CN115540731A - Precision micro-displacement measuring equipment - Google Patents

Abstract

The invention relates to a displacement sensing device and a displacement sensing technology which have low cost, small volume and simple structure and can precisely measure micro displacement of the order of sub-micron. The basic concept is to amplify the micro displacement to be measured by a mechanical displacement amplifier with a precision level of 10 to 100 times to more than micron, and then to read the amplified value by a displacement sensor with lower cost to obtain the measurement of the actual displacement. The present invention includes an improved mechanically balanced lever structure that allows the mechanical displacement amplifier to operate in different settings without recalibration. While being better resistant to the effects of external vibrations. The invention also includes a packaging design for isolating the external magnetic field, which better resists the influence of external vibration when the Hall magnetic induction component is used for reading the amplified value.

Description

Precision micro-displacement measuring equipment

Technical Field

The invention relates to a precise micro-displacement measuring device; in particular to a device which has low cost, small volume and simple structure and can precisely measure micro displacement.

Background

High-precision displacement sensors and displacement gauges are widely used in the field of machine tools and other related fields for measuring dimensions of a workpiece, positioning a machining system, and positioning and analyzing an assembly. A conventional displacement meter, such as a dial gauge or a caliper, is composed of a gear and a spring, and the precision of the displacement meter is mostly about 2m (micrometer), which is not suitable for sub-micrometer measurement. Although high precision measurement systems such as laser interferometers can measure sub-micron levels, they are expensive, bulky and heavy, and are not suitable for use in manufacturing processes or in tools. The table in FIG. 1 shows the precise displacement sensors commonly used in manufacturing processes or machines, mainly including capacitance type displacement meters, eddy current type displacement meters, contact type digital sensing meters (such as Keyence products, built-in CMOS photosensitive scales), and non-contact type color confocal laser displacement meters. These displacement meters can achieve 1m accuracy and sub-micron resolution, but are very expensive.

Since the high precision displacement sensor is expensive and needs to measure multiple points simultaneously in practice, the cost of construction becomes very high, and if a sensor with relatively low cost can be manufactured while maintaining high precision and high resolution, it is beneficial to mass construction. For example, in the application of machine tool or positioning platform, the deformation or positioning error of machine tool caused by thermal deformation or strain generated by load can be tracked in real time through multi-point measurement. The real-time feedback information can effectively increase the precision of the manufacturing process.

Disclosure of Invention

The invention relates to a small displacement meter, which has simple structure, can measure the displacement from micro to sub-micron, and has far lower cost than the existing precision displacement sensor product. The invention relates to a contact type precision micro-displacement measuring device and a contact type precision micro-displacement measuring technology which are low in cost, small in size and simple in structure, and can measure micro-displacement of a target surface, the measuring range (measurement range) can be from several micrometers to hundreds of micrometers, the resolution (resolution) can reach 0.01 micrometer to 1 micrometer, and the precision (repeatability) and the accuracy (accuracy) can also reach the same order of magnitude. The basic principle is to use a mechanical amplification mechanism with good repeatability to amplify the micro-displacement by about 1 to 2 orders of magnitude (i.e., about 10 to 100 times), so that the amplified displacement is within the range measurable by a displacement sensor with lower cost. Thus, by using the mechanical amplification mechanism, the displacement sensor with lower cost can measure the micro displacement, and the precision and accuracy can be improved by 1 to 2 orders of magnitude compared with the displacement sensor with lower cost.

Based on the above principle, the contact type precision micro-displacement measuring device of the present invention comprises a displacement amplifying mechanism capable of amplifying micro-displacement. The displacement amplification mechanism comprises an integrated structure fixedly mounted on a substrate. The integrated structure can elastically deform when stressed. The integrated structure has a geometric configuration such that when a force applied to a portion (referred to as a contact portion) varies, the integrated structure elastically deforms, and the elastic deformation causes a displacement of the contact portion (relative to the substrate) and a displacement of another portion (referred to as a measurement portion) of the integrated structure, wherein the displacement of the measurement portion is obtained by multiplying the displacement of the contact portion by a displacement amplification factor, and the displacement amplification factor can be designed to be about 10 to 100 times.

The contact type precision micro-displacement measuring equipment also comprises a contact piece, wherein the contact piece is in contact with the target surface to be measured and transmits the displacement variation of the target surface to the contact part of the integrated structure. That is, the displacement change amount of the target surface can be transmitted to the contact portion in its entirety, and after amplification, an amplified displacement amplified to the magnification of the displacement magnification is generated at the measurement portion.

The contact type precision micro-displacement measuring device of the invention also comprises a non-contact type displacement sensor which is fixedly arranged on the substrate and used for measuring the amplified displacement of the measuring part (namely the displacement relative to the substrate). The desired measurement range of the present invention is from several micrometers to several hundred micrometers, and the resolution, accuracy and accuracy of the present invention is from about 0.01 micrometer to about 1 micrometer. If the displacement magnification is designed to be 100 times, the measurement range is magnified to 0.1 to several millimeters (mm), and the resolution and precision accuracy is about 1 micron to 100 microns. The measurement range, resolution and accuracy requirements can be achieved using a low cost non-contact displacement sensor. As shown in the table of fig. 1, the Hall magnetic sensor (Hall effect sensor) has a suitable specification and a low cost, and is suitable for the present invention.

The integrated structure can be made of a single solid material or several parts can be combined and fixed into an integrated body. Thus, the integrated structure has no parts that move in contact with each other, and its magnification of displacement is purely caused by its geometry and elastic deformation of the structure. This ensures good repeatability accuracy.

One of the embodiments of the integrated structure is a multi-lever system formed by connecting a plurality of lever structures in series. Each lever structure includes a base, a rod, and a flexible hinge (flexual bearing or flexual hinge). The base is fixed on the base plate, and the flexible pivot is connected with the rod piece and the base and used as a fulcrum of the lever. Therefore, a lever structure can also be regarded as an integrated structure, and the elastic deformation of the flexible pivot enables the rod to rotate around the flexible pivot as a fulcrum to generate displacement. The output end (load end) of a lever structure and the input end (effect end) of the next lever structure are connected with each other by a flexible connection structure, so that the output end displacement of a lever structure can be transmitted to the input end of the next lever structure. The displacement of adjacent lever structures of a multi-stage lever system can be transferred in stages, or amplified in stages.

If the displacement magnification of the multi-stage lever system is designed to be about 100, a 2-stage or 3-stage lever can be used. If a 2-stage lever structure is used, the magnification of each lever structure can be set to 10. If a 3-level lever structure is used, the magnification of each lever structure can be set to about 5. Although the foregoing embodiments refer to a multi-stage lever system, a single stage lever configuration may be used if the required magnification is not high, e.g., within 10 to tens.

The lever structures of each level in the multi-level lever system can be distributed in the upper and lower positions, so that the motion planes of all the rod pieces are in the same plane. The lever structures at all levels can also be distributed in the left-right adjacent positions, so that the rod pieces move on different motion planes, but the motion planes are parallel to each other. In order to make the overall size of the multi-stage lever system smaller, the output ends of adjacent lever structures preferably point in opposite directions. When the lever structures at each stage are distributed at left and right adjacent positions, the flexible connecting structure connecting the adjacent input end and output end preferably comprises two mutually perpendicular flexible sections, one section is used for adapting to the relative rotational displacement between the left and right adjacent rod pieces, and the other section is used for adapting to the relative linear displacement between the two rod pieces.

In order to improve the efficiency of displacement transmission, reduce the loss of amplification and improve the repeatability, the multi-stage lever system is preferably constructed such that the forces applied to the flexible pivot and the flexible connecting structure when the multi-stage lever system is applied with a force are mainly bending and tension, thereby avoiding compressive or shearing forces.

The contact element in contact with the target surface to be measured may comprise an object having a high hardness level protruding shape, such as a bead made of zirconia, alumina or ruby. The beads may be directly attached to the contact portions of the integral structure.

When the target surface to be measured has a lateral motion (i.e. its main moving direction is perpendicular to the micro-displacement measuring direction), it is desirable to avoid the lateral motion from affecting the measurement of the micro-displacement in the vertical direction. Therefore, the contact type precision micro-displacement measuring device of the present invention may comprise a contact transmission mechanism for ensuring that the displacement of the contact portion of the integrated structure is not affected by the lateral movement of the target surface. The contact transmission mechanism may comprise a thin and wide flexible cantilever beam, the beam being substantially parallel to the plane of lateral movement of the target surface, the fixed end of the flexible cantilever beam being fixed to the substrate or to a structure fixed to the substrate, and the free end of the flexible cantilever beam being fixed to a rigid end mount. The contact element is fixedly arranged on the upper surface of the rigid end seat and is contacted with a target surface to be measured. A second contact member is fixedly mounted on the contact portion of the integrated structure and contacts with the bottom surface of the rigid end seat. In this way, the flexible cantilever beam can resist the influence of the lateral movement of the target surface, ensuring that only the vertical displacement (i.e. the allowed displacement direction of the flexible cantilever beam) can be transmitted to the contact portion of the integrated structure.

The non-contact displacement sensor may use a Hall magnetic sensing element and a small magnet. The small magnet is fixedly arranged at the measuring part of the integrated structure, and the Hall assembly is fixedly arranged on the substrate facing the small magnet so as to measure the displacement variable of the measuring part.

The contact type precision micro displacement measuring device of the present invention further comprises a housing, wherein the housing and the substrate form an outer package to package and protect the displacement amplifying mechanism and the non-contact type displacement sensor. When the non-contact displacement sensor can be used as a Hall magnetic sensing assembly, the package can contain a magnetic interference-proof sheet, such as a mu-metal sheet, to prevent the reading of the Hall assembly from being interfered by an external magnetic field.

In order to make the contact type precise micro-displacement measuring equipment of the invention capable of measuring under various seats and keep the same amplification rate of the multi-level lever system under various seats, the invention further comprises an improved lever structure with mechanical balance, so that the mechanical displacement amplifier can operate under different seats without recalibration and better resist the influence of external vibration. In the lever structure for improving mechanical balance, at least one rod piece comprises a connecting part and a balance weight structure formed by a balance weight block, so that the gravity center of the rod piece is positioned on a fulcrum, and the rod piece can keep balance under various seats. In particular, the rod of the last level lever structure includes a counterweight structure design, so that the center of gravity of the whole rod is located on the flexible pivot fulcrum of the lever structure, thereby achieving mechanical balance, and making the operation of the multi-level lever system basically not influenced by the action direction of gravity. When the Hall magnetic induction component is used for reading the amplified numerical value, the invention also comprises a local packaging design for isolating the external magnetic field, and the influence of the external magnetic field is better resisted.

Based on the above characteristics, the advantages of the invention include low cost, small volume, simple structure, precision equivalent to the current expensive commercial product, capability of outputting electric signals, convenience for reading and tracking, and capability of being used for system control.

Drawings

FIG. 1 illustrates the basic concept of the present invention;

FIG. 2 is an example of a single-stage lever structure according to an embodiment of the present invention;

FIG. 3 is an integrated form of a flexible pivot that can be used with embodiments of the present invention;

FIG. 4 is an exploded view of an exemplary 3-level amplification lever structure according to an embodiment of the present invention;

FIG. 5 is an assembly view of an exemplary 3-level magnifying lever structure according to an embodiment of the present invention;

FIG. 6 illustrates an example of an assembly of an embodiment of the present invention including a 3-level amplification lever structure;

FIG. 7 is a cross-sectional view of a contact and housing opening of an assembled example of an embodiment of the present invention;

FIG. 8 is an assembly diagram of an exemplary displacement amplification mechanism using a two-stage lever system in accordance with an embodiment of the present invention;

FIG. 9 is an example of a contact transfer mechanism at a contact and housing opening according to an embodiment of the present invention;

FIG. 10 is a diagram of an exemplary system of the present invention comprising a lever system with mechanical balance;

FIG. 11 is a diagram of a second embodiment of the present invention comprising a lever system with mechanical balance;

FIG. 12 is an example of a partial packaging embodiment of the present invention containing isolation from external magnetic fields;

FIG. 13 is an example of an assembly of an embodiment of the present invention including a two-stage amplification lever structure.

Description of the reference numerals

10: projection structure

100: coordinates of the object

L1, L2, L3 first or second or third lever structure

LH2 second lever structure flexible pivot

LA1 first lever structure rod

LA2 rod with second lever structure

LA3 third lever structure rod piece

Base of LB1: first lever structure

Base of LB2: second lever structure

LA2e, LB2e: projecting column

Base of LB3: third lever structure

LH1: flexible pivot of first lever structure

LH2: flexible pivot of second lever structure

LH3: flexible pivot of third lever structure

LHd: spring leaf

P1L1: base joint surface

P1L2: first connection surface

P2L2: second connecting surface

P3L2: third connecting surface

P3L1, P2L3: connecting surface

AL1: distance from fulcrum of lever structure to input point

AL2: distance from the first connection face to the third connection face

AL3: distance between two adjacent plates

BL1: fulcrum of lever structure to end of rod LA1

BL2: distance from the first connection surface to the second connection surface

BL3: distance between two adjacent plates

L2b is a second lever structure and is balanced mechanically

LA2b is a second lever structure rod piece with mechanical balance

CF12: l-shape flexible connection structure

CF23: spring leaf

SP12, SP23: long gasket

101 flexible cantilever beam

102 rigid end mount

5 contact element

5b second contact member

7 displacement amplifying mechanism

8: substrate

CA outer casing

CAOC shell opening

CP contact point

CFd1, CFd bare section

CW1: connection

CW2, CW2b counterweight block

DF damping oil

HS Hall assembly

MAG magnet sheet

MP measuring point

And (3) FSF: film(s)

MS: object to be measured

120: the rod being at the end thereof near the flexible pivot

121: vertical column

300c: supporting point

300. 300x, 300y, 300z: axial line

MB: tubular antimagnetic shield

Detailed Description

From the comparison of Table 1, it can be seen that the Hall device has the advantage of being relatively inexpensive in the micrometer-scale sensor, but has a resolution of about 5m, an accuracy of 0.1% -1% of the measurement range, and a measurement range of 0.25-2.5 mm. Therefore, for the displacement with the measuring range of about 1mm and the accuracy and the resolution of 1-5 m, the Hall component is a very economical and practical choice. Now, if the displacement is measured in the sub-micron scale, for example, 0.1m, and if the small displacement can be amplified by 100 times, the displacement is measured to be 10m. This falls within the measurement specifications of the hall element. In other words, if a reliable mechanical amplification mechanism is available to amplify sub-micron displacements with good repeatability, then the use of the hall element can measure small displacements in the range of 10m at a resolution of 0.1m, whereas the hall element itself actually measures amplified displacements in the range of 1mm (1000 m) at a resolution of 10m. The basic concept is shown in FIG. 1, which takes the Hall device specification of a displacement sensor with lower cost as an example, the measurement range is 0.25-2.5 mm, the accuracy is 0.1% -1% of the measurement range, and the resolution is 5 μm. Therefore, the displacement amplifying mechanism can be made into a low-cost and small-size precise displacement meter only by being light and small and being combined with a Hall assembly or other equivalent displacement sensors with lower cost.

Table 1: the specification and price of a common commercial precision displacement sensor are compared

# general model GT2-PK12A

* General model CL-L030

One embodiment of the displacement amplification mechanism uses a multi-lever system formed by connecting a plurality of lever structures in series, and the multi-lever system is an integrated structure capable of generating elastic deformation. FIG. 2 shows an example of a single lever structure, comprising a base LB2, a lever LA2 and a flexible pivot LH2 connecting the lever to the base. For convenience of the subsequent description, this lever structure is referred to as a lever structure L2. In practice, the base and the lever may be made of metal or other hard materials. The flexible pivot LH2 is formed by a foil-type spring, such as a spring steel plate. The foil spring is fixed to the base attachment surface P1L2 of the base, and the other end is fixed to one end of the lever. The fixing means can be screwed or soldered or glued. The flexure pivot has a small section of spring plate (LHd) exposed, i.e., there is no contact with the base or lever, for the purpose of functioning as a flexure pivot. The base and lever may also be connected via another flexible pivot mechanism in one piece, as shown in figure 3. In any flexible pivot, the lever and the base form an integrated structure which can only rotate through the flexible pivot, and the mechanism part does not slide in any contact. The rod LA2 includes a protruding structure 10 having a second connection surface P2L2 parallel to the first connection surface P1L2 of the base. The second connection surface P2L2 is used for connecting with the lever structure of the previous stage. When the protruding structure is pushed downward (i.e. according to the z-direction with coordinates of 100), the displacement on the connection plane P2L2 will be amplified BL2/AL2 times on the third connection plane P3L2 of the rod end, depending on the distance ratio of these two planes to the first connection plane P1L 2.

To amplify a small displacement by two orders of magnitude requires 2 to 3 lever structures in series to amplify the displacement step by step. The lever structures at each level are distributed at left and right adjacent positions, so that the rod pieces move on different motion planes, but the motion planes are parallel to each other. The output end of one lever structure is interconnected with the input end of the next lever structure by a flexible connection structure, so that the output end displacement of one lever structure can be transmitted to the input end of the next lever structure. Fig. 4 shows an exploded view of a 3-level amplification lever structure. The three lever structures are substantially similar to the lever structure shown in FIG. 2. The first-stage lever structure L1 includes a base LB1, a lever member LA1, and a flexible pivot LH1. The flexible pivot LH1 is partially fixed to the base connection plane P1L1 of the base, and partially fixed to one end of the rod LA1, which is a fulcrum of the lever structure. The stem LA1 includes a protruding structure, which may be considered as the contact portion CP of the integrated structure, on which the device contact 5 (e.g., zirconia beads) is the input point of the displacement amplification mechanism. The magnification ratio of the displacement from this input point to the end connecting surface P3L1 of the rod LA1 is BL1/AL1.BL1 and AL1 are distances from the fulcrum of the lever structure to the connecting plane P3L1 at the end of the rod LA1 and to the input point CP, respectively. In fig. 4, the end connecting surface P3L1 of the first-stage lever structure rod LA1 is directed in the x direction.

Second stage lever structure L2 is mounted parallel to lever structure L1, as described above with respect to fig. 2, but with end P3L2 of rod LA2 facing in the + x direction. That is, to make the overall volume of the multi-stage lever system smaller, the output ends of adjacent lever structures point in opposite directions. In addition, the connection surface P2L2 of the rod LA2 is aligned with the connection surface P3L1 at the end of the rod LA1, and a flexible connection structure (foil spring) CF12 with a shape of "Γ" is used to connect the rod LA2 with the rod LA1. The L-shaped spring plate has a lower half portion attached to the P3L1 connecting surface of the rod LA1 and an upper half portion attached to the P2L2 surface of LA 2. Thus, the displacement at the end of the rod LA1 can be transmitted to the input end P2L2 of the second-stage lever structure L2.

Third stage lever structure L3 is substantially similar to lever structure L1, and is composed of base LB3, rod member LA3, and flexible pivot LH 3. The end of the rod LA3 faces in the-x direction. The stem LA3 also has a convex feature as a connection surface P2L3 that will align with the connection surface P3L2 at the end of the stem LA 2. In the same manner as the above connection, the L-shaped leaf spring CF23 has a lower half portion attached to the P3L2 surface of the rod LA2 and an upper half portion attached to the connection surface P2L3 of the rod LA 3. The amplification rate of this stage is BL3/AL3 from the input point P3L2 to the LA3 end measurement point MP.

When the left and right adjacent lever structures are assembled, long gaskets (SP 12 and SP 23) are used for keeping a gap between the adjacent rod structures so as to avoid collision and friction with each other. Fig. 5 shows an assembly of a three-stage lever structure 7. The leverage effect above can be derived from the magnification from the contact point CP to the final measurement point MP as:

total magnification = (BL 1/AL 1) (BL 2/AL 2) (BL 3/AL 3)

Assuming that the magnification of each layer of levers is 5, the magnification will be 125 times through the three-layer magnification mechanism, and the effect of two orders of magnitude magnification can be obtained.

To achieve better measurement results, each lever is preferably designed to be light to reduce the influence of gravity and vibration, and each flexible pivot can bear no more than a fatigue limit in the operating range. Ideally, all of the flexible pivots and foil springs should be planar (undeformed) and parallel to each other when there is no input value. The flexible connecting structure connecting the adjacent input end and output end preferably comprises two mutually perpendicular flexible sections, i.e. exposed sections on the spring plate. As shown in FIG. 7, the L-shaped flexible connection structure CF12 has a horizontal exposed section CFd with the rod L1 and a vertical exposed section CFd with the rod L2, and the same applies to the spring plate CF23. The exposed sections in two directions are used for providing flexibility for rotation and translation of the lever during movement, one section is used for adapting to relative rotation displacement between the two adjacent rods at the left and right, and the other section is used for adapting to relative linear translation between the two rods, so that the displacement can be smoothly transmitted.

Finally, the amplified displacement at the measurement point MP can be measured by the hall element HS fixed to the base 8. FIG. 6 shows a complete assembly of a precision micro-displacement measurement device, which includes a mechanical displacement amplifier (three-stage lever structure) 7 and a Hall element HS for measuring the displacement. The base of the tertiary lever structure 7 is fixedly arranged on the base plate 8. The bottom surface of the end (measuring point MP) of the third lever member LA3 is attached with a magnet piece MAG facing the hall element HS. The Hall element measures the change of the magnetic field to obtain the corresponding displacement. The assembly is packaged with a housing CA.

The contact pieces (contact balls) 5 of the device on the contact point CP must be exposed outside the housing CA, which has an opening CAOC, as shown in the cross-sectional view of fig. 7. A thin film (e.g., polymer film) FSF is adhered to the periphery of the contact ball 5 and the edge of the opening CAOC to form a thin film oil seal. By giving appropriate dimensions to the membrane oil seal, the effect of encapsulation can be achieved with little effect on input force. In the figure, MS is the object to be measured, and is contacted with the measuring ball.

If necessary, the housing CA may be filled with damping oil DF for damping. In particular, the third lever member LA3 is a cantilever beam, and the vibration thereof may affect the measurement value of the displacement meter, so the damping oil is used to reduce the error effect that the vibration may generate.

According to the above concept, if the magnification ratio of each stage is 10 times, the two-layer lever can achieve the magnification effect of 10 × 10=100 times. Fig. 8 is a conceptual diagram of a displacement amplification mechanism using a two-stage lever system.

When the target surface to be measured has a lateral motion (i.e. its main moving direction is perpendicular to the micro-displacement measuring direction), it is desirable to avoid the lateral motion from affecting the measurement of the micro-displacement in the vertical direction. Therefore, the contact type precision micro-displacement measuring device of the present invention may comprise a contact transmission mechanism for ensuring that the displacement of the contact portion of the integrated structure is not affected by the lateral movement of the target surface. As shown in the cross-sectional view of fig. 9, the contact transfer mechanism may comprise a thin, wide, flexible cantilever beam 101, which is substantially parallel to the plane of lateral movement of the target surface MS, and which is fixed at its fixed end to a housing CA that is fixed to the substrate, and at its free end to a rigid end mount 102. The contact element 5 is fixed on the upper surface of the rigid end seat, exposed outside the shell CA through the shell opening CAOC, and contacts with the target surface to be measured. The membrane FSF may be bonded to the rigid end mount or flexible cantilever beam surface that contacts the periphery of the ball 5 and the edge of the opening CAOC to form a membrane oil seal. A second contact member 5b is fixedly mounted on the contact portion CP of the integrated structure, and the second contact member is in contact with the bottom surface of the rigid terminal base. In this way, the flexible cantilever beam can resist the influence of the lateral movement of the target surface, ensuring that only the vertical displacement (i.e. the allowed displacement direction of the flexible cantilever beam) can be transmitted to the contact portion of the integrated structure.

Although the above-mentioned amplifying mechanism is assembled by multiple layers, the concept can be to manufacture an integrally formed multi-layer structure by injection molding, and the material can be selected from polymer to achieve the effect of lighter weight.

In order to make the contact type precision micro displacement measuring device of the invention can measure under various seats and keep the same magnification of the multi-level lever system under various seats, the lever in the lever structure can contain a counterweight structure to make the center of gravity of the lever fall on the fulcrum, so as to reduce the influence of external vibration and keep the balance under various seats. This problem of dynamic balancing is illustrated by way of example in fig. 8. For the purpose of amplifying the displacement, the fulcrums of the two-stage levers of fig. 8 are both biased to one end of the rod members, so that the two rod members are both long at one end and short at the other end, and the centers of gravity of the rod members are also far away from the fulcrums. Therefore, when external shock occurs, the rod member, particularly the rod member LA2, is caused to vibrate back and forth, being supported by only one end. In addition, when the orientation of the device is changed, the equilibrium position of the amplifying mechanism will be different. For example, with the seat in fig. 8 facing downward, the output end of the rod LA2 will hang downward (z-direction), so that the distance between the magnet piece MAG and the sensor HS becomes smaller; if the measurement apparatus is inverted, the distance between the magnet piece MAG and the sensor HS becomes longer. This complicates the calibration procedure of the metrology apparatus.

One solution to the above problem is to balance the rods in the lever structure so that the center of gravity of the rods falls on their fulcrum. A first example of the modification will be described by taking the two-stage lever system of fig. 8 as an example. Fig. 10 shows an example of the two-stage lever system with a counterweight structure added in fig. 8, wherein a connecting portion CW1 is added to one end 120 of the rod LA2 of the second-stage lever structure near the flexible pivot LH2, and the connecting portion laterally bypasses the vertical column 121 of the base LB2 to the rear thereof, so that a counterweight CW2 can be added behind the vertical column 121 to adjust the center of gravity of the rod LA2 to a position close to the pivot LH2, thereby achieving balance or approaching balance. Rod LA1 is less prone to center of gravity balance problems because it is supported at both ends by flexible pivot LH1 and flexible connection CF12, respectively, but the same counterweight structure can be used for rod LA1.

Fig. 11 shows a second example of the structure of the mechanical balance lever, which can make the center of gravity of the rod exactly at the position of the fulcrum, i.e. the middle point of the bendable section of the flexible pivot LH2. The problem will be described first with reference to fig. 10. The location of the fulcrum in fig. 10 is the midpoint of the bendable segment of the flexible pivot LH2, indicated at 300c, and three perpendicular axes 300x, 300y, 300z are drawn through the point. The design of the rod LA2 for the second level lever structure is taken from fig. 8, with most of the material (mass) below the axis 300 x. Therefore, in terms of mechanical balance, simply placing the weight CW2 on the other side (x direction) of the fulcrum 300c can shift the center of gravity to the axis 300z, but not necessarily to the fulcrum 300 c. To move the center of gravity to the fulcrum 300c, the position (z direction) of the weight CW2 must be simultaneously raised. However, since most of the mass of rod LA2 is located below axis 300x, the position of weight CW2 may need to be increased so much that the overall size of the mechanism is increased. Fig. 11 shows a modification of the design of the rod shape to make most of the material as close as possible to the axis 300x passing through the fulcrum 300c, as compared with the rod LA2b with the balanced shape, the rod at the output end is thinned and moved up to be nearly centered on the axis 300 x. At the same time, the weight CW2b is also raised to approximately the center axis of the 300 x. Therefore, the gravity center of the rod can be accurately located at the position of the fulcrum, i.e. the middle point of the bendable section of the flexible pivot LH2, and the overall dimension of the mechanism is prevented from being excessively increased.

Generally, the rod is designed to have a shape that the distribution of most of the materials is as close as possible to the axis passing through the fulcrum, i.e., a more balanced shape, and the position arrangement of the counterweight structure (connecting part and counterweight block) can make the gravity center of the rod accurately fall on the position of the fulcrum. In order to reduce the size of the whole mechanism as much as possible, the balancing weight is made of a material with higher density.

When the Hall magnetic sensing component is used as a non-contact displacement sensor, under the general condition, the micro displacement measuring equipment of the invention is not affected as long as a strong magnetic field does not exist in a few centimeters near the sensor. Designs to prevent external magnetic interference may be included if further protection against more intense magnetic fields is desired. For example, one or more layers of anti-magnetic sheet(s) such as a mu-metal sheet can be laid on the inner wall of the housing CA and the substrate 8 to prevent the reading of the hall element from being interfered by external magnetic field. The alloy is a material containing an alloy of nickel, iron, molybdenum, or the like. Another design is to use a resistive plate to more closely block the portion of the mechanism near the hall element HS from the corresponding magnet plate MAG. As shown in fig. 12, the hall element HS is disposed on a pillar LB2e of the base LB2, and the corresponding magnet piece MAG is disposed on a lower surface of the pillar LA2e downward from the end of the rod LA 2. The anti-magnetic sheet forms a tubular anti-magnetic cover MB covering the Hall assembly HS, the magnet sheet MAG and the side peripheries of the two studs. The tubular shield MB may be fixed to the base LB2 or the base plate 8 without contacting the rod LA2 or the post LA2e, and thus does not affect the operation of the rod LA 2. The local anti-magnetic cover can be used with the anti-magnetic cover on the inner wall of the shell and the substrate to improve the effect of anti-magnetic interference.

FIG. 13 shows an assembly example of the two-stage amplification lever structure with mechanical balance according to the embodiment of the present invention, which includes a housing CA, a substrate 8 and the contact transmission mechanism shown in FIG. 9. Wherein the first lever structure L1 comes from fig. 10 and the second lever structure L2b comes from fig. 11.

While the invention has been described with reference to specific examples, the invention can be practiced in other ways that will vary from the specific details disclosed herein without departing from the spirit and scope of the invention. For example, the fulcrum of the above-mentioned lever knot examples is disposed at one end of the rod, such as between two ends of the rod. And the mechanical magnification is not necessarily an integer.

Claims (7)

1. A precision micro-displacement measuring apparatus for measuring micro-displacement of a target surface, the apparatus comprising:

the displacement amplification mechanism comprises an integrated structure fixedly arranged on the substrate, the integrated structure has a geometric configuration, when the force applied to a contact part of the integrated structure is changed, the integrated structure generates elastic deformation, the elastic deformation can generate displacement on the contact part, and simultaneously, another measurement part of the integrated structure generates displacement, and the displacement generated by the measurement part is the displacement multiplied by the amplification rate of the contact part;

a contact member which is in contact with the target surface to be measured and transmits the displacement variation of the target surface to the contact part of the integrated structure;

and the non-contact displacement sensor is fixedly arranged on the substrate and used for measuring the amplified displacement of the measuring part and outputting an electrical signal.

2. The micro-displacement measuring apparatus of claim 1, wherein the micro-displacement measuring apparatus comprises

The integrated structure in the displacement amplification mechanism comprises a multi-level lever system formed by connecting a plurality of lever structures in series, each lever structure comprises a base, a rod piece and a flexible pivot, the base is fixedly arranged on the substrate, the flexible pivot is connected with the rod piece and the base and serves as a fulcrum of a lever, the output end of one lever structure is connected with the input end of the next-level lever structure by a flexible connection structure, so that the displacement of the output end of the lever structure can be transmitted to the input end of the next-level lever structure, and the multi-level lever structure of the multi-level lever system comprises at least one lever structure with the rod piece subjected to mechanical balance;

the contact part comprises the input end of a first-stage lever structure of the multi-stage lever system, the measuring part comprises the output end of a last-stage lever structure of the multi-stage lever system, and a rod piece of the last-stage lever structure comprises a balance weight structure design so that the center of gravity of the whole rod piece is positioned on a flexible pivot fulcrum of the lever structure to achieve mechanical balance and ensure that the operation of the multi-stage lever system is basically not influenced by the action direction of gravity;

the non-contact displacement sensor comprises a Hall assembly fixedly arranged on the substrate and a magnet piece attached to the measuring part.

3. The micro-displacement measuring apparatus of claim 2, wherein the micro-displacement measuring apparatus comprises

Each level of lever structure is distributed in a left-right adjacent position, so that each rod piece moves on different motion planes, but the motion planes are parallel to each other;

the output ends of the adjacent lever structures point to opposite directions;

the flexible connecting structure for connecting the input end and the output end of the adjacent lever structures comprises two sections of flexible sections which are perpendicular to each other, one section is used for adapting to the relative rotation displacement between the two adjacent left and right rod pieces, and the other section is used for adapting to the relative linear displacement between the two rod pieces.

4. The micro-displacement measuring apparatus of claim 3, wherein the micro-displacement measuring apparatus

The geometrical configuration of each lever structure ensures that the forces borne by the flexible pivot and the flexible connecting structure are mainly bending and tension when the lever structure is stressed, and compression force or shearing force is avoided.

5. The micro-displacement measuring apparatus of claim 3, wherein the micro-displacement measuring apparatus

The contact element is fixedly arranged on a contact transmission mechanism, and the contact transmission mechanism limits the contact element to be capable of changing only in the measuring direction of the micro-displacement measuring equipment;

and a second contact member fixedly mounted on the contact portion;

the contact transmission mechanism is in contact with the second contact piece, and exerts a pre-force on the second contact piece so as to keep the displacement of the target surface to be measured, the contact piece and the second contact piece consistent.

6. The micro-displacement measuring apparatus of claim 5, further comprising a housing for protecting the displacement amplifying mechanism, wherein the contact transmitting mechanism is disposed on the housing, the inner wall of the housing is coated with a magnetic resisting sheet, and the housing contains damping oil.

7. The micro-displacement measuring apparatus of claim 2, wherein the end of the rod of the last lever structure includes a downward protrusion for positioning the magnet piece thereunder, the micro-displacement measuring apparatus further comprising:

a sensor stud for mounting the Hall device thereon;

and the tubular anti-magnetic cover is used for covering the Hall assembly, the magnet sheet and the side edges of the two protruding columns without contacting with the Hall assembly, the magnet sheet and the side edges of the two protruding columns.

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