Servo type vibration detector

Abstract

To solve an issue of a servo type vibration detector of a moving coil type made of a coil, a permanent magnet, and a displacement detector, the issue being that processing an extremely thin line of the coil is complicated and a high yield cannot be obtained at the time of mass production due to a high cost resulting from the complexity of a structure.SOLUTION: A mobile side is made of a permanent magnet and a yoke material and a metal coil bobbin is attached to a fixation side so that a moving magnet type (MM type) vibration detector is formed. Attachment means having a function of narrowing the space between the coil bobbin and the fixation member increases the heat discharge effect of the coil and reduces the restriction on the number of windings of the coil, for example. This increases the generation force which compensates for the mass increase of a mobile part, which is a weakness of the MM type.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

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

[0004] FIG. 13 shows a model diagram of a conventional active vibration isolation table. This active vibration isolation table is well known, as described in Patent Documents 1 and 2. A plurality of pairs of pneumatic actuators (502a, 502b) for supporting a surface plate 501 are arranged on a floor 500. A precision device (not shown) is mounted on this surface plate 501. Reference numeral 503 denotes an acceleration sensor for detecting the vertical and horizontal acceleration of the surface plate 501, and reference numeral 504 denotes an acceleration sensor for detecting the acceleration of the floor 500 (the vibration state of the foundation). Reference numerals 505a and 505b denote displacement sensors for detecting the vertical and horizontal relative displacement of the surface plate 501 with respect to the floor 500, respectively. Output signals from these sensors are input to a controller 506. A servo valve 508 controlled by the controller 506 is connected to the pneumatic actuator 502a via piping 507. This servo valve 508 adjusts the flow rate of compressed air supplied to and exhausted from the pneumatic actuator 502a, thereby controlling the internal pressure of the actuator 502a and driving the pneumatic actuator.

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

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

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

[0008] 3. Role of vibration sensors in active vibration isolation systems Active vibration control employs a control method based on state feedback. This is a method of controlling a control device based on acceleration, velocity, and displacement information from vibration sensors placed at multiple locations on the structure to be vibration controlled. In order to obtain vibration isolation performance over a wide frequency range, for example, acceleration signals are used to control state quantities above 10 Hz, velocity signals are used to control state quantities between 1 and 10 Hz, and displacement signals are used to control state quantities below 1 Hz. For example, a. If acceleration feedback is performed using a signal from an acceleration sensor (acceleration sensor in Figure 15) placed on the surface 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. b. If the signal from the acceleration sensor is converted into an absolute velocity or absolute displacement signal and feedback or feedforward is applied, the vibration isolation performance can be significantly improved over a wide frequency range. c. By using the signal from the acceleration sensor placed directly below the surface plate 501, converting the signal into an absolute velocity or absolute displacement signal and similarly applying feedforward, it is possible to improve vibration isolation performance over a wide frequency range.

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

[0010] 4. Basic configuration and detection principle of acceleration sensors Figure 14 is a model diagram showing the basic configuration and detection principle of a capacitance-type acceleration sensor. 301 is a main body that houses each component of the sensor, 302 is a mass, 303 is a spring that mechanically supports mass 302 with respect to vibration measurement surface A, and 304 is a damper. Mass 302 also serves as the movable electrode of the capacitance-type sensor. 305 is a fixed electrode located on the opposite side of the movable electrode (mass 302), and 306 is the gap between the two electrodes.

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

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

[0013]

number

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

[0015]

number

[0016]

number

[0017] Proportional gain constant K P is sufficiently large, and the first and third terms on the right side of Eq. (3) are If the second term can be ignored,

[0018]

number

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

[0020] 5. Specific structure of conventional servo-type acceleration sensors The specific structures of servo-type accelerometers can be broadly divided into two types: (1) a type in which the mass part moves linearly, and (2) a type in which the mass part moves oscillatingly. Below, examples of these two types of conventional sensors will be explained.

[0021] [5-1] Conventional example of a linear motion acceleration sensor Figure 15 is a front cross-sectional view showing an example of the specific structure of a conventional linear motion acceleration sensor. The basic principle of the linear motion type is disclosed in Patent Document 3. It is constructed using the basic structure and detection principle shown in Figure 14. Reference numeral 11 denotes a permanent magnet, 12 denotes a pole piece portion, 13 denotes a pole piece protrusion, 14 denotes a permanent magnet side yoke material, 15 denotes a coil side yoke material, 16a denotes a force coil, 16b denotes a calibration coil, 17 denotes a coil bobbin, 18 and 19 denote coil bobbin support members made of nonmagnetic and nonconductive material, 20 denotes a front side disc-shaped spring, 21 denotes a rear side disc-shaped spring, 22 denotes a front side connecting member between the front side disc-shaped spring 20 and the coil side yoke material 15, and 23 denotes a rear side connecting member between the rear side disc-shaped spring 21 and the coil side yoke material 15. Reference numeral 24 denotes a movable electrode, 25 denotes a fixed electrode, 26 denotes a front panel, 27 denotes a center plate, and 28 denotes a fastening member for fastening the fixed electrode 25 and the front panel 26 together.

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

[0023] [5-2] Conventional example of a swing-motion acceleration sensor (1) Overall configuration of the sensor Figure 17 is a front cross-sectional view showing an example of an oscillating motion type disclosed in Patent Document 4, in which reference numeral 590a denotes a pendulum located within a disk-shaped frame 590. Pendulum 590a is formed in a tongue shape with part of its periphery cut out, and is supported by frame 590 via hinge 590b. Frame 590, pendulum 590a, and hinge 590b are integrally formed from, for example, quartz glass. Hinge 590b is thin and elastically deformable, allowing pendulum 590a to be displaced in the vertical direction in the figure due to input acceleration.

[0024] Numerals 591 and 592 denote a pair of magnetic yokes. These magnetic yokes are made of Invar alloy, a low-thermal expansion material. Invar alloy is a difficult-to-process material made by adding 36% nickel and 0.7% manganese to iron. Numeral 593 denotes the pole piece bottom, 594 denotes a permanent magnet, and 595 denotes the pole piece top. Permanent magnet 594 is magnetized in the thickness direction, forming annular magnetic gaps 596 between the inner circumferential surfaces of the open ends of magnetic yokes 591 and 592 and the outer circumferential surface of pole piece top 598. Coil bobbins 598, around which torque coils 597 are wound, are attached to both plate surfaces of pendulum 590a so as to be positioned within these annular magnetic gaps 596.

[0025] On both plate surfaces of pendulum 590a, arc-shaped capacitance electrodes 590c are formed along the outer periphery of the tongue-shaped tip. Electrode surfaces 591e and 592e face capacitance electrode 590c with a predetermined gap therebetween.

[0026] In a servo-type accelerometer with this configuration, the displacement of pendulum 590a due to acceleration input is detected as a change in capacitance between capacitance electrode 590c and electrode surfaces 591e and 592e. Electrode surfaces 591e and 592e are at a common potential, and the detection signals from capacitance electrodes 590c on both surfaces of pendulum 590a are differentially amplified by a servo amplifier (not shown). Torque currents based on the capacitance difference are passed through a pair of torque coils 597. The interaction between this torque current and the magnetic field generated by permanent magnet 594 returns the displaced pendulum 590a to its original position and balances it at the neutral point. Since the torque current at this time is proportional to the acceleration applied to pendulum 590a, the input acceleration can be calculated from this current. Coil terminals 597a and 597b of torque coil 597 are electrically connected by adhesive to a metal conductor (not shown) on pendulum 590a.

[0027] (2) Pendulum structure FIG. 18 shows a plan view of pendulum 590a. FIG. 18(a) shows one side, and FIG. 18(b) shows the other side. Frame 590, pendulum 590a, and hinges 590b1 and 590b2 are formed, for example, by etching a single disk of quartz glass. Pendulum conductor A is formed on one side of frame 590 in an arc shape with a width approximately half the width of frame 590. One end of the arc-shaped metal conductor extends along one hinge 590b1 in its extension direction, passes beyond the center of pendulum 590a, and is then folded back toward the center in a hook-like shape. Arc-shaped pendulum conductor A constitutes one input / output end of the torque current.

[0028] Pendulum conductor B is formed on one surface from the end of pendulum conductor A located in the center of pendulum 590a, across the center of pendulum 590a, at a position spaced apart at a distance approximately equal to the distance between bobbin conductors (described later), toward the outer edge of pendulum 10a, with the same width as pendulum conductor A. Furthermore, pendulum conductor B is formed continuously along the side surface of the outer edge of pendulum 590a between a pair of hinges 590b1, 590b2 to the other surface. The shape of pendulum conductor B on the other surface is the same as the shape on one surface described above. Pendulum conductor B connects two torque coils 597, one on the left and one on the right, in series.

[0029] Pendulum conductor C is formed on the other surface in approximately the same shape as the pendulum conductor A described above. The end of pendulum conductor C is formed in an arc shape on frame 590 on one surface with a width approximately equal to that of frame 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 590. The arc-shaped pendulum conductor C constitutes the other input / output end of the torque current.

[0030] The capacitance detection electrode D is formed in an arc shape along the outer edge of the pendulum 590a on one surface of the pendulum 590a, and further extends over the hinge 590b2 to form an arc-shaped end on the frame 590 along the outer periphery of the frame 590 with a width approximately half the width of the frame 590.

[0031] 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 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).

[0032] Each of the pendulum conductors described above is formed as a thin film of gold (Au) sputtered or vacuum-deposited on the surface of frame 590, pendulum 590a, and hinges 590b1 and 590b2 made of quartz glass.

[0033] The basic structural differences between the linear motion acceleration sensor and the oscillating motion acceleration sensor mentioned above can be categorized by the method of elastically supporting the moving part. In the linear motion type, the direction of movement of the moving part is the axis, and springs are arranged circumferentially around this axis. In the oscillating motion type, the moving part is supported by a cantilever with one end fixed and the other free. [Prior art documents] [Patent documents]

[0034] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-283966 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-155038 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-205284 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-96509 Summary of the Invention [Problem to be solved by the invention]

[0035] The linear motion acceleration sensor disclosed in Patent Document 3 had major issues in terms of production technology due to its basic operating principle and structure. Fig. 16(a) is a front view showing the shape of the front-side disk-shaped spring, and Fig. 16(b) is a front cross-sectional view of the entire sensor (Fig. 15) with the front panel 26, fixed electrode 25, etc. removed. Fig. 16(c) is an enlarged view of part A in Fig. 16(b), showing the state in which the movable electrode 24 is deformed in the axial direction.

[0036] Four conductive paths are required to connect the terminals of the force coil 16a and the calibration coil 16b to an externally installed control circuit. Including the conductive path connecting the movable electrode 24 and the displacement detector 31 (FIG. 15), a total of five independent conductive paths are required. Because the two coils and the movable electrode move axially, it is not possible to connect the five terminals to the external fixed part with lead wires. Therefore, as shown in FIGS. 16(a) and 16(c), the five conductive paths are formed using the front disc-shaped spring 20 and the rear disc-shaped spring 21. In other words, the two disc-shaped springs 20 and 21 serve both to elastically support the movable part (coil bobbin 17, movable electrode 24, etc.) and to provide the five independent conductive paths.

[0037] In FIG. 16(a), 34a, 34b, and 34c denote the outer peripheral fixing portions of the front-side disk-shaped spring 20. These three outer peripheral fixing portions are cut at three circumferential locations as indicated by the chain-line circle AA to ensure electrical insulation. 35a, 35b, and 35c denote the inner peripheral spring portions of the front-side disk-shaped spring. These three inner peripheral spring portions are cut at three circumferential locations as indicated by the chain-line circle BB to ensure electrical insulation. 36a, 36b, and 36c denote soldering portions for electrically connecting the coil terminals to the inner peripheral spring portions. FIG. 12(c) shows the state in which the terminal of the test coil 16b is electrically connected to the inner peripheral spring portion 35c at the soldering portion 36c. Incidentally, the coil wire diameter used in servo-type acceleration sensors is, for example, an extremely fine wire with a diameter of approximately 30 μm.

[0038] Conventional servo-type acceleration sensors pose a production technology challenge due to their basic operating principles and structure, requiring the processes of "cutting, insulating, and soldering" between the disk-shaped spring and the coil. This complicated process reduces yield and reliability during mass production. Considering long-term reliability, small-diameter disk-shaped springs used in linear motion acceleration sensors must be made of metal. This is because, from the perspective of sensor performance, the mechanical resonance frequency, determined by the inertial mass of the moving part and the spring stiffness, must be sufficiently low, and the spring stiffness value must be set small. Small-diameter disk-shaped springs deform significantly with small external forces. This makes it difficult to adopt a structure combining a non-metallic material (such as quartz glass) with a conductive thin film (conductive path), as is used in oscillatory motion acceleration sensors.

[0039] The conventional oscillating acceleration sensor disclosed in Patent Document 4 uses thin-film techniques, such as sputtering and vacuum deposition, which require expensive processing equipment. This is because it requires (i) conductive paths connecting a pair of oscillating torque coils to an external control circuit, and (ii) conductive paths connecting capacitance electrodes formed on the surface of oscillating pendulum 590a to an external control circuit. These multiple independent conductive paths are formed as thin films on the surfaces of thin, elastically deformable hinges 590b1 and 590b2. Figure 19 shows an enlarged view of pendulum 590a as it oscillates.

[0040] Another possible alternative is to solder multiple thin wires to the moving and fixed components, or to connect them with conductive adhesive. In this case, the spring load caused by the deformation of the wires is applied in parallel to the spring stiffness of the hinge, affecting the mechanical resonance frequency. Furthermore, the repeated stress on the wires can lead to fatigue failure and other degradation in reliability.

[0041] 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. As a result, a complex structure and production method are required, which increases costs and is a major factor in reducing yield and reliability during mass production.

[0042] As an example of configuring an active vibration isolation table, let's consider four-point support active control. In this case, actuators are placed at the four corners, with two points in the horizontal X direction and two points diagonally in the Y direction. Each actuator also incorporates an actuator that supports the load in the Z direction. This means that a total of eight actuators are placed, and eight acceleration sensors are required to control each actuator. If a sensor to detect floor acceleration is included, a total of nine expensive acceleration sensors are required. Therefore, in the case of a multi-axis control active vibration isolation table, the large number of acceleration sensors required poses a serious problem in that it accounts for a high proportion of the overall cost. [Means for solving the problem]

[0043] 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 returns 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: a permanent magnet, a coil, and a yoke material. If the coil, one of these three elements, can be fixed, the fatal issue of the moving coil type (MC type), namely the difficulty of wiring, which is the main cause of yield reduction, can be solved in one fell swoop.

[0044] The inventors have focused on the moving magnet (MM) type, which eliminates the need for ultra-fine wire processing because the permanent magnet moves and the coil is fixed, and have already proposed it. Conventional servo-type acceleration sensors use a moving coil (MC) type, in which the coil moves linearly or oscillates in the axial direction. In contrast, the proposed MM sensor uses a fixed coil and a moving permanent magnet in the axial direction. However, there has been no precedent for an MM-type servo-type acceleration sensor. This is likely due to a tacit assumption (blind spot) that the MM type has a disadvantage in terms of high-frequency transmission characteristics and high-speed response due to the increased inertial mass of the moving part. The previously proposed invention addresses this "blind spot" through the following innovations: (i) a magnetic circuit configuration that reduces the weight of the moving part; (ii) a magnetic pole shape that reduces the effects of leakage flux; and (iii) a coil specification that utilizes the increased coil storage volume to simultaneously increase power generation and suppress heat generation. The present invention has discovered a way to compensate for the weaknesses of the MM type from a new perspective not found in previous proposals.

[0045] Thus, the servo type vibration detector of the first invention of the present application comprises a housing which is a fixed member, a movable member which is disposed relative to the housing via a radial gap and is provided so as to be movable in a predetermined direction relative to the housing, an elastic member which supports the movable member so as to be disposed relative to the housing via the gap, a displacement detection unit which detects displacement of the movable member in the predetermined direction, a driving means which is driven by a servo amplifier so as to generate a force which returns the movable member to the original position when a relative displacement of the movable member from the original position is detected by the displacement detection unit, a movable side electrode provided on the movable member, a fixed side electrode provided on the housing side opposite to the movable side electrode, a metallic coil bobbin attached to the inner peripheral surface of the housing, and a coil housed in the coil bobbin. and a permanent magnet arranged so that magnetic flux flows through the gap, the displacement detection unit is configured by detecting the electrostatic capacitance formed in the gap between the movable-side electrode and the fixed-side electrode, the movable member is configured by the permanent magnet and a movable-side yoke material connecting the permanent magnet to a magnetic path, the driving means is configured to generate an electromagnetic force that moves the movable member in the axial direction by forming a closed loop magnetic circuit with the movable member, the gap, the fixed member, and the permanent magnet, and the means for mounting the coil bobbin on the inner peripheral surface of the fixed member has the effect of narrowing the radial gap between the fixed member and the coil bobbin and has the effect of restricting axial movement of the coil bobbin relative to the fixed member.

[0046] That is, this invention focuses on the weakness of conventional MC servo acceleration sensors, which install coils suspended in the air. In conventional MC types, the coil is placed between air gaps on the top and bottom (or left and right), which have thermal conductivity that is only about one-ten-thousandth that of metal. Increasing the number of coil turns to increase the generated force increases the coil's electrical resistance, which increases the amount of heat generated and the coil temperature. As the coil temperature increases, thermal noise increases. Therefore, the coil specifications, such as the number of coil turns, in conventional servo acceleration sensors are limited by the allowable upper limit of thermal noise.

[0047] Therefore, we focused on the feature of the MM type, which allows the coil to be tightly fixed to the housing. The coil bobbin that houses the coil is made of a metal (aluminum) with high thermal conductivity, and the coil bobbin is attached to the inner peripheral surface of the fixing member. The attachment method is configured to have the effect of narrowing the radial gap between the fixing member and the coil bobbin, so that the two members are attached in a state close to metal-to-metal contact. By easing the coil specifications due to heat generation, the number of coil turns can be increased, which improves the generated force (Lorentz force) under the same input current conditions. As a result, the weakness of the MM type, which is the increased inertial mass of the moving part, is eliminated.

[0048] A servo type vibration detector according to a second aspect of the present invention is characterized in that the coil bobbin is fastened to the fixed member by a plurality of bolts arranged in the circumferential direction.

[0049] In other words, the present invention achieves close contact between the outer peripheral surface of the coil bobbin and the inner peripheral surface of the coil side yoke by arranging multiple fastening bolts at close intervals in the circumferential direction. The gap determined by the outer diameter of the coil bobbin and the inner diameter of the coil side yoke material is set to have a narrow tolerance close to that of an interference fit. Furthermore, the coil bobbin has low rigidity and is made of a material that easily deforms elastically, thereby improving the contact between the two components.

[0050] A servo type vibration detector according to a third aspect of the present invention comprises a housing which is a fixed member, a movable member which is disposed relative to the housing via a radial gap and which is provided so as to be movable in a predetermined direction relative to the housing, an elastic member which supports the movable member so as to be disposed relative to the housing via the gap, a displacement detection unit which detects displacement of the movable member in the predetermined direction, drive means which is driven by a servo amplifier so as to generate a force which returns the movable member to the original position when a relative displacement of the movable member from an original position is detected by the displacement detection unit, a movable side electrode provided on the movable member, a fixed side electrode provided on the housing side opposite to the movable side electrode, and a metal coil bobbin attached to the inner peripheral surface of the fixed member. and a coil housed in the coil bobbin, and a permanent magnet arranged so that magnetic flux flows in the gap, wherein the displacement detection unit is configured to detect the electrostatic capacitance formed in the gap between the movable electrode and the fixed electrode, the movable member is composed of the permanent magnet and a movable yoke material that connects the permanent magnet to a magnetic path, and the driving means is configured to generate an electromagnetic force that moves the movable member in the axial direction by forming a closed loop magnetic circuit with the movable member, the gap, the fixed member, and the permanent magnet, and the coil bobbin is formed with ridges that divide the space housing the coil, through which current flows in the same direction, into multiple parts, and the tips of the ridges are arranged close to the inner surface of the fixed member.

[0051] In other words, the present invention increases the number of ridges that separate the space in which the coil is housed, thereby increasing the area of ​​proximity between the outer surface of the coil bobbin and the opposing surface, thereby improving the heat dissipation effect of the coil through thermal conduction.

[0052] If the axial length of the coil bobbin is increased by the width of the intermediate ridge and the number of coil turns is the same as when there is no intermediate ridge, the generated force remains unchanged. Coil wire (copper wire) is often covered with a resin insulating film, and the thermal conductivity between the coil wires is lower than that of metals. By providing an intermediate ridge, the heat transfer effect due to heat conduction from the coil wire to the coil bobbin is improved.

[0053] The servo-type vibration detector of the fourth invention of the present application is characterized in that the coil bobbin is divided by the ridge into a space for accommodating the force coil which serves as the driving means and a space for accommodating the calibration coil.

[0054] In other words, the present invention provides a space for accommodating a calibration coil, which is used as a calibration coil during sensor manufacturing, independently formed on the coil bobbin. By adding more ridges to the above-described embodiment that separate the space for accommodating the calibration coil, the heat dissipation effect of the coil through thermal conduction is further improved.

[0055] The servo-type vibration detector of the fifth invention of the present application is characterized in that it further comprises a threaded structure consisting of a male thread formed on the outer peripheral surface of the coil bobbin and a female thread formed on the inner peripheral surface of the fixing member, and the coil bobbin and the fixing member are threadedly engaged with each other.

[0056] In other words, in the present invention, a male thread is formed on the outer peripheral surface of the coil bobbin, and a female thread is formed on the inner peripheral surface of the fixing member, and the two are screwed together. This screw connection increases the heat transfer area between the two members, and by reducing the proximity distance between the two members, it is possible to improve the heat dissipation effect of the coil by thermal conduction.

[0057] The servo-type vibration detector of the sixth invention of the present application is characterized in that it further comprises a tapered fitting portion consisting of a first tapered portion formed on the outer peripheral surface of the coil bobbin and a second tapered portion formed on the inner peripheral surface of the fixed member, and there is a tapered fit between the coil bobbin and the fixed member.

[0058] That is, in the present invention, the coil bobbin, whose outer circumferential surface is tapered (conical), is attached to the fixing member, whose inner circumferential surface is tapered. The coil bobbin is inserted into the fixing member, and the coil bobbin is fixed with a fastening bolt while applying an appropriate axial force F. The tapered fit of the two members eliminates even the slightest gap between the two members, ensuring complete metal-to-metal contact, dramatically improving the heat dissipation effect of the coil.

[0059] The servo-type vibration detector of the seventh invention of the present application is characterized in that a pressing means is provided between the coil bobbin and the fixed member to apply an axial force to the coil bobbin so that the gap of the tapered fitting portion narrows when the coil bobbin is stored in the fixed member.

[0060] That is, the present invention provides a function (pressure means) for further strengthening the adhesion between the coil bobbin and the fixing member when they are tapered together. The tapered members can be further tightly adhered together by this pressure means, which further enhances the effect of intermetallic heat conduction.

[0061] The servo-type vibration detector of the eighth invention of the present application is characterized in that a heat sink is attached to the outer surface of the external case that houses the main body of the servo-type vibration detector, including the fixing member or the components described in claim 1, thereby increasing the surface area of ​​the part that comes into contact with the atmosphere.

[0062] The servo-type vibration detector of the ninth invention of the present application is characterized in that the movable member further comprises a front pole piece portion, a rear pole piece portion arranged axially in line with the front pole piece portion, a front coil fixed to the fixed member within a gap between the outer periphery of the front pole piece portion and the inner periphery of the fixed member, and a rear coil fixed to the fixed member within a gap between the outer periphery of the rear pole piece portion and the inner periphery of the fixed member, and the movable member is composed of the coil bobbin that houses the front coil and the rear coil. [Effects of the Invention]

[0063] According to the present invention, the fixed member and the coil bobbin are in a state close to metal-to-metal contact, which can relax the coil specifications due to heat generation and increase the number of coil turns, thereby improving the generated force (Lorentz force) under the same input current conditions, and as a result, it becomes possible to allow an increase in the inertial mass of the moving part. [Brief explanation of the drawings]

[0064] [Figure 1] 1A is a front cross-sectional view of a servo-type acceleration sensor according to a first embodiment of the present invention, and FIG. 1B is a view taken along the arrow CC in FIG. 1A. [Figure 2] FIG. 1 is a diagram showing the flow of heat (heat transfer) from the inside of the sensor, which uses a coil as a heat source, to the atmosphere in the MM servo acceleration sensor of this embodiment. [Figure 3] Fig. 3(a) shows the heat flow from inside the sensor to the atmosphere, similar to Fig. 2, and Fig. 3(b) is an enlarged view of the coil bobbin area in Fig. 3(a). [Figure 4] Graph of applied voltage versus coil current for MM servo type acceleration sensor [Figure 5] Graph of applied voltage versus coil current of MC servo type acceleration sensor [Figure 6] Coil current vs. power consumption graph [Figure 7] FIG. 10 is a front cross-sectional view of a servo-type acceleration sensor according to a second embodiment of the present invention. [Figure 8] FIG. 10 is a front cross-sectional view of a servo-type acceleration sensor according to a third embodiment of the present invention. [Figure 9] 9A and 9B show a servo-type acceleration sensor according to a fourth embodiment of the present invention, in which FIG. 9A is a front cross-sectional view, and FIG. 9B is an enlarged view of a portion AA in FIG. 9A. [Figure 10] 10A shows a servo-type acceleration sensor according to a fifth embodiment of the present invention, in which FIG. 10A is a front cross-sectional view showing a method for mounting a coil bobbin on the sensor of the embodiment, and FIG. 10B is a front cross-sectional view of the sensor after the coil bobbin has been mounted. [Figure 11] 11A and 11B show a servo-type acceleration sensor according to a sixth embodiment of the present invention, in which FIG. 11A is a front cross-sectional view, and FIG. 11B is an enlarged view of a portion AA in FIG. 11A. [Figure 12] 10 is a front cross-sectional view of a servo-type acceleration sensor according to a seventh embodiment of the present invention. [Figure 13] Model diagram of a conventional active vibration isolation table [Figure 14] Model diagram showing the basic configuration and detection principle of a conventional capacitance-type acceleration sensor [Figure 15] A front cross-sectional view showing a specific example of the structure of a conventional linear motion acceleration sensor. [Figure 16] In a conventional linear motion acceleration sensor, FIG. 16(a) is a front view showing the shape of the front-side disk-shaped spring, FIG. 16(b) is a front cross-sectional view with the front-side panel 26 and the fixed-side electrode 25 removed from FIG. 15, and FIG. 16(c) is an enlarged view of part A in FIG. 16(b). [Figure 17] FIG. 1 is a front cross-sectional view showing an example of a conventional swing-motion acceleration sensor. [Figure 18] 18(a) shows a plan view of the pendulum of the swing-motion acceleration sensor, and FIG. 18(b) shows the other side of the pendulum. [Figure 19] An enlarged view showing the state in which the pendulum of the swinging motion type acceleration sensor swings. DETAILED DESCRIPTION OF THE INVENTION

[0065] As mentioned above, the present invention has discovered a way to compensate for the weaknesses of the MM system from a new perspective not found in previous proposals.

[0066] (1) Restrictions on coil specifications in conventional MC type acceleration sensors Increasing the number of coil turns to increase the generated force increases the coil's electrical resistance, which increases the amount of heat generated and causes the coil temperature to rise. As the coil temperature rises, thermal noise also increases. Therefore, the coil specifications, such as the number of coil turns, in conventional servo-type acceleration sensors are limited by the allowable upper limit of thermal noise.

[0067] (2) Basic proposition of MM type sensor As mentioned above, the biggest challenge with MM sensors, which greatly simplify wiring, is the increase in inertial mass of the moving part. The force generated by the actuator must be increased by the amount of the increased inertial mass. This was the basic premise of MM sensors. In order to overcome the weaknesses of the MM type, this invention has found a way to improve the force generated by the actuator (force constant) by means other than the magnetic circuit configuration.

[0068] (3) Focusing on the structural features of the MM formula If the temperature rise of the coil can be suppressed, the number of coil turns can be increased, which should increase the generated power. Therefore, we focused on a feature of the MM type that allows the coil to be fixed to the housing. This feature is not available in MC type sensors, which have a coil that is installed floating in the air. By tightly fixing the coil to the housing, the heat generated by the coil is efficiently transferred to the housing by metal-to-metal thermal conduction. Heat radiation from the surface of the housing that comes into contact with the air can suppress the temperature rise of the coil.

[0069] [First embodiment] Axially magnetized permanent magnet FIG. 1 shows a servo-type acceleration sensor according to a first embodiment of the present invention, with FIG. 1(a) being a front cross-sectional view and FIG. 1(b) being a view taken along the CC arrow in FIG. 1(a). The chain line AA in FIG. 1(a) is a moving magnet type (MM type) actuator that drives the movable part in the axial direction. The chain line BB indicates a displacement detection part that detects electrostatic capacitance. The inventors have already filed a patent application for an MM type servo-type acceleration sensor, but this embodiment applies a new MM type sensor structure that was not disclosed in the previous application. The specific structure will be explained below, dividing it into the actuator part and the displacement detection part.

[0070] [1] Sensor structure of this embodiment (using MM-type structure limited patent) [1-1] Actuator section In the actuator section (shown by imaginary line AA) in Figure 1(a), reference numeral 801 denotes an axially magnetized permanent magnet, 802a denotes a front pole piece, and 802b denotes a rear pole piece. The front pole piece 802a and rear pole piece 802b form part of a closed-loop magnetic circuit as a movable yoke member. Reference numeral 803 denotes a coil-side yoke member (fixed member), and 803a denotes a gap formed in the coil-side yoke member. Reference numeral 804 denotes a metal coil bobbin, 805 denotes a fastening bolt connecting the coil bobbin to the coil-side yoke member, 806a denotes a front coil, and 806b denotes a rear coil. The winding direction of each coil is set so that the Lorentz forces acting on the front coil and rear coil are in the same direction. Reference numerals 807a and 807b denote gaps formed in the centers of the front and rear pole piece members 802a and 802b. As will be described later, the coil bobbin 804 is made of aluminum, which has high thermal conductivity.

[0071] The front pole piece and rear pole piece are configured as stepped hollow shapes with a cross-sectional area that does not cause magnetic saturation. The magnetic flux Φ flowing through the closed loop magnetic circuit is constant, and if the cross-sectional area of ​​the magnetic path is S, then the magnetic flux density is B (= Φ / S).

[0072] The reason why the cross-sectional shape of the two pole piece parts is made to be a stepped hollow shape is because the magnetic flux density decreases as it moves away from permanent magnet 801, that is, as it approaches the tip of the pole piece part. This stepped hollow shape makes it possible to reduce the weight of the moving part.

[0073] 808a is a front-side magnetic gap, and 808b is a rear-side magnetic gap, each representing a radial gap between the two pole piece parts and the coil-side yoke material. A closed loop magnetic circuit B is formed by "permanent magnet 801 → front-side pole piece part 802a → front-side magnetic gap 808a → coil-side yoke material 803 → rear-side magnetic gap 808b → permanent magnet 801". MThe pole piece portion 802a is formed with a front inner peripheral support member 809a and a rear inner peripheral support member 809b. The front and rear inner peripheral support members are made of a non-conductive material. The front inner peripheral support member and the rear inner peripheral support member are pre-adhered to the two pole piece portions 802a and 802b. 810a is a front disk, 810b is a rear disk, and 811 is a movable electrode. 812 is a screw fastening portion formed between the inner peripheral side of the front inner peripheral support member 809a and the movable electrode 811. The inner peripheral side of the front disk 810a is clamped between the front inner peripheral support member 809a and the movable electrode 811 by screw fastening. 813 is a rear fastener, and 814 is a screw fastening portion formed between the inner peripheral side of the rear inner peripheral support member 809b and the rear fastener. The inner periphery of the rear disc 810b is held by screw fastening between the rear inner periphery support member and the rear fastener, similar to the front disc.

[0074] The outer periphery of front-side disk 810a is fastened to coil-side yoke material 803 with bolts 817, sandwiching insulating sheets 815a and 815b between them and washer 816. The outer periphery of rear-side disk 810b is fastened to coil-side yoke material 803 with bolts 819, sandwiching washers 818a and 818b between them.

[0075] 1(b) is a view taken along the arrow CC in FIG. 1(a), and 805a to 805f are fastening bolts that are means for attaching the coil bobbin 804 to the coil side yoke material (fixing member) 803. In this embodiment, a plurality of the fastening bolts are arranged at narrow intervals in the circumferential direction, thereby achieving close contact between the outer peripheral surface of the coil bobbin and the inner peripheral surface of the coil side yoke.

[0076] In this embodiment, the gap determined by the outer diameter of the coil bobbin and the inner diameter of the coil side yoke material is set to have a narrow tolerance close to that of an interference fit. Furthermore, the coil bobbin is made of aluminum, which has low rigidity and is prone to elastic deformation, and both components are fixed together with the multiple fastening bolts arranged circumferentially within the gap 803a of the coil side yoke material.

[0077] Numeral 820 denotes a groove formed in the axial direction on the inner peripheral surface of coil-side yoke material 803 for coil lead wires. Numeral 821 denotes a radial through-hole formed in the coil-side yoke material, with an opening in the groove. In FIG. 1(b), numeral 822 denotes lead wires for front-side force coil 806a and rear-side force coil 806b. Lead wires 822 are installed axially along groove 820 and are led to the outside through radial through-hole 821.

[0078] The movable part of this embodiment is primarily composed of a permanent magnet 801, pole pieces 802a and 802b, a movable electrode 811, and a rear fastener 813. The fixed part is composed of a coil bobbin 804 housing each coil and a coil-side yoke material 803. In this acceleration sensor, the movable part's driving mechanism uses an improved structure of a previously proposed moving magnet type. As is well known, when a current flows through a conductor placed in a magnetic field, a Lorentz force, an electromagnetic force, is generated. In all actuators, regardless of the driving principle, the force relationship between the fixed side and the movable side is relative. In other words, if either the fixed side or the movable side is fixed, the other side moves. In this embodiment, when a current flows through force coils 806a and 806b housed in the coil bobbin 804, a Lorentz force reaction is generated, moving the movable part axially.

[0079] [1-2] Displacement detection unit In the displacement detection section (part indicated by imaginary line BB) in Figure 1(a), 820 is a fixed electrode, 821 is an insulating ring, 822 is a fixed ring, and 823 is a central through-hole formed in the center of the fixed electrode. The fixed electrode 820 is clamped against the fixed ring with the insulating ring interposed therebetween. 824 is a positioning bolt for the fixed electrode, and 825 is a threaded portion formed in the coil side yoke material 803. After setting the inter-electrode gap between the fixed electrode 820 and the movable electrode 811, the positioning bolt 824 fixes the fixed ring 822 to the coil side yoke material 803.

[0080] [2] Comparison of heat flow between MM and MC types Figure 2 shows the heat flow (heat transfer) from the inside of the MM servo acceleration sensor of this embodiment, where the coil is the heat source, to the atmosphere. Figure 3 shows a conventional MC servo acceleration sensor, and Figure 3(a) is a diagram showing the heat flow from the inside of the sensor to the atmosphere, similar to Figure 2. Figure 3(b) is an enlarged view of the vicinity of the coil bobbin in Figure 3(a). The MM formula and the MC formula will be compared below for explanation.

[0081] As is well known, there are three ways that heat is transported: thermal conduction, convection, and thermal radiation (radiation), which are known as the three principles of heat transfer. The heat generated by the coil is dissipated into the atmosphere through each component of the sensor by one of these three methods, or a combination of these three methods. [2-1] Heat transfer in MM type acceleration sensors 2, 804a is the left-end support portion, 804a is the central support portion, and 804c is the right-end support portion. At the boundaries between the outer circumferential surfaces of the support portions and the inner circumferential surface of the coil-side yoke material 803 (housing), 805a is the left-end boundary portion, 805b is the central boundary portion, and 805c is the right-end boundary portion. Also, 826a is the gap between the front-side coil 806a and the inner circumferential surface of the coil-side yoke material (housing) 803, and 826b is the gap between the rear-side coil 806b and the inner circumferential surface of the coil-side yoke material.

[0082] (1) Main path of heat transfer In the case of an MM-type acceleration sensor in which the coil does not move, it is important to note that the coil (including the coil bobbin) can be tightly attached to the fixed member. Here, we assume that the boundaries 805a, 805b, and 805c are in an ideal state, with both members tightly attached without any gaps. In this case, the heat generated by the coils 806a and 806b is transferred to the coil bobbin via thermal conduction between the coils. Furthermore, as indicated by the solid arrows, heat transfer occurs from the coil bobbin 804 to the housing (the fixed member) 803 via metal-to-metal thermal conduction. Therefore, assuming the above ideal conditions, the main path of heat transfer from the coil to the housing surface is metal-to-metal thermal conduction. Furthermore, heat is dissipated from the housing surface to the atmosphere via heat transfer involving thermal radiation and convection.

[0083] (2) Secondary heat transfer pathways A secondary path for heat transfer inside the sensor is through gaps. Gaps 826a and 826b between the coil and the inner circumferential surface of the housing, and gaps 808a and 808b between the inner circumferential surface of coil bobbin 804 and the pole piece are the paths for heat transfer. Because the thermal conductivity of air is only about 1 / 10,000 that of metal, the amount of heat transfer due to thermal conduction in the gaps (0.2 to 0.5 mm) is minimal. In narrow gaps, there is no heat transfer due to convection, and heat transfer due to radiation (electromagnetic waves, which are far infrared rays) is the secondary path for heat transfer.

[0084] [2-2] Heat transfer in MC type acceleration sensors In the conventional linear motion acceleration sensor (MC type) shown in Figure 3, 34 is a gap between the outer periphery of the coil and the coil side yoke material 15, and 35 is a gap between the inner periphery of the coil bobbin 17 and the pole piece part 12.

[0085] In the case of the conventional MC type, the coil (including the coil bobbin) is installed suspended in the air, sandwiched between gaps 34 and 35 above and below. This is a fundamental difference from the MM type, in which the coil (including the coil bobbin) can be attached to a fixed member. The coil bobbin support members 18 and 19 that support the coil bobbin 17 are made of a non-magnetic and non-conductive material (ceramic material). Furthermore, because the disk-shaped springs 20 and 21 are thin plates, heat dissipation from the coil by thermal conduction cannot be expected. Therefore, in the case of the conventional MC type, the main route of heat transfer from the heating coil to the housing (coil side yoke material 15) is heat transfer by radiation through the gaps 34 and 35. Heat dissipation from the housing surface to the atmosphere is by heat transfer involving thermal radiation and convection, just like the MM type.

[0086] The same is true for the conventional oscillating moving coil type (MC type) shown in Figure 17. The heat conduction path connecting torque coil 597 and the fixed part (magnetic yokes 591, 592) involves quartz glass (a non-magnetic and non-conductive material) with low thermal conductivity, so heat dissipation by thermal conduction of the coil cannot be expected.

[0087] [3] Experiment to evaluate the temperature dependence of coil electrical resistance An experiment was conducted to determine the coil electrical resistance from the coil current relative to the applied voltage using the MM sensor of this embodiment and a conventional MC sensor. The sensor body was installed so as to maintain thermal insulation from the outside, and the heat dissipation conditions for each sensor relative to the atmosphere were the same. Electrical resistance changes depending on temperature, as shown in the well-known formula (5). Because the coil is a heat source, the aim of this experiment was to determine whether a difference in the heat dissipation effect between the MM and MC sensors would result in a difference in the change in electrical resistance (ratio of applied voltage to coil current) relative to power consumption.

[0088]

number

[0089] In equation (5), R0 is the coil electrical resistance at 20°C, α is the temperature coefficient determined by the resistor material, T is the coil temperature, and R Tis the coil electrical resistance at coil temperature T.

[0090] Figures 4 and 5 are the measured data showing the relationship between the applied voltage and the coil current for the MM type and the MC type. Table 1 shows the coil specifications used in the experiment. For the coil specifications of the MM type, considering in advance that the superiority of the heat dissipation effect over the MC type can contribute to the improvement of the generated force, the number of turns (for two) is set to be larger.

[0091] [Table 1]

[0092] In the measured results of the MM type in Figure 4, in the range of 0 < I < 20 mA, the relationship between the applied voltage V and the coil current I is approximately proportional. However, when I ≥ 20 mA, the relationship between the applied voltage and the coil current becomes non-linear, and it can be seen that the electrical resistance R (= V / I) increases. In the figure, the solid-line graph is the envelope of the measured values (dotted line) in the range of 0 < I < 20 mA. The MC type in Figure 5 shows a similar trend. That is, the current I0 ≈ 20 mA (point A in Figure 4 and point B in Figure 5) is the "branch point" where the electrical resistance changes from the linear characteristic to the non-linear characteristic.

[0093] Figure 6 is organized based on the above experimental data so that the "branch point" where the power consumption W (= IR) of the coil changes from the linear characteristic to the non-linear characteristic can be compared considering the difference in electrical resistance between the MM type and the MC type. The horizontal axis of the graph is the current I 2 . The branch point I0 2 of the MM type and the MC type is 2 = 0.0005 (I 2 ), and the power consumption at this value is W = 0.35 W for the MM type and W = 0.23 W for the MC type. Therefore, if evaluated by replacing it with the heat generation amount (= power consumption × time), it can be seen that the coil electrical resistance of the MM type in this embodiment is less affected by up to about 1.5 times the heat generation amount compared to that of the conventional MC type.

[0094] Table 2 shows the force (Lorentz force) generated by the moving parts of the MM and MC types configured with the coil specifications in Table 1, determined by numerical magnetic field analysis. Incidentally, the permanent magnets used are neodymium for the MM type and samarium cobalt for the MC type.

[0095] [Table 2]

[0096] The mass of the moving part of the MM type is 2.29 times that of the MC type, but the generated force is even greater, at 2.77 times. This result shows that the weakness of the MM type, that of a larger moving part mass compared to the MC type, is eliminated. Furthermore, by taking advantage of the structural feature of the MM type that allows for a larger coil storage volume, the number of coil turns is set to 2.4 times that of the MC type. In other words, in addition to the ingenious design of the magnetic circuit configuration, the effect of this embodiment, which improves the heat dissipation effect of the coil, suppresses coil heat generation that leads to thermal noise and eliminates the weakness of the MM type, that of an increased moving part mass.

[0097] [supplement] In this embodiment, the coil specifications for the MM type are set with a larger number of turns (equivalent to two turns), taking into consideration the superior heat dissipation effect of the MM type compared to the MC type, which contributes to increased power generation. However, by increasing the coil storage volume, it is possible to select a coil with a larger wire diameter for the same number of turns, making it easy to achieve the same or lower electrical resistance as the MC type. To achieve this, the axial lengths of the front and rear pole pieces must be increased. However, because the magnetic flux density at the tip of the pole piece is low and the radial thickness can be made sufficiently thin, the increase in mass of the moving part is minimal. Therefore, even when the electrical resistance is the same as or lower than the MC type, the present invention can improve the coil's heat dissipation effect and reduce the coil temperature rise that leads to thermal noise.

[0098] [Second embodiment] 7 is a front cross-sectional view of a servo-type acceleration sensor according to embodiment 2 of the present invention. By adding more ridges that separate the space in which the coil is housed, the area of ​​proximity between the outer circumferential surface of the coil bobbin and the opposing surface is increased, improving the heat dissipation effect of the coil through thermal conduction.

[0099] Reference numeral 901 denotes the coil bobbin of this embodiment, which is configured with a toothed shape. 901a denotes the left end support portion of the coil bobbin, 901a denotes the central support portion, and 901c denotes the right end support portion. 902a denotes a newly added front-side intermediate ridge portion, and 902b denotes a rear-side intermediate ridge portion. 903a and 903b denote front coils whose storage space is divided by the front-side intermediate ridge portion. The magnetic flux at the locations where the front-side coils 903a and 903b are placed is in the same direction, and the total number of turns of the front-side coils is set to the same as in the first embodiment (without an intermediate ridge portion). The same applies to the rear-side intermediate ridge portion 902b and the rear-side coils 904a and 904b. Therefore, the generated force (Lorentz force) is unchanged regardless of the presence or absence of the intermediate ridge portions 902a and 902b. However, the axial length of the coil bobbin is increased by the width of the two intermediate ridge portions 902a and 902b.

[0100] Furthermore, since the coil wire (copper wire) is often covered with a resin insulating film, the thermal conductivity between the coil wires is lower than that of metal. By providing an intermediate ridge, the heat transfer effect due to heat conduction from the coil wire to the coil bobbin is improved.

[0101] [Third embodiment] 8 is a front cross-sectional view of a servo-type acceleration sensor according to a third embodiment of the present invention. A space for accommodating a calibration coil used as a calibration coil during sensor manufacturing is formed independently on the coil bobbin. In addition to the second embodiment described above, the number of ridges separating the space accommodating the calibration coil has been increased, further improving the heat dissipation effect of the coil through thermal conduction.

[0102] Reference numeral 911 denotes the coil bobbin of this embodiment, which is configured with seven tooth shapes, with 911a being the left end support portion of the coil bobbin, 911a being the central support portion, and 911c being the right end support portion. 912a is the front-side first intermediate ridge portion, and 912b is the front-side second intermediate ridge portion. 913a is the rear-side first intermediate ridge portion, and 913b is the rear-side second intermediate ridge portion. 914a and 914b are front-side coils whose storage space is divided by the front-side second intermediate ridge portion. 915a and 915b are front-side coils whose storage space is divided by the rear-side second intermediate ridge portion. 916a is the front-side test coil, and 916b is the rear-side test coil.

[0103] [Fourth embodiment] 9 shows a servo-type acceleration sensor according to a fourth embodiment of the present invention, with Fig. 9(a) being a front cross-sectional view and Fig. 9(b) being an enlarged view of part A in Fig. 9(a). A male thread is formed on the outer peripheral surface of the coil bobbin, and a female thread is formed on the inner peripheral surface of the fixed member (coil side yoke material 803), and the two are screwed together. This screw connection increases the heat transfer area between the two members, and by reducing the proximity distance between the two members, the heat dissipation effect of the coil by thermal conduction is improved.

[0104] In the coil bobbin 921 in Fig. 9(a), 921a is the left end support portion, 921a is the central support portion, and 921c is the right end support portion. As shown in Fig. 9(b), a male thread 922 is formed on the outer circumferential surface of each support portion. Also, a female thread 923 is formed on the inner circumferential surface of the coil side yoke material 803 (housing).

[0105] [Fifth embodiment] 10(a) is a front cross-sectional view showing a method for mounting a coil bobbin on the sensor of the embodiment, and FIG. 10(b) is a front cross-sectional view of the sensor after the coil bobbin has been mounted. In this embodiment, the coil bobbin and the fixing member are tapered together to bring the two members into complete contact, thereby ensuring intermetallic heat conduction between the two members.

[0106] In Figures 10(a) and 10(b), 931 denotes a coil bobbin configured with a toothed shape similar to that of the second embodiment. 931a denotes the left end support portion of the coil bobbin, 931b denotes the central support portion, 931c denotes the right end support portion, 932a denotes the front-side middle ridge portion, and 932b denotes the rear-side middle ridge portion. 933a and 933b denote front-side coils whose storage space is divided by the front-side middle ridge portion, and 934a and 934b denote rear-side coils whose storage space is divided by the rear-side middle ridge portion. 803a denotes a tapered portion formed on the inner circumferential surface of the fixing member (coil-side yoke member 803). 935 denotes a fastening bolt for fixing the coil bobbin to the coil-side yoke member, and 936 denotes a through-hole for the fastening bolt formed in the coil-side yoke member.

[0107] 10(a) is a diagram showing the process of mounting the coil bobbin, which has a tapered (conical) outer circumferential surface, onto the fixing member, which has a tapered inner circumferential surface. The coil bobbin is inserted into the fixing member, and with an appropriate axial force F (shown in the figure) applied, the coil bobbin is fixed with a fastening bolt 935. Due to the tapered fit, the diameter of the through hole 936 is designed to have a sufficient margin relative to the axial diameter of the fastening bolt 935, taking into account errors in the relative axial positions of the two members. If the tapered fit of the two members results in complete metal-to-metal contact without even the slightest gap between them, the heat dissipation effect of the coil is dramatically improved.

[0108] In this embodiment, the toothed bobbin used in the second embodiment is used as the coil bobbin. The shape of the coil bobbin to which the present invention can be applied and the method of fixing the coil bobbin to the fixing member are not limited to the above-mentioned methods.

[0109] In order to bring the support portions and the tips of the ridges of the coil bobbin into closer contact with the tapered portion 803a of the fixing member, a method may be used in which the support portions and the ridges are elastically deformed when the coil bobbin is inserted into the fixing member.

[0110] For example, the outer diameter of the coil bobbin can be made smallest at both the left and right ends and largest at the center, forming a mirror-symmetrical tapered shape.The fixing member can also be divided into two, and these fixing members can be sandwiched between the tapers on the left and right sides of the coil bobbin, and then bolted together in the axial direction.

[0111] [Sixth embodiment] 11 shows a servo-type acceleration sensor according to a sixth embodiment of the present invention, with Fig. 11(a) being a front cross-sectional view and Fig. 11(b) being an enlarged view of part AA in Fig. 11(a). This embodiment is an improvement over the fifth embodiment in which the coil bobbin and the fixing member are tapered together, and the bolt fastening portion is provided with a function (pressing means) for making the two members more firmly adhere to each other.

[0112] Reference numeral 941 denotes a coil bobbin configured with a toothed shape similar to that of the fifth embodiment. 941a denotes a left end support portion of the coil bobbin, 941b denotes a central support portion, 941c denotes a right end support portion, 942a denotes a front-side intermediate ridge portion, and 942b denotes a rear-side intermediate ridge portion. In the enlarged view of portion AA in FIG. 11(a), 943 denotes a fastening bolt, 943a denotes a spherical tip portion of this fastening bolt, and 944 denotes a V-shaped hole with a V-shaped cross section formed in the central support portion. 944a denotes a tapered portion of this V-shaped hole, and 944b denotes a vertical wall portion. When the spherical tip 943a of the fastening bolt is pressed against the tapered portion 944a, a normal force T0 is generated at the contact point of the tapered portion 944a of the coil bobbin. In response to this normal force T0, a horizontal component F of the reaction force T (= T0) acting on the coil bobbin side is Z This is the force that moves the coil bobbin to the left. In other words, the two tapered members can be tightly attached to each other by the fastening bolt, which can improve the effect of intermetallic heat conduction.

[0113] [Seventh embodiment] 12 is a front cross-sectional view of a servo-type acceleration sensor according to embodiment 7 of the present invention. The heat transferred from the coil to the coil bobbin and from the coil bobbin to the fixing member is dissipated from the fixing member to the atmosphere by heat transfer involving thermal radiation and convection.

[0114] In this embodiment, 951 is a fixed member (coil side yoke material), and 951a is a heat sink formed on this fixed member. By forming heat sink 951a on the outer surface of fixed member 951, the surface area of ​​the fixed member that comes into contact with the atmosphere is increased, thereby improving the heat dissipation effect.

[0115] This embodiment uses the toothed coil bobbin used in the previous embodiment, but the effect of using a heat sink in a servo-type acceleration sensor is not limited to the shape of the coil bobbin or the configuration of the magnetic circuit (arrangement of the permanent magnet, coil, pole piece, etc.). The shape of the heat sink is not limited to that of this embodiment, and it may have any shape that can increase the surface area of ​​the fixing member that comes into contact with the atmosphere. For example, if the servo-type acceleration sensor main body is housed in an external case made of a separate material, this external case and the fixing member (for example, coil-side yoke material 803 in Figure 1) are configured in close contact. This external case may be made of aluminum, which has high thermal conductivity, and a heat sink may be formed on the outer surface of the external case (not shown).

[0116] The servo-type acceleration sensor used in the above-described embodiment of the present invention has a magnetic circuit structure in which a permanent magnet magnetized in the axial direction is sandwiched between two pole pieces, and two coils are arranged on the fixed side of the outer periphery. However, the application effects of the present invention are not limited to this structure.

[0117] For example, pole pieces are arranged axially on the front and rear sides, and radially magnetized permanent magnets are attached to encase each pole piece. A magnetic circuit configuration with two coils arranged on the fixed side of the outer periphery of the two permanent magnets is also possible. Alternatively, the MY type proposed in a previously applied patent application, in which only the coil moves, is also possible. [Explanation of symbols]

[0118] 801 Permanent Magnets 802a, 802b Movable side yoke material 803 Fixing member 804 Coil bobbin 805 Attachment means 806a, 806b coils 808a, 808b void area 811 Movable side electrode 820 Fixed side electrode

Claims

1. a housing that is a fixed member; a movable member disposed with respect to the housing via a radial gap and movable in a predetermined direction with respect to the housing; an elastic member that supports the movable member so that the movable member is disposed with a gap in the housing; a displacement detection unit that detects a displacement of the movable member in a predetermined direction; a driving means driven by a servo amplifier so as to generate a force that returns the movable member to the original position when the displacement detection unit detects a relative displacement of the movable member from the original position; a movable-side electrode provided on the movable member; a fixed electrode provided on the housing side to face the movable electrode; a metal coil bobbin attached to the inner circumferential surface of the housing; a coil housed in the coil bobbin; a permanent magnet arranged so that magnetic flux flows in the gap, the displacement detection unit is configured by detecting electrostatic capacitance formed in a gap between the movable electrode and the fixed electrode, the movable member is composed of the permanent magnet and a movable-side yoke material that connects the permanent magnet to a magnetic path, the driving means is configured to generate an electromagnetic force that moves the movable member in the axial direction by forming a closed loop magnetic circuit with the movable member, the gap, the fixed member, and the permanent magnet, A servo-type vibration detector characterized in that the means for attaching the coil bobbin to the inner surface of the fixed member has the effect of narrowing the radial gap between the fixed member and the coil bobbin, and also has the effect of restricting axial movement of the coil bobbin relative to the fixed member.

2. 2. The servo type vibration detector according to claim 1, wherein the coil bobbin is fastened to the fixing member by a plurality of bolts arranged in the circumferential direction.

3. a housing that is a fixed member; a movable member disposed with respect to the housing via a radial gap and movable in a predetermined direction with respect to the housing; an elastic member that supports the movable member so that the movable member is disposed with a gap in the housing; a displacement detection unit that detects a displacement of the movable member in a predetermined direction; a driving means driven by a servo amplifier so as to generate a force that returns the movable member to the original position when the displacement detection unit detects a relative displacement of the movable member from the original position; a movable-side electrode provided on the movable member; a fixed electrode provided on the housing side opposite the movable electrode; a metallic coil bobbin attached to the inner circumferential surface of the fixing member; The coil housed in this coil bobbin, a permanent magnet arranged so that magnetic flux flows in the gap, the displacement detection unit is configured to detect electrostatic capacitance formed in a gap between the movable electrode and the fixed electrode, the movable member is composed of the permanent magnet and a movable-side yoke material that connects the permanent magnet to a magnetic path, the driving means is configured to generate an electromagnetic force that moves the movable member in the axial direction by forming a closed loop magnetic circuit with the movable member, the gap, the fixed member, and the permanent magnet, A servo-type vibration detector characterized in that the coil bobbin has a ridge portion that divides the space that houses the coil, through which current flows in the same direction, into multiple parts, and the tip of this ridge portion is positioned close to the inner surface of the fixed member.

4. 4. A servo type vibration detector according to claim 3, wherein said coil bobbin is divided by said ridge into a space for accommodating a force coil serving as said driving means and a space for accommodating a calibration coil.

5. A servo-type vibration detector as described in claim 1, characterized in that it further comprises a threaded structure consisting of a male thread formed on the outer peripheral surface of the coil bobbin and a female thread formed on the inner peripheral surface of the fixing member, and the coil bobbin and the fixing member are threadedly engaged with each other.

6. A servo-type vibration detector as described in claim 1, characterized in that it further comprises a tapered fitting portion consisting of a first tapered portion formed on the outer peripheral surface of the coil bobbin and a second tapered portion formed on the inner peripheral surface of the fixing member, and the coil bobbin and the fixing member are fitted together tapered.

7. A servo-type vibration detector as described in claim 6, characterized in that a pressing means for applying an axial force to the coil bobbin is provided between the coil bobbin and the fixed member so that the gap of the tapered fitting portion narrows when the coil bobbin is stored in the fixed member.

8. A servo-type vibration detector as described in claim 1, characterized in that a heat sink is attached to the outer surface of the external case that houses the fixing member or the main body of the servo-type vibration detector including the components described in claim 1, increasing the surface area of ​​the part that comes into contact with the atmosphere.

9. The movable member is The front pole piece and a rear pole piece portion arranged in line with the front pole piece portion in the axial direction, The coil may include: a front coil fixed to the fixed member within a gap between the outer periphery of the front pole piece portion and the inner periphery of the fixed member; a rear-side coil fixed to the fixed member within a gap between the outer circumferential side of the rear-side pole piece portion and the inner circumferential side of the fixed member, 2. The servo type vibration detector according to claim 1, wherein the coil bobbin is fixed to the fixed member, and the front side coil and the rear side coil are housed in the coil bobbin.

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