JP2007104318A - Ultrasonic sensor, its manufacturing method, and its optimal design device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic sensor which can ease stress generated in each component and a component interface at manufacturing time without limiting material of the structure and the composing component. <P>SOLUTION: The sensor is provided with a piezoelectric element 2; a cushion component 7 which covers at least a part of a sound matching layer 1 which is joined and formed with the piezoelectric element 2 and the piezoelectric element 2, and functions to make stress generated according to thermal expansion difference of the piezoelectric element 2 and a component adjoining the piezoelectric element 2 ease; sealing components 3, 4 for sealing the piezoelectric element 2; a reinforcement component 8 which contacts with at least a part of the sealing components 3, 4, and functions to reinforce the piezoelectric element 2; and a case 5 which covers the reinforcement component 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic sensor using a piezoelectric element, a manufacturing method thereof, and an optimum design apparatus thereof, and more particularly to a technique for improving accuracy and reliability.

  Conventionally, an ultrasonic sensor applied to a flow meter that measures the flow rate of a fluid is known. For example, this ultrasonic sensor measures the propagation time of an ultrasonic wave propagating between two ultrasonic sensors (ultrasonic transducers) disposed diagonally opposite to the direction of fluid flow. The flow rate is obtained, and high accuracy of the order of ns (nanosecond) is required. Further, since the service life of the flowmeter is about 10 years, long-term reliability of the ultrasonic sensor is required.

  However, the accuracy and reliability of the ultrasonic sensor are reduced due to internal residual stress and deformation caused by the difference in thermal expansion of each component during manufacture.

  For this reason, the piezoelectric element and the case constituting the ultrasonic sensor are softer and more flexible than the piezoelectric element and the case, and are bonded with an adhesive whose curing strain is a predetermined value or less, and this adhesive is used as a buffer material. An ultrasonic sensor that reduces a thermal expansion difference between a piezoelectric element and a case is disclosed (Patent Document 1).

Also, different characteristics between the acoustic matching layer and the case and between the case and the piezoelectric element (hardness, thermal expansion coefficient, reaction to organic solvents, water absorption, thermal degradation, reaction to sulfur compounds, etc. An ultrasonic sensor having a structure in which connection deterioration between a plurality of components is prevented by using an adhesive) is disclosed (Patent Document 2).
JP 2003-270013 A JP 2004-48241 A

  However, the above-described conventional ultrasonic sensor relieves stress generated due to the difference in thermal expansion of the component interface by an adhesive that bonds the piezoelectric element and the case and between the case and the piezoelectric element. That is, it has been studied on the basis of a specific sensor structure and component material, and applicable sensor structures and component materials are limited. For this reason, it is difficult to obtain sufficient accuracy and reliability if the materials of the sensor structure and component parts are different.

  In addition, since the design for improving the structure of the conventional ultrasonic sensor has been performed by repeated trials based on experience, it is difficult to easily obtain an optimum structure. Therefore, a design device corresponding to diversifying sensor structures and material of components is necessary, but such a design device does not exist.

  An object of the present invention is to provide an ultrasonic sensor, a manufacturing method thereof, and an optimal design apparatus thereof that can relieve stress generated at each component part and part interface at the time of manufacture without limiting the material of the structure and the component parts. is there.

  The present invention employs the following means in order to solve the above problems. According to a first aspect of the present invention, there is provided a piezoelectric element, an acoustic matching layer formed by bonding to the piezoelectric element, and at least a part of the piezoelectric element, and heat generated between the piezoelectric element and a member adjacent to the piezoelectric element. A buffer member for relieving stress generated due to an expansion difference, a sealing member for sealing the piezoelectric element, and a reinforcing member for contacting the at least part of the sealing member and reinforcing the piezoelectric element And a case for covering the reinforcing member.

  According to a second aspect of the present invention, in the ultrasonic sensor according to the first aspect, the buffer member is made of a polymer material that is softer than the acoustic matching layer, the piezoelectric element, or the reinforcing member.

  According to a third aspect of the present invention, in the ultrasonic sensor according to the second aspect, the buffer member is made of silicon resin.

  According to a fourth aspect of the present invention, in the ultrasonic sensor according to any one of the first to third aspects, the buffer member has a thickness of 10 to 100 μm.

  According to a fifth aspect of the invention, in the ultrasonic sensor according to any one of the first to fourth aspects, the buffer member has a longitudinal elastic modulus of 0.001 to 0.01 GPa.

  The invention of claim 6 is the ultrasonic sensor according to claim 1, wherein the reinforcing member is made of a polymer material harder than the sealing member or the case.

  The invention according to claim 7 is the ultrasonic sensor according to claim 1, wherein the reinforcing member is made of a metal material harder than the sealing member or the case.

  According to an eighth aspect of the present invention, there is provided a step of forming a buffer member for relaxing stress generated by a difference in thermal expansion between a piezoelectric element and a member adjacent to the piezoelectric element so as to cover at least a part of the piezoelectric element. Attaching the piezoelectric element to a reinforcing member for reinforcing the piezoelectric element; forming an acoustic matching layer by bonding the piezoelectric element; and a sealing member for sealing the piezoelectric element It has the process of forming so that it may contact | connect at least one part of a reinforcement material, and the process of attaching a case so that the said reinforcement member may be covered, It is characterized by the above-mentioned.

  According to the ninth aspect of the present invention, an ultrasonic sensor including a piezoelectric element and an acoustic matching layer is optimized and optimized so as to relieve stress generated due to a difference in thermal expansion between the piezoelectric element and a member adjacent to the piezoelectric element. The design device, the sensor structure data of the ultrasonic sensor, the material property data and manufacturing condition data of each component constituting the ultrasonic sensor, the constraint condition indicating the constraint condition when optimizing the ultrasonic sensor Input means for inputting data and required value data indicating an allowable range of stress required for the ultrasonic sensor, the sensor structure data, the material property data, the manufacturing condition data, and the stress inputted by the input means Storage means for storing the first relation data indicating the relation of the sensor, the sensor structure data input by the input means, the material property data, and the manufacturing conditions When the stress is obtained based on the data and the first relation data stored in the storage means and the stress does not satisfy the required value data, the stress is within the range of the constraint condition given by the constraint condition data. And based on the first relation data, the sensor structure data, the material property data, and the manufacturing condition data are changed, and the sensor structure data, the material property data, and so on, so that the stress satisfies the required value data. An optimization unit that optimizes the manufacturing condition data, and an output unit that outputs a result optimized by the optimization unit.

  According to a tenth aspect of the present invention, in the optimum design apparatus according to the ninth aspect, the storage means stores the first relation data and a member adjacent to the piezoelectric element in order to relieve the stress. Second relational data indicating the relationship between the stress, the material, shape, dimensions, and position of the cushioning member inserted into the interface of the sensor, and the optimization means is the sensor structure data input by the input means, The stress is obtained based on the material property data, the manufacturing condition data, and the first relation data stored in the storage means, and the stress does not satisfy the required value data and as the constraint condition data When the data indicating that the buffer member can be inserted into the interface between the piezoelectric element and a member adjacent to the piezoelectric element is input by the input means, the constraint condition data The buffer member is changed so that the stress satisfies the required value data by changing the material, shape, dimension, and position of the buffer member based on the second relational data within the range of the constraint condition given more. It is characterized by optimization.

  According to an eleventh aspect of the present invention, in the optimum design apparatus according to the ninth aspect, the sensor structure data of the ultrasonic sensor includes data indicating a shape, a dimension, and a position of each component.

  The invention of claim 12 is the optimum design apparatus according to claim 9, wherein the material property data of each component is material data indicating chemical composition, mass density, hardness, solvent resistance, flexibility, fluidity, Mechanical property data indicating longitudinal elastic modulus, Poisson's ratio, tensile strength, toughness, linear expansion coefficient, thermal conductivity, heat transfer coefficient, specific heat, Curie temperature, glass transition temperature, thermal property data indicating thermal decomposition temperature, Electrical characteristic data indicating conductivity, capacitance, relative dielectric constant, piezoelectric strain constant, piezoelectric stress constant, electromechanical coupling constant, piezoelectric characteristic data indicating acoustic impedance, and processing when components are processed in advance It is characterized by having residual stress and residual strain data.

  According to a thirteenth aspect of the present invention, in the optimum design apparatus according to the ninth aspect, the manufacturing condition data includes a restraint load when joining the component parts, a pressurization condition data indicating a restraint displacement, and a heating time during manufacturing. It has at least one of temperature condition data indicating a temperature before heating, a heating rate, a heating temperature, a heating holding time, a cooling rate, and a temperature after cooling.

  According to a fourteenth aspect of the present invention, in the optimum design apparatus according to the ninth aspect, the constraint data includes data indicating a constraint or tolerance of an applied material of each component, the entire ultrasonic sensor, and the shape of each component. -It has at least one of the data which shows the restrictions or tolerance of a dimension and a position, and the data which shows the restrictions or tolerance of manufacturing conditions.

  According to a fifteenth aspect of the present invention, in the optimum design apparatus according to the ninth aspect, the required value data is an allowable maximum stress generated in at least one of the entire ultrasonic sensor, the component parts, and the interface of the component parts. And data indicating the allowable minimum stress.

  The invention of claim 16 is the optimum design apparatus according to claim 9, wherein the relational data stored in the storage means is obtained by at least one of testing, inspection, observation, and analysis. To do.

  According to a seventeenth aspect of the present invention, in the optimum design apparatus according to the ninth aspect, the optimization means satisfies the constraint condition data or the required value data without changing a component included in the ultrasonic sensor. If this is not possible, a part not included in the ultrasonic sensor is added or a part included in the ultrasonic sensor is deleted.

  According to an eighteenth aspect of the present invention, in the optimum design apparatus according to the ninth aspect, the optimized result output from the output means includes sensor structure data of the ultrasonic sensor, material property data of each component, It includes at least one of manufacturing condition data.

  According to a nineteenth aspect of the present invention, in the optimum design apparatus according to the ninth aspect, the optimized result output from the output means includes at least one of a stress distribution, a strain distribution or a deformation distribution of the ultrasonic sensor. It is characterized by that.

  According to the ultrasonic sensor of the present invention, the stress generated by the difference in thermal expansion between the piezoelectric element and the member adjacent to the piezoelectric element is reduced by covering at least a part of the piezoelectric element with the buffer member. In addition, the material of the component parts is not limited, and stress generated at each component part and the part interface at the time of manufacture can be relaxed.

  Moreover, since at least a part of the sealing member for sealing the piezoelectric element is covered with the reinforcing member and the piezoelectric element is reinforced, the stress generated in the piezoelectric element is further reduced, deformation is suppressed, and accuracy and reliability are improved. Can be improved.

  Further, according to the optimum design apparatus of the present invention, the sensor structure data of the ultrasonic sensor before optimization, the material property data of each component, the manufacturing condition data, the constraint condition data, and the required value data are input by the input means, The optimization means obtains stress based on the sensor structure data, material characteristic data, manufacturing condition data, and first relation data constructed in the storage means, and if the stress does not satisfy the required value data, The sensor structure data, the material property data is changed so that the stress satisfies the required value data by changing the sensor structure data, the material property data, and the manufacturing condition data within the range of the given constraints and based on the first relation data. In addition, the manufacturing condition data is optimized, so that the sensor structure and the material of the component are not limited. There can easily be performed to optimize the design of the ultrasonic sensor is relaxed.

  Hereinafter, an ultrasonic sensor, a manufacturing method thereof, and an optimal design apparatus thereof according to embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a sectional view of an ultrasonic sensor according to Embodiment 1 of the present invention. As shown in FIG. 1, the ultrasonic sensor according to the first embodiment of the present invention includes an acoustic matching layer 1, a piezoelectric element 2, a silicon resin 3, an epoxy resin 4, a case 5, an adhesive 6, a buffer material 7, and a reinforcing material. 8 is configured.

  The piezoelectric element 2 has an upper surface (ultrasonic wave transmission / reception surface 2 a) bonded to the acoustic matching layer 1 with an adhesive 6 and is covered with the acoustic matching layer 1. A buffer material 7 is formed on part of the side surface and the lower surface of the piezoelectric element 2 to relieve stress generated by a difference in thermal expansion between the piezoelectric element 2 and a component adjacent to the piezoelectric element 2. The side surface 2, the acoustic matching layer 1, a part of the lower surface of the piezoelectric element 2, and the reinforcing material 8 are joined together via a buffer material 7. Further, the piezoelectric element 2 and the acoustic matching layer 1 may be joined by applying pressure without using the adhesive 6.

  The buffer material 7 may be any material that is softer than the softest component of the acoustic matching layer 1, the piezoelectric element 2, and the reinforcing material 8. By covering at least a part of the piezoelectric element 2, the ultrasonic sensor Although the stress which generate | occur | produces in each component and component interface which comprise is relieve | moderated, it is preferable that thickness is 10-100 micrometers and a longitudinal elastic modulus is 0.001-0.01 GPa. The buffer material 7 is made of, for example, a silicon resin (longitudinal elastic modulus: 0.0025 GPa) having a thickness of 80 μm. Further, the buffer material 7 may be made of the same material as the adhesive 6 for bonding the piezoelectric element 2 and the acoustic matching layer 1.

  FIG. 2 is a diagram showing the relationship between the thickness of the buffer material 7 and the stress generated in the piezoelectric element 2 and the case 5. As shown in FIG. 2, it can be seen that the stress generated in the piezoelectric element 2 and the case 5 decreases as the thickness of the buffer material 7 increases. Therefore, the stress generated in the piezoelectric element 2 is reduced by covering at least a part of the piezoelectric element 2 with the buffer material 7.

  For example, as shown in FIG. 1, the reinforcing material 8 is a hollow member having a side wall with an upper portion protruding inward, and the upper surface 8 a of the reinforcing material 8 is joined to the acoustic matching layer 1 and through the buffer material 7. Bonded to the piezoelectric element 2. The reinforcing material 8 is made of, for example, a metal material such as glass fiber reinforced plastic having a thickness of 10 mm or stainless steel. The reinforcing material 8 may be any material that is harder than the epoxy resin 4 or the case 5 and is not limited in shape or size.

  The silicon resin 3 is formed so as to be in contact with the lower surface 2 b of the piezoelectric element 2 and the inner side surface 8 b of the reinforcing material 8, and the epoxy resin 4 is formed so as to be in contact with the silicon resin 3 and the inner side surface 8 c of the reinforcing material 8. . The epoxy resin 4 and the silicon resin 3 are potting materials (sealing materials) for sealing the piezoelectric elements 2. The case 5 covers the outer surface 8d of the reinforcing material 8, and the reinforcing material 8 is provided between the case 5 and the potting material (silicon resin 3 and epoxy resin 4).

  In the ultrasonic sensor, the piezoelectric element 2 is reinforced by covering at least a part of the potting material with the reinforcing material 8, and the stress generated in the piezoelectric element 2 is dispersed in the reinforcing material 8 and generated in the piezoelectric element 2. Stress to be reduced, and deformation of the entire sensor is suppressed.

  FIG. 3 is a diagram showing the relationship between the thickness of the reinforcing material 8 and the degree of deformation of the sensor (maximum displacement of the entire sensor). As shown in FIG. 3, it can be seen that as the thickness of the reinforcing material 8 increases, the stress generated at the component interface decreases, and the degree of deformation of the entire sensor decreases. It has also been confirmed that the stress generated at the component interface decreases as the rigidity of the reinforcing material 8 increases. Therefore, the stress generated in the piezoelectric element 2 is reduced by covering at least a part of the potting material with the reinforcing material 8.

  Next, the manufacturing method of the ultrasonic sensor which concerns on Example 1 of this invention is shown. FIG. 4 is a process diagram illustrating an example of a method for manufacturing the ultrasonic sensor according to the first embodiment. As shown in FIG. 4, first, the buffer material 7 is coated on the piezoelectric element 2 (FIG. 4A). Next, the piezoelectric element 2 coated with the buffer material 7 is attached to the reinforcing material 8 (FIG. 4B). Next, the silicon resin 3 is filled so as to be in contact with the inner surface 8b of the reinforcing material 8 and the lower surface 2b of the piezoelectric element 2 (FIG. 4C). Next, the acoustic matching layer 1 is attached so as to cover the piezoelectric element 2 and the buffer material 7 (FIG. 4D). At this time, the acoustic matching layer 1 and the ultrasonic transmission / reception surface 2 a of the piezoelectric element 2 are joined by the adhesive 6. Next, the epoxy resin 4 is filled and heated so as to be in contact with the inner side surface 8c of the reinforcing material 8 and the silicon resin 3, and the epoxy resin 4 is cured by cooling after the heating (FIG. 4E). Next, the case 5 is attached (FIG. 4 (f)).

  In the above process, the buffer material 7 is coated on the piezoelectric element 2 before the piezoelectric element 2 is attached to the reinforcing material 8. However, the buffer material 7 is attached after the piezoelectric element 2 is attached to the reinforcing material 8 and the acoustic matching layer 1 is attached. It is good also as what fills.

  Further, the reinforcing material 8 is attached with the reinforcing material 8 after attaching the parts other than the reinforcing material 8 and the epoxy resin 4 and then filled with the epoxy resin 4, leaving a gap for inserting the reinforcing material 8 in advance. It is good also as what inserts the reinforcement material 8 after attaching other components in a state and filling the epoxy resin 4. FIG.

  Thus, in the ultrasonic sensor according to the first embodiment, the stress generated by the thermal expansion difference between the piezoelectric element 2 and the component adjacent to the piezoelectric element 2 by covering at least a part of the piezoelectric element 2 with the buffer material 7. Since the sensor structure and the material of the component parts are not limited, the stress generated at each component part and the part interface at the time of manufacture can be relaxed.

  Further, in the ultrasonic sensor according to Example 1, since the piezoelectric element 2 is reinforced by covering at least a part of the potting material with the reinforcing material 8 in order to seal the piezoelectric element 2, the stress generated in the piezoelectric element 2 is further increased. And the deformation of the entire sensor is suppressed, and the accuracy and reliability can be improved.

  The optimum design apparatus according to the second embodiment of the present invention is an apparatus that optimizes the sensor structure (size, shape, and position of each part) of the ultrasonic sensor, the material of each component, manufacturing conditions, and the like.

  FIG. 5 is a diagram illustrating a functional configuration of the optimum design apparatus for an ultrasonic sensor according to the second embodiment of the present invention. As shown in FIG. 5, the optimal design apparatus according to the second embodiment of the present invention includes an input unit 10, a storage unit 11, an optimization calculation unit 12, and an output unit 13.

  The input unit 10 includes data (hereinafter referred to as sensor structure data) indicating the structure of an ultrasonic sensor (hereinafter referred to as a prototype sensor) before optimization, and data (hereinafter referred to as material characteristics) of each component constituting the prototype sensor. Design data of manufacturing conditions (hereinafter referred to as manufacturing condition data) and data indicating the constraint conditions for optimization (hereinafter referred to as constraint data) And data indicating an allowable range (required value) of stress required for the ultrasonic sensor (hereinafter referred to as required value data).

  The sensor structure data is data indicating the shape, size, and position of each component, and the prototype sensor to which the sensor structure data is input only needs to include a piezoelectric element and an acoustic matching layer. FIG. 6 is a cross-sectional view showing an example of the structure of the prototype sensor. The prototype sensor shown in FIG. 6 includes an acoustic matching layer 14, a piezoelectric element 15, a silicon resin 16, an epoxy resin 17, a substrate 18, and a case 19. The sensor structure data is, for example, coordinate information when the structure of the prototype sensor shown in FIG. 6 is coordinated as shown in FIG. 7, and this coordinate information is input to the input unit 10 as sensor structure data.

  This sensor structure data can be obtained by reading the drawings showing the structure of the prototype sensor with a scanner, etc., and obtaining the coordinate values, and then manually inputting the shape, dimensions, and position of each component to clarify the prototype sensor. Digital data such as CAD data indicating the structure may be input.

  Material property data includes material (chemical composition, mass density, hardness, solvent resistance, flexibility, fluidity, etc.) and mechanical properties (longitudinal elastic modulus, Poisson's ratio, tensile strength) of the prototype sensor. Thickness, toughness, etc.), thermal characteristics (linear expansion coefficient, thermal conductivity, heat transfer coefficient, specific heat, Curie temperature, glass transition temperature, pyrolysis temperature, etc.), electrical characteristics (conductivity, capacitance, etc.), It is data showing piezoelectric characteristics (relative permittivity, piezoelectric strain constant, piezoelectric stress constant, electromechanical coupling constant, acoustic impedance).

  As the material characteristic data, for example, as shown in FIG. 8, the longitudinal elastic modulus, Poisson's ratio, and linear expansion coefficient of the acoustic matching layer 14, the piezoelectric element 15, and the case 19 are input. In addition, when it is desired to take into account the influence of components that have been processed in advance, residual stress, residual strain, and the like during the processing may be input. Note that the material characteristic data of the silicon resin 16, the epoxy resin 17, and the substrate 18 is read from a material data table (described later) stored in the storage unit 11. The material characteristic data of the acoustic matching layer 14, the piezoelectric element 15, and the case 19 may also be read from the material data table. In this case, it is only necessary to input to the input unit 10 what the material of each component is.

  Manufacturing condition data are temperature conditions, pressurizing conditions, etc. in each process at the time of manufacturing the prototype sensor, data indicating the restraint load or restraint displacement when joining each component, the temperature before heating when heating during manufacture, At least one of data indicating a heating rate, a heating holding time, a cooling rate, and a temperature after cooling is included.

  As shown in FIG. 9, the manufacturing condition data includes, for example, a temperature condition of a step of filling and curing the epoxy resin 17 as shown in FIG. The heating holding time is input for 1 hour, the cooling rate is 10 ° C./min, and the temperature after cooling is 25 ° C. In this manufacturing condition data, as a pressurizing condition, for example, as shown in FIG. 10, a sensor restraint load of 0 kg and a restraint displacement of 0 mm are input. This manufacturing condition data is obtained when the room temperature curing resin or adhesive that does not require heating is used in place of the epoxy resin 17, the temperature condition is not input, and the restraint load and restraint displacement (between each component) You may input the force and displacement which are pressurized when adhering.

  The constraint data is data indicating constraint conditions given when the ultrasonic sensor is optimized. That is, when optimizing the prototype sensor, data indicating the constraints or tolerances of materials applicable as each component of the ultrasonic sensor, the constraints or tolerances of the shape, size, and position of the entire ultrasonic sensor and each component At least one of data indicating the degree, and data indicating a restriction or tolerance of manufacturing conditions when the ultrasonic sensor is manufactured.

  This constraint data includes the possibility of changing the material, dimensions, shape, position and manufacturing conditions of each component of the prototype sensor, the possibility of inserting a member (buffer material, reinforcing material, etc.) at the part interface, and the material and dimensions of the member to be inserted. Enter constraints, tolerances, shape, position and manufacturing conditions. As shown in FIG. 11, for example, (1) the dimensions, shape, and position of the acoustic matching layer 14 and the piezoelectric element 15 are not changed, (2) no member is inserted at the component interface, (3) Data indicating that the material and manufacturing conditions of the component parts are not changed is input.

  The required value data is data indicating performance (required value) required for the ultrasonic sensor, and data indicating allowable maximum stress and allowable minimum stress generated in the target region or deformation displacement amount due to stress generated in the ultrasonic sensor. This is data indicating the permissible value.

  As the required value data, for example, as shown in FIG. 12, an allowable maximum stress generated in the piezoelectric element 15 is input as 0 MPa, and an allowable minimum stress is −120 MPa. The target part of the request value data may be any of the whole sensor, each component constituting the sensor, and the interface of each component.

  The storage unit 11 is a database in which a plurality of data tables such as a data table indicating a relationship between design data and stress of sensor structure data, material property data, and manufacturing condition data input by the input unit 10 are stored. The plurality of data tables include, for example, a material data table indicating characteristics (linear expansion coefficient, etc.) for each material of each component, and a linear expansion coefficient difference data table indicating a relationship between a linear expansion coefficient difference and a stress between each component. And a buffer material film thickness data table showing the relationship between the thickness of the buffer material formed at the interface between the piezoelectric element 15 and a component adjacent to the piezoelectric element 15 and the stress fluctuation value. The storage unit 11 outputs these data tables to the optimization calculation unit 12 in response to a request from the optimization calculation unit 12.

  FIG. 13 is a diagram showing the relationship between the difference in linear expansion coefficient between the piezoelectric element 15 and the case 19 and the stress generated in the piezoelectric element 15 and the case 19. FIG. 14 is a diagram showing the relationship between the difference in linear expansion coefficient between the piezoelectric element 15 and the case 19 and the stress generated at the component interface between the piezoelectric element 15 and the case 19. As shown in FIGS. 13 and 14, generally, when the difference in linear expansion coefficient between two adjacent parts is large, the generated stress also increases. These relationships are obtained by testing, inspection, observation, analysis, etc., and the database constructed in the storage unit 11 is a storage of data obtained by testing, inspection, observation, analysis, etc. is there.

  When the input data of sensor structure data, material property data, manufacturing condition data, constraint condition data, and required value data is input to the optimization calculation unit 12 by the input unit 10, data related to the input data input A table is searched from the database constructed in the storage unit 11, and a plurality of data tables related to each input data are extracted. The optimization calculation unit 12 optimizes the sensor structure data, material property data, and manufacturing condition data of the prototype sensor so as to satisfy the required value data input by the input unit 10 based on the extracted plurality of data tables.

  In addition, the optimization calculation unit 12 adds a part not included in the prototype sensor or is included in the prototype sensor when the required value cannot be satisfied without changing the component included in the prototype sensor. Optimize the prototype sensor by deleting existing parts. For example, if the prototype sensor shown in FIG. 6 does not contain a buffer material, but the required value cannot be satisfied without changing the components included in the prototype sensor, a buffer material is added. To optimize to meet the required value.

  The output unit 13 includes design data of sensor structure data, material property data, and manufacturing condition data optimized by the optimization calculation unit 12, stress data indicating stress generated in the optimized ultrasonic sensor, or the stress The deformation data indicating the deformation displacement due to is output. The stress data and deformation data may include data indicating the stress distribution and the deformation distribution, respectively.

  Next, a method for optimizing the ultrasonic sensor using the ultrasonic sensor optimal design apparatus according to Embodiment 2 of the present invention will be described with reference to the flowchart shown in FIG. Here, as an example, the case of optimizing the ultrasonic sensor shown in FIG. 6 will be described.

  First, the design data of the ultrasonic sensor (prototype sensor) before optimization, the material characteristic data of the component parts, and the design data of manufacturing condition data are input by the input unit 10 (step S1). The optimization calculation unit 12 searches the database constructed in the storage unit 11, extracts a data table related to each design data, and obtains stress generated in the prototype sensor based on the extracted data table (step) S2).

  For example, as shown in FIG. 16, when the input unit 10 inputs that the material of the piezoelectric element 15 is A2 and the material of the case 19 is B1, the optimization calculation unit 12 configures the piezoelectric element 15. Material data tables 100 a and 100 b indicating the material to be used and the linear expansion coefficient of the material constituting the case 19 are extracted from the storage unit 11. Next, the optimization calculation unit 12 acquires the linear expansion coefficient K2 of the material A2 constituting the piezoelectric element 15 from the extracted material data table 100a, and linear expansion of the material B1 constituting the case 19 from the material data table 100b. The coefficient L1 is acquired. Next, the optimization calculation unit 12 obtains a difference (linear expansion coefficient difference) between the linear expansion coefficient K2 of the piezoelectric element 15 and the linear expansion coefficient L1 of the case 19. Next, the optimization calculation unit 12 extracts the linear expansion coefficient difference data table 101 indicating the relationship between the linear expansion coefficient difference and the stress, and obtains the obtained linear expansion coefficient difference and the linear expansion coefficient difference data table 101. Based on this, the stress generated in the prototype sensor is obtained. In this case, if the difference in linear expansion coefficient between the piezoelectric element 15 and the case 19 is α2, the optimization calculation unit 12 obtains the stress F2 generated in the prototype sensor based on the linear expansion coefficient difference data table 101. be able to.

  Next, the required value data is input to the input unit 10 (step S3). The optimization calculation unit 12 determines whether or not the stress of the prototype sensor satisfies the required value (step S4), and if it satisfies the required value, outputs that fact to the output unit 13 (step S10). If the required value is not satisfied, the constraint condition data is input by the input unit 10 (step S5).

  Next, the optimization calculation unit 12 determines whether or not the fact that the buffer material can be inserted is input as the constraint condition data (step S6). When it is input that the buffer material can be inserted, the buffer material is optimized (step S7).

  The optimization of the buffer material changes the material, size, shape, position, etc. of the buffer material within the range of given constraints, and the buffer material, size, shape, Find position etc.

  For example, the input unit 10 inputs that the material is silicon resin, the shape is a thin film with a uniform thickness, and the insertion position is the interface between the piezoelectric element 15 and the case 19 as a constraint condition of the buffer material. In this case, that is, when the constraint condition that only the size (thickness) of the buffer material can be changed is input, the optimization calculation unit 12 has a relationship between the thickness of the buffer material and the stress correction amount as shown in FIG. Buffer material film thickness data table 102 is extracted. The optimization calculating unit 12 changes the thickness of the buffer material based on the buffer material film thickness data table 102, and obtains the stress correction amount at this time. Moreover, the optimization calculation part 12 calculates | requires the stress after inserting buffer material based on the calculated | required stress correction amount and the stress of a prototype sensor. The optimization calculation unit 12 compares the obtained stress after insertion of the buffer material with the required value, and searches for the buffer material thickness at which the stress after insertion of the buffer material satisfies the required value. In this case, if the stress after insertion of the buffer material satisfies the required value when the stress correction amount is Fx3, the optimization calculation unit 12 calculates the buffer material thickness based on the buffer material film thickness data table 102. The optimum value D3 can be obtained.

  It should be noted that the optimization of the buffer material is that if the stress cannot satisfy the required value even if the material, dimensions, shape, position, etc. of the buffer material are changed within the range of the given constraints, the stress will be reduced to the required value. The material, size, shape, position, etc., of the cushioning material when the closest value is reached shall be the optimum value.

  Next, the optimization calculation part 12 determines whether the stress after inserting the buffer material which has the optimal value calculated | required by step S7 satisfy | fills the required value (step S8). If the required value is satisfied, data indicating the material, size, shape, position, etc. of the buffer material whose stress satisfies the required value, and data indicating the stress at this time are output to the output unit 13 (step S10). If the required value is not satisfied, each design data of the prototype sensor is optimized (step S9).

  Each design data is optimized by changing the material, dimensions, shape, position, and manufacturing conditions of each component of the prototype sensor within the range of the given constraint conditions, so that the stress meets the required values. Find the material, dimensions, shape, position, and manufacturing conditions of the part.

  For example, when the input unit 10 inputs a constraint condition that only the material of the piezoelectric element 15 and the case 19 can be changed as a constraint condition of each design data, the optimization calculation unit 12 displays the material data shown in FIG. Based on the tables 100a and 100b, the material of the piezoelectric element 15 is changed to A1, A2,..., And the material of the case 19 is changed to B1, B2,. 19 is obtained. The optimization calculation unit 12 obtains the stress based on the obtained linear expansion coefficient difference and the linear expansion coefficient difference data table 101. The optimization calculation unit 12 compares the obtained stress with the required value and searches for the material of the piezoelectric element 15 and the case 19 where the stress satisfies the required value. In this case, if the stress F3 satisfies the required value, and the linear expansion coefficient difference α3 at this time is obtained when the material of the piezoelectric element 15 is A1 and the material of the case 19 is B2, the optimization calculation is performed. The unit 12 optimizes the material of the piezoelectric element 15 to A1 and the material of the case 19 to B2.

  Note that the optimization of each setting data does not satisfy the required value even if the material, dimensions, shape, position, and manufacturing conditions of each component of the prototype sensor are changed within the range of the given constraints. In this case, the material, size, shape, position, and manufacturing condition of each component when the stress is the closest to the required value are set as the optimum values.

  If the input unit 10 inputs that the buffer material cannot be inserted as constraint data in step S5, it is determined in step S6 that the buffer material cannot be inserted, and the process proceeds to step S9, where only the design data is optimized. Done.

  In FIG. 18, in step S5, the fact that the buffer material can be inserted is input as the constraint condition data, and the buffer material is made of silicon resin. The buffer material is thin, and the buffer material is inserted at the piezoelectric element 15 and the case. 19 is a cross-sectional view showing an ultrasonic sensor after optimization in a case where it is input that an interface with 19 is used. FIG. In this case, the buffer material is optimized as described above in step S7, and the optimization calculation unit 12 determines that the required value can be satisfied by setting the optimum value of the thickness of the buffer material to 50 μm or more. As shown in FIG. 18, the optimized ultrasonic sensor has a structure in which a buffer material 20 having a thickness of 50 μm is inserted at the interface between the piezoelectric element 15 and the case 19.

  As described above, the optimum design apparatus according to the second embodiment of the present invention includes, in the input unit 10, the design data of the ultrasonic sensor before optimization, the material characteristic data of each component, the design data of manufacturing conditions data, When the constraint condition data and the required value data are input, the optimization calculation unit 12 obtains stress based on each design data and the database constructed in the storage unit 11, and the stress does not satisfy the required value data Changes the design data within the range of the constraint condition given by the constraint condition data and based on the database, and optimizes the design data so that the stress satisfies the required value data.

  Further, the optimization calculation unit 12 is given by the constraint condition data when the constraint condition data allowing the buffer material to be inserted into the interface between the piezoelectric element 15 and the part adjacent to the piezoelectric element 15 is input by the input unit 10. Within the constraints and based on the database, the material, shape, dimensions, and position of the buffer material are changed to optimize the buffer material so that the stress satisfies the required value data. Since the output unit 13 outputs the optimized result, the optimization structure of the ultrasonic sensor in which stress generated at each component part and component interface is relaxed at the time of manufacture is not limited to the material of the sensor structure and the component part. Can be easily performed.

  In addition, you may use the optimal design apparatus of this invention as an optimal design apparatus of sensors other than an ultrasonic sensor.

  Of course, the ultrasonic sensor according to the first embodiment can be designed using the optimum design apparatus according to the second embodiment.

  INDUSTRIAL APPLICABILITY The present invention can be used as various ultrasonic sensors for flowmeters, defect detection, distance measurement, and the like, a manufacturing method thereof, and an optimum design apparatus thereof.

It is sectional drawing of the ultrasonic sensor which concerns on Example 1 of this invention. It is a figure which shows the relationship between the thickness of buffer material, and the stress which generate | occur | produces in a piezoelectric element or a case. It is a figure which shows the relationship between the thickness of a reinforcing material, and the displacement of a sensor deformation. It is process drawing which shows the manufacturing process of the ultrasonic sensor which concerns on Example 1 of this invention. It is a figure which shows the function structure of the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention. It is a figure which shows the sensor structure before performing optimization by the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention. It is a figure which shows the method of inputting the sensor structure data before optimization to the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention. It is a figure which shows the method of inputting the material characteristic data of a component into the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention. It is a figure which shows the method of inputting manufacturing condition data into the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention. It is a figure which shows the method of inputting manufacturing condition data into the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention. It is a figure which shows the method of inputting constraint data into the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention. It is a figure which shows the method of inputting required value data into the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention. It is a figure which shows the relationship between the linear expansion coefficient difference and the stress which generate | occur | produces in a piezoelectric element or a case. It is a figure which shows the relationship between a linear expansion coefficient difference and the stress of a component interface. It is a flowchart which shows the method of optimizing and designing an ultrasonic sensor using the optimal design apparatus based on Example 2 of this invention. It is a figure which shows an example of the method of optimizing a buffer material using the optimal design apparatus which concerns on Example 2 of this invention. It is a figure which shows an example of the method of optimizing the material of a piezoelectric element and a case using the optimal design apparatus based on Example 2 of this invention. It is a figure which shows an example of the sensor structure optimized by the optimal design apparatus of the ultrasonic sensor which concerns on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 14 Acoustic matching layer 2, 15 Piezoelectric element 3, 16 Silicon resin 4, 17 Epoxy resin 5, 19 Case 6 Adhesive 7 Buffer material 8 Reinforcement material 9 Ultrasonic transmission / reception direction 10 Input part 11 Storage part 12 Optimization calculation part 13 Output unit 18 Substrate 20 Buffer material

Claims (19)

A piezoelectric element;
An acoustic matching layer formed by bonding to the piezoelectric element;
A buffer member for covering at least a part of the piezoelectric element and relieving stress generated by a difference in thermal expansion between the piezoelectric element and a member adjacent to the piezoelectric element;
A sealing member for sealing the piezoelectric element;
A reinforcing member that is in contact with at least a portion of the sealing member and reinforces the piezoelectric element;
A case covering the reinforcing member;
An ultrasonic sensor comprising:   The ultrasonic sensor according to claim 1, wherein the buffer member is made of a polymer material that is softer than the acoustic matching layer, the piezoelectric element, or the reinforcing member.   The ultrasonic sensor according to claim 2, wherein the buffer member is made of silicon resin.   4. The ultrasonic sensor according to claim 1, wherein the buffer member has a thickness of 10 to 100 μm.   The ultrasonic sensor according to any one of claims 1 to 4, wherein the buffer member has a longitudinal elastic modulus of 0.001 to 0.01 GPa.   The ultrasonic sensor according to claim 1, wherein the reinforcing member is made of a polymer material harder than the sealing member or the case.   The ultrasonic sensor according to claim 1, wherein the reinforcing member is made of a metal material harder than the sealing member or the case. Forming a buffer member for relieving stress generated by a difference in thermal expansion between the piezoelectric element and a member adjacent to the piezoelectric element so as to cover at least a part of the piezoelectric element;
Attaching the piezoelectric element to a reinforcing member for reinforcing the piezoelectric element;
Bonding with the piezoelectric element to form an acoustic matching layer;
Forming a sealing member for sealing the piezoelectric element so as to be in contact with at least a part of the reinforcing material;
Attaching a case so as to cover the reinforcing member;
A method for producing an ultrasonic sensor, comprising: An optimum design apparatus for optimizing an ultrasonic sensor including a piezoelectric element and an acoustic matching layer so as to relieve stress generated by a difference in thermal expansion between the piezoelectric element and a member adjacent to the piezoelectric element,
Sensor structure data of the ultrasonic sensor, material property data and manufacturing condition data of each component constituting the ultrasonic sensor, constraint data indicating a constraint condition when the ultrasonic sensor is optimized, and the ultrasonic sensor An input means for inputting required value data indicating an allowable range of required stress;
Storage means for storing first relationship data indicating a relationship between the sensor structure data, the material property data, the manufacturing condition data, and the stress inputted by the input means;
The stress is obtained based on the sensor structure data, the material property data and the manufacturing condition data inputted by the input means, and the first relation data stored in the storage means, and the stress is the required value data. Is not satisfied, the sensor structure data, the material property data, and the manufacturing condition data are changed within the range of the constraint condition given by the constraint condition data and based on the first relation data, An optimization means for optimizing the sensor structure data, the material property data, and the manufacturing condition data so that a stress satisfies the required value data;
Output means for outputting the result optimized by the optimization means;
An optimal design apparatus characterized by comprising: The storage means
Relationship between the stress, the material, shape, dimensions, and position of the buffer member inserted in the interface between the piezoelectric element and a member adjacent to the piezoelectric element in order to store the first relation data and relieve the stress Storing second relational data indicating
The optimization means includes
The stress is obtained based on the sensor structure data, the material property data and the manufacturing condition data inputted by the input means, and the first relation data stored in the storage means, and the stress is the required value data. And when the data indicating that the buffer member can be inserted into the interface between the piezoelectric element and a member adjacent to the piezoelectric element is input by the input unit as the constraint condition data, The material, shape, size, and position of the buffer member are changed within the range of the constraint condition given by the constraint condition data and based on the second relation data so that the stress satisfies the required value data. The optimal design apparatus according to claim 9, wherein the buffer member is optimized.   The optimal design apparatus according to claim 9, wherein the sensor structure data of the ultrasonic sensor includes data indicating a shape, a dimension, and a position of each component.   The material property data of each of the above components includes chemical data, chemical properties, mass density, hardness, solvent resistance, flexibility, material data indicating fluidity, longitudinal elastic modulus, Poisson's ratio, tensile strength, and toughness. Data, linear expansion coefficient, thermal conductivity, heat transfer coefficient, specific heat, Curie temperature, glass transition temperature, thermal characteristic data indicating thermal decomposition temperature, electrical characteristics data indicating conductivity, capacitance, relative dielectric constant, A piezoelectric strain constant, a piezoelectric stress constant, an electromechanical coupling constant, piezoelectric characteristic data indicating acoustic impedance, and residual stress and residual strain data at the time of processing when a component is processed in advance. 9. Optimal design apparatus according to 9.   The manufacturing condition data includes a restraint load when joining each component, a pressurization condition data indicating restraint displacement, a pre-heating temperature, a heating rate, a heating temperature, a heating holding time, a cooling rate when heating during manufacturing, 10. The optimum design apparatus according to claim 9, further comprising at least one of temperature condition data indicating a temperature after cooling.   The constraint condition data includes data indicating the constraint or tolerance of the applied material of each component, the entire ultrasonic sensor, data indicating the shape, size, position, or tolerance of each component, and manufacturing condition constraint. The optimal design apparatus according to claim 9, further comprising at least one of data indicating tolerance.   The required value data includes data indicating an allowable maximum stress and an allowable minimum stress generated in at least one of the entire ultrasonic sensor, each component, and an interface of each component. The optimum design device described.   10. The optimum design apparatus according to claim 9, wherein the relation data stored in the storage means is obtained by at least one of testing, inspection, observation, and analysis.   When the optimization means cannot satisfy the constraint condition data or the required value data without changing the component parts included in the ultrasonic sensor, the optimization means selects a part not included in the ultrasonic sensor. The optimal design apparatus according to claim 9, wherein parts added or deleted from the ultrasonic sensor are deleted.   10. The optimized result output from the output means includes at least one of sensor structure data of the ultrasonic sensor, material property data of each component, and manufacturing condition data. The optimum design device described. The optimized design apparatus according to claim 9, wherein the optimized result output from the output unit includes at least one of a stress distribution, a strain distribution, and a deformation distribution of the ultrasonic sensor.

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