Servo type vibration detector and assembly method

Abstract

To solve the issue that optical means of observing a slit between two electrodes from an outer surface has been the only way to measure a gap between a mobile side electrode and a fixation side electrode determining the capacitance in a mass-production assembly step of a servo-type vibration detector and the measurement accuracy of the gap is therefore limited.SOLUTION: A servo-type acceleration sensor structure in which both ends of a sensor mobile member form an open structure is noted. A gap adjusting sheet is inserted into a gap between electrodes while both ends of the mobile member is provisionally fixed to a fixation member, the fixation side electrode is moved to the mobile side electrode and the fixation side electrode is fixed to the fixation member. After that, the provisional fixation of the mobile member is cancelled and the gap adjusting sheet is released from the gap between electrodes.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

[0001] The present invention relates to a servo-type vibration sensor that detects, in a wide frequency band, the acceleration of a controlled object that is supported on a foundation and vibrates due to external disturbances, or the absolute velocity or absolute displacement relative to the inertial space, and an assembly method thereof. [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. 31 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 (vibration state of the foundation). Reference numerals 505a and 505b denote displacement sensors for detecting the vertical and horizontal relative displacement of the surface plate 501 with respect to the floor 500, respectively. Output signals from these sensors are input to a controller 506. A servo valve 508 controlled by the controller 506 is connected to the pneumatic actuator 502a via piping 507. This servo valve 508 adjusts the flow rate of compressed air supplied to and exhausted from the pneumatic actuator 502a, thereby controlling the internal pressure of the actuator 502a and driving the pneumatic actuator.

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

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

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

[0008] 3. Role of vibration sensors in active vibration isolation systems Active vibration control employs a control method based on state feedback. This is a method of controlling a control device based on acceleration, velocity, and displacement information from vibration sensors placed at multiple locations on the structure to be vibration controlled. In order to obtain vibration isolation performance over a wide frequency range, for example, acceleration signals are used to control state quantities above 10 Hz, velocity signals are used to control state quantities between 1 and 10 Hz, and displacement signals are used to control state quantities below 1 Hz. For example,

[0009] a. If acceleration feedback is performed using a signal from an acceleration sensor (such as acceleration sensor 503 in Figure 31) placed on the base plate 501, this is equivalent to an increase in mass M, and has the effect of lowering the natural frequency and reducing the resonance peak. b. If the signal from the acceleration sensor (503 in FIG. 31) 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 (504 in Figure 31) placed directly below the surface plate 501 and converting the signal into an absolute velocity or absolute displacement signal and similarly applying feedforward, it is possible to improve vibration isolation performance over a wide frequency range.

[0010] 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.

[0011] 4. Basic configuration and detection principle of acceleration sensors Figure 32 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.

[0012] 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.

[0013] 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:

[0014]

number

[0015] The proportional gain constant K is set so that the relative displacement ux becomes zero. P The amplifier controls the actuator current i0.

[0016]

number

[0017]

number

[0018] Proportional gain constant K P If is sufficiently large and the first and second terms can be ignored compared to the third term on the right-hand side of equation (3), then

[0019]

number

[0020] If the current i0 flowing through the actuator is detected from equations (2) and (4), the acceleration of the mass body 302 can be approximately calculated.

[0021] 5. Specific structure of conventional servo-type acceleration sensors Figure 33 is a front cross-sectional view showing an example of the specific structure of a conventional capacitance-type acceleration sensor [Patent Document (3)], which is configured using the basic configuration and detection principle shown in Figure 32. Reference numeral 11 denotes a permanent magnet, 12 denotes a pole piece portion, 13 denotes a pole piece protrusion portion, 14 denotes a permanent magnet side yoke material, 15 denotes a coil side yoke material, 16a denotes a force coil, 16b denotes a calibration coil, 17 denotes a coil bobbin, 18 and 19 denote coil bobbin support members made of a non-magnetic and non-conductive material, 20 denotes a front side disc-shaped spring, 21 denotes a rear side disc-shaped spring, 22 denotes a front side connecting member between the front side disc-shaped spring 20 and the coil side yoke material 15, and 23 denotes a rear side connecting member between the rear side disc-shaped spring 21 and the coil side yoke material 15.

[0022] 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.

[0023] A magnetic gap 29 is formed in the radial direction 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 B is formed by "permanent magnet 11 → pole piece portion 12 → magnetic gap 29 → coil side yoke material 15 → permanent magnet side yoke material 14". C 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 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, by measuring the 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. The servo circuit is made up 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 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 determined, as described above. [Prior art documents] [Patent documents]

[0024] [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]

[0025] As mentioned above, the capacitance C detected by the servo type acceleration sensor is determined by the size of the gap 30 formed between the movable electrode 24 and the fixed electrode 25. As is well known, when the area of ​​two parallel-placed conductive plates is A, the gap is d, and the dielectric constant is ε0, the capacitance C is

[0026]

number

[0027] In other words, the larger the electrode area A and the narrower the inter-electrode gap d, the larger the capacitance C and the improved sensor output (sensitivity).However, the electrode area A and inter-electrode gap d have a significant effect on the dynamic characteristics of the sensor due to the damping effect caused by the air viscosity present in the gap.

[0028]

number

[0029] In the above equation, D is the damping constant (attenuation coefficient) and μ is the viscosity coefficient of air. Therefore, if the electrode area A is increased and the gap d is narrowed in order to increase the capacitance C, the damping constant D increases in proportion to the square of the electrode area A and inversely proportional to the cube of the gap d. Therefore, from equations (5) and (6), the electrode area A and the electrode gap d must be set to appropriate values ​​(d=d0) taking into account both the sensor sensitivity and the sensor dynamic characteristics.

[0030] Figure 34 shows the problems encountered in the mass production process of conventional acceleration sensors. In the mass production process of conventional acceleration sensors, the fixed electrode 25 needs to be corrected (Δd → 0) to bring the inter-electrode gap d closer to the target value d0, and the gap adjustment is required to correct the inclination angle of the gap (Δθ → 0). The reason that the inclination angle correction of the inter-electrode gap (Δθ → 0) is required is because if the gap is non-uniform in the circumferential direction, it restricts the stroke of the movable electrode 24, i.e., the upper limit of the allowable acceleration.

[0031] As shown in the specific structure of a conventional acceleration sensor, the movable section, including the movable electrode 24, is manufactured by bonding many components together. In Figure 33, the components that make up the movable section are the movable electrode 24, force coil 16a, calibration coil 16b, coil bobbin 17, and coil bobbin support members 18 and 19. The reason for using the bonding method is that the inertial mass of the movable section must be as light as possible to achieve sensor performance with a wide frequency band and high response. Therefore, the machining accuracy of each individual component, the thickness of the adhesive, and other error factors accumulate, limiting the accuracy of the perpendicularity of the movable electrode surface relative to the axis.

[0032] In the mass production assembly process of conventional acceleration sensors, the absolute value of the inter-electrode gap and the inclination angle of the gap could only be determined by observing the slit (gap) between the electrodes from the outer surfaces of the two electrodes using optical means such as a high-magnification camera. However, the practical measurement limit of the optical gap adjustment method was a slit width of d = 20 to 30 μm. The difficulty of adjusting the inter-electrode gap described above was a major issue that prevented improvements in the sensitivity of servo-type acceleration sensors, and was also a major factor in reducing yield and reliability during mass production. [Means for solving the problem]

[0033] Therefore, a servo type vibration detector according to a first aspect of the present invention comprises a fixed member, a movable member provided so as to be movable in a predetermined direction relative to the fixed member, an elastic member supporting the movable member so as to be disposed with a gap therebetween, a displacement detection unit which detects displacement of the movable member in the predetermined direction, and drive means which generates a force to return 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, and the displacement detection unit includes a movable-side electrode provided on one axial end face of the movable member, and a drive means for generating a force to return the movable member to its original position. a fixed-side electrode disposed opposite the movable-side electrode, and a fixed-side electrode support member that supports the fixed-side electrode or is integrated with the fixed-side electrode, and is configured to detect the capacitance formed in the gap between the movable-side electrode and the fixed-side electrode, an opening to which a gap adjustment means for the gap between the movable-side electrode and the fixed-side electrode can be applied is formed in the fixed member or the fixed-side electrode support member, and both axial ends of the movable member are release axes, or the end opposite the movable-side electrode is a release axis.

[0034] That is, the present invention applies an actuator structure that can open both ends of the shaft of the movable part or the end of the movable member opposite the movable electrode. By combining this actuator structure with a gap adjustment means that utilizes the opening, it becomes possible to adjust the gap between the electrodes with high precision, without being limited to optical means.

[0035] The servo-type vibration detector of the second invention of the present application is structured so that the movable member can be grasped from the outside or its axial movement can be restricted using the release shafts at both ends of the axial direction or the release shaft at the end of the movable member opposite the movable side electrode.

[0036] In other words, the present invention can fix the movable member without applying an external moment to the movable member by using a support method in which both ends of the movable member are pressed from the outside on the same axis. Alternatively, the same effect can be obtained by holding the end of the movable member opposite the movable electrode in all axial directions (X-axis, Y-axis, Z-axis). As a result, even if the movable electrode is slightly tilted, the tilted state can be maintained while a gap adjusting means using a shim, spacer, or the like can be applied between the electrodes.

[0037] The servo-type vibration detector according to the third invention of the present application is characterized in that the gap adjustment means is a gap adjustment member including a shim or spacer, and the opening is formed so that this gap adjustment member can be inserted into the gap between the movable electrode and the fixed electrode.

[0038] That is, the present invention forms an opening divided into at least three parts in the circumferential direction so that the inter-electrode gap can be adjusted uniformly in the circumferential direction by a gap adjusting member such as a shim or spacer inserted through the opening. Alternatively, the opening is formed in a shape that allows the insertion of a shim having a width close to the diameter of the electrode and a gap in the center that is equal to or larger than the outer diameter of the support rod.

[0039] In a servo type vibration detector according to a fourth aspect of the present invention, a through hole is formed in the center of the fixed electrode, into which a small diameter member can be inserted from the outside.

[0040] In other words, in the sensor structure of the present invention, a through hole is formed in the center of the fixed electrode so that a support rod that presses the movable member can be inserted. Therefore, the movable member can be fixed from both the left and right ends. Because the through hole can be small in diameter, it does not have a significant effect on the capacitance, which is determined by the total area.

[0041] The servo type vibration detector according to the fifth invention of the present application is one in which a fastening portion for fixing the fixed electrode support member to the fixed member is provided on the fixed member or on the outer peripheral surface of the fixed electrode support member.

[0042] That is, with the sensor structure of the present invention, the fixed electrode support member can be screwed radially using the fastening portion while maintaining a predetermined inter-electrode gap. Furthermore, because the fastening portion is provided on the outer peripheral surface of the sensor body, a sufficiently large working space is provided, making fastening easy. Furthermore, even if left and right support rods are provided on both end surfaces of the sensor body, or a jig is provided to press the fixed electrode support member against the movable electrode, the screw fastening operation is not hindered. A specific example of such a configuration is to insert a gap adjustment sheet into the inter-electrode gap as a means for maintaining a predetermined inter-electrode gap, and to maintain the fixed electrode pressed against the movable electrode, use an axial fastening bolt that fastens the fixed ring and the coil side yoke material. Instead of this method, the state in which a predetermined inter-electrode gap is maintained may be measured by optical means using the opening, and the fixed electrode may be screwed in a state in which the axial position and angle of the fixed electrode are constrained. Either method allows the sensor structure of the present invention to achieve inter-electrode gap adjustment without using adhesive.

[0043] The servo type vibration detector of the sixth invention of the present application is provided with a fastening portion on the fixed member for fixing the main body of the servo type vibration detector to the outside, and the fastening portion is formed so that the main body of the servo type vibration detector can be fastened in an engaged state to an external member so that the position of the axis of the movable member is determined.

[0044] That is, the servo type vibration detector main body of the present invention is fixed to the sensor main body fixing member using the fastening portion. By installing this sensor main body fixing member on the base, the movable member can be fixed and supported from both ends by support rods arranged on the left and right sides of the base. Furthermore, the main body of the servo type vibration detector is fixed in an engaged state to the sensor main body fixing member. Since the axis of the movable member can be aligned with the axis of the support rods arranged on the base, moment loads due to eccentricity of the axes of the left and right support rods can be reduced.

[0045] The servo-type vibration detector of the seventh invention of the present application further comprises a permanent magnet arranged on the movable member or the fixed member, a coil arranged on the member opposite the permanent magnet and an elastic member supporting the movable member near both ends of the movable member's axis, and a closed-loop magnetic circuit formed by the movable member, a gap between the movable member and the fixed member, the fixed member and the permanent magnet, and is characterized in that the driving means is configured to generate an electromagnetic force that moves the movable member in the axial direction by the closed-loop magnetic circuit, and is configured so that magnetic flux flows in the gap between the movable member and the fixed member near both ends of the movable member's axis.

[0046] That is, the servo-type vibration detector of the present invention is equipped with the driving means using electromagnetic force, and the magnetic circuit is configured to have gaps in which magnetic flux flows between the movable member and the fixed member near both ends of the movable member's shaft. Also, disk springs supporting the movable member are provided on the left and right. As a result, both ends of the movable member's shaft are open, making it possible to adjust the gap between the electrodes using a gap adjustment member.

[0047] The servo-type vibration detector of the eighth invention of the present application is such that the coil is fixed to the fixed member, and the movable member is composed of the permanent magnet and a movable-side yoke material that connects the permanent magnet to a magnetic path.

[0048] That is, the present invention shows the basic configuration of an MM (moving magnet) type acceleration sensor in which a permanent magnet is arranged on the movable member side and a coil is arranged on the fixed member. The closed-loop magnetic circuit formed among the permanent magnet, the movable member, and the fixed member has magnetic gaps in at least two locations, left and right, between both ends of the movable member side and the fixed member. As a result, both ends of the movable member's shaft are open, and the electrode gap adjustment method of the present invention can be applied.

[0049] The servo-type vibration detector of the ninth invention of the present application is characterized in that the displacement detection unit is configured as a differential sensor having one pair of the movable side electrode and the fixed side electrode at each axial end of the movable member, and detects the difference in two capacitances formed between each pair of the movable side electrode and the fixed side electrode, and an opening into which the gap adjustment member can be inserted is provided at each axial end.

[0050] The servo-type vibration detector of the tenth invention of the present application is characterized in that the permanent magnet is fixed to the fixed member, the coil is arranged in the gap between the movable member and the fixed member and fixed to the movable member, and further comprises an inner yoke material connecting the permanent magnet to a magnetic path, an outer yoke material arranged via a radial gap with the permanent magnet or the inner yoke material, and an elastic member supporting the coil, and the closed loop magnetic circuit is formed by the permanent magnet, the inner yoke material, the gap between the movable member and the fixed member, and the outer yoke material, a through hole is formed in the permanent magnet and / or the inner yoke material, and the movable electrode is formed with an extension axis extending to the through hole.

[0051] [Assembly method] A method for assembling a servo type vibration detector according to an eleventh aspect of the present invention includes a fixed member, a movable member provided so as to be movable in a predetermined direction relative to the fixed member, an elastic member supporting the movable member so as to be disposed with a gap between the movable member and the fixed member, a displacement detection unit detecting a displacement of the movable member in the predetermined direction, and drive means generating a force to return the movable member to the original position when the displacement detection unit detects a relative displacement of the movable member from the original position, wherein the displacement detection unit includes a movable side electrode provided on one axial end face of the movable member, a fixed side electrode provided opposite to the movable side electrode, and a fixed side electrode supporting the fixed side electrode or integrated with the fixed side electrode. a support member, and a gap adjustment member inserted into the gap formed between the movable electrode and the fixed electrode while the movable electrode is temporarily fixed to the fixed member, the fixed electrode is moved relative to the movable electrode toward the movable electrode so that the gap between the movable electrode and the fixed electrode becomes a predetermined gap, the fixed electrode is then fixed to the fixed member, the temporary fixation of the movable member to the fixed member is released, and the gap adjustment member is removed from the gap between the movable electrode and the fixed electrode.

[0052] That is, in the present invention, even if the movable electrode surface is installed at an angle with respect to the axis, the movable electrode is temporarily fixed to the fixed member, and by fixing the fixed electrode with the gap adjusting member inserted between the electrodes, the inter-electrode gap in the circumferential direction and the axial direction becomes the thickness of the gap adjusting member, and as a result, the inter-electrode gap can be set with a high accuracy that exceeds the measurement limit of optical means.

[0053] The assembly method for a servo-type vibration detector according to the twelfth invention of the present application comprises gripping the movable member against the fixed member by a pressing means that presses one axial end face of the movable member against the other axial end face of the movable member.

[0054] In other words, the present invention uses a support method that presses both the left and right ends of the movable member on the same axis, thereby fixing the movable member without applying an external moment to the movable member. Therefore, even if the movable electrode is slightly tilted, the movable member can be mechanically fixed while maintaining that tilted state.

[0055] A method for assembling a servo type vibration detector according to a thirteenth aspect of the present invention is a method for assembling a servo type vibration detector, in which a fine feed mechanism is used to press both end surfaces of the movable member with the tip of the output shaft of the fine feed mechanism. That is, in the present invention, the movable member is fixed so that the axial position of the movable member is maintained in the initial state by using a fine feed mechanism such as a micrometer as the pressing means.

[0056] The method of assembling a servo type vibration detector according to the fourteenth aspect of the present invention measures the capacitance of the gap to detect the displacement of the movable member pressed by the output shaft of the fine feed mechanism. That is, the present invention utilizes the capacitance type displacement sensor function of the servo type vibration detector itself to measure the amount of movement of the tip of the output shaft of the fine feed mechanism with high accuracy of 1 μm or less.

[0057] The assembly method for the servo-type vibration detector according to the fifteenth invention of the present application involves measuring the capacitance C=C0 when the gap in the gap portion is temporarily set, bringing the output shaft of the first fine feed mechanism R close to one end face R of the movable member, stopping the movement of the first fine feed mechanism R when the capacitance becomes C>C0, bringing the output shaft of the second fine feed mechanism L close to a position where it can move to the opposite end face L of the movable member, pressing the movable member, and then inserting the gap adjustment member into the gap portion between the movable side electrode and the fixed side electrode.

[0058] That is, in the present invention, at the stage where the electrode gap is provisionally set, the capacitance C = C0 is measured in advance, and the position where the tip of the output shaft of the fine feed mechanism R starts to contact the movable member is set by using the change in the capacitance C > C0. Then, the output shaft of the fine feed mechanism L is moved to press the movable member from both sides, so that the gap adjusting member can be inserted.

[0059] The assembly method of the servo type vibration detector according to the 16th invention of the present application measures the capacitance C = C0 at the stage where the gap of the void is provisionally set, brings the output shaft of the first fine feed mechanism R close to one end face R of the movable member, and stops the movement of the first fine feed mechanism R at the timing when the capacitance becomes C > C0. Then, the output shaft of the first fine feed mechanism R is moved away from the end face R again, and the minute movement of the first fine feed mechanism R is stopped at the timing when the capacitance becomes C = C0. The output shaft of the second fine feed mechanism L is brought close to one end face L of the movable member, and the movement of the second fine feed mechanism L is stopped at the timing when the capacitance becomes C < C0. Then, the output shaft of the second fine feed mechanism L is moved away from the end face L again, and the minute movement of the second fine feed mechanism R is stopped at the timing when the capacitance becomes C = C0. The first fine feed mechanism R and the second fine feed mechanism L are simultaneously moved minutely in the direction of both end faces to press the movable member from both end faces, and then the gap adjusting member is inserted into the void.

[0060] That is, in the present invention, at the stage where the electrode gap is provisionally set, the capacitance C = C0 is measured in advance, and after detecting the position where the tip of the output shaft of the fine feed mechanism R starts to contact the movable member by using the change in capacitance C > C0, the output shaft of the fine feed mechanism R is stopped after being displaced minutely away from the end face R again. Similarly, the output shaft of the fine feed mechanism L is stopped after being displaced minutely away from the end face L. At this stage, the movable member is in an unconstrained state that can be called "quasi-rigid body". Next, if the fine feed mechanisms R and L are simultaneously moved minutely in the direction of both end faces, the movable member is constrained from both end faces, so that the gap adjusting member can be inserted.

[0061] In the method for assembling a servo type vibration detector according to the seventeenth aspect of the present invention, the means for fixing the fixed electrode to the fixed member uses screw fastening, which allows for disassembly and reassembly.

[0062] That is, in the final stage of the electrode gap adjustment process, the present invention uses screws, which allow for disassembly and reassembly, as a means for fixing the fixed electrode to the fixed member without using adhesive. By applying the present invention, if a defect in the quality of a product is found in the basic performance evaluation stage or reliability evaluation stage of the product, it becomes possible to go through the basic cycle of "disassembling the sensor body → investigating the cause → taking measures → reassembly → reevaluation." Since products in which defects are found can be reused, the yield can be significantly improved.

[0063] The assembly method for a servo-type vibration detector according to the 18th invention of the present application involves screwing the fixed electrode to the fixed member, evaluating the quality of the servo-type vibration detector body, and then adhesively fixing the fixed electrode to the fixed member.

[0064] That is, in the present invention, the fixed electrode is fastened to the fixing member by screw fastening, and after completing a basic performance evaluation or reliability evaluation of the product and confirming that the mass production specifications are reliably satisfied, the fixed electrode is adhesively fixed to the fixing member. An adhesive may be used at the screw fastening location to prevent the screws from loosening. Alternatively, a separate location may be provided for adhesively fastening both members.

[0065] A method for assembling a servo type vibration detector according to a nineteenth aspect of the present invention is characterized in that a displacement sensor for measuring the amount of movement of the fine feed mechanism is installed externally.

[0066] A method for assembling a servo type vibration detector according to a twentieth aspect of the present invention is characterized in that the displacement sensor is an air micrometer installed at the tip of the output shaft of the fine feed mechanism.

[0067] The method for assembling a servo-type vibration detector according to the 21st invention of the present application is characterized in that the air micrometer is used both to measure the displacement between its tip and the movable member and as a means for pressing against the movable member.

[0068] The assembly method for a servo-type vibration detector according to the 22nd invention of the present application is characterized in that the servo-type vibration detector main body is fixed to the floor surface so that the axis of the movable member and the axis of the output shaft of the fine feed mechanism are on the same line.

[0069] The assembly method for a servo-type vibration detector according to the 23rd invention of the present application is characterized in that when the screw fastening is used to fix the fixed side electrode to the fixed member, the tip of the screw is held in a state where it is embedded into the opposing surface by plastic deformation. [Effects of the Invention]

[0070] The servo-type vibration detector of the present invention employs an actuator structure that can open both ends of the axis of the movable part, or the end of the movable member opposite the movable electrode. Therefore, by combining this actuator structure with a gap adjustment means that utilizes the opening, high-precision electrode gap adjustment is possible without being limited to optical means. [Brief explanation of the drawings]

[0071] [Figure 1a] 1A and 1B show an example of an MM servo type acceleration sensor according to a first embodiment of the present invention, and FIG. 1A is a side view of FIG. 1B. [Figure 1b] 1B is a cross-sectional view taken along the line AA in FIG. 1A, showing an example of an MM servo acceleration sensor according to a first embodiment of the present invention. [Figure 1c] 1C is a cross-sectional view of an example of an MM servo type acceleration sensor according to the first embodiment of the present invention, and FIG. 1C is a cross-sectional view of FIG. 1B. [Figure 1d] 1D is a side view of a rear disk showing an example of an MM servo type acceleration sensor according to the first embodiment of the present invention. FIG. [Figure 2] This is a diagram showing that in the conventional MC system, adjustment of the electrode gap is limited to optical means. [Figure 3] This is a diagram showing that in the MM type of the present invention, both ends of the movable part can be clamped to adjust the gap between the electrodes. [Figure 4a] 4A is a general view showing the arrangement of the acceleration sensor main body and the gap adjusting jig, illustrating an outline of the electrode gap adjusting jig of the MM servo acceleration sensor according to the first embodiment of the present invention. FIG. [Figure 4b] FIG. 4b shows an outline of an electrode gap adjustment jig for an MM servo acceleration sensor according to the first embodiment of the present invention, in which the moving part of the acceleration sensor is clamped between left and right support rods and a shim is inserted between the electrodes. [Figure 5] FIG. 10 is a diagram showing the provisional setting of capacitance in Step 1 of the gap adjustment process. [Figure 6] FIG. 10 is a diagram showing the fixing of the right end of the sensor movable part in Step 2 of the gap adjustment process. [Figure 7] FIG. 10 is a diagram showing fixing of the left end of the sensor movable part in Step 3 of the gap adjustment process. [Figure 8] FIG. 10 is a diagram showing the setting of the electrode gap using a shim in Step 4 of the gap adjustment process. [Figure 9] This is a diagram showing how the fixing ring is glued in place in Step 5 of the gap adjustment process. [Figure 10] 10 is a diagram showing the completion of the gap adjustment process between electrodes in Step 6 of the gap adjustment process. [Figure 11] FIG. 6 is a front cross-sectional view of an MM servo type acceleration sensor according to a second embodiment of the present invention. [Figure 12] FIG. 10 is a diagram showing the setting of the electrode gap using a shim in Step 1 of the gap adjustment process. [Figure 13] FIG. 10 is a diagram showing the fixing of the fixing ring with radial fastening bolts in Step 2 of the gap adjustment process. [Figure 14] This is a diagram showing the removal of shims and other components from the sensor body in Step 3 of the gap adjustment process. [Figure 15] A diagram showing the disassembled product. [Figure 16a] This is a partial improvement of the second embodiment of the present invention, and FIG. 16a is a front cross-sectional view of the vicinity of the movable electrode. [Figure 16b]This is a partial improvement of the second embodiment of the present invention, and FIG. 16b is an exploded view. [Figure 17a] 17A is a side view of FIG. 17 showing an example of an MM servo type acceleration sensor according to a third embodiment of the present invention; FIG. [Figure 17b] 17B is a cross-sectional view taken along the line AA in FIG. 17A, showing an example of an MM servo type acceleration sensor according to a third embodiment of the present invention. [Figure 18a] 18A is a diagram showing an outline of an inter-electrode gap adjusting jig for an MM servo acceleration sensor according to a third embodiment of the present invention, and FIG. 18A is an overall view showing the arrangement of the acceleration sensor main body and the gap adjusting jig. FIG. [Figure 18b] FIG. 18b is a diagram showing an outline of an electrode gap adjustment jig for an MM servo acceleration sensor according to a third embodiment of the present invention, in which FIG. 18b shows that the movable part of the acceleration sensor is clamped between left and right support units and a shim is inserted between the electrodes. [Figure 19] This is a diagram showing how both the left and right ends of the sensor's moving part are fixed in Step 1 of the gap adjustment process. [Figure 20] FIG. 10 is a diagram showing the setting of the electrode gap using a shim in Step 2 of the gap adjustment process. [Figure 21] FIG. 10 is a diagram showing the fixing of the fixed electrode with a temporary fastening screw in Step 3 of the gap adjustment process. [Figure 22] This is a diagram showing how the fixing ring is glued in place in Step 4 of the gap adjustment process. [Figure 23] 10 is a diagram showing the completion of the gap adjustment process between electrodes in Step 5 of the gap adjustment process. [Figure 24] 24A and 24B are supplementary views of the first embodiment, in which FIG. 24A is a view taken along the line AA in FIG. 24B, and FIG. 24B is a cross-sectional view. [Figure 25] 10A and 10B are diagrams showing the configuration of a jig for aligning the axis of a movable member with the axis of a support rod in the electrode gap adjustment process; [Figure 26a] 26a is a side view of FIG. 26b, supplementing the first embodiment. FIG. [Figure 26b] FIG. 26b is a cross-sectional view supplementing the first embodiment. [Figure 27] FIG. 1 is a model diagram showing the mechanical basis for electrode gap adjustment. [Figure 28] FIG. 10 is a front cross-sectional view of an MC servo type acceleration sensor according to a fourth embodiment of the present invention. [Figure 29] 29(a) and 29(b) show a method for adjusting the gap of the sensor of this embodiment, in which FIG. 29(a) is a front cross-sectional view during gap adjustment, and FIG. 29(b) is an enlarged view of the dashed circle in FIG. 29(a). [Figure 30] FIG. 10 is a front cross-sectional view of a differential servo type acceleration sensor according to a fifth embodiment of the present invention. [Figure 31] A model diagram of a conventional active vibration isolation table. [Figure 32] A model diagram showing the basic configuration and detection principle of a capacitive acceleration sensor. [Figure 33] FIG. 10 is a front cross-sectional view showing a specific structural example of a conventional linear motion acceleration sensor. [Figure 34] FIG. 1 is a diagram showing a problem in the mass production process of a conventional acceleration sensor. [Figure 35] A diagram showing why it is difficult to disassemble and reassemble a conventional servo-type acceleration sensor. DETAILED DESCRIPTION OF THE INVENTION

[0072] [Background to the invention] In addition to adjusting the gap between the electrodes, the servo-type acceleration sensor described above (Figure 33) also faced production technology challenges related to yield and reliability during mass production. These challenges stem from the basic operating principle of the moving coil (hereafter referred to as the MC type), in which sensor signals must be transmitted between the coil (16a, 16b), which is the moving part, and the fixed side due to the movement of the coil. Conductive paths for transmitting multiple signals connecting the moving part and the fixed side must be formed using elastic members (disk-shaped springs 20, 21) connecting the two. As a result, it requires (1) dividing the disk-shaped springs to form multiple conductive paths, (2) insulating the signal lines, and (3) complex production methods involving the soldering of ultra-fine wires, which are major factors that reduce yield and reliability during mass production.

[0073] The present inventors have proposed and are currently filing a patent application for a moving magnet type (hereafter referred to as MM type) servo acceleration sensor, which does not require ultra-fine wire processing by fixing the coil and moving the permanent magnet. However, there has never been a precedent for an MM type servo acceleration sensor. The reason for this is thought to be that there was a fixed idea (blind spot) that could be called an implicit assumption that "the inertial mass of the moving part of the MM type increases, making the transmission characteristics and responsiveness in the high frequency range disadvantageous." The previously proposed invention exploited this "blind spot" through the following ingenuity. That is, (1) Magnetic circuit configuration that reduces the weight of the moving part (moving component) (2) Magnetic pole shape that reduces the effects of leakage flux (3) The electromagnet structure has been designed to increase the coil volume, increasing the generated force and suppressing heat generation. Find a coil specification (number of turns, wire diameter) that can achieve both of these. By doing so, we were able to eliminate the weaknesses of the MM type and, by taking advantage of the features of the MM type, achieve sensor performance that far surpasses that of the MC type.

[0074] In addition to the above-mentioned features of the MM servo acceleration sensor, the present invention focuses on the fact that both ends of the movable member can be made open. In other words, if the movable member can be fixed and supported by utilizing the "open structure at both ends of the movable shaft," it may be possible to adjust the gap between electrodes with higher precision, without being limited to optical measurement means. This was the origin of the idea behind the present invention.

[0075] [First embodiment] (hereinafter referred to as MM formula) 1 shows an example of an MM servo acceleration sensor according to embodiment 1 of the present invention. The electrode gap adjustment method in this embodiment utilizes changes in the capacitance of the acceleration sensor itself to detect the axial position of the sensor's moving part.

[0076] Figure 1a is a side view of Figure 1b, Figure 1b is a cross-sectional view taken along line AA in Figure 1a, Figure 1c is a cross-sectional view taken along line BB in Figure 1b, and Figure 1d is an external view of the spiral disc spring alone. As mentioned above, the MM servo acceleration sensor is a patent application pending by the inventors, and has been further improved to allow for highly accurate electrode gap adjustment.

[0077] [1] Sensor structure of this embodiment [1-1] Actuator section In Figure 1b, 100 denotes the sensor body. 101 denotes a front permanent magnet, 102 denotes a rear permanent magnet, and 103 denotes a pole piece (movable yoke material). As shown in Figure 1c, both the front and rear permanent magnets are composed of multiple segment-type permanent magnets magnetized in the radial direction and are attached to the pole piece 103. The radial magnetization directions of the front permanent magnet 101 and the rear permanent magnet 102 are opposite. 104 and 105 denote cylindrical gaps formed on the left and right sides of the pole piece 103 to reduce its weight. 106 denotes a front spiral disc spring (hereinafter referred to as the front disc), and 107 denotes a rear spiral disc spring (hereinafter referred to as the rear disc). As shown in Figure 1d, the front and rear discs are formed with spiral-shaped ridges 107a and grooves 107b. The front-side disk 106 also serves as a signal transmission path that transmits the electrical signal from the movable electrode to an external control circuit. In this embodiment and in the following embodiments, the spring shape is not limited to this spiral curve. Based on the characteristics required of the acceleration sensor, a spring structure and specifications that achieve low rigidity and low resonant frequency can be selected. For example, a well-known arc spring can also be used. Reference numeral 108 denotes the movable electrode supported by the front-side disk, 109 denotes a coil-side yoke material (housing), 110 denotes a coil bobbin, 111 denotes a front-side force coil and a calibration coil, and 112 denotes a rear-side force coil and a calibration coil. The winding directions of the coils 111 and 112 are opposite. Reference numeral 113 denotes a magnetic gap formed between the inner circumferential surface of the coil bobbin 110 and two permanent magnets. Reference numeral 113a denotes a front-side magnetic gap, and 113b denotes a rear-side magnetic gap. As shown by the chain arrow, a closed loop magnetic circuit B is formed by "permanent magnet 102 → coil side yoke material 109 → permanent magnet 101 → pole piece part 103 → permanent magnet 102". MThe front-side disc 106 serves both as support for the movable portion and as a conductive path for detecting capacitance. In order to detect minute capacitance signals between the movable-side electrode 108 and the fixed-side electrode (described later), the conductive path connecting the movable-side electrode 108 to the outside is completely electrically insulated. That is, the front-side disc 106 is fastened to the coil-side yoke material 109 by bolts 115 via an outer ring 114. The outer ring 114 is made of a non-conductive material, and the front-side disc 106 and the outer ring 114 are fixed in advance with an adhesive. In addition, the bolt hole diameter formed in the front-side disc 106 is larger than the bolt diameter, so that the bolt 115 and the front-side disc 106 are electrically insulated. The movable-side electrode 108 is adhesively fixed to the front-side disc 106 at a joint 116. In addition, the center of the movable-side electrode 108 is adhesively fixed to the end face of the pole piece portion via a non-conductive material 117. Eddy currents occur in the pole piece section and the coil-side yoke material, but the electrical insulation measures (non-conductive materials 114, 117) prevent the capacitance signal between the two electrodes (movable side and fixed side) from being affected by these eddy currents. Non-conductive materials that can be used include inorganic solid insulating materials such as mica, porcelain (ceramics), glass, and polyimide (super engineering plastic). To control the current flowing through the two force coils 111, 112, the lead wires from these coils pass through the coil-side yoke material 109 and are connected to an external control circuit (not shown).

[0078] Reference numeral 118 denotes the rear end face of the pole piece portion 103, which is a disk fastening member fastened by a bolt 119, and 120 denotes a rear end face portion located in the center of this disk fastening member. Reference numeral 121 denotes a front end face portion located in the center of the movable electrode 108.

[0079] The movable part (movable member) of this embodiment is composed of two permanent magnets 101 and 102, a pole piece 103, a movable electrode 108, and a disk fastening member 118. The fixed part is composed of a coil bobbin 110 housing each coil and a coil-side yoke material 109. In this acceleration sensor, the driving mechanism for the movable part is a previously proposed moving magnet (MM) 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 the force coils 111 and 112 housed in the coil bobbin 110, a reaction force of the Lorentz force is generated, which moves the movable part axially.

[0080] The MM type sensor of this embodiment is a closed loop magnetic circuit B M The permanent magnets and coils are arranged so as to form two independent magnetic gaps 113a, 113b on the left and right sides of the shaft. Disc springs that support the moving part are also provided at two locations 106, 107 on the left and right sides. As a result, the moving part including the pole piece part 103 has an open structure at both ends of the shaft.

[0081] [1-2] Displacement detection unit Reference numeral 122 denotes the fixed electrode, 123 an insulating ring, and 124 a fixed ring (fixed electrode support member). The fixed electrode 122 is supported against the fixed ring with the insulating ring interposed therebetween. Reference numeral 125 denotes an adhesive application portion for fixing the fixed ring 124 to the coil side yoke member 109 (fixed member), and 126 denotes a fastening bolt for temporarily fixing the fixed ring 124 and the coil side yoke member 109. Reference numeral 127 denotes a through hole formed in the center of the fixed electrode 122. Reference numeral 128 denotes a gap between the fixed electrode 122 and the movable electrode 108.

[0082] In FIGS. 1a and 1b, reference numeral 129 denotes an opening for inserting a gap adjustment sheet (described later) into the gap (inter-electrode gap) 128. In this embodiment, the openings 129 are formed at three locations (dashed lines 129a, 129b, and 129c) around the circumference of the coil-side yoke member (fixing member) 109. Reference numerals 208a, 208b, and 208c denote gap adjustment sheets (dashed lines) that are gap adjustment members. In a gap adjustment step (Step 4) described later, the gap adjustment sheets are inserted into the gap 128 through the openings. This adjustment process corrects the inter-electrode gap d to approach the target value d0 (Δd→0) and corrects the gap inclination angle (Δθ→0). In FIG. 1b, reference numeral 131 denotes a screw fastening portion for fastening the sensor main body 100 to a sensor main body fixing member (described later).

[0083] [2] Main points of the present invention Figure 2 shows the conventional MC type, in which adjustment of the gap between electrodes is limited to optical means, and Figure 3 shows the MM type of the present invention, in which adjustment of the gap between electrodes is not limited to optical means by pressing both ends of the movable part to fix the movable part. Below, we will explain the focus of the present invention based on a comparison between the conventional MC type (Figure 2) and the MM type of the present invention (Figure 3).

[0084] (1) Conventional MC system As shown in an example of the conventional MC structure (Figures 33 and 34), the lightweight moving part (coil 16 and coil bobbin 17) with the movable electrode 24 attached is housed so as to encase the large-mass fixed part (permanent magnet 11 and pole piece 12). The reason for adopting this structure is that, as mentioned above, to obtain sensor performance with a wide frequency band and high responsiveness, the inertial mass of the moving part must be as light as possible. In this structure, there is no way to mechanically fix the moving part while maintaining the slight tilt of the movable electrode 24 (Figure 34) during electrode gap adjustment. Therefore, to adjust the electrode gap in a conventional MC system, the interelectrode gap (slit) is observed from the outer surface using optical means (e.g., a high-definition microscope). In other words, one must choose a method such as adjusting the tilt of the fixed electrode so that the interelectrode gap (gap 30) is uniform in the circumferential direction according to the tilt of the movable electrode 24.

[0085] (2) In the case of the MM system of the present invention In the case of the MM type of the present invention, it is noted that both ends of the moving part can be made open. The reason why both ends of the moving part can be made open is that, as mentioned above, the MM type sensor of this embodiment has a closed loop magnetic circuit B M This is because the permanent magnets and the coils are arranged so as to have two independent magnetic gaps 113a and 113b on the left and right sides.

[0086] Figure 3 shows the state in which both ends of this movable part are pressed by an axial force F applied by the front support rod 131 and the rear support rod 132 during electrode gap adjustment. The movable part is composed of two permanent magnets 101 and 102, a pole piece 103, a movable electrode 108, and a disk fastener 118. The spherical tips of the two support rods 131 and 132 are in point contact with the front end surface 121 and the rear end surface 120. In other words, by pressing both ends of the movable part on the same axis, the movable part can be fixed without applying an external moment to the movable part. Therefore, in the MM-type electrode gap adjustment process of the present invention, even if the movable electrode 108 is slightly tilted, the movable part can be mechanically fixed while maintaining that tilted state. In other words, it is expected that gap adjustment sheets (gap adjustment members) such as shims, shim rings, and spacers used for gap adjustment in precision machinery can be applied.

[0087] If one or both electrodes are made convex, for example, a gap adjusting member can be inserted where the distance between the electrodes is large to adjust the gap. In this case, the gap adjusting member does not have to be sheet-shaped, and can be a block-shaped member with sufficient thickness (not shown).

[0088] (3) Why both ends of the MM-type moving part can be open from the magnetic circuit Below, we will consider the characteristics of the MM type of the present invention by comparing it with closed loop magnetic circuits. In the MM type, a permanent magnet is placed in the moving part (pole piece part 103), and the coil is placed on the outer periphery so as to enclose the permanent magnet. The reason why the reverse placement is inappropriate is that it increases the inertial mass of the moving part. As shown in Figure 3, where a permanent magnet is placed in the moving part, closed loop magnetic circuit B MThe magnetic gaps 113a and 113b must be provided at two locations, one on the left and one on the right. The disk springs 106 and 107 supporting the moving part (pole piece part 103) are also provided at two locations, one on the left and one on the right. As a natural consequence, both ends of the moving part have an open structure (open shaft). As mentioned above, the MM type can solve the issues of the MC type related to processing ultra-fine wires, but its weakness is the increased inertial mass of the moving part. However, by eliminating the weaknesses of the MM type through a previously applied patent, a solution has emerged to solve another major issue in production technology, namely, adjusting the gap between the electrodes. In other words, the effect of the present invention on adjusting the gap between the electrodes during mass production is a newly discovered feature of the MM type of the present invention.

[0089] [3] Electrode gap adjustment process The electrode gap adjustment method in this embodiment utilizes the change in capacitance possessed by the sensor itself to detect the axial position of the sensor moving part.

[0090] [3-1] Overall view of the gap adjustment jig Figure 4 shows an outline of an inter-electrode gap adjustment jig for an MM-type servo acceleration sensor according to embodiment 1 of the present invention. Figure 4a is an overall view showing the arrangement of the acceleration sensor main body (chain line A) and the gap adjustment jig. Figure 4b shows an example of the gap adjustment process, showing that a shim is inserted into the inter-electrode gap as a gap adjustment means (Step 4, described below) while the movable part of the acceleration sensor is pressed by left and right support rods.

[0091] In FIG. 4a, 201a and 201b are front and rear micrometers (fine feed mechanisms). 202a and 202b are front and rear micrometer fixing parts, and 203 is a base. 204a and 204b are front and rear support rods attached to the ends of the output shafts of the front and rear micrometers. 205 is a sensor main body fixing member fixed to the base 203. In FIG. 4b, the sensor main body 100 is fastened to the sensor main body fixing member 205 with bolts 206.

[0092] [3-2] Example of gap adjustment process (part 1) Step 1: Temporary capacitance setting In FIG. 5, 207 is shim A, which is inserted into the gap formed by the coil side yoke material 109 and the fixed ring (fixed side electrode support member) 124 with the bolt 126 open, and then the bolt 126 is fastened. At this stage, the accuracy of the tilt angle of the fixed side electrode 122 has not yet been adjusted. Therefore, the thickness t of the shim A A is sufficiently thick compared to the gap of the void portion 128 at this stage, and in the embodiment, for example, t A = 100 μm. In this state of Step 1, the capacitance C = C0 of the sensor is measured.

[0093] Step 2: Fix the right end of the sensor moving part In Figure 6, while measuring the capacitance C = C0 of the sensor, the rear support rod 204b is slightly moved to the left. When the capacitance becomes C > C0, the movement of the rear support rod is stopped. At this stage, the spherical tip of the rear support rod is in point contact with the rear end surface 120 of the pole piece portion 103.

[0094] Step 3 Fix the left end of the sensor moving part In Figure 7, the front support rod 204a is slightly moved to the right. When the spherical tip of the front support rod comes into contact with the front end surface 121 of the pole piece portion 103, the front support rod becomes immovable, so the operation is stopped at this stage. By the above steps 2 and 3, the sensor moving part including the pole piece portion is clamped.

[0095] Step 4: Set the gap between electrodes using shims In Fig. 8, in the state of Step 3 where the sensor moving part is clamped, the fastening bolt 126 is loosened to release the temporary fixation between the fixing ring 124 and the coil side yoke material 109. 208 is shim B. In this state, the shim B is inserted into the gap between the electrodes (gap 128) from the opening 129, and the fixing ring 124 and the coil side yoke material 109 are fixed again with the fastening bolt 126. The thickness t of the shim B isB corresponds to the gap between the electrodes at the final stage that determines the capacitance. The thickness of shim B, t B is the thickness t of shim A used for the provisional setting of the gap (Step 1) A is sufficiently small compared with t A ≫t B In the example, the plate thickness t B = 15 μm.

[0096] In this step (Step 4), a means other than the fastening bolt 126 may be used to apply a "pressing force" to the fixing ring 124 against the coil-side yoke material 109. For example, a uniform force may be applied to the fixing ring 124 in the circumferential direction by using an elastic member that encases the outer periphery of the front-side support rod 204a. This method can also be applied to other embodiments described later (not shown).

[0097] Step 5 Glue the fixing ring 9, while maintaining the state in which shim B is inserted into the inter-electrode gap (Step 4), adhesive is applied to the circumferentially formed adhesive application portion 125. At this stage, the fixing ring 124 and the fixed-side electrode 122 are completely fixed to the coil-side yoke material 109 (housing). The reason for introducing the bonding process in this step is that in this embodiment, it is assumed that mass-production specifications such as product specifications and production methods have been finalized.

[0098] Step 6: Completion of electrode gap adjustment process 9 is completed, the front support rod 204a and rear support rod 204b are released. Since the axial direction of the sensor moving part including the movable electrode 108 is no longer restricted, the shim B can be easily removed from the sensor body. At this stage, the process of adjusting the gap between the electrodes is complete.

[0099] [3-3] Example of gap adjustment process (part 2) Hereinafter, an embodiment further improving the above-described gap adjustment process (Part 1) will be described. The use of the change in capacitance possessed by the sensor itself for detecting the axial position of the sensor movable part is the same as in the process (Part 1). For the improved process, it is preferable to use a micrometer with a piezo actuator (described later) or the like that can easily achieve a positioning accuracy of 1 μm or less for the fine feed mechanism. The processes of Step 1 and Step 2 are the same as in [Embodiment 1].

[0100] When the positioning accuracy of the fine feed mechanism is high at the stage where the above-described Step 2 ends and the timing position accuracy (z = z 10 ) where C > C0 can be obtained accurately, the rear support rod is returned in the reverse direction to a position immediately before the start of point contact (for example, z = z 10 +5 μm). At this stage, the rear support rod will maintain a non-contact state (a 5-μm gap) with respect to the rear end face portion 120.

[0101] At the stage of Step 3, the movement of the front support rod 204a is also performed while measuring the capacitance C = C0 of the sensor. Contrary to the case of Step 2, the front support rod 204a is stopped at the timing position (z = z 20 ) where C < C0. Then, the front support rod is returned in the reverse direction to a position immediately before the start of point contact (for example, z = z 20 -5 μm). At this stage, the left and right end portions of the pole piece portion (sensor movable part) are in a state of maintaining an extremely small gap (5 μm) with respect to each support rod. That is, the sensor movable part is in a no-load balanced state that can also be called "quasi-rigid body formation". "

[0102] In the next step, the rear support rod and the front support rod are moved simultaneously. For simultaneous movement, voltages are applied to the left and right piezo actuators simultaneously.

[0103] The rear support rod is at the position where it first stopped (z = z 10) and gives a small displacement signal that moves the front support rod in the negative direction further than the position where it first stopped (z = z 20 ) in the positive direction. By performing the above steps, the movable part can maintain its axial position when no load is applied, even when a sufficiently large load F is applied to both ends of the movable part (see Figure 3).

[0104] [Second embodiment] (Adhesive-free gap adjustment...can be disassembled and reassembled by fastening screws) FIG. 11 shows an example of an MM servo type acceleration sensor according to the second embodiment of the present invention, and shows a structure in which the fixed and movable electrodes are fastened together without using adhesive in the final stage of the inter-electrode gap adjustment process.

[0105] [1] Issues with conventional acceleration sensors One of the major issues with conventional acceleration sensors (Fig. 33) is that they are unable to achieve a high yield rate during mass production. As explained above in the specific structure of a conventional acceleration sensor (Fig. 33), the moving part, including the moving-side electrode 24, is manufactured using an adhesive method that connects many parts. The reason for using an adhesive method is that in order to obtain sensor performance with a wide frequency band and high response, the inertial mass of the moving part must be as light as possible.

[0106] In the case of servo-type acceleration sensors, in order to create a product that can be evaluated for performance, it was necessary to use an adhesive method to adjust the gap between the electrodes in the final stage of the mass production process. It is not easy to detach the bonded parts from the main body and restore the sensor body to its pre-bonded state. As a result, if a defect in the product quality was found during the basic performance evaluation or reliability evaluation stage, the basic cycle of "disassembling the sensor body → investigating the cause → taking measures → reassembling → reevaluating" could not be carried out. This issue stems from the basic operating principle and structure of conventional servo-type acceleration sensors. Products that were found to be defective had to be discarded because they could not be reused, which was the biggest factor in reducing yield.

[0107] [2] Sensor structure of this embodiment Since the "actuator section" and "displacement detection section" of this embodiment have many parts in common with the first embodiment, only the main parts are shown with reference numbers. Parts with shapes different from those of the first embodiment are indicated with the symbol C.

[0108] Fig. 11 is a front cross-sectional view of this embodiment, and Figs. 12 to 14 show the inter-electrode gap adjustment process (Steps 1 to 3). In Fig. 11, the coil side yoke material (housing) 109 goes to 109C, the fixed ring (fixed side electrode support member) 124 goes to 124C, and the opening 129 goes to 129C (Fig. 12). In this embodiment, the openings 129C are formed at three locations (chain lines 129Ca, 129Cb, and 129Cc) in the circumferential direction of the coil side yoke material (fixed member) 109C (details not shown). 600 is the sensor main body.

[0109] 11 shows the state after the assembly process for this embodiment of the sensor is completed, i.e., the state in which the fixing ring 124C is fixed by bolts attached to the coil-side yoke member 109C at the location indicated by the chain circle E. Reference numerals 601a and 601b denote tapered portions formed on the outer peripheral surface of the fixing ring 124C, 602a and 602b denote threaded portions (see FIG. 13) formed on the coil-side yoke member 109C, and 603a and 603b denote radial fastening bolts. The horizontal components of the normal forces acting from the tapered surfaces of the left and right fastening bolts are balanced on the left and right, so the fixed-side electrode 122 is securely fixed to the coil-side yoke member 109C.

[0110] [3] Example of gap adjustment process The following description of this embodiment starts from a state in which both left and right ends of the sensor movable part are already fixed by the front support rod 204a and the rear support rod 204b.

[0111] Step 1: Setting the electrode gap using shims In FIG. 12, shim 208 is inserted into the inter-electrode gap (gap 128) from opening 129C, and fixing ring 124C and coil side yoke material 109C are fixed with axial fastening bolt 126C.

[0112] Step 2: Fix the movable electrode and fixed electrode with the radial fastening bolts In Figure 13, with shim 208 inserted into inter-electrode gap 128, fixed ring 124C is fixed from the outer circumferential surface of the coil-side yoke material by radial fastening bolts 603a and 603b. At this stage, front support rod 204a and rear support rod 204b that support the movable part are provided on both axial end surfaces of the sensor body. However, the radial fastening bolts 603a and 603b are located on the outer circumferential surface of the sensor body, and the working space required for fastening is sufficiently large. Therefore, fixing the fixed electrode side by the radial fastening bolts can be easily performed.

[0113] Step 3: Remove the support rod, shim, etc. from the sensor body In Figure 14, the front support rod 204a, rear support rod 204b, and axial fastening bolt 126C are released. Since the axial restriction on the sensor moving part including the movable electrode 108 is no longer present, the shim can be easily removed from the sensor body. At this stage, the process of adjusting the gap between the electrodes, which does not involve adhesive bonding, is complete.

[0114] After completing Step 3 above, the product is ready for basic performance evaluation or reliability evaluation, etc. If a defect is found in the product during the evaluation stage, the basic cycle of "disassembling the sensor body → investigating the cause → taking measures → reassembling → reevaluation" can be repeated, as mentioned above.

[0115] FIG. 15 shows the disassembled state of the final product after Step 3 is completed.

[0116] When this invention is applied to an MM type with an open shaft end structure, not only the fixed electrode member can be disassembled. The individual components that make up the acceleration sensor, as well as the sensor body itself, can be disassembled into the following units consisting of multiple components. (i) Fixed electrode side unit 604: Comprised of a fixed side electrode 122, an insulating ring 123, and a fixed ring 124C. (ii) Movable electrode side unit 605: Comprised of a movable electrode 108, a front side disk 106, a pole piece portion 103, a front side permanent magnet 101, a rear side permanent magnet 102, and an outer ring 114. (iii) Coil unit 606: Comprised of a coil bobbin 110, a front force coil 111, and a rear force coil 112.

[0117] Furthermore, the coil side yoke material 109C, rear side disc 107, rear side end face portion 120, etc. can be disassembled as individual components.

[0118] The unit is composed of multiple components secured together with adhesive. Unitization is limited to areas where weight reduction and electrical insulation between moving parts are required. If a quality defect is found in the product after Step 3, the unit can be disassembled and inspected for the following: For example, detailed inspections are required for dust particles floating in the narrow gaps between electrodes, component processing accuracy, basic specifications of each component (disk rigidity, permanent magnet magnetization characteristics), assembly accuracy (magnetic circuit air gaps, etc.), and electrical insulation characteristics (insulating support sections 114 and 117 of the front disk 106, etc.). This allows for rapid identification of the cause of the defect and allows for reprocessing and reuse of each component. With conventional servo-type acceleration sensors, as described in Supplementary Note (2), not only is the electrode gap adjustment process difficult, but identifying the cause of the defect is also challenging. In many cases, the entire product must be discarded.

[0119] [4] Screw fastening structure between the movable electrode and the movable part FIG. 16 shows an improved structure of the second embodiment of the present invention. The movable electrode unit 605, which is constructed by bonding multiple components, has been reconstructed so that it can be disassembled down to the components that can be fastened with screws. FIG. 16a is a front cross-sectional view of the movable electrode and its vicinity, and FIG. 16b is an exploded view. Hereinafter, parts with shapes different from those of the first embodiment are indicated with the symbol D. The movable electrode 108D is secured to the pole piece 103D by bolts 653, with insulating sheets 651a and 651b sandwiched between them and washer 652 interposed between them. 654 denotes a threaded portion formed on the end surface of the pole piece 103D. The front-side disk 106D is previously secured to the movable electrode 108D by adhesive bonding at joint 655. The front-side disk 106D is secured to the coil-side yoke member 109D by bolts 657, with insulating sheets 655a and 655b sandwiched between them and washer 656 interposed between them.

[0120] By fastening the movable side electrode 108D and the pole piece portion 103D with screws, the perpendicularity of the electrode surface B of the movable side electrode 108 relative to the axis A of the movable member (pole piece portion 103D) can be ensured with high precision, compared to adhesive techniques which tend to result in uneven thickness.

[0121] In this embodiment, as a means for maintaining a predetermined inter-electrode gap, gap adjustment sheet 208 is inserted into inter-electrode gap 128, and axial fastening bolts 126C are used to fasten fixed ring 124C and coil side yoke member 109C to maintain a state in which fixed electrode 122 is pressed against movable electrode 108. Instead of this method, as a gap adjustment means, the state in which a predetermined inter-electrode gap is maintained may be measured by an optical method using opening 129C, and the fixed electrode 122 may be screwed in a state in which the axial position and angle are constrained by another means. Either method allows the sensor structure of the present invention to achieve inter-electrode gap adjustment without using adhesive.

[0122] In the acceleration sensor of the present invention, if it is confirmed after quality evaluation that the mass production specifications are completely satisfied, in order to further ensure long-term reliability, adhesive may be used to prevent loosening of the fastening bolts 603a, 603b at the screw fastening points (chain circle E in FIG. 11). Alternatively, separate points (for example, tapered portion 601a) where adhesive is applied and fastened may be provided on both components. In this case, the fastening bolts 603a, 603b may be removed at the final stage.

[0123] In FIG. 11, 604 is a rear-direction stopper (shown by an imaginary line) for the movable part (pole piece part 103). In the front direction, the fixed electrode 122 serves as a stopper that prevents movement of the movable part. These two stoppers can prevent axial displacement of the movable part so that the front-side disc 106 and the rear-side disc remain within the range of elastic deformation when a large acceleration exceeding the measurable range is applied. The rear-direction stopper 604 may be attached to the sensor body after the above-described gap adjustment process is completed.

[0124] [Third embodiment] (Third version of MM type...air micrometer type) Figure 17 shows an example of an MM servo acceleration sensor according to a third embodiment of the present invention. The electrode gap adjustment method in this embodiment uses an air micrometer to detect the axial position of the sensor's movable part. Figure 17a is a side view of Figure 17b, and Figure 17b is a cross-sectional view taken along the line AA in Figure 17a.

[0125] [1] Sensor structure of this embodiment Since the "actuator section" and "displacement detection section" of this embodiment share many commonalities with the first embodiment, only parts with shapes different from those of the first embodiment are indicated with the symbol A. In FIG. 17b, the parts are: coil side yoke material (housing) 109 → 109A, fixing ring (fixed side electrode support member) 124 → 124A, adhesive application section 125 → 125A, and opening 129 → 129A. In this embodiment, openings 129A are formed at three locations (chain lines 129Aa, 129Ab, 129Ac) in the circumferential direction of coil side yoke material (fixed member) 109A. Also, reference numeral 400 denotes the sensor main body.

[0126] [2] Electrode gap adjustment process [2-1] Overall view of the gap adjustment jig FIG. 18 shows an outline of an electrode gap adjustment jig for an MM servo acceleration sensor according to a third embodiment of the present invention. Air micrometers are attached to the tips of the front and rear support units to detect the axial position of the sensor's moving part. FIG. 18a is an overall view showing the arrangement of the acceleration sensor main body (chain line B) and the gap adjustment jig. FIG. 18b shows an example of the gap adjustment process, showing the moving part (movable member) of the acceleration sensor being clamped between the left and right support units and a shim being inserted between the electrodes (Step 2, described below).

[0127] In Figure 18a, 401a and 401b are front and rear micrometers (fine feed mechanisms). In this embodiment, the two left and right micrometers are equipped with piezo actuators. That is, a piezo actuator capable of positioning to within 1 μm is arranged in series at the output end of a normal micrometer, enabling even higher precision positioning. 402a and 402b are the front and rear micrometer fixing parts, and 403 is the base.

[0128] Reference numerals 404a and 404b denote a front-side support unit and a rear-side support unit, which are attached to the ends of the output shafts of the front-side and rear-side micrometers. Reference numeral 405 denotes a sensor main body fixing member fixed to a base 403. In FIG. 17b, sensor main body 400 is the sensor main body, and is fastened to sensor main body fixing member 405 with bolts 406b. The front-side support unit and the rear-side support unit also serve as a means for fixing an air micrometer that measures displacement and the sensor moving part including pole piece 103. Below, the components that make up the rear-side support unit (denoted by symbol b) will be explained, but the components of the front-side support unit (denoted by symbol a) are also similar.

[0129] Reference numeral 406b denotes the unit main body, 407b denotes the supply channel, 408b denotes the supply nozzle, 409b denotes the measurement flow path, 410b denotes the nozzle, and 411b denotes the nozzle tip. The principle of an air micrometer is well known, and it is composed of two nozzles, namely, a fixed air resistance and a variable air resistance. The fixed air resistance is determined by the supply nozzle 408b, and the variable air resistance is determined by the distance between the nozzle tip and the object to be measured. By measuring the intermediate pressure in the measurement flow path 409b, the distance between the nozzle tip and the rear measurement end 120, which is the opposing surface, can be measured.

[0130] [3-2] Example of gap adjustment process Step 1 Fix both the left and right ends of the sensor moving part In Figure 19, first, the rear support unit 404b is moved slightly toward the sensor main body 400 while measuring the distance between the nozzle tip and the opposing surface (the intermediate pressure in the measurement-side flow path 409b). The distance between the nozzle tip and the opposing surface is δ, and the movement of the rear support unit is stopped when δ≈0. A similar operation is performed for the front support unit. This process places the sensor moving part, including the pole piece, in a clamped state with extremely high positional accuracy. Here, the state in which no external force is applied to the sensor moving part is referred to as the "unloaded equilibrium state." This process, which combines a micrometer with a piezoelectric actuator and an air micrometer, allows the left and right ends of the sensor moving part to be fixed in a state close to the "unloaded equilibrium state."

[0131] Step 2: Set the gap between electrodes using shims In Figure 20, in the state of Step 1 where the sensor moving part is clamped, the fastening bolt 126A is loosened to release the temporary fixation between the fixing ring 124A and the coil side yoke material 109A. 412 is a shim C. In this state, the shim C is inserted into the gap between the electrodes (gap 128), and the fixing ring 124A and the coil side yoke material 109A are fixed again with the fastening bolt 126A. The thickness t of the shim C is B corresponds to the inter-electrode gap at the final stage that determines the capacitance. In this embodiment, the thickness t B = 15 μm.

[0132] Step 3 Fix the fixed electrode with temporary fastening screws 21, while maintaining the state of Step 2, the coil side yoke material 109A and the fixed side electrode 122 are fixed together. To do this, the threaded portion 413 formed on the coil side yoke material 109A is used to fix the fixing ring 124A with the temporary fastening screw 414.

[0133] By attaching the temporary fastening screws 414, the front and rear support units, the fastening bolts 126A, and the shims C are released, and the electrode gap (gap 128) reaches a predetermined target value (t B= 15 μm). In other words, it is possible to perform a basic performance evaluation or reliability evaluation of the product with the temporary fastening screw 414 attached. If a defect is found in the product, the same process as in the second embodiment can be repeated: "disassembly of the sensor body → investigation of the cause → countermeasures → reassembly → reevaluation."

[0134] Step 4 Glue the fixing ring 22, adhesive is applied to the circumferentially formed adhesive application portion 125A in the state of Step 3. At this stage, the fixing ring 124A and the fixed-side electrode 122 are completely fixed to the coil-side yoke material 109A (housing).

[0135] Step 5: Completion of the electrode gap adjustment process 23, the temporary fastening screw 414 and the fastening bolt 126A are removed from the sensor body. At this stage, the process of adjusting the gap between the electrodes is completed.

[0136] [Supplementary notes on the first to third embodiments] (Part 1) Shim shape In the first embodiment, as shown in FIG. 1a, the shims 208a, 208b, and 208c are inserted into the gap 128 through the three openings 129 formed in the coil-side yoke member 109. Alternatively, as shown in FIG. 24, a single shim 209 may be inserted through a single opening 210. FIG. 24(a) is a view taken along the arrow AA in FIG. 24(b), and FIG. 24(b) is a cross-sectional view of a portion of the sensor. When inserting the shim, the fastening bolts 126 near the openings are removed. The shim 209 may be U-shaped with a width d greater than the inner diameter of the through-hole 127 in the fixed-side electrode 127. There may be only one opening through which a single shim 209 is inserted into the gap 128, as shown in FIG. 24. However, if the process is to be rechecked using optical means at the final stage, a high-magnification camera may be installed at opening 210, and two or more openings may be provided so that light sources can be installed at positions 180 degrees apart (not shown).

[0137] (2) Forming a fitting / fastening part on the sensor body to expose the axis of the sensor body Figure 25 shows the jig configuration for aligning the axis of the movable member (103 in Figure 1b) with the axis of the support rods that press the movable member from the left and right in the electrode gap adjustment process. 204a is the front support rod, and 204b is the rear support rod.

[0138] The outer peripheral surface of sensor body 400A is engaged with sensor body fixing member 405A, which is fixed to the base, at the point indicated by the chain circle AA, and the two are fastened together with bolts 206. This jig configuration allows the axes of the movable member and the two support rods to maintain the same height H.

[0139] (3) Shim insertion opening on the fixed electrode support member In the first embodiment, as shown in FIG. 1, an opening 129 is provided on the coil side yoke member 109 side. Alternatively, as shown in FIG. 26, an opening for inserting a shim may be provided on the fixed ring (fixed-side electrode support member) side. FIG. 26a is a side view of FIG. 26b, and FIG. 26b is a cross-sectional view taken along the line AA in FIG. 26a. Because the "actuator unit" and "displacement detection unit" share many commonalities with the first embodiment, only components with shapes different from those in the above embodiment are indicated with the symbol E. In FIG. 26b, the order is as follows: coil side yoke member (housing) 109 → 109E, fixed ring (fixed-side electrode support member) 124 → 124E, adhesive application portion 125 → 125E, and opening 129 → 129E. These openings 129E are formed at three locations (chain lines 129Ea, 129Eb, and 129Ec) around the circumference of coil side yoke member (fixed member) 109E. Reference numeral 600 denotes the sensor main body. By applying the gap adjustment method used in the above-described embodiment, it is possible to achieve highly accurate adjustment of the gap between the electrodes.

[0140] [Mechanical basis for the construction method of the present invention] This invention utilizes the "open shaft end structure" of the MM servo acceleration sensor to fix and support the moving part, thereby achieving highly accurate electrode gap adjustment. The mechanical basis for this is explained below using the model diagram in Figure 27.

[0141] (1) Moment equilibrium equation F A is the force with which the front support rod 251a and rear support rod 251b press against the end face of the movable member, L is the length of the movable member 252, and μ is the coefficient of static friction between the tip of the support rod and the end face of the movable member. A is the static friction force, M A is the moment that suppresses the start of rotation of the movable member due to an external force. M A =μLF A ·····(7)

[0142] D is the outer diameter of the movable electrode 253, f B is the external force acting due to the insertion of the gap adjustment sheet, M B is the moment acting on the movable member due to the insertion of the gap adjustment sheet. M B =Df B ·····(8)

[0143] If δ is the amount of eccentricity between the shaft centers of the front support rod and the rear support rod, then M δ is the moment acting on the movable member due to the eccentricity of each support rod. M δ = δF A ·····(9)

[0144] Hereinafter, a case where the gap adjusting step (part 2) of section [3-3] in the first embodiment is used will be described. After the support rods are placed near the front and rear ends of the movable member, both ends are pressed by the support rods simultaneously. At this time, an axial load F is applied to both ends of the movable member. A In this state, insert the gap adjustment sheet into the gap. A >M B +M δ If so, the movable member will maintain its initial position before being pressed by the support rod. μLF A >Df B +δF A ·····(10)

[0145] From equation (10), the larger the length L of the movable member, the larger the static friction coefficient μ between the tip of the support rod and the end face of the movable member, and the larger the external force f B The initial state of the moving part can be maintained without being affected by the

[0146] (2) Specific examples It is assumed that the length of the movable member is L=15 mm, the outer diameter of the movable electrode is D=13 mm, the static friction coefficient of iron is μ=0.3, and the eccentricity of the support rods at both ends of the movable member is δ=0.2 mm.

[0147] μLF A ≫δF A Therefore, the second term on the right side of equation (10) can be ignored. Since the dimensions L and D are of the same order, in summary, μF A >f B If the above is satisfied, the method of the present invention is valid. B is the force required to bring the fixed electrode into close contact with the movable electrode 253. For example, the axial fastening bolt (126C in FIG. 12) can be fastened to the minimum required tightening force using a torque wrench that can set the torque. A is the axial external force generated by, for example, a micrometer with a piezoelectric actuator, and its upper limit can be set arbitrarily. Therefore, it is expected that equation (10) can be established.

[0148] [Fourth embodiment] (The present invention is applied to the MC system) Figure 28 shows an example of a moving coil type (MC type) servo acceleration sensor according to embodiment 4 of the present invention. In conventional MC type sensors, both ends of the moving part are not open, so the moving part cannot be fixed, and it seems that the use of optical means to adjust the gap between the electrodes was an inevitable choice. This embodiment utilizes knowledge gained from MM type sensors to the structure of conventional acceleration sensors, and has been devised to make the present invention applicable.

[0149] Reference numeral 711 denotes a permanent magnet, 712 a pole piece portion, 713 a pole piece protrusion portion, 714 a permanent magnet side yoke material, 715 a coil side yoke material, 716 a force coil and a calibration coil, 717 a coil bobbin, 718 and 719 coil bobbin support members made of non-magnetic and non-conductive material, 720 a front side disc-shaped spring, 721 a rear side disc-shaped spring, 722 a front side connecting member between the front side disc-shaped spring 720 and the coil side yoke material 715, and 723 a rear side connecting member between the rear side disc-shaped spring 721 and the coil side yoke material 715. 724 a movable side electrode, 725 a fixed side electrode, 726 a front side panel, 727 an opening for inserting a gap adjustment sheet, and 728 a fastening member between the fixed side electrode 725 and the front side panel 726. A radial magnetic gap 729 is formed between the outer periphery of the pole piece portion 712 and the inner periphery of the coil-side yoke material 715. 729a is the permanent magnet-side gap, and 729b is the yoke-material-side gap. A closed-loop magnetic circuit is formed by "permanent magnet 711 → pole piece portion 712 → magnetic gap 729 → coil-side yoke material 715 → permanent magnet-side yoke material 714." 730 is the gap formed by the movable-side electrode 724 and the fixed-side electrode 725.

[0150] Reference numeral 731 denotes a through hole a formed in the center of the fixed electrode, through which a front support rod can be inserted. Reference numeral 732 denotes a through hole b formed in the pole piece portion 712, 733 denotes a through hole c formed in the permanent magnet 711, and 734 denotes a through hole d formed in the permanent magnet side yoke material 714. Reference numeral 735 denotes an extension rod (extension shaft) formed to extend from the movable side electrode 724 to the through hole b in the pole piece portion. This extension rod 735, movable side electrode 724, coil 716, etc. form the movable members of the sensor of this embodiment.

[0151] Fig. 29(a) shows a method for adjusting the gap of the sensor of this embodiment, and shows that a shim 753 is inserted into the gap 730 between the electrodes while the movable members, such as the movable electrode 724 and the extension rod 735, are pressed by the left and right support rods 751 and 752. Fig. 29(b) is an enlarged view of the chain circle in Fig. 29(a). Ais the force with which the support rod presses the end face of the movable member, L is the length of the movable member, μ is the coefficient of static friction between the tip of the support rod and the end face of the movable member, D is the outer diameter of the electrode, f B is the external force acting due to the insertion of the gap adjustment sheet. As mentioned above, the condition under which the movable member can be fixed without being affected by the insertion of the gap adjustment sheet is as follows: μLF A >Df B +δF A (10-2)

[0152] The sensor of this embodiment focuses on forming an extension rod 735 on the movable-side electrode 724 and setting a sufficiently long dimension L so that equation (10-2) holds. Furthermore, as shown in enlarged view 29(b), the tip 751a of the support rod 751 is trapezoidal, and is supported in surface contact with the movable member, thereby increasing the static friction coefficient μ.

[0153] Because this embodiment is a moving coil (MC) type, the conductive paths connecting the movable part and the fixed side, through which multiple signals flow, must be formed using elastic members (disk-shaped springs 720, 721) that connect the two. As a result, it requires (1) dividing the disk-shaped springs to form the multiple conductive paths, (2) insulating the signal lines, and (3) a complex production method involving a soldering process for ultra-fine wires. Due to this complex structure, it is difficult to disassemble the sensor body (composed of each part and each unit) as shown in the MM type embodiment.

[0154] However, if a detachable bolt fastening structure (not shown in this embodiment) is used between the coil side yoke material 715 and the front side panel 726 as shown in the second embodiment, the fixed side electrode can be disassembled from the movable side electrode. If a defect that is thought to be caused by the capacitance detection unit (for example, noise generation) is found during the quality evaluation stage of the product, it is sufficient to inspect, for example, dust floating in the narrow gap between the electrodes, adhesion of scattered solder balls and flux to the electrode surfaces, and the processing accuracy of the electrode surfaces.

[0155] [Fifth embodiment] (The present invention is applied to a MM differential type) 30 is a front cross-sectional view of a differential servo acceleration sensor according to a fifth embodiment of the present invention. Taking note of the structural characteristics of the linear MM type, in which both left and right output shafts are open ends, this differential capacitance sensor is constructed by providing electrodes for detecting capacitance in two locations, left and right. Making the acceleration sensor differential makes it possible to realize a high-resolution sensor whose sensor output is less susceptible to the influence of disturbance signals such as noise and drift.

[0156] (1) Explanation of the basic structure Unlike the second embodiment, which uses radially magnetized permanent magnets, the acceleration sensor in Figure 30 forms a closed-loop magnetic circuit by placing an axially magnetized permanent magnet in the center of the pole piece. Reference numeral 801 denotes the axially magnetized permanent magnet, 802a denotes the front pole piece, 802b denotes the rear pole piece, 803 denotes the coil side yoke material, 804 denotes the coil bobbin, 805 denotes the fastening bolt connecting the coil bobbin and the coil side yoke material, 806a denotes the front coil, and 806b denotes the rear coil. Reference numerals 807a and 807b denote gaps formed in the centers of the front and rear pole piece parts 802a and 802b. Reference numerals 808a and 808b denote the front magnetic gap and the rear magnetic gap, respectively, which represent the radial gaps between the two pole piece parts and the coil side yoke material. Closed loop magnetic circuit B is formed by "permanent magnet 801 → front pole piece 802a → front magnetic gap 808a → coil side yoke material 803 → rear magnetic gap 808b → permanent magnet 801". M Reference numeral 809a denotes a front-side inner peripheral support member for the pole piece portion, 809b denotes a rear-side inner peripheral support member, 810a denotes a front-side disk, and 810b denotes a rear-side disk. Reference numeral 811a denotes a front-side movable electrode, 811b denotes a rear-side movable electrode, 812a denotes a front-side fixed electrode, 812b denotes a rear-side fixed electrode, 813a denotes a front-side insulating ring, 813b denotes a rear-side insulating ring, 814a denotes a front-side fastening ring, and 814b denotes a rear-side fastening ring.

[0157] The front inner peripheral support member 809a and the front pole piece portion 802a, and the rear inner peripheral support member 809b and the rear pole piece portion 802b are electrically insulated by insulating coatings 815a and 815b. The front disc 810a and the coil side yoke material 803, and the rear disc 810b and the coil side yoke material 803 are electrically insulated by outer peripheral insulating rings 816a and 816b, respectively. 817a and 817b are gaps between the left and right electrodes.

[0158] (2) Components for adjusting the electrode gap The components and gap adjusting tool used to apply the electrode gap adjusting process of the present invention will be described below.

[0159] 850L and 850R are shims AL and AR for temporarily setting the capacitance. 851L and 851R are front and rear support rods. As shown in the first embodiment of the present invention, the temporary setting of the capacitance is utilized to press and fix the movable part from the left and right by the left and right support rods.

[0160] Reference numerals 852a and 852b denote shims BL and BR to be inserted into inter-electrode gaps 817a and 817b. Reference numerals 853L and 853R denote axial fastening bolts for temporarily fixing two fastening rings 814a and 814b to the coil-side yoke material 803 with the shims BL and BR inserted into the inter-electrode gaps.

[0161] 854a and 854b are radial fastening bolts. With the shims BL and BR inserted in the inter-electrode gaps, the front and rear fastening rings are fixed to the coil-side yoke material 803 by the radial fastening bolts.

[0162] After the above steps, the left and right support rods, the axial fastening bolts, and the shims BL and BR are released. At this stage, the movable electrode side member is fixed to the fixed electrode side with a predetermined gap maintained. The radial fastening bolts 854a and 854b used in this embodiment are "pointed-point screws" with tapered screw tips. These pointed-point screws are specified in JIS B 1125 as having threads extending to the pointed tip. The two fastening rings 814a and 814b are made of aluminum, which is prone to plastic deformation. The use of these pointed-point screws ensures reliable fastening of the fastening rings 814a and 814b to the coil-side yoke material (fixing member) 803. In other words, the inter-electrode gap can be maintained at a constant value without being affected by slippage between the screw tip and the opposing surface. The dashed circle in the figure shows the tip of the radial fastening bolt 854a biting into the fastening ring 814a (plastically deformed portion 855a).

[0163] Incidentally, the method of this embodiment in which the tip of the fastening bolt bites into the soft metal of the opposing surface and fixes the fixed electrode member by plastic deformation can be applied to other embodiments as well. Whether or not the tip of the screw effectively plastically deforms the fixed electrode member can be easily verified by disassembling this sensor.

[0164] (3) Effects of this embodiment The inventors have already proposed and applied for an MM type differential sensor, but by applying the sensor structure and gap adjustment method of the present invention to the differential type, the following effects can be obtained. In the case of a normal sensor (Fig. 33) in which the electrodes are installed on only one side, the gap δ set by the conventional gap adjustment method (Fig. 2) X can be readjusted to the target gap δ0 by passing a bias current I0 through the coil. In other words, the error Δδ=δ X -δ0 can be corrected by adjusting the bias current so that Δδ becomes 0. By changing the linear acceleration sensor to a differential type and completing the electrode gap adjustment, the left and right gaps are adjusted to δ L , δ R In this case, the gap δ L , δ R It is difficult to adjust the bias current I0 so that both become the target value δ0. This is because, in the case of a differential type, after completing the adjustment of the gap between the electrodes, L +δ RThis is because it is restricted to "= constant value".

[0165] By using the method of the present invention in which a gap adjusting sheet is inserted into the gap between the electrodes while both ends of the movable member are temporarily fixed to the fixed members, the left and right gaps δ L , δ R can be obtained with sufficiently high accuracy during the gap adjustment stage. It is known that the electrode gap δ0 of a servo-type acceleration sensor has a significant effect on the dynamic characteristics (gain and phase characteristics) of the sensor, even with a gap accuracy on the order of a few microns. By applying this invention, a differential sensor can be realized that not only is it less susceptible to disturbance signals such as noise and drift, but also has ideal dynamic characteristics.

[0166] [Supplement 1] How to fix the moving parts In the above-described embodiment, the fact that both ends of the shaft of the movable member are open is utilized to fix the movable member. The left and right ends of the movable member need only be supported by external pressure during the electrode gap adjustment stage. In the final form of the completed product, the left and right ends of the movable member may be sealed with a case or the like.

[0167] The same applies to openings formed in the fixing member or the fixed-side electrode support member, or in the second embodiment, adhesiveless fastening portions that fasten the fixed-side electrode support member to the fixing member, etc. The openings, fastening portions, etc. may be sealed or additionally machined in a state that is difficult to reproduce in the final form of the product.

[0168] In the electrode gap adjustment process, a method has been shown in which support rods driven by fine feed mechanisms are provided on the left and right sides to fix the movable member. By utilizing a structure in which both ends of the shaft of the movable member are open, it is possible to press one end against the wall surface and apply an axial load to the other end using the fine feed mechanism.

[0169] Alternatively, only the shaft end portion opposite the movable electrode may be gripped from the outside, so that the axial position or tilt angle of the movable member is maintained in the initial state.

[0170] The means for pressing the fixed electrode against the fixed movable electrode via a shim does not have to be a fastening bolt. For example, the sensor body may be arranged vertically, and a weight may be mounted on the fixed electrode to apply a vertical load.

[0171] [Supplement 2] Why is it difficult to disassemble and reassemble conventional servo-type acceleration sensors? The linear motion MC type acceleration sensor disclosed in Patent Document (1) had major issues in terms of production technology due to its basic operating principle and structure. Figure 35(a) is a front view showing the shape of the front disk-shaped spring, and Figure 35(b) is a front cross-sectional view of the sensor as a whole (Figure 33) with the front panel 26, fixed electrode 25, etc. removed. Figure 35(c) is an enlarged view of part A in Figure 35(b), showing the state in which the movable electrode 24 is deformed in the axial direction.

[0172] 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. 33), 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. 35(a) and 35(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.

[0173] In Figure 35(a), 34a, 34b, and 34c are outer peripheral fixing portions of the front-side disc-shaped spring 20. These three outer peripheral fixing portions are cut at three circumferential locations as indicated by the chain circle AA to ensure electrical insulation. 35a, 35b, and 35c are inner peripheral spring portions of the front-side disc-shaped spring. These three inner peripheral spring portions are cut at three circumferential locations as indicated by the chain circle BB to ensure electrical insulation. 36a, 36b, and 36c are soldered portions for electrically connecting the coil terminals to the inner peripheral spring portions. Figure 34c shows the terminal of the test coil 16b connected to the inner peripheral spring portion 35c at soldered portion 36c. 37 is an insulating pipe, and 38 is a signal wire inserted into this insulating pipe. The insulating pipe and the signal wire are attached at several locations, penetrating the disc-shaped spring 20. Incidentally, the coil wire diameter used in servo-type acceleration sensors is extremely fine, about 30 to 40 μm. In other words, conventional servo-type acceleration sensors have a production technology issue stemming from their basic operating principle and structure, which requires the processes of "cutting, insulating, and soldering" between the disk-shaped spring and the coil. Because of the structure manufactured using the above complex processes, it has been difficult to disassemble and reassemble the sensor body and reuse the parts.

[0174] [Supplementary Note 3] Servo-type accelerometers are broadly divided into two types of specific structures: (1) a type in which the mass moves linearly, and (2) a type in which the mass moves oscillatingly. In the above-described embodiments, the present invention has been applied to the linear motion type (1). However, even in the case of a servo-type sensor driven by an oscillating motion actuator, the change in the relative gap between the fixed electrode and the movable electrode can be regarded as a pseudo-linear motion. Therefore, the electrode gap adjustment method and sensor structure of the present invention can be applied.

[0175] [Supplementary Note 4] For example, in the MM-type sensor structure of the second embodiment of the present invention (FIG. 11), if the permanent magnets 101 and 102 and the coils 111 and 112 are reversed, it can be converted into an MC-type sensor structure. In other words, the permanent magnet side is fixed and the coil side is driven. However, even in this case, (1) division of the disk-shaped spring to form multiple conductive paths, (2) insulation of the signal wire, and (3) a complex production method involving a soldering process for ultra-fine wires are still required, so the advantages of the MM type remain unchanged. [Explanation of symbols]

[0176] 101 Permanent Magnet 102 Movable side member 105 Fixed side member 116, 104 Movable side yoke material 106 Coil 110 Moving part of displacement detector 117 Cavity

Claims

1. A fixing member; a movable member provided so as to be movable in a predetermined direction relative to the fixed member; an elastic member that supports the movable member so that the movable member is disposed relative to the fixed member via a gap; a displacement detection unit that detects a displacement of the movable member in a predetermined direction; a driving means for generating a force for returning 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 displacement detection unit a movable-side electrode provided on one axial end surface of the movable member; a fixed electrode provided opposite the movable electrode; a fixed-side electrode support member that supports the fixed-side electrode or is integrated with the fixed-side electrode, The electrostatic capacitance formed in the gap between the movable electrode and the fixed electrode is detected. an opening to which a gap adjusting means for adjusting a gap between the movable electrode and the fixed electrode can be applied is formed in the fixed member or the fixed electrode support member, A servo type vibration detector characterized in that both axial ends of the movable member are release shafts, or the end opposite to the movable electrode is a release shaft.

2. A servo-type vibration detector as described in claim 1, characterized in that the movable member can be grasped from the outside or its axial movement can be restricted using the release shafts at both axial ends or the release shaft at the end of the movable member opposite the movable side electrode.

3. The servo-type vibration detector according to claim 2, characterized in that the gap adjustment means is a gap adjustment member including a shim or a spacer, and the opening is formed so that this gap adjustment member can be inserted into the gap between the movable electrode and the fixed electrode.

4. 3. The servo type vibration detector according to claim 2, wherein a through hole is formed in the center of said fixed electrode, into which a small diameter member can be inserted from the outside.

5. 2. The servo type vibration detector according to claim 1, wherein a fastening portion for fastening the fixed electrode support member to the fixed member is provided on the outer peripheral surface of the fixed member or the fixed electrode support member.

6. A servo-type vibration detector as described in claim 1, characterized in that the fixed member is provided with a fastening portion for fixing the main body of the servo-type vibration detector to the outside, and the fastening portion is formed so that the main body of the servo-type vibration detector can be fastened in an engaged state to an external member so that the axis position of the movable member is determined.

7. a permanent magnet disposed on the movable member or the fixed member; a coil disposed on the member opposite the permanent magnet; an elastic member supporting the movable member near both ends of the shaft of the movable member; a closed loop magnetic circuit formed by the movable member, a gap between the movable member and the fixed member, the fixed member, and the permanent magnet, the driving means is configured to generate an electromagnetic force by the closed loop magnetic circuit to move the movable member axially; 3. A servo type vibration detector according to claim 2, wherein a magnetic flux flows in a gap between said movable member and said fixed member near both ends of the shaft of said movable member.

8. the coil is fixed to the fixed member, 8. A servo type vibration detector according to claim 7, wherein the movable member is made up of the permanent magnet and a movable yoke material connecting the permanent magnet to a magnetic path.

9. The servo-type vibration detector of claim 2, characterized in that the displacement detection unit is configured as a differential sensor having one pair of the movable side electrode and the fixed side electrode at each axial end of the movable member, and detects the difference in two capacitances formed between each pair of the movable side electrode and the fixed side electrode, and the gap adjustment means is a gap adjustment member including a shim or spacer, and the opening into which the gap adjustment member can be inserted is provided at each axial end.

10. A permanent magnet is fixed to the fixed member side, a coil is disposed in a gap between the movable member and the fixed member and fixed to the movable member; an inner yoke material that connects the permanent magnet to the magnetic path; an outer yoke material disposed with a radial gap between the permanent magnet or the inner yoke material; an elastic member supporting the coil, a closed loop magnetic circuit is formed by the permanent magnet, the inner yoke material, a gap between the movable member and the fixed member, and the outer yoke material, a through hole is formed in the permanent magnet and / or the inner periphery side yoke material, 2. The servo type vibration detector according to claim 1, wherein the movable electrode has an extension shaft formed thereon that extends to the through hole.

11. a displacement detection unit that detects displacement of the movable member in the predetermined direction; and drive means that generates a force to return the movable member to its original position when the displacement detection unit detects a relative displacement of the movable member from its original position, wherein the displacement detection unit comprises a movable-side electrode provided on one axial end face of the movable member, a fixed-side electrode provided opposite the movable-side electrode, and a fixed-side electrode support member that supports the fixed-side electrode or is integrated with the fixed-side electrode, and the servo vibration detector is configured to detect a capacitance formed in a gap between the movable-side electrode and the fixed-side electrode, a gap adjusting member is inserted into a gap formed between the movable electrode side and the fixed electrode side in a state where the movable member is temporarily fixed to the fixed member; The fixed electrode is moved relatively toward the movable electrode so that the gap between the movable electrode and the fixed electrode becomes a predetermined gap, and then The fixed electrode is fixed to the fixed member, A method for assembling a servo type vibration detector, comprising the steps of releasing the movable member from the fixed member while removing the gap adjusting member from the gap between the movable electrode and the fixed electrode.

12. 12. A method for assembling a servo-type vibration detector as described in claim 11, characterized in that the movable member is gripped against the fixed member by a pressing means that presses one axial end face and the other axial end face of the movable member against each other.

13. 12. A method for assembling a servo type vibration detector according to claim 11, wherein both end surfaces of said movable member are pressed by the tip of an output shaft of said fine feed mechanism.

14. 14. The method for assembling a servo type vibration detector according to claim 13, wherein the capacitance of the gap is measured to detect the displacement of the movable member pressed by the output shaft of the fine feed mechanism.

15. The capacitance C=C0 is measured when the gap of the air gap is provisionally set. The output shaft of the first fine feed mechanism R is brought close to one end face R of the movable member, and the movement of the first fine feed mechanism R is stopped at a timing when the capacitance becomes C>C0; The output shaft of the second fine feed mechanism L is brought close to the end face L on the opposite side of the movable member to a position where it can move, and then the movable member is pressed.

15. The method for assembling a servo type vibration detector according to claim 14, further comprising inserting the gap adjusting member into a gap between the movable electrode and the fixed electrode.

16. The capacitance C=C0 is measured when the gap of the air gap is provisionally set. The output shaft of the first fine feed mechanism R is brought close to one end face R of the movable member, and the movement of the first fine feed mechanism R is stopped at a timing when the capacitance becomes C>C0; The output shaft of the first fine-motion feed mechanism R is again moved in a direction away from the end face R, and the fine movement of the first fine-motion feed mechanism R is stopped at the timing when the capacitance becomes C=C0, The output shaft of the second fine feed mechanism L is brought close to one end face L of the movable member, and the movement of the second fine feed mechanism L is stopped at a timing when the capacitance becomes C<C0; The output shaft of the second fine-motion feed mechanism R is again moved in a direction away from the end surface L, and the fine movement of the second fine-motion feed mechanism R is stopped at the timing when the capacitance C becomes C=C0. The first fine feed mechanism R and the second fine feed mechanism L are simultaneously slightly moved in the direction of both end faces to press the movable member from both end faces, and then 15. The method for assembling a servo type vibration detector according to claim 14, further comprising inserting the gap adjusting member into the gap portion.

17. 12. The method for assembling a servo type vibration detector according to claim 11, wherein the means for fixing the fixed electrode to the fixed member is screw fastening, which allows disassembly and reassembly.

18. A method for assembling a servo-type vibration detector as described in claim 16, characterized in that the fixed side electrode is screwed to the fixed member, and after evaluating the quality of the servo-type vibration detector body, the fixed side electrode is adhesively fixed to the fixed member.

19. 14. The method for assembling a servo type vibration detector according to claim 13, wherein a displacement sensor for measuring the amount of movement of said fine feed mechanism is installed outside.

20. 20. A method for assembling a servo type vibration detector according to claim 19, wherein the displacement sensor is an air micrometer installed at the tip of the output shaft of the fine feed mechanism.

21. 21. A method for assembling a servo type vibration detector according to claim 20, wherein said air micrometer is used both to measure the displacement between its tip and said movable member and as a means for pressing said movable member.

22. A method for assembling a servo type vibration detector according to claim 13, characterized in that the servo type vibration detector body is fixed to the floor surface so that the axis of the movable member and the axis of the output shaft of the fine feed mechanism are on the same line.

23. A method for assembling a servo-type vibration detector as described in claim 11, characterized in that when fastening the screw to fix the fixed side electrode to the fixed member, the tip of the screw is held in a state where it is embedded into the opposing surface by plastic deformation.

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