JP6077398B2 - Water detection device and water detection method - Google Patents

Description

  The present invention relates to a water-detecting device and a water-detecting method for detecting a water-covering state at a water-detecting location.

  A moisture detection device that detects a moisture condition at a moisture detection location is used, for example, to detect a moisture condition in an exhaust pipe of an internal combustion engine. More specifically, there is known a water detection device that detects a state in which condensed water adheres to various sensors provided in an exhaust pipe (a wet state) immediately after the internal combustion engine is started.

  As a sensor provided in an exhaust pipe of an internal combustion engine, there is a gas sensor (oxygen sensor, NOx sensor, etc.) that detects a specific component in exhaust gas. These gas sensors include a sensor element that is in an activated state where gas detection is possible when the gas sensor is in a high temperature state, and includes a heater that heats the sensor element.

  In these gas sensors, the sensor element is heated by the heater immediately after the start because of a request for emission reduction at the start of the internal combustion engine for the early sensor activation. However, immediately after the start of the internal combustion engine, condensed water may exist in the exhaust pipe, and if the condensed water comes along with the exhaust and adheres to the high-temperature sensor element, the sensor element may be damaged by thermal shock.

  On the other hand, the apparatus which determines the presence or absence of moisture using the gas sensor (oxygen sensor) used for actual gas detection is proposed (patent document 1). In this device, the presence or absence of water is determined using a gas sensor having a heater and a sensor element, and the degree of change in element temperature is measured based on the element impedance of the sensor element. If it is larger, it is determined that “there is water”.

  In this apparatus, when it is determined that the sensor element has been submerged, energization of the heater is prohibited to prevent the sensor element from being damaged.

JP 2000-283948 A

  However, in the above conventional apparatus, the presence or absence of water is determined using a gas sensor that is actually used for gas detection, that is, the sensor element is heated by a heater and activated based on the element impedance of the activated sensor element. However, in the above configuration, the amount of change in the element impedance is small, and even if the presence or absence of water can be determined, the amount of water cannot be accurately quantified.

  Therefore, an object of the present invention is to provide a water detection device and a water detection method capable of accurately quantifying the amount of water as well as determining the presence or absence of water.

  The present invention relates to a moisture detection device for detecting a moisture condition at a moisture detection location, a moisture detection element having a long insulating member with a heating resistor embedded at the tip, and a heating resistor. Is detected by a temperature control unit that energizes the heating resistor, a resistance change detection unit that detects a change state of the resistance value in the heating resistor, and a resistance change detection unit so that the temperature becomes a predetermined target temperature. A moisture determination unit that determines a moisture condition of the moisture detection element based on a change state of the resistance value, and the moisture detection element includes at least a peripheral portion of the insulating member in the embedded portion of the heating resistor. A water-detecting device comprising a porous layer having a thickness of 400 μm or less, covering the entire circumference in the direction.

  In this water detection apparatus, since the water detection element includes a porous layer, the adhered water can be held in the porous layer. If a member having a smooth surface that is not porous is exposed, if a large amount of water splashes on the member, the water is repelled from the surface of the member, and at least part of the water is covered with water. Immediately away from the sensing element.

  On the other hand, the water detection element of the present invention includes a porous layer that covers the entire circumference in the circumferential direction of at least the portion where the heating resistor is embedded in the insulating member, so that the amount of attached water is large. However, since water can be retained in the porous layer, it is possible to suppress water from being splashed and immediately separated from the water detection element, and the temperature of the water detection element can be changed according to the amount of attached water. .

  Moreover, when the thickness of the porous layer is 400 μm or less, the water attached to the porous layer can easily reach the insulating member through the porous layer. The resistance value of the heating resistor that is controlled to the target temperature by the temperature controller changes with the temperature change due to the influence of water attached to the insulating member via the porous layer. The resistance change detection unit detects a change state of the resistance value in the heating resistor, and the water determination unit determines the water supply state of the water detection element based on the change state of the resistance value. Can be reliably detected.

  In addition, since the change start time of the resistance value in the resistance value change state of the heating resistor corresponds to the time of water adhesion to the water detection element (water exposure timing), the water determination unit determines the resistance value change state. Based on the above, it is possible to determine the wet timing of the wet detection element.

  In addition, the resistance value of the heating resistor shows various changes depending on the amount of water (water exposure) attached to the insulating member through the porous layer. In addition, the resistance value of the heating resistor has a greater amount of change due to moisture compared to the element impedance of the sensor element as in the prior art.

For this reason, the moisture determination unit can quantitatively determine not only the presence / absence of moisture but also the amount of moisture in determining the moisture condition of the moisture detection element based on the change state of the resistance value. Become.
In other words, the water detection device of the present invention can simultaneously measure the water timing and the amount of water, which conventionally had to be measured separately, thereby reducing the man-hours for measuring the water timing and the amount of water. it can.

  Therefore, according to the water detection apparatus of the present invention, it is possible to quantify not only the presence / absence of water but also the amount of water with high accuracy. Furthermore, according to the present invention, it is possible to reduce the man-hours required for measuring the timing of water exposure and the amount of water.

In the water detection device of the present invention, the porous layer preferably has a thickness of 200 μm or less.
By setting the thickness of the porous layer to 200 μm or less, the water adhering to the porous layer reaches the insulating member more quickly.

As a result, it is possible to shorten the time from the actual flooding timing to the start of the resistance value change of the heating resistor, and the response speed of the moisture detection can be improved.
Next, in the moisture detection device of the present invention, the moisture determination unit includes at least a moisture content based on information on a correlation between the moisture content attached to the moisture detection element and the change amount of the resistance value. A configuration in which the water state is determined can be adopted.

  That is, the moisture determination unit determines the amount of moisture corresponding to the change state of the resistance value detected by the resistance change detection unit based on the correlation information. This moisture detection apparatus can determine the moisture state including at least the amount of moisture.

Thereby, since this moisture detection apparatus can determine not only mere "presence / absence of moisture" but also the amount of moisture, it can determine the detailed moisture condition at the detection location.
Therefore, according to the water detection device of the present invention, it is possible to determine a water-containing state that includes at least the amount of water at the water-detection location, and therefore it is possible to suppress a decrease in the determination accuracy of water.

  Next, the method of the present invention is a water detection method for detecting a water exposure state at a water detection location, wherein a water detection element having a long insulating member with a heating resistor embedded at the tip is provided. This is a method of detecting moisture to be used, a temperature control process for energizing the heating resistor so that the heating resistor has a predetermined target temperature, and a resistance change detection for detecting a change state of the resistance value in the heating resistor. And a moisture determination step for determining a moisture condition of the moisture detection element based on the change state of the resistance value detected in the resistance change detection process. It is a wet detection method characterized by including a porous layer having a thickness of 400 μm or less, covering at least the entire circumference in the circumferential direction of the embedded portion of the heat generating resistor in the conductive member.

  In this water detection method, since the water detection element includes the porous layer, the attached water can be retained in the porous layer. If a member having a smooth surface that is not porous is exposed, if a large amount of water splashes on the member, the water is repelled from the surface of the member, and at least part of the water is covered with water. Immediately away from the sensing element.

  On the other hand, the water detection element used in the method of the present invention includes a porous layer that covers at least the entire circumference in the circumferential direction of the insulating member in the embedded portion of the heating resistor, so that the amount of attached water is reduced. Even when there are many, water can be retained in the porous layer, so it is possible to suppress water from being splashed and immediately leaving the water detection element, and it is possible to change the temperature of the water detection element according to the amount of attached water It becomes.

  Moreover, when the thickness of the porous layer is 400 μm or less, the water attached to the porous layer can easily reach the insulating member through the porous layer. In the temperature control step, the resistance value of the heating resistor controlled to the target temperature changes with a temperature change due to the influence of water attached to the insulating member via the porous layer. In the resistance change detection step, the change state of the resistance value in the heating resistor is detected, and in the water coverage determination step, the water coverage state of the water detection element is determined based on the change state of the resistance value. The state can be detected reliably.

  In addition, since the change start time of the resistance value in the resistance value change state of the heating resistor corresponds to the time of water adhesion to the water detection element (water exposure timing), the resistance value change state in the water determination process Based on the above, it is possible to determine the wet timing of the wet detection element.

  In addition, the resistance value of the heating resistor shows various changes depending on the amount of water (water exposure) attached to the insulating member through the porous layer. In addition, the resistance value of the heating resistor has a greater amount of change due to moisture compared to the element impedance of the sensor element as in the prior art.

  For this reason, in the moisture determination step, it is possible to quantitatively determine not only the presence / absence of moisture but also the amount of moisture in determining the moisture condition of the moisture detection element based on the change state of the resistance value. It becomes.

  That is, by using the method of the present invention, it is possible to simultaneously measure the wet timing and the wet amount, which conventionally had to be measured separately, and the man-hour required for measuring the wet timing and the wet amount can be reduced. .

  Therefore, according to the water detection method of the method of the present invention, it is possible to quantify not only the presence / absence of water but also the amount of water with high accuracy. Furthermore, according to the method of the present invention, it is possible to reduce the man-hours required for measuring the timing and amount of water.

In the wet detection method of the present invention, the porous layer preferably has a thickness of 200 μm or less.
By setting the thickness of the porous layer to 200 μm or less, the water adhering to the porous layer reaches the insulating member more quickly.

As a result, it is possible to shorten the time from the actual flooding timing to the start of the resistance value change of the heating resistor, and the response speed of the moisture detection can be improved.
Next, in the moisture detection method of the method of the present invention, in the moisture determination step, at least the amount of moisture is determined based on the information on the correlation between the amount of moisture attached to the moisture detection element and the amount of change in the resistance value. The wet state including can be determined.

  That is, in the moisture determination step, the amount of moisture corresponding to the change state of the resistance value detected by the resistance change detector is determined based on the correlation information. With this moisture detection method, it is possible to determine a moisture state including at least the amount of moisture.

Thereby, in this moisture detection method, since it is possible to determine not only the “presence / absence of moisture” but also the amount of moisture, it is possible to determine the detailed moisture condition at the location of detection of moisture.
Therefore, according to the water detection method of the method of the present invention, it is possible to determine the water exposure state including at least the amount of water at the water detection location, and therefore it is possible to suppress a decrease in the determination accuracy of water exposure.

In the water detection method of the present invention, the target temperature is preferably 300 ° C. or higher and 400 ° C. or lower.
If it is used in such a temperature range, it can suppress that an excessive thermal shock arises with water exposure, and can prevent damage to the water detection element by water exposure.

  According to the water detection apparatus or the water detection method of the present invention, it is possible to reliably detect the water condition at the water detection location, and it is possible to suppress a decrease in the determination accuracy of water.

It is a whole block diagram of a moisture detection apparatus. It is a perspective view which shows schematic structure of a to-be-watered detection element. It is AA sectional drawing in the to-be-watered detection element of FIG. It is a flowchart showing the processing content of the moisture detection process. It is the measurement result which measured the resistance value change state of the heater part accompanying adhesion of water. It is a measurement result regarding the correlation between the amount of moisture and the resistance value change amount ΔR. It is the measurement result which measured about the correlation of the amount of moisture and resistance value variation | change_quantity (DELTA) R using the two moisture detection elements from which the thickness dimension of a porous layer differs.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
In addition, this invention is not limited to the following embodiment at all, and it cannot be overemphasized that various forms may be taken as long as it belongs to the technical scope of this invention.

[1. First Embodiment]
[1-1. overall structure]
FIG. 1 is an overall configuration diagram of a water detection device 1 as an embodiment to which the present invention is applied.

The moisture detection apparatus 1 is used for detecting the moisture condition at an oxygen sensor installation location in an exhaust pipe of an internal combustion engine.
The oxygen sensor is used to detect the concentration of a specific gas (oxygen) in the exhaust gas of various internal combustion devices such as boilers and automobile engines. The detected gas concentration can be used, for example, for air-fuel ratio feedback control in various internal combustion engines.

  And when the wet condition immediately after the start of the internal combustion engine is detected using the wet detection apparatus 1, the detection result (the wet condition) is for suppressing the damage of the oxygen sensor element due to the thermal shock of the wet water. Available. In other words, the oxygen sensor temperature control (heater temperature control) is performed so as to avoid the oxygen sensor element from reaching a high temperature state at the timing of water exposure based on the detected water exposure situation. It can suppress that an oxygen sensor element is damaged by an impact.

The water detection device 1 includes a water detection element 3, a power supply device 5, a switch 6, a resistance element 7, and a control unit 9.
FIG. 2 is a perspective view showing a schematic structure of the moisture detection element 3, and FIG. 3 is a cross-sectional view taken along line AA in the moisture detection element 3 of FIG.

In FIG. 2, the intermediate portion in the axial direction (longitudinal direction) is omitted to represent the water detection element 3, and the internal structure of the heater unit 13 and the like is schematically represented by a dotted line.
The water detection element 3 includes an insulating member 11, a heater unit 13, a pair of electrode terminals 15, and a porous layer 17. The details of the moisture detection element 3 will be described later.

  The power supply device 5 is a power supply device that supplies power at a predetermined output voltage value (for example, 18 [V]), and via the switch 6, the resistance element 7 and the water detection element 3 (in detail, the heater unit 13). ).

The switch 6 is configured to be switchable to an ON state (energized state) or an OFF state (blocked state) based on a command signal from the control unit 9.
Note that the output voltage of the power supply device 5 and the resistance value of the resistance element 7 are set to appropriate values in advance so that the temperature of the tip of the moisture detection element 3 (specifically, the heater part 13) becomes the target temperature. Has been. The target temperature of the water detection element 3 is set to a temperature at which the water detection element 3 is not damaged by thermal shock. In the present embodiment, the target temperature is set to 350 [° C.].

  The control unit 9 controls the entire water detection apparatus 1 and executes each process for detecting the water condition. The control unit 9 is configured by a so-called microcomputer, and although not shown in detail, has a known configuration, a microprocessor that performs calculation, a RAM that temporarily stores programs and data, a ROM that stores programs and data, An A / D conversion circuit that converts an analog signal into a digital signal is included.

  In addition, the control unit 9 includes an A / D conversion unit (not shown) for inputting a potential at a connection point between the moisture detection element 3 (specifically, the heater unit 13) and the resistance element 7. Since this potential shows a value equal to the voltage across the heater section 13, the control section 9 is configured to detect the voltage across the heater section 13 using this potential.

  The control unit 9 detects the change state of the resistance value of the heater unit 13 based on the voltage between both ends of the heater unit 13 in the water detection element 3, and applies water to the water detection element 3 based on the resistance value change state. A moisture determination process for determining the state is performed. The processing content of the water determination process will be described later.

[1-2. Water detection element 3]
As shown in FIGS. 2 and 3, the moisture detection element 3 includes an insulating member 11, a heater portion 13, a pair of electrode terminals 15, and a porous layer 17.

The insulating member 11 is formed in a long flat plate shape extending in the axial direction (left and right direction in FIG. 2), and is mainly composed of alumina.
The heater unit 13 is composed of a heating resistor and is provided inside the insulating member 11 on the tip side. The pair of electrode terminals 15 are electrically connected to the heater portion 13 via the pair of lead portions 14 and are provided outside the rear end side of the insulating member 11.

  The porous layer 17 is made of a porous material having a layer thickness dimension of 200 [μm]. Further, the porous layer 17 is configured to cover at least the entire circumference in the circumferential direction in the embedded portion of the heater portion 13 of the insulating member 11.

That is, the moisture detection element 3 is configured such that the heater unit 13 generates heat when the heater unit 13 is energized from the external power supply device 5 through the pair of electrode terminals 15.
In addition, the to-be-watered detection element 3 is installed instead of an oxygen sensor in the installation location of the oxygen sensor in the exhaust pipe of an internal combustion engine, for example. Thereby, the water-detecting element 3 can capture water droplets (condensed water, etc.) flying to the location where the oxygen sensor is installed, and can detect the water-covered state at the location where the oxygen sensor is installed.

  Moreover, since this water-detecting device 1 is not provided with a protective cover that covers the water-detecting element 3, the water-detecting element 3 is installed at the location where the oxygen sensor is installed with the porous layer 17 exposed to the outside. Installed. For this reason, the water droplets flying to this installation location are directly attached to the porous layer 17 of the water detection element 3. In other words, the temperature of the moisture detection element 3 is surely changed by the influence of the incoming water, and the temperature of the heater portion 13 (heat generating resistor) inside thereof is surely changed.

  Moreover, since the to-be-water-detected element 3 is equipped with the porous layer 17 which covers the perimeter of the circumferential direction in the embedding part of the heater part 13 among the insulating members 11, it hold | maintains the adhering water in the porous layer 17. Can do. If a member having a smooth surface that is not porous is exposed, if a large amount of water splashes on the member, the water is repelled from the surface of the member, and at least part of the water is covered with water. Immediately away from the sensing element.

  On the other hand, when the moisture detection element 3 includes the porous layer 17 covering the entire circumference in the circumferential direction of at least the embedded portion of the heater portion 13 in the insulating member 11, the amount of attached water is large. However, since water can be retained in the porous layer 17, it is possible to suppress water from being splashed and immediately separated from the water detection element 3, and to change the temperature of the water detection element 3 according to the amount of attached water. It becomes possible.

[1-3. Water detection process]
Next, the moisture detection process performed by the control unit 9 will be described.
In FIG. 4, the flowchart showing the processing content of the moisture detection process is shown.

The water detection process starts as an internal process in the control unit 9 when the water detection apparatus 1 is activated.
When the moisture detection process is started, first, in S110 (S represents a step), a process of starting voltage application to the heater unit 13 of the moisture detection element 3 is executed. Specifically, the switch 6 is controlled to be in an ON state (energization state), and energization from the power supply device 5 to the heater unit 13 and the resistance element 7 is started.

  In the next S120, it is determined whether or not a predetermined temperature stabilization time has elapsed after starting the energization of the heater unit 13 in S110. If the determination is affirmative, the process proceeds to S130, and a negative determination is made. In this case, the same step is repeatedly executed and the process waits until the temperature stabilization time elapses.

  Note that the temperature stabilization time is set to a heating time required for the water detection element 3 at room temperature (for example, 20 ° C.) to reach the target temperature from the start of energization to the heater unit 13. In the present embodiment, the temperature stabilization time is set to 300 [sec]. However, the temperature stabilization time is not limited to this, and a time during which the temperature of the moisture detection element 3 is sufficiently stabilized at the target temperature may be set as appropriate.

  When an affirmative determination is made in S120 and the process proceeds to S130, a standby process for a measurement start signal is activated in S130. Specifically, in order to receive the measurement start signal S1 representing the measurement start timing of the detection of water from the outside, the state of the signal input unit (not shown) of the control unit 9 is set to the standby state in which the measurement start signal can be received. Set to. In the present embodiment, a start signal indicating the start of the internal combustion engine is output from the control device for the internal combustion engine, and the start signal is input to the control unit 9 as the measurement start signal S1.

  In next step S140, it is determined whether or not the internal combustion engine has been started. If the determination is affirmative, the process proceeds to S150, and if the determination is negative, the same step is repeatedly executed to wait until the internal combustion engine is started. To do. In S140, it is determined whether or not the internal combustion engine has been started based on whether or not the measurement start signal S1 (start signal) has been input from the internal combustion engine.

  When an affirmative determination is made in S140 and the process proceeds to S150, in S150, a process of measuring a change amount of the resistance value in the heater unit 13 of the moisture detection element 3 (hereinafter also referred to as a resistance value change amount ΔR) is executed. Moreover, in S150, based on the change state of the resistance value in the heater part 13 of the water detection element 3, the process which measures the water adhesion time (watering timing) to the water detection element 3 is also performed.

  Note that the voltage across the heater section 13 varies according to the change in resistance value of the heater section 13. Moreover, the heater part 13 has a temperature characteristic in which a resistance value changes according to its own temperature change. For this reason, when water adheres to the moisture detection element 3, a temperature change occurs in the heater unit 13, and the resistance value of the heater unit 13 changes and the voltage across the heater unit 13 changes. That is, the amount of change in the resistance value of the heater unit 13 due to the temperature change can be measured based on the change state of the voltage across the heater unit 13.

  Here, in FIG. 5, the measurement result which measured the resistance value change state of the heater part 13 accompanying adhesion of water is shown. In FIG. 5, the horizontal axis represents time, and the vertical axis represents the resistance value of the heater unit 13.

  In FIG. 5, the time T1 is the time of water adhesion to the water detection element 3, and the resistance value is the normal resistance value R1 at a time earlier than the time T1, but the resistance value decreases immediately after the time T1. I understand that. Then, the resistance value of the heater unit 13 decreases to the minimum resistance value R2, and then gradually increases to return to the normal resistance value R1 again.

  In other words, the temperature of the wet detection element 3 is constant (specifically, the target temperature) at a time earlier than the time T1, the temperature decreases immediately after the time T1, and the resistance value of the heater unit 13 is the lowest resistance. When the value R2 is reached, the temperature drops to the lowest temperature. Thereafter, the temperature of the moisture detection element 3 gradually increases and returns to the original target temperature.

In S150, among the resistance value change states of the heater unit 13, the time T1, which is the resistance value change start time, is determined as the water adhesion time (water exposure timing) to the water detection element 3.
At this time, the resistance value change amount ΔR (= R1−R2) of the heater unit 13 changes according to the amount of moisture.

Here, in FIG. 6, the measurement result regarding the correlation between the amount of moisture and the resistance value change amount ΔR is shown.
As shown in FIG. 6, it can be seen that the resistance value change amount ΔR of the heater unit 13 increases as the amount of water adhering to the water detection element 3 (in other words, the amount of water) increases.

  That is, in S150, the change amount of the voltage across the heater portion 13 (in other words, the potential difference) is measured, and the resistance value change amount ΔR of the heater portion 13 is measured based on the potential difference.

In next S160, the amount of water adhering to the water detection element 3 is calculated based on the resistance value change amount ΔR of the heater unit 13 measured in S150.
Specifically, the amount of water corresponding to the resistance value change amount ΔR is calculated using a map (or a calculation formula or the like) relating to the correlation between the water amount and the resistance value change amount ΔR as shown in FIG.

  In the next S170, a process of stopping the voltage application to the heater unit 13 is executed. Specifically, the switch 6 is controlled to be in an OFF state (cut-off state), and energization of the heater unit 13 and the resistance element 7 from the power supply device 5 is stopped.

When the process in S170 ends, the water detection process ends.
That is, in the moisture detection process, the process of measuring the water adhesion timing (water exposure timing) to the moisture detection element 3 based on the resistance value change state of the heater unit 13 is performed, and the heater unit in the moisture detection element 3 13 is measured, and a process of calculating the amount of water adhering to the water detection element 3 is performed based on the resistance value change ΔR.

  The water detection apparatus 1 can determine the presence or absence of water with respect to the location where the oxygen sensor is installed immediately after the start of the internal combustion engine by executing the water detection process as described above, and can also determine the amount of water and the timing of water exposure. The wet state including can be determined.

[1-4. effect]
As described above, in the water detection device 1 according to the present embodiment, since the porous layer 17 of the water detection element 3 is provided at the water detection location in a state of being exposed to the outside, Water, etc.) adheres directly to the porous layer 17 of the water detection element 3 without being hindered by the protective cover. For this reason, unlike the sensor having a protective cover, the moisture detection element 3 is surely changed in temperature by the influence of the incoming water, and the temperature of the heater portion 13 (heating resistor) in the inside is surely changed. Change.

  Moreover, since the to-be-water-detected element 3 is equipped with the porous layer 17 which covers the perimeter of the circumferential direction in the embedding part of the heater part 13 among the insulating members 11, it hold | maintains the adhering water in the porous layer 17. Can do. If a member having a smooth surface that is not porous is exposed, if a large amount of water splashes on the member, the water is repelled from the surface of the member, and at least part of the water is covered with water. Immediately away from the sensing element.

  On the other hand, since the water detection element 3 includes the porous layer 17, water can be retained in the porous layer 17 even when the amount of attached water is large. 3 can be prevented from immediately leaving, and the temperature of the water detection element 3 can be changed according to the amount of attached water.

  In addition, the porous layer 17 is made of a porous material having a layer thickness dimension of 200 [μm], and the layer thickness dimension is 400 [μm] or less, so that water adhering to the porous layer 17 is It becomes possible to easily reach the insulating member 11 through the porous layer 17.

  Furthermore, in the water-detecting device 1, since the layer thickness dimension of the porous layer 17 is 200 [μm] or less, the water adhering to the porous layer 17 reaches the insulating member 11 more quickly. Thereby, the time from the actual flooding timing to the start of the resistance value change of the heater unit 13 can be shortened, and the response speed of the flooding detection can be improved.

  The resistance value of the heater unit 13 (heating resistor) that is controlled to the target temperature by the power supply device 5 and the resistance element 7 changes with a temperature change due to the influence of water adhering to the water detection element 3.

  The water detection apparatus 1 detects the change state of the resistance value in the heater unit 13 (specifically, the resistance value change amount ΔR) in S150 of the water detection process, and the resistance value is detected in S160 of the water detection process. By determining the wet state (specifically, the wet amount) of the wet detection element 3 based on the change state (specifically, the resistance value change amount ΔR), the wet state including at least the wet amount can be reliably ensured. It can be detected.

  The resistance value change start time (time T1) in the resistance value change state of the heater unit 13 corresponds to the water adhesion time (water exposure timing) to the water detection element 3, and therefore, S150 of the water determination process. Then, based on the resistance value change state of the heater unit 13, the wet timing of the wet detection element 3 can be determined.

  Further, the resistance value of the heater unit 13 shows various changes depending on the amount of water (water exposure) attached to the insulating member 11 through the porous layer 17. Further, the resistance value of the heater unit 13 made of a heating resistor has a greater amount of change due to moisture compared to the element impedance of the sensor element as in the prior art.

  For this reason, the water detection device 1 quantitatively determines not only the presence / absence of water but also the amount of water in determining the wet state of the water detection element 3 based on the change state of the heater unit 13. Is possible.

  In other words, the water detection apparatus 1 can simultaneously measure the water timing and the amount of water that had conventionally been required to be measured separately, and can reduce the number of steps for measuring the water timing and the amount of water.

  Therefore, according to the water detection device 1 of the present embodiment, not only the determination of the presence or absence of water but also the amount of water can be accurately quantified. Furthermore, according to the water detection device 1 of the present embodiment, it is possible to reduce the man-hours required for measuring the timing of the water exposure and the amount of water.

  In addition, in S160 of the water detection process, the water detection device 1 uses a map (or a calculation formula or the like) relating to the correlation between the amount of water and the resistance value change ΔR, and uses the map corresponding to the resistance value change ΔR. Calculate the amount of water. In other words, the water detection device 1 determines a water coverage state including at least the water content based on information on the correlation between the water content attached to the water detection element 3 and the resistance value change amount ΔR of the heater unit 13. .

  In other words, the control unit 9 that executes S160 of the water detection process executes S150 of the water detection process based on a map (or a calculation formula or the like) regarding the correlation between the water quantity and the resistance value change amount ΔR. The amount of water corresponding to the resistance value change amount ΔR detected by the control unit 9 is determined. For this reason, this moisture detection apparatus 1 can determine the moisture state including at least the amount of moisture.

Thereby, since this moisture detection apparatus 1 can determine not only the presence or absence of moisture, but the amount of moisture, it can determine the detailed moisture condition in a moisture detection location.
Therefore, according to the moisture detection device 1 of the present embodiment, it is possible to determine the moisture condition including at least the amount of moisture at the moisture detection location, and therefore it is possible to suppress a decrease in the determination accuracy of the moisture.

[1-5. Correspondence with Claims]
Here, the correspondence of the words in the claims and the present embodiment will be described.
The heater unit 13 corresponds to an example of a heating resistor, the insulating member 11 corresponds to an example of an insulating member, and the power supply device 5 and the resistance element 7 correspond to an example of a temperature control unit.

  The controller 9 that executes the water detection process S150 corresponds to an example of a resistance change detection unit, the resistance value change amount ΔR corresponds to an example of a “resistance value change state”, and executes the water detection process S160. The control part 9 to perform corresponds to an example of a water determination part.

  The execution time of S110 and S120 in the water detection process corresponds to an example of a temperature control process, the execution time of S150 in the water detection process corresponds to an example of a resistance value change detection process, and the execution of S160 in the water detection process The time corresponds to an example of the water determination step.

[2. About the thickness of the porous layer]
Next, measurement results obtained by measuring the correlation between the thickness dimension of the porous layer 17 and the resistance value change amount ΔR in the moisture detection element 3 will be described.

  FIG. 7 shows measurement results obtained by measuring the correlation between the moisture content and the resistance change ΔR using two moisture sensing elements having different thickness dimensions of the porous layer. In this measurement, the moisture detection element (hereinafter also referred to as the first element) having a thickness dimension of the porous layer of 200 [μm] and the moisture detection of a porous layer having a thickness dimension of 400 [μm]. An element (hereinafter also referred to as a second element) was used.

  As illustrated in FIG. 7, the first element has a larger resistance value change amount ΔR than the second element, even if the moisture content is the same. For example, when the amount of moisture is 1.0 [μL], it can be seen that the first element has a larger resistance value change ΔR by the difference ΔRa than the second element.

  This is considered to be because the amount of water reaching the insulating member 11 through the porous layer 17 increases as the thickness dimension of the porous layer 17 decreases, and the temperature change amount of the heater unit 13 increases. .

  On the other hand, when the thickness dimension of the porous layer 17 is too large, the temperature change amount of the heater unit 13 becomes small and the resistance value change amount ΔR becomes small.

  In addition, if the resistance value change amount ΔR in the second element used in this measurement is large, it is possible to determine the difference in the resistance value change amount ΔR for each amount of water, and thus it is possible to detect the amount of water. For this reason, if the thickness dimension of the porous layer 17 is 400 [μm] or less, the amount of water can be sufficiently detected.

  In addition, if the resistance value change amount ΔR in the first element used in this measurement is large, the difference in the resistance value change amount ΔR for each water amount becomes even larger, so that the water amount can be detected with high accuracy. It becomes possible. For this reason, if the thickness dimension of the porous layer 17 is 200 [micrometers] or less, the detection accuracy of the amount of moisture will improve more.

[3. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, in the above-described embodiment, the moisture detection element having the porous layer having a thickness of 200 [μm] has been described, but the thickness of the porous layer is not limited to this value. That is, it is possible to provide a porous layer having an appropriate thickness according to the environment or application of the water detection location.

  Further, the target temperature of the heater unit 13 (heating resistor) is not limited to 350 [° C.], but a temperature range in which the water detection element 3 is not damaged by thermal shock (for example, 300 to 400 [° C.]). ), Any number can be taken. The target temperature of the heater unit 13 can be set to an arbitrary numerical value by changing the voltage value of the power supply device 5 or the resistance value of the resistance element 7.

  Further, the water-detecting element is not limited to the above-described long flat plate-shaped element, and may be a long cylindrical element or a long columnar element as long as the element can be installed at a water-detecting point. Any shape can be adopted.

  Moreover, although the said embodiment demonstrated the structure which is not provided with the protective cover which covers a to-be-watered detection element, the structure provided with a protective cover may be sufficient. The gas sensor is usually used with a protective cover in many cases, and the water detection element 3 is provided with the protective cover so that it approaches the mode of the gas sensor. Can do.

  DESCRIPTION OF SYMBOLS 1 ... Water detection apparatus, 3 ... Water detection element, 5 ... Power supply device, 7 ... Resistance element, 9 ... Control part, 11 ... Insulating member, 13 ... Heater part, 15 ... Electrode terminal, 17 ... Porous layer .

Claims (7)

A moisture detection device for detecting a moisture condition at a moisture detection location,
A wet detection element having a long insulating member with a heating resistor embedded at the tip;
A temperature control unit for energizing the heating resistor so that the heating resistor has a predetermined target temperature;
A resistance change detecting unit for detecting a change state of a resistance value in the heating resistor;
Based on the change state of the resistance value detected by the resistance change detection unit, a wetness determination unit that determines the wetness state of the wetness detection element;
With
The water-detecting element includes a porous layer having a thickness of 400 μm or less that covers at least the entire circumference of the insulating member in the circumferential direction of the embedded portion of the heating resistor.
A water detection device characterized by the above. The porous layer has a thickness of 200 μm or less;
The water-detecting device according to claim 1. The water determination unit determines the wet state including at least the amount of water based on information on the correlation between the amount of water attached to the water detection element and the amount of change in the resistance value,
The water-detecting device according to claim 1 or 2, wherein A water detection method for detecting a water exposure state at a water detection location,
A wet detection method using a wet detection element having a long insulating member with a heating resistor embedded at the tip,
A temperature control step of energizing the heating resistor such that the heating resistor has a predetermined target temperature;
A resistance change detecting step of detecting a change state of a resistance value in the heating resistor;
Based on the change state of the resistance value detected in the resistance change detection step, a water determination step for determining a water exposure state of the water detection element;
Have
The water-detecting element includes a porous layer having a thickness of 400 μm or less that covers at least the entire circumference of the insulating member in the circumferential direction of the embedded portion of the heating resistor.
A method for detecting water exposure. The porous layer has a thickness of 200 μm or less;
The water detection method according to claim 4. In the moisture determination step, based on the information on the correlation between the amount of moisture adhering to the moisture detection element and the amount of change in the resistance value, determining the moisture condition including at least the amount of moisture;
The method for detecting water exposure according to claim 4 or 5, wherein: The target temperature is 300 ° C. or more and 400 ° C. or less,
The water detection method according to any one of claims 4 to 6, wherein: