Gas cell housing for gas sensor and gas sensor equipped therewith

Abstract

To provide a gas cell housing molding mold, a method for manufacturing a gas cell housing, a gas cell housing for a gas sensor, and a gas sensor including the same, which eliminate the need for incorporation of a mirror section in the gas cell housing and can simplify a step of adjusting assembly tolerance of a sensitive optical component, thereby obtaining high robustness of a multiple reflection optical path folded back in multiple stages.SOLUTION: A gas sensor 10 includes, in a single housing section 30, a substrate mounting surface 31 provided with a substrate 20 including a light emitter 21 and a light receiver 22, and a mirror section 40 including multiple reflectors 41-45. In the housing section 30, all of the multiple reflectors 41-45 are integrally molded on an inner surface of the housing section 30 for multiply reflecting light emitted from the light emitter 21 and causing the light to enter the light receiver 22 in an opposing direction of one side and the other side in an extension direction of the substrate mounting surface 31.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gas sensor, and particularly to a mold for forming a gas cell housing, a method for manufacturing the gas cell housing, a gas cell housing for a gas sensor, and a gas sensor including the same.

Background Art

[0002] Conventionally, as a gas concentration measuring device for measuring the concentration of a measurement target gas in the atmosphere, a non-dispersive infrared absorption type gas sensor that measures the gas concentration by detecting the amount of absorption using the fact that the wavelength of infrared light absorbed by the gas varies depending on the type of gas is known.

[0003] For example, Patent Document 1 discloses a gas sensor including a gas cell (OBA) having a light emitting unit, a light receiving unit, and a mirror unit. In the technology described in this document, the light emitting unit and the light receiving unit are arranged at the condensing points of the mirror units provided corresponding to the light emitting unit and the light receiving unit, respectively, and the light emitted from the light emitting unit is made to enter the light receiving unit via the mirror unit. At that time, by introducing the measurement target gas into the gas cell, the concentration of the measurement target gas is detected according to the output signal of the light receiving unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In this type of gas sensor, the mirror section within the gas cell housing needs to be optimized for multi-stage optical path folding in order to acquire a highly accurate detection signal and achieve a high signal-to-noise ratio. For example, gas cells designed for low-concentration gases achieve a long optical path length by using multiple reflections within the gas cell housing.

[0006] To obtain a mirror with excellent reflective properties, a gas cell is desired that has a mirror surface with high reflectivity and aging characteristics that can withstand climatic and air pollution environments. Therefore, the molds for molding the housing and mirror parts of the gas cell from resin are designed with extremely high precision based on deep knowledge of optical properties and, for example, optical path simulations using the Lambert-Beer law.

[0007] However, the housing structure of conventional gas cells consists of multiple parts, with the housing and mirror sections being separate components. As a result, because the housing and mirror sections of the gas cell are separate parts, it is difficult to obtain high robustness in the multi-reflection optical path created by the mirror surfaces of the multi-stage folded mirror section. In contrast, with current 3D printing technology, it is extremely difficult to precisely form the surface roughness required for the mirror surface that constitutes the multiple reflection light path of the mirror section, as well as the multi-stage folding optical system, within the gas cell housing and as an integral part of the housing.

[0008] Therefore, the present invention has been made in view of these problems, and aims to provide a mold for molding a gas cell housing, a method for manufacturing a gas cell housing, and a gas cell housing for a gas sensor, which eliminate the need to incorporate a mirror portion into the housing portion of the gas cell, simplify the process of adjusting the assembly tolerances of sensitive optical components, and obtain high robustness of a multi-stage folded multiple reflection optical path. [Means for solving the problem]

[0009] To solve the above problems, a mold for molding a gas cell housing according to one aspect of the present invention is a mold for injection molding a gas cell housing from a resin material, the mold having a mirror portion having a plurality of reflectors arranged to reflect light emitted from the light-emitting portion in multiple directions opposite to one side of the substrate mounting surface on which a substrate having a light-emitting portion and a light-receiving portion is mounted, so as to incident light emitted from the light-emitting portion on the light-receiving portion. The mold is characterized in that the release direction of the lower mold and the upper mold during demolding is provided at an angle to a direction perpendicular to the extending direction of the substrate mounting surface so that not all of the plurality of reflectors are undercut, so that all of the plurality of reflectors are integrally molded on the inner surface of a gas cell housing to be molded.

[0010] Furthermore, in order to solve the above problems, a method for manufacturing a gas cell housing according to one aspect of the present invention is characterized in that, using a mold for molding a gas cell housing according to one aspect of the present invention, the removal direction when demolding the lower mold and the upper mold is inserted and removed at an angle to a direction perpendicular to the extending direction of the substrate mounting surface so that no undercut occurs on any of the plurality of reflective parts, thereby integrally molding all of the plurality of reflective parts with the inner surface of a single housing part to manufacture a gas cell housing.

[0011] Furthermore, in order to solve the above problems, a gas cell housing for a gas sensor according to one aspect of the present invention is a gas cell housing for a gas sensor comprising a substrate mounting surface on which a substrate having a light-emitting part and a light-receiving part is mounted, and a mirror part having a plurality of reflective parts, wherein all of the plurality of reflective parts are integrally molded on the inner surface of the housing so as to reflect light emitted from the light-emitting part in multiple directions in opposing directions between one side and the other side of the substrate mounting surface and cause it to enter the light-receiving part.

[0012] Furthermore, in order to solve the above problems, a gas sensor according to one aspect of the present invention is characterized by comprising a gas cell housing for a gas sensor according to one aspect of the present invention.

[0013] According to the present invention, since all of the multiple reflective surfaces of the mirror portion of the gas sensor according to the present invention are integrally molded on the inner surface of the gas cell housing, the process of assembling the mirror portion into the gas cell housing is unnecessary, and the process of adjusting the assembly tolerances of sensitive optical components can be simplified. As a result, high robustness of the multi-folded multiple reflective optical path can be obtained. [Effects of the Invention]

[0014] As described above, according to the present invention, the process of assembling the mirror portion into the gas cell housing is unnecessary, and the process of adjusting the assembly tolerances of sensitive optical components can be simplified. As a result, high robustness of the multi-folded multiple reflection optical path can be obtained. [Brief explanation of the drawing]

[0015] [Figure 1] Figures (a) and (b) illustrate an embodiment of a gas sensor according to one aspect of the present invention, with the main components inside the gas cell housing shown by dashed lines in figure (b). [Figure 2] This is an explanatory diagram of one embodiment of a gas sensor according to one aspect of the present invention, where (a) is a front view, (b) is a bottom view, (c) is a cross-sectional view of XX in (a), and (d) is a cross-sectional view of YY in (b). [Figure 3] This is an explanatory diagram of one embodiment of a gas cell housing constituting a gas sensor according to one aspect of the present invention. Figure (a) is a perspective view taken from the front, right side, and above in the plan view direction, and Figure (b) is a perspective view taken from the front, left side, and below in the bottom view direction. [Figure 4] This is an explanatory diagram of one embodiment of a gas cell housing that constitutes a gas sensor according to one aspect of the present invention, where (a) is a front view, (b) is a bottom view, (c) is a left side view showing the main components inside the housing with dashed lines, and (d) is a ZZ cross-sectional view of (a). [Figure 5] This is an explanatory diagram of a gas cell molding die for manufacturing a gas cell housing according to one aspect of the present invention, and the diagram schematically shows the cross-sectional shape corresponding to the cross-sectional portion shown in Figure 4(d). [Modes for carrying out the invention]

[0016] Hereinafter, an embodiment of the present invention will be described with appropriate reference to the drawings. Note that the drawings are schematic. Therefore, it should be noted that the relationship between the thickness and the planar dimensions, the ratio, etc. are different from the actual ones, and there are also parts where the dimensional relationships and ratios are different between the drawings. In addition, the embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the materials, shapes, structures, arrangements, etc. of the constituent parts in the following embodiments.

[0017] As shown in FIGS. 1 and 2, the gas sensor 10 according to this embodiment includes a gas cell housing 30 having a rectangular parallelepiped appearance and a rectangular parallelepiped plate-like substrate 20 mounted on the bottom surface side of the gas cell housing 30. In this specification, for the sake of convenience of explanation, when the longitudinal direction of the rectangular parallelepiped is defined as the front-rear direction and the short-side direction is defined as the left-right direction, in the front-rear direction of the longitudinal direction of the gas cell housing 30, the wall surface on the front side in the figure is referred to as the front wall surface 35. Similarly hereinafter, the back side in the longitudinal direction is referred to as the back wall surface 34, the right side in the short-side direction is referred to as the right wall surface 36, the left side in the short-side direction is referred to as the left wall surface 37, the upper surface is referred to as the upper surface 33, and the lower surface is referred to as the bottom surface 32.

[0018] A cavity is formed inside the gas cell housing 30 of the gas sensor 10, and as shown in FIGS. 1(b) and 2(c), (d), a mirror portion 40 having a plurality of reflection portions 41 to 45 is provided on the inner surface of the gas cell housing 30. The bottom surface 32 of the gas cell housing 30 is formed with a recess that opens largely downward except for both sides in the longitudinal direction as a substrate mounting surface 31, and the rectangular parallelepiped plate-like substrate 20 is mounted on the substrate mounting surface 31 so as to be fitted into the recess. At this time, the substrate 20 is mounted such that the light emitting portion 21 and the light receiving portion 22 are located on one side in the front-rear direction.

[0019] As shown in FIGS. 3 and 4, in the housing 30 for the gas cell of the present embodiment, all of the plurality of reflecting portions 41 to 45 are integrally formed on the inner surface of the housing 30 for the gas cell so as to multiply reflect the light emitted from the light emitting portion 21 in the direction facing one side and the other side in the extending direction of the substrate mounting surface 31 and make it incident on the light receiving portion 22.

[0020] In the example of the present embodiment, two reflecting portions 42 and 44 are arranged on the side opposite to the side where the light emitting portion 21 and the light receiving portion 22 are located, and a rectangular opening 30k is formed so as to be located above the two reflecting portions 42 and 44. In the gas sensor 10 of the present embodiment, the opening 30k that opens upward is used as an introduction / discharge port for the measurement target gas, and the measurement target gas is introduced into the gas cell housing 30 through the particle filter 50 from this opening 30k.

[0021] Then, the gas sensor 10 of the present embodiment allows the measurement target gas to pass between the light emitting portion 21 and the light receiving portion 22 and the mirror portion 40, and based on the output signal of the light receiving portion 22 at this time, the concentration of the measurement target gas can be calculated by a concentration calculation unit (not shown).

[0022] Thereby, this gas sensor 10 is configured to be able to calculate the concentration of the measurement target gas in the optical path from the light emitting portion 21 to the light receiving portion 22 based on the output signal of the light receiving portion 22 acquired by the concentration calculation unit, and functions as a gas concentration measuring device. Note that the shapes of the light receiving surface 22a and the light emitting surface 21a are not limited to being rectangular and can be arbitrary shapes. For example, the light receiving surface 22a may be elliptical or the light emitting surface 21a may be elliptical.

[0023] More specifically, as shown in FIGS. 1 and 2, the gas sensor 10 according to the present embodiment has two openings formed above and below the housing 30 for the gas cell, and the two openings communicate with a plurality of reflecting portions 41 to 45 formed on the inner surface of the housing 30 for the gas cell to define an internal cavity.

[0024] The upper opening 30k is sealed from above by a particle filter 50 so as to cover the opening 30k. The particle filter 50 is formed in the shape of a rectangular plate that is slightly larger than the opening 30k and is installed so as to cover the opening 30k.

[0025] The lower opening is the substrate mounting surface 31, and a substrate 20 of a similar shape is mounted to cover the opening. As shown in Figures 1(b) and 2(d), the substrate 20 is provided with a light-emitting section 21 and a light-receiving section 22, and a mirror section 40 is provided on the inner surface of the gas cell housing 30. In this example, the light-emitting section 21 and the light-receiving section 22 are arranged on a single substrate 20.

[0026] The substrate 20 is a circuit board that also functions as a base substrate, and for example, a printed circuit board can be used. Note that the light-emitting unit 21 and the light-receiving unit 22 are not limited to being mounted on the same substrate 20, but may be mounted on separate substrates.

[0027] The light-emitting unit 21 has a light-emitting surface 21a and is configured to emit light including infrared light. The light emitted from the light-emitting surface 21a of the light-emitting unit 21 is multiple-reflected by the multiple reflectors 41-45 of the mirror unit 40, and the point of focus is positioned to overlap with the light-receiving surface 22a of the light-receiving unit 22.

[0028] The light-emitting unit 21 is not particularly limited as long as it outputs light that includes wavelengths absorbed by the gas being measured. Specific examples include MEMS (microelectromechanical systems) light sources and light-emitting diodes. Among these, it is preferable that the light-emitting unit outputs only light in the wavelength band in which the gas being measured has high absorption, from the viewpoint of reducing noise caused by light absorption by components other than the gas being measured.

[0029] Specifically, from the viewpoint of being able to control the emission wavelength band with the band gap of the active layer, the light-emitting section 21 may preferably be a light-emitting diode structure. The light-emitting diode may be formed on a semiconductor substrate. Furthermore, it is preferable that the diodes be connected in series or parallel by wiring to enhance the light emission intensity. In addition, a sensor unit for monitoring the amount of light emitted may be provided at the position where the light emitted from the light-emitting diode and reflected off the back surface of the semiconductor substrate is incident.

[0030] The light-emitting unit 21 may further include an optical filter having desired optical properties in accordance with the gas being measured. For example, when the gas being measured is carbon dioxide, the light-emitting unit 21 may be equipped with a bandpass filter that can filter out infrared rays in the wavelength band where a lot of infrared absorption by carbon dioxide occurs (typically around 4.3 μm).

[0031] The light-receiving unit 22 has a light-receiving surface 22a and is configured to receive at least a portion of the light emitted from the light-emitting unit 21. The light-receiving unit 22 is positioned so that the light-receiving surface 22a coincides with the light-collecting point of the mirror unit 40.

[0032] A photodiode may be preferable as the light-receiving unit 22. The photodiode is preferably sensitive to a light band that includes wavelengths absorbed by the gas being measured. The shape of the photodiode is not particularly limited as long as a sufficient signal-to-noise ratio can be obtained.

[0033] The photodiode may further include an optical filter having desired optical properties in accordance with the gas being measured. For example, when the gas being measured is carbon dioxide, the photodiode may be equipped with a bandpass filter that can filter out infrared radiation in the wavelength band where carbon dioxide absorbs a lot of infrared radiation (typically around 4.3 μm).

[0034] As described above, the mirror section 40 has a plurality of reflective sections 41 to 45, and the plurality of reflective sections 41 to 45 are arranged to form a multi-stage reflective optical path by multiple reflections of the light emitted from the light-emitting section 21 toward the light-receiving section 22.

[0035] Furthermore, the mirror section 40 is configured with a multi-stage reflective optical path that can collect light emitted from the light-emitting surface 21a of the light-emitting section 21 and also collect light directed toward the light-receiving surface 22a of the light-receiving section 22. In this embodiment, the mirror section 40 performs multiple reflections of light emitted from the light-emitting section 21 so that the point of focus is located at a position that overlaps with the light-receiving surface 22a of the light-receiving section 22.

[0036] As a result, the gas sensor 10 of this embodiment has a small and compact gas cell housing 30 while realizing a gas sensor with a long optical path length, thereby improving the accuracy of gas concentration detection. In this embodiment, all of the multiple reflective parts 41 to 45 are integrally molded onto the inner surface of a gas cell housing 30 of a specific shape using a resin substrate, and then a reflective surface is formed by vapor deposition or plating of an alloy containing aluminum, gold, silver, or a laminate thereof on the light-reflecting portion.

[0037] The focal point is a position uniquely determined by the relative positions of the light-emitting section 21, the light-receiving section 22, and the mirror section 40, as well as the shapes and arrangements of the multiple reflecting sections 41-45. Examples of reflecting sections with a focal point include spherical mirrors, elliptical mirrors, and parabolic mirrors. When converting light into parallel light using spherical or parabolic mirrors, a plane mirror may be included between the two spherical or parabolic mirrors to increase the optical path length.

[0038] Here, the gas cell housing 30 of the gas sensor 10 according to this embodiment is configured such that the demolding directions Lu and Ls satisfy the conditions for forming a predetermined integrated structure including the mirror portion 40, as shown in Figure 4(d). As a result, as will be described later, all of the multiple reflective portions 41 to 45 constituting the mirror portion 40 are molded integrally on the inner surface of a single housing 30 using a mold (see Figure 5).

[0039] Therefore, according to the gas sensor 10 of this embodiment, all of the multiple reflective parts 41 to 45 constituting the mirror part 40 are integrally molded on the inner surface of a single housing 30, so that changes in the output signal at the light receiving part 22 due to the effects of the expansion and contraction of the adhesive can be suppressed. As a result, almost all of the light reflected by the mirror part 40 can be accurately received by the light receiving surface 22a of the light receiving part 22.

[0040] The gas cell housing 30 of the gas sensor 10 according to this embodiment is molded using a mold for molding gas cell housings, which will be described later. As a result, the gas cell housing 30 has an undercut shape in a direction perpendicular to the extending direction of the substrate mounting surface 31 to be molded. On the other hand, it does not have an undercut shape in a direction tilted by a specific angle with respect to the extending direction of the substrate mounting surface 31 to be molded. As a result, in the direction perpendicular to the extending direction of the molded substrate mounting surface 31, the gas cell housing 30 has the reflective parts 41-45 and the like integrated with an undercut shape. Therefore, there is no risk of the resin adhesive expanding or contracting due to external environmental factors, or of the mirror part 40 being misaligned, and the shape of the mirror is not restricted. This results in high robustness and enables stable detection of gas concentration with high accuracy.

[0041] <Mold for molding gas cell housings and method for manufacturing gas cell housings using the same> The following describes the mold for molding the gas cell housing of this embodiment and the method for manufacturing the gas cell housing using the same. The gas cell housing 30 of this embodiment is molded using a dedicated mold for molding the gas cell housing, for example, as schematically shown in Figure 5. In the mold for molding the gas cell housing of this embodiment, the method of setting the ejection direction Lu of the upper mold 100 and the ejection direction Ls of the lower mold 200 to a predetermined value is employed, and the method of pressing and cutting together the contact surfaces (including the parting surface) of the fixed lower mold 200 and the movable upper mold 100 are rubbed together to create a tight seal.

[0042] More specifically, as shown in Figure 5, the molding die for the gas cell housing 30 according to this embodiment comprises at least a lower die 200 and an upper die 100. The demolding directions Lu,Ls of these dies are set at an angle (angle θ) relative to the direction perpendicular to the extending direction of the substrate mounting surface 31 to be molded, so that not all of the multiple reflective portions 41 to 45 become undercut shapes. Here, the angle θ is preferably 5° to 85° or -5° to -85°, and more preferably 10° to 80° or -10° to -80°. As a result, this mold for molding the gas cell housing allows for integral molding such that all of the multiple reflective portions 41-45 on the inner surface of a single gas cell housing 30 to be molded do not have an undercut shape. However, if the release direction of the mold for molding the gas cell housing 30 is perpendicular to the extending direction of the substrate mounting surface 31 to be molded, the gas cell housing 30 according to this embodiment has an undercut shape, and therefore cannot be integrally molded with a two-way release die.

[0043] The cavity forming section CA shown in the figure will be a cavity corresponding to the molded shape shown in Figures 3 and 4. To ensure that this cavity corresponding to the molded shape is formed, the lower mold 200 has a cavity forming projection 240 that protrudes upward, and the upper mold 100 has a cavity forming projection 140 that protrudes downward.

[0044] In the example shown in the figure, the butt surfaces PL1 and PL3 of the lower mold 200 and the upper mold 100 are perpendicular to the demolding directions Lu and Ls, and the demolding directions Lu and Ls are perpendicular. In this mold for forming the gas cell housing, the demolding directions Lu and Ls are provided at an angle (angle θ) relative to the direction perpendicular to the extending direction of the substrate mounting surface 31 to be formed. Therefore, as shown in Figure 2(c), the inner surface slanted 38 of the upper opening 30k is formed by a push-cutting mating surface PL2 that is aligned with the demolding directions Lu and Ls.

[0045] In other words, the shape of this cutting mating surface PL2 is formed along the sliding contact surfaces 138 and 238 of the cavity forming protrusions 240 of the lower mold 200 and the cavity forming protrusions 140 of the upper mold 100, and it is an inclined surface corresponding to the angle (angle θ) of the demolding direction Lu,Ls.

[0046] In other words, the push-cut mating surface PL2 is parallel to the demolding directions Lu and Ls. If a protrusion were provided on only one of the upper mold 100 or the lower mold 200, an undercut shape would result. However, by dividing the protrusion into a cavity-forming protrusion 240 and a cavity-forming protrusion 140, an undercut shape can be avoided. Furthermore, by making the push-cut mating surface PL2 between the cavity-forming protrusion 240 and the cavity-forming protrusion 140 parallel to the demolding directions Lu and Ls, demolding between the upper mold 100 and the lower mold 200 becomes possible.

[0047] The method for manufacturing the gas cell housing 30 using a mold for molding gas cell housings according to this embodiment involves injection molding the gas cell housing 30 with a resin material using an injection molding machine (not shown). In this embodiment, the gas cell housing 30 is integrally molded on the inner surface of a housing portion 30 using a single material such as resin (material: PPS). In the mold for molding the gas cell housing according to this embodiment, the removal direction Lu,Ls when the lower mold 200 and the upper mold 100 are separated from each other is such that no undercut occurs on the reflective surfaces of the multiple reflective portions 41 to 45, and the mold is removed by inserting and removing the mold at an angle (angle θ) with respect to a direction perpendicular to the extending direction of the substrate mounting surface 31.

[0048] As a result, in the manufacturing method of the gas cell housing 30 using the mold for molding the gas cell housing according to this embodiment, the mirror portion 40 can be integrally molded onto the inner surface of the gas cell housing 30 using a two-way molding die without using a core or insert. Furthermore, in this embodiment, forced molding does not occur for any of the multiple reflective portions 41 to 45 of the mirror portion 40, and draft angles are not required for all of the outer surfaces of the rectangular parallelepiped gas cell housing 30. This simplifies the design of the mold and reduces product costs. In addition, problems such as thermal expansion coefficients and humidity expansion coefficients caused by mixing different materials are mitigated.

[0049] Thus, the mold for molding the gas cell housing and the method for manufacturing the gas cell housing 30 using the same make it possible to realize a gas sensor 10 that is highly robust and can detect gas concentration with higher accuracy. In other words, since the mirror portion 40 is integrally molded on the inner surface of the gas cell housing 30, changes in the output signal of the light receiving portion 22 due to the effects of the expansion and contraction of the adhesive can be suppressed.

[0050] Therefore, with the mold for molding the gas cell housing and the method for manufacturing the gas cell housing 30 using the present embodiment, a gas cell housing 30 in which all of the multiple reflective parts 41 to 45 are integrally molded with the inner surface of a single housing can be manufactured efficiently and inexpensively. In this embodiment, the gas sensor 10 is completed by fixing the substrate 20 to the gas cell housing 30, which has a mirror portion 40 integrally provided on its inner surface, using a resin adhesive at the substrate mounting surface 31 of the gas cell housing 30, so as to cover the entire opening.

[0051] As a result, the mirror portion 40, which is integrally molded with the gas cell housing 30, receives more light emitted from the light-emitting portion 21 through the multiple reflective portions 41-45, and also allows more light reflected by the multiple reflective portions 41-45 to be received by the light-receiving portion 22.

[0052] <Regarding the effects and benefits> Next, the effects and advantages of the gas cell housing 30 of this embodiment, the gas sensor 10 equipped therewith, the mold for molding the gas cell housing 30, and the method for manufacturing the gas cell housing 30 will be described. Conventionally, this type of gas cell housing was constructed by incorporating two mirror sections, which were separate components from the housing, into the housing and fixing them together using a resin adhesive. For example, a housing section made of liquid crystal polymer (LCP) and a mirror section made of resin plate (material: PPS) were joined together by adhesive or heat scribing.

[0053] However, if a mirror, which is a separate component, is fixed inside the housing of the gas cell using a resin adhesive, the adhesive may expand or contract due to external environmental factors, potentially causing the mirror to shift position relative to the light-emitting and light-receiving parts of the substrate fixed to the housing. If such a positional shift occurs, the output signal of the light-receiving unit may change even though the gas concentration of the gas being measured has not changed, potentially preventing accurate detection of the gas concentration.

[0054] In contrast, according to the gas sensor 10 of this embodiment, the above-mentioned mold for molding the gas cell housing is used, and the multiple reflective parts 41 to 45 are inserted and removed at an angle θ that is oblique to the direction perpendicular to the extending direction of the substrate mounting surface 31, so as not to cause undercuts that would result from forcibly removing all of the reflective surfaces of the multiple reflective parts 41 to 45, and molded in such a way that the multiple reflective parts 41 to 45 are integrally molded with the inner surface of a single housing to manufacture the gas cell housing 30. As a result, a mirror part 40 can be integrally molded on the inner surface of the gas cell housing 30 in which no undercuts occur on the reflective surfaces of the multiple reflective parts 41 to 45.

[0055] Therefore, according to the gas sensor 10 of this embodiment, all of the multiple reflective parts 41 to 45 of the mirror part 40 are integrally molded into a single housing 30, resulting in an integrated structure that eliminates the need for the conventional process of assembling two mirror parts (mirror assemblies) into the housing part of the gas cell housing 30 and the bonding process, thereby simplifying the process of adjusting the assembly tolerances of sensitive optical components.

[0056] Furthermore, in this embodiment, the mirror portion 40 of the gas cell housing 30 has all of the reflective surfaces of the multiple reflective portions 41 to 45 integrally molded into a single gas cell housing 30. Therefore, there is no risk of the resin adhesive expanding or contracting due to external environmental factors, or of the mirror portion 40 being misaligned during assembly. As a result, it is highly robust and can detect the gas concentration with high accuracy and stability.

[0057] Here, in order to efficiently direct the light emitted from the light-emitting unit 21 into the light-receiving unit 22 and increase the output signal of the light-receiving unit 22, it is better for the mirror unit 40 to focus the light towards the light-receiving surface 22a of the light-receiving unit 22 over the smallest possible area. In contrast, as in this embodiment, when multiple reflective sections 41 to 45 constituting the mirror section 40 of the gas cell are integrally molded into a single gas cell housing 30, the multiple optical reflective surfaces are integrally molded into a single housing. This simplifies the process of adjusting the assembly tolerances of sensitive optical components and reduces individual and lot differences due to manufacturing variations in the optical path. Therefore, a gas sensor with strong robustness and the ability to detect gas concentration with higher precision can be realized.

[0058] Furthermore, the gas cell housing 30 of this embodiment reduces the problem of misalignment caused by mixing different materials (such as thermal expansion coefficients and humidity expansion coefficients), and allows almost all of the light that has been multiple-reflected by the mirror unit 40 to be received by the light receiving unit 22a of the light receiving unit 22 with greater precision.

[0059] Furthermore, according to the gas cell housing 30 of this embodiment, the perimeter of the rectangular parallelepiped gas cell housing 30 is integrally constructed with four continuous walls, an upper opening 30k is formed so as to coincide with the ejection direction Lu of the upper mold 100, and this upper opening 30k is sealed from above by the particle filter 50, and an opening is formed in the portion of the substrate mounting surface 31 formed on the bottom surface so as to coincide with the ejection direction Ls of the lower mold 200, and this opening in the portion of the substrate mounting surface 31 is sealed from below by the substrate 20.

[0060] As a result, the gas cell housing 30 of this embodiment makes it possible to realize a gas sensor 10 that is highly robust and can detect gas concentration with higher accuracy. Furthermore, by simplifying the design of the mold for molding the gas cell housing 30, it is possible to create a gas sensor 10 with high ingress protection (IP rating) while reducing product costs.

[0061] Furthermore, according to this embodiment, since the mirror portion 40 is integrally molded on the inner surface of the gas cell housing 30, the assembly structure is simplified, and the number of parts required to assemble the gas sensor 10 is reduced, thus simplifying the assembly process.

[0062] In particular, according to this embodiment, since the upper mold 100 and lower mold 200 that constitute the upper and lower molds are set to have their respective ejection directions Lu and Ls parallel, all the parts constituting the gas sensor 10 can be efficiently assembled from two directions along a single axis that is the insertion and removal direction of the upper and lower molds. [Explanation of Symbols]

[0063] 10 Gas sensors 20 circuit boards 21 Light-emitting part 21a Light-emitting surface 22 Light receiving section 22a Photosensitive surface 30 Gas cell housing (housing section) 31 Board mounting surface 40 Mirror section 41~45 Reflector 50 particle filter 100 upper mold 200 Lower mold

Claims

1. A gas cell housing for a gas sensor comprising a first opening and a mirror portion having a plurality of reflective portions in one housing portion, The housing portion has at least one of the plurality of reflective portions in an undercut shape in a direction perpendicular to the opening surface of the first opening, The gas cell housing for a gas sensor is such that all of the plurality of reflective parts are integrally molded on the inner surface of the housing so that the light emitted from the light-emitting part is multiple-reflected in opposing directions between one side and the other side in a direction parallel to the opening surface of the first opening and incident on the light-receiving part.

2. The housing portion has a second opening on the side opposite to the first opening, The gas cell housing for a gas sensor according to claim 1, wherein the second opening is used as an introduction and discharge port for the gas to be measured.

3. A gas sensor comprising a gas cell housing for a gas sensor according to claim 1 or 2.

4. At least one of the plurality of reflective parts has a recess, The gas cell housing for a gas sensor according to claim 1, wherein the undercut shape is defined as the x-axis being the direction parallel to the opening surface of the first opening and the y-axis being the direction perpendicular to the opening surface of the first opening, and the surface of the recess is not in the shape of a single-valued function.

5. The gas cell housing for a gas sensor according to claim 2, wherein the second opening is rectangular in plan view.

6. The second opening has an inner side slope, The gas cell housing for a gas sensor according to claim 2, wherein the inner side slope is oblique to a direction perpendicular to the opening surface of the first opening.

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