Odor sensor unit

Abstract

To provide a smell sensor unit having little adverse effect on a detection result.SOLUTION: An odor sensor unit 1 includes an odor sensor 10, a chamber 20 for housing the odor sensor 10 on a flow path of gas from an inflow port 21 to an outflow port 22, and a heater 50 for heating the gas on the flow path from the odor sensor 10 to the outflow port 22 to generate or accelerate the flow of the gas toward the outflow port 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an odor sensor unit. [Background technology]

[0002] In order to sense odors, it is necessary to expose the target gas to an odor sensor. For example, Patent Document 1 discloses a configuration that includes a heating means for increasing the ambient temperature inside a container that houses an odor sensor in order to promote the movement of gas inside the container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 07-027731 Summary of the Invention [Problem to be solved by the invention]

[0004] However, a rise in the temperature of the gas that hits the odor sensor may affect the detection results. In light of the above-described circumstances, an object of one aspect of the present invention is to provide an odor sensor unit that has little adverse effect on the detection results. [Means for solving the problem]

[0005] An odor sensor unit according to one aspect of the present invention comprises an odor sensor, a chamber that houses the odor sensor on a gas flow path from an inlet to an outlet, and a heater that heats the gas on the flow path from the odor sensor to the outlet, thereby generating or accelerating a flow of the gas toward the outlet. [Effects of the Invention]

[0006] According to the above aspect, it is possible to provide an odor sensor unit that has little adverse effect on the detection results. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating the configuration of an odor sensor unit according to a first embodiment. [Figure 2] 10A and 10B are diagrams illustrating the configuration of an odor sensor unit according to a modified example. [Figure 3] FIG. 10 is a diagram illustrating the configuration of an odor sensor unit according to another modified example. [Figure 4] FIG. 10 is a diagram illustrating the configuration of an odor sensor unit according to a second embodiment. [Figure 5] FIG. 10 is a diagram illustrating the configuration of an odor sensor unit according to a third embodiment. [Figure 6] FIG. 10 is a diagram illustrating the configuration of an odor sensor unit according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] The odor sensor unit 1 according to the first embodiment shown in FIG. 1 is a unit including an odor sensor 10 and a chamber 20 that houses the odor sensor 10. When odor molecules in a gas are adsorbed to the odor sensor 10, the electrical characteristics change. The odor sensor unit 1 detects and measures odors by detecting the change in the electrical characteristics of the odor sensor 10 that occurs due to the adsorption of odor molecules.

[0009] Any odor sensor can be used as the odor sensor 10, and is not particularly limited. The odor sensor 10 may be, for example, a semiconductor sensor such as a metal oxide semiconductor (MOS), an electrochemical sensor that uses an oxidation-reduction reaction on an electrode surface, or a sensor that uses a chemical reaction on a catalyst surface, such as a catalytic combustion sensor. Alternatively, the odor sensor 10 may be a quartz crystal oscillator sensor, a surface acoustic wave sensor, a conductive polymer sensor, or the like.

[0010] The chamber 20 has an inlet 21 and an outlet 22, and a gas flow path from the inlet 21 to the outlet 22 is formed within the chamber 20. The chamber 20 accommodates the odor sensor 10 in the gas flow path from the inlet 21 to the outlet 22. Although not particularly limited, the chamber 20 is preferably made of a material that is less likely to adsorb or react with odor molecules, and also has a certain level of heat resistance. The material of the chamber 20 may be, for example, glass, stainless steel, plastic, etc.

[0011] The odor sensor unit 1 is a naturally aspirated odor sensor unit, and does not perform forced intake using mechanical movement such as a pump or fan. For this reason, various measures have been taken in the odor sensor unit 1 to supply gas to the odor sensor 10 at a sufficient flow rate by natural intake.

[0012] The odor sensor unit 1 further includes a heater 50 that heats the gas in the chamber 20. The heater 50 includes a heating element and heats the gas by infrared rays emitted from the heating element, Joule heat generated by the heating element, or the like. By heating the gas in the chamber 20, the heater 50 generates natural convection in the gas in the chamber 20, promoting the intake of gas into the chamber 20 and the supply of gas to the odor sensor 10. This makes it possible to intake a sufficient flow rate of gas and supply it to the odor sensor 10, even with a natural intake system. This allows for the realization of an odor sensor unit 1 with high responsiveness.

[0013] The gas heated by the heater 50 becomes hotter than at least the gas outside the odor sensor unit 1 (hereinafter referred to as outside air). The odor sensor unit 1 is originally designed to detect and measure the odor (components) of the gas outside the odor sensor unit 1 (outside air), and the gas taken into the chamber 20 is merely a sample of the outside air. Changing the sample gas to a state different from that of the outside air (here, a heated state) and performing detection and measurement processes in the changed state may affect the reliability of the detection and measurement results, and is therefore undesirable. For this reason, it is undesirable to heat the gas with the heater 50 in the flow path from the inlet 21 to the odor sensor 10 and supply the heated gas to the odor sensor 10. Furthermore, even if the gas is heated by the heater 50 in the flow path from the odor sensor 10 to the outlet 22, it is undesirable for the heated gas to flow back toward the odor sensor 10 and be supplied to the odor sensor 10.

[0014] Therefore, in the odor sensor unit 1, the heater 50 is configured to heat the gas in the flow path between the odor sensor 10 and the outlet 22, thereby generating or accelerating a flow of gas toward the outlet 22. More specifically, the heater 50 may be positioned so that a vector along the flow path from the odor sensor 10 to the outlet 22 has a vertically upward component at the point where the gas is heated by the heater 50. This allows the gas heated by the heater 50 to be discharged from the outlet 22 without heading toward the odor sensor 10, thereby preventing the heated gas from adversely affecting detection. Furthermore, the negative pressure generated by the flow from the heater 50 toward the outlet 22 promotes intake of air from the inlet 21, allowing a sufficient flow rate of gas to be supplied to the odor sensor 10. Therefore, the odor sensor unit 1 can achieve both high responsiveness and reliability.

[0015] Furthermore, in the odor sensor unit 1, the chamber 20 includes a first chamber 30 that houses the odor sensor 10 and has an inlet 21 formed therein, and a second chamber 40 that has a heater 50 that has an outlet 22 formed therein. As shown in Fig. 1, the flow path in the first chamber 30 and the flow path in the second chamber 40 are connected at a position lower than the upper surface 31 of the first chamber 30. This configuration makes it possible to reduce the height of the odor sensor unit 1 while avoiding adverse effects on detection.

[0016] In order for the odor sensor unit 1 to obtain sufficient exhaust capacity through natural convection using the heater 50, it is desirable to effectively create a chimney effect in the second chamber 40. Since the chimney effect generally increases as the vertical length of a structure increases, it is desirable for the second chamber 40 to have a so-called vertically elongated shape, as shown in FIG. 1 . By connecting the flow paths in the first chamber 30 and the second chamber 40 at a position lower than the top surface 31 of the first chamber 30, the inlet of the vertically elongated second chamber 40 can be positioned at a low position. This allows the overall height of the odor sensor unit 1 to be reduced even when a vertically elongated second chamber 40 such as that shown in FIG. 1 is used. Therefore, with the odor sensor unit 1, the height of the odor sensor unit 1 can be reduced while ensuring exhaust capacity by creating a high chimney effect in the second chamber 40.

[0017] Additionally, it is desirable that the second chamber 40 has the outlet 22 at a position higher than the heater 50, i.e., above the portion heated by the heater 50. This allows for efficient exhaust of the ascending air current accelerated by the chimney effect. Furthermore, heating by the heater 50 generates or accelerates an upward gas flow in the heated portion, thereby generating a gas flow from the inlet 21 to the odor sensor 10. This also improves the efficiency of intake air. Note that while FIG. 1 shows an example in which the outlet 22 is formed to exhaust gas sideways, the outlet 22 may be formed to face upward in order to reduce pressure loss at the outlet 22 and thereby exhaust gas more efficiently.

[0018] Furthermore, when the first chamber 30 and the second chamber 40 are connected at a position lower than the top surface 31, it is desirable that the inlet 21 formed in the first chamber 30 be located at a position higher than the odor sensor 10 housed in the first chamber 30. Such an arrangement of the inlet 21 allows gas to traverse from top to bottom within the first chamber 30, thereby making it possible to effectively utilize the space within the first chamber 30. Specifically, by effectively utilizing the space, it is possible to house a sufficient volume of gas necessary for odor measurement within the first chamber 30 while preventing the gas from stagnating and not being sufficiently replaced within the first chamber 30. Therefore, with the odor sensor unit 1, by configuring the first chamber 30 compactly, it is possible to reduce the overall size of the odor sensor unit 1 while achieving high performance.

[0019] Furthermore, as described above, the odor sensor unit 1 is a naturally aspirated odor sensor unit and does not have a mechanical structure such as a fan for forced air intake. This contributes to the unit's compact size and quiet operation, and also contributes to reduced manufacturing costs. Therefore, the odor sensor unit 1 makes it possible to provide a small, quiet odor sensor unit at low cost.

[0020] Although FIG. 1 illustrates an example in which the odor sensor unit 1 includes the heater 50 on the underside of the second chamber 40, the placement of the heater 50 is not limited to this example. The heater 50 may be placed so that heated gas flows toward the outlet 22, not the inlet 21. Therefore, the heater 50 may be attached to the side of the second chamber 40, as in the odor sensor unit 2 shown in FIG. 2, or may be placed inside the second chamber 40, as in the odor sensor unit 3 shown in FIG. 3. As shown in FIGS. 2 and 3, placing the heater 50 higher than the connection path between the first chamber 30 and the second chamber 40 can suppress backflow of gas into the first chamber 30. Alternatively, the backflow of gas may be suppressed more actively. For example, a mechanism, such as a valve, that blocks the flow of gas from the second chamber 40 to the first chamber 30 may be provided at the connection between the odor sensor 10 and the chamber 20. This prevents backflow of heated gas even if the odor sensor unit 1 is installed in the wrong orientation.

[0021] 4 differs from the odor sensor unit 1 in that it includes a flow rate sensor 60 that acquires information about the flow rate of gas, and a control unit 70 that controls the heater 50. The odor sensor unit 4 is similar to the odor sensor unit 1 in that it includes an odor sensor 10, a chamber 20, and a heater 50.

[0022] In the odor sensor unit 4, the control unit 70 controls the amount of heat generated by the heater 50 in accordance with the output of the flow rate sensor 60. The control unit 70 may control the amount of heat generated by the heater 50 in accordance with the output of the flow rate sensor 60 so that the gas flow rate falls within a certain range. Specifically, the control unit 70 may be electrically connected to the flow rate sensor 60 and the heater 50 and output a control signal to the heater 50 based on the output signal from the flow rate sensor 60. The control unit 70 may control the heater 50 to an ON state when the output of the flow rate sensor 60 (e.g., corresponding to the flow rate) falls below a certain value, and may control the heater 50 to an OFF state when the output of the flow rate sensor 60 exceeds the certain value. Here, the ON state refers to a state in which the heater 50 generates heat and heats the gas, and the OFF state refers to a state in which the heater 50 does not heat the gas. The control unit 70 may also control the amount of heat generated by the heater 50 in multiple stages in accordance with the output of the flow rate sensor 60. The control unit 70 may control the heater 50 to an ON state with high heat generation when the output of the flow velocity sensor 60 falls below a first threshold, control the heater 50 to an ON state with low heat generation when the output of the flow velocity sensor 60 (e.g., equivalent to the flow velocity) is greater than or equal to the first threshold and less than a second threshold, and control the heater 50 to an OFF state when the output of the flow velocity sensor 60 is greater than or equal to the second threshold.

[0023] If the flow rate of the gas supplied to the odor sensor 10 is too slow, odor molecules may not be adsorbed to the surface of the odor sensor 10 due to, for example, the influence of a boundary layer formed on the surface of the odor sensor 10, resulting in a decrease in the sensitivity of the odor sensor 10. Furthermore, if the flow rate is too fast, odor molecules may flow away without adsorbing to the surface of the odor sensor 10. In response to this, in the odor sensor unit 4, the control unit 70 performs feedback control based on information regarding the flow rate within the chamber 20, thereby controlling the flow rate (flow rate per unit time) of the gas supplied to the odor sensor 10. This allows gas to be supplied to the odor sensor 10 at an appropriate flow rate, enabling the odor sensor 10 to detect and measure odor molecules with high sensitivity. Therefore, the odor sensor unit 4 can detect and measure odor molecules with even higher sensitivity while maintaining both responsiveness and reliability similar to the odor sensor unit 1.

[0024] In the example shown, the control unit 70 controls the heat output of the heater 50 so that the gas flow rate falls within a certain range. However, this certain range of flow rate may be changeable by setting, or may be changed depending on the odor molecules to be detected. By changing the flow rate taking into account the differences in the properties of the odor molecules, stable detection and measurement are possible regardless of the detection target. The control unit 70 may operate in one of multiple pre-prepared operating modes, and may control the heat output of the heater 50 so that the gas flow rate falls within a different certain range in each operating mode. In this configuration, stable detection and measurement are possible regardless of the detection target simply by switching the operating mode depending on the odor molecules to be detected.

[0025] The specific relationship between flow rate and odor molecules is as follows, for example. The flow rate may be changed taking into account the weight of the odor molecules to be detected, and by increasing the flow rate for heavy molecules, differences in responsiveness depending on the detection target may be suppressed. The flow rate may also be changed taking into account the volatility and reactivity of the odor molecules to be detected, and may be increased for low-volatility molecules and for molecules with high chemical reactivity. The flow rate may also be changed taking into account the expected concentration of odor molecules in the gas, and may be set to a high flow rate when odor molecules are expected to be present at low concentrations. This is expected to have the effect of lowering the detection limit.

[0026] Although the above describes an example in which the control unit 70 performs feedback control, the control unit 70 may perform open-loop control by omitting the flow rate sensor 60. For example, the control unit 70 may control the gas flow rate within a certain range by turning the heater 50 on or off at a predetermined timing. Note that even when performing open-loop control, the control unit 70 may adjust the on-period and heat generation amount of the heater 50 so that the flow rate changes depending on the odor molecules to be detected.

[0027] 5 differs from the odor sensor unit 4 in that it includes a mechanical flow switch 80 that outputs an on / off signal to a heater 50 in response to the flow rate of gas passing through the flow path, instead of a flow rate sensor 60. Furthermore, because the output signal of the mechanical flow switch 80 is output directly to the heater 50, the control unit 70 is also omitted. Note that the odor sensor unit 5 is similar to the odor sensor unit described above in that it includes an odor sensor 10, a chamber 20, and a heater 50.

[0028] The mechanical flow switch 80 is disposed on a flow path formed within the chamber 20. The mechanical flow switch 80 is a switch in which the state of its internal contacts is switched by the physical operation of its actuator due to the flow (fluid force) of a fluid (gas). In the mechanical flow switch 80, when the flow rate exceeds a predetermined level, the actuator, which is in direct contact with the gas in the flow path, falls over, switching the state of the internal contacts to the ON state and outputting an ON signal to the heater 50. Upon receiving the ON signal from the mechanical flow switch 80, the heater 50 switches its state to the ON state and heats the gas in the flow path. On the other hand, when the flow rate decreases and falls below a predetermined level, the actuator of the mechanical flow switch 80 returns to its initial state, switching the state of the internal contacts to the OFF state and outputting an OFF signal to the heater 50. Upon receiving the OFF signal from the mechanical flow switch 80, the heater 50 switches its state to the OFF state and stops heating the gas in the flow path.

[0029] In the odor sensor unit 5, the amount of heat generated by the heater 50 is controlled by directly outputting a signal to the heater 50 according to the flow rate detected by the mechanical flow switch 80 without going through the control unit 70. Therefore, according to the odor sensor unit 5, by pre-adjusting the predetermined flow rate at which the mechanical flow switch 80 switches so that the flow rate of the gas supplied to the odor sensor 10 converges to an appropriate flow rate in response to a signal from the mechanical flow switch 80, it is possible to obtain the same effect as the odor sensor unit 4 with a configuration that is simpler and less expensive than the odor sensor unit 4. In other words, it is possible to detect and measure odor molecules with even higher sensitivity while maintaining both responsiveness and reliability.

[0030] 6 differs from the odor sensor unit 5 in that it includes a flip mechanism 90 that switches the heater 50 on and off depending on the flow rate of gas passing through the flow path, instead of a mechanical flow switch 80. The odor sensor unit 6 is similar to the odor sensor unit 5 described above in that it includes an odor sensor 10, a chamber 20, and a heater 50, but does not include the control unit 70.

[0031] The flip mechanism 90 is a mechanism that is disposed on a flow path formed in the chamber 20 and whose state is switched by the flow (fluid force) of a fluid (gas). When the flow rate of the gas in the flow path exceeds a predetermined amount, the flip mechanism 90 yields to the fluid force and switches on the heater 50, causing the heater 50 to heat the gas in the flow path. On the other hand, when the flow rate falls below the predetermined amount, the mechanism returns to its initial state and switches off the heater 50, causing the heater 50 to stop heating the gas in the flow path. In other words, the flip mechanism 90 corresponds to the actuator of the mechanical flow switch 80 in the odor sensor unit 5 according to the third embodiment.

[0032] In the odor sensor unit 6, the amount of heat generated by the heater 50 is controlled by directly switching the heater 50 on and off in accordance with the flow rate detected by the flip mechanism 90 without going through the control unit 70. Therefore, with the odor sensor unit 6, the same effect as that of the odor sensor unit 5 can be achieved by pre-adjusting the predetermined flow rate at which the flip mechanism 90 switches its state so that the flow rate of the gas supplied to the odor sensor 10 converges to an appropriate flow rate when the flip mechanism 90 switches on and off the heater 50.

[0033] The above-described embodiments are illustrative examples provided to facilitate understanding of the invention. The present invention is not limited to the above-described embodiments, and should be understood to encompass various modifications and alternative forms of the above-described embodiments. For example, it will be understood that the above-described embodiments can be embodied by modifying the components without departing from the spirit of the invention. It will also be understood that various embodiments can be implemented by appropriately combining multiple components disclosed in the above-described embodiments. Furthermore, it will be understood by those skilled in the art that various embodiments can be implemented by deleting some components from all of the components shown in the embodiments, or by adding some components to the components shown in the embodiments.

[0034] The odor sensor unit according to the above-described embodiment can be used for a variety of purposes. For example, it may be used to detect the freshness of food, to detect harmful substances in the air, or to analyze exhaled breath for early detection of illness. It may also be used for other purposes. On the other hand, configuring an odor sensor unit to accommodate a variety of applications can easily result in excessive specifications for normal use. Therefore, the odor sensor unit described above may include a replaceable odor sensor 10 depending on the application, or the odor sensor 10 may be replaced appropriately depending on the odor molecules to be detected. Furthermore, the mechanical flow switch 80 and flip mechanism 90 may also be replaced along with the odor sensor 10, or may be selected appropriately depending on the target flow rate to be controlled. By configuring the odor sensor 10 and other components to be replaceable in this manner, it is not necessary to provide an odor sensor unit with excessively high functionality to accommodate various applications in advance, making it possible to provide an odor sensor unit with high performance tailored to the application at low cost. Furthermore, while an example in which one odor sensor 10 is housed in the chamber 20 has been shown, multiple odor sensors 10 may also be housed. The multiple odor sensors 10 may each be odor sensors with different types or characteristics, thereby enabling them to be used for various detection targets.

[0035] Although not specifically mentioned in the above-described embodiment, the mechanical flow switch 80 and flip mechanism 90 are exemplified as mechanisms disposed in the flow path that turn the heater 50 on or off based on the fluid force exerted by the gas passing through the flow path. However, mechanisms that turn the heater 50 on or off based on fluid force are not limited to these. For example, while FIG. 5 illustrates a so-called paddle flow switch as the mechanical flow switch 80, a piston flow switch may also be used. Furthermore, while an example in which the mechanical flow switch 80 is disposed upstream of the odor sensor 10 has been shown, the mechanical flow switch 80 may also be disposed downstream of the odor sensor 10. Disposing the mechanical flow switch 80 downstream is desirable because even if odor molecules adhere to the mechanical flow switch 80 and remain in the odor sensor unit, the remaining odor molecules do not affect the measurement results. Furthermore, although an example in which the flip mechanism 90 is disposed downstream of the odor sensor 10 has been shown, the flip mechanism 90 may also be disposed upstream of the odor sensor 10.

[0036] Although not specifically mentioned in the above-described embodiments, the odor sensor unit may be a stationary unit that is fixed to a facility such as a factory or to a vehicle such as a car. Furthermore, taking advantage of the aforementioned features of the naturally aspirated system, which make it easy to make it small and quiet, the odor sensor unit may be configured as a mobile unit or as a wearable unit that can be worn by a person. [Explanation of symbols]

[0037] 1 to 6: sensor unit, 10: odor sensor, 20: chamber, 21: inlet, 22: outlet, 30: first chamber, 31: upper surface, 40: second chamber, 50: heater, 60: flow rate sensor, 70: control unit, 80: mechanical flow switch, 90: flip mechanism

Claims

1. An odor sensor, a chamber that accommodates the odor sensor on a gas flow path from an inlet to an outlet; a heater that heats the gas in a flow path from the odor sensor to the outlet, thereby generating or accelerating a flow of the gas toward the outlet. Odor sensor unit.

2. The odor sensor unit according to claim 1, the outlet is provided above a portion heated by the heater in the chamber, By heating with the heater, an upward flow of the gas is generated or accelerated in the heating unit, thereby generating a flow of the gas from the inlet to the odor sensor. Odor sensor unit.

3. The odor sensor unit according to claim 1 or 2, The chamber comprises: a first chamber in which the inlet is formed and which accommodates the odor sensor; a second chamber in which the outlet is formed and in which the heater is attached; The flow path in the first chamber and the flow path in the second chamber are connected at a position lower than the upper surface of the first chamber. Odor sensor unit.

4. The odor sensor unit according to claim 3, the inlet is formed at a position higher than the odor sensor, The outlet is formed at a position higher than the heater. Odor sensor unit.

5. The odor sensor unit according to claim 1 or 2, further comprising: a flow rate sensor for acquiring information about the flow rate of the gas; a control unit that controls the heat generation amount of the heater in accordance with the output of the flow velocity sensor. Odor sensor unit.

6. The odor sensor unit according to claim 1 or 2, further comprising: a mechanism disposed on the flow path that turns the heater on or off based on a fluid force received from the gas; Odor sensor unit.

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