JPS59218904A - Device for measuring rotating accuracy of rotary shaft - Google Patents

Abstract

PURPOSE:To appreciate the rotating accuracy of a rotary shaft of a machine tool or the like by providing plural laser interference measuring machine measuring the distance between a surface to be worked and a constant point other than the surface to be measured. CONSTITUTION:A metallic mirror surface 1 which is a surface to be worked is attached to the rotary shaht 2 of the machine tool. The mirror surface 1 is attached so that its rotating center approximately coincides with the rotary shaft 2. A laser interference measuring maching 3 is arranged in the direction of the rotating center position D of the mirror surface 1 and other laser interference measuring machines 4-6 are arranged in the directions of three points A, B, C on a virtual circle. Shape components are detected, distinguished and compensated from the output signals of these laser interference measuring machines, so that the rotating accuracy of the rotary shaft of the machine tool or the like can be correctly appriciated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring device for measuring rotation 1rIljta of a rotating shaft of a machine tool or the like.

In recent years, as the required processing precision has increased in the fields of precision machinery and precision optics, attempts have been made to develop ultra-precision machine tools.

Metal mirrors are one of the fields of processing using ultra-precision machine tools.

Conventionally, mirrors were made of optical glass and made from °C, but metal mirrors, which are advantageous in terms of accuracy, reflectance, aging, and production speed, have been made using specialized machines. It began to be manufactured by cutting.

However, currently, the large diameter of the mirror I' that can be processed in our 1llf, 1 is approximately 300 mm. 5 in the future
Since it is thought that there will be a demand for manufacturing aspherical metal vAl'J with a diameter of 00 In In or more and about 2000 mm, four efforts were made to develop an ultra-precision lathe capable of machining aspheric surfaces.

The rotary shaft is the most important component in ultra-precision machine tools, and it is no exaggeration to say that the shape accuracy and surface roughness of the machined surface are determined by the performance of the rotary shaft. There is a need to establish a technology to manufacture a rotor and accurately evaluate its rotational accuracy.

Among rotational accuracy measurements, rotational errors in the radial direction of the rotating shaft can be measured relatively easily using a measurement reference ball, whereas angular runout of the shaft is important in the FLL plate processing of the reflecting mirror. There is no established technique for measuring the axial direction of the shaft.

This invention was made in view of the above circumstances, and is a device that can measure the angular deflection of a rotating shaft and the movement in and out of the shaft in the axial direction, and can accurately evaluate the rotation accuracy of a rotating shaft. The object of the present invention is to provide a rotation accuracy measuring device for a rotating shaft of a machine or the like.

Corresponding to this purpose, the rotational accuracy measuring device for a rotating shaft of the present invention is provided with a workpiece surface that is mounted so that its center of rotation coincides with the rotational shaft, and that is mounted at the rotation center position of the workpiece surface. a laser interferometric length measuring device that measures the distance between a fixed point outside the workpiece surface; and another laser interference length measuring device for measuring the distance between the two fixed points, and the movement of the work surface is measured by each of the laser interference sub length measuring devices, and the rotation accuracy component of the rotating shaft is measured. Detecting and distinguishing the shape component from the output signal of each of the laser interference length measuring devices including the shape component of the surface to be processed, and determining the displacement output signal of the laser interference sub length measuring device based on the shape of the surface to be processed. It is characterized in that the rotation accuracy of the rotation axis is measured by correction.

The details of this invention will be described below with reference to the drawings showing one embodiment.

In Figures 1 and 2, reference numeral 1 is a mirror surface of metal that is the surface to be machined, and the center of rotation of the mirror surface 1 is It is attached so as to roughly coincide with the shaft 2. A laser interferometric length measuring device 3 is disposed toward the rotation center position of the mirror surface 1, and another laser interferometric length measurement device is installed toward three points A1B1C on an imaginary circle centered around the rotation center position. Vessel 4
．． 5.6 are arranged, and are configured to measure the movement of the mirror surface at points ASB, C, and D, respectively, by means of the respective laser interferometers.

Since the output signals of each laser interferometric length measuring device 3, 4, 5, and 6 include a rotation accuracy component of the rotating shaft 2 and a shape component of the mirror surface 1, the shape component is detected and distinguished from each output signal, By correcting the displacement horn signal of each laser interference sub-length device for the displacement based on the shape of the mirror surface 1, the rotation accuracy of the rotating shaft 2 can be measured.

If we look at the rotation accuracy of the rotary axis of an ultra-precision lathe in terms of the shape accuracy of mirror surface 1 and the surface roughness, we can see that the rotational accuracy of the axis in the generatrix direction Z(θ) and the angular runout of the axis ωx(0) ,
ω/(θ) is the main component.

4.5.6 Laser interferometric length measurement device, the angle between them is φ, τ
Arrange it so that Let the shape of the mirror surface 1 on the circumference of a radius d/2 be expressed as follows.

1゛(θ)=r0+Σ(Ak003 kθ+Bk5ln
kθ) (1)1 Output change sL, sb of each laser interferometric length measuring device 4.5.6
,s,,s, is as follows.

ω(θ) and ω/(θ) are expressed as follows.

s, L, s, , s, by deleting SL from each is SL, S'6 N S2, which is expressed as follows.

The following equation is derived from equations (1) to (4).

(5) Therefore, the output signal of each laser length measuring device is 3H1S and S'
After expanding into a Fourier series and finding G and H, (5
) Solving the equation gives Ak ~F.

Since (k=2...,oo) is obtained, the shape of the mirror surface 1 and ω, (θ), and ωy(θ) can be estimated.

Note that the rotation error component 2 (θ) in the generatrix direction is S, (
(θ) is given directly.

In this invention, a capacitance type or eddy current type displacement meter is not used as a displacement meter, but a laser interferometric length measuring device is used. The sub-length accuracy of the laser interference sub-length method is determined by the wavelength of the laser beam, and stability of o, ippm has been achieved. Furthermore, the wavelength of the laser beam is affected by the temperature, humidity, and atmospheric pressure of the air in the propagation path, but since these can be measured, it is easy to correct errors. In addition, temperature drift must be taken into account when using the analog displacement g1.
This is not necessary with the laser interference sub-length device. Furthermore, with analog displacement meters, output signal transmission, amplification, and A-
Although errors occur during D conversion, there is no need to worry about this because the laser interference sub-meter can handle the measurement results as digital values.

The wSa diagram shows an example of an IC using a plane mirror as the measurement target surface, and since the measurement light makes two round trips between the interference δ17 and the plane mirror 8, the measurement resolution is λ/80. Therefore, considering that the wavelength of the laser beam is 6328A, the resolving power is 0.00791μIl.

(Measurement example) An attempt was made to measure the rotational accuracy of a rotating shaft using the present measuring device using a Borley ultra-precision lathe (DW4-1-13-P) as an example.

Next, the aluminum alloy covering material was ground to a mirror surface according to the accepted conditions, and this was used as the target surface.

Conditions (1) Rotating shaft rotation speed: 1987 rpm (2) Feed: 15n+m/min (3) Depth of cut: 30μm (4) Chuck: 3-jaw scroll chuck (5) Workpiece vJ = Aluminum alloy (No. 5083) Diameter 200mm , thickness 35 mm (6) Tool: R bit made by Winter (γ-1, 34 mm) Figure 4a shows the shape of the mirror surface estimated by this measuring device in polar coordinates. However, as shown in FIG. 3, in the laser interference g1 used here, the measurement light is reflected at two points on the plane mirror.

Therefore, since this interferometer is used as the laser interferometric length measuring device 4.5.6 shown in Fig. 2, the shape of the mirror surface determined by this measuring device is two circles with different radii centered on the dot. It is a quantity that represents the unevenness of the surface along the circumference. The solid line represents the shape measured immediately after the rotation axis is rotated.
Moreover, the broken line and the chain line indicate the shape measured after 3 hours or more had elapsed after the rotation (1=1). As is clear from the figure, while the shapes of the mirror surfaces sequentially measured after rotation are almost the same, the shapes measured immediately after rotation are significantly different.

This is thought to be due to thermal deformation of the mirror surface.

The rotating shaft of this lathe uses a dynamic pressure bearing that uses oil as the working fluid, so as the rotating shaft rotates, the oil temperature drops to 40°C in 3 hours.
The temperature rises by approximately .degree. C., and this heat not only stretches the rotating shaft, but also thermally deforms the tip and mirror surface.

Figure 4 shows the angular motion ω/ around the y-axis and the distance d /2 between the center of rotation and the measurement position (d = 82
mm) is calculated for 8 rotations of the rotation axis, and is expressed in polar coordinates.

Since the bearing of this rotating shaft is a fluid bearing, the rotation accuracy is much better than that of a rotating shaft using a rolling bearing.
The locus of each rotation of the rotation axis is not the same, and the trajectory is 0.1μ
It has a cloud-like spread with a width of about m.

The shape and angular motion of the mirror surface evaluated by the minimum area circle radius difference method are 0.0.
They are 27 μm and 0.25 μm, which are in close agreement.

FIG. 5 is a power spectrum curve of the mirror surface shape and angular motion shown in FIG. 4.

Among the shape components of the mirror surface, the 3-peak and 6-peak components are predominant. Judging from the small amplitude of the 3- and 6-peak components that are pulled into the angular motion, these components are considered to be related to the three-jaw chuck that holds the mirror surface.

As is clear from the above description, according to the present invention, it is possible to measure the angular deflection of the rotating shaft and the movement in and out of the shaft in the axial direction, and the rotational accuracy of the rotating shaft can be accurately evaluated. 1q of equipment can be installed.

[Brief explanation of drawings]

Fig. 1 is a perspective explanatory view, not showing a rotation accuracy measuring device for a rotating shaft according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the measurement principle, and Fig. 3 is a rotational accuracy measuring device according to an embodiment of the present invention. An explanatory diagram showing the optical system used in the shaft rotational accuracy measurement device. Fig. 4 is a graph showing the shape of the mirror surface and angular motion in polar coordinates, and Fig. 5 is a graph showing the shape of the mirror surface and angular motion.
This is the power spectrum of motion. 1... Mirror surface 2... Rotating axis 3.4.5.6.
... Laser interference sub-length device Fig. 1 Fig. 2 Fig. 3 Fig. 4 1111'' 4 -'-43,5

Claims (1)

[Claims] a laser interference sub-length device for measuring the distance between the workpiece surface and a fixed point outside the workpiece surface at the rotation center position of the workpiece surface, which is attached so that the rotation center coincides with the rotation axis; and the workpiece surface and another laser interferometric length measuring device for measuring the distance between the workpiece surface and a fixed point outside the workpiece surface at at least three locations on a circle centered on the rotation center position of the workpiece, J
: The shape component is detected and distinguished from the output signal of each of the laser interferometers including the rotation accuracy component of the rotating shaft and the shape component of the workpiece surface, and the laser interference length measurement is performed. A device for measuring rotational accuracy of a rotating shaft, characterized in that the rotational accuracy of the rotating shaft is measured by correcting the displacement output signal of the machine for displacement based on the shape of the surface to be machined.