JP2005265648A - Contact displacement length measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact displacement length measurement apparatus which allows accurate, reproducible measurement results without allowing a contact pressure detection section which detects contact with an object to be measured to provide a position detection section for detecting a length measuring position with an influence of measurement errors. <P>SOLUTION: The apparatus comprises a probe which is attached to one end of a spindle. the contact pressure detection section which allows the probe to be contact with the object to be measured to detect the contact pressure, a displacement detection section placed between the probe and the contact pressure detection section, a linear actuator which actuates the spindle in the axial direction, and a movable shaft of the linear actuator which is placed coaxially with the spindle. One end of the movable shaft of the linear actuator and the other end of the spindle are fixed through the contact pressure detection section, so that the spindle is actuated up and down according to an output of the contact pressure detection section to keep the contact pressure between the probe and the object to be measured constant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a contact-type displacement measuring instrument. In particular, the present invention relates to a contact-type displacement measuring device configured such that a measuring element provided at the tip of a spindle is brought into contact with an object to be measured at a low pressure and a constant pressure is maintained within an operating range of the spindle.

  In the known configuration of the contact-type displacement measuring device, a contact pressure detection unit for detecting contact with the object to be measured is provided at the tip of the spindle, and the displacement of the spindle is detected at the center of the spindle. And a linear actuator for moving the spindle in the axial direction is attached to the rear end of the spindle (see, for example, Non-Patent Document 1).

  In this type of contact-type displacement measuring instrument, a contact pressure detector for detecting contact with the object to be measured is attached to the tip of the spindle, and the measurement of the object to be measured is performed via this contact pressure detector. This is performed by a position detector for detecting a displacement at the center of the spindle.

  Hereinafter, a contact-type displacement measuring instrument in the prior art will be described with reference to the drawings. FIG. 4 is a plan view showing the background art. A spindle 101 that moves in the vertical direction is provided at the center of the frame 100, and a capacitive displacement detector 103 and a stylus 104 are attached to the tip of the spindle 101 via a piezoelectric element 102 that generates minute displacement. . The stylus 104 used here is composed of a vibrator that resonates in a primary mode with a support point as a vibration node and both ends as antinodes of vibration, and the horn tip of the vibrator in this resonance state is brought close to the object 150 to be measured. When the tip is restrained by the object to be measured 150, the resonance state changes. The contact state is detected by detecting this change with the detection electrode. A moving coil actuator 105 that generates a coarse displacement is disposed at the rear end of the spindle 101. In the follow-up operation of the tip of the stylus 104 to the shape of the object to be measured, a fine driving method in which a minute displacement is performed by the piezoelectric element 102 and a large displacement is performed by the moving coil actuator 105 is adopted. A value detected by the capacitive displacement detector 103 disposed in the immediate vicinity of the stylus 104 is used as the measurement amount of the shape of the object to be measured in the Z-axis direction.

Kunitoshi Nishimura, 7 others, “Development of non-contact surface shape nanometers”, [online], New Energy and Industrial Technology Development Organization, [Search January 30, 2004], Internet <URL: http: //www.nedo.go.jp/itd/teian/ann-mtg/fy11/seika/98y28001/98y28001s.html>

  However, in the contact-type displacement measuring instrument shown in the background art, the measurement of the object to be measured is performed at the center part of the spindle via the contact pressure detection part that detects that the object to be measured is provided at the tip of the spindle. This is performed by a displacement detector for detecting a displacement in When the contact pressure detection unit for detecting contact with the object to be measured comes into contact with the object to be contacted, the vibration mode changes, and this change causes distortion and changes its own size. This dimensional change becomes an error when measuring the object to be measured, and there is a problem that correct measurement results and reproducible measurement results cannot be obtained.

In addition, since the portion in contact with the object to be measured is composed of a stylus, it is not possible to attach and measure a measuring element suitable for the shape of the object to be measured used in a general contact displacement measuring instrument. was there.

  Accordingly, the present invention provides a contact-type displacement length measuring device that measures a dimension of a measured object by a part of the length measuring device coming into contact with the measured object, a measuring element attached to one end of a spindle, and the measuring element A contact pressure detector for contacting the object to be measured and detecting the contact pressure, a displacement detector disposed between the probe and the contact pressure detector, and a linear for operating the spindle in the axial direction. An actuator and a movable shaft of a linear actuator arranged coaxially with the spindle, and one end of the movable shaft of the linear actuator and the other end of the spindle are fixed via a contact pressure detector, The spindle is moved in the axial direction according to the output, and the contact pressure between the measuring element and the object to be measured is kept constant.

  As described above, according to the present invention, the probe is attached to one end of the spindle, and the contact pressure detector for contacting the probe with the object to be measured and detecting the contact pressure is provided at the other end of the spindle. An error due to distortion of the contact pressure detection unit itself for detecting contact with the object to be measured is included in the length measurement result by arranging a displacement detection unit between the probe and the contact pressure detection unit. Therefore, the contact pressure can be kept constant and low in the spindle movement area, so that the load applied to the object to be measured is small and the deformation of the object to be measured is suppressed, resulting in more accurate and reproducible measurement results. A highly accurate contact displacement measuring instrument can be constructed.

  Furthermore, according to the configuration of the contact-type displacement measuring instrument of the present invention, the measuring element used in a general contact-type displacement measuring instrument can be replaced and installed at the tip of the spindle, and the shape of the object to be measured Since various types of measuring elements can be attached to the measurement object, versatile measurement is possible without restricting the shape of the object to be measured.

  Hereinafter, specific examples of the contact-type displacement measuring instrument according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of a specific example of a contact-type displacement measuring instrument according to the present invention. The contact-type displacement measuring instrument 40 of the present invention has a frame 1 for incorporating main structural members, and a stem 2 having a hole in the axial direction is attached to a part of the frame 1. A retainer 3 containing a linear ball bearing as a bearing portion is disposed in the hole of the stem 2, and a spindle 4 is slidably disposed in the retainer 3. A scale 5 in which bright and dark stripes of equal pitch are formed on a part of the spindle 4 is bonded so that the stripes are perpendicular to the axial direction of the spindle 4. And move in the axial direction. A measuring element 6 is attached to the tip of the spindle 4, and the measuring element 6 comes into contact with the object 50 to be measured. Light receiving and emitting elements are arranged so as to sandwich the scale 5, and a reflective LED 7 is attached on the frame 1 as the light emitting element. As the light receiving element, a light receiving IC 8 in which a fixed scale pattern is baked on a photodiode is used, and the light receiving IC 8 is disposed on a substrate 9 on which electronic components such as a power source are mounted so as to face the scale 5. The substrate 9 is fixed on the frame 1 so that the light receiving surface of the light receiving IC 8 and the striped surface on the scale 5 maintain a certain distance. In this way, the displacement detection unit 10 is configured by the scale 5, the LED 7, and the light receiving IC 8. The configuration of the displacement detector 10 is not limited to the optical type described above, but may be a magnetic type or a capacitance type.

At the rear end of the spindle 4, a contact pressure detection unit 11 for detecting a contact pressure to the object to be measured by a change in resistance of a strain gauge described later or a change in capacitance between metal plates is attached. . A movable shaft 12 is mounted on the surface of the contact pressure detector 11 opposite to the surface on which the spindle 4 is fixed, on the same axis as the spindle 4. A cylindrical bobbin 13 for constituting a linear actuator 18 is attached to the tip of the movable shaft 12, and a copper wire is wound around the bobbin 13 to form a coil 14. A magnet 15 and a yoke 16 are arranged so that a magnetic circuit is formed between the inner and outer circumferences of the bobbin 13. A compression coil spring 17 is provided between the inner wall surface of the bobbin 13 on the axis of the spindle 4 and the end surface of the yoke 16 so as to push down the spindle 4 toward the bottom dead center. Here, in the present invention, the configuration in which the initial position of the spindle 4 is on the bottom dead center side by the action of the compression coil spring 17 has been described, but the compression coil spring 17 is replaced with a tension coil spring, and the direction of the current flowing through the coil 14 is changed. The initial position of the spindle 4 may be the top dead center side.

  FIG. 2 is a side view showing a configuration of a contact pressure detecting unit for detecting a contact pressure with respect to an object to be measured of the contact-type displacement measuring instrument according to the present invention. The contact pressure detecting unit 11 for detecting the contact pressure to the object to be measured according to the present invention has a strain gauge 21 bonded to four upper, lower, left and right target positions on the upper and lower surfaces of the rectangular thin spring plate 20. In the thin plate 20 to which the strain gauge 21 is bonded, both end portions of the thin plate 20 are fixed to the supporting member 22 having a U-shaped side surface by an adhesive 23. A hole is provided in the central portion of the thin plate 20 to which the strain gauge 21 is bonded, and the rear end of the spindle 4 is fixed by a screw 24. On the other hand, a movable shaft 12 for transmitting the operation of the linear actuator to the spindle 4 side in a direction coinciding with the axis of the spindle 4 is attached to the surface of the support member 22 opposite to the surface to which the thin plate 20 is fixed. ing.

  The operation of the contact pressure detector 11 in the above-described configuration is that the thin plate 20 is deformed into a curve as indicated by a two-dot chain line 25 when the probe 4 is pushed up against the object to be measured and the strain gauge 21 This causes stress in the bending direction. By moving the linear actuator 18 shown in FIG. 1 in the axial direction so that the stress generated in the strain gauge 21 is constant, the probe 6 connected to the linear actuator 18 contacts the object 50 to be measured at a constant pressure. Will do.

  FIG. 3 is a side view showing another example of the contact pressure detecting unit for detecting the contact pressure to the object to be measured of the contact type displacement length measuring device according to the present invention. The contact pressure detection unit 11 for detecting the contact pressure to the object to be measured according to the present invention includes a metal plate 31 and a support member 30 having an opening so that a part of the side shape can be deformed. The metal plates 32 are arranged to face each other and maintain a gap, and the metal plates 31 and 32 are fixed to the support member 30 with an adhesive 33 so as to be electrically insulated. The metal plate 31 and the metal plate 32 are attached with lead wires 34 for connection to a circuit unit that detects a change in capacitance not shown. The spindle 4 is fixed to one surface of the support member 30, and the operation of the linear actuator is performed on the surface opposite to the surface on which the spindle 4 is fixed in the direction that coincides with the axis of the spindle 4. A movable shaft 12 is attached for transmission.

  The operation of the contact pressure detection unit 11 in the above-described configuration is that the contact between the measurement object and the spindle 4 is pushed up, the gap between the metal plate 31 and the metal plate 32 is changed, and the electrostatic force between the metal plates is changed. The capacity will change. The linear actuator 18 shown in FIG. 1 is moved in the axial direction so that the capacitance between the metal plates is constant, so that the measuring element 6 connected to the linear actuator 18 is kept at a constant pressure against the object 50 to be measured. Will be in contact.

As described above, with the configuration of the contact-type displacement measuring instrument shown in the present embodiment, a probe is attached to one end of the spindle, the probe contacts the object to be measured, and the contact pressure is detected. The contact pressure detection unit is attached to the other end of the spindle, and the displacement detection unit is arranged between the probe and the contact pressure detection unit. Since the measurement result does not include errors due to distortion of the detector itself, the contact pressure can be kept constant and low in the moving area of the spindle, so the load applied to the object is small and the deformation of the object is suppressed. Therefore, more accurate and reproducible measurement results can be obtained.

  Furthermore, according to the configuration of the contact-type displacement measuring instrument of the present invention, the measuring element used in a general contact-type displacement measuring instrument can be replaced and installed at the tip of the spindle, and the shape of the object to be measured Since various types of measuring elements can be attached to the measurement object, versatile measurement is possible without limiting the shape of the object to be measured.

It is the schematic which shows the structure of one specific example of the contact-type displacement measuring device of this invention. It is a side view which shows the structure of the detection part for detecting the contact pressure to the to-be-measured object in the contact-type displacement length measuring device of this invention. It is a surface measurement diagram showing a configuration of a detection unit for detecting a contact pressure to a measurement object in the contact-type displacement measuring instrument of the present invention. It is the schematic which shows the structure of the contact-type displacement length measuring device of background art.

Explanation of symbols

1 Frame 2 Stem 3 Retainer 4 Spindle 5 Scale 6 Measuring element 7 LED
8 Light receiving IC
DESCRIPTION OF SYMBOLS 9 Board | substrate 10 Displacement detection part 11 Contact pressure detection part 12 Movable shaft 13 Bobbin 14 Coil 15 Magnet 16 Yoke 17 Compression coil spring 18 Linear actuator 20 Metal plate 21 Strain gauge 22 Support member 23 Adhesive 24 Screw 25 Two-dot chain line 30 Support member 31 , 32 Metal plate 33 Adhesive 34 Lead wire 40 Contact-type displacement measuring instrument 50 DUT

Claims (4)

A contact-type displacement measuring instrument having a spindle movably mounted with a scale and detecting the displacement of the spindle in the axial direction.
A measuring element attached to one end of the spindle, a contact pressure detecting unit for contacting the measuring element to an object to be measured, and detecting the contact pressure between the measuring element and the contact pressure detecting unit A displacement detection unit disposed; a linear actuator for operating the spindle in an axial direction; and a movable shaft of the linear actuator disposed coaxially with the spindle; and one end of the movable shaft of the linear actuator; The other end of the spindle is fixed via the contact pressure detector, and the spindle is operated in the axial direction according to the output of the contact pressure detector, so that the contact pressure between the probe and the object to be measured is constant. It is comprised so that it may be kept in contact type displacement measuring instrument characterized by the above-mentioned.   The contact pressure detection unit has a thin plate with a strain gauge attached thereto and a support member that holds both ends of the thin plate, and the thin plate with the strain gauge attached thereto is fixed to the other end of the spindle, The support member is fixed to a movable shaft of the linear actuator, and configured to detect a contact pressure between the measuring element and the object to be measured based on strain data of the strain gauge. The contact-type displacement measuring instrument according to 1.   The contact pressure detector includes a support member having a substantially C-shaped side surface and an opening, and a pair of metal plates fixed to both end faces of the opening. 2. The structure according to claim 1, wherein the contact pressure between the pair of metal plates and the object to be measured is detected based on a capacitance between the pair of metal plates. Contact displacement measuring instrument as described. 2. The contact-type displacement measuring instrument according to claim 1, further comprising a bearing portion of the spindle between the measuring element and the scale, wherein the bearing portion is of a linear ball bearing system.

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