JPS6225682Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a shape measuring instrument that measures the surface shape of a workpiece by tracing the surface of the workpiece with a stylus attached to one end of the arm. In addition to providing target arc error correction means, the mounting structure of the differential transformer that detects the displacement of the arm has been improved.

Generally, in a shape measuring instrument, a stylus that contacts the surface of the object to be measured is attached to one end of an arm, and the vicinity of the other end of this arm is rotatably supported by an arm support, and the center of gravity of this arm is centered around the stylus. It is positioned so that the sides are slightly heavier, so that the stylus is always in contact with the surface of the object to be measured. To measure the surface shape with this shape measuring instrument, the arm support is moved in the axial direction of the arm, and as the arm support moves, the stylus is displaced according to the surface shape of the object to be measured, and the arm is moved. Swings around a pivot point,
This swinging motion of the arm is detected by a differential transformer, and the detection signal from the differential transformer and the sending signal of the arm support are combined to measure the shape.

This conventional shape measuring instrument is provided with an arc error correction means, and the mounting position of the differential transformer is
It is set at a position that includes the rotation center of the arm and is spaced a predetermined distance from a plane parallel to the feeding direction of the arm support.

Figures 1 and 2 show the schematic configuration of a conventional shape measuring instrument, and in particular, the movement of the stylus along an arc accompanying the rotation of the arm is changed to a linear movement in the vertical direction. This is an example of a shape measuring instrument equipped with a so-called arc error correction mechanism.

As shown in FIGS. 1 and 2, this shape measuring instrument rotates a first link bar 4 via a cross spring 5 to an arm support 3 attached to a slider 2 that slides on a base 1. The base of the second link bar 6 is attached to the tip of the first link bar 4 via a cross spring 7, and one end of the second link bar 6 is attached to an arm support. The tip of the third link bar 8, which is pivotally supported by the third link bar 3, is pivotally supported. The base end of an arm 10 to which a stylus 9 is attached is further attached to the tip of the second link bar 6, and as the stylus 9 traces the outer surface of the object to be measured, the arm 10 and the second link bar 6 are attached. The link bar 6 rotates, the core 11 fixed to the second link bar 6 moves relative to the coil 12, and the displacement of the stylus 9 is measured. At this time, a differential transformer 13 is configured by the core 11 and the coil 12, and the axial direction of the core 11 is a radius of the line connecting the center of the core 11 and the center of the cross spring 7. It is provided so that it is tangential to the circular arc. Further, the differential transformer 13 is provided at a position away from a plane P that includes the center of rotation of the arm 10, that is, the center of the cross spring 7, and is parallel to the feeding direction of the arm support 3, which is indicated by an arrow in FIG. ing.

By the way, the arm 10 is rotated around the cross spring 7, but since the second link bar 6 is restrained by the rotation of the third link bar 8, the cross spring 7 is rotated around the cross spring 5. Rotated. As a result, the tip of the stylus 9 is located at the dotted line 1 in FIG.
By drawing an approximate straight line indicated by 9, the surface shape of the object to be measured can be accurately measured.

However, since the core 11 attached to the second link bar 6 swings and moves with respect to the coil 12 as shown in FIG. It was not proportionate to that.

For this reason, a shape measuring instrument using a linear motion mechanism of the core 11 as shown in FIG. 3 has also been proposed. That is, one end of the fourth link bar 15 is attached to the shaft support of the second link bar 6 and the third link bar 8 by the shaft 14, and the other end of the fourth link bar 15 is connected to the third link bar 15. A fifth link bar 16 is provided in parallel with the link bar 8 and has one end rotatably supported on the arm support 3, and is rotatably attached to the other end of the fifth link bar 16 via a shaft 17. 4. 5th
The link bars 8, 15, and 16 constitute a four-node rotating chain (parallel links) with opposite sides of equal length. The shape measuring device is constructed by standing upright parallel to the link bar 15 of No. 4.

However, in the measuring instruments shown in FIGS. 1 and 2, in addition to the above-mentioned rocking, the core 11 also moves in the direction indicated by arrow A in FIG. 2 as the arc error is corrected. Not only does the amount of movement cause a measurement error,
Since the position of the core 11 is far from the reference plane P, the amount of movement of the core 11 in the direction of arrow A differs when the arm 10 moves above and below the reference plane P, and this also occurs. There are drawbacks that can lead to errors. In addition, in the case of the measuring instrument shown in Fig. 3, errors caused by the swinging motion and the rotating direction of the arm 10 can be prevented, but the structure is complicated and expensive, and due to the complicated structure, each part The disadvantage is that the accumulation of errors due to backlash and the like at the joints is relatively large.

An object of the present invention is to provide a shape measuring instrument with a simple structure and less measurement error.

In this invention, a mechanical arc error correction means is provided to prevent arc errors, and the stylus of the arm is positioned on a reference plane that includes the rotation center of the arm and is parallel to the feeding direction of the arm support. At the arm reference position, the center positions of the core and coil of the differential transformer are set to be exactly on the reference plane, and the core does not move when the arm rotates in any direction from the reference position. This aims to achieve the above object by moving symmetrically to eliminate the difference in rotation direction and by eliminating a complicated structure.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

A pair of brackets 22 are provided on the base 21 at a predetermined interval, and between these pair of brackets 22 is a guide bar 2 with a thick shaft extending upwardly in FIG.
3 is provided, and a feed screw shaft 24 is provided below.
is provided. One end of this feed screw shaft 24 protrudes from the bracket 22 on the right side in the figure, and a rotary encoder 25 and a geared motor 26 are connected in series to this protrusion.

A slider 27 is mounted across the guide bar 23 and the feed screw shaft 24, and this slider 27 has a female threaded portion that meshes with the feed screw shaft 24, and guides the guide bar 23 as the feed screw shaft 24 rotates. It is designed to move in the left and right directions in the figure.

The slider 27 has a flat arm support 28.
is fixed, and is adapted to be sent in the direction of the arrow X in FIG. 4 as the slider 27 moves. On the surface of the arm support 28 opposite to the surface on which it is fixed to the slider 27, a needle support bracket 29 is protruded from the lower part on the right side of the center in FIG. 4, and a correction link support bracket 29 is provided at the lower left end. A bracket 30 is provided to protrude, and a differential transformer supporting bracket 31 is further provided to protrude from the lower part of the center portion.

A needle 32 is fixed on the needle support bracket 29, and the upper surface of the needle 32 is in contact with the circumferential surface of a roller 33. The center of the roller 33 is rotatably supported by a fulcrum shaft 34, and the fulcrum shaft 34 is attached to a base structure 36 that constitutes a part of the arm 35. In addition to the base structure 36, the arm 35 includes a cylindrical central arm 37 and a cylindrical tip arm 38. One end of the central arm 37 is fixed to the base structure 36. One end of a tip arm 38 is attached to the other end via a joint 39, and a stylus 40 is fixed to the other end of the tip arm 38 so as to protrude in a direction perpendicular to the arm axis. As a result, the arm 35
It is rotatably supported by the arm support 28 via the roller 33, needle 32 and bracket 29 so as to rotate about the fulcrum shaft 34, and is movable on the needle 32 via the roller 33. has been done.

A balancer weight 42 is attached to the side of the base structure 36 of the arm 35 opposite to the side to which the central arm 37 is fixed via a weight support shaft 41 so that the position of the balancer weight 42 can be adjusted.
4, the weight of the arm 35 on the opposite side of the balancer weight 42 about the fulcrum shaft 34 is almost balanced with the weight on the balancer weight 42 side, and the balancer weight 42 is fixed at the fixed position.
The opposite side, that is, the stylus 40 side is at a position where it is slightly heavier.

One end of a correction link 44 is rotatably supported by the correction link support bracket 30 via a pair of pivot bearings 43.
The other end is rotatably supported near a fixed portion of the central arm 37 of the base structure 36 via a pair of pivot bearings 45 . Here, needle 3
2, a roller 33, a base structure 36, a correction link 44, and pivot bearings 43, 45 constitute a mechanical arc error correction means.

The differential transformer supporting bracket 31 includes:
A through hole 46 that penetrates in the vertical direction is formed, and a slot groove 47 that communicates with this through hole 46 is provided from the side surface of the bracket 31, so that the diameter of the through hole 46 can be changed to some extent. ing. A housing 49 of the differential transformer 48 is inserted into the through hole 46 of the bracket 31 and is firmly supported by the mounting screws 50 of the bracket 31. A coil 51 is housed in this housing 49, and the center of this coil 51 in the vertical direction in FIG.
4, and is parallel to the feeding direction indicated by the arrow The distance to both end faces is equal and is defined as a dimension L. Also,
One end of a core shaft 52 is attached to the center of the base structure 36 of the arm 35, and this core shaft 52 is extended into the center hole of the coil 51, and a core 53 is fixed at a position inside the center hole. There is. The mounting position of the core 53 is such that the center of the core 53 is exactly on the reference plane P when the arm 35 is arranged so that the tip of the stylus 40 is exactly on the reference plane P, that is, in the arm reference position. As a result, the distance from the point where the reference plane P crosses the core 53 at the arm reference position to the upper and lower end surfaces of the core 53 is equal and has a dimension l.

In such a configuration, in order to measure the shape of the object to be measured, as in the conventional example, the motor 26 is driven to rotate the feed screw shaft 24, and the arm support 28 is moved through the slider 27 as indicated by the arrow X. Measure by moving it in the feeding direction. That is, as the arm support 28 is fed, the stylus 40 attached to one end of the arm 35 is moved in the feeding direction and moves up and down according to the surface shape of the object to be measured, and the movement of the stylus 40 is caused by the fulcrum axis of the arm 35. 34 is converted into a swinging motion, and this swinging motion is caused by the core 53
As a relative movement between the coil 51 and the differential transformer 4
Detected at 8. On the other hand, the amount of movement of the arm support 28 in the feed direction is detected by the rotary encoder 25 as the number of revolutions of the feed screw shaft 24, and the feed signal from the rotary encoder 25 and the vertical movement of the stylus 40 from the differential transformer 48 are detected by the rotary encoder 25. By combining the motion signal and the motion signal, the shape of the object to be measured can be measured.

Note that during the measurement, a mechanical arc error correction means works, that is, the correction link 44 causes the center of rotation of the arm 35 to align with the roller 3 when the arm 35 rotates.
3 and the needle 32 move in the feeding direction, the arc error of the stylus 40 is corrected. In addition, the coil 51 and core 53 of the differential transformer 48
Since the center of the arm 35 is located on the apex reference plane P at the reference position of the arm 35, rotation of the arm 35 in any direction from the reference position changes the relative position of the core 53 and the coil 51 completely symmetrically. The relationship will change.

According to this embodiment as described above, since the center of the differential transformer 48 is set exactly on the reference plane P, no error occurs due to the direction of rotation of the arm 35. Further, since the structure is simple and does not require any new links, it can be manufactured at low cost. Furthermore, since the differential transformer 48 does not protrude from the arm 35 in a direction away from the reference plane P, the entire device can be made smaller. Furthermore, when the correction link 44 for arc error correction is provided as in this embodiment, even when the arm 35 moves in the feeding direction of the arm support 28, measurement differences due to the rotating direction of the arm 35 can be avoided. It is particularly effective.

In addition, in the above embodiment, the differential transformer 4
8 is an intermediate position between the fulcrum shaft 34 and the pivot bearing 43, and the center line of the core 53 is exactly aligned with the arm 3.
Although an example has been described in which the central axis of the central axis of 5 is perpendicular to the central axis, the present invention is not limited to this. For example, in FIG. 4,
The differential transformer 48 may be provided to the right of the fulcrum shaft 34 or to the left of the pivot bearing 43, and in FIG.
It may be provided at a position shifted above the central axis of 5, that is, toward the guide bar 23, or vice versa. In short, it is sufficient that the center positions of the coil 51 and core 53 of the differential transformer 48 are on the reference plane P. Furthermore, in the embodiment, the differential transformer 48
Although an example has been described in which the coil 51 is attached to the arm support 28 side and the core 53 is attached to the arm 35 side, the present invention is not limited to this.
The coil 51 may be attached to the arm 35 side, and the core 53 may be attached to the arm support 28 side.

As described above, the present invention has the effect of providing a shape measuring instrument with a simple structure and less measurement error.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an example of a conventional shape measuring instrument, Fig. 2 is an explanatory diagram of the operation of Fig. 1, and Fig. 3 is a front view of main parts showing another example of the conventional shape measuring instrument. 4
The figure is a longitudinal cross-sectional view showing one embodiment of the shape measuring device according to the present invention, and FIG. 5 is a cross-sectional view of FIG. 4 with the cross-sectional position of the main part changed. 28... Arm support, 34... Fulcrum shaft, 35
... Arm, 40 ... Stylus, 48 ... Differential transformer, 51 ... Coil, 53 ... Core, P ...
…Reference plane.

Claims (1)

[Scope of utility model registration request] An arm having a stylus at one end is supported on an arm support so as to be rotatable around the rotation axis included in the reference plane, and the stylus follows the surface shape of the object to be measured. In the shape measuring instrument that measures the shape of the object to be measured by detecting the rotational change of the arm that rotates by using a differential transformer, the arm support and the base structure that supports the arm are provided at both ends, respectively. includes a correction link rotatably supported, and is configured to move the arm support as the arm tilts and rotates while preventing the rotation axis from departing from a reference plane, thereby correcting arc errors. a circular arc error correction means, and the differential transformer is arranged such that the center position of the coil and core thereof is positioned on the reference surface when the arm is in the reference position with the tip of the stylus located on the reference surface. A shape measuring instrument, characterized in that the shape measuring instrument is attached to the arm and the arm support.