Servo type vibration detector and vibration control device

Abstract

To solve the problem in which regarding a conventional servo type vibration detector composed of a coil, a permanent magnet, and a displacement detector, cost is high due to the complexity of ultra-fine wire processing of a coil and the complexity of structure, and high yield cannot be obtained during mass production.SOLUTION: A movable member connected to a displacement detector via a gap is placed with respect to a fixed member in which a coil is fixed. By placing the coil within a closed loop magnetic circuit composed of a permanent magnet and the movable member and the fixed member, Lorentz force that moves the movable member in an axial direction is generated. The above configuration makes complicated wiring processing of the coil unnecessary, and mass productivity can be greatly improved.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] 1. Trends The use of vibration control to block and suppress minute vibrations is becoming more widespread in various fields such as semiconductor manufacturing processes, liquid crystal manufacturing processes, and precision machining. Microfabrication 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 more highly integrated and miniaturized, the processing speed will increase and the equipment size will grow, 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 a control signal is created based on displacement, velocity, and acceleration information from vibration sensors placed in multiple locations on a structure to be vibration controlled (for example, a precision vibration isolation table), and the control device is then controlled.

[0004] FIG. 52 shows a model diagram of a conventional active vibration isolation table. This active vibration isolation table is well known as described in Patent Document 3. A plurality of pairs of pneumatic actuators (502a, 502b) for supporting a base plate 501 are arranged on a floor surface 500. A precision device (not shown) is mounted on the base plate 501. 503 is an acceleration sensor for detecting the acceleration of the base plate 501 in the vertical and horizontal directions, and 504 is an acceleration sensor for detecting the acceleration of the floor surface 500 (vibration state of the foundation). 505a, 505b are displacement sensors for detecting the vertical and horizontal relative displacements of the base plate 501 with respect to the floor surface 500, respectively. Output signals from each of 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 a pipe 507. By adjusting the flow rate of compressed air supplied to and exhausted from the pneumatic actuator 502a by the servo valve 508, the internal pressure of the actuator 502a is controlled to drive the pneumatic actuator.

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

[0006] Sources of vibration that can cause ground disturbances include walking vibration caused by human movement, which is 1 to 3 Hz, motors such as air conditioners, which are 6 to 35 Hz, and the resonance points of floors and walls, which are around 10 to 100 Hz. Ultra-high rise and vibration-isolated buildings have natural frequencies in the vicinity of 0.2 to 0.3 Hz. Wind sway also causes micro-vibrations of 0.1 to 1.0 Hz in buildings. Therefore, vibration isolation tables are required to not only suppress high-frequency vibrations, but also to eliminate 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 due to linear disturbance, the structure including the vibration isolation table will be struck by the acceleration and deceleration of the stage, and will oscillate due to the driving reaction force. The performance of the stage cannot be maintained unless the vibration due to the strike and the oscillating caused by the driving reaction force are suppressed. In short, a vibration isolation device is required to have the function of both "vibration isolation" due to ground disturbance and "vibration control" due to linear disturbance.

[0008] 3. Role of vibration sensors in active vibration isolation systems Active vibration control employs a control method using state feedback. This is a method of controlling a control device based on acceleration, velocity, and displacement information from vibration sensors placed in 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 mainly used to control state quantities above 10 Hz, velocity signals to control state quantities between 1 and 10 Hz, and displacement signals to control state quantities below 1 Hz. For example, (i) If acceleration feedback is performed using a signal from an acceleration sensor (using acceleration sensor 503 in FIG. 52) placed on the base plate 501, it becomes equivalent to an increase in mass M, and has the effect of lowering the natural frequency and reducing the resonance peak. (ii) If the signal from the acceleration sensor (503 in FIG. 52) is converted into an absolute velocity or absolute displacement signal and feedback or feedforward is applied, the vibration isolation performance can be significantly improved in a wide frequency range. (iii) If the signal from the acceleration sensor (504 in FIG. 52) placed directly under the base 501 is converted into an absolute velocity or absolute displacement signal and feedforward is similarly performed, the vibration isolation performance can be improved over a wide frequency range.

[0009] To carry out the above controls (ii) and (iii), velocity and position information for the inertial space is required. Since an acceleration sensor can measure acceleration for the inertial space, the acceleration applied to the controlled object can be detected by attaching an acceleration sensor to the controlled object. Therefore, conventional active vibration isolation devices adopt a method in which the output of the acceleration sensor is integrated once to obtain a velocity signal, and then integrated twice to obtain a displacement signal.

[0010] 4. Basic structure and detection principle of acceleration sensors Figure 53 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 body 302 against vibration measurement surface A, and 304 is a damper. Mass body 302 also serves as the movable electrode of the capacitance type sensor. 305 is a fixed electrode arranged on the opposing surface of the movable electrode (mass body 302), and 306 is the gap between the two electrodes.

[0011] 307 is an electromagnetic actuator that drives the mass body 302 in a vertical direction relative to the vibration measurement surface A. Since the capacitance C is determined by the size of the gap 306, By measuring the absolute displacement U of the ground motion and the absolute displacement X of the mass body, the relative displacement A servo circuit 310 (shown by a two-dot chain line) uses the relative displacement signal UX to Profitable K P The amplifier 311 amplifies the input signal by a displacement amplifier 311.

[0012] The detection principle of the acceleration sensor will be described 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]

number

[0015]

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[0016]

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[0017] 5.Specific structure of conventional servo-type acceleration sensor The specific structure of servo-type accelerometers can be roughly divided into two types: (1) a type in which the mass part moves linearly, and (2) a type in which the mass part moves in an oscillating manner. Below, examples of these two types of conventional sensors are explained.

[0018] (5-1) Conventional example of linear motion acceleration sensor Fig. 54 is a front cross-sectional view showing a specific structural example of a conventional linear motion acceleration sensor. The basic principle of the linear motion type is disclosed in Patent Document 1. It is configured based on the basic structure and detection principle shown in Fig. 53. 11 is a permanent magnet, 12 is a pole piece portion, 13 is a pole piece protrusion portion, 14 is a permanent magnet side yoke material, 15 is a coil side yoke material, 16a is a force coil, 16b is a calibration coil, 17 is a coil bobbin, 18 and 19 are coil bobbin support members made of non-magnetic and non-conductive material, 20 is a front side disc-shaped spring, 21 is a rear side disc-shaped spring, 22 is a front side connecting member between the front side disc-shaped spring 20 and the coil side yoke material 15, and 23 is a rear side connecting member between the rear side disc-shaped spring 21 and the coil side yoke material 15.

[0019] Reference numeral 24 denotes a movable electrode, 25 a fixed electrode, 26 a front panel, 27 a central plate, and 28 a fastening member for fastening the fixed electrode 25 and the front panel 26 .

[0020] A radial magnetic gap 29 is formed between the outer periphery of the pole piece portion 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 "permanent magnet 11 → pole piece portion 12 → magnetic gap 29 → coil side yoke material 15 → permanent magnet side yoke material 14". When a current flows through the force coil 16a arranged in the space of the magnetic gap 29, a Lorentz force is generated that moves the movable side electrode 24 in the axial direction. 30 is a gap formed by the movable side electrode 24 and the fixed side electrode 25. Since the capacitance C is determined by the size of the gap 30, 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, can be detected by measuring the capacitance C. The servo circuit is composed of a displacement detector 31, an amplifier 32, and a driver 33. The amplifier 32 and the driver 33 convert the relative displacement signal UX into a signal with 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 obtained, as described above.

[0021] (5-2) Conventional example of a swing-type acceleration sensor (1) Overall configuration of the sensor Fig. 56 is a front cross-sectional view showing an example of the oscillating motion type sensor disclosed in Patent Document 2, in which 590a is a pendulum located within a disk-shaped frame body 590. Pendulum 590a is formed in a tongue shape with a portion of its circumference cut out, and is supported by frame body 590 via hinge 590b. Frame body 590, pendulum 590a, and hinge 590b are integrally formed from, for example, quartz glass. Hinge 590b is thin and elastically deformable, and input acceleration allows pendulum 590a to be displaced in the vertical direction of the figure.

[0022] Reference numerals 591 and 592 denote a pair of magnetic yokes, 593 a pole piece bottom, 594 a permanent magnet, and 595 a ball piece top. The permanent magnet 594 is magnetized in the thickness direction, and annular magnetic gaps 596 are formed between the inner peripheral surfaces of the open ends of the magnetic yokes 591 and 592 and the outer peripheral surface of the pole piece top 595. Coil bobbins 598 around which torque coils 597 are wound are attached to both plate surfaces of the pendulum 590a so as to be positioned within the annular magnetic gaps 596.

[0023] On both plate surfaces of the pendulum 590a, a capacitance electrode 590c is formed in an arc shape along the outer periphery of the tip side of the tongue shape. Electrode surfaces 591e and 592e face the capacitance electrode 590c with a predetermined gap therebetween.

[0024] In a servo-type accelerometer having such a configuration, the displacement of the pendulum 590a due to the acceleration input is detected as a change in the capacitance between the capacitance electrode 590c and the electrode surfaces 591e, 592e. The electrode surfaces 591e, 592e are at a common potential, and the detection signals of the capacitance electrodes 590c on both plate surfaces of the pendulum 590a are differentially amplified by a servo amplifier (not shown), and a torque current based on the capacitance difference is passed through a pair of torque coils 597. The interaction between this torque current and the magnetic field of the permanent magnet 594 causes the displaced pendulum 590a to return to its original position and balance at the neutral point. Since the torque current at this time is proportional to the acceleration applied to the pendulum 590a, the input acceleration can be obtained from this current. The coil terminals 597a, 597b of the torque coil 597 are bonded and electrically connected to a metal conductor (not shown) on the pendulum 590a.

[0025] (2) Pendulum structure FIG. 58 shows a plan view of the pendulum 590a. FIG. 58(a) shows one side, and FIG. 58(b) shows the other side. The frame 590, the pendulum 590a, and the hinges 590b1 and 590b2 are formed, for example, by etching from a single disk of quartz glass. The pendulum conductor A is formed in an arc shape with a width approximately half the width of the frame 590 on one side of the frame 590, and one end of the arc-shaped metal conductor is extended in the extension direction on one hinge 590b1, and is formed in a shape that is folded back in a hook shape toward the center after passing the center of the pendulum 590a. The arc-shaped pendulum conductor A constitutes one input / output end of the torque current.

[0026] The pendulum conductor B is formed on one surface with the same width as the pendulum conductor A, from an end of the pendulum conductor A located at the center of the pendulum 590a, sandwiching the center of the pendulum 590a, toward the outer edge of the pendulum 10a at a position spaced apart from the end of the pendulum conductor A at a distance substantially equal to the distance between the bobbin conductors described below. Furthermore, the pendulum conductor B is formed continuously along the side surface of the outer edge of the pendulum 590a between the pair of hinges 590b1, 590b2 to the other surface. The shape of the pendulum conductor B on the other surface is the same as the shape on the one surface described above. The pendulum conductor B connects the two torque coils 597, left and right, in series.

[0027] Pendulum conductor C is formed on the other surface in approximately the same shape as the above-mentioned pendulum conductor A. The end of pendulum conductor C is formed in an arc shape on frame body 590 on one surface with a width approximately equal to that of frame body 590. The end of pendulum conductor C on one surface and pendulum conductor C on the other surface are formed continuously along the inner diameter side surface of frame body 590. The arc-shaped pendulum conductor C constitutes the other input / output end of the torque current.

[0028] The capacitance detection electrode D is formed in an arc shape along the outer edge of the pendulum 590a on one side of the pendulum 590a, and further passes over the hinge 590b2 to form an arc-shaped end portion on the frame body 590 along the outer periphery of the frame body 590 with a width approximately half the width of the frame body 590.

[0029] Furthermore, a capacitance detection electrode E is formed on the other surface of the pendulum 590a in the same manner as the capacitance detection electrode D. Furthermore, the capacitance detection electrode E continues along the inner diameter side surface of the frame body 590 onto one surface of the frame body 590, and an end portion is formed on one surface of the frame body 590 in an arc shape with approximately the same width as the frame body 10. The respective ends of the capacitance detection electrodes D and E on one surface of the frame body 590 are connected to a servo amplifier (not shown).

[0030] Each of the pendulum conductors described above is formed as a thin film of gold (Au) sputtered or vacuum-deposited on the surfaces of frame 590, pendulum 590a, and hinges 590b1, 590b2 made of quartz glass.

[0031] The basic structure of the linear motion acceleration sensor and the oscillatory motion acceleration sensor described above can be classified according to the elastic support method for the moving part. In the linear motion type, the direction of movement of the moving part is the axis, and springs are arranged in the circumferential direction of this axis. In the oscillatory motion type, the moving part is supported by a cantilever with one end as a fixed end and the other as a free end. [Prior art documents] [Patent documents]

[0032] [Patent Document 1] JP 2004-205284 A [Patent Document 2] JP 2010-96509 A [Patent Document 3] JP 2006-283966 A Summary of the Invention [Problem to be solved by the invention]

[0033] In the case of the linear motion acceleration sensor disclosed in Patent Document 1, there was a big problem in terms of production technology due to the basic operating principle and structure. Fig. 55a is a front view showing the shape of the front side disk-shaped spring 20, and Fig. 55b is a front cross-sectional view with the front side panel 26, fixed side electrode 25, etc. removed from the overall view of the sensor mentioned above (Fig. 54). Fig. 55c is an enlarged view of part A in Fig. 55b, showing the state in which the movable side electrode 24 is deformed in the axial direction.

[0034] Four conductive paths are required to connect each terminal of the force coil 16a and the calibration coil 16b to an externally installed control circuit. If the conductive path connecting the movable electrode 24 and the displacement detector 31 (FIG. 54) is further included, a total of five independent conductive paths are required. Since the two coils and the movable electrode move in the axial direction, it is not possible to connect the five terminals and the external fixed part with lead wires. Therefore, as shown in FIG. 55a and FIG. 55c, the five conductive paths are formed by using the front side disc-shaped spring 20 and the rear side disc-shaped spring 21. That is, the two disc-shaped springs 20 and 21 are formed to elastically support the movable part (coil bobbin 17, movable electrode 24, etc.) and also to function as the five independent conductive paths.

[0035] In FIG. 55a, 34a, 34b, and 34c are the outer peripheral fixed parts of the front disk-shaped spring 20. These three outer peripheral fixed parts are cut at three circumferential positions as shown by the chain circle AA in order to provide electrical insulation. 35a, 35b, and 35c are the inner peripheral spring parts of the front disk-shaped spring. These three inner peripheral spring parts are cut at three circumferential positions as shown by the chain circle BB in order to provide electrical insulation. 36a, 36b, and 36c are soldering parts for conducting each coil terminal and the inner peripheral spring parts. FIG. 55c shows a state in which the terminal of the calibration coil 16b and the inner peripheral spring part 35c are conducted by the soldering part 36c. Incidentally, the coil wire diameter used in the servo type acceleration sensor is, for example, an extremely fine wire of about 30 μm.

[0036] That is, conventional servo type acceleration sensors require the process of "cutting, insulating, and soldering" between the disk-shaped spring and the coil as a production technology issue due to the basic operating principle and structure. This complicated process was the main factor that reduced the yield rate during mass production and reduced reliability. When considering long-term reliability, the small-diameter disk-shaped spring used in linear motion acceleration sensors must be made of metal. The reason for this is that the mechanical resonance frequency determined by the inertial mass of the moving part and the spring stiffness must be sufficiently low from the perspective of sensor performance, and the spring stiffness value must be set small. Small-diameter disk-shaped springs are greatly deformed by small external forces. Therefore, it is difficult to adopt a structure that combines a non-metallic material (e.g., quartz glass) and a conductive thin film (conductive path), as used in oscillatory motion acceleration sensors.

[0037] The reason why the conventional oscillating acceleration sensor disclosed in Patent Document 2 uses a thin-film technique that requires expensive processing equipment such as sputtering and vacuum deposition is that it requires (i) a conductive path connecting a pair of oscillating torque coils to an external control circuit, and (ii) a conductive path connecting a capacitance electrode formed on the surface of the oscillating pendulum 590a to an external control circuit. The above-mentioned multiple independent conductive paths are formed as a thin film on the surface of the elastically deformable thin hinges 590b1, 590b2. Figure 57 shows an enlarged view of the state in which the pendulum 590a oscillates.

[0038] In addition to this method, it is possible to use a method in which multiple thin conductors (wires) are soldered to the moving member and the fixed member, or connected with a conductive adhesive. In this case, the spring load caused by the deformation of the wire is applied in parallel to the spring stiffness of the hinge part, which affects the mechanical resonance frequency. In addition, the repeated stress applied to the wires can cause fatigue failure and other deterioration in reliability.

[0039] Therefore, in both linear motion and oscillating motion servo acceleration sensors, the conductive paths that connect the movable and fixed parts and carry multiple signals must be formed using elastic materials that connect the two. This requires a complex structure and production method, which increases costs and is a major factor in reducing yields and reliability during mass production.

[0040] As an example of configuring an active vibration isolation table, four-point support active control is assumed. In this case, actuators are placed at the four corners, and the actuators are installed diagonally, with two points in the horizontal X direction and two points in the Y direction. Each actuator also incorporates an actuator that supports the load in the Z direction. Therefore, a total of eight actuators are placed, and eight acceleration sensors are required to control each actuator. Furthermore, if a sensor to detect the acceleration of the floor surface is included, a total of nine expensive acceleration sensors are required. Therefore, in the case of a multi-axis control active vibration isolation table, there is a serious issue in that the large number of acceleration sensors required makes it a high cost ratio to the overall system. [Means for solving the problem]

[0041] As mentioned above, the difficulty of wiring, which is the main cause of yield reduction, is an unavoidable issue with the moving coil type (MC type) due to the movement of the coil in the moving part. This invention goes back to the origin of this issue and focuses on the fact that the actuator part of a servo type acceleration sensor forms a closed loop magnetic circuit with three elements, namely, "permanent magnet," "coil," and "yoke material." If the "coil," one of these three elements, can be fixed, the fatal issue of the moving coil type (MC type), i.e., the difficulty of wiring, which is the main cause of yield reduction, can be solved in one fell swoop.

[0042] However, The first aspect of the present disclosure The servo type vibration detector of the present invention comprises a fixed member, a movable member that is movable in a predetermined direction relative to the fixed member and configured to allow magnetic flux to flow therethrough, an elastic member that supports the movable member so that it is positioned relative to the fixed member via a gap, a displacement detection unit that detects displacement of the movable member in the predetermined direction, and a driving means that generates an electromagnetic force that returns the movable member to its original position when a relative displacement of the movable member from its original position is detected by the displacement detection unit, wherein the driving means comprises a coil fixed to the fixed member and the movable member comprises at least a movable side yoke material that forms part of a closed loop magnetic circuit.

[0043] That is, in this invention, the coil is fixed to the fixed member, a permanent magnet is arranged so that magnetic flux flows in the gap between the fixed member and the movable member, and the movable member is composed of a permanent magnet and a yoke material, or just this yoke material. The movable member is driven by the electromagnetic force generated by forming a closed loop magnetic circuit. This invention eliminates the need for complex wiring processing in the production process as with moving coil types, greatly simplifying mass production methods and reducing production costs.

[0044] The present disclosureIn the servo type vibration detector of the invention related to 2, the movable member further comprises a permanent magnet which forms the closed loop magnetic circuit, the movable yoke material is connected to one of the magnetic pole faces of the permanent magnet and is arranged within the coil, and the driving means is configured to apply a current to the coil, thereby moving the permanent magnet and the movable yoke material in the specified direction by the reaction force of the Lorentz force that a current-carrying conductor is subjected to in a magnetic field.

[0045] That is, in the present invention, when a current flows through a conductor placed in a magnetic field, the Lorentz force, which is an electromagnetic force, is generated in the conductor. In all actuators, regardless of the type of driving principle, the force relationship between the fixed side and the moving side is relative. That is, in the present invention, when a current flows through the fixedly arranged coil, the reaction force of the Lorentz force that moves the permanent magnet in the axial direction is utilized.

[0046] The present disclosure The servo type vibration detector of the invention relating to 3 further comprises a permanent magnet fixed to the fixed member and forming the closed loop magnetic circuit, the movable yoke is spaced apart from either of the magnetic pole faces of the permanent magnet, the movable yoke material is disposed within the coil, and the driving means is configured to move the movable yoke material in the specified direction by the reaction force of the Lorentz force that a current-carrying conductor is subjected to in a magnetic field when a current is applied to the coil.

[0047] That is, in this invention, not only the coil but also the permanent magnet is fixed, and only the yoke material is moved to configure the actuator of a servo type acceleration sensor. In other words, this is a proposal for a moving yoke type (MY type (provisional name)) that can be called the "third linear motor." The features of the MY type acceleration sensor are: (1) As with the MC type, the mass of the moving parts can be reduced. (2) As with the MM type, there is no need to process the extremely fine wire of the coil. In other words, it is possible to eliminate the disadvantages of both the MM and MC types and combine the advantages of both.

[0048] The present disclosure In the servo type vibration detector of the invention related to 4, the displacement detection unit comprises a movable side electrode provided on the movable member and a fixed side electrode fixed to the fixed member so as to face the movable side electrode, and is configured so that the displacement of the movable member is detected based on a change in electrostatic capacitance formed between the movable side electrode and the fixed side electrode.

[0049] That is, the present invention realizes a high-resolution servo-type acceleration sensor by applying the electrostatic capacitance type, which provides the highest detection accuracy among various sensors.

[0050] The present disclosure In the servo type vibration detector of the invention related to item 5, the gap portion comprises a first gap portion and a second gap portion which form a radial gap between the movable member and the fixed member within the closed loop magnetic circuit, a coil for generating the Lorentz force is fixedly arranged in the first gap portion, and the second gap portion is a magnetic connecting portion for passing magnetic flux between the movable member and the fixed member.

[0051] That is, in the present invention, while the conventional MC type has only one gap that forms a closed loop magnetic circuit, the MM type or MY type of the present invention requires two gaps to form a closed loop magnetic circuit. By providing a sub gap (second gap) as a "magnetic coupling part" to the main gap (first gap) that interposes the coil, the coil can be fixedly installed in a magnetic field with high magnetic flux density, and Lorentz force can be generated in this coil.

[0052] The present disclosureThe servo type vibration detector of the invention according to claim 6 is composed of a pole piece portion which is connected to one of the magnetic pole faces of the permanent magnet and constitutes part of the movable side yoke material, the coil which is fixedly arranged on the fixed member via this pole piece portion or the radially opposing surface of the permanent magnet and the first gap portion, and the magnetic coupling portion which is arranged so that magnetic flux flows between the other magnetic pole face of the permanent magnet and the fixed member, and a closed loop magnetic circuit is formed by the permanent magnet, the pole piece portion, the first gap portion, the fixed member and the magnetic coupling portion.

[0053] That is, in the present invention, a magnetic coupling part is provided so that magnetic flux flows between the other magnetic pole surface of the permanent magnet, which is the movable member, and the fixed member. This magnetic coupling part, the permanent magnet, the pole piece part, the gap part, and the fixed member form a closed loop magnetic circuit for driving the pole piece part with the Lorentz force.

[0054] The present disclosure The servo type vibration detector of the invention related to claim 7 comprises a pole piece portion constituting a part of a movable side yoke material, a coil fixedly arranged on the fixed member within the gap between the pole piece portion and the fixed member, the pole piece portion being arranged via the magnetic connecting portion to one of the magnetic pole faces of the permanent magnet, the permanent magnet being fixedly arranged so that magnetic flux flows between the other magnetic pole face of the permanent magnet and the fixed member, and a closed loop magnetic circuit is formed by the permanent magnet, the magnetic connecting portion, the pole piece portion and the fixed member.

[0055] In other words, in the present invention, one of the magnetic pole faces of the permanent magnet, which is a fixed member, forms a magnetic path with the pole piece part via the magnetic connecting part, which is a movable member, and one of the magnetic pole faces of the permanent magnet forms a closed loop magnetic circuit with the fixed member so that magnetic flux can flow.

[0056] The present disclosure In the servo type vibration detector of the invention according to claim 8, the pole piece portion is configured to have a substantially cylindrical shape.

[0057] That is, the present invention has been made by finding that the following effects can be obtained by forming the pole piece portion into a cylindrical shape and configuring this cylindrical portion to be thin and long. (1) The force constant (electrical-mechanical conversion efficiency) of the voice coil motor can be increased. (2) The increase in the inertial mass of the moving part can be reduced. (3) Even if the number of coil turns is increased to increase the generated force, heat generation can be suppressed. The above (1) is a finding that the effect of leakage magnetic flux on the generated force can be reduced by lengthening the pole piece portion. The above (2) is that even if the pole piece portion is lengthened, the increase in mass is small if the thickness of the cylindrical portion is thin. The above (3) utilizes the fact that the coil storage space on the opposing surface can be increased by lengthening the pole piece portion. In other words, the coil wire diameter is increased to suppress the increase in the electrical resistance of the coil that accompanies an increase in the number of coil turns. Therefore, the above (1) to (3) solve the problem of the increase in the mass of the moving part caused by replacing the MC type with the MM type. The present invention makes it possible to realize an MM type acceleration sensor that has signal transmission characteristics that extend to high frequency ranges (for example, 400 to 500 Hz or more) and has high responsiveness.

[0058] The present disclosure The servo type vibration detector of the invention according to claim 9 is composed of a permanent magnet magnetized in the axial direction, a pole piece portion connected to one magnetic pole face of the permanent magnet, a coil fixedly arranged on the inner surface of the housing via a gap portion on the radially opposing surface of the pole piece portion, and a magnetic connecting portion arranged so that magnetic flux flows between the other magnetic pole face of the permanent magnet and the housing.

[0059] That is, the present invention makes it possible to realize a servo type acceleration sensor with a simple component configuration by connecting the permanent magnet magnetized in the axial direction to the pole piece portion.

[0060] The present disclosureThe servo-type vibration detector of the invention of claim 10 is configured such that the radial separation distances between the movable member and the fixed member in the first gap and the second gap are δ1 and δ2, respectively, such that δ1>δ2.

[0061] In other words, the present invention can reduce the effect of the magnetic coupling part on the generated force by making the gap (sub-gap part) of the magnetic coupling part narrower than the void part (main gap part) and making the magnetic resistance of the magnetic coupling part smaller than that of the void part.

[0062] The present disclosure In the servo type vibration detector of the invention according to claim 11, the mass of the movable part including the movable magnetic material member is m, and the mass of the permanent magnet is m p , the lower limit value m of the movable part mass min =2m p As,K PT The position sensor sensitivity K S and adjustment gain K C and proportional gain K P The electrical gain, K, is determined by the product t is the force constant of the actuator, R a is the electrical resistance of the coil, K T = K PT K t / R a f0 is the resonant frequency required for the acceleration sensor, and m max =K T / (2πf0) 2 Then, m min ≦m≦m max The range is set as follows.

[0063] In other words, in the present invention, the lower limit of the mass m of the movable part of the MM type acceleration sensor is the mass m of the permanent magnet. p By devising the shape of the magnetic material member (pole piece portion) that is connected to the permanent magnet, it is possible to obtain an actuator generating force greater than that of the conventional MC type, and at the same time, to reduce the lower limit m of the moving part mass m. min =2m p In addition, the upper limit value m of the moving part mass m can be set to maxis the resonance frequency f0 required for the acceleration sensor, and the electrical gain K PT , the force constant of the actuator K t , the electrical resistance of the coil R a It can be determined by:

[0064] The present disclosure In the servo type vibration detector of the invention according to claim 12, the magnetic connecting portion is composed of an auxiliary permanent magnet magnetized in the radial direction, and an auxiliary coil fixedly arranged on the inner surface of the housing via a gap on the radially opposing surface of the auxiliary permanent magnet.

[0065] That is, in the present invention, the magnetic coupling part is composed of an auxiliary permanent magnet magnetized in the radial direction and an auxiliary coil arranged on its opposing surface. With this configuration, the magnetic coupling part functions as a sub-actuator, thereby improving the force generated by the drive part. Also, the air gap between the auxiliary permanent magnet and the auxiliary coil can be set to be sufficiently large, making assembly easy. If the axis of the movable part becomes eccentric with respect to the fixed side, the radial force applied to the movable part is also very small.

[0066] The present disclosure A servo type vibration detector according to the invention of claim 13 includes a first transmission part and a second transmission part in the closed loop magnetic circuit for transmitting magnetic flux in a radial direction between the movable member and the fixed member, the first transmission part has a radial gap between the movable member and the fixed member, and the coil for generating the Lorentz force is fixedly disposed in the gap, The second transmission part is fixed between the movable member and the fixed member by a disk-shaped spring made of a magnetic material in which magnetic flux flows in the radial direction, and this disk-shaped spring also serves as the elastic member supporting the movable member.

[0067] That is, in the present invention, the first transmission part is not an air gap, but a disk-shaped spring made of a magnetic material itself is a magnetic path that forms a closed loop magnetic circuit. This embodiment does not require a magnetic coupling part, and a servo type acceleration sensor can be realized with a simple configuration.

[0068] The present disclosure In the servo type vibration detector of the invention related to claim 14, the permanent magnet is a front side permanent magnet and the coil is a front side coil, the magnetic connecting portion is composed of a radially magnetized rear side permanent magnet, the pole piece portion connected to one magnetic pole face of the rear side permanent magnet, and the rear side coil fixedly arranged on the inner surface of the housing via the gap portion on the radially opposing surface of the other magnetic pole face of the rear side permanent magnet, and the front side permanent magnet, the gap portion, the housing, the gap portion, the rear side permanent magnet, and the pole piece portion form a closed loop magnetic circuit.

[0069] That is, in the present invention, the front permanent magnet is configured with a magnet magnetized in the radial direction, and the magnetic coupling part is configured with a magnet magnetized in the radial direction and a fixed coil. Both the front side and the rear side function as voice coil motors, so the generated force can be improved. In addition, the radial gap of the magnetic gap between the coil mounting part and the two permanent magnets can be made sufficiently large, for example, δ = about 0.5 mm. Compared to the above-mentioned embodiment in which the annular gap is configured with a narrow gap, assembly during mass production is also easier.

[0070] The present disclosure In the servo-type vibration detector of the invention related to claim 15, the elastic member is made of a conductive material having an approximately flat, circular ring shape, and at least the outer periphery of the elastic member is fixed to the fixed member via a non-conductive material.

[0071] That is, in the present invention, the elastic member (disk-shaped spring) serves as a conductive path connecting the movable electrode to the outside, and is electrically insulated from the fixed side supporting the elastic member, so that minute capacitance signals between the fixed electrode and the movable electrode can be detected without being affected by disturbance noise.

[0072] The present disclosure The servo type vibration detector according to the sixteenth aspect of the present invention is configured such that a non-conductive material is interposed between the movable electrode and the pole piece portion.

[0073] That is, in the present invention, although eddy currents are generated on the surface of the pole piece, the movable electrode and the pole piece are electrically insulated from each other, so that the capacitance signal can avoid being affected by the eddy currents.

[0074] The present disclosure The servo type vibration detector of the invention of claim 17 is a differential sensor that detects the output difference between two sets of capacitance sensors formed between the electrode surfaces of the movable side electrode member and the fixed side electrode member, the movable side electrode member being provided on each of the two end faces of the movable member and the fixed side electrode member being provided on the fixed member opposite these movable side electrode members.

[0075] That is, the present invention takes note of the structural features of the linear MM type or MY type in which both left and right output shafts are open ends, and configures a differential capacitance sensor by providing electrodes for detecting capacitance in two locations, left and right.

[0076] The present disclosure The servo-type vibration detector of the invention of claim 18 is characterized in that two flat-plate-shaped movable side electrode members are provided with a gap between them at one axial end of the movable member, and the flat-plate-shaped fixed side electrode member is arranged in the gap so as to be sandwiched between the two movable side electrode members, thereby forming a first capacitance sensor between the electrode surface Sa of the movable side electrode member and the electrode surface SA of the fixed side electrode member facing it, and forming a second capacitance sensor between the electrode surface SB on the back side of the electrode surface SA and the electrode surface Sb of the movable side member facing it.

[0077] That is, the present invention is a capacitance sensor consisting of two movable electrodes and one fixed electrode provided at one end of the shaft of the movable part. It can also be applied to an acceleration sensor having an actuator that can use only the main force end of one shaft on one side.

[0078] The present disclosureThe servo-type vibration detector of the invention of claim 19 has a single flat-plate-shaped movable side electrode member at the end of the movable member, and electrode surfaces SAA and SBB are formed on the front and back surfaces of this movable side electrode member, and two flat-plate-shaped fixed side electrode members are arranged to sandwich the movable side electrode member with a gap between them, so that a first capacitance sensor is formed between the electrode surface Saa of the fixed side electrode member facing the electrode surface SAA, and a second capacitance sensor is formed between the electrode surface SBB and the electrode surface Sbb of the fixed side electrode member facing the electrode surface SBB.

[0079] That is, the present invention is a capacitance sensor that is configured by two sets of one movable electrode and two fixed electrodes provided on one shaft end of the movable part. As in the above-mentioned embodiment, the present invention can also be applied to an acceleration sensor having an actuator that can use only the main force end of one shaft on one side.

[0080] The present disclosure In the servo type vibration detector of the invention according to claim 20, the coil is housed in a non-magnetic metal bobbin, and this metal bobbin is fitted to the inner surface of the hollow cylindrical portion of the fixed member.

[0081] That is, a non-magnetic material with good thermal conductivity (for example, aluminum) is used for the coil bobbin, and this coil bobbin is attached in close contact with the inner surface of the housing. As a result, heat generated by the coil can be easily dissipated, reducing sensor noise that leads to thermal noise. In the case of conventional MC type sensors, the coil bobbin and coil are installed in a suspended state in the air. Because the member supporting the coil bobbin is made of a non-magnetic and non-conductive material, it is not possible to expect heat dissipation from the coil through thermal conduction. The present invention utilizes the structural features of the MM type, which allows the coil to be fixed.

[0082] The present disclosure The servo type vibration detector of the invention of claim 21 has a recess formed on the inner surface of the housing near the axial end face of the coil which is in close contact with the inner surface of the fixed member, in which the radial distance between the movable member and the fixed member is larger than at both ends.

[0083] That is, the present invention takes note of the fact that while the magnetic flux flowing vertically through the magnetic gap contributes effectively to the force generated by the actuator, the magnetic flux flowing from the corner of the surface opposing the coil to the corner of the inner peripheral surface of the coil-side yoke material is leakage flux and does not contribute to the force generated. The recesses formed in the coil-side yoke material contribute greatly to reducing leakage flux.

[0084] The present disclosure The servo type vibration detector of the invention related to claim 22 is configured so that at least one of the following is fastened with a bolt of M0.5 to M1.0 mm between the permanent magnet and the pole piece portion, between the coil bobbin housing the coil and the fixed member, between the elastic member and the fixed member, or between the elastic member and the pole piece portion.

[0085] That is, the present invention applies the M0.5 to M1.0mm ultra-small bolt fastening method used in specialized fields such as watches to an acceleration sensor composed of micro components. The reason that the ultra-small bolt fastening method can be applied is that attention is focused on the characteristics of the MM type, which does not require ultra-fine wire processing and can simplify the component configuration of the moving part.

[0086] In the case of conventional acceleration sensors constructed using adhesive techniques, if the product is found to be unsatisfactory at the quality evaluation stage during mass production, the product itself must be discarded. In the sensor of the present invention, many parts can be reused, greatly improving the yield rate during mass production. In addition, in the case of adhesive techniques, the thickness of the adhesive between the parts to be bonded and the unevenness of this thickness were factors that reduced assembly accuracy. In the case of the present invention, high assembly accuracy can be ensured as long as the processing accuracy of each part is obtained. In addition, since the worker does not need to be skilled, variation in product performance can be reduced.

[0087] The present disclosureIn the servo-type vibration detector of the invention related to claim 23, the elastic member is formed of a disk-shaped conductive material, and the inner and outer periphery of the elastic member are integrated with a thin plate material made of a non-conductive material.

[0088] That is, the present invention combines the advantages of both adhesive and bolt fastening methods. For example, in the assembly preparation stage, for parts that require electrical insulation, conductive materials (metals) and insulating materials (ceramics, etc.) are integrated in advance with adhesive. If the bolt fastening method is used after this process, the production process can be carried out efficiently with a simple configuration.

[0089] The present disclosure The servo type vibration detector of the invention of claim 24 further comprises a movable unit including at least the movable member and having a movable side electrode attached thereto, and a fixed unit having a fixed side electrode attached thereto and arranged opposite to the movable side electrode, wherein the displacement detection unit is formed to detect the electrostatic capacitance formed between the movable side electrode and the fixed side electrode, an interlocking structure is formed between the movable unit and the fixed unit so that the movable unit and the fixed unit can move axially relative to each other while the relative radial movement of the movable unit and the fixed unit is restricted, and a groove portion for adhesively fixing the movable unit and the fixed unit is formed on the outer surfaces of the movable unit and the fixed unit.

[0090] In other words, by applying this invention, a structure can be created in which the gap between the movable and fixed electrodes can be adjusted to an optimal value by applying an adhesive technique in the final assembly stage while measuring the capacitance. This method can absorb all errors accumulated in the final process. For example, when the capacitance reaches the target value, the two units can be fastened by irradiating the ultraviolet-curing adhesive with an LED light to harden the adhesive.

[0091] The present disclosureThe servo type vibration detector of the invention related to claim 25 comprises a fixed member, a bolt and an elastic member made of a conductive material, the elastic member being adhesively fixed to a thin plate made of a non-conductive material, the non-conductive material being fastened to the fixed member by a bolt, and the bolt head being configured so as to be not in electrical contact with the elastic member.

[0092] That is, the present invention uses the elastic member (disk) as a conductive path for the capacitance signal between the electrodes, and fastens the elastic member to the housing with a metal bolt and a non-conductive member (e.g., ceramics) so that the elastic member is not in electrical contact with the housing. This method allows the transmission of minute capacitance signals without being affected by external noise.

[0093] The present disclosure In the servo type vibration detector of the invention related to claim 26, the elastic member is composed of a cantilever having one fixed end and the other free end, and the movable member is provided on the free end side of this cantilever.

[0094] That is, in the present invention, a cantilever (pendulum structure) with one end fixed and the other end free is applied to the elastic member. The cantilever structure allows low-rigidity support with a simple configuration, so the resonance frequency (eigenvalue) of the moving part can be set sufficiently small.

[0095] The present disclosure In the servo type vibration detector of the invention related to claim 27, a part of the cantilever is made of a conductive material to form a signal transmission path connecting the signal from the displacement detection section to the fixed member side.

[0096] That is, the present invention utilizes the feature of the MM type in which the coil is fixed, and utilizes the fact that only one electrical signal, a capacitance signal, is required to be extracted from the oscillating movable side. In the case of the MC type in which the coil moves, multiple signal transmission paths are formed by using thin film formation technology on a cantilever made of a non-conductive material such as quartz glass. In the case of the sensor of the present invention, a conductive (metallic) material can be applied to the cantilever.

[0097] The present disclosure In the servo type vibration detector of the invention according to claim 28, the radial stiffness K of the elastic member is r The amount of eccentricity of the axis of the movable magnetic material member with respect to the axis of the fixed magnetic material member is δ r The radial force generated by the magnetic attraction force when r As the negative spring stiffness K mr =F r / δ r Define K r >K mr The present invention is configured so that:

[0098] That is, in the present invention, when the parts precision and assembly precision are not sufficiently obtained in the magnetic coupling portion and the shaft core of the fixed side and the movable side are eccentric, the magnetic attraction force F in the centrifugal direction is r The negative spring stiffness K formed in the magnetic circuit mr =F r / δ r The centripetal stiffness of the disk is K r >K mr If the disk specifications are selected so that the magnetic coupling portion can be maintained in a stable state.

[0099] The present disclosure In the servo type vibration detector of the invention related to claim 29, the magnetic connecting portion is constituted of a MY type acceleration sensor including the permanent magnet magnetized in the radial direction and the outer peripheral surface of the pole piece portion arranged with a gap between the inner peripheral surface of the permanent magnet and the pole piece portion.

[0100] In other words, the present invention uses multiple radially magnetized segment-type permanent magnets to form a magnetic circuit, so that when no current is applied to the force coil, no axial electromagnetic force is generated in the pole piece, and the pole piece can be kept in the same position.

[0101] The present disclosureIn the servo type vibration detector of the invention related to claim 30, the magnetic connection part is composed of the permanent magnet magnetized in the axial direction, a pole piece side yoke material arranged to be connected to either the N pole or S pole of the permanent magnet, and the inner surface of the pole piece part arranged with a radial gap maintained relative to the outer surface of the pole piece side yoke material.

[0102] In other words, the present invention configures a magnetic circuit using a permanent magnet magnetized in the axial direction. The magnetic circuit can be configured simply, and the performance of the permanent magnet can be selected from a wide range. Since there are no restrictions on the dimensions and shape of the permanent magnet, the demagnetization characteristics (retentive force H c , saturation magnetic flux density B r ) can be selected from a wide range. Since there is a margin in the performance of the permanent magnet, the air gap in the magnetic coupling part can be sufficiently large. Although this air gap creates magnetic resistance, the performance of the permanent magnet is sufficient to compensate for this loss.

[0103] The present disclosure The servo type vibration detector of the present invention according to claim 31 comprises a fixed member, a movable member arranged to be movable in a predetermined direction relative to the fixed member and configured so that a magnetic flux flows inside the movable member, an elastic member that supports the movable member so that the movable member is disposed with a gap between the fixed member and the elastic member, a displacement detection unit that detects a displacement of the movable member in the predetermined direction, and a driving means that generates an electromagnetic force that 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, and a fixed electrode member having two electrode surfaces provided on the fixed member, whereby two sets of capacitance sensors are constituted by combining the electrode surfaces of the movable electrode member and the fixed electrode member facing each other, and the movable electrode member and the fixed electrode member are arranged so that the gaps between the electrode surfaces of the two sets of capacitance sensors change in opposite phases as the movable member moves in a predetermined direction, and a differential sensor is constituted by taking the difference in output signals of the two sets of capacitance sensors.

[0104] That is, the present invention makes it possible to realize a highly sensitive sensor whose sensor output is less susceptible to the influence of disturbance signals such as noise and drift by using a differential acceleration sensor.

[0105] The absolute velocity signal and absolute displacement signal obtained by completely integrating the acceleration output of the sensor of the present invention do not easily diverge. Therefore, when the sensor of the present invention is applied to an active vibration isolation table, in addition to the effect of improving the sensor sensitivity (for example, improving the positioning accuracy of the stage), a significant improvement in vibration isolation characteristics can be obtained in the low frequency range.

[0106] The present disclosure The vibration control device of the invention according to claim 32 is The present disclosure In order to obtain vibration isolation performance in the low frequency range, absolute velocity feedback and / or absolute displacement feedback is applied to a vibration control device using a servo type vibration detector of the invention according to claim 31 and an absolute velocity signal obtained by integrating the acceleration signal output by the servo type vibration detector once or an absolute displacement signal obtained by integrating it twice.

[0107] That is, in the present invention, by taking the difference between two sets of electrode outputs whose gaps change in opposite phases, the noise and drift that are commonly applied to the two electrode outputs are cancelled.

[0108] As a result, the absolute velocity signal and absolute displacement signal obtained by completely integrating the acceleration output do not diverge. When the acceleration sensor of this embodiment is applied to an active vibration isolation table, in addition to the effect of improving the sensor sensitivity (for example, improving the positioning accuracy of the stage), a significant improvement in vibration isolation characteristics can be obtained in the low frequency range.

[0109] The present disclosureThe servo type vibration detector of the present invention according to claim 33 comprises a fixed member, a movable member arranged to be movable in a predetermined direction relative to the fixed member and configured so that a magnetic flux flows inside, an elastic member supporting the movable member so that the movable member is disposed with a gap therebetween relative to the fixed member, a displacement detection unit detecting a displacement of the movable member in the predetermined direction, and a driving means generating an electromagnetic force for returning the movable member to its original position when a relative displacement of the movable member from its original position is detected by the displacement detection unit, the driving means comprising: a fixed yoke material provided to pass through a coil; A movable yoke material is arranged with a gap between the open end of the fixed yoke material and the movable yoke material, and a closed loop magnetic circuit is formed by this fixed yoke material, the gap and the movable yoke material to constitute an electromagnet, which serves as attraction force generating means A for attracting the movable member including the movable yoke material towards the coil, and attraction force generating means B for generating a force in the opposite direction to attraction force generating means A is arranged across the movable member, and by controlling the current flowing through the coil, the driving means uses Maxwell stress to move the movable member in the axial direction.

[0110] That is, the present invention uses magnetic attraction force due to Maxwell stress to drive the moving part. If comparing the external dimensions of the actuator under the same conditions, the Maxwell stress has an overwhelmingly higher electromechanical conversion efficiency (thrust constant) of the generated force relative to the input current than the Lorentz force, usually 20 times higher. By utilizing this point, the acceleration sensor of this embodiment can greatly increase the upper limit of measurable acceleration. Effect of the Invention

[0111] The servo-type vibration detector of the present invention is configured so that the yoke or permanent magnet can move while the coil is fixed, eliminating the need for complicated wiring processes as with conventional moving coil type servo-type vibration detectors, thereby significantly simplifying mass production methods and reducing production costs. [Brief description of the drawings]

[0112] [Figure 1]FIG. 1A shows a servo-type acceleration sensor according to a first embodiment of the present invention, and FIG. 1B shows a front cross-sectional view of a sensor body. [Diagram 2] A model diagram of the magnetic circuit of the MM type acceleration sensor of the present invention. [Diagram 3] Model diagram of the magnetic circuit of a conventional MC type acceleration sensor [Figure 4] Graph of analysis results showing the relationship between generated force F and pole piece length L [Diagram 5] A graph showing the analysis results showing the relationship between the leakage coefficient σ and the pole piece length L [Figure 6] A graph showing the inertial mass m of the moving part of the pole piece versus the length L [Figure 7] A graph showing the coil storage volume VC versus the pole piece length L [Figure 8] Control block diagram of the acceleration sensor used in the theoretical analysis [Figure 9] (1) Conventional MC type, (2) MM type of the present invention, (3) Conventional MC type with inertia mass m four times larger. A graph comparing the gain and phase characteristics for (1) to (3) above. [Figure 10] A graph comparing the force generated by the actuator over time for (1) the conventional MC type and (2) the MM type of the present invention. [Figure 11] A graph comparing the effect of mechanical noise on sensor output for (1) the conventional MC type and (2) the present invention's MM type. [Figure 12] (1) Conventional MC type, (2) MM type of the present invention, (3) Conventional MC type with inertia mass m four times larger. A graph comparing the coil current for (1) to (3) above. [Figure 13] FIG. 5 is a front sectional view of a servo-type acceleration sensor according to a second embodiment of the present invention. [Figure 14] FIG. 11 is a front sectional view of a servo-type acceleration sensor according to a third embodiment of the present invention. [Figure 15] FIG. 11 is a front sectional view of a servo-type acceleration sensor according to a fourth embodiment of the present invention. [Figure 16] FIG. 13 is a front sectional view of a servo-type acceleration sensor according to a fifth embodiment of the present invention. [Figure 17] FIG. 13 is a front sectional view of a servo-type acceleration sensor according to a sixth embodiment of the present invention. [Figure 18] A diagram showing the flow of magnetic flux in embodiment 6 with arrows (chain lines). [Figure 19] A diagram showing the flow of heat in the sixth embodiment with arrows (chain lines). [Figure 20] 20A is a front cross-sectional view of a servo-type acceleration sensor according to a seventh embodiment of the present invention, and FIG. 20B is a cross-sectional view taken along the line AA of FIG. 20A. [Figure 21] FIG. 13 is a front sectional view of a servo-type acceleration sensor according to an eighth embodiment of the present invention. [Figure 22] 22A is a front cross-sectional view of a servo-type acceleration sensor according to a ninth embodiment of the present invention, and FIGS. 22B and 22C are cross-sectional views showing a segment-type permanent magnet. [Figure 23] FIG. 16 is a front sectional view of a servo-type acceleration sensor according to a tenth embodiment of the present invention. [Figure 24] FIG. 13 is a diagram showing that the differential servo type acceleration sensor according to the tenth embodiment can be composed of three units. [Diagram 25] A diagram showing the relationship between electrode output, noise and drift, and sensor acceleration output for a conventional acceleration sensor. [Figure 26] FIG. 23 is a diagram showing the relationship between two electrode outputs, noise and drift, and sensor acceleration output in the case of the acceleration sensor according to the tenth embodiment. [Figure 27] FIG. 15 is a front sectional view of a servo-type acceleration sensor according to an eleventh embodiment of the present invention. [Figure 28] FIG. 28 shows a swing motion servo type acceleration sensor according to a twelfth embodiment of the present invention, in which FIG. 28a is a front cross-sectional view, and FIG. 28b is a schematic side view of a pendulum, which is one component of the sensor. [Figure 29] FIG. 12 is a diagram showing an example of an assembly method of the twelfth embodiment. [Diagram 30] 13 is a front sectional view of an oscillatory motion servo type acceleration sensor according to a thirteenth embodiment of the present invention; [Diagram 31] FIG. 14 is a front sectional view of a servo-type acceleration sensor according to a fourteenth embodiment of the present invention. [Diagram 32]FIG. 23 shows Step 1 of the assembly process of the fourteenth embodiment. [Diagram 33] FIG. 23 shows Step 2 of the assembly process of the fourteenth embodiment. [Diagram 34] FIG. 23 shows Step 3 of the assembly process of the fourteenth embodiment. [Diagram 35] FIG. 23 shows Step 4 of the assembly process of the fourteenth embodiment. [Diagram 36] FIG. 23 shows Step 5 of the assembly process of the fourteenth embodiment. [Figure 37] FIG. 14 shows a spiral disk according to embodiment 14. [Figure 38] FIG. 19 shows Step 6 of the assembly process of the fourteenth embodiment. [Figure 39] FIG. 23 shows Step 7 of the assembly process of the fourteenth embodiment. [Diagram 40] FIG. 19 shows Step 8 of the assembly process of the fourteenth embodiment. [Diagram 41] 41A shows a servo-type acceleration sensor according to a fifteenth embodiment of the present invention, and FIG. 41B shows a front cross-sectional view of a fixed electrode unit. [Diagram 42] FIG. 23 is a front cross-sectional view showing a state in which two units are fastened together in the fifteenth embodiment. [Diagram 43] 16 is a front sectional view of a servo-type acceleration sensor according to a sixteenth embodiment of the present invention; [Diagram 44] FIG. 23 is a front sectional view of a servo-type acceleration sensor according to a seventeenth embodiment of the present invention. [Diagram 45] FIG. 45 shows a servo-type acceleration sensor according to an eighteenth embodiment of the present invention, in which FIG. 45a shows the shape of the front spiral disk, FIG. 45b is a front cross-sectional view of the acceleration sensor, and FIG. 45c shows the shape of the rear disk. [Diagram 46] 23 is a front sectional view of a servo-type acceleration sensor according to a nineteenth embodiment of the present invention. [Figure 47] 47A shows a servo-type acceleration sensor according to a twentieth embodiment of the present invention, FIG. 47A being a front cross-sectional view, and FIG. 47B being a cross-sectional view taken along the line AA of FIG. 47A. [Figure 48] 21 is a front sectional view of a servo-type acceleration sensor according to a twenty-first embodiment of the present invention. [Figure 49]22 is a front sectional view of a servo-type acceleration sensor according to a twenty-second embodiment of the present invention. [Figure 50] 23 is a front sectional view of a servo-type acceleration sensor according to a twenty-third embodiment of the present invention; [Figure 51] A front sectional view of a servo type acceleration sensor to which an optical sensor according to the present invention is applied. [Figure 52] Model diagram of a conventional active vibration isolation table [Diagram 53] Model diagram showing the basic configuration and detection principle of a capacitive acceleration sensor [Figure 54] FIG. 1 is a front cross-sectional view showing a specific example of the structure of a conventional linear motion acceleration sensor; [Figure 55] In a conventional linear motion acceleration sensor, FIG. 55a is a front view showing the shape of the front side disk-shaped spring, FIG. 55b is a front cross-sectional view with the front side panel 26 and the fixed side electrode 25 removed from FIG. 54, and FIG. 55c is an enlarged view of part A in FIG. 55b. [Figure 56] FIG. 1 is a front cross-sectional view showing an example of a conventional swing motion type acceleration sensor. [Figure 57] FIG. 1 is an enlarged view showing the state in which the pendulum of the swinging motion type acceleration sensor swings. [Figure 58] 58(a) shows a plan view of a pendulum of a swing-type acceleration sensor, and FIG. 58(b) shows one side of the pendulum, and FIG. 58(b) shows the other side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0113] Returning to the basics, let us now turn our attention to the fact that the actuator section of a servo-type acceleration sensor forms a closed-loop magnetic circuit with three elements, namely, a "permanent magnet," a "coil," and a "yoke material." If the "coil," one of these three elements, can be fixed, then the fatal problem of the moving coil type (MC type), namely, the difficulty of wiring processing, which is the main cause of reduced yields, can be solved in one fell swoop. Below, we will explain this invention in two steps. (I) Moving magnet type (MM type) acceleration sensor (II) Moving yoke type (MY type) acceleration sensor First, the above (I) will be explained.

[0114] (First embodiment) This embodiment focuses on the moving magnet type (MM type), which does not require ultra-fine wire processing because the permanent magnet moves and the coil is fixed. Conventional servo type acceleration sensors are moving coil type (MC type) in which the coil moves linearly in the axial direction or oscillatingly, whereas in this embodiment, the coil is fixed and the permanent magnet moves in the axial direction. However, there has been no precedent for an MM type servo type acceleration sensor in the past. The reason for this is thought to be that there was a fixed idea (blind spot) that could be called an implicit premise that "the inertial mass of the moving part of the MM type is increased, which makes the transmission characteristics and high-speed response in the high-frequency range disadvantageous." The present invention addresses this "blind spot" by the following ingenuity. That is, in this embodiment, (i) a magnetic circuit configuration that can reduce the weight of the moving part, (ii) a magnetic pole shape that reduces the effect of leakage magnetic flux, and (iii) a coil specification that utilizes the increased coil storage volume to achieve both increased generated force and reduced heat generation. By such ingenuity, it has been possible to eliminate the weaknesses of the MM type and achieve sensor performance that surpasses that of the MC type. In the following, (1) the specific structure and structural features of this embodiment will be explained, and in (2) the effect of the present invention on the basic performance of the acceleration sensor will be verified by theoretical analysis.

[0115] (1-1) Specific structure of this embodiment FIG. 1 shows an example of a servo-type acceleration sensor according to a first embodiment of the present invention, in which FIG. 1a is an external view of only a spiral disk, which will be described later, taken from the view taken along the arrow AA in FIG. 1b, and FIG. 1b is a front sectional view of the sensor body.

[0116] Reference numeral 101 denotes a permanent magnet, 102 denotes a front pole piece portion, and 103 denotes a cylindrical gap portion (an inertial mass adjustment portion to be described later) formed to reduce the weight of the front pole piece portion. Reference numeral 104 denotes a rear pole piece portion, 105 denotes a coil side yoke material, 106a denotes a force coil, 106b denotes a calibration coil, and 107 denotes a protrusion formed on the inner surface of the coil side yoke material. Reference numeral 108 denotes a front side spiral disk spring (hereinafter, the front side disk), and 109 denotes a rear side spiral disk spring (hereinafter, the rear side disk). The front side disk shown in FIG. 1a is formed of a ridge portion 108a and a groove portion 108b, and the rear side disk is also an elastic member of a similar shape. That is, the movable side magnetic material member (movable side yoke material) is composed of the front side pole piece portion 102 and the rear side pole piece portion 104. The fixed side magnetic material member is the coil side yoke material 105. Reference numeral 110 denotes a movable electrode, 111 a fixed electrode, 112a a front panel, 112b a rear panel, 113 a center plate, and 114 a fastening member made of a non-conductive material that fastens the fixed electrode and the front panel. The movable electrode 110 and the fixed electrode 111 form a capacitance-type displacement detection unit. Reference numeral 115 denotes the inner peripheral surface of the coil side yoke material 105, which is a coil mounting portion for the two coils (106a, 106b), and 116 a coil opposing surface of the front pole piece portion 102. In this embodiment, the force coil 106a and the calibration coil 106b are bobbinless and are mounted on the coil mounting portion 115, whose outer peripheral surface is convex.

[0117] A radial magnetic gap 117 (first gap) is formed between the coil facing surface 116 and the coil mounting portion 115. A narrow gap is provided between the protruding portion 107 of the coil side yoke material and the rear side pole piece portion 104 to form an annular gap 118 (a magnetic connection portion that is a second gap). A closed loop magnetic circuit is formed by "permanent magnet 101 → front side pole piece portion 102 → magnetic gap 117 → coil side yoke material 105 → annular gap 118 → rear side pole piece portion 104" as shown by the dashed arrow. The annular gap 118 shown in the dashed circle B is set so that the magnetic resistance is sufficiently smaller than that of the magnetic gap 117. The annular gap 118 is a magnetic connection portion for forming a closed loop magnetic circuit in a magnetic circuit using a permanent magnet. As is well known, when a current flows through a conductor placed in a magnetic field, a Lorentz force, which is an electromagnetic 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 the force coil 106a fixedly disposed in the space of the magnetic gap 117, a reaction force of the Lorentz force that moves the moving part in the axial direction is generated. The moving part in this embodiment is composed of a permanent magnet 101, a front pole piece part 102, a rear pole piece part 104, and a moving side electrode 110.

[0118] Reference numerals 119a and 119b denote lead wires from the force coil 106a, and 120a and 120b denote lead wires from the calibration coil 106b. These four lead wires pass through the coil side yoke material 105 and the front side panel 112a, and are connected to an externally installed control circuit.

[0119] Reference numeral 121 denotes an inner disk support ring, 121a denotes a cylindrical gap formed to reduce the weight of the inner disk support ring, and 122 denotes an outer disk support ring. The inner disk support ring 121 and the outer disk support ring 122 are made of a non-conductive material (insulating material).

[0120] The inner disk support ring 121 can electrically insulate the front pole piece portion 102, which is made of a magnetic material, from the movable electrode 110. Although eddy currents are generated on the surface of the pole piece portion, this electrical insulation measure can prevent the capacitance signal between the two electrodes from being affected by the eddy currents. The outer disk support ring 122 electrically insulates the outer side of the front disk 108 from the coil yoke material 105. As the insulating material, inorganic solid insulating materials such as mica, porcelain (ceramics), and glass can be used. The inner disk support ring 121 is bonded and fixed between the movable electrode 110, which is made of a conductive material, and the front pole piece portion 102. The inner side of the front disk 108 is held between the movable electrode 110 and the inner disk support ring 121. The outer side of the front disk 108 is bonded and fixed to the outer disk support ring 122. Reference numeral 123 denotes one of two conductors (leads) for detecting the capacitance between the movable electrode 110 and the fixed electrode 111. An end of this conductor 123 is electrically connected to the disk-shaped spring 108 and is fitted in a groove (not shown) formed in the outer disk support ring 122. The front disk 108 serves both to support the movable part and as a conductive path for detecting the capacitance. That is, in order to detect a minute capacitance signal between the fixed electrode 111 and the movable electrode 110, the conductive path (front disk 108, conductor (lead) 123) connecting the movable electrode 110 to the outside is completely electrically insulated.

[0121] In this embodiment, the force coil 106a and the calibration coil 106 are arranged so as to enclose the permanent magnet 101 and the entire front pole piece portion 102 that connects the permanent magnet 101 in series from the outer periphery. Furthermore, an annular gap portion 118 having a sufficiently small magnetic resistance compared to the magnetic gap portion 117 is arranged in the closed loop magnetic circuit. The movable members that move in the axial direction are the permanent magnet 101, the front pole piece portion 102, the rear pole piece portion 104, the movable electrode 110, and the inner circumference side disc support ring 121. Each movable member has a cavity on the inner circumference side to reduce its weight.

[0122] In this embodiment, the front and rear disks 108, 109 are disk-shaped springs formed with a spiral curve. In this embodiment and in the embodiments described below, the shape of the spring is not limited to this spiral curve. It is sufficient to select a spring structure and specifications that provide low rigidity and a low resonance frequency based on the characteristics required of the acceleration sensor, and for example, the well-known cloud spring can also be used.

[0123] (1-2) Features of this embodiment In this embodiment, the axial length of the front pole piece portion 102 is set to L, and this axial length L is made sufficiently long, and a cylindrical gap portion 103 (inertial mass adjustment portion) with a thin radial thickness is provided inside the front pole piece portion. It is noted that this configuration provides the following effects. That is, (1) The force constant (electrical-mechanical conversion efficiency) of the actuator can be increased. (2) The increase in the inertial mass of the moving part can be reduced. (3) Even if the number of coil turns is increased to increase the generated force, heat generation can be suppressed.

[0124] The effect of (1) above will be explained with reference to Figs. 2 to 7. Fig. 2 is a model diagram of the magnetic circuit of the MM type acceleration sensor of the present invention, and Fig. 3 is a model diagram of the magnetic circuit of a conventional MC type acceleration sensor. The symbols of each element in Fig. 2 correspond to the symbols of each element in Fig. 1b. Similarly, the symbols of each element in Fig. 3 correspond to the symbols of each element in Fig. 54. Incidentally, in the conventional MC type, as shown in Fig. 3, there is only one gap 29 forming a closed loop magnetic circuit. In the case of the MM type of the present invention, two gaps (117, 118) are required to form a closed loop magnetic circuit, as shown in Fig. 2. By providing a sub gap (second gap) as a magnetic coupling part with respect to the main gap (first gap) through which the coil is interposed, the coil can be fixedly disposed in a magnetic field with a high magnetic flux density, and a large Lorentz force can be generated in this coil. Furthermore, the gap of the first gap is δ1, and the gap of the second gap is δ2, with δ1>δ2. By making the magnetic resistance of the magnetic coupling portion sufficiently smaller than that of the first gap, the effect of the magnetic coupling portion on the generated force can be reduced.

[0125] The analysis results of the permanent magnet magnetic circuit using the above analysis model are shown below. Figure 4 is a graph showing the analysis results showing the relationship between the generated force F and the pole piece length L, and Figure 5 is a graph showing the analysis results showing the relationship between the leakage coefficient σ and the pole piece length L.

[0126] In FIG. 4, characteristic curve (1) uses a samanium-cobalt magnet, and the total coil length is the basic specification (l=l0) in Table 1 described later. Characteristic curve (2) shows the case where a samanium-cobalt magnet is used and the total coil length is l=l0×1.6. Characteristic curve (3) shows the sensor of this embodiment (FIG. 1), where a neodymium magnet is used and the total coil length is l=l0×1.6. Point A in the figure is the pole piece length L of the conventional MC type, L=L A = 0.3 cm, and the generated force F = 0.0064 N. Point B in the figure indicates that the pole piece length L of the MM formula of the present invention is L = L B = 0.6 cm, and generated force F = 0.018 N. Therefore, the generated force of the MM type of the present invention is 2.8 times larger than that of the conventional MC type.

[0127] In the graph of FIG. 5 showing the leakage factor versus pole piece length L, the leakage factor σ indicates the ratio of "magnetic flux contributing to generated force" to "total magnetic flux", and as σ approaches 1, a larger generated force can be obtained. As shown in FIG. 5, by making the axial length L of the pole piece larger, the ratio of the effective magnetic flux (gap permeance) passing vertically through the magnetic gap 117 to the leakage magnetic flux (leakage permeance) can be made smaller. The gap permeance is the magnetic flux that contributes to the generated force, and the leakage permeance does not contribute to the generated force. In other words, the configuration of this embodiment can increase the generated force (electrical-mechanical conversion efficiency) for the same current.

[0128] In FIG. 4, the characteristic curve (1) is divided into curve α and curve β, which have significantly different gradients, and the intersection point of the envelopes of these curves is C. <L<L A In the range of L>L, the generated force F increases significantly as the pole piece length L increases. A Within this range, the increase in the generated force F is small. Therefore, the pole piece length of the conventional MC sensor is L = L A (In the case of Fig. 2, L A = 0.3 cm). The reason for this is that in the case of an MC type sensor, if you increase the number of coil turns to increase the length L, the inertial mass also increases, and the required generated force also increases. In other words, the effect of increasing the length L is offset.

[0129] The above (2) focuses on the fact that if the pole piece is made into a cylindrical shape with a thin plate thickness, the mass does not increase significantly even if the pole piece is lengthened. Figure 6 is a graph showing the inertial mass m of the movable part against the length L of the pole piece. The front pole piece has an outer diameter ΦD P , and is cylindrical with a radial thickness of t. Here, ΦD P In Figure 6, the pole piece length L A = 3mm, the total inertial mass of the moving parts m = 4.48g, L AWhen t = 6 mm, m = 5.16 g. Therefore, if the pole piece length is doubled, the increase in the total inertial mass is 15%. Furthermore, assume that the pole piece has the same outer diameter and a thickness of t = 0.5 mm. In this case, if the pole piece length is doubled, the increase in the total inertial mass is 8.4%.

[0130] The feature of (3) above is based on the knowledge of (2) above. Figure 7 shows the relationship between the length of the pole piece L and the coil storage volume V C In this embodiment, the radial gap of the magnetic gap 117 is 2.5 mm, the radial thickness of the coil housed in the magnetic gap 117 is 2 mm, and the radial gap between the coil facing surface 116 and the coil is 0.5 mm. By changing the pole piece length L from 3 mm to 6 mm under the above conditions, the coil housing volume V C However, as mentioned above, the inertial mass of the moving part increases by only 15% when the thickness t of the pole piece is 1 mm, and by only 8.4% when the thickness t is 0.5 mm.

[0131] By taking advantage of the fact that the coil storage volume can be increased, heat generation that leads to thermal noise can be suppressed even if the number of coil turns is increased to increase the generated force. The electrical resistance of a coil is proportional to the total length of the coil and inversely proportional to the coil cross-sectional area. Therefore, when the total length of the coil is increased by n times, if the coil cross-sectional area is increased by n times and the coil linearity is increased by √n times, the electrical resistance will not increase. In this case, the coil storage area should be √n×n.

[0132] (2) Comparison of specifications between the present invention and conventional sensors In this section, we will verify by theoretical analysis the effects that the structural features (1) to (3) described in Section (1) have on the basic performance of the acceleration sensor, in comparison with a conventional MC type sensor.

[0133] (2-1) Specifications of the linear MC acceleration sensor and the sensor of the present invention Here, we will use theoretical analysis to evaluate the basic performance of the linear moving magnet type (hereafter referred to as linear MM type) sensor of the present invention and the conventional linear moving coil type (hereafter referred to as linear MC type). Table 1 shows a comparison of the specifications of the conventional linear MC type and the sensor of the present invention (MM type).

[0134] (1) Specifications of inertial mass m The inertial mass m of the MC type is 1.25 g, whereas that of the MM type is 5 g. In Fig. 54, the inertial mass m = 1.25 g of the MC type is determined by the movable electrode 24, the force coil 16a, the calibration coil 16b, the coil bobbin 17, and the coil bobbin support members 18, 19. The inertial mass m = 5 g of the MM type is the sum of the masses of the movable electrode 110, the inner circumferential disk support ring 121, the front pole piece portion 102, the permanent magnet 101, and the rear pole piece portion 104. As described above, the value of the inertial mass m = 5 g is set based on the conditions of (i) improving the sensor sensitivity in the low frequency range, and (ii) the wideband frequency characteristics required of an active vibration isolation table, and the compatibility of the above (i) and (ii). (Mass m of the permanent magnet p (The mass m of the moving part is defined based on the above)

[0135] (2) Specifications for total coil length and coil resistance Ra The total coil length for the MM type was set to n = 1.6 times that of the MC type. As mentioned above, in order to make the coil resistance Ra the same, the coil cross-sectional area for the MM type was set to n times and the coil wire diameter was set to √n = 1.26 times. Therefore, the coil storage space Sn = n × √n = 2.0 times. With this configuration, when the same current I is passed through both sensors, the MM type generates less heat (W = I 2 × Ra) remains the same, the above (ii) can be satisfied. Furthermore, the force generated by the actuator can be increased by more than n times.

[0136] (3) Electrical gain specifications The position sensor sensitivity is Ks, the adjustment gain is Kc, and the proportional gain is Kp, and the electrical total gain Kpt is Ks × Kc × Kp. This Kpt is set to be the same for the MM type and the MC type.

[0137] [Table 1]

[0138] (2-2) Theoretical analysis results Fig. 8 is a control block diagram of the acceleration sensor used in the theoretical analysis. Equations (1) to (3) showing the detection principle of the above-mentioned capacitance type acceleration sensor are replaced with a control block diagram.

[0139] (i) Comparison of gain and phase characteristics FIG. 9 shows a comparison of gain and phase characteristics for the following three cases (1) to (3) in the specifications of Table 1, namely, (1) the conventional MC type, (2) the MM type of the present invention, and (3) the conventional MC type specifications in Table 1 with only the inertial mass m being four times larger. Below, the performance merits and demerits of the above three cases are evaluated based on the gain characteristics, assuming that they are mounted on an active vibration isolation table. The gain characteristics of (1) and (2) do not change significantly. In (2) the MM type of the present invention, the resonance frequency is f0=380Hz. In the case of (3), the resonance frequency is f0=380→220Hz, and the bandwidth is reduced. The phase characteristics are evaluated for the above (1) to (3) in terms of the phase delay near f=100Hz (chain line circle A). The phase characteristics near f=100Hz are an important performance evaluation index when applying an acceleration sensor to an active vibration isolation table, as will be described later in Supplementary (2). It is preferable to make the phase delay near f=100Hz as small as possible. The higher the resonant frequency f0, the smaller the phase delay can be in the vicinity of f=100Hz. The phase characteristics of (1) and (3) are almost the same at f=100Hz. However, at f>100Hz, a significant phase delay occurs in the case of (3) above. In the MM formula of the present invention (2) above, the phase delay is significantly improved compared to (1) and (3).

[0140] (ii) Comparison of actuator generated forces FIG. 10 shows a comparison of the actuator force versus time for (1) the conventional MC type and (2) the MM type of the present invention, with the specifications in Table 1. The input acceleration has an amplitude of 1.0×10 -6 m / s 2A sine wave of (0.1 mGal) is assumed. The MM type of the present invention generates four times more force in proportion to the inertial mass than the conventional MC type. The effect of increasing the generated force due to the increase in inertial mass can compensate for the weakness of the capacitance type, which has a decrease in sensitivity in the low frequency range.

[0141] (iii) Comparison of the effects of mechanical noise FIG. 11 compares the effect of mechanical noise on the sensor output for (1) the conventional MC type and (2) the MM type of the present invention, using the specifications in Table 1. Here, mechanical noise is assumed to be a disturbance factor that hinders the smooth operation of the moving part. Amplitude 1.0×10 -6 It is assumed that a sinusoidal external force (mechanical noise) of N is applied to the output shaft of the actuator (see the control block diagram in Figure 8). It can be seen that in this invention, the effect of mechanical noise applied to the actuator on the sensor output is reduced to 1 / 4 compared to the conventional type. This effect is due to the fact that an increase in inertial mass increases the force generated by the actuator. In other words, this shows that the weakness of the MM type, that the inertial mass of the moving part is increased compared to the MC type, is conversely an advantage when it comes to dealing with mechanical noise.

[0142] (iv) Coil current comparison FIG. 12 shows a comparison of the coil current for the following three cases, namely, (1) the conventional MC type, (2) the MM type of the present invention, and (3) the conventional MC type specifications in Table 1 with only the inertial mass m being four times larger, for the above (1) to (3). The input acceleration is an amplitude of 1.0×10 -6 m / s 2A sine wave of (0.1 mGal) is assumed. The increase in coil current in the MM type of the present invention is small compared to the conventional MC type. However, when the inertial mass m of the conventional MC type is increased by four times, the coil current increases in proportion to the inertial mass. The reason for this is that in the present invention, the total coil length (number of turns) is increased by 1.6 times and the coil wire diameter is increased by 1.26 times. The reason why this configuration is possible is that a large coil storage space can be formed by providing a sufficiently long cylindrical gap 103 (an inertial mass adjustment section with a length L) in the front pole piece section 102, as described above. In this embodiment, the gap 103 uses a perfect cylindrical shape, but since the purpose is to reduce the inertial mass, the gap does not have to be a perfect circle. For example, it may be a polygonal shape, or a shape with a different inner diameter in the axial direction. These are all referred to as an approximate cylindrical shape.

[0143] To summarise the features of the MM type embodiment of the present invention shown in (i) to (iv) above, the difficulty of processing extremely fine lines, which is an inherent weakness of the MC type, can be fundamentally overcome and the following effects can be obtained. (1) The MM type of the present invention can obtain high-frequency characteristics that are comparable to those of the conventional MC type. In other words, the weaknesses of the MM system are eliminated. (2) The effect of mechanical noise on the sensor output can be reduced to 1 / 4 compared to the conventional MC type. In addition, the effect of increased generated force due to the increase in inertial mass can compensate for the weakness of the capacitive type, which has a decrease in sensitivity in the low frequency range. (3) Compared to conventional MC types, the increase in coil current and heat generation that leads to thermal noise is minimal.

[0144] (2-3) Setting range of moving part mass m We will consider the range in which the movable part mass m of the MM type sensor of the present invention can be set. First, we will consider the lower limit to which the movable part mass m can be set. If the movable part mass m can be made as close as possible to that of the MC type by reducing the weight, the transfer characteristics of the MM type will be equivalent to that of the MC type. In this case, the movable part mass m is the mass of the permanent magnet m p Since it cannot be made smaller than mass m pThe value of m is the basis for determining the limit. In this embodiment (FIG. 1b), the pole piece portion (102, 104) for forming a magnetic circuit is essential for the movable portion including the permanent magnet 101. In this embodiment, m p = 1.52g, the mass m1 of the front pole piece portion 102 = 1.36g, the mass m2 of the rear pole piece portion 104 = 0.63g, and the mass m3 including the movable electrode 111 and the inner peripheral side disc support ring 353 = 1.45g. Therefore, the total mass m of the movable portion is m p + m1+m2+m3=4.96≒5.0g. To reduce the weight, the plate thickness of components m1 and m2 can be changed from t=1.0 to 0.5mm, making m1+m2 1.0g. If the movable electrode is made of aluminum and the plate thickness of each component is changed from t=1.0 to 0.5mm, then m3 0.5g. Incidentally, taking into consideration the magnetic resistance of the magnetic path and the precision of the components during machining, a plate thickness of t=0.5mm was the limit. As a result, the total mass of the movable part m=m p +m1+m2+m3=2.5g. Therefore, the lower limit m of the moving part mass of the MM type sensor of the present invention min is the mass of the permanent magnet m p Based on this, m min =2m p Therefore, the range of the mass of the movable part in which the present invention can be used as an acceleration sensor is m ≥ 2m. p It is.

[0145] Next, let us consider the upper limit to which the mass m of the moving part can be set. The upper limit to which the mass m of the moving part can be set is closely related to the frequency bandwidth (resonant frequency f0) of the acceleration sensor.

[0146]

number

[0147]

number

[0148] In equation (6), as shown in Table 1, K PTis the position sensor sensitivity K S , adjustment gain K C , proportional gain K P It is the product of K t is the force constant of the actuator, R a is the electrical resistance of the coil. From equation (5), the upper limit of the moving mass m max is determined by the resonant frequency f0 (frequency bandwidth) required for the sensor.

[0149]

number

[0150] Therefore, the range of the mass of the movable part in which the present invention can be used as an acceleration sensor is m≦m max As mentioned above, when the sensor of the present invention is applied to an active vibration isolation table, the phase characteristic in the vicinity of f=100Hz is an important performance evaluation index. It is preferable to make the phase delay in the vicinity of f=100Hz as small as possible, and in order to do so, it is necessary to set the resonance frequency f0 high. In practice, sufficient performance was obtained if f0>250Hz.

[0151] Second embodiment 13 is a front cross-sectional view of a servo-type acceleration sensor according to a second embodiment of the present invention. As mentioned above, one of the features of the MM type acceleration sensor of the present invention is that it does not require the complicated ultra-fine wire processing that is the fate of the MC type, and this allows for a significant cost reduction in the production process. However, it was previously thought that the MM type has a larger inertial mass of the moving part than the MC type, resulting in a deterioration in high-frequency characteristics. However, the basic concept advocated by this invention was that the weaknesses of the MM type can be compensated for by innovating the magnetic circuit and the shapes of the parts that make up the magnetic circuit.

[0152] This embodiment is a further thorough implementation of the basic concept of the present invention. That is, by selecting the part shape and magnetic material, the inertial mass m of the moving part is made closer to that of the MC type, even though it is an MM type. 351 is a front pole piece, 352 is a rear pole piece, and 353 is an inner disk support ring. 354 is a ring-shaped permanent magnet magnetized in the axial direction, and 355 is a cylindrical gap formed inside the front pole piece. The front pole piece 351 is a main component that constitutes the magnetic circuit, and accounts for a large proportion of the mass of the moving part. In this embodiment, permalloy, which is a soft magnetic material that can be manufactured by pressing, is used for the front pole piece. Permalloy is a material with low coercive force and high magnetic permeability. Therefore, even if the thickness t of the cylindrical front pole piece is made sufficiently thin, the length L can be made sufficiently long without being affected by magnetic resistance. As mentioned above, the longer the length L of the front pole piece, the more the effect of magnetic flux leakage on the generated force can be reduced, and the generated force can be increased even with the same current. At the same time, the coil storage volume can be increased, so that it is possible to select coil specifications (number of turns, wire diameter) that can suppress the heat generation of the coil. In the embodiment, a magnetic circuit that does not affect the generated force of the actuator even if the thickness is less than 0.5 mm is configured. Furthermore, in this embodiment, the permanent magnet 354, the rear pole piece 352, the inner disk support ring 353, etc. are also hollow in order to reduce weight.

[0153] Third embodiment As described above in the first embodiment, the present invention focuses on the following points.

[0154] That is, the point is that "the weakness of the MM type, that the inertial mass of the moving part is increased, becomes an advantage in improving the sensor sensitivity in the low frequency range." In particular, the capacitance type has low sensor sensitivity in the low frequency range, and this can compensate for this weakness. FIG. 14 is a front cross-sectional view of a servo type acceleration sensor according to the third embodiment of the present invention, which makes full use of the above-mentioned advantages of the MM type. That is, contrary to the second embodiment described above, the inertial mass of the moving part is set to be thoroughly large to significantly improve the sensor sensitivity in the low frequency range. However, in exchange, the high frequency band is restricted. 381 is a front pole piece, 382 is a rear pole piece, and 383 is an inner circumference side disk support member. The front pole piece 381 and the rear pole piece 382 are the moving side yoke material. None of the parts that make up the moving part form a cavity. The effect of making the front pole piece 381, which accounts for a large proportion of the moving part mass, a solid member is large.

[0155] When the sensor of this embodiment is applied to an active vibration isolation table, for example, it is possible to design a control system that places emphasis on improving the vibration isolation characteristics in the low frequency range. Furthermore, by combining the above two sensors (1) and (2), namely (1) an acceleration sensor in which the inertial mass of the moving part is thoroughly reduced in weight (second embodiment) and (2) an acceleration sensor in which the inertial mass of the moving part is sufficiently large (this embodiment), and mounting them on a vibration isolation table, it is possible to realize an active vibration isolation / control system that can cover a wide range from low to high frequencies (not shown).

[0156] (Fourth embodiment) 15 is a front cross-sectional view of a servo-type acceleration sensor according to embodiment 4 of the present invention. In the above-mentioned embodiments, a closed loop magnetic circuit is formed by providing an annular gap (for example, the chain circle B in FIG. 1b) with a narrow gap. In this embodiment, instead of the annular gap, the spiral disk spring itself is used as the member that forms the magnetic circuit.

[0157] Reference numeral 401 denotes a rear disk (second transmission section), 402 denotes a front disk made of a conductive material, 403 denotes a permanent magnet, and 404 denotes a positioning pin, which is attached to the center of the permanent magnet. Reference numeral 405 denotes a front pole piece section, 406 denotes an outer disk support ring, 407 denotes an inner disk support member, 408 denotes a coil side yoke material, and 409 denotes a magnetic gap section (first transmission section). As shown by the chain line arrow, a closed loop magnetic circuit is formed by "permanent magnet 403 → front pole piece section 405 → coil side yoke material 408 → rear disk 401 → permanent magnet 403". This is not limited to this embodiment, and is the same as in other embodiments, but the disks 401 and 402, which are elastic support members, do not have to be spiral-shaped, and may be, for example, a known cloud spring.

[0158] The rear disk 401 and the front disk 402 do not have to be of the same shape or material. An inner disk support member 407 made of a non-conductive material is interposed on the inner periphery of the front disk 402 to electrically insulate it from the front pole piece portion 405. The front disk 402 is preferably made of a non-magnetic material. An outer disk support ring 406 made of a non-conductive material is interposed on the outer periphery to electrically insulate it from the coil side yoke material 408. However, electrical insulation of the rear disk 401 is not necessary. This embodiment does not require a magnetic coupling portion, making it possible to realize a servo type acceleration sensor with a simple configuration.

[0159] Fifth embodiment 16 is a front cross-sectional view of a servo-type acceleration sensor according to a fifth embodiment of the present invention. The sensor body is made compact by utilizing the cylindrical gap in the front pole piece portion and arranging a permanent magnet in this gap. 251 is a permanent magnet magnetized in the axial direction, 252 is a front pole piece portion, and 253 is a space formed between the outer surface of the permanent magnet and the inner surface of the front pole piece. 254 is a rear pole piece portion, 255 is a coil side yoke material, 255a is a protrusion formed on the inner surface of the coil side yoke material, 256 is a force coil, and 257 is a calibration coil. Reference numeral 258 is a front side disk, 259 is a rear side disk, 260 is a movable side electrode, 261 is a fixed side electrode, 262a is a front side panel, 262b is a rear side panel, 263 is a central plate, 264 is a fastening member, 265 is a coil mounting portion on the inner surface of the coil side yoke material, 266 is a coil opposing surface in the front side pole piece portion 252, and a radial magnetic gap portion 267 is formed between the coil opposing surface 266 and the coil mounting portion 265.

[0160] Similar to the previously described embodiment, a narrow annular gap 268 is provided between the protruding portion 255a of the coil side yoke material and the rear side pole piece portion 254. Reference numeral 269 denotes an outer peripheral support ring, and 270 denotes an inner peripheral support ring.

[0161] The permanent magnet is housed inside a cylindrical gap 253, and one end face of the permanent magnet is fixed to a front end face 271 of the front pole piece, and the other end face of the permanent magnet is fixed to the rear pole piece.

[0162] A closed loop magnetic circuit is formed by "permanent magnet 251 → front pole piece portion 252 → magnetic gap portion 267 → coil side yoke material 255 → protrusion portion 255a → annular gap portion 268 → rear pole piece portion 254 → permanent magnet 251" as indicated by the dashed arrow.

[0163] Sixth embodiment 17 is a front cross-sectional view of a servo-type acceleration sensor according to a sixth embodiment of the present invention. The coil bobbin is made of a material with good thermal conductivity to improve the heat dissipation effect, and the magnetic path shape is configured to reduce leakage magnetic flux. In other words, it achieves both the reduction of sensor noise that leads to thermal noise and the improvement of the force generated by the actuator.

[0164] Reference numeral 201 denotes a permanent magnet magnetized in the axial direction, 202 a front pole piece portion, 203 a cylindrical gap portion formed inside the front pole piece portion, 204 a rear pole piece portion, 205 a coil side yoke material, 206a a force coil, and 206b a calibration coil. Reference numeral 207 denotes a protrusion formed on the inner surface of the coil side yoke material, 208 a front side disk, 209 a rear side disk, 210 a movable side electrode, 211 a fixed side electrode, 212a a front side panel, 212b a rear side panel, 213 a center plate, 214 a fastening member, 215 a coil mounting portion on the inner peripheral surface of the coil side yoke material, 216 a coil opposing surface in the front pole piece portion 202, and a radial magnetic gap portion 217 is formed between the coil opposing surface 216 and the coil mounting portion 215. Similar to the previously described embodiment, a narrow annular gap 218 is provided between the protruding portion 207 of the coil side yoke material and the rear side pole piece portion 204. Reference numeral 219 denotes an outer peripheral support ring, and 220 denotes an inner peripheral support member.

[0165] Reference numeral 221 denotes a coil bobbin, 223 denotes a recess formed between the outer periphery of this coil bobbin and the coil side yoke material 201, and in this embodiment, the coil bobbin 221 is made of a non-magnetic material, aluminum, which has good thermal conductivity.

[0166] FIG. 18 illustrates the flow of magnetic flux in this embodiment with arrows (chain lines). Non-magnetic members constituting the acceleration sensor are shown as "sand". Members using magnetic materials are shown with normal "diagonal lines". That is, the front panel 212a, the rear panel 212b, the coil bobbin 221, the force coil 206a, the calibration coil 206b, the outer circumferential support ring 220, the inner circumferential support member 220, the front disk 208, the rear disk 209, and the movable electrode 210 are made of non-magnetic members. As shown by the chain arrows, a closed loop magnetic circuit is formed by "permanent magnet 201 → front pole piece portion 202 → magnetic gap portion 217 coil side yoke material 205 → protrusion portion 207 → annular gap portion 218 → rear pole piece portion 204 → permanent magnet 201".

[0167] Magnetic flux A flowing vertically through magnetic gap 217 effectively contributes to the generated force of this actuator. Magnetic fluxes B1 and B2 flowing from the corners of coil facing surface 216 to the corners of coil side yoke material inner peripheral surface 205 are leakage fluxes and do not contribute to the generated force. The ease with which magnetic flux flows in a magnetic circuit is expressed by permeance, which is the reciprocal of magnetic resistance. In other words, the gap permeance of the magnetic path through which magnetic flux A flows is expressed as P g The leakage permeance of the magnetic path through which the leakage fluxes B1 and B2 flow is P f1 , P f2 Do. P g ≫P f1 , or P g ≫P f2 The recessed portion 223 formed in the coil side yoke material reduces the leakage magnetic flux B2 and the leakage permeance P f2 This recess 223 is formed on the inner surface of the coil side yoke material in such a way that the radial distance between the movable part and the fixed member is longer near the axial end face of the coil compared to both ends. The effect of reducing leakage flux by this recess 223 is not limited to this embodiment. In addition, since the surrounding members through which leakage flux B1 flows are all made of non-magnetic materials, the leakage permeance P f1 can be made small enough.

[0168] 19 illustrates the flow of heat in this embodiment with arrows (chain lines). The outer peripheral surface of the coil bobbin 221 is in close contact with the inner peripheral surface 215 of the coil side yoke material. It extends to cover the recessed portion 223 and is in close contact with the side surface and inner peripheral surface 215a of the protruding portion 207. Therefore, the heat generated by the coil can be easily dissipated to the front side panel 212a and the rear side panel 212b via the aluminum bobbin 221 → coil side yoke material 205, as shown by the arrows in the figure.

[0169] In the case of the conventional linear motion acceleration sensor (MC type) shown in Fig. 54, the coil bobbin 17 and the coils 16a and 16b are installed in a suspended state in the air. The coil bobbin support members 18 and 19 that support the coil bobbin 17 are made of non-magnetic and non-conductive materials. Also, because the disk-shaped springs 20 and 21 are made of thin plate material, the heat dissipation effect of the coils by thermal conduction cannot be expected.

[0170] The same is true for the conventional oscillating motion moving coil type (MC type) shown in Figure 56. Quartz glass (a non-magnetic and non-conductive material) with low thermal conductivity is present in the thermal conduction path connecting torque coil 597 and the fixed part (magnetic yokes 591, 592), so heat dissipation from the coil cannot be expected. In other words, the reason that the coil's heat dissipation effect is sufficient in the sensor of this embodiment compared to the conventional type is that it utilizes the characteristics of the MM type, which allows the coil to be fixed and attached to the wall surface.

[0171] Seventh embodiment Fig. 20a is a front cross-sectional view of a servo-type acceleration sensor according to embodiment 7 of the present invention, and Fig. 20b is a cross-sectional view taken along line AA in Fig. 20a. The above-mentioned embodiments all have sensor structures using permanent magnets magnetized in the axial direction. In this embodiment, a magnetic circuit is formed using multiple permanent magnets called segment type magnetized in the radial direction.

[0172] Reference numeral 451 denotes a permanent magnet, and 452 denotes a front pole piece section. The permanent magnet is composed of radially magnetized segment-type permanent magnets 451a, 451b, 451c, and 451d, and is attached to the front pole piece section 452. Reference numeral 453 denotes a cylindrical gap section formed to reduce the weight of the front pole piece section. Reference numeral 454 denotes a rear pole piece section, 455 denotes a coil side yoke material, and 456 denotes a force coil, or a coil section composed of a force coil and a calibration coil. Reference numeral 457 denotes a protrusion formed on the inner surface of the coil side yoke material, 458 a front side disk, 459 a rear side disk, 460 a movable side electrode, 461 a fixed side electrode, 462a a front side panel, 462b a rear side panel, 463 a center plate, 464 a fastening member, 465 a coil mounting part on the inner peripheral surface of the coil side yoke material, 466 an outer peripheral surface of a permanent magnet, which corresponds to a coil facing surface. A radial magnetic gap 467 is formed between the coil facing surface 466 and the coil mounting part 465. A ring-shaped gap 468 is provided between the protrusion 457 of the coil side yoke material and the rear pole piece part 454 by a narrow gap, as in the previous embodiment. 469 denotes an outer peripheral support ring, and 470 an inner peripheral support ring. A closed loop magnetic circuit is formed by "permanent magnet 451 → magnetic gap portion 467 → coil side yoke material 455 → protrusion portion 457 → annular gap portion 468 → rear side pole piece portion 454 → front side pole piece portion 452 → permanent magnet 451" as indicated by the dashed arrow.

[0173] Eighth embodiment 21 is a front cross-sectional view of a servo-type acceleration sensor according to embodiment 8 of the present invention. In the above-mentioned embodiments, a closed-loop magnetic circuit is formed by providing an annular gap (for example, the chain circle B in FIG. 1b) with a narrow gap. In this embodiment, instead of the annular gap, a magnetic coupling section for forming a closed-loop magnetic circuit is formed by combining a segment-type permanent magnet magnetized in the radial direction with a fixed coil.

[0174] Reference numeral 651 denotes a segmented permanent magnet (auxiliary magnet), and 652 denotes a rear pole piece portion. The segmented permanent magnet is composed of a plurality of segmented permanent magnets (see FIG. 20b) magnetized in the radial direction as in the seventh embodiment, and is attached to the rear pole piece portion 652. Reference numeral 653 denotes a cylindrical gap portion formed to reduce the weight of the rear pole piece portion. Reference numeral 654 denotes a front pole piece portion, 655 denotes a permanent magnet magnetized in the axial direction, 656 denotes a front end face of the front pole piece, and 657 denotes a cylindrical gap portion formed inside the front pole piece. The permanent magnet 655 is housed inside the cylindrical gap portion 657, and one end face is fixed to the front end face 656 of the front pole piece. The other end face of the permanent magnet is fixed to the rear pole piece. In the present embodiment, similarly to the fifth embodiment, a cylindrical gap 657 in a front pole piece portion 654 is utilized, and a permanent magnet 655 is disposed in this gap, thereby making the sensor body more compact.

[0175] Reference numeral 658 denotes a coil side yoke material, 659 denotes a front side force coil, 660 denotes a rear side force coil (auxiliary coil), and 661 denotes a calibration coil section.

[0176] Reference numeral 662 denotes a front disk, 663 a rear disk, 664 a movable electrode, 665 a fixed electrode, 666a a front panel, 666b a rear panel, 667 a center plate, 668 a fastening member, 669 a coil mounting portion on the inner peripheral surface of the coil side yoke material, 670 a coil opposing surface (the outer peripheral surface of the front side pole piece portion), 671 a magnetic gap portion, 672 an outer peripheral support ring, and 673 an inner peripheral support ring. A closed loop magnetic circuit is formed by "permanent magnet 655 → front side pole piece portion 654 → magnetic gap portion 671 → coil side yoke material 658 → permanent magnet 651 → rear side pole piece portion 652 → permanent magnet 655" as shown by the dashed arrow.

[0177] In this embodiment, the magnetic coupling portion is configured with a radially magnetized magnet and a fixed coil, so that both the front side and the rear side function as a voice coil motor, improving the generated force. As in the first embodiment, the radial gap of the magnetic gap portion 671 is 2.5 mm, and the radial gap between the coil facing surface 670 and the coil is about 0.5 mm. Therefore, assembly during mass production is easier than when the annular gap portion is configured with a narrow gap (for example, the annular gap portion 118 in the first embodiment).

[0178] Ninth embodiment 22a is a front cross-sectional view of a servo-type acceleration sensor according to a ninth embodiment of the present invention, and FIGS. 22b and 22c are cross-sectional views showing radially magnetized segment-type permanent magnets used in this embodiment.

[0179] In this embodiment, the front permanent magnet is composed of a segment magnet magnetized in the radial direction, and the magnetic coupling section is also composed of a segment magnet magnetized in the radial direction and a fixed coil. Both the front and rear sides function as voice coil motors, improving the generated force. 701 is a front permanent magnet, 702 is a rear permanent magnet, and 703 is a pole piece section (movable yoke material). Both the front permanent magnet and the rear permanent magnet are composed of multiple segment permanent magnets magnetized in the radial direction and are attached to the pole piece section 703. As shown in Figures 22b and 22c, the radial magnetization directions of each permanent magnet are opposite to each other.

[0180] Reference numeral 704 denotes a gap of the pole piece part, 705 a front disk, 706 a rear disk, 707 a movable electrode, 708 a fixed electrode, 709a a front panel, 709b a rear panel, 710 a center plate, 711 a fastening member, 712 a coil side yoke material, 713 a coil bobbin, 714 a front coil, and 715 a rear coil. Reference numeral 716 denotes an outer peripheral support ring, 717 an inner peripheral support ring, 718 a front end face of the pole piece part, 719 a rear end face of the pole piece part, 720 a support ring for the rear disk spring, and 721 a coil mounting part which is the inner peripheral surface of the coil side yoke material 712. Reference numerals 722a and 722b denote magnetic gaps formed between the coil mounting part and the two permanent magnets on the front and rear sides. A closed loop magnetic circuit is formed by "permanent magnet 701 → coil side yoke material 712 → permanent magnet 702 → pole piece part 703 → permanent magnet 713" as shown by the dashed arrow. In this embodiment, the space formed by the rear side permanent magnet and the rear side coil is the magnetic coupling part. In this embodiment, both the front side and the rear side function as voice coil motors, so that the generated force can be improved. In addition, the radial gap of the magnetic gap parts 722a and 722b is 2.5 mm, and the radial gap between the outer peripheral surfaces of the two permanent magnets and the coil bobbin is about 0.5 mm. Therefore, compared with the case where the annular gap part is formed with a narrow gap (for example, the annular gap part 118 in the first embodiment), assembly during mass production is also easier.

[0181] Tenth embodiment 23 is a front cross-sectional view of a differential servo type acceleration sensor according to a tenth embodiment of the present invention. That is, by focusing on the structural feature of the linear MM type, in which both the left and right output shafts are open ends, a differential capacitance type sensor is constructed by providing electrodes for detecting capacitance in two places, left and right. By making the acceleration sensor differential, a high-resolution sensor can be realized in which the sensor output is less susceptible to the effects of disturbance signals such as noise and drift.

[0182] (i) Description of structure Reference numeral 301 denotes a permanent magnet, 302 a front pole piece portion, and 303 a cylindrical gap portion (inertial mass adjustment portion). 304 a rear pole piece portion, 305 a coil side yoke material, 306a a force coil, 306b a calibration coil, and 307 a protrusion formed on the inner surface of the coil side yoke material. 308 a front disk, and 309 a rear disk. 310a a front movable electrode, 311a a front fixed electrode, 310b a rear movable electrode, and 311b a rear fixed electrode.

[0183] Reference numeral 312a denotes a front panel, 312b denotes a rear panel, 313a denotes a front center plate, 313b denotes a rear center plate, 314a denotes a front fastening member, and 314b denotes a rear fastening member. Reference numeral 315 denotes the inner peripheral surface of the coil side yoke material 305, 316 denotes the coil opposing surface of the front side pole piece portion, and 317 denotes a radial magnetic gap portion formed between the coil opposing surface 316 and the coil mounting portion 315. Between the protruding portion 307 of the coil side yoke material and the rear side pole piece portion 304, there is provided an annular gap 318 formed by a narrow gap.

[0184] The annular gap 318 is set to a narrow gap that has a sufficiently small magnetic resistance compared to the magnetic gap 317. As in the first embodiment, a closed loop magnetic circuit is formed by "permanent magnet 301 → front pole piece 302 → magnetic gap 317 → coil side yoke material 305 → annular gap 318 → rear pole piece 304". As in the first embodiment, the lead wires of the force coil 306a and the calibration coil 306b pass through the coil side yoke material 305 and the front panel 312a and connect to an externally installed control circuit (not shown). 319a is a front side disk inner circumference side support ring, 319b is a rear side disk inner circumference side support ring, 320a is a front side disk outer circumference side support ring, and 320b is a rear side disk outer circumference side support ring. The four rings are made of non-conductive materials.

[0185] The method of fastening the front side disk 308 and the rear side disk 309 is the same as in embodiment 1. The method of connecting the conductor for detecting the capacitance between the movable electrode and the fixed electrode to the outside is also the same as in embodiment 1 (not shown).

[0186] FIG. 24 is a diagram showing that the differential servo acceleration sensor according to this embodiment can be composed of three units. 330 is a front unit, 331 is a drive unit, and 332 is a rear unit. Each unit can be equipped with its own parts as an independent unit. When the parts of each unit are equipped, the three units are combined as shown by the arrows in the figure. After the combination, the gap between the movable electrode and the fixed electrode on the front side and the gap between the movable electrode and the fixed electrode on the rear side can be adjusted. In the servo acceleration sensor of this invention, it is extremely easy to select between a differential type and a non-differential type compared to conventional acceleration sensors. Here, the non-differential type of the first embodiment (FIG. 1) is compared with the differential type of this embodiment 10 (FIGS. 23 and 24). To make it a differential type, it is only necessary to add a rear side movable side electrode 310b to the drive unit 331 and attach a rear side fixed side electrode 311b to the rear side unit 332. Therefore, the selection from a non-differential type to a differential type does not result in a large increase in cost.

[0187] In addition, the adjustment of the gap between the rear movable electrode 310b and the rear fixed electrode 311b, which is performed in the final stage of mass production, can be performed independently of the front side. For example, the adjustment of the rear side can be performed after the adjustment of the front side is completed.

[0188] (ii) Explanation of the drift noise reduction effect The drift and noise reduction effect of the sensor of this embodiment will be explained below in comparison with the conventional type. Figure 25 shows the relationship between the electrode output, noise and drift, and sensor acceleration output in the case of a conventional acceleration sensor (see Figure 54). The electrode output is obtained by detecting the electrostatic capacitance determined by the gap between the movable electrode 24 and the fixed electrode 25. Graph A of noise and drift is obtained by adding a small positive bias value to a sine wave. The sensor acceleration output (graph C) is the result of applying noise and drift (graph A) to the electrode output (graph B).

[0189] Furthermore, in the active vibration isolation table, absolute velocity feedback and absolute displacement feedback are applied to obtain vibration isolation performance in the low frequency range. To obtain an absolute velocity signal, the acceleration signal must be integrated once, and to obtain an absolute displacement signal, the acceleration signal must be integrated twice. Graph D in Fig. 25 shows the absolute velocity output obtained by integrating the sensor acceleration output (graph C) once by perfect integration. The velocity signal with noise superimposed on it diverges due to the influence of drift. To solve the above problem, in an actual active vibration isolation table, perfect integration 1 / s cannot be used, and an approximate velocity signal is obtained by integrating the acceleration sensor output by imperfect integration 1 / (s+a). Furthermore, a method is adopted in which this velocity signal is integrated by a similar integrator to obtain an approximate displacement signal. However, the phase delay angle of the signal that has passed through imperfect integration does not become the value in the case of the above perfect integration in the low frequency range, and as a result, an accurate negative feedback signal cannot be obtained. As a result, there is a problem that sufficient vibration isolation characteristics cannot be obtained because the phase is delayed in the low frequency range and the gain increases.

[0190] FIG. 26 shows the relationship between the two electrode outputs, noise and drift, and the sensor acceleration output in the case of the acceleration sensor according to this embodiment.

[0191] Front electrode output B f is the capacitance determined by the gap between the movable electrode 310a and the fixed electrode 311a, and the rear electrode output B ris obtained by detecting the capacitance determined by the gap between the movable electrode 310b and the fixed electrode 311b. The front electrode output B f →C f and rear electrode output B r →C r As a result, the acceleration output C of the differential sensor s is a waveform in which noise and drift have been cancelled. Furthermore, the absolute velocity signal D obtained by fully integrating the acceleration output, and the absolute displacement signal (not shown) do not diverge. Therefore, when the acceleration sensor of this embodiment is applied to an active vibration isolation table, in addition to the effect of improving the sensor sensitivity (for example, improving the positioning accuracy of the stage), a significant improvement in vibration isolation characteristics can be obtained in the low frequency range.

[0192] Eleventh embodiment 27 is a front cross-sectional view of a differential servo acceleration sensor according to an eleventh embodiment of the present invention. As in the above-mentioned tenth embodiment, a differential capacitance sensor is configured by providing electrodes for detecting capacitance at two locations, one on the left and one on the right. As in the ninth embodiment, the front permanent magnet is configured by a radially magnetized segment magnet, and the magnetic coupling part is also configured by a radially magnetized segment magnet and a fixed coil.

[0193] Reference numeral 801 denotes a front side permanent magnet, 802 denotes a rear side permanent magnet, 803 denotes a pole piece portion, 804 denotes a gap portion of the pole piece portion, 805 denotes a front side disk, 806 denotes a rear side disk, 807 denotes a front side movable electrode, 808 denotes a front side fixed electrode, 809a denotes a front side panel, 809b denotes a rear side panel, 810 denotes a front side central plate, 811 denotes a front side fastening member, 812 denotes a coil side yoke material, 813 denotes a coil bobbin, 814 denotes a front side coil, and 815 denotes a rear side coil. Reference numeral 816 denotes a front outer peripheral support ring, 817 a front inner peripheral support ring, 818 a front end face of the pole piece, 819 a rear end face of the pole piece portion, 820 an outer peripheral support ring of the rear disk, 821 a coil mounting portion which is the inner peripheral surface of the coil side yoke material, 822 a magnetic gap formed between this coil mounting portion and the two permanent magnets, 823 a rear movable electrode, 824 a rear fixed electrode, 825 a rear center plate, 826 a rear fastening member, and 827 a rear inner peripheral support ring. Two embodiments of the differential sensor have been described above. The proposals shown in the other embodiments (linear type MM type) of the present invention can be applied to the configuration of the differential actuator unit.

[0194] (Twelfth embodiment) Swing type (1) Fig. 28 shows an oscillatory motion servo acceleration sensor according to embodiment 12 of the present invention, with Fig. 28a being a front cross-sectional view and Fig. 28b being a schematic diagram of the side of a pendulum, one of the components that make up this sensor. Since the servo acceleration sensor of this embodiment has a magnetic circuit including a permanent magnet that is configured symmetrically, the components on the right side will be described first.

[0195] 901a is a permanent magnet, 902a is a front pole piece, 903a is a cylindrical gap formed to reduce the weight of the front pole piece, 904a is a rear pole piece, 905a is a coil side yoke material, 906a is an electromagnetic coil, 907a is a coil bobbin, and 908a is a protrusion formed on the inner surface of the coil side yoke material. The front pole piece part 902a and the rear pole piece part 904a are the movable yoke material. 909 is a pendulum made of a non-magnetic and conductive material. This pendulum is composed of a cantilever beam with one end fixed and the other end free, and the movable part is provided on the free end side of this cantilever beam. 910 is a housing with a cylindrical cavity at the top. This housing is made of a non-magnetic material. 911a is a plate material made of an insulating material at the lower end of the pendulum. The pendulum is fixed in a state where it is sandwiched between plate materials 911a and 911b. 912 is a hinge portion. The spring stiffness of the entire pendulum that swings is determined by this hinge portion. 913a is a movable electrode formed on the pendulum, and 914a is a fixed electrode. An electrically insulating coating is formed on the wall surface where the fixed electrode and the housing 910 are in close contact (not shown). The pendulum 909 made of conductive material also serves as a conductor that connects the detection signal of the electrostatic capacitance between the left and right electrodes to a control circuit as a common earth. 915a is the coil facing surface of the pole piece 902a, and 916a is the coil mounting surface. A radial magnetic gap 917a is formed between the coil facing surface 915a and the coil mounting surface 916a. An annular gap 918a is provided by a narrow gap between the protruding portion 908a of the coil side yoke material and the rear side pole piece portion 904a. As in the first embodiment described above, a closed loop magnetic circuit (not shown) is formed by "permanent magnet 901a → front pole piece portion 902a → magnetic gap portion 917a → coil side yoke material 905a → annular gap portion 918a → rear pole piece portion 904a." The gap of annular gap portion 918a is set so that the magnetic resistance is sufficiently smaller than that of magnetic gap portion 917a. The annular gap portion is a magnetic coupling portion for forming a closed loop magnetic circuit in a magnetic circuit using a permanent magnet.The lead wires for transmitting and receiving signals between the electromagnetic coil 906a and an externally installed control circuit are provided using through holes formed in the coil side yoke material 905a and the housing 910 (not shown), as in the first embodiment described above.

[0196] Reference numeral 919a denotes a convex member made of an insulating material, and is adhesively fixed to the upper portion of the pendulum 909. This convex member 919a is adhesively fitted to the front pole piece portion 902a. Because the convex member is made of an insulating material, the front pole piece portion 902a and the pendulum 909 can maintain electrical insulation. Reference numeral 920 denotes a control circuit provided in the lower gap of the housing 910.

[0197] In this embodiment, each component is configured symmetrically with the pendulum 909 as the central axis. The reference numbers of each component, such as the permanent magnet 901a and the pole piece portion 902a, are designated by the symbol a for the right-side component and the symbol b for the left-side component. Focusing on the right-side components, as in the first embodiment described above, the electromagnetic coil 906a is arranged so as to enclose the entire permanent magnet 901a and the front pole piece portion 902a that connects the permanent magnet in series from the outer periphery. Furthermore, the annular gap portion 918a, which has a sufficiently small magnetic resistance compared to the magnetic gap portion 917a, is arranged in the closed loop magnetic circuit. The movable components that move in the axial direction are the permanent magnet 901a, the front pole piece portion 902a, and the rear pole piece portion 904a.

[0198] An example of a method for assembling the acceleration sensor according to this embodiment is shown in Fig. 29. The three components, the front pole piece portion 902a, the permanent magnet 901a, and the rear pole piece portion 904a, are integrated with adhesive and then attached to the convex member 919a of the pendulum. Furthermore, the coil bobbin 907a housing the electromagnetic coil 906a is attached to the coil side yoke material 905a, and then fitted into the hollow portion of the housing 910.

[0199] The components of the magnetic circuit can be the same as those of the linear acceleration sensors in the first to eleventh embodiments described above. For example, the magnetic coupling part does not have to be an annular gap, and may be a combination of a radially magnetized segment-type permanent magnet and a fixed coil.

[0200] The features of this embodiment will be described in comparison with the conventional oscillating acceleration sensor disclosed in Patent Document 1. In this embodiment, the pendulum 909 can be made of a conductive metal material. In the conventional oscillating acceleration sensor shown in FIG. 56, the reason why a non-conductive material such as quartz glass is used for the pendulum 590a is that it is necessary to transmit and receive multiple independent signals (coil and electrode signals) between the movable side and the fixed side control circuit of the sensor. A conductive path for processing multiple independent signals is formed on the surface of this quartz glass by a thin film of gold (Au) sputtered or vacuum-deposited. In other words, the selection of materials and special construction method were necessary because of the MC type. In the case of this embodiment, which is an MM type, the only signal transmitted and received from the movable part to the fixed side is a common ground for the left and right electrode signals. Therefore, there is no need for expensive sputtering equipment, etc., which is required in the production process of the conventional oscillating MC type (FIG. 56), and the production process can be greatly simplified and the cost can be reduced. The contact point of the common ground can be provided by using the fixed parts 911a and 911b of the pendulum (not shown).

[0201] Thirteenth embodiment 30 shows a swing motion type servo acceleration sensor according to embodiment 13 of the present invention. This embodiment is a simplification of embodiment 12 described above, and is configured with only one set of capacitance detection electrodes.

[0202] Reference numeral 951 denotes a permanent magnet, 952 denotes a front pole piece portion, 953 denotes a rear pole piece portion, 954 denotes a coil side yoke material, 955 denotes a force coil, 956 denotes a coil bobbin, and 957 denotes a protrusion formed on the inner surface of the coil side yoke material.

[0203] Reference numeral 958 denotes a pendulum made of a non-magnetic and conductive material, 959 denotes a rear housing made of a non-magnetic material having a cylindrical cavity at the top, 960 denotes a fixed part of the pendulum, and 961a and 961b denote plates made of an insulating material at the lower end of the pendulum. The fixed part 960 of the pendulum is fixed while being sandwiched between plates 961a and 961b. Reference numeral 962 denotes a hinge part (elastic deformation part). The spring rigidity of the entire pendulum that swings is determined by this hinge part. Reference numeral 963 denotes a movable electrode formed at the upper end of the pendulum, and 964 denotes a fixed electrode. The pendulum 958 made of a conductive material also serves as a conductive path as a common ground that connects the detection signal of the capacitance between the left and right electrodes to a control circuit.

[0204] Reference numeral 965 denotes a convex-shaped member made of an insulating material, which is adhesively fixed to the upper portion of pendulum 958. This convex-shaped member 965 is adhesively fitted to front pole piece portion 952. Because the convex-shaped member is made of an insulating material, the front pole piece portion 952 and pendulum 958 can maintain electrical insulation.

[0205] Reference numeral 966 denotes a magnetic gap, and 967 denotes an annular gap. The gap of this annular gap is set so that the magnetic resistance is sufficiently smaller than that of the magnetic gap 966. The annular gap is a magnetic coupling portion for forming a closed loop magnetic circuit in a magnetic circuit using a permanent magnet. As in the first and twelfth embodiments described above, a closed loop magnetic circuit (not shown) is formed by "permanent magnet 951 → front pole piece portion 952 → magnetic gap portion 966 → coil side yoke material 954 → annular gap portion 967 → rear pole piece portion 953." Reference numeral 968 denotes a rear housing made of a non-magnetic material, and at its upper portion, a center plate 969 and a fixed electrode 964 are fastened by a fastening member 970. Reference numeral 971 denotes a control circuit provided in the lower gap of the rear housing 959.

[0206] As described above, if the basic structure of the linear motion acceleration sensor and the oscillating motion acceleration sensor is classified according to the elastic support method of the movable part, the linear motion type has a spring arranged in the circumferential direction of the axis centered on the moving direction of the movable part. As shown in the twelfth and thirteenth embodiments, the oscillating motion type has a structure in which the movable part is supported by a cantilever with one end fixed and the other free. The operating principle of both the linear motion type and the oscillating motion type is the same in that they detect the gap between the fixed electrode and the movable electrode. Therefore, the proposals shown in the other embodiments of the present invention can also be applied to the oscillating motion type. For example, the method of mounting a coil bobbin with good thermal conductivity shown in the sixth embodiment, and the method of forming a magnetic circuit using a segment-type magnet magnetized in the radial direction shown in the seventh and eighth embodiments can also be applied.

[0207] Fourteenth embodiment FIG. 31 shows a servo type acceleration sensor according to the fourteenth embodiment of the present invention, and shows a structure in which many components constituting the sensor are fastened with bolts. FIGS. 32 to 41 show the assembly process of the sensor of this embodiment. Conventional servo type MC acceleration sensors were constructed by an adhesive technique, as shown in the examples of FIGS. 54 and 56. The main reasons for this are (1) the component shapes are microscopic, and (2) the moving part needs to be lightweight, that is, (1) and (2) above. In the case of a linear motion acceleration sensor, the complicated structure requires "cutting, insulating, and soldering" of the disk springs that support both ends of the moving part, so it was difficult to construct it by a bolt fastening technique. When a product was constructed by an adhesive technique, if it was found to be a non-conforming product at the quality evaluation stage during mass production, the product body had to be discarded.

[0208] In this embodiment, a very small bolt fastening method of M0.5 to M1.0mm, which is applied in special fields such as watches, is applied to a servo type acceleration sensor composed of micro parts. The outer diameter of the servo type acceleration sensor to which the present invention is applied is about Φ25mm, which is smaller than the outer diameter of a 500 yen coin. The reason why the bolt fastening method can be applied in this embodiment is that attention is paid to the characteristics of the MM type, which does not require ultra-fine wire processing and can simplify the component configuration of the moving part. The acceleration sensor of this embodiment can reuse many parts, and the yield rate during mass production can be greatly improved. In addition, in the case of the adhesive method, the thickness of the adhesive interposed between the parts to be bonded and the unevenness of this thickness are factors that reduce the assembly accuracy. In the case of the bolt fastening method, high assembly accuracy can be ensured as long as the processing accuracy of each part is obtained. In addition, since the worker does not need to be skilled, the variation in product performance can be reduced.

[0209] (1) Overall configuration of the sensor 31, 751 is a permanent magnet having a hollow portion, 752 is a front pole piece portion, 753 is a cylindrical gap portion, 754 is a rear pole piece portion, 755 is a coil side yoke material, 756a is a force coil, 756b is a calibration coil, and 757 is a protrusion formed on the rear side inner surface of the coil side yoke material. 758 is a front side disk, 759 is a rear side disk, 760 is a movable side electrode, 761 is a fixed side electrode, 762a is a front side panel, 762b is a rear side panel, 763 is a center plate, and 764 is a fastening member made of a non-conductive material between the fixed side electrode and the front side panel.

[0210] Reference numeral 765 denotes a coil bobbin, 766 denotes a coil bobbin mounting portion formed on the inner surface of the coil side yoke material, and 767 denotes a coil opposing surface which is the outer surface of the front side pole piece portion. A radial magnetic gap 768 is formed between the coil opposing surface 767 and the coil bobbin mounting portion 766. An annular gap (magnetic coupling portion) 769 formed by a narrow gap is provided between the protruding portion 757 of the coil side yoke material and the rear side pole piece portion 7544.

[0211] Reference numeral 770 denotes an inner disk support member, and 771 denotes an outer disk support member. The two disk support members 770, 771 are made of a non-conductive material (insulating material). Reference numeral 772 denotes a ring-shaped nut made of a metallic material attached to one end face of the inner disk support member 770. The bolts that fasten the respective members together will be described below.

[0212] (2) Functions of each fastening bolt Reference numeral 773a denotes a bolt that fastens together three components, namely, the movable electrode 760, the inner peripheral side disc support member 770, and the ring-shaped nut 772. The front-side disc 758 is sandwiched between the movable electrode 760 and the inner peripheral side disc support member 770. Reference numeral 773b denotes a bolt that fixes the outer peripheral side disc support member 771 to the coil side yoke material 755. As described below, the front-side disc 758 is adhesively fixed to the outer peripheral side disc support member. Therefore, the bolt 773b has the role of fixing the outer peripheral end of the front-side disc 758.

[0213] Reference numeral 773c denotes a bolt that fastens three components, namely, the front pole piece portion 752, the permanent magnet 751, and the rear pole piece portion 754. Reference numeral 773d denotes a bolt that fastens the outer periphery of the rear disc 759 to the coil side yoke material 755, and reference numeral 773e denotes a bolt that fastens the inner periphery of the rear disc 759 to the rear pole piece portion 754. Reference numeral 773f denotes a bolt that fastens the coil bobbin 765 to the coil side yoke material 755. Reference numeral 773g denotes a bolt that fastens the front panel 762a to the rear panel 762b.

[0214] (3) Description of the Assembly Process The assembly process will be described below in stages.

[0215] (3-1) Assembly preparation stage The assembly process of the sensor of this embodiment is based on bolt fastening. However, it is not necessary to fasten all parts with bolts. For example, parts that need to be electrically insulated may be previously integrated with conductive material (metal) and insulating material (ceramics, etc.) by adhesive. Figures 32 to 34 show the assembly preparation stage. In Step 1, an outer peripheral side disc support member 771 made of ceramic and a front side disc 758 are bonded and fixed at the location of a chain line circle A. In Step 2, an inner peripheral side disc support member 770 made of ceramic and a ring-shaped nut 772 made of metal are bonded and fixed at the location of a chain line circle B. In Step 3, the part in which the inner peripheral side disc support member 770 and the ring-shaped nut 772 are integrated is bonded and fixed to the opening of the front side pole piece part 752.

[0216] (3-2) Attaching the coil bobbin and processing the coil lead wire 35 and 36 show the process of mounting the coil bobbin 765 and processing the coil lead wires. Reference numeral 774 denotes lead wires of the force coil 756a and the calibration coil 756b, 775 denotes an inner groove formed on the inner surface of the coil side yoke material 755, 776 denotes a through hole formed in the radial direction of the coil side yoke material, and 777 denotes an outer groove formed on the outer periphery of the coil side yoke material. The inner groove 775, the through hole 776, and the outer groove 777 are not shown in FIG. 31.

[0217] In Step 4, the coil bobbin 765 is inserted into the coil side yoke material, and at the same time, the tip of the coil lead wire 774 is pulled out to the outside using the inner groove, the through hole, and the outer groove. In Step 5, the coil bobbin 765 is fastened to the coil side yoke material 755 by the bolt 773f.

[0218] (3-3) Wire processing of the movable electrode and installation of the front pole piece FIG. 37 shows the shape of the front side disk 758 applied to this embodiment. In the chain line D, 778 is a protruding end, and 779 is a through hole formed in this protruding end. In Step 6, FIG. 38a shows the state in which the front side pole piece part 752 is mounted inside the coil side yoke material 755. FIG. 38b is a partial enlarged view of the chain line E part. 780 is an electrode groove part formed on the outer circumferential surface of the coil side yoke material 755, and 781 is a lead wire of the movable side electrode 760. 782 shows the state in which the lead wire 781 and the front side disk 758 are electrically connected to each other using the through hole 779 with the coating of the lead wire 781 peeled off. As a means for electrically connecting the lead wires, soldering, conductive adhesive, etc. can be selected. 783 is a plurality of through holes formed in the front side disk 758, and the inner diameter is formed to be larger than the head 773bH of the fastening bolt 773b.

[0219] As described above, the front side disk 758 and the outer peripheral disk support member 771 are already bonded and fixed. Therefore, if the outer peripheral disk support member 771 is fixed to the coil side yoke material 755 by the fastening bolt 773b, electrical insulation between the front side disk 758 and the coil side yoke material 755 can be maintained. The head 773bH of the fastening bolt 773b and the through hole 783 are kept out of contact. The movable side electrode 760 is fastened to the ring-shaped nut 772 by the fastening bolt 773a while holding the front side disk 758 and the inner peripheral disk support member 770. As described above, the disk support member 770 and the ring-shaped nut 772 are integrated in advance by an adhesive.

[0220] (3-4) Final assembly stage Step 7 shows the process of fastening permanent magnet 751 and rear-side disk 759. As shown in Fig. 39, permanent magnet 751 is fastened to front-side pole piece portion 752 via rear-side pole piece portion 754 by fastening bolt 773c. Rear-side disk 759 is fastened to coil-side yoke material 755 and rear-side pole piece portion 754 by fastening bolts 773d and 773e.

[0221] Step 8 shows the final step of attaching the sensor storage case. As shown in Fig. 40, the fixed electrode 761 is temporarily fixed to the front panel 762a by the fastening member 764. This front panel 762a is fastened to the rear panel 762b by the fastening bolt 773g so as to house the coil side yoke material 755.

[0222] Incidentally, the structure for taking out the electrode signal line 781 and the coil lead wire 774 to the outside is not limited to the bolt fastening structure of this embodiment, but can be similarly applied to other embodiments using an adhesive technique.

[0223] Fifteenth embodiment In the above-mentioned embodiment, the bolt fastening method is applied up to the final assembly stage, except for the initial preparation stage. In this embodiment, the adhesive method is applied in the final assembly stage, and the gap between the movable and fixed electrodes is adjusted to an optimal value while measuring the capacitance. In other words, this is a measure to absorb all errors accumulated in the final process.

[0224] Figure 41 shows two units to be fastened, and Figure 41a will be called the fixed electrode unit 850, and Figure 41b will be called the movable electrode unit 851. Figure 42 shows the state in which the two units are joined with an adhesive.

[0225] Only the points to be noted in the fifteenth embodiment will be described below. 852 is a movable electrode, 853 is a fixed electrode, 854a is a front panel, 854b is a rear panel, 855 is a center plate, and 856 is a fastening member made of a non-conductive material between the fixed electrode and the front panel. 857 is a coil side yoke material, 858a is a movable unit side fitting element, 858b is a fixed unit side fitting element, and 859 is a bolt for fastening the rear panel and the coil side yoke material. 860a is a movable unit side joint surface, 860b is a fixed unit side joint surface, and 860bc is a tapered portion formed on the fixed unit side joint surface. The movable unit side fitting element 858a and the fixed unit side fitting element 858b form a fitting structure.

[0226] In FIG. 42, 861 denotes an adhesive applied between the movable unit side joint surface 860a and the fixed unit side joint surface 860b. In this embodiment, an ultraviolet-curing type adhesive is used. This adhesive is cured by irradiating it with LED light. Therefore, before the stage of irradiating the LED light, the two units can move relatively in the axial direction while radial movement is restricted by the mating elements 858a, 858b that form the mating structure. Electrode gap δ z The gap (between the movable electrode 852 and the fixed electrode 853) can be found from the measured capacitance. For example, while the fixed unit 851 is fixed, the movable unit 850 is moved in the axial direction (arrow C). When the capacitance reaches the target value, the adhesive is hardened by irradiating it with an LED light, and the two units can be fastened together.

[0227] The actuator function of the sensor can be measured and evaluated before the two units are fastened together (Fig. 41b), that is, in the state of the movable electrode unit 851 alone. For example, if a displacement sensor that detects the axial displacement of the movable electrode 852 is separately arranged, the frequency response characteristics and transient response characteristics with respect to the current of the force coil 756a can be evaluated. Depending on the evaluation results, each part can be easily replaced and reused by taking advantage of the characteristics of the bolt fastening method.

[0228] Gap between two electrodes δ z In addition to the above-mentioned method of adjusting the inclination angle δ θ A fastening member 856 may be used to adjust the gap δ between the two electrodes shown in this embodiment. z (or δ θ ) can also be applied to other embodiments of the present invention.

[0229] Sixteenth embodiment Fig. 43 is a front cross-sectional view of a differential servo type acceleration sensor according to the sixteenth embodiment of the present invention. However, the moving part is of a moving coil type (MC type) in which the coil moves. 51 is a permanent magnet, 52 is a pole piece part, 53 is a pole piece protrusion part, 54 is a permanent magnet side yoke material, 55 is a coil side yoke material, 56a is a force coil, 56b is a calibration coil, 57 is a coil bobbin, 58 and 59 are coil bobbin support members, 60 is a front side disk, 61 is a rear side disk, 62 is a front side connecting member between the front side disk 60 and the coil side yoke material 55, and 63 is a rear side connecting member between the rear side disk-shaped spring 61 and the coil side yoke material 55. A radial magnetic gap 64 is formed between the outer periphery of the pole piece part 52 and the inner periphery of the coil side yoke material 55. 64a is a permanent magnet side gap, and 64b is a yoke material side gap. The closed loop magnetic circuit is formed by "permanent magnet 51 → pole piece portion 52 → magnetic gap portion 64 → coil side yoke material 55 → permanent magnet side yoke material 54", which is the same as in the conventional MC type servo type acceleration sensor.

[0230] 65 is a movable-side first electrode (electrode surface Sa), 66 is a movable-side second electrode (electrode surface Sb), 67 is a cylindrical member, and 68 is a fixed-side electrode support member formed of a non-conductive material. 69 is a fixed-side first electrode (electrode surface SA) formed on the fixed-side electrode support member 68, 70 is a fixed-side second electrode (electrode surface SB), 71 is a first gap formed by the movable-side first electrode 65 and the fixed-side first electrode 69, and 72 is a second gap formed by the movable-side second electrode 66 and the fixed-side second electrode 70. The movable-side first electrode 65 and the movable-side second electrode 66 are bonded and fixed with the cylindrical member 67 interposed therebetween. The movable-side first electrode 65 is also bonded and fixed to the front-side disk-shaped spring 60 at its outer periphery. If the capacitance signal A is determined by the gap of the first gap 71 and the capacitance signal B is determined by the gap of the second gap 72, the two capacitance signals A and B have opposite phases. That is, a differential sensor is formed by independently detecting two capacitance signals A and B. Reference numeral 73a denotes an axial conductor wire that transmits capacitance signal B in the axial direction, and 73b denotes a radial conductor wire that transmits capacitance signal B in the radial direction. The two capacitance signals A and B and the currents flowing through the force coil 56a and calibration coil 56b are transmitted to the fixed side via the front disc-shaped spring 60 and the rear disc-shaped spring 61. The two disc-shaped springs are divided in the circumferential direction to form a plurality of independent signal transmission paths (not shown). Reference numeral 74 denotes a front panel.

[0231] In Fig. 43, the portion indicated by the two-dot chain line AA indicates an actuator section that drives the two movable electrodes 65, 66 in the axial direction. In this embodiment, an MC type (moving coil type) is applied to this actuator section. Instead of this MC type, the MM type (moving magnet type) shown in the above-mentioned embodiment may be used. Alternatively, any type of actuator may be applied, such as the MC type, MM type, or MI type.

[0232] Seventeenth embodiment In the above-described embodiment, two sets of capacitance sensors are configured by sandwiching one fixed-side electrode support member between two movable electrodes. Conversely to this configuration, two sets of capacitance sensors can be configured by sandwiching one movable electrode member between two fixed-side electrode support members. In FIG. 44, 151 is a first fixed-side electrode support member, 152 is a second fixed-side electrode support member, 153 is a movable-side electrode member, 154 is a cylindrical connecting member, 151a is a fixed-side first electrode (electrode surface Saa) formed on the surface of the first fixed-side electrode support member 151, and 153a is a movable-side first electrode (electrode surface SAA) formed on the surface of the movable-side electrode member 153. 152a is a fixed-side second electrode (electrode surface Sbb) formed on the surface of the second fixed-side electrode support member 153, and 153b is a movable-side second electrode (electrode surface SBB) formed on the surface of the movable-side electrode member 153. Reference numeral 155 denotes a first gap formed between the first movable electrode 153a and the first fixed electrode 151a, and reference numeral 156 denotes a second gap formed between the second movable electrode 153b and the second fixed electrode 152a.

[0233] If the capacitance signal A is determined by the gap of the first gap 155, and the capacitance signal B is determined by the gap of the second gap 156, the two capacitance signals A and B have opposite phases. That is, similar to the above-mentioned embodiment, a differential sensor is configured by independently detecting the two capacitance signals A and B. The two-dot chain line BB in the figure is an actuator section that outputs the connecting member 154. This actuator section BB may be of the MC type, MM type, or any other type.

[0234] (18th embodiment) Fig. 45 shows a servo type acceleration sensor according to the eighteenth embodiment of the present invention, with Fig. 45a showing the shape of the front disk, Fig. 45b showing a front cross-sectional view of the acceleration sensor body, and Fig. 45c showing the shape of the rear disk. In the magnetic coupling section (chain circle BB) which is the magnetic path constituting the closed loop magnetic circuit, if the component precision and assembly precision are not sufficient and the shaft cores of the fixed side and the movable side are eccentric, the magnetic attraction force in the centrifugal direction (F in the figure) r ) occurs. This embodiment shows a disk shape that reduces this effect as much as possible.

[0235] Reference numeral 151 denotes a permanent magnet magnetized in the axial direction, 152 a front pole piece portion, 153 a space formed inside the pole piece, 154 a rear pole piece portion, 155 a coil side yoke material, 156 a force coil, 157 a protrusion formed on the inner surface of the coil side yoke material, 158 and 159 a front disk and a rear disk supporting the movable portion. Reference numeral 160 denotes a movable electrode, 161 a fixed electrode, 162a a front panel, 162b a rear panel, 163 a center plate, 164 a fastening member, and 165 a magnetic gap portion. As in the previous embodiment, an annular gap portion 166 is provided between the protrusion portion 157 of the coil side yoke material and the rear pole piece portion 154 by a narrow gap. Reference numeral 167 denotes an outer peripheral support ring, and 168 an inner peripheral support ring. As shown by the dashed arrow, a closed loop magnetic circuit is formed by "permanent magnet 151 → front pole piece portion 152 → magnetic gap portion 165 → coil side yoke material 155 → protrusion portion 157 → annular gap portion 166 → rear pole piece portion 154 → permanent magnet 151", which is the same as the previously described embodiment. The shape of the rear pole piece portion 154 is different from that of the previously described embodiment. Reference numeral 169 denotes a convex portion formed in the center of the rear pole piece portion, 169a denotes a central convex portion for positioning the center of the rear disc, and 170 denotes a gap portion.

[0236] In this embodiment, as shown in Figures 45a and 45c, the shapes of the disks supporting the movable part are significantly different between the front side and the rear side. The front side disk (Figure 45a) is a spiral spring having long ridges 158a and grooves 158b in the circumferential direction. In contrast, the rear side disk (Figure 45c) is composed of six ridges 159a perpendicular to the circumferential direction and grooves 159b between each ridge. The axial stiffness K of the rear side disk is aIn order to reduce this, the width of the ridge 159a is narrow, and the support interval R between the center and outer periphery is set sufficiently long. The thickness of the rear disc is sufficiently thinner than that of the front disc. Since the stiffness of a disc is inversely proportional to the cube of the thickness, for example, if the thickness is reduced to 1 / 2, the stiffness becomes 1 / 8. The axial stiffness k of the rear disc is a is small like the front disk, and the radial stiffness K r In other words, when the axis of the fixed side and the movable side of the magnetic coupling part BB are offset, the centripetal stiffness k is sufficiently high against the magnetic attraction force Fr generated in the centrifugal direction. r The movable shaft can be kept at the same radial position by the above. Here, the eccentricity of the movable shaft with respect to the fixed shaft is δ r Let δ r If = 0, the magnetic attraction force F r = 0. However, δ r When eccentricity occurs, the magnetic attraction force F r and eccentricity δ r The centrifugal magnetic attraction force F r and eccentricity δ r The relationship between is nonlinear, and the movable shaft placed in the magnetic field is in an unstable equilibrium condition. Here, K mr =F r / δ r If we define it as K mr is the negative spring stiffness formed in the magnetic circuit. r >0 and K mr >0. Therefore, the centripetal stiffness of the disk is defined as K r >K mr If the axial stiffness k is selected so that the magnetic coupling portion BB can be kept in a stable state, the shape of the rear disk is not limited to that shown in this embodiment. a For radial stiffness k r Any shape is acceptable as long as the radial stiffness k is sufficiently high. For example, in the case of a spiral shape, if the spiral angle α (see FIG. 45a) is defined as the gradient of the curve with respect to the circumferential direction, the curve may have a sufficiently large angle α. If the range is 45≦α≦90deg, the radial stiffness k is sufficiently high.r The shape of the front disk is not limited to the spiral curve shown in this embodiment. If the disk thickness is sufficiently thin and can be within the elastic limit of the material, the shape may be similar to that of the rear disk in this embodiment.

[0237] In this embodiment, precipitation hardened high strength stainless steel (SUS631) is used for the rear disk shown in FIG. 45c. This material is a stainless steel that can obtain extremely high hardness by generating fine intermetallic compounds containing Al in martensite through precipitation hardening treatment after cold rolling. The reason for using a special steel material is as follows. The axial rigidity k is high while maintaining a small disk outer diameter. a In order to reduce this, it is necessary to make the plate thickness thinner and the width of the ridge narrower. Therefore, it is necessary to withstand a larger generated stress than when the spiral angle α shown in FIG. 45a is sufficiently small. The high-strength stainless steel used has a tensile strength (1400-1500N / m) that is about three times that of ordinary steel materials such as SUS304. 2 ) and spring limit value. Others, such as SUS632J1 and other stainless steels, with tensile strength >1000N / m 2 The above findings and measures regarding the disk shape and the strength of the disk material shown in this embodiment can be applied to all embodiments of the present invention.

[0238] (II) Moving yoke type (MY type) acceleration sensor The embodiment of the present invention described above proposed the MM type, in which the permanent magnet moves, as opposed to the conventional MC type, in which the coil moves. Here, going back to the basics, it is noted that the magnetic circuit of the actuator part that constitutes the servo type acceleration sensor forms a closed loop with only three elements: the "permanent magnet," the "coil," and the "yoke material." The proposal of this embodiment is whether it is possible to configure a servo type acceleration sensor by fixing both the "permanent magnet" and the "coil" and moving only the "yoke material." In other words, it is a proposal for a moving yoke type (MY type (tentative name)), which could be called a "third linear motor." The features of the MY type acceleration sensor are: (1) As with the MC type, the mass of the moving parts can be reduced. (2) As with the MM type, there is no need to process the extremely fine wire of the coil.

[0239] In other words, it is possible to eliminate the disadvantages of both the MM and MC types and combine the advantages of both.

[0240] Nineteenth embodiment Fig. 46 is a front cross-sectional view of an MY type servo type acceleration sensor according to a nineteenth embodiment of the present invention. 851 is a permanent magnet magnetized in the axial direction, 852 is a fixed pole piece part (pole piece side yoke material), 852a is a tapered part of this fixed pole piece part, and 852b is a cylindrical part of the fixed pole piece part. 853 is a movable pole piece part (movable side yoke material), and 853a is the opposing surface of the cylindrical part 852b in the fixed pole piece part. 854 is a space formed inside the movable pole piece part to reduce weight. 855 is a coil side yoke material, 855a is a permanent magnet side yoke material, 856 is a force coil, and 857 is a bias coil. Reference numeral 858 denotes a front disk, 859 a rear disk, 860 a movable electrode, 861 a fixed electrode, 862a a front panel, 862b a rear panel, 863 a center plate, 864 a fastening member, 865 a coil mounting portion on the inner peripheral surface of the coil side yoke material, 866 a coil opposing surface in the movable pole piece portion, and a radial magnetic gap 867 (first gap) is formed between the coil opposing surface 866 and the coil mounting portion 865. A narrow gap (chain line circle B) is provided between the cylindrical portion 852B of the fixed pole piece portion and its opposing surface 853a. This chain line circle B is a magnetic coupling portion. Reference numerals 869 and 870 denote an outer peripheral support ring and an inner peripheral support member made of a non-conductive material. In this embodiment, when a small axial force is generated in the movable pole piece portion 853 with no current applied to the force coil 856, the pole piece portion 853 can be kept in a fixed position by passing a bias current through the bias coil 857. A closed loop magnetic circuit is formed by "permanent magnet 851 → fixed pole piece portion 852 → gap portion 868 → movable pole piece portion 853 → magnetic gap portion 867 → coil side yoke material 855 → permanent magnet side yoke material 855a → permanent magnet 851", as shown by the dashed arrow.

[0241] The operating principle of the sensor of this embodiment is the same as that of the MM type described above. When a current is applied to the force coil 856, the reaction force of the Lorentz force, which is the operating principle of a linear motor, acts on the movable pole piece portion 853. Since the current of the force coil 856 and the acceleration due to an external force are proportional to each other, the acceleration is measured by detecting the current of the force coil 856. The method of taking out the lead wires of the force coil 856 and the bias coil 857 and the signal wires of the electrodes to the outside is the same as that of the above-mentioned embodiments. A method similar to that shown in FIG. 1b of the first embodiment or FIG. 36 and FIG. 38a of the 14th embodiment with a bolt fastening structure may be used. As shown in FIG. 36, an example of the method is to form an outer groove portion 777 on the outer periphery of the coil side yoke material 755 and install the lead wire of the coil 774 in this groove portion. A similar configuration can be applied to this embodiment and to the embodiments described later (not shown).

[0242] The features of the MY type acceleration sensor according to the present invention can be summarized as follows. (1) The inertial mass of the movable part can be selected from a wide range. In this embodiment, the movable pole piece part 853 is formed in a cylindrical shape, but if the cylindrical part is made thinner and lighter, it is possible to achieve performance that emphasizes high frequency characteristics, which is a feature of the MC type. If the movable pole piece part 853 is made into a solid cylindrical shape and the inertial mass is increased, it is possible to achieve performance that emphasizes low frequency characteristics, which is a feature of the MM type. In other words, depending on the shape of the movable pole piece part 853, it is possible to arbitrarily select sensor specifications that match the characteristics required by the object to which this sensor is applied (such as an active vibration isolation table). (2) Permanent magnet performance can be selected from a wide range. Since there are no restrictions on the size and shape of the permanent magnet, the demagnetization characteristics (retentive force H c , saturation magnetic flux density B r ) can be selected from a wide range. Since there is a margin in the performance of the permanent magnet, the gap 868 in the magnetic coupling part B may be sufficiently large. This gap 868 becomes a magnetic resistance, but the performance of the permanent magnet is sufficient to compensate for the loss. (3) Coil specifications can be selected from a wide range. As shown in this embodiment, if the movable pole piece portion 853 is made cylindrical with a thin plate thickness, the increase in inertial mass is minimal even if the movable pole piece portion 853 is made longer. By utilizing this point, the coil storage volume can be made sufficiently large, so that the coil wire diameter and the number of coil turns can be selected without increasing the electrical resistance. Furthermore, due to the above features (1) to (3), the force generated by the actuator can be selected from a wide range, so that an acceleration sensor with excellent sensor sensitivity from low frequency characteristics to high frequency characteristics can be realized.

[0243] This is also true for the present embodiment of the MY type acceleration sensor, and for the embodiments described below, but many of the findings and ideas regarding the MM type acceleration sensor of the present invention described in section (I) above can also be applied to the MY type. For example, (i) a structure in which the heat generated by the coil is dissipated using a non-magnetic and highly thermally conductive coil bobbin, (ii) a cantilever pendulum structure in which one end of the elastic member supporting the moving part is fixed and the other end is free, (iii) a structure in which adhesive techniques and extremely small bolt fastening techniques are combined to join the various members, (iv) a structure in which the inner and outer circumferential sides of the elastic member are fastened to the fixed side via a non-conductive material to achieve electrical insulation, (v) a structure in which electrical insulation is achieved between the movable side electrode and the movable member (pole piece), and (vi) a structure in which a disk-shaped spring made of a magnetic material with sufficiently small axial rigidity is used in the magnetic coupling section can be applied.

[0244] Further, a laminated steel plate (e.g., 0.1 to 0.2 mm thick) made of thin ring-shaped disks is attached to the fixed pole piece part 852 constituting the magnetic coupling part B and the movable pole piece part 853, which is the opposing surface of the fixed pole piece part 852. As applied to motors, magnetically controlled bearings, etc., it is possible to reduce eddy current loss occurring at the relative moving part, and thus advantageous characteristics can be obtained for high frequency characteristics. This is not limited to this embodiment, but also applies to the embodiments described later and the magnetic coupling part in the MM type described in section (I) (e.g., part B in FIG. 1, which is the first embodiment) (not shown).

[0245] (Twentieth embodiment) Fig. 47 shows an MY type servo type acceleration sensor according to embodiment 20 of the present invention, with Fig. 47a being a front sectional view and Fig. 47b being a sectional view taken along line AA of Fig. 47a. In this embodiment, a magnetic circuit is formed using a plurality of segment-type permanent magnets magnetized in the radial direction.

[0246] Reference numeral 551 denotes a permanent magnet, 552 denotes a pole piece portion (movable yoke material), and 553 denotes a fixed yoke material. The permanent magnet is composed of radially magnetized segment-type permanent magnets 551a, 551b, 551c, and 551d, and is attached to the yoke material. Reference numeral 554 denotes an internal space of the pole piece portion, 555 denotes a force coil, 556 denotes a calibration coil, 557 denotes a front disk, 558 denotes a rear disk, 559 denotes a movable electrode, 560 denotes a fixed electrode, 561a denotes a front panel, 561b denotes a rear panel, 562 denotes a center plate, 563 denotes a fastening member, 564 denotes a coil attachment portion on the inner circumferential surface of the yoke material, 565 denotes a coil opposing surface in the pole piece portion, and a radial magnetic gap 566 (first gap) is formed between the coil opposing surface 565 and the coil attachment portion 564. A narrow gap 568 (second gap) is provided between the inner circumferential surfaces 567a, 567b, 567c, and 567d of the permanent magnet 551 and the pole piece portions facing each other. This gap 568 is a magnetic coupling portion. 569 and 570 are an outer circumferential support ring and an inner circumferential support member made of a non-conductive material. A closed loop magnetic circuit is formed by "permanent magnet 551 → gap 568 → pole piece portion 552 → magnetic gap 566 → fixed side yoke material 553 → permanent magnet 551" as shown by the dashed arrow.

[0247] In this embodiment, since the permanent magnet uses a segment type permanent magnet magnetized in the radial direction, no axial electromagnetic force (unbalanced force) is generated in the pole piece portion 552 when no current is applied to the force coil 555. Therefore, the pole piece portion 552 can be kept in the same position, and fine adjustment by the bias coil current as in the previous embodiment is not necessary. Instead of using a segmented permanent magnet magnetized in the radial direction, a permanent magnet magnetized in the axial direction may be used and connected to a yoke material through which magnetic flux flows in the radial direction. The shape of this yoke material may be the same as that of the segmented permanent magnet described above. This fixed yoke material may be arranged so as to enclose the outer periphery of the pole piece portion (not shown).

[0248] Alternatively, a plurality of thin segment-type permanent magnets magnetized in the radial direction may be attached to the outer peripheral surface of the pole piece portion 552 that faces the inner peripheral surfaces 567a-567d of the permanent magnet 551. That is, this is a hybrid structure of the MY type and the MC type. With this configuration, the magnetic resistance of the magnetic coupling portion (magnetic gap portion 568) can be reduced.

[0249] (21st embodiment) Fig. 48 is a front cross-sectional view of an MY type differential servo type acceleration sensor according to embodiment 21 of the present invention. This sensor takes note of the fact that the magnetic circuit is configured using a radially magnetized permanent magnet in the MY type, and that both the left and right output shafts become open ends. A differential type capacitance sensor can be realized by providing electrodes for detecting capacitance in two locations, left and right. By making the acceleration sensor a differential type, a high-resolution sensor can be realized in which the sensor output is less susceptible to the effects of disturbance signals such as noise and drift.

[0250] Reference numeral 501 denotes a permanent magnet, 502 denotes a pole piece portion, and 503 denotes a yoke material. The permanent magnet is composed of a plurality of segment-type permanent magnets magnetized in the radial direction and is attached to the yoke material. Reference numeral 504 denotes an internal space of the pole piece portion, 505 denotes a force coil, 506 denotes a calibration coil, 507 denotes a front disk, 508 denotes a rear disk, 509 denotes a front movable electrode, 510 denotes a front fixed electrode, 511 denotes a rear movable electrode, 512 denotes a rear fixed electrode, 513a denotes a front panel, 513b denotes a rear panel, 514 denotes a front center plate, 515 denotes a rear center plate, 516 denotes a front fastening member, and 517 denotes a rear fastening member. Reference numeral 518 denotes a coil mounting portion on the inner peripheral surface of the yoke material, 519 denotes a coil opposing surface of the pole piece portion, 520 denotes a magnetic gap portion, 521 denotes a gap portion which is a magnetic coupling portion, 522 and 523 denote a front outer peripheral support ring and a front inner peripheral support member made of a non-conductive material, and 524 and 525 denote a rear outer peripheral support ring and a rear inner peripheral support member made of a non-conductive material.

[0251] The method of connecting the conductor for detecting the capacitance between the movable electrode and the fixed electrode to the outside is the same as in the above-described embodiment (not shown).

[0252] The absolute velocity signal and absolute displacement signal obtained by completely integrating the acceleration output of the differential sensor of the present invention do not diverge easily. Therefore, when the sensor of the present invention is applied to an active vibration isolation table, in addition to the effect of improving the sensor sensitivity (for example, improving the positioning accuracy of the stage), a significant improvement in vibration isolation characteristics can be obtained in the low frequency range.

[0253] (III) Other embodiments The above-mentioned embodiments (I) and (II) are examples of MM-type and MY-type acceleration sensors that are composed of a voice coil that generates a Lorentz force and a permanent magnet. The embodiment shown below applies an electromagnet that generates a magnetic attraction force due to Maxwell stress instead of Lorentz force. It is common to embodiments (I) and (II) in that the coil that constitutes the electromagnet is fixed. Also, in that neither the coil nor the permanent magnet is moved, but only the yoke material that constitutes the closed loop magnetic circuit is moved, this embodiment may be considered as an alternative form of the MY-type in section (II).

[0254] (Twenty-second embodiment) 49 is a front sectional view of a servo type acceleration sensor according to embodiment 22 of the present invention. The servo type acceleration sensor is configured by combining an electromagnet that generates a magnetic attraction force with a permanent magnet.

[0255] Reference numeral 601 denotes a permanent magnet magnetized in the axial direction, 602 denotes a pole piece portion on the permanent magnet side, 603 denotes a surface of the pole piece portion 602 facing the permanent magnet side, 604 denotes a surface of the permanent magnet facing the pole piece portion side, 605 denotes a space formed inside the pole piece portion 602, and 606 denotes a yoke material on the permanent magnet side. 607 denotes a coil bobbin, 608 denotes a force coil (control coil) of the electromagnet, and 609 denotes a bias coil. 610 and 611 constitute the yoke material on the electromagnet side, with 610 being the outer periphery yoke material relative to the axis of the coils 608 and 609, and 611 being the yoke material on the axis core side.

[0256] Reference numeral 612 denotes the pole piece portion on the electromagnet side (yoke material on the movable member side), 613 denotes the surface of pole piece portion 612 facing the central axis, 614 denotes the surface of the central axis facing the pole piece portion, and 615 denotes the space formed inside pole piece portion 612.

[0257] 616 is the electromagnet side housing, 617 is the permanent magnet side housing, 618 is a movable member made of a non-magnetic material, and 619 and 620 are fastening members that hold the movable member 618 from the left and right. The fastening members are fixed from the left and right by the permanent magnet side housing and the electromagnet side housing. 621a and 621b are the movable side electrode R and the fixed side electrode R. 622a and 622b are the movable side electrode L and the fixed side electrode L. The two electrodes formed on the left and right of the movable part constitute a differential acceleration sensor. The imaginary line 623 in the shaft core side yoke material 611 and the electromagnet side housing 616 is a through passage necessary when using a displacement sensor other than the capacitance type (described later in Supplementary Note (3)).

[0258] The permanent magnet side pole piece section 602 and the electromagnet side pole piece section 612 are made of a magnetic material, and are fixed on the left and right sides at the center of a movable member 618 made of a non-magnetic material. The electromagnet side forms a closed loop magnetic circuit with members including "central axis 611 → electromagnet side yoke material 610 → electromagnet side pole piece section 612". The permanent magnet side forms a closed loop magnetic circuit with members including "permanent magnet 601 → permanent magnet side pole piece section 602 → permanent magnet side yoke material 606". As shown in the figure, the movable section 618 is subjected to an attractive force F by the permanent magnet 601. m is always operating. When the acceleration sensor is in operation, a current is passed through bias coil 609 to keep movable part 618 at the origin position. In this state, if an external force is applied to the entire movable part, a current passes through force coil 608 to return movable part 618 to the origin position. Since the current in force coil 608 and the acceleration due to the external force are proportional to each other, the acceleration can be measured by detecting the current in force coil 608.

[0259] The acceleration sensor of this embodiment uses magnetic attraction force due to Maxwell stress to drive the moving part. If comparing actuators with the same external dimensions under the same conditions, the electromechanical conversion efficiency (thrust constant) of the generated force relative to the input current of the Maxwell stress is overwhelmingly higher than that of the Lorentz force, usually 20 times higher. By utilizing this point, the acceleration sensor of this embodiment can greatly increase the upper limit of measurable acceleration.

[0260] However, if a small upper limit value of the measurable acceleration is acceptable, a configuration combining the Lorentz force actuator of the embodiment in section (I) and a permanent magnet may be used instead of the Maxwell stress actuator (not shown).

[0261] (Twenty-third embodiment) 50 is a front cross-sectional view of a servo-type acceleration sensor according to embodiment 23 of the present invention. The servo-type acceleration sensor is configured by combining two electromagnets, which generate a magnetic attraction force due to Maxwell stress, symmetrically on the left and right.

[0262] Since the components of this acceleration sensor are symmetrical, the subscript on the right side of the drawing number is a and the subscript on the left side is b. First, the components on the right side will be explained. 631a is the coil bobbin, and 632a is the force coil of the electromagnet.

[0263] 633a and 634a constitute the electromagnet side yoke material, 633a is the outer periphery side yoke material with respect to the axis of coil 632a, and 634a is the axis side yoke material (center axis). 635a is a cylindrical part of the pole piece made of a non-magnetic material, 636a is a flat part of the pole piece made of a magnetic material (movable member side yoke material), 637a is a housing, 638 is a movable member made of a non-magnetic material, and 640a and 640b are fastening members that hold the movable member 638 from the left and right. The movable member is fastened from the left and right by fastening members 640a and 640b. 641a is a movable side electrode, and 642a is a fixed side electrode. A differential acceleration sensor is constituted by two electrodes formed on the left and right of the movable part. 643a is a first magnetic pole that is the tip of the center axis, and 644a is a second magnetic pole that is the tip of the yoke material on the outer periphery side of the center axis. A closed loop magnetic circuit is formed by "central shaft 634a → yoke material 633a → second magnetic pole 644a → flat plate portion 636a of the pole piece → first magnetic pole 643a → central shaft 634a".

[0264] Incidentally, the shape of the yoke material constituting the electromagnet, the position of the coil, etc. may be any shape as long as a closed loop magnetic circuit is formed between the yoke material and the movable member.

[0265] When no current is applied to the force coils 632a and 632b of the left and right electromagnets, no attractive force acts on the movable member 638, so the movable member 638 maintains its original position. When an external force is applied to the entire movable portion, a current flows in the opposite direction through each of the force coils 632a and 632b to return the movable portion 638 to its original position. For example, when I is applied to the right force coil 632a, R A current of I = I0 + δI flows through the left force coil 632b. L At this time, the current difference between the left and right is ΔI = I R -I L = 2δI. Because the current difference ΔI between the force coils and the acceleration due to an external force are proportional, the acceleration can be measured by detecting this current difference ΔI.

[0266] As mentioned above, the Maxwell stress has an overwhelmingly higher electromechanical conversion efficiency (thrust constant) of the generated force relative to the input current than the Lorentz force, and by utilizing this point, the acceleration sensor of this embodiment can measure extremely large acceleration. In addition, if the purpose is to measure micro-vibrations, a large force can be generated even with a small number of coil turns, so the entire acceleration sensor including the actuator can be significantly miniaturized.

[0267] (Supplementary Note) (1) Magnetic materials Below, the following provides additional information common to the embodiments described in sections (I) to (III).

[0268] The magnetic materials used for the actuator of a servo type acceleration sensor can be electromagnetic stainless steel, pure iron, permalloy, toughperm, permendur, amorphous, etc. Also, magnetic materials can be used for the parts that make up the closed loop magnetic circuit, and non-magnetic materials can be used for the housing that houses the actuator.

[0269] (2) Characteristics of the acceleration sensor required when mounting on an active vibration isolation table For example, we will explain why a high resonance frequency of several hundred Hz is required for an acceleration sensor used in an active pneumatic servo vibration isolation system, where the response (eigenvalue) of the entire system is on the order of several Hz to several tens of Hz. In an active vibration isolation table, acceleration feedback is applied in addition to proportional displacement feedback. The application of acceleration feedback is an essential condition for reducing the resonance peak. Now, as is well known, if the following two points are satisfied on the Bode diagram of the open-loop transfer function, the system is stable. (i) There is a positive gain margin at the phase crossing point (ii) There is a positive phase margin at the gain crossover point. By applying acceleration feedback, the gain increases and the phase lags by 180 degrees.

[0270] Therefore, even if the response (eigenvalue) of the entire system is on the order of a few Hz to 10-odd Hz, applying acceleration feedback will have an effect on the gain margin and phase margin at high frequencies. For this reason, a high resonance frequency (high-speed response) is required for the acceleration sensor and pneumatic servo valve, which are the control elements that make up the active vibration isolation table. The higher the resonance frequency f0, the smaller the phase lag can be in the vicinity of f=100Hz. Many experimental results have shown that f0>200Hz is within the acceptable range, but as mentioned above, f0≧250Hz is more preferable. Furthermore, in the vicinity of f=100Hz, the phase lag ΔΦ p <20deg is within the acceptable range, but ΔΦ p It is more preferable if it is ≦10 deg.

[0271] (3) Types of Displacement Detectors Applicable to the Present Invention The displacement detection means in the embodiments of the present invention described in sections (I) to (III) are all capacitive type. However, the feature of the present invention is the unique effect of the servo type sensor obtained by applying an actuator structure different from the conventional one. For example, (i) Since the processing of extremely fine wires that handle signals from multiple coils is simplified, the yield rate during mass production can be significantly improved. (ii) While maintaining the feature (i) above, the high-frequency characteristics can be improved by reducing the weight of the moving part. Alternatively, by selecting the inertial mass of the moving part, an acceleration sensor can be realized that prioritizes either high-frequency or low-frequency characteristics. (iii) By applying the differential method, drift and noise in the sensor signal can be reduced, etc.

[0272] Therefore, the form of the displacement detection means that can obtain the above-mentioned effects of the present invention is not limited to the electrostatic capacitance type. Figure 51 shows a case where an optical displacement detection means using a triangulation distance measurement method as the detection principle is used in the displacement detection section as an alternative to the electrostatic capacitance type. 575 is an actuator section provided with the driving means, and 576 is the displacement detection section. The displacement detection section 576 is composed of a light source 577, a light projecting lens 578, a light receiving lens 579, and a light receiving element 580, and these elements are shown in an image diagram. The actuator section 575 shows a case where the MM type acceleration sensor structure of the above-mentioned embodiment is applied. 581 is a permanent magnet, 582a is a front pole piece section, and 582b is a rear pole piece section, and 582a and 582b form a movable side yoke material. Reference numeral 583 denotes a fixed yoke material, 584 a force coil, 585 a calibration coil, 586 a front disk, 587 a rear disk, 588a a front panel, 588b a rear panel, and a narrow gap 589 is provided between the inner peripheral surface of the rear pole piece part and the fixed yoke material facing it, and this gap is a magnetic coupling part. Reference numerals 590 and 591 denote an outer peripheral support ring and an inner peripheral support member made of a non-conductive material. Reference numeral 592 denotes a laser beam, and 593 a laser beam reflector attached to the inner peripheral support member.

[0273] Reference numeral 594 denotes an opening formed in the front panel 588a through which the laser light passes. The light receiving element 580 is called a PSD (Position Sensitive Device), and measures displacement from the difference in the image position on the PSD caused by the change in the position of the laser light reflector 593. As an optical displacement means, a CMOS method, a CCD method, a regular reflection method, a diffuse reflection method, a line beam method, etc. can be applied. As a displacement detection method other than the optical type, a linear proximity sensor that uses the change in inductance of a coil caused by eddy currents generated in the measurement object can also be applied.

[0274] In Fig. 51, an optical displacement sensor is applied to an MM type acceleration sensor structure, but the MY type acceleration sensor structure using a Maxwell stress electromagnet, which is an embodiment of Sections (II) and (III), can also be applied. For example, in the case of the MY type acceleration sensor structure in Fig. 46, which is the 19th embodiment, the member corresponding to the inner circumference support member 870 may be made into a laser light reflecting surface (corresponding to 593 in Fig. 51).

[0275] 49 which is the 22nd embodiment, a through passage 623 (shown by imaginary lines) formed in the axis-side yoke material 611 and the electromagnet-side housing 616 may be used as a path for the laser light, and the central-axis-side opposing surface 613 of the pole piece portion 612 may be used as a laser light reflecting surface. Alternatively, an eddy current linear proximity sensor may be attached inside the through passage 623.

[0276] For example, when an optical displacement means is used to make the servo-type acceleration sensor a differential type, the displacement detection unit 576 in FIG. 51 may be installed on the right side as well. In this case, a member equivalent to the inner periphery support member 591 may be provided on the right side of the rear pole piece portion 582b, and a laser light reflector may be attached to the rear pole piece portion. The same applies when a displacement detection means other than the capacitance type is applied to the differential sensor embodiments in sections (I) to (III). For example, in the case of the MY type (FIG. 48) of the 21st embodiment, the locations equivalent to the front and rear inner periphery support members 523 and 525 may be used as the laser light reflecting surfaces or the detection surfaces of the eddy current linear proximity sensor. [Explanation of symbols]

[0277] 101 Permanent Magnets 102 Movable side member 105 Fixed side member 116, 104 Movable yoke material 106 Coil 110 Moving part of displacement detector 117 Cavity

Claims

1. A fixing member; a movable member that is movable in a predetermined direction relative to the fixed member and through which a magnetic flux flows; an elastic member that supports the movable member with respect to the fixed member so that the movable member is disposed with a gap therebetween; a displacement detection unit that detects a displacement of the movable member in the predetermined direction; a driving means for generating an electromagnetic 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, The movable member includes at least a movable yoke member that forms a part of a closed loop magnetic circuit, The movable member is Further comprising a permanent magnet forming the closed loop magnetic circuit, the driving means includes a force coil that is fixed to the fixed member and that, when a current is applied, moves the permanent magnet and the movable yoke material in the predetermined direction by a reaction force of a Lorentz force that a current-carrying conductor receives in a magnetic field, and the force coil is attached to a coil attachment portion on an inner peripheral surface of a coil side yoke material provided on the fixed member, A servo-type vibration detector in which the force coil is arranged to envelop the entire pole piece, including the movable side yoke material that is connected radially or axially to the permanent magnet of the movable member, from its outer periphery.

2. A fixing member; a movable member that is movable in a predetermined direction relative to the fixed member and through which a magnetic flux flows; an elastic member that supports the movable member with respect to the fixed member so that the movable member is disposed with a gap therebetween; a displacement detection unit that detects a displacement of the movable member in the predetermined direction; a driving means for generating an electromagnetic 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, the driving means includes a coil fixed to the fixed member, The movable member includes at least a movable yoke member that forms a part of a closed loop magnetic circuit, The displacement detection unit A movable side electrode provided on the movable member; a fixed electrode fixed to the fixed member so as to face the movable electrode, The displacement of the movable member is detected based on a change in electrostatic capacitance formed between the movable electrode and the fixed electrode, A servo-type vibration detector characterized in that the elastic member is made of a disk-shaped conductive material, and at least the outer peripheral side of the elastic member is fixed to the fixed member with a non-conductive material interposed therebetween.

3. A fixing member; a movable member that is movable in a predetermined direction relative to the fixed member and through which a magnetic flux flows; an elastic member that supports the movable member with respect to the fixed member so that the movable member is disposed with a gap therebetween; a displacement detection unit that detects a displacement of the movable member in the predetermined direction; a driving means for generating an electromagnetic 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, the driving means includes a coil fixed to the fixed member, The movable member includes at least a movable yoke member that forms a part of a closed loop magnetic circuit, a permanent magnet fixed to the fixed member and forming the closed loop magnetic circuit, the movable yoke being spaced apart from any one of the pole faces of the permanent magnet, and the movable yoke material being disposed within the coil; A servo-type vibration detector in which the driving means is configured to move the movable yoke material in the specified direction by the reaction force of the Lorentz force that a current-carrying conductor is subjected to in a magnetic field when a current is applied to the coil.

4. the gap portion includes a first gap portion and a second gap portion that form a radial gap between the movable member and the fixed member in the closed loop magnetic circuit, A coil for generating the Lorentz force is fixedly disposed in the first gap, 4. A servo type vibration detector according to claim 1, wherein the second gap is a magnetic coupling portion for allowing a magnetic flux to flow between the movable member and the fixed member.

5. The servo type vibration detector of claim 4, characterized in that it is composed of a pole piece portion that is connected to any one of the magnetic pole faces of the permanent magnet and constitutes part of the movable side yoke material, the coil fixed to the fixed member via this pole piece portion or the radially opposing surface of the permanent magnet and the first gap portion, and the magnetic connecting portion that is arranged so that magnetic flux flows between the other magnetic pole face of the permanent magnet and the fixed member, and a closed loop magnetic circuit is formed by the permanent magnet, the pole piece portion, the first gap portion, the fixed member, and the magnetic connecting portion.

6. 5. The servo type vibration detector according to claim 4, characterized in that the detector comprises a pole piece portion constituting a part of a movable yoke material, the coil fixedly arranged on the fixed member within a gap between the pole piece portion and the fixed member, the pole piece portion being arranged via the magnetic connecting portion and one of the magnetic pole faces of the permanent magnet, the permanent magnet being fixedly arranged so that magnetic flux flows between the other magnetic pole face of the permanent magnet and the fixed member, and a closed loop magnetic circuit is formed by the permanent magnet, the magnetic connecting portion, the pole piece portion and the fixed member.

7. 7. The servo type vibration detector according to claim 5, wherein the pole piece portion is formed in a substantially cylindrical shape.

8. 7. A servo type vibration detector as claimed in claim 6, characterized in that it comprises: a permanent magnet magnetized in the axial direction; a pole piece portion connected to one of the magnetic pole faces of the permanent magnet; a coil fixedly arranged on the inner surface of the fixed member via a gap portion on the radially opposing surface of the pole piece portion; and a magnetic connecting portion arranged so that magnetic flux flows between the other magnetic pole face of the permanent magnet and the fixed member.

9. The mass of the movable part including the movable side yoke material is m, and the mass of the permanent magnet is m p , the lower limit value m of the movable part mass min =2m p As,K PT The position sensor sensitivity K S and adjustment gain K C and proportional gain K P The electrical gain, K, is determined by the product t is the force constant of the actuator, R a is the electrical resistance of the coil, K T = K PT K t / Ra, f 0 The resonance frequency required for the acceleration sensor, the upper limit value m of the mass of the moving part max =K T / (2πf 0 ) 2 Then, m min ≦m≦m max 2. The servo type vibration detector according to claim 1, wherein the range is set to 0.

5.

10. The servo type vibration detector according to claim 4, characterized in that the magnetic connecting portion is composed of an auxiliary permanent magnet magnetized in the radial direction and an auxiliary coil fixedly arranged on the inner surface of the fixed member via a gap on the radially opposing surface of the auxiliary permanent magnet.

11. A servo type vibration detector as described in claim 1 or 3, characterized in that the closed loop magnetic circuit includes a first transmission unit and a second transmission unit that transmit magnetic flux radially between the movable member and the fixed member, the first transmission unit has a radial gap between the movable member and the fixed member, and the coil for generating the Lorentz force is fixedly arranged in this gap, and the second transmission unit is fixed between the movable member and the fixed member by a disk-shaped spring made of a magnetic material through which magnetic flux flows radially, and this disk-shaped spring also serves as the elastic member supporting the movable member.

12. The servo type vibration detector of claim 4, characterized in that the permanent magnet is a front side permanent magnet, the coil is a front side coil, the magnetic connecting portion is composed of a radially magnetized rear side permanent magnet, a pole piece portion connected to one of the magnetic pole faces of the rear side permanent magnet, and a rear side coil fixedly arranged on the inner surface of the fixed member via the gap portion on the radially opposing surface of the other magnetic pole face of the rear side permanent magnet, and a closed loop magnetic circuit is formed by the front side permanent magnet, the gap portion, the fixed member, the gap portion, the rear side permanent magnet, and the pole piece portion.

13. The displacement detection unit, A movable side electrode provided on the movable member; a fixed electrode fixed to the fixed member so as to face the movable electrode, A servo type vibration detector as described in claim 5 or 6, characterized in that a non-conductive material is interposed between the movable side electrode and a pole piece portion which is connected to any one of the magnetic pole faces of the permanent magnet and forms part of the movable side yoke material.

14. The servo-type vibration detector of claim 13, characterized in that a differential sensor is constructed by detecting the output difference between two sets of capacitance sensors formed between the electrode surfaces of the movable side electrode provided on each of the two end faces of the movable member, the fixed side electrode provided on the fixed member opposite these movable side electrodes, and the movable side electrode and the fixed side electrode.

15. The servo-type vibration detector of claim 13, characterized in that two flat movable side electrodes are provided at the end of the movable member with a gap between them, and the flat fixed side electrode is arranged in the gap so as to be sandwiched between the two movable side electrodes, thereby forming a first capacitance sensor between the electrode surface Sa of the movable side electrode and the electrode surface SA of the fixed side electrode that faces it, and forming a second capacitance sensor between the electrode surface SB on the back side of the electrode surface SA and the electrode surface Sb of the movable member that faces it.

16. The servo type vibration detector of claim 13, characterized in that one flat movable side electrode is provided at the end of the movable member, and two electrode surfaces SAA and SBB are formed on the front and back surfaces of the movable side electrode, and two flat fixed side electrodes are arranged to sandwich the movable side electrode with a gap between them, so that a first capacitance sensor is formed between the electrode surface Saa of the fixed side electrode facing the electrode surface SAA, and a second capacitance sensor is formed between the electrode surface SBB and the electrode surface Sbb of the fixed side electrode facing the electrode surface SBB.

17. The servo-type vibration detector according to claim 2, characterized in that the elastic member is formed of a disk-shaped conductive material, and the inner and outer peripheral portions of the elastic member are integrated with a thin plate material made of a non-conductive material.

18. A servo type vibration detector as described in claim 1 or 3, further comprising a movable unit including at least the movable member and having a movable side electrode attached thereto, and a fixed unit having a fixed side electrode attached thereto and arranged opposite the movable side electrode, wherein the displacement detection unit is formed to detect the electrostatic capacitance formed between the movable side electrode and the fixed side electrode, an interlocking structure is formed between the movable unit and the fixed unit so that the movable unit and the fixed unit can move axially relative to each other while the relative radial movement of the movable unit and the fixed unit is restricted, and a groove portion for adhesively fixing the movable unit and the fixed unit is formed on the outer surfaces of the movable unit and the fixed unit.

19. A servo-type vibration detector as described in claim 2, characterized in that the fixed member made of a conductive material and the elastic member are adhesively fixed to each other by a thin plate made of a non-conductive material, and this non-conductive material is fastened to the fixed member by a bolt, and the bolt head is configured so as to be not in electrical contact with the elastic member.

20. 6. A servo type vibration detector as claimed in claim 5, characterized in that the magnetic coupling portion is composed of the permanent magnet magnetized in the radial direction and the outer peripheral surface of the pole piece portion arranged with a gap between the inner peripheral surface of the permanent magnet and the pole piece portion.

21. The servo type vibration detector as described in claim 5, characterized in that the magnetic connection part is composed of the permanent magnet magnetized in the axial direction, a pole piece side yoke material arranged to be connected to either the N pole or S pole of the permanent magnet, and the inner surface of the pole piece part arranged with a radial gap maintained relative to the outer surface of the pole piece side yoke material.

22. A fixing member, a movable member that is movable in a predetermined direction relative to the fixed member and through which a magnetic flux flows; an elastic member that supports the movable member with respect to the fixed member so that the movable member is disposed with a gap therebetween; a displacement detection unit that detects a displacement of the movable member in the predetermined direction; a driving means for generating an electromagnetic 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 fixed yoke material is provided penetrating the coil, a movable yoke material is disposed with a gap between the open end of the fixed yoke material, and a closed loop magnetic circuit is formed by the fixed yoke material, the gap, and the movable yoke material to constitute an electromagnet, which serves as attraction force generating means A for attracting the movable member including the movable yoke material to the coil, and a magnetic field generating means for generating magnetic field in a direction opposite to that of the ...

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