Servo accelerometer

Abstract

To solve the problem in which in a conventional servo accelerometer, a support part of a pendulum is deformed by an adhesive, a hinge receives stress and the movement of a weight part changes, and sensor accuracy may be reduced.SOLUTION: A servo accelerometer comprises: a pendulum 1 that is displaced according to acceleration; Toluca coils 11, 12 that are provided on the pendulum 1; and yokes 15, 16 that pass therethrough a magnetic flux received by the Toluca coils 11, 12 to form a magnetic circuit. The servo accelerometer supplies a current for controlling the displacement of the pendulum 1 to the Toluca coils 11, 12. A support part 10b of the pendulum 1 is fixed to the yokes 15, 16 by a stress relaxation layer 41 provided on a surface of the support part 10b, and an adhesive layer 40 provided on surfaces of the yokes 15, 16 and in contact with the stress relaxation layer 41. The Young's modulus of the stress relaxation layer 41 is smaller than the Young's modulus of the support part 10b.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a force servo accelerometer using a pendulum. [Background technology]

[0002] A conventional servo accelerometer is equipped with a yoke unit that forms a magnetic circuit and a pendulum that swings with input acceleration. The yoke unit is composed of a permanent magnet that generates magnetic flux, and a pole piece and yoke through which the magnetic flux passes. The pendulum is composed of a weight that is displaced by acceleration, a hinge that suspends the weight, and a support that fixes the weight via the hinge. A torque cup is fixed to the surface of the weight, and a torque coil is wound around the torque cup. In detecting acceleration, the displacement of the weight caused by acceleration is detected by the electrostatic capacitance generated in the gap between the electrodes formed on the pendulum and yoke unit, and is converted and amplified into a voltage and supplied to the torque coil. The displacement of the weight is controlled to zero by the magnetic field in the magnetic gap of the yoke unit and the Lorentz force (restoring force) generated by the current flowing through the torque coil. Since the restoring force at this time is equal to the inertial force, the acceleration can be detected from the torque coil current.

[0003] In vehicles or moving objects that require inertial navigation, such as submarines, aircraft, and rockets, servo accelerometers with a sensor resolution of 10 μG (G: gravitational acceleration) or less are used to calculate the position and speed with high accuracy. In order to obtain high sensor accuracy, it is necessary to suppress unintended deformation of the weight, hinge, and support that constitute the pendulum. When the support is deformed, the hinge fixed to the support is deformed under stress, and the position of the weight changes relative to other parts. These affect the displacement of the weight, and become a cause of error in the servo accelerometer. For example, in the servo accelerometer of Patent Document 1, the support of the pendulum is fixed to the yoke unit with an adhesive. Since the adhesive shrinks as it hardens, the support is deformed under stress, and the sensor accuracy of the servo accelerometer may decrease. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-070356 A Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional servo speedometers, adhesives can distort the pendulum support and stress the hinges, altering the motion of the weight and reducing the accuracy of the sensor. [Means for solving the problem]

[0006] In order to solve the above problems, the servo accelerometer of the present invention is a servo accelerometer comprising a pendulum that displaces according to acceleration, a torque coil provided on the pendulum, and a yoke that forms a magnetic circuit by passing magnetic flux received by the torque coil through its interior, and supplies a current to the torque coil that controls the displacement of the pendulum, characterized in that the support part is fixed to the yoke by a stress relaxation layer provided on the surface of the support part of the pendulum and an adhesive layer provided on the surface of the yoke and in contact with the stress relaxation layer, and the Young's modulus of the stress relaxation layer is smaller than the Young's modulus of the support part. Effect of the Invention

[0007] By reducing the stress that the adhesive exerts on the support, a high-precision servo accelerometer is provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is an exploded perspective view of a servo accelerometer according to the present embodiment. [Diagram 2] 1 is a cross-sectional view of a servo accelerometer according to the present embodiment; [Diagram 3] Front view of the pendulum in the first embodiment [Figure 4] Rear view of the pendulum in Example 1 [Diagram 5] Adhesive layer and stress relaxation layer in Example 1 [Figure 6]Adhesive layer and stress relaxation layer in Example 2 [Figure 7] Yoke unit in the second embodiment [Figure 8] Yoke unit in the second embodiment [Figure 9] Adhesive layer and stress relaxation layer in Example 3 [Figure 10] Adhesive layer and stress relaxation layer in Example 3 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present invention will be described below. Fig. 1 shows the configuration of one embodiment of a servo accelerometer according to the present invention, and is an exploded perspective view of the components. Fig. 2 shows a cross-sectional view of the servo accelerometer. The servo accelerometer is a device in which disk- or cylindrical-shaped parts are stacked, and the central axes of these parts are aligned.

[0010] The pendulum 1 has torque cups 13 and 14, on which torque coils 11 and 12 are wound, fixed to the surface of the base 10 of the pendulum. Fixing methods include adhesion using epoxy adhesives, mechanical fixing using screws, and joining using welding. The torque cups 13 and 14 are suitable for non-magnetic and lightweight materials, such as aluminum alloys, titanium alloys, and resin materials. The torque coils 11 and 12 are made of linear conductive wires made of metal materials, and since the material must have high conductivity, copper, copper alloys, aluminum, and aluminum alloys are suitable. The conductive wires are provided with an insulating layer made of polyurethane, polyester, polyesterimide, and the like on the outer periphery, and a fusion layer made of polyvinyl butyral, polyamide, polyester, and the like on the outer periphery. After the conductive wire 24 is wound around the torque cups 13 and 14, the adjacent fusion layers are bonded to each other, thereby fixing the shape of the torque coils 11 and 12. The fusion layers can be bonded by applying a solvent or by softening and melting the layers by heating.

[0011] Figure 3 shows a front view of pendulum 1, and Figure 4 shows a rear view of pendulum 1. Weight 10a of the tongue-shaped pendulum is located within support part 10b, which is a cylindrical frame. Weight 10a is connected to hinge 10c and supported by support part 10b. When acceleration is generated in the direction of acceleration detection axis 30, thin hinge 10c elastically deforms relative to support part 10b of the pendulum, and weight 10a rotates around the longitudinal center of hinge 10c as an axis.

[0012] The method of manufacturing the weight section 10a, the support section 10b, and the hinge 10c will be explained. A plate is cut out from a base material of metal or glass material, and polished to produce a substrate with the desired thickness and surface accuracy. The surface of the pendulum 1 serves as the reference for the positions of the torque cups 13, 14 and the yokes 15, 16. Therefore, the higher the surface accuracy of the pendulum surface, the higher the assembly accuracy of each part. Next, parts of the base material are removed by cutting, wet etching, laser, etc. to produce the shapes of the weight section 10a, the support section 10b, and the hinge 10c.

[0013] The configuration of the yoke units 2 and 3 will be described. One end of the yokes 15 and 16 is closed by the circular yokes 17 and 18, and the other end, i.e., the open end side, is fixed to the support part 10b. The pole pieces 19 and 20 are provided around the central hole of the open end faces of the yokes 15 and 16, and the cylindrical permanent magnets 21 and 22 are in contact with the pole pieces 19 and 20 and housed inside the yokes 15 and 16. With this configuration, magnetic flux passes through each component, and a magnetic circuit is formed by the yoke unit. Then, annular magnetic gaps are formed between the inner peripheral surfaces of the open ends of the yokes 15 and 16 and the outer peripheral surfaces of the pole pieces 19 and 20, respectively. The seal band 23 is fixed to the outer periphery of the yokes 15 and 16 using an adhesive or the like. As a result, the pendulum 1 and the yokes 15 and 16 are integrated.

[0014] The permanent magnets 21 and 22 are made of neodymium, samarium cobalt, or alnico magnets magnetized in the thickness direction, and the yokes 15 and 16, the circular yokes 17 and 18, and the pole pieces 19 and 20 are made of soft magnetic materials. The permanent magnets 21 and 22, the circular yokes 17 and 18, and the pole pieces 19 and 20 are fixed with adhesive, and the yokes 15 and 16 and the circular yokes 17 and 18 are joined by laser welding.

[0015] The electrode surfaces 15e and 16e on the surface of the yoke and the thin-film electrode 10d of the mass part 10a facing them function as two electrodes of a capacitor. The displacement of the mass part 10a caused by the input of acceleration changes the electrostatic capacitance between the electrodes, and the difference is detected as a voltage and differentially amplified by a servo amplifier (not shown). Then, a servo current based on the electrostatic capacitance difference is supplied to the pair of torque coils 11 and 12. The electric signal detecting the electrostatic capacitance and the servo current flow to the servo amplifier via the thin-film electrode 10d, the thin-film wiring 10e formed on the surface of the hinge 10c and the support part 10b, the conductive wire 24, and the terminal 25.

[0016] When acceleration is applied in a direction perpendicular to the plane of the pendulum 1 (acceleration detection axis 30), the weight section 10a that receives the acceleration is displaced, but the displacement returns to the neutral point due to the Lorentz force generated by the torque current and the magnetic field in the magnetic gap, and the forces generated by the acceleration, i.e., the inertial force and the Lorentz force, are balanced. At this time, the magnitude of the torque current directly corresponds to the magnitude of the acceleration along the acceleration detection axis, so acceleration can be detected.

[0017] The conductive wire 24 and the terminal 25 are mainly made of a material with high conductivity, for example, a single metal such as copper, aluminum, or iron, or an alloy thereof. Copper is particularly suitable because of its high electrical conductivity. However, since copper is easily oxidized, it is preferable to form a thin Au film on the surface to prevent oxidation. Methods for fixing the terminal 25 and the conductive wire 24 include wire bonding, soldering, and laser welding.

[0018] Example 1 Fig. 5 shows a cross section of the portion where support portion 10b is fixed to yokes 15 and 16. Fig. 5 is a schematic diagram of the accelerometer cut along line AA in Fig. 3, and showing surrounding support portion 10b and yokes 15 and 16. A stress relaxation layer 41 is provided on the surface of support portion 10b, and an adhesive layer 40 made of an adhesive is provided between stress relaxation layer 41 and the yoke. Two adhesive layers 40 and two stress relaxation layers 41 are provided, similar to yokes 15 and 16, and are arranged symmetrically around the support portion 10b in the thickness direction of support portion 10b.

[0019] The adhesive may be made of any material, including, for example, an epoxy adhesive, an acrylic adhesive, a cyanoacrylate adhesive, a urethane adhesive, and a silicone adhesive. The outgassing emitted by the cured adhesive layer may adhere to the inside of the servo accelerometer as fine particles, which may cause a malfunction. In addition, the outgassing changes the composition of the gas filled inside the servo accelerometer, which changes the flow resistance (squeeze film damping) generated in the gap between the pendulum and the yoke, changing the movement of the pendulum and reducing the sensor accuracy of the servo speedometer. The less outgassing the adhesive used in a high-precision servo speedometer is, the more preferable it is. For example, in a high-precision servo accelerometer with a resolution of 10 μG used for inertial navigation, the mass loss ratio (TML: Total Mass Loss) is 1% or less, and the re-condensed volatile condensable materials (CVCM: Collected Volatile Condensable Materials) is 0.5% or less. When the adhesive hardens and becomes an adhesive layer 40, the adhesive layer applies stress to the support portion and deforms it due to the change in volume. If the deformation is large, the hinge 10c is subjected to stress from the support portion 10b and deforms significantly, and the weight portion 10a is pressed against the electrode surfaces 15e and 16e, so that the weight portion 10a does not rotate even when accelerated. In other words, the accelerometer does not work properly. Even if the deformation is small, the internal stress and deformation of the hinge change the rotational motion of the weight portion, which reduces the sensor accuracy of the servo speedometer. Furthermore, the posture of the weight portion 10a suspended on the hinge 10c moves from the ideal position, and the distance between the thin film electrode 10d of the pendulum 1 and the electrode surfaces 15e and 16e varies. The variation in the distance between the thin film electrode 10d and the electrode surfaces 15e and 16e makes the squeeze film damping that the weight portion 10a receives when accelerated unstable, causing minute vibrations in the rotational motion of the weight portion. This vibration becomes a noise component in the torque coil current and reduces the sensor accuracy of the servo speedometer.

[0020] The stress relaxation layer 41 is provided on the surface of the support portion 10b, contacts the adhesive layer 40, and has a smaller Young's modulus than the support portion 41. The contact surface between the support portion 10b and the stress relaxation layer 41 is wider than the contact surface between the adhesive layer 40 and the stress relaxation layer 41, and the adhesive layer is not in direct contact with the support portion. The strain that the adhesive layer 40 imparts to the support portion 10b is reduced by sandwiching the stress relaxation layer 41, which is more easily deformed than the support portion 10b, and deformation of the support portion 10b is suppressed. The Young's modulus is measured at a temperature of 25°C using a nanoindentation method in accordance with ISO14577.

[0021] Although the yokes 15 and 16 shown in FIG. 5 each have an adhesive layer 40 on their surfaces, the servo accelerometer can be assembled with only the adhesive layer 40 on the surface of the yoke 15. For example, after the support 10b is fixed to the yoke 15 with an adhesive, the open end side of the yoke 16 is placed over the support and pressed against the support 10b, and the seal band 23 is fixed to the yokes 15 and 16. The yoke 16 applies force to the support 10b, and the support 10b is fixed to the yoke 16 by static friction. In this method, the fixing portion of the support 10b, which requires the adhesive layer 40, is one-sided, and compared to the case where the support 10b and the yokes 15 and 16 are fixed using the adhesive layer 40, the amount of adhesive used can be halved, and the effect of stress due to the adhesive layer 40 can be reduced. In addition, in the process of connecting the terminal 25 of the yoke unit 2 and the wiring 10e of the pendulum with the conductive wire 24, for example, in a wire bonding or soldering process, the support 10b is fixed to the yoke 15 with an adhesive, so that the support 10b does not shift in position relative to the terminal 25. In other words, it is possible to suppress the misalignment of parts that would hinder processing, and obtain a joint with high reliability. On the other hand, since the yoke 16 does not have a terminal or conductive wire, it is not necessarily required to fix it with an adhesive layer. In addition, although the servo accelerometer shown in FIG. 5 has two yoke units, the same applies to a servo accelerometer that uses only one yoke unit.

[0022] The material of the pendulum 1 is quartz glass. The linear expansion coefficient of quartz glass is about 0.5×10-6 / K, which is about 1 / 10 of that of general commercial metals. Therefore, the change in the motion of the weight part 10a due to temperature change is small, and the deformation of the pendulum can be suppressed. Furthermore, since quartz glass is an insulating material, it is not conductive to the thin film wiring 10e formed on the surface of the pendulum 1, so that the sensor accuracy is not deteriorated due to leakage current. Furthermore, since it is a non-magnetic material, it does not change the magnetic field in the magnetic gap formed by the yoke units 2 and 3. A pendulum made of quartz glass is suitable for a servo accelerometer, and it is particularly easy to obtain a resolution of 10 μG, which is necessary for inertial navigation.

[0023] The material of the stress relaxation layer may be at least one selected from, for example, Au and Au alloys, Al and Al alloys, and Mg and Mg alloys. Among them, Au and Au alloys are preferred from the viewpoints of chemical stability and ductility, and a thin gold film of less than 1 μm is more suitable from the viewpoints of Young's modulus and economic efficiency.

[0024] The Young's modulus of an Au ingot (bulk material) produced by typical metallurgy is about 74 GPa, which is equal to or greater than the 70 GPa of quartz glass. On the other hand, the Young's modulus of a thin gold film less than 1 μm thick produced by microfabrication techniques such as physical vapor deposition is 20 to 50 GPa. The crystal structure of a thin Au film is amorphous, or polycrystalline with crystallite sizes of only a few nanometers. Compared to bulk materials with large crystal sizes, the resistance to deformation against strain is smaller, so the Young's modulus tends to be smaller. This tendency is also true for Au alloys, Al and Al alloys, and Mg and Mg alloys.

[0025] Au and Au alloys are more ductile than other metal materials. Even if the stress relief layer is subjected to high stress locally at the interface with the adhesive layer, the stress relief layer undergoes plastic deformation, absorbing the strain and reducing the stress on the support.

[0026] Example 2 Figure 6 shows the configuration of another embodiment of a servo accelerometer according to the present invention. Figure 6 is a schematic diagram of the accelerometer cut along line AA in Figure 3, with the peripheral support portion 10b and yokes 15 and 16 extracted. Figures 7 and 8 show the open end sides of the yoke units 2 and 3. The surfaces of the yokes 15 and 16 have grooves 15a and 16a and are provided with an adhesive layer 40a, with the upper surface of the adhesive layer 40a in contact with the stress relaxation layer 41. The adhesive layers 40a are provided in correspondence with the grooves 15a and 16a of the same shape and are arranged symmetrically.

[0027] Since the support 10b is fixed between the yokes 15 and 16, the support 10b receives forces in opposite directions from the opposing yokes 15 and 16 through the adhesive layer 40a and the stress relaxation layer 41. Ideally, the support 10b is symmetrical at the center of the thickness of the support, but if the position of the adhesive layer 40a is shifted due to inconsistencies in the adhesive application process, the base point of the two opposite forces that the support 10b receives from the adhesive layer 40a shifts, and the support 10b receives a bending moment and deforms. The same can be said about the stress that the adhesive layer 40a applies to the support 10b due to the hardening and shrinkage of the adhesive. In addition, if the deformation amount of the support 10b due to the adhesive layer 40a differs for each fixed point, the support 10b is fixed at an angle to the yokes 15 and 16, and the attitude of the pendulum 1 relative to the yokes 15 and 16 is tilted. To suppress deformation of the support portion, the adhesive layer 40a and the stress relief layer 41 must be located symmetrically about the center of the thickness of the support portion 10b, and the size of the adhesive layer 40a, that is, the amount of adhesive applied, must be constant.

[0028] In the above embodiment, since the grooves 15a and 16a are filled with adhesive, the positional deviation and the variation in the amount of application of the adhesive layer 40a depend on the dimensional accuracy of the grooves 15a and 16a and the assembly accuracy of each part. These can be controlled by processing technology and assembly technology, but in the method of applying a liquid adhesive to the surfaces of the yokes 15 and 16 and the support part 10b, the size and position of the adhesive layer 40a change greatly depending on the surface tension of each part and the positional relationship of the parts, so it is difficult to control. On the other hand, if the grooves 15a and 16a can be processed with high precision and the yokes 15 and 16 can be assembled with high precision, the positional deviation of the two adhesive layers 40a located symmetrically at the center of the thickness of the support part 10b will be small. As a result, the rotational moment that the support part 10b receives through the adhesive layer 40a will be small, and the deformation of the support part 10b will also be small. Furthermore, since the thickness of the adhesive layer 40a is uniform, the amount of deformation at each fixed point will be equal, and the attitude of the pendulum 1 relative to the yokes 15 and 16 will not easily tilt. Similarly, if the two stress relaxation layers 41 are located symmetrically about the thickness of the support portion 10b, the rotation moment applied to the support portion 10b is reduced.

[0029] In thin film production methods such as physical vapor deposition, energy is applied to the atoms of the raw material, causing them to deposit on the surface of the base material. A thin film is formed on the surface of the base material when multiple atoms that adhere to the surface of the base material aggregate and crystallize. The base material is deformed by the thermal energy it receives from the atoms, and by the stress caused by the aggregation and crystallization of the atoms. It is possible to reduce the stress applied to the base material by adjusting the processing conditions, but some residual stress still remains.

[0030] The stress relaxation layers 41 symmetrically arranged on the support portion 10b are each manufactured using the same material and processing conditions. Since the stresses applied to the support portion 10b by each stress relaxation layer 41 are equal, the deformation of the support portion 10b is balanced in the thickness direction. Therefore, compared to the case where the stress relaxation layers 41 are formed asymmetrically arranged, the deformation of the support portion 10b in the thickness direction is less. Since the ring-shaped support portion 10b is more likely to deform in the thickness direction than in the planar direction, the deformation suppression effect of the symmetrically arranged stress relaxation layers 41 is large.

[0031] Since the grooves 15a and 16a are filled with adhesive, the amount of adhesive used is greater than in the conventional servo accelerometer. When only the effect of one adhesive layer 40a is considered, the stress applied to the support portion 10b by the adhesive layer 40a increases, and therefore more stress relief layers 41 are required to relieve the stress.

[0032] Example 3 FIG. 9 shows the configuration of another embodiment of the servo accelerometer according to the present invention. FIG. 9 is a schematic diagram of the accelerometer cut along line BB in FIG. 3, and showing the surrounding support parts, yokes 15, 16, and thin-film electrode 10d. The thickness of the stress relaxation layer 41 is 5 to 30 μm, and the surfaces of the yokes 15, 16 facing the surfaces of the support parts 10b are not convex from the electrode surfaces 15e, 16e, and at least a part of the contact surfaces 15b, 16b between the adhesive layer 40a and the yokes 15, 16 is a flat surface that is at the same height as the electrode surfaces 15e, 16e. The distance between the surface of the support part 10b facing the flat surface and the flat surface is equal to the sum of the height of the damping gap 44 provided in the space between the thin-film electrode 10d and the electrode surfaces 15e, 16e and the thickness of the thin-film electrode 10d.

[0033] If the heights of the electrode surfaces 15e, 16e and the adhesive layer 40a at which the yokes 15, 16 are in contact are different, the parallelism between the surfaces is increased because each surface is machined separately. On the other hand, the flat surface portions of the contact surfaces 15b, 16b are at the same height, so the flatness and parallelism can be reduced by simultaneous machining. Similarly, if the thicknesses of the support portion 10b and the weight portion 10a are made uniform, the flatness and parallelism of each surface can be reduced. And, since the stress relaxation layer 41 and the thin-film electrode 10d are fabricated by a microfabrication technique typified by physical vapor deposition, it is possible to control the thickness with high precision. That is, the damping gap between the thin-film electrode 10d and the electrode surfaces 15e, 16e can be formed with high precision. And, the non-uniformity of the flow resistance caused by the gap deviation is reduced, and high sensor precision can be obtained.

[0034] The thickness of the adhesive layer 40a is 100 nm or more and less than 1 μm. The smaller the thickness of the adhesive layer 40a, the less the stress applied to the support portion, but the smaller the shear strength, so an appropriate thickness is required. A servo accelerometer for a vehicle or moving object that requires inertial navigation, such as a submarine, an aircraft, or a rocket, requires an impact resistance of at least 50 G. The servo accelerometer described in this embodiment is a cylinder with a diameter of about 1 inch, weighs 20 g to 90 g, and has an input acceleration of at least ±20 G. At such servo acceleration, the thickness of the adhesive layer 40a that does not separate the support portion 10b from the yokes 15 and 16 is required to be at least 100 nm. On the other hand, if the adhesive layer 40a is thick, the thickness of each adhesive layer 40a varies greatly, so that the support portion 10b is fixed at an angle to the yokes 15 and 16, and the parallelism between the thin film electrode 10d and the electrode surface 15e decreases. If the parallelism between them decreases, the damping gap 44 becomes non-uniform, but since the damping gap 44 is 5 to 30 μm, the effect of thickness variations of less than 1 μm in the adhesive layer 40a is negligibly small. Furthermore, the thickness of the stress relaxation layer 41 is 5 to 300 times that of the adhesive layer 40a, and has a thickness that can sufficiently relax the stress caused by the cure shrinkage of the adhesive layer 40a.

[0035] One form of the stress relaxation layer is shown in FIG. 10. An adhesive layer 42 is provided at the interface between the stress relaxation layer 41 and the support portion 10b, and an anti-oxidation layer 43 covers the surface of the stress relaxation layer 41 that is not in contact with the adhesive layer 42. The adhesive layer 42 may be at least one selected from Ti and a Ti alloy, Cr, Ni and a Ni alloy. The stress relaxation layer 41 may be at least one selected from Al and an Al alloy, Mg and a Mg alloy. The anti-oxidation layer 43 is Au or an Au alloy. The adhesive layer has a thickness of 200 nm or less, and the anti-oxidation layer 43 has a thickness of less than 1 μm.

[0036] Although Au or an Au alloy is excellent for the stress relaxation layer 41, the manufacturing cost is high when a thin film structure having a thickness of 5 to 30 μm is produced. In the servo acceleration of the present invention, high economic efficiency can be obtained by using an inexpensive commercial alloy for the stress relaxation layer 41. On the other hand, since Au has a lower chemical stability than Au and is therefore more susceptible to oxidation, the stress relaxation layer 41 has an anti-oxidation layer 43 on its surface.

[0037] The adhesion between glass materials and metal thin films tends to be low. At least one adhesion layer selected from Ti and Ti alloys, Cr, Ni and Ni alloys, which is produced by the above-mentioned film formation method, can form a chemically stable and high-strength mixed layer at the interface with the quartz glass, which is the pendulum material. For example, in the case of titanium, it bonds with oxygen atoms and silicon atoms of the quartz glass to form an amorphous Si-Ti mixed layer or an amorphous Si-O-Ti mixed layer at the interface. These are in a metastable state and have high strength, so titanium and quartz glass can obtain strong adhesion. [Explanation of symbols]

[0038] 1 pendulum 2, 3 Yoke unit 10 Pendulum base 10a Pendulum weight 10b Pendulum support 10c Pendulum Hinge 10d Pendulum Thin Film Electrode 10e Thin film wiring formed on the surface of the hinge, support, or weight 10f Mounting Pad 15, 16 York 15a, 16a Yoke groove 15b, 16b Contact surface between yoke and adhesive layer 15e, 16e Electrode surface of yoke 17, 18 Circular yoke 23 Seal Band 24 Conductive Wire 25 Terminals 30 acceleration sensing axes 40 Adhesive layer 40a Adhesive layer provided in groove 41 Stress relief layer 42 Adhesion layer 43 Antioxidant layer 44 Damping Gap

Claims

1. A servo accelerometer comprising: a pendulum that displaces in response to acceleration; a torque coil provided on the pendulum; and a yoke that forms a magnetic circuit by passing magnetic flux received by the torque coil through the inside of the yoke, the servo accelerometer supplying a current to the torque coil that controls the displacement of the pendulum, a stress relaxation layer provided on a surface of the support portion of the pendulum; An adhesive layer is provided on the surface of the yoke and in contact with the stress relief layer, The support is fixed to the yoke, 13. A servo accelerometer, comprising: a stress relaxation layer having a Young's modulus smaller than that of the support portion.

2. The surface of the yoke has a groove. The adhesive layer is disposed in the groove; Two of the yokes and two of the stress relief layers are provided, 2. The servo accelerometer according to claim 1, wherein the support members are arranged symmetrically about the support member in a thickness direction of the support member.

3. the pendulum has thin-film electrodes that function as electrodes of a capacitor; the yoke has an electrode surface that functions as another electrode of the capacitor; the thickness of the weight part of the pendulum having the thin-film electrode on a surface thereof is equal to the thickness of the support part, The thickness of the stress relaxation layer is 5 to 30 μm, the surface of the yoke facing the surface of the support portion does not protrude from the electrode surface, At least a part of a contact surface between the adhesive layer and the yoke is a flat surface that is flush with the electrode surface, 2. The servo accelerometer according to claim 1, wherein a distance between the surface of the support portion facing the flat surface and the flat surface is equal to a sum of a height of a damping gap provided in a space between the thin-film electrode and the electrode surface and a thickness of the thin-film electrode.

4. The contact surface between the support portion and the stress relaxation layer is wider than the contact surface between the adhesive layer and the stress relaxation layer, and the adhesive layer is not in contact with the support portion.

2. The servo accelerometer of claim 1.

5. The thickness of the adhesive layer is 100 nm or more and less than 1 μm.

2. The servo accelerometer of claim 1.

6. an adhesion layer is provided at an interface between the stress relaxation layer and the support portion, The stress relaxation layer has an antioxidant layer on its surface.

2. The servo accelerometer of claim 1.

7. The support is made of quartz glass.

2. The servo accelerometer of claim 1.

8. The stress relaxation layer is at least one selected from the group consisting of Au and Au alloys, Al and Al alloys, Mg and Mg alloys. A servo accelerometer according to any one of the preceding claims.

9. The thickness of the stress relaxation layer is less than 1 μm.

9. The servo accelerometer of claim 8.

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