Odor detection apparatus

Abstract

To provide a novel odor detection apparatus capable of improving detection sensitivity by reducing an influence of photoacoustic waves (noise) caused by a resist on a substrate.SOLUTION: A photoacoustic sensor used in an odor detection apparatus includes a detection chamber 14 formed by a space defined by a box-shaped housing 13 having one open side and a substrate 11 covering the opening. On a surface 11A of the substrate 11 on a detection chamber 14 side, at least a light-emitting element 17 and a control / drive module for the light-emitting element 17 are mounted. Further, on the surface 11A of the substrate 11 forming the detection chamber 14, a resist 21 is absent, or even if the resist 21 is present, the resist is not exposed to the detection chamber side. According to this configuration, an influence of photoacoustic waves (noise) caused by the resist is reduced, thereby improving detection sensitivity.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an odor detection device that detects components of a gas (hereinafter also referred to as gas) that causes an odor, and more particularly to an odor detection device that detects an odor using a photoacoustic sensor. [Background technology]

[0002] At manufacturing sites for fermented products such as miso and soy sauce, as well as at cosmetics manufacturing sites and food storage warehouses, smell (also known as aroma) is a quality control item, but it is difficult to implement digital transformation (DX).As a result, smell identification relies on the experience and senses of on-site workers, resulting in increased management and training costs.

[0003] Recently, attempts have been made to improve the efficiency of quality control through digitalization by using odor sensors to quantify odors (type of gas, concentration, etc.). Quantifying odors requires gas sensors that can detect gas components or odor components according to the purpose. For example, photoacoustic sensors using the photoacoustic effect, as described in Patent Document 1, have been proposed as sensors for detecting gas components and odor components.

[0004] The photoacoustic effect is a phenomenon in which, when light of a specific wavelength (laser light, LED light, etc.) is irradiated onto molecules of specific components that make up a gas, the molecules that absorb the light release heat, which causes them to expand and generate photoacoustic waves.Photoacoustic sensors can apply this acoustic effect to distinguish gases and scents, and because they are small and can detect gas components with high sensitivity, they are being applied to a variety of manufacturing sites. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-26652 Summary of the Invention [Problem to be solved by the invention]

[0006] In a photoacoustic sensor, for example, a light-emitting cell control / drive module that applies a pulsed electric signal to a light-emitting element such as an LED element, and a microphone control / drive module for a microphone that detects the generated photoacoustic waves are arranged on a substrate that forms a detection chamber. This detection chamber consists of a space formed by a box-shaped housing with one open end and a substrate that covers the opening of the box-shaped housing.

[0007] The light-emitting cell control / drive module of the light-emitting element and the microphone control / drive module of the microphone are surface-mounted on the surface of the substrate facing the space. For this reason, a resist is provided on the surface of the substrate to protect the circuit pattern and to cover it so that solder does not adhere to unnecessary parts.

[0008] Light emitted from the light-emitting element, such as infrared light, is reflected by the inner wall of the box-shaped housing and irradiates the resist on the substrate. It has been discovered that specific components contained in the resist are thermally excited by the infrared light, generating photoacoustic waves. Because this photoacoustic wave generates a signal synchronized with the photoacoustic wave of the target gas component, it is impossible to separate the signal due to the target gas from the signal component due to the resist, and the photoacoustic wave due to the resist becomes unnecessary noise. This noise reduces the noise-to-signal ratio, resulting in the inability to detect low concentrations of gas and the inability to improve detection sensitivity.

[0009] An object of the present invention is to provide a novel odor detection device that can reduce the influence of photoacoustic waves (noise) caused by the resist of a substrate and improve detection sensitivity. [Means for solving the problem]

[0010] The present invention is an odor detection device equipped with a photoacoustic wave sensor, which has a detection chamber consisting of a space formed by a box-shaped housing with one open end and a substrate covering the opening of the housing, and is characterized in that at least a light-emitting cell is mounted on the surface of the substrate facing the detection chamber, and no resist is present on the surface of the substrate forming the detection chamber, or even if resist is present, the resist is not exposed on the detection chamber side. [Effects of the Invention]

[0011] According to the present invention, the influence of photoacoustic waves (noise) caused by the resist can be reduced, and detection sensitivity can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a photoacoustic sensor used in a conventional odor detection device. [Figure 2] 1 is a configuration diagram showing the configuration of a photoacoustic sensor according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a configuration diagram showing a circuit pattern of the photoacoustic sensor shown in FIG. 2. [Figure 4] FIG. 4 is a configuration diagram showing the configuration of a photoacoustic sensor according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a configuration diagram showing the configuration of a photoacoustic sensor according to a third embodiment of the present invention. [Figure 6] FIG. 6 is a configuration diagram showing a circuit pattern of the photoacoustic sensor shown in FIG. 5. [Figure 7] FIG. 10 is a configuration diagram showing the configuration of a photoacoustic sensor according to a fourth embodiment of the present invention. [Figure 8] FIG. 10 is a configuration diagram showing the configuration of a photoacoustic sensor according to a fifth embodiment of the present invention. [Figure 9] FIG. 10 is a configuration diagram showing the configuration of a photoacoustic sensor according to a sixth embodiment of the present invention. [Figure 10] FIG. 10 is a configuration diagram showing the configuration of a photoacoustic sensor according to a seventh embodiment of the present invention. [Figure 11]FIG. 13 is a configuration diagram showing the configuration of a photoacoustic sensor according to an eighth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and application examples within the technical concept of the present invention are also included within its scope.

[0014] First, the configuration and operation of the photoacoustic sensor used in the odor detection device, as well as the above-mentioned problems, will be briefly described.

[0015] In Fig. 1, the odor detection device includes at least a photoacoustic sensor 10. The photoacoustic sensor 10 is disposed on one surface (hereinafter referred to as the "surface") of a flat substrate (e.g., a resin substrate, etc.) 11. In particular, the photoacoustic sensor 10 is provided on surface 11A of the substrate 11, on which a control / drive module, etc., is mounted. In this way, the substrate 11 and the photoacoustic sensor 10 are integrated into an assembly as a whole. Therefore, this assembly can be incorporated into a box made of metal, synthetic resin, or the like, and assembled into an odor detection device.

[0016] The control / drive module mounted on the substrate 11 has the function of controlling the light emission frequency and light intensity of the light emitting means described below, and the function of measuring photoacoustic waves from the microphone 12. For this reason, by placing the control / drive module of the photoacoustic cell 10 on the surface 11A of the substrate 11, it is possible to easily connect wiring to the LED element and microphone.

[0017] The photoacoustic sensor 10 includes a housing 13 made of a metal material or a resin material, and a detection chamber 14 having a predetermined spatial volume is formed inside the housing 13. The detection chamber 14 is a hollow space formed by the substrate 11 and the housing 13, and the shape of this space can be formed into a cylindrical shape or a rectangular parallelepiped shape. In this embodiment, which will be described later, the shape of the space is determined to be a cylindrical shape.

[0018] A through hole 15 that fluidly connects the detection chamber 14 to the outside is formed in the wall of the housing 13 on the side opposite the substrate 11 from the detection chamber 14.

[0019] The number of through-holes 15 may be one or more, as long as they have an inflow area that allows the necessary amount of measurement gas to be smoothly introduced into the detection chamber 14. An open / close lid 16 is provided on the light-transmitting hole 15, which closes the light-transmitting hole 15 to prevent the pressure in the detection chamber 14 from escaping to the outside when the measurement gas is being detected.

[0020] Here, the outside refers to a space where the gas to be measured, such as the atmosphere, exists, and corresponds to the manufacturing site or storage warehouse described above. Therefore, the measurement gas present in the manufacturing site or storage warehouse flows into the detection chamber 14 through the through hole 15.

[0021] A light-emitting cell 17 is placed in the detection chamber 14. The light-emitting cell 17 is composed of an LED element 18, which is a light-emitting element, a cell housing 19 that surrounds the LED element 18 from the outside, and an optical filter 20 provided in the cell housing 19.

[0022] The optical filter 20 and the LED element 18 are arranged so as to overlap in the light-emitting direction, and have the function of transmitting light of a predetermined wavelength from the LED element 18. In this example, an optical filter 20 that transmits infrared light is used.

[0023] The LED element 18 emits light in a pulsed manner at a predetermined frequency, thermally exciting a specific component of the measurement gas in the detection chamber 14. The LED element 18 is provided on the surface 11A side of the substrate 11, and is controlled and driven by a light-emitting cell control / drive module (not shown). Note that instead of the LED element 18, a semiconductor laser, an IR emitter, or the like may also be used as light-emitting means.

[0024] A microphone 12 for measuring the intensity of the photoacoustic wave is disposed in the detection chamber 14. The microphone 12 is provided on the surface 11A side of the substrate 11, and is controlled and driven by a microphone control / drive module (not shown).

[0025] In this way, the photoacoustic wave AW generated by the light emission of the LED element 18 is measured by the microphone 12, and the intensity of the photoacoustic wave AW measured by the microphone 12 is converted into an electrical signal. These processes are performed by a control circuit such as that shown in Patent Document 1, for example.

[0026] In the photoacoustic sensor 10 described above, the light emitting cell control / drive module for the LED element 18 and the microphone control / drive module for the microphone 12 are surface-mounted on the surface 11A on the space side (detection chamber side) of the substrate 11. For this reason, a resist 21 is provided on the surface 11A of the substrate 11 to protect the circuit pattern and to cover it so that solder does not adhere to unnecessary portions. Note that the thickness of the resist 21 is exaggerated in the drawing.

[0027] Incidentally, light emitted from the LED element 18, such as infrared light, is reflected by the inner wall of the box-shaped housing 13 and irradiates the resist 21 on the surface 11A of the substrate 11. It has been found that at this time, components contained in the resist 21 are thermally excited by the infrared light and generate photoacoustic waves AWn. Since these photoacoustic waves AWn are synchronized with the photoacoustic waves of the gas components to be measured, the photoacoustic waves AWn originating from the resist 21 become unnecessary noise. This causes a problem in that it is not possible to improve detection sensitivity.

[0028] In order to solve the above problems, the present invention proposes an odor detection device having the following configuration.

[0029] That is, it is an odor detection device equipped with a photoacoustic wave sensor, and the photoacoustic sensor has a detection chamber consisting of a space formed by a box-shaped housing with one opening and a substrate covering the opening of the housing, and at least a light-emitting cell is mounted on the surface of the substrate facing the detection chamber, and there is no resist on the surface of the substrate forming the detection chamber, or even if there is resist, the resist is not exposed on the detection chamber side.

[0030] This makes it possible to reduce the influence of photoacoustic waves (noise) caused by the resist and improve detection sensitivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [Example]

[0031] First, a first embodiment of the present invention will be described with reference to the drawings. In the drawings of the following embodiments, the same reference numbers as those shown in Figure 1 indicate the same or similar components and parts, and therefore, explanations thereof will be omitted unless necessary.

[0032] 2, housing 13 has an opening on one side and a space formed on the other side with an upper wall 13A, and substrate 11 is disposed on the open side so as to cover the opening, thereby forming detection chamber 14. As described above, light-emitting cell 17 and microphone 12 are surface-mounted on surface 11A of substrate 11 on the detection chamber 14 side.

[0033] The microphone 12 may be mounted on the back surface 11B opposite to the front surface 11A of the substrate 11. This will be described in another embodiment.

[0034] Resist 21 is provided on the contact surface between the housing 13 and the surface 11A of the substrate 11, and on the surface 11A of the substrate 11 located outside the housing 13. Resist 21 has the function of protecting the circuit pattern and preventing solder from adhering to unnecessary areas.

[0035] However, this resist 21 is not provided on the surface 11A of the substrate 11 corresponding to the detection chamber 14, that is, the resist 21 is not present on the surface 11A of the substrate 11 that forms the detection chamber 14. Therefore, it is possible to prevent components contained in the resist 21 from being thermally excited by infrared light and generating photoacoustic waves AWn.

[0036] Here, taking into consideration the problem of solder adhering to unnecessary areas due to the absence of resist, this embodiment addresses the problem of solder flow caused by not applying resist by connecting the light-emitting cell 17, the control / drive module that applies an electrical signal to this light-emitting cell 17, and the circuit pattern via a through hole.

[0037] 2 and 3, circuit patterns 22L and 22M are embedded inside the substrate 11. Note that the letter "L" in the numbers indicates a component related to the LED element 18, and the letter "M" indicates a component related to the microphone 12. This also applies to some of the embodiments described below.

[0038] Here, the circuit patterns 22L and 22M are connected to a "control means" (not shown). The control means transmits a light emission signal to the light emitting cell control / drive module via the circuit pattern 22L, and receives a photoacoustic wave signal from the microphone control / drive module via the circuit pattern 22M. In other embodiments described below, the circuit patterns 22L and 22M have similar functions.

[0039] In addition, through holes 23L, 23M are formed from the front surface 11A to the back surface 11B of the substrate 11, and these through holes 23L, 23M are electrically connected to the corresponding circuit patterns 22L, 22M. Furthermore, the through holes 23L, 23M are electrically connected to the corresponding component wiring patterns 24L, 24M formed on the front surface 11A of the substrate 11.

[0040] The control / drive modules of the light emitting cell 17 and the microphone 12 are connected to the component wiring patterns 24L, 24M by solder 25L, 25M or bumps 25L, 25M, so that the circuit patterns 22L, 22M are formed independently. With this configuration, it is possible to prevent problems (solder flow) caused by not applying resist even in areas where the resist 21 does not exist.

[0041] In the above configuration, when the odor detection device is operated, the LED element 18 is caused to emit light in pulses by the light-emitting cell control / drive module, and only infrared light from the light is transmitted by the optical filter 20. The transmitted infrared light is emitted into the detection chamber 14, and the specific gas component to be measured in the detection chamber 14 repeatedly expands and contracts in response to the pulsed infrared light, generating photoacoustic waves.

[0042] The generated photoacoustic waves are picked up by a microphone 12, which is an acoustic sensor, and converted into an electrical signal. The electrical signal is then amplified by a microphone control / drive module, and the gas is identified and its concentration is measured by a downstream control device.

[0043] During this measurement process, the infrared light incident on the detection chamber 14 is reflected by the wall of the detection chamber 14 and irradiates the surface 11A of the substrate 11. However, since no resist 21 is present on the surface 11A of the substrate 11, no photoacoustic waves are generated due to the components contained in the resist 21 when irradiated with infrared light. Therefore, this makes it possible to reduce the influence of photoacoustic waves (noise) caused by the resist and improve detection sensitivity. [Example]

[0044] Next, a second embodiment of the present invention will be described with reference to the drawings. In the drawings of the following embodiment, the same reference numbers as those shown in Figure 2 indicate the same or similar components and parts, and therefore, explanations thereof will be omitted unless necessary.

[0045] The second embodiment is characterized in that the through-holes shown in the first embodiment are omitted, and is otherwise substantially the same as the first embodiment.

[0046] 4, housing 13 has an opening on one side and a space formed on the other side with an upper wall 13A, and substrate 11 is disposed on the open side to cover the opening, thereby forming detection chamber 14. As described above, light-emitting cell 17 and microphone 12 are surface-mounted on surface 11A of substrate 11 on the detection chamber 14 side.

[0047] Resist 21 is provided on the contact surface between housing 13 and surface 11A of substrate 11, and on surface 11A of substrate 11 located outside housing 13. However, as described in the first embodiment, this resist 21 is not provided on surface 11A of substrate 11 corresponding to detection chamber 14; in other words, no resist 21 exists on surface 11A of substrate 11 that forms detection chamber 14.

[0048] Here, taking into consideration the possibility of solder adhering to unnecessary areas due to the absence of resist 21, this embodiment addresses the problem of solder flow caused by not applying resist by arranging the control / drive module and circuit pattern on a step formed on the substrate.

[0049] 4, circuit patterns 22L and 22M are formed to be embedded inside substrate 11. However, these circuit patterns 22L and 22M are exposed to detection chamber in the region corresponding to detection chamber .

[0050] That is, a step 26 is formed in the substrate 11 corresponding to the opening of the detection chamber 14 down to the depth at which the circuit patterns 22L and 22M are located. Therefore, the circuit patterns 22L and 22M are exposed at the step 26. With this configuration, a through hole can be omitted.

[0051] The light emitting cells 17 and the control / drive module of the microphone 12 are connected to the circuit patterns 22L, 22M by solder 25L, 25M or bumps 25L, 25M. With this configuration, it is possible to prevent problems (flow of solder) caused by not applying resist even in areas where the resist 21 does not exist.

[0052] In the above configuration, when the odor detection device is operated, the LED element 18 is caused to emit light in pulses by the light-emitting cell control / drive module, and only infrared light from the light is transmitted by the optical filter 20. The transmitted infrared light is emitted into the detection chamber 14, and the specific gas component to be measured in the detection chamber 14 repeatedly expands and contracts in response to the pulsed infrared light, generating photoacoustic waves.

[0053] The generated photoacoustic waves are picked up by a microphone 12, which is an acoustic sensor, converted into an electrical signal, amplified by a microphone control / drive module, and then a downstream control device identifies the gas and measures its concentration.

[0054] During this measurement process, the infrared light incident on the detection chamber 14 is reflected by the wall of the detection chamber 14 and irradiates the surface 11A of the substrate 11. However, since no resist 21 is present on the surface 11A of the substrate 11, no photoacoustic waves are generated due to the components contained in the resist 21 when irradiated with infrared light. Therefore, this makes it possible to reduce the influence of photoacoustic waves (noise) caused by the resist and improve detection sensitivity. [Example]

[0055] Next, a third embodiment of the present invention will be described with reference to the drawings. In the drawings of the following embodiment, the same reference numbers as those shown in Figure 2 indicate the same or similar components and parts, and therefore, explanations thereof will be omitted unless necessary.

[0056] The third embodiment is characterized in that solder pools are provided in parts of the component wiring patterns formed on the surface of the substrate.

[0057] 5 and 6, housing 13 has an opening on one side and a space formed on the other side with an upper wall 13A, and substrate 11 is disposed on the open side so as to cover the opening, thereby forming detection chamber 14. As described above, light-emitting cell 17 and microphone 12 are surface-mounted on surface 11A of substrate 11 on the detection chamber 14 side.

[0058] Resist 21 is provided on the contact surface between housing 13 and surface 11A of substrate 11, and on surface 11A of substrate 11 located outside housing 13. However, as described in the first embodiment, this resist 21 is not provided on surface 11A of substrate 11 corresponding to detection chamber 14; in other words, no resist 21 exists on surface 11A of substrate 11 that forms detection chamber 14.

[0059] Here, taking into consideration the adhesion of solder to unnecessary areas due to the absence of resist 21, this embodiment addresses the problem (solder flow) caused by not applying resist by changing the plating composition on some patterns of component wiring patterns 24L, 24M formed on surface 11A of substrate 11 to form solder pools 27L, 27M that prevent solder from flowing.

[0060] 5 and 6, component circuit patterns 24L and 24M are formed on the surface of the substrate 11. The light-emitting cell 17 and the control / drive module for the microphone 12 are connected to the circuit patterns 22L and 22M by solder 25L and 25M, or by bumps 25L and 25M and through-holes 23L and 23M. With this configuration, problems caused by not applying resist (solder flow) can be prevented even in areas where there is no resist 21. In other words, the solder pools 27L and 27M block the solder flow, eliminating problems caused by solder flow.

[0061] In the above configuration, when the odor detection device is operated, the LED element 18 is caused to emit light in pulses by the light-emitting cell control / drive module, and only infrared light from the light is transmitted by the optical filter 20. The transmitted infrared light is emitted into the detection chamber 14, and the specific gas component to be measured in the detection chamber 14 repeatedly expands and contracts in response to the pulsed infrared light, generating photoacoustic waves.

[0062] The generated photoacoustic waves are picked up by a microphone 12, which is an acoustic sensor, converted into an electrical signal, amplified by a microphone control / drive module, and then used by a downstream control device to identify the gas and measure its concentration.

[0063] During this measurement process, the infrared light incident on the detection chamber 14 is reflected by the wall of the detection chamber 14 and irradiates the surface 11A of the substrate 11. However, since no resist 21 is present on the surface 11A of the substrate 11, no photoacoustic waves are generated due to the components contained in the resist 21 when irradiated with infrared light. Therefore, this makes it possible to reduce the influence of photoacoustic waves (noise) caused by the resist and improve detection sensitivity. [Example]

[0064] Next, a fourth embodiment of the present invention will be described with reference to the drawings. In the drawings of the following embodiment, the same reference numbers as those shown in Figure 5 indicate the same or similar components and parts, and therefore, explanations thereof will be omitted unless necessary.

[0065] The fourth embodiment is characterized in that the microphone is provided in a resonance tube that is independent of the detection chamber. The resonance tube is provided inside the housing.

[0066] 7, housing 13 has an opening on one side and a space formed on the other side with an upper wall 13A, and substrate 11 is disposed on the open side so as to cover the opening, thereby forming detection chamber 14. As described above, light-emitting cell 17 is surface-mounted on surface 11A of substrate 11 on the detection chamber 14 side.

[0067] Resist 21 is provided on the contact surface between housing 13 and surface 11A of substrate 11, and on surface 11A of substrate 11 located outside housing 13. However, as described in the first embodiment, this resist 21 is not provided on surface 11A of substrate 11 corresponding to detection chamber 14; in other words, no resist 21 exists on surface 11A of substrate 11 that forms detection chamber 14.

[0068] Also, inside the housing 13, a curved communicating path 29 is formed, one end of which is connected to the detection chamber 14 and the other end of which is connected to a microphone housing chamber 28 that houses the microphone 12. The microphone housing chamber 28 and the curved communicating path 29 can generate Helmholtz resonance. In this way, the microphone housing chamber 28 and the communicating path 29 function as a resonance tube. Here, a conventional resist 21 is arranged around the microphone control / drive module of the microphone 12.

[0069] Here, since the microphone 12 and the microphone control / drive module are disposed in the microphone housing chamber, the infrared light incident on the detection chamber 14 is blocked by the curved communicating path 29. Therefore, the infrared light does not reach the microphone control / drive module of the microphone 12, and the infrared light does not cause thermal excitation of the components contained in the resist 21. Therefore, compared to when the microphone is disposed inside the detection chamber 14, the influence of the photoacoustic waves (noise) caused by the resist 21 can be reduced, and the detection sensitivity can be improved.

[0070] In the above configuration, when the odor detection device is operated, the LED element 18 is caused to emit light in pulses by the light-emitting cell control / drive module, and only infrared light from the light is transmitted by the optical filter 20. The transmitted infrared light is emitted into the detection chamber 14, and the specific gas component to be measured in the detection chamber 14 repeatedly expands and contracts in response to the pulsed infrared light, generating photoacoustic waves.

[0071] The generated photoacoustic waves are picked up by a microphone 12, which is an acoustic sensor, converted into an electrical signal, amplified by a microphone control / drive module, and then used by a downstream control device to identify the gas and measure its concentration.

[0072] During this measurement process, the infrared light incident on the detection chamber 14 is reflected by the wall of the detection chamber 14 and irradiates the surface 11A of the substrate 11. However, since no resist 21 is present on the surface 11A of the substrate 11, no photoacoustic waves are generated due to the components contained in the resist 21 when irradiated with infrared light. Therefore, this makes it possible to reduce the influence of photoacoustic waves (noise) caused by the resist and improve detection sensitivity.

[0073] Although the microphone 12 is shown housed in a microphone housing chamber 28 formed inside the housing 13, it can also be provided on the rear surface 11B of the substrate 11, as shown in Figure 8, which will be described later. [Example]

[0074] Next, a fifth embodiment of the present invention will be described with reference to the drawings. In the drawings of the following embodiments, the same reference numbers as those shown in Figure 5 indicate the same or similar components and parts, and therefore, explanations thereof will be omitted unless necessary.

[0075] The fifth embodiment is characterized in that a microphone is provided on the back surface of the substrate, independent of the detection chamber.

[0076] 8, the housing 13 has an opening on one side and a space with an upper wall 13A on the other side, and the substrate 11 is disposed on the open side so as to cover the opening, thereby forming the detection chamber 14. As described above, the light emitting cells 17 and the light emitting cell control / drive module (not shown) are surface-mounted on the surface 11A of the substrate 11 on the detection chamber 14 side.

[0077] Resist 21 is provided on the contact surface between housing 13 and surface 11A of substrate 11, and on surface 11A of substrate 11 located outside housing 13. However, this resist 21 is not provided on surface 11A of substrate 11 corresponding to detection chamber 14, that is, no resist 21 exists on surface 11A of substrate 11 that forms detection chamber 14.

[0078] In addition, inside the substrate 11 (from the front surface to the back surface), a communication path 30 is formed, one end of which is connected to the detection chamber 14 and the other end of which is connected to the microphone 12 arranged on the back surface 11B of the substrate 11.

[0079] Here, the microphone 12 is disposed on the rear surface of the substrate 11, and is connected to a circuit pattern 22M formed on the rear surface 11B by solder 25M or bumps 25M.

[0080] Furthermore, infrared light incident on detection chamber 14 is less likely to reach microphone 12 on rear surface 11B of substrate 11. In other words, infrared light does not reach pattern 22M around microphone 12, so thermal excitation of components contained in resist 21 by infrared light does not occur. Therefore, compared to when a microphone is installed inside detection chamber 14, the influence of photoacoustic waves (noise) caused by resist 21 can be reduced, and detection sensitivity can be improved.

[0081] In the above configuration, when the odor detection device is operated, the LED element 18 is caused to emit light in pulses by the light-emitting cell control / drive module, and only infrared light from the light is transmitted by the optical filter 20. The transmitted infrared light is emitted into the detection chamber 14, and the specific gas component to be measured in the detection chamber 14 repeatedly expands and contracts in response to the pulsed infrared light, generating photoacoustic waves.

[0082] The generated photoacoustic waves are picked up by a microphone 12, which is an acoustic sensor, converted into an electrical signal, amplified by a microphone control / drive module, and then used by a downstream control device to identify the gas and measure its concentration.

[0083] During this measurement process, the infrared light incident on the detection chamber 14 is reflected by the wall of the detection chamber 14 and irradiates the surface 11A of the substrate 11. However, since no resist 21 is present on the surface 11A of the substrate 11, no photoacoustic waves are generated due to the components contained in the resist 21 when irradiated with infrared light. Therefore, this makes it possible to reduce the influence of photoacoustic waves (noise) caused by the resist and improve detection sensitivity. [Example]

[0084] Next, a sixth embodiment of the present invention will be described with reference to the drawings. In the drawings of the following embodiments, the same reference numbers as those shown in Figure 7 indicate the same or similar components and parts, and therefore, explanations thereof will be omitted unless necessary.

[0085] The sixth embodiment is characterized by the formation of a reflective layer that reflects light on the surface of the substrate that forms the detection chamber. The embodiment shown in Figure 9 has a configuration that is substantially the same as the embodiment in Figure 7, so only the differences will be explained. In this case, there is no resist on the surface of the substrate in the detection chamber.

[0086] 9, a light reflecting layer 31 that reflects light that enters the detection chamber 14 is formed on the surface 11A of the substrate 11 that forms the detection chamber 14. The light reflecting layer 31 is provided directly on the surface 11A of the substrate 11. For example, a gold-plated layer 31 is formed on the surface 11A of the substrate 11 as the light reflecting layer 31.

[0087] The infrared light incident on the detection chamber 14 is reflected by the inner wall of the detection chamber 14, and naturally also by the gold plating layer 31. In this embodiment, since the resist 21 is not present, the infrared light does not cause thermal excitation of the components contained in the resist 21. This reduces the influence of photoacoustic waves (noise) caused by the resist, thereby improving detection sensitivity. Furthermore, since the infrared light is efficiently reflected by the gold plating layer 31, the intensity of the photoacoustic waves can be increased. [Example]

[0088] Next, a seventh embodiment of the present invention will be described with reference to the drawings. In the drawings of the following embodiments, the same reference numbers as those shown in Figure 7 indicate the same or similar components and parts, and therefore, explanations thereof will be omitted unless necessary.

[0089] The seventh embodiment is characterized in that a resist is disposed on the surface of the substrate forming the detection chamber as in the conventional case, and a covering member is provided to cover the resist so as to prevent the resist from being exposed. Note that the embodiment shown in Figure 10 has a configuration similar to that of the embodiment in Figure 7, so only the differences will be explained. In this case, a resist is present on the surface of the substrate in the detection chamber.

[0090] 10, resist 21 is disposed on surface 11A of substrate 11, which forms detection chamber 14, as in the conventional case. A covering member 32 is provided to cover this resist 21 and prevent exposure of resist 21. Covering member 32 is, for example, a mirror-finished annular metal plate 32. Infrared light incident on detection chamber 14 is reflected by the inner wall of detection chamber 14, and naturally is also reflected by metal plate 32.

[0091] Therefore, since the resist 21 is covered with the metal plate 32 and not exposed, the components contained in the resist 21 are not thermally excited by the infrared light. This reduces the influence of the photoacoustic wave (noise) caused by the resist, and improves the detection sensitivity. Furthermore, since the infrared light is efficiently reflected by the metal plate 32, the intensity of the photoacoustic wave can be increased. [Example]

[0092] Next, an eighth embodiment of the present invention will be described with reference to the drawings. In the drawings of the following embodiments, the same reference numbers as those shown in Figure 10 indicate the same or similar components and parts, and therefore, explanations thereof will be omitted unless necessary. The eighth embodiment is characterized in that the covering member extends to the optical filter of the light-emitting cell.

[0093] 11, the metal body 33, which is the covering member, is an annular metal body that circumferentially surrounds the light-emitting cell 17, for example, with a mirror-finished surface on the detection chamber 14 side. The area in which this metal body 33 exists extends up to the position where the optical filter 20 exists, as seen in the direction in which light from the light-emitting cell 17 travels. In other words, the space around the light-emitting cell 17 in the radial direction is filled with the metal body 33.

[0094] 10, it is expected that light will be repeatedly reflected between the outer periphery of the light-emitting cell 17 and the inner periphery of the detection chamber 14, resulting in attenuation of the light intensity. In contrast, if a ring-shaped metal body 33 such as that shown in Fig. 11 is used, light will not be reflected between the outer periphery of the light-emitting cell 17 and the inner periphery of the detection chamber 14, and therefore attenuation of the light intensity can be reduced.

[0095] As described above, the present invention is an odor detection device equipped with a photoacoustic wave sensor, which has a detection chamber consisting of a space formed by a box-shaped housing with one open end and a substrate covering the opening of the housing, and is characterized in that at least a light-emitting cell is mounted on the surface of the substrate facing the detection chamber, and no resist is present on the surface of the substrate forming the detection chamber, or even if resist is present, the resist is not exposed on the detection chamber side.

[0096] This reduces the influence of photoacoustic waves (noise) caused by the resist, and improves detection sensitivity.

[0097] The present invention is not limited to the above-described embodiments, but includes various modifications. The above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations with respect to the configuration of each embodiment. [Explanation of symbols]

[0098] 10...Photoacoustic sensor, 11...Substrate, 12...Microphone, 13...Housing, 14...Detection chamber, 17...Light-emitting cell, 18LED element, 19...Cell housing, 20...Optical filter, 21...Resist, 22L, 22M...Circuit pattern, 23L, 23M...Through hole, 24L, 24M...Component circuit pattern, 25L, 25M...Solder, 26...Step portion, 27L, 27M...Solder pool, 28...Microphone storage chamber, 29...Communicating passage

Claims

1. An odor detection device including a photoacoustic sensor, The photoacoustic sensor comprises: a detection chamber including a space formed by a box-shaped housing having an opening on one side and a substrate covering the opening of the housing; At least a light-emitting cell is mounted on the surface of the substrate on the side of the detection chamber, and The surface of the substrate that forms the detection chamber is free of resist, or even if resist is present, a covering member that prevents the resist from being exposed to the side of the detection chamber is provided. An odor detection device characterized by:

2. The odor detection device according to claim 1, The light-emitting cell is composed of a light-emitting element, a housing surrounding the light-emitting element, and an optical filter that transmits specific light from the light-emitting element. An odor detection device characterized by:

3. The odor detection device according to claim 2, A microphone is further mounted on the surface of the substrate on the side of the detection chamber. An odor detection device characterized by:

4. The odor detection device according to claim 3, a component circuit pattern to which a light emitting cell control / drive module and a microphone control / drive module are connected is provided on the surface of the substrate, and a circuit pattern to which a control means is connected is embedded and formed inside the substrate; The component circuit pattern and the circuit pattern are connected by through holes provided in the substrate. An odor detection device characterized by:

5. The odor detection device according to claim 3, A circuit pattern connected to a control means is embedded inside the substrate, and a step portion where the circuit pattern is exposed is formed on the surface of the substrate corresponding to the detection chamber, The step portion includes a control / driving portion for the light emitting cell connected to the exposed circuit pattern. The module and microphone control / drive module are located An odor detection device characterized by:

6. The odor detection device according to claim 3, A component circuit pattern is provided on the surface of the substrate, to which a light emitting cell control / driving module and a microphone control / driving module are connected; A solder pool is formed in a part of the component circuit pattern. An odor detection device characterized by:

7. The odor detection device according to claim 2, A communication passage connected to the detection chamber and a microphone storage chamber connected to the communication passage are formed inside the housing, The microphone storage chamber stores a microphone. An odor detection device characterized by:

8. The odor detection device according to claim 2, A microphone is mounted on the back surface of the substrate opposite to the detection chamber side. The detection chamber and the microphone are connected by a communication path provided in the substrate. An odor detection device characterized by:

9. The odor detection device according to claim 2, The surface of the substrate that forms the detection chamber is free of the resist and has a light-reflecting layer formed thereon. An odor detection device characterized by:

10. The odor detection device according to claim 2, The resist is present on the surface of the substrate that forms the detection chamber, and a covering member is provided to cover the resist so that the resist is not exposed. An odor detection device characterized by:

11. The odor detection device according to claim 10, The covering member is shaped to extend to the position of the optical filter of the light emitting cell. An odor detection device characterized by:

Images