JP2008180548A - Measurement method and measuring device for mass unbalance of rotator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure mass unbalance of a small-sized rotator, such as, a dental turbine of a dental hand piece, highly accurately, without having to use calibration weight or the like. <P>SOLUTION: A centrifugal force caused by mass imbalance is converted into deflection amount of a soft structure, and the magnitude and the phase thereof are calculated. Vibrations in an elastic beam 4, during rotation of a rotator 1, is detected in a noncontact state by a displacement sensor 5, the rotation position is also detected in the noncontact state by a rotation sensor, and each detection value is computed by specific means, to thereby calculate the magnitude and the phase of the imbalance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for measuring a mass unbalance of a rotating body having a mass distribution around a rotation axis, and a mass imbalance measuring apparatus using the measurement method, and measurement is difficult by a conventional method. The present invention relates to a method and apparatus suitable for measuring mass unbalance of a small rotating body.

  There is an increasing demand for the development of a method and apparatus that can easily reduce the mass imbalance of a rotating body mounted on a device for the purpose of reducing noise and vibration of the device having the rotating body. In order to reduce mass unbalance, it must first be possible to reliably detect its size and phase (angular position), but with the recent miniaturization of equipment, its measurement has become difficult for the following reasons. It was.

  One is that there is no sensor that can measure vibration due to mass imbalance of a small rotating body with high accuracy. Usually, a piezoelectric acceleration sensor is often used to measure vibrations of a rotating body due to mass imbalance (see, for example, Patent Document 1). However, since the mass of the vibration detection weight incorporated in the sensor is larger than that of the rotating body to be measured, it is not possible to sufficiently secure the sensitivity necessary for vibration detection of the small rotating body. In addition, since such a vibration sensor is mounted directly in the vicinity of the bearing that supports the rotating body and detects vibration, there is a concern that the vibration system to be measured may be changed.

Furthermore, another reason why it has become difficult to measure the mass unbalance of small rotating bodies is that it has become difficult to apply conventional measurement algorithms to mass unbalance measurements of small rotating bodies. . For example, as shown in Patent Document 2, the influence coefficient method measures vibration when a calibration weight is directly added to and removed from a rotating body, and numerically calculates the result to calculate the magnitude and phase of mass imbalance. Although it is an algorithm for calculating (position), it is often difficult to secure a space for adding or removing a calibration weight from a small rotating body.
JP-A-10-134502 JP 2000-310576 A

  As shown in the background art, it is not possible to apply the conventional mass unbalance measurement method used in balance measuring instruments used for diagnosis and maintenance of rotating machinery on site to the mass unbalance measurement of small rotating bodies. It is a problem to be solved by the invention. In particular, since it is difficult to install a calibration weight, the most difficult problem to be solved is that the general influence coefficient method cannot be applied.

  In order to solve such a problem, the present invention has conceived a method of measuring a centrifugal force due to mass unbalance by converting it into a deflection amount of a flexible structure, and the mass unbalance is large without following a measurement algorithm based on an influence coefficient method. And a device capable of calculating the phase and a device using the method are completed.

  According to the first aspect of the present invention, a bearing that supports a rotating shaft of a rotating body that is driven by a fluid colliding from outside is supported by an elastic member, and the vibration of the elastic member is displaced during the rotation of the rotating body. This is a method for measuring the mass unbalance of a rotating body, which detects the rotation position of the rotating body in a non-contact manner using a sensor, detects the rotational position of the rotating body in a non-contact manner, and holds and calculates the output of the displacement sensor and the rotation sensor. Detecting the rotational speed of the rotating body, determining the rotational speed of the rotating body has reached a steady state, and detecting the displacement sensor when the rotational speed of the rotating body has reached a steady state. The output of the elastic member into the arithmetic device, the step of calculating the displacement amplitude of the elastic member from the output of the rotation sensor and the displacement sensor taken into the arithmetic device, and the change of the elastic member. A step of calculating a centrifugal force of the rotating body from an amplitude; and a step of calculating a mass unbalance amount of the rotating body from a calculation result of the centrifugal force of the rotating body. This is a measurement method.

  The invention according to claim 2 of the present invention comprises means for causing a fluid to collide with the rotating body from the outside, a supporting means comprising an elastic member for supporting a bearing for supporting the rotating shaft of the rotating body driven by the fluid collision, A displacement sensor that detects the vibration of the elastic member during rotation of the rotating body in a non-contact manner, a rotation sensor that detects the rotational position of the rotating body in a non-contact manner, and holds the outputs of the displacement sensor and the rotation sensor. A mass imbalance measuring device for a rotating body comprising a computing device for computing, a means for detecting the rotation of the rotating body, a means for determining that the rotational speed of the rotating body has reached a steady state, Means for taking the outputs of the rotation sensor and the displacement sensor into the arithmetic device when the rotating body reaches a steady state, and the output of the displacement sensor taken into the arithmetic device, Means for calculating the displacement amplitude, means for calculating the centrifugal force of the rotating body from the displacement amplitude of the elastic member, means for calculating the mass unbalance amount of the rotating body from the calculation result of the centrifugal force of the rotating body, It is the measuring apparatus of the mass imbalance of the rotary body characterized by including.

  The invention according to claim 3 of the present invention is characterized in that an elastic coefficient of the elastic member is smaller than any of the elastic coefficients of the bearing and the rotating body. It is.

  The invention according to claim 4 of the present invention is characterized in that the elastic member has an elastic coefficient smaller than any of the elastic coefficient of the bearing and the rotating body. It is.

  Since the present invention is configured as described above, it is not necessary to use a calibration weight, and the magnitude and phase of the unbalance can be measured with a single measurement. Further, since the measurement range (measurement sensitivity) can be arbitrarily changed by changing the cross-sectional shape of the elastic member that supports the bearing that supports the rotating shaft, the sensitivity can be adjusted by the mass of the rotating body. Furthermore, the measurement sensitivity can be set in consideration of the measurement range of the displacement sensor. In addition to the above-described effects, the inventions according to claims 3 and 4 have an effect of obtaining a higher output.

  There are a wide variety of rotating bodies to which the present invention can be applied, and the present invention is realized in various embodiments. Hereinafter, one embodiment will be described with reference to the drawings.

FIG. 1 is a diagram for explaining a method and an apparatus for measuring mass unbalance of a rotating body in one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a rotating body, which corresponds to, for example, a turbine for mounting a cutting tool for a dental handpiece or a spindle rotating body for mounting a tool in a machine tool, a so-called tool holder. Reference numeral 2 denotes a compressed air supply body that rotates the rotating body 1 by the air flow. The compressed air may be water or the rotating body 1 can be rotated by a high-speed water flow. Reference numeral 4 denotes an elastic beam as an example of an elastic member that supports the bearing 3 that supports the rotating body 1. Reference numeral 5 denotes a displacement sensor for detecting the vibration of the elastic beam 4 during the rotation of the rotating body 1 without contact, and reference numeral 6 denotes a rotation sensor for detecting the rotational position of the rotating body 1 without contact. An example of a displacement sensor is a capacitance-type non-contact displacement sensor (VE-521 manufactured by Ono Sokki Co., Ltd.) with a measurement range of 0 to 0.5 mm, a measurement resolution of 0.1 μm, and a frequency range of DC to 2.7 kHz. did. As an example of the rotation sensor, Keyence photoelectric sensor LV-H32 using a visible light semiconductor laser having a wavelength of 650 nm was used. The elastic beam has a length of 165 mm, a width of 18 mm, and a thickness of 0.6.
A rolled steel sheet for general structure of mm was used. The output of the displacement sensor 5 is input to an FFT analyzer (fast Fourier transformer) 9 via an amplifier (signal amplifier) 7 and a filter 8, and the output of the rotation sensor 6 is input to the FFT analyzer 9 via an amplifier 10. Reference numeral 11 denotes a surface plate, which is mounted with an elastic beam at an appropriate interval from the surface of the surface plate.

  Next, it will be described that the mass unbalance amount can be calculated by the above-described apparatus. When the rotating body 1 is rotated, the elastic beam 4 is displaced according to the mass imbalance of the rotating body. FIG. 2 and FIG. 3 are diagrams showing mass unbalance for explaining the calculation method, and a diagram showing a deflection state of an elastic beam due to mass unbalance, respectively.

  The mass imbalance of the rotating body is expressed by a vector having a magnitude and a phase, and the magnitude mr is expressed by the product of the eccentric mass m of the rotating body and the distance r of the eccentric mass from the rotation axis.

Now, assuming that the mass unbalance is mr, the rotational speed of the rotating body is ω, and the phase of the rotating body is θ, the vertical component F of the force acting on the elastic beam 4 due to the centrifugal force due to the mass unbalance. Is
It is represented by The amount of deflection δ when F acts on the elastic beam is expressed by equation (2) from the deflection equation in the case of both-end support.
Here, E is the longitudinal elastic modulus of the elastic beam, I is the moment of inertia of the cross section of the elastic beam, and l is the distance between the support portion 12 of the elastic beam 4 and the rotating shaft of the rotating body. By transforming the above equation (2), it can be seen that the mass unbalance amount mr can be uniquely calculated from the measured value of the deflection amount δ by the following equation.

Here, b and h are the width and height of the elastic beam, respectively, and the section moment of inertia I of the rectangular section is
Was used. As apparent from the equation (3), the mass imbalance amount mr is derived from the measurement result of the deflection amount δ. In this case, since the unbalance amount mr varies depending on the rotational speed ω of the rotating body, it is necessary to keep the flow rate of compressed air or the like constant and keep the rotational speed constant.

  FIG. 4 is a diagram for explaining that the mass imbalance of the rotating body can be detected by the method and apparatus according to the present invention. It is the figure which showed the result of having measured the deflection | deviation (delta) of the elastic beam 4 in rotation of the dental dental turbine which has mass imbalance using the displacement sensor 5 using the measuring apparatus shown in FIG. As indicated by the circles in FIG. 4, as the rotational speed of the dental turbine 1 increases, the vibration frequency caused by the mass imbalance of the rotating body 1 as shown in FIGS. It can be seen that is rising. From this, it can be said that if the deflection of the elastic beam 4 is measured, the magnitude of mass imbalance at the rotational frequency of the rotating body 1 can be extracted.

  FIG. 5 is a diagram for explaining that phase detection is possible in the present invention. The deflection of the elastic beam 4 during rotation of the dental dental turbine 1 having mass imbalance was measured using the reference signal of the rotation sensor 6 as a base point, using the measurement apparatus of FIG. In FIG. 5, the respective outputs of the displacement sensor 5 when the reference signals having a phase difference of 180 ° around the rotation axis of the dental turbine 1 are marked are measured. The marking of the reference signal was performed by applying a white oil paint to the rotating shaft 13 of the dental turbine. FIG. 5 shows the result of measuring the output waveform of the displacement sensor with the FFT analyzer 9 in each case. By reversing the marking of the reference signal, the peak position of the signal waveform of the displacement sensor was reversed. From this measurement result, it can be seen that the phase detection method of this measurement apparatus is appropriate.

It is a figure for demonstrating the measuring method and measuring apparatus of mass imbalance in one Example of this invention. It is a figure for demonstrating the amount of unbalance of a rotary body, and mass unbalance is represented by vector. It is a figure which shows the bending state of the elastic beam by the mass unbalance of the rotary body in the mass unbalance measuring apparatus in one Example of this invention. It is a figure which shows the measurement result of the deflection amount of the elastic beam by the mass unbalance of a rotary body in the mass unbalance measuring apparatus in one Example of this invention. It is a figure which shows the result of having measured the deflection | deviation phase of the elastic beam by the mass unbalance of a rotary body in the mass unbalance measuring apparatus in one Example of this invention.

Explanation of symbols

1 Rotating body (dental dental turbine)
2 Compressed air supply body 3 Bearing 4 Elastic beam 5 Displacement sensor 6 Rotation sensor 7 Amplifier (signal amplifier)
8 Filter 9 FFT analyzer (Fast Fourier Transformer)
10 Amplifier (signal amplifier)
11 Surface plate 12 Support section of elastic beam 13 Rotating shaft

Claims (4)

  A bearing that supports a rotating shaft of a rotating body that is driven by collision of fluid from outside is supported by an elastic member, and vibration of the elastic member during rotation of the rotating body is detected in a non-contact manner by a displacement sensor. A rotating body mass imbalance measurement method for detecting the rotational position of the rotating body in a non-contact manner by a rotation sensor and holding and calculating the displacement sensor and the output of the rotation sensor, wherein the rotational speed of the rotating body is determined. A step of detecting, a step of determining that the rotational speed of the rotating body has reached a steady state, and a step of taking the output of the displacement sensor into an arithmetic device when the rotational speed of the rotating body has reached a steady state; Calculating the displacement amplitude of the elastic member from the output of the rotation sensor and the displacement sensor taken into the arithmetic device, and the distance of the rotating body from the displacement amplitude of the elastic member. Process and method of measuring the mass imbalance of the rotating body, characterized in that it comprises a step of calculating a mass unbalance of the rotating body from the calculation result of the centrifugal force of the rotating body for calculating the force.   Means for causing fluid to collide with the rotating body from the outside; support means comprising an elastic member for supporting a bearing for supporting the rotating shaft of the rotating body driven by the fluid collision; and the elastic member during rotation of the rotating body A rotation sensor comprising: a displacement sensor that detects the vibration of the rotation body in a non-contact manner; a rotation sensor that detects the rotation position of the rotating body in a non-contact manner; and an arithmetic device that holds and calculates the output of the displacement sensor and the rotation sensor. A body mass imbalance measuring device, comprising: means for detecting rotation of the rotating body; means for determining that the rotational speed of the rotating body has reached a steady state; and the rotating body has reached a steady state. Means for fetching the output of the rotation sensor and the displacement sensor into the arithmetic device, and means for calculating the displacement amplitude of the elastic member from the output of the displacement sensor taken into the arithmetic device; And a means for calculating a centrifugal force of the rotating body from a displacement amplitude of the elastic member, and a means for calculating a mass unbalance amount of the rotating body from a calculation result of the centrifugal force of the rotating body. Measuring device for mass imbalance of rotating bodies.   The method for measuring a mass imbalance of a rotating body according to claim 1, wherein an elastic coefficient of the elastic member is smaller than any of the elastic coefficients of the bearing and the rotating body. The apparatus for measuring mass unbalance of a rotating body according to claim 2, wherein an elastic coefficient of the elastic member is smaller than any of the elastic coefficients of the bearing and the rotating body.