JP6622559B2 - Heat flux sensor and calibration method thereof, measurement object abnormality detection method, and engine operation abnormality detection method - Google Patents

Description

  The present invention relates to a heat flux sensor and a calibration method thereof, an abnormality detection method for an object to be measured, and an operation abnormality detection method for an engine.

  Measurement of the heat flux passing through the inner wall of the engine has been regarded as important in research and development of the engine in order to grasp the heat loss from the engine. As a method for measuring the heat flux passing through the inner wall surface of an engine, there is a conventional measurement method that combines surface temperature measurement using a coaxial thermocouple sensor or thin film thermocouple sensor and unsteady heat conduction analysis (for example, Patent Document 1). To 4).

Yoshiaki Enomoto and two others, "Direct heat loss to the combustion chamber wall of a four-cycle gasoline engine: (1st report, Heat loss to piston and cylinder liner)" Transactions of the Japan Society of Mechanical Engineers (Part B), Volume 50, 456 No. (1984), p1972-1980 Yoshiteru Enomoto and 1 other "Direct Heat Loss to the Combustion Chamber Wall of a Four-Cycle Gasoline Engine: (2nd Report, Heat Loss to Cylinder Head and Suction / Exhaust Valves)", Transactions of the Japan Society of Mechanical Engineers (B) 51 Volume 471, (1985), p3631- 3640 Hironori Nakao and five others "Instant heat flux measurement technology on highly responsive thermal barrier walls", Mazda Technical Report, No. 32 (2015), p222-227 LeFeuvre, T., Myers, P., and Uyehara, O., "Experimental Instantaneous Heat Fluxes in a Diesel Engine and Their Correlation," SAE Technical Paper 690464, 1969, doi: 10.4271 / 690464. P1717-1738

  However, the heat flux measurement methods disclosed in the above non-patent documents 1 to 4 combine the temperature of the engine inner wall surface measured by a thermocouple with the unsteady heat conduction analysis. There is a difficulty in the calibration method of the heat transfer model including the structure of the sensor and the thermophysical value of each layer when performing. For this reason, there is a problem that accurate measurement is difficult unless the sensor is produced as designed.

  Therefore, the problem to be solved by the present invention is to provide a heat flux sensor capable of accurately detecting the heat flux of the object to be measured, a calibration method thereof, a method for detecting abnormality of the object to be measured, and a method for detecting abnormal operation of the engine. It is to be.

A heat flux sensor according to an embodiment of the present invention that solves the above problems includes a substrate, and a stacked structure in which an insulating layer, a resistor layer, and a protective layer are stacked in this order from the substrate side. ,
A resistor is provided in the resistor layer,
The representative scale of the resistor satisfies the following formula (2):
In addition to the first resistor set to the representative scale = L, one or more second resistors having a representative scale smaller than the representative scale of the first resistor are provided,
A heat flux sensor, wherein a heat flux is obtained based on a resistance value of the resistor.
L ≧ 4 × (a / f) ^0.5 (2)
L: Representative scale of resistor (m)
a: Thermal conductivity of substrate
f: Frequency of heat generation fluctuation for calibration

In measuring the heat flux in an object to be measured such as an engine, in recent years, a technique for forming a thin film resistance thermometer by fine processing as a means for measuring the surface temperature has become practical. In the present invention, the microfabrication technology is applied to the heat flux sensor on the wall surface of the object to be measured, and the insulating layer, the resistor layer provided with the resistor, and the protective layer are laminated on the substrate in this order. The thin film-like laminated structure is provided. By obtaining the heat flux based on the resistance value of the resistor provided in the resistor layer in the thin-film laminated structure, for example, the heat transfer model is appropriately calibrated when performing an unsteady heat conduction analysis, for example. be able to. Therefore, the heat flux of the object to be measured can be detected with high accuracy.
In addition, when the heat flux sensor satisfies the above equation (2), the heat transfer model can be calibrated more accurately when the heat flux is obtained.
Therefore, by providing a second resistor whose representative scale is smaller than the representative scale of the first resistor, the heat transfer model calibrated with the first resistor can be used for unsteady heat conduction analysis of the measured value by the second resistor. Can be used. In particular, a resistor of a representative scale L and a small resistor are manufactured on the same substrate through the same micro-fabrication process, so that a heat transfer model calibrated with the first resistor of the representative scale L is reduced to a small size with a small representative scale. It can be used for unsteady heat conduction analysis of the measured value by the second resistor. Furthermore, by providing a plurality of second resistors, the heat flux can be measured at a number of points inside the object to be measured. For this reason, the local heat flux inside the object to be measured can be measured at a plurality of positions, and turbulent heat transfer can be grasped.

  In addition, the heat flux sensor according to an embodiment of the present invention may determine the temperature change of the resistor based on a resistance value of the resistor and a resistance temperature coefficient of the resistor.

  Thus, by obtaining the temperature change of the resistor based on the resistance value measured by the resistor and the resistance temperature coefficient of the resistor, the heat flux of the object to be measured can be accurately detected.

  In the heat flux sensor according to one embodiment of the present invention, the laminated structure may include a shielding layer made of a conductive material laminated on the protective layer.

  As described above, the laminated structure includes the shielding layer laminated on the protective layer, so that the influence of electromagnetic noise in the engine can be reduced, and the measurement resolution of heat flux can be increased.

In the heat flux sensor according to one embodiment of the present invention, the substrate thickness of the substrate may satisfy the following expression (1).
D ≧ 2.3 × (a / f) ^0.5 (1)
Where D: substrate thickness (m)
a: Thermal conductivity of substrate (m ² / s)
f: Cut-off frequency (Hz) required for periodic fluctuation measurement

  When the heat flux sensor satisfies the above equation (1), it is possible to accurately detect the frequency component of the heat flux that is equal to or higher than the required frequency when a periodic variation occurs in the heat flux of the object to be measured. Here, the cutoff frequency of the periodic fluctuation is a periodic fluctuation when the heat flux in the object to be measured is periodically generated. For example, when the object to be measured is an engine, the rotational frequency of the engine has a periodic variation, and the cutoff frequency f is a cutoff frequency required for measuring the periodic variation of the engine.

Further, a heat flux sensor calibration method according to an embodiment of the present invention is the above-described heat flux sensor calibration method,
While giving a known applied heat flux due to AC heat generation to the resistor, and measuring a temperature change of the resistor during the known applied heat flux,
Obtain the measured heat flux by unsteady heat conduction analysis using a heat transfer model of the heat flux sensor,
A heat transfer model of the heat flux sensor is adjusted based on a comparison result between the applied heat flux and the measured heat flux.

  In this way, a known applied heat flux due to AC heat generation is given to the resistor, and the measured heat flux is measured by unsteady heat conduction analysis from the temperature change of the resistor during the application of the known applied heat flux. . Since the heat transfer model is adjusted so that the measured heat flux matches the applied heat flux, a highly accurate heat transfer model can be generated.

An abnormality detection method for an object to be measured according to an embodiment of the present invention is an abnormality detection method for an object to be measured that detects an abnormality of the object to be measured by the heat flux sensor.
While causing periodic heat generation to the resistor, the temperature change of the resistor is measured by the heat flux sensor,
An abnormality of the object to be measured is detected based on a temperature change amount of the resistor.

  As described above, while causing the resistor to periodically generate heat, the temperature change of the resistor is measured by the heat flux sensor, and the abnormality of the object to be measured is detected based on the temperature change amount of the resistor. Thus, the abnormality of the object to be measured can be detected using the heat flux sensor. In addition, as abnormality of a to-be-measured object, when a non-measured object is an engine, there exists a state change of the deposit | attachment of the inner wall surface of an engine, for example. In this case, it is possible to detect an abnormality caused by the occurrence of deposits on the inner wall surface of the engine. When the deposits such as oil and soot increase with respect to the inner wall surface of the engine, the temperature change amount decreases. When such an abnormality is detected, there is a possibility that the efficiency of the engine may be lowered. Therefore, for example, it is possible to take measures such as adjusting a control mode when performing traveling control.

An engine operation abnormality detection method according to an embodiment of the present invention is an engine operation abnormality detection method for detecting an engine operation abnormality by the heat flux sensor,
The wall temperature or wall heat flux of the engine during operation is continuously measured by the heat flux sensor,
An abnormal operation of the engine is detected based on the measurement result of the wall surface temperature or the wall surface heat flux.

  Thus, the wall temperature or wall heat flux during operation of the engine is continuously measured by the heat flux sensor, and an abnormal operation of the engine is detected based on the measurement result of the wall temperature or wall heat flux. Abnormal operation of the engine can be detected using the bundle sensor.

  According to the heat flux sensor and the calibration method thereof, the abnormality detection method of the measurement object, and the abnormal operation detection method of the engine according to the present invention, the heat flux of the measurement object (engine) can be detected with high accuracy.

(A) is a sectional side view of a heat flux sensor according to an embodiment, and (B) is an explanatory view in plan view of a resistor layer in the heat flux sensor. It is a sectional side view of the engine to which the heat flux sensor was attached. It is explanatory drawing of a heat transfer model. It is a figure which shows the calibration procedure of heat flux measurement. It is a figure which shows the measurement procedure of a heat flux. FIG. 3 is a schematic diagram of a main part of a heat flux sensor used in an experiment of Example 1. 3 is a graph showing the results of Example 1. 5 is a schematic diagram of an experimental apparatus used in an experiment of Example 2. FIG. 10 is a graph showing the results of Example 2.

  Hereinafter, a heat flux sensor according to an embodiment of the present invention will be specifically described with reference to the drawings.

  FIG. 1A is a side sectional view of a heat flux sensor according to an embodiment, and FIG. 1B is an explanatory view in plan view of a resistor layer in the heat flux sensor. FIG. 2 is a cross-sectional side view of an engine with a heat flux sensor attached. For example, as shown in FIG. 2, the heat flux sensor 1 is attached to the engine 5 and detects the heat flux in the combustion chamber 51 of the engine 5. As shown in FIG. 1, the heat flux sensor 1 according to this embodiment includes a substrate 10 and a laminated structure 20. The board 10 is accommodated in the adapter 40 and is attached to the engine 5 via the adapter 40.

  The substrate 10 is made of a material common to the material constituting the engine block 52 in the engine 5. By configuring the substrate 10 with a material common to the engine block 52, the measurement accuracy of the heat flux on the engine wall surface can be increased. In the present embodiment, the engine block 52 is made of an aluminum alloy, and the substrate 10 is also made of an aluminum alloy. The engine block 52 of the engine 5 and the substrate 10 of the heat flux sensor 1 may be cast iron. The engine block 52 of the engine 5 and the substrate 10 of the heat flux sensor 1 may be made of a different material. Examples of the material used for the substrate 10 include copper alloy, brass, stainless steel, carbon steel, silicon, and the like in addition to the above-described aluminum alloy and cast iron. When the substrate 10 is made of a material different from that of the engine block 52, it is preferable that the material of the engine block 52 and the material having a temperature conductivity a be close.

The substrate 10 in the heat flux sensor 1 has a wall surface heat flux having a frequency equal to or higher than the rotational frequency of the engine 5 as a measurement target, and the substrate thickness D of the substrate 10 is set to a thickness that satisfies the following expression (1).
D ≧ 2.3 × (a / f) ^0.5 (1)
Where D: substrate thickness (m)
a: Thermal conductivity of substrate (m ² / s)
f: Cut-off frequency (Hz) required for periodic fluctuation measurement

Specifically, in the present embodiment, the substrate thickness D = 4 (mm), the temperature conductivity of the substrate temperature a = 50 × 10 ⁻⁶ (m ² / s), the cutoff frequency f = 16.7 (Hz ). The method of calculating the heat flux from the surface temperature data by heat conduction analysis has a high-pass filter characteristic in which the high frequency component of the heat flux is obtained correctly and the low frequency component is attenuated. For this reason, in the heat flux sensor 1, when the substrate thickness D of the substrate 10 satisfies the above equation (1), the frequency component of the heat flux more than the required frequency in the engine 5 in which the heat flux undergoes periodic fluctuations is accurately measured. it can. The upper limit for accurately measuring the frequency component of the heat flux above the required frequency is not set for the substrate thickness D, but for example, the upper limit is the thickness of the engine member to which the heat flux sensor 1 is attached. can do. Further, the required frequency is determined by the fluctuation cycle of the heat flux in the object to be measured, and is determined based on the rotational frequency of the engine in this embodiment.

  A laminated structure 20 is provided on the substrate 10. The laminated structure 20 includes an insulating layer 21, a resistor layer 22, a protective layer 23, and a shielding layer 24. Among these, the insulating layer 21 and the protective layer 23 are dielectrics having a thickness of micrometer level, and the shielding layer 24 is a conductor having a thickness of submicron level. The thickness and material of the insulating layer 21, the protective layer 23, and the shielding layer 24 are desirable, but other thicknesses and materials may be used.

  An insulating layer 21 is stacked on the substrate 10, and a resistor layer 22 is stacked on the insulating layer 21. Further, a protective layer 23 is laminated on the resistor layer 22, and a shielding layer 24 is laminated on the protective layer 23. Thus, the insulating layer 21, the resistor layer 22, the protective layer 23, and the shielding layer 24 are laminated in this order from the substrate side.

  The insulating layer 21 is formed of an insulating material, and examples of the material used for the insulating layer 21 include an aluminum oxide film, a silicon nitride film, and a silicon carbide film in addition to the silicon oxide film described above. The thickness of the insulating layer 21 is desirably 0.5 to 2 (μm). The resistor layer 22 is formed of a conductive material, and examples of the material used for the resistor layer 22 include platinum, nickel, pure iron, and tungsten.

  A resistor layer 22 shown in FIG. 1A includes a resistor 25 and thin film wirings 31 and 32 shown in FIG. The resistor 25 serves as a temperature measuring unit, and as shown in FIG. 1A, a first resistor 25A formed by bending a plurality of straight lines, and a representative scale than the first resistor 25A. Are provided with two second resistors 25B. A current thin film wiring 31 and a voltage thin film wiring 32 are connected to both the first resistor 25A and the second resistor 25B. Both the current thin-film wiring 31 and the voltage thin-film wiring 32 are connected to the drive / measurement circuit 60.

As the first resistor 25A, one having a resistance value of 100 (Ω) level and a temperature coefficient of 0.002 (1 / K) level or more is general-purpose and suitable. The resistance value and the temperature coefficient are the same for the second resistor 25B. Moreover, the representative scale L of the resistor outer shape in the first resistor 25A has a length that satisfies the following (2).
L ≧ 4 × (a / f) ^0.5 (2)
L: Representative scale of resistor (m)
a: Thermal conductivity of substrate (m ² / s)
f: Frequency of heat generation fluctuation for calibration

The representative scale (representative length) is an equivalent diameter. When the outer shape is a rectangle like the first resistor 25A of the present embodiment, the representative scale L is expressed by the following equation (3). Can be represented.
L = (4 × area ÷ circumference) (3)

Specifically, the first resistor 25A has a square outer shape, the frequency f of the fluctuating heat generation f = 1000 Hz, the substrate temperature conductivity a = 60 × 10 ⁻⁶ (m ² / s), and the representative scale L = 1. (Mm). Since the representative scale L (m) of the resistor has a length that satisfies the above equation (2), the one-dimensional unsteady heat conduction analysis can be suitably applied to the calibration of the heat flux measurement. The second resistor 25B is a resistor having a smaller representative scale than the first resistor 25A.

  The protective layer 23 laminated on the resistor layer 22 is formed of an insulating material. As a material used for the protective layer 23, for example, an aluminum oxide film, a silicon nitride film, a carbonized carbon other than the silicon oxide film described above. A silicon film can be mentioned. The insulating layer 21 and the protective layer 23 may be formed of a common material or different materials. The thickness of the protective layer 23 is desirably 0.5 to 2 (μm).

  Further, the shielding layer 24 laminated on the protective layer 23 covers the entire surface of the protective layer 23. Examples of the material used for the shielding layer 24 include chromium, aluminum, titanium, tungsten, and copper in addition to the nickel film. The thickness of the shielding layer 24 is preferably 0.1 to 1 (μm). The shielding layer 24 is electrically connected to the substrate 10, and the substrate 10 is electrically connected to the ground potential. The shielding layer 15 protects the protective layer 23, the resistor layer 22, and the insulating layer 21 from electromagnetic noise in the combustion chamber 51 of the engine 5.

Moreover, it is preferable that the sum total of the thermal resistance per unit area of the insulating layer 21, the resistor layer 22, the protective layer 23, and the shielding layer 24 is 10 K / (MW / m ² ) or less. Specifically, a silicon oxide film having a thickness of 2 μm can be used for the insulating layer 21 and the protective layer 23, and a nickel film having a thickness of 0.5 μm can be used for the shielding layer 24. By setting the sum of the thermal resistance per unit area of each layer to 10 K / (MW / m ² ) or less, the heat flux on the inner wall surface of the engine 5 can be measured within 2% error, for example.

  Further, a through hole 26 penetrating in the thickness direction is formed in the substrate 10, and a through wiring 33 is inserted into the through hole 26, and the thin film wirings 31 and 32 on the surface side of the substrate 10, The wiring 34 on the back side of the substrate is connected. Further, the through hole 26 is filled with an insulator 27 to protect the through wiring 33 inserted into the through hole 26 from being electrically connected to the substrate 10. One end of the thin film wirings 31 and 32 is connected to the resistors 25A and 25B, and the other end is connected to the through wiring 33. One end of the wiring 34 is connected to the through wiring 33, and the other end is connected to the drive / measurement circuit 60. The resistors 25 </ b> A and 25 </ b> B are connected to the drive / measurement circuit 60 through the thin film wires 31 and 32, the through wires 33, and the wires 34, thereby eliminating the wires floating from the laminated structure 20. For this reason, the surface of the laminated structure 20 can be easily made flush with the wall surface of the engine.

  The drive / measurement circuit 60 includes a power source and supplies current to the resistors 25A and 25B. The drive / measurement circuit 60 includes an ammeter and a voltmeter, and measures the current value and voltage value of the current supplied to the resistors 25A and 25B. The drive / measurement circuit 60 measures the resistance values of the resistors 25A and 25B from the measured current value and voltage value.

  A data collection device 70 is connected to the drive / measurement circuit 60, and a computer 80, which is an arithmetic device, is connected to the data collection device 70. The drive / measurement circuit 60 stores the resistance values of the resistors 25 </ b> A and 25 </ b> B in the data collection device 70. The computer 80 calculates the temperature change of the resistors 25A and 25B based on the resistance values of the resistors 25A and 25B, the resistance temperature coefficient of the resistors 25A and 25B, and the reference resistance value stored in the data collection device 70. . Further, a one-dimensional unsteady heat conduction analysis is performed based on the calculated temperature change to obtain a heat flux.

  As shown in FIG. 2, the engine 5 to which the heat flux sensor 1 is mounted includes an intake valve 53, an exhaust valve 54, and an ignition plug (not shown) in addition to the combustion chamber 51 and the engine block 52 described above. The engine 5 includes a piston 56 that moves up and down in the combustion chamber 51 and a connecting rod 57 that moves the piston 56 up and down.

  In the present embodiment, the heat flux sensor 1 is embedded and attached to the engine block 52 in the vicinity of the exhaust valve 54 in the engine 5, but may be attached to another position of the engine 5. For example, it may be attached to the side of the spark plug in the engine block 52 or the upper surface of the piston 56.

  The heat flux sensor 1 is attached to the engine 5 such that the laminated structure 20 is exposed to the combustion chamber 51 of the engine 5. The surface of the laminated structure 20 (the surface of the shielding layer 24) is flush with the inner surface of the combustion chamber 51 of the attached engine. For this reason, the surface of the laminated structure 20 (the surface of the shielding layer 24) is along the curved surface of the side wall of the cylinder formed inside the engine block 52, for example, when attached to the side of the combustion chamber 51. It may be curved. In addition, when attached to the piston 56, the surface of the laminated structure 20 (the surface of the shielding layer 24) may be planar. However, the shape of the cylinder that is flush with the surface of the laminated structure 20 (the surface of the shielding layer 24) is not necessarily the same. For example, when the heat flux sensor 1 is attached to the side wall of the cylinder, the laminated structure is used. The shape of the surface at 20 (the surface of the shielding layer 24) may be planar. Further, the surface of the laminated structure 20 (the surface of the shielding layer 24) is flush with the combustion chamber 51 of the attached engine, but it is not flush and slightly protrudes from the surface. On the contrary, it may be a mode in which it is retracted.

  In the heat flux sensor 1 having the above configuration, the heat flux is obtained based on the resistance value of the resistor 25 in the laminated structure 20. For this reason, it is possible to appropriately calibrate the heat transfer model when performing the unsteady heat conduction analysis. Therefore, the heat flux of the object to be measured can be detected with high accuracy. Further, the resistors 25 </ b> A and 25 </ b> B in the laminated structure 20 are covered with the shielding layer 24. For this reason, when measuring the heat flux of the combustion chamber 51 in the engine 5, the protective layer 23, the resistor layer 22, and the like can be protected from electromagnetic noise in the combustion chamber 51.

  Further, in measuring the heat flux, it is required to calibrate the quantitative property of the heat flux. As calibration of the heat flux quantitativeness, for example, adjustment is performed to match the measurement heat flux with radiation from a black body furnace or irradiation with laser light. However, since it is difficult to estimate the absorptance of the sensor surface and it is difficult to accurately grasp the input amount of light energy, there is a concern about the quantitativeness of the heat flux. In this respect, in the heat flux sensor 1 of the present embodiment, heat is generated by the resistor 25 in the laminated structure 20, and the quantitative determination of the heat flux is performed based on the measured resistance value. This makes it possible to calibrate the heat flux quantitativeness without estimating the absorptance of the sensor surface or grasping the input amount of light energy, so that an accurate unsteady heat conduction analysis can be performed. When the heat flux sensor 1 is provided in the engine 5, it is difficult to perform calibration using a laser beam or the like. However, the heat flux is quantitatively determined based on the heat flux generated by the resistor and the resistance value. The calibration of the heat flux in the heat flux sensor 1 provided in the engine 5 can be easily calibrated.

  During operation of the engine 5, oil or soot may adhere to the surface of the heat flux sensor 1. Further, when the heat flux sensor 1 is used for a long period of time, an error may occur in the measured value due to a change in heat transfer characteristics inside the sensor due to a change with time. In order to eliminate such an error, it is preferable to recalibrate the heat flux sensor. However, conventional calibration using a laser beam or the like cannot be performed during operation of the engine, and the accuracy of the measured value during operation of the engine cannot be verified. In this regard, in the heat flux sensor 1 of the present embodiment, recalibration of the heat flux sensor 1 can be executed even during operation of the engine. Therefore, it is possible to verify the accuracy of the measured value during operation of the engine. Furthermore, it is possible to accurately detect the lubrication status and the combustion status during engine operation. Therefore, it is possible to approach ideal energy-saving operation when executing operation control with the purpose of energy-saving operation.

  Further, in the engine 5, electromagnetic noise is at a high level due to the electrical conductivity of the flame, the presence of various radicals, and the discharge from the spark plug, and the temperature measurement by the resistor 25 may be obstructed. In this case, a shielding layer 24 made of a conductive material is formed on the protective layer 23, and the shielding layer 24 is electrically connected to a ground potential substrate. For this reason, since the electromagnetic noise can be reduced by the shielding layer 24, the wall surface temperature with reduced noise can be measured, and the measurement resolution of the heat flux can be increased.

  Next, measurement of heat flux using the heat flux sensor 1 in the present embodiment will be described. In the heat flux sensor 1, the heat transfer model used for the one-dimensional unsteady heat conduction analysis is calibrated based on the measured resistance value of the first resistor 25A, and the calibrated heat transfer model and the measured first The heat flux is measured based on the resistance value of the two-resistor 25B. Therefore, the heat transfer model will be described, followed by a description of the heat transfer model calibration procedure, followed by a description of the heat flux measurement procedure.

  In the measurement of heat flux using the heat flux sensor 1, one-dimensional unsteady heat conduction of a heat transfer model reflecting the structure and heat transfer characteristics of the heat flux sensor 1 from the surface temperature measured by the second resistor layer 22B. Through the analysis, the heat flux is calculated. The heat transfer model of the heat flux sensor 1 has the configuration shown in FIG. 3, and includes a protective layer thermal resistance Rh in the protective layer 23, a sensor layer thermal resistance Rt in the resistive layer 22, and between the resistive layer 22 and the insulating layer 21. A thermal resistance Ri of the interface thermal resistance 28 at the interface, an insulating layer thermal resistance Rz in the insulating layer 21, and a substrate layer thermal resistance Rk in the substrate 10 are provided.

ここで、ρ：密度
ｃ：比熱
λ：熱伝導率
Ｔ：温度
ｔ：時間
ｘ：厚さ方向距離 In order to reflect the heat transfer model in the unsteady heat conduction equation, the thickness d, density ρ, specific heat c, and thermal conductivity λ of each layer are given. About these numerical values, the interface thermal resistance Ri between the resistor layer 22 and the insulating layer 21 and the heat capacity of the insulating layer 21 are adjusted by calibration. In the heat conduction analysis, the discretization formula obtained by discretizing the one-dimensional unsteady heat conduction equation is algebraically solved. As the boundary condition, the measurement temperature measured by the resistor layer 22 is given to the surface of the heat flux sensor 1, and the heat insulation condition is given to the back surface. By this analysis, time series data is obtained for the temperature distribution in the heat flux sensor 1. Finally, using the temperature distribution, the heat flux is calculated by calculating the time derivative of the total heat quantity per unit area of the heat flux sensor 1. The one-dimensional unsteady heat conduction equation is given by the following equation (4).

Where ρ: density
c: Specific heat
λ: thermal conductivity
T: Temperature
t: time
x: Distance in thickness direction

  In the heat transfer model shown in FIG. 3, the temperature of each layer is converted into a model according to the one-dimensional unsteady heat conduction equation shown in the above equation (4), and the thickness d, density ρ, specific heat c, and thermal conductivity λ of each layer are expressed as follows. give.

Next, calibration of heat flux measurement will be described. Calibration of heat flux measurement is calibration of a heat transfer model, and is performed according to the procedure shown in FIG. First, an alternating current of the voltage signal V _exc. (T) and the current signal I _exc. (T) is supplied to the first resistor 25A to cause periodic heating of the first resistor 25A (S1). ). Until this periodical heat generation occurs, it is an experimental process. The subsequent steps up to S7 are analysis steps. At this time, a known applied heat flux q _exc. (T) is given (S2), and the temperature change T _meas. (T) of the first resistor 25A due to periodic heat generation is measured (S3).

Next, a one-dimensional unsteady heat conduction analysis of the heat transfer model is performed using the measured temperature change data (S4), and a calculated heat flux q _meas. (T) is calculated (S5). Note that the heat transfer model for performing the one-dimensional unsteady heat conduction analysis is based on the design values of sensor information (S11) such as the thickness and temperature conductivity of each layer of the substrate 10 and the laminated structure 20 of the heat flux sensor 1. A design heat transfer model determined based on the heat transfer model is set as a default of the heat transfer model (S12).

Then, applying heat flux given by S2 q _exc. (T) and the calculated heat flux q _meas calculated in _S5. (T) and comparing the, imparting heat flux q _exc. (T) and calculated heat flux q _{meas .} the absolute value of (t) and the difference determines whether or not it is less than the determination value (S6). The determination value may be 1% of the applied heat flux q _exc. (T) or the calculated heat flux q _meas. (T), for example, and may be a value that is appropriately raised or lowered from the value of 1%. For example, the determination value may be 2% or 0.5% of the applied heat flux q _exc. (T) or the calculated heat flux q _meas. (T), for example.

Here, applying heat flux q _exc. (T) and calculated heat flux q _meas. (T) and the difference between the absolute value of applied heat flux q _exc. (T) or 1% of the calculated heat flux q _meas. (T) When it is determined that it is not less than (S6: NO), the heat transfer model is corrected (S7). In correcting the heat transfer model, if the calculated heat flux q _meas. (T) is larger, the interfacial thermal resistance of the heat transfer model is reduced, and if the calculated heat flux q _meas. (T) is smaller, the interfacial heat Adjust to increase resistance. Subsequently, returning to S4, the one-dimensional unsteady heat conduction analysis of the heat transfer model is performed again.

In S6, imparting heat flux q _exc. (T) and calculated heat flux q _meas. (T) and the absolute value of applied heat flux q _{exc difference.} (T) or calculated heat flux q _meas. 1% of the (t) The process from S4 to S7 is repeated until it is determined that the value is less than the value. Then, applying heat flux q _exc. Less than 1% of the (t) and calculated heat flux q _meas. (T) and the difference between the absolute value of applied heat flux q _exc. (T) or calculated heat flux q _meas. (T) Is determined (S6: YES), a calibrated heat transfer model is generated (S8), and the calibration of the heat transfer model is completed. The calibration of the heat transfer model of the heat flux sensor 1 can be performed both when the engine 5 is stopped and during operation.

Next, a procedure for measuring the heat flux will be described. In the measurement of the heat flux, as shown in FIG. 5, a measurement process for measuring the resistance value of the resistor and an analysis process for calculating the temperature change and the heat flux are performed. The measurement process is performed based on a temperature change in the second resistor 25B in the heat flux sensor 1. When measuring the heat flux, as shown in FIG. 5, the resistance value of the second resistor 25B is measured to obtain the resistance signal R _meas. (T) (S21).

In the subsequent analysis process, the temperature change T _meas. (T) of the second resistor 25B is calculated from the measured resistance value (S22). The temperature change of the second resistor 25B is calculated based on the resistance value of the second resistor 25B and the resistance temperature coefficient of the second resistor 25B. Subsequently, a one-dimensional unsteady heat conduction analysis is performed using the calculated temperature change of the second resistor 25B and the calibrated heat transfer model (S23). A measured heat flux is obtained by this one-dimensional unsteady heat conduction analysis (S24).

  In the present embodiment, when the heat flux of the engine 5 is measured by the heat flux sensor 1, the heat transfer model is calibrated based on the resistance value measured by the first resistor 25A. The first resistor 25A has a representative scale that satisfies the above formula (2). For this reason, it is possible to accurately calibrate the heat transfer model when measuring the heat flux.

  Further, the heat flux is measured based on the heat transfer model calibrated using the resistance value measured by the first resistor 25A and the temperature change and the resistance value measured by the second resistor 25B. Here, the first resistor 25A that measures the resistance value for calibrating the heat transfer model and the second resistor 25B that measures the resistance value for measuring the heat flux of the engine 5 are provided on the common substrate 10. The protective layer 23 and the shielding layer 24 are further laminated. Thus, the first resistor 25A and the second resistor 25B are formed in a common environment. For this reason, it is possible to accurately measure the heat flux using the heat transfer model calibrated based on the resistance value measured by the first resistor 25A and the resistance value measured by the second resistor 25B. The first resistor 25A has a length that the representative scale L satisfies the above expression (2). Further, a plurality of second resistors 25 </ b> B are provided with respect to the substrate 10, and resistance values and temperature changes can be measured at a plurality of points in the combustion chamber 51 of the engine 5. For this reason, the local heat flux in the combustion chamber 51 can be measured at a plurality of positions, and turbulent heat transfer can be grasped.

  Thus, in the heat flux sensor 1 according to the present embodiment, the heat flux is obtained based on the resistance value of the resistor 25 in the laminated structure 20. For this reason, it is possible to appropriately calibrate the heat transfer model when performing the unsteady heat conduction analysis, and it is possible to accurately detect the heat flux of the engine. Further, the temperature change of the resistor layer is obtained based on the measured resistance value of the resistor 25 and the resistance coefficient of the resistor 25. Therefore, the thermal resistance of the engine can be detected with higher accuracy.

  The laminated structure 20 includes a shielding layer 24 made of a conductive material laminated on the protective layer 23. The shielding layer 24 protects the protective layer 23, the resistor layer 22, and the like from electromagnetic noise in the combustion chamber 51 of the engine. For this reason, since the influence of the electromagnetic noise at the time of measuring resistance value with the resistor 25 can be made small, the measurement resolution of heat flux can be improved.

  Furthermore, the substrate thickness D of the substrate 10 satisfies the above equation (1). For this reason, it is possible to accurately detect the frequency component of the heat flux equal to or higher than the required frequency that is the frequency of the engine 5. The representative scale of the resistor satisfies the above formula (2). Therefore, calibration of the heat transfer model when measuring the heat flux can be performed with higher accuracy.

  Further, the heat flux sensor 1 according to the present embodiment can be used not only for measuring the heat flux in the combustion chamber 51 but also for determining an abnormality of the engine 5. Hereinafter, a mode in which the heat flux sensor 1 is used for determining abnormality of the engine 5 will be described. If oil or soot adheres to the inner wall surface of the combustion chamber 51 during the operation of the engine 5, it may cause a combustion failure of the engine 5, so that the state of the engine 5 decreases and an abnormality occurs in the engine 5. May end up. It was difficult to determine the state of oil or soot adhesion in the combustion chamber 51. Further, when the combustion state of the engine 5 is not stable, for example, when abnormal combustion or the like occurs, the energy saving operation may be hindered.

  For these problems, it is possible to continuously measure the temperature change of the resistor 25 while periodically supplying an alternating current to the resistor 25 of the heat flux sensor 1 and causing the resistor 25 to generate heat periodically. it can. More specifically, a sinusoidal alternating current is supplied to the resistor 25, and a third harmonic signal in the temperature change signal is detected by a lock-in amplifier, and an abnormality of the engine 5 is detected. In this case, an abnormality of the engine 5 can be detected when the temperature change amount of the resistor 25 exceeds a predetermined threshold value. The engine abnormality includes, for example, a change in the state of deposits on the inner wall surface of the engine 5. In this case, it is possible to detect an abnormality caused by the occurrence of deposits on the inner wall surface of the engine 5. When such an abnormality is detected, there is a possibility that the efficiency of the engine may be reduced. For example, it is possible to take measures such as adjusting the control mode when performing the travel control.

  Further, as another monitoring method, by using the heat flux sensor 1 according to the present embodiment, the inside of the combustion chamber 51 of the engine 5 can be monitored. Specifically, the temperature data or heat flux data of the resistor 25 is continuously measured by the heat flux sensor 1 and compared with data during normal operation to determine whether the engine 5 is operating abnormally. it can. As data during normal operation, data stored in advance can be used, and data based on past history can also be used. As a specific operation abnormality determination procedure, the temperature or heat flux of the resistor 25 is continuously measured in cycles every predetermined time, and the temperature data or heat flux data in the most recent cycle is used as the temperature of the past several cycles. Compare with data or heat flux data. When these data differences exceed a predetermined threshold, it can be determined that abnormal combustion or the like has occurred. Furthermore, normal operation can be continued by controlling the operating conditions of the engine for the detected abnormality. Further, by accumulating / analyzing abnormality information, it can be used for trouble prevention and trouble improvement of the engine 5.

Next, examples of the heat flux sensor 1 according to this embodiment will be described.
[Example 1]
In Example 1, an experimental example of calibration of a heat transfer model based on periodic heat generation of the resistor 25 and a temperature change measured by a heat flux sensor will be described. In the experiment, a heat flux sensor including the resistor 25 and the thin film wirings 31 and 32 shown in FIG. 6 was used. In the heat flux sensor used in the experiment, silicon having a thickness of 0.2 mm was used for the substrate, and silicon oxide having a thickness of 2 μm was used for the insulating layer. The resistor layer 22 laminated on the insulating layer has a square shape with an outer shape of 1 mm, and has a wiring width of 25 μm and a wiring interval of 25 μm. The resistance value of the resistor 25 is 210Ω, and the temperature coefficient of the resistor layer 22 is 0.0022 (1 / K).

The heat transfer model was created by adopting the sensor structure of the substrate, the insulating layer, and the resistor layer and the standard physical property values of the materials constituting them. Further, as a calibration operation, a rectangular wave-shaped periodic heat generation with a frequency of 1000 Hz is applied to the resistor layer 22, the temperature of the resistor layer 22 is measured, and the resistor layer is adjusted so that the measured heat flux matches the applied heat flux. The interfacial thermal resistance between 22 and the insulating layer was adjusted. As a result of calibration, an interface thermal resistance of 2.7 K / (MW / m ² ) was introduced.

Applying heat flux q _{_Cal} during calibration in FIG 7 (± 355kW / square wave ^{m 2)} and the measured temperature _ΔT _exc, showing the measured heat flux q _{_ exc} after calibration. As can be seen from Figure 7, the applied heat flux q _{_Cal} during calibration, measuring the heat flux q _{_ exc} after calibration except high frequency noise has a waveform that approximates. The difference between the applied heat flux q _{_Cal} during calibration, a measurement heat flux q _{_ exc} after calibration, was 1.4% of the applied heat flux _q _cal. From this result, it was found that the heat transfer model was calibrated so that highly accurate measurement can be performed by calibration of the heat transfer model.

[Example 2]
In the second embodiment, the heat flux sensor 1 shown in the first embodiment is used to show a temperature change and heat flux measurement example by the heat flux sensor 1 in a butane gas / air premixed combustion field. As shown in FIG. 8, the experimental apparatus 4 includes an open container 41. The capacity of the open container 41 is 0.51 liter. A spark plug 42 is attached to the open container 41. The heat flux sensor 1 is attached to the lower end of the open container 41.

  An open container 41 shown in FIG. 8 was filled with a premixed gas with an equivalence ratio of 1.2, ignited by discharge of the spark plug 42, and the surface temperature Tw and heat flux qw of the heat flux sensor 1 were measured. Further, an integrated value ew for the heat flux was calculated. The measurement results are shown in FIG. In addition, the moving average value qw_avg10 of 10 measurement points of the heat flux qw is also shown.

In the measurement results shown in FIG. 9, the surface temperature of the heat flux sensor increased from the time of about 80 ms when the flame reached the sensor surface, and the heat flux showed a sharp peak having a maximum value of about 230 kW / m ² . It was also found that the heat flux converged in the subsequent time of about 30 ms. Thus, it was found that the heat flux of the premixed combustion field in the open container 41 can be measured by using the heat flux sensor 1.

  In addition, it is possible to appropriately replace the constituent elements in the above-described embodiments with well-known constituent elements without departing from the spirit of the present invention, and the above-described modified examples may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 ... Heat flux sensor 4 ... Experimental apparatus 10 ... Board | substrate 20 ... Laminated structure 21 ... Insulating layer 22 ... Resistor layer 23 ... Protective layer 24 ... Shielding layer 25 ... Resistor 25A ... 1st resistor 25B ... 2nd resistor 26 ... Through-hole 27 ... Insulator 28 ... Interfacial thermal resistance 31 ... Thin film wiring for current 32 ... Thin film wiring for voltage 33 ... Through wiring 34 ... Wiring 40 ... Adapter 41 ... Opening container 42 ... Spark plug 5 ... Engine 51 ... Combustion chamber 52 ... Engine block 53 ... Intake valve 54 ... Exhaust valve 56 ... Piston 57 ... Connecting rod 60 ... Drive / measurement circuit 70 ... Data collection device 80 ... Computer (computing device)

Claims (7)

A substrate, and a laminated structure in which an insulating layer, a resistor layer, and a protective layer are laminated in this order from the substrate side,
A resistor is provided in the resistor layer,
The representative scale of the resistor satisfies the following formula (2):
In addition to the first resistor set to the representative scale = L, one or more second resistors having a representative scale smaller than the representative scale of the first resistor are provided,
A heat flux sensor, wherein a heat flux is obtained based on a resistance value of the resistor.
L ≧ 4 × (a / f) ^0.5 (2)
L: Representative scale of resistor (m)
a: Thermal conductivity of substrate
f: Frequency of heat generation fluctuation for calibration   The heat flux sensor according to claim 1, wherein a temperature change of the resistor is obtained based on a resistance value of the resistor and a temperature coefficient of resistance of the resistor.   The heat flux sensor according to claim 1 or 2, wherein the laminated structure includes a shielding layer made of a conductive material laminated on the protective layer. The heat flux sensor according to any one of claims 1 to 3, wherein the substrate thickness of the substrate satisfies the following expression (1).
D ≧ 2.3 × (a / f) ^0.5 (1)
Where D: substrate thickness (m)
a: Thermal conductivity of substrate (m ² / s)
f: Cut-off frequency (Hz) required for periodic fluctuation measurement A method for calibrating a heat flux sensor according to any one of claims 1 to 4 ,
While giving a known applied heat flux due to AC heat generation to the resistor, and measuring a temperature change of the resistor during the known applied heat flux,
Obtain the measured heat flux by unsteady heat conduction analysis using a heat transfer model of the heat flux sensor,
A method for calibrating a heat flux sensor, comprising adjusting a heat transfer model of the heat flux sensor based on a comparison result between the applied heat flux and the measured heat flux. An abnormality detection method for an object to be measured for detecting an abnormality of the object to be measured by the heat flux sensor according to any one of claims 1 to 4 .
While causing periodic heat generation to the resistor, the temperature change of the resistor is measured by the heat flux sensor,
An abnormality detection method for an object to be measured, wherein an abnormality of the object to be measured is detected based on a temperature change amount of the resistor. An engine operation abnormality detection method for detecting an engine operation abnormality by the heat flux sensor according to any one of claims 1 to 4 ,
The wall temperature or wall heat flux of the engine during operation is continuously measured by the heat flux sensor,
An abnormal operation detection method for an engine, wherein an abnormal operation of the engine is detected based on a measurement result of the wall surface temperature or the wall surface heat flux.

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