JP2009080069A - Acceleration sensor, and load sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration sensor for improving the detection accuracy. <P>SOLUTION: The acceleration sensor 10 includes: a support 20 as a fixed end; a movable mass 30 coupled by the support 20 and a hinge joint 40; and vibrating bodies 50, 60 extended between the support 20 and the movable mass 30 along both side faces of the movable mass 30. The vibrator 50 includes: a main vibrating arm 51 extended between a support base 25 and a mass base 35; and sub vibrating arms 52, 53 extended from the support base 25 and the mass base 35 along the main vibrating arm 51. The vibrator 60 includes: a main vibrating arm 61 extended between a support base 26 and a mass base 36; and sub vibrating arms 62, 63 extended from the support base 25 and the mass base 35 along the main vibrating arm 61. Resonance frequencies between the main vibrating arms 51, 61 and the sub vibrating arms 52, 53, 62, 63 are matched. A change in the resonance frequencies of the vibrators 50, 60 is detected by applying an acceleration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an acceleration sensor and a load sensor that detect changes in the resonance frequency of a vibrating body when acceleration or a load is applied.

  Utilizing the fact that the resonant frequency of the vibrating body changes when a load along the vibrating arm is applied to a vibrating body having one or two beam-like vibrating arms, changes the reference resonant frequency and resonant frequency of the vibrating body. A load sensor that measures the magnitude of an applied load by comparing the amount is proposed.

  As an application of such a load sensor to an acceleration sensor, a rotating mass unit that is connected to a support portion by a hinge joint and that is rotatable in a sensing direction orthogonal to the hinge joint connecting direction, There is an acceleration sensor having a vibrating body (sometimes referred to as a double tuning fork vibrating body) composed of two vibrating arms interposed between support parts. These vibrating bodies (vibrating arms) are parallel to the hinge joint connection direction on both sides of the rotating mass portion, and when the acceleration is applied, the movable mass portion rotates around the hinge joint as a rotation center. As the movable mass part rotates, one vibrating body contracts and the other vibrating body expands. It is detected that the resonance frequency of the vibrating body changes as the vibrating body contracts and expands (see, for example, Patent Document 1).

  Further, as specific examples of the load sensor, a supporting portion, a protruding portion at an end portion of the supporting portion, a lever portion that is continuous with the protruding portion and has a force point and an emphasis at both ends, a force point and a supporting point A vibrating body (sometimes referred to as a double tuning fork) that includes two vibrating arms that extend through a connecting portion between the load portion and a load receiving portion that is provided via a tension piece at the emphasis point. The load applied to the load receiving portion is detected as a change in the resonance frequency of the vibrating body by being expanded or reduced and transmitted to the vibrating body via the lever, and the magnitude of the applied load is detected. There is a load sensor that measures the thickness (see, for example, Patent Document 2).

JP-A-1-302166 (pages 2, 3 and 6) Japanese Patent Laid-Open No. 60-10122 (pages 2, 3 and 1)

  In such an acceleration sensor according to Patent Document 1, the vibrating body is in the form of a double tuning fork, and there are four vibrating arms. Therefore, since the acceleration applied to the movable mass is received by the four vibrating arms, the amount of displacement due to the acceleration is small and the generated stress per vibrating arm is small. Insufficient sensitivity.

  In addition, as will be described in detail in the embodiments described later, the axial force acting on the vibrating body is such that the distance from the hinge joint to the center of gravity of the movable mass portion is L, the mass is m, and the center axis of the vibrating body from the center axis of the hinge joint When the distance to the axis is h, the axial force F acting on the vibrating body when the acceleration g is applied can be expressed as F = (L / 2h) mg. Here, it is considered that amplification having a gain of (L / 2h) is possible. In the structure of Patent Document 1, since the vibrating body is composed of two vibrating arms, the distance h is a distance to the central axis of the two vibrating arms, so that the distance h increases and the amplification gain (L / 2h) becomes smaller, so the detection sensitivity is insufficient.

  In addition, such a configuration of the prior art cannot obtain sufficient detection sensitivity by the inventors' investigation, and this is because the distortion of the two pairs of vibrating arms when acceleration is applied is not uniform. The cause is considered to be the occurrence of leakage, the resonance frequency of the movable mass portion affecting the resonance frequency of the vibrating body, and the like.

  Also, in the load sensor according to Patent Document 2, as in Patent Document 1, the measurement load applied to the load receiving portion is received by the two vibrating arms. Since the generated stress per book is small, the amount of change in the resonance frequency is small. Furthermore, since the distance h to the vibrating arm cannot be reduced, there is a problem that detection sensitivity is insufficient because the magnification rate of the measurement load by the lever is limited.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  [Application Example 1] An acceleration sensor according to this application example is an acceleration sensor that is developed in a plane and detects that the resonance frequency of the vibrating body is changed by applying acceleration, and includes a support portion as a fixed end, and A movable mass portion provided alongside the support portion; and a vibrating body extending along a longitudinal side surface of the movable mass portion and extending between the support portion and the movable mass portion. The vibrating body includes one main vibrating arm extending between a support base that is continuous with the support and a mass base that is continuous with the movable mass; the support base; and A sub-vibration arm extending along the main vibration arm from each of the mass bases, and excitation means provided at least on the main vibration arm, and the resonance frequency of the main vibration arm and the sub-vibration arm is An acceleration sensor characterized by matching.

  According to such a configuration, since one vibrating body is composed of one main vibrating arm, strain and stress generated in the main vibrating arm due to acceleration applied to the movable mass portion are increased, and therefore, the same magnitude. Since the amount of change in the resonance frequency with respect to the acceleration increases, the acceleration detection sensitivity can be increased.

  Also, a sub-vibration arm having the same resonance frequency as the main vibration arm is provided, and by making the vibration of the sub-vibration arm in reverse phase with the vibration of the main vibration arm, a kind of tuning-fork type vibrator is obtained. The vibration energy of the connecting part of the sub-vibration arm is canceled, and the occurrence of vibration leakage to the base part or the additional mass part can be suppressed. As a result, the stability (represented by the Q value) of the resonance frequency is improved. If the Q value increases, the fluctuation of the resonance frequency is reduced, and therefore the acceleration detection accuracy can be improved.

  The excitation means may be provided only on the main vibration arm, and the sub-vibration arm may be configured to resonate with the vibration of the main vibration arm, or the sub-vibration arm may be provided with excitation means so as to match the resonance frequency.

  Application Example 2 In the acceleration sensor according to the application example described above, the vibration body is provided on both sides of the movable mass portion, and the difference between the resonance frequency changes of each vibration body is a detected acceleration value. .

According to such a configuration, when acceleration is applied and the movable mass portion is displaced, one main vibrating arm receives a compressive force and the other main vibrating arm receives a tensile force. For this reason, the resonance frequency of either one of the vibrators is set as a reference frequency, and by taking the difference between them, there is an effect that a frequency change amount approximately twice (hereinafter, sometimes referred to as a frequency deviation) can be obtained.
Further, when acceleration other than the sensing direction is applied, the detection sensitivity (other-axis sensitivity) other than the sensing direction can be made extremely small by taking the difference.

  Moreover, the acceleration sensor of the said application example can be integrally formed with the same material, and can suppress the stress change by thermal expansion, etc. Further, by taking the difference, the influence of the frequency temperature characteristic (frequency change of the main vibrating arm due to temperature) on the main vibrating arm can be made extremely small.

  Application Example 3 The acceleration sensor according to Application Example 1 is an acceleration sensor in which the vibrating body is provided along one side surface of the movable mass unit.

  According to such a configuration, the resonance frequency of the main vibrating arm when no acceleration is applied can be used as a reference frequency, and the difference from the resonance frequency when acceleration is applied can be used as a detected acceleration value. Moreover, the acceleration sensor can be reduced in size by using one vibrating body.

  Application Example 4 The acceleration sensor according to any one of Application Examples 1 to 3 is an acceleration sensor in which the main vibration arm is disposed between the movable mass portion and the sub vibration arm.

  According to such a configuration, the main vibrating arm is disposed closer to the movable mass portion than the sub vibrating arm. Therefore, the above-described distance h is considered to be a distance from the axis passing through the center of gravity of the movable mass portion to the vibration axis of the main vibrating arm, and therefore can be made smaller than the distance h according to the configuration of Patent Document 1, and the amplification gain ( L / 2h) can be increased, so that the detection sensitivity can be increased.

  Application Example 5 In the acceleration sensor according to any one of Application Examples 1 to 4, a constriction portion is provided between the support portion base portion and the support portion, and between the mass portion base portion and the movable mass portion. Provided acceleration sensor.

  As described above, by providing the constricted portion at the portion where the vibrating body connects to the support portion and the movable mass portion, it is possible to further suppress vibration leakage of the main vibrating arm and the sub vibrating arm.

  [Application Example 6] In the acceleration sensor according to any one of Application Examples 1 to 5, the movable mass portion includes a notch portion in which a part of the support portion base portion and the mass portion base portion enter in a planar direction. Acceleration sensor.

  With such a configuration, since the main vibrating arm can be brought closer to the movable mass portion side, the distance h can be reduced, the amplification gain can be improved, and the acceleration sensor can be further miniaturized.

  Application Example 7 In the acceleration sensor according to any one of Application Example 1 to Application Example 6, the support portion and the movable mass portion are coupled by a hinge joint on a surface where the support portion and the movable mass portion face each other. Acceleration sensor.

  According to such a configuration, the distance from the hinge joint to the center of gravity of the movable mass portion is constant, the acceleration sensing direction is regulated, the axial force F acting on the vibrating body is stably obtained, and the sensing direction is regulated. In addition, the sensitivity of other axes can be suppressed.

  [Application Example 8] The acceleration sensor according to Application Example 7 has a difference that the resonance frequency of the movable mass portion having the hinge joint as a vibration fulcrum does not affect the resonance frequency of the main vibration arm. Acceleration sensor.

  In the configuration of Patent Document 1 described above, it is conceivable that the vibration of the movable mass part affects the resonance frequency of the vibrating body as a cause of insufficient detection sensitivity. Therefore, by making the resonance frequency of the movable mass part sufficiently lower than the resonance frequency of the main vibrating arm, the influence can be suppressed and the detection sensitivity can be increased.

  Application Example 9 In the acceleration sensor according to Application Example 1 or Application Example 2, two of the support portions are provided across the movable mass portion, and one of the vibrating bodies is the movable mass portion and one of the support portions. The acceleration sensor is extended between the first and second vibration bodies, and the other vibrating body is extended between the movable mass portion and the other support portion.

  According to such a configuration, since the support portions are disposed on both sides of the movable mass portion, the movable mass portion has a pseudo both-end fixed structure, and a stable support structure can be realized. Further, since the force due to the acceleration is uniformly applied to the cross section of each vibrating arm, there is an effect that the detection sensitivity of the acceleration is increased.

  Application Example 10 The acceleration sensor according to Application Example 9 is an acceleration sensor in which at least the vibrator is made of a single crystal piezoelectric material.

  In this way, the acceleration sensor can be easily integrally formed with high accuracy by a photolithography technique or the like, and an acceleration sensor that is easy to manufacture and low cost can be provided. In particular, when quartz is used as the single crystal piezoelectric material, it is possible to obtain an acceleration sensor having good frequency temperature characteristics and a high Q value and having highly accurate vibration characteristics.

  Application Example 11 The acceleration sensor according to any one of Application Examples 1 to 9 is an acceleration sensor in which at least the vibrating body is made of a constant elastic material.

In this way, the constant elastic material has an effect that it has a high structural strength and can cope with measurement in a strong acceleration region.
When a constant elastic material is used, a piezoelectric element is formed as an excitation means on the side surface in the vibration direction of the main vibrating arm.

  Application Example 12 A load sensor according to this application example is a load sensor that is developed in a plane and detects that the resonance frequency of the vibrating body changes when a load is applied. Two support portions provided across the mass portion, and two vibrations extending along both sides of the longitudinal side surface of the movable mass portion and extending between the support portion and the movable mass portion And one of the vibrating bodies extends between the movable mass portion and the one supporting portion, and the other vibrating body extends between the movable mass portion and the other supporting portion. Each of the two vibrators extends between a support base that is continuous with the support and a mass base that is continuous with the movable mass, the support base, and the mass. A secondary extending along the main vibrating arm from each of the bases And Doude, load sensor has at least an excitation means provided on the main vibration arm, is provided.

According to such a configuration, when a load is applied to the movable mass portion, a tensile force or a compressive force is applied to the main vibrating arm to change the resonance frequency. It is possible to detect the change in the resonance frequency and measure the magnitude of the applied load.
Note that the load sensor according to this application example includes a force sensor and a pressure sensor.

  Application Example 13 The load sensor according to this application example is a load sensor that detects a change in the resonance frequency of the vibrating body by applying a load, and includes a support unit fixed to a base, A projecting portion provided at an end, a lever that is continuous with the projecting portion with the projecting portion as a fulcrum, and has a force point and an emphasis at both ends, and extends between the force point and the support portion via a connecting piece The vibrating body and a load receiving portion provided via a tension piece at the point of tension, and the vibrating body includes a support base that is continuous with the support and a power point base that is continuous with the power point. A main vibrating arm extending between, a sub-vibrating arm extending along the main vibrating arm from each of the support base and the force point base, and excitation means provided at least on the main vibrating arm, The load applied to the load receiving portion is Load sensor is enlarged or is reduced transmitted to the vibrating body via the lever portion.

  According to such a configuration, the vibration body is configured by one main vibration arm and a sub vibration arm, thereby increasing the stress generated in the main vibration arm, and the two vibration arms according to Patent Document 2 described above are configured. In comparison with the structure, the detection sensitivity can be increased about twice.

  Moreover, if the main vibrating arm is arranged on the support side with respect to the sub vibrating arm, the distance between the fulcrum and the force point can be reduced, and the load applied to the load receiving part (emphasis) can be expanded (amplified). As a result, the amplification gain increases. Moreover, vibration leakage is suppressed by providing the main vibration arm and the sub vibration arm to have the same resonance frequency. Therefore, the detection sensitivity can be increased and a minute load (force) can be detected with high accuracy.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the first embodiment, FIG. 2 shows the second embodiment, FIG. 3 shows the third embodiment, FIG. 4 shows the fourth embodiment, FIG. 5 shows the acceleration sensor according to the fifth embodiment, and FIG. Show. FIG. 5 is also used as a reference diagram showing another example of the load sensor.
Note that the drawings referred to in the following description are schematic views in which the vertical and horizontal scales of members or portions are different from actual ones for convenience of illustration.
(Embodiment 1)

  FIG. 1 is a plan view showing the acceleration sensor according to the first embodiment. In FIG. 1, an acceleration sensor 10 is developed in the XY plane of a substrate made of a single crystal as a single crystal piezoelectric material, and includes a support portion 20 as a fixed end fixed to a base (not shown) and the like. The movable mass unit 30 provided along with the support unit 20, the vibrating body 50 extending along one of the longitudinal side surfaces of the movable mass unit 30, and the other of the opposing longitudinal side surfaces of the movable mass unit 30. And a vibrating body 60 that extends.

  The support part 20 and the movable mass part 30 are integrally coupled by hinge joints 40 on their opposing surfaces. The hinge joint 40 passes through the center of gravity 42 of the movable mass portion 30 and is provided on the central axis P along the longitudinal side surface. That is, the acceleration sensor 10 of this embodiment is symmetric with respect to the central axis P.

  The vibrating body 50 includes a main vibrating arm 51 extending between a support base 25 that is continuous to the support 20 and a mass base 35 that is continuous to the movable mass 30, and the main vibrating arm 51 from the support base 25. The sub-vibration arm 53 extends in parallel along the main vibration arm 51, and the sub-vibration arm 52 extends in parallel from the mass base 35 along the main vibration arm 51.

  The vibrating body 60 includes a main vibrating arm 61 that extends between a support base 26 that is continuous to the support 20 and a mass base 36 that is continuous to the movable mass 30, and the main vibration from the support base 26. A sub-vibration arm 63 extending in parallel along the arm 61 and a sub-vibration arm 62 extending in parallel along the main vibration arm 61 from the mass base 36 are configured. The main vibrating arms 51 and 61 are disposed outside the movable mass unit 30 with respect to the sub vibrating arms 52 and 53 and the sub vibrating arms 62 and 63, respectively.

  The support bases 25 and 26 are connected to the support 20 via the connection parts 21 and 23, respectively. The connection part 21 is provided with a constriction part 22 and the connection part 23 is provided with a constriction part 24. , 26 is narrower.

  Further, the mass base portions 35 and 36 are respectively connected to the movable mass portion 30 via the connecting portions 31 and 33, the constricted portion 32 is provided in the connecting portion 31, and the constricted portion 34 is provided in the connecting portion 33, so The width is narrower than the base portions 35 and 36. These constricted portions 22, 24, 32, 34 are provided in order to suppress the vibration of the vibrating bodies 50, 60 from leaking to the support portion 20 and the movable mass portion 30.

  The main vibrating arms 51 and 61 are beam-like vibrating arms having a support structure at both ends, and excitation electrodes (not shown) serving as excitation means are provided on the respective surfaces. The excitation electrode also serves as a detection electrode, is connected to a connection electrode on the front surface or the back surface of the support portion 20, and is connected to a transmission circuit and a detection circuit (both not shown).

  The main vibrating arm 51 is a secondary flexural vibration, sub-vibrating arm 52, 53 having the support base 25 and the mass base 35 as vibration nodes and the longitudinal center of the main vibrating arm 51 as a vibration antinode. Are first-order flexural vibrations in phase opposite to the vibration of the main vibrating arm 51 having the mass base 35 and the support base 25 as nodes of vibration.

  In the vibrating body 50, the sub-vibrating arms 52 and 53 substantially match the vibration nodes of the main vibrating arm 51 and the resonance frequency in the mass base 35 and the support base 25, respectively. Accordingly, when the main vibration arm 51 is excited, the sub vibration arms 52 and 53 resonate, and therefore the sub vibration arms 52 and 53 do not necessarily have an excitation electrode. Since the vibrating body 60 is also symmetrical with the vibrating body 50 with respect to the central axis P, the same resonance vibration as that of the vibrating body 50 is performed.

  A specific example will be described. When the arm length of the main vibrating arm 51 is 7000 μm and the arm width is 200 μm, the resonance frequency is 22 kHz. Here, in order to set the resonance frequency of the auxiliary vibrating arms 52 and 53 to 22 kHz, if the arm width of each of the auxiliary vibrating arms 52 and 53 is 200 μm, the arm length may be adjusted to 2700 μm. Note that the arm length may be fixed and the arm width may be adjusted.

  In addition, the auxiliary vibrating arms 52 and 53 may be provided with excitation electrodes. At this time, the excitation electrodes are configured so as to have vibrations in the opposite phase to the main vibrating arm 51.

  Subsequently, a detection method of the acceleration sensor 10 will be described. When acceleration g in the + X direction is applied to the acceleration sensor 10, the support portion 20 is fixed, and a moment is generated in the −X direction about the center 41 of the hinge joint 40 as a rotation axis in the movable mass portion 30 due to the inertia effect. . Accordingly, the main vibrating arm 51 is stretched to generate a tensile stress. On the other hand, the main vibrating arm 61 is contracted to generate a compressive stress. At this time, the resonance frequency of the main vibrating arm 51 decreases and the resonance frequency of the main vibrating arm 61 increases. Then, the magnitude of the acceleration can be detected by comparing the difference in the amount of change in the resonance frequency of each of the main vibrating arms 51 and 61 with the reference resonance frequency to which no acceleration is applied. Note that the acceleration application directions in the + X direction and the −X direction can be recognized by increasing or decreasing the resonance frequency of each of the vibrating bodies 50 and 60.

Next, the amplification gain will be described. When acceleration g in the + X direction is applied to the acceleration sensor 10, a moment M ₁ is generated in the −X direction around the center 41 of the hinge joint 40 in the movable mass 30 due to the inertia effect. The relationship between the distance L ₁ from the center 41 of the hinge joint 40 to the center of gravity 42 of the movable mass portion 30, the mass m of the movable mass portion 30, and the axial force F ₁ acting on the center of gravity 42 when the center 41 is the rotation axis is M ₁ = F ₁ L ₁ = mgL ₁ .

At this time, the moment M ₁ is displaced to a place where it balances with the moment M ₂ that appears so as to maintain the movable mass portion 30 in an equilibrium state by the main vibrating arms 51 and 61. From this moment balance (M ₁ = M ₂ ), the axial force F ₂ acting on the main vibrating arms 51, 61 is the distance from the central axis P to the center line of vibration of each of the main vibrating arms 51, 61 as h ₁ . Then, a relationship of 2F ₂ h ₁ = mgL ₁ is established. From here, the axial force F ₂ acting on the main vibrating arms 51 and 61 is represented by F ₂ = (L1 / 2h ₁ ) mg. That is, it means that amplification with a gain of (L1 / 2h ₁ ) is possible. Therefore, this gain is called an amplification gain, and it can be said that the larger the gain, the higher the amplification factor and the higher the detection sensitivity.

  Further, in the present embodiment, the shape and size are such that the resonance frequency of the movable mass unit 30 having the hinge joint 40 as a vibration fulcrum has a difference that does not affect the resonance frequency of the main vibrating arms 51 and 61. Is set. Specifically, if the resonance frequency of the movable mass unit 30 is set to 6 kHz when the resonance frequency of the main vibration arms 51 and 61 is set to 22 kHz, the resonance vibration of the movable mass unit 30 is changed to the main vibration arms 51 and 61. It has been confirmed that the resonance vibration of 61 is hardly affected.

  Therefore, according to the first embodiment, since each of the vibrating bodies 50 and 60 is configured by the single main vibrating arms 51 and 61, the vibration is generated in the main vibrating arms 51 and 61 due to the acceleration applied to the movable mass unit 30. Since the strain and stress increase, the change in the resonance frequency for the same magnitude of acceleration increases, so that the acceleration detection sensitivity can be increased.

  Further, main vibration arms 51 and 61 and sub vibration arms 52, 53, 62, and 63 having the same resonance frequency are provided, and the vibration of the sub vibration arm is made to have a phase opposite to that of the main vibration arm. By using the tuning fork type vibrator, the vibration energy of the connecting portion between the main vibrating arm and the sub vibrating arm is canceled out, and vibration leakage to the support base portions 25 and 26 and the mass base portions 35 and 36 can be suppressed. As a result, the stability (represented by the Q value) of the resonance frequency is improved. As the Q value increases, the fluctuation of the resonance frequency is reduced, and thus there is an effect that the accuracy of detection sensitivity can be improved.

Moreover, the vibrating bodies 50 and 60 are provided on both sides of the movable mass unit 30. According to such a configuration, when acceleration is applied and the movable mass unit 30 is displaced, one of the main vibrating arms 51 and 61 receives a compressive force and the other receives a tensile force. For this reason, the resonance frequency of either one of the vibrating bodies is used as a reference frequency, and by taking the difference between them, a frequency deviation of about twice is obtained, and the detection sensitivity can be increased.
Further, when acceleration other than the sensing direction is applied, the detection sensitivity (other-axis sensitivity) other than the sensing direction can be made extremely small by taking the difference in frequency change as described above.

  Further, by providing the constricted portions 22, 24, 32, 34 in the connecting portions 21, 23 between the support portion base portions 25, 26 and the connecting portions 31, 33 between the mass portion base portions 35, 36, respectively. The vibration leakage of the main vibrating arms 51 and 61 and the sub vibrating arms 52, 53, 62, and 63 can be further suppressed.

In addition, since the support unit 20 and the movable mass unit 30 are coupled by the hinge joint 40 on the surface where the support unit 20 and the movable mass unit 30 face each other, the center of the hinge joint 40 is connected to the movable mass unit 30. The distance L ₁ to the center of gravity 42 is constant, the axial force F ₁ acting on the vibrating bodies 50 and 60 can be obtained stably, the sensing direction can be restricted, and the sensitivity of other axes can be suppressed.

  In this embodiment, the shape and size are such that the resonance frequency of the movable mass portion 30 having the hinge joint 40 as a vibration fulcrum has a difference that does not affect the resonance frequencies of the main vibrating arms 51 and 61. Yes. In the configuration of Patent Document 1 described above, it is conceivable that the vibration of the movable mass part affects the resonance frequency of the vibrating body as a cause of insufficient detection sensitivity. Therefore, by making the resonance frequency of the movable mass portion 30 sufficiently lower than the resonance frequency of the main vibrating arms 51 and 61, the influence can be suppressed and the detection sensitivity can be increased.

  Furthermore, in this embodiment, the acceleration sensor 10 is comprised from the quartz substrate. In this way, the acceleration sensor 10 can be easily integrally molded with high accuracy by a photolithography technique or the like, and an acceleration sensor that is easy to manufacture and low cost can be provided. In addition, since quartz has good frequency-temperature characteristics and high Q value, it can realize an acceleration sensor with high-accuracy vibration characteristics, and stress change due to thermal expansion that is likely to occur in a combination structure with other materials Etc. can be suppressed.

In the acceleration sensor 10 shown in FIG. 1, the main vibrating arms 51 and 61 are symmetrical with respect to the central axis P, and the shape extending in parallel is exemplified. , It does not have to be parallel. Accordingly, the resonance frequencies of the main vibrating arms 51 and 61 may be set to different values as long as the resonance frequencies of the sub vibrating arms 52, 53, 62, and 63 are combined.
(Example of acceleration sensor using constant elastic material)

  Moreover, although the acceleration sensor by Embodiment 1 mentioned above demonstrated the structure which consists of quartz, this invention can make an acceleration sensor the structure which consists of a constant elastic material. The shape of the acceleration sensor can be the same as that shown in FIG. 1 for the vibrating body, the support part, and the movable mass part, and will be described with reference to FIG.

  The acceleration sensor 10 according to the present embodiment is made of a constant elastic material made of nickel, iron, chromium, titanium, or an alloy such as Elinba or iron-nickel alloy, and is selected according to a desired resonance frequency and size. Is done. And the piezoelectric element (illustration omitted) as an excitation means is provided in the side surface of the main vibration arms 51 and 61 in the strong vibration direction. Excitation electrodes are formed on the front and back surfaces of the piezoelectric element. The piezoelectric elements may be provided on both sides of the main vibrating arms 51 and 61 or on one side. An insulating film is formed between the side surfaces of the main vibrating arms 51 and 61 and the back side excitation electrodes of the piezoelectric elements.

When excitation signals having opposite potentials are input to the excitation electrodes on both the front and back surfaces of the piezoelectric element, the main vibrating arms 51 and 61 perform secondary bending vibration and continue stable vibration at a predetermined resonance frequency.
Moreover, it is good also as a structure which provides a piezoelectric element also in each bending-vibration direction side surface of sub vibration arm 52,53,62,63 with the main vibration arms 51 and 61. FIG.

  In this way, the constant elastic material has an effect that it has a high structural strength and can cope with measurement in a strong acceleration region.

  Even if the acceleration sensor 10 has a structure composed of a constant elastic material and a piezoelectric element, each of the vibrating bodies 50 and 60 is composed of one main vibrating arm 51 and 61 as in the first embodiment. A kind of tuning fork type vibrating body composed of the main vibrating arms 51 and 61 and the sub vibrating arms 52, 53, 62 and 63, and the vibrating bodies 50 on both sides of the movable mass portion 30. 60, the same effects as those of the first embodiment can be obtained.

Also in this embodiment, the shape and size are such that the resonance frequency of the movable mass portion 30 having the hinge joint 40 as a vibration fulcrum has a difference that does not affect the resonance frequency of the main vibrating arms 51 and 61. Thus, the influence of the resonance frequency of the movable mass unit 30 on the resonance frequency of the main vibrating arms 51 and 61 can be suppressed, and the detection sensitivity can be increased.
(Embodiment 2)

Next, the acceleration sensor according to the second embodiment will be described with reference to the drawings. The second embodiment is characterized in that the arrangement of the main vibrating arm and the sub vibrating arm is different from that of the first embodiment (see FIG. 1). Since other structures are the same as those of the first embodiment, the description thereof is omitted, and the same functional parts are denoted by the same symbols.
FIG. 2 is a plan view showing the acceleration sensor according to the second embodiment. In FIG. 2, in the acceleration sensor 10, the main vibrating arms 51 and 61 are respectively disposed between the movable mass portion 30, the sub vibrating arms 52 and 53, and the sub vibrating arms 62 and 63. That is, the main vibrating arm 51 is disposed on the inner side of the sub vibrating arms 52 and 53 and the main vibrating arm 61 is disposed on the inner side of the sub vibrating arms 62 and 63 with respect to the movable mass unit 30.

At this time, the axial force F ₂ acting on the main vibrating arms 51 and 61 is a distance h ₂ from the central axis P to the vibration center line of each of the main vibrating arms 51 and 61, and the relationship 2F ₂ h ₂ = mgL ₁ is established. It holds. From here, the axial force F ₂ acting on the main vibrating arms 51 and 61 is expressed by F ₂ = (L ₁ / 2h ₂ ) mg.

Here, the distance h ₁ from the central axis P in the first embodiment to the vibration center line of each of the main vibrating arms 51 and 61 corresponds to the distance from the central axis of the sub vibrating arms 62 and 63 in the second embodiment. To do. Therefore, when h ₂ and h ₁ are compared, h ₂ <h _{1 is obtained} , and the amplification gain is (L ₁ / 2h ₁ )> (L ₁ / 2h ₂ ).

Therefore, according to such a configuration, since the amplification gain can be increased as compared with the first embodiment, the detection sensitivity can be further increased.
The same effect can be obtained even in a configuration in which the acceleration sensor uses a constant elastic material.
(Embodiment 3)

Next, an acceleration sensor according to Embodiment 3 will be described with reference to the drawings. The third embodiment is characterized in that the arrangement position of the vibrating body is different from that of the second embodiment described above in order to further increase the amplification gain. Since other structures are the same as those of the first embodiment, the same functional parts are denoted by the same reference numerals and described with a focus on different parts.
FIG. 3 is a plan view showing the acceleration sensor according to the third embodiment. In FIG. 3, the movable mass portion 30 is provided with notches 37 a to 37 d in which part of the support base portions 25 and 26 and the mass portion base portions 35 and 36 enter the plane direction of the movable mass portion 30.

Each of the notches 37 a to 37 d is provided at the four corners of the movable mass portion 30. The support portion base 25 is inserted into the cutout portion 37a, the support portion base portion 26 is inserted into the cutout portion 37b, the mass portion base portion 35 is inserted into the cutout portion 37c, and a portion of the mass portion base portion 36 is inserted into the cutout portion 37d. It is out. Since the vibrating bodies 50 and 60 are the same as those in the second embodiment (see FIG. 2), the distance h ₃ from the central axis P to the center lines of the main vibrating arms 51 and 61 is the center 41 of the hinge joint 40. Assuming that the distance L ₂ from the center of gravity 42 of the movable mass portion 30 is h ₃ <h ₂ with respect to the distance h _{2 of the second} embodiment, the amplification gain is (L ₂ / 2h ₃ )> (L ₂ / 2h ₂ ).

Here, the distance L ₂ is determined from the central axis P if the size of the notches 37a and 37b and the size of the notches 37c and 37d (particularly the long side) are set to satisfy L ₂ ≧ L _1. In addition to reducing the distance h ₃ to the vibration center line of each of the vibrating arms 51 and 61, the amplification gain can be further increased. Note that the mass m of the movable mass portion 30 can be set so as not to decrease the amount reduced by the cutout portions 37 a to 37 d by slightly extending the movable mass portion 30 at the opposite end surface of the support portion 20.

With such a configuration, the main vibrating arms 51 and 61 can be brought closer to the movable mass unit 30 side. Therefore, the distance h ₃ between the main vibrating arms 51 and 61 from the central axis P is reduced, and the amplification gain is increased. The acceleration sensor 10 can be further reduced in size in the width direction.

Even in the configuration of the third embodiment, the acceleration sensor 10 can be configured by a constant elastic material and a piezoelectric element, and the same effect can be obtained.
(Embodiment 4)

Next, an acceleration sensor according to Embodiment 4 will be described with reference to the drawings. The fourth embodiment is characterized in that a single vibrating body is used as compared with the first to third embodiments described above. The present embodiment can be adapted to the technical ideas of the above-described first to third embodiments. However, the vibration body according to the second embodiment will be exemplified and different parts will be mainly described with common reference numerals. .
FIG. 4 is a plan view showing the acceleration sensor according to the fourth embodiment. In FIG. 4, the acceleration sensor 10 is configured such that one vibrating body 50 is provided along one side surface in the longitudinal direction of the movable mass unit 30.

  The support part 20 and the movable mass part 30 are integrally coupled by hinge joints 40 on their opposing surfaces. The hinge joint 40 passes through the center of gravity 42 of the movable mass portion 30 and is on the central axis P along the longitudinal side surface.

The vibrating body 50 includes a main vibrating arm 51 extending between a support base 25 that is continuous to the support 20 and a mass base 35 that is continuous to the movable mass 30, and the main vibrating arm 51 from the support base 25. The sub-vibration arm 53 extends in parallel along the main vibration arm 51, and the sub-vibration arm 52 extends in parallel from the mass base 35 along the main vibration arm 51.
The support portion base 25 is continuous to the support portion 20 via the connecting portion 21, and the constricted portion 22 is provided in the connecting portion 21, and the width is narrower than the support portion base 25.

  The mass portion base 35 is continuous to the movable mass portion 30 via the connecting portion 31, and the constricted portion 32 is provided in the connecting portion 31, and the width is narrower than that of the mass portion base 35.

  That is, the acceleration sensor 10 of the present embodiment has a form in which the vibrating body 60 shown in the second embodiment (see FIG. 2) is omitted. Moreover, it can be adapted to the configuration of the third embodiment in which the notches 37a and 37c are provided in the movable mass portion 30.

  In the configuration according to the present embodiment, the resonance frequency of the main vibrating arm 51 when no acceleration is applied is set as a reference frequency, and the difference from the resonance frequency when acceleration is applied is set as a detected acceleration value. The size can be measured.

In this way, although the detection sensitivity is slightly inferior to the embodiment that takes the difference in the change in the resonance frequency of the two vibrating bodies, the movable body can be moved by using one vibrating body (one main vibrating arm). Since the strain and stress generated in the main vibrating arm 51 due to the acceleration applied to the mass unit 30 increase, the change in the resonance frequency with respect to the same magnitude of acceleration increases, so that the acceleration detection sensitivity can be increased. In addition, the acceleration sensor can be reduced in size.
(Embodiment 5)

Next, an acceleration sensor according to Embodiment 5 will be described with reference to the drawings. The fifth embodiment is characterized in that two support portions are provided with the movable mass portion interposed therebetween. The present embodiment can be adapted to the technical ideas of the first to third embodiments described above, but will be described by exemplifying an application development having the basic structure of the second embodiment. Common parts are given the same reference numerals.
FIG. 5 is a plan view showing an acceleration sensor according to the fifth embodiment. In FIG. 5, the acceleration sensor 10 includes a movable mass portion 30, support portions 71 and 72 as fixed ends that are arranged so as to face each other with the movable mass portion 30 interposed therebetween, and the movable mass portion 30 and the support portion 71. The vibrating body 60 extends between the vibrating body 50 and the vibrating body 50 extending between the movable mass portion 30 and the support portion 72. The vibrators 50 and 60 have the same configuration as that of the above-described second embodiment (see FIG. 2).

In such a configuration, when acceleration in the + Y direction is applied to the movable mass unit 30, the movable mass unit 30 is displaced in the −Y direction due to the inertia effect. At this time, the main vibrating arm 51 is stretched to generate a tensile stress. On the other hand, the main vibrating arm 61 is contracted to generate a compressive stress. At this time, the resonance frequency of the main vibrating arm 51 decreases and the resonance frequency of the main vibrating arm 61 increases. Then, the magnitude of the acceleration can be detected by comparing the difference in the amount of change in the resonance frequency of each of the main vibrating arms 51 and 61 with the reference resonance frequency to which no acceleration is applied. When acceleration in the -Y direction is applied, the behavior is opposite to that of the main vibrating arms 51 and 61 described above.
Note that the acceleration application directions in the + Y direction and the −Y direction can be recognized by increasing or decreasing the resonance frequency of each of the vibrating bodies 50 and 60.

  According to such a configuration, since the support portions 71 and 72 are disposed on both sides of the movable mass portion 30, the movable mass portion 30 has a pseudo-both fixed structure, and a stable support structure can be realized.

In the configurations of the fourth and fifth embodiments described above, the vibrating bodies 50 and 60 can be configured by a constant elastic material and a piezoelectric element, and similar effects can be obtained.
(Embodiment 6)

  Next, a vibration sensor having the main vibration arm and the sub-vibration arm in the acceleration sensor described above, and a load sensor that applies the technical idea of configuring one main vibration arm among the vibration bodies will be described as a sixth embodiment. . The load sensor includes a force sensor and a pressure sensor. In addition, since the load sensor of this embodiment is the same shape as the acceleration sensor shown in Embodiment 5, detailed description of each structure is abbreviate | omitted with reference to FIG. Further, the description will be made by replacing the acceleration sensor with a load sensor.

The operation of the load sensor will be described with reference to FIG. When a load in the + Y direction is applied to the movable mass portion 30, the main vibrating arm 51 contracts to generate a compressive stress, and the main vibrating arm 61 expands to generate a tensile stress. At this time, the resonance frequency of the main vibrating arm 51 increases and the resonance frequency of the main vibrating arm 61 decreases. The magnitude of the load can be detected by comparing the difference in the amount of change in the resonance frequency between the main vibrating arms 51 and 61 and the reference resonance frequency to which no load is applied. When a load in the −Y direction is applied, the behavior opposite to that of the main vibrating arms 51 and 61 described above is exhibited.
In addition, as for the application direction of the load of + Y direction and -Y direction, it is possible to recognize the direction of acceleration by the increase / decrease in the resonant frequency of each of the vibrating bodies 50 and 60.

  As a modification of the present embodiment, a structure in which one of the support portions 71 and 72 is a fixed end and the other is a movable support portion and a load is applied to the movable support portion is also possible. Specifically, when the fixed end is the support portion 72 and the movable support portion is the support portion 71, when a load in the + Y-axis direction is applied to the support portion 71, the main vibrating arm 51 expands and tensile stress is generated. The main vibrating arm 61 contracts to generate a compressive stress. At this time, the resonance frequency of the main vibrating arm 51 decreases and the resonance frequency of the main vibrating arm 61 increases. The magnitude of the load can be detected by comparing the difference in the amount of change in the resonance frequency between the main vibrating arms 51 and 61 and the reference resonance frequency to which no load is applied. Further, when a load in the −Y direction is applied, the behavior opposite to that of the main vibrating arms 51 and 61 described above is exhibited.

Therefore, when a load is applied to the movable mass portion or the movable support portion, a tensile force or a compressive force acts on the main vibrating arms 51 and 61 to change the resonance frequency. The change in resonance frequency can be detected and the magnitude of the applied load can be measured.
The load sensor having such a configuration can be employed in a precision balance, a force sensor that detects a minute force, a pressure sensor that measures a minute pressure, and the like.
(Embodiment 7)

Next, a load sensor according to the seventh embodiment will be described with reference to the drawings.
FIG. 6 is a perspective view showing a load sensor according to the seventh embodiment. In FIG. 6, a load sensor 100 is integrally formed of a constant elastic material, and is fixed to a base (not shown) in mounting holes 117 and 118 using fixing means such as screws, and a supporting portion. 111, a projecting portion provided at the end of 111, this projecting portion as a fulcrum 113, a lever portion 110 continuous with the projecting portion (fulcrum 113) and having a force point 112 and a point 114 at both ends, and one side surface side of the supporting portion 111 , The support base portion 125 between the force point 112 and the support portion 111, the vibrating body 150 extending via the force point base portion 135, and the tension 114 on the other side of the support portion 111 via the tension piece 115. And a load receiving portion 116 provided.

  The vibrating body 150 includes a main vibrating arm 151 that extends between a support base portion 125 that continues to the support portion 111 via the connecting piece 140 and a power point base portion 135 that continues to the power point 112 via the connecting piece 130. The sub-vibration arms 152 and 153 in the form of cantilevers extending along the main vibration arm 151 from the support base 125 and the force point base 135, respectively, and piezoelectric elements as excitation means provided at least on the main vibration arm 151 160.

  The main vibrating arm 151 is a beam-like vibrating arm having a both-ends support structure, and a secondary portion having a support base portion 125 and a force point base portion 135 as vibration nodes, and a central portion in the longitudinal direction of the main vibration arm 151 as a vibration antinode. And the sub-vibration arms 152 and 153 perform primary bending vibrations in the opposite phase to the resonance vibration of the main vibration arm 151 having the force point base 135 and the support base 125 as nodes of vibration, respectively.

  Each of the sub-vibration arms 152 and 153 substantially matches the vibration node of the main vibration arm 151 and the resonance frequency at the force point base 135 and the support base 125. Accordingly, when the main vibration arm 151 is excited, the sub vibration arms 152 and 153 resonate and vibrate, and the sub vibration arms 152 and 153 do not necessarily have a piezoelectric element.

  Next, the operation of load measurement will be described. When a measurement load is applied to the hook 119 suspended from the load receiving portion 116, the load F is applied to the point 114 via the tension piece 115. The lever 110 applies a force in the direction opposite to the measured load to the force point 112 via the fulcrum 113 to extend the main vibrating arm 151. Tensile stress is generated in the main vibrating arm 151, and the resonance frequency decreases. At this time, the load applied to the load receiving portion 116 is enlarged or reduced and transmitted to the vibrating body 150 via the lever portion 110.

  Specifically, assuming that the distance from the fulcrum 113 to the point 114 is the distance b, the distance from the fulcrum 113 to the force point 112 is the distance a, and the measurement load F, the force applied to the main vibrating arm 151 is a <b At this time, it is amplified by F (b / a) and applied to the main vibrating arm 151. (B / a) is an enlargement rate (or reduction rate). In the present embodiment, the distance a is a distance from the fulcrum 113 to the central axis of the main vibrating arm 151. Therefore, if a <b, the load applied to the main vibrating arm 151 is transmitted with the measured load enlarged to (b / a). In this embodiment, (b / a) is considered an amplification gain.

  In the conventional structure in which the vibrating body is composed of two vibrating arms, since the power point is located at the center of the two vibrating arms, the distance from the fulcrum 113 to the power point 112 is represented by a distance a ′. The relationship between the main vibrating arm 151 and the distance a in the present embodiment is a <a ′. Accordingly, the amplification gain becomes (b / a)> (b / a ′), and the amplification gain becomes large and the detection sensitivity can be increased as in the case of the acceleration sensor described above.

  Further, by using one main vibrating arm 151, the stress generated in the main vibrating arm 151 can be increased, and the detection sensitivity can be improved about twice as compared with the case where there are two vibrating arms. Further, by improving the detection sensitivity, a minute load (force) can be detected with high accuracy.

FIG. 2 is a plan view showing the acceleration sensor according to the first embodiment. FIG. 6 is a plan view showing an acceleration sensor according to a second embodiment. FIG. 6 is a plan view showing an acceleration sensor according to a third embodiment. FIG. 6 is a plan view showing an acceleration sensor according to a fourth embodiment. FIG. 10 is a plan view showing an acceleration sensor according to a fifth embodiment and a load sensor according to the sixth embodiment. FIG. 10 is a perspective view showing a load sensor according to a seventh embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Acceleration sensor, 20 ... Support part, 25, 26 ... Support part base, 35, 36 ... Mass part base, 30 ... Movable mass part, 40 ... Hinge joint, 50, 60 ... Vibrating body, 51, 61 ... Main vibration Arm, 52, 53, 62, 63... Sub-vibration arm.

Claims (13)

An acceleration sensor that is developed in a plane and detects that the resonance frequency of the vibrating body changes by applying acceleration,
A support part as a fixed end, a movable mass part provided alongside the support part,
A vibrating body extending along a longitudinal side surface of the movable mass portion and extending between the support portion and the movable mass portion,
The vibrating body includes one main vibrating arm that extends between a support base that is continuous with the support and a mass base that is continuous with the movable mass, the support base, and the mass base. A sub-vibrating arm extending along the main vibrating arm from each of the
An excitation means provided at least on the main vibrating arm,
An acceleration sensor characterized in that resonance frequencies of the main vibration arm and the sub vibration arm coincide with each other. The acceleration sensor according to claim 1,
An acceleration sensor, wherein the vibrating body is provided on both sides of the movable mass portion, and a difference in resonance frequency change between the vibrating bodies is used as a detected acceleration value. The acceleration sensor according to claim 1,
The acceleration sensor, wherein the vibrating body is provided along one side surface of the movable mass portion. The acceleration sensor according to any one of claims 1 to 3,
An acceleration sensor, wherein the main vibrating arm is disposed between the movable mass portion and the sub vibrating arm. The acceleration sensor according to any one of claims 1 to 4,
An acceleration sensor, wherein a constriction portion is provided between the support portion base portion and the support portion, and between the mass portion base portion and the movable mass portion. The acceleration sensor according to any one of claims 1 to 5,
The acceleration sensor, wherein the movable mass portion includes a notch portion in which a part of the support portion base portion and the mass portion base portion enter the planar direction. The acceleration sensor according to any one of claims 1 to 6,
The acceleration sensor, wherein the support part and the movable mass part are coupled by a hinge joint on a surface where the support part and the movable mass part are opposed to each other. The acceleration sensor according to claim 7, wherein
An acceleration sensor characterized in that a resonance frequency of the movable mass portion having the hinge joint as a vibration fulcrum has a difference that does not affect a resonance frequency of the main vibration arm. The acceleration sensor according to claim 1 or 2,
Two supporting parts are provided across the movable mass part,
One of the vibrating bodies extends between the movable mass portion and one of the support portions,
The acceleration sensor, wherein the other vibrating body extends between the movable mass portion and the other support portion. The acceleration sensor according to any one of claims 1 to 9,
An acceleration sensor, wherein at least the vibrator is made of a single crystal piezoelectric material. The acceleration sensor according to any one of claims 1 to 9,
An acceleration sensor, wherein at least the vibrator is made of a constant elastic material. A load sensor that is developed in a plane and detects that the resonance frequency of the vibrating body changes by applying a load,
A movable mass part, and two support parts provided across the movable mass part,
Two vibrating bodies extending along both sides of the longitudinal side surface of the movable mass portion and extending between the support portion and the movable mass portion,
One of the vibrating bodies extends between the movable mass portion and one of the support portions,
The other vibrating body extends between the movable mass portion and the other support portion;
Each of the two vibrating bodies includes a main vibrating arm extending between a support base that is continuous with the support and a mass base that is continuous with the movable mass, the support base, and the mass base. A sub-vibrating arm extending along the main vibrating arm from each of the
Excitation means provided at least on the main vibrating arm;
A load sensor comprising: A load sensor that detects a change in the resonance frequency of a vibrating body by applying a load,
A support portion fixed to the base, a protrusion provided at an end of the support portion,
Using the protrusion as a fulcrum, a lever part continuous with the protrusion and having a force point and an emphasis at both ends;
The vibrator extending through a connecting piece between the force point and the support;
A load receiving portion provided via a tension piece at the emphasis, and
The vibrating body includes a main vibrating arm extending between a support base that is continuous with the support and a power point base that is continuous with the power point, and the main vibrating arm from each of the support base and the power point base. A sub-vibrating arm extending along the
Excitation means provided at least on the main vibrating arm,
A load sensor, wherein a load applied to the load receiving portion is enlarged or reduced and transmitted to the vibrating body through the lever portion.

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