JP2005265711A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor capable of preventing measured gas flowing into a measuring chamber from being directly crossed with a propagation route of an ultrasonic wave. <P>SOLUTION: A flow-in hole 28 and a flow-out hole 29 are opened in a side wall 4 of a casing 2 of this gas sensor 1, and are connected respectively with a flow-in pipe 26 and a flow-out pipe 27. The measuring chamber 30 is provided in an inside of the casing 2, and the purge gas flows from the flow-in hole 28 into the measuring chamber 30 and flows out from the flow-out hole 29. A gas concentration by the ultrasonic wave is detected in a measuring area 31 formed between an ultrasonic element 53 provided on an upper wall 6, and a reflecting face 15 provided on a bottom wall 3. The purge gas flowing from the flow-in hole 28 into the measuring chamber 30 is prevented from intruding directly into the measuring area 31 by a shielding wall 40 provided on a flow-in-directional extension line, and the ultrasonic wave is hardly attenuated in the measuring area 31 to measure thereby accurately the gas concentration. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gas sensor for measuring the concentration of a combustible gas such as evaporated fuel supplied to an internal combustion engine.

  Conventionally, a gas sensor (gas concentration) that transmits ultrasonic waves by an ultrasonic element, receives ultrasonic waves propagated over a predetermined distance, and measures the concentration of the gas to be measured by measuring the propagation time from transmission to reception of ultrasonic waves Sensor) is known (for example, see Patent Document 1). This gas sensor is provided, for example, in a fuel supply line supplied to an internal combustion engine such as an automobile. More specifically, separately from the fuel supply line for injecting the fuel pumped up from the fuel tank into the intake pipe by the injector, the evaporated fuel generated in the fuel tank is temporarily stored in the canister, and further the intake air A gas sensor is provided in a supply line (purge line) to be sent to the pipe.

  As an example of such a gas sensor, in a gas sensor using ultrasonic waves, an ultrasonic element is provided on one wall surface of a pair of opposing wall surfaces in a measurement chamber, and a reflective surface for reflecting ultrasonic waves is provided on the other wall surface. It has been. The ultrasonic wave transmitted from the ultrasonic element propagates through the measurement chamber, is reflected by the reflecting surface, and is received by the ultrasonic element. In this measurement chamber, an inflow passage and an outflow passage connected to the purge line are provided, and a purge gas containing evaporated fuel as a gas to be measured is introduced.

In such a gas sensor, when a purge gas having a high flow rate flows into the measurement chamber and the flow of the purge gas passing through the measurement chamber is disturbed, the concentration of the purge gas on the ultrasonic propagation path is not stable and accurate. The gas concentration cannot be measured. Therefore, the gas sensor is provided with a bypass passage in parallel with the measurement chamber for connecting the inflow passage and the outflow passage and allowing a part of the purge gas to pass therethrough. The flow of the purge gas is branched by this bypass passage, and a stable gas concentration measurement is performed by suppressing the flow rate of the purge gas flowing into the measurement chamber.
JP 2000-241398 A

  However, in a gas sensor having a bypass passage, when the flow rate of the purge gas is low, the purge gas is difficult to flow into the measurement chamber, so that the gas replacement property is deteriorated, and accurate gas concentration measurement may be difficult. For this reason, it is conceivable to eliminate the bypass passage so that accurate gas concentration measurement can be performed even when the flow rate of the purge gas is slow. However, if the bypass passage is simply eliminated, the flow velocity is high in the measurement chamber. When the purge gas flows in, a vortex due to so-called boundary separation occurs at the boundary between the inflow passage and the measurement chamber. In particular, as in the gas sensor disclosed in Patent Document 1, if the purge gas flow direction toward the measurement chamber is perpendicular to the ultrasonic propagation path, the generated vortex is applied to the propagation path. As a result, the ultrasonic wave propagated by the sound may be attenuated and it may be difficult to accurately measure the gas concentration.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to realize a gas sensor in which a measurement gas flowing into a measurement chamber is not directly applied to an ultrasonic propagation path.

  In order to achieve the above object, a gas sensor according to a first aspect of the present invention includes a measurement chamber in which an inflow hole and an outflow hole into which a gas to be measured flows in and out are opened on a wall surface, and the inflow hole and the outflow hole. A wall surface of the measurement chamber that is different from the wall surface, provided on one wall surface of a pair of wall surfaces facing each other, on a reflection surface for reflecting ultrasonic waves, and on the other wall surface of the pair of wall surfaces An ultrasonic element that transmits ultrasonic waves toward the reflecting surface and receives ultrasonic waves reflected by the reflecting surface; and from the outside of the measuring chamber through the inflow hole through the measuring chamber. When viewed, a blocking wall provided in the measurement chamber is provided so that the measurement region is not visible with respect to the measurement region formed between the ultrasonic element and the reflecting surface.

  Further, in the gas sensor according to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the blocking wall is provided along a virtual plane parallel to the outer surface of the ultrasonic element.

  According to a third aspect of the present invention, in addition to the configuration of the second aspect of the invention, the ultrasonic element is housed in an element case arranged to face the measurement chamber, and the blocking wall is Projecting from the element case.

  According to a fourth aspect of the present invention, in addition to the configuration of the second or third aspect of the present invention, the inflow hole has a cylindrical inflow cylinder that guides the flow of the gas to be measured into the measurement chamber. The blocking wall has a width that is at least as large as the cross-sectional area of the inner periphery of the inflow tube, and intersects the virtual plane when the inner periphery of the inflow tube extends toward the measurement region. It is provided in the part.

  In the gas sensor according to the first aspect of the present invention, when the measurement chamber is viewed from the inflow hole, a blocking wall is provided so that the measurement region formed between the ultrasonic element and the reflecting surface cannot be seen in the measurement chamber. Therefore, the gas to be measured flowing into the measurement chamber through the inflow hole directly blocks into the measurement region by the blocking wall. As a result, even if a vortex due to boundary separation occurs at the boundary between the inflow hole and the measurement chamber, the vortex collides with the blocking wall and does not enter the measurement region and does not affect the measurement of the gas concentration. In addition, the barrier wall is partly provided at the boundary between the measurement area and other areas. By eliminating the wall that completely separates the two from the configuration, the measurement chamber can be downsized and the gas sensor can be downsized. Can be achieved. Furthermore, since the bypass passage is eliminated, accurate gas concentration measurement is possible in a wide flow rate range from a low flow rate to a high flow rate.

  In addition, in the gas sensor of the invention according to claim 2, in addition to the effect of the invention according to claim 1, the gas to be measured can be smoothed by disposing a blocking wall along a virtual plane parallel to the outer surface of the ultrasonic element. It is possible to flow into the measurement region, and it is possible to suppress the deterioration of the gas substituting property due to pressure loss.

  Moreover, in the gas sensor of the invention according to claim 3, in addition to the effect of the invention according to claim 2, since the shielding wall protrudes from the element case that houses the ultrasonic element, the ultrasonic element is housed when the gas sensor is assembled. By simply assembling the element case (hereinafter also referred to as “element assembly”), the blocking wall can be provided in the measurement chamber. Thus, the gas sensor does not need to be provided with an engaging portion or an opening for incorporating the blocking wall, that is, when the gas sensor is assembled, a seal for enhancing the sealing property of the measurement chamber is provided to the element assembly. If it does, it can carry out also with respect to a shielding wall, and the structural reliability of a gas sensor can be improved by reducing the part to seal.

  Moreover, in the gas sensor of the invention according to claim 4, in addition to the effect of the invention according to claim 2 or 3, since the blocking wall is provided at the tip of the inner periphery of the inflow cylinder extending toward the measurement region, There is a blocking wall in the inflow direction of the gas to be measured flowing into the measurement chamber through the cylinder, and the gas to be measured does not directly enter the measurement region. For this reason, the attenuation of the ultrasonic wave due to the turbulence of the gas flow of the gas to be measured in the measurement region can be prevented, and the accurate gas concentration can be measured.

  Hereinafter, a gas sensor 1 according to an embodiment of the gas sensor of the present invention will be described with reference to the drawings. The gas sensor 1 is a gas sensor that uses a method of measuring the propagation time of ultrasonic waves, and measures the gas concentration of a specific gas in the gas to be measured (that is, the atmosphere to be measured). The gas sensor 1 can be used for various devices that measure gas concentration. As an example, the gas sensor 1 is installed in a purge line of a canister that temporarily stores fuel evaporated in a gasoline tank of an automobile, and evaporative fuel in purge gas. It can be used to measure the concentration of

  First, the structure of the gas sensor 1 of this Embodiment is demonstrated with reference to FIGS. FIG. 1 is a longitudinal sectional view of the gas sensor 1. FIG. 2 is a partial cross-sectional view of the element assembly 50. FIG. 3 is a bottom view of the element assembly 50 as seen from the direction of the arrow A shown in FIG. FIG. 4 is an exploded perspective view showing a fixing position of the blocking wall 40 to the element assembly 50.

  The gas sensor 1 of the present embodiment is an ultrasonic gas sensor that generates an ultrasonic wave using a piezoelectric element. In particular, an ultrasonic transmission / reception element (hereinafter simply referred to as “ultrasonic wave”) that is used for both transmission and reception of ultrasonic waves. Element 53 ") is used. As shown in FIG. 1, the gas sensor 1 includes a circuit board 12 that performs driving and calculation processes necessary for gas concentration detection, an ultrasonic element 53 that transmits and receives ultrasonic waves, and a purge gas that is a measurement gas including a specific gas. Is introduced into the measurement chamber 30, the reflection surface 15 provided to reflect the ultrasonic waves in the measurement chamber 30, an inflow hole 28 into which purge gas flows, a cylindrical inflow pipe 26 connected to the inflow hole, It is composed of an outflow hole 29 through which purge gas flows out, a cylindrical outflow pipe 27 connected to the outflow hole, and a blocking wall 40 that partitions a partial region in the measurement chamber 30.

  In the gas sensor 1, the inside of the cylindrical housing 2 whose both ends are closed is configured as a measurement chamber 30. An opening 5 is provided in the upper wall 6 provided on one end side of the housing 2, and an element assembly 50 described later is engaged therewith. The bottom wall 3 on the other end side of the housing 2 is provided with a reflecting table 14 projecting into the measurement chamber 30, and the reflecting surface 15 provided at the tip of the reflecting table 14 is in the axial direction of the housing 2. It is comprised as a plane orthogonal to. The reflecting surface 15 is provided so as to reflect the ultrasonic wave transmitted from the ultrasonic element 53 and receive it again as a received wave by the ultrasonic element 53. The bottom wall 3 corresponds to “one wall surface of a pair of opposing wall surfaces” in the present invention, and the upper wall 6 corresponds to “the other wall surface of the pair of opposing wall surfaces” in the present invention. To do.

  In the side wall 4 of the housing 2, an inflow hole 28 and an outflow hole 29 are opened on the same side with respect to the axial direction of the housing 2. The inflow hole 28 is opened in the vicinity of the upper wall 6, and a cylindrical inflow pipe 26 having an axial direction in a direction orthogonal to the axial direction of the housing 2 is connected to the inflow hole 28. The outflow hole 29 is opened near the bottom wall 3, and similarly, a cylindrical outflow pipe 27 having an axial direction in a direction perpendicular to the axial direction of the housing 2 is connected. A part of the inner peripheral surface of the outflow pipe 27 has a portion continuous with the inner surface of the bottom wall 3. The ends of the inflow pipe 26 and the outflow pipe 27 are connected to the purge line, and the gas sensor 1 is installed. The side wall 4 corresponds to the “wall surface in which the inflow hole and the outflow hole are opened” in the present invention. The inflow pipe 26 corresponds to an “inflow cylinder” in the present invention.

  Next, the element assembly 50 will be described. As shown in FIGS. 2 and 3, the element assembly 50 has an ultrasonic element (piezoelectric element) 53 fixed inside a cylindrical element case 51, and a film member on the bottom surface (the lower surface in FIG. 2). 54 has a stretched structure. A flange 52 is formed on the upper surface of the element case 51, and when the element assembly 50 is engaged with the opening 5 (see FIG. 1) of the upper wall 6 of the housing 2, the element assembly 50 is in the measurement chamber 30. In addition, the flange portion 52 is fixed to the upper wall 6. Further, a terminal 55 connected to the ultrasonic element 53 protrudes from the upper surface of the flange portion 52. When the gas sensor 1 is assembled, the terminal 55 is soldered to the circuit board 12 (see FIG. 1) and electrically connected to the pattern on the circuit board 12, whereby the ultrasonic element 53 is controlled. ing. The ultrasonic element 53 has a cylindrical shape and is accommodated in the element case 51 so that the axis of the ultrasonic element 53 and the axis of the element case 51 coincide. That is, the ultrasonic element 51 is housed in the element case 51 so that the outer surface of the ultrasonic element 51 and the outer surface of the element case 51 are parallel to each other.

  A part of the side surface of the element case 51 is formed in a concave shape, and the base 41 of the blocking wall 40 is fixed at this position. When the element assembly 50 is assembled to the housing 2, the blocking wall 40 is positioned on an extension line in the flow direction of the purge gas flowing into the measurement chamber 30 from the inflow hole 28. As shown in FIG. 4, the blocking wall 40 is a plate body whose lateral direction is curved along the outer periphery of the element case 51 of the element assembly 50, and is provided at the other end opposite to the one end (base 41) in the longitudinal direction. A tapered portion 42 that is tapered toward the other end is formed on the outer peripheral side.

  As shown in FIG. 1, the element assembly 50 is engaged with the opening 5 of the upper wall 6 of the housing 2 with the bottom surface on which the film member 54 is stretched facing the reflecting surface 15 of the measurement chamber 30. Is done. At this time, the assembly direction of the element assembly 50 is adjusted and fixed so that the side surface on the side where the blocking wall 40 is provided faces the inflow hole 28. The blocking wall 40 is large enough to cover the field of view so that the measurement region 31 cannot be seen when looking into the measurement chamber 30 through the inflow hole 28. This is to prevent the purge gas from directly entering the measurement region 31 so that the blocking wall 40 exists on the extension of the purge gas flowing in from the inflow hole 28 in the flow path direction.

  Here, the measurement region 31 is a region formed between the ultrasonic element 53 and the reflection surface 15 in the measurement chamber 30. Of the ultrasonic waves transmitted from the ultrasonic element 53, the measurement region 31 is formed on the reflection surface 15. The surrounding area centering on the propagation path (indicated by the alternate long and short dash line in the figure) of the ultrasonic wave transmitted in the direction toward. More specifically, it refers to a region in the measurement chamber 30 when the outer periphery of the film member 54 is temporarily extended along the propagation direction of ultrasonic waves.

  When the element assembly 50 is assembled to the housing 2 in this manner, the blocking wall 40 is along a virtual plane (indicated by a two-dot chain line in the drawing) extending from the outer peripheral edge of the element case 51 of the element assembly 50. It is provided in a protruding shape. By disposing the blocking wall 40 away from the inflow hole 28, a flow path for the purge gas flowing in from the inflow hole 28 can be secured, and the flow rate of the purge gas can be reduced due to pressure loss without reducing the flow rate of the purge gas. Reduced. The gas sensor 1 is provided with a temperature sensor (not shown) for measuring the temperature in the measurement chamber 30 and is electrically connected to the circuit board 12.

  Next, with reference to FIG. 1, the operation when the concentration of the purge gas is measured in the gas sensor 1 will be described. As shown in FIG. 1, when the concentration of the purge gas is measured by the gas sensor 1, the measurement is performed once (the ultrasonic wave transmitted from the ultrasonic element 53 is reflected by the reflecting surface 15, and the ultrasonic element 53 again. In this case, the ultrasonic wave is transmitted from the ultrasonic element 53 toward the reflecting surface 15. As described above, the reflecting surface 15 is orthogonal to the axial direction of the housing 2. For this reason, when the ultrasonic wave transmitted from the ultrasonic element 53 arranged to face the reflecting surface 15 is reflected by the reflecting surface 15, only the direction component orthogonal to the reflecting surface 15 is directed to the ultrasonic element 53. . The ultrasonic element 53 receives this as a received wave, and obtains the gas concentration based on the measurement result of the time taken from transmission to reception.

  On the other hand, the purge gas flowing into the measurement chamber 30 from the inflow hole 28 through the inflow pipe 26 flows into the measurement chamber 30 with the direction along the axial direction of the inflow pipe 26 as the flow path direction. A blocking wall 40 is provided on the axial extension of the inflow pipe 26, and the purge gas strikes the blocking wall 40 and the flow path direction is bent. At this time, the purge gas is guided in a direction toward the bottom wall 3 of the measurement chamber 30, that is, a direction toward the opening of the outflow hole 29 by the tapered portion 42 provided on the blocking wall 40.

  Negative pressure is applied to the purge line, and purge gas is drawn in the direction of flowing out from the outflow pipe 27. Most of the purge gas passing through the measurement chamber 30 flows out of the gas sensor 1 from the outflow hole 29 via the outflow pipe 27 as it is. However, since there is no isolation wall except for the blocking wall 40 in the measurement chamber 30, a part of the purge gas is within the measurement region 31 from the short end of the blocking wall 40 or the tip of the tapered portion 42 of the blocking wall 40. Will invade. At this time, the purge gas existing in the measurement region 31 is pushed out by the penetrated purge gas or drawn by the negative pressure applied through the outflow hole 29, and therefore flows from the side close to the outflow hole 29 to the outside of the measurement region 31. . Thereby, gas replacement in the measurement region 31 is always performed.

  Due to the high flow velocity of the purge gas, the vortex generated by boundary separation at the boundary between the inflow hole 28 and the measurement chamber 30 travels along the flow direction of the purge gas and collides with the blocking wall 40, so that the measurement region 31. It does not penetrate inside. In addition, since the purge gas having a high flow velocity does not directly enter the measurement region 31 due to the blocking wall 40, the turbulence of the purge gas in the measurement region 31 is small. In addition, the purge gas whose flow direction is bent by the blocking wall 40 is mainly in the direction toward the outflow hole 29, and the flow velocity in that direction is fast. Therefore, at the tip of the tapered portion 42 of the blocking wall 40, boundary purge occurs. A vortex may occur. However, since the generated vortex advances toward the outflow hole 29 along the flow path direction of the purge gas, it does not enter the measurement region 31.

  Then, ultrasonic waves are transmitted and received by the ultrasonic element 53 as described above, and the concentration of the purge gas in the measurement region 31 that is constantly replaced is measured. That is, the propagation time from when the ultrasonic wave transmitted from the ultrasonic element 53 is reflected by the reflecting surface 15 until it is received by the original ultrasonic element 53 is measured. The propagation time from when the ultrasonic element 53 transmits the transmission wave to when it receives the reflected wave (received wave) varies depending on the gas concentration of the specific gas (evaporated fuel) in the purge gas. Therefore, the gas concentration in the gas to be measured can be detected by taking out the sensor output corresponding to this propagation time. In addition, since the propagation speed of an ultrasonic wave changes with temperature besides gas concentration, detection of gas concentration is performed using the output from a temperature sensor (not shown).

  As described above, in the gas sensor 1 according to the present embodiment, when purge gas having a high flow velocity flows into the measurement chamber 30, vortices generated due to boundary separation at the boundary between the inflow hole 28 and the measurement chamber 30 40, and does not enter the measurement region 31. In addition, when the purge gas whose flow direction is bent by the blocking wall 40 passes through the tip of the tapered portion 42 of the blocking wall 40, a vortex due to boundary separation may occur. Since the direction is not toward the measurement region 31, the vortex does not enter the measurement region 31. For this reason, attenuation of the ultrasonic wave transmitted / received in the measurement region 31 hardly occurs, and accurate gas concentration measurement can be performed.

  Further, the purge wall having a high flow velocity is prevented from directly entering the measurement region 31 by the blocking wall 40, and the purge gas flowing into the measurement chamber 30 from the inflow hole 28 by the tapered portion 42 of the blocking wall 40 is , Guided in the direction toward the outflow hole 29. That is, it is not necessary to provide a wall or the like inside the measurement chamber 30 so that a purge gas having a high flow velocity does not enter the measurement region 31, and the structure inside the measurement chamber 30 is simplified to reduce the size, and thus the gas sensor 1 can be reduced in size. Can be achieved.

  Further, since the blocking wall 40 is fixed to the element assembly 50, the blocking wall 40 can be assembled by assembling the element assembly 50 when the gas sensor 1 is assembled. That is, the measurement chamber 30 has only three openings, that is, the inflow hole 28, the outflow hole 29, and the opening 5 for assembling the element assembly 50. Since there are few openings in which a sealing gap is formed in order to improve the sealing property of the measurement chamber 30, the structural reliability of the gas sensor 1 can be improved.

    Further, the blocking wall 40 is provided along a virtual plane extending from the outer peripheral edge of the element case 51 of the element assembly 50, and the measurement region 31 is viewed when looking into the measurement chamber 30 through the inflow pipe 26. It is large enough to cover its field of view. That is, when the main flow of the purge gas flows from the inflow hole 28 to the outflow hole 29, the flow path and the measurement region 31 are not largely blocked, so that the purge gas in the measurement region 31 can be easily replaced and measured. The gas replacement property of the region 31 is improved. By disposing the blocking wall 40 away from the inflow hole 28, a flow path for the purge gas flowing in from the inflow hole 28 can be ensured, and a decrease in the flow rate of the purge gas due to pressure loss can be reduced.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, a configuration in which a blocking wall protrudes from a wall surface inside the measurement chamber 30 may be adopted. As an example, as shown in FIG. 5, a blocking wall 45 may protrude from the upper wall 6. Note that the size, shape, and the like of the blocking wall 45 are the same as those of the blocking wall 40 of the present embodiment. Moreover, you may comprise the element case 51 and the interruption | blocking wall 40 by one member.

  In addition, as shown in FIG. 6, a guide wall 25 extending the peripheral wall of the inflow pipe 26 is provided at the end of the inflow pipe 26 on the measurement chamber 30 side, and when the inflow pipe 26 is connected to the inflow hole 28, The flow channel direction may be guided so that the flow channel direction is directed toward the outflow hole 29. At this time, if the wall surface of the guide wall 25 is configured so that the guide wall 25 exists on the extension in the flow direction of the purge gas in the inflow pipe 26 excluding the portion of the guide wall 25 as in the present embodiment. The purge gas does not enter the measurement region 31 directly.

  Moreover, it is good also as a structure which provided the downward slope toward the outflow hole 29 in the inner surface of the bottom wall 3. FIG. In this way, the moisture contained in the purge gas easily flows in the direction of the outflow hole 29, and does not accumulate in the measurement chamber 30, but is easily discharged outside the gas sensor 1 as the purge gas passes. Further, the reflecting surface 15 may also be configured to have a gentle convex surface so that moisture contained in the purge gas hardly remains on the reflecting surface 15.

  The present invention is not limited to various gas sensors, but can be applied to various sensors that use ultrasonic propagation time for measurement.

1 is a longitudinal sectional view of a gas sensor 1. FIG. 3 is a partial cross-sectional view of the element assembly 50. FIG. FIG. 3 is a bottom view of the element assembly 50 as seen from the direction of an arrow A shown in FIG. 2. FIG. 6 is an exploded perspective view showing a fixing position of the blocking wall 40 to the element assembly 50. It is a longitudinal cross-sectional view of the modification of the gas sensor 1. FIG. It is a longitudinal cross-sectional view of the modification of the gas sensor 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas sensor 3 Bottom wall 4 Side wall 6 Top wall 15 Reflecting surface 26 Inflow pipe 28 Inflow hole 29 Outflow hole 30 Measurement chamber 31 Measurement area 40 Blocking wall 50 Element assembly 53 Ultrasonic element

Claims (4)

A measurement chamber in which an inflow hole and an outflow hole into and out of the gas to be measured are opened on the wall surface;
A wall surface of the measurement chamber different from the wall surface in which the inflow hole and the outflow hole are opened, provided on one wall surface of a pair of wall surfaces facing each other, and a reflection surface for reflecting ultrasonic waves;
Among the pair of wall surfaces, an ultrasonic element that is provided on the other wall surface, transmits ultrasonic waves toward the reflection surface, and receives ultrasonic waves reflected by the reflection surface;
When the measurement chamber is viewed from the outside of the measurement chamber through the inflow hole, the measurement region is not visible with respect to the measurement region formed between the ultrasonic element and the reflection surface. A blocking wall provided in the measurement chamber;
A gas sensor comprising:   The gas sensor according to claim 1, wherein the blocking wall is provided along a virtual plane parallel to an outer surface of the ultrasonic element.   The gas sensor according to claim 2, wherein the ultrasonic element is housed in an element case disposed so as to face the measurement chamber, and the blocking wall protrudes from the element case. The inflow hole is provided with a cylindrical inflow tube for guiding the flow of the gas to be measured into the measurement chamber,
The blocking wall is at least as wide as the cross-sectional area of the inner periphery of the inflow tube, and is provided at a portion that intersects the virtual surface when the inner periphery of the inflow tube extends toward the measurement region. The gas sensor according to claim 2, wherein the gas sensor is provided.

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