JPS63311101A - Apparatus for measuring rotational accuracy of main shaft - Google Patents

Abstract

PURPOSE:To measure the displacement of a main shaft with high accuracy by preventing the change in electrostatic capacity, by mounting the sphere to be measured provided to the end surface of the main shaft to a ceramic holder low in permittivity. CONSTITUTION:The sphere 22 to be measured provided to the end surface of a main shaft 10 is mounted to a sphere holder 21 formed of mica ceramic low in permittivity and this holder 21 is arranged to the end surface of the main shaft 10 through a centering plate 20 and displacement sensors 26, 27 for measuring the displacements of the main shaft 10 in the thrust and radial directions of the axial line thereof as static capacities are provided to the sphere 22 to be measured. In measurement, since the line of magnetic force passing through the main shaft 10 from the rotor 13 of a motor is blocked by a sphere holder 21, the change in the electrostatic capacity of the sphere 22 to be measured is prevented to make it to possible to measure the displacement of the main shaft 10 with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a spindle rotational accuracy measuring device for measuring the rotational accuracy of a spindle of a lathe or the like.

<Prior art> Conventionally, lathes and the like have adopted a built-in motor system in which the rotor of the motor is fixed to one end of the spindle and driven.To measure the rotational accuracy of the spindle, the ball to be measured is attached to the end face of the spindle using an iron centering plate. The displacement of the ball to be measured was detected using a non-contact displacement sensor.

<Problems to be Solved by the Invention> In such a built-in motor system, when the motor is driven, a magnetic field is generated which passes from the rotor through the main shaft and magnetizes the ball to be measured.

This causes a problem in that the displacement sensor cannot accurately detect displacement because the capacitance of the ball to be measured changes.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned problems, and includes mounting a ball to be measured on the end face of the main shaft in a ball holder made of ceramic with a low dielectric constant, The ball to be measured is attached to the end face of the main shaft via a centering plate that centers the ball to be measured on the axis of the main shaft, and the ball to be measured is mounted on the main shaft rotation axis of the ball to be measured and in the radial direction orthogonal to the main shaft rotation axis. A displacement sensor is provided that measures the capacitance between the balls and detects the displacement of the ball to be measured.

<Function> The ball holder made of ceramic blocks the lines of magnetic force passing through the main shaft to prevent changes in the capacitance of the ball to be measured, allowing the displacement sensor to accurately detect displacement.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 1 denotes a main shaft body provided on a support base 2. As shown in FIG. A main shaft 10 is provided within the main shaft body 1, and a motor constituted by a stator 12 and a rotor 13 surrounded by a motor housing 17 is attached to one end of the main shaft 10. A sleeve 14 is engaged with the rotor 13, and the sleeve 14 is attached to the main shaft 10.

15 is a hydrostatic bearing that supports the main shaft 10.

This hydrostatic bearing I5 has a bearing pocket 1 formed on the inner peripheral surface.
Pressure fluid is supplied to 6 through a fixed throttle, and the main shaft 10 is rotatably held by static pressure holding force.

Further, a thrust bearing pocket 19 is formed at the end of the hydrostatic bearing 15 so as to face the flange portion 18 protruding from the main shaft 10, and provides thrust support using static pressure. A ball to be measured 22 is attached to the end surface of the main shaft 10 via a centering plate 20 and a ball holder 21 . The centering plate 20 is composed of an adapter plate 23 fixed to the main shaft 10 and a plate 25 fixed to the adapter blade in a floating manner by a centering screw 24. The center can be aligned on the axis of the main shaft 10.

The ball holder 21 is made of mica ceramic having a low dielectric constant, and the ball 22 to be measured is adhered to the center of its tip. Displacement sensors 26 and 27 are provided on the axis of rotation of the main shaft 10 and in the radial direction of the ball to be measured 22 perpendicular to the axis to detect displacement of the main shaft 10 in the thrust direction and the radial direction.

The displacement sensors 26 and 27 measure the capacitance up to the ball 22 to be measured and detect displacement based on a change in the capacitance.

The displacement sensors 26 and 27 have an amplifier 28. filter 2
9. A computer 31 is connected via an A/D converter 30, and displacement signals due to the deflection of the ball to be measured detected by the displacement sensors 26 and 27 are stored in the computer 31.

With the above configuration, the magnetic field lines passing through the main shaft 10 from the motor during measurement are blocked by the ball holder 21, preventing changes in the capacitance of the ball 22 to be measured, and making it possible to measure accurate rotation accuracy. do.

<Effects> As described above, in the present invention, the ball holder for blocking the magnetic lines of force from the motor is made of ceramic, so that the rotation accuracy of the main shaft can be measured with high precision.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a spindle rotation accuracy measuring device according to an embodiment of the present invention. 10... Main shaft, 15... Static pressure bearing, 16... Static pressure bearing pocket, 19... Thrust bearing pocket, 20
...Centering plate, 21...Ball holder, 22...
- Ball to be measured, 26.27...Displacement sensor.

Claims (1)

[Claims] (1) A spindle rotation accuracy measuring device that connects a spindle rotatably supported on a headstock body with a rotor of a drive motor coaxially provided with the spindle, and detects runout, etc. of the spindle in the radial and axial directions. A ball to be measured is mounted on the end face of the main shaft in a ball holder made of ceramic with a low dielectric constant, and this ball holder is mounted on the end face of the main shaft via a centering plate that centers the ball to be measured on the axis of the main shaft. and on the main shaft rotation axis,
A spindle rotational accuracy measuring device characterized by being provided with a displacement sensor that measures the capacitance between the spindle and the ball to be measured in a radial direction perpendicular to the spindle's rotational axis to detect displacement of the ball to be measured.