JPS5832644B2 - coordinate measuring machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate measuring machine that measures the normal direction of a surface of an object to be measured at a measuring point.

Conventionally, to calculate the normal direction vector of a curved surface, the coordinates of three arbitrary points near the measurement point on the curved surface are measured, the equation of the plane containing the three points is calculated, and the normal direction vector is calculated from this. However, this method was time-consuming and inefficient.

In view of the above points, the present invention provides x, y, which are detected by pressing a contact point against a curved surface of a workpiece by a certain amount of displacement.
, provides a coordinate measuring machine that can calculate and output the normal direction component of a curved surface by measuring one point using each displacement signal of the z-axis, shorten measurement time, and obtain highly accurate normal vector data. This is what I am trying to do.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. The coordinate measuring machine according to the present invention has a measuring probe that is brought into contact with a measuring point of an object to be measured A. A detection device B is provided that is displaced in the normal direction of the contact surface of the object to be measured A and outputs each component value of the X, Y, and Z axes with respect to the displacement as an electric signal, and measures the component value at the measurement point. By doing so, the normal direction of the surface of the object to be measured at the measurement point is measured.

That is, the measuring device of this example includes the detection device B, an analog-to-digital conversion circuit (hereinafter referred to as an A/D conversion circuit) C that converts the detected analog displacement signals Ex, Ey, and Ez into digital signals, The resultant displacement amount E
The value of displacement Eo calculated by ot calculation and the value E of each axis displacement
x tEy, unit vector CI in the normal direction from Ez,
J.

K) It is composed of a normal direction vector calculation circuit which outputs t-calculation.

Note that FIG. 3 is a longitudinal cross-sectional view of the detection device, and in the drawing, reference numeral 1 denotes a cylindrical case, and an opening 2 is formed in the lower end surface of the case.

A shaft 3 is inserted vertically into the center of the case 1, and a part of its lower side protrudes from the opening 2 to the bottom of the case 1. A hemispherical measuring element 4 that follows the shape is attached.

Reference numeral 5 denotes a support cylinder disposed inside the case 1 and into which the shaft 3 is fitted.The shaft 3 is supported by slide bearings 6.1 each disposed in the gap between the support cylinder 5 and the shaft 3. It is supported slidably in the vertical direction.

On the entire outer circumference of the support tube 5, eight or more small-diameter bullets 8, such as piano wires, are arranged at equal intervals in the shape of a cylindrical basket (although not shown, the lower side may be shaped like a truncated conical foil with a diameter of several n).

), and the upper end of each of the small diameter bullets 8 is fixed to a retaining ring 9 integrally fixed to the case 1,
Its lower end is fixed to a collar 10 formed to project horizontally from the lower end of the support tube 5, and the support tube 5 is suspended by these small diameter bullets 8.

The upper side of the shaft 3 is a small diameter part 12 on which a stepped part 11 is formed, and a large diameter ring 13 is fixed to the lower part of the shaft 3 that does not protrude outside the case 1. A compression spring 14 is attached to the lower shaft 3 of the portion 12 and the large diameter ring 13, respectively.
15 is fitted.

The lower ends of the upper springs 14 are supported by the stepped portions 11 of the shaft 3 in spring receivers 16 formed horizontally protruding inside the support cylinder 5, thereby pressing the shaft 3 downward. On the other hand, the lower spring 15 has its upper end supported on the lower surface of the large-diameter ring 13 and its lower end supported on the spring seat 18 supported on the lower surface of the case 1 via a ball 17, thereby supporting the shaft. 3 is pressed upward.

The shaft 3 is elastically held at a neutral position in the vertical direction by these springs 14 and 15.

Reference numeral 19 denotes a cylindrical elastic body that is elastic in the vertical and horizontal directions but not in the torsional direction. The elastic body 19 prevents the shaft 3 from rotating.

Three detectors 21, 22, and 27 are installed inside the case 1 and above the support tube 5, and - of these detectors 21 extend upward from the upper end of the shaft 3. The other detectors 22 and 27 are connected to the extended detection rod 23 to detect vertical displacement of the shaft 3, and the other detectors 22 and 27 are connected to the guide pieces 24 and 24' that project upward from the upper end of the support tube 5. It is connected to a detection rod 25.degree. 28 fixed in the horizontal direction to detect the horizontal displacement of the support tube 5 and the shaft 3 supported by the support tube 5.

Further, in this embodiment, the case 1 is filled with an appropriate amount of viscous oil 26 to prevent the small diameter bullet 8 from bouncing too much in the horizontal direction.

An example of the detector 21, 22, 27 is a differential transformer, which consists of a cylinder with secondary coils placed on both sides of the primary coil and a core inside the cylinder. The displacement of the core is electrically measured because the degree of magnetic coupling between the primary coil and the secondary coil changes when the core is moved in the longitudinal direction.

Next, the present invention will be explained in detail.

In this embodiment shown in FIG. 3, when a longitudinal force is applied to the probe 4 of the detection device B, the longitudinal displacement of the shaft 3 is directly detected by the detector 21, and the spring 14
．． Since the neutral position of the shaft 3 is elastically held by the shaft 3, vertical displacement can be accurately detected without any problem.

At this time, the support tube 5 does not move, but the shaft 3 moves inside it.

In FIG. 4, the support cylinder 5 is omitted and the shaft 3 is shown fixed directly to the part corresponding to the collar 10.
If only horizontal forces are considered and it is assumed that the shaft 3 does not move in the vertical direction, such a configuration can be sufficiently explained.

In FIG. 4, when a horizontal force F is applied to the measuring element 4, the measuring element 4, the shaft 3, the collar 10, and the small-diameter bullet 8 are displaced to positions shown by dotted lines while maintaining their horizontal positions.

This is based on the fact that when several springs of the same length and quality are joined at both ends and a load is applied to one end, the displacement is always parallel to the original position. moves with the axis 3 always kept parallel, that is, perpendicular to the horizontal plane.

Therefore, returning to FIG. 3, when a horizontal force is applied to the probe 4, the horizontal displacement is caused by the displacement of the probe 4 in the upper position via the support tube 5 because the shaft 3 always moves in parallel. It can be accurately detected by the attached detectors 22 and 27.

In addition, since the small-diameter bullet rays 8 are arranged evenly around the entire outer circumference of the support tube 5, they can be equally displaced in any horizontal direction, and have no directionality at all, and the three detectors 21. 22,2
7, the vertical and horizontal displacements are detected independently.

Furthermore, in the detection device B of this embodiment, the viscosity of the oil 26 filled in the case 1 provides horizontal resistance to the support tube 5 and the small diameter bullet 8, causing the small diameter bullet 8 to bounce and accurately displace. This prevents it from becoming undetectable.

In this way, the horizontal X-axis, Y-axis, and vertical Z-axis displacement signals Ex, E are detected independently by the detection device B.
As shown in Fig. 6, y and Ez are inputted into the A/D conversion circuit (a in the figure), and the analog signals are converted to digital signals (opening in the figure), resulting in their combined displacement amount E.
o is calculated (C in the figure).

Note that the combined displacement amount Eo is calculated by the following equation.

Next, each component value I, J, K of the normal direction vector is calculated from the calculated value of Eo and the value of each axis displacement in a normal direction vector calculation circuit (2 in the figure). Each component of the linear direction vector is calculated by the following equation.

I=Ex/Eo, J=Ey/Eo, Ni=Ez/Eo ・
...<2) Each component value I, J of the normal direction vector calculated in this way is typed out (ho in the figure).
It is used for coordinate measurement and shape and dimension measurement.

As is clear from the above description, in the present invention, by bringing the gauge head into contact with a measurement point of the workpiece, the gauge head is displaced in the normal direction of the contact surface of the workpiece, and A detection device that outputs each value on the Y and Z axes as an electrical analog displacement signal, an analog-to-digital conversion circuit that converts the analog displacement signal from the detection device into a digital signal, and a composite displacement amount calculated from the digital signal. and a normal direction vector calculation circuit that calculates and outputs a unit vector in the normal direction from the value of the composite displacement amount and the value of each axis displacement, and the detection device has a case movable in the axial direction, a measuring element protruding from the bottom of the case, a shaft fixed to the upper end of the measuring element and inserted vertically into the case, and the shaft sliding in the axial direction. A support tube that is freely fitted inside the support tube, and eight or more straight small diameter bullet rays arranged in a cylindrical basket shape at equal intervals around the entire outer circumference of the support tube, the upper end of which is fixed to the case. Its lower end is fixed to the lower end of the support cylinder, a spring provided to elastically maintain the neutral position in the vertical direction of the shaft, and It consists of three detectors for detecting component values.

Therefore, according to the present invention, in order to calculate the normal direction vector, the normal vector can be calculated by one-point measurement using the displacement signals of each axis from the detection device having the measuring head, and the normal vector can be calculated more easily than before. The normal direction of the surface can be measured, the measurement time can be shortened, and the detection device is eight or more straight small diameter bullets arranged in a cylindrical cage shape at equal intervals around the entire outer circumference of the support tube. , since its upper end is fixed to the case and its lower end is fixed to the lower end of the support cylinder, the measuring element is always at an angle of X with respect to the shaft supporting it or the case.

Since displacement movement can be performed parallel to the three directions of the Y and Z axes, the displacement detector in each axis direction can perform detection with almost no errors, and even if the length of the probe changes, it will not affect the detection. The amount of displacement can be detected even for minute displacements in the normal direction of the contact point, and the X, Y,
The amount of displacement in the three axial directions of Z is detected as an electrical signal, the combined amount of displacement in the normal direction is calculated, and the value of each axis component of the normal direction vector is calculated from this combined amount of displacement and the amount of displacement in each axial direction. output, the probe can perform measurements with low-pressure contact with the object to be measured, making it possible to handle extremely soft objects, and the spherical diameter of the probe can be freely selected to obtain highly accurate normal vector data. There are effects such as being able to.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a coordinate diagram showing displacement signals and normal direction vectors, FIG. 3 is a vertical cross-sectional view of the detection device, and FIG. A simplified partial side cross-sectional view for explaining the operation, FIG.
The 1-line sectional view and the rod 6 diagram are also flowcharts for explaining the operation. A: Object to be measured, B: Detection device, C: Analog-to-digital conversion circuit, D = Normal direction vector calculation circuit, 1: Case, 3: Axis, 4: Measuring head, 5: Support tube, 8: Small diameter bullet line,
14, 15: Spring, 21, 22° 27: Detector, 26 Two oils.

Claims (1)

[Claims] 1. By bringing the probe into contact with the measurement point of the object to be measured, the probe is displaced in the normal direction of the contact surface of the object, and the component values of the X, Y, and Z axes for the displacement are expressed as electrical analogs. A detection device that outputs a displacement signal, an analog-to-digital conversion circuit that converts the analog displacement signal from the detection device into a digital signal, and a composite displacement amount calculated from the digital signal and a value of the composite displacement amount and each axis displacement. and a normal direction vector calculation circuit that calculates and outputs a unit vector in the normal direction from the value of . a measuring element protruding from the lower part; a shaft fixed to the upper end of the measuring element and inserted vertically into the case; a support tube into which the shaft is slidably fitted in the axial direction; Eight or more straight small-diameter bullet rays arranged in a cylindrical basket shape at equal intervals around the outer circumference of the tube, the upper end of which is fixed to the case, and the lower end of which is fixed to the lower end of the support tube. a spring provided to elastically hold the neutral position of the shaft in the vertical direction;
A coordinate measuring machine comprising three detectors for detecting each component value of Y and Z axes.