CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of PCT International Application No. PCT/JP2020/041347 filed on Nov. 5, 2020 claiming priority under 35 U.S.0 § 119(a) to Japanese Patent Application No. 2019-211559 filed on Nov. 22, 2019. Each of the above applications is hereby expressly incorporated by reference, in their entirety, into the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a surface shape measuring device and a surface shape measuring method, and relates to a technique of using a freely detachable index table.

2. Description of the Related Art

A roundness measuring device for measuring roundness of a workpiece is known as a surface shape measuring device. For example, a roundness measuring device of Japanese Patent Application Laid-Open No. 2001-343228 (hereinafter referred to as “Patent Literature 1”) includes a tilt cross table attached to a rotation drive mechanism. A workpiece is placed on the tilt cross table, and then centering and tilting are performed on the workpiece using a tilt cross table such that a center axis of the workpiece and a rotation center axis of the rotation drive mechanism are aligned with each other (which is also referred to as centering operation).

Citation List

Patent Literature 1: Japanese Patent Application Laid-Open No. 2001-343228

SUMMARY OF THE INVENTION

However, since a movable range of the tilt cross table is generally as narrow as several millimeters from the rotation center axis, it is necessary to position the workpiece near the rotation center axis when the workpiece is placed. Therefore, it is not easy to place a plurality of workpieces within the movable range and continuously perform centering on each of the plurality of workpieces.

Therefore, as means for extending the movable range, it is conceivable to add an index table on the tilt cross table. However, the index table serves to drive the table, and does not have any mechanism for suppressing fluctuation of a position of a center of gravity (centroid). Therefore, when a shape measurement is performed while a workpiece is placed on the index table, there is a concern that the measurement accuracy may deteriorate due to the fluctuation of the position of the center of gravity.

The present invention has been made in view of such circumstances, and aims to provide a surface shape measuring device and a surface shape measuring method that are capable of suppressing deterioration in measurement accuracy when a surface shape of a workpiece is measured by using an index table.

A surface shape measuring device according to a first aspect includes: a rotary table which is configured to place a workpiece thereon and to be freely rotatable around a rotation center axis; and a detector including a probe to be brought into contact with the workpiece placed on the rotary table, the detector configured to detect a displacement of the probe, wherein the rotary table has a centering mechanism configured to align a center axis of the workpiece and the rotation center axis, an index table freely detachably mounted on the rotary table is provided, the index table configured so as to be able to perform indexing along a first axis and a second axis which are perpendicular to the rotation center axis, and eccentric load cancelling means configured to cancel an eccentric load caused by the indexing of the index table.

A surface shape measuring device according to a second aspect further includes a sensor configured to detect a tilt amount of the rotation center axis to acquire the eccentric load.

A surface shape measuring device according to a third aspect further includes: a shared drive circuit configured to drive the rotary table and the index table; a switching circuit configured to switch the drive circuit between the rotary table and the index table; and a detachable mechanism configured to electrically connect the switching circuit and the index table.

In a surface shape measuring device according to a fourth aspect, a maximum movable range of the index table is larger than a maximum movable range of the rotary table.

In a surface shape measuring device according to a fifth aspect, a moving speed of the index table is higher than a moving speed of the rotary table.

In a surface shape measuring device according to a sixth aspect, the eccentric load cancelling means is a counterweight provided to the index table, and the counterweight is provided movably in the index table.

In a surface shape measuring device according to a seventh aspect, the eccentric load cancelling means is movement of the rotary table.

A surface shape measuring method according to an eighth aspect is a surface shape measuring method using the above-mentioned surface shape measuring device, the surface shape measuring method including: a placing step of placing a workpiece on either the rotary table or the index table, a detection step of detecting a displacement of the probe which is brought into contact with the workpiece by the detector, and a cancelling step of cancelling an eccentric load before the detection step, in a case where the workpiece is placed on the index table.

According to the present invention, it is possible to suppress deterioration in measurement accuracy in a case where an index table is installed on a rotary table to measure a surface shape of a workpiece.

