JPS5853843B2 - How to measure rotational accuracy of rotating shaft - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the rotation accuracy of a rotating shaft such as a main shaft of a machine tool or a rotating shaft of a turbine.

In this specification, rotational accuracy refers to JIS, B,
6201-1973 refers to the runout of the rotating shaft and/or axial movement during rotation.

For example, in machine tools such as lathes, many efforts have been made to improve the rotational accuracy of the spindle because the rotational accuracy of the spindle is closely related to the machining accuracy of the rigid material. Therefore, it is necessary to measure the rotational accuracy of the spindle and reflect it in the design so that the rotational accuracy of the spindle is improved.

Various methods have been developed to measure the rotational accuracy of the main spindle. For example, VC is a method that measures the rotation of the workpiece being machined in a lathe, etc. includes both the rotational accuracy component of the spindle (due to rotational runout of the spindle) and the shape component of the workpiece (due to runout caused by the shape of the workpiece). Therefore, the rotational accuracy component of the spindle It was difficult to know exactly.

Next, a method has been developed in which a measurement ring or ball that is processed with high precision and can be considered to be a perfect circle is attached to the main shaft and the rotation of this ring or ball is measured.

However, with this method, it is not always easy to evaluate the rotational accuracy during machining, the roundness of the measurement ring or sphere may affect the measurement results, it may cause a decrease in the rigidity of the shaft, and the measurement There are problems in that it is not always easy to accurately align the center of the ring or sphere with the center of the shaft, and it is also difficult to accurately measure the rotation accuracy of the rotating shaft.

Also, when measuring the rotational accuracy of the end face of the rotating shaft in the axial direction (axial motion), only the rotational accuracy can be accurately measured without being affected by the shape or surface condition of the end face of the rotating shaft. This is quite difficult.

This invention was made in view of the above circumstances, and it is possible to perform high-precision measurement of the rotation accuracy of a rotating shaft even during processing of a workpiece, and the measurement can be automated. Another object of the present invention is to provide a method for measuring rotational accuracy of a rotating shaft that does not require a measuring ring, a measuring ball, or the like.

In order to achieve this purpose, a method for measuring rotational accuracy of a rotating shaft according to the present invention includes arranging three or more non-contact displacement meters located in the same plane at fixed positions facing the surface of a rotating body, Measuring the motion of the rotating body with the displacement meter, detecting and distinguishing the shape component from the output signal of the displacement meter that includes a rotation accuracy component of a rotation axis of the rotating body and a shape component of the rotating body,
The present invention is characterized in that the rotational accuracy of the rotating shaft of the rotating body is measured by correcting the displacement output signal of the displacement meter with respect to the displacement based on the shape of the rotating body.

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

FIGS. 1, 2, 3, and 4 show an embodiment in which the present invention is applied to measurement of rotation accuracy regarding radial motion of a rotating shaft.

In Fig. 1, 1 is a workpiece attached to a rotating shaft 2 whose rotation accuracy is to be measured, and three displacement gauges AB and C are installed in a plane including a specific cross section of the workpiece 1. Place.

As the displacement meters A, B, and C, a capacitive displacement meter, an eddy current displacement meter, or any other displacement meter can be used.

The movement of the rotating workpiece 1 is measured by displacement meters A, B, and C.

The outputs of the displacement meters A, B, and C include not only the rotation accuracy component of the rotating shaft but also the shape component of the workpiece 1.

A shape component is detected from the output of the displacement meter, and the output of the displacement meter is corrected accordingly.

In this embodiment, a three-point roundness measuring method is applied to detect the shape of the workpiece, and therefore the shape of the workpiece is detected by the following calculation.

The centers of the three displacement meters A, B, and C are O, and the angles between the displacement meters are φ and τ.

Further, let the rectangular coordinate system passing through point O be x-y, and let the rotation angle of the axis from the y-axis be θ.

The rotation center α of the workpiece generally does not coincide with the point O, but α is close to the 0 point, so the average radius of the workpiece is r.

Therefore, the shape of the workpiece is expressed as follows.

Here, Ra t Rb t Rc corresponds to the distance between each displacement meter and point O, and X and y correspond to the displacement component of the workpiece, that is, the rotation accuracy component of the shaft.

Next, when the output of each displacement meter is multiplied by the coefficient L at b and added together, the total output is as follows.

S(θtalk(θ+r)−ycosτ−xs in
τ...(11) From equation (11), the estimated amount of the displacement component of the workpiece, that is, the rotational error component of the main shaft, is obtained as follows.

In the above case, capacitance type displacement meters (DISA TYPE 51D11) are used as each displacement meter A, B, and C, and the angle between displacement meter A and displacement meter B and between displacement meter A and displacement meter C is φ. -134° and τ-122°.

In addition, to detect the rotation angle of the main shaft, a rotary encoder (NIKON R
X-2000), the output pulse frequency divider circuit
5,250,5001000 and 2000 pulses/re
The displacement meter output signal is sampled using an arbitrary division number of vy.

The displacement meter output signal is first transferred to a transient recorder (BIO).
MATION 1015), convert it to paper tape data, and input it to a minicomputer (YHP 2100A).
) was used for analysis.

Example The radial motion of the lathe in the cutting direction of the tool was measured.

A 545C workpiece with a diameter of 50mm and a length of 150mff1 was cantilevered onto a chuck, and the radial motion at a position 45mm from the end surface of the workpiece was measured.

Prior to measurement, light cutting was performed to minimize eccentricity that occurred when attaching the workpiece to the chuck.

Furthermore, the displacement gauges are arranged in the same manner as shown in FIG. 1 when viewed from the direction of the tailstock of the lathe, and the tool cutting direction is aligned with the X-axis.

The measurement was performed in an unloaded state with the main shaft rotating at 600 rpm.

Data sampling is performed in synchronization with the output pulse of the rotary encoder, and for each displacement meter, 25
Four rotations were recorded at 0 point.

Figure 2 shows the shape of the workpiece detected by this device and the shape measured by the capacitive displacement meter mentioned above when the same workpiece was placed on the rotary table of the roundness measuring machine (Loncom 2C-07). This is a comparison.

Although there is a difference of about 0.05 μm in some parts, the two agree well.

Note that the diameter of the tip of the displacement meter is 8 myt, which is quite large, and as is clear from FIG. 2, high-order shape components of the workpiece are not detected.

Therefore, it is sufficient to calculate the shape component in five orders of magnitude.

FIG. 3 shows the X component of the radial motion calculated according to Equation 12, that is, the component of four rotations in the cutting direction of the tool, expressed in polar coordinates using Equation 13.

Here, X (θ) is the shaft runout at the rotation angle θ, do is the basic circle diameter when displayed in polar coordinates, and the figure shown in Figure 3 corresponds to the roundness of the workpiece processed by this lathe. It is something to do.

Further, the power spectrum of X((0 x θ x 8π) is shown in FIG.

Since the signal power spectrum for four rotations is calculated, the resolution is 0.25 peaks, r ev.

In the case of axis rotation accuracy, a longer signal is required to improve the resolution at low orders, which is important, but from Fig. 4, 0
．． It can be seen that components of 5 peaks, 1 peak, 2 peaks, and 24 peaks/rev appear.

Of these, the component of 0.5 peaks/r ev appears to be due to the main shaft bearing.

Furthermore, the fact that two peaks/rev components occur also coincides with the fact that the shape of the workpiece shown in FIG. 2 includes an elliptical component.

The 24 peak rev component corresponds to the frequency of 240H2 when the spindle rotation speed is 60 Or pm, which corresponds to the natural frequency of the workpiece spindle system.

1 pile/r.e.v. The component is thought to include the eccentricity of the work material.

Next, a description will be given of an embodiment in which the present invention is applied to measurement of rotation accuracy regarding axial motion of a shaft end face.

As shown in FIGS. 5 and 6, three displacement gauges A', B', and C' are placed in the same plane and on the same circumference, facing the end surface of the rotating shaft 2'. do.

As in the previous embodiment, displacement meters A'B', C'
Since the output of includes both the displacement component of the rotating shaft and the shape component of the end face of the rotating shaft, the output of ", C' is corrected for the shape component of the end face of the rotating shaft by the above calculation on the displacement meter. By doing so, it is possible to measure the rotation accuracy regarding the axial motion of the rotating shaft.

As is clear from the above description, according to the present invention, it is possible to highly measure the rotational accuracy of a rotating shaft without using a measuring ring, a measuring ball, etc., and even during machining of a workpiece. can be automated.

In addition, in the conventional measurement method, the output signal of the eddy current displacement meter changes depending on the stress distribution of the rotating body such as the workpiece, so there was a problem with measurement accuracy, especially when the material was iron-based. For example, even if the displacement meter is an eddy current displacement meter, the signal caused by the stress distribution is common to the three displacement meters A, B, and C, or to the displacement meters A' and C'. Errors based on stress distribution can be easily detected, and accurate measurements can be made by correcting them. Therefore, eddy current type displacement meters, which were previously thought to be unusable, can also be used.

The above explanation has been made regarding an example in which the present invention is applied to measuring the rotational accuracy of a main shaft of a machine tool such as a lathe, but this invention is also applicable to measuring the rotational accuracy of a rotating shaft of a turbine or other rotating body. Of course, the method 11 can also be applied to the method.

[Brief explanation of drawings]

Fig. 1 is an explanatory front view showing the principle of measuring rotational accuracy regarding the radial motion of the rotary shaft according to this first invention, Fig. 2 is an explanatory view showing the shape of the workpiece, and Fig. 3 is an illustration of four rotations of the workpiece. FIG. 4 is a graph showing the power spectrum of the radial motion of the workpiece, and FIG. 5 is a front view showing the principle of measuring rotational accuracy related to the axial motion of the rotating shaft according to the present invention. 6 and 6 are side explanatory views showing the principle of measuring rotation accuracy regarding the axial motion of a rotating shaft according to the present invention. 1... Work material, 2. z...Rotation axis, A
, B, C. A', B: C'...Displacement meter.

Claims (1)

[Claims] 1. Three or more non-contact displacement meters located in the same plane are arranged at fixed positions facing the surface of the rotating body, and the movement of the rotating body is measured by the displacement meters, and the movement of the rotating body is measured by the displacement meters. Detecting and distinguishing the shape component from the output signal of the displacement meter including a rotation accuracy component of the rotating shaft and a shape component of the rotating body, and correcting the displacement output signal of the displacement meter for the displacement based on the shape of the rotating body. A method for measuring rotational accuracy of a rotating shaft, characterized in that the rotational accuracy of the rotating shaft of the rotating body is measured by: