Device with gas detection function

Abstract

The present application provides a kind of equipment with gas detection function, which can detect the detected gas with high precision.The equipment with gas detection function has a housing (10), a vibration source (20) and a gas measurement part (40) arranged in the interior of the housing and separated by a partition, the vibration source is arranged outside the gas measurement part, the gas measurement part is configured to include a detection part (41) arranged on a substrate (30) and a gas detection space (42) provided with a hole (43) for gas to pass through, in the case where the volume of the gas detection space is V, the cross-sectional area of the hole is S, the effective length of the hole is L, and the speed of sound is c, the frequency f shown in the following formula (1) is 500Hz or more, 【Mathematical formula 1】

Description

Technical Field

[0001] This disclosure relates to equipment with gas detection capabilities. Background Technology

[0002] Gas sensors for detecting gases are used in a wide variety of fields. With the development of semiconductor technology and MEMS technology, the miniaturization of gas sensors has made progress, enabling gas sensors to be integrated into the housings of devices that emit sound, such as smart home devices (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-91489 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In the device disclosed in Patent Document 1, the gas sensor is subjected to air vibrations such as music and sound emanating from a speaker located within the same housing. Additionally, the gas sensor is subjected to air vibrations from a motor in an air conditioning unit, etc. Consequently, the gas within the gas sensor sometimes resonates and vibrates. Due to the noise caused by vibration, the detection accuracy of the gas sensor deteriorates. In the case of miniaturization, where the light source, detection unit, etc., used in the gas sensor are configured as microstructures suspended in the air using MEMS technology, they are particularly susceptible to noise caused by vibration, sometimes resulting in a significant deterioration in detection accuracy.

[0008] The purpose of this disclosure, made in view of this situation, is to provide a device with a gas detection function that can detect the gas being detected with high precision.

[0009] Solution for solving the problem

[0010] [1] One of the technical solutions of this disclosure includes a device with gas detection function, which has the following features:

[0011] case;

[0012] Vibration source; and

[0013] The gas measuring unit, which is disposed inside the housing and separated by a partition,

[0014] The vibration source is located outside the gas measuring unit.

[0015] The gas measuring unit is configured to include a detection unit disposed on a substrate and a gas detection space having a hole for gas to pass through.

[0016] With the volume of the gas detection space set as V, the cross-sectional area of ​​the orifice set as S, the effective length of the orifice set as L, and the speed of sound set as c, the frequency f shown in the following formula (1) is above 500 Hz.

[0017]

Mathematical Formula 1

[0018]

[0019] [2] As a technical solution of this disclosure, according to [1],

[0020] The hole is equipped with a vent pipe.

[0021] With the length obtained by adding the lengths of the hole and the vent pipe as L', and the radius of the hole as a, the effective length is given by the following formula (2).

[0022]

Mathematical Formula 2

[0023] The formula is L = L′ + 1.5a...

[0024] [3] As a technical solution of this disclosure, according to [1],

[0025] The hole is equipped with a vent pipe.

[0026] The outlets of the hole and the vent pipe become flat.

[0027] With the length obtained by adding the lengths of the hole and the vent pipe as L', and the radius of the hole as a, the effective length is given by the following formula (3).

[0028]

Mathematical Expression 3

[0029] L=L′+1.7a... (3).

[0030] [4] As a technical solution of this disclosure, according to [1],

[0031] The hole is equipped with a vent pipe.

[0032] The cross-sectional shapes of the hole and the vent pipe are irregular.

[0033] Let L' be the length obtained by adding the lengths of the hole and the vent pipe, and let S be the area of ​​the outlet opening of the hole and the vent pipe. out In this case, the effective length is given by the following formula (4),

[0034]

Mathematical Expression 4

[0035]

[0036] [5] As a technical solution of this disclosure, according to any one of [1] to [4],

[0037] The frequency f is above 1.0 kHz.

[0038] [6] As a technical solution of this disclosure, according to any one of [1] to [5],

[0039] The frequency f is above 2.0 kHz.

[0040] [7] One technical solution of this disclosure includes a device with gas detection function, which has the following features:

[0041] case;

[0042] Vibration source; and

[0043] The gas measuring unit is disposed inside the housing.

[0044] The gas measuring unit is configured to include a detection unit disposed on a substrate and a gas detection space having a hole for gas to pass through.

[0045] The hole is equipped with a vent pipe.

[0046] The cross-sectional shapes of the hole and the vent pipe are irregular.

[0047] Let L' be the length obtained by adding the lengths of the hole and the vent pipe, and let S be the area of ​​the outlet opening of the hole and the vent pipe. out In this case, the effective length L of the hole is given by the following formula (5).

[0048] With the volume of the gas detection space set as V, the cross-sectional area of ​​the hole set as S, and the speed of sound set as c, the frequency f shown in the following formula (6) is below 100Hz.

[0049]

Mathematical Expression 5

[0050]

[0051]

[0052] [8] As one embodiment of this disclosure, according to any one of [1] to [7],

[0053] The vibration source or the detection unit exists on a plane of symmetry of a cuboid approximately defined relative to the housing.

[0054] [9] As a technical solution of this disclosure, according to any one of [1] to [8],

[0055] The vibration source or the detection unit exists on a cylindrical axis of symmetry approximately defined relative to the housing.

[0056]

[10] As a technical solution of this disclosure, according to any one of [1] to [9],

[0057] The vibration source or the detection unit is located at the center point of a sphere approximately defined relative to the housing.

[0058]

[11] As a technical solution of this disclosure, according to any one of [1] to

[10] ,

[0059] The vibration source or the detection unit is located at one end of a rectangle approximately defined relative to the substrate.

[0060]

[12] As a technical solution of this disclosure, according to any one of [1] to

[11] ,

[0061] Let the typical length of the housing be L. hus In the case of the following equation (7), the frequency f is shown. hus Above 500Hz

[0062]

Mathematical Expression 6

[0063]

[0064]

[13] As a technical solution of this disclosure, according to

[12] ,

[0065] The frequency f hus It is above 1.0kHz.

[0066]

[14] As a technical solution of this disclosure, according to

[12] or

[13] ,

[0067] The frequency f hus It is above 2.0kHz.

[0068]

[15] As a technical solution of this disclosure, according to any one of [1] to

[14] ,

[0069] Let the area of ​​the substrate be S sub Let the longitudinal elastic modulus of the substrate be E, the thickness of the substrate be h, the Poisson's ratio be σ, the dimensionless constant γ be 3.65, and the square root of the area of ​​the substrate be the typical length L. sub In the case of the following equation (8), the frequency f is shown. sub Above 500Hz

[0070]

Mathematical Expression 7

[0071]

[0072]

[16] As a technical solution of this disclosure, according to

[15] ,

[0073] The frequency f sub It is above 1.0kHz.

[0074]

[17] As a technical solution of this disclosure, according to

[15] or

[16] ,

[0075] The frequency f sub It is above 2.0kHz.

[0076]

[18] As a technical solution of this disclosure, according to any one of [1] to

[17] ,

[0077] The hole is equipped with a dust filter.

[0078] The acoustic impedance of the dust filter is 4000 kg / m. 2 s or more.

[0079]

[19] As a technical solution of this disclosure, according to any one of [1] to

[18] ,

[0080] The detection unit is configured to include a microstructure suspended in the air.

[0081]

[20] As a technical solution of this disclosure, according to any one of [1] to

[19] ,

[0082] The vibration source is located inside the housing.

[0083] The effects of the invention

[0084] According to this disclosure, a device with gas detection function that can detect the gas being detected with high precision can be provided. Attached Figure Description

[0085] Figure 1 This is a diagram illustrating a structural example of a device with gas detection function according to this embodiment.

[0086] Figure 2 This is a diagram illustrating a structural example of a device with a vent pipe and gas detection function.

[0087] Figure 3 This is a diagram illustrating a structural example of a device with a gas detection function and a dust filter at the aperture.

[0088] Figure 4 This is a graph showing an example of the numerical calculation results for noise intensity.

[0089] Figure 5 This is another example of a graph representing the numerical calculation results of noise intensity.

[0090] Explanation of reference numerals in the attached figures

[0091] 1. Equipment with gas detection function; 10. Housing; 20. Vibration source; 30. Base plate; 40. Gas measuring unit; 41. Detection unit; 42. Gas detection space; 43. Hole; 44. Vent pipe; 45. Dust filter; 50. Circuit. Detailed Implementation

[0092] Hereinafter, an embodiment of the device with gas detection function according to the present disclosure will be described with reference to the accompanying drawings. In the drawings, the same or equivalent parts are labeled with the same reference numerals. In the description of this embodiment, the description of the same or equivalent parts will be appropriately omitted or simplified.

[0093] <Equipment>

[0094] Figure 1 This diagram illustrates the structure of the device 1 with gas detection function according to this embodiment. The gas detection function refers to, for example, the function of detecting the concentration of a gas to be detected, such as air. The device with gas detection function includes a housing 10, a vibration source 20, a substrate 30, and a gas measuring unit 40. The gas measuring unit 40 includes a detection unit 41 and a gas detection space 42. An opening 43 for gas to pass through is provided in the gas detection space 42. Here, the gas, as an example, can include air, i.e., the gas to be detected. In the following description, air will be used as the gas. As in this embodiment, device 1 may include a circuit 50. Furthermore, device 1 may further include a display unit such as a display.

[0095] In this embodiment, the device 1 has a vibration source 20 mounted on a housing 10, and a gas measuring unit 40 disposed inside the housing 10. Furthermore, the gas measuring unit 40 is separated within the housing 10 by a partition, and a gas detection space 42 exists within this partitioned space. The device 1 is configured to have a gas measuring unit 40 and a circuit 50 on a substrate 30. The gas measuring unit 40 is configured to include a detection unit 41 provided on the substrate 30 and a gas detection space 42 with a hole 43. The gas detection space 42 can be configured as the internal space of a partition with a partially provided hole 43.

[0096] Device 1 includes a wide variety of devices, such as electrical products, especially electronic devices. Device 1 can be an electronic device with an audio function, which enables communication, entertainment, and information notification based on sound and music. Specific examples include a music player, smart speaker, smart home device, smartphone, or headset. Additionally, device 1 can be a device that provides air conditioning functionality. Specific examples include an air conditioner, air purifier, exhaust fan, and HVAC (Heating, Ventilation, and Air Conditioning) equipment. Here, the aforementioned audio function or air conditioning function operates independently of the gas detection function, for example, based on the user's operation. Therefore, during the detection of the gas in the gas measuring unit 40, noise may increase due to irregular sounds, vibrations, etc. (hereinafter referred to as "noise").

[0097] <Shell>

[0098] Housing 10 is the outer shell of device 1 and functions to hold vibration source 20. Housing 10 may also hold substrate 30. Housing 10 can be made of metal, glass, resin, or composite materials thereof. Housing 10 may include switches, power connectors, communication connectors, displays, antennas, input interfaces, cameras, LiDAR (light detection and ranging) sensors, infrared cameras, microphones, indicator lights, heat sinks, etc.

[0099] <Vibration Source>

[0100] The vibration source 20 vibrates to perform an acoustic function or an air conditioning function. In this embodiment, the vibration source 20 emits sound. As a specific example, the vibration source 20 is a loudspeaker. As another example, the vibration source 20 can circulate air. As a specific example, the vibration source 20 is a motor. The vibration source 20 is located outside the gas measuring unit 40. In this embodiment, the vibration source 20 is mounted on the housing 10, but the mounting position is not limited. For example, the vibration source 20 can be mounted on the substrate 30. In addition, the vibration source 20 can be located inside or outside the housing 10.

[0101] <Substrate>

[0102] The substrate 30 functions to hold the gas measuring unit 40. In this embodiment, the substrate 30 also holds the circuit 50. Additionally, the substrate 30 sometimes also holds the vibration source 20. The substrate 30 is made of materials such as paper, glass cloth, polyimide film, PET film, or ceramic. The resin used is, for example, phenolic resin, epoxy resin, polyimide resin, bismaleimide triazine resin, fluororesin, or polyphenylene ether resin.

[0103] <Gas Measurement Department>

[0104] The gas measuring unit 40 detects the gas to be detected. In detail, the gas measuring unit 40 measures the concentration of the gas to be detected in the air and outputs an electrical signal indicating the measurement result. The gas measuring unit 40 can be a known non-dispersive infrared absorption type gas concentration measuring device. Examples of gases to be detected include carbon dioxide, water vapor, carbon monoxide, nitric oxide, ammonia, sulfur dioxide, alcohols, formaldehyde, and hydrocarbon gases such as methane and propane. The gas measuring unit 40 has a detection unit 41, a gas detection space 42, and an aperture 43.

[0105] <Testing Department>

[0106] In measuring the concentration of the gas to be detected in the gas (air) present in the gas detection space 42, the detection unit 41 detects changes corresponding to the amount of the gas to be detected. In this embodiment, the detection unit 41 includes a light-emitting element and a light-receiving element. The light emitted by the light-emitting element passes through the gas detection space 42, is absorbed and attenuated according to the amount of the gas to be detected, and is received by the light-receiving element. The amount of the gas to be detected can be measured based on the amount of light attenuation. Examples of light-emitting elements include LEDs (Light Emitting Diodes), lamps, lasers (light amplification by stimulated emission of radiation), organic light-emitting elements, MEMS (Micro Electro Mechanical Systems) heaters, VCSELs (Vertical Cavity Surface Emitting Lasers), etc. Examples of light-receiving elements include photodiodes, phototransistors, thermopile, thermoelectric sensors, calorimeters, etc. The detection unit 41 can be configured to include a microstructure suspended in the air using MEMS technology. The detection unit 41 can include resin materials, metal encapsulation, etc., as protective components to protect the light-emitting element and the light-receiving element. The detection unit 41 may be equipped with an optical filter that limits the wavelength of light.

[0107] Here, as another structural example, the detection unit 41 can include a heating element and a resistor. For example, by flowing current, heat emitted from the heating element is conducted to the gas to be detected in the gas detection space 42, and the temperature rise of the heating element corresponding to the amount of gas to be detected is detected as a change in resistance. The heating element is, for example, a MEMS heater, a lamp, etc. Alternatively, as another structural example, the detection unit 41 can include a light-emitting element and a pressure-sensitive element. The light emitted by the light-emitting element is absorbed in the gas detection space 42 according to the amount of gas to be detected, causing the temperature and pressure of the air in the gas detection space 42 to rise. Based on the pressure rise detected by the pressure-sensitive element, the amount of gas to be detected can be measured. The pressure-sensitive element is, for example, a MEMS pressure sensor, a microphone, etc.

[0108] <Gas Detection Space>

[0109] The gas detection space 42 is separated from the outer wall and has the function of containing gases such as air within its interior space. The gas contained in the gas detection space 42 is replaced through the hole 43. The outer wall of the gas detection space 42 is formed of metal or resin, etc.

[0110] <Kong>

[0111] Hole 43 is a hole provided on the outer wall of the gas detection space 42. Gas passes through hole 43, replacing the gas inside the gas detection space 42. Sometimes there may be multiple holes 43.

[0112] Here, as Figure 2 As shown, the orifice 43 may additionally be equipped with a vent pipe 44. The vent pipe 44 provides a space to restrict gas flow and guides the gas to the gas detection space 42. The vent pipe 44 may be an additional component, possibly a portion of the housing 10 that is tubular and connected to the external space, or it may be formed by extending the orifice 43 in a tubular shape. Furthermore, as... Figure 3 As shown, hole 43 can be equipped with a dust filter 45 for dust prevention.

[0113] <Circuit>

[0114] Circuit 50 can control the entire device 1. For example, circuit 50 can control vibration source 20. Additionally, circuit 50 can perform calculations on the output signal from gas measuring unit 40 to obtain the concentration of the gas being detected. Circuit 50 can be configured to include more than one processor. The processor can be, for example, a general-purpose processor or a dedicated processor for a specific process, but is not limited to this; any processor can be used.

[0115] <Explanation of the principle>

[0116] In the gas detection space 42, gas is replaced through the hole 43, i.e., it enters and exits, but resonance occurs due to the entry and exit of gas near a specific frequency. This is similar to the Helmholtz resonance phenomenon, in which the sound of a specific pitch resonates and echoes due to external vibration and airflow in musical instruments such as guitars and ocarinas, as well as in bottles, with holes in the cavity. The Helmholtz resonance phenomenon is a phenomenon in which the gas inside the cavity acts as an air spring, and the gas around the hole acts as a weight and as an oscillator with a resonant frequency. Due to the Helmholtz resonance phenomenon, the gas in the gas detection space 42 vibrates. The density change caused by the vibration is detected by the detection unit 41 as a change in the concentration of the gas being detected, thereby leading to a deterioration in detection accuracy. In particular, when the detection unit 41 is configured to include a fine structure suspended in the air, the fine structure may sometimes deform due to the vibration of the gas, further leading to a deterioration in detection accuracy.

[0117] The resonant frequency f (sometimes simply called frequency f) of the Helmholtz resonance phenomenon depends on the volume V of the gas detection space 42, the effective length L of the aperture 43, and the cross-sectional area S of the aperture 43. The frequency band with high noise intensity caused by music or sound in an indoor environment is the 100Hz to 2.0kHz band, with a peak particularly near 500Hz. The frequency band with high noise intensity caused by the operation of air conditioners, etc., is the 10Hz to 300Hz band, with a peak particularly near 100Hz. As described above, device 1 provides an acoustic function or air conditioning function, with noise emitted by vibration source 20. In cases where the resonant frequency f of the gas measuring unit 40 overlaps with the peak of the high-intensity noise band, the Helmholtz resonance phenomenon is considered easily excited, affecting the detection unit 41 and thus degrading the detection accuracy. In this embodiment, the gas measuring unit 40 is designed to separate the resonant frequency f from the peak wavelength of the noise intensity to avoid exciting the Helmholtz resonance phenomenon. That is, it is designed so that the resonant frequency f satisfies the condition 500Hz < f < 100Hz. More preferably, the design separates the resonant frequency f from the peak wavelength of the noise intensity, and also from the harmonics, satisfying the condition 1.0 kHz < f < ◆ Hz. Even more preferably, the design separates the resonant frequency f from the frequency band with higher noise intensity, satisfying the condition 2.0 kHz < f < ◆ Hz or ◆ Hz < f < 100 Hz. The frequency is given as in the following equation (9).

[0118]

Mathematical Expression 3

[0119]

[0120] Here, Figure 4This represents the numerical calculation result of the noise intensity brought to the detection unit 41 due to the Helmholtz resonance phenomenon when the resonant frequency f of the gas measuring unit 40 is changed. As a model of the sound emitted from the vibration source 20, the long-term average sound spectrum of male and female Japanese under the "loud" condition in Fig. 3 of the reference (Kimio Shiraishi et al. "Amplification rationale for hearing aids based on chracteristecs of the Japanese language" May 15, 2021) is used. The sound passes through the gas measuring unit 40 along the hole 43. When the resonant frequency f is changed by changing the shape of the gas measuring unit 40, the air vibration energy generated in the gas measuring unit 40 is simulated, and the noise energy intensity brought to the detection unit 41 is calculated. In the cavity with the hole that causes the Helmholtz resonance phenomenon, for the resonant frequency f determined by the shape of the cavity, the excitation action shows the same Lorentz distribution pattern as in the case of forced vibration with an applied external force. The excitation action, especially when energy loss within the cavity is small, picks up specific sounds near the resonant frequency f, approximating the excitation characteristics of the Dirac delta distribution. The model of the sound emitted from the vibration source 20 has a sharp intensity peak near 500 Hz, and the noise energy intensity is also the same, but by moving the resonant frequency f away from 500 Hz, the noise intensity can be rapidly reduced.

[0121] Here, Figure 5 This represents a numerical calculation of the additional noise intensity introduced to the detection unit 41 due to the Helmholtz resonance phenomenon when the resonant frequency f of the gas measuring unit 40 is varied. As a model of the sound emitted from the vibration source 20, measurement data of the noise from the air supply section during heating operation of the Hitachi central air conditioning "RAS-AJ36D(W)" indoor unit were used. Figure 4 Similarly, the air vibration energy generated when sound passes through the gas measuring section 40 along the hole 43, causing a change in the shape of the gas measuring section 40 and thus a change in the resonant frequency f, is simulated, and the noise energy intensity brought to the detection section 41 is calculated. The model of the sound emitted from the vibration source 20 has a sharp peak intensity near 100Hz, and the noise energy intensity is also the same, but by moving the resonant frequency f away from 100Hz, the noise intensity can be rapidly reduced.

[0122] Here, when the orifice 43 is equipped with a vent pipe 44, the cross-sectional area S is the average cross-sectional area of ​​the orifice 43 and the vent pipe 44. Additionally, c is the speed of sound, for example, 337.7 m / s in air at 10°C, 346.5 m / s in air at 25°C, and 349.4 m / s in air at 30°C. t is approximated as 331.5 + 0.61t [m / s], taking the temperature in Celsius. When the concentration of the gas being detected is low, these values ​​can be appropriately selected based on the room temperature. When the concentration of the gas being detected is high, if the density of the gas in the gas detection space 42 is set as ρ, γ as the specific heat ratio, and p as the pressure, the speed of sound c is given as in the following equation (10).

[0123]

Mathematical Expression 4

[0124]

[0125] <Effective Length L>

[0126] Here, the effective length L of the hole 43 varies depending on the shape of the hole 43 and the length L' obtained by adding the length of the hole 43 and the length of the vent pipe 44. If the opening shape is circular and the radius is set to a, the following formula (11) is given.

[0127]

Mathematical Expression 5

[0128] L=L′+1.5a... Equation (11)

[0129] When the outlets of orifice 43 and vent pipe 44 become flat, the following equation (12) is given.

[0130]

Mathematical Expression 6

[0131] L=L′+1.7a... Equation (12)

[0132] Furthermore, when the cross-sectional shapes of the orifice 43 and the vent pipe 44 are irregular, the following formula (13) is given. Here, S out It is the area of ​​the outlet opening of hole 43 and vent pipe 44.

[0133]

Mathematical Expression 7

[0134]

[0135] The effective length L is calculated relative to the length L' obtained by adding the lengths of orifice 43 and vent pipe 44, and is adjusted according to the shape of the opening of orifice 43. This adjustment corresponds to the opening end correction. In addition to the amount of gas vibration within vent pipe 44, the gas near the opening also contributes to the vibration. Therefore, opening end correction is required. The vibration of the gas near the opening depends on the area of ​​the outlet opening, as shown in equation (13), to the area S out The gas up to the square root of the height contributes to vibration.

[0136] When the aperture 43 is small enough, a Helmholtz resonance phenomenon occurs. Furthermore, the Helmholtz resonance phenomenon occurs when the amount of gas in the gas detection space 42, which acts as an air spring, is greater than the amount of gas that contributes to vibration as a weight. In the device 1 with gas detection function, the volume V of the gas detection space 42 is relatively large, and in this embodiment, the following equation (14) holds true.

[0137]

Mathematical Expression 8

[0138] V>10LS...Equation (14)

[0139] In addition, in order for the detection unit 41 to detect the gas being detected, the volume V of the gas detection space 42 needs to be relative to the volume V of the detection unit 41. sen Sufficiently large, in this embodiment, the following formula (15) holds. Here, the volume V of the detection unit 41 is... sen It is the external dimension of the detection unit 41, and the volume of the smallest cuboid including the detection unit 41.

[0140]

Mathematical Expression 9

[0141] V > 2V sen ...formula (15)

[0142] Furthermore, when the ratio of the detection unit 41 to the gas detection space 42 is relatively large, the proportion of vibration energy absorbed due to the Helmholtz resonance generated within the gas measurement unit 40 increases, thus significantly affecting the small gas sensor. By designing the resonant frequency f to be in a noise-free frequency band, the detection accuracy can be significantly improved. In other words, in this embodiment, the volume V of the gas detection space 42 is relatively large compared to the volume V of the detection unit 41. sen In this regard, the following formula (16) holds, and more preferably, formula (17) holds.

[0143]

Mathematical Formula 10

[0144] V > 400V sen ...formula (16)

[0145]

Mathematical Expression 11

[0146] V < 100V sen ...formula (17)

[0147] Furthermore, especially when a thermal light source is used in the detection unit 41, the chopping frequency based on so-called chopping control cannot be increased because the intermittent switching of the light source at high speed cannot be performed. Therefore, it is difficult to separate noise caused by noise from the output signal modulated by chopping using frequency separation. By designing the resonant frequency f to be in a noise-free band, the detection accuracy can be significantly improved. That is, when the chopping frequency fc is below 500Hz, the detection accuracy can be significantly improved by designing the resonant frequency f to be in a noise-free band. Moreover, even without a thermal light source, the detection accuracy can be significantly improved without the need for high-speed chopping control using a dedicated control IC that requires significant design technology and expense.

[0148] <Configuration of vibration sources and detection units within the housing>

[0149] As described above, by designing the gas measuring unit 40 in a way that limits the range of frequency f, the detection accuracy of the gas being detected can be improved. Here, to further improve detection accuracy, it is preferable to also address the transmission path of vibration from the vibration source 20. The vibration emitted by the vibration source 20 is transmitted to the detection unit 41, for example, through the gas inside the housing 10 and the substrate 30. Therefore, it is preferable to design the system to adjust the relative positional relationship between the vibration source 20 inside the housing 10 and the detection unit 41 on the substrate 30 to weaken the vibration transmitted to the detection unit 41.

[0150] First, when studying the transmission path of the gas through the housing 10, the housing 10 is considered to function as a resonant chamber. Due to the vibration of the resonant mode, the vibration of the gas inside the housing 10 increases. When the vibration source 20 is located at the trough of the resonant mode (a position with large variation), a large vibration is applied to the detection unit 41, resulting in a deterioration in detection accuracy. Therefore, in order to improve the detection accuracy of the gas being detected, the vibration source 20 is preferably placed away from the trough of the resonant mode of the housing 10, preferably at a node position. Here, since the low-order mode of the resonant mode has a defined shape, the position of the node can be determined in the design. Specifically, when the housing 10 is cuboid, cylindrical, or spherical, the plane of symmetry, axis of symmetry, or center point becomes the node of the resonant mode of the sound pressure. For example, the center of opposite sides is a node. By placing the vibration source 20 here, the amount of vibration transmitted from the vibration source 20 to the detection unit 41 is reduced, and as a result, the detection accuracy of the device 1 can be improved.

[0151] Here, the crest-to-crest length of the resonance mode is determined by the dimensions of the housing 10. Let the volume of the housing 10 be V. husThe typical length L hus Let the volume be V hus The length of the cube root, or the distance from the inner wall of the shell 10 to the node, is the length along a certain direction at a distance L from the node. hus The detection unit 41 can be placed at position / 10. Typical length L hus Depending on the shape of the housing 10, the cube root can be used when the length of the side of the housing 10 is the same in three directions, and the distance from the inner wall surface to the nodal can be used for other shapes.

[0152] Furthermore, the end portion of the housing 10 becomes the location of the wave crest of the resonance mode. Therefore, by removing the end portion of the housing 10 and arranging the vibration source 20, the amount of vibration transmitted from the vibration source 20 to the detection unit 41 is reduced, and as a result, the detection accuracy of the device 1 can be improved. For example, the detection unit 41 can be arranged at a distance L from the end of the housing 10. hus The / 5 position can be placed closer to the inside.

[0153] Here, the housing 10 is sometimes formed into a shape more complex than a cuboid, cylindrical, or spherical shape. However, since the operation of low-order resonance modes is qualitatively the same, a cuboid, cylindrical, or spherical shape is used to approximate the housing 10 with minimal volume error. The vibration source 20 or the detection unit 41 is positioned at the defined nodes, rather than at the crests. For example, the vibration source 20 or the detection unit 41 can be located on the plane of symmetry (node ​​position) of a cuboid approximately defined relative to the housing 10. Alternatively, the vibration source 20 or the detection unit 41 can be located on the axis of symmetry (node ​​position) of a cylinder approximately defined relative to the housing. Furthermore, the vibration source 20 or the detection unit 41 can be located at the center point (node ​​position) of a sphere approximately defined relative to the housing.

[0154] <Configuration of vibration source and detection unit on substrate>

[0155] With the periphery of the substrate 30 fixed, it operates as a resonant plate that does not vibrate in its surroundings. When the vibration source 20 is located at the trough of the resonance mode, the resonance mode vibration of the substrate 30 effectively transfers energy. At this time, the vibration of the substrate 30 increases, and vibration is applied to the detection unit 41 through the substrate 30. As a result, the vibration is detected by the detection unit 41 as an electrical signal, resulting in a deterioration in detection accuracy. In addition, since the detection unit 41 is located at the trough of the resonance mode, a large vibration is applied to the detection unit 41. As a result, the vibration is detected by the detection unit 41 as an electrical signal, thereby leading to a deterioration in detection accuracy.

[0156] At this point, based on the resonance mode analysis of the rectangular or circular plate, the ends and axis of symmetry of the substrate 30 are nodes. By arranging the vibration source 20 or the detection unit 41 at the node positions, the amount of vibration emitted by the vibration source 20 transmitted to the detection unit 41 is reduced. As a result, the detection accuracy of the device 1 can be improved.

[0157] Here, the crest-to-crest length of the resonant mode is determined by the dimensions of the substrate 30. If the area of ​​the substrate 30 is set as S... sub The typical length L sub Let the area be S sub If the square root is obtained, then the vibration source 20 or the detection unit 41 only needs to be positioned at a distance L from the node. sub The position is / 10.

[0158] Furthermore, the central portion of the substrate 30 is referred to as the location of the wave crest of the resonance mode. Therefore, by removing the central portion of the substrate 30 and arranging the vibration source 20, the amount of vibration transmitted from the vibration source 20 to the detection unit 41 is reduced, thereby improving the detection accuracy of the device 1. The vibration source 20 or the detection unit 41 only needs to be arranged at a position L from the center of the substrate 30. sub The / 10 position can be placed on the outer side.

[0159] Here, the substrate 30 is sometimes formed into a shape more complex than a rectangular or circular plate. However, since the operation of low-order resonance modes is qualitatively the same, a rectangular or circular plate can be used to approximate the structure relative to the housing 10 in a way that minimizes volume error. The vibration source 20 or the detection unit 41 can be positioned at the nodes of the defined structure, rather than at the crests. For example, the vibration source 20 or the detection unit 41 can be located at the ends of a rectangle that is approximated relative to the substrate 30.

[0160] <House Dimensions>

[0161] Based on the resonance mode analysis of the cuboid case, the shell 10 has a frequency f approximately represented by the following equation (18). hus The lowest resonant frequency mode. By making the frequency f hus By moving away from the frequency band with high noise intensity or the frequency band with high noise intensity caused by the air conditioner, the vibration applied to the detection unit 41 can be suppressed, thereby improving the detection accuracy of the gas being detected in the device 1.

[0162]

Mathematical Expression 12

[0163]

[0164] f hus Preferably above 500Hz. hus More preferably, it is 1.0 kHz or higher. husFurther preferably, it is 2.0 kHz or higher. Additionally, f hus Preferably below 100Hz.

[0165] <Substrate Size>

[0166] Based on the resonance mode analysis of the rectangular plate, substrate 30 has a frequency f approximately represented by the following equation (19). sub The lowest resonance mode. By making the frequency f sub By moving away from the frequency band with high noise intensity or the frequency band with high noise intensity caused by the air conditioner, the vibration applied to the detection unit 41 can be suppressed, thereby improving the detection accuracy of the device 1 for the gas being detected.

[0167]

Mathematical Expression 13

[0168]

[0169] Here, E is the longitudinal elastic modulus. g is at a gravitational acceleration of 9.80665 m / s². 2 Given: σ is Poisson's ratio. h is the substrate thickness (30). γ is a dimensionless constant assigned by 3.65. f sub Preferably above 500Hz. sub More preferably, it is 1.0 kHz or higher. sub Further preferably, it is 2.0 kHz or higher. Additionally, f sub Preferably below 100Hz.

[0170] <Dust Filter>

[0171] Sometimes the aperture 43 is equipped with a dust filter 45, but the dust filter 45 is used to reflect or attenuate the vibration (sound) of the gas in the gas detection space 42, thereby suppressing the vibration applied to the detection unit 41. Therefore, the detection accuracy of the device 1 can be improved. The higher the acoustic impedance of the dust filter 45, the better its reflection or attenuation performance. Preferably, the acoustic impedance is sufficiently large relative to air, about 10 times or more, i.e., 4000 kg / m. 2 Above s. A more preferred acoustic characteristic impedance is 40000 kg / m. 2 Above s. Here, the acoustic characteristic impedance is determined by the dielectric density ρm [kg / m 3 The product of ] and the sound velocity Cm in the medium is given.

[0172] As described above, the device with gas detection function in this embodiment, based on the structure described above, can detect the gas being detected with high precision by suppressing the generation of vibrations that affect the gas measuring unit 40.

[0173] The embodiments of this disclosure have been described based on the accompanying drawings and examples. However, it should be noted that those skilled in the art can readily make various modifications or alterations based on this disclosure. Therefore, it should be understood that such modifications or alterations are included within the scope of this disclosure. For example, the functions included in each structural component can be reconfigured in a logically consistent manner, and multiple structural components can be combined into one or divided.

Claims

1. A device with gas detection function, wherein, This device with gas detection function has the following features: case; Vibration source; and The gas measuring unit, which is disposed inside the housing and separated by a partition, The vibration source is located outside the gas measuring unit. The gas measuring unit is configured to include a detection unit disposed on a substrate and a gas detection space having a hole for gas to pass through. With the volume of the gas detection space set as V, the cross-sectional area of ​​the orifice set as S, the effective length of the orifice set as L, and the speed of sound set as c, the frequency f shown in the following formula (1) is above 500 Hz. 。 2. The device with gas detection function according to claim 1, wherein, The hole is equipped with a vent pipe. With the length obtained by adding the lengths of the hole and the vent pipe as L', and the radius of the hole as a, the effective length is given by the following formula (2). 。 3. The device with gas detection function according to claim 1, wherein, The hole is equipped with a vent pipe. The outlets of the hole and the vent pipe become flat. With the length obtained by adding the lengths of the hole and the vent pipe as L', and the radius of the hole as a, the effective length is given by the following formula (3). 。 4. The device with gas detection function according to claim 1, wherein, The hole is equipped with a vent pipe. The cross-sectional shapes of the hole and the vent pipe are irregular. Let L' be the length obtained by adding the lengths of the hole and the vent pipe, and let S be the area of ​​the outlet opening of the hole and the vent pipe. out In this case, the effective length is given by the following formula (4), 。 5. The device with gas detection function according to any one of claims 1 to 4, wherein, The frequency f is above 1.0 kHz.

6. The device with gas detection function according to any one of claims 1 to 4, wherein, The frequency f is above 2.0 kHz.

7. A device with gas detection function, wherein, This device with gas detection function has the following features: case; Vibration source; and The gas measuring unit is disposed inside the housing. The gas measuring unit is configured to include a detection unit disposed on a substrate and a gas detection space having a hole for gas to pass through. The hole is equipped with a vent pipe. The cross-sectional shapes of the hole and the vent pipe are irregular. Let L' be the length obtained by adding the lengths of the hole and the vent pipe, and let S be the area of ​​the outlet opening of the hole and the vent pipe. out In this case, the effective length L of the hole is given by the following formula (5), With the volume of the gas detection space set as V, the cross-sectional area of ​​the orifice set as S, and the speed of sound set as c, the frequency f shown in the following formula (6) is below 100Hz. 。 8. The device with gas detection function according to claim 1 or 7, wherein, The vibration source or the detection unit exists on a plane of symmetry of a cuboid approximately defined relative to the housing.

9. The device with gas detection function according to claim 1 or 7, wherein, The vibration source or the detection unit exists on a cylindrical axis of symmetry approximately defined relative to the housing.

10. The device with gas detection function according to claim 1 or 7, wherein, The vibration source or the detection unit is located at the center point of a sphere approximately defined relative to the housing.

11. The device with gas detection function according to claim 1 or 7, wherein, The vibration source or the detection unit is located at one end of a rectangle approximately defined relative to the substrate.

12. The device with gas detection function according to claim 1 or 7, wherein, Let the cube root of the volume of the shell be a typical length L. hus In the case of the following equation (7), the frequency f is shown. hus Above 500Hz 。 13. The device with gas detection function according to claim 1 or 7, wherein, The volume V of the gas detection space, the effective length L, and the cross-sectional area S satisfy the following formula (14). 。 14. The device with gas detection function according to claim 1 or 7, wherein, Let the volume of the detection unit be V. sen In the case of the gas detection space volume V and the detection unit volume V sen The following equations (15) and (16) are satisfied. 。 15. The device with gas detection function according to claim 12, wherein, The detection unit is positioned at an end L that is at a distance from the housing. hus / 5 is located in the inner part.

16. The device with gas detection function according to claim 12, wherein, The frequency f hus It is above 1.0kHz.

17. The device with gas detection function according to claim 12, wherein, The frequency f hus It is above 2.0kHz.

18. The device with gas detection function according to claim 1 or 7, wherein, Let the acceleration due to gravity be g, and the area of ​​the substrate be S. sub Let the longitudinal elastic modulus of the substrate be E, the thickness of the substrate be h, the Poisson's ratio be σ, the dimensionless constant γ be 3.65, and the square root of the area of ​​the substrate be the typical length L. sub In the case of the following equation (8), the frequency f is shown. sub Above 500Hz 。 19. The device with gas detection function according to claim 18, wherein, The frequency f sub It is above 1.0kHz.

20. The device with gas detection function according to claim 18, wherein, The frequency f sub It is above 2.0kHz.

21. The device with gas detection function according to claim 18, wherein, The vibration source or the detection unit is positioned at a distance L from the center of the substrate. sub / 10 is located on the outer side.

22. The device with gas detection function according to claim 1 or 7, wherein, The hole is equipped with a dust filter. The acoustic impedance of the dust filter is 4000 kg / m. 2 s or more.

23. The device with gas detection function according to claim 1 or 7, wherein, The detection unit is configured to include a microstructure suspended in the air.

24. The device with gas detection function according to claim 1 or 7, wherein, The vibration source is located inside the housing.

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