable of measuring a planar moisture content distribution by combining detection in the transport direction and the width direction.

<Third Embodiment>
FIG. 5 is a block diagram of the image forming apparatus according to the third embodiment, and FIG. 6 is an explanatory diagram of the configuration of a humidity sensor that detects the moisture content of the sheet material. In the third embodiment, the image forming apparatus 400 is shown as a functional block diagram, but is mechanically configured similarly to the image forming apparatus 300 of the first embodiment. Therefore, in FIG. 5, the same reference numerals are given to the same components as those in FIG. 1, and detailed description thereof will be omitted.

  As shown in FIG. 5, the image forming apparatus 400 separates the sheet material 150 stacked on the cassette 321 one by one by the feeding roller 322 and feeds the sheet material 150 onto the conveying belt 112. The conveyance belt 112 conveys the sheet material 150 and sends it to the image forming process unit 340.

  The image forming apparatus 400 forms an image on the sheet material 150 using an electrophotographic technique. The sheet material 150 to which the toner image has been transferred by the image forming process unit 340 is sent to the heating roller fixing device 335 and subjected to heat and pressure, and the toner image is fixed on the surface of the sheet material 150.

  The sensor unit unit 200 arranged to face the cassette 321 contacts the surface of the uppermost sheet material 150 loaded and stored in the cassette 321, and an output signal corresponding to the humidity of the air near the surface of the sheet material 150. Is transmitted to the sheet material information calculation unit 120A, which is a moisture amount estimation unit. The sheet material information calculation unit 120 </ b> A controls the sensor unit unit 200 to estimate and calculate the moisture content of the sheet material 150 together with the detection result of the environmental temperature sensor 121.

  The control unit 120B adjusts the image transfer conditions in the image forming process unit 340 and the temperature of the fixing roller in the heating roller fixing unit 335 according to the amount of water calculated by the sheet material information calculation unit 120A. The control unit 120B is connected to the external PC 130 via the network, operates the image forming apparatus 400 according to the print job transmitted from the external PC 130, and prints out the sheet material 150.

  The sensor unit 200 according to the third embodiment is a humidity sensor whose main body portion is formed of a thin film and outputs a voltage signal corresponding to the humidity of air. The sensor unit 200 detects the humidity of the air in the vicinity of the surface of the sheet material 150 balanced with the moisture content of the sheet material 150.

  As shown in FIG. 6, the sensor unit 200 controls the humidity sensor 201 that responds to humidity to a close distance by controlling the distance to the sheet material 150, and contacts the air near the surface of the sheet material 150. Output according to the humidity. The humidity sensor 201 supports a three-layer structure in which a dielectric film 203 is disposed between an upper electrode 202 and a lower electrode 204 by a substrate 205. Above the humidity sensor 201, a water vapor transmission plate 206 is disposed so as to be supported by a fixing member 208 and a spring 209. The spring 209 and the substrate 205 are supported by a pedestal 207, and the whole is suspended by a support mechanism (not shown) so as to be lifted and lowered from above the cassette 321 shown in FIG. When the cassette 321 is raised and the sheet material 150 is positioned at the delivery height, the water vapor transmission plate 206 of the sensor unit 200 comes into contact with the surface of the uppermost sheet material 150 loaded and stored in the cassette 321. At this time, the humidity sensor 201 is located in the air near the surface of the sheet material 150.

  In the humidity sensor 201, a lower electrode 204 made of a metal thin film, a dielectric film 203, and an upper electrode 202 made of a metal thin film patterned into a thin line are sequentially laminated on a substrate 205 etched into a thin plate shape. The operation of the humidity sensor 201 is to detect a change in capacitance due to the humidity of the dielectric film 203. Alternatively, the upper electrode 202 may be energized with the same configuration, and it may be detected that the resistance value at that time changes depending on the amount of water vapor in the air. With such a humidity sensor 201, the humidity in the vicinity of the sheet material P that varies in accordance with the moisture content of the sheet material P is detected.

<Background of development>
In an image forming apparatus using electrophotographic technology, toner transfer conditions, fixing conditions, and the like vary depending on the moisture content of the sheet material (paper, etc.) used. For this reason, the moisture content of the sheet material on which image formation is performed is detected.

  In the image forming apparatus disclosed in Patent Document 2, water vapor generated by forcibly evaporating moisture in the sheet material using heat of the fixing device is used for a predetermined time after the sheet material passes through the fixing device. A humidity sensor detects the amount of water vapor. Therefore, the moisture content can be measured for each sheet material, and the moisture content of the sheet material that varies from moment to moment can be detected.

  The humidity sensor disclosed in Patent Document 2 is an example of a heat conduction type humidity sensor, and measures humidity by utilizing the fact that heat dissipation from a temperature-sensitive resistor that self-heats due to Joule heat changes. Such a thermal humidity sensor can be miniaturized by using the MEMS technology or the like, so that the heat capacity can be reduced and the reaction rate can be extremely increased.

<Correspondence with Invention>
The image forming apparatus 300 according to the first embodiment includes an image forming process unit 340 that forms an image on the sheet material 150. Further, a sensor unit 109 that detects the moisture content of the sheet material 150 supplied to the image forming process unit 340 and a control unit 120 that adjusts processing conditions in the image forming process unit 340 based on the detected moisture content. Prepare. The sensor unit 109 has a heat transfer rate sensor 101 that detects the humidity of the air near the surface of the sheet material 150, and a control unit 120 that estimates the amount of moisture based on the output of the heat transfer rate sensor 101.

  The image forming apparatus 300 detects the humidity of the air in the vicinity of the surface where the humidity changes sensitively in balance with the moisture content of the surface layer of the sheet material 150 at a position upstream from the image forming process unit 340, and Estimate the moisture content of the layer. Therefore, the moisture content of the surface layer of the sheet material 150 to be imaged from now on can be finely identified with high responsiveness and high accuracy and fed back to the image forming conditions.

  In the image forming apparatus 300 according to the first embodiment, the heat transfer coefficient sensor 101 detects the humidity of the air in the vicinity of the surface at a plurality of positions that are separated from each other (shifted) in a direction that intersects the conveyance direction of the sheet material 150. The control unit 120 estimates the moisture content distribution in the intersecting direction, and the control unit 120 changes the processing condition in the intersecting direction based on the estimated distribution.

  In the third embodiment, the sheet material 150 is stacked on the cassette 321 and sent out one by one for image formation. The humidity sensor 201 is disposed so as to be able to enter the air in the vicinity of the surface of the uppermost stacked sheet material.

  In the first embodiment, the sheet material 150 is transported on the transport belt 112 toward the image forming process unit 340. The heat transfer coefficient sensor 101 is disposed on the conveyor belt 112 and selectively detects the humidity of the air near the surface of the sheet material being conveyed.

  The sensor unit 109 of the first embodiment detects the moisture content of the moving sheet material 150. An air guide duct 108 is provided in the conveyance path of the sheet material 150 to separate air in the vicinity of the surface of the conveyed sheet material 150 from the sheet material 150 and guide it to a space away from the surface of the sheet material 150. Furthermore, the heat transfer coefficient sensor 101 which is arrange | positioned in the said space and detects the humidity of the said space, and the control part 120 which estimates the moisture content of the sheet | seat material 150 based on the detected humidity of the said space are provided.

  The sensor unit 109 selectively detects the humidity of the air near the surface of the sheet material 150 while the sheet material 150 is moving on the conveyance path of the sheet material 150. Without heating and pressurization as in the moisture amount detection device shown in Patent Document 2, air near the surface is peeled off from the surface of the conveyed sheet material 150 by the air duct 108 and the moisture amount is estimated from the air. To do. At this time, air near the surface is guided to a space away from the surface of the sheet material 150 using the movement of the air near the surface that moves together with the sheet material 150. Since the air near the surface continuously peeled off from the surface of the sheet material 150 is integrated and efficiently occupies the space, if the high-sensitivity heat transfer coefficient sensor 101 is provided in the space, the precision that fully utilizes the high sensitivity Can perform highly responsive humidity detection and estimate the amount of moisture by humidity.

  The sensor unit portions 109a, 109b, and 109c of the second embodiment are provided with a plurality of air guide ducts 108 that are spaced apart from each other (shifted in position) in a direction that intersects the conveying direction of the sheet material 150. A heat transfer coefficient sensor 101 is disposed at 108. The controller 120 estimates the moisture distribution in the intersecting direction using the outputs of the plurality of heat transfer coefficient sensors 101.

  The dry sheet material 150 loaded in a high humidity environment has a higher moisture content in the peripheral portion than in the central portion. In such a case, it is desirable to lower the transfer bias at the center in the width direction of the sheet material 150 than at both ends, and to lower the temperature setting of the heating roller fixing device. In combination with such a processing device capable of division control, fine adjustment of processing conditions according to the in-plane distribution of moisture content and uniform image formation within the plane can be realized.

  The heat transfer rate sensor 101 in the sensor unit 109 of the first embodiment is a heat conduction humidity sensor in which a temperature sensitive resistor is formed by MEMS technology.

  The sensor unit 109 in the first embodiment detects the characteristics of the sheet material 150 as an image forming recording medium. A heat transfer rate sensor 101 that detects humidity as an example of a physical property of gas and an air guide duct 108 that takes air from the air inlet 102 located near the surface of the sheet material 150 and guides it to the heat transfer rate sensor 101 are provided. A distance control mechanism (not shown) that adjusts the relative position between the air guide duct 108 and the sheet material 150 in the height direction is provided. This distance control mechanism supports the sensor unit 109 in a balance-type manner and can move up and down with a very small load by a balancer weight, and is provided with a damper for avoiding vibration. The sheet material 150 passes below the sensor unit 109 in a state where the sensor unit 109 is pushed up by the thickness.

  In the distance control mechanism according to the first embodiment, the sensor unit 109 is raised by the thickness of the sheet material 150 when the edge of the air inlet 102 contacts the sheet material 150. The air inlet 102 is disposed opposite to the conveying direction of the sheet material 150, and the heat transfer rate sensor 101 detects the humidity of the gas by detecting the heat transfer rate of the gas.

  The control unit 120 in the first embodiment estimates the relative humidity of air near the surface of the sheet material 150 based on the output of the heat transfer coefficient sensor 101. In other words, the control unit 120 estimates the characteristic value or moisture content of the sheet material 150 based on the output of the heat transfer coefficient sensor 101.

  The image forming apparatus 300 according to the first embodiment includes a sensor unit unit 109, an image forming process unit 340 that forms an image on the sheet material 150, a conveyance belt 112 that conveys the sheet material 150, and a detection result of the sensor unit unit 109. And a control unit 120 that adjusts at least one of the image forming conditions in the image forming process unit 340 and the conveying speed of the conveying belt 112.

It is explanatory drawing of a structure of the image forming apparatus of 1st Embodiment. It is explanatory drawing of a structure of the moisture content detection apparatus of 1st Embodiment. It is explanatory drawing of a structure of a wind guide duct. It is explanatory drawing of arrangement | positioning of the sensor unit part in 2nd Embodiment. FIG. 10 is a block diagram of an image forming apparatus according to a third embodiment. It is explanatory drawing of the structure of the humidity sensor which detects the moisture content of a sheet | seat material.

Explanation of symbols

101 Humidity detection means, gas property detection means (heat transfer coefficient sensor)
102 opening (air inlet)
103 Air channel 104 Space (Air outlet)
108 Air guide means (wind guide duct)
109, 109a, 109b, 109c Water content detection device (water content detection unit, sensor unit)
112 Conveyance route, Conveyance means (Conveyor belt)
113 Sheet material conveying device 120: estimation means, control means, humidity estimation means (control unit)
121 Environmental temperature sensor 150 Sheet material 200 Sensor unit section 300, 400 Image forming apparatus 321 Cassette 323 Photosensitive drum 325 Pre-exposure lamp 326 Pre-charger 327 Primary charger 328 Laser beam scanner 329 Developer 330 Transfer drum 331 Adsorption corona discharger 332 Transfer corona discharger 335 Heating roller fixing unit 340 Image forming means (image forming process section)

Claims (14)

Image forming means for forming an image on a recording medium;
Detecting means for detecting the moisture content of the recording medium supplied to the image forming means;
A control unit that adjusts a processing condition in the image forming unit based on the detected water content;
The detection means includes humidity detection means for detecting the humidity of the air near the surface of the recording medium;
An image forming apparatus comprising: an estimation unit configured to estimate the moisture amount based on an output of the humidity detection unit. The humidity detecting means detects the humidity of the air near the surface at a plurality of positions separated from each other in a direction intersecting with the conveyance direction of the recording medium,
The estimation means estimates the moisture content distribution in the intersecting direction,
The image forming apparatus according to claim 1, wherein the control unit changes the processing condition based on the estimated distribution. The recording medium is a sheet material that is stacked and sent one by one for the image formation,
3. The image forming apparatus according to claim 1, wherein the humidity detecting unit is arranged so that air near a surface of the uppermost stacked sheet material can enter. 3. The recording medium is a sheet material conveyed along a conveyance path toward the image forming unit,
The image forming apparatus according to claim 1, wherein the humidity detection unit is disposed in the conveyance path and detects the humidity of the air in the vicinity of the surface of the sheet material to be conveyed. In the moisture amount detection device that detects the moisture content of the sheet material,
An air guide means arranged in the sheet material conveyance path, separating the air in the vicinity of the surface of the sheet material to be conveyed from the sheet material, and guiding the air to a space away from the surface of the sheet material;
A humidity detecting means arranged in the space for detecting the humidity of the space;
A moisture amount detection apparatus comprising: estimation means for estimating a moisture content of a sheet material based on the detected humidity of the space. A plurality of the air guiding means are arranged apart from each other in a direction intersecting with the conveying direction of the sheet material,
The humidity detecting means is disposed in each of the air guiding means,
The moisture amount detection apparatus according to claim 5, wherein the estimation unit estimates a distribution of the moisture amount in the intersecting direction using outputs of the plurality of humidity detection units.   The moisture detection device according to claim 5 or 6, wherein the humidity detection means is a heat conduction type humidity sensor in which a temperature sensitive resistor is formed by MEMS technology. In an image forming apparatus sensor for detecting characteristics of an image forming recording medium,
A gas property detecting means for detecting a gas property,
An air guiding means for taking air from an opening located near the surface of the recording medium and guiding it to the gas property detecting means;
An image forming apparatus sensor comprising: a distance control mechanism that adjusts a relative position between the air guiding unit and the recording medium.   The sensor for an image forming apparatus according to claim 8, wherein an edge of the opening is in contact with a recording medium.   10. The sensor for an image forming apparatus according to claim 8, wherein the opening is disposed to face the recording medium in the conveying direction.   11. The image forming apparatus sensor according to claim 8, wherein the gas property detecting unit detects a humidity of the gas or detects a heat transfer coefficient of the gas.   12. The sensor for an image forming apparatus according to claim 8, further comprising a humidity estimation unit that estimates a relative humidity of air near the surface of the recording medium based on an output of the gas property detection unit.   12. The sensor for an image forming apparatus according to claim 8, further comprising a moisture content estimation unit that estimates a characteristic value of the recording medium or a moisture content based on an output of the gas property detection unit. . A sensor for an image forming apparatus according to any one of claims 8 to 13,
Image forming means for forming an image on a recording medium;
Conveying means for conveying the recording medium;
An image forming apparatus comprising: a control unit that adjusts at least one of an image forming condition in the image forming unit and a conveying condition in the conveying unit based on a detection result of the sensor for the image forming apparatus. .

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