Servo type vibration detector and method for assembling the servo type vibration detector

Abstract

To solve the issue that improvement of performance of an existing servo-type acceleration sensor is limited since the sensor had to be formed in a small range that satisfies the three contradicting objectives of (1) reduction of a resonance peak, (2) increase of responsivity, and (3) increase of the sensor sensitivity.SOLUTION: Since a mechanical attenuation action due to a dynamic fluid pressure in a gap part between electrodes can be reduced by forming a circulation hole or a circulation groove in a relative moving surface of electrodes, at least one of the groove and the hole is formed so that the proportional gain KP of a servo amplifier, an inertia mass m, and the attenuation ratio ζ0 determined by the attenuation coefficient C satisfy the relation of 0.2≤ζ0≤0.6. In that way, the sensor sensitivity can be increased, and the resonance peak value and the responsivity of the sensor (phase delay) can be contained in an acceptable range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vibration sensor or vibration isolation control device that detects signals over a wide frequency band of the acceleration, absolute velocity relative to inertial space, or absolute displacement of a control object that is supported on a foundation and vibrates due to external disturbances. [Background technology]

[0002] 1. Trends in the world The use of vibration control to block and suppress minute vibrations is becoming more widespread in various fields, including semiconductor manufacturing processes, liquid crystal manufacturing processes, and precision machining. The fine processing and inspection equipment used in these processes, such as scanning electron microscopes and semiconductor exposure equipment (steppers), require strict vibration tolerance conditions to ensure equipment performance. In the future, as products become increasingly highly integrated and miniaturized, processing processes will become faster and equipment will become larger, and vibration tolerance conditions will tend to become increasingly strict.

[0003] 2. Disturbances that the vibration isolation system should remove In recent years, active vibration control technology has become widespread, in which control devices are controlled by creating control signals based on displacement, velocity, and acceleration information from vibration sensors placed at multiple locations on the structure to be vibration-controlled (for example, a precision vibration isolation table).

[0004] FIG. 26 shows a model diagram of a conventional active vibration isolation table. This active vibration isolation table is well known, as described in Patent Documents 1 and 2. A plurality of pairs of pneumatic actuators (502a, 502b) for supporting a surface plate 501 are arranged on a floor 500. A precision device (not shown) is mounted on this surface plate 501. Reference numeral 503 denotes an acceleration sensor for detecting the vertical and horizontal acceleration of the surface plate 501, and reference numeral 504 denotes an acceleration sensor for detecting the acceleration of the floor 500 (the vibration state of the foundation). Reference numerals 505a and 505b denote displacement sensors for detecting the vertical and horizontal relative displacement of the surface plate 501 with respect to the floor 500, respectively. Output signals from these sensors are input to a controller 506. A servo valve 508 controlled by the controller 506 is connected to the pneumatic actuator 502a via piping 507. This servo valve 508 adjusts the flow rate of compressed air supplied to and exhausted from the pneumatic actuator 502a, thereby controlling the internal pressure of the actuator 502a and driving the pneumatic actuator.

[0005] Disturbances to be removed by a vibration isolation system are roughly divided into ground motion disturbances caused by vibrations of the installation floor and direct-acting disturbances input from above the vibration isolation table.

[0006] Sources of vibration that cause ground disturbances include walking vibrations caused by people moving about, which are 1 to 3 Hz, motors such as those for air conditioners, which are 6 to 35 Hz, and the resonance points of floors and walls being around 10 to 100 Hz. High-rise, seismically isolated buildings have a natural frequency of around 0.2 to 0.3 Hz. Wind sway also causes buildings to generate micro-vibrations of 0.1 to 1.0 Hz. Therefore, vibration isolation tables are required to not only suppress high-frequency vibrations, but also to remove low-frequency vibrations.

[0007] If the vibration isolation table is equipped with, for example, a positioning stage 509 as a source of high-frequency vibration caused by linear disturbance, the structure including the vibration isolation table will be struck by the stage's acceleration / deceleration operation and will oscillate due to the drive reaction force. The performance of the stage cannot be maintained unless the vibration caused by this strike and the oscillating due to the drive reaction force are suppressed. In short, a vibration isolation device is required to have the function of both "isolating" from ground disturbances and "damping" from linear disturbances.

[0008] 3. Role of vibration sensors in active vibration isolation systems Active vibration control employs a control method based on state feedback. This is a method of controlling a control device based on acceleration, velocity, and displacement information from vibration sensors placed at multiple locations on the structure to be vibration controlled. In order to obtain vibration isolation performance over a wide frequency range, for example, acceleration signals are used to control state quantities above 10 Hz, velocity signals are used to control state quantities between 1 and 10 Hz, and displacement signals are used to control state quantities below 1 Hz. For example, a. If acceleration feedback is performed using a signal from an acceleration sensor (such as acceleration sensor 403 in Figure 44) placed on the base plate 401, this is equivalent to an increase in mass M, and has the effect of lowering the natural frequency and reducing the resonance peak. b. If the signal from the acceleration sensor (403 in FIG. 44) is converted into an absolute velocity or absolute displacement signal and feedback or feedforward is applied, the vibration isolation performance can be significantly improved over a wide frequency range. c. By using the signal from the acceleration sensor (404 in Figure 38) placed directly below the surface plate 401 and converting the signal into an absolute velocity or absolute displacement signal and similarly applying feedforward, it is possible to improve vibration isolation performance over a wide frequency range.

[0009] To control the above bc, velocity and position information relative to inertial space is required. Since an acceleration sensor can measure acceleration relative to inertial space, attaching an acceleration sensor to the controlled object makes it possible to detect the acceleration applied to the controlled object. Therefore, conventional active vibration isolation systems employ a method in which the velocity signal is obtained by integrating the output of the acceleration sensor once, and then the displacement signal is obtained by integrating it twice.

[0010] 4. Basic configuration and detection principle of acceleration sensors Figure 27 is a model diagram showing the basic configuration and detection principle of a capacitance-type acceleration sensor. 301 is a main body that houses each component of the sensor, 302 is a mass, 303 is a spring that mechanically supports mass 302 with respect to vibration measurement surface A, and 304 is a damper. Mass 302 also serves as the movable electrode of the capacitance-type sensor. 305 is a fixed electrode located on the opposite side of the movable electrode (mass 302), and 306 is the gap between the two electrodes.

[0011] Reference numeral 307 denotes an electromagnetic actuator that drives the mass body 302 in a direction perpendicular to the vibration measurement surface A. Since the capacitance C is determined by the size of the gap in the gap portion 306, by measuring this capacitance C, it is possible to detect the relative displacement UX, which is the difference between the absolute displacement U of the ground motion and the absolute displacement X of the mass body. A servo circuit 310 (shown by a two-dot chain line) outputs a gain K P The amplifier 312 amplifies the signal by a proportional amplifier.

[0012] The detection principle of the acceleration sensor will be explained below using mathematical expressions. The mass of the mass body 302 is m, the spring constant of the mechanical spring 303 supporting the mass body is k, the damping coefficient of the damper 304 is c, and the driving force of the actuator 307 is F=A f If we set i0, the following equation of motion holds:

[0013]

number

[0014] The proportional gain constant K is set so that the relative displacement ux becomes zero. P The amplifier controls the actuator current i0.

[0015]

number

[0016]

number

[0017] Proportional gain constant K P If is sufficiently large and the first and second terms can be ignored compared to the third term on the right-hand side of equation (3), then

[0018]

number

[0019] If the current i0 flowing through the actuator is detected from equations (2) and (4), the acceleration of the mass body 302 can be approximately calculated.

[0020] 5. Specific structure of conventional servo-type acceleration sensors Figure 28 is a front cross-sectional view showing an example of a specific structure of a conventional capacitance-type acceleration sensor [Patent Document (3)], which is configured using the basic configuration and detection principle shown in Figure 27. Reference numeral 11 denotes a permanent magnet, 12 denotes a pole piece portion, 13 denotes a pole piece protrusion portion, 14 denotes a permanent magnet side yoke material, 15 denotes a coil side yoke material, 16a denotes a force coil, 16b denotes a calibration coil, 17 denotes a coil bobbin, 18 and 19 denote coil bobbin support members made of non-magnetic and non-conductive material, 20 denotes a front side disc-shaped spring, 21 denotes a rear side disc-shaped spring, 22 denotes a front side connecting member between the front side disc-shaped spring 20 and the coil side yoke material 15, and 23 denotes a rear side connecting member between the rear side disc-shaped spring 21 and the coil side yoke material 15.

[0021] Reference numeral 24 denotes a movable electrode, 25 denotes a fixed electrode, 26 denotes a front panel, 27 denotes a center plate, and 28 denotes a fastening member for fastening the fixed electrode 25 and the front panel 26 together.

[0022] A radial magnetic gap 29 is formed between the outer periphery of the pole piece 12 and the inner periphery of the coil-side yoke material 15. 29a is the permanent magnet-side gap, and 29b is the yoke material-side gap. A closed-loop magnetic circuit is formed by the permanent magnet 11 → pole piece 12 → magnetic gap 29 → coil-side yoke material 15 → permanent magnet-side yoke material 14. When current flows through the force coil 16a located in the space of the magnetic gap 29, a Lorentz force is generated that moves the movable electrode 24 in the axial direction. 30 is the gap formed by the movable electrode 24 and the fixed electrode 25. Since the capacitance C is determined by the size of the gap 30, measuring the capacitance C allows the detection of relative displacement UX, which is the difference between the absolute displacement U of the ground motion and the absolute displacement X of the mass body. The servo circuit is composed of a displacement detector 31, an amplifier 32, and a driver 33. The amplifier 32 and driver 33 convert the relative displacement signal UX into a gain K. P The proportional gain constant K is set so that the relative displacement ux becomes zero. P The current i0 of the actuator is controlled by this amplifier. By detecting the current i0 flowing through the force coil 16a, the acceleration acting on the movable part can be determined, as described above. [Prior art documents] [Patent documents]

[0023] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-283966 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-155038 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-205284 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-96509 Summary of the Invention [Problem to be solved by the invention]

[0024] When applying a servo-type acceleration sensor to an active vibration isolation table, the following three conditions must be satisfied simultaneously. (1) The resonance frequency is sufficiently high and the resonance peak value is small. (2) Improved response (reduced phase delay in the frequency range below the resonance point) (3) Obtaining high sensor sensitivity

[0025] The resonance frequency of passive element devices such as pneumatic actuators that are the control targets of an active vibration isolation table is typically f0 = 4 to 6 Hz. In order to control these passive elements, the control range of the active vibration isolation table must be 0 to 50 Hz. To obtain sufficient control performance within this control range, high responsiveness is required for the control elements other than the pneumatic actuators that are the control targets (accelerometers, servo valves). As an evaluation index based on many empirical values, it has been considered ideal for an acceleration sensor to have a phase delay (responsiveness) of Δθ≦10° at f=100 Hz.

[0026] In (1) above, the reason why a high resonance frequency f0 is required for the acceleration sensor is that the higher the resonance frequency f0, the smaller the phase delay in the frequency range below the resonance point, which is the evaluation index in (2) above. However, the resonance frequency of a servo-type acceleration sensor is determined by the mass m of the moving part and the servo stiffness K that provides a restoring force to the actuator, as shown in the following equation:

[0027]

number

[0028] Servo stiffness K is proportional to the control gain. The magnitude of this control gain is limited by delay elements such as the coil inductance, in addition to the second-order delay elements due to the mass m and stiffness K. For this reason, the resonant frequency of servo-type acceleration sensors has usually been limited to f0 = 350 to 500 Hz.

[0029] In the above (1), assuming that the range of the resonance frequency f0 of the acceleration sensor (f0 = 350 to 500 Hz) cannot be changed significantly, it is desirable to make the resonance peak value at the resonance point as small as possible. The reason for this is that the smaller the resonance peak value, the larger the gain margin that determines the stability margin of the control system, and the larger the control gain that determines the servo stiffness can be. The greater the damping, the smaller this resonance peak value can be. However, if the damping is too large, the responsiveness will decrease and the phase lag at f = 100 Hz will increase. Therefore, the above (1) and (2) are in a contradictory relationship (a trade-off relationship).

[0030] In the above (3), the most effective way to obtain high sensor sensitivity is to set the capacitance of the displacement detector to a large value. As is well known, the area of ​​two parallel-placed conductive plates is A, the gap is d, the dielectric constant is ε0, and the relative dielectric constant of air is ε. r When this is done, the capacitance C S teeth

[0031]

number

[0032] That is, the narrower the gap between the electrodes d and the larger the electrode area A, the greater the capacitance C S is large, improving the sensor sensitivity. In order to meet the demand for improved sensor sensitivity, experiments were conducted to determine sensor performance using the conventional capacitance-type acceleration sensor shown in Figure 28, with the inter-electrode gap d narrowed sufficiently, for example, from 30 to 15 μm. In this case, the sensor output is expected to double. However, it was found that this measure deteriorates the dynamic characteristics of the sensor to the point where it cannot function properly as a servo-type sensor. The reason for this is as follows: the damping force applied to the moving parts of a servo-type acceleration sensor is proportional to the damping constant (damping coefficient) D in the following equation.

[0033]

number

[0034] As mentioned above, conventional servo-type acceleration sensors have had to be designed within a narrow range of requirements, namely, to simultaneously satisfy three conflicting objectives: (1) reduction of resonance peaks, (2) improvement of responsiveness (reduction of phase lag), and (3) improvement of sensor sensitivity. This has resulted in limitations on performance improvement. The origin of the idea behind this invention was the search for a way to resolve these three trade-offs and resolve each objective separately. In the case of capacitive servo-type acceleration sensors, due to their structural characteristics, we focused on the fact that the damping action that governs the three characteristics above is the dynamic fluid pressure (squeeze pressure) generated in the gap between the electrodes.

[0035] Thus, the servo type vibration detector of the first invention of the present application comprises a housing which is a fixed member, a movable member provided so as to be movable in a predetermined direction relative to the housing, an elastic member which supports the movable member so as to be disposed with a gap in relation to the housing, a displacement detection unit which detects displacement of the movable member in the predetermined direction, driving means which is driven by a servo amplifier so as to generate a force which returns the movable member to the original position when a relative displacement of the movable member from the original position is detected by the displacement detection unit, a movable side electrode provided on the movable member, and a spring which faces the movable side electrode and is connected to the housing. and a fixed electrode provided on the movable side, the displacement detection unit is configured to detect the capacitance formed in the gap between the movable electrode and the fixed electrode, and a groove or hole having a flow path connected to the atmosphere is formed on the relative moving surface between the movable electrode and the fixed electrode to reduce the damping effect due to dynamic fluid pressure generated in the gap, and the groove or hole is formed so as to satisfy 0.2≦ζ0≦0.6, where ζ0 is the damping ratio calculated from the dynamic characteristics of the sensor output when the vibration detector body is subjected to a sweep vibration.

[0036] Specifically, the present invention focuses on the fact that the drawbacks of measures to improve sensor sensitivity are due to the dynamic pressure (squeeze pressure) of the air-viscous fluid generated in the narrow gap between electrodes. This squeeze pressure can be reduced by forming a groove or multiple holes on the electrode surface that communicate with the atmosphere. By utilizing the fact that this reduction in squeeze pressure reduces the damping effect, sensor sensitivity can be improved without increasing the damping effect by narrowing the gap between electrodes or increasing the electrode outer diameter. However, assuming that the range of the acceleration sensor's resonance frequency f0 (f0 = 350 to 500 Hz) cannot be significantly changed, it is desirable to satisfy the above two requirements: (1) minimize the resonance peak value at the resonance point, and (2) increase the sensor's responsiveness. This is because satisfying these two requirements increases the gain margin, which determines the stability margin of the control system, and therefore allows for a large control gain, which determines the servo stiffness.

[0037] Therefore, the proportional gain K of the servo amplifier P If the groove and / or hole are formed so that the damping ratio ζ0, which is determined by the inertia mass m and the damping coefficient C, satisfies the range of 0.2≦ζ0≦0.6, using this as an evaluation index based on many empirical values, the sensor sensitivity can be significantly improved, and the upper limit of the resonance peak value required for a servo-type acceleration sensor can be met, and the sensor responsiveness (phase delay) can be kept within an acceptable range.

[0038] In the servo type vibration detector of the second invention of the present application, the damping ratio calculated from the dynamic characteristics of the sensor output when the vibration detector body is subjected to sweep vibration in a state where the flow path connecting the groove or the hole to the atmosphere is blocked is defined as ζ d Then, ζ d The present invention is characterized in that it is configured so that the ratio is greater than 0.6.

[0039] That is, the present invention verifies that it has the effect of simultaneously satisfying the following conditions (1) and (2). (1) The electrode specifications enable improved sensor sensitivity. (2) The sensor dynamic characteristics are within the allowable range. For example, a through-hole connected to the atmosphere is shielded by a channel shielding plate. As a result, the inside of the groove connecting the through-hole and the channel cannot maintain a constant atmospheric pressure. In other words, there is no longer any suppression effect on the dynamic fluid pressure (squeeze pressure) generated in the gap between the electrodes. In this state, the sensor body is subjected to a sweep vibration to determine the dynamic characteristics (gain and phase characteristics) of the sensor output. The damping ratio obtained from this dynamic characteristic is called ζ d The damping ratio before the installation of the flow path blocking plate is compared with ζ0. As a result, the sensor dynamic characteristics do not satisfy the allowable range, and ζ d If the value is >0.6, it is verified that the grooves and / or holes having flow paths connected to the atmosphere formed on the electrode surface function effectively to realize the present invention.

[0040] The servo-type vibration detector of the third invention of the present application is characterized in that the groove portion is a flow groove that is approximately concentric with the axis of the fixed side electrode or the movable side electrode, or approximately radially oriented in the radial direction.

[0041] That is, in the present invention, grooves communicating with the atmosphere are formed approximately concentrically with the axis of the fixed electrode or the movable electrode, or approximately radially in the radial direction. By forming the groove width narrow and the groove depth sufficiently deeper than the inter-electrode gap, each groove can maintain atmospheric pressure regardless of the size of the inter-electrode gap.

[0042] The servo-type vibration detector of the fourth invention of the present application is characterized in that a plate-shaped member in which the groove or hole is formed by surface processing technology is attached to the movable electrode and the fixed electrode with bolts or adhesive.

[0043] That is, in the present invention, the grooves and / or holes are formed in a thin plate-like member by etching, and the plate-like member is attached to the relative movement surface of the movable electrode and the fixed electrode with bolts or adhesive. By applying the etching method, it is possible to simultaneously produce several dozen joined microgrooved electrodes on a single large-area metal plate. When in use, it is sufficient to cut the joints (bridges) between the individual plates. This allows for excellent mass productivity, significant cost reductions, and minimal variation in damping performance (damping coefficient C).

[0044] The servo-type vibration detector of the fifth invention of the present application is characterized in that a plurality of small diameter holes communicating with the atmosphere are opened on the relative moving surface between the movable electrode and the fixed electrode, and the plurality of small diameter holes are arranged approximately axially symmetrically.

[0045] In other words, the present invention aims to reduce the squeeze pressure by forming only a large number of through holes, rather than a continuous groove shape. The key point of the present invention is that the squeeze pressure reduction effect is adjusted by the number n of through holes, rather than the number of ring grooves, etc. The arrangement of the through holes is axially symmetric so that moment load due to damping force is not applied to the electrode. The greater the number n of through holes, the smaller the damping effect (damping coefficient), and conversely, the smaller n, the greater the damping effect (damping coefficient). By setting this n, the damping coefficient can be finely adjusted.

[0046] The servo-type vibration detector of the sixth invention of the present application comprises a housing which is a fixed member, a movable member which is arranged so as to be movable in a predetermined direction relative to the housing, an elastic member which supports the movable member so as to be positioned relative to the housing via a gap, a displacement detection unit which detects the displacement of the movable member in the predetermined direction, a driving means which is driven by a servo amplifier so as to generate a force which returns the movable member to the original position when the displacement detection unit detects a relative displacement of the movable member from its original position, a movable side electrode which is arranged on the movable member, and a fixed side electrode which is arranged on the housing side opposite the movable side electrode, wherein the displacement detection unit is configured to detect the electrostatic capacitance formed in the gap between the movable side electrode and the fixed side electrode, and a discontinuous groove which communicates with the atmosphere is formed on the relative movement surface of the movable side electrode and the fixed side electrode so as to reduce the damping effect due to dynamic fluid pressure which occurs in the gap between the movable side electrode and the fixed side electrode, and the discontinuous groove is formed by surface processing technology to penetrate the plate-like member.

[0047] In other words, the present invention allows for the simultaneous production of several dozen bonded microgrooved electrodes on a single large-area metal plate through through-etching. For example, in addition to multiple discontinuous ring-shaped grooves, multiple discontinuous radial grooves can be formed. The flow paths connecting the "grooved areas" and the "grooves" need only be sufficiently narrow. The plate need not be divided by the formation of the grooves. Therefore, the viscous fluid resistance of the flow paths between each groove can be sufficiently small. For example, the discontinuous ring-shaped grooves can be considered "pseudo-circumferential grooves" compared to circumferential grooves formed by machining. Furthermore, the pressure within each groove is maintained at atmospheric pressure through through-holes that connect to the atmosphere, resulting in a sufficiently large reduction in damping effect.

[0048] The servo-type vibration detector of the seventh invention of the present application is characterized in that the plate-shaped member, which has an outer diameter larger than that of the movable electrode, is attached to the fixed electrode at its outer periphery, and a hole portion connecting the discontinuous groove portion to the atmosphere is formed in the fixed electrode or the movable electrode.

[0049] That is, in the present invention, the outer diameter of the plate-shaped member (fixed electrode plate) is formed larger than that of the movable electrode. Therefore, the plate-shaped member is adhesively fixed to the fixed electrode base at the outer periphery. Since no discontinuous grooves are formed in the outer periphery, adhesive fixation is not hindered. In addition, bolt fastening can be performed by utilizing the space in the outer periphery.

[0050] The servo-type vibration detector of the eighth invention of the present application is characterized in that the outer periphery of the plate-shaped member is attached to the fixed electrode, and the area where the discontinuous groove portion is formed is open to the atmosphere.

[0051] That is, in the present invention, each discontinuous groove (microgroove) formed on the fixed electrode plate is directly open to the atmosphere on the side opposite to the movable electrode. Therefore, through holes connecting the grooves to the atmosphere as shown in the above-mentioned embodiment are not required. If the electrode is configured with through holes connecting the grooves to the atmosphere, the viscous fluid resistance R for air to flow along the grooves will be large.m The groove width h is set so that is sufficiently small. G had to be set.

[0052] Groove width h G The wider the grooves are and the more grooves there are, the smaller the effective area of ​​capacitance becomes. In the present invention, where each groove is open to the atmosphere at the back side, the viscous fluid resistance R m = 0. As a result, each groove width h G Since the width of the microgroove can be made sufficiently narrow, the effect of the electrostatic capacitance due to the formation of the microgroove can be made sufficiently small.

[0053] In the servo type vibration detector of the ninth invention of the present application, the mass of the movable member of the servo type vibration detector is m, and the proportional gain of the servo amplifier is K P , m and K P The resonant frequency determined by f n , the first resonance frequency when the outer periphery of the plate-like member is fixed is f P As, f P The grooves are formed in a discontinuous shape so as to satisfy the condition f0.

[0054] That is, the present invention provides conditions for the shape of discontinuous grooves that can avoid the influence on the dynamic characteristics (gain and phase characteristics) of the sensor. For example, consider a case where discontinuous grooves are formed in a ring shape and a cross shape on the plate-like member. When the gap between the two discontinuous grooves becomes narrower, the axial rigidity of the plate-like member decreases, and therefore the resonant frequency f of the plate-like member whose outer periphery is fixed and supported decreases. P However, the narrower the gap between the discontinuous grooves, the greater the effect of reducing the squeeze pressure. P The resonant frequency determined by f n As, f P If >f0 is satisfied, the discontinuous grooves do not affect the sensor dynamics.

[0055] A servo type vibration detector according to a tenth aspect of the present invention comprises a housing which is a fixed member, a movable member provided so as to be movable in a predetermined direction relative to the housing, an elastic member which supports the movable member so as to be disposed relative to the housing via a gap, a displacement detection unit which detects displacement of the movable member in the predetermined direction, drive means which is driven by a servo amplifier so as to generate a force which returns the movable member to the original position when a relative displacement of the movable member from an original position is detected by the displacement detection unit, a movable side electrode provided on the movable member, and a fixed side electrode provided on the housing side opposite the movable side electrode. The displacement detection unit is configured to detect the electrostatic capacitance formed in the gap between the movable electrode and the fixed electrode, and grooves communicating with the atmosphere are formed on the relative moving surfaces of the movable electrode and the fixed electrode so as to reduce the damping effect due to dynamic fluid pressure generated in the gap between the movable electrode and the fixed electrode, and the grooves are formed in a roughly symmetrical shape by half-etching on the front and back of the plate-like member, one surface of the plate-like member is attached to the electrode surface with bolts or adhesive, and the other electrode surface opposite the plate-like member has holes formed therein communicating with the atmosphere.

[0056] That is, in the present invention, microgrooves are formed on the front and back surfaces of the plate-like member by fine groove processing using double-sided half etching. (1) The optimal microgrooves can be formed to suppress the damping effect caused by large squeeze pressure. (2) Double-sided half etching can eliminate warping of the plate-shaped member. (3) The plate-shaped member with microgrooves formed thereon is adhesively fixed to the movable electrode base. This configuration allows adhesive to flow into the fluid grooves, significantly increasing adhesive strength.

[0057] The servo type vibration detector of the eleventh invention of the present application comprises a housing which is a fixed member, a movable member provided so as to be movable in a predetermined direction relative to the housing, an elastic member which supports the movable member so as to be disposed with a gap between the movable member and the housing, a displacement detection unit which detects displacement of the movable member in the predetermined direction, a driving means which is driven by a servo amplifier so as to generate a force which returns the movable member to the original position when the displacement detection unit detects a relative displacement of the movable member from the original position, a movable side electrode provided on the movable member, a fixed side electrode provided on the housing side opposite the movable side electrode, and the displacement detection unit The capacitance-type displacement detector is configured to detect the capacitance formed in the gap between the fixed electrodes, and one of the relative moving surfaces between the movable electrode and the fixed electrode is made of a non-conductive material, and includes a plurality of electrode surfaces divided and fixed in the circumferential direction on the non-conductive material surface, and approximately radial circulation grooves formed at the boundary between these electrode surfaces, which circulation grooves are formed to reduce the damping effect due to dynamic fluid pressure generated in the gap between the movable electrode and the fixed electrode and to provide electrical insulation between the electrode surfaces, and the plurality of electrode surfaces and the opposing electrode surfaces form a plurality of sets of independent capacitance-type displacement detectors.

[0058] In other words, the present invention forms radial grooves in the circumferential direction on one of the two electrode surfaces to reduce squeeze pressure. These radial grooves also serve as electrical insulation between the divided electrode surfaces. This invention improves the sensor's dynamic characteristics (gain and phase characteristics), and realizes a multi-electrode servo-type vibration detector that detects multiple independent displacement, velocity, and acceleration signals.

[0059] The assembly method for a servo-type vibration detector of the 12th invention of the present application is an assembly method for the servo-type vibration detector of the 11th invention of the present application, in which the inclination angle of the gap portion of the relative moving surface is measured based on the signals of the plurality of sets of capacitance-type displacement detectors, and the inclination is corrected based on this measurement.

[0060] That is, in the present invention, for example, radial grooves are divided into four in the circumferential direction and formed axially symmetrically. In this case, the tilt angle of the gap between the movable electrode and the fixed electrode can be measured from two displacement signals from the electrode surfaces spaced 180 degrees apart. The tilt of the fixed electrode relative to the movable electrode can be corrected so that this tilt angle Δθ becomes 0.

[0061] The servo-type vibration detector of the 13th invention of the present application is characterized in that it comprises a coil fixed to the fixed member side, a movable member arranged with a gap between it and the fixed member, a permanent magnet arranged so that magnetic flux flows through the gap, and the movable member being composed of the permanent magnet and a movable side yoke material connecting the permanent magnet to a magnetic path, or just the movable side yoke material, and the movable member, the gap, the fixed member, and the permanent magnet form a closed loop magnetic circuit, thereby constituting the driving means using electromagnetic force to move the movable member axially.

[0062] The servo-type vibration detector of the 14th invention of the present application further comprises a coil fixed to the fixed member side and a permanent magnet arranged so that magnetic flux flows in the gap, and the movable member is composed of the permanent magnet and a movable side yoke material connecting the permanent magnet to a magnetic path, or of only the movable side yoke material, and is characterized in that the movable member, the gap, the fixed member, and the permanent magnet form a closed loop magnetic circuit, thereby constituting the driving means using electromagnetic force to move the movable member axially. [Effects of the Invention]

[0063] According to the servo type vibration detector of the present invention, the proportional gain K P The damping ratio ζ0, which is determined by the inertia mass m and the damping coefficient C, is used as an evaluation index based on many empirical values, and the grooves and / or holes are formed so that the range of 0.2≦ζ0≦0.6 is satisfied. This significantly improves the sensor sensitivity, and not only meets the upper limit of the resonance peak value required for a servo-type acceleration sensor, but also keeps the sensor responsiveness (phase delay) within an acceptable range. [Brief explanation of the drawings]

[0064] [Figure 1] FIG. 1 is a model diagram showing the basic configuration and detection principle of a capacitance-type acceleration sensor according to a first embodiment of the present invention. [Figure 2] 2A and 2B show an example of a servo-type acceleration sensor according to the first embodiment, in which FIG. 2A is a view taken along the arrow DD in FIG. 2B, and FIG. 2B is a front cross-sectional view of the sensor main body. [Figure 3] Graph of the input waveform applied to the electrode gap. [Figure 4] Graph of squeeze pressure at maximum load versus radial position of electrode. [Figure 5] Graph of the sinusoidal response of the generated load applied to the electrode. [Figure 6] 10 is a graph showing the relationship between the attenuation coefficient and the gap between electrodes. [Figure 7] FIG. 2 is a control block diagram including a displacement detection unit and a control circuit unit according to the first embodiment. [Figure 8] 10 is a graph showing the gain-phase characteristics of the sensor of the present invention and a conventional sensor when the electrode gap h0 is 30 μm. [Figure 9] 10 is a graph comparing the gain and phase characteristics of the sensor of the present invention configured as Case 2 in Table 1 when the inter-electrode gap h0 is 20 to 40 μm. [Figure 10] 1 is a graph comparing the gain and phase characteristics of sensors of the present invention configured as Cases 1 to 3 in Table 1. [Figure 11] 11A and 11B show an example of a servo-type acceleration sensor according to a second embodiment of the present invention, with FIG. 11A being a view taken along the line AA in FIG. 11B, and FIG. 11B being a front cross-sectional view of the sensor main body. [Figure 12] FIG. 10 is a diagram showing the shape of a single fixed electrode plate in the second embodiment. [Figure 13] In the second embodiment, the fixed electrode plate is fastened with a bolt. FIG. 13(a) is a view taken along the arrow BB in FIG. 13(b), and FIG. 13(b) is a front cross-sectional view of only the electrode portion. [Figure 14]14A and 14B show an example of a servo-type acceleration sensor according to a third embodiment of the present invention, in which FIG. 14A is a view taken along the arrow CC in FIG. 14B, and FIG. 14B is a front cross-sectional view of only the electrode portion. [Figure 15] 15(a) shows an example of a servo-type acceleration sensor according to a fourth embodiment of the present invention, in which FIG. 15(a) is a view taken along the line AA in FIG. 15(c), FIG. 15(b) is a view taken along the line BB in FIG. 15(c), and FIG. 15(c) is a front cross-sectional view of only the electrode portion of the sensor body. [Figure 16] 16(a) shows the shape of a plate alone in the fourth embodiment, with FIG. 16(a) being a front view of the plate, FIG. 16(b) being a side view, and FIG. 16(c) being a back view of FIG. 16(a). [Figure 17] This shows the case where microgrooves are formed on the movable electrode plate by one-sided half etching and through holes. Figure 17(a) is a front view of the movable electrode plate, Figure 17(b) is a side view, and Figure 17(c) is a back view. [Figure 18] 18A and 18B show an example of a servo-type acceleration sensor according to a fifth embodiment of the present invention, in which FIG. 18A is a view taken along the line AA in FIG. 18B, and FIG. 18B is a front cross-sectional view of the acceleration sensor. [Figure 19] 19A and 19B show an example of a servo-type acceleration sensor according to a sixth embodiment of the present invention, with FIG. 19A being a front view of a sensor body and FIG. 19B being a front cross-sectional view. [Figure 20] 20(a) and 20(b) are diagrams showing a state in which a fixed electrode plate is attached to a fixed electrode base, with FIG. 20(a) being a side cross-sectional view and FIG. 20(b) being a front view. [Figure 21] A diagram showing Step 1, "mass production processing by etching." [Figure 22] A diagram showing the state after "cutting out one electrode" in Step 2. [Figure 23] A diagram showing the state after Step 3: "Attaching electrodes to the ceramic plate." [Figure 24] A diagram showing the state after "cutting and removing unnecessary parts" in Step 4. [Figure 25] FIG. 20 is a model diagram showing a method for measuring the gap between electrodes and the tilt angle using a sensor of the present invention incorporating multiple electrodes in embodiment 6. [Figure 26]A model diagram of a conventional active vibration isolation table. [Figure 27] A model diagram showing the basic configuration and detection principle of a conventional capacitive acceleration sensor. [Figure 28] FIG. 10 is a front cross-sectional view showing a specific structural example of a conventional linear motion acceleration sensor. DETAILED DESCRIPTION OF THE INVENTION

[0065] [First embodiment] [1] Specific structure of this embodiment (hereinafter referred to as MC type prototype) FIG. 1 shows an example of a servo-type acceleration sensor according to a first embodiment of the present invention, with FIG. 1(a) being a view taken along the arrow DD in FIG. 1(b), and FIG. 1(b) being a front cross-sectional view of the sensor body. The dashed line AB in FIG. 1(b) indicates a moving coil type (MC type) actuator that drives the moving part in the axial direction. The dashed line BB indicates a displacement detection part that detects capacitance. The dashed line CC indicates an outline of a control circuit part that incorporates a servo amplifier that drives the actuator. As mentioned above, the MC type actuator part has a known structure. Below, the specific structure of this embodiment will be explained, dividing it into the actuator part, displacement detection part, and control circuit part.

[0066] [2-1] Actuator section In the actuator section (area AB indicated by the two-dot chain line) in FIG. 1(b), 201 is a permanent magnet, 202 is a pole piece section, 203 is a pole piece convex section, 204 is a permanent magnet side yoke material, 205 is a coil side yoke material, 206a is a force coil, 206b is a calibration coil, 207 is a coil bobbin, 208 and 209 are coil bobbin support members made of a non-magnetic and non-conductive material, 210 is a front side disc-shaped spring, 211 is a rear side disc-shaped spring, 212 is a front side connecting member between the front side disc-shaped spring and the coil side yoke material, 213 is a rear side connecting member between the rear side disc-shaped spring and the coil side yoke material, 214 is a movable side electrode, and 215 is a junction between the movable side electrode and front side disc-shaped spring 210.

[0067] A magnetic gap 216 is formed in the radial direction between the outer periphery of the pole piece portion 202 and the inner periphery of the coil side yoke material 205. 216a is the permanent magnet side gap, and 216b is the yoke material side gap. A closed loop magnetic circuit B is formed by "permanent magnet 201 → pole piece portion 202 → magnetic gap 216 → coil side yoke material 205 → permanent magnet side yoke material 204". M When a current flows through the force coil 206a disposed in the space of the magnetic gap 216, a Lorentz force is generated that moves the movable electrode 214 in the axial direction.

[0068] [2-2] Displacement detection unit In the displacement detection section (area BB indicated by the two-dot chain line) in Figure 1(b), reference numeral 217 denotes a fixed electrode, 218 an insulating ring, and 219 a fixed ring. The fixed electrode 217 is held against the fixed ring with the insulating ring interposed therebetween. 218 denotes an adhesive application portion for fixing the fixed ring 219 to the coil side yoke material 205. 220 denotes a gap between the fixed electrode and the movable electrode. During the assembly adjustment stage, the position of the fixed ring 219 relative to the coil side yoke material 205 is adjusted so that the gap d of the gap 220 becomes the target value.

[0069] Ring-shaped grooves and through-holes are formed on the surface of the fixed electrode 217 facing the movable electrode 214. 221 is a central through-hole, 223 is a first ring-shaped groove, and 224 is a second ring-shaped groove. When the gap h0 of the gap 220 between the two electrodes changes, dynamic pressure (squeeze pressure) is generated due to the viscosity of air. The first ring-shaped groove and the second ring-shaped groove are formed to reduce this squeeze pressure. Hereinafter, the grooves (the first and second ring-shaped grooves) formed on the electrode surfaces to reduce the squeeze pressure will be collectively referred to as microgrooves. 223a, 223b, 223c, and 223d are through-holes formed inside the first ring-shaped groove 223. 224a, 224b, 224c, and 224d are through-holes formed inside the second ring-shaped groove 224. 225 is a recessed portion open to the atmosphere. The microgroove depth is sufficiently large compared to the expected inter-electrode gap h (10 to 50 μm), allowing each groove to maintain atmospheric pressure regardless of the size of the inter-electrode gap h. As a result, the large electrode surface is divided into multiple independent electrode surfaces. The electrode surface between the central through-hole 221 and the first ring-shaped groove 223 is referred to as the first electrode 217a, the electrode surface between the first ring-shaped groove 223 and the second ring-shaped groove 224 is referred to as the second electrode 217b, and the electrode surface between the second ring-shaped groove 224 and the outer periphery of the fixed electrode 217 is referred to as the third electrode 217c. The three independent electrode surfaces 217a, 217b, and 217c may be formed, for example, by mounting three ring-shaped members on a flat plate.

[0070] In this embodiment, the groove width of the first ring-shaped groove and the second ring-shaped groove is h G = 0.1 mm, and four through holes communicating with the atmosphere are formed in each groove. The central through hole ΦD1 = 0.8 mm, and the electrode outer diameter ΦD2 = 13 mm. The inner circumferential side of the first ring-shaped groove 223 is formed at a position of radius r1 = 2.0 mm, and the inner circumferential side of the second ring-shaped groove 224 is formed at a position of radius r2 = 4.5 mm. The total groove area of ​​the first and second ring-shaped grooves 223 and 224 is S m =6.15mm 2 , the electrode area without the above two grooves is S T =132mm 2Therefore, the area of ​​the ring-shaped grooves 223 and 224 accounts for 4.66% of the total electrode area. In summary, the reduction in capacitance due to the ring-shaped grooves is just under 5%. Therefore, by slightly increasing the outer diameter of the electrode, in this embodiment, by changing ΦD2 from 13 mm to 13.2 mm, the reduction in capacitance can be compensated for.

[0071] [2-3] Control circuit section The area indicated by the two-dot chain line CC in Figure 1(b) shows an overview of the control circuit, with 226 being a displacement detector and 227 being an amplifier. Since the capacitance C is determined by the gap 220 formed between the movable electrode 214 and the fixed electrode 217, measuring the capacitance C makes it possible to detect the relative displacement, which is the difference between the absolute displacement U due to ground motion and the absolute displacement X of the mass body. The current i0 of the actuator is controlled via the amplifier 227 so that the relative displacement UX becomes zero. By detecting the current i0 flowing through the force coil 206a, the acceleration acting on the movable part can be determined.

[0072] [3] Theoretical analysis In order to verify the effect of this embodiment, theoretical analysis will be performed on the following three cases. (i) The electrode structure of the conventional acceleration sensor is maintained, and the electrode gap h0 is set to 30 μm. (ii) Without changing the conventional electrode structure, in order to improve the sensor sensitivity, the inter-electrode gap is set to 1 / 2 of the above, that is, h0=15 μm. (iii) Microgrooves are formed on the electrode surface to set the electrode gap h0 to 15 μm. Table 1 shows the specific specifications (for the three cases above) of the servo-type acceleration sensor that is the subject of this theoretical analysis. Figure 8 shows the control block diagram.

[0073] [3-1] Viscous fluid analysis of displacement detection unit When a viscous fluid (air) is present in the narrow gap (electrode gap) between two opposing flat surfaces, and the gap changes rapidly over time, dynamic fluid pressure (squeeze pressure) occurs due to the viscosity of the air. The effect of this squeeze pressure on the function of the electrostatic acceleration sensor is clarified by solving the following Reynolds equation.

[0074]

number

[0075] (1) Assuming a sinusoidal input waveform Figure 2 shows the input waveform applied to the electrode gap. Assume that the electrode gap vibrates with a sine wave. The graph in Figure 2 shows the case where the vibration center value is h0 = 0.015 mm, the vibration amplitude Δh = 0.001 mm, and the frequency f = 200 Hz.

[0076]

number

[0077] (2) Radial distribution of squeeze pressure Figure 3 shows the squeeze pressure at the time of maximum load occurrence versus the radial position of the electrode, comparing the following three cases. (i) Conventional type: electrode gap h0 = 30 μm (ii) Conventional type: electrode gap h0 = 15 μm (iii) This invention: Microgrooves are formed on the electrode surface, and the electrode gap h0 = 15 μm The boundary conditions for the numerical analysis are the outer periphery of the central through-hole r = 0.4 mm, the outer periphery of the electrode r = 6.5 mm, and the pressure (gauge pressure) is atmospheric pressure P = 0. In the case of the conventional method, the squeeze pressure reaches its maximum value at the position of r = 2.5 mm, and P max =47.0 Pa.

[0078] Compare the conventional electrode gap h0 = 30 μm and h0 = 15 μm. When the electrode gap h0 = 30 μm (chain line), the squeeze pressure reaches its maximum value at r = 3.0 mm, and Pmax = 27.5 Pa. When the electrode gap h0 = 15 μm (dotted line), the squeeze pressure is P max =275Pa.

[0079] In the case of the present invention (solid line) in which microgrooves are formed, the pressure becomes atmospheric pressure P = 0 at the location where the first ring-shaped groove 223 is formed (radius r1 = 2.0 mm) and at the location where the second ring-shaped groove 224 is formed (radius r2 = 4.5 mm). As is clear from comparing the two, the formation of microgrooves significantly reduces the generated pressure, even though the inter-electrode gap h0 = 15 μm.

[0080] (3) Sinusoidal response of generated load Figure 4 shows the sinusoidal response of the load applied to the electrodes. A comparison is made between the conventional electrode gap h0 = 30 μm (two-dot chain line) and h0 = 15 μm (single-dot chain line). Narrowing the electrode gap from h0 = 30 μm to h0 = 15 μm increases the maximum generated load by approximately eight times. In this case, the damping coefficient increases from C = 3.85 Ns / m to C = 31.8 Ns / m. The present invention, with microgrooves (solid line: h0 = 15 μm), produces a waveform at the same level as the conventional electrode gap (two-dot chain line: h0 = 30 μm).

[0081] [3-2] Sensor dynamic characteristics analysis (1) Actuator responsiveness Figures 5 and 6 are graphs comparing the actuator response using the indicial response under the conditions (i) to (iii) above. To evaluate the effect of the electrode gap h0 on the response, the servo-type sensor actuator is assumed to be a second-order lag element with a squeeze damper. The specific specifications of the acceleration sensor are shown in Table 1.

[0082] Figure 5 compares the electrode gaps h0 = 30 μm (solid line) and h0 = 15 μm (dotted line) for both conventional electrode structures. The rise time T rWhen the electrode gap h0 is narrowed from 30 to 15 μm in order to improve the sensor sensitivity [(ii) above], the response is significantly reduced and the rise time is 12 times longer (T r =0.97→11.5ms) longer.

[0083] Figure 6 compares the conventional method (dotted line: h0 = 30 μm) with the present invention (solid line: h0 = 15 μm). No significant difference in responsiveness is observed between the two. From the above results, it can be seen that the sensor of the present invention with microgrooves formed [above (iii)] is able to maintain the same level of responsiveness despite doubling the sensor sensitivity.

[0084] However, the graphs shown in Figures 5 and 6 do not represent the transient response characteristics of an actual servo-type acceleration sensor. In a servo-type acceleration sensor, when an impulsive acceleration is applied, the electrode gap h is controlled so that the deviation (ε = h0 - h) from the set value (target value) h0 becomes 0. The graphs shown in Figures 5 and 6 are a relative evaluation of the degree to which the magnitude of damping affects the responsiveness of the actuator.

[0085] (2) Gain-phase characteristics Figure 7 is a graph comparing the gain and phase characteristics of the servo-type sensor when the electrodes are configured under the above conditions (i) to (iii). The control block diagram is shown in Figure 8. (i) Conventional type: electrode gap h0 = 30 μm (ii) Conventional type: electrode gap h0 = 15 μm (iii) This invention: Microgrooves are formed on the electrode surface, and the electrode gap h0 = 15 μm

[0086] Comparing (i) and (iii) above, no significant difference is observed in the gain-phase characteristics of the two. In the case of (ii) above, the gain at the resonance point drops to around -20 dB. Furthermore, the phase delay Δθ at f = 100 Hz drops from 14.5 to 64.7 dB. Therefore, if an attempt is made to improve sensor sensitivity while retaining the conventional electrode structure, it will clearly result in overdamping, and cannot be applied to an active vibration isolation table.

[0087] In summary, in this embodiment in which microgrooves are formed on the electrode surface, the sensor sensitivity can be improved by two times while maintaining the gain-phase characteristics and responsiveness of the sensor.

[0088] [Table 1]

[0089] In the control block diagram of Figure 8, K S is the sensor sensitivity gain, K PE is the electrical proportional gain, K C is the adjustment gain, R a is the coil resistance, K t is the force constant of the actuator, where the proportional gain K P is defined as follows:

[0090] [4] Numerical limitations of the present invention In order to comprehensively evaluate the characteristics and effects of the present invention in comparison with conventional sensors, the axis of frequency f is made dimensionless, and the damping coefficient C, inertia mass m, and proportional gain K are expressed as follows: P In the control block diagram of Figure 8, K S is the sensor sensitivity gain, K PE is the electrical proportional gain, K C is the adjustment gain, R a is the coil resistance, K t is the force constant of the actuator, where the proportional gain K P is defined as follows:

[0091]

number

[0092] The transfer function G (=Z / Λ) of the sensor output Z with respect to the acceleration input Λ is

[0093]

number

[0094] Here, the mechanical spring stiffness is k. Usually, K P ≫k, so the resonant frequency ω n can be approximated as follows:

[0095]

number

[0096] The damping ratio ζ is given by the following equation.

[0097]

number

[0098] In the above equation, if the mechanical spring stiffness k cannot be ignored, K P +k→K P As the proportional gain K P The gain-phase characteristics obtained when the frequency axis is made dimensionless are shown in Figure 9. Figure 10 shows the gain-phase characteristics obtained when the frequency axis is made dimensionless. n The graph shows the gain-phase characteristics limited to the range of <0.3. From the graph above, we evaluate the following conditions required for a servo-type acceleration sensor. (1) The peak value at the resonance point is 10 dB or less (2)ω / ω n Phase delay Δθ at =0.2 is 15 deg or less The range of ζ that satisfies the above conditions (1) and (2) is determined. The evaluation index in (2) is set based on the following assumption: The upper limit of the resonance frequency of the servo-type acceleration sensor is set to f n = 500Hz, then f = 100Hz, that is, ω / ω n The phase delay at f = 0.2 is used as the evaluation index. As mentioned above, the resonant frequency that can be achieved by an actual servo type acceleration sensor is n = 500 Hz or less, the above (2) is a sufficient condition for satisfying the ideal sensor dynamic characteristics.

[0099] The condition for ζ that satisfies the above (1) is given by the following formula from the graph in FIG.

[0100]

number

[0101] The condition for ζ to satisfy the phase delay condition (2) above is as follows: From the graph in Figure 10, ω / ω n The condition for the phase delay to be 15 degrees or less at =0.2 is

[0102]

number

[0103] In equation (7), m = K P / ω 2 n Then, ζ= Cω n / 2K P If the mass m cannot be easily determined, as in the case of an oscillatory motion sensor, the above formula can be used.

[0104] [postscript] The damping effect acting on the moving part is not just mechanical damping, which depends on the air viscosity in the gap between the electrodes. If a damping circuit is provided in the servo amplifier, electrical damping by the damping circuit will be added to the mechanical damping. Also, in the acceleration sensor, there are other damping elements in addition to the mechanical and electrical damping. For example, in Figure 1(b), if a conductor (aluminum) is used for the coil bobbin 207, damping due to eddy currents will occur. However, the damping due to eddy currents is sufficiently small compared to other dampings, and is usually a negligible value in many cases. Here, the damping coefficient determined by the mechanical damping is defined as C M , the damping coefficient determined by the electrical damping is C E , for example, the damping coefficient that depends on the eddy current is C ME Evaluate the present invention as the damping coefficient C = C M + C E +C METherefore, the damping ratio ζ in equation (13) uses the damping coefficient C defined above.

[0105] [5] Verification method of the present invention The present invention has the effect of simultaneously satisfying the following conditions (1) and (2). We propose a method for verifying this effect without disassembling the sensor body. (1) The electrode specifications enable improved sensor sensitivity. To improve the sensor sensitivity, it is necessary to take the measures (i) and (ii) mentioned above: (i) narrowing the gap between the electrodes, and (ii) increasing the outer diameter of the electrodes. However, both of these measures increase attenuation. (2) The sensor dynamic characteristics are within the allowable range. Even though the measure (1) above is taken, the sensor dynamic characteristics satisfy the allowable range (0.2≦ζ0≦0.6) due to the grooves and / or holes with flow paths connected to the atmosphere formed on the relative moving surfaces of the electrodes.

[0106] [5-1] Specific method for verifying this invention 1(b), reference numeral 228 denotes a flow path shielding plate (shown in imaginary lines). This flow path shielding plate is attached to the surface of the fixed electrode 217 opposite to the movable electrode 214, as indicated by the arrow in the figure.

[0107] As a result, the through holes 223a to 223d and the through holes 224a to 224d, which were connected to the atmosphere, are sealed. Furthermore, the inside of the first ring-shaped groove 223 and the second ring-shaped groove 224, which connect the through holes to the flow path, can no longer maintain a constant atmospheric pressure. In other words, the suppression of the dynamic fluid pressure (squeeze pressure) generated in the gap between the electrodes is lost. In this state, the sensor body is subjected to a sweep vibration to determine the dynamic characteristics (gain and phase characteristics) of the sensor output. The damping ratio obtained from this dynamic characteristic is called ζ d The damping ratio before the flow path blocking plate is mounted is compared with ζ0.

[0108] As a result, the sensor dynamics do not meet the tolerance range, and ζ dIf the value is >0.6, it is verified that the grooves and / or holes having flow paths connected to the atmosphere formed on the electrode surface function effectively to realize the present invention.

[0109] [5-2] Definition of damping ratio The force generated by the actuator unit is in dynamic balance with the inertial force determined by the acceleration and inertial mass of the movable member, the damping force determined by the velocity and damping coefficient of the movable member, and the restoring force determined by the displacement of the movable member and the rigidity of the elastic member. The proportional gain of the servo amplifier that generates the generated force is defined as K P , where m is the inertial mass and C is the damping coefficient, the damping ratio ζ = C / 2 (m K P ) 0.5 is.

[0110] The method for eliminating the effect of the grooves and / or holes formed on the electrode surface is not limited to the flow path shielding plate. For example, the openings of the holes 223a to 223d and the through-holes 224a to 224d may be sealed with detachable setscrews or the like. The verification method of the present invention described in this section can be applied to all embodiments described later.

[0111] [Second embodiment] Eliminating the weaknesses of etching (part 1) Penetration of discontinuous grooves Fig. 11 shows an example of a servo-type acceleration sensor according to embodiment 2 of the present invention, in which Fig. 11(a) is a view taken along the line AA in Fig. 11(b), and Fig. 11(b) is a front cross-sectional view of the sensor body. Fig. 12 is a diagram showing the shape of the fixed electrode plate alone.

[0112] In Figure 11(b), the dashed line AA indicates a moving magnet type (MM type) actuator that drives the movable part in the axial direction. The dashed line BB indicates a displacement detection part that detects electrostatic capacitance. In this invention, by using an etching method to form microgrooves in the electrodes, (i) the formation of a groove shape that obtains optimal damping performance, and (ii) a significant improvement in mass productivity, the above (i) and (ii) are simultaneously achieved. The MM type servo acceleration sensor in this embodiment is a patent application pending by the inventors, and is an improvement on that actuator part. Below, the specific structure of this embodiment will be explained, dividing it into the actuator part and the displacement detection part.

[0113] [1-1] Actuator section Reference numeral 801 denotes an axially magnetized permanent magnet, 802a denotes a front pole piece, 802b denotes a rear pole piece, 803 denotes a coil-side yoke material, 804 denotes a coil bobbin, 805 denotes a fastening bolt connecting the coil bobbin to the coil-side yoke material, 806a denotes a front coil, and 806b denotes a rear coil. The winding direction of each coil is set so that the Lorentz force acting on the front coil and the rear coil is in the same direction. 807a and 807b denote gaps formed in the centers of the front and rear pole piece parts 802a and 802b. 808a denotes a front magnetic gap, and 808b denotes a rear magnetic gap, each representing a radial gap between the two pole piece parts and the coil-side yoke material. Closed loop magnetic circuit B is formed by "permanent magnet 801 → front pole piece 802a → front magnetic gap 808a → coil side yoke material 803 → rear magnetic gap 808b → permanent magnet 801". M Reference numeral 809a denotes a front-side inner peripheral support member for the pole piece portion, 809b denotes a rear-side inner peripheral support member, 810a denotes a front-side disc, and 810b denotes a rear-side disc. Reference numeral 811 denotes a movable-side electrode. Reference numeral 812 denotes a fastening bolt connecting the movable-side electrode 811 and the inner peripheral support member 809a. Reference numerals 813a and 813b denote bolts that fasten the two discs 810a, 810b to the coil-side yoke material 803 on the outer periphery.

[0114] The movable portion of this embodiment is composed of a permanent magnet 801, pole piece portions 802a and 802b, and a movable electrode 811. The fixed portion is composed of a coil bobbin 804 in which each coil is housed, and a coil side yoke material 803.

[0115] In the acceleration sensor of this embodiment, the driving means for the movable part uses a moving magnet type that has already been proposed. As is well known, when a current flows through a conductor placed in a magnetic field, an electromagnetic force, the Lorentz force, is generated. In all actuators, regardless of the type of driving principle, the force relationship between the fixed side and the moving side is relative. In other words, if either the fixed side or the moving side is fixed, the other side moves. In this embodiment, when a current flows through force coils 806a and 806b housed in coil bobbin 804, a reaction force of the Lorentz force is generated that moves the movable part in the axial direction.

[0116] [1-2] Displacement detection unit In the displacement detection section (dash line BB) in Figure 11(b), 814 is a fixed-side electrode base, and 815 is a fixed-side electrode plate. This fixed-side electrode plate is adhesively fixed to the fixed-side electrode base 814 at its outer periphery 816. 817 is an insulating ring, and 818 is a fixing ring. The fixed-side electrode base 814 is held against the fixing ring via the insulating ring. 819 is an adhesive application section for fixing the fixing ring 818 to the coil-side yoke material 803.

[0117] In this embodiment, the outer diameter of the fixed electrode plate is formed to be larger than that of the movable electrode 811. Therefore, the fixed electrode plate is adhesively fixed to the fixed electrode base 814 at the outer periphery 816. Since no discontinuous grooves are formed in the outer periphery 816, adhesive fixation is not hindered. As will be described later, this outer periphery 816 can also be used for bolt fastening.

[0118] (1) Etching of the fixed electrode plate The fixed electrode plate 815 has two rows of discontinuous ring-shaped grooves, a central through-hole, and four discontinuous radial grooves formed by through-etching. Figure 12 shows the shape of the fixed electrode plate alone. Reference numeral 820 denotes a central through-hole, and reference numerals 821a, 821b, 821c, and 821d denote first discontinuous ring-shaped grooves divided into four equal parts in the circumferential direction. Reference numerals 822a, 822b, 822c, and 822d denote second discontinuous ring-shaped grooves similarly divided into four equal parts in the circumferential direction. Furthermore, in addition to the two rows of discontinuous ring-shaped grooves, the fixed electrode plate also has four discontinuous radial grooves. Reference numeral 823a denotes a first discontinuous radial groove, 823b denotes a second discontinuous radial groove, 823c denotes a third discontinuous radial groove, and 823d denotes a fourth discontinuous radial groove.

[0119] In this embodiment, microgrooves are formed on the electrode surface as both discontinuous circumferential grooves and discontinuous radial grooves in order to reduce the increase in attenuation effect when the gap between the electrodes is narrowed to improve sensor sensitivity. A similar method can be used to increase the outer diameter of the electrodes to improve sensor sensitivity.

[0120] (2) Drilling holes in the fixed electrode base In the two rows of discontinuous ring-shaped grooves and the four discontinuous radial grooves formed in the fixed-side electrode plate 815, through-holes for equalizing the pressure inside the grooves to atmospheric pressure are formed in the fixed-side electrode base 814. For example, 824a and 824b are through-holes for the discontinuous second radial grooves, and 824c and 824d are through-holes for the discontinuous fourth radial grooves. These through-holes are formed larger than the groove width. The same applies to through-holes connecting to the other grooves (detailed explanations are omitted).

[0121] In the first embodiment, as shown in FIG. 1(a), continuous ring-shaped grooves and through-holes are formed in the fixed-side electrode 217 by machining. In this embodiment, the discontinuous ring-shaped grooves and discontinuous radial grooves are formed in the fixed-side electrode plate 815, which is a thin plate, by through-etching. These discontinuous grooves and the through-holes communicating with atmospheric pressure are formed in the fixed-side electrode base 814. Therefore, these discontinuous grooves can always maintain atmospheric pressure. The present invention provides the following effects.

[0122] (1) A groove shape can be formed that provides optimal damping performance. For example, if the electrode outer diameter is increased and the gap between the electrodes is narrowed to obtain high sensor sensitivity, the damping due to squeeze pressure will further increase. In order to reduce this damping, not only the ring-shaped grooves (FIG. 1(a)) shown in the first embodiment but also radial grooves are required. In order to minimize the decrease in capacitance, for example, the groove width h G = 0.1 mm. In the case of machining, lathe processing is difficult, and both ring-shaped grooves and radial grooves require end mill processing, which is expensive to produce. However, in this invention, the microgrooves are formed by etching, so the selection of the number and shape of the grooves does not affect production costs.

[0123] Furthermore, the present invention allows the required damping performance (damping coefficient C) to be selected from a wide range of options. As described in the first embodiment, when the electrode outer diameter and interelectrode gap are determined, the allowable range of damping performance (damping coefficient C) required to obtain optimal gain-phase characteristics is extremely narrow. This is because, as mentioned above, there is a trade-off between the three sensor dynamic characteristics: (i) resonance peak value, (ii) phase lag, and (iii) sensor sensitivity. If damping is too large, overdamping occurs, increasing the phase lag (item (ii)). If damping is insufficient, the resonance peak value (item (i)) increases. Furthermore, when considering the sensor sensitivity (item (iii)), the allowable range of damping performance (the value of the damping coefficient C) is extremely narrow. The shape of the microgrooves required to obtain a predetermined damping coefficient C under given conditions can be predicted with high accuracy using the aforementioned viscous fluid analysis. The etching pattern is not subject to the constraints of mechanical processing, and any shape can be selected. Therefore, the present invention enables the realization of microgrooved electrodes with optimal damping performance at low cost.

[0124] (2) Excellent mass productivity Through-etching allows for the simultaneous production of several dozen joined microgrooved electrodes (fixed electrode plates in Figure 12) on a single large-area metal plate. When in use, the joints (bridges) between the individual plates can be cut off. This makes it suitable for mass production, significantly reducing costs, and minimizing variations in damping performance (damping coefficient C).

[0125] In this embodiment, in addition to the two rows of discontinuous ring-shaped grooves, four discontinuous radial grooves are formed. In this embodiment, the flow paths connecting the "groove-free areas" and the "grooves" can be sufficiently narrow. For example, as shown in FIG. 12, the distance between the left end (A) of the first ring-shaped groove 822a and the second radial groove 823b (B) can be sufficiently narrow. As long as a single plate is not divided by the formation of grooves, this does not pose a practical problem, and the viscous fluid resistance of the flow paths between each groove [between (A) and (B)] can be reduced. Therefore, compared to the circumferential groove shown in the first embodiment, the discontinuous ring-shaped groove in this embodiment can be considered a "pseudo-circumferential groove." Furthermore, because the pressure inside each groove is maintained at atmospheric pressure via through-holes communicating with the atmosphere, a sufficiently large damping effect can be achieved. Conversely, if the damping effect is too large, the damping effect can be adjusted by increasing the distance between the discontinuous grooves, for example, the distance between (A) and (B).

[0126] [Supplementary information: bolted structure] Figure 13 shows the fixed electrode plate fastened to the fixed electrode base with bolts without significantly changing the structure of this embodiment. Figure 13(a) is a view taken along the arrow B-B in Figure 13(b), and Figure 13(b) is a front cross-sectional view of only the electrode portion. Reference numeral 830 denotes a fastening ring, and 831 denotes a fastening bolt. The fixed electrode plate 815a is fixed to the fixed electrode base 814a with the fastening bolt 831 via the fastening ring 830.

[0127] [Third embodiment] Fixed electrode made of one plate through-etched Figure 14 shows an example of a servo-type acceleration sensor according to embodiment 3 of the present invention, in which the fixed electrode is formed using only one plate with grooves formed by etching. Figure 14(a) is a view taken along the CC arrow in Figure 14(b), and Figure 14(b) is a front cross-sectional view of only the electrode portion.

[0128] Reference numeral 850 denotes a fixed-side electrode plate, 851 a fixed-side electrode base, 852 an insulating ring, 853 a fixed ring, 854 a coil-side yoke material, 855 a movable-side electrode, and 856a a front-side disk. Similarly to the second embodiment, the fixed-side electrode plate 850 is formed with discontinuous first ring-shaped grooves (857a-857d), discontinuous second ring-shaped grooves (858a-858d), and discontinuous radial grooves (859a-859d). The fixed-side electrode plate is adhesively fixed to the fixed-side electrode base with adhesive portion 860.

[0129] In this embodiment, each discontinuous groove (microgroove) formed on the fixed electrode plate is directly open to the atmosphere on the side opposite to the movable electrode. Therefore, through holes connecting the grooves to the atmosphere as shown in the previous embodiment are not required. If the electrode is configured with through holes connecting the grooves to the atmosphere, the viscous fluid resistance R for air to flow along the grooves will be large. m The groove width h is set so that is sufficiently small. G The groove width h G The wider the grooves are and the more grooves there are, the smaller the effective area of ​​the capacitance becomes. m = 0. As a result, each groove width h G However, the shape of the discontinuous grooves must satisfy the following conditions: (i) The formation of discontinuous grooves ensures that the fixed electrode plate maintains its strength and is not deformed or broken. (ii) The first resonance frequency when the outer periphery of the fixed electrode plate alone is fixed is f P The mass m of the entire moving part of the acceleration sensor and the proportional gain K of the servo amplifier are P The resonant frequency determined by f n When f P >f n Set to.

[0130] As mentioned above, the resonant frequency of a servo-type acceleration sensor is usually f nThe limit is set to 350 to 500 Hz. If the shape of the discontinuous grooves is selected so as to satisfy the above (ii), the influence on the dynamic characteristics (gain and phase characteristics) of the sensor can be avoided.

[0131] [supplement] In Figure 14(b), 861 is an air filter (imaginary line) attached to the opening of the fixed electrode base 851. This air filter is attached to prevent dirt, dust, etc. from entering the gap between the electrodes and to keep the gap between the electrodes clean at all times. The effect of attaching the air filter can be applied to all embodiments of the present invention. Furthermore, the location where the air filter is attached is not limited to the fixed electrode base.

[0132] [Fourth embodiment] Micro-groove processing by double-sided half etching Fig. 15 shows an example of a servo-type acceleration sensor according to a fourth embodiment of the present invention, in which microgrooves are formed on the plate surface by double-sided half-etching. Fig. 15(a) is a view taken along the arrow AA in Fig. 15(c), Fig. 15(b) is a view taken along the arrow BB in Fig. 15(c), and Fig. 15(c) is a front cross-sectional view of only the electrode portion of the sensor body. Fig. 16 shows the shape of the plate alone, with Fig. 16(a) being a front view of the plate, Fig. 16(b) being a side view, and Fig. 16(c) being the back surface of Fig. 16(a).

[0133] Reference numeral 951 denotes a fixed electrode base, 952 denotes an insulating ring, 953 denotes a fixed ring, 954 denotes a coil side yoke material, 955 denotes a movable electrode base, 956 denotes a movable electrode plate, 957a denotes a front side disk, and 958 denotes a central through hole formed in the fixed electrode base.

[0134] The front and back surfaces of the movable electrode plate 956 are symmetrically formed with various grooves and a central recess, as described below. FIG. 16(a) shows the front surface of the movable electrode plate 956. A first ring-shaped groove 959 and a second ring-shaped groove 960 are concentrically formed on the front surface of the movable electrode plate 956. Furthermore, two grooves, a horizontal radial groove 961 and a vertical radial groove 962, are formed in a cross shape around the axis. Reference numeral 963 denotes a recess formed in the axis portion, and 964 denotes the outer periphery of the movable electrode plate 956. The section between the recess 963 and the first ring-shaped groove 959 is section A 965A, the section between the first ring-shaped groove 959 and the second ring-shaped groove 960 is section B 965B, and the section between the second ring-shaped groove 960 and the outer periphery 964 is section C 965C. For example, a number of radial grooves are formed in the section A, such as a radial groove 966a, a radial groove 966b in the section B, and a radial groove 966c in the section C.

[0135] In FIG. 15(a), through holes communicating with the atmosphere are formed in the fixed electrode base 951. 959a is a circle corresponding to the first ring-shaped groove, and 960a is a circle corresponding to the second ring-shaped groove. Through holes communicating with atmospheric pressure, such as 967a, 967b, 967c, and 967d, are formed at the positions of these two equivalent circles. These through holes allow the first ring-shaped groove 959 and the second ring-shaped groove 960 to maintain atmospheric pressure. These through holes, including the central through hole 958, may be formed by etching. FIG. 16(c) shows the back surface (detailed illustration numbers omitted) of the movable electrode plate, which has the same groove shape as the front surface (corresponding to FIG. 15(b)). This back surface is fixed to the movable electrode base 955 with an adhesive.

[0136] This embodiment, in which microgrooves are formed on the plate surface by fine groove processing using double-sided half etching, provides the following effects (1) to (3). (1) The optimum groove shape can be selected. Unlike the through-etching method described above, this method allows for the formation of minute, complex, continuous grooves. This allows for the formation of optimum microgrooves that can suppress the damping effect caused by larger squeeze pressures. (2) Warping of the substrate can be eliminated. In the case of single-sided half etching, as shown in FIG. 17(b), as the substrate becomes thinner, its rigidity decreases, and warping occurs due to residual stress. In this embodiment, in which double-sided half etching is applied, warping of the substrate (movable-side electrode plate 956) can be eliminated. FIG. 17 shows a case in which microgrooves are formed in the movable-side electrode plate 968 by single-sided half etching and through holes, where FIG. 17(a) is a front view of the movable-side electrode plate 968, FIG. 17(b) is a side view, and FIG. 17(c) is a back view. (3) Increased adhesive strength. The back surface (Fig. 16(c)) of the movable electrode plate 956, which has microgrooves formed by double-sided half-etching, is adhesively fixed to the movable electrode base. This configuration allows adhesive to flow into the fluid grooves of the movable electrode plate 956, significantly increasing adhesive strength.

[0137] [Fifth embodiment] A large number (n) of small diameter holes are formed on the electrode surface, and the damping effect can be finely adjusted by the number n. FIG. 18 shows an example of a servo-type acceleration sensor according to a fifth embodiment of the present invention, where FIG. 18(a) is a view taken along the line AA in FIG. 18(b), and FIG. 18(b) is a front cross-sectional view of the acceleration sensor.

[0138] In the above-described embodiment, ring-shaped grooves or cross-shaped radial grooves are formed on the electrode surface to reduce the dynamic pressure of the air viscous fluid. In this embodiment, the squeeze pressure is reduced by forming only a large number of through holes, rather than a continuous groove shape. The key point of this embodiment is that the squeeze pressure reduction effect is adjusted by the number n of through holes, rather than the number of ring grooves. The arrangement of the through holes is axisymmetric so that moment load due to damping force is not applied to the electrode. The greater the number n of through holes, the smaller the damping effect (damping coefficient); conversely, the smaller n, the greater the damping effect (damping coefficient). By setting this n, the damping coefficient can be finely adjusted.

[0139] In FIG. 18(a), 751 is a fixed electrode made of a thin disk, and 752 is a central through-hole. In this embodiment, 52 through-holes 753 are formed in the fixed electrode 751. In FIG. 18(b), 754 is an inner circumferential fixed ring, 755 is an insulating ring, 756 is an outer circumferential fixed ring, and 757 is a movable electrode. A disk-shaped fixed electrode 751 is fixed to the surface of the inner circumferential fixed ring 754 facing the movable electrode. When the total area of ​​the through-holes is ΔS, the total electrode area S A The area excluding ΔS is the effective area S of the capacitance sensor. E If the thickness of the movable electrode is made thin, the diameter of the through holes can be made sufficiently small. When the outer diameter of the electrode is Φ13 mm, the total electrode area S A =133mm 2 In the case of a through-hole diameter of Φ0.1 mm, the number of through-holes is n=52, and the total area is ΔS=0.41 mm 2 The effective area S of the capacitance sensor E =132.6mm 2 The capacitance reduction rate is only 0.3%. When the through-hole diameter is Φ0.3mm, ΔS=3.67mm 2 The capacitance reduction rate is 2.76%. In both cases, the capacitance reduction rate is negligible.

[0140] [Sixth embodiment] Electrode tilt measurement using a multi-electrode structure Figure 19 shows an example of a servo-type acceleration sensor according to a sixth embodiment of the present invention, in which multiple independent electrodes are attached to the electrode surface, making it possible to measure the inter-electrode gap and tilt angle from the electrostatic capacitance of each electrode. Figure 19(a) is a front view of the sensor body, and Figure 19(b) is a front cross-sectional view. The dashed line AA in Figure 19(b) is a moving magnet type (MM type) actuator that drives the movable part in the axial direction. The dashed line BB indicates a displacement detection part that detects electrostatic capacitance.

[0141] [1-1] Actuator configuration In the actuator section (area AA indicated by the two-dot chain line) in Figure 19(b), reference numeral 101 denotes a front permanent magnet, 102 denotes a rear permanent magnet, and 103 denotes a pole piece section (movable side yoke material). Both the front and rear permanent magnets are composed of multiple segment-type permanent magnets magnetized in the radial direction and are attached to the pole piece section 103. The radial magnetization direction of the rear permanent magnet 102 is opposite to that of the front permanent magnet 101. Reference numerals 104 and 105 denote cylindrical gaps formed on the left and right sides of the pole piece section 103 to reduce the weight of the pole piece section. Reference numeral 106 denotes a front-side disc, 107 a rear-side disc, 108 a movable-side electrode supported by the front-side disc, 109 a coil-side yoke material, 110 a coil bobbin, 111a a front-side force coil, 111b a front-side calibration coil, 112a a rear-side force coil, 112b a rear-side calibration coil, and 113 a coil bobbin fastening bolt (shown by imaginary lines).

[0142] Numeral 114 denotes a magnetic gap formed between the inner circumferential surface of the coil bobbin 110 and the two permanent magnets, with 114a being the front magnetic gap and 114b being the rear magnetic gap. As shown by the chain arrow, a closed loop magnetic circuit B is formed by "rear permanent magnet 102 → rear magnetic gap 114b → coil side yoke material 109 → front magnetic gap 114a → permanent magnet 101 → pole piece part 103 → rear permanent magnet 102." MThe front-side disc 106 serves both as support for the movable portion and as a conductive path for detecting capacitance. In order to detect minute capacitance signals between the movable-side electrode 108 and the fixed-side electrode (described later), the conductive path connecting the movable-side electrode 108 to the outside is completely electrically insulated. That is, the front-side disc 106 is fastened to the coil-side yoke member 109 by bolts 116 via an outer ring 115. The outer ring 115 is made of a non-conductive material, and the front-side disc 106 and the outer ring 115 are fixed in advance with an adhesive. In addition, the bolt hole diameter formed in the front-side disc 106 is larger than the bolt diameter, so that the bolt 116 and the front-side disc 106 are electrically insulated. The movable-side electrode 108 is adhesively fixed to the front-side disc 106 at a joint 117. In addition, the center of the movable-side electrode 108 is adhesively fixed to the end face of the pole piece portion via a non-conductive material 118. Although eddy currents occur in the pole piece section and the coil-side yoke material, the electrical insulation measures (non-conductive materials 115, 118) prevent the capacitance signal between the two electrodes (movable side and fixed side) from being affected by these eddy currents. Examples of non-conductive materials that can be used include inorganic solid insulating materials such as mica, porcelain (ceramics), glass, and polyimide (engineering plastic). To control the currents flowing through the two force coils 111a, 112a and the calibration coils 111b, 112b, the lead wires from these coils pass through the coil-side yoke material 109 and are connected to an external control circuit (not shown).

[0143] The movable part of this embodiment is composed of two permanent magnets 101 and 102, a pole piece part 103, and a movable side electrode 108. The fixed part is composed of a coil bobbin 110 in which each coil is housed, and a coil side yoke material 109.

[0144] [1-2] Configuration of displacement detection unit In the displacement detection section (dash line BB) in Figure 19(b), 119 is the fixed electrode base and 120 is the fixed electrode plate. The fixed electrode base 119 is made of a non-conductive material (ceramic material). The fixed electrode plate is adhesively fixed to the fixed electrode base. 121 is an insulating ring and 122 is a fixing ring. The fixed electrode base is held against the fixing ring via the insulating ring. 123 is an adhesive application section for fixing the fixing ring 121 to the coil side yoke material 109.

[0145] Figure 20 shows the state in which fixed-side electrode plate 120 is attached to fixed-side electrode base 119, with Figure 20(a) being a side cross-sectional view and Figure 20(b) being a front view. Fixed-side electrode plate 120 is composed of four independent electrodes. In Figure 20(b), 120A is fixed electrode A, 120B is fixed electrode B, 120C is fixed electrode C, and 120D is fixed electrode D. 124a is the groove between fixed electrode A and fixed electrode B, 124b is the groove between fixed electrode B and fixed electrode C, 124c is the groove between fixed electrode C and fixed electrode D, and 124d is the groove between fixed electrode B and fixed electrode A. Each of these grooves (1) provides electrical insulation between electrodes and (2) reduces the squeeze pressure of the air viscous fluid, achieving the effects of (1) and (2) above. Reference numeral 125 denotes a central through hole formed in the fixed electrode plate, and 126 denotes a central through hole formed in the fixed electrode base 119. Reference numerals 127a to 127h denote eight communication holes formed in the outer periphery of each fixed electrode. A circumferential groove 128 is formed in the outer periphery of each fixed electrode to accommodate these communication holes.

[0146] In Fig. 20(a), 129A and 129C are signal lines for detecting the capacitance of the fixed electrode A and the fixed electrode C. 130A and 130C are through holes for drawing out the signal lines. Similar signal lines and through holes are also formed in the fixed electrode B and the fixed electrode D (not shown).

[0147] [2] Manufacturing the fixed electrode plate using the etching method 21 to 24 show an example in which the fixed electrode plate is mass-produced by an etching method.

[0148] FIG. 21 shows Step 1, "mass production by etching," in which several dozen etched parts, including the fixed electrode plate, are bonded to a single large-area metal plate. Reference numeral 131 denotes a ring-shaped portion, 132 denotes a bridge (joint) A connecting this ring-shaped portion to another ring-shaped portion (not shown), and 133 denotes a bridge B connecting ring-shaped portion 131 to fixed electrode 120A. FIG. 22 shows Step 2, "cutting out one electrode," in which four bridges A between each ring-shaped portion have been cut off. FIG. 23 shows Step 3, "attaching an electrode to a ceramic plate." The fixed electrode plate, including the ring-shaped portion cut off in Step 2, is adhesively fixed to the fixed electrode base, which is made of a non-conductive material (ceramic material).

[0149] 24 shows the state after "cutting and removing unnecessary portions" in Step 4. By cutting the bridges B at four locations connecting ring-shaped portion 131 to fixed electrodes 120A, 120B, 120C, and 120D, ring-shaped portion 131 is separated from each fixed electrode.

[0150] [3] Measurement of the gap between electrodes and the tilt angle Figure 25 is a model diagram showing how to measure the gap between electrodes and the tilt angle using a sensor of the present invention incorporating multiple electrodes. The Z axis is defined in the direction of the center of the drawing relative to the X and Y axes shown in Figure 22. Furthermore, the Z axis in the direction of rotation around the Z axis is defined as Θ axis and the Y axis in the rotation direction Θ Define the axis. In this case, the Z axis Θ , Y Θ The value of Z is the inclination angle of the gap between the electrodes. Θ , Y Θ To determine the value of , four sets of independent electrodes were placed in the circumferential direction.

[0151] For example, if the capacitance between the fixed electrode A and the movable electrode 108 facing the fixed electrode C is measured, the gap Z between the electrodes can be calculated. Θ The tilt angle in the axial direction can be calculated. Θ The tilt angle in the axial direction is calculated. Θ and Y Θ The tilt angle and X-axis position of the fixed electrode base 119 can be adjusted so that the value of →0 and the capacitance reaches the target value (adjustment tools, etc., are not shown). In the mass production assembly process of conventional acceleration sensors, the absolute value of the inter-electrode gap and the tilt angle of the gap were determined only by observing the slit (gap) between the electrodes from the outer surfaces of the two electrodes using optical means such as a high-magnification camera. However, the practical measurement limit of the optical gap adjustment method was a slit width of d = 20 to 30 μm. This difficulty in adjusting the inter-electrode gap was a major issue that hindered improvements in the sensitivity of servo-type acceleration sensors and was also a major factor in reducing yield and reliability during mass production.

[0152] By applying the sensor structure and manufacturing method of the present invention, the absolute value of the inter-electrode gap and the allowable tilt angle can be brought sufficiently close to the target value. For example, by narrowing only the gap while keeping the outer diameter of the electrodes the same, the capacitance can be increased, improving the sensor sensitivity. Since the sensor structure and manufacturing method can be applied to etching, which is excellent for mass production, the only work required is to draw out the signal lines of each electrode, so there is no significant increase in cost. Furthermore, the behavior of the moving part during sensor operation can be observed in real time by observing changes in the capacitance (gap) of each fixed electrode, which is effective in devising measures to improve the dynamic stability of the moving part. [Explanation of symbols]

[0153] 204 Fixing member 210, 211 Elastic member 214 Movable side electrode 217 Fixed side electrode 223 Groove 224a~224d Hole

Claims

1. a housing that is a fixed member; a movable member provided so as to be movable in a predetermined direction relative to the housing; an elastic member that supports the movable member so that the movable member is disposed with a gap in the housing; a displacement detection unit that detects a displacement of the movable member in a predetermined direction; a driving means driven by a servo amplifier so as to generate a force that returns the movable member to the original position when the displacement detection unit detects a relative displacement of the movable member from the original position; a movable-side electrode provided on the movable member; a fixed electrode provided on the housing side to face the movable electrode, the displacement detection unit is configured to detect electrostatic capacitance formed in a gap between the movable electrode and the fixed electrode, a groove or hole having a flow path connected to the atmosphere is formed on the relative moving surface between the movable electrode and the fixed electrode so as to reduce a damping effect due to dynamic fluid pressure generated in the gap, The damping ratio obtained from the dynamic characteristics of the sensor output when the vibration detector body is subjected to sweep excitation is defined as ζ 0 Then, 0.2≦ζ 0 1. A servo type vibration detector, wherein the groove or the hole is formed so as to satisfy the condition ≦0.

6.

2. The damping ratio calculated from the dynamic characteristics of the sensor output when the vibration detector body is subjected to sweep vibration in a state where the flow path connecting the groove or hole to the atmosphere is blocked is defined as ζ d Then, ζ d 2. The servo type vibration detector according to claim 1, wherein the vibration detector is configured so that the value of the vibration ratio is greater than 0.

6.

3. 2. The servo type vibration detector according to claim 1, wherein the grooves are substantially concentric circular grooves or substantially radial grooves extending radially with respect to the axis of the fixed electrode or the movable electrode.

4. A servo-type vibration detector as described in claim 1, characterized in that a plate-shaped member in which the groove or hole is formed by surface processing technology is attached to the movable electrode and the fixed electrode with bolts or adhesive.

5. 2. A servo-type vibration detector according to claim 1, characterized in that a plurality of small diameter holes communicating with the atmosphere are opened on the relative moving surface between the movable electrode and the fixed electrode, and the plurality of small diameter holes are arranged approximately axially symmetrically.

6. a housing that is a fixed member; a movable member provided so as to be movable in a predetermined direction relative to the housing; an elastic member that supports the movable member so that the movable member is disposed with a gap in the housing; a displacement detection unit that detects a displacement of the movable member in a predetermined direction; When the displacement detection unit detects a relative displacement of the movable member from an origin position, a driving means driven by a servo amplifier to generate a force that returns the movable member to its original position; a movable-side electrode provided on the movable member; a fixed electrode provided on the housing side to face the movable electrode, the displacement detection unit is configured to detect electrostatic capacitance formed in a gap between the movable electrode and the fixed electrode, a discontinuous groove portion communicating with the atmosphere is formed on a surface of the movable electrode and the fixed electrode that moves relative to each other so as to reduce a damping effect due to dynamic fluid pressure generated in a gap between the movable electrode and the fixed electrode, A servo type vibration detector characterized in that the discontinuous groove portion is formed by surface processing technology to penetrate the plate-like member.

7. A servo-type vibration detector as described in claim 6, characterized in that the plate-shaped member, which has an outer diameter larger than that of the movable electrode, is attached to the fixed electrode at its outer periphery, and a hole portion connecting the discontinuous groove portion to the atmosphere is formed in the fixed electrode or the movable electrode.

8. A servo-type vibration detector as described in claim 6, characterized in that the outer periphery of the plate-shaped member is attached to the fixed electrode, and the area where the discontinuous groove portion is formed is open to the atmosphere.

9. The mass of the movable member of the servo type vibration detector is m, and the proportional gain of the servo amplifier is K. P , m and K P The resonant frequency determined by f n , the first resonance frequency when the outer periphery of the plate-like member is fixed is f P As, f P >f 0 9. The servo type vibration detector according to claim 8, wherein the discontinuous grooves are formed so as to satisfy the following condition.

10. a housing that is a fixed member; a movable member provided so as to be movable in a predetermined direction relative to the housing; an elastic member that supports the movable member so that the movable member is disposed with a gap in the housing; a displacement detection unit that detects a displacement of the movable member in a predetermined direction; When the displacement detection unit detects a relative displacement of the movable member from an origin position, a driving means driven by a servo amplifier to generate a force that returns the movable member to its original position; a movable-side electrode provided on the movable member; a fixed electrode provided on the housing side to face the movable electrode, the displacement detection unit is configured to detect electrostatic capacitance formed in a gap between the movable electrode and the fixed electrode, a groove communicating with the atmosphere is formed on a surface of the movable electrode and the fixed electrode that moves relative to each other so as to reduce a damping effect due to dynamic fluid pressure generated in a gap between the movable electrode and the fixed electrode; A servo-type vibration detector characterized in that the groove portions are formed in an approximately symmetrical shape on the front and back of the plate-shaped member by half-etching, one surface of the plate-shaped member is attached to the electrode surface with bolts or adhesive, and the other electrode surface opposite the plate-shaped member has a hole formed therein that communicates with the atmosphere.

11. a housing that is a fixed member; a movable member provided so as to be movable in a predetermined direction relative to the housing; an elastic member that supports the movable member so that the movable member is disposed with a gap in the housing; a displacement detection unit that detects a displacement of the movable member in a predetermined direction; When the displacement detection unit detects a relative displacement of the movable member from an origin position, a driving means driven by a servo amplifier to generate a force that returns the movable member to its original position; a movable-side electrode provided on the movable member; a fixed electrode provided on the housing side to face the movable electrode; the displacement detection unit is configured to detect electrostatic capacitance formed in a gap between the movable electrode and the fixed electrode, One of the relative movement surfaces between the movable electrode and the fixed electrode is made of a non-conductive material, and a plurality of electrode surfaces are divided and fixed in the circumferential direction on the non-conductive material surface, and approximately radial circulation grooves are formed at the boundaries between these electrode surfaces, and these circulation grooves are formed to reduce the damping effect due to dynamic fluid pressure generated in the gap between the movable electrode and the fixed electrode and to provide electrical insulation between the electrode surfaces, A servo type vibration detector, characterized in that a plurality of sets of independent capacitance type displacement detectors are formed by the plurality of electrode surfaces and opposing electrode surfaces.

12. 12. A method for assembling a servo type vibration detector according to claim 11, characterized in that the tilt angle of the gap between the movable side electrode and the fixed side electrode is measured based on the signals from the plurality of sets of capacitance type displacement detectors, and the tilt is corrected based on the measurement results.

13. A servo-type vibration detector as described in claim 1, characterized in that it comprises a coil fixed to the fixed member, a movable member arranged with a gap between it and the fixed member, a permanent magnet arranged so that magnetic flux flows through the gap, and the movable member being composed of the permanent magnet and a movable side yoke material connecting the permanent magnet to a magnetic path, or only the movable side yoke material, and the movable member, the gap, the fixed member, and the permanent magnet form a closed loop magnetic circuit, thereby constituting the driving means using electromagnetic force to move the movable member axially.

14. a coil fixed to the fixed member; a permanent magnet arranged so that magnetic flux flows in the gap, The servo-type vibration detector described in claim 1, characterized in that the movable member is composed of the permanent magnet and a movable side yoke material connecting the permanent magnet to a magnetic path, or only the movable side yoke material, and the movable member, the gap, the fixed member, and the permanent magnet form a closed loop magnetic circuit, thereby constituting the driving means using electromagnetic force to move the movable member axially.

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