A disclosed detector element includes a substrate including a void, a heating unit including a heat generating electrode bridged across the void, and a temperature sensor including a temperature sensor electrode provided above the void. The heat generating electrode and the temperature sensor electrode are warped, cantilevered, and standing up in space. The temperature sensor measures heat quantity transported from the heating unit. Distribution of an atmosphere surrounding an object surface with respect to the object surface, and the transportation state of the atmosphere are measured by using at least one of temperature, humidity, a direction or velocity of flow, pressure, and composition of gas in the atmosphere. Behavior of the gas adhering and aggregating onto the object surface, and behavior of aggregated liquid undergoing transpiration from the object surface are detected, based on the distribution and the transportation state measured.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to non-contact condensation detecting methods and non-contact condensation detecting apparatuses, and more particularly to a non-contact condensation detecting method and a non-contact condensation detecting apparatus to easily detect dew condensation.

2. Description of the Related Art

Conventionally, there are methods of measuring the flow velocity and the flow rate of a fluid, and components and density of an atmosphere by detecting heat transported by the fluid and heat propagating in the atmosphere. A sensor serving as a detecting unit in a thermal flowmeter is configured as follows. A heater serving as a heat generation source is arranged on an upstream side of a flow of gas, and a temperature sensor is arranged on a downstream side of the flow of gas. The sensor measures the flow velocity and the flow rate based on the heat quantity (amount of temperature change) conveyed to the downstream side or the time it takes for the heat to reach the downstream side. Further, a sensor serving as a detecting unit in a hygrometer or a gaschromatograph measures humidity or components and density of gas based on heat quantity (amount of temperature change) propagated, or the time it takes for heat to be transported from a heater serving as a heat generation source in an atmosphere. The heat conductivity changes according to components or the density of the atmosphere. In the sensor serving as the detecting unit, the heat quantity of the heater serving as the heat generation source and the temperature sensor can be reduced, and the heater and the temperature sensor can be arranged extremely close to each other. With such a configuration, it is possible to accelerate thermal response, and detect rapid changes, a slight flow velocity/flow rate, minute amounts of components, or a minute level of density. The sensor is realized by microfabrication technology used for constructing integrated circuits. These types of sensors are conventionally called a flowsensor, a flow velocity sensor, a heat conductivity humidity sensor, or a heat conductivity gas sensor.

A flowsensor disclosed in Patent Document 1 includes a substrate having a through hole or a void, and a membrane heater section and a membrane detecting section bridged or cantilevered above the through hole or the void. The heater sections and the detecting sections are formed by laminating two or more layers along the flow direction of fluid to be measured, and interlayer spaces are provided. The spaces are formed by the thickness of layers, and are therefore formed highly accurately at minute intervals. Accordingly, the space distance between the membrane heater section and the membrane detecting section can be reduced so as to achieve fast responses, high precision, low fluid rates, and high efficiency.

A flowsensor disclosed in Patent Document 2 is realized by making a heater wire circular, making an isothermal line of a temperature distribution by the heat of the heater wire concentric, and also making temperature sensor wires at both sides of the heater wire concentric. Accordingly, whichever direction a fluid comes from, an isothermal line for each direction expands in the same shape with respect to the heater wire and the temperature sensor wire. Thus, detected values and detection sensitivity are not dependent on the direction of the fluid, so that the flow velocity or the flow rate can be detected regardless of the direction of the fluid. Specifically, a heater and a temperature sensor are arranged adjacent to each other on a plane. Gas is heated according to heat and the flow rate generated by the heater arranged at an upstream side. The heat quantity transported by the gas is captured (sensed) by the temperature sensor arranged at a downstream side, and is detected as a rise in the temperature. Moreover, the temperature sensor wire is shaped in accordance with the shape of the isothermal line of a temperature distribution of the heat from the heater wire. According to the configuration described in Patent Document 2, the temperature sensor wire is shaped in accordance with the shape of the isothermal line of a temperature distribution of the heat generated by the heater wire, and therefore, slight shifts of the isothermal line caused by slight changes in the flow rate or the flow velocity can be detected in substantially the entire area of the temperature sensor line. Thus, a highly sensitive flowsensor can be provided.

According to the Patent Documents 1, 2, it is understood that heat diffused in a three-dimensional space can be captured by making the temperature sensor three-dimensional, so as to surround the heater. Moreover, because it is necessary to detect the flow where influence from the surface of the substrate is minimal, the temperature sensor is to be arranged at a position distant from the substrate. The temperature sensor is to have a three-dimensional structure.

Patent Document 3 proposes a technology for fabricating three-dimensional components. According to the Patent Document 3, for low pressures of plasma gas, film stress in sputter-deposited coatings is compressive. As the pressure of the plasma gas increases, the film stress in a deposited sub-layer changes to a tensile stress. The intrinsic stress of many sputtered thin films depends on the ambient pressure at which the material is deposited. By varying the pressure during sputtering, films can be obtained that are compressively stressed near the substrate-film interface and tensile stressed at the film surface. A bottom gold layer forms the outer skin of a coil when released, and a release layer is removed by wet undercut etching. A possible etchant for a Si release layer includes KOH (wet processing). After removing a release window, each elastic member coils back on itself, due to an intrinsic stress profile of the elastic member. The foregoing techniques can also be used to manufacture a new type of high-Q variable capacitor (varicap). These varicaps use the same micro-spring technology described above, have the requisite capacitance values, and can be integrated on-chip. A varicap structure based on micro-springs allows both otherwise missing on-chip RF passive components, inductors and varicaps, to be fabricated using the same process technology. These micro-spring varicaps have the additional benefit of requiring lower bias voltages than parallel plate MEMS capacitors. By using a spring as the second electrode in a photolithographically patterned capacitor, and varying the voltage between a fixed plate and the spring, the capacitance of the structure varies.

Patent Document 3: Japanese Publication of International Application No. 2003-533897

However, the following difficulties are faced according to Patent Document 1. Specifically, the heat from the heater at the upstream side diffuses three-dimensionally toward the downstream side, but the flow does not diffuse three-dimensionally because the flow path narrows. Therefore, the heat is easily transported to the temperature sensor. However, as the flow path is a solid object having higher heat conductivity than that of the fluid, excessive heat is conducted to the inner walls of the flow path due to the narrowed shape. As a result, the temperature sensor receives heat conduction components from the flow path, and a precise measurement cannot be performed. Moreover, because the heat quantity is large, heat accumulates in the substrate, and heat transferred from the substrate is added to the flow. This also affects the measurement of the temperature sensor located downstream. Further, as the units are arranged close to each other with high positional accuracy, adverse affects may be minimal. However, the positional relationship between the heater, the temperature sensor, and the substrate needs to be considered. Specifically, the distance between the heater and the temperature sensor is to be shorter than the distance between the heater and the substrate, and the heater and the temperature sensor need to be as far away from the substrate as much as possible.

According to Patent Document 2, the sensor is supposed to measure the flow in the middle of the flow; however, the sensor actually detects the flow at the surface of the substrate. More specifically, the sensor needs to detect the flow at a position least affected by the substrate surface. As the flow comes closer to the substrate surface, it flows less smoothly due to frictional resistance in the substrate surface. Thus, as the distance between the substrate becomes shorter, interference from the substrate increases. Accordingly, a slight flow rate cannot be measured. In addition, it is difficult to measure fluid of high viscosity, and at a temperature where the viscosity increases. In this configuration, the heater and the temperature sensor are arranged adjacent to each other on the plane. Gas is heated according to heat and the flow rate of the heat generated by the heater arranged at an upstream side. The heat quantity transported by the gas is captured by the temperature sensor arranged at a downstream side, and is detected as a rise in temperature. Moreover, the temperature sensor wire is shaped in accordance with the shape of the isothermal line of a temperature distribution of the heat of the heater wire. However, the heater and the temperature sensor are arranged adjacent to each other on the same plane, and the heat from the heater at the upstream side diffuses three-dimensionally toward the downstream side, and therefore, the temperature sensor can only capture a single plane component of the diffused heat components. As a result, the conveyance efficiency of heat and sensitivity is low, such that a low-noise, high resolution signal processing circuit is required. Also, in order to address the impact of a turbulence element, the temperature sensor needs to capture the three-dimensional isothermal line of three-dimensional heat diffusion.

Patent Document 3 discloses a three-dimensional coil formed on a chip. However, this structure is used as a contact point in variable capacitors and magnet coils, and is not intended for a heater and temperature sensor in a heat transportation mechanism. Due to the difference in functions, materials, shapes, and arrangements are different from those of a heat transportation mechanism. Thus, new configurations need to be added to realize a heater and temperature sensor in a heat transportation mechanism. To realize a sensor in a heat transportation mechanism for measuring the flow velocity or the flow rate of a fluid in a pipe and a space, the distance between the heater and the temperature sensor needs to be shorter than the distance between the heater and the substrate, and the heater and the temperature sensor need to be as far away from the substrate as possible. The temperature sensor needs to capture the three-dimensional isothermal line of three-dimensional heat diffusion as much as possible.

Conventionally, dew condensation has been a problem in various devices. Specifically, elements made of materials having high specific heat, and devices of large mass cannot adjust to rapid changes in the temperature/humidity in the surrounding environment. Therefore, dew condensation occurs on the surface, which causes malfunction of the device. Examples of such elements include optical recording media such as VTR head cylinders, hard disks, and optical disks; optical equipment such as lenses, light emitting devices, mirror reflectors, prisms, filters; optical devices including these optical equipment items; and components of image forming apparatuses such as photoconductive drums, polygon mirrors, and windows of automobiles and aircrafts. Dew condensation on the surfaces of these elements significantly affects functions of devices.

Moisture and gas adhering on recording sheets in electrophotographic image forming apparatuses significantly affect the image quality. Thus, it is required to accurately detect how the behavior of moisture adhering on the material surface is associated with the atmosphere, and control the behavior in an optimal manner. When a recording sheet dries as moisture in the sheet evaporates due to environmental changes, or when a recording sheet dries as moisture in the sheet undergoes rapid transpiration by receiving heat from a fixing unit, the recording sheet may deform by shrinking, curling, or creasing. Deformation needs to be prevented, because conveyance failures may occur while the sheet is being conveyed. In the fields of plants/animals and medicine, it is also necessary to detect water absorption phenomena or transpiration phenomena on surfaces of biologic objects, to examine the association with metabolism of biologic objects.

Japanese Laid-Open Patent Application No. 2002-310876 discloses a porous waterproof moisture permeable film that is porous on one side, allowing water vapor to permeate, but waterproof on the other side. If dew condensation water is formed on the porous side, the pores are blocked, and permeability to water vapor deteriorates. Accordingly, it is necessary to detect dew condensation.

Japanese Laid-Open Patent Application No. 2002-369885 discloses a power generating unit in which an electrocatalytic layer and a solid electrolyte membrane are combined. Gas transportation is less pronounced when dew condensation water is adhering, in a liquid state, on the solid electrolyte membrane. Gas transportation is more pronounced in a highly water-retentive state immediately before the condensation, and reaction efficiency of hydrogen and air is enhanced. Accordingly, it is necessary to detect the water retention rate of the solid electrolyte membrane.

In a cooling system, etc., disclosed in WO00/14522, in order to control cooling and dehumidifying operations in an optimal manner, it is necessary to detect the dew condensation on the surface of frozen materials near the surface of a heat exchanger in the cooling system side.

In a method of separating an organic solvent by distillation disclosed in Japanese Laid-Open Patent Application No. 2004-083385, the temperatures of aggregation and transpiration can be more precisely controlled by directly observing the gas behavior in the atmosphere, rather than detecting the temperature of the heat exchanger.

As described above, it is required in various fields to detect hydrophilia/hydrophoby on surfaces by quickly detecting aggregation and transpiration behaviors with high sensitivity, and detecting the differences in absorption of gas vapor molecules onto various surfaces.

There are conventional technologies for detecting dew condensation. Patent Document 4 discloses a condensation detection device. A VTR rotatable cylinder device has large heat capacity and dew condensation is thus likely to occur. Due to dew condensation, magnetic tape may adhere to the rotatable cylinder and get tangled. To prevent this problem, the condensation detection device determines whether the atmosphere is shifting into a supersaturation state. Specifically, the condensation detection device measures the surface temperature of the rotatable cylinder and the temperature and the humidity of the atmosphere near the rotatable cylinder, and then refers to data of the moisture amount in the air (psychrometric diagram), to make the determination.

Patent Document 5 discloses a method for measuring dew point or gas concentration, and an ice accretion predicting device. Dew condensation is detected based on a dew point obtained from the relative humidity of the atmosphere and the temperature of the subject of measurement. This method employs a relative humidity sensor employing a dielectric polymer, which responds more quickly to dew condensation than a mirror cooling method. An electrostatic capacity type, quick-response relative humidity sensor employing a dielectric polymer is cooled externally when the relative humidity is low. When the temperature is near the dew point, where the relative humidity rises, the relative humidity sensor is under a highly humid environment and is likely to maintain moisture, which makes it difficult to predict ice accretion. Thus, the relative humidity sensor is heated externally so as to change the temperature of the relative humidity sensor, thereby enhancing measurement precision.

Patent Document 6 discloses a dew condensation predicting device. Dew condensation is predicted by thermally binding a thermoelectric element to a dew condensation sensor to lower the temperature of the dew condensation sensor lower than the atmospheric temperature. In performing this operation, if water droplets are retained on the dew condensation sensor for a long time, the material of the sensor deteriorates. Thus, the dew condensation sensor is heated with the thermoelectric element to remove the dew condensation water from the dew condensation sensor.

Patent Document 7 discloses a sensor for predicting change of phase and a device for preventing frosting and dewing. Specifically, a dew condensation sensor is mounted onto a detection subject through a Peltier element. Heat is prevented from being transferred to/from the detection subject, so that the temperature of the dew condensation sensor is constantly lower by a fixed value than the surface of the detection subject. Dew condensation thus occurs faster on the dew condensation sensor than on the detection subject, so that frosting and dewing can be predicted.

Patent Document 8 discloses a temperature sensor for vehicles. The casing of a sensor for detecting the temperatures in various areas in a vehicle and the windshield of the vehicle are connected by a cup-shaped heat bonding member made of a heat conductive material. Incident infrared rays from the various areas are detected by a sensor element. When the temperature distributions at the various areas enter a predetermined range, the sensor determines that dew condensation has occurred on the windshield.

Patent Document 9 discloses a non-contact temperature measuring apparatus that utilizes the fact that heat flow between a reference object and an external object is proportional to the temperature of the external object. The non-contact temperature measuring apparatus detects, using a temperature sensor, temperatures of a first reference object and a second reference object that are spaced apart from each other by a certain distance along a moving continuous body. Accordingly, the temperature of the moving body is calculated.

Patent Document 10 discloses a technology for preventing a conveyance failure of a recording sheet in an electrophotographic image forming apparatus, caused by curling or creasing of the recording sheet while being conveyed. Specifically, an infrared ray moisture meter is used to detect the amount of moisture included in various parts of a recording sheet. According to the detected amount of moisture, the amount of air to be blown against various parts of the recording sheet is adjusted. This prevents the recording sheet from curling partially due to uneven amounts of moisture. In a technology disclosed in Patent Document 11, the amount of moisture included in a recording sheet is detected based on variations in transmission of a certain wavelength of infrared light reflected from the recording sheet. Based on the detected amount of moisture, the fixing temperature of a fixing device and roller pressure in a paper conveying path are controlled. In a technology disclosed in Patent Document 12, moisture included in a recording sheet is detected by using a moisture meter equipped for measuring the absorption of microwaves. The extent to which the recording sheet will curl is predicted based on the detected moisture amount and the type of the recording sheet, i.e. the strength (body) of the recording sheet. According to the prediction, curling of the recording sheet is corrected.

In the condensation detection device disclosed in Patent Document 4, the dew condensation sensor needs to be attached to the rotatable cylinder of the VTR rotatable cylinder, in accordance with dew condensation properties of the rotating cylinder. If the dew condensation sensor is attached like a generic sensor, it cannot detect dew condensation. Moreover, there are restrictions in attaching the dew condensation sensor to the rotatable cylinder, because of functions of a magnetic head and electrical signals received by the rotatable member.

According to the method of dew condensation detection disclosed in Patent Document 5, or the devices disclosed in Patent Documents 6, 7, the sensor is heated externally, or the sensor is cooled to a temperature lower than the atmosphere. Accordingly, the temperature of the atmosphere measured by the sensor is different from that of the atmosphere of the subject of dew condensation. As a result, precision of detection deteriorates, because the sensor detects a different temperature from that of the atmosphere of the subject of condensation.

In the method of estimating dew condensation disclosed in Patent Document 8, the sensor needs to be mounted onto the surface that is the subject of dew condensation, and thus cannot be used generically. The non-contact temperature measuring apparatus disclosed in Patent Document 9 is capable of measuring the temperature of a remote object in a non-contact manner by measuring the temperature gradient of gas; however, gas-liquid phase changes cannot be measured by this method.

Each of the dew condensation sensors described above detects whether dew condensation has occurred on itself. However, these dew condensation sensors cannot detect whether dew condensation has occurred on the actual subject.

The dew condensation sensors described above require special means in thermal structures to accommodate properties of dew condensation on the subject. Therefore, the dew condensation sensors cannot detect dew condensation of the subject by simply being attached to the subject, or being disposed near the subject.

The dew condensation sensors described above have dew condensation prediction functions. However, each of these sensors operates as a system using a dew condensation prediction algorithm obtained by adding a detected temperature of a specific location in the device. Accordingly, these sensors can only be applied to specific devices, and cannot be used universally.

By using an optical means such as a mirror cooling type dew point meter to measure dew condensation of a subject object from a remote location, only a mirror surface can be measured. Accordingly, this type of means cannot be generically used to measure any type of surface. A conceivable method is to detect a dew condensation phenomenon by combining a humidity sensor with an infrared thermometer. However, the emissivity differs according to surface conditions, and therefore, an accurate temperature cannot be measured. The temperature can be measured only for the portions of the surface where emissivity is known, and it is not certain whether the humidity of the surface of the subject object is detected.

In an image forming apparatus, deformation of a recording sheet, such as curling, is caused when the recording sheet dries rapidly. Specifically, the direct cause of the deformation is the speed of drying. The drying speed of a recording sheet depends on the speed at which moisture in the recording sheet is reduced by transpiration. The transpiration behavior reflects the quality and structure of the recording sheet, and the strength of the recording sheet determined by the quality and structure thereof. Thus, as described in Patent Documents 10, 12, it is difficult to predict deformation such as curling of a recording sheet with high precision, even by detecting the amount of moisture included in the recording sheet.

SUMMARY OF THE INVENTION

Accordingly, the present invention may provide a detector element, a non-contact condensation detecting method, and a non-contact condensation detecting apparatus in which the above-described disadvantage is eliminated.

A preferred embodiment of the present invention provides a detector element that can capture (detect) three-dimensional heat diffusion with a three-dimensional temperature sensor, capture a three-dimensional isothermal line with the temperature sensor, make the distance between a heating unit and the temperature sensor shorter than the distance between the heater and a substrate, and engage in a phenomenon in a three-dimensional space including heat elements.

A preferred embodiment of the present invention provides a non-contact condensation detecting method and a non-contact condensation detecting apparatus that can detect gas aggregation and transpiration on the surface of a measurement subject from a remote location in a non-contact manner based on physical changes in the atmosphere that is a continuous space in contact with the measurement subject without mounting a dew condensation sensor directly onto the subject object, and quickly detect the state of dew condensation on the surface of the subject object so as to accurately predict dew condensation on the surface of the subject object.

A preferred embodiment of the present invention provides a recording sheet deformation preventing method and an image forming apparatus that can detect, in real time, the transpiration speed of moisture included in a recording sheet on which an image is to be formed, predict with high precision whether the recording sheet will deform by curling, etc., due to rapid drying, and prevent deformation of the recording sheet, by employing the non-contact condensation detecting apparatus according to the present invention.

An embodiment of the present invention provides a detector element including a substrate including one of a through hole and a void; a heating unit including a heat generating electrode bridged across said one of the through hole and the void, the heat generating electrode being warped, cantilevered, and standing up in space; and a temperature sensor including a temperature sensor electrode provided above said one of the through hole and the void, the temperature sensor electrode being warped, cantilevered, and standing up in space, wherein the temperature sensor measures heat quantity transported from the heating unit.

An embodiment of the present invention provides a non-contact condensation detecting method including the steps of measuring distribution of an atmosphere surrounding an object surface with respect to the object surface and a transportation state of the atmosphere, by using at least one element selected among temperature, humidity, a direction or velocity of flow, pressure, and composition of gas in the atmosphere; and detecting a behavior of the gas adhering and aggregating onto the object surface, and a behavior of aggregated liquid transpiring from the object surface, based on the distribution and the transportation state measured at the measuring step.

An embodiment of the present invention provides a non-contact condensation detecting apparatus, including a measurement unit disposed at least at two locations, near an object surface and distant from the object surface, the measurement unit including a temperature/humidity sensor configured to measure temperature and humidity of gas of an atmosphere surrounding the object surface, and a flowsensor configured to measure one of a flow direction and flow velocity of the gas of the atmosphere surrounding the object surface; and a processing unit configured to determine distribution of the atmosphere with respect to the object surface and a transportation state of the atmosphere based on measurement results of the temperature/humidity sensor and the flowsensor, and detect a behavior of the gas adhering and aggregating onto the object surface, and a behavior of aggregated liquid undergoing transpiration from the object surface.

According to one embodiment of the present invention, three-dimensional heat diffusion can be captured with a three-dimensional temperature sensor, a three-dimensional isothermal line can thereby be captured with the temperature sensor, and the distance between a heating unit and the temperature sensor can be made shorter than the distance between the heater and a substrate.

According to one embodiment of the present invention, it is possible to detect states of dew condensation on the object surface in a non-contact manner, accurately predict dew condensation and transpiration on the object surface, and efficiently prevent dew condensation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description is given, with reference to the accompanying drawings, of an embodiment of the present invention.

FIG. 1is a perspective view of a configuration of a detector element1according to a first embodiment of the present invention. The detector element1includes a substrate10, bridges12disposed across voids11in the substrate10, a heating unit13, and two temperature sensors14,15disposed on the bridges12, respectively. The two temperature sensors14,15are disposed in parallel one on each side of the heating unit13. The temperature sensors14,15include temperature sensor electrodes14-1,15-1, respectively, which are shaped like the curved surface of a pipe, and are arranged facing each other. The heating unit13includes a heat generating electrode13-1connected to power supply leads13-2. An electrode pad13-3is connected to each power supply lead13-2. The heating unit13generates Joule heat using power supplied from the electrode pads13-3. Further, detection leads14-2,15-2are connected to the ends of the temperature sensor electrodes14-1,15-1of the temperature sensors14,15, respectively. Electrode pads14-3,15-3are connected to the detection leads14-2,15-2, respectively. The temperature sensors14,15have temperature dependent properties, according to heat transferred from a neighboring space. Heat from the heating unit13located upstream in a flow along the x axis is diffused in the space according to the flow velocity. The heat is captured inside the pipe-shaped curved surfaces of the temperature sensors14,15. The flow velocity and the flow rate of the fluid flowing inside the pipe-shaped temperature sensor electrodes14-1,15-1of the temperature sensors14,15are measured. The heat diffuses not only along the flow in the x axis direction, but also in a three-dimensional space. In the flow along the x axis, the temperature sensors14,15are arranged in a three-dimensional space with respect to the heating unit13. Accordingly, the temperature sensors14,15capture the heat diffused from the heating unit13in a three-dimensional space, and therefore, their heat transfer efficiency is high. Due to friction, the flow velocity of the fluid near the surface of the substrate10is lower than the flow velocity of the fluid distant from the surface of the substrate10. However, the heating unit13and the temperature sensors14,15are standing on the substrate10, rising up on the surface of the substrate10. With this configuration, even a slight flow velocity can be measured, unlike a case where the heating unit13and the temperature sensors14,15are disposed flat on the surface of the substrate10. Moreover, even at high velocity, the captured fluid is less likely to flow away from the surface and cause turbulence. The advantages of measuring a slight flow velocity at a position distant from the surface of the substrate10are described below.FIG. 2is a graph for describing flow velocity measurement properties of air by the distance along the substrate surface from the edge of the substrate and the distance away from the substrate surface. As shown inFIG. 2, it is necessary to measure the flow velocity of air at a position distant from the surface of the substrate10. Specifically, at a distance less than the thickness of the boundary layer, the property values of the fluid and dependence on the substrate structure intricately affect each other. Accordingly, the measured value needs to be corrected in order to obtain the actual flow velocity, which entails indeterminacy (may be indeterminate). Thus, in a case of measuring a slight flow velocity, it is even more advantageous to measure the flow velocity at a position distant from the surface of the substrate10. According to Stokes' law, the thickness of the boundary layer at which the laminar flow velocity receives friction resistance along a flat plane surface can be obtained with the following formula:
δ≅5*(νx/U)1/2
where v=η/ρ, η: kinematic viscosity coefficient, ρ:density, x:distance from edge, U: flow velocity.

The temperature sensor14, which is located upstream of the heating unit13, is used for capturing the first temperature information of the fluid using temperature properties of temperature-sensitive material. Alternatively, the temperature sensor14is used for measuring the temperature information when the flow of the fluid is reversed. The temperature sensor14can capture diffused heat from the heating unit13in a three-dimensional space. If the temperature sensor14were to be disposed flat on the surface of the substrate10, the sensitivity would be affected by a change in the angle with respect to the flow, and therefore, maximum sensitivity could only be obtained in a single direction. However, because the temperature sensors14,15according to the present embodiment are arranged in a three dimensional manner with respect to the heating unit13, the temperature sensors14,15can accommodate changes in the angle of the flow. Accordingly, even if the angle of the flow along the x axis changes, because the flow is captured in a three-dimensional space, the position of the sensor can be easily adjusted with respect to the axis of the flow. Moreover, the vertical posture of the substrate significantly affects the heat flow. Because heated gas flows upward, if the substrate were facing downward, heat would accumulate in the voids. If the substrate is facing upwards, heat does not accumulate in the voids. However, because the heating unit13and the temperature sensors14,15are standing up on the substrate10, rising up on the surface of the substrate10, measurement of temperature is unaffected by the posture of the substrate10. Accordingly, the detector element1can be installed in various locations.

Although the heating unit13and the temperature sensors14,15have three-dimensional structures, they can be fabricated by plane machining. The fabricating method is described with reference toFIGS. 3 through 5.FIGS. 3,4A,5A are plan views,FIG. 4Bis a side view,FIG. 5Bis a cross-sectional view taken along line A-A′ ofFIG. 5A, andFIG. 5Cis a cross-sectional view taken along line B-B′ ofFIG. 5A. Elements corresponding to those inFIG. 1are denoted by the same reference numbers.

As shown inFIG. 3, patterns made of conductive material films are formed on the substrate10for the heat generating electrode13-1and the power supply leads13-2of the heating unit13, and the temperature sensor electrodes14-1,15-1, the detection leads14-2,15-2, and the electrode pads14-3,15-3of the temperature sensors14,15, respectively. A metal material having a high resistance temperature coefficient such as Pt, W is used for the heating unit13and the temperature sensors14,15. The power supply leads13-2and the detection leads14-2,15-2are formed with the same material, and can therefore be formed at the same time, thus enhancing convenience. The power supply leads13-2and the detection leads14-2,15-2must have low electric resistance values so as not to generate heat. Accordingly, the power supply leads13-2and the detection leads14-2,15-2are made wider in the direction of current flow, and arranged on the substrate10so as to increase heat capacity. The temperature sensors14,15can be formed of a thermoelectric material having a Seebeck effect. In the case of using such a thermoelectric material, the cold junction is arranged on the substrate10in an area where there is no void.

An insulating layer on the substrate10shown inFIG. 4Ais removed by etching in the area of the heat generating electrode13-1of the heating unit13and the temperature sensor electrodes14-1,15-1of the temperature sensors14,15. As a result, as shown inFIG. 4B, the heating unit13and the temperature sensors14,15are partly detached from the lower layer, forming cantilevered structures. The heating unit13and the temperature sensors14,15then form curved surfaces due to warping, and stand up on the substrate10. The insulating layer underneath the patterns is etched away, by undercut etching, from the edge to half the width of the patterns of the heating unit13and the temperature sensors14,15. Accordingly, the heating unit13and the temperature sensors14,15are warped and form cantilevered structures.

Further, as shown inFIG. 5A, the voids11are formed by etching only the area of the surface of the substrate10exposed after the insulating layer is removed. In the configuration shown inFIG. 4B, the heating unit13and the temperature sensors14,15stand up on the substrate. Compared to the configuration shown inFIG. 4B, the heating unit13and the temperature sensors14,15are further away from the substrate10that has a large heat capacity, in the configuration shown inFIGS. 5B,5C, and are thus less affected by the heat from the substrate10. Accordingly, the configuration shown inFIGS. 5B,5C is even more effective. A conventional technology is employed to etch the substrate10up to inner edges of the insulating layer indicated by dashed lines inFIG. 5A. As a result, the bridges12are formed across the voids11, so that the cantilevered heating unit13and the temperature sensors14,15are supported by the bridges12fixed at both ends.

FIG. 6is a cross-sectional schematic diagram for describing a method of forming three-dimensional temperature sensors. A heat-resistant substrate20is made of, for example, Si, Al, Cu, Ni, Cr, stainless steel, kovar, Mo, W, Al2O3, SiO2, glass, ceramic, epoxy resin, or polyimide resin. A lower layer21is formed by a film formation method such as evaporation coating, sputtering, or CVD, using approximately 0.3 μm to 3 μm of an electrical insulating material such as SiO2, MgO, Al2O3, Ta2O5, or TiO2. The degree of vacuum is preferably 0.133 to 133 mPa (10−6to 10−3Torr) or less during the film formation. In order to prevent the lower layer21from contracting due to an increase in density at the baking/tightening process to be described later, it is necessary to form the film in a high vacuum (low pressure) atmosphere, so as to reduce the porosity and increase the density of the lower layer21as much as possible. Next, an upper layer22including a heat generating layer and an extraction electrode, etc., is formed by a film formation method such as evaporation coating or sputtering, using approximately 0.1 μm to 3μm of conductive resistor heat generating material such as NiCr, Ir, Pt, Ir—Pt alloy, SiC, TaN, or Kanthal alloy. The upper layer22is photo-etched to form a pattern of a predetermined shape. Further, a protective covering layer23can be laminated over the upper layer22by using a similar electrical insulating material and under similar conditions to those of the lower layer21. The upper layer22and the protective covering layer23are formed after the lower layer21is formed. Thus, the surfaces of the upper layer22or the protective covering layer23is more rough and uneven than that of the lower layer21. Moreover, as the thickness of the film increases, the particle sizes increase, thus increasing pores and deficiencies. As a result, the upper layers shrink more easily than the lower layer21at the baking/tightening process, so that beam parts are caused to warp. By lowering the degree of vacuum when forming the upper layer22and the protective covering layer23to approximately 13.3 mPa to 1.33 Pa (10−4to 10−2Torr), which is lower than that when forming the lower layer21, a porous film can be formed. Thus, the upper layers can be made to shrink more easily than the lower layer21at the baking/tightening process. By forming a void24in the substrate20by etching, a beam configured with the lower layer21and the upper layer22, or a beam configured with the lower layer21, the upper layer22, and the protective covering layer23is formed. Further, a predetermined warp shape can be formed by baking/tightening this beam at 350° C. to 800° C. The warp shape can be formed even if the baking/tightening process is performed before forming the void24. In this case, the upper layer22and the protective covering layer23is caused to shrink after the void24is formed, and this shrinking force eliminates a binding force from the substrate20. Accordingly, the baking/tightening process and the formation of the void24can be performed in any order.

The thermal tracing technique used for measuring the flow rate of a fluid is described below. For example, in a flow rate measuring instrument disclosed in Japanese Laid-Open Patent Application No. S60-186714, a heating unit provided inside a piping generates and supplies a predetermined heat pulse to the fluid flowing through the piping. A temperature sensor is located downstream at a predetermined distance from the heating unit. The instrument supplies a heat pulse to flowing fluid, and detects, at a predetermined location, the maximum temperature of heat distribution of the fluid. The instrument then obtains the flow rate of the fluid based on the amount of time from when the heat pulse is supplied, to when the maximum temperature is detected.

FIG. 7is a plan view of a configuration of a detector element2according to a second embodiment of the present invention. Elements corresponding to those inFIG. 1are denoted by the same reference numbers. The detector element2according to the second embodiment includes plural temperature sensors15arranged in parallel. The heating unit13is intermittently heated, and the flow velocity is measured by capturing the time that it takes for each heat wave to reach each of the temperature sensors15located at predetermined distances.

FIG. 8is a perspective view of a configuration of a detector element3according to a third embodiment of the present invention. Elements corresponding to those inFIG. 1are denoted by the same reference numbers. In the detector element3according to the third embodiment, the heating unit13is disposed at an x axis position inside the two temperature sensors14,15standing up on the substrate10. The fluid flows along the x axis, and heat from the heating unit13is supplied to the fluid. The heat diffuses not only along the flow, but also in a three-dimensional space. Accordingly, the temperature sensors14,15can capture the heat diffused from the heating unit13in a three-dimensional space. The heat generating section of the heating unit13is inside of the flow, while the temperature sensors14,15are outside the flow. Thus, even if the angle of the flow along the x axis changes, the flow can be captured in a three-dimensional space. Accordingly, the position of the sensor can be easily adjusted with respect to the axis of the flow. Compared to the flowsensor structure according to the first and second embodiments in which the heating unit13and the temperature sensors14,15are arranged in parallel, the heating unit13is located closer to the temperature sensors14,15in the third embodiment. Thus, the third embodiment is highly effective for detecting an extremely small amount of flow.

A method of fabricating the detector element3according to the third embodiment is described with reference toFIGS. 9 and 10.FIGS. 9 and 10Aare plan views, andFIG. 10Bis a cross-sectional view taken along line C-C′ ofFIG. 10B. Elements corresponding to those inFIG. 1are denoted by the same reference numbers.

As shown inFIG. 9, the heating unit13overlaps the temperature sensors14,15, and therefore, the heating unit13is to be formed by using a sacrifice layer, in a subsequent step after the temperature sensors14,15are formed. First, patterns made of conductive material films are formed on the substrate10for the temperature sensor electrodes14-1,15-1, the detection leads14-2,15-2, and the electrode pads14-3,15-3of the temperature sensors14,15, respectively. A metal material having a high resistance temperature coefficient such as Pt, W is used for the heating unit13and the temperature sensors14,15. Next, patterns made of, for example, Ni, are formed in areas to become the heating unit13, in a sacrifice layer that can be selectively etched and removed later. Patterns made of conductive material films are formed for the heat generating electrode13-1, the power supply leads13-2, and the electrode pads13-3of the heating unit13. Then, the sacrifice layer in the area corresponding to the heating unit13, and the insulating layer in the area corresponding to the heating unit13and the temperature sensors14,15on the substrate10are removed by etching. Subsequently, only the exposed areas of the surface of the substrate10are etched to form the voids11. As shown inFIG. 10B, the heating unit13and the temperature sensors14,15are partly detached from the lower layer, forming cantilevered structures. The heating unit13and the temperature sensors14,15form curved surfaces due to warping, and stand up on the substrate10. Heat is captured from the heating unit13, which is positioned along the axis of the temperature sensors14,15. As shown inFIG. 10B, the heating unit13has a bridged structure fixed at both ends, supporting a cantilevered structure. Therefore, the bridged beam structure is hardly warped, and is almost a straight line.

FIG. 11is a perspective view of a configuration of a detector element4according to a fourth embodiment of the present invention. The detector element4according to the fourth embodiment has a flowsensor structure similar to that of the detector element3according to the third embodiment, in that a heating unit41is disposed inside a temperature sensor40. However, the operations are different from the third embodiment. Specifically, the fluid is guided to a y-z surface, and is made to flow substantially perpendicular to the pipe-shaped temperature sensor40and the heating unit41. Because the heating unit41is located at the axis of the pipe, even if the flow shifts within a range of an angle θ at the z-y surface, effects on detections are small. The allowable range of shift in the angle at the x-y surface is large because the temperature sensor40extends transversely. Moreover, the temperature sensor40has a rectifying function due to its comb-teeth shape, so that stable output can be obtained even under turbulent conditions, without requiring a rectifying device.

A method of fabricating the detector element4according to the fourth embodiment is described with reference toFIGS. 12A through 12C.FIG. 12is a plan view,FIG. 12Bis a cross-sectional view taken along line D-D′ ofFIG. 12A, andFIG. 12Cis a cross-sectional view taken along line E-E′ ofFIG. 12A. In the fabrication method of the detector element3according to the third embodiment shown inFIG. 8, the heating unit13is made to overlap the temperature sensors14,15, and therefore, the heating unit13is formed in a subsequent step by using the sacrifice layer. However, the detector element can also be fabricated by plane machining by making use of the warping effect. Either method can be employed as long as the heating unit13is located inside the temperature sensors14,15when the temperature sensors14,15stand up on the substrate10. Accordingly, as shown inFIG. 12, a pattern for a heat generating electrode41-1of the heating unit41is formed between temperature sensor electrodes40-1so as not to overlap the temperature sensor40on the substrate10. Patterns of the temperature sensor40and the heating unit41are warped due to cantilevered structures, thereby forming the heating unit41inside the temperature sensor40. Only a single film made of Pt is needed, for both the heating unit41and the temperature sensor40. On the film, a pair of patterns opposite to each other is formed for the temperature sensor40, and a pattern for the heating unit41is formed therebetween. Thus, convenience is enhanced, as a sacrifice layer is not required.

FIG. 13is a perspective view of a configuration of a detector element5according to a fifth embodiment of the present invention. Similar to the flowsensor structure of the detector element4according to the fourth embodiment shown inFIG. 11, a heating unit51is disposed in a temperature sensor50. In the detector element5according to the fifth embodiment, a temperature sensor electrode50-1of the temperature sensor50is ring-shaped. Similar to the ring-shaped temperature sensor electrode50-1of the temperature sensor50, detection leads50-2, power supply leads51-2of the heating unit51, and electrode pads50-3,51-3are arranged radially, although only half of these are shown inFIG. 13. The temperature sensor electrode50-1of the temperature sensor50and a heat generating electrode51-1of the heating unit51are arranged reversed to each other, so as to face each other when they are warped. In the detector element5according to the fifth embodiment, the fluid is guided to an x-y surface, and the heating unit51is located in the center of the temperature sensor50, surrounded by the curved surface of the temperature sensor50. Therefore, even if the flow shifts slightly along the z axis, effects on detections are small. Accordingly, the flow can be detected in any direction along the x-y surface. Moreover, the temperature sensor50has a rectifying function due to its comb-teeth shape, so that stable output can be obtained even under turbulent conditions, without requiring a rectifying device.

A method of fabricating the detector element5according to the fifth embodiment is described with reference toFIGS. 14,15A, and15B.FIG. 14andFIG. 15Aare plan views, andFIG. 15Bis a cross-sectional view taken along line F-F′ ofFIG. 15A. As shown inFIG. 14, patterns made of conductive material films are formed on the substrate10for the temperature sensor electrode50-1of the temperature sensor50, the detection leads50-2, the heat generating electrode51-1and the power supply leads51-2of the heating unit51, and the electrode pads50-3,51-3. As shown inFIGS. 15A,15B, the insulating layer in the area corresponding to the temperature sensor electrode50-1of the temperature sensor50and the heat generating electrode51-1of the heating unit51on the substrate10are removed by etching. The temperature sensor50and the heating unit51are partly detached from the lower layer, forming cantilevered structures. The temperature sensor50and the heating unit51then form curved surfaces due to warping, and stand up on the substrate10. Further, only the exposed areas of the surface of the substrate10are etched to form voids52.

FIGS. 16A,16B are diagrams of a configuration of a heating unit60of a detector element6according to a sixth embodiment of the present invention.FIGS. 17A,17B are diagrams of a configuration of a temperature sensor61of the detector element6according to the present embodiment.FIGS. 18A,18B are diagrams of the overall configuration of the detector element6according to the present embodiment.FIGS. 16A,17A are plan views,FIG. 16Bis a cross-sectional view taken along line G-G′ ofFIG. 16A,FIG. 17Bis a cross-sectional view taken along line H-H′ ofFIG. 17A, andFIG. 18Bis a cross-sectional view taken along line I-I′ ofFIG. 18A. In the detector element6according to the present embodiment shown inFIG. 18, a substrate on which the heating unit60shown inFIGS. 16A,16B is formed, is combined with another substrate, on which the temperature sensor61shown inFIGS. 17A,17B is formed. Fluid is made to flow through a void62formed by combining these substrates. According to the conventional technology, before heat is transported from the heating unit to the temperature sensor, the heat is affected by heat exchange between the substrate walls. However, in the present embodiment, the temperature sensor is disposed in front of the position where the fluid reaches the substrate wall, so that the effect of heat exchange can be reduced. Compared to a case of using a single substrate, the configuration of the present embodiment requires the extra work of combining the two substrates with precision. On the other hand, the present embodiment is advantageous in that the microstructure of the heating unit and the temperature sensor is protected in between the substrates, instead of standing up and being exposed on a substrate. Accordingly, the microstructure is resistant to damage, and thus easy to handle.

FIGS. 19A,19B are diagrams of a configuration of a heating unit70of a detector element7according to a seventh embodiment of the present invention.FIGS. 20A,20B are diagrams of a configuration of a temperature sensor71of the detector element7according to the present embodiment.FIG. 21provides schematic diagrams of the overall configuration of the detector element7according to the present embodiment.FIGS. 19A,20A are plan views,FIG. 19Bis a cross-sectional view taken along line J-J′ ofFIG. 19A, andFIG. 20Bis a cross-sectional view taken along line K-K′ ofFIG. 20A. In the detector element7, the heating unit70is located inside the temperature sensor71. Accordingly, as shown inFIGS. 19A,19B, the heating unit20has a bridged structure fixed at both ends without being warped, while the temperature sensor71is warped as shown inFIG. 20. Thus, the heating unit70is formed inside the temperature sensor71as shown inFIG. 21.

FIG. 22is a diagram of a configuration of a detector element8according to an eighth embodiment of the present invention.FIG. 23Ais a plan view of the detector element8according to the present embodiment, andFIG. 23Bis a cross-sectional view taken along line L-L′ ofFIG. 23A. Elements corresponding to those inFIG. 1are denoted by the same reference numbers. The detector element8according to the present embodiment shown inFIGS. 22,23A,23B is disposed on the substrate10, including a single, comb-teeth shaped resistive element80that is warped, forming a cantilevered structure. According to the sensing manner of an atmosphere measuring device and flow sensor disclosed in U.S. Pat. No. 5,551,283, the resistive element80serves as both a heating unit and a temperature sensor. The resistive element80has applied a small current or a small voltage, which is small enough so as not to heat the resistive element80. At a different timing, the resistive element80has applied a large current or a large voltage, so as to be heated. A resistance value detecting unit, not shown in the figure, detects a first resistance value indicated by the resistive element80when a small current or a small voltage is applied, and a second resistance value indicated by the resistive element80when a large current or a large voltage is applied. The first resistance value is subtracted from the second resistance value, and the flow rate is calculated based on the result of subtraction.

According to one embodiment of the present invention, three-dimensional heat diffusion can be captured with a three-dimensional temperature sensor, a three-dimensional isothermal line can thereby be captured by using the temperature sensor, and the distance between a heating unit and the temperature sensor can be made shorter than the distance between the heater and a substrate.

Further, according to one embodiment of the present invention, it is possible to fabricate a detector element by plane machining, and use the detector element as a flowsensor for measuring a flow velocity and a flow rate of a fluid.

Further, according to one embodiment of the present invention, it is possible to provide a sensor capable of measuring the time it takes for heat to be transported, and calculating flow velocity.

Further, according to one embodiment of the present invention, it is possible to make the distance between the heating unit and the temperature sensor even shorter so as to detect minute amounts of change.

Further, according to one embodiment of the present invention, it is possible to detect the direction of a fluid flow.

Further, according to one embodiment of the present invention, it is possible to perform measurements even if the angle of the flow shifts, and even under turbulent conditions.

Further, according to one embodiment of the present invention, it is possible provide a detector element with a high degree of freedom in structure and shape.

Further, according to one embodiment of the present invention, it is possible to perform measurements even if the angle of the flow shifts within a range of an angle θ at the x-y surface and the z-y surface. Accordingly, the allowable range of shift is wide.

Further, according to one embodiment of the present invention, loss of heat due to heat transfer is small, and measurements can be performed corresponding to the direction of the flow.

A description of another embodiment according to the present invention is given below. First, a description is given of changes in an atmosphere surrounding an object, as gas in the atmosphere adheres, aggregates, and condenses on the surface of the object, and the aggregated liquid undergoes transpiration. As shown inFIG. 24, when gas in a surrounding atmosphere200adheres and aggregates on the surface of an object100, the gas in the atmosphere200more distant remote from the surface of the object100flows toward the surface of the object100. When the gas adhered on the surface of the object100is desorbed, or when the liquid aggregated on the surface of the object100undergoes transpiration, the gas of the atmosphere200near the surface of the object100flows away from the surface of the object100.

A temperature distribution or a density distribution is generated in the atmosphere200along the direction of gas flow, according to the absorption or the aggregation on the surface of the object100.FIGS. 25A,25B are graphs of the temperature distribution and the relative humidity distribution of the atmosphere200, which change according to the distance of the atmosphere200from the surface of the object100. It is assumed inFIGS. 25A,25B that the temperature of the atmosphere200at a remote location is T1, and the temperature of the surface of the object100is T1, T2, T3, and T4, where T1>T2>T3>T4, and a dew-point temperature of the atmosphere Td is between the temperature T2and the temperature T3. InFIG. 25A, the horizontal axis represents the temperature of the atmosphere200, and the vertical axis represents the distance from the surface of the object100. InFIG. 25B, the horizontal axis represents the relative humidity in the atmosphere200, and the vertical axis represents the distance from the surface of the object100.

When the temperature of the surface of the object is T1, which is the same as the temperature T1of the atmosphere200, the distribution of the relative humidity of the atmosphere200is even. When the temperature of the surface of the object is T2, which is lower than the temperature T1of the atmosphere200, the temperature of the atmosphere200near the surface of the object100decreases. This is caused by thermodynamic interactions between gas molecules of air and moisture and the surface of the object100. As the temperature of the atmosphere200near the surface of the object100decreases, the saturated water vapor pressure decreases, thus increasing the relative humidity indicated by water vapor pressure/saturated water vapor pressure. At this stage, the amount of water vapor molecules adhering on the surface of the object100increases, but more water vapor molecules are desorbed. Therefore, water molecules, which cause dew condensation, are not yet formed on the surface of the object100.

When the temperature of the surface of the object is T3, which is lower than the temperature T1of the atmosphere200and even lower than the dew-point temperature of the atmosphere Td, the amount of water molecules adhering on the surface of the object100exceeds the amount of water molecules desorbed. As a result, water vapor molecules form clusters of water molecules, causing dew condensation on the surface of the object100. Even if the amount of water vapor molecules transported from a remote location from the surface of the object100toward the surface of the object100increases, the amount of water vapor molecules typically becomes insufficient near the surface of the object100. Specifically, 1 mol, 22,400 cc of water vapor is aggregated into 18 cc of water near the surface of the object100, such that the volume becomes 1/1,244, although variations may be caused by the temperature of the atmosphere200near the surface of the object100. Accordingly, even if the temperature of the surface of the object100decreases to T3, the relative humidity in the atmosphere200near the surface of the object100becomes lower than a remote location. As shown inFIGS. 25A,25B, in the atmosphere200in the middle of a location near the surface of the object100and a location remote from the surface of the object100, the temperature decreases, and the relative humidity thus increases. When the temperature of the surface of the object further decreases to T4, which is lower than the temperature T1of the atmosphere200, dew condensation further progresses. Accordingly, compared to when the temperature of the surface of the object100is T3, the relative humidity in the atmosphere200near the surface of the object100becomes lower than a remote location to a greater degree.

The dew condensation progresses as long as the temperature of the surface of the object100is equal to or less than the dew-point temperature of the atmosphere Td. When the temperature of the surface of the object100exceeds the dew-point temperature of the atmosphere Td, the water undergoes transpiration, and water vapor molecules are transported from the surface of the object100to a remote location. As described above, the transportation state of the atmosphere200with respect to the surface of the object100, i.e., whether the atmosphere200is in the absorption/aggregation process, the balanced status, or the transpiration process, can be detected from a remote location. Specifically, dew condensation behavior and transpiration behavior on the surface of the object100can be detected from a location remote from the surface of the object100in a non-contact manner by measuring changes in the temperature gradient, the humidity gradient, and the flow of the atmosphere200.

FIG. 26is a block diagram of a non-contact condensation detecting apparatus300according to an embodiment of the present invention, configured to remotely detect dew condensation behavior and transpiration behavior on the surface of the object100in a non-contact manner. As shown inFIG. 26, the non-contact condensation detecting apparatus300includes plural humidity/temperature sensors400a,400b,400c, a flowsensor500, and a processing unit600.FIGS. 27A,27B,27C are diagrams of a first example of a measurement unit according to the present invention. As shown inFIGS. 27A,27B,27C, the humidity/temperature sensor400ais arranged near the surface of the object100and at a distance h from the surface of the object100, and detects a temperature Ta and a humidity Ha of the atmosphere200near the surface of the object100. The humidity/temperature sensor400bis disposed in the middle of (in between) a location near the surface of the object100and a location remote from the surface of the object100, and detects a temperature Tb and a humidity Hb of the atmosphere200in the middle location. The humidity/temperature sensor400cis disposed remote from the surface of the object100, and detects a temperature Tc and a humidity Hc of the atmosphere200remote from the surface of the object100. The flowsensor500is arranged in the middle of a location near the surface of the object100and a location remote from the surface of the object100, and detects a flow direction Fz and a flow velocity Wa of the atmosphere200. Referring back toFIG. 26, the processing unit600includes an operations unit700, a calculating unit800, a storing unit900, and an alarm output unit1000. The calculating unit800receives the temperature, the flow direction, the flow velocity, etc., of the atmosphere200detected by the humidity/temperature sensors400a,400b,400cand the flowsensor500at predetermined timings. The calculating unit800stores the received temperature, humidity, and flow direction into the storing unit900, and determines dew condensation behavior and transpiration behavior on the surface of the object100based on changes in the received temperatures, humidity levels, and flow direction. The alarm output unit1000outputs a dew condensation alarm signal or a transpiration signal to a temperature/humidity control unit when a corresponding dew-concentration signal or transpiration signal is received from the calculating unit800.

A process performed by the non-contact condensation detecting apparatus300for detecting dew condensation on the surface of the object100is described with reference to a flowchart inFIG. 28, andFIGS. 27A,27B.

The calculating unit800in the processing unit600receives temperatures T, humidity levels H, and flow directions Fz of the atmosphere200detected by the humidity/temperature sensors400a,400b,400cand the flowsensor500at predetermined timings. The calculating unit800stores the received temperatures T, the humidity levels H, and the flow directions Fz in the storing unit900(step S1). Then, when time passes from a time t(n) to a time t(n+1) (step S2), the calculating unit800compares a nearby temperature Ta(n+1) received from the humidity/temperature sensor400awith a remote temperature Tc(n+1) received from the humidity/temperature sensor400c, and compares a nearby humidity Ha(n+1) received from the humidity/temperature sensor400awith a remote humidity Hc(n+1) received from the humidity/temperature sensor400c, at the time t(n+1) (step S3). When the nearby temperature Ta(n+1) and the remote temperature Tc(n+1) are the same as shown inFIG. 27A(No in step S3), the calculating unit800determines that the temperature T1of the surface of the object100and the remote temperature Tc(n+1) are the same, and that the amount of water vapor molecules of the atmosphere adhering on the surface of the object100is small (step S7). When the nearby temperature Ta(n+1) received from the humidity/temperature sensor400ais lower than the remote temperature Tc(n+1) received from the humidity/temperature sensor400c, and the nearby humidity Ha(n+1) received from the humidity/temperature sensor400ais higher than the remote humidity Hc(n+1) received from the humidity/temperature sensor400c(Yes in step S3), the calculating unit800determines that there is a possibility that water vapor molecules of the atmosphere200will adhere on the surface of the object100. The calculating unit800compares the humidity levels received from the humidity/temperature sensor400aand the humidity/temperature sensor400cat the time t(n+1) with those previously received at the time t(n) (step S4). When the nearby humidity Ha(n+1) received at the time t(n+1) is lower than a nearby humidity Ha(n) received at the time t(n) from the humidity/temperature sensor400a, the remote humidity Hc(n+1) received at the time t(n+1) is higher than a remote humidity Hc(n) received at the time t(n) from the humidity/temperature sensor400c, and the flow direction Fz of the atmosphere200at the time t(n+1) received from the flow sensor5is directed toward the surface of the object100as shown inFIG. 27B(Yes in step S4), the calculating unit800determines that a large amount of water vapor molecules of the atmosphere200will adhere and aggregate on the surface of the object100. The calculating unit800outputs to the alarm output unit1000a dew condensation signal, indicating that there is a possibility of dew condensation on the surface of the object100(step S5). When the dew condensation signal is received from the calculating unit800, the alarm output unit1000outputs a dew condensation alarm signal to the temperature/humidity control unit, such as a dehumidifier (step S6). When it is found from comparing the humidity levels received from the humidity/temperature sensor400aand the humidity/temperature sensor400cat the time t(n+1) with those previously received at the time t(n), that the nearby humidity Ha(n+1) received at the time t(n+1) is equal to or higher than the nearby humidity Ha(n) received at the time t(n), the remote humidity Hc(n+1) received at the time t(n+1) is equal to or higher than the remote humidity Hc(n) received at the time t(n), and the flow direction Fz of the atmosphere200at the time t(n+1) received from the flow sensor5is directed away from the surface of the object100(No in step S4), the calculating unit800determines that the amount of water vapor molecules of the atmosphere200adhering the surface of the object100is small (step S7). This process is repeated while measurement is continued (step S8, S2).

A process performed by the non-contact condensation detecting apparatus300for detecting transpiration from the surface of the object100is described with reference to a flowchart inFIG. 29andFIG. 27C.

The calculating unit800receives temperatures T, humidity levels H, and flow directions Fz of the atmosphere200detected by the humidity/temperature sensors400a,400b,400cand the flowsensor500at predetermined timings. The calculating unit800stores the received temperatures T, the humidity levels H, and the flow directions Fz in the storing unit900(step S11). Then, when time passes from a time t(n) to a time t(n+1) (step S12), the calculating unit800compares a nearby humidity Ha(n+1) received from the humidity/temperature sensor400awith a remote humidity Hc(n+1) received from the humidity/temperature sensor400c, at the time t(n+1) (step S13). When the nearby humidity Ha(n+1) is lower than the remote humidity Hc(n+1) (No in step S13), the calculating unit800determines that there is substantially no transpiration from the surface of the object100(step S17). When the nearby humidity Ha(n+1) is higher than the remote humidity Hc(n+1) (Yes in step S13), the calculating unit800determines that there is a possibility that water vapor molecules are undergoing transpiration from the surface of the object100. The calculating unit800determines whether the flow direction Fz of the atmosphere200received from the flowsensor500at the time t(n+1) has changed from the time t(n), and the flow direction Fz of the atmosphere200at the time t(n+1) is in an opposite direction to the surface of the object100(step S14). When the flow direction Fz of the atmosphere200at the time t(n+1) is in the opposite direction to the surface of the object100as shown inFIG. 27C(Yes in step S14), the calculating unit800determines that water vapor molecules are undergoing transpiration from the surface of the object100(step S15). The calculating unit800outputs to the alarm output unit1000a transpiration signal, indicating that water vapor molecules are undergoing transpiration from the surface of the object100. When the transpiration signal is received from the calculating unit800, the alarm output unit1000outputs a transpiration alarm signal to the temperature/humidity control unit, such as the dehumidifier (step S16). When the flow direction Fz of the atmosphere200at the time t(n+1) is not in the opposite direction to the surface of the object100(No in step S14), the calculating unit800determines that there is substantially no transpiration from the surface of the object100(step S17). This process is repeated while measurement is continued (step S18, S12).

As described above, a dew condensation behavior and a transpiration behavior on the surface of the object100can be detected from a location remote from the surface of the object100in a non-contact manner by measuring changes in the temperature gradient, the humidity gradient, and the flow of the atmosphere200with respect to the surface of the object100.

FIGS. 30A,30B are diagrams of a second example of a measurement unit. In the above description, the humidity/temperature sensors400a,400b,400cand the flowsensor500are arranged in a perpendicular direction with respect to the surface of the object100. However, as shown inFIGS. 30A,30B, a wall110can be disposed perpendicular to the surface of the object100, at a distance h from the surface of the object100. The humidity/temperature sensors400a,400band the flowsensor500can be disposed at a distance h1from the surface of the object100, corresponding to the middle of the wall110. The humidity/temperature sensor400aand the flowsensor500can be disposed remotely from the wall110, and the humidity/temperature sensor400bcan be disposed near the wall110. When the humidity/temperature sensors400a,400b,400cand the flowsensor500are arranged in a perpendicular direction with respect to the surface of the object100the humidity/temperature sensor400alocated near the surface of the object100is affected by the surface of the object100at an early stage, while the humidity/temperature sensor400clocated remote from the surface of the object100is affected by the surface of the object100at a later stage than the humidity/temperature sensor400a. Considering this behavior, as shown inFIGS. 30A,30B, the wall110is disposed, and the humidity/temperature sensor400aand the flowsensor500are disposed at the same distance h1from the surface of the object100, so that the sensors are affected by the object100at different timings.

The wall110provides a transportation friction resistance on gas with respect to the surface of the object100. Specifically, a thickness δ of a boundary layer at which the laminar flow velocity receives friction resistance of the wall110can be obtained with the following formula according to Stokes' law, where a distance from the top edge (as viewed inFIG. 30A) of the wall110along the wall110is x, the flow velocity is U, and the friction resistance of the wall110is ν:
δ≅5*(νx/U)1/2
FIG. 31is a graph indicating changes in the thickness of the boundary layer δ with respect to the distance x from the top edge of the wall110along the wall110, at the flow velocities U of 1 mm/sec, 5 mm/sec, 10 mm/sec, 100 mm/sec, and 1000 mm/sec, in an air temperature of 20° C. A flow at the flow velocity of U=5 mm/sec moves 0.5 mm in 0.1 second. However, due to the friction resistance from the wall110, this flow moves as indicated by flow F in the dashed-line circle inFIG. 31. The flow F represents the flow at a point where the distance from the wall edge is x=1 mm, as the distance away from the wall110becomes 9 mm, 10 mm, and 11 mm.

As the humidity/temperature sensor400aand the flowsensor500are disposed distant from the wall110, and the humidity/temperature sensor400bis disposed near the wall110, the atmosphere200detected by the humidity/temperature sensor400aat a certain time t is further away from the wall110than that detected by the humidity/temperature sensor400b. As shown inFIG. 30A, the flow reaches the humidity/temperature sensor400abefore the humidity/temperature sensor400b. Specifically, at the time t, the humidity/temperature sensor400bis closer to the wall110, where the flow decelerates due to the friction resistance and thus reaches the surface of the object100at a delayed time. This means that the humidity/temperature sensor400bdetects the atmosphere200under the same conditions as detecting the atmosphere200at a remote location. Accordingly, a dew condensation behavior and a transpiration behavior on the surface of the object100can be detected from a location remote from the surface of the object100by measuring changes in the temperature gradient, the humidity gradient, and the flow of the atmosphere200with respect to the surface of the object100, according to the atmosphere temperatures Ta, Tb detected by the humidity/temperature sensors400a,400band the flow direction Fz detected by the flowsensor500.

To achieve detection resolution, the distance of a path of gas that is transported in association with absorption and aggregation on the surface of the object100needs to be made long. If the humidity/temperature sensors are arranged along such a long path, the overall size of the measurement unit becomes large. However, as shown inFIGS. 30A,30B, by disposing the wall110perpendicular to the surface of the object100, and disposing the humidity/temperature sensors400a,400band the flowsensor500at the distance h1from the surface of the object100, corresponding to the middle of the wall110, the measurement unit can be made compact.

Depending on the gas transportation mechanism, the status of the atmosphere may change at a moderate gradient according to the transportation velocity. In this case it is difficult to perform measurements. However, as shown inFIGS. 30A,30B, by arranging the wall110that provides a transportation friction resistance on gas with respect to the surface of the object100, the atmosphere200can be made to change at a steep gradient.

Elements of gas forming the atmosphere200may cause a density gradient within a minute space according to the distance from the surface of the object100. Examples of the elements include a temperature gradient, viscosity, density, heat conductivity, gravity, and vapor pressure. Accordingly, a remote location from the surface of the object100is less influenced by the surface of the object100and more influenced by fluctuations in the surrounding environment. If the humidity/temperature sensors400a,400bare disposed at a remote location from the surface of the object100, the measurements are affected by these fluctuations. However, as shown inFIGS. 30A,30B, by disposing the wall110perpendicular to the surface of the object100, and disposing the humidity/temperature sensors400a,400band the flowsensor500at the distance h1from the surface of the object100, the measurement unit is made compact, and measurements can be less influenced by fluctuations in the surrounding environment.

In order to prevent the wall110, which has friction resistance, the humidity/temperature sensors400a,400b, and the flowsensor500from affecting the thermal status of the atmosphere200, these components are preferably made of a material of extremely small heat capacity or of similar heat conductivity to that of the atmosphere200.

InFIGS. 30A,30B, the humidity/temperature sensors400a,400band the flowsensor500are disposed at a location corresponding to the middle of the wall110. However, as shown in a third example of a measurement unit inFIG. 32A, the humidity/temperature sensors400a,400band the flowsensor500can be disposed near the top edge of the wall110, opposite to the surface of the object100. Alternatively, as shown inFIG. 32B, the humidity/temperature sensors400a,400band the flowsensor500can be disposed near the surface of the object100. In the configuration shown inFIG. 32A, in which the humidity/temperature sensors400a,400band the flowsensor500are disposed near the top edge of the wall110opposite to the surface of the object100, as the distance x from the top edge of the wall110along the wall110becomes closer to0, the boundary layer becomes close to the wall110even if the flow velocity range is large, so that the thickness δ of the boundary layer is narrow. Accordingly, the humidity/temperature sensors400a,400band the flowsensor500can be disposed near the wall110, the measurement unit is made even more compact, and measurements can be performed for a wide flow velocity range. In the configuration shown inFIG. 32B, because the humidity/temperature sensors400a,400band the flowsensor500are disposed near the surface of the object100, the length of the wall110can be made short. This facilitates measurement of flows of the atmosphere200flowing in opposite directions for aggregation and transpiration.

The atmosphere200at the surface of the object100increases in specific gravity as the temperature decreases, and the atmosphere200descends more easily than rising due to gravity. The temperature gradient changes accordingly. On the other hand, the higher the temperature and the lower the humidity, the specific gravity of the atmosphere200becomes small and light. According to temperature conditions at the surface of the object100, the distributions of temperature and humidity of the atmosphere200with respect to the distance from the surface of the object100are different between the upper surface and the lower surface of the object100.FIG. 33Aprovides distribution charts of the temperature and the humidity of the atmosphere200at the upper surface and the lower surface of the object100. At the upper surface, when the temperature at the surface of the object100is lower than the temperature of the atmosphere200, the atmosphere200near the object100is cooled by the surface of the object100, increases in specific gravity, and thus descends due to gravity. Accordingly, the distance at which the atmosphere200is influenced by the heat from the surface of the object100becomes short. At the lower surface, when the temperature at the surface of the object100is lower than the temperature of the atmosphere200, the atmosphere200near the object100is cooled by the surface of the object100, increases in specific gravity, and thus descends due to gravity. Accordingly, the distance at which the atmosphere200is influenced by the heat from the surface of the object100becomes long. If the transportation velocity of the gas transported in association with absorption and aggregation on the surface of the object100is extremely low, the atmosphere200may be more affected by fluctuations of the surrounding environment. To eliminate influences of fluctuations of the surrounding environment, the difference in dew condensation behavior between the upper surface and the lower surface is obtained, as shown inFIG. 33B. Specifically, measurements are made under conditions where fluctuations of the surrounding environment, the surface condition, the specific heat, the capacity, and the dew condensation phenomenon are substantially the same for both surfaces of the object100.

As shown in a fourth example of a measurement unit inFIG. 34A, the humidity/temperature sensors400a,400band the flowsensor500are arranged above the object100, and humidity/temperature sensors410a,410band a flowsensor510are arranged below the object100. This measurement unit detects behavior of the gas adhering and aggregating on the surface of the object100, and behavior of the aggregated liquid transpiring, based on the difference in measured values between the upper surface and the lower surface of the object100. Accordingly, influences of fluctuations of the surrounding environment can be eliminated.

The flow direction Fz of the atmosphere can be detected by the flowsensor500disposed above the object100. Therefore, as shown inFIG. 34B, it is possible to dispose the flowsensor500only on one side of the object, for example the upper side. Moreover, even if the measurement unit is tilted as shown inFIG. 34C, influences of fluctuations of the surrounding environment can be eliminated by transporting the atmosphere200along the direction of gravity. The distance of gas transportation is longer at the lower surface than the upper surface of the object100due to gravity, and therefore, the measurement interval is longer, resulting in high sensitivity. Thus, even if the transportation velocity is extremely low, depending on the fluctuation of the surrounding environment, the dew condensation behavior can be detected from only the lower surface.

In measurement units120a,120baccording to fifth and sixth examples, respectively, the humidity/temperature sensors400a,400band the flowsensor500are disposed so as to be unaffected by fluctuations of the surrounding environment, and eliminate disturbances. As shown inFIGS. 35A,35B, the humidity/temperature sensors400a,400band the flowsensor500are disposed in a flow path inside a cylindrical rectifying tube130. The atmosphere200at the surface of the object100is isolated from the surrounding environment by the rectifying tube130, so as to eliminate the influence of fluctuations of the surrounding environment and turbulences. In the measurement unit120ashown inFIG. 35A, the humidity/temperature sensors400a,400band the flowsensor500are disposed along the wall of the rectifying tube130. In the measurement unit120bshown inFIG. 35B, the humidity/temperature sensors400a,400band the flowsensor500are disposed perpendicular to the wall of the rectifying tube130. In the measurement unit120bshown inFIG. 35B, the wall of the rectifying tube130makes the atmosphere200change at a steep gradient, similar to the wall110shown inFIGS. 30A,30B. Also, the rectifying tube130eliminates the influence of fluctuations of the surrounding environment and turbulences. In order to prevent the rectifying tube130from affecting the thermal status of the atmosphere200, the rectifying tube130is also preferably made of a material of small heat capacity or of similar heat conductivity to that of the atmosphere200, such as resin or ceramic.

If the flow velocity of the atmosphere200on the surface of the object100is extremely small, the values measured by the humidity/temperature sensors400a,400band the flowsensor500that detect the conditions of the atmosphere200flowing in the rectifying tube130need to be extracted to a greater degree. A seventh example of a measurement unit120caddresses this aspect.FIG. 36Ais a perspective view andFIG. 36Bis a cross-sectional schematic diagram of the seventh example of the measurement unit. As shown in the figures, the cross-sectional area of the rectifying tube130is smaller on the side away from the surface of the object100, than on the side near the surface of the object100, so as to increase the flow velocity. This increases the accuracy of measurements performed by the humidity/temperature sensors400a,400band the flowsensor500disposed in this area.

Sensors capable of quickly detecting the process of gas transportation, having fine spatial resolution, are preferably employed as the humidity/temperature sensors400a,400band the flowsensor500, for measuring changes in the temperature gradient, the humidity gradient, and the flow of the atmosphere200with respect to the surface of the object100. The sensors having resistive elements of fine structures formed of thin films are recommended, such as those disclosed in U.S. Pat. No. 5,551,283 or Japanese Patent Nos. 2889909, 2621982, 2780911, or Japanese Laid-Open Patent Application No. H6-18465.

FIGS. 37A,37B,37C are diagrams of an eighth example of a measurement unit120d.FIG. 37Ais a perspective view,FIG. 37Bis a cross-sectional schematic diagram ofFIG. 37Ain a horizontal plane direction, andFIG. 37Cis a cross-sectional schematic diagram ofFIG. 37Ain a vertical plane direction. As shown in the measurement unit120dinFIG. 37B, a groove140is located at the center of a substrate150in a vertical direction. Plural sensor sensing units170having a resistive element160of a fine structure formed of thin films are passed over the groove140. A cover190, having a groove180in the center thereof in a vertical direction, is connected onto the sensor sensing units170. The substrate150and the cover190form the rectifying tube130, with the groove140of the substrate150and the groove180of the cover190serving as flow paths. The substrate150, the sensor sensing units170, and the cover190can be easily fabricated by mass production with high precision, by using the so-called MEMS (Micro Electro Mechanical System) employing an integrated circuit fine-machining technology. The sensor sensing units170can be arrayed at different distances from the surface of the object100, and can have different capabilities and functions. Therefore, with the measurement unit120d, a wide range of temperature/humidity conditions and different speeds of dew condensation behaviors can be detected, the structure can be made compact, the external influence on the atmosphere200can be reduced, positional accuracy of measurement locations can be enhanced, and highly precise measurement values can be obtained. Moreover, installation locations are less limited, thereby improving versatility. Further, the same type of sensors that output signals of similar levels can be employed in the measurement unit120d, so that processes performed by the processing unit600can simplified.

In the measurement unit120cshown inFIGS. 37A,37B,37C, the humidity/temperature sensors400athrough400cand the flowsensor500are disposed along the rectifying tube130, i.e., along the grooves140,180of the substrate150and the cover190, respectively. However, when the humidity/temperature sensors400a,400band the flowsensor500are disposed perpendicular to the wall of the rectifying tube130, as shown inFIG. 35B, the humidity/temperature sensors400a,400band the flowsensor500can have resistive elements of fine structures formed of thin films and can be formed integrally with the rectifying tube130.FIGS. 38A,38B are diagrams of a ninth example of a measurement unit120e.FIG. 38Ais a plan view andFIG. 38Bis a cross-sectional schematic diagram. In the measurement unit120e, a sensor substrate220is formed at the center of a wall2000. The sensor substrate220has a constant cross-sectional area and includes plural through holes210. Plural sensor sensing units170including resistive elements160are disposed on the through holes210of the sensor substrate220, thereby forming the humidity/temperature sensors400a,400band the flowsensor500. As is described with reference toFIGS. 30A and 35B, the flowsensor500can be disposed distant from the wall2000that provides friction resistance to gas transportation, so as to enhance measurement sensitivity. For example, by disposing the sensor substrate220that is 1 mm wide, 5 mm long, and 0.5 mm thick, at the center of the wall2000that is 2 mm long; and disposing the humidity/temperature sensor400bat a position 0.5 mm away from the wall2000and the humidity/temperature sensor400aat a position 3 mm away from the wall2000; the condition of the atmosphere flowing at 10 mm/sec to 100 mm/sec can be measured, according to the change of the thickness δ of the boundary layer in an air temperature of 20° C., as indicated inFIG. 31.

Moreover, plural measurement units120dcan be stacked, as shown a tenth example of a measurement unit120finFIGS. 39A,39B.FIG. 39Ais a plan view andFIG. 39Bis a cross-sectional schematic diagram. With this configuration, the rectifying function can be further improved. Both the measurement unit120eand the measurement unit120fcan be easily fabricated by MEMS employing an integrated circuit fine-machining technology.

In the description above, dew condensation occurs as water vapor molecules aggregate on the surface of the object100. However, the technology according to the present invention can be applied to various fields, such as purification/separation of multicomponent gas. Specifically, a gas component sensor or a gas concentration sensor can be used instead of the humidity/temperature sensor to detect components, density, and concentration of gas.

For example, the measurement unit120ashown inFIGS. 35A,35B was formed as follows. The rectifying tube130with an internal diameter of 11 mm and a length of 30 mm is made with acrylic resin. The rectifying tube130is spaced apart from the surface of the object100by 1 mm. The humidity/temperature sensor400ais disposed at a position 2 mm from the bottom edge of the rectifying tube130, the humidity/temperature sensor400bis disposed at a position 15 mm from the bottom edge of the rectifying tube130, the humidity/temperature sensor400cis disposed at a position 28 mm from the bottom edge of the rectifying tube130, and the flowsensor500is disposed in the middle of the humidity/temperature sensor400aand the humidity/temperature sensor400b. Measurements obtained by the measurement unit120athus formed are shown inFIGS. 40 to 42. By way of comparison in performance, a conventional measurement unit was also employed. Specifically, a surface contact-type condensation sensor, which detects changes in electric resistance values between electrodes caused by water adherence, was disposed on the surface of the object100.

FIG. 40is a variation property graph of temperature and humidity measured by the measurement unit120aformed as above. The temperature of the surrounding environment of the rectifying tube130is fixed at 25° C., and the relative humidity is fixed at 80% RH (dew point=21.3° C.). After ten minutes, the temperature of the surface of the object100is gradually lowered from 25° C. by 2° C. at a time. After 28 minutes, the temperature of the surface of the object100is the same as the dew point 21.3° C. of the surrounding environment, and is to be further lowered. The humidity/temperature sensor400aand the humidity/temperature sensor400bare influenced by the temperature decline of the surface of the object100. When the temperature of the surface of the object100exceeds the dew point of the surrounding environment, the temperature is decreased further and the relative humidity increases further in the surrounding environment. When the temperature of the surface of the object100is equal to or less than the dew point of the surrounding environment, the relative humidity is decreased in the surrounding environment. Moreover, the humidity/temperature sensor400ais closer to the surface of the object100than the humidity/temperature sensor400b, and therefore, when the temperature of the surface of the object100exceeds the dew point of the surrounding environment, the temperature decreases further and the relative humidity increases further in the surrounding environment, and when the temperature of the surface of the object100is equal to or less than the dew point of the surrounding environment, the relative humidity decreases further in the surrounding environment. The flowsensor500indicates that the flow towards the surface of the object100is increasing, based on the tendency around the dew point. Being located furthest from the surface of the object100, the humidity/temperature sensor400cis less affected by the temperature of the surface of the object100, and more affected by the temperature of the surrounding environment.

Based on the behaviors of the humidity/temperature sensors400a,400b,400cand the flowsensor500, a dew condensation phenomenon can be observed. The humidity/temperature sensors400a,400bstarted reacting 29-30 minutes after dew condensation occurred on the surface of the object100. This was faster than the surface contact-type condensation sensor, which started reacting after 32 minutes. Thus, response is quicker than the surface contact-type condensation sensor, detections can be performed in a non-contact manner, and a slight condensation behavior can be detected.

FIG. 41is another variation property graph of temperature and humidity measured under a second condition, by the measurement unit120aformed as above. The temperature of the surface of the object100is fixed at 20° C. Initially, the temperature is 25° C. and the relative humidity is 60% RH (dew point=16.7° C.) in the surrounding environment of the rectifying tube130. After nine minutes, the relative humidity is gradually increased by 5% RH at a time, so that after 38 minutes, the dew point of the surrounding environment is 20° C., and is to be further increased. The humidity/temperature sensor400cis distant from the surface of the object100, and is therefore less affected by the surface of the object100and more affected by the humidity of the surrounding environment, and indicates that the relative humidity is increasing. The humidity/temperature sensors400a,400bare closer to the surface of the object100, and are therefore more affected by the humidity near the surface of the object100. Specifically, water vapor aggregates when dew condensation occurs on the surface of the object100as the dew point of the surrounding environment becomes equal to or greater than the temperature of the surface of the object100, and water vapor density decreases. Accordingly, the relative humidity detected by the humidity/temperature sensors400a,400bdoes not increase as much as that detected by the humidity/temperature sensor400c. Further, the flowsensor500indicates that the flow toward the surface of the object100is increasing, based on the tendency around the dew point.

Based on the behaviors of the humidity/temperature sensors400a,400b,400cand the flowsensor500, a dew condensation phenomenon can be observed. The humidity/temperature sensors400a,400bstarted to react 38 minutes after dew condensation occurred on the surface of the object100. This was faster than the surface contact-type condensation sensor, which started reacting after 40 minutes. Thus, response is quicker than the surface contact-type condensation sensor, detections can be performed in a non-contact manner, and a slight condensation behavior can be detected.

FIG. 42is still another variation property graph of temperature and humidity measured under a third condition, by the measurement unit120aformed as above. The temperature of the surrounding environment of the rectifying tube130is fixed at 25° C., and the relative humidity is fixed at 80% RH (dew point=21.3° C.). The temperature of the surface of the object100is fixed at 19° C. Accordingly, dew condensation is made to occur. After seven minutes, the temperature of the surface of the object100is increased to 25° C., so that dew condensation water undergoes transpiration as water vapor.

When the temperature of the surface of the object100starts rising from 19° C. to 25° C., desorption of the water vapor is accelerated, the humidity/temperature sensors400a,400bindicate that the relative humidity is increasing, and transpiration is observed. The increase rate per time is higher at the humidity/temperature sensor400a, as it is closer to the surface of the object100than the humidity/temperature sensor400b. The flowsensor500indicates that the flow in the direction opposite to the surface of the object100is increasing, based on the tendency around the time that the temperature of the surface of the object100is increasing.

Based on the behaviors of the humidity/temperature sensors400a,400b,400cand the flowsensor500, a transpiration phenomenon can be observed. The humidity/temperature sensors400a,400bindicated increases in relative humidity for 40 minutes, indicated dew condensation, and indicated that the transpiration process continued for 33 minutes, between the time points of 7 minutes and 40 minutes after commencement of the experiment. As it is also clear from the behavior of humidity/temperature detected by the humidity/temperature sensor400c, the temperatures detected by the humidity/temperature sensors400a,400bincrease in association with the increase in the temperature of the surface of the object100. Accordingly, the relative humidity decreased when the transpiration process ended, compared to when it started. The humidity/temperature sensors400a,400bstarted to react 8 minutes after transpiration from the surface of the object100occurred. This was faster than the surface contact-type condensation sensor, which started reacting after 12 minutes. The surface contact-type condensation sensor indicated after 12 minutes that dew condensation was eliminated; however, in reality, the dew condensation lasted for 40 minutes. Thus, response is quicker than the surface contact-type condensation sensor, detections can be performed in a non-contact manner, and a slight condensation behavior can be detected in real time.

The following is a description of an image forming apparatus employing the above-described non-contact condensation detecting apparatus300capable of detecting transpiration behavior of moisture in real time. This image forming apparatus detects the behavior of moisture undergoing transpiration from a recording sheet onto which an image is to be transferred, and prevents the recording sheet from curling when heat is applied at a heating unit.

FIG. 43is a schematic diagram of an image forming unit3000included in the image forming apparatus. A charging unit320, a laser light source, and a polygon mirror, etc., are disposed around a photoconductive drum310. The image forming unit3000further includes a writing unit330that writes an image by irradiating laser beams onto the image forming unit3000, a developing unit340, a transferring unit350, a cleaning unit360, a heating roller370, a pressurizing roller380, and a fixing unit4000that fixes a toner image transferred onto a recording sheet390.

In the image forming unit3000, the writing unit330irradiates a laser beam onto the surface of the photoconductive drum310that is charged by the charging unit320, thereby forming an electrostatic latent image on the photoconductive drum310. The developing unit340makes visible the electrostatic latent image by forming a toner image. The transferring unit350transfers the toner image formed on the photoconductive drum310onto the recording sheet390that is fed from a paper feeding unit or a manual feed tray. Toner remaining on the photoconductive drum310after the toner image is transferred onto the recording sheet390is removed by the cleaning unit360. The recording sheet390onto which the toner image is transferred is conveyed to the fixing unit4000. The fixing unit4000applies heat and pressure onto the recording sheet390so as to fix the toner image. The recording sheet390onto which the image is fixed is discharged from a discharging unit. When the fixing unit4000applies heat and pressure onto the recording sheet390to fix the toner image, the recording sheet390dries suddenly, and therefore curls. The speed at which the recording sheet390dries depends on the transpiration behavior of moisture included in the recording sheet390.

A description on how the recording sheet390deforms due to the transpiration behavior of moisture included in the recording sheet390is given below. The recording sheet390moves on a high-temperature heating member401, as shown inFIG. 44. The transpiration behavior of moisture included in the recording sheet390in the non-contact condensation detecting apparatus300was examined by changing the temperature of the heating member401, and the results are shown inFIGS. 45A,45B,45C, andFIGS. 46A,46B,46C,46D. InFIGS. 45A,45B,45C, transpiration property A is when the contact temperature difference between the heating member401and the recording sheet390is 60° C., transpiration property B is when the contact temperature difference between the heating member401and the recording sheet390is 70° C., transpiration property C is when the contact temperature difference between the heating member401and the recording sheet390is 80° C., and transpiration property D is when the contact temperature difference between the heating member401and the recording sheet390is 90° C.FIG. 45Aindicates the variation in temperature increase of the recording sheet390with respect to the heating time of the recording sheet390.FIG. 45Bindicates the variation in the increase in the transpiration amount of moisture included in the recording sheet390with respect to the heating time of the recording sheet390.FIG. 45Cindicates the variation in the deformation amount α of the recording sheet390with respect to the heating time of the recording sheet390.FIGS. 46A,46B,46C,46D indicate the variation in the temperature increase, the increase in moisture transpiration, and the deformation amount of the recording sheet390for the transpiration properties A, B, C, and D, respectively.

As shown inFIGS. 45A,45B, as the recording sheet390is heated and the temperature rises, the moisture included in the recording sheet390undergoes transpiration. As the contact temperature difference between the heating member401and the recording sheet390increases from 60° C. to 90° C., the transpiration amount and the transpiration speed (transpiration amount per time) gradually increase. After the moisture undergoes transpiration to some extent, the transpiration amount starts to decrease. As shown inFIGS. 45B,45C, the faster the moisture transpiration speed, the greater the deformation amount α of the recording sheet390, and the deformation amount changes more quickly. Accordingly, the amount of moisture included in the recording sheet390affects the extent of deformation of the recording sheet390, and the deformation amount of the recording sheet390is determined by the moisture transpiration speed.

Sometimes, deformation of the recording sheet390does not occur as shown by transpiration property A, even though the moisture undergoes transpiration from the recording sheet390. This means that the strength (body) of the recording sheet390affects deformation. Specifically, the recording sheet390is prevented from deforming immediately when moisture undergoes transpiration, due to its strength. Considering this property, even if recording sheet390contains a large amount of moisture, the deformation amount can be reduced by slowing down the transpiration speed, i.e., by drying the recording sheet390slowly.

The recording sheet390deforms, as shown inFIGS. 46A,46B,46C,46D, due to transpiration behavior of moisture included in the recording sheet390. Initially, the shape of the recording sheet390is maintained due to its strength. As moistures starts to undergo transpiration, the recording sheet390starts deforming. The deformation amount is larger when the transpiration speed is higher. Thus, the deformation amount of the recording sheet390can be predicted by measuring the transpiration speed before the recording sheet390starts deforming.FIG. 47is a variation property graph indicating the deformation amount of the recording sheet390when 0.1 second has passed after deformation started, with respect to the transpiration speed from when transpiration starts, which is before the recording sheet390starts deforming, until 0.1 second passes. As shown inFIG. 47, the extent of deformation of the recording sheet390can be determined by measuring the transpiration speed from when transpiration starts, which is before the recording sheet390starts deforming, until 0.1 second passes.

As described above, the deformation amount of the recording sheet390can be determined by measuring the transpiration speed of the recording sheet390. Further, deformation of the recording sheet390can be predicted by measuring transpiration speed when the transpiration starts and before the deformation with respect to the temperature applied to the recording sheet390.

FIGS. 48A,48B are variation property graphs of the transpiration amount of moisture for different types of recording sheets39, when the contact temperature difference between the heating member401and the recording sheet390is 70° C. InFIGS. 48A,48B, compared to the recording sheet390for transpiration property B, the recording sheet390for transpiration property E is thinner, has a smaller heat capacity, and has properties that make moisture undergo transpiration easily. As shown inFIGS. 48A,48B, transpiration and deformation occur earlier for transpiration property E than for transpiration property B. In other words, the thicker recording sheet390has a stronger body. Accordingly, by detecting the transpiration behavior of moisture included in the recording sheet390, i.e., the transpiration speed, the transpiration starting time, and temperature, it is possible to predict deformation of the recording sheet390, and the deformation amount can be determined. This can be achieved without distinguishing the type of recording sheet390. Although a special type of paper such as coated paper may need to be distinguished, plain paper such as recycled paper need not be distinguished.

As shown inFIG. 43, the following components are provided in a sheet conveying path in the image forming unit3000in order to detect transpiration behavior of the recording sheet390. In an upstream side of the transferring unit350are disposed a first position sensor415aand a first measurement unit420a, which is, for example, the measurement unit120cof the non-contact condensation detecting apparatus300shown inFIGS. 37A,37B,37C. On the downstream side of the transferring unit350in the sheet conveying path there are disposed a second position sensor415band a second measurement unit420b. A third measurement unit420cis disposed in the fixing unit4000. The first position sensor415aand the first measurement unit420aare disposed at substantially the same position, and the second position sensor415band the second measurement unit420bare disposed at substantially the same position.

FIG. 49is a block diagram of a deformation prediction control unit430in a control unit of the image forming apparatus. The deformation prediction control unit430predicts deformation of the recording sheet390based on detection results of the first position sensor415a, the second position sensor415b, the first measurement unit420a, the second measurement unit420b, and the third measurement unit420c. The deformation prediction control unit430includes a transpiration behavior calculating unit440, a timekeeping unit450, a standard information storing unit460, a deformation prediction processing unit470, and a deformation avoidance control unit480. The transpiration behavior calculating unit440detects the transpiration behavior of moisture included in the recording sheet390and calculates the transpiration amount, based on measurement signals received from the first measurement unit420a, the second measurement unit420b, and the third measurement unit420c. Further, the transpiration behavior calculating unit440calculates the transpiration speed of moisture from the recording sheet390from the calculated transpiration amounts, and the time difference between when the first position sensor415aand the second position sensor415brespectively detect the leading edge of the recording sheet390. In the standard information storing unit460, the following information items are previously stored: a standard property indicating the temperature increase, the increase in the transpiration amount, and the deformation amount, with respect to the heating time of the recording sheet390as described withFIGS. 46A,46B,46C,46D; and a standard value of transpiration speed from when transpiration starts before the recording sheet390starts deforming, until deformation starts e.g. after 0.1 second passes, as described withFIG. 47. The deformation prediction processing unit470compares the transpiration speed calculated by the transpiration behavior calculating unit440and the standard values stored in the standard information storing unit460, and predicts deformation of the recording sheet390and determines how much the moisture transpiration amount increases in the fixing unit4000. The deformation avoidance control unit480receives conveyance speed information of the recording sheet390and fixing temperature information of the fixing unit4000. The deformation avoidance control unit480varies the conveyance speed information and the fixing temperature information received, based on deformation prediction information of the recording sheet390received from the deformation prediction processing unit470, and a standard property indicating the temperature increase, the increase in the transpiration amount, and the deformation amount, with respect to the heating time, stored in the standard information storing unit460. Accordingly, the deformation avoidance control unit480generates control information for conveyance speed and fixing temperature of the recording sheet390, and outputs the control information to a conveyance speed control unit490and a fixing temperature control unit505, which are equipped to control conveyance speed and fixing temperature for the recording sheet390, respectively. Further, the deformation avoidance control unit480stops the recording sheet390from being conveyed and outputs an alarm signal to an alarm unit510, when there is an abnormality in the deformation prediction information of the recording sheet390received from the deformation prediction processing unit470, the transpiration amount, or the control information for conveyance speed and fixing temperature.

A process performed by the deformation prediction control unit430for predicting deformation of the recording sheet390and avoiding deformation is described with reference to a flowchart inFIG. 50. The recording sheet390is conveyed to the image forming unit3000, a toner image formed on the photoconductive drum310is transferred to the recording sheet390, and the recording sheet390is conveyed to the fixing unit4000.

When the image forming unit3000starts an image forming process, and the first position sensor415adetects the leading edge of the recording sheet390being conveyed (step S21), the transpiration behavior calculating unit440receives a time t0from the timekeeping unit450(step S22). After a predetermined timing determined by the positions of the first position sensor415aand the first measurement unit420a, the transpiration behavior calculating unit440calculates a transpiration amount H0, based on measurement information measured by the first measurement unit420aindicating transpiration behavior of moisture included in the leading edge of the recording sheet390(step S23). The recording sheet390is conveyed to the transferring unit350where a toner image is transferred onto the recording sheet390. As the recording sheet390is further conveyed to the fixing unit4000, the second position sensor415bdetects the leading edge of the recording sheet390(step S24), and the transpiration behavior calculating unit440receives a time t1from the timekeeping unit450(step S25). After a predetermined timing, the transpiration behavior calculating unit440calculates a transpiration amount H1, based on measurement information measured by the second measurement unit420bindicating transpiration behavior of moisture included in the leading edge of the recording sheet390(step S26). After calculating the transpiration amount H1based on the measurement information measured by the second measurement unit420b, the transpiration behavior calculating unit440calculates a transpiration speed V by the following equality, based on the transpiration amount H0calculated previously, the transpiration amount H1calculated currently, and the time t0and the time t1at which the first position sensor415aand the second position sensor415bdetected the leading edge of the recording sheet390, respectively:
V=(H1−H0)/(t1−t0)
The transpiration behavior calculating unit440sends the calculated transpiration speed V to the deformation prediction processing unit470(step S27)

The transpiration behavior of moisture included in the leading edge of the recording sheet390is detected, because the edge of the recording sheet390conveyed to the image forming unit3000is well-ventilated, undergoes transpiration of a large amount of moisture to the surrounding environment, dries easily, and is likely to lack moisture. Therefore, the edge of the recording sheet390will quickly start to demonstrate a drying behavior, which significantly causes deformation of the recording sheet390. The transpiration behavior of the leading edge of the recording sheet390is measured at the first position sensor415aand at the second position sensor415b, to obtain an accurate transpiration speed by measuring the same position of the recording sheet390that is being conveyed.

The deformation prediction processing unit470compares the transpiration speed V received with the standard value of transpiration speed, stored in the standard information storing unit460, from when transpiration starts before the recording sheet390starts deforming, until a certain time when deformation starts. When the transpiration speed V is below the standard value (Yes in step S28), the deformation prediction processing unit470determines that the recording sheet390will not deform. When the transpiration speed V is equal to or higher than the standard value (No in step S28), the deformation prediction processing unit470determines that the recording sheet390will deform, and sends deformation prediction information to the deformation avoidance control unit480. When the deformation prediction information is received, the deformation avoidance control unit480acquires the conveyance speed information of the recording sheet390and the fixing temperature information of the fixing unit4000. The deformation avoidance control unit480varies the conveyance speed information and the fixing temperature information received, based on deformation prediction information of the recording sheet390being conveyed, and a standard property indicating the temperature increase, the increase in the transpiration amount, and the deformation amount, with respect to the heating time, stored in the standard information storing unit460. Accordingly, the deformation avoidance control unit480generates control information for conveyance speed and fixing temperature for the recording sheet390, and outputs the control information to the conveyance speed control unit490and the fixing temperature control unit505for the recording sheet390. Based on the control information for conveyance speed and fixing temperature, the conveyance speed control unit490and the fixing temperature control unit505control the conveyance speed of the recording sheet390and the fixing temperature of the fixing unit4000, respectively (hereinafter, “deformation avoidance process”) (step S29). When the control information used for performing the deformation avoidance process is abnormal (No in step S30), the deformation avoidance control unit480stops the recording sheet390from being conveyed, and outputs an alarm signal to the alarm unit510(step S31).

As described above, the deformation avoidance control unit480calculates the transpiration speed V of moisture included in the recording sheet390before being sent to the fixing unit4000, predicts whether deformation will occur, and performs the deformation avoidance process. Accordingly, it is possible to prevent the recording sheet390from deforming when heated by the fixing unit4000, and thus prevent occurrence of a paper jam.

When the leading edge of the recording sheet390reaches the fixing unit4000, the third measurement unit420cmeasures the transpiration behavior of moisture included in the leading edge of the recording sheet390, and inputs this measurement information to the transpiration behavior calculating unit440. The transpiration behavior calculating unit440calculates a transpiration amount H2based on the measurement information received, and sends the transpiration amount H2to the deformation avoidance control unit480. The deformation avoidance control unit480compares the transpiration amount H2received with the standard property indicating the temperature increase, the increase in the transpiration amount, and the deformation amount, with respect to the heating time, stored in the standard information storing unit460. When the transpiration amount H2has increased more than a predetermined amount, the deformation avoidance control unit480outputs an alarm signal to the alarm unit510.

By calculating the transpiration amount H2of the recording sheet390to be fixed in the fixing unit4000based on measurement information received from the third measurement unit420c, it is possible to confirm whether the recording sheet390will finally be deformed. Specifically, as the recording sheet390conveyed to the image forming unit3000approaches the fixing unit4000, the amount of heat received by the recording sheet390increases. Due to this heat, the transpiration amount of moisture included in the recording sheet390gradually increases. When passing through the fixing unit4000, maximum heat is applied to the recording sheet390, such that the transpiration amount is large. It is possible to estimate how much the transpiration amount would increase in the fixing unit4000, by calculating the transpiration amount H2of the recording sheet390when entering the fixing unit4000, based on the measurement information form the third measurement unit420c.

For example, by using the measurement unit120dof the non-contact condensation detecting apparatus300shown inFIGS. 37A,37B,37C, as the first measurement unit420a, the second measurement unit420b, and the third measurement unit420c, the transpiration behavior of the recording sheet390can be measured in a non-contact manner. Accordingly, the transpiration behavior can be measured without affecting a toner image transferred onto the recording sheet390, and a real-time transpiration amount can be obtained. Moreover, the measurement unit120dof the non-contact condensation detecting apparatus300shown inFIGS. 37A,37B,37C is structured to include the rectifying tube130. Therefore, the transpiration behavior can be measured accurately, without affecting the flow of transpiration at the measurement position of the recording sheet390.

As shown inFIG. 51, by incorporating the first measurement unit420aand the second measurement unit420bin between conveying rollers520in the sheet conveying path of the recording sheet390, the spacing between the measurement units and the recording sheet390can be maintained precisely. The first measurement unit420aand the second measurement unit420bcan be disposed near the conveying rollers520. When a conveying belt is employed as a conveying means, the first measurement unit420aand the second measurement unit420bcan be disposed at a certain distance from the conveying belt.

In the description above, the measurement unit120dshown inFIGS. 37A,37B,37C is used as the first measurement unit420a, the second measurement unit420b, and the third measurement unit420c. Alternatively, the measurement unit120ashown inFIG. 35A, or the measurement unit120bshown inFIG. 35B, or the measurement unit120eshown inFIGS. 38A,38B can be used.

An eleventh example of a measurement unit120gshown inFIGS. 52A,52B can be used as the first measurement unit420a, the second measurement unit420b, or the third measurement unit420c. As shown in a front view ofFIG. 52Aand a cross-sectional schematic diagram ofFIG. 52B, the sensor substrate220includes voids530at positions where the humidity/temperature sensors400a,400band the flowsensor500are disposed. The humidity/temperature sensors400a,400band the flowsensor500are disposed along the flow direction of moisture transpiration. Flow path plates540are provided on both sides of the sensor substrate220to prevent the transpiration flow from fluctuating.

A twelfth example of a measurement unit120hshown inFIGS. 53A,53B can be used as the first measurement unit420a, the second measurement unit420b, or the third measurement unit420c. As shown in a perspective view ofFIG. 53Aand a cross-sectional schematic diagram ofFIG. 53B, on a top surface220aof the sensor substrate220, a pyroelectric element540, such as a thermopile or a infrared sensor having a pyroelectric structure, the humidity/temperature sensors400a,400b, and the flowsensor500are disposed along the conveying direction of the recording sheet390. A radiating element550is disposed on a bottom surface220bof the sensor substrate220, opposite the pyroelectric element540. The center of the sensor substrate220is removed by etching, thereby forming a gap560for allowing a side edge of the recording sheet390pass through. When the measurement unit120his used as the first measurement unit420a, the second measurement unit420b, or the third measurement unit420c, heat radiated from the radiating element550crosses the gap560, and is detected by the pyroelectric element540. When the recording sheet390is being conveyed through the gap560, a slight amount of heat, e.g. several tens mW, radiated by the radiating element550in a short time, e.g. several tens ms, slightly increases the temperature at a small area at the edge of the recording sheet390, e.g. by 0.1° C., and a slight amount of moisture undergoes transpiration. By measuring this transpiration behavior with the humidity/temperature sensors400a,400band the flowsensor500, the transpiration amount and the temperature can be measured. Moreover, when the recording sheet390is conveyed into the gap560, by detecting the amount of infrared radiation penetrating the recording sheet390with the pyroelectric element540, the quality (fiber density) of the recording sheet390and moisture included in the recording sheet390can be measured. Accordingly, precision in detecting sheet deformation can be enhanced.

The position sensor415acan be provided on the sensor substrate220. By providing the position sensor415aon the sensor substrate220, the transpiration occurring at the leading edge of the recording sheet390can be surely detected.

In the above description, the deformation prediction control unit430includes the transpiration behavior calculating unit440, the deformation prediction processing unit470, and the deformation avoidance control unit480. However, as shown in a block diagram ofFIG. 54, a CPU570can process the functions of the transpiration behavior calculating unit440, the deformation prediction processing unit470, and the deformation avoidance control unit480. In this case, measurement information from the first position sensor415a, the second position sensor415b, the first measurement unit420a, the second measurement unit420b, and the third measurement unit420ccan be input to the CPU570from an input unit580. The CPU performs the transpiration behavior calculation process, the deformation detection process, and the deformation avoidance process. An output unit590sends results of the processes to the conveyance speed control unit490and the fixing temperature control unit505, which correct the conveyance velocity and the fixing temperature for the recording sheet390. Accordingly, the recording sheet390is prevented from deforming.

In the above description, the first measurement unit420aand the second measurement unit420bare disposed on the upper side of the sheet conveying path of the recording sheet390. However, the measurement units of the non-contact condensation detecting apparatus300are compact and respond quickly. Therefore, the measurement units can be disposed on a lower side of the sheet conveying path, to detect transpiration behavior from under the recording sheet390, and obtain the transpiration amount.

An electrophotographic image forming apparatus is described above. However, the same technology can be applied to another type of image forming apparatus such as an ink-jet type, to prevent failures in sheet conveyance such as a paper jam.

According to one embodiment of the present invention, a sensor can be used generically.

Further, according to one embodiment of the present invention, distribution conditions of the surrounding environment on the object surface and transpiration processes can be measured accurately, and behaviors of dew condensation and transpiration on the object surface can be precisely detected in real time.

Further, according to one embodiment of the present invention, it is possible to reduce the distance of the area to be measured in the transportation direction of the atmosphere, measure the atmosphere that is not much influenced by fluctuations in the surrounding environment near the object surface, and accurately measure distribution conditions of the surrounding environment on the object surface and transpiration processes.

Further, according to one embodiment of the present invention, influence by fluctuations in the surrounding environment can be removed, and distribution conditions of the surrounding environment on the object surface and transpiration processes can be measured accurately.

Further, according to one embodiment of the present invention, without directly mounting a dew condensation sensor on the object surface, it is possible to detect processes of dew condensation on the object surface in a non-contact manner, accurately predict dew condensation and transpiration on the object surface, and efficiently prevent dew condensation.

Further, according to one embodiment of the present invention, it is possible to prevent deformation of a sheet caused by transpiration of moisture included in the sheet.

Further, according to one embodiment of the present invention, it is possible to prevent deformation of a recording sheet, so as to stably convey the recording sheet.

Further, according to one embodiment of the present invention, deformation of a recording sheet can be surely prevented by detecting the dryness caused by moisture transpiration at a portion of the recording sheet that significantly affects the deformation.

Further, according to one embodiment of the present invention, transpiration behavior is measured at the same portion of the recording sheet, so that an accurate transpiration speed can be obtained.

Further, according to one embodiment of the present invention, the transpiration amount of moisture included at the leading edge of the recording sheet can be surely measured, so that an accurate transpiration speed can be obtained.

The present invention also has the following aspects.

A detector element comprises:

a substrate including one of a through hole and a void;

a heating unit including a heat generating electrode bridged across said one of the through hole and the void, the heat generating electrode being warped, cantilevered, and standing up in space; and

a temperature sensor including a temperature sensor electrode provided above said one of the through hole and the void, the temperature sensor electrode being warped, cantilevered, and standing up in space, wherein

the temperature sensor measures heat quantity transported from the heating unit, and

the heat generating electrode and the temperature sensor electrode are shaped like a curved surface of a pipe.

The detector element according to the present invention as described above has

the heating unit disposed inside the temperature sensor and along a direction of a flow of a fluid.

The detector element according to the present invention as described above further comprises:

a resistive element including an electrode that is bridged across one of the through hole and the void, the electrode being sloped, wherein

the resistive element generates heat and indicates a first resistance value in response to receiving a heat generation current at a heat generation timing,

indicates a second resistance value in response to receiving a detection current at a detection timing, and

a transported heat quantity is calculated based on a value obtained by subtracting the second resistance value from the first resistance value.

The detector element according to the present invention as described above further comprises:

a first resistive element including an electrode that is bridged across one of the through hole and the void, the electrode being sloped;

a second resistive element including an electrode that is bridged across one of the through hole and the void, the electrode being sloped; wherein

the second resistive element measures heat quantity transported from the first resistive element, or

the first resistive element measures heat quantity transported from the second resistive element.

A vacuum gauge comprises

the detector element according to the present invention as described above enclosed in a vacuum container, wherein

wires are extended from an electrode pad of the heating unit and an electrode pad of the temperature sensor to outside the vacuum container,

the vacuum gauge is configured to acquire pressure dependence of heat conductivity of gas inside the vacuum container as temperature variation obtained from the temperature sensor, and

to convert the acquired value into a degree of vacuum.

A vacuum gauge comprises

the detector element according to the present invention as described above enclosed in a vacuum container, wherein

wires are extended from an electrode pad of the heating unit and an electrode pad of the temperature sensor to outside of the vacuum container, and

the heating unit serves as a filament, the temperature sensor serves as a grid, and the substrate serves as a collector,

the vacuum gauge is configured to measure a current flowing between the filament and the collector, and

to convert the measured current into a degree of vacuum.

A non-contact condensation detecting method comprises the steps of:

measuring distribution of an atmosphere surrounding an object surface with respect to the object surface and a transportation state of the atmosphere, by using at least one of temperature, humidity, a direction or velocity of flow, pressure, and composition of gas in the atmosphere, measured at least at two locations, near the object surface and distant from the object surface, in two directions opposite to each other with respect to gas components being transported along gravity; and

detecting a behavior of the gas adhering and aggregating onto the object surface, and a behavior of aggregated liquid transpiring from the object surface, based on a difference between values measured, at the measuring step, in the two directions opposite to each other with respect to gas components being transported along gravity.

The non-contact condensation detecting method according to the present invention as described above has

a wall is disposed where the elements of the gas are measured, near the object surface and in the flow direction of the gas in the atmosphere, the wall providing friction resistance with respect to the gas of the atmosphere, and the wall is a cylindrical rectifying tube including a portion that has a smaller diameter than that of another portion thereof.

A sheet deformation preventing method comprises the steps of:

measuring a transpiration amount of a volatile component included in a sheet of any type according to the non-contact condensation detecting method according to the present invention as described above,

calculating a transpiration speed, which is a transpiration amount per unit time, based on the measured transpiration amount, and

setting drying conditions for the sheet such that the calculated transpiration speed does not exceed a standard value of transpiration speed for a predetermined period until the sheet starts deforming.

The sheet deformation preventing method according to an embodiment of the present invention as described above is provided, wherein,

the measuring includes measuring a transpiration amount of a volatile component included in a leading edge of the sheet while the sheet is being conveyed, at plural locations along a sheet conveyance path.

The present application is based on Japanese Priority Patent Application No. 2005-198744, filed on Jul. 7, 2005, and Japanese Priority Patent Application No. 2006-147865, filed on May 29, 2006, the entire contents of which are hereby incorporated by reference.