Gas cell housing for gas sensor, and gas sensor including the same

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 more particularly to a mold for forming a gas cell housing, a method for manufacturing a 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 gas to be measured in the atmosphere, a non-dispersive infrared absorption type gas sensor that measures the gas concentration by detecting the absorption amount by utilizing the fact that the wavelength of infrared light absorbed by a gas varies depending on the type of the 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 technique described in the same 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 gas to be measured into the gas cell, the concentration of the gas to be measured 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] Here, in order for the gas cell of this type of gas sensor to obtain a highly accurate detection signal and achieve a high signal-to-noise ratio, the mirror section provided in the housing of the gas cell requires optimization of the optical path that folds back in multiple stages. For example, a gas cell designed for low-concentration gases obtains a long optical path length by using multiple reflections inside the housing of the gas cell.

[0006] In order to obtain a mirror section with excellent reflection characteristics, a gas cell equipped with a mirror surface having a high reflectivity and aging characteristics that can withstand the atmospheric environment of climate and air pollution is desired. Therefore, the mold for molding the housing section and the mirror section of the gas cell is precisely designed with extremely high accuracy based on in-depth knowledge of optical physics and, for example, optical path simulation according to Lambert-Beer's law.

[0007] However, in the conventional housing structure of a gas cell, the housing section and the mirror section are prepared as separate parts and are composed of a plurality of parts. Therefore, since the housing section and the mirror section of the gas cell are separate parts, there is a problem that it is difficult to obtain high robustness of the multiple reflection optical path by the mirror surface of the mirror section that folds back in multiple stages. On the other hand, for example, in the current 3D printer technology, it is extremely difficult to accurately form, integrally with the housing section, the surface roughness required as the mirror surface constituting the multiple reflection optical path of the mirror section and the optical system that folds back in multiple stages inside the gas cell housing.

[0008] Therefore, the present invention has been made paying attention to such problems, and eliminates the need to incorporate the mirror section into the housing section of the gas cell, simplifies the adjustment process of the assembly tolerance of sensitive optical components, and provides a high robustness of the multiple reflection optical path that folds back in multiple stages. An object of the present invention is to provide a mold for molding a gas cell housing, a method for manufacturing a gas cell housing, a gas cell housing for a gas sensor, and a gas sensor including the same.

Means for Solving the Problems

[0009] In order to solve the above problems, a mold for molding a gas cell housing according to one aspect of the present invention includes a mirror portion having a plurality of reflecting portions arranged to multiply reflect light emitted from a light emitting portion in a direction facing one side and the other side of a substrate mounting surface on which a substrate having the light emitting portion and a light receiving portion is mounted and to make the light incident on the light receiving portion, and is a mold for molding a gas cell housing made of a resin material, wherein the mold for molding the gas cell housing is configured such that the demolding direction when the lower mold and the upper mold are separated from each other is provided obliquely with respect to a direction perpendicular to the extending direction of the substrate mounting surface so that all of the plurality of reflecting portions do not have an undercut shape, and all of the plurality of reflecting portions are integrally molded on the inner surface of one gas cell housing to be molded.

[0010] Further, in order to solve the above problems, a method for manufacturing a gas cell housing according to one aspect of the present invention uses a mold for molding a gas cell housing according to one aspect of the present invention, and inserts and removes the mold obliquely with respect to a direction perpendicular to the extending direction of the substrate mounting surface so that no undercut occurs in all of the plurality of reflecting portions when the lower mold and the upper mold are separated from each other, and molds the gas cell housing by integrally molding all of the plurality of reflecting portions on the inner surface of one housing portion.

[0011] Further, in order to solve the above problems, a gas cell housing for a gas sensor according to one aspect of the present invention includes a substrate mounting surface on which a substrate having a light emitting portion and a light receiving portion is mounted, and a mirror portion having a plurality of reflecting portions, in one housing portion, wherein all of the plurality of reflecting portions are integrally molded on the inner surface of the housing portion so as to multiply reflect light emitted from the light emitting portion in a direction facing one side and the other side of the substrate mounting surface and make the light incident on the light receiving portion.

[0012] Further, in order to solve the above problems, a gas sensor according to one aspect of the present invention includes 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 plurality of reflecting portions of the mirror portion of the gas sensor according to the present invention are integrally formed on the inner surface of the gas cell housing, there is no need for a process of incorporating the mirror portion into the gas cell housing, and the process of adjusting the assembly tolerance of sensitive optical components can be simplified. Therefore, high robustness of the multiple reflection optical path that folds back in multiple stages can be obtained.

Advantages of the Invention

[0014] As described above, according to the present invention, there is no need for a process of incorporating the mirror portion into the gas cell housing, and the process of adjusting the assembly tolerance of sensitive optical components can be simplified. Therefore, high robustness of the multiple reflection optical path that folds back in multiple stages can be obtained.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode 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 portions 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 components in the following embodiments.

[0017] As shown in FIGS. 1 and 2, the gas sensor 10 according to the present embodiment includes a gas cell housing 30 having a rectangular parallelepiped appearance and a rectangular parallelepiped plate-shaped substrate 20 mounted on the bottom surface side of the gas cell housing 30. In this specification, for 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 rear 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 significantly downward except for both sides in the longitudinal direction as a substrate mounting surface 31, and the rectangular parallelepiped plate-shaped 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 gas to be measured, and the gas to be measured 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 gas to be measured 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 gas to be measured 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 gas to be measured 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 the particle filter 50 so as to cover the opening 30k. The particle filter 50 is formed in a plate shape having a rectangular shape slightly larger than the opening 30k and is mounted so as to cover the opening 30k.

[0025] The lower opening is the substrate mounting surface 31, and a substrate 20 having a similar shape is mounted so as to cover the opening. As shown in FIGS. 1(b) and 2(d), a light emitting portion 21 and a light receiving portion 22 are provided on the substrate 20, and a mirror portion 40 is provided on the inner surface of the gas cell housing 30. In this example, the light emitting portion 21 and the light receiving portion 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 portion 21 and the light receiving portion 22 are not limited to being mounted on the same substrate 20, and may be mounted on separate substrates.

[0027] The light emitting portion 21 has a light emitting surface 21a and is configured to be able to emit light including infrared light. The light emitted from the light emitting surface 21a of the light emitting portion 21 is multiply reflected by the plurality of reflecting portions 41 to 45 of the mirror portion 40, and the light emitting portion 21 is installed at a position where the condensing point overlaps with the light receiving surface 22a of the light receiving portion 22.

[0028] The light emitting portion 21 is not particularly limited as long as it outputs light including a wavelength absorbed by the gas to be measured. Specific examples include MEMS (microelectromechanical systems) light sources and light emitting diodes. Among them, from the viewpoint of reducing noise due to light absorption of components other than the gas to be measured, it is preferable that the light emitting portion 21 outputs only light in a wavelength band with a large absorption of the gas to be measured.

[0029] Specifically, from the viewpoint that the emission wavelength band can be controlled by the band gap of the active layer, the light emitting portion 21 may preferably have a light emitting diode structure. The light emitting diode may be formed on a semiconductor substrate. In addition, it is also preferable that they are connected in series or in parallel by wiring in order to enhance the emission intensity. Further, a sensor unit for monitoring the emission amount may be provided at a position where the light radiated from the light-emitting diode and reflected by the back surface of the semiconductor substrate is incident.

[0030] The light-emitting unit 21 may further include an optical filter having desired optical characteristics according to the gas to be measured. For example, when the gas to be measured is carbon dioxide, an example is a form in which a band-pass filter capable of filtering infrared light in a wavelength band (typically around 4.3 μm) where a large amount of infrared absorption by carbon dioxide occurs is mounted on the light-emitting unit 21.

[0031] The light-receiving unit 22 has a light-receiving surface 22a and is configured to be able to receive at least a part of the light radiated from the light-emitting unit 21. The light-receiving unit 22 is installed at a position where the light-receiving surface 22a overlaps with the condensing point of the mirror unit 40.

[0032] A photodiode may be desirable as the light-receiving unit 22. The photodiode preferably has sensitivity in a band of light including the wavelength absorbed by the gas to be 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 characteristics according to the gas to be measured. For example, when the gas to be measured is carbon dioxide, an example is a form in which a band-pass filter capable of filtering infrared light in a wavelength band (typically around 4.3 μm) where a large amount of infrared absorption by carbon dioxide occurs is mounted on the photodiode.

[0034] As described above and as shown in FIGS. 3 and 4, the mirror unit 40 has a plurality of reflecting portions 41 to 45, and the plurality of reflecting portions 41 to 45 are arranged to multiply reflect the light emitted from the light-emitting unit 21 toward the light-receiving unit 22 and constitute a multi-stage reflection optical path.

[0035] Furthermore, the mirror unit 40 is configured with a multi-stage reflection optical path that can condense the light emitted from the light emitting surface 21a of the light emitting unit 21 and can also condense the light directed toward the light receiving surface 22a of the light receiving unit 22. The mirror unit 40 according to the present embodiment performs multiple reflections so that the condensing point is located at a position overlapping the light receiving surface 22a of the light receiving unit 22 for the light emitted from the light emitting unit 21.

[0036] Thereby, the gas sensor 10 of the present embodiment realizes a gas sensor with a long optical path length while configuring the gas cell housing 30 to be small and compact, and can improve the accuracy of gas concentration detection. In the present embodiment, all of the plurality of reflecting portions 41 to 45 are integrally formed on the inner surface of the gas cell housing 30 having a specific shape with a resin base material, and then, on the portion that reflects light, an alloy containing aluminum, gold, silver, or a laminate thereof, etc. is vapor-deposited or plated to form a reflecting surface.

[0037] Note that the condensing point is a position uniquely determined by the relative positional relationship among the light emitting unit 21, the light receiving unit 22, and the mirror unit 40 and the shapes and arrangements of the plurality of reflecting portions 41 to 45. Examples of the type of reflecting portion having a condensing point include a spherical mirror, an elliptical mirror, a parabolic mirror, etc. When converting light to parallel light using a spherical mirror or a parabolic mirror, in order to increase the optical path length, a plane mirror may further be included between two spherical mirrors or parabolic mirrors.

[0038] Here, the gas cell housing 30 of the gas sensor 10 according to the present embodiment is configured such that the conditions for a predetermined integrated structure including the mirror unit 40 are satisfied by the demolding directions Lu and Ls at the time of demolding, as particularly shown in FIG. 4(d). As a result, as will be described later, all of the plurality of reflecting portions 41 to 45 constituting the mirror unit 40 are molded by a mold (see FIG. 5) that can be integrally formed on the inner surface of a single housing 30.

[0039] Therefore, according to the gas sensor 10 according to the present embodiment, since all of the plurality of reflecting portions 41 to 45 constituting the mirror portion 40 are integrally formed on the inner surface of one housing 30, it is possible to suppress a change in the output signal at the light receiving portion 22 due to the influence of the expansion and contraction of the adhesive or the like. As a result, most of the light multiply reflected by the mirror portion 40 can be accurately received by the light receiving surface 22a of the light receiving portion 22.

[0040] The gas cell housing 30 of the gas sensor 10 according to the present embodiment is formed by a mold for forming a gas cell housing, 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 formed. On the other hand, in a direction inclined by a specific angle with respect to the extending direction of the substrate mounting surface 31 to be formed, it does not have an undercut shape. As a result, in the direction perpendicular to the extending direction of the substrate mounting surface 31 to be formed, the gas cell housing 30 has the reflecting portions 41 to 45 and the like integrated while having an undercut shape. Therefore, there is no possibility that the resin adhesive expands and contracts due to external environmental factors or that the mounting position of the mirror portion 40 is displaced. In addition, since the shape of the mirror is hardly restricted, the robustness is strong and the gas concentration can be stably detected with high accuracy.

[0041] <Mold for Forming Gas Cell Housing and Method for Manufacturing Gas Cell Housing Using the Same> Hereinafter, a mold for forming a gas cell housing according to the present embodiment and a method for manufacturing a gas cell housing using the same will be described. The gas cell housing 30 of the present embodiment is formed by a dedicated mold for forming a gas cell housing, as shown in a schematic diagram in FIG. 5, for example. In the mold for forming a gas cell housing according to the present embodiment, a device for setting the ejection direction Lu of the upper mold 100 and the ejection direction Ls of the lower mold 200 to a predetermined value, and a mutual contact surface (including the parting surface) between the fixed-side lower mold 200 and the movable-side upper mold 100 are rubbed and brought into close contact with each other.

[0042] Specifically, as shown in FIG. 5, the mold for molding the gas cell housing 30 according to the present embodiment includes at least a lower mold 200 and an upper mold 100. The demolding directions Lu and Ls when these are separated from each other are provided obliquely (angle θ) relative to the direction in which the substrate mounting surface 31 to be molded extends, so that all of the plurality of reflecting portions 41 to 45 do not have an undercut shape. Here, as the angle θ, 5° to 85° or -5° to -85° is preferable, and 10° to 80° or -10° to -80° is more preferable. Thereby, this mold for molding the gas cell housing can integrally mold all of the plurality of reflecting portions 41 to 45 so that they do not have an undercut shape on the inner surface of one gas cell housing 30 to be molded. When the demolding direction at the time of demolding the mold for molding the gas cell housing 30 is a direction perpendicular to the extending direction of the substrate mounting surface 31 to be molded, the gas cell housing 30 according to the present embodiment has an undercut shape, so that it cannot be integrally molded with a two-way demolding mold.

[0043] Note that the cavity forming portion CA shown in the figure becomes a cavity corresponding to the molding shape shown in FIGS. 3 and 4. In order to form a cavity corresponding to this molding shape, the lower mold 200 is formed with a cavity forming convex portion 240 protruding upward, and the upper mold 100 is formed with a cavity forming convex portion 140 protruding downward.

[0044] In the example of the figure, the butting surfaces PL1 and PL3 of the lower mold 200 and the upper mold 100 are orthogonal to the demolding directions Lu and Ls at the time of demolding, and the demolding directions Lu and Ls at the time of demolding are in the vertical direction. Then, in this mold for molding the gas cell housing, the demolding directions Lu and Ls are provided obliquely (angle θ) relative to the direction perpendicular to the extending direction of the substrate mounting surface 31 to be molded. Therefore, as shown in FIG. 2(c), the inner surface side inclined surface 38 of the upper opening 30k is constituted by a butting surface PL2 along the demolding directions Lu and Ls.

[0045] In other words, the cut mating surface PL2 is formed in a shape along the sliding contact surfaces 138 and 238 between the cavity forming convex portion 240 of the lower mold 200 and the cavity forming convex portion 140 of the upper mold 100 that constitute the cut mating surface PL2, and is an inclined surface corresponding to the oblique angle (angle θ) of the demolding directions Lu and Ls during demolding.

[0046] That is, the cut mating surface PL2 is parallel to the demolding directions Lu and Ls during demolding. Even if an undercut shape is formed when a convex portion is provided only on one of the upper mold 100 and the lower mold 200, the convex portion is formed separately into the cavity forming convex portion 240 and the cavity forming convex portion 140 so as not to form an undercut shape, and the cut mating surface PL2 between the cavity forming convex portion 240 and the cavity forming convex portion 140 is made parallel to the demolding directions Lu and Ls during demolding, so that the upper mold 100 and the lower mold 200 can be demolded.

[0047] In the method for manufacturing the gas cell housing 30 using the mold for molding the gas cell housing according to the present embodiment, the above-described gas cell housing 30 is injection-molded with a resin material by an injection molding machine (not shown). The gas cell housing 30 according to the present embodiment has a mirror portion 40 integrally molded on the inner surface of one housing portion 30 with a single material such as resin (material: PPS). In the mold for molding the gas cell housing according to the present embodiment, when the lower mold 200 and the upper mold 100 are demolded, the demolding directions Lu and Ls are obliquely inserted (angle θ) with respect to the direction perpendicular to the extending direction of the substrate mounting surface 31 so that no undercut occurs on the reflecting surfaces of the plurality of reflecting portions 41 to 45.

[0048] Thereby, in the method for manufacturing the gas cell housing 30 using the mold for molding the gas cell housing according to the present embodiment, the mirror portion 40 can be integrally molded on the inner surface of the gas cell housing 30 with a two-way demolding mold without using cores or inserts. Further, in the present embodiment, forced demolding does not occur for all of the plurality of reflecting portions 41 to 45 of the mirror portion 40, and a demolding gradient for all of the outer surfaces of the rectangular parallelepiped gas cell housing 30 is also unnecessary. Thereby, the design of the mold can be simplified and the product cost can be reduced. In addition, problems such as the coefficient of thermal expansion and the coefficient of humidity expansion due to the mixing of different materials are reduced.

[0049] Thus, in the mold for forming the gas cell housing according to this embodiment and the method for manufacturing the gas cell housing 30 using the same, a gas sensor 10 with strong robustness and capable of detecting gas concentration with higher accuracy can be realized. That is, since the mirror portion 40 is integrally formed on the inner surface of the gas cell housing 30, changes in the output signal of the light receiving portion 22 due to the influence of elongation and contraction of the adhesive can be suppressed.

[0050]

[0049] Therefore, in the mold for forming the gas cell housing according to this embodiment and the method for manufacturing the gas cell housing 30 using the same, a gas cell housing 30 in which all of the plurality of reflecting portions 41 to 45 are integrally formed with the inner surface of a single housing portion can be efficiently and inexpensively manufactured. And, the gas sensor 10 according to this embodiment is completed by fixing a substrate 20 to a position of a substrate mounting surface 31 of the gas cell housing 30 with a resin adhesive so as to cover the entire opening with respect to the gas cell housing 30 in which the mirror portion 40 is integrally provided on the inner surface.

[0051] As a result, the mirror portion 40 integrally formed on the gas cell housing 30 allows more light radiated from the light emitting portion 21 to be incident through the plurality of reflecting portions 41 to 45, and more light reflected by the plurality of reflecting portions 41 to 45 to be incident on the light receiving portion 22.

[0052] <Regarding the effects>

[0050] Next, the effects of the gas cell housing 30 of this embodiment, the gas sensor 10 including the same, the mold for forming the gas cell housing 30, and the method for manufacturing the gas cell housing 30 will be described. Here, conventionally, this type of gas cell housing is composed of parts separate from the housing portion. For example, two mirror portions are assembled inside a single housing portion and fixed using a resin adhesive to form the gas cell housing. Conventionally, for example, a housing portion made of liquid crystal polymer (LCP) and a mirror portion made of a resin plate (material: PPS) were integrated by an adhesive or heat caulking.

[0053] However, when a mirror part made of separate components is fixed inside the housing part of the gas cell housing using a resin adhesive, if the adhesive expands and contracts due to external environmental factors, the mirror part may be displaced with respect to the light emitting part and the light receiving part of the substrate fixed to the housing part side. When such displacement occurs, even though the gas concentration of the gas to be measured has not changed, the output signal of the light receiving part may change, and there is a risk that the gas concentration cannot be detected with sufficient accuracy.

[0054] On the other hand, according to the gas sensor 10 of the present embodiment, using the above-described mold for molding the gas cell housing, for all the reflecting surfaces of the plurality of reflecting parts 41 to 45, an angle θ that is oblique with respect to the direction perpendicular to the extending direction of the substrate mounting surface 31 is provided so that no undercut that causes forced ejection occurs, and the plurality of reflecting parts 41 to 45 are inserted and molded to be integrally formed with the inner surface of one housing part to manufacture the gas cell housing 30. Therefore, on the inner surface of the gas cell housing 30, a mirror part 40 in which no undercut occurs on all the reflecting surfaces of the plurality of reflecting parts 41 to 45 can be integrally formed.

[0055] Therefore, according to the gas sensor 10 of the present embodiment, due to the integrated structure in which all of the plurality of reflecting parts 41 to 45 of the mirror part 40 are integrally formed in one housing 30, the process of incorporating and adhering two conventional mirror parts (mirror assemblies) inside the housing part of the gas cell housing 30 is unnecessary, and the adjustment process of the assembly tolerance of sensitive optical components can be simplified.

[0056] And, since all the reflecting surfaces of the plurality of reflecting parts 41 to 45 of the mirror part 40 of the gas cell housing 30 of the present embodiment are integrally formed in one gas cell housing 30, there is no possibility that a resin adhesive expands and contracts due to external environmental factors or that the incorporated position of the mirror part 40 is displaced. Therefore, the robustness is strong, and the gas concentration can be stably detected with high accuracy.

[0057] Here, in order to make the light emitted from the light emitting unit 21 enter the light receiving unit 22 without waste and increase the output signal of the light receiving unit 22, it is better for the mirror unit 40 to condense the light toward the light receiving surface 22a of the light receiving unit 22 in a range as small as possible. On the other hand, when the plurality of reflecting portions 41 to 45 constituting the mirror unit 40 of the gas cell are integrally formed in one gas cell housing 30 as in the present embodiment, since the optical multi-reflection surface is integrally formed in one housing, the adjustment process of the assembly tolerance of sensitive optical components is simplified, and individual differences and lot differences due to manufacturing variations in the optical path can be reduced. Therefore, a gas sensor with strong robustness and capable of detecting gas concentration with higher accuracy can be realized.

[0058] Further, according to the gas cell housing 30 of the present embodiment, the problem of displacement caused by mixing of different materials (such as thermal expansion coefficient and humidity expansion coefficient) is reduced, and most of the light multi-reflected by the mirror unit 40 can be received more accurately by the light receiving surface 22a of the light receiving unit 22 for the light incident from the light emitting unit 21 to the mirror unit 40, multi-reflected, and then received by the light receiving unit 22.

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

[0060] Thereby, according to the gas cell housing 30 of the present embodiment, a gas sensor 10 with strong robustness and capable of detecting gas concentration with higher accuracy can be realized. In addition, the design of the mold for molding the gas cell housing 30 is simplified, the product cost can be reduced, and a gas sensor 10 with high ingress protection (IP rating) can be created.

[0061] Moreover, according to this embodiment, since it has a simplified assembly structure with the mirror part 40 integrally formed on the inner surface of the gas cell housing 30, there are fewer parts for assembling the gas sensor 10, and its assembly process can also be simplified.

[0062] In particular, according to this embodiment, the upper mold 100 and the lower mold 200 that constitute the upper and lower molds set their respective drawing directions Lu and Ls in parallel. Therefore, the assembly work of all the parts that make up the gas sensor 10 can be efficiently carried out from two directions along one axis that is the insertion and extraction direction of the upper and lower molds.

Explanation of Reference Numerals

[0063] 10 Gas sensor 20 Substrate 21 Light-emitting part 21a Light-emitting surface 22 Light-receiving part 22a Light-receiving surface 30 Gas cell housing (housing part) 31 Substrate mounting surface 40 Mirror part 41 - 45 Reflecting part 50 Particle filter 100 Upper mold 200 Lower mold

Claims

1. A mold for injection-molding a gas cell housing made of a resin material, the mold comprising a mirror part having a plurality of reflecting parts arranged to multiply reflect light emitted from a light-emitting part in a direction facing one side and the other side of a substrate mounting surface on which a substrate having the light-emitting part and a light-receiving part is mounted, and to make the light enter the light-receiving part, wherein at least one of the plurality of reflecting parts has an undercut shape with respect to a direction perpendicular to the extending direction of the substrate mounting surface, and all of the plurality of reflecting parts are configured not to have an undercut shape with respect to a first direction that is oblique with respect to a direction perpendicular to the extending direction of the substrate mounting surface, and all of the plurality of reflecting parts are integrally formed on an inner surface of one gas cell housing to be molded. The mold for molding a gas cell housing is characterized by this.

2. The mold for molding a gas cell housing includes a lower mold and an upper mold, wherein the lower mold and the upper mold each have a convex part, and a pushing and mating surface is formed by a sliding contact surface of the mutual convex parts, and the pushing and mating surface is parallel to the first direction. The mold for molding a gas cell housing according to Claim 1.

3. A mold for molding a gas cell housing made of a resin material, the mold having a lower mold and an upper mold for injection-molding a gas cell housing including a mirror part having a plurality of reflecting parts arranged to multiply reflect light emitted from a light-emitting part in a direction facing one side and the other side of a substrate mounting surface on which a substrate having the light-emitting part and a light-receiving part is mounted, and to make the light enter the light-receiving part, wherein at least one of the plurality of reflecting parts has an undercut shape with respect to a direction perpendicular to the extending direction of the substrate mounting surface. Using the mold for molding a gas cell housing, when the lower mold and the upper mold are separated from each other, the drawing direction is obliquely inserted and drawn with respect to a direction perpendicular to the extending direction of the substrate mounting surface so that no undercut occurs in all of the plurality of reflecting parts, and all of the plurality of reflecting parts are integrally molded with an inner surface of one housing part to manufacture a gas cell housing. A method for manufacturing a gas cell housing is characterized by this.

4. A gas cell housing for a gas sensor, the housing 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 reflecting parts, in one housing part, wherein at least one of the plurality of reflecting parts has an undercut shape with respect to a direction perpendicular to the extending direction of the substrate mounting surface, The housing portion is integrally formed on the inner surface of the housing portion such that all of the plurality of reflecting portions multiply reflect the light emitted from the light emitting portion in the direction facing one side and the other side in the extending direction of the substrate mounting surface and make the light incident on the light receiving portion. A gas cell housing for a gas sensor, characterized by this.

5. The housing portion has openings on the side of the substrate mounting surface and on the side facing the side of the substrate mounting surface, respectively. The opening on the side of the substrate mounting surface is formed on the substrate mounting surface. The gas cell housing for a gas sensor according to claim 4, wherein the opening on the side facing the side of the substrate mounting surface is an inlet / outlet for the gas to be measured.

6. A gas sensor, characterized by comprising the gas cell housing for a gas sensor according to claim 4 or 5.

7. At least one of the plurality of reflecting portions has a concave portion. The undercut shape is such that when the extending direction of the substrate mounting surface is the x-axis and the direction perpendicular to the extending direction of the substrate mounting surface is the y-axis, the surface of the concave portion is not in the shape of a unary function. The gas cell housing for a gas sensor according to claim 4.

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