JP2009047489A - Contactless type ae sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the sensitivity irregularity of a contactless type AE sensor having no active element in its rotary part and to easily detect whether the contactless type AE sensor gets out of order. <P>SOLUTION: The contactless type AE sensor is equipped with the rotary part 40 provided to the end part of the rotary shaft of a rotor and constituted of an AE converter 31 and a first inductance element 41 and the fixing part 50 provided in opposed relation to the rotary part and having the second inductance element 51 electromagnetically coupled with the first inductance element 41, a transmission circuit 61 for applying a pulse signal to the second inductance element and a receiving circuit 62 for detecting the electric signal of the second inductance element. The fixing part 50 is equipped with a variable gain amplifier 64, an AD converter 65, a spectrum analyzing part 66 for performing the spectral analysis of a digital signal to calculate the spectral intensity of the frequency component of a detection target and a gain control part 66 for controlling the gain of the variable gain amplifier so as to make the spectral intensity constant. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an AE sensor that detects a high-frequency acoustic signal (AE (Acoustic Emission) signal) propagating in a solid medium, and more particularly to a non-contact AE sensor that detects an AE wave of a rotating body such as a rotating shaft. .

  In a processing device that performs processing by bringing a tool into contact with a workpiece (work), for example, a grinding machine that grinds a rotating grindstone in contact with the rotating workpiece, contact between the tool (grinding stone) and the workpiece (air cut) ) Detection, completion detection of dressing of the tool (grinding stone) by the dressing tool (dresser), positioning of the tool by detecting that the tool (grinding stone) contacts a predetermined reference pin, and the tool (grinding stone) and the processing device An AE sensor is used to detect a collision with other parts. An AE sensor detects an acoustic signal propagating in a solid, and there are various methods depending on a target frequency, but an AE sensor used in a processing apparatus such as a grinding machine has several tens of kHz to several Targeting a 100 MHz ultrasonic region, it is composed of piezoelectric elements.

  Hereinafter, although an AE sensor used in a grinding machine will be described as an example, the present invention is not limited to this, and any AE sensor can be applied.

  For AE sensors, NDIS No. Since the grinding machines using the AE sensor in 2106-79, 2106-91 and the like are widely known as described in Patent Document 1, the detailed explanation of the AE sensor is omitted here. Only the portion directly related to the present invention will be described.

  FIG. 1 is a diagram illustrating an example of use of an AE sensor, and is a diagram illustrating a configuration in which an AE sensor is provided in a processing system including a grinding machine. In the following description, the case where the AE sensor is applied to the configuration as shown in FIG. 1 is taken as an example. In FIG. 1, a mechanism for holding and rotating a workpiece W and a moving base 12 are provided on a base 11. The moving base 12 is provided with a grindstone rotating mechanism 13 that rotates a grindstone (tool) 14. The grinding machine is controlled by a processing machine control device 15. In addition, when the grindstone 14 is replaced with a new one or used for a certain period of time, a process called a dressing process is performed in order to make the surface of the grindstone 14 suitable for grinding. In this process, the surface of the grindstone 14 is treated by bringing a dresser into contact with the rotating grindstone 14. The above part is the same as the processing system including a normal grinding machine.

  An AE (Acoustic Emission) sensor 21 is attached to the housing of the grindstone rotating mechanism 13, and an AE wave generated by the grindstone 14 is transmitted to the AE sensor 21 through the housing of the grindstone rotating mechanism 13, and the AE sensor 21 transmits an AE signal. appear. The AE signal processing device 22 processes the AE signal, detects that the grindstone 14 has contacted the workpiece W, and notifies the processing machine control device 15 of it.

  FIG. 2 is a diagram illustrating a circuit configuration of the AE sensor. In FIG. 2, reference numeral 31 indicates an AE converter, and 32 indicates a case in which the AE converter 31 is accommodated. The AE converter 31 is made of a piezoelectric material such as lead zirconate titanate-based piezoelectric ceramic (PZT), lithium niobate, or quartz, and electrically corresponds to a capacitance. The AE converter 31 is connected to the preamplifier 33, and an output corresponding to a change in impedance of the AE converter 31 due to the AE wave is obtained from the preamplifier 33. In the example of FIG. 1, the case 32 is attached to the housing of the grindstone rotating mechanism 13 as the AE sensor 21, and the preamplifier 33 is provided in the AE signal processing device 32.

  Depending on the application, AE waves in various parts are detected, but there are applications that detect AE waves generated by a rotating tool (grindstone). In the conventional example of FIG. 1, AE waves generated by a rotating tool (grindstone) are converted into AE waves that pass through a bearing that holds a rotating body (shaft) that is attached to the tool and rotates together with the tool. It is detected as an AE wave propagating through the body. Such detection is possible when the bearing is a bearing that propagates AE waves, such as a sliding bearing (such as a static pressure bearing). On the other hand, a rolling bearing (such as a ball bearing) has a problem that the AE wave of the rotating body does not sufficiently propagate through the bearing and cannot be detected.

  Therefore, Patent Document 2 is provided with a rotating part having an AE sensor and one of a non-contact coupling (generally using an electromagnetic induction coupler) connected to the AE sensor. A non-contact type AE sensor is described in which a fixed part having the other of the contact couplings is provided on the fixed side so that the AE wave of the rotating body can be directly detected. With this AE sensor, the AE wave of the rotating body can be detected even when a bearing that does not pass the AE wave is used.

  In the non-contact AE sensor described in Patent Document 2, an electromagnetic induction coupler different from the electromagnetic induction coupler that transmits the AE signal is provided, and power is supplied from the fixed portion to the amplifier of the rotating portion. However, as shown in FIG. 3, the rotating part 40 which has the 1st inductance element (coil) 41 which comprises AE converter 31 and a non-contact coupling, and the 2nd inductance element (coil) which comprises a non-contact coupling There is also a non-contact type AE sensor including a fixing unit 50 having an amplifier 52 that amplifies an electric signal generated in the first inductance element 51 and the second inductance element 51. In the configuration of FIG. 3, a circuit including the AE converter 31 and the amplifier 52 is formed through the first inductance element 41 and the second inductance element 51 in the same manner as a normal AE sensor. The rotating unit 40 does not have an active element, and the AE converter 31 and the first inductance element 41 of the rotating unit 40 form an LC circuit. The non-contact AE sensor in FIG. 3 has an advantage that the rotating part can be made smaller than the non-contact AE sensor described in Patent Document 2.

JP-A-6-114692 JP 2005-519265 A

  The AE sensor is not limited to the non-contact type, and the AE sensor has a large individual difference in sensitivity of the AE transducer itself due to a manufacturing problem, and the problem that the detected AE signal varies greatly, that is, the sensitivity variation of the AE sensor is large. There is. Therefore, in general, calibration data is attached at the time of shipment from the manufacturer, and the gain of the amplifier is adjusted or the measurement data is corrected based on the calibration data. However, in order to perform this calibration method, the circuits other than the AE converter are required to be stable.

  The sensitivity of the AE sensor varies depending on the mounting method. In particular, the non-contact AE sensor described in Patent Document 2 transmits an AE signal amplified by an amplifier via a non-contact coupling, whereas the non-contact AE sensor of FIG. Since the circuit is formed through the coupling, the non-contact type AE sensor of FIG. 3 is difficult to accurately align between the rotating part and the fixed part, and the problem of poor alignment reduces transmission efficiency and sensitivity. There is. In addition, there is a reliability-related defect in that transmission efficiency decreases due to adhesion of coolant and chips to the non-contact coupling portion.

  As described above, the non-contact AE sensor shown in FIG. 3 has a problem that not only the sensitivity variation of the sensor itself is large, but also the sensitivity variation is further increased depending on the state of the non-contact coupling portion. Since it is difficult to evaluate the detection signal unless the sensitivity of the sensor is constant, it is necessary to adjust the sensitivity. However, this sensitivity variation is difficult to adjust using the calibration data as described above because the state of the non-contact coupling portion is uncertain.

  There is also a problem that even when a failure occurs in which a good AE signal cannot be obtained, the occurrence of the failure cannot be detected.

  The present invention solves such a problem and reduces the sensitivity variation of a non-contact AE sensor that does not have an active element in the rotating part, and whether a failure has occurred including a non-contact coupling part. It is intended to make it possible to easily detect.

  In order to achieve the above object, according to the first aspect of the present invention, the amplifier of the fixed unit is a variable gain amplifier having a variable amplification factor, the output is converted into a digital signal, spectrum analysis is performed, and the detection target The gain of the variable gain amplifier is controlled so that the spectrum intensity of the frequency component is constant.

  That is, the AE sensor according to the first aspect of the present invention is provided on the rotating shaft of the rotating body, and is provided so as to face the rotating portion, the rotating portion including the AE converter and the first inductance element. A second inductance element that is electromagnetically coupled to the inductance element of the rotating unit, a transmission circuit that applies a pulse signal to the second inductance element, and a reception circuit that detects an electrical signal of the second inductance element. A non-contact type AE sensor that detects an AE wave of the rotating body with a fixed fixing unit, and the fixing unit amplifies the electrical signal detected by the receiving circuit, A variable gain amplifier having a variable amplification factor, an AD converter that converts the output of the variable gain amplifier into a digital signal, and a spectrum of the digital signal output from the AD converter And a spectrum analysis unit that calculates the spectrum intensity of the frequency component to be detected, and the transmission circuit is controlled to output a measurement pulse according to an adjustment command from the outside, and a resonance signal that responds to the measurement pulse And a gain control unit that controls an amplification factor of the variable gain amplifier so as to make a spectrum intensity of the frequency component to be detected constant based on a spectrum analysis result.

  The fixing unit preferably further includes a filter that removes a noise component from the electrical signal detected by the receiving circuit.

  Further, according to the second aspect of the present invention, when the spectrum analysis result of the resonance signal responding to the measurement pulse indicates that the spectrum intensity of the frequency component to be detected is smaller than the threshold value, the occurrence of abnormality is notified.

  That is, the AE sensor according to the second aspect of the present invention is provided on the rotating shaft of the rotating body, and is provided to face the rotating portion, the rotating portion including the AE converter and the first inductance element. A second inductance element that is electromagnetically coupled to the inductance element of the rotating unit, a transmission circuit that applies a pulse signal to the second inductance element, and a reception circuit that detects an electrical signal of the second inductance element. A non-contact type AE sensor that detects an AE wave of the rotating body with a fixed fixing unit, the fixing unit amplifying the electrical signal detected by the receiving circuit And an AD converter that converts the output of the amplifier into a digital signal, and a spectrum analysis of the digital signal output from the AD converter to calculate a spectrum intensity In response to a spectrum analysis unit and an adjustment command from the outside, the transmission circuit is controlled to output a measurement pulse, and in the spectrum analysis result of the resonance signal responding to the measurement pulse, when the spectrum intensity is smaller than a threshold value And a control unit that outputs a signal for notifying the occurrence of abnormality.

  The first aspect and the second aspect may be combined to adjust the sensitivity when there is no abnormality.

  According to the first aspect of the present invention, it is possible to reduce the sensitivity variation of the non-contact AE sensor that does not have an active element in the rotating portion, and the usability is improved.

  According to the second aspect of the present invention, in the non-contact AE sensor having no active element in the rotating part, it is possible to easily detect whether a failure has occurred including the non-contact coupling portion.

  FIG. 4 is a diagram showing the configuration of the non-contact AE sensor according to the embodiment of the present invention. As shown in FIG. 4, the non-contact AE sensor of the present embodiment has a rotating part 40 and a fixed part 50. The rotating unit 40 is attached to an end of a rotating body such as a rotating shaft, and the fixed unit 50 is disposed to face the rotating unit 40. Note that the sensor may be embedded in the rotating body.

  The rotating unit 40 includes an AE converter 31 and a first inductance element (coil) 41 that forms a non-contact coupling. The fixing unit 50 includes a second inductance element (coil) 51 that forms a non-contact coupling, a transmission circuit (pulse generation circuit) 61 that generates and applies a measurement pulse to the second inductance element 51, and a second inductance. A receiving circuit 62 that outputs an electric (voltage) signal generated in the element 51, a filter 63 that removes a noise component from the voltage signal output from the receiving circuit 62, and an output of the filter 63 are amplified, and an amplification factor (gain) is obtained. A variable variable gain amplifier 64, an AD converter (ADC) 65 that converts the output of the variable gain amplifier 64 into a digital signal, and a processing control circuit that performs spectrum analysis processing of the digital signal and controls the transmission circuit 61 and the variable gain amplifier. 66.

  As the second inductance element (coil) 51 of the rotating portion 40 and the fixed portion 50, the conventional one shown in FIG. 3 can be used.

  The transmission circuit 61 applies a measurement pulse described later to both ends of the second inductance element 51.

  The filter 63 is realized by, for example, a bandpass filter that passes the frequency range to be measured of the AE signal and removes other frequency ranges. Since the high frequency component is substantially removed at the sampling frequency of the ADC 65, the filter 63 can be configured by a low pass filter. Further, the filter 63 may not be provided depending on noise conditions.

  As the variable gain amplifier 64, a known one can be used as long as it has a band of about 500 kHz.

  Similarly, the ADC 65 having a sampling frequency of about 500 kHz can be used. For example, a ADC having a resolution of about 10 bits is used.

  The processing control circuit 66 is realized by combining a processor with a DSP and the like, and constitutes a spectrum analysis unit and a gain control unit. The spectrum analysis unit performs spectrum analysis processing of digital data of the AE signal output from the ADC 65, and calculates the spectrum intensity of the frequency component to be detected in the AE signal. The gain control unit feedback-controls the amplification factor of the variable gain amplifier so that the spectrum intensity of the frequency component to be detected is constant.

  Further, upon receiving an external command for instructing the start of measurement, the process control circuit 66 starts the measurement / setting operation. In the measurement / setting operation, the processing control circuit 66 first controls the transmission circuit 61 so as to output a measurement pulse as shown in FIG. This measurement pulse is applied to the AE transducer 31 of the rotating unit 40 by electromagnetic induction between the coil 51 and the coil 41 constituting the non-contact coupling, and a resonance signal (AE) as shown in FIG. Signal) is generated. This resonance signal is transmitted to the receiving circuit 62 of the solid part 50 by electromagnetic induction between the coil 41 and the coil 51. The resonance signal output from the receiving circuit 62 passes only the frequency component to be measured by the filter 63, is amplified by the variable gain amplifier 64, and is input to the ADC 65. Here, it is desirable that the amplitude of the AE signal amplified by the variable gain amplifier 64 is substantially equal to the quantization range of the ADC 65. If the amplitude of the AE signal exceeds the quantization range of the ADC 65, clipping with a predetermined level of intensity becomes the same level, and if the amplitude of the AE signal is significantly smaller than the quantization range of the ADC 65, There arises a problem that the actual resolution is lowered and high-precision measurement cannot be performed. The processing control circuit 66 analyzes the spectrum (frequency) of the digital data output from the ADC 65 using FFT or the like.

  The process control circuit 66 outputs a signal for notifying the occurrence of an abnormality because it is considered that some abnormality has occurred when the spectrum intensity in a predetermined range is smaller than the threshold in the spectrum analysis result. FIG. 5C is an example of an AE signal when an abnormality occurs, and only an output corresponding to the measurement pulse appears, and no resonance signal appears. Such an abnormality occurs, for example, when the wiring in the rotating unit 40 is disconnected. In addition to the case where no resonance signal appears as shown in FIG. 5C, the resonance signal is weaker than that shown in FIG. When the alignment of the rotating part 40 and the fixed part 50 is poor, for example, the case where the alignment of the coil 41 and the coil 51 is misaligned or the time between them is too wide is considered as the cause of the abnormality.

  Further, the processing control circuit 66 feedback-controls the gain (amplification factor) of the variable gain amplifier 64 so that the spectrum intensity of the frequency component to be detected is constant. When the spectrum intensity of the frequency component to be detected becomes constant, the gain is maintained.

  When the above process is completed, the measurement / setting operation is completed, and the process returns to the state where the normal AE signal detection and analysis process is performed.

  FIG. 6 is a flowchart showing the measurement / setting operation.

  In step 101, a measurement pulse is output from the transmission circuit 61.

  In step 102, the reception circuit 62 receives the resonance signal (AE signal) generated by the AE converter 31 in accordance with the measurement pulse.

  In step 103, the processing control unit 66 performs spectrum analysis based on the digital data of the AE signal.

  In step 104, the process control unit 66 extracts a target resonance spectrum from the result of spectrum analysis.

  In step 105, it is determined whether or not the intensity of the target resonance spectrum is larger than a predetermined threshold value.

  In step 106, the occurrence of abnormality is notified.

  In step 107, the gain correction value of the variable gain amplifier 64 is calculated.

  In step 108, the calculated gain correction value is set in the variable gain amplifier 64 to perform gain control.

  The measurement / setting operation is preferably performed by inputting an external command when the device or system to which the AE sensor is attached is started. As a result, even when there is a change in sensitivity due to temperature fluctuation or the like, the sensitivity becomes constant and the occurrence of abnormality can be detected. In addition, it is desirable that the measurement / setting operation is performed at any time after the apparatus or system is started, and that a constant sensitivity is always maintained to monitor whether any abnormality has occurred.

  FIG. 7 shows a non-contact AE sensor according to the present embodiment, in which the distance between the rotating unit 40 and the fixed unit 50 is changed to 1.0 mm, 2.0 mm, and 3.0 mm when very close to each other. The horizontal axis is frequency and the vertical axis is power. For example, when attention is paid to the frequency of 195 kHz, it can be seen that the power sequentially changes in accordance with the change in distance.

  FIG. 8 is a diagram illustrating the relationship between the distance between the rotating unit 40 and the fixed unit 50 and the power at a frequency of 195 kHz. As shown in FIG. 8, the power monotonously decreases as the distance increases. If it is determined in advance that the measurement can be performed if the distance is within the predetermined value and attention is paid to the power corresponding to the frequency in the vicinity of 195 kHz, it can be determined whether the distance is within the usable range. If the gain is within the range, the AE signal can be processed with an appropriate resolution by correcting the gain of the amplifier so that the AE signal having a predetermined amplitude is input to the ADC. If the power becomes smaller than the threshold value, it is considered that the distance between the rotating unit 40 and the fixed unit 50 is increased for some reason or other failure has occurred. Notification is made so that the user can take measures against the failure.

  In the graph of FIG. 7, there are other frequencies where the power changes monotonously with respect to the distance between the rotating unit 40 and the fixed unit 50, such as a frequency of 195 kHz. For example, the frequency of 140.02 kHz in FIG. As shown in FIG. 9, since the voltage (power) of the AE signal monotonously decreases with respect to the distance between the rotating unit 40 and the fixed unit 50, it is possible to set such a frequency as the target frequency. .

  As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that various modifications are possible. For example, in the above embodiment, the gain adjustment of the variable gain amplifier 64 is performed when the intensity of the target resonance spectrum is larger than a predetermined threshold. However, only the gain adjustment is performed without performing the threshold comparison. Good. Alternatively, only threshold comparison may be performed and gain adjustment may not be performed. In this case, the amplifier does not have to be a variable gain amplifier.

  The present invention is applicable to any non-contact type AE sensor that does not have an active element in the rotating part.

FIG. 1 is a diagram illustrating a configuration example of a machining system in which an AE sensor is used. It is a figure which shows the circuit structure of an AE sensor. It is a figure which shows the basic composition of the non-contact type AE sensor which does not have an active element in a rotation part. It is a figure which shows the structure of the non-contact-type AE sensor of embodiment of this invention. It is a figure which shows the example of a measurement pulse, a resonance signal, and an abnormal signal. It is a flowchart which shows the measurement and setting operation | movement in the non-contact AE sensor of embodiment. It is a figure which shows the power spectrum at the time of changing the distance between the rotation part 40 and the fixing | fixed part 50 with the non-contact-type AE sensor of this embodiment. It is a figure which shows the relationship between the distance between the rotation part 40 in the frequency of 195 kHz, and the fixed part 50, and the change of power. It is a figure which shows the relationship between the distance between the rotation part 40 and the fixing | fixed part 50, and the change of power in frequency 140.02kHz.

Explanation of symbols

31 AE converter 40 Rotating part 41 First inductance element (coil)
50 Fixed portion 51 Second inductance element (coil)
61 Transmission Circuit 62 Reception Circuit 63 Filter 64 Variable Gain Amplifier 65 AD Converter (ADC)
66 Processing control circuit (processor)

Claims (4)

A rotating unit that is provided on the rotating shaft of the rotating body and includes an AE converter and a first inductance element;
A second inductance element provided opposite to the rotating part and electromagnetically coupled to the first inductance element of the rotating part; a transmission circuit for applying a pulse signal to the second inductance element; and a second inductance element A non-contact AE sensor for detecting an AE wave of the rotating body with a fixed part, comprising: a receiving part that detects an electric signal;
The fixing part is
A variable gain amplifier that amplifies the electrical signal detected by the receiving circuit and has a variable amplification factor;
An AD converter for converting the output of the variable gain amplifier into a digital signal;
Performing a spectrum analysis of the digital signal output from the AD converter, and calculating a spectrum intensity of a frequency component to be detected;
The transmission circuit is controlled to output a measurement pulse in accordance with an adjustment command from the outside, and the spectrum intensity of the frequency component to be detected is constant based on the spectrum analysis result of the resonance signal responding to the measurement pulse. A non-contact AE sensor comprising: a gain control unit that controls an amplification factor of the variable gain amplifier. The fixing part is
A filter that removes a noise component from the electrical signal detected by the receiving circuit;
The non-contact AE sensor according to claim 1, wherein the variable gain amplifier amplifies the output of the filter.   3. The non-contact AE sensor according to claim 2, wherein the gain control unit notifies the occurrence of an abnormality when the spectrum intensity of the frequency component to be detected is smaller than a threshold in the spectrum analysis result of the resonance signal responding to the measurement pulse. . A rotating unit that is provided on the rotating shaft of the rotating body and includes an AE converter and a first inductance element;
A second inductance element provided opposite to the rotating part and electromagnetically coupled to the first inductance element of the rotating part; a transmission circuit for applying a pulse signal to the second inductance element; and a second inductance element A receiving circuit for detecting an electrical signal, and a fixed part having
A non-contact AE sensor that detects an AE wave of the rotating body with a fixed part;
The fixing part is
An amplifier for amplifying the electrical signal detected by the receiving circuit;
An AD converter for converting the output of the amplifier into a digital signal;
Performing a spectrum analysis of the digital signal output from the AD converter, and calculating a spectrum intensity of a predetermined frequency;
A control unit for controlling the transmission circuit to output a measurement pulse, and outputting a signal for notifying the occurrence of an abnormality when the spectrum intensity is smaller than a threshold in a spectrum analysis result of a resonance signal responding to the measurement pulse; A non-contact AE sensor comprising:

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