Gas detection equipment

Abstract

To provide a gas detector that can suppress generation of distortions in a light path and has a gas detection sensitivity which changes less.SOLUTION: A gas detector 1 includes: a substrate 2; a light emission element 3 for emitting light, located in a first region 21 of a main surface 20 of the substrate 2; a light receiving element 4 for receiving light, located in a second region 22 of the main surface 20 of the substrate 2; a light guidance member 5 for guiding the light emitted from the light emission element 3 to the light receiving element 4; and a joint member 6 for joining the substrate 2 and the light guidance member 5 to each other, the joint member serving as a shaft of rotation when the light guidance member 5 moves to the substrate 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to gas detection devices. [Background technology]

[0002] Gas detection devices for detecting gases are used in various fields. For example, Patent Document 1 discloses a device that includes a light source that emits infrared rays and a detector that detects infrared rays of a specific wavelength in the same case, and is configured so that a gas to be detected is introduced into the case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-184211 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the gas detection device described in Patent Document 1, the optical path tube is firmly joined to the substrate and case by the groove and fixture of the substrate fixing part. Therefore, for example, distortion of the substrate and case due to thermal expansion may be transmitted to the optical path tube, causing distortion of the optical path or changing the relative position of the optical surfaces, which may cause fluctuations in gas detection sensitivity.

[0005] In view of the above, an object of the present disclosure is to provide a gas detection device in which the occurrence of distortion in the optical path is suppressed and changes in gas detection sensitivity are reduced. [Means for solving the problem]

[0006] A gas detection device according to an embodiment of the present disclosure includes: A substrate; a light emitting element provided in a first region of a main surface of the substrate and emitting light; a light receiving element provided in a second region of the main surface of the substrate and configured to receive the light; a light guiding member that guides the light emitted by the light emitting element to the light receiving element; The light guide member includes a joining member that joins the substrate and the light guide member and serves as a rotation axis when the light guide member moves relative to the substrate.

[0007] A gas detection device according to an embodiment of the present disclosure includes: A substrate having a light emitting element that emits light and a light receiving element that receives the light provided on a main surface thereof; a light guiding member that guides the light emitted by the light emitting element to the light receiving element; a joining member that is a columnar body and has a first bottom surface portion joined to the substrate and a second bottom surface portion joined to the light guiding member; The substrate and the light guide member are joined only by the joining member.

[0008] A gas detection device according to an embodiment of the present disclosure includes: A substrate; a light emitting element provided in a first region of a main surface of the substrate and emitting light; a light receiving element provided in a second region of the main surface of the substrate and configured to receive the light; a light guiding member that guides the light emitted by the light emitting element to the light receiving element; a joining member that joins the substrate and the light-guiding member and fixes the light-guiding member to the substrate, and a maximum strain ratio under normal application of unit pressure is 143 / GPa or more and 10,000 / GPa or less. Effect of the Invention

[0009] According to one embodiment of the present disclosure, a gas detection device can be provided in which the occurrence of distortion in the optical path is suppressed and changes in gas detection sensitivity are reduced. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a partially see-through perspective view of a gas detection device according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram showing an example of a cross section of the gas detection device. [Diagram 3]FIG. 3 is a diagram showing an example of the arrangement and shape of the joining members. [Figure 4] FIG. 4 is a diagram for explaining the intensity distribution on the object plane (light emitting portion) and the illuminance distribution on the image plane. [Diagram 5] FIG. 5 is a diagram illustrating the shape of a gas detector of a comparative example before thermal expansion. [Figure 6] FIG. 6 is a diagram illustrating the shape of a gas detector of a comparative example after thermal expansion. [Figure 7] FIG. 7 is a diagram illustrating an example of an optical path before thermal expansion in a gas detector of a comparative example. [Figure 8] FIG. 8 is a diagram illustrating an example of an optical path after thermal expansion of a gas detector of a comparative example. [Figure 9] FIG. 9 is a diagram illustrating a shape of a gas detection device according to an embodiment of the present disclosure before thermal expansion. [Figure 10] FIG. 10 is a diagram illustrating a shape of a gas detection device according to an embodiment of the present disclosure after thermal expansion. [Figure 11] FIG. 11 is a diagram showing another example of the arrangement of the joint members. [Figure 12] FIG. 12 is a diagram showing another example of a cross section of the gas detection device. [Figure 13] FIG. 13 is a diagram showing another example of the arrangement and shape of the joining members. [Figure 14] FIG. 14 is a diagram showing another example of the shape of the joining member. [Figure 15] FIG. 15 is a diagram showing another example of the shape of the joining member. [Figure 16] FIG. 16 is a diagram illustrating another configuration example of the light guide member. [Figure 17] FIG. 17 is a graph showing the relationship between unit thermal expansion strain angle and maximum strain ratio under normal application of unit pressure. [Figure 18] FIG. 18 is a diagram showing the shape of a part of the gas detection device used in the simulation of FIG. [Figure 19] FIG. 19 is a diagram showing the shape of a part of the gas detection device used in the simulation of FIG. [Figure 20]FIG. 20 is a diagram showing the shape of a part of the gas detection device used in the simulation of FIG. [Figure 21] FIG. 21 is a diagram showing the shape of a part of the gas detection device used in the simulation of FIG. [Figure 22] FIG. 22 is a diagram for explaining the arrangement of the joining members. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (First embodiment) 1 is a partially see-through perspective view of a gas detection device 1 according to an embodiment of the present disclosure. Gas detection device 1 is, for example, a small device measuring 30 mm×20 mm×10 mm, and is also referred to as a gas sensor. In this embodiment, gas detection device 1 is an NDIR (Non Dispersive InfraRed) type device that measures the concentration of a detection target gas based on infrared light that has passed through an introduced gas. The detection target gas is, for example, carbon dioxide, water vapor, methane, propane, formaldehyde, carbon monoxide, nitric oxide, ammonia, sulfur dioxide, alcohol, or the like.

[0012] Gas detection device 1 includes a substrate 2, a light-emitting element 3, a light-receiving element 4, a light-guiding member 5, and a bonding member 6. In Fig. 1, an example configuration of gas detection device 1 is shown through a portion of light-guiding member 5, and light-emitting element 3 and light-receiving element 4 provided on main surface 20 of substrate 2 are visible. In this embodiment, main surface 20 is the surface of substrate 2 that has the largest area and faces light-guiding member 5.

[0013] 1, orthogonal coordinates are set so that the xy plane is parallel to the main surface 20 of the substrate 2. The z-axis direction is perpendicular to the main surface 20 of the substrate 2. The x-axis and y-axis directions are parallel to the sides of the main surface 20 of the substrate 2. Here, the y-axis direction corresponds to the direction in which a first reflecting portion 51 and a second reflecting portion 52, which will be described later, face each other.

[0014] The substrate 2 is a plate-like member on which the components of the gas detection device 1 are mounted and which electrically connects the mounted electronic components. The substrate 2 has the light-emitting element 3 and the light-receiving element 4 provided on the main surface 20. The substrate 2 may further have other electronic components mounted thereon. For example, the substrate 2 may have a controller for controlling at least one of the light-emitting element 3 and the light-receiving element 4 provided on the main surface 20 or the bottom surface opposite to the main surface 20. The substrate 2 may also have a calculation unit on the main surface 20 or the bottom surface that performs calculations for calculating the gas concentration. The calculation unit may include at least one of a general-purpose processor that performs functions according to a loaded program and a dedicated processor specialized for a specific process. The dedicated processor may include an application specific integrated circuit (ASIC). The processor may include a programmable logic device (PLD). The calculation unit may be integrated with the controller.

[0015] The light-emitting element 3 is a component that emits light used to detect the gas to be detected. The light-emitting element 3 is not particularly limited as long as it outputs light including a wavelength that is absorbed by the gas to be detected. In this embodiment, the light emitted by the light-emitting element 3 is infrared light, but is not limited thereto. In this embodiment, the light-emitting element 3 is an LED (light emitting diode), but other examples may include a semiconductor laser, an organic light-emitting element, or a MEMS (Micro Electro Mechanical Systems) heater. The light-emitting element 3 is provided in a first region 21 of the main surface 20 of the substrate 2. The first region 21 is determined to be at a position facing a first mirror 511 (described later) in the z-axis direction.

[0016] The light receiving element 4 is a component that receives light that has passed through the introduced gas. The light receiving element 4 is not particularly limited as long as it has sensitivity to a band of light including a wavelength absorbed by the gas to be detected. In this embodiment, the light received by the light receiving element 4 is infrared light, but is not limited thereto. In this embodiment, the light receiving element 4 is a photodiode, but may be a phototransistor, a thermopile, a pyroelectric sensor, a bolometer, or the like as another example. The light receiving element 4 converts the received light into an electric signal and outputs the converted electric signal. The electric signal is output to, for example, a calculation unit. The calculation unit that receives the electric signal calculates the concentration of the gas to be detected based on the light transmittance and the like. The light receiving element 4 is provided in the second region 22 of the main surface 20 of the substrate 2. The second region 22 is determined to be opposite to a fifth mirror 513 (described later) in the z-axis direction. The light receiving element 4 may include an optical filter having a wavelength selection function.

[0017] The light guiding member 5 is a member that guides the light emitted by the light emitting element 3 to the light receiving element 4. The light guiding member 5 is an optical system of the gas detection device 1. The light guiding member 5 includes optical members and constitutes an optical path from the light emitting element 3 to the light receiving element 4. In other words, the light guiding member 5 optically connects the light emitting element 3 and the light receiving element 4. Here, the optical members are, for example, a mirror, a lens, etc.

[0018] In this embodiment, the light guide member 5 includes a first reflecting portion 51 and a second reflecting portion 52. The first reflecting portion 51 includes a first mirror 511, a third mirror 512, and a fifth mirror 513 as optical members. The first reflecting portion 51 has a mirror that first reflects the light emitted from the light emitting element 3, and has a mirror that finally reflects the light received by the light receiving element 4. The second reflecting portion 52 includes a second mirror 521 and a fourth mirror 522 as optical members. The second reflecting portion 52 reflects light between the first reflecting portion 51. The light guide member 5 reflects the light emitted by the light emitting element 3 in the order of the first mirror 511, the second mirror 521, the third mirror 512, the fourth mirror 522, and the fifth mirror 513, and guides the light to the light receiving element 4. The optical path is configured to pass through a cell 54 into which a gas is introduced, which is provided between the light-guiding member 5 and the substrate 2. As another example, the number of mirrors included in the light-guiding member 5 may be one or more other than five. Furthermore, the light-guiding member 5 may be configured to include a lens or a diffractive optical element in a part of the optical path.

[0019] In the light guide member 5, the first reflecting portion 51 is fixed in a relative position with respect to the second reflecting portion 52. For example, the first reflecting portion 51 and the second reflecting portion 52 may be made of resin and integrally formed. The mirrors of the first reflecting portion 51 and the second reflecting portion 52 may be processed by metal plating after integral formation. As another example, the first reflecting portion 51 and the second reflecting portion 52 may be formed separately and strongly fixed by adhesive, screws, claws, fitting, grommets, welding, or the like.

[0020] The first mirror 511 is a collecting mirror that reflects the light emitted from the focal point. The first mirror 511 is, for example, a concave mirror. The shape of the first mirror 511 may be an ellipsoid. In this embodiment, the first mirror 511 reflects the light emitted in the z-axis direction from the light-emitting element 3 at the focal point in the xy plane direction. Here, the xy plane direction is a direction having at least one component in the x-axis direction and the y-axis direction. However, the direction cosine of the light ray reflected by the first mirror 511 may further have a z-axis component.

[0021] The second mirror 521, the third mirror 512, and the fourth mirror 522 reflect the incident light. At least one of the second mirror 521, the third mirror 512, and the fourth mirror 522 may be a light-collecting mirror having a light-collecting function. At least one of the second mirror 521, the third mirror 512, and the fourth mirror 522 may be, for example, a concave mirror. As shown in FIG. 1, the second mirror 521 reflects the incident light from the first mirror 511 to the third mirror 512. The third mirror 512 reflects the incident light from the second mirror 521 to the fourth mirror 522. The fourth mirror 522 reflects the incident light from the third mirror 512 to the fifth mirror 513.

[0022] The fifth mirror 513 is a focusing mirror that focuses the incident light on the light receiving element. The fifth mirror 513 is, for example, a concave mirror. The shape of the fifth mirror 513 may be an ellipsoid. In this embodiment, the fifth mirror 513 reflects the incident light in the xy plane direction from the fourth mirror 522 so as to have a component in the z-axis direction. Specifically, the fifth mirror 513 reflects the incident light so as to focus it on the light receiving element 4 at the focal point.

[0023] The materials constituting the first mirror 511, the second mirror 521, the third mirror 512, the fourth mirror 522 and the fifth mirror 513 may be, for example, metal, glass, ceramics, stainless steel, etc., but are not limited thereto. From the viewpoint of improving the detection sensitivity, it is preferable that the materials constituting these mirrors are composed of a material having a small light absorption coefficient and a high reflectance. Specifically, a resin housing coated with an alloy containing aluminum, gold, or silver, a dielectric, or a laminate of these is preferable. From the viewpoint of reliability and change over time, a resin housing coated with a gold or an alloy layer containing gold is preferable. Furthermore, it is preferable to form a dielectric laminate film on the surface of the metal layer to increase the reflectance. When the first mirror 511 and the fifth mirror 513 are formed by deposition or plating, it is possible to improve high productivity and weight reduction compared to when they are formed from a metal material. Furthermore, the difference in thermal expansion coefficient with the substrate 2 is reduced, thermal deformation is suppressed, and sensitivity is less likely to fluctuate. In addition, the light guide member 5 may be formed by cutting, and from the viewpoint of productivity, it is more preferable to form it by injection molding.

[0024] The joining member 6 is a member that joins the substrate 2 and the light guiding member 5. In this embodiment, the joining member 6 is a columnar body, and has a first bottom surface portion 61 (see FIG. 2) that is joined to the substrate 2, and a second bottom surface portion 62 that is joined to the light guiding member 5. The first bottom surface portion 61 and the substrate 2 are joined by, for example, an adhesive, a grommet or a screw, welding, a claw, a fit, or the like. The second bottom surface portion 62 and the light guiding member 5 are joined in the same manner. Furthermore, from the viewpoint of productivity, it is desirable that the joining member 6 and the light guiding member 5 are integrally molded in order to reduce the number of components.

[0025] FIG. 2 is a diagram showing an example of a cross section of the gas detection device 1. In FIG. 2, a cross section of the substrate 2, the light guide member 5 including the third mirror 512, and the joining member 6 is shown cut along a plane parallel to the yz plane. The cell 54 is formed inside the gas detection device 1, sandwiched between the substrate 2 and the light guide member 5. The light guide member 5 includes a vent 53 for introducing gas into the cell 54. The vent 53 may also be used to exhaust gas from the cell 54. In this embodiment, the joining member 6 is a hollow cylinder. The first bottom surface portion 61 is joined to the substrate 2 by inserting a screw into the hollow portion from the bottom surface of the substrate 2. The second bottom surface portion 62 is joined to the light guide member 5 by inserting a grommet into the hollow portion and expanding it. As another example, the joining member 6 may be a solid cylinder. The first bottom surface portion 61 and the substrate 2, and the second bottom surface portion 62 and the light-guiding member 5 may be joined by adhesive, welding, tabs, fitting, etc. Here, the first mirror 511, the main surface 20 of the substrate 2, and the light-emitting element 3 in Fig. 2 are the same as the elements with the same numbers in Fig. 1, and therefore descriptions thereof will be omitted.

[0026] FIG. 3 is a diagram showing an example of the arrangement and shape of the bonding member 6. In FIG. 3, the main surface 20 of the substrate 2 viewed in the negative direction of the z-axis is shown. The vertical projection image 6i is an image of the bonding member 6 projected perpendicularly onto the main surface 20 of the substrate 2. In this embodiment, the vertical projection image 6i onto the main surface 20 of the substrate 2 is a hollow circle. As another example, when the bonding member 6 is a solid cylinder, the vertical projection image 6i is a solid circle. Here, in FIG. 3, the midpoint 24 of the line segment connecting the center 21c of the first region 21 and the center 22c of the second region 22 is shown. Also, in FIG. 3, the perpendicular bisector 23 of the line segment connecting the center 21c of the first region 21 and the center 22c of the second region 22 is shown. In this embodiment, the bonding member 6 is arranged so that the vertical projection image 6i onto the main surface 20 of the substrate 2 is on the perpendicular bisector 23. Here, the vertical projection image 6 i may be the cross-sectional shape of the bonding member 6 directly above the main surface 20 of the substrate 2 .

[0027] The joining member 6 can be made of a material having a large elastic modulus and being difficult to deform. For example, the material of the joining member 6 is LCP (liquid crystal polymer), PP (polypropylene), PEEK (polyether ether ketone), PA (polyamide), PPE (polyphenylene ether), PC (polycarbonate), PPS (polyphenylene sulfide), PMMA (polymethyl methacrylate resin), PAR (polyarylate resin), or a hard resin made by mixing two or more of these. The joining member 6 and the light guide member 5 may be made of the same material. If the joining member 6 and the light guide member 5 are made of the same material, there is no difference in thermal expansion, so that thermal distortion can be suppressed. The substrate 2 and the light guide member 5 are joined only via the joining member 6. Therefore, even if the substrate 2 is deformed due to, for example, thermal expansion, the light guide member 5 is not affected by the deformation of the substrate 2. For example, if the substrate 2 is deformed so as to expand in the y-axis direction, since the light-guiding member 5 is connected to the substrate 2 at only one point, the optical member shrinks (expands) similarly around the one point without distortion, and therefore the optical performance is not affected.

[0028] In addition, when different forces act on the substrate 2 and the light guide member 5, the joint member 6 is unlikely to deform in the direction along the axis, but on the other hand, twisting deformation and bending deformation may occur. Therefore, the light guide member 5 is not displaced in the z-axis direction relative to the substrate 2. At this time, the distance (optical path length) between the first reflecting portion 51 and the light emitting element 3 and the light receiving element 4 is maintained, so that the accuracy of gas detection can be maintained. On the other hand, the light guide member 5 may rotate around the joint member 6 as the rotation axis relative to the substrate 2. In other words, the joint member 6 becomes the rotation axis when the light guide member 5 moves relative to the substrate 2. Here, the movement may mean that the light guide member 5 and the substrate 2 rotate relatively when the substrate 2 is fixed and a shear stress parallel to the main surface 20 of the substrate 2 is applied to the side surface of the light guide member 5. Alternatively, moving may mean that the substrate 2 is fixed, and rotates when an external force is applied to the light-guiding member 5 in a direction parallel to the main surface 20 of the substrate 2 and perpendicular to the straight line connecting the starting point and the joining member 6, with the point on the surface of the light-guiding member 5 farthest from the joining member 6 as the starting point.

[0029] Here, a structure that can move in a certain direction against an external force perpendicular or parallel to the main surface 20 but cannot move in other directions is not considered to be a joining member 6 because even if thermal expansion occurs, the light guide member is not deformed and does not bring about additional constraints. In other words, a structure that can move in parallel is not considered to be a joining member 6. As shown in FIG. 4, when the joining member 6 is arranged so that the vertical projection image 6i is on the perpendicular bisector 23, the intensity distribution on the object plane (light emitting portion) and the illuminance distribution on the image plane are distributed point symmetrically with respect to the rotation axis. Therefore, even if the light guide member 5 rotates relative to the substrate 2 (i.e., the light emitting portion), the movement of the illuminance distribution on the light receiving portion created by the light emitting portion coincides with the rotation movement of the light receiving portion in both direction and amount. Therefore, no change occurs in the illuminance distribution received by the light receiving surface, and fluctuations in gas detection sensitivity are suppressed. By providing the joining member 6 as the rotation axis in this way, a gas detection device in which gas detection sensitivity is less likely to fluctuate can be realized. Here, the object surface is the surface of the light-emitting part of the element that comes into contact with the gas and is made of an optically transparent material, and the image surface is the surface of the light-receiving part of the element that comes into contact with the gas and is made of an optically transparent material.

[0030] Also, as shown in Fig. 22, if the perpendicular projection image of the bonding member onto the main surface of the substrate is located in region Rt, for the same reason, even if the light guide member 5 rotates relative to the substrate 2 (i.e., the light emitting portion), the movement of the illuminance distribution in the light receiving portion created by the light emitting portion will be approximately the same in both direction and amount as the rotational movement of the light receiving portion. Here, line Lp is the perpendicular bisector 23 of the line segment connecting the center of the first region 21 and the center of the second region 22. Line Le is a line passing through the first region 21 parallel to line Lp. Line Ld is a line passing through the second region 22 parallel to line Lp. Region Rt is the largest region within the main surface of the substrate sandwiched between lines Le and Ld.

[0031] 5 and 6 are diagrams showing the results of a simulation showing deformation due to thermal expansion of gas detector 101 of a comparative example in which first reflecting portion 51 and second reflecting portion 52 both have bonding member 6. FIG. 5 shows the shape of gas detector 101 before thermal expansion, and FIG. 6 shows the shape of gas detector 101 after thermal expansion. Gas detector 101 of the comparative example includes substrate 2 and light guiding member 5, similar to gas detector 1 according to the present embodiment. Gas detector 101 of the comparative example also includes first bonding member 106 and second bonding member 107 that firmly bond substrate 2 and light guiding member 5. In the simulation, the temperature rise change was set to 100° C. Light guiding member 5 was made of polycarbonate, with a Young's modulus of 2.35 GPa, an expansion coefficient of 70 ppm / ° C., and a Poisson's ratio of 0.38. The substrate 2 has a Young's modulus of 25.0 GPa, an expansion coefficient of 20 ppm / ° C., a Poisson's ratio of 0.2, a thickness of 2.0 mm, a long side of 20.0 mm, and a short side of 10.0 mm. As shown in FIG. 7 and FIG. 8, the central parts of the first reflecting part 51 and the second reflecting part 52 are bent due to thermal expansion deformation, and the relative angle of the second reflecting part 52 to the first reflecting part 51 changes. FIG. 7 shows the state before thermal expansion, and FIG. 8 shows the state after thermal expansion. Hereinafter, the thermal expansion distortion angle is the amount of change in the relative angle before and after thermal expansion, which is the angle between the normal vectors at an arbitrary representative point of the first reflecting part 51 and an arbitrary representative point of the second reflecting part 52 as shown in FIG. 7 and FIG. 8. Here, the representative point of the first reflecting portion 51 and the representative point of the second reflecting portion 52 may be selected from any of the points existing at the position that maximizes the minimum distance, which is defined as the minimum distance among the geodesic lines between the geometric center of each surface of the first reflecting portion 51 or the second reflecting portion 52, or between each point on the outer periphery of each surface and a certain point. As shown in FIG. 8, the optical path is distorted due to thermal expansion, and the gas detection sensitivity varies. In the simulation results, the surface of the light guide member 5 that is farthest from the substrate 2 (also called the upper surface) is displaced by an average of 40.6 μm at the center of the upper surface with respect to the peripheral end, the thermal expansion distortion angle is 0.73°, and the illuminance distribution on the image surface moves by 76.6 μm. If the length of a typical side of the light emitting element 3 is 1000 μm, the amount of movement of the illuminance distribution on the image surface, 76.6 μm, is 5% or more of the distance, and a large characteristic variation is caused.

[0032] 9 and 10 are diagrams showing deformation due to thermal expansion of gas detector 1 having only one joint member 6 on light guide member 5. FIG. 9 shows the shape of gas detector 1 before thermal expansion, and FIG. 10 shows the shape of gas detector 1 after thermal expansion. As shown in FIG. 9 and FIG. 10, the central portions of first reflecting portion 51 and second reflecting portion 52 are not bent due to thermal expansion deformation, and the relative angle of second reflecting portion 52 with respect to first reflecting portion 51 does not change. In other words, the deformation at point B at the end is -17 μm, and the deformation at point A, which is the midpoint, is -8.5 μm, so the thermal expansion distortion angle is 0.0°, and the reference position, point A, and point B are located on a straight line. Therefore, the optical path is maintained, and the gas detection sensitivity does not fluctuate.

[0033] Here, FIG. 11 is a diagram showing another example of the arrangement of the bonding member 6. Each element in FIG. 11 is the same as the element with the same reference numeral in FIG. 3, and therefore the description is omitted. As shown in FIG. 11, the bonding member 6 may be provided at a different position on the main surface 20 of the substrate 2. That is, the bonding member 6 may be provided so that the vertical projection image 6i onto the main surface 20 of the substrate 2 is not on the perpendicular bisector 23. In addition, the bonding member 6 may be provided at a position closer to the second mirror 521 and the fourth mirror 522 than the first mirror 511 and the fifth mirror 513 in the y-axis direction. However, as described above, in order to maintain the optical path, it is necessary that the light-emitting element 3 and the light-receiving element 4 face the first reflecting portion 51. Therefore, it is preferable that the bonding member 6 is provided at a position where the movement amount of the first reflecting portion 51 is smaller than the movement amount of the second reflecting portion 52 when the light-guiding member 5 moves relative to the substrate 2. In other words, the joint member 6 serving as the rotation axis is preferably provided at a position closer to the first reflecting portion 51 than to the second reflecting portion 52. Specifically, it is preferable that the vertical projection image 6i of the joint member 6 is closer to the midpoint 24.

[0034] As described above, in gas detection device 1 according to this embodiment, due to the above-described configuration, even if distortion occurs in substrate 2 due to thermal expansion, light guiding member 5 is not affected by the deformation. Therefore, gas detection device 1 can suppress distortion of the optical path and deterioration of sensitivity.

[0035] Moreover, the optical member included in the light guide member 5 is fixed to the substrate 2 via the joining member 6. Therefore, it is possible to suppress deterioration of the optical characteristics due to distortion of the optical member that occurs when the optical member and the substrate 2 are directly joined together.

[0036] Furthermore, in gas detection device 1, even if different forces act on substrate 2 and light guiding member 5, light guiding member 5 rotates about joining member 6 as a rotation axis. Therefore, by providing joining member 6 at a position where the amount of movement of first reflecting portion 51 is smaller than the amount of movement of second reflecting portion 52, the effect on the optical path can be suppressed.

[0037] In addition, the gas detector 1 is arranged so that the vertical projection image 6i on the main surface 20 of the substrate 2 is on the perpendicular bisector of the line segment connecting the center of the first region 21 and the center of the second region 22. This minimizes the longest distance between the joining member 6 and the side of the substrate 2 extending in the y-axis direction, and as a result, the bending rigidity of the gas detector 1 is increased, and the influence of the vibration of the substrate 2 on the optical path can be further suppressed. In addition, when the substrate 2 is deformed due to thermal expansion, the deformation occurs symmetrically with respect to the perpendicular bisector. Here, as shown in FIG. 4, the illuminance distribution on the image plane is rotated by approximately 180° with respect to the intensity distribution on the object plane (light emitting portion), and the illuminance distribution on the image plane due to the movement of the intensity distribution on the object plane is the same as the movement of the image plane, so the illuminance distribution on the image plane is not changed. Therefore, the fluctuation of the gas detection sensitivity is suppressed.

[0038] Second embodiment FIG. 12 is a diagram showing an example of a cross section of a gas detection device 1 according to another embodiment of the present disclosure. Gas detection device 1 according to this embodiment differs from gas detection device 1 according to the above-described first embodiment in the configuration of joining member 6. The other components are the same as those of gas detection device 1 according to the first embodiment. For example, a perspective view of gas detection device 1 according to this embodiment is shown in FIG. 1, as in the first embodiment. Moreover, the same components as those of gas detection device 1 according to the first embodiment are given the same reference numerals as in FIGS. 1 to 3, and detailed description thereof will be omitted.

[0039] 12, in this embodiment, the joining member 6 is not a columnar body. The joining member 6 includes a first portion 6a including a first bottom surface portion 61, a second portion 6b including a second bottom surface portion 62, and a joining portion 63 that joins the first portion 6a, the second portion 6b, and the third mirror 512. By joining the third mirror 512 to the joining member 6, the relative position of the first reflecting portion 51 to the second reflecting portion 52 is more firmly fixed.

[0040] FIG. 13 is a diagram showing an example of the arrangement and shape of the bonding member 6 in this embodiment. FIG. 13 shows the main surface 20 of the substrate 2 as viewed in the negative direction of the z-axis. In this embodiment, the vertical projection image 6i onto the main surface 20 of the substrate 2 is arch-shaped. The bonding member 6 is arranged so that the vertical projection image 6i onto the main surface 20 of the substrate 2 includes the midpoint 24 of the line segment connecting the center 21c of the first region 21 and the center 22c of the second region 22. As described above, the vertical projection image 6i of the bonding member 6 being close to the midpoint 24 contributes to maintaining the optical path by making the movement amount of the first reflecting portion 51 smaller than the movement amount of the second reflecting portion 52.

[0041] As described above, gas detection device 1 according to this embodiment has the above-mentioned configuration and thereby achieves the same effects as embodiment 1. Furthermore, gas detection device 1 according to this embodiment is provided with joining member 6 having joining portion 63 to which third mirror 512 is also joined, thereby enabling the relative position of first reflecting portion 51 to second reflecting portion 52 to be fixed even more firmly.

[0042] (Modification) Although the embodiment has been described above based on the drawings and examples, it should be noted that a person skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these modifications and corrections are included in the scope of the present disclosure. For example, the functions included in each member, each means, etc. can be rearranged so as not to be logically inconsistent, and multiple means, etc. can be combined into one or divided.

[0043] For example, the vertical projection image 6i of the joining member 6 may be a polygon. As a modification, the vertical projection image 6i may be a rectangle and the joining member 6 may be a square prism, as shown in FIG.

[0044] For example, in the above embodiment, the joining member 6 is described as being composed of one part. The joining member 6 may be composed of multiple parts. Here, the multiple parts are arranged to be separated from each other but somewhat close to each other so that they collectively form a rotation axis when the light guide member 5 moves relative to the substrate 2. As one modified example, as shown in FIG. 15, the vertical projection image 6i may be multiple solid circles. In this case, the joining member 6 can join the substrate 2 and the light guide member 5 more firmly.

[0045] For example, in the above embodiment, it has been described that the relative position of the first reflecting portion 51 with respect to the second reflecting portion 52 is fixed by integral formation, adhesive, or the like. As one modified example, the second reflecting portion 52 may be strongly joined together with the first reflecting portion 51 to the second bottom surface portion 62 of the joining member 6 by adhesive, welding, tabs, fitting, or the like, as shown in Fig. 16. In this case, the second reflecting portion 52 may be formed integrally with the second mirror 521 and the fourth mirror 522, and may include an extension portion 523 extending to the first reflecting portion 51.

[0046] FIG. 17 is a graph showing the unit thermal expansion strain angle and the maximum strain ratio under normal pressure based on the simulation results of the thermal expansion strain angle and maximum strain under normal pressure of the light-guiding member 5 in several examples using bonding members 6 of various shapes.

[0047] Here, the maximum vertical strain amount refers to the maximum strain length in the application direction of light-guiding member 5 when a part of substrate 2 is restrained so as not to be displaced and a stress of 5000 Pa is applied vertically to the entire upper surface of light-guiding member 5.

[0048] From the viewpoint of structural mechanics, the vertical maximum strain increases linearly with the applied pressure and behaves approximately similarly with respect to the maximum length of the light-guiding member 5. The unit pressure / vertical maximum strain ratio is the vertical maximum strain per unit pressure divided by the maximum length of the light-guiding member 5. In this simulation, the vertical maximum strain per unit pressure is the vertical maximum strain / 5000 Pa. In addition, in this simulation, the maximum length of the light-guiding member 5 is 22.9×10 -3 m. When bonding member 6 is firmly bonded to substrate 2 and light guiding member 5 by increasing the bonding area or the number of bonding locations, the rigidity of the entire structure of gas detection device 1 is improved, and the maximum strain ratio under normal application of unit pressure decreases. In other words, the maximum strain ratio under normal application of unit pressure is an index representing the degree of bonding between substrate 2 and light guiding member 5. A small value for the maximum strain ratio under normal application of unit pressure corresponds to an over-constrained state in which substrate 2 and light guiding member 5 are firmly bonded. A large value for the maximum strain ratio under normal application of unit pressure corresponds to a less constrained state.

[0049] As described above, the thermal expansion strain angle is the relative angle of the second reflecting portion 52 with respect to the first reflecting portion 51. The unit thermal expansion strain angle shown in FIG. 17 is the angle per 1° C. of the thermal expansion strain angle. The unit thermal expansion strain angle is the amount of change in angle per 1° C. when the state before thermal expansion is set to 0° and the thermal expansion strain angle due to a temperature rise of 100° C. is obtained. From this simulation result, the unit thermal expansion strain angle increases rapidly in a structure in which the unit pressure vertical application maximum strain ratio is in a region smaller than 143 / GPa. Therefore, by forming the bonding member 6 so that the unit pressure vertical application maximum strain ratio is 143 / GPa or more, the thermal expansion strain is suppressed, and the optical path is maintained, thereby realizing a gas detection device 1 in which the gas detection sensitivity does not fluctuate. Here, 143 / GPa is a value located between Examples i and j in FIG. 17. In other words, if the unit pressure normal application maximum strain ratio is 143 / GPa or more, the joint member 6 serves as a rotation axis when the light guide member moves relative to the substrate.

[0050] In addition, when the bonding member 6 is provided only in the first reflecting portion 51, and the bonding member 6 is, for example, extremely thin and has a very small area, and the bonding between the substrate 2 and the light guide member 5 is weak, the maximum strain ratio when the unit pressure is applied vertically may exceed 10000 / GPa. 2 When 5000 Pa is applied vertically to the upper surface of the light guide member 5, the maximum amount of strain due to vertical application can reach 5.0% of the maximum length of the light guide member 5. For example, when the maximum length of the light guide member 5 is 22.9 mm, the amount of strain is 1.15 mm, and the light guide member 5 and the substrate 2 come into contact with each other at places other than the joint member 6 due to deformation, and a strain occurs in the relative angle between the first reflecting portion 51 and the second reflecting portion 52. In other words, a thermal expansion strain angle occurs, and through the fluctuation of the optical path, a fluctuation of the gas detection sensitivity occurs. Here, the maximum strain ratio due to vertical application of unit pressure can be experimentally calculated and determined by fixing the substrate 2 of the gas detector 1, applying an arbitrary load to the upper surface, measuring the amount of strain displacement with a displacement meter, and using the value of the average vertical stress per upper area from the load. The unit thermal expansion strain angle of the examples a to p in FIG. 17 was calculated by a simulation using the gas detector 1 having the shape shown in FIGS. 18 to 21. 18 to 21, a to p correspond to the same reference characters as those in Fig. 17. In Figs. 18 to 21, the left side of the reference characters a to p is a side view, and the right side is a top view. [Explanation of symbols]

[0051] 1 Gas detection equipment 2. Board 3 Light emitting element 4 Photodetector 5 Light guide member 6 Joining materials 6a First Part 6b Second Part 6i vertical projection image 20 Main Surface 21 The First Area 21c Center of the First Region 22 The Second Area 22c Center of the Second Region 23 Perpendicular bisector 24 Midpoint 51 First reflector 52 Second reflector 53 Vent 54 Cells 61 First bottom part 62 Second bottom part 63 Joint 101 Gas detection equipment 106 First joining member 107 Second joining member 511 First Mirror 512 The Third Mirror 513 The Fifth Mirror 521 Second Mirror 522 The Fourth Mirror 523 Extension

Claims

1. A substrate; a light emitting element provided in a first region of a main surface of the substrate and emitting light; a light receiving element provided in a second region of the main surface of the substrate and configured to receive the light; a light guiding member that guides the light emitted by the light emitting element to the light receiving element; a joining member that joins the substrate and the light guiding member and serves as a rotation axis when the light guiding member moves relative to the substrate, a perpendicular bisector of a line segment connecting the center of the first region and the center of the second region is defined as a straight line Lp, a straight line passing through the first region and parallel to the straight line Lp is defined as a straight line Le, a straight line passing through the second region and parallel to the straight line Lp is defined as a straight line Ld, the largest area within a main surface of the substrate sandwiched between the straight lines Le and Ld is defined as a region Rt, and a vertical projection image of the bonding member onto the main surface of the substrate exists in the region Rt.

2. The gas detection device according to claim 1 , wherein a vertical projection image of the bonding member onto the main surface of the substrate is disposed on the straight line Lp.

3. 3. The gas detection device according to claim 2, wherein the bonding member is disposed so that a vertical projection image of the bonding member onto the main surface of the substrate includes a midpoint of a line segment connecting a center of the first region and a center of the second region.

4. The gas detection device according to claim 1 , wherein the light guiding member comprises a first reflecting portion and a second reflecting portion.

5. The gas detection device according to claim 4 , wherein a relative position of the first reflecting portion with respect to the second reflecting portion is fixed.

6. the first reflecting portion directly reflects the light emitted from the light-emitting element and the light received by the light-receiving element, The gas detection device according to claim 4 , wherein the second reflecting portion reflects the light between itself and the first reflecting portion.

7. 7. The gas detection device according to claim 6, wherein the joining member is provided at a position such that, when the light guide member moves relative to the substrate, an amount of movement of the first reflecting portion is smaller than an amount of movement of the second reflecting portion.

8. The gas detection device according to claim 1 , wherein the joining member is made up of a plurality of parts.

9. The gas detection device according to claim 1 , wherein the joining member is constituted by a single part.

10. 10. The gas detection device according to claim 9, wherein a vertical projection image of the joining member onto the main surface of the substrate has a shape that is a solid circle, a hollow circle, an arcuate shape, or a polygonal shape.

11. 11. The gas detection device according to claim 1, wherein the joining member fixes the substrate and serves as a rotation axis when the light-guiding member and the substrate rotate relatively when a shear stress parallel to a main surface of the substrate is applied to a side surface of the light-guiding member.

12. 12. The gas detection device according to claim 1, wherein the joining member fixes the substrate and serves as a rotation axis when an external force is applied to the light-guiding member in a direction parallel to a main surface of the substrate and perpendicular to a straight line connecting a point on a surface of the light-guiding member farthest from the joining member as a starting point.

Images