PM sensor

Abstract

To provide a PM sensor that has better characteristics than before.SOLUTION: A PM sensor (1) comprises: a vibrator (3) whose vibration characteristics change due to the adhesion of PMs; and a removal mechanism (5) that removes the PMs adhering to the vibrator from the vibrator. The vibration characteristics of the vibrator change due to the adhesion of PMs to the vibrator. This change in vibration characteristics makes it possible to detect the adhesion or the adhering amount of PMs to the vibrator. By removing the PMs adhering to the vibrator from the vibrator by the removal mechanism, it is possible to initialize the vibrator to the former state with PMs removed. This enables the PM sensor to be repeatedly used.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a PM sensor. Here, PM is an abbreviation for Particulate Matter.

Background Art

[0002] Conventionally, various sensors of this type are known. For example, the PM sensor described in Patent Document 1 includes a sensor element that is a plate-shaped insulator and a cover that covers the entire sensor element. A pair of electrodes are formed on the surface of the sensor element, that is, the surface to which PM adheres. A large number of holes are formed in the cover. PM flows from the holes into the inside of the cover and adheres and accumulates on the sensor element due to its own adhesiveness. Since PM has conductivity, when the electrodes are connected due to the PM deposited on the sensor element, the electrodes become conductive. A voltage is applied from a DC power source between the electrodes based on a command from an ECU (i.e., Electronic Control Unit). When a voltage is applied when the electrodes are in a conductive state, a current flows between the electrodes. The value of the current is measured by an ammeter and output to the ECU as a sensor output.

[0003] Also, the PM sensor described in Patent Document 1 includes a heater and a heater control unit. The heater is, for example, a metal wire having an electrical resistance formed on the back surface of the sensor element, that is, the surface opposite to the surface to which PM adheres. The heater control unit heats the heater by passing a current based on a command from the ECU and burns and removes the PM deposited on the surface of the sensor element. Thereby, the PM sensor is regenerated and returned to the initial state in which no PM adheres.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventors have been diligently pursuing further improvements in this type of sensor, for example, in terms of sensor size, detection sensitivity, detection accuracy, PM removal capability, etc. This invention has been made in view of the circumstances exemplified above. That is, this invention provides, for example, a PM sensor having superior characteristics compared to conventional sensors. [Means for solving the problem]

[0006] The PM sensor (1) described in claim 1 is A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with picture, The removal mechanism is Formed integrally with the vibrator, Plasma or ozone is generated to remove PM attached to the oscillator from the oscillator. . The PM sensor (1) described in claim 2 is A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism is It includes a discharge generating section (52) that generates dielectric barrier discharge, Formed integrally with the vibrator, Plasma or ozone is generated to remove PM attached to the oscillator from the oscillator. The PM sensor (1) described in claim 3 is A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism includes a discharge generating unit (52) that generates dielectric barrier discharge, and generates plasma or ozone to remove PM attached to the oscillator from the oscillator. The discharge generation section includes a high-voltage dielectric layer (523) made of an ALD film. The PM sensor (1) described in claim 4 is A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) is formed integrally with the vibrator and removes PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism includes a discharge generating unit (52) that generates dielectric barrier discharge, and generates plasma or ozone to remove PM attached to the oscillator from the oscillator. The discharge generation section includes a high-voltage dielectric layer (523) made of an ALD film. The PM sensor (1) described in claim 5 is A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism includes a coating layer (319) formed on the vibrator, which is made of a film that reduces adhesion force. The PM sensor (1) described in claim 11 is A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism includes a drive power supply (41) for exciting the vibrator.

[0007] In each column of the application documents, each element may be provided with a reference sign in parentheses. In this case, the reference sign is merely an example showing the correspondence between the same element and the specific configuration described in the embodiments described later. Therefore, the present invention is not limited in any way by the description of the reference signs.

Brief Description of the Drawings

[0008] [Figure 1] It is a diagram showing a schematic configuration of a PM sensor according to a first embodiment of the present invention. [Figure 2] It is a diagram showing a schematic configuration of a PM sensor according to a second embodiment of the present invention. [Figure 3] It is a diagram showing a schematic configuration of a PM sensor according to a third embodiment of the present invention. [Figure 4] It is a diagram showing a schematic configuration of a PM sensor according to a fourth embodiment of the present invention. [Figure 5] It is a side sectional view showing an example of a schematic configuration of the vibrator shown in FIG. 1 and the like. [Figure 6] It is a side sectional view showing another example of a schematic configuration of the vibrator shown in FIG. 1 and the like.

Modes for Carrying Out the Invention

[0009] (Embodiment) Hereinafter, embodiments of the present invention will be described based on the drawings. Note that various modifications applicable to a single embodiment may be impeded in the middle of a series of descriptions relating to that embodiment if they are inserted into the description. Therefore, modifications will not be inserted in the middle of a series of descriptions relating to that embodiment, but will be described collectively afterward. Furthermore, the descriptions in each drawing, and the corresponding descriptions of the device configurations, functions, or operations described below, are simplified for the purpose of concisely explaining the content of the present invention and do not limit the content of the present invention in any way. Therefore, it goes without saying that the exemplary configurations shown in each drawing do not necessarily correspond to the specific configurations actually manufactured and sold. In other words, unless explicitly limited by the applicant in the application history, the present invention should not be interpreted restrictively by the descriptions in each drawing, or the corresponding descriptions of the device configurations, functions, or operations described below.

[0010] (First embodiment: configuration) Referring to Figure 1, the PM sensor 1 according to the first embodiment will be described. The PM sensor 1 according to this embodiment is installed in the flow path 2 of the fluid F, which is conditioned air, and is configured to output an electrical signal (e.g., voltage) corresponding to the PM concentration in the fluid F. Specifically, the PM sensor 1 comprises an oscillator 3, a control unit 4, and a removal mechanism 5.

[0011] The oscillator 3 is configured such that its vibration characteristics, i.e., its resonant frequency, changes due to the adhesion of PM. Specifically, the oscillator 3 has a configuration as a thin plate-shaped or thin film piezoelectric element. The oscillator 3 is formed, for example, in a cantilevered beam shape, a double-sided cantilevered beam shape, or a diaphragm shape. In this embodiment, the oscillator 3 has a configuration as a so-called MEMS transducer. MEMS is an abbreviation for Micro Electro Mechanical Systems. The oscillator 3 has a detection surface 30 to which PM adheres. The detection surface 30 is a surface of the oscillator 3 that faces the flow path 2 and is provided along the flow path 2 of the fluid F containing PM. More specifically, the detection surface 30 is provided parallel to or slightly inclined with respect to the flow direction of the fluid F (i.e., the direction indicated by the dashed arrow in the figure) so that PM contained in the fluid F can adhere to it.

[0012] The control unit 4 is provided to control the operation of the PM sensor 1. Specifically, the control unit 4 comprises a drive power supply 41, a detection circuit 42, and a PM removal power supply 43. The drive power supply 41 is electrically connected to the vibrator 3 to apply drive power to the vibrator 3 for exciting the vibrator 3. The detection circuit 42 is electrically connected to the vibrator 3 to detect changes in the vibration characteristics of the vibrator 3, i.e., the resonant frequency, due to the adhesion of PM to the detection surface 30. The PM removal power supply 43 is electrically connected to the removal mechanism 5 to apply PM removal power to the removal mechanism 5 for driving the removal mechanism 5.

[0013] The removal mechanism 5 is configured to remove PM attached to the oscillator 3, i.e., the detection surface 30, from the oscillator 3. In this embodiment, the removal mechanism 5 includes an ozone generator 51. The ozone generator 51 has a configuration that allows it to generate ozone by a discharge phenomenon such as dielectric barrier discharge. Alternatively, the ozone generator 51 includes, for example, a light-emitting diode light source that emits ultraviolet light of a short wavelength (i.e., a wavelength of 185 nm or less). Thus, the removal mechanism 5 according to this embodiment is configured to generate ozone using the ozone generator 51, and to remove PM attached to the oscillator 3, i.e., the detection surface 30, from the oscillator 3 using the generated ozone.

[0014] (First embodiment: effect) The following describes the operation of this embodiment, along with the effects achieved by this configuration, with reference to the drawings.

[0015] In the PM sensor 1 having the configuration described above, the transducer 3 is excited by the drive power supply 41. The detection circuit 42 continuously detects the vibration state of the transducer 3. When PM adheres to the transducer 3, the vibration characteristics of the transducer 3, i.e., the resonant frequency, change. This change in vibration characteristics makes it possible to detect the presence or absence of PM adhesion to the transducer 3 and the amount of adhesion. Furthermore, by removing the PM attached to the transducer 3 using the removal mechanism 5, the transducer 3 can be initialized to a state from which PM has been removed. This makes the PM sensor 1 reusable.

[0016] The characteristics required for this type of PM sensor 1 include, for example, sensor size, detection sensitivity, detection accuracy, and PM removal capability. In this embodiment, the PM sensor 1 has a configuration as a MEMS sensor and detects the change in mass due to PM adhesion to the oscillator 3 as a change in vibration characteristics. Therefore, with this configuration, it is possible to simultaneously achieve miniaturization of the sensor and improvement of detection sensitivity. In particular, by adopting a MEMS structure, it is possible to detect trace amounts of PM0.1 in air-conditioned air with high sensitivity. Furthermore, the PM sensor 1 removes PM attached to the oscillator 3 with ozone generated by the removal mechanism 5. Specifically, by supplying ozone from the removal mechanism 5 to the oscillator 3, i.e., the detection surface 30, to which PM has adhered, the PM is effectively removed from the oscillator 3 by sublimation, i.e., combustion, due to active oxygen. In particular, extremely small carbon particles corresponding to PM0.1, which were difficult to remove with conventional heater heating due to their large adhesion force (i.e., van der Waals force, etc.), can be effectively removed. Therefore, with this configuration, the initialization of the PM sensor 1 can be performed stably, thereby improving the detection accuracy of the PM sensor 1 compared to conventional methods.

[0017] (Second embodiment) The second embodiment will be described below with reference to Figure 2. The following description of the second embodiment will primarily focus on the differences from the first embodiment. Parts that are identical or equivalent in the first and second embodiments are denoted by the same reference numerals. Therefore, in the following description of the second embodiment, the explanation in the first embodiment can be appropriately applied to components having the same reference numerals as those in the first embodiment, unless there is a technical inconsistency or additional explanation required. The same applies to the third embodiment and others described later.

[0018] In this embodiment, the removal mechanism 5 is configured to generate plasma to remove PM attached to the oscillator 3. Specifically, the removal mechanism 5 includes a discharge generation unit 52 that generates dielectric barrier discharge. With this configuration, the same effects as in the first embodiment can be achieved. Specifically, the PM sensor 1 according to this embodiment removes PM attached to the oscillator 3 using plasma generated by the removal mechanism 5. Specifically, by supplying plasma from the removal mechanism 5 to the oscillator 3 to which PM is attached, the PM is effectively removed from the oscillator 3 by sublimation, i.e., combustion, by active oxygen. In particular, extremely small carbon particles corresponding to PM0.1 can be effectively removed. Therefore, with this configuration, the initialization of the PM sensor 1 can be performed stably, and thereby the detection accuracy of the PM sensor 1 can be improved compared to conventional methods.

[0019] (Third embodiment) The third embodiment will now be described with reference to Figure 3. In this embodiment, the removal mechanism 5 is realized by providing the detection surface 30 along the fluid flow path 2 of the fluid F. Specifically, the detection surface 30 is provided substantially parallel to the flow direction of the fluid F so that any PM that has adhered can be removed by the flow velocity of the fluid F. In this configuration, for example, by temporarily flowing the fluid F at a flow velocity higher than the normal flow velocity for PM removal, it is possible to remove PM from the oscillator 3, i.e., the detection surface 30. This embodiment can be applied in combination with other embodiments such as the first and second embodiments described above. That is, for example, by combining removal by the flow velocity of the fluid F with removal by plasma or ozone, the removal of PM from the oscillator 3 can be performed more reliably.

[0020] (Fourth embodiment) The fourth embodiment will now be described with reference to Figure 4. In this embodiment, the removal mechanism 5 is realized by providing the detection surface 30 along the vertical direction. With this configuration, PM adhering to the detection surface 30 can be effectively removed from the detection surface 30, i.e., the oscillator 3, by falling from the detection surface 30 due to its own weight caused by gravity. This embodiment can be applied in combination with other embodiments such as the first to third embodiments described above. That is, for example, by combining the removal of PM by its own weight with the removal by the flow velocity of the fluid F, the removal of PM from the detection surface 30 can be made more reliable. Also, for example, by combining the removal of PM by its own weight with the removal by plasma or ozone, the removal of PM from the oscillator 3 can be made more reliable.

[0021] (Fifth embodiment) The fifth embodiment will now be described with reference to Figures 1 to 4. In this embodiment, the removal mechanism 5 is configured to remove PM attached to the transducer 3, i.e., the detection surface 30, by forcibly exciting the transducer 3. Specifically, in this embodiment, the removal mechanism 5 is equipped with a drive power supply 41 for exciting the transducer 3. The drive power supply 41 selectively outputs a first drive power of a first frequency for PM detection and a second drive power of a second frequency for PM removal. The first frequency is the frequency corresponding to the resonance frequency of the transducer 3 when no PM is attached. The second frequency is the frequency corresponding to the resonance frequency of the transducer 3 when a predetermined amount of PM is attached. With this configuration, by utilizing the vibration energy of the transducer 3, the removal of PM from the transducer 3 can be performed more reliably. Furthermore, by utilizing MEMS resonance, it is possible to remove PM with low energy. Note that this embodiment can be applied in combination with other embodiments such as the first to fourth embodiments described above. In other words, for example, by combining removal by forced excitation of the oscillator 3 with removal by the flow velocity of the fluid F, the removal of PM from the oscillator 3 can be performed more reliably. Also, for example, by combining removal by forced excitation of the oscillator 3 with removal by the PM's own weight, the removal of PM from the oscillator 3 can be performed more reliably. Also, for example, by combining removal by forced excitation of the oscillator 3 with removal by plasma or ozone, the removal of PM from the oscillator 3 can be performed more reliably.

[0022] (Sixth Embodiment) The sixth embodiment will now be described with reference to Figures 1 to 4. In this embodiment, the removal mechanism 5 is realized by making the detection surface 30 the surface of a film that reduces adhesion. Suitable films for this purpose include, for example, water-repellent films such as SAM films and graphene films. SAM is an abbreviation for self-assembled monolayer film. Furthermore, a water-repellent surface can be realized by making the detection surface 30 a fine uneven structure supported by nanoparticles (e.g., silica particles). According to the configuration of this embodiment, adhesion due to van der Waals forces and liquid crosslinking forces caused by moisture in the air is effectively reduced. In addition, by using a two-dimensional multilayer thin film such as a graphene film, PM can be detached and removed together with the film. Therefore, with this configuration, the removal of PM from the detection surface 30, i.e., the oscillator 3, can be performed more reliably. Note that this embodiment can be applied in combination with other embodiments such as the first to fifth embodiments described above.

[0023] (First example) The following describes one embodiment of the oscillator 3 having a MEMS structure, i.e., a specific configuration example, with reference to Figure 5. The oscillator 3 shown in Figure 5 can be used in the first to sixth embodiments described above. Note that Figure 5 is a schematic diagram for the purpose of simply explaining an example of the MEMS structure in the oscillator 3, and the specific dimensions and other details do not necessarily match those of the actual product. Also, for the sake of explanation, the right-handed XYZ coordinate system is set as shown in Figure 5. The same applies to Figure 6.

[0024] In this embodiment, the oscillator 3 has an SOI structure in which each layer is stacked in the Z-axis direction in the figure. SOI is an abbreviation for Silicon on Insulator. Specifically, the oscillator 3 has a diaphragm 311 with a thickness direction in the Z-axis direction in the figure. The diaphragm 311 is provided by reusing the p-type silicon layer, which is the functional layer, or SOI layer, in a so-called SOI wafer. Furthermore, the diaphragm 311 is ion-doped to impart conductivity so that it also serves as the ground electrode in the piezoelectric element.

[0025] The diaphragm 311 has a vibrating portion 311a and a non-vibrating portion 311b. The vibrating portion 311a has a diaphragm configuration in which the central part in the in-plane direction (i.e., the direction parallel to the XY plane in the figure) that is perpendicular to the thickness direction (i.e., the Z-axis direction in the figure) moves along the thickness direction. The non-vibrating portion 311b is the portion surrounding the outer edge of the vibrating portion 311a in the diaphragm 311, and is fixedly supported by a support portion 312. The support portion 312 is a silicon support substrate and has a cavity portion 312a that penetrates in the thickness direction. The cavity portion 312a is provided at a position corresponding to the vibrating portion 311a in the in-plane direction. The shape of the cavity portion 312a, i.e., the vibrating portion 311a, in the in-plane direction is formed to be circular, elliptical, or polygonal. The support portion 312 is joined to the diaphragm 311 via a bonding layer 313, which is an embedded oxide film layer. Thus, the vibrating portion 311a is the vibrable part of the diaphragm 311 that is not joined to the support portion 312 and the bonding layer 313, and is supported by the support portion 312 and the bonding layer 313 so as to be able to flex and deform. On the other hand, the non-vibrating portion 311b is the part of the diaphragm 311 that is joined to the support portion 312 and the bonding layer 313. The boundary between the vibrating portion 311a and the non-vibrating portion 311b of the diaphragm 311 is configured to constitute a fixed end in flexural vibration.

[0026] A piezoelectric layer 314 is bonded to the upper surface of the diaphragm 311, that is, the surface opposite to the lower surface bonded to the bonding layer 313. The piezoelectric layer 314 is formed from a piezoelectric material such as ScAlN, in a layered or film-like manner with the Z-axis direction in the figure as the thickness direction. The piezoelectric layer 314 is provided along the in-plane direction from the non-vibrating portion 311b to the vibrating portion 311a. Specifically, the piezoelectric layer 314 is formed in a tongue-like shape extending in the negative X-axis direction in the figure.

[0027] A drive electrode layer 315 is bonded to the upper surface of the piezoelectric layer 314, that is, the surface opposite to the lower surface bonded to the diaphragm 311. The drive electrode layer 315 is formed of a conductive thin film (e.g., a metal thin film) and is provided along the in-plane direction. Specifically, the drive electrode layer 315 is formed in the shape of a tongue extending in the negative X-axis direction in the figure. In this way, the piezoelectric element is constructed by a bonded body in which the piezoelectric layer 314 is sandwiched between the diaphragm 311 and the drive electrode layer 315. One end of the drive electrode layer 315 in the in-plane direction (i.e., the end on the positive X-axis side in the figure), which corresponds to the non-vibrating portion 311b, is covered with an insulating layer 316. The insulating layer 316 is formed of an oxide film similar to that of the bonding layer 313. The insulating layer 316 is provided with a through hole 316a that penetrates in the thickness direction. A contact portion 317 made of a conductive thin film (e.g., a metal thin film) is arranged inside the through hole 316a. The contact portion 317 is provided to electrically connect the drive electrode layer 315 and the power supply portion 318. The power supply portion 318, which is made of a conductive thin film (for example, a metal thin film), is the end of the wiring portion for supplying power to the drive electrode layer 315 and is formed on the insulating layer 316.

[0028] A coating layer 319 is formed on the transducer 3. The coating layer 319, which constitutes the detection surface 30, is the outermost layer on the transducer 3, i.e., it is located furthest towards the positive Z-axis direction in the figure. That is, the coating layer 319 is provided as a protective layer or protective film that covers the diaphragm 311, piezoelectric layer 314, drive electrode layer 315, insulating layer 316, and power supply unit 318. Specifically, the coating layer 319 can be formed from, for example, a synthetic resin material such as a resist, or a dense inorganic thin film such as a nitride film. Here, the coating layer 319 can be provided as a film that reduces the adhesion force of PM, as described in the sixth embodiment. That is, the coating layer 319 can be formed from, for example, a water-repellent film such as a SAM film or a graphene film.

[0029] (Second embodiment) The following describes another embodiment of the oscillator 3 having a MEMS structure, with reference to Figure 6. This embodiment is a configuration in which the oscillator 3 and the discharge generation unit 52 constituting the removal mechanism 5 are integrally formed as a MEMS element. In the following description of the second embodiment, the differences from the first embodiment will be mainly described. Also, parts that are the same or equivalent in the first and second embodiments are denoted by the same reference numerals. Therefore, in the following description of the second embodiment, with respect to components that have the same reference numerals as in the first embodiment, the description in the first embodiment can be appropriately applied unless there is a technical inconsistency or additional explanation is required.

[0030] In this embodiment, the piezoelectric layer 314 is provided over the entire vibrating portion 311a and is formed in a larger in-plane shape than the vibrating portion 311a. That is, the vibrating portion 311a is located inside the piezoelectric layer 314 in the in-plane direction. The portion of the piezoelectric layer 314 that is outside the vibrating portion 311a is joined to the non-vibrating portion 311b. The piezoelectric layer 314 and the outer portion of the non-vibrating portion 311b that is not joined to the piezoelectric layer 314 are covered by an insulating layer 316. A first drive electrode 325a and a second drive electrode 325b are formed on the insulating layer 316. The first drive electrode 325a is the ground-side electrode in the piezoelectric element and is positioned corresponding to the non-vibrating portion 311b. The first drive electrode 325a is provided so as to overlap one end of the piezoelectric layer 314 in the in-plane direction (i.e., the end on the negative X-axis side in the figure). The second drive electrode 325b is located on the other side in the in-plane direction (i.e., the positive X-axis direction in the figure) of the first drive electrode 325a, and is spaced apart from the first drive electrode 325a. The first drive electrode 325a and the second drive electrode 325b, which are made of a conductive thin film (e.g., a metal thin film), are electrically connected to the drive power supply 41 and the detection circuit 42.

[0031] The discharge generation unit 52 comprises a base insulating layer 521, a first discharge electrode 522, a high-voltage dielectric layer 523, and a second discharge electrode 524. The base insulating layer 521 is formed of an oxide film similar to that of the bonding layer 313. The base insulating layer 521 is provided to cover the portion of the second drive electrode 325b other than the contact portion for electrical connection with the drive power supply 41 and the detection circuit 42. The first discharge electrode 522 is a ground-side electrode and is formed of a conductive thin film (e.g., a metal thin film). The first discharge electrode 522 is provided on the base insulating layer 521. The first discharge electrode 522 is electrically connected to the PM removal power supply 43. The high-voltage dielectric layer 523 is composed of an ALD film. ALD is an abbreviation for Atomic Layer Deposition. Specifically, the high-voltage dielectric layer 523 has a multilayer laminated film structure of TiO2 and Al2O3. The high-voltage dielectric layer 523 is provided to cover the portion of the first discharge electrode 522 other than the contact portion for electrical connection with the PM removal power supply 43. The second discharge electrode 524 is formed by a conductive thin film (e.g., a metal thin film) so that its in-plane shape is comb-like. The second discharge electrode 524 is electrically connected to the PM removal power supply 43.

[0032] In this configuration, the vibrator 3, or vibrating part 311a, is excited by applying an AC voltage between the first drive electrode 325a and the second drive electrode 325b using the drive power supply 41. Furthermore, by detecting the vibration characteristics of the vibrating part 311a, i.e., the change in the resonant frequency, using the detection circuit 42, it becomes possible to detect the presence or absence and amount of PM adhesion to the vibrator 3, or detection surface 30. In addition, when removing PM from the vibrator 3, or detection surface 30, a PM removal voltage is applied between the first discharge electrode 522 and the second discharge electrode 524 to generate a dielectric barrier discharge. The generated plasma then removes PM from the vibrator 3. With this configuration, the size of the sensor can be reduced by integrally forming the vibrator 3 and the discharge generation part 52 that constitutes the removal mechanism 5 as a MEMS element.

[0033] (modified version) The present invention is not limited to the embodiments described above. Therefore, the embodiments can be modified as appropriate. Representative modifications are described below. In the following description of modifications, the differences from the embodiments will be mainly described. In addition, parts that are the same or equivalent to each other in the embodiments and modifications are denoted by the same reference numerals. Therefore, in the following description of modifications, with respect to components that have the same reference numerals as in the embodiments, the descriptions in the embodiments can be appropriately applied unless there is a technical inconsistency or additional explanation is required.

[0034] The present invention is not limited to the specific device configurations described in the above embodiments. That is, as stated above, the descriptions of the above embodiments have been simplified in order to briefly explain the content of the present invention. For this reason, components that are usually provided in products actually manufactured and sold, such as casings, joining materials, terminals, and wiring, are appropriately omitted from the illustrations and descriptions in the above embodiments and corresponding drawings.

[0035] The PM sensor 1 according to the present invention is not limited to applications for detecting PM in air-conditioned air. That is, for example, the PM sensor 1 according to the present invention can also be suitably applied to applications for detecting PM in exhaust gas.

[0036] The oscillator 3 and the ozone generator 51, which constitutes the removal mechanism 5, may be formed as a single MEMS element.

[0037] Ozone may be generated by dielectric barrier discharge in the discharge generation unit 52. Therefore, the discharge generation unit 52 may also function as an ozone generator 51. In other words, the removal mechanism 5 may be configured to generate plasma and / or ozone to remove PM attached to the oscillator 3 from the oscillator 3.

[0038] The specific configuration examples of the oscillator 3 shown in Figures 5 and 6 are schematic for the sake of explanation, and the specific configuration in the actual product may be modified as appropriate from the examples in Figures 5 and 6. For example, intermediate layers may be provided at the junctions of each layer as appropriate. Also, if the oscillator 3 is provided with a conductive thin film (e.g., a metal thin film) that constitutes the ground electrode of the piezoelectric element, the diaphragm 311 does not need to be ion-doped.

[0039] In the above description, multiple components that were formed as a single, seamless unit may be formed by bonding together separate components. Similarly, multiple components that were formed by bonding together separate components may be formed as a single, seamless unit. Furthermore, in the above description, multiple components that were formed from the same material may be formed from different materials. Similarly, multiple components that were formed from different materials may be formed from the same material.

[0040] It goes without saying that the elements constituting the above embodiments are not necessarily essential unless explicitly stated to be particularly essential or considered to be fundamentally essential. Furthermore, when numerical values ​​such as the number of components, numerical values, quantities, or ranges are mentioned, the present invention is not limited to those specific numbers unless explicitly stated to be particularly essential or considered to be fundamentally limited to those specific numbers. Similarly, when the shape, direction, positional relationship, etc., of components are mentioned, the present invention is not limited to those shapes, directions, positional relationships, etc., unless explicitly stated to be particularly essential or considered to be fundamentally limited to those specific shapes, directions, positional relationships, etc.

[0041] The variations are not limited to the examples given above. That is, for example, multiple embodiments may be applied in combination. In other words, a part of one embodiment may be combined with a part of another embodiment. There are no particular limitations on the number or manner in which multiple embodiments are combined. Furthermore, any one of the multiple embodiments and any one of the multiple variations may be combined with each other, as long as it is not technically contradictory. Similarly, one of the multiple variations and another may be combined with each other, as long as it is not technically contradictory.

[0042] (Disclosure details) As is evident from the above description of embodiments and modifications, this specification discloses at least the following: <Perspective 1> PM sensor (1) is, A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, It is equipped with. <Perspective 2> From perspective 1, The removal mechanism generates plasma or ozone to remove PM attached to the oscillator from the oscillator. <perspective 3> From perspective 2, The removal mechanism includes a light-emitting diode light source (51) that emits ultraviolet light with a wavelength of 185 nm or less. <Perspective 4> From perspective 2, The removal mechanism includes a discharge generating unit (52) that generates dielectric barrier discharge. <Perspective 5> From perspectives 2 and 4, The removal mechanism is formed integrally with the vibrator. <Perspective 6> From perspectives 4 and 5, The discharge generation section includes a high-voltage dielectric layer (523) made of an ALD film. <Perspective 7> In perspectives 1-6, The removal mechanism includes a coating layer (319) formed on the vibrator, which is made of a film that reduces adhesion force. <Perspective 8> In perspectives 1-7, The vibrator has a detection surface (30) to which PM adheres, The detection surface is provided along the flow path (2) of the fluid (F) containing PM. <Perspective 9> In perspectives 1-8, The vibrator has a detection surface (30) to which PM adheres, The detection surface is provided along the vertical direction. <Perspective 10> In perspectives 1-9, The removal mechanism includes a drive power supply (41) for exciting the vibrator. <Perspective 11> From perspective 10, The aforementioned drive power supply selectively outputs a first drive power at a first frequency for PM detection and a second drive power at a second frequency for PM removal. [Explanation of Symbols]

[0043] 1 PM sensor 2 Flow Channels 3. Oscillator 30 detection surface 319 Covering layer 41 Power supply 5 Removal mechanism 51 Ozone Generator 52 Discharge generation section 523 High-voltage dielectric layer

Claims

1. PM sensor (1), A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism is Formed integrally with the vibrator, Plasma or ozone is generated to remove PM attached to the oscillator from the oscillator. PM sensor.

2. PM sensor (1), A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism is It includes a discharge generating section (52) that generates dielectric barrier discharge, Formed integrally with the vibrator, Plasma or ozone is generated to remove PM attached to the oscillator from the oscillator. PM sensor.

3. PM sensor (1), A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism includes a discharge generating unit (52) that generates dielectric barrier discharge, and generates plasma or ozone to remove PM attached to the oscillator from the oscillator. The discharge generation section includes a high-voltage dielectric layer (523) made of an ALD film. PM sensor.

4. PM sensor (1), A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) is formed integrally with the vibrator and removes PM adhering to the vibrator from the vibrator, Equipped with, The removal mechanism includes a discharge generating unit (52) that generates dielectric barrier discharge, and generates plasma or ozone to remove PM attached to the oscillator from the oscillator. The discharge generation section includes a high-voltage dielectric layer (523) made of an ALD film. PM sensor.

5. PM sensor (1), A vibrator (3) whose vibration characteristics change due to PM adhesion, A removal mechanism (5) for removing PM attached to the vibrator from the vibrator, Equipped with, The removal mechanism includes a coating layer (319) formed on the vibrator, which is made of a film that reduces adhesion force. PM sensor.

6. The removal mechanism includes a light-emitting diode light source (51) that emits ultraviolet light with a wavelength of 185 nm or less. The PM sensor according to claim 5.

7. The vibrator has a detection surface (30) to which PM adheres, The detection surface is provided along the flow path (2) of the fluid (F) containing PM, The PM sensor according to any one of claims 1 to 6.

8. The vibrator has a detection surface (30) to which PM adheres, The detection surface is provided along the vertical direction, The PM sensor according to any one of claims 1 to 6.

9. The removal mechanism includes a drive power supply (41) for exciting the vibrator. The PM sensor according to any one of claims 1 to 6.

10. The aforementioned drive power supply selectively outputs a first drive power of a first frequency for PM detection and a second drive power of a second frequency for PM removal. The PM sensor according to claim 9.

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