JP2015025796A - Load sensor with quartz crystal resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load sensor with a quartz crystal resonator, which offers not only relative compactness, high sensitivity, and a wide measurement range but also high responsiveness and measurement accuracy.SOLUTION: Load receiving members 12f and 54f, which receive a load F and transmit it to one end part of a quartz crystal resonator 14, are allowed to be moved by a minute displacement in a direction toward base portions 12b and 54b of the load receiving members 12f and 54f because of elastic deformation of leaf spring-like elastic hinge members 12c and 54c joining top ends of a pair of side poll portions 12d and 12e, and 54d and 54e with the load receiving members 12f and 54f, which prevents generation of sliding friction when the minute displacement is made in response to a change in the load F. This leads to sufficient measurement responsiveness, a waveform of measured biological information or the like with no deformation, and no hysteresis in measured loads due to hysteresis caused by the sliding friction, which in turn leads to sufficient accuracy of the waveform and absolute values of the load.

Description

  The present invention relates to a load sensor using a crystal resonator, and more particularly to a packaging technique for the load sensor.

  In recent years, excellent load sensors are required in fields such as robots, medical care, and nursing care. For example, simultaneous measurement of distributed load applied to a bed, etc. and biological signals such as breathing and heart rate, and robots hold heavy objects and perform delicate work on vulnerable objects in the same way as human hands In order to be able to do so, a load sensor capable of wide range measurement with high sensitivity is required.

  A load sensor including a semiconductor strain gauge has been proposed. According to this, high sensitivity is obtained, but the load measurement range is small. On the other hand, as a load sensor capable of high sensitivity and wide range measurement, there is a sensor using a crystal. As a sensor using a crystal, a load sensor using a crystal resonator as described in Patent Document 1 has been proposed. This load sensor converts the direction of a load applied between a container and a lid fitted in the opening of the container and the container and the cover into a horizontal direction, A pair of leaf springs acting on both ends are provided, and a load is detected based on a change in the resonance frequency of the crystal resonator. According to this, it has excellent characteristics such as oscillation with high stability, relatively small size, high sensitivity and wide measurement range due to frequency change exactly proportional to external force. A load sensor is obtained.

JP 2008-281387 A

  However, in the above conventional load sensor, there is sliding friction between the container and the upper lid fitted in the opening thereof, and sufficient response of measurement cannot be obtained, and waveforms such as biological information are distorted, Since hysteresis occurs in the measured load due to the sliding friction, there is a drawback that sufficient accuracy cannot be obtained with respect to the load waveform and the absolute value of the load.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is relatively small, not only providing high sensitivity and a wide measurement range, but also high responsiveness and measurement accuracy. Is to provide a load sensor using a crystal resonator.

  To achieve the above object, the gist of the present invention is: (a) a holder for holding one end and the other end of a thin plate-shaped crystal resonator, and the other end at one end of the crystal resonator. A load sensor using a crystal resonator that detects the external load by receiving an external load in a direction toward the portion, wherein (b) the cage is a pair of (b-1) separated by a predetermined dimension A holding part that has a base part that connects the side pillar part and the base ends of the pair of side pillar parts, and the other end part of the crystal unit located between the pair of side pillar parts is fixed to the base part A member, and (b-2) a load receiving member that protrudes from the one end of the pair of side pillars to the opposite side of the base and receives the external load and transmits it to one end of the crystal resonator And (b-3) a plate that connects the tip of the pair of side column portions and the load receiving portion while allowing displacement of the load receiving portion in the direction toward the base portion. A root-like pair of elastic hinge members is to contain.

  In this way, in the load sensor, the retainer that holds the one end and the other end of the thin plate-shaped crystal resonator includes (b-1) a pair of side column portions and a pair of sides separated by a predetermined dimension. A holding member that has a base portion that connects the base ends of the column portions, and the other end portion of the crystal unit located between the pair of side column portions is fixed to the base portion; (b-2) A load receiving member that protrudes from the one end portion of the pair of side column portions to the opposite side of the base portion and receives the external load and transmits the external load to one end portion of the crystal resonator; (b-3) Including a pair of leaf spring-like elastic hinge members that connect the distal ends of the pair of side column portions and the load receiving portion while allowing displacement of the load receiving portion in the direction toward the base portion. The load receiving member that receives the load and transmits the load to the one end of the crystal resonator is a leaf spring-like connection that connects the tip of the pair of side column portions and the load receiving portion. By the elastic deformation of the sexual hinge member, the displacement in the direction toward the base of the 該荷 heavy receiving is allowed, there is no sliding friction when the micro-displacement in response to changes in load. For this reason, sufficient response of the measurement is obtained, the waveform of the measured biological information is not distorted, there is no hysteresis due to sliding friction, and no hysteresis is included in the measurement load. Therefore, sufficient accuracy can be obtained for the load waveform and the absolute value of the load.

  Here, preferably, the holding member including the side column portion and the base portion, the load receiving member, and the pair of elastic hinge members are integrally formed from a common plate material. For this reason, for example, a minute processing can be performed by the MEMS technology, and the load sensor including a small cage is further reduced in size.

  Preferably, an opening is formed at one end to accommodate the retainer, a cylindrical case having an internal thread on the inner peripheral surface on the opening side, and the holding housed in the case A screw member that is tightened to the screw thread in a state in which a force is applied to the crystal resonator in the same direction as the external load via a container, and forms a casing together with the case, and the screw member and the case It is arrange | positioned between the surfaces of the other end, and it suppresses that the force of the twist direction at the time of the screw fastening by the said screw member acts on the said holding member, and the said force of the longitudinal direction is transmitted to the said holding member. And a thrust bearing that permits this. For this reason, in a load sensor using a crystal unit, the crystal unit is held by a cage, an external load is applied to the crystal unit as a simple compression load, and a holding member is enclosed in a case by a screw member and held. A preload is applied to the member, and the torsion acting on the holding member when the preload is applied is suppressed or not generated by the thrust bearing. In this way, by adding a mechanism for applying a preload in the case formation of a load sensor using a crystal resonator, the assembly of the case is completed together with the application of the preload. Therefore, a preload application step is included in the housing assembly process, and for example, the three steps of sensor wiring, housing assembly, and preload application are simplified to two steps of sensor wiring and housing assembly. In addition, the preload can be applied by the holding member or the housing without providing a dedicated component for applying the preload, and the number of components of the load sensor using the crystal resonator is reduced. Therefore, a load sensor using a crystal resonator that can simplify the process for applying the preload and suppress the increase in the number of parts for applying the preload is provided.

  Preferably, the retainer has a substantially rectangular frame shape that sandwiches one end portion and the other end portion of the crystal resonator from the holding member, the load receiving member, and the elastic hinge member. The elastic hinge members are each formed of one or a plurality of leaf springs. For this reason, in the load sensor using a crystal resonator, the retainer substantially holds one end and the other end of the crystal resonator from the holding member, the load receiving member, and the elastic hinge member. Because it has a long square frame shape, the crystal unit is stably held by the holding member, and external load is efficiently applied to the crystal unit as a simple compressive load along one axis from one end to the other. The In addition, the assembly can be simplified by the integrated cage. Further, the external load other than the longitudinal direction is reduced by the pair of elastic hinge members, and generation of sliding resistance is prevented. Further, the preload applied to the holding member by the screw member is appropriately transmitted to the crystal resonator through the holding member. At this time, since the pair of side column portions function as a stopper in the longitudinal direction by tightening the screw member, it is possible to apply a substantially constant preload without requiring any special adjustment for applying the preload. Is possible.

  Preferably, the load receiving member is partially protruded out of the housing through a through hole formed in the other end surface of the case, or the screw member is formed on the screw member. A part is projected outside the housing through a through-hole penetrating in the longitudinal direction. For this reason, an external load is efficiently applied as a simple compression load to the crystal resonator by the holding member.

  Preferably, the screw member is formed with a groove for receiving a part of the cage in a relatively non-rotatable manner, and is fastened to the screw thread in a state where the holding member is accommodated in the groove. The thrust bearing is disposed between the cage and the surface of the other end of the case. For this reason, the holding member is enclosed in a state appropriately fixed in the case by the screw member, and the torsion acting on the holding member when a preload is applied is appropriately suppressed or not caused by the thrust bearing.

  Preferably, the apparatus includes a pair of electrodes opposed to each other in a thickness direction provided on both planes of the crystal resonator, and an electric wire directly or indirectly connected to each of the electrodes, The electric wire is led out of the housing through a communication groove or a communication hole communicating with the longitudinal direction formed in the screw member. For this reason, a load sensor using a crystal resonator is appropriately configured.

  Preferably, the thin plate-shaped quartz crystal resonator has a pair of linear cut grooves formed on one side thereof and cut in the thickness direction from one end portion to the other end portion. Is composed of a pair of holding plates fixed to the periphery of the crystal unit and sandwiching the crystal unit, and the pair of holding plates includes a space between the pair of linear cut grooves of the crystal unit. A concave surface that forms a gap therebetween, a pair of side column portions that are in close contact with the outside of the pair of linear cut grooves of the crystal resonator, a base portion that is in close contact with the other end portion of the crystal resonator, A load receiving portion that is in close contact with one end of the crystal resonator, and a connection between the tip end portion of the pair of side column portions and the load receiving portion while allowing displacement of the load receiving portion in a direction toward the base portion. A pair of leaf spring-like elastic hinge members are formed. For this reason, the load receiving portion that is not constrained by the pair of linear cut grooves of the crystal resonator and is in close contact with one end portion of the crystal resonator is the tip of the pair of side column portions and the load receiving portion. A pair of leaf spring-like elastic hinge members that connect between the two portions allow displacement in the direction toward the base portion, so that there is no sliding friction when a minute displacement occurs in response to a change in load. . For this reason, sufficient response of the measurement is obtained, the waveform of the measured biological information is not distorted, there is no hysteresis due to sliding friction, and no hysteresis is included in the measurement load. Therefore, a load sensor having sufficient accuracy with respect to the load waveform and the absolute value of the load can be obtained.

  Preferably, a plurality of the holding plates are manufactured simultaneously by being subjected to photo etching for forming the concave surface and the elastic hinge member on the silicon substrate, and are divided from the silicon substrate. . In this way, the productivity of the load sensor is increased and the assembly becomes easy, so that an inexpensive load sensor can be obtained.

  Preferably, a plurality of the quartz resonators are manufactured simultaneously by applying sputtering to form electrodes and sandblasting to form the linear cut grooves to the quartz substrate, and the quartz resonator is divided from the quartz substrate. It has been done. In this way, the productivity of the load sensor is increased and the assembly is facilitated, so that a more inexpensive load sensor can be obtained.

It is a perspective view which illustrates the load sensor of Example 1 to which the present invention is applied. It is a perspective view which shows typically the structure inside the load sensor of FIG. It is a perspective view which shows the holding member accommodated in the inside of the load sensor of FIG. 1 with a crystal oscillator. FIG. 4 is a front view of the holding member and the crystal resonator shown in FIG. 3. It is a figure explaining an example of the composition of the whole system containing a load sensor. It is a figure which shows an example of the characteristic of the crystal oscillator with respect to a load load, Comprising: It is a result of the load load experiment in the state which mounted only the holding member. It is a figure which shows an example of the characteristic of the crystal oscillator with respect to a load load, Comprising: It is a result of the load load experiment in the load sensor which loaded the preload. It is a figure which shows the characteristic of a load sensor when a micro load is added at the time of a high load. It is a schematic diagram which shows the other example of the load sensor to which this invention is applied. It is a schematic diagram which shows the other example of the holding member to which this invention is applied. It is a perspective view which illustrates the load sensor of Example 2 to which the present invention is applied. It is the perspective view which cut | disconnected the load sensor of the Example of FIG. 11 to the vertical direction in the center of the width direction. It is a perspective view which shows the state before the assembly of the load sensor of the Example of FIG. It is a figure which shows the frequency characteristic with respect to the load load in the load sensor shown by FIG. It is process drawing explaining the manufacturing process of the load sensor shown by FIG. FIG. 12 is a cross-sectional view illustrating a processing state during a manufacturing process of a crystal resonator included in the load sensor illustrated in FIG. 11. It is sectional drawing which each shows the processing state in the manufacturing process of the holding plate contained in the load sensor shown by FIG. It is sectional drawing which shows the assembly state of the load sensor shown by FIG.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a perspective view showing a load sensor 10 to which the present invention is applied. FIG. 2 is a perspective view schematically showing an internal configuration of the load sensor 10 of FIG. FIG. 3 is a perspective view showing the holder 12 housed in the load sensor 10 of FIG. FIG. 4 is a front view showing the retainer 12 and the crystal resonator 14 shown in FIG. 1 to 4, the load sensor 10 includes a cage 12, a crystal resonator 14, a case 16, a screw member 18, a thrust bearing 20, an electric wire 22, an electric wire 24, and the like. The load sensor 10 uses a crystal resonator 14 that detects an external load F by applying a force to the crystal resonator 14 in a longitudinal direction L perpendicular to the thickness direction D along the center line C of the cross section. It is a load sensor. The crystal unit 14 has a thickness that is ten parts thinner than the cage 12.

  The case 16 has a cylindrical container shape with one end opened, and a female thread 16a is provided on the inner surface on the opening side. The case 16 has a through-hole 16c formed on the other end surface 16b. The case 16 forms a casing 26 together with the screw member 18 by fastening the screw member 18 to the screw thread 16a. That is, the casing 26 of the load sensor 10 has a cylindrical shape as a whole, and the cage 12, the crystal resonator 14, the thrust bearing 20, and the like are enclosed in the casing 26 by the screw member 18. The material of the housing 26 is stainless steel (SUS302) having high rigidity, for example. The casing 26 is formed by machining a lathe or the like.

  The retainer 12 holds the crystal resonator 14 by holding one end portion and the other end portion in the longitudinal direction L with respect to the crystal resonator 14 so that the external load F can be transmitted to the thin plate-shaped crystal resonator 14. The cage 12 is accommodated in the case 16 so that the external load F can be transmitted to the crystal resonator 14. Specifically, the retainer 12 stably holds the crystal unit 14 and efficiently loads the external load F on the crystal unit 14 as a simple compressive load in the direction of the cross-sectional center line C. The configuration described is adopted. That is, the cage 12 has a pair of side column portions 12d and 12e that are parallel to each other with a predetermined dimension and a base portion 12b that connects the base ends of the pair of side column portions 12d and 12e. The holding member 12a in which the other end portion of the crystal resonator 14 located between 12d and 12e is fixed to the base portion 12b and the one end portion of the pair of side column portions 12d and 12e to the side opposite to the base portion 12b. A load receiving member 12f that protrudes and receives an external load F and transmits it to one end of the crystal resonator, and a displacement of the pair of side column portions 12d and 12e while allowing displacement in the direction toward the base portion 12b of the load receiving member 12f. A pair of leaf spring-like elastic hinge members 12c that connect between the distal end portion and the load receiving member 12f are provided to form a substantially frame shape. The load receiving member 12f of the present embodiment includes a contact portion 12g that protrudes toward the base portion 12b and holds the crystal resonator 14 between the base portion 12b. The length of the contact portion 12g in the width direction W is equal to or greater than the length of the crystal resonator 14 in the width direction W.

  The cage 12 configured as described above has an integral structure in order to simplify assembly. Specifically, the material of the cage 12 is formed, for example, from a phosphor bronze (C5210) plate material that is strong against repeated stress and has high rigidity and excellent properties as a leaf spring, by processing by an end mill or wire discharge. . The thickness of the cage 12 is set to be thicker than that of the crystal resonator 14.

  For the crystal resonator 14, for example, an AT cut crystal having excellent temperature stability is used. The AT-cut quartz resonator generates thickness shear vibration in the electrode portion by an externally applied voltage, and can obtain an output as an electrical periodic signal at a resonance frequency that is accurately proportional to the external force. In order to increase the load stress on the crystal with respect to the load load by reducing the cross section in the longitudinal direction L, that is, the load loading direction, for example, the quartz resonator 14 has a long length in the longitudinal direction L. The direction L is longer than the length in the width direction W perpendicular to the direction L. A pair of electrodes 28 facing each other in the thickness direction D are provided in a substantially circular shape at a substantially central portion on the plane of the crystal unit 14. Each pattern extends to the vicinity of the end of the electrode 28 so as to contradict the diagonal direction on the plane of the crystal unit 14. The electric wire 22 is connected at the pattern near the end. In this embodiment, the Q value is improved by taking the distance from the substantially circular electrode 28 serving as the oscillation source to the electric wire 22 and the cage 12.

  The crystal resonator 14 configured as described above is formed, for example, by forming electrodes on both surfaces of a thin plate-shaped AT-cut crystal wafer using a lift-off process and performing division by dicing. Specifically, a sacrificial layer is first patterned on an AT-cut quartz wafer, and then an electrode is formed by sputtering Cr and Au, and then the sacrificial layer is removed. This series of processes is performed on both sides to pattern the electrodes, and after completion of the electrodes, a plurality of crystal resonators 14 are formed by cutting with a dicing saw.

  The screw member 18 encloses the cage 12 in the case 16 and applies a preload (preload) Fpre to the cage 12 to vibrate the quartz crystal through the cage 12 accommodated in the case 16. It is fastened to the thread 16a of the case 16 in a state where a force is applied to the child 14 in the longitudinal direction L. Specifically, the screw member 18 is formed with a groove 18a for receiving a part of the holding member 12a in a relatively non-rotatable manner so as to enclose the cage 12 in a state of being appropriately fixed in the case 16. Then, the screw member 18 is fastened to the screw thread 16a in a state in which the cage 12 is accommodated in the groove 18a (for example, in a fixed state), and forms the casing 26 together with the case 16. Further, the screw member 18 is formed with a communication groove 18b by notching a part of the outer periphery to cause a loss. The communication groove 18b may be a communication groove that communicates in the longitudinal direction L so as to communicate the inside and outside of the housing 26, and various modes such as a substantially semi-cylindrical shape and a substantially rectangular shape may be employed.

  The electric wire 22 is a copper wire for wiring that is connected to and electrically connected to each of the electrodes 28 on the pattern of the electrode 28 extending to the vicinity of the end on the plane of the crystal resonator 14. The electric wire 24 is a copper wire for wiring having a diameter larger than that of the electric wire 22, and (or directly) the electric wire 22 via a relay substrate 30 fixed on the inner surface 18 c of the screw member 18. And are electrically connected. The electric wires 24 indirectly connected to each of the electrodes 28 through the electric wires 22 and the like are led out of the housing 26 through the communication grooves 18b. Note that the electric wire 22 directly connected to each of the electrodes 28 may be led out of the housing 26 through the communication groove 18b as it is.

  The thrust bearing 20 is disposed between the screw member 18 and the surface 16b at the other end of the case 16 so as to suppress or prevent torsion acting on the cage 12 when the preload Fpre is applied. For example, a known ball bearing that suppresses the force in the torsional direction S from acting on the cage 12 during the screw tightening by the member 18 and allows the force in the longitudinal direction L to be transmitted to the cage 12. Specifically, the thrust bearing 20 is disposed between the cage 12 and the surface 16 b at the other end of the case 16. The thrust bearing 20 is formed with a groove 20a for receiving a part of the cage 12 so as not to be relatively rotatable.

  In the load sensor 10 including the case 16, the thrust bearing 20, the cage 12, and the screw member 18, a preload Fpre is applied to the cage 12 by the screw member 18, and the preload Fpre is transmitted via the cage 12. It is appropriately transmitted to the crystal unit 14. At this time, the pair of side column portions 12 d and 12 e of the cage 12 functions as a stopper with respect to the longitudinal direction L due to tightening of the screw member 18. Therefore, it is possible to apply a substantially constant front load Fpre without special adjustment regarding the application of the preload Fpre due to the tightening of the screw member 18. In addition, by applying the preload Fpre, the gap between the cage 12 and the crystal unit 14 generated when the load sensor 10 is assembled can be filled, and the load sensor 10 can be raised.

  FIG. 5 is a diagram illustrating the configuration of the entire system including the load sensor 10. The elements constituting the system of the load sensor 10 include the load sensor 10, an oscillation circuit 32 for continuously oscillating the crystal resonator 14 that is a main part of the load sensor 10, and a period output from the oscillation circuit 32. A frequency counter 34 for reading the signal frequency, a power supply circuit 36 for supplying power to the oscillation circuit 32, and the like. The oscillation circuit 32 uses a CMOS gate type that has few circuit components and can be easily reduced in size, and is provided with a bypass capacitor or the like for noise removal.

Below, the dimension of the main site | part in an example of the load sensor 10 made as an experiment is shown. As shown in this, the load sensor 10 of the present embodiment is configured to be sufficiently small.
・ Case 26: φ6 [mm], height (longitudinal direction L) 8 [mm]
・ Crystal resonator 14: Longitudinal direction L3.5 [mm], width direction W2.0 [mm], thickness direction D0.1 [mm]
-Cage 12: Longitudinal direction L7 [mm], width direction W4.2 [mm]
・ Contact part 12g: Longitudinal direction L1.0 [mm]
-Hinge member 12c: longitudinal direction L0.1 [mm]
-Electrode 28 (central part): φ1 [mm], thickness direction D250 [nm]
・ Wire 22: φ0.05 [mm]

  Below, the analysis result in the load sensor 10 made as an experiment as described above will be described. In the state where only the cage 12 sandwiching the crystal unit 14 is mounted (see FIGS. 3 and 4), the load applied to the crystal unit 14 when the external load F of 10 [N] from the longitudinal direction L is applied is 8.6. [N] (calculated from the stress 43 [MPa] at the center of the crystal unit 14 and the crystal cross section 2.0 [mm] × 0.1 [mm]). Here, if the “load applied to the crystal resonator 14 with respect to a given external force” is defined as “force conversion rate”, the force conversion rate of the load sensor 10 of this embodiment is 86 (= ( 8.6 / 10) x 100) [%], and the sensitivity was improved. The allowable load load of the crystal resonator 14 calculated by analysis was 36 [N].

  6 and 7 are diagrams illustrating characteristics of the crystal resonator 14 with respect to a load applied to the crystal resonator 14. FIG. 6 shows the result of a load test in a state where only the cage 12 sandwiching the crystal unit 14 is mounted (see FIGS. 3 and 4). FIG. 7 shows the result of a load load experiment in the load sensor 10 (see FIG. 1) in which the preload Fpre is applied by 10 [N] by tightening with the screw member 18. In this load load experiment, only the cage 12 or the load sensor 10 is arranged on the experimental apparatus table vertically so as to match the longitudinal direction L, and a load is applied. The applied load is measured by the load cell, and at the same time, the output from the crystal resonator 14 connected to the oscillation circuit 32 is measured by the frequency counter 34, thereby measuring the change in frequency with respect to the load applied to the crystal resonator 14. did.

  In FIG. 6, the resonance frequency of the crystal resonator 14 was not changed until a load of approximately 5 [N] was applied. Further, the resonance frequency of the crystal resonator 14 was changed with a high linearity after a load of about 10 [N] was applied. Therefore, in the load sensor 10 of the present embodiment, it is understood that when a preload Fpre of approximately 10 [N] is applied, it is possible to configure a load sensor that can rise well and obtain a value that is accurately proportional to the external force. The analysis result shown in FIG. 7 is an experimental result in the load sensor 10 reflecting the experimental result of FIG.

In FIG. 7, an approximate straight line A indicating the relationship between the external load F and the resonance frequency of the crystal resonator 14 is expressed by the following equation (1) (x: external load F [N], Y: resonance frequency [MHz]. ]). The correlation coefficient in the approximate straight line A is R ² = 0.9972, and good linearity is obtained. The sensor sensitivity was 896 [Hz / N], and the sensitivity was improved.
Y = 896x × 10 ⁻⁶ +16.491 (1)

  FIG. 8 is a diagram illustrating the characteristics of the load sensor 10 when a minute load is applied during a high load. In this experiment, a weight of 2.0 [kg] was suspended from the prototype load sensor 10 and then a weight of 1.0 [g] was placed thereon, and the change in the output of the load sensor 10 (that is, the change in frequency) was measured. In this experiment, after suspending the weight, enough time was taken until the fluctuation of the output due to the shaking of the weight was settled, and then a weight of 1.0 [g] was placed. In FIG. 8, there was no damage of the load sensor 10 with respect to the weight of 2.0 [kg], and the output of the load sensor 10 showed a fluctuation of about 19,200 [Hz]. In addition, the output of the load sensor 10 varied about 10 [Hz] with respect to a weight of 1.0 [g]. Thereby, it turns out that the load sensor 10 can measure a micro force at a high load. That is, it can be seen that the load sensor 10 is a wide range and high sensitivity load sensor.

  As described above, according to the load sensor 10 using the crystal resonator 14 of the present embodiment, the holder 12 that holds one end and the other end of the thin plate-shaped crystal resonator 14 is (b-1) A pair of side column portions 12d and 12e spaced apart from each other by a predetermined dimension and a base portion 12b connecting the base ends of the pair of side column portions 12d and 12e, and between the pair of side column portions 12d and 12e. A holding member 12a in which the other end portion of the quartz crystal resonator 14 located at the base is fixed to the base portion 12b; and (b-2) a side opposite to the base portion 12b from one end portions of the pair of side column portions 12d and 12e. And a load receiving member 12f that receives the external load F and transmits it to one end of the crystal resonator 14, and (b-3) while allowing displacement in the direction toward the base portion 12b of the load receiving member 12f. The tip of the pair of side column portions 12d and 12e and the load receiving member 12f are connected to each other. Shaped two leaf springs and a pair of elastic hinge members 12c, including. As a result, the load receiving member 12f that receives the load F and transmits it to one end of the crystal resonator 14 is a leaf spring that connects the tip of the pair of side column portions 12d and 12e and the load receiving member 12f. Due to the elastic deformation of the elastic hinge member 12c, a minute displacement in the direction toward the base portion 12b of the load receiving member 12f is allowed, so that sliding friction does not occur when the displacement is caused in response to a change in the load F. For this reason, sufficient response of the measurement is obtained, the waveform of the measured biological information is not distorted, there is no hysteresis due to sliding friction, and no hysteresis is included in the measurement load. Therefore, sufficient accuracy can be obtained for the load waveform and the absolute value of the load.

  Further, according to the load sensor 10 using the crystal resonator 14 of the present embodiment, the holding member 12a including the pair of side column portions 12d and 12e and the base portion 12b, the load receiving member 12f, and the pair of elastic hinge members 12c Is formed integrally from a phosphor bronze plate, which is a common plate material, and therefore, microfabrication can be performed by, for example, MEMS technology, and the load sensor 10 including the small cage 12 is further downsized.

  Further, according to the load sensor 10 using the crystal resonator 14 of the present embodiment, the cage 12, the case 16, the screw member 18, and the thrust bearing 20 are provided. The external load F is efficiently applied as a simple compressive load to the crystal unit 14 and is held in a state in which the holder 12 is appropriately fixed in the case 16 by the screw member 18 and is attached to the holder 12. The preload Fpre is applied, and the torsion acting on the cage 12 when the preload Fpre is applied is appropriately suppressed or not generated by the thrust bearing 20. As described above, by adding a mechanism for applying the preload Fpre in the formation of the casing 26 of the load sensor 10, the assembly of the casing 26 is completed together with the application of the preload Fpre. Therefore, the process of assembling the casing 26 includes a process of applying the preload Fpre, and for example, the three processes of sensor wiring, casing assembly, and application of the preload are simplified to two processes of sensor wiring and casing assembly. In addition, the preload Fpre can be applied by the cage 12 and the casing 26 without providing a dedicated component for applying the preload Fpre, and the number of components of the load sensor 10 is reduced. Therefore, the load sensor 10 using the crystal resonator 14 that can simplify the process for applying the preload Fpre and suppress the increase in the number of parts for applying the preload Fpre is provided.

  Further, according to the present embodiment, the assembly can be simplified by the retainer 12 having an integral structure. Further, the external load other than the longitudinal direction L is further reduced by the hinge member 12c. Further, the preload Fpre applied to the cage 12 by the screw member 18 is appropriately transmitted to the crystal unit 14 via the cage 12. At this time, the side column portions 12d and 12e of the holding member 12a function as a stopper with respect to the longitudinal direction L due to tightening of the screw member 18, so that the application of the preload Fpre does not require special adjustment and is substantially constant. It is possible to apply a preload Fpre.

  Further, according to the present embodiment, the load receiving portion 12f of the cage 12 is partly projected out of the housing 26 through the through hole 16c of the case 16, so that the external load F is efficiently crystallized. The vibrator 14 is loaded as a simple compression load.

  Further, according to the present embodiment, since the electric wire 22 or the electric wire 24 is led out of the housing 26 through the communication groove 18b of the screw member 18, the load sensor 10 using the crystal resonator 14 is appropriately set. Composed.

  Next, a load sensor 50 according to another embodiment of the present invention will be described. In the following description, parts common to those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 11 is a perspective view showing the load sensor 50, FIG. 12 is a perspective view of the load sensor 50 cut in the longitudinal direction at the center in the width direction, and FIG. 13 is an assembly before explaining the three-layer structure of the load sensor 50 FIG.

  The load sensor 50 includes a holder 52 that holds one end and the other end of the thin plate-shaped crystal resonator 14, and an axis C passing through the one end of the crystal resonator 14 in the direction toward the other end, that is, the center of the cross section. The external load F is detected by receiving the external load F in the direction of. The holder 52 is composed of two holding plates 54 that are in close contact with the bottom and sides of the crystal unit 14 by adhesion or bonding and sandwich the sandwiched plate. The two holding plates 54 are similarly configured in an integrated manner, for example, from a Si substrate by deep photoetching used in MEMS technology.

  The two holding plates 54 constituting the holder 52 have a pair of side column portions 54d and 54e spaced apart from each other by a predetermined dimension and a base portion 54b that connects the base ends of the pair of side column portions 54d and 54e. A holding member 54a in which the other end portion of the crystal unit 14 positioned between the pair of side column portions 54d and 54e is fixed to the base portion 54b, and a base portion rather than one end portion of the pair of side column portions 54d and 54e. A pair of a load receiving member 54f that protrudes to the opposite side of 54b and receives the external load F and transmits it to one end of the crystal resonator 14 and a pair of displacements in a direction toward the base portion 54b of the load receiving member 54f. A pair of leaf spring-like elastic hinge members 54c for connecting between the front end portions of the side column portions 54d and 54e and the load receiving member 54f are provided.

  The crystal unit 14 includes a pair of parallel cut grooves 14a that are cut from one end portion toward the other end portion to reach the base portion 54b and communicate with each other in the thickness direction. The crystal resonator 14 is not in contact with the pair of linear cut grooves 14a, and is located below the pair of linear cut grooves 14a and below the pair of linear cut grooves 14a. It is clamped by the cage 52 with the portion located on the side.

  The pair of holding plates 54 includes a rectangular concave surface D that forms a gap S between a surface between the pair of linear cut grooves 14a of the crystal unit 14, a load receiving member 54f, and a pair of elastic hinges. A hat-shaped slot 56 penetrating in the thickness direction to separate the member 54c and a lead wire hole 60 through which a lead wire 58 having one end connected to the electrode 28 of the crystal resonator 14 are formed. Has been.

  As a result, the pair of holding plates 54 are positioned outside the concave surface D and are closely connected to the outside of the pair of linear cut grooves 14a of the crystal unit 14 and the concave surface D. Located on the lower side of the crystal unit 14, the base portion 54 b in close contact with the other end of the crystal unit 14, and on the upper side of the concave surface D, that is, on one end side of the crystal unit 14. Thus, the load receiving member 54f that is in close contact with one end of the crystal resonator 14 and the displacement in the direction toward the base portion 54b of the load receiving member 54f are positioned on the upper side of the concave surface D, that is, on one end of the crystal resonator 14. A pair of leaf spring-like elastic hinge members 54c that connect between the tip ends of the pair of side column portions 54d and 54e and the load receiving member 54f while being allowed are formed.

  The load sensor 50 configured as described above has a height of about 5.5 mm, for example, when the crystal resonator 14 has a height of about 3.5 mm, a width of about 2.0 mm, and a thickness of about 0.1 mm. It has a width of about 4.2 mm and a thickness of about 0.8 mm, and is sufficiently small.

14 shows a power supply for the load sensor 50 to the oscillation circuit 32, the frequency counter 34 for reading the frequency of the periodic signal output from the oscillation circuit 32, the oscillation circuit 32, and the like, similar to those shown in FIG. The output characteristic measured using the power supply circuit 36 for supplying the power is shown. In FIG. 14, an approximate straight line B indicating the relationship between the external load F and the resonance frequency of the crystal resonator 14 is expressed by the following equation (2) (x: external load F [N], Y: resonance frequency [MHz]. ]). The approximate straight line B indicates that the resonance frequency of the crystal resonator 14 has high linearity with respect to the load F. The correlation coefficient is R ² = 0.993297, and good linearity is obtained. The sensor sensitivity was 1191 [Hz / N], and the sensitivity was improved.
Y = 0.001191x + 15.910815 (2)

  15 is a process diagram for explaining the manufacturing process of the load sensor 50. FIG. 16 shows an intermediate shape of the crystal unit 14 in each of the manufacturing processes P1 to P4 of the load sensor 50. FIG. The intermediate shape of the holding plate 54 in the manufacturing processes P5 to P8 is shown, and FIG. 18 shows the assembled state of the crystal resonator 14 and the holding plate 54 before separation into individual load sensors 50.

  In FIG. 15, in the electrode forming process P <b> 1, the material Cr / Au of the electrode 28 is sputtered from a photoresist (not shown) fixed on both surfaces of the quartz substrate CP and from which a pattern having a shape corresponding to the plurality of electrodes 28 is removed. Then, the photoresist is lifted off, and a plurality of Cr / Au electrodes 28 of the pattern shown in FIG. 13 are fixed to both surfaces of the quartz substrate CP using a sputtering apparatus. FIG. 16A shows this state. The quartz crystal substrate CP has a thickness that is sufficiently thinner than the silicon substrate Si.

  Next, in the photoresist lamination step P2, a positive photoresist film PPR for etching is laminated (dry film lamination) on one surface of the quartz crystal substrate CP. FIG. 16B shows this state.

  In the subsequent patterning step P3, of the positive resist film PPR laminated on one surface of the quartz substrate CP, the slit-like portions corresponding to the outer shapes of the pair of linear cut grooves 14a and the load receiving member 54f are locally exposed by exposure. Removed. FIG. 16 (c) shows this state.

  In the hole punching step P4, a pair of linear cut grooves 14a and the like are formed by sandblasting or etching the quartz substrate CP through the patterned positive resist film PRF, and then a positive electrode is formed by a stripping solution. The mold resist film PPR is removed. FIG. 16 (c) shows this state. As a result, a large number of crystal resonators 14 with electrodes that are integrally connected to each other in the crystal substrate CP are manufactured simultaneously (at once).

  In the first resist patterning step P5 of FIG. 15, a negative photoresist NPR is applied to one surface of the silicon substrate Si with a predetermined thickness, and then exposed to a shape corresponding to the concave surface D of the silicon substrate Si in the photoresist NPR. The pattern is exposed. FIG. 17A shows this state. Next, in the first etching step P6, deep etching used in the MEMS technology is performed on one surface of the silicon substrate Si through the photoresist NPR, and a plurality of concave surfaces D are formed on one surface of the silicon substrate Si. As a result, the photoresist NPR is removed. FIG. 17B shows this state.

  Next, in the second resist patterning step P7, a negative photoresist NPR is applied to one surface of the silicon substrate Si on which the concave surface D is formed with a predetermined thickness, and then exposed to a hat of the silicon substrate Si in the photoresist NPR ( The pattern of the shape corresponding to the slot 56 and the lead wire hole 60 of the hooked cap) shape is exposed. FIG. 17 (c) shows this state. Next, in the second etching step P8, deep etching used in the MEMS technology is performed on one surface of the silicon substrate Si through the photoresist NPR, and after the slot 56 and the lead wire hole 60 penetrating the silicon substrate Si are formed, The photoresist NPR is removed by the stripping solution. As a result, a large number of holding plates 54 constituting a large number of retainers 52 integrally connected to each other in the silicon substrate Si are manufactured simultaneously (at once).

  In the assembling process P9 of FIG. 15, a pair of silicon substrates Si on which a large number of holding plates 54 are formed are bonded or bonded to each other with a crystal substrate CP on which a large number of crystal resonators 14 with electrodes are formed. A large number of load sensors 50 are assembled by fixing them. The lead wire 58 may be bonded to the electrode 28 before assembling, or may be bonded to the electrode 28 after assembling. After assembling in this manner, the load sensor 50 shown in FIGS. 11 to 13 is obtained by separation using, for example, laser light at the position indicated by the one-dot chain line in FIG.

  As described above, according to the load sensor 50 using the crystal resonator 14 of the present embodiment, the retainer 52 that holds one end and the other end of the thin plate-shaped crystal resonator 14 is (b-1) A pair of side column portions 54d and 54e spaced apart from each other by a predetermined dimension and a base portion 54b connecting the base ends of the pair of side column portions 54d and 54e, and between the pair of side column portions 54d and 54e. A holding member 54a in which the other end portion of the quartz crystal resonator 14 located at the base is fixed to the base portion 54b; And a load receiving member 54f that receives the external load F and transmits it to one end of the crystal resonator 14, and (b-3) while allowing displacement in the direction toward the base 54b of the load receiving member 54f. The tip of the pair of side column portions 54d and 54e and the load receiving member 54f are connected to each other. Shaped single leaf spring and a pair of elastic hinge members 54c, including. As a result, the load receiving member 54f that receives the load F and transmits it to one end of the crystal resonator 14 is a leaf spring that connects the tip of the pair of side column portions 54d and 54e and the load receiving member 54f. Due to the elastic deformation of the elastic hinge member 54c, a minute displacement in the direction toward the base portion 54b of the load receiving member 54f is allowed, so that a sliding friction does not occur when the displacement is caused in response to a change in the load F. For this reason, sufficient response of the measurement is obtained, the waveform of the measured biological information is not distorted, there is no hysteresis due to sliding friction, and no hysteresis is included in the measurement load. Therefore, sufficient accuracy can be obtained for the load waveform and the absolute value of the load.

  Further, according to the load sensor 50 using the crystal resonator 14 of the present embodiment, the holding member 54a including the pair of side column portions 54d and 54e and the base portion 54b, the load receiving member 54f, and the pair of elastic hinge members 54c Is integrally formed from a silicon substrate Si, which is a common plate material, so that microfabrication can be performed by, for example, MEMS technology, and the load sensor 50 including the small cage 52 is further reduced in size.

  Further, according to the load sensor 50 of the present embodiment, a plurality of holding plates 54 are simultaneously manufactured by photoetching the silicon substrate Si to form the concave surface D and the elastic hinge member 54c. The substrate is divided from the substrate Si. For this reason, the productivity of the load sensor 50 is increased and the assembly is facilitated, so that an inexpensive load sensor can be obtained.

  Further, according to the quartz crystal resonator 14 of the present embodiment, a plurality of quartz crystal resonators 14 are formed by applying sputtering for forming the electrodes 28 and sandblasting for forming the linear cut grooves 14a to the quartz crystal substrate CP. It is manufactured at the same time and divided from the crystal substrate CP. For this reason, the productivity of the load sensor 50 is increased and the assembly is facilitated, so that a more inexpensive load sensor 50 can be obtained.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this invention is applied also in another aspect.

  For example, in the above-described embodiment, the screw member 18 has the groove 18a formed therein and is fastened to the case 16 in a state where the holding member 12a is accommodated in the groove 18a. For example, as shown in FIG. 9A, the screw member 18 may be fastened to the case 16 in a state where the groove 18a is not formed and the holding member 12a is in contact with the surface 18c. Moreover, although the electric wire 24 (or electric wire 22) was derived | led-out outside the housing | casing 26 via the communication groove 18b of the screw member 18, it is not restricted to this aspect. For example, with respect to leading the electric wire 24 out of the casing 26, any configuration may be used as long as the inner and outer sides of the casing 26 communicate with each other. As shown in FIG. 9A, the longitudinal direction L formed in the screw member 18 is sufficient. An aspect such as a communication hole 18d that communicates with each other can also be adopted. Even in this case, the load sensor 10 using the crystal resonator 14 is appropriately configured.

  In the above-described embodiment, the load receiving portion 12f of the holding member 12a is partially protruded out of the housing 26 through the through hole 16c of the case 16, but this is not restrictive. For example, as shown in FIG. 9B, even if a part of the load receiving portion 12f protrudes outside the housing 26 through a through hole 18e that penetrates in the longitudinal direction L formed in the screw member 18, good. Even in this case, the external load F is efficiently applied to the crystal unit 14 as a simple compression load.

  In the above-described embodiment, the thrust bearing 20 is disposed between the holding member 12a and the surface 16b of the case 16, but this is not restrictive. For example, when the screw member 18 is tightened to the case 16 with the holding member 12a in contact with the surface 18c of the screw member 18 (see FIG. 9A), the thrust bearing 20 is 18 and the surface 16b of the case 16 may be disposed, and may be disposed between the screw member 18 and the holding member 12a as shown in FIG. 9C. Even if it does in this way, the torsion which acts on the holding member 12a at the time of the load of the preload Fpre is suppressed by the thrust bearing 20, or is not produced. Even in the case where the load receiving portion 12f is partially protruded outside the housing 26 through the through hole 18e formed in the screw member 18 (see FIG. 9B), this concept can be applied. Needless to say.

  In the above-described embodiment, the load sensor 10 and the circuit such as the oscillation circuit 32 are separate bodies, but the present invention is not limited to this mode. For example, the load sensor 10 and the oscillation circuit 32 may be integrated. By miniaturizing the entire system and integrating it to shorten the wiring distance, it is possible to suppress the influence of noise in the connection between devices. FIG. 9D shows an example in which the substrate of the oscillation circuit 32 is downsized and the load sensor 10 and the oscillation circuit 32 are integrated. In FIG. 9D, the influence of the disturbance can be suppressed by arranging the oscillation circuit 32 around the load sensor 10 and performing shielding with the metal case 38. In the embodiment shown in FIG. 9D, the size can be reduced to φ12 [mm] × height (longitudinal direction L) 11 [mm].

  In the above-described embodiment, the holding member 12a has the two-stage hinge member 12c. However, the present invention is not limited to this mode. For example, the hinge member 12c may have three or more stages, or may have one stage as shown in FIG. Even in this case, the external load F other than the longitudinal direction L is reduced by the hinge member 12c.

  In the above-described embodiment, the contact portion 12g is integrally formed on the load receiving member 12f of the retainer 12, but this is not a limitation. For example, as shown in FIG. 10B, the load receiving member 12f may be in direct contact with the crystal resonator 14.

  In the second embodiment, a large number of crystal resonators 14 are simultaneously formed on the crystal substrate CP and divided therefrom, and a plurality of holding plates 54 are simultaneously formed on the silicon substrate Si and then divided. However, one of the crystal unit 14 and the holding plate 54 may be manufactured by such a manufacturing method.

  The above description is only an embodiment, and the present invention can be implemented in variously modified and improved forms based on the knowledge of those skilled in the art.

  The present invention can be used in fields such as robots, medical care, welfare, nursing care, moving objects, health equipment, fine work, and biological signal detection. Specifically, since the load sensor using the crystal resonator of the present invention can measure a micro force at a high load, a large load such as a distributed load applied to a bed, a weight, a grip force (grip force), etc. It can be used for simultaneous measurement of force and biological signals such as respiration and heart rate (pulse). Further, it can be used when a robot performs a range of tasks from holding a heavy object to delicate work on a fragile object.

10, 50: Load sensor (load sensor using crystal resonator)
12, 52: Cage 12a, 54a: Holding member 12b, 54b: Base part 12c, 54c: Hinge members 12d, 12e, 54d, 54e: Side column parts 12f, 54f: Load receiving part (load receiving member)
14: Crystal resonator 14a: Linear cut groove 16: Case 16a: Thread 16b: Surface 16c: Through hole 18: Screw member 18a: Groove 18b: Communication groove 18d: Communication hole 18e: Through hole 20: Thrust bearing 22 24: Electric wire 26: Housing 28: Electrode 54: Holding plate 56: Hat-shaped slot 58: Lead wire 60: Lead wire hole D: Concave surface Si: Silicon substrate (plate material)
CP: Crystal plate (plate material)

Claims (10)

A crystal having a holder for holding one end and the other end of a thin plate-shaped crystal resonator, and detecting the external load by receiving an external load in a direction toward the other end at one end of the crystal resonator A load sensor using a vibrator, wherein the cage is
A pair of side pillars spaced apart from each other by a predetermined dimension, and a base part that connects the base ends of the pair of side pillars, and the other end of the crystal unit located between the pair of side pillars is A holding member fixed to the base,
A load receiving member that protrudes from the one end of the pair of side pillars to the opposite side of the base, and that receives the external load and transmits it to one end of the crystal unit;
A pair of leaf spring-like elastic hinge members that connect between the tip of the pair of side column portions and the load receiving portion while allowing displacement of the load receiving portion in the direction toward the base portion. A load sensor using a crystal resonator. The load sensor using a crystal resonator according to claim 1, wherein the holding member, the load receiving member, and the elastic hinge member are integrally formed from a common plate material. A cylindrical case in which an opening is formed at one end to accommodate the retainer, and an internal thread is formed on the inner peripheral surface of the opening;
A screw member that is tightened to the screw thread in a state in which a force is applied to the crystal resonator in the same direction as the external load via the cage accommodated in the case, and forms a casing together with the case When,
It is arrange | positioned between the said screw member and the surface of the other end of the said case, and it suppresses that the force of the twist direction at the time of the screw fastening by the said screw member acts on the said holding member, and the said force of the said longitudinal direction is A thrust bearing that allows transmission to the holding member;
The load sensor using the crystal resonator according to claim 1 or 2, further comprising: The retainer includes a holding member including the pair of side column portions and a base portion, the load receiving member, and the pair of elastic hinge members. It has a square frame shape,
The load sensor using a crystal resonator according to claim 3, wherein each of the pair of elastic hinge members is formed of one or a plurality of leaf springs. The load receiving member is partially protruded out of the housing through a through hole formed in the other end surface of the case, or penetrated in the longitudinal direction formed in the screw member. 5. The load sensor using a crystal resonator according to claim 3, wherein a part of the load protrudes outside the housing through a hole. The screw member is formed with a groove for receiving a part of the holding member so as not to be relatively rotatable, and is fastened to the screw thread in a state in which the holding member is accommodated in the groove.
The load sensor using the crystal resonator according to any one of claims 3 to 5, wherein the thrust bearing is disposed between the holding member and a surface of the other end of the case. . A pair of electrodes provided on both planes of the crystal resonator and facing in the thickness direction;
An electric wire directly or indirectly connected to each of the electrodes;
The said electric wire is derived | led-out outside the said housing | casing through the communicating groove | channel or communicating hole which is connected to the said longitudinal direction formed in the said screw member, The any one of Claim 3 thru | or 6 characterized by the above-mentioned. A load sensor using a crystal unit. The thin plate-shaped crystal resonator has a pair of linear cut grooves that are cut from one end to the other end and communicate in the thickness direction.
The holder is composed of a pair of holding plates that are fixed to the periphery of the crystal unit and sandwich the crystal unit,
The pair of holding plates are in close contact with a concave surface that forms a gap between the pair of linear cut grooves of the crystal resonator and the outside of the pair of linear cut grooves of the crystal resonator. A pair of side pillars, a base portion in close contact with the other end portion of the crystal resonator, a load receiving portion in close contact with one end portion of the crystal resonator, and a direction of the load receiving portion toward the base portion The pair of leaf spring-like elastic hinge members that connect between the tip end portions of the pair of side column portions and the load receiving portion while allowing displacement are formed respectively. Or a load sensor using a crystal resonator of 2. A plurality of the holding plates are manufactured at the same time by being subjected to photo etching that forms the concave surface and the elastic hinge member on the silicon substrate, and are divided from the silicon substrate. A load sensor using the crystal resonator according to Item 8. A plurality of the quartz resonators are manufactured simultaneously by being sputtered to form electrodes and sandblasting to form the linear cut grooves on the quartz substrate, and are divided from the quartz substrate. A load sensor using the crystal unit according to claim 8 or 9.

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