JPS6034068B2 - Moving elements for transducers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to transducers such as accelerometers, and more particularly to a structure for supporting a sensing element having position sensing means within the instrument. It is about things.

In prior art structures, one example of which is represented by the accelerometer vibration assembly disclosed in U.S. Pat. No. 3,702,073, the transducer assembly, in this case the vibration assembly, is The support ring is supported between the upper and lower stator assemblies and is supported on a flexible element connected to an outer member of the support ring.

The vibrating element in this particular example includes a force recovery coil and an arcuate pickoff capacitive plate, and is coupled to an annular external support ring by one or more flexible elements. In this instrument, the vibrating assembly, including the support ring and flexure elements, is formed from a one-piece piece of fused silica. One of the objectives in designing instrument assemblies and their associated support structures, such as those shown in U.S. Pat. The aim is to minimize the effect of stress on the Strains resulting from stresses in the support structure within the flexible element supporting the vibrating mass can cause significant bias errors. In the example of U.S. Pat. No. 3,702,073, which discloses a servo-based accelerometer vibration assembly, a pickoff element is used to generate a signal indicative of the position of the assembly within the instrument; The elements themselves are also used to generate an electrical current in a recovery coil attached to the vibratory assembly to restore the vibrating mass to a predetermined position within the instrument. Stress in the flexure element at the servoed position can cause undesired bias in the output signal. This is because the instrument attempts to overcome any forces that are generated within the deflecting element. In the case of an open loop instrument, the stress in the flexure element allows free movement of the pickoff and also introduces bias errors in the output. One source of stress that can be transferred to the flexure element results from the manner in which the support member is secured to the stator element of the assembly. Since the surface of the stator element that joins the annular support ring cannot practically be made completely flat, the fixation of the support ring to the fixation element, which is also not completely flat, is in most cases This creates stresses in both the external support member and the flexure element. One means for reducing the stress transferred to flexural elements in a transducer assembly is disclosed in U.S. Pat.
No. 02073.

The annular external support member is clamped between the fixation elements where a spacer element or pad is interposed between the surface of the stator member and the support ring. In this method, three pairs of pads are placed around the supporting part at a distance of 120 degrees.
are spaced apart. However, even with this measure, undesirable stresses are generated in the annular support O-ring and these are transmitted to the flexure element supporting the vibrating mass. A second means for reducing the effects of attachment stresses is shown in U.S. Pat. No. 3,339,419.

This patent discloses that the support member is cantilevered and a movable member having cantilever beams attached thereto is supported by a circular pick-off device on essentially one half of the circular movable member and each side of the support green of the cantilever beam. The design is disclosed. This measure reduces sensitivity to strain rotation by having essentially equal areas of the movable element and circular pickoff device on each side of the zero attachment line of the support member. However, using Enkei's pickoff area is usually not practical or even desirable.

It is actually more effective to concentrate the pickoff area at the largest radius from the pivot axis in the pendulum transducer in order to maximize the angular gain of the pickoff. Therefore, an outer annular support member (hereinafter also referred to as ``support village'' or ``support ring'') that flexibly supports a movable member including a non-circular pick-off area, and a stator structure (hereinafter ``fixed member''). between the supporting member (also referred to as “child member” or “stator”) and the supporting member,
for use in a transducer having at least one stator section including at least one support element interposed such that its green is substantially aligned with the center locus of the pick-off area; It is an object of the present invention to obtain an assembly for.

an annular support member secured between the stator members; a non-circular pickoff area flexibly suspended from the support member; and a non-circular pick-off area flexibly coupled to the movable member between the stator and the support member. a plurality of spacer elements secured to permit movement relative to the stator of the support member, and the green of the spacer elements on which the support member flexes or rotates; Obtaining a proof mass assembly for use within an accelerometer having first and second stator members aligned with the center locus of the pickoff area to minimize stress in the members. That is,
It is an additional object of the invention.

a stator member; a movable member that includes a pickoff device and is supported by a flexible element connected to a support member that is partially affixed to the stator; In order to minimize the stresses in the support member resulting from securing the village to the stator, the flexible member is placed at a minimum distance from the part secured to the stator and allows the support member to flex in the radial direction. It is another object of the invention to provide a support structure for use inside a transducer in which the support member additionally includes a portion. As will be explained below, in the present invention, the majority of the support member is moved from the stator of the transducer so that the resultant mounting strain in the cantilevered axis of rotation is the axis that contains the center locus of the pickoff device. It is cantilevered from the stator of the transducer so that it occurs around the periphery.

The center locus of an object of homogeneous material is defined as the center of gravity of this object. Mounting stress sensitivity in the instrument is also reduced by maximizing the separation of the flexure elements that connect the movable member to the support member from the cantilever points where mounting stresses are induced. This measure has the additional advantage of not having to use a symmetrical pickoff area profile or having the pickoff area centered on a moving element. ing. It must be noted that the large and low pickoffs are not only insensitive to the rotation angle of the pickoff area, but are likewise insensitive to the linear motion of the pickoff center trajectory. If the pickoff area is essentially circular, as in the case of U.S. Pat. cause However, in the area of precision transducers, the complete elimination of all such sources of translation error is an ongoing goal. In this way, rotation of the support member about an axis containing the pickoff center trajectory produces the greatest reduction in angular motion sensitivity when the pickoff area is neither circular nor necessarily symmetrical. If it were possible to place the center locus of the pickoff area precisely on the axis of rotation of the support member, the transducer pickoff, which is sensitive only to linear motion, would Zero error is induced by angular rotation of the support member around.

For example, up to 1/10 of the rotation-induced error, or
Further theoretical reductions are possible in a one inch diameter circular acceleration transducer of the type disclosed in US Pat. No. 3,702,073. This improvement places the axis of rotation of the support village on the center locus of the arcuate pickoff area, as opposed to placing it in the center of the circular pickoff area, as described in U.S. Pat. No. 3,339,419. arises from that. As a practical matter, the reduction of actual errors is, of course,
Depending on the manufacturing tolerances used in the construction of the instrument. below,
The present invention will be explained based on examples thereof.

In FIG. 1, the movable member is shown in an exploded view in the form of an acceleration transducer of the type disclosed in detail in the aforementioned U.S. Pat. No. 3,702,073 for a pickoff device.

In this example, for purposes of illustration, the accelerometer includes an upper magnet or stator structure 10 and a lower magnet or stator structure 12. Additionally, lower stator structure 12 includes support posts for electrical leads, as indicated by 16 and 18. Also shown in FIG. 1 is a moving element assembly in the form of a proof mass assembly, generally designated by two lines, of the subordinate technology. Included within the proof mass assembly 20 is an outer annular support member 22 that is connected to opposing planar surfaces 19 and 21 of the upper stator structure 10 and lower stator structure 12. In between, it is supported by a pair of spacer elements or mounting pads 24 on the section 22. The lower pad of each pair of mounting pads 24 is not depicted in the figures. As shown in FIG.
The prior art position of each pair of is such that there is a spacing of about 1200 degrees from each other around the support ring 22. Also included in the proof mass assembly 20,
There is a flapper or movable lead 26 extending radially inwardly from the support ring 22. There is an arcuate conductive material 28 deposited on each side of the flapper 26, which serves as a capacitive pickoff area or pickoff plate or element. Capacitive pickoff plates 28 on the upper and lower surfaces of flapper 26 cooperate with opposing surfaces 19 and 21 of upper and lower stator structures 10 and 12 to form a capacitive pickoff device. . A force recovery coil 3 mounted on each side of the flapper 26
There is 0.

As is well known to those skilled in the art, the force recovery or torque coil 30 cooperates with the permanent magnet 14;
The flapper 26 is held within a predetermined position with respect to the support ring 22. A flapper 26, including a force recovery coil 30, is connected to the support ring 22 by a pair of flexure elements 32 and 34.

The flexure elements 32 and 34 are connected to the flapper 26 and the coil 3.
0 is allowed to move in a rotating pendulum manner with respect to the annular support ring 22. flapper 26
moves in response to a force along the accelerometer's axis of sensitivity. Also,
Overlying the support ring 22 and flexure elements 32 and 34 are thin film pickoff conductors 36 and 38 which provide electrical connections to the capacitive plate 28 and force recovery coil 30. As previously discussed, the securing of support ring 22 to fixation members 10 and 12
2, resulting in strain being transferred to the flexure elements 32 and 34. The deflections created in the flexure elements 32 and 34 may require current to be conducted through the force coils in the servo accelerometer. In this way, a significant bias error is introduced into the signal output of the accelerometer. A preferred embodiment of the invention is shown in FIG. 2, in which a vibratory assembly having a circularly contoured configuration of the type indicated generally by 20 in FIG. Also shown in this assembly is a pair of pad or spacer elements on the outer annular support member 22.
The upper stator 10 and the lower stator 12 are arranged to reduce the effects of stresses in the support ring 22 when mounted vertically together.

It should be noted that the inventive concept applies equally to the attachment of non-circular structures and continuous surfaces and pads. The concept of the invention also applies to transducers in which the support member 22 is fixed to only one stator by vertical mounting, gluing or other methods. The invention also applies to the use of other types of pickoff devices, including optical types that do not require a pickoff element, such as on a moving part. In Figure 2, reference numerals 22, 26, 28
, 30, 32 and 34 correspond to similar elements as described with respect to FIG.

In particular, the first and second pairs of support elements or pads 40,4
4 are placed on the top surface of the circular support member 22 and one pad (not shown) on the bottom surface of the circular support member 22.
, preferably the green of the pad, is essentially aligned with the center locus of the pickoff element 28, as shown by line 42. Note that the center locus of the pickoff element 28 is indicated by 41 in FIG. Pickoff element 28
In the case of planar elements of uniform thickness, such as thin precipitates of conductive metal, such that the pickoff element 28 forms a capacitive plate, the center locus 41 of the pickoff element 28 is the center locus of the pickoff area. The area of the pickoff on one side of the axis 42 x the radius of the center locus of that area with respect to the center locus 41 of the pickoff area 28 of FIG. 2 is equal to the same amount on the side of the axis. A second pair of spacer elements or members 44 are disposed on the other side of support ring 22 and essentially aligned with axis 42 . A third pair of flexible elements 46 is placed on the support ring 22 on the reflective side with the flexible elements 32 and 34.
In order to reduce the stress within the support ring 22,
Although it is generally considered desirable to make the spacer elements 40, 44, and 46 as small as possible, the spacer elements 40, 44, and 46
There may be circumstances in which it is desirable to combine 0, 44 and 46 into just one member. As discussed above, separate spacer elements may be used, as shown in FIG. 2, or a single arcuate spacer member may
The effective axis of rotation of the cantilevered portion of the support ring 22 is defined by a line or axis 42 passing through the center locus 41 of the pickoff element 28, regardless of whether it is used extending from the location of the support ring 40 to the location of the spacer member 44. To essentially match the
considered the most desirable. By positioning the spacer elements or pads in this manner, the sensitivity axis of the instrument due to the stresses induced in support ring 22 by tightening stator members 10 and 12 together, as shown in FIG. Center locus 4 of parallel pickoff elements 28
1 movement is significantly reduced. This is due to the fact that rotation about the center locus of the pickoff area produces an equal pickoff effect on either side of the axis of rotation, thus canceling the pickoff error due to stresses in the flexural elements. It is something. Also, as shown in the embodiment of FIG. 2, hinges such as those shown by flexure elements 32 and 34 supporting flapper 26 are used to minimize strain in flexure elements 32 and 34. It is desirable to position it as far from axis 42 as possible. Pickoff plate 28 should be positioned on movable member 26 as far as possible from flexure elements 32 and 34 in order for them to receive maximum benefit from the angular rotation of flapper 26. The sensitivity of the pickoff increases as a function of the distance of the pickoff area from the point of rotation of the flapper 26. In this way, the pickoff area is
As shown, by contouring in an arcuate shape, the maximum pickoff area can be positioned as far as possible from the flexure elements 32 and 34. In FIG. 3, additional flexures 48 and 50 are shown on support member 22.
Preferably, the mounting spacer element or pad 40 in
An embodiment is shown provided by an arcuate recess positioned at a maximum distance from and 44.

These additional flexures 48 and 50' allow portions of the support ring 22 to flex in the radial direction. This arrangement is desirable even when a continuous mounting surface is used from pad 40 to pad 44. The support ring 22 with respect to the stresses or strains created in the pivots 32 and 34 in a flexure type due to the combination of the flexure portions 48 and 50 and the maximum separation of the flexure elements 32 and 34 from the axis of rotation 42 of the support ring 22. The sensitivity to radial deflections within is reduced.

[Brief explanation of the drawing]

FIG. 1 is an exploded view of an accelerometer including a prior art device for supporting a moving element with respect to a pick-off device in the form of a vibrating mass, and FIG. 2 is a preferred embodiment of the invention for use in an accelerometer. FIG. 3 is a plan view of a portion of a proof mass assembly showing an additional embodiment of the present invention. 10, 12... Stator section, 20...
Guaranteed mass assembly, 22...Supporting member, 26...
... Flapper, 28 ... Pickoff area, 32
, 34... Deflection element, 40, 44, 46...
...Subesa element, 41... Center locus, 48,
50...Deflection part. FIG. 2FIG. 3 FIG. l

Claims (1)

Claims: 1. In a movable element for use inside a transducer having first and second stator structures 10, 12, including at least one non-circular pick-off area 28. a movable flapper 26 that is interposed between and supported by the first and second stator structures 10 and 12; the movable flapper 26 is supported in the form of a rotating pendulum; a support member 22 including flexure elements 32, 34 for making the stator structure 10 and at least one spacer member 40 interposed between said support member 22 The spacer member 40 is arranged so as to provide support by a cantilever beam for a portion of the support member 22, and the rotation axis 42 of the cantilever beam passes through a center locus 41 of the pick-off area 28. A movable element for a converter, characterized in that the movable element is configured to 2. Movable element according to claim 1, characterized in that the flexible elements (32, 34) are placed on the support member (22) at a maximum distance from the axis of rotation (41). 3. The spacer members 40, 44 are interposed between each of the stator structures 10, 12 and the support member 22, and the spacer members 40, 44 are arranged along the center locus 41 of the pick-off area 28. A movable element according to claim 1, wherein the movable element is substantially aligned with the movable element. 4. The movable element of claim 3, wherein one edge of each of said spacer members (40, 44) is substantially aligned with a center locus (41) of said pick-off area (28). 5 said support member 22 is of generally circular profile and configured to permit radial deflection of said support member 22;
5. A movable element as claimed in claim 4, including two flexible portions (48, 50).