JP2009145152A - Measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor holder capable of scanning and moving on a surface to be measured, in order to achieve a multipoint method by combining a point in contact with the surface to be measured with a displacement sensor or an angle sensor, as a tool in place of a level vial for measuring a lengthy straight shape or a large-size plane shape. <P>SOLUTION: The sensor holder movable relatively to the surface to be measured has a shape having at least two contact points to the surface to be measured, and a differential output similar to a three-point method for straight shape measurement is acquired by three points, namely, the two contact points between the sensor holder and the surface to be measured and a measuring point of a sensor held by the sensor holder, and the shape is determined from the output. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a measurement technique, and more particularly to a measurement apparatus that performs measurement of a straight shape and a surface shape easily and with high accuracy.

In order to measure a surface shape or a cross-sectional linear shape, a comparative measurement with a standard straight ruler is often performed. If the standard ruler cannot be used, use a spirit level to measure the slope between the points where the bottom surface of the spirit level contacts the surface to be measured at the required location on the surface to be measured. A method for calculating the surface shape is used. In principle, the contact-type two-point method or the multipoint method that measures the inclination between two points with respect to the direction of gravity (normal direction of the horizontal plane) is mainly used. As an example of the measuring method, a three-point method as shown in Non-Patent Document 1 is known.
Makoto Oo, Susumu Furukawa: Consideration of straightness measurement by sequential point measurement method (1st report, Expression analysis of sequential point measurement method and theoretical analysis of error) Transactions of the Japan Society of Mechanical Engineers C, 57, 542, (1991) 85-89

  As the measuring object becomes larger, the standard ruler becomes longer, which makes it difficult to create a standard straight ruler, as well as difficulties when transporting a high-precision ruler. However, there are problems such as elastic deformation and thermal deformation at the time of use, which degrade the reference accuracy.

  This means that, with high-grade straight edge (straight ruler) JISA class products that are commercially available, straightness is guaranteed only up to 6 μm at 4 m and 18 μm at 4 m, which is one of the measurement standards for high-precision machine tools. This is reflected in the current situation where the accuracy is more than a digit.

  On the other hand, with a spirit level, the sensitivity cannot be increased due to the influence of disturbance vibrations, and the higher the sensitivity, the slower the response speed, and the longer it takes to measure the tilt of many points on a large plane. There are difficulties.

  In view of such problems, the present invention aims to realize a contact-type multipoint method similar to a multipoint method using a spirit level in the measurement of a cross-sectional linear shape and surface shape, and to realize a displacement sensor and an angle sensor. It is an object of the present invention to provide a method for quickly and accurately implementing a surface to be measured.

  The present invention relates to a sensor holder having two convex portions each having a known interval between the contact points with which the surface to be measured is in contact, and the two contact points of the convex portions that are attached to the sensor holder. A displacement sensor that measures the shape height of the measured surface at a known distance from the contact point on the straight line, and detects the position of the sensor holder along the desired straight line without affecting the output of the displacement sensor And a guide for moving while moving.

  Furthermore, the present invention provides a contact-type sensor using a displacement sensor or an angle sensor on a line connecting two protrusions whose contact points are in contact with the surface to be measured and the points where the protrusions are in contact with each other. A probe for performing multipoint measurement is configured. In addition, the present invention is characterized in that a multipoint probe for plane measurement is constituted by three points in contact with the surface to be measured and one or more displacement sensors or angle sensors.

  The present invention reduces the number of necessary sensors in a multipoint probe for measuring a straight shape or a planar shape by substituting a part of the required sensor with a convex part that abuts the surface to be measured. It is characterized by that.

  The present invention is also characterized in that the convex portion that comes into contact with the surface to be measured is rotatable, facilitating scanning that moves the object to be measured and the multipoint probe along the surface to be measured.

  In the sensor holder of the present invention, since the straight line connecting the two points in contact indicates the inclination of the two points of the measured surface, the displacement sensor in the middle reads the measured surface in the height direction of the measured surface from the inclined straight line. It will indicate displacement. This can provide information equivalent to the output of the displacement three-point method for straight shape measurement. If the sensor is an angle sensor, information equivalent to the angle two-point method or the mixing method is given.

  Two displacement sensors attached to the sensor holder, a two-dimensional angle sensor, or an angle sensor and a displacement sensor, and two-dimensional shape measurement can be performed by scanning and moving in two directions. If the point of contact with the surface to be measured of the sensor and the arrangement of the sensor have a two-dimensional spread, information equivalent to the multipoint method output for surface shape measurement can be obtained from the output of the sensor.

  The present invention will be described below with reference to the drawings and formulas. FIG. 1A shows a schematic structure of a side surface of a sensor holder SH for straight shape measurement by a three-point method, which is the basis of the present invention, and FIG. 1B shows a back side (surface to be measured) of the sensor holder SH. The sphere (measurement surface contact sphere) SP as a convex portion is in contact with the back surface of the elongated plate-shaped sensor holder SH in the X-axis direction. Two displacement sensors SN for detecting the shape height of the surface to be measured are arranged on a straight line parallel to the X axis that connects two vertices Lx and connects the vertices of both spheres SP. The sensor SN may be a non-contact sensor such as an electromagnetic type or an optical type, or may be a device that electrically reads the height displacement of the surface to be measured by a contact type probe called an electric micrometer, or a machine such as a dial gauge. A contact displacement sensor of the type may be used.

For the sake of simplicity, taking the case of Ls = Lx / 2 as an example, the straight line connecting the two points (x−Ls) and (x + Ls) at the coordinates of the vertices of two spheres SP with an interval Lx is It is determined from the difference in shape height (in the Z-axis direction) of the contact points of both spheres SP. Based on this inclination, the movement of the origin of the sensor SN at the point x is evaluated, and the relationship between the sensor output value ms (x) and the cross-sectional linear shape f (x) is as follows.
ms (x) = f (x) − {f (x−Ls) + f (x + Ls)} / 2 (1)

  The output of this sensor has the same form as the differential output when the scanning motion error is removed from the three sensors according to the so-called three-point method (see Non-Patent Document 1) and expressed only by the amount related to the shape.

  However, in equation (1), α corresponds to a zero point error between sensors in the three-point method, and is calibrated from readings of the sensor SN when the two points of the sensor holder SH are brought into contact with each other along a straight line whose shape is known. it can. As shown in FIG. 1B, along the straight line connecting the vertices of the sphere SP by reading the value of the sensor SN while moving the sensor holder SH along the guide GD that is a linear rigid body. The shape of the measured surface can be measured with high accuracy. At this time, it is preferable that the relative movement amount of the sensor holder SH with respect to the guide GD can be detected by, for example, a linear encoder.

  In FIG. 1, the sensor SN is placed between the two contacts, but the sensor SN may be located between the two contacts or outside as long as it is on a straight line connecting the two contacts. Further, when the formula is derived, conditions of 2Ls = Lx and Ls = xs are given. However, when Ls = xs does not hold, data processing may be performed as a general three-point method instead of the sequential three-point method. . As a more general form, 2Ls = Lx is not an essential condition.

  FIG. 2A shows a schematic structure of the side surface of the sensor holder SH of the embodiment embodying the invention of claim 2, and FIG. 2B shows the back side of the sensor holder SH (the side facing the surface to be measured). ) In order to prevent the sensor holder SH from inclining in the Y-axis direction, the contact point by the ball SP3 is increased by one. As a result, the sensor holder SH is supported at three points and can stand on its own to perform stable measurement. In FIG. 2A, in order to scan on a straight line along the X-axis direction, one side of the triangular plate-shaped sensor holder SH (preferably parallel to a straight line connecting the vertices of the sphere SP) is linear. The same effect as in FIG. 1 can be obtained by sliding along the guide GD, which is a rigid body. It is also preferable that the linear guide has a positioning function. A plurality of protrusions may be brought into contact with the sensor holder SH instead of the linear guide.

  FIG. 3 shows the back surface of a sensor holder SH according to another embodiment. The sensor SN is placed on a line between the point P4 between the contacts of two spheres SP arranged in the Y-axis direction and the third contact P3. Has been placed. In this arrangement, an exact cross-sectional linear shape in the X-axis direction cannot be measured unless the shape heights at the two contacts P1, P2 arranged in the Y-axis direction are known. However, when the shape change in the Y-axis direction is small, regarding the cross-sectional linear shape measurement in the X-axis direction, the average value of the shape heights of the two points P1 and P2 in the Y-axis direction, the sensor SN and the third contact P3 If the cross-sectional shape of the straight line passing through is approximately the same, the three-point method is established. Here, it is preferable that the distance between the two points P1 and P2 is narrow with a stable shape. The sensor holder SH is moved in the direction of a line connecting one contact point P3 and the measurement point of the sensor SN, and the straight shape in the moving direction can be measured. However, the smaller the distance between the remaining two contact points P1 and P2, the more the measurement is performed. The certainty increases. Although a guide is not shown in FIG. 3, a wall parallel to a line connecting the intermediate point P4 and the third contact P3 is provided on the upper surface of the sensor holder SH, and a guide (not shown) (FIGS. 1 and 2) is provided. The sensor holder SH may be slid while being in contact with (see).

  FIG. 4 shows a back surface of a sensor holder SH according to another embodiment, and a straight line along the X-axis direction that connects two intermediate points of two contacts P1, P2 arranged in the Y-axis direction and the displacement sensor SN. As for the cross-sectional shape, an approximate three-point method is established for the same reason as in FIG. Of course, in this arrangement, the exact cross-sectional linear shape in the X-axis direction cannot be measured unless the shape heights at the two contacts P1, P2 arranged in the Y-axis direction are known. However, when the shape change in the Y-axis direction is small, with respect to the measurement of the cross-sectional linear shape in the X-axis direction, the average value of the shape height of the pair of two contact points P1 and P2 arranged in the Y-axis direction and the sensor SN And the three-point method is established with the average value of the shape heights of the two contact points P1, P2 arranged in the other Y-axis direction.

  FIG. 5 shows a sensor holder SH for embodying claim 4. In the form of FIG. 5, the sensor holder functions of FIGS. 3 and 4 are combined. More specifically, the first sensor SN1 is arranged in the middle of the two contacts P1 and P2 in the Y-axis direction to realize the three-point method in the Y-axis direction, and the second sensor SN2 is connected to the third sensor A structure in which the three-point method of measuring the cross-sectional linear shape along the X-axis is established by the point on the line connecting the contact P3 and the first sensor SN1 and the shape height of the point known by the three-point method in the Y-axis direction It has become. Thereby, a two-dimensional surface shape can be measured. About the guide of sensor holder SH, it is the same as that of the aspect of FIG.

  FIG. 6 is a perspective view of a sensor holder that can be used for the same purpose as in FIG. 1, and shows a form in which two cylinders CY that abut against a surface to be measured are used instead of a sphere. Although the cylinder CY may be fixed, it is desirable that the cylinder CY be rotatable via a bearing (not shown) with respect to the sensor holder SH. By rotating the cylinder CY, the sensor holder SH is a separate body. Even if a guide is not provided, it can be displaced in one direction (for example, the X-axis direction) with respect to the surface to be measured. That is, the cylinder CY serves as a guide. According to the present embodiment, the contact point becomes ambiguous by using the cylinder CY instead of the sphere, and the cross-sectional straight line in the strict sense cannot be defined. However, when the shape change in the Y-axis direction is small, the contact point is ambiguous. This is effective in suppressing the inclination of the sensor holder SH in the Y-axis direction and supporting it stably.

  Further, when the cylinder CY is used for the contact configuration of the sensor holder SH for two-dimensional scanning shown in FIG. 6, it is preferable to have a structure in which the rotation axis of the cylinder CY can be changed in accordance with the scanning direction. For example, if the rotation axis of the cylinder CY is changed by 90 degrees, the sensor holder SH can be displaced in the Y-axis direction without using a guide.

  Further, the example shown in FIG. 8A has a structure in which a plurality of spheres SP having the same diameter are arranged in a straight line instead of a cylinder, and is fitted into a pair of V grooves VG on the sensor holder SH side holding the sensor SN. Each of the four spheres SP touches at a point on a straight line of a surface to be measured (not shown), thereby forming a contact configuration similar to a cylinder. The V-groove VG is effective to hold the sphere SP on a straight line and to make a structure that allows the sphere to rotate smoothly when the sensor holder SH is slid on the surface to be measured. Of course, the cylinder of FIG. 6 may be received by such a V groove VG. Similarly, in the case of a single sphere SP, as shown in FIG. 8 (b), if the ball SP is held by opening a triangular pyramid-shaped hole TA in the sensor holder SH, the sensor holder holding the sensor SN. It is preferable that the movement of SH on the surface to be measured can be performed smoothly.

  In this way, not only the convex portion of the sensor holder is fixed to the sensor holder, but also the sphere or cylinder that is the convex portion constituting the contact point with the surface to be measured is attached to the sensor holder as described in claim 3. It is also preferable that the sensor holder is held in contact with the surface to be measured while being moved in the scanning direction by being held by a spherical bearing or a cylindrical roller bearing.

  In this case, the sphericity or roundness of the sphere or cylinder affects the shape measurement results. By averaging the sensor output during approximately one or several revolutions of the sphere or cylinder, The influence of the roundness can also be reduced by using the moving average value of the shape in the range in which the top is moved.

  The sensor holder is provided with a device (for example, an encoder) for detecting that the sphere or cylinder has been rotated by a predetermined amount, and while the sphere or cylinder is rotated by a predetermined amount (that is, the sensor holder has a predetermined distance in the X-axis direction, for example). By taking the average of the output of the displacement sensor collected during the displacement), it is possible to reduce the influence of the round shape error of the sphere or cylinder by the average effect.

  In addition to the three-point method using three displacement meters, a two-angle method using two angle sensors and a method using both an angle sensor and a displacement sensor are also known as multipoint methods for measuring a straight shape. If the sensor SN in FIG. 1 is an angle sensor that measures the inclination in the X-axis direction, a kind of angle two-point method such as the following equation is established using the inclination of the two contacts and the inclination measurement result by the angle sensor. The straight shape measurement mixing method is also established when the sensor SN is a mixed sensor that simultaneously measures the angle and displacement.

  If the sensor SN in FIG. 3 is a two-dimensional angle sensor, a multipoint method for measuring a planar shape is established. If the sensor SN is an angle sensor that detects the inclination in the Y-axis direction and a displacement sensor that detects the height direction, a mixing method for two-dimensional measurement is established.

  FIG. 7 shows an example of a method for calibrating the zero point error of the three-point method including two contacts and a displacement sensor. In FIG. 7A, a sphere SP that forms one contact P1 of the sensor holder SH shown in FIG. 1 is placed at the center of the rotating disk RD whose surface shape is known, and a sphere SP that forms the other contact P2. Is placed on the circumference of radius 2R which is equal to the distance between both contacts P1, P2. In this state, while rotating the rotating disk RD, the circumference of the radius R is measured by the displacement sensor SN. If the surface shape of the rotating disk RD is known, the zero point error of the displacement sensor SN is determined from the output of the displacement sensor SN that measures the circumference of the radius R. Subsequently, as shown in FIG. 7B, when the measurement point of the sensor SN is placed at the center of the rotating disk RD and the center of the rotating disk RD is measured by the displacement sensor SN while rotating the rotating disk RD. The average value of the contacts P1, P2 in the Z-axis direction is obtained. When the calibration value is at one point on the radius R, the influence of an accidental error or the like becomes large, but the influence can be reduced by using the average value at one rotation of the rotating disk RD.

It is a figure which shows the example of the sensor holder which is an example of this invention. It is a figure which shows the example of the sensor holder which is another example of this invention. It is a figure which shows the example of the sensor holder which is another example of this invention. It is a figure which shows the example of the sensor holder which is another example of this invention. It is a figure which shows the example of the sensor holder which is another example of this invention, and is using the cylinder instead of the ball | bowl. It is a figure which shows the example of the sensor holder for the two-dimensional shape measurement which is another example of this invention. It is a figure which shows the calibration apparatus for calibrating the zero point error of the three-point method probe which consists of a contact of a sensor holder and a displacement sensor. It is a perspective view which shows another example of a sensor holder.

Explanation of symbols

CY Cylindrical GD Guide P1 Contact P2 Contact P3 Contact P4 Contact R Radius RD Rotating disc SH Sensor holder SN Sensor SN1 Sensor SN2 Sensor SP Sphere

Claims (5)

  A sensor holder having two protrusions each of which has a known contact point interval with respect to the surface to be measured, and the straight line that is attached to the sensor holder and connects the two contact points of the protrusions. A displacement sensor that measures the shape height of the surface to be measured at a known distance from the contact point, and moves the sensor holder along a desired straight line without affecting the output of the displacement sensor. A surface shape measuring device comprising a guide for the purpose.   The surface shape measuring apparatus according to claim 1, wherein there are three contact points with the surface to be measured, and the sensor holder can stand and maintain a posture on the surface to be measured.   The convex portion in contact with the surface to be measured is a rotatable sphere or cylinder attached to the sensor holder, and the sensor holder smoothly and continuously moves relative to the surface to be measured. The shape measuring device according to claim 1, wherein the shape measuring device serves as a bearing or a wheel.   The shape measuring apparatus according to claim 1, wherein a two-dimensional shape measurement is performed using a displacement sensor attached to the sensor holder.   A device for detecting that the sphere or cylinder has rotated by a predetermined amount, and taking an average of the outputs of the displacement sensors collected while the sphere or cylinder rotates by the predetermined amount; The shape measuring apparatus according to claim 1, wherein an influence of a spherical or cylindrical perfect circle shape error is reduced by an average effect.