JPH0431710A - Three-dimensional measuring probe - Google Patents

Abstract

PURPOSE:To make the main body of a block compact by providing an X spring part, a Y spring part and a Z spring part which are elastically deformed along the direction X, the direction Y and the direction Z, respectively, in the main body of the probe, and detecting the amount of the deformation of each spring part with a strain gage. CONSTITUTION:A block main body 2 is formed by sequentially laminating an X block body 4, a Y block body 5 and a Z block body 6. Each of the block bodies comprises cube-shaped single crystal silicon. The single crystal silicon undergoes gouging machining so that cavity parts 7, 8 and 9 whose cross sections have the approximately H-shaped pattern. When the cavity parts 7, 8 and 9 are gouged out in the block bodies 4, 5 and 6, an X spring part 11, a Y spring part 12 and a Z spring part 13 comprising pairs of facing parallel springs 11a, 12a and 13a which are separated in parallel are formed in the block bodies 4, 5 and 6. The inner surfaces of both end parts of the parallel springs 11a, 12a and 13a are formed as thin hinge parts 11b, 12b and 13b of parts of the cavity parts 7, 8 and 9. The spring 11, 12 and 13 can be elastically deformed with the above described hinge parts 11b, 12b and 13b as supporting parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Application Field) This invention relates to a three-dimensional measuring probe used in a three-dimensional measuring machine or the like.

(Prior Art) Generally, when measuring the shape of a three-dimensional free-form surface, a three-dimensional measuring machine is used. As is well known, a three-dimensional measuring machine is equipped with a three-dimensional measuring probe that comes into contact with an object to be measured. Three-dimensional measurement methods include the touch method, which detects the coordinates of the contact point between the three-dimensional measurement probe and the object to be measured, and the touch method, which detects the coordinates of the contact point between the three-dimensional measurement probe and the object to be measured, and the touch method, which detects the displacement of the three-dimensional measurement probe by continuously contacting the object to be measured. There is a tracing method that detects the amount in an analog manner.

However, the former touch method is basically indirect,
Since it is an estimated measurement, the latter tracing method has recently been attracting attention.

As a three-dimensional measuring probe used in the scanning method, one manufactured by ZEISS of West Germany is known. This prior art includes a probe body having three sets of parallel spring parts that are deformable in the X direction, the Y direction, and the Z direction;
and a contact body provided at the tip of the probe body.

A probe ball is provided at the tip of the contact body, and the probe ball is brought into contact with the object to be measured to cause the three-dimensional measurement probe to scan. As a result, the three sets of parallel springs deform in the X direction, Y direction, and Z direction, respectively, along the three-dimensional free-form surface of the object to be measured, and by detecting the amount of deformation, the shape of the object to be measured can be determined. It is now possible to measure it.

(Problems to be Solved by the Invention) Incidentally, in the conventional three-dimensional measurement probe described above, the amount of deformation of each spring portion was measured using a differential transformer. In other words, a differential transformer is made up of a shaft that displaces according to the deformation of the spring part, and a coil that is installed in a position that does not displace even if the spring part deforms, into which the shaft is slidably inserted. The probe body that detects the amount as a change in voltage value must be large enough to incorporate three sets of differential transformers in the X, Y, and Z directions, so the - side is quite large, at 20 mts or more. This was unavoidable, and the configuration also became complicated.

As the probe body becomes larger, its natural vibration becomes lower, so there is a problem in that it picks up external vibrations from the floor surface on which the coordinate measuring machine is installed and is more likely to resonate.

The present invention has been made in view of the above circumstances, and its object is to provide a three-dimensional measuring probe that has a simple configuration and can be downsized.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to solve the above problems, the present invention comprises a probe body and a contact body provided at the tip of the probe body and in contact with the object to be measured. The probe body includes an X spring section, a Y spring section, and a Z spring section that elastically deform along the X direction, Y direction, and Z direction, respectively, and an X strain gauge that detects the amount of deformation of each spring section. , a Y strain gauge, and a Z strain gauge.

With this configuration, each strain gauge can be provided without increasing the size of the probe body, so the probe body can be sufficiently miniaturized.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show a first embodiment of the invention. FIG. 1 shows the overall configuration of a three-dimensional measuring probe 1, which is composed of a probe body 2 and a contact body 3 provided on the tip surface (lower end surface) of the probe body 2. There is. The probe main body 2 is formed by sequentially laminating an X block body 4, a Y profile body 5, and a Z block body 6.

Each block 4.5.6 is made of cubic monocrystalline silicon, which is hollowed out to form a cavity 7.8.9 having an approximately H-shaped cross section.

In this way, each block body 4.5.6 has a cavity 7.8.
9 is hollowed out, each block body 4.5.6 has a pair of parallel springs 11a, 12a, 13a spaced apart and facing each other in parallel.
X spring part 11, Y spring part 12 and Z spring part 1 consisting of
3 is formed. Each of the above parallel springs lla, 12a%13
The inner surfaces of both ends of a are formed into thin hinge parts 11b, 12b, 13b by a part of the cavity 7.8.9. Each spring portion 11.12.13 has the hinge portion 11b,
It can be elastically deformed using fulcrums 12b and 13b.

When each of the blocks 4.5.6 is made of single crystal silicon, it is more homogeneous than ordinary metal materials.
Young's modulus and thermal characteristics of the hinge parts 11b, 12b, 13b,
Furthermore, mechanical properties such as stress stress characteristics can be made uniform. Therefore, since the mechanical properties of the probe body 1 are constant, it is possible not only to obtain uniform performance but also to improve the manufacturing yield.

A first protruding strip 6a is provided on one end side of the outer surface of the pair of parallel springs 13a of the Z block body 6 in parallel with the hinge portion 13b, and a hinge portion 1 is provided on the other end side of the other outer surface.
A second protruding strip 6b is provided in parallel with the protruding strip 6b.

Hinge parts 11b, 12b, 1 of each block body 4.5.6
3b, an X strain gauge 14 and a Y strain gauge 14 are installed at the center of the outer surface, respectively.
A strain gauge 15 and a Z strain cage 16 are provided. That is, each block body 4.5.6 is provided with four strain gauges. These strain gauges 14
．． 15.16 is the hinge portion 11b as shown in FIG.
A plurality of piezoresistors 17 formed in parallel and spaced apart in a direction perpendicular to the longitudinal direction of 12b and 13b, and a plurality of conductive pads 17a in which each piezoresistor 17 is electrically connected in series.
and wiring pads 17b for taking out lead wires provided at both ends of the electrically connected piezoresistor 17. Since each block body 4.5.6 is made of single crystal silicon, each strain gauge 14.15.16 is formed by diffusing impurities such as boron. That is, each strain gauge 14, 15, 16 is formed by photolithography technology, similar to forming a circuit pattern on a semiconductor.

Therefore, the characteristics of the strain gauge are not affected by the adhesive, unlike when the strain gauge is attached to the measurement area with adhesive, which improves detection accuracy and prevents it from peeling off. Strain gauges of the same quality can be precisely formed on the body. In other words, the quality of each block body 4.5.6 can be made uniform.

The block bodies 4.5.6 formed in this manner are sequentially stacked as shown in FIG. In other words, the lower mounting plate 18 is adhesively fixed to one side of the X block body 4 out of a pair of side surfaces that are not formed on the parallel spring 11a, and the lower mounting plate 18 is adhesively fixed to the other side surface that is formed on the parallel spring 12a of the Y block body 5. One of the pair of sides that is not attached is fixed with adhesive.

A first protrusion 6a of a two-block body 6 is adhesively fixed to one end side of the other side of the Y-block body 5.

The upper mounting plate 1 is attached to the second protrusion 6b of this Z block body 6.
9 is fixed with adhesive. In other words, xSy shown in FIG.
, z, the X block body 4 has a pair of parallel springs Ila along the X direction, and the Y block body 5
A pair of parallel springs 12a are arranged along the Y direction orthogonal to the X direction. Furthermore, the Z block body 6 has a pair of spring parts 13a arranged along the Z direction perpendicular to the plane formed by the X direction and the Y direction.

The contact body 3 having a probe ball 3a at its tip is vertically disposed on the lower mounting plate 18, and the upper mounting plate 19 is attached to an arm of a coordinate measuring machine (not shown). Therefore, when the probe ball 3a of the contact body 3 comes into contact with an object to be measured (not shown) and an external force acts on the contact body 3, each block body 4, 5, .
The spring portions 11, 12, and 13 of 6 are deformed in the X, , YSZ directions, respectively.

The four strain gauges 14.15.16 provided on each block 4.5.6 form a bridge circuit. FIG. 4 shows a bridge circuit 25 formed by the X strain gauges 14 (the four X strain gauges are denoted by 14a to 14d in FIGS. 3 and 4) provided in the X block body 4. . 4 X strain gauges 14a
~14d, compressive strain occurs in 14a and 14c when the X block body 4 is deformed as shown in FIG.
4b and 14d are subjected to tensile strain.

A constant voltage vec is applied to this bridge circuit 25, so that an output V outx can be obtained. Output V
outx is input to the processing circuit 26 and processed.

Although details are not shown, each has four Y strain gauges 15.
and the Z strain gauge 16 are also assembled into bridge circuits 26 and 27 similar to the X strain gauge 14, and these bridge circuits 26.
The output V outysv outz from 27 is also input to the processing circuit 26.

Here, the external force in the X direction applied to the X block body 4 is fx,
The spring constant of the X spring part 11 is kx, and the amount of deformation in the X direction is dx.
Then, the following equation is obtained: fx −kx −dx −(1).

Furthermore, when the X spring portion 11 is deformed by the external force fx as shown in FIG. 3, the strain gauges 14a, 14c
A compressive strain ε is generated in the strain gauges 14b and 14d, and a tensile strain ε is generated in the strain gauges 14b and 14d. Since the hinge portions 11b at the locations where each strain gauge is provided are formed into geometrically equal shapes, the compressive strain ε and the tensile strain −ε have the same absolute value.

When strain ε occurs in each strain gauge, the changes δR in the resistance values R of these strain gauges also become equal. Bridge circuit 2 in Fig. 4 when the resistance value R of the strain gauge changes by δR
The output voltage V outx of 5 is as follows. Therefore, if the output voltage V outx is detected, the change in resistance value δR
can be found.

Since the change in resistance value δR is proportional to the strain ε, and the strain ε is proportional to the amount of deformation dx of the X spring portion 11, the output voltage v o
The amount of deformation dx can be determined from utx.

In this way, the amount of deformation dy, z is applied to the Y spring portion 12, and the spring 8
If the amount of deformation dz of 13 is calculated, x, y applied to the contact body 3
, the external force fx Sfy s fz in the z direction can be calculated.

Deformation amount in x, y, and z directions d x Sd y % d z
From this, the relative position of the probe ball 3a at the tip of the contact body 3 with respect to the upper mounting plate 19 can be determined, and the external force f
From X, fyS fz, the direction F of the force acting on the object to be measured or the probe ball 3a can be determined. From the direction F of this force, the direction of the contact point between the object to be measured and the probe ball 3a can be determined.

Once the direction of the contact point is determined, the center position and radius of the probe sphere 3a are known, so the three-dimensional spatial coordinates of the contact point between the object to be measured and the probe sphere 3a can be calculated, and this value can be expressed as a three-dimensional This is the final output from the contact body 3 of the measuring machine. Since the spatial coordinates of the point of contact with the object to be measured can be determined from the output from the contact body 3, this becomes the output from the three-dimensional measuring machine.

FIG. 5 is a graph showing the characteristics of the three-dimensional measurement probe 1 of the present invention. The horizontal axis of this graph is the length of one side of the block from 10-'-0,1m to 10-'-0,1tI
When changing up to tx, the amount of deformation of the block body (DI
SPLACEMENT), strain applied to the strain gauge (
The vertical axis shows how the minimum natural frequency (FREQUENCY) generated in the spring section changes.

In the figure, the straight lines D1 to D4 indicate the external force (measured pressure) applied to the block body at 0. 81-84 shows the relationship between the size of the block body and the amount of deformation when changing it to IBw, 1 gwx 10 mgν, and 100 mgv.
, and the relationship between the block size and distortion when changed to 100 gw. Further, in the figure, F indicates the relationship between the size of the block body and the natural frequency.

As can be seen from this graph, as the size of one side of the block body becomes smaller, the amount of deformation, distortion, and natural frequency all increase. That is, if monocrystalline silicon is processed and the strain gauge is formed by photolithography as in the present invention, it is possible to form a block body with a negative side size of about 21 m, for example.

A block body of this size is 0.04μ with an external force of 80mgv.
m deformation, and the natural frequency becomes 10 KHz. Further, the strain at this time was 4XlO-6, which is a value that can be sufficiently detected by a normal semiconductor strain gauge.

These results mean that if the size of one side of the block is 2cm, it is possible to realize a probe with a sensitivity of 0.04 μm or less and an external force of 80Il1g'w or less during parenthesis. Furthermore, since the natural frequency is as high as about 10 KHz (normal probes are about 100 Hz), it has the advantage of being less likely to vibrate due to external vibrations or floor vibrations.

In the first embodiment, each block of X5YSZ was formed separately and fixed by adhesive. However, X
The block body and the Y block body may be formed integrally, and only the Z block body may be adhesively fixed as a separate body.
Alternatively, all three blocks may be formed integrally. In that case, the probe body is divided into two blocks.
The condition is that it has a shape that allows the formation of a strain gauge.

FIGS. 6 to 8 show second to fourth embodiments of the present invention, respectively, showing modified examples of the block body.

The block body 31 shown in FIG. 6 has a pair of grooves 32 on the inner surface.
It is formed by adhesively fixing two single crystal silicon plates 33 on which hinge parts 32 are formed by processing a to both end surfaces of a pair of fixing plates 34 spaced apart in parallel. Even in this case, the strain gauge 35 can be printed and formed at a location corresponding to the hinge portion 32. In this case, the fixed plate 34 may not be made of single crystal silicon, but may be made of another metal plate.

The block body 41 shown in FIG. 7 has one end in the width direction of a thin elastic plate 43 formed of single-crystal silicon attached to both end faces of a band-shaped member 42, and the other end attached to a fixed plate 44. It was designed so that it could be formed. According to such a configuration, the elastic plate 43 serves as a hinge and is elastically deformed, and the strain gauge 45 can be printed on the elastic plate 43.

FIG. 8 has almost the same configuration as the embodiment shown in FIG. 6, but
A groove 32b formed in a single crystal silicon plate 33 is formed into a trapezoidal tapered shape using anisotropic etching.

FIG. 9 shows a fifth embodiment of the present invention showing a modification of the strain gauge. This strain gauge 51 has a piezoresistor 52 formed in a continuous meandering shape, and wiring pads 53 are formed at both ends of the piezoresistor 52. It is something.

[Effects of the Invention] As described above, the present invention provides a probe main body with an
A spring part, a Y spring part, and a 2-spring part were provided, and the amount of deformation of each spring part was detected by an X strain gauge, a Y strain gauge, and a 2-strain gauge, respectively. Therefore, the probe main body can be made smaller than when the amount of deformation of each spring portion is detected using a differential transformer.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the overall configuration of the first embodiment of the present invention, FIG. 2 is an enlarged perspective view of a portion provided with a strain gauge, and FIG. 3 is a perspective view of the block body in a deformed state. A side view, FIG. 4 is a bridge circuit diagram also formed by the strain gauge, FIG. 5 is a graph showing the characteristics of the block body, and FIGS. 6 to 8 are respectively the second to fourth embodiments of the present invention. FIG. 9 is an enlarged view of a strain resistor showing a fifth embodiment of the present invention. 2...Probe body, 3...Contact body, 11...X
Spring part, 12...Y spring part, 13...Z spring part, 1
4...X strain gauge, 15...Y strain gauge, 16
...Z strain gauge. Applicant's Representative Patent Attorney Takehiko Suzue No. 1

Claims (1)

[Claims] The probe body includes an X spring portion that elastically deforms along the X direction, the Y direction, and the Z direction, respectively. , a Y spring section, a Z spring section, and an X strain gauge, a Y strain gauge, and a Z strain gauge that respectively detect the amount of deformation of each spring section.