JP2008082842A - Gas sensor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor element and a gas sensor using a tuning-fork oscillation piece. <P>SOLUTION: A gas sensor element 10 comprises a tuning-fork oscillation piece 12 equipped with a plurality of bending oscillating oscillation arms 14 and a sensitive film 18 set at the tip part of the oscillation arm 14. This sensitive film 18 may be set at the upper face 14a and the lower face 14b of the oscillation arm 14, or at the upper face 14a, the lower face 14b and the side face 14c of the oscillation arm 14. And, using a hydrogen-occluded metal alloy film as a sensitive film 18, the gas sensor element 10 can detect hydrogen gas and measure hydrogen concentration. The sensitive film 18 may be a phosphoric acid zirconium film, a lipid film, an olefin oxide film or a tin oxide film. Here, the tuning-fork oscillation piece 12 may be a piezoelectric tuning-fork piece formed with a piezoelectric element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gas sensor element and a gas sensor.

Gas sensors include hydrogen sensors and ammonia sensors that use thickness-shear vibration and bending vibration. In the sensor using the thickness shear vibration, two driving electrodes are provided on each of the front and back surfaces of the vibrator, a detection electrode is provided between the driving electrodes, and a film that adsorbs hydrogen or ammonia on one driving electrode. Is provided. In this sensor, when hydrogen or ammonia adheres to the adsorption film, the mass of the adsorption film increases, and the mass balance with respect to the central axis of the vibrator is lost. Therefore, the mass is detected based on the vibration voltage generated thereby. In addition, a sensor using bending vibration has two sets of detection vibration pieces provided between two drive vibration pieces, a weight portion or a hammer head is provided at the tip of each vibration piece, and an electrode on the drive vibration piece. An adsorption film is provided on the top. (Patent Document 1)
JP 2006-153859 A (page 5-6)

  The vibration of the thickness-slip system described above has a higher oscillation frequency than other vibration modes. In order to oscillate the thickness-slip type vibrator, it is necessary to supply a large amount of current to the oscillation amplifier circuit in order to obtain a gain. For this reason, the sensor using the vibration mode of thickness sliding will increase power consumption.

  Further, as described above, since this sensor has a high oscillation frequency, the frequency of a signal output from a circuit (oscillation circuit) that drives (oscillates) this sensor also increases. However, if the logic circuit connected to the subsequent stage of the oscillation circuit does not support a high frequency, a signal output from the oscillation circuit cannot be input. Therefore, a prescaler or the like is provided at the input of the logic circuit to reduce the frequency of the signal. Must. Further, a logic circuit such as TTL (Transistor Transistor Logic) may be connected to the subsequent stage of the oscillation circuit. If Colpitts type or the like is used for the oscillation circuit, it is necessary to amplify the signal by providing an amplifier or the like because the one-stage oscillation of the oscillation circuit does not reach a voltage level at which the signal can be input to the logic circuit. For this reason, a sensor using a thickness-slip vibration mode becomes complicated and large by connecting peripheral circuits such as a prescaler and an amplifier.

  In addition, this sensor supplies an electrical signal to the drive electrode of the vibrator to vibrate the substrate, and the vibration transmitted to the detection electrode is detected by the detection electrode, so the vibration is indirectly measured. Therefore, the concentration of hydrogen and ammonia will be measured. For this reason, there exists a possibility that the detection sensitivity of a sensor may fall.

  Moreover, the sensor using the bending vibration described above has a shape in which six vibrating pieces extend from the base of the vibrator, so that the vibrator becomes large and the shape is complicated. For this reason, the number of vibrators obtained from one wafer is small, and the processing becomes complicated, so that the cost for obtaining the sensor becomes high. Further, in this sensor, since the adsorption film is provided on one detection vibrating piece constituting the above-described set, the distance between the adsorption films is separated. For this reason, when the gas concentration in the measurement environment is not uniform, the amount of adhesion to the adsorption film varies greatly, and if this sensor is used, the concentration of hydrogen or ammonia cannot be detected accurately.

  It is an object of the present invention to provide a gas sensor element using a tuning fork type resonator element. Another object of the present invention is to provide a gas sensor using this gas sensor element.

  A gas sensor element according to the present invention is characterized by including a tuning fork type vibrating piece having a vibrating arm that bends and vibrates, and a gas sensitive film provided at the tip of the vibrating arm. As a result, the gas sensitive film becomes heavier when the gas to be detected is adsorbed, so that the tip of the vibrating arm becomes heavier and the frequency of flexural vibration can be changed. Then, by detecting this frequency change, the detection and concentration of the gas to be detected can be measured. Further, since the frequency of the flexural vibration performed by the tuning fork type resonator element is several tens of kHz, it is not necessary to increase the gain of the oscillation circuit connected to the gas sensor element, and oscillation can be performed with a small current. Therefore, the gas sensor element can reduce current consumption. Further, since the gas sensor element is provided with a gas sensitive film on the vibrating arm and directly captures the change in the frequency of the bending vibration, there is no possibility that the detection sensitivity is lowered. Further, since the distance between the vibrating arms is narrow, the distance between the gas sensitive films can also be narrowed. For this reason, even if the gas concentration in the measurement environment where the gas sensor element is arranged is not uniform, the measurement can be performed in a narrow range, and the gas concentration can be accurately measured. In addition, since the tuning fork type vibrating piece is small, the number of vibrating pieces obtained from one wafer can be increased, and the tuning fork type vibrating piece can be easily processed because it has a simple shape. Therefore, the cost for obtaining the gas sensor element can be reduced.

  Further, since the frequency of the frequency signal output from the oscillation circuit is several tens of kHz depending on the bending vibration frequency, it is not necessary to provide a means for lowering the frequency such as a prescaler in the subsequent stage of the oscillation circuit. Further, since the gas sensor element using the tuning fork type resonator element can be oscillated by a single-stage oscillation circuit, it is not necessary to provide means for adjusting the voltage level of an amplifier or the like.

  Further, the gas sensor element according to the present invention is characterized in that a gas sensitive film is provided at a tip portion of at least one of the upper and lower surfaces or side surfaces of the vibrating arm. As a result, the gas sensor element can adsorb the gas to be detected by the gas-sensitive film to increase the tip of the vibrating arm and reduce the frequency of flexural vibration.

  The gas sensor element according to the present invention is characterized in that a gas sensitive film is provided on a side surface of the vibrating arm. As a result, the gas sensor element can adsorb the gas to be detected by the sensitive film, increase the tip of the vibrating arm, and lower the frequency of bending vibration. If a gas sensitive film is provided on the side surface in addition to the upper and lower surfaces of the vibrating arm, the surface area of the gas sensitive film is increased, so that more gas to be detected can be adsorbed and the detection sensitivity of the gas sensor element can be improved.

  In the gas sensor element according to the present invention, a gas sensitive film is provided from the tip of the vibrating arm to L / 2, where L is the length in the longitudinal direction of the vibrating arm at the weight provided at the tip of the vibrating arm. It is characterized by. If a gas sensitive film is provided closer to the tip of the vibrating arm, the gas sensitive film can effectively affect the bending vibration when the mass increases due to adsorption of the gas to be detected. Can be changed sensitively. This facilitates detection of the gas to be detected and concentration measurement, and can improve the detection sensitivity of the gas sensor element.

  Further, the gas sensor element according to the present invention is characterized in that a concave portion or a convex portion is provided at the tip of the vibrating arm, and a gas sensitive film is provided in the concave portion or the convex portion, respectively. As a result, the surface area of the gas sensitive film is increased, so that more gas to be detected can be adsorbed and the detection sensitivity of the gas sensor element can be improved.

  The gas sensor element according to the present invention is characterized in that a wide portion having a width wider than that of the other portion of the vibrating arm is provided at the tip of the vibrating arm, and a gas sensitive film is provided in the wide portion. As a result, the surface area of the gas-sensitive film provided in the wide portion is increased, so that more gas to be detected can be adsorbed and the detection sensitivity of the gas sensor element can be improved.

  The gas-sensitive film described above is a hydrogen storage alloy. As a result, when the gas sensor element occludes hydrogen gas, the frequency of bending vibration changes, so that the presence of hydrogen gas in the measurement environment can be detected, and the concentration of hydrogen gas can be measured.

  The gas-sensitive membrane described above is characterized by being any one of zirconium phosphate, lipid, oleic acid, and tin oxide. The gas sensor element can detect and measure the concentration of ammonia gas if the gas sensitive membrane is made of zirconium phosphate, and can detect and measure the concentration of volatile organic chlorine compounds if the gas sensitive membrane is made of lipid. If acid is used, ethanol can be detected and its concentration measured, and if gas sensitive film is tin oxide, hydrogen sulfide, ammonia and alcohol can be detected and its concentration measured.

  The tuning fork type resonator element described above is formed of a piezoelectric material. That is, the tuning fork type vibrating piece may be a tuning fork type piezoelectric vibrating piece formed of a piezoelectric material. If the tuning fork type piezoelectric vibrating piece is used, various characteristics of the tuning fork type vibrating piece including the stability of the oscillation frequency can be improved. Further, if the tuning fork type vibrating piece is made of quartz, the characteristics of the tuning fork type quartz vibrating piece can be further improved.

  The gas sensor according to the present invention is characterized in that an oscillation circuit is connected to the above-described gas sensor element and a frequency measuring means is connected to the oscillation circuit. The frequency signal output from the oscillation circuit has a frequency corresponding to the frequency of the bending vibration performed by the gas sensor element. Thereby, the gas sensor can detect the gas to be detected by measuring the frequency of the frequency signal output from the oscillation circuit, and can measure the concentration of the gas to be detected from the change in the frequency signal.

  Further, since the frequency of the flexural vibration performed by the tuning fork type resonator element is several tens of kHz, it is not necessary to increase the gain of the oscillation circuit connected to the gas sensor element, and oscillation can be performed with a small current. Therefore, the gas sensor can reduce current consumption. Further, since the frequency of the frequency signal output from the oscillation circuit is several tens of kHz depending on the bending vibration frequency, it is not necessary to provide a means for lowering the frequency such as a prescaler in the subsequent stage of the oscillation circuit. Furthermore, since the gas sensor element using the tuning fork type resonator element can oscillate with a single-stage oscillation circuit, it is not necessary to provide means for adjusting the voltage level of an amplifier or the like. Therefore, the gas sensor can prevent the peripheral circuit connected to the gas sensor element from becoming complicated or large.

  Hereinafter, the best embodiments of the gas sensor element and the gas sensor according to the present invention will be described. FIG. 1 is an explanatory diagram of a gas sensor element. 1A is a plan view of the gas sensor element, and FIG. 1B is a schematic side view. The gas sensor element 10 has a tuning fork type vibrating piece 12. The tuning fork-type vibrating piece 12 includes two vibrating arms 14 (141, 142) arranged in parallel and a base 16 provided at one end (root) of these vibrating arms 14. The vibrating arm 14 and the base portion 16 (tuning fork type vibrating piece 12) are formed of a piezoelectric body. The piezoelectric body can be a crystal, for example. By forming the resonating arm 14 and the base portion 16 from quartz, various characteristics of the tuning-fork type resonator element 12 including the stability of the oscillation frequency with respect to the temperature characteristic can be improved.

  Excitation electrodes 20 are provided on the upper surface 14 a, the lower surface 14 b, and the side surface 14 c of each vibrating arm 14, and a weight portion 22 is provided at the tip of each vibrating arm 14. The excitation electrode 20 provided on the upper surface 14a and the lower surface 14b of one vibration arm 141 and the excitation electrode 20 provided on the side surface 14c of the other vibration arm 142 are electrically connected, and the side surface 14c of the one vibration arm 141 is electrically connected. The excitation electrode 20 provided is electrically connected to the excitation electrode 20 provided on the upper surface 14a and the lower surface 14b of the other vibrating arm 142. In addition, a connection electrode 24 is provided on the base 16 and is electrically connected to the excitation electrode 20 on a one-to-one basis. In FIG. 1B, illustration of the excitation electrode 20, the weight portion 22, and the connection electrode 24 is omitted.

  In the gas sensor element 10, a sensitive film (gas sensitive film) 18 is provided on the weight portion 22 of the upper surface 14 a and the lower surface 14 b of each vibrating arm 14. The sensitive film 18 occludes or adsorbs the gas to be detected (hereinafter referred to as “adsorption”). Specifically, if the sensitive film 18 is a hydrogen storage alloy, hydrogen gas can be adsorbed. As an example of the hydrogen storage alloy, a palladium-nickel alloy or the like may be used, and the hydrogen storage alloy may be provided on the weight portion 22 by using a film formation method such as sputtering. If the sensitive membrane 18 is zirconium phosphate, ammonia gas can be adsorbed. If the sensitive membrane 18 is lipid (artificial lipid), volatile organochlorine compounds (trichloroethylene and tetrachloroethylene) can be adsorbed. (Unsaturated fatty acid) can adsorb ethanol, and if the sensitive film 18 is tin oxide (tin dioxide), it can adsorb hydrogen sulfide, ammonia and alcohol.

  FIG. 2 is a block diagram of the gas sensor. The gas sensor 30 uses the gas sensor element 10 described above. Specifically, in the gas sensor 30, an oscillation circuit 32 is connected to the gas sensor element 10, and a frequency measuring unit 34 is connected to the oscillation circuit 32. The oscillation circuit 32 oscillates the gas sensor element 10 and outputs a signal (frequency signal) generated by this oscillation. The frequency measuring means 34 inputs a frequency signal and measures the frequency of the frequency signal. For example, it may be a frequency counter.

  Next, operations of the gas sensor element 10 and the gas sensor 30 will be described. Hereinafter, as an example of gas detection and concentration measurement, a case where hydrogen gas is detected and the concentration is measured using the gas sensor element 10 and the gas sensor 30 will be described. Therefore, the sensitive film 18 is a hydrogen storage alloy.

  The electric signal supplied from the oscillation circuit 32 to the gas sensor element 10 is input to the excitation electrode 20 through the connection electrode 24. As a result, the vibrating arm 14 of the gas sensor element 10 is flexibly vibrated. When hydrogen gas is present in the measurement environment where the gas sensor element 10 is disposed, the hydrogen storage alloy stores the hydrogen gas and becomes heavy. As a result, the tip of the vibrating arm 14 becomes heavy, the bending vibration frequency (oscillation frequency) decreases, and the frequency of the frequency signal output from the oscillation circuit 32 also decreases. If the frequency measurement means 34 measures the frequency of the frequency signal output from the oscillation circuit 32, detects this frequency change, and obtains the hydrogen gas concentration based on this frequency change amount, the presence of hydrogen gas can be detected, In addition, the concentration of hydrogen gas can be measured.

  As described above, since the gas sensor element 10 is provided with the sensitive film 18 at the tip of the vibrating arm 14 constituting the tuning fork type vibrating piece 12, the gas to be detected that reacts with the sensitive film 18 can be adsorbed. Thereby, since the mass of the vibrating arm 14 becomes heavy, the gas sensor element 10 can change the frequency of bending vibration. The gas sensor 30 can detect the gas to be detected by measuring the frequency of the frequency signal output from the oscillation circuit 32, and can obtain the concentration of the gas to be detected from the change in the frequency signal.

  Further, since the gas sensor element 10 uses the tuning fork type vibrating piece 12, the frequency of the bending vibration can be set to several tens of kHz. Therefore, it is not necessary to increase the gain of the oscillation circuit 32 in order to cause the gas sensor element 10 to bend and vibrate, and the gas sensor element 10 can oscillate with a smaller current than that using the thickness shear vibration. Therefore, current consumption can be reduced.

  Further, since the gas sensor element 10 has a bending vibration frequency of several tens of kHz, it is not necessary to provide a prescaler or the like for lowering the frequency of the frequency signal at the subsequent stage of the oscillation circuit 32. Further, since the gas sensor element 10 uses the tuning fork type resonator element 12, the oscillation circuit 32 connected to the gas sensor element 10 can be made using a CMOS inverter circuit. Therefore, even if the gas sensor element 10 is oscillated using one stage of the oscillation circuit 32, a frequency signal having a sufficient voltage level can be output to a circuit connected to the subsequent stage of the oscillation circuit 32. That is, it is not necessary to provide an amplifier after the oscillation circuit 32. Therefore, the gas sensor element 10 and the gas sensor 30 can prevent the peripheral circuit from becoming complicated or large.

  Further, since the gas sensor element 10 is a tuning fork type having two vibrating arms 14, one size of the tuning fork type vibrating piece 12 is reduced in size and shape is simplified. Therefore, the number of vibrating pieces obtained from one wafer can be increased and the processing is easy, so that the cost for obtaining the gas sensor element 10 can be reduced. Furthermore, since the gas sensor element 10 is provided with the sensitive film 18 on the upper surface 14a and the lower surface 14b of each vibrating arm 14, it can be easily provided, and productivity can be improved.

  Further, since the gas sensor element 10 is provided with the sensitive film 18 on the vibrating arm 14 and directly captures the change in the frequency of the bending vibration, there is no possibility that the detection sensitivity is lowered. Further, since the gas sensor element 10 is provided with the sensitive film 18 at the tip of the vibrating arm 14, the interval between the sensitive films 18 can be narrowed, and the variation in adsorption of the gas to be detected to the sensitive film 18 can be reduced. For this reason, even if the gas concentration in the measurement environment is not uniform, detection in a narrow range can be performed, and accurate gas concentration detection can be performed.

  Next, a modified example of the gas sensor element 10 described above will be described. First, a modified example of how to provide the sensitive film 18 will be described. FIG. 3 is an explanatory diagram of a gas sensor element according to a first modification. Here, FIG. 3 (A) is a plan view of the gas sensor element, and FIG. 3 (B) is a schematic side view. In FIG. 3, the description of the excitation electrode and the connection electrode is omitted. In the gas sensor element 40 according to the first modification, the sensitive film 18 is provided on the upper surface 14a, the lower surface 14b, and the weight portion 22 of the side surface 14c of the tip portion of each vibrating arm 14. As described above, since the sensitive film 18 is also provided on the side surface 14c of each vibrating arm 14, the surface area of the sensitive film 18 can be increased as compared with the above-described embodiment, and the mass to be detected is increased by adsorbing more detection gas. This can be transmitted to the vibrating arm 14 quickly. That is, the gas sensor element 40 can increase the detection ability of the gas to be detected.

  FIG. 4 is a plan view of a gas sensor element according to a second modification. The gas sensor element 44 according to the second modified example regulates a portion where the sensitive film 18 is provided. Since the vibrating arm 14 performs bending vibration, the bending vibration can be affected when the tip end is heavier than when the base side connected to the base portion 16 is heavy. That is, if the sensitive film 18 is provided only on the side closer to the tip of the vibrating arm 14, the bent portion near the base portion 16 of the vibrating arm 14 is compared with the configuration in which the sensitive film 18 is formed on the entire vibrating arm 14. Therefore, when the mass of the sensitive film 18 increases, the frequency of the bending vibration changes sensitively. Therefore, in the gas sensor element 44 according to the second modification, the sensitive film 18 is provided from the tip of the vibrating arm 14 to a range of L / 2, where L is the length of the weight portion 22 in the longitudinal direction of the vibrating arm 14. . The sensitive film 18 may be provided on the upper surface 14a and the lower surface 14b of each vibrating arm 14, or may be provided on the upper surface 14a, the lower surface 14b, and the side surface 14c of each vibrating arm 14. If only the upper surface 14a and the lower surface 14b are provided, the coating amount of the sensitive film 18 can be reduced. As a result, the flexural vibration of the vibrating arm 14 is easily affected, so that detection of the gas to be detected and concentration measurement are facilitated, and the detection sensitivity of the gas sensor element 44 can be improved. In addition, since the sensitive film | membrane 18 is provided to the length of L / 2 from the front-end | tip, the to-be-detected gas can be adsorbed and the mass change which can influence a bending vibration can be obtained.

  Next, a modified example of the vibrating arm 14 constituting the gas sensor element 10 will be described. FIG. 5 is an enlarged perspective view of the tip portion of the vibrating arm of the gas sensor element according to the third modification. In FIG. 5, the description of the weight portion is omitted. In the third modification, at least one of a concave portion and a convex portion is formed in a portion where the sensitive film is provided on the vibrating arm. The vibrating arm 14 shown in FIG. 5A is provided with grooves (recesses 50) on the upper surface 14a and the lower surface 14b of the tip, and is provided on the upper surface 14a and lower surface 14b of the tip and the inside of the groove (recess 50). A sensitive film 18 is provided. 5B is provided with holes (recesses 50) in the upper surface 14a and the lower surface 14b of the tip, and the upper surface 14a and the lower surface 14b of the tip and the inside of the hole (recess 50). A sensitive film 18 is provided. Such a recess 50 can be formed by etching or the like. Thereby, since the surface area of the sensitive film | membrane 18 increases, the detection sensitivity of the gas sensor element 10 can be improved.

  One concave portion 50 may be provided at a location where the sensitive film 18 is provided on the vibrating arm 14, or two or more concave portions 50 may be provided. The recess 50 may be provided only on one of the upper surface 14 a and the lower surface 14 b of the vibrating arm 14. 5A and 5B, the sensitive film 18 may be provided on the upper surface 14a and the lower surface 14b of the vibrating arm 14 and the inside of the recess 50, and the upper surface 14a and the lower surface 14b of the vibrating arm 14. Further, it may be provided on the side surface 14 c and the inside of the recess 50. In addition to the recess 50 shown in FIG. 5, in order to increase the surface area of the sensitive film 18, it is possible to provide a convex part at the tip of the vibrating arm 14, that is, the place where the sensitive film 18 is formed. This convex portion can be formed when the vibrating arm 14 is formed large in advance and the vibrating arm 14 is reduced to a desired shape by etching or the like.

  In the fourth modification described with reference to FIG. 6, the distal end portion of the vibrating arm 14 is made wider than the other portions, and the sensitive film 18 is provided in the wide portion. FIG. 6 is a schematic plan view of a gas sensor element according to a fourth modification. In FIG. 6, the description of the excitation electrode, the connection electrode, and the weight portion is omitted. By increasing the width of the tip of the vibrating arm 14 compared to the central portion or the root portion, the surface area can be increased. And if the sensitive film | membrane 18 is provided in the part (wide part 56) which widened this width | variety, the surface area of the sensitive film | membrane 18 can be enlarged and the detection sensitivity of the gas sensor element 10 can be improved. In addition to the form shown in FIG. 6, the wide portion 56 has a tapered shape in which the width increases from the root portion of the vibrating arm 14 toward the tip portion, and the width from the center portion of the vibrating arm 14 toward the tip portion. The taper shape may become wider. The sensitive film 18 may be provided on the upper surface and the lower surface of the wide portion 56, or may be provided on the upper surface, the lower surface, and the side surface of the wide portion 56.

  In the embodiment and the modification described above, the sensitive film 18 is provided on the weight portion 22 provided on the vibrating arm 14. However, in some embodiments, the weight portion 22 is not provided, that is, on the vibrating arm 14. The form which provided the sensitive film | membrane 18 directly may be sufficient. Further, a form in which a base film for improving the adhesion between the sensitive film 18 and the vibrating arm 14 may be provided. Thereby, the sensitive film 18 can be used in place of the weight part 22.

  In addition, the gas sensor element 10 having a structure in which a sensitive film is formed on a plurality of surfaces (the upper surface 14a and the lower surface 14b) of the vibrating arm 14 as in the above-described embodiment can provide a high gas detection sensitivity capability. If the sensitive film 18 is provided at the tip of at least one of the upper, lower, and side surfaces, the gas sensor element 10 having gas detection capability can be obtained.

  In particular, if the gas sensor element 10 is required instead of the gas detection capability as high as that of the above-described embodiment, the sensitive film 18 may be any of the upper surface 14a, the lower surface 14b, and the side surface 14c of the vibrating arm 14. A configuration in which a film is formed on one surface is effective.

It is explanatory drawing of a gas sensor element. It is a block diagram of a gas sensor. It is explanatory drawing of the gas sensor element which concerns on a 1st modification. It is a top view of the gas sensor element which concerns on a 2nd modification. It is the perspective view which expanded the front-end | tip part of the vibrating arm of the gas sensor element which concerns on a 3rd modification. It is a schematic plan view of the gas sensor element which concerns on a 4th modification.

Explanation of symbols

10, 40, 44, 54 ......... Gas sensor element, 12 ......... Tuning fork type vibrating piece, 14 ......... Vibrating arm, 18 .... Sensitive membrane, 22 ..... Weight part, 30 ....... Gas sensor, 32 ......... oscillation circuit, 50 ......... concave, 56 ......... wide part.

Claims (8)

  A gas sensor element comprising: a tuning fork-type vibrating piece having a vibrating arm that bends and a gas-sensitive film provided at a tip of the vibrating arm.   The gas sensor element according to claim 1, wherein the gas sensitive film is provided on a tip portion of at least one of the upper and lower surfaces or side surfaces of the vibrating arm.   The gas sensitive film is provided from the tip of the vibrating arm to L / 2, where L is the length in the longitudinal direction of the vibrating arm at the weight provided at the tip of the vibrating arm. Item 3. The gas sensor element according to Item 1 or 2.   The gas sensor element according to any one of claims 1 to 3, wherein a concave portion or a convex portion is provided at a tip portion of the vibrating arm, and the gas sensitive film is provided in the concave portion or the convex portion, respectively.   5. The tip of the vibrating arm is provided with a wide portion that is wider than other portions of the vibrating arm, and the gas sensitive film is provided on the wide portion. The gas sensor element according to claim 1.   6. The gas sensor element according to claim 1, wherein the gas sensitive film is a hydrogen storage alloy.   6. The gas sensor element according to claim 1, wherein the gas sensitive film is any one of zirconium phosphate, lipid, oleic acid, and tin oxide.   8. The gas sensor element according to claim 1, wherein the tuning fork type vibrating piece is formed of a piezoelectric body.

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