Sensor unit

Abstract

This invention provides a sensor unit that can measure oxygen concentration without gas directly hitting the oxygen concentration sensor located in the sub-channel. [Solution] The sensor unit 14 comprises a main flow path 22, a venturi tube 24 connected in series with the main flow path 22 and having a narrowed cross-sectional area, a sub-flow path 26 connected to the main flow path 22 and the venturi tube 24, a housing chamber 28 provided in the middle of the sub-flow path 26, and an oxygen concentration sensor 30 housed in the housing chamber 28. The oxygen concentration sensor 30 has a detection unit 42 and a base unit 40 that supports the detection unit 42. The housing chamber 28 has a gas introduction unit 32 that directs the gas flowing through the sub-flow path 26 onto the back surface 40b of the base unit 40.

Description

Technical Field

[0001] The present disclosure relates to a sensor unit used for managing the oxygen concentration contained in gas.

Background Art

[0002] For example, in an inert gas supply line that supplies inert gas (nitrogen) to a factory production line, a sensor unit that detects oxygen concentration is used for the purpose of oxygen concentration management. In addition, the sensor unit that detects oxygen concentration is also used in various applications such as managing the oxygen concentration in exhaust gas from internal combustion engines and combustion equipment, and managing the oxygen concentration in oxygen-rich gas in various production facilities.

[0003] As a sensor unit for detecting oxygen concentration, for example, a sensor unit that detects oxygen concentration in exhaust gas as disclosed in Japanese Unexamined Patent Application Publication No. 2007-198893 is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0005] The sensor unit of Japanese Unexamined Patent Application Publication No. 2007-198893 prevents water from contacting the detection element by providing a water-repellent filter near the inlet of the storage chamber.

[0006] However, in the conventional technology, the arrangement is such that gas directly strikes the oxygen concentration sensor disposed in the sub-flow path, which makes moisture and foreign matter easily come into contact with the sensor element, leading to the problem that the oxygen concentration sensor is prone to deterioration. In addition, when the flow rate in the main flow path changes, the temperature of the oxygen concentration sensor tends to change, resulting in large fluctuations in measured values due to flow velocity and flow rate, and there is also the problem that the measurement results are difficult to stabilize.

[0007] This disclosure aims to solve the problems described above. [Means for solving the problem]

[0008] An aspect of the present disclosure is a sensor unit comprising: a main flow path; a venturi tube connected in series with the main flow path and having a constricted portion with a narrowed cross-sectional area; a sub-flow path having an upstream end opening to the side of the main flow path and a downstream end opening to the side of the venturi tube; a containment chamber provided in the sub-flow path; and an oxygen concentration sensor housed in the containment chamber, wherein the oxygen concentration sensor has a detection unit and a base supporting the detection unit, and the containment chamber has a gas introduction portion that directs the gas flowing through the sub-flow path to the back of the base. [Effects of the Invention]

[0009] According to this disclosure, deterioration of the oxygen concentration sensor can be prevented, and temperature changes in the detection part of the oxygen concentration sensor are suppressed, improving the stability of the measurement results. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a front view of a sensor module according to an embodiment. [Figure 2] Figure 2 is a cross-sectional view of the main part of the sensor unit. [Figure 3] Figure 3 is an explanatory diagram showing the gas flow in the containment chamber. [Modes for carrying out the invention]

[0011] As shown in Figure 1, the sensor module 10 of this embodiment is connected downstream of a nitrogen enrichment membrane module that supplies nitrogen gas and is used to manage the oxygen concentration in the nitrogen gas (inert gas) supply line. The sensor module 10 can be used, for example, in nitrogen filling equipment that fills food packaging containers with nitrogen gas, blow gas supply equipment for painting, and inert gas supply lines to explosion-proof areas.

[0012] The sensor module 10 is an in-line sensor capable of measuring the oxygen concentration in the supply line piping, enabling continuous measurement of oxygen concentration, eliminating the need for external purging, and allowing for space savings in oxygen concentration management equipment. The sensor module 10 comprises a main body 12 and a sensor unit 14. The main body 12 includes a display operation unit 16 and a signal processing circuit for processing the detection signal from the sensor unit 14.

[0013] The display and operation unit 16 includes, for example, a color dot matrix liquid crystal display and operation buttons. The display and operation unit 16 notifies the oxygen concentration by displaying the measured oxygen concentration numerically. The display and operation unit 16 also accepts various settings for the sensor module 10. A connector 18 for connecting an I / O-Link communication cable is provided at the lower end of the main body 12. By supporting I / O-Link communication, the sensor module 10 enables automated monitoring of the supply line status and prediction of failures in the nitrogen enrichment membrane module, allowing for rapid fault response.

[0014] The sensor unit 14 is mounted on the upper part of the main body 12. As shown in Figure 2, the sensor unit 14 comprises a housing 20, a main flow path 22, a venturi tube 24, a secondary flow path 26, a containment chamber 28, and an oxygen concentration sensor 30. The main flow path 22 extends horizontally inside the sensor unit 14. The first horizontal end 22a and the second horizontal end 22b of the main flow path 22 are connected to the piping of an inert gas supply line.

[0015] The Venturi tube 24 is positioned in the center of the main flow path 22 and is connected in series with the main flow path 22. Most of the gas flowing through the main flow path 22 flows into the Venturi tube 24. The Venturi tube 24 extends horizontally along the same axis as the main flow path 22. The Venturi tube 24 comprises a narrowed diameter section 24a, a constricted section 24b, and an expanded diameter section 24c. The narrowed diameter section 24a is connected to the first end 22a of the main flow path 22, and its cross-sectional area gradually decreases as it moves in the second direction (downstream). The constricted section 24b is located in the center of the Venturi tube 24 and is the part of the Venturi tube 24 with the smallest cross-sectional area. The expanded diameter section 24c is located between the constricted section 24b and the second end 22b, and its cross-sectional area gradually increases as it moves in the second direction. The gas flowing through the Venturi tube 24 has the highest flow velocity in the constricted section 24b, creating a low-pressure region.

[0016] The secondary channel 26 is provided in parallel with the main channel 22. The secondary channel 26 has an upstream end 26a and a downstream end 26b. The upstream end 26a of the secondary channel 26 opens above the first end 22a of the main channel 22. Compressed gas flows inside the main channel 22, but water may flow on the inner wall of the main channel 22 due to condensation of water vapor, etc. By positioning the upstream end 26a above the main channel 22, it is possible to prevent water that may flow in the main channel 22 from entering the secondary channel 26.

[0017] The upstream portion 26c of the sub-channel 26 extends upward from the upstream end 26a, then bends in a second direction and connects to the containment chamber 28. The downstream portion 26d of the sub-channel 26 connects to the second side end of the containment chamber 28. The downstream portion 26d extends downward, then bends back in a first direction and connects to the constricted portion 24b through the downstream end 26b. The downstream end 26b is located above the venturi tube 24 and can prevent water condensed on the inner surface of the venturi tube 24 from entering.

[0018] The containment chamber 28 is located in the middle of the sub-channel 26. Here, the sub-channel 26 includes either the upstream end 26a or the downstream end 26b. In the illustrated example, the containment chamber 28 is located between the upstream end 26a and the downstream end 26b. In the illustrated example, the containment chamber 28 is formed as a cylindrical cavity extending horizontally. The oxygen concentration sensor 30 is housed inside the containment chamber 28. Near the side of the containment chamber 28 in the first direction, a gas introduction section 32 is formed to introduce gas into the containment chamber 28. The gas introduction section 32 communicates with the sub-channel 26 and has a nozzle 34 that guides the gas in a second direction from the radial centerline of the containment chamber 28. The nozzle 34 ejects gas from near the circuit board 38 of the oxygen concentration sensor 30.

[0019] The containment chamber 28 has a gas discharge section 36 at its end in the second direction. The gas discharge section 36 is positioned on the radial centerline of the containment chamber 28 and is aligned with the gas introduction section 32 on the same axis. This arrangement allows for uniform gas flow around the oxygen concentration sensor 30. The inner diameter of the containment chamber 28 is formed to be slightly larger than the outer diameter of the oxygen concentration sensor 30, and a gas flow path 28b is formed between the outer part of the oxygen concentration sensor 30 and the inner circumferential surface 28a of the containment chamber 28. The gas flow path 28b is formed to surround the entire circumference of the oxygen concentration sensor 30 and extends substantially parallel to the outer part of the oxygen concentration sensor 30.

[0020] The oxygen concentration sensor 30 includes a circuit board 38, a pedestal portion 40, and a detection portion 42. The circuit board 38 is formed in a disk shape, and connection pins 40a extending from the pedestal portion 40 are joined thereto by a method such as soldering, so that the circuit board 38 is electrically connected to the detection portion 42 (sensor element). The circuit board 38 is provided with a mounting seat 38a extending in the vertical direction. The mounting seat 38a is disposed in recesses 28d provided above and below the accommodation chamber 28. The oxygen concentration sensor 30 is fixed to the housing 20 through the mounting seat 38a. Connection wiring (not shown) extends out from the circuit board 38 and is electrically connected to the signal processing circuit inside the main body portion 12. A through hole 38b is formed in the central portion of the circuit board 38. The through hole 38b is disposed at a position aligned with the outlet of the nozzle 34, and penetrates the circuit board 38 in the thickness direction. The gas discharged from the nozzle 34 is configured to pass through the through hole 38b and strike the back surface 40b of the pedestal portion 40.

[0021] The pedestal portion 40 is formed in a disk shape, and supports the detection portion 42 on its axially oriented front surface 40c. The outer peripheral portion of the pedestal portion 40 forms a narrow portion 40d spaced apart from the inner peripheral surface 28a of the accommodation chamber 28. The narrow portion 40d has a smaller flow passage cross-sectional area than the gas flow passage 28b. The gas blown onto the back surface 40b of the pedestal portion 40 flows along the inner peripheral surface 28a of the accommodation chamber 28 through the narrow portion 40d. The narrow portion 40d allows the gas to smoothly flow around the detection portion 42 in the second direction.

[0022] The detection portion 42 includes a limiting current type sensor element using a zirconia solid electrolyte having oxygen ion conductivity at high temperatures. The sensor element incorporates a heater or the like for heating the zirconia solid electrolyte. The sensor element is covered with a dome-shaped cover member 42a formed of a metal mesh material.

[0023] The sensor module 10 of the present embodiment is configured as described above. Hereinafter, the operation of the sensor unit 14 will be described.

[0024] When gas flows through the main channel 22, the sensor unit 14 increases the flow velocity in the venturi tube 24, which restricts the fluid flow, and generates a low pressure in the constricted section 24b where the flow velocity is high. This creates a pressure difference in the sub-channel 26, causing some of the gas from the main channel 22 to flow into the sub-channel 26, which branches off from the main channel 22. The gas that flows into the sub-channel 26 flows through the containment chamber 28, and the oxygen concentration is detected by the oxygen concentration sensor 30.

[0025] As shown in Figure 3, the gas passes through the nozzle 34 of the gas introduction section 32 and strikes the center of the base section 40 of the oxygen concentration sensor 30. The gas that strikes the base section 40 spreads radially outward along the base section 40 and flows from the periphery of the base section 40 through the gas flow path 28b that surrounds the detection section 42. In the gas flow path 28b, the direction of gas flow is along the outer surface of the cover member 42a. This prevents direct impact of the gas flow on the sensor element inside the detection section 42, and prevents damage to the sensor element due to contact with water droplets or dust.

[0026] Furthermore, since the detection unit 42 is located in a place where it is not directly hit by the gas flow, temperature changes of the sensor element due to fluctuations in gas flow velocity are suppressed. As a result, variations in measurement results due to changes in the gas flow rate of the main channel 22 are suppressed, and stable measurement results can be obtained.

[0027] In the above example, the sensor module 10 and sensor unit 14 were described as being applied to an inert gas supply line, but the sensor module 10 and sensor unit 14 of this embodiment are not limited to such applications. The sensor module 10 and sensor unit 14 may also be used to control the oxygen concentration of combustion gases in internal combustion engines and incineration equipment. Furthermore, the sensor module 10 and sensor unit 14 may also be used to control the oxygen concentration of oxygen-rich gases used in the manufacturing processes of various production equipment.

[0028] With regard to the above embodiments, the following additional information is disclosed.

[0029] (Note 1) The sensor unit (14) of the present disclosure comprises a main flow path (22), a venturi tube (24) connected in series with the main flow path and having a constricted portion (24b) with a narrowed cross-sectional area, a sub-flow path (26) whose upstream end (26a) opens to the side of the main flow path and whose downstream end (26b) opens to the side of the venturi tube, a housing chamber (28) provided in the sub-flow path, and an oxygen concentration sensor (30) housed in the housing chamber, wherein the oxygen concentration sensor has a detection unit (42) and a base unit (40) that supports the detection unit, and the housing chamber has a gas introduction unit (32) that directs the gas flowing through the sub-flow path to the back surface (40b) of the base unit.

[0030] The above sensor unit prevents deterioration of the oxygen concentration sensor and suppresses temperature changes in the detection part (sensor element) of the oxygen concentration sensor, resulting in excellent stability of measurement results.

[0031] (Note 2) The sensor unit described in Appendix 1 may include a circuit board (38) to which a connecting pin (40a) extending from the base portion is joined and which has a through hole (38b) formed in the center, and a nozzle (34) that communicates with the sub-flow channel and extends toward the through hole of the circuit board. This sensor unit can reliably guide the gas to a part where the gas flow does not directly hit the detection portion.

[0032] (Note 3) The sensor unit described in Appendix 1 may have a dome-shaped cover member (42a) that covers the base portion of the detection unit, and the housing chamber may have a gas flow path (28b) that flows gas along the cover member around the cover member. This sensor unit can prevent direct impact of the gas flow on the detection unit and can distribute the gas evenly around the detection unit, thereby improving the stability of the measurement results.

[0033] (Note 4) The sensor unit described in Appendix 3 is provided with a narrow section (40d) between the outer periphery of the base and the containment chamber, the narrow section having a narrower flow path cross-sectional area than the gas flow path, and gas may be guided into the gas flow path through the narrow section. This sensor unit can align the gas flow in the narrow section in a direction along the outer periphery of the detection unit, thereby suppressing direct impact of the gas flow on the detection unit due to turbulence in the gas flow.

[0034] (Note 5) The sensor unit described in Appendix 1 may have the sub-channel and the oxygen concentration sensor positioned above the main channel and the venturi tube. This sensor unit can prevent backflow of condensation water generated in the main channel and venturi tube into the sub-channel and offers excellent durability.

[0035] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0036] 14...Sensor unit 22...Main flow path 24...Venturi tube 24b...Constriction 26...Sub-channel 26a...Upstream end 26b... Downstream end 28... Containment chamber 28b...Gas flow path 30...Oxygen concentration sensor 32...Gas inlet 34...Nozzle 38...Circuit board 38b...Through hole 40...Base part 40a...Connecting pin 40b…back side 40d…narrow part 42...Detection unit 42a...Cover member

Claims

1. Main channel and A venturi tube connected in series to the main flow path and having a constricted section with a reduced cross-sectional area, A sub-channel whose upstream end opens to the side of the main channel and whose downstream end opens to the side of the venturi tube, A containment chamber provided in the middle of the aforementioned sub-channel, The system comprises an oxygen concentration sensor housed in the aforementioned containment chamber, The oxygen concentration sensor is It has a detection unit and a base unit that supports the detection unit, The aforementioned containment chamber is a sensor unit having a gas introduction section that directs the gas flowing through the sub-channel onto the back surface of the base section.

2. A sensor unit according to claim 1, The gas introduction section is joined to a circuit board to which a connecting pin extending from the base is attached, and to which a through hole is formed in the center. A sensor unit comprising a nozzle that communicates with the aforementioned sub-channel and extends toward the aforementioned through-hole of the circuit board.

3. A sensor unit according to claim 1, The detection unit has a dome-shaped cover member that covers the base portion. The aforementioned containment room is A sensor unit having a gas channel around the cover member for flowing gas along the cover member.

4. A sensor unit according to claim 3, wherein a narrow section is provided between the outer periphery of the base and the housing chamber, the narrow section having a narrower cross-sectional area than the gas flow path, and gas is guided into the gas flow path through the narrow section.

5. A sensor unit according to claim 1, wherein the sub-channel and the oxygen concentration sensor are located above the main channel and the venturi tube.

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