CN105988093A - Magnetic property evaluation method and magnetic property evaluation apparatus - Google Patents
Magnetic property evaluation method and magnetic property evaluation apparatus Download PDFInfo
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- CN105988093A CN105988093A CN201610170128.1A CN201610170128A CN105988093A CN 105988093 A CN105988093 A CN 105988093A CN 201610170128 A CN201610170128 A CN 201610170128A CN 105988093 A CN105988093 A CN 105988093A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The present invention relates to a magnetic property evaluation method and a magnetic property evaluation apparatus. The magnetic property evaluation method comprises: an evaluation sample measuring process for performing electromagnetic induction measurement on an evaluation sample formed by an unmagnetized magnet material, wherein an alternating magnetic field is applied to the sample, and an induced current is generated in the sample and detected by synchronous detection so as to obtain a synchronous detection signal; a standard sample measuring process for performing the electromagnetic induction measurement on a plurality of unmagnetized standard samples formed in a substantially same mode with the evaluation sample; a magnetic property value measuring process for magnetizing the plurality of standard samples and measuring magnetic properties of the plurality of standard samples; a corresponding process for estimating relationships between synchronous detection signals of the plurality of standard samples and magnetic property values of the plurality of standard samples; and an evaluating process for estimating, based on the estimated relationships, a magnetic property value of the evaluation sample according to the synchronous detection signal of the evaluation sample.
Description
Technical field
The present invention relates to magnetic characteristic evaluation method and magnetic characteristic valuator device.In more detail, the present invention relates to evaluate as follows
Method and the equipment using the method: in the state of magnet material to be magnetized also is not magnetized, to this magnet material
Magnetic characteristic evaluate.
Background technology
The magnet with excellent magnetic properties such as high residual magnetic flux densities, typically for example rare-earth magnet etc. are developed
(for example, patent document 1).Such magnet is owing to having higher magnetic characteristic, so being generally inconvenient at magnetized state
Lower transport.Therefore, manufacturer will be generally at the magnet of magnetic virgin state and transports (shipment) from such as factory and go out, then by buying
Magnet is magnetized by family, user etc. after a purchase.Generally, even if using identical material to manufacture magnet with identical method
Material, the magnetic characteristic after each magnet material is magnetized also can be inevitably present difference.As a result, manufacturer needs from having not
With potential magnetic characteristic unmagnetized magnet product in select each after magnetization magnetic characteristic can reach the magnet of predetermined grade
Product.
Up to now, owing to typically requiring the post-evaluation magnetic characteristic in magnetization, even if so will be at magnet material not by magnetic
Transporting magnet material in the state of change, magnet material also to be magnetized by manufacturer.For example, patent document 2 discloses one
Use the method to measure the distribution of the magnetic flux density of each magnetized ferrimagnet for the device with Hall element array.
So, the magnet material that will transport at magnetic virgin state is being carried out magnetizing and entering the magnetic characteristic of magnet material
In the case that row is evaluated, generally a part of product is sampled, then carry out magnetizing and carry out magnet characteristics inspection.Major part
It is transported away in the case of without the evaluation of magnetic characteristic after not accepting to magnetization of the product of sample examination.
Patent document 1:JP-A-H11-329810
Patent document 2:JP-A-2013-245958
Content of the invention
The magnet material to be transported being in magnetic virgin state is implemented magnetization and is examined by sampling as described above
Look into carry out magnetic characteristic evaluate in the case of, even if the magnet material carrying out sample examination has predetermined magnetic after being confirmed to be magnetization
Characteristic, after remaining magnet material (for example actual magnet material transporting) not carrying out sample examination is likely to not show magnetization
Predetermined magnetic characteristic.As a result, manufacturer is difficult to select and transport be in magnetic virgin state and can stably show after magnetization
Go out the magnet material of excellent magnetic characteristic.
Therefore, it can consider that all over products that will transport carries out magnetizing then to evaluate the magnetic characteristic of all over products
And from all over products, select the method for excellent product, to replace sample examination.In this case, after inspection, selected
The product going out is demagnetized and is transported.But, all experience magnetization due to all over products, check and demagnetize each process, then selected
Transporting to selecting property, therefore the time length needed for the method, the amount of labour are big and with high costs, so being unpractiaca.
Accordingly, it is considered to situation mentioned above, present invention aim at offer can be simply to being subjected to magnetization
The magnetic characteristic evaluation method evaluated of the magnetic characteristic of magnet material and magnetic characteristic valuator device.
In order to reach above-mentioned target, the main idea of the magnetic characteristic evaluation method according to the present invention includes:
Evaluating sample measurement process, it performs electromagnetic induction to the evaluation sample being formed by unmagnetized magnet material and surveys
Amount, in the measurement of described electromagnetic induction, by being applied on sample alternating magnetic field (AC magnetic field) in this examination
Sample produces induced-current and by synchronization detect (synchronous detection) carry out to this induced-current detecting from
And obtain synchronous detection signal；
Process measured by standard specimen, and it performs electromagnetic induction measurement, the plurality of mark to multiple unmagnetized standard specimens
Quasi-sample is all formed in the way of roughly the same with evaluating sample；
Magnetic characteristic value measures process, and it carries out magnetizing and measuring the magnetic characteristic value of multiple standard specimen to multiple standard specimens；
Corresponding process, it is to the synchronization detection letter with regard to multiple standard specimens obtained in standard specimen measurement process
Number and the magnetic characteristic value with regard to multiple standard specimens obtained in magnetic characteristic value measurement process between relation estimate
(estimating)；And
Evaluation procedure, it, based on the relation estimating in corresponding process, obtains according to during evaluating sample measurement
With regard to evaluate sample synchronous detection signal estimate evaluate sample magnetic characteristic value.
The detection being carried out induced-current by synchronization detection can be utilized to the conduct detection line being produced by induced-current
The magnetic flux of the electromotive force of circle (or following coil: this coil also acts as the magnet exciting coil producing alternating magnetic field) measure and
It is easily implemented with.
Preferably, magnetic characteristic value is magnetic flux.
Preferably, described alternating magnetic field is flow through magnet exciting coil by making alternating current (AC current) and produces；
Described induced-current is as benchmark by the described alternating current to flow through described magnet exciting coil, produces to because of electromagnetic induction
And the electric current flowing through detection coil carries out described synchronization detection and detects, described detection coil also serves as described magnet exciting coil
Or described detection coil arrange independently relative to described magnet exciting coil；Further, by the letter detected by described synchronization detection
Number value of real part in described corresponding process and described evaluation procedure, both function as described synchronous detection signal.
Preferably, in described corresponding process, by the synchronization detection letter corresponding with the magnetic characteristic value in predetermined scope
Number range set be excellent product scope；And in described evaluation procedure, if the synchronous detection signal evaluating sample exists
Within the scope of described excellent product, then described evaluation sample is evaluated as excellent product.
Magnet material is preferably the magnet material of heat distortion magnet.
The main idea of the magnetic characteristic valuator device according to the present invention includes: magnetic field generation unit, its produce alternating magnetic field and
It is applied to alternating magnetic field on sample, and induced-current detector unit, it is detected in described sample by synchronizing detection
The induced-current producing, and magnetic characteristic valuator device is performed magnetic characteristic evaluation method as described above.
In the magnetic characteristic evaluation method according to the present invention, only each standard specimen not being magnetic characteristic evaluation objective is entered
Row magnetization, and standard specimen magnetic characteristic after magnetization is measured.In contrast, not to the evaluation mesh as magnetic characteristic
Target is evaluated sample and is carried out magnetizing and only carrying out electromagnetic induction measurement to the evaluation sample being in magnetic virgin state.Then, based on
Use the magnetic characteristic after the magnetization that obtained of standard specimen and electromagnetic induction survey is carried out to the standard specimen being in magnetic virgin state
Measure the relation between obtained synchronous detection signal, estimate to evaluate from the synchronous detection signal obtained in evaluation sample
Sample magnetic characteristic after magnetization.Formed in this way it is possible to easily estimate by the magnet material under magnetic virgin state
Evaluate sample magnetic characteristic after magnetization, and without implementing magnetization or implementing demagnetization after a measurement before evaluation.Furthermore, it is possible to
All carry out evaluating to all over products to transport from factory etc. and be not necessarily to take a long time and very high cost.Therefore, with enforcement
The situation of sample examination is different, even if manufacturing condition etc. there are differences, it is also possible to high accuracy select for example for transport
Show the excellent product of predetermined magnetic characteristic after magnetization.
In the case that magnetic characteristic value is magnetic flux, magnetic characteristic value is better with the correlation of synchronous detection signal, more energy
Enough accurately the magnetic characteristic evaluating sample is evaluated.
In the case that described alternating magnetic field is to be produced by making alternating current flow through magnet exciting coil, by flow through
State the described alternating current of magnet exciting coil as benchmark, to producing because of described electromagnetic induction and flow through the electric current of detection coil
Row synchronization detection detects induced-current, and described detection coil also serves as described magnet exciting coil or only relative to described magnet exciting coil
On the spot arrange；Further, and described evaluated in described corresponding process by the value of real part of the detected signal of described synchronization detection
Both functioning as described synchronous detection signal in journey, described synchronization detection can be more easily detected the induced-current flowing through sample.
Value of real part owing to being obtained by this way compared with the imaginary values and absolute value with signal has more preferable phase with magnetic characteristic value
Guan Xing, therefore uses value of real part can evaluate the magnetic characteristic value evaluating sample more accurately as index.
In corresponding process, will be excellent with the corresponding range set of synchronous detection signal in predetermined magnetic characteristic value scope
Good product scope；And in evaluation procedure, if the synchronous detection signal of evaluation sample is within the scope of excellent product,
Evaluation sample is evaluated as excellent product, in these cases, can be for example more easily from the magnet material as multiple samples
Material is selected and is transported the excellent product of magnetic characteristic value within the scope of being respectively provided with predetermined.
In the case of the magnet material that magnet material is heat distortion magnet, form homogeneous magnet material easily by heat treatment
Material.Therefore, the more preferable correlation between magnetic characteristic and synchronous detection signal can be obtained in electromagnetic induction measurement.As a result,
More accurately the magnetic characteristic evaluating sample can be estimated.
In the case of using the magnetic characteristic valuator device according to the present invention, apply the magnetic characteristic evaluation method being constructed such that
Can easily estimate the magnetic characteristic of the magnet material being in magnetic virgin state.
Brief description
Fig. 1 is provided in showing of the electromagnetic induction measurement apparatus in magnetic characteristic valuator device according to an embodiment of the invention
Meaning property sectional view.(a) in Fig. 1 electromagnetic induction shown partially measurement apparatus is along the cross section of the axis direction checking coil, in Fig. 1
(b) electromagnetic induction shown partially measurement apparatus along the cross section with the vertical direction of axis checking coil.
Fig. 2 is the block diagram illustrating the signal processing in electromagnetic induction measurement apparatus.
Fig. 3 is the sectional view of the detailed configuration illustrating electromagnetic induction measurement apparatus along the axis direction checking coil.
Fig. 4 is the schematic sectional view of another example of electromagnetic induction measurement apparatus.(a) in Fig. 4 electromagnetism shown partially
Induction measurement devices along the cross section of axis direction checking coil, the electromagnetic induction shown partially measurement apparatus of (b) in Fig. 4 along with
Check the cross section in the vertical direction of axis of coil.
Fig. 5 is the relation between the magnetic flux after illustrating the value of real part of synchronous detection signal and magnetizing master sample
The schematic diagram of example.
Detailed description of the invention
Hereinafter, with reference to the accompanying drawings magnetic characteristic evaluation method according to an embodiment of the invention and magnetic characteristic evaluation are set
Standby illustrate.
(magnetic characteristic valuator device)
Magnetic characteristic valuator device includes electromagnetic induction measurement apparatus 1 according to an embodiment of the invention, and electromagnetic induction is measured
The sample S being in magnetic virgin state is implemented electromagnetic induction measurement by device 1.Fig. 1 and Fig. 2 diagrammatically illustrates according to the present invention's
The construction of the electromagnetic induction measurement apparatus 1 of embodiment.
As it is shown in figure 1, the electromagnetic induction measurement dress in being arranged on magnetic characteristic valuator device according to an embodiment of the invention
Put 1 to include checking coil 10, check that coil 10 is the assembly being made up of magnet exciting coil 11 and detection coil 12.Magnet exciting coil 11 by
The substantially cylindric coil with hollow space is constituted, and substantially cylindric sample S may be inserted into and be arranged in this hollow bulb
In Fen.Magnet exciting coil 11 is used as magnetic field generation unit.Detection coil 12 is to be arranged in coaxial fashion inside magnet exciting coil 11
Substantially cylindric coil, and be used as induced-current detector unit.This detection coil 12 He including being coaxially disposed
Magnet exciting coil 11 and be also used as eddy current inspection based on the detection device (electromagnetic induction measurement apparatus 1) of electromagnetic induction principle
Device.Therefore, conventional eddy-current crack detector can be converted and be made electromagnetic induction measurement apparatus 1.
As in figure 2 it is shown, in electromagnetic induction measurement apparatus 1, oscillator 21 supplies alternating current to magnet exciting coil 11.So
After, the electric current flowing through detection coil 12 is exaggerated device 22 and amplifies, and as detection electric current input sync detection circuit 23.Carry out self-vibration
Swing the output signal of device 21 and from the output signal of 90 ° of phase shifters 24 as two contrast signals input sync detection circuits 23
In, wherein, the output signal carrying out self-oscillator 21 is phase-shifted 90 ° in 90 ° of phase shifters 24.
Based on the alternating current flowing through magnet exciting coil 11, sync detection circuit 23 is to carrying out Autonomous test coil 12 and via amplification
The detection electric current that device 22 inputs sync detection circuit 23 implements synchronization detection (phase-detection).Specifically, detection electric current is made
Waveform is multiplied with the current waveform of both of the aforesaid contrast signal respectively, thus detection electric current is divided into real part and imaginary part, i.e. with
In the identical current component (impedance component) of the alternating current phase place of excitation and the phase place phase with the alternating current for excitation
Differ from the current component (reactive component) of 90 °, and real part and the imaginary part of detection electric current are detected as synchronous detection signal.
Furthermore, it is possible to calculate absolute value (amplitude) and the phase difference of detection signal according to value of real part and imaginary values.Incidentally, amplify
Device the 22nd, sync detection circuit 23 and phase shifter 24 can be configured to lock-in amplifier etc. integratedly.
The sample S being carried out electromagnetic induction measurement by electromagnetic induction measurement apparatus 1 includes that the evaluation that will be described later tries
Sample and standard specimen, and these samples are all formed by unmagnetized magnet material.When alternating current is arranged in excitation at sample S
When flowing through magnet exciting coil 11 in the state of in coil 11, the hollow space of magnet exciting coil 11 produces alternating magnetic field.Then, alternation
Magnetic field is applied on sample S, thus produces induced-current (vortex flow) on the surface of sample S.Additionally, induced-current forms sensing
Magnetic field, and owing to this induced field makes the flowing in detection coil 12 of another induced-current.Flowing in detection coil 12
Induced-current as detection electric current sync detection circuit 23 is synchronized detection.
Fig. 3 is the schematic diagram of the specific configuration being shown in the electromagnetic induction measurement apparatus 1 being above briefly described.At figure
In electromagnetic induction measurement apparatus 1 shown in 3, check that coil 10 is fixed on the top of the support member 17 being erected on support 16.?
It on support 16, is also provided with, in the way of coaxial with inspection coil 10, the positioning fixture being formed by insulating materials such as resins
13.Positioning fixture 13 includes the generally cylindrical insertion portion 13a being positioned at its top ends office.The external diameter of insertion portion 13a
Cylindric internal diameter than sample S is slightly smaller.Additionally, positioning fixture 13 includes the retaining portion being positioned at the base end side of insertion portion 13a
13b, the internal diameter more than sample S for the external diameter of retaining portion 13b.When sample S is arranged in the axial centre checking coil 10, keep
The tip portion (boundary member between insertion portion 13a and retaining portion 13b) of part 13b and the position of the lower end of sample S
Substantially concordant.
On support 16, the lifting unit 15 of cylinder etc. is fixed on the outside of positioning fixture 13.Magnet releases fixture
14 are connected to lifting unit 15 so that magnet is released fixture 14 and risen under the effect of lifting unit 15 and fall (along inspection
On the direction of the axis of coil 10).Magnet is released fixture 14 and is formed as cylindrical shape, and its internal diameter is than the holding of positioning fixture 13
The external diameter of part 13b is slightly larger.In the state of magnet release fixture 14 is fallen by lifting unit 15, magnet releases the top of fixture 14
End part is substantially concordant with the position of the tip portion of retaining portion 13b of positioning fixture 13.Fig. 3 illustrates that magnet releases fixture 14
Above-mentioned fall state.
In above-mentioned construction, as it is shown on figure 3, so that the tip portion of insertion portion 13a to be injected the cylindrical portion of sample S
Mode sample S is installed on positioning fixture 13, then by lifting unit 15 by magnet release fixture 14 fall.In this state
Under, in the hollow space checking coil 10, the top end surface of retaining portion 13b of positioning fixture 13 and magnet release fixture
Sample S is stablely supported at the axially vertical side axially and with inspection coil 10 checking coil 10 by the top end surface of 14
Middle position upwards.It is therefoie, for example, sample during the position difference of sample S and measurement during owing to can make to measure every time
The impact that position temporarily changes reduces, it is possible to implement electromagnetic induction measurement accurately and reproducibly.On the other hand,
In the state of magnet release fixture 14 is risen by lifting unit 15, sample S is from the hollow space removal checking coil 10 cloth
Put and checking above coil 10.As such, it is possible to easily perform installation and the replacing of sample S in electromagnetic induction measurement apparatus 1.
Due to sample S installation and replacing also can be automation, it is possible to easily, automatically successively to batch production each
Magnet material carries out electromagnetic induction measurement.
As described above, electromagnetic induction measurement apparatus 1 applies alternating magnetic field and detects because of alternating magnetic field in examination to sample S
The induced-current producing in sample S.Therefore, the measuring unit of known eddy-current crack detector can be converted and be made electromagnetic induction measurement dress
Put.The electromagnetic induction measurement apparatus of the present invention is not limited to the device with the construction roughly the same with electromagnetic induction measurement apparatus 1,
And can be any device, as long as this device is configured to produce alternating magnetic field and implements to produce in sample S to because of AC magnetic field
Raw faradic synchronization detects.
For example, in electromagnetic induction measurement apparatus 1, substantially cylindric sample S is inserted the hollow bulb checking coil 10
Divide and implement measurement, checking that coil 10 is made up of substantially cylindric magnet exciting coil 11 and substantially cylindric detection coil 12.
But, in the case that sample S is plate-shaped, check coil 10 it is so structured that have flat and substantially rectangular tubular form,
Thus sample S may be inserted in inspection coil 10.As such, it is possible to can highly homogeneously apply magnetic field on whole sample S
And the mode detecting, at random select the next shape with sample S of shape of the inspection coil 10 inserting for sample S
Join.The coil checking in coil 10 that electromagnetic induction measurement apparatus is not limited to insert sample and be arranged in hollow shape inserts
Type, but also it is so structured that sonde-type electromagnetic induction measurement apparatus 1 ' as shown in Figure 4.That is, electromagnetic induction measurement apparatus
It is so structured that: by include check coil 10 detection probe 10 ' be arranged in sample S surface subregion and not with examination
Sample S contact, and implement electromagnetic induction measurement to this region.Incidentally, from the point of view of eliminating measure error, preferably
It is: in any coil insert type and sonde-type electromagnetic induction measurement apparatus all to implement to survey near the middle body of sample S
Amount, and avoid the end of sample S.
Moreover, it is not necessary to be always provided as independent as in electromagnetic induction measurement apparatus 1 in checking coil 10
The detection coil 12 of unit and magnet exciting coil 11, and single coil can be used as magnet exciting coil 11 double detection coil 12 and implement
Excitation and detection.In such a case, it is possible to by synchronization detection to produce flow through line because of the electromagnetic induction in sample S
Modulation product in the alternating current of circle detects.Specifically, it may be preferred to ground will use the type of this single coil
Electromagnetic induction measurement apparatus be used as sonde-type electromagnetic induction measurement apparatus 1 '.
(magnetic characteristic evaluation method)
It follows that magnetic characteristic evaluation method according to an embodiment of the invention is illustrated.Present inventor sends out
Show after carrying out the obtained synchronous detection signal of electromagnetic induction measurement to the magnet material being in magnetic virgin state and magnetizing
Good correlation between the magnetic characteristic value of magnet material.Then, inventor has developed following magnetic characteristic evaluation method: right
Be in magnetic virgin state magnet material implement electromagnetic induction measurement, thus do not need actual enforcement magnetized in the case of to magnetic
The magnetic characteristic value of the magnet material after change is evaluated.
This evaluation method utilizes and includes that the magnetic characteristic valuator device of electromagnetic induction measurement apparatus performs, and electromagnetic induction is measured
The magnet material being in magnetic virgin state can be implemented electromagnetic induction measurement by synchronization detection by device.Hereinafter, will
Include that the magnetic characteristic valuator device of above-mentioned electromagnetic induction measurement apparatus 1 evaluates the to be magnetized magnetic flux evaluating sample to using
The situation of amount (magnetic flux) illustrates.
In this evaluation method, when carrying out electromagnetic induction measurement to sample S, except commenting as magnetic characteristic evaluation objective
Outside valency sample, use multiple standard specimen as the object of reference evaluating the magnetic characteristic evaluating sample.Evaluate sample and mark
Quasi-sample is the magnet material that can be become permanent magnet by magnetization.Standard specimen is with the side roughly the same with evaluating sample
The magnet material that formula is formed.That is, within foozle scope, multiple standard specimens are all by the composition identical with evaluating sample
Composition the magnet material manufacturing with the manufacture method identical with evaluating sample.Preparation is in the evaluation sample of magnetic virgin state
And standard specimen, then carry out electromagnetic induction measurement.As mentioned below, owing to the magnetic characteristic of the magnet material after magnetization is at magnet
Change within the foozle scope of material, so for improving and evaluating accuracy, multiple standard specimens are preferably chosen to
The magnetic characteristic making each standard specimen after magnetization is distributed in scope wide as far as possible.
In this evaluation method, perform (1) and evaluate sample measurement process, (2) standard specimen measurement process, (3) magnetic characteristic
Value measurement process, (4) corresponding process and (5) evaluation procedure.These processes in turn will be illustrated.
(1) sample measurement process is evaluated
First, preparation is in the evaluation sample as magnetic characteristic evaluation object of magnetic virgin state, such as will be as product
The magnet material etc. transporting.Then, electromagnetic induction measurement apparatus 1 is used and based on synchronization detection to the evaluation examination as sample S
Sample carries out electromagnetic induction measurement.Result, it is thus achieved that from value of real part and the imaginary values of the detection electric current of detection coil 12 output.This
In the case of, store value of real part.
(2) master sample measurement process
It follows that under the measuring condition identical with process (1), use electromagnetic induction measurement apparatus 1 unmagnetized to being in
Multiple standard specimens respectively as sample S of state all carry out electromagnetic induction measurement.Then, storage obtained with regard to each
The value of real part of the detection electric current of standard specimen.Thus, owing to electromagnetic induction measurement apparatus 1 includes determining as shown in Figure 3
Position fixture 13, it is possible to prevent from evaluating the change of the measuring condition between sample and standard specimen and each standard specimen it
Between the change of measuring condition.
(3) magnetic characteristic value measurement process
It follows that during the measurement of magnetic characteristic value, at identical conditions multiple standard specimens are magnetized respectively.
Magnetization condition is set as and carries out magnetized supposition matching criteria when manufacturing actual magnet product to evaluation sample.Permissible
It is appropriately carried out magnetization by using magnetostatic field, pulsed magnetic field etc..
It follows that measure and store as each of magnetic characteristic value by the magnetic flux of so magnetized standard specimen.Permissible
Use the known measurement apparatus such as fluxmeter to measure magnetic flux.In this case, for improving and evaluating accuracy,
Preferably: confirm the Distribution value of each magnetic flux that obtained using required in the case of magnetized as the evaluation sample of product
Magnetic flux within the scope of and outside.
(4) corresponding process
It follows that in corresponding process, estimate to be obtained by electromagnetic induction measurement during the measurement of (2) standard specimen
The value of real part with regard to standard specimen with obtained in (3) magnetic characteristic value measurement process the magnetic flux with regard to standard specimen it
Between relation.Specifically, rise corresponding respectively to the value of real part being obtained by the measurement to standard specimen and the value of magnetic flux
Coming, thus estimating the corresponding relation between value of real part and the value of magnetic flux, the instruction of this corresponding relation is to being in magnetic virgin state
Standard specimen electromagnetic induction measurement in obtain this standard specimen expected magnetic flux after magnetization during a certain value of real part.
Fig. 5 is shown in each value of real part obtained in the electromagnetic induction measurement of the multiple standard specimens being in magnetic virgin state
And the relation between each magnetic flux of being obtained after the magnetization of the plurality of standard specimen, the plurality of standard specimen all by subjected to specially
The Nd-Fe-B magnet material of the heat treatment that the heat treatment disclosed in profit document 1 is similar to is formed.The unit of magnetic flux is mWb
T, T represent the number of turns of the search coil of the fluxmeter for magnetic flux measurement.According to Fig. 5, obtained in electromagnetic induction measurement
Value of real part bigger, the value of magnetic flux is less.It is understood that be in magnetic virgin state electromagnetic induction measure in institute
There is strong linear dependence between the value of the magnetic flux after the value of real part obtaining and magnetization.It means that can be based on being in
The value of real part as index obtained in the electromagnetic induction measurement of magnetic virgin state is estimated and estimates the magnetic flux after magnetizing.
So, in (4) corresponding process, obtained during the electromagnetic induction using synchronization detection is measured under magnetic virgin state
The relation between each magnetic flux after the value of real part obtaining and magnetization is estimated.With regard to being positioned at the electromagnetism to multiple standard specimens
The value of real part in the region between measurement point obtained in measurement of inductance, can be inserted by being appropriately carried out linear interpolation etc.
Value processes the value calculating the magnetic flux corresponding to this value of real part.Alternatively, as shown in solid lines in fig. 5, can be by song
Line matching calculates the corresponding expression formula between value of real part and the value of magnetic flux.In Figure 5, although by first-order expression be used as right
Answer expression formula but it also may use any expression formula according to the distribution of measurement point.
Additionally, based on the relation between the value of real part obtaining in the above described manner and magnetic flux, preferably will be with predetermined magnetic flux
The scope of the corresponding value of real part of weight range is redefined for excellent product scope, and this determined magnetic flux range is to will transport
That send etc. evaluates scope required when sample magnetizes as product.In Figure 5, so set excellent product scope by
Article two, the Range Representation between dotted line.Incidentally, said process (2), (3) and (4) preferably performs successively, but process (1)
Can perform in the random time before process (5).
(5) evaluation procedure
Finally, it in evaluation procedure, is being in the electromagnetism of magnetic virgin state based on estimated in (4) corresponding process
Relation between the value of the value of real part obtained in measurement of inductance and the magnetic flux after magnetization, evaluates sample measurement according in (1)
During to be in magnetic virgin state evaluation sample electromagnetic induction measurement obtained in value of real part estimate evaluate sample
Expected magnetic flux after magnetization.Specifically, in order to judge whether the value evaluating sample magnetic flux after magnetization is making a reservation for
Allowed band within, to obtained in (1) sample evaluation measurement process evaluation sample value of real part whether based on (4)
Relation between the value of real part obtaining in corresponding process and the value of magnetic flux and judge within the excellent product scope that sets.
In the case that the value of real part evaluating sample is within excellent product scope, may be made that evaluation sample is sentencing of excellent product
Fixed, this excellent product is estimated that there is a strong possibility and is obtained the magnetic flux within predetermined allowed band after magnetization.On the contrary,
Evaluate the value of real part of sample in the case of be in outside excellent product scope, may be made that evaluation sample is sentencing of bad product
Fixed, this bad product estimates that there is a strong possibility can not obtain the magnetic flux within predetermined allowed band after magnetization.Additionally,
In addition to evaluation sample being differentiated between excellent product and bad product, need also exist for evaluation examination to be magnetized
The situation that the numerical value of the magnetic flux of sample is predicted.In this case, will evaluate obtained in sample measurement process in (1)
The relation that the value of real part of evaluation sample is updated between value of real part and the value of magnetic flux is (such as by shown in solid one in Fig. 5
Rank expression formula etc.) in, thus calculate the value evaluating sample expected magnetic flux after magnetization.
In the magnetic characteristic evaluation method including each process above-mentioned, it is only necessary to real to the evaluation sample being in magnetic virgin state
Execute the expected magnetic flux after magnetization is estimated in electromagnetic induction measurement, and without this evaluation sample is magnetized.As it is shown in figure 5,
Between the value of the magnetic flux after the result of the electromagnetic induction measurement obtained by using synchronization to detect under magnetic virgin state and magnetization
Strong correlation ensure that the reliability of this estimation.
The magnets exhibit being obtained by carrying out magnetizing to magnet material goes out the possibility of desired performance to a great extent
On depend on magnetization after the magnetic characteristic such as magnetic flux that produces in magnet whether within the scope of predetermined.But, institute
It is inevitably present uncontrollable difference (size difference of crystal grain in for example organizing) among each magnet material manufacturing.Magnetic
The magnetic characteristics such as the magnetic flux after inevitable difference may result in magnetization in each magnet material before change huge
Difference.Judge that the most straightforward approach whether magnet material that each is to be transported can show desired performance is by each magnet
Material carries out magnetizing and measuring the magnetic characteristic of each magnet material.But, for example, under each magnet material is at magnetic virgin state
In the case of being transported, if implementing to check after once magnetizing each magnet material, implement after magnetization to check then
The process of implementing demagnetization takes long enough and very high cost.Therefore, actually this method is difficult to put into practice.Normally,
In the case of only implementing sampling, magnetization to a part for whole magnet materials and check, can save and check required cost
And the time.But, in which case it is difficult to for the inevitable difference of whole magnet materials detection magnetic characteristic.On the contrary
Ground, in the evaluation method according to the present invention, can without to evaluate sample carry out magnetized in the case of, to magnetic to be subjected to
The expected magnetic characteristic of the evaluation sample changed is estimated.Therefore, it can implement to check to whole samples of evaluating, and easily high
The excellent evaluation being expected to excellent magnetic property within the scope of reaching predetermined is selected on accuracy ground from whole evaluation samples
Sample, and without spending cost and time to carry out magnetizing and demagnetizing.Specifically, if as it is shown on figure 3, using and be suitable to automation
Electromagnetic induction measurement apparatus 1 automatically change to evaluating sample and automatically measure, then can be effectively realized to wanting
The inspection of whole magnet materials of batch production.
The microstructure being in the magnet material of magnetic virgin state and the difference (difference of such as crystallite dimension) of composition
The magnetic characteristic of the magnet material that can be obtained after largely affecting magnetization, but it in the case of the overwhelming majority, is in non-magnetic to measurement
The various physical properties that each magnet material of change state is obtained will not produce significant impact.Accordingly, it is difficult to detect non-magnetic
Difference under change state.But, in the evaluation method according to the present invention, come to the surface at magnet material by synchronization detection
The induced-current producing detects, and synchronization detection is very sensitive to the slight change of electric current.Therefore, it can with high-sensitivity detection
To microscopic differences on faradic impact.Specifically, electromagnetic induction measurement apparatus 1 is used can be more precisely detected magnetic
The faradic slight change that the surface of body material produces, electromagnetic induction measurement apparatus 1 can be by utilizing as shown in Figure 3
Electromagnetic induction measurement is implemented on positioning fixture 13 high repeatability ground.
When implementing electromagnetic induction measurement, although being applied on magnet material and this magnetic field by magnet exciting coil 11 by magnetic field
For alternating magnetic field, but the size in this magnetic field be used for implementing compared with magnetized magnetic field being inappreciable.Therefore, sample is evaluated exhausted
Will not measure due to electromagnetic induction and be magnetized.For example, the Nd-Fe-B magnet material being used as example shown in Fig. 5 is generally by about
The magnetic field of 30kOe to 50kOe (about 2500kA/m to 4000kA/m) magnetizes.In contrast, for example, the alternation electricity of 1A is made
Stream flows through a diameter of 50mm, the number of turn be 100 circles magnet exciting coil to implement electromagnetic induction measurement when, estimate be applied on sample
Alternating magnetic field is 2kA/m or less, this alternating magnetic field by applied when magnetization the 1/1000 of magnetic field or less.Carry in passing
And, for obtaining, in synchronization detection measurement, the signal that can detect with enough accuracy, flow through the friendship of magnet exciting coil 11
The frequency setting of time-dependent current is within the scope of such as 100Hz to 10kHz.
In the above description, as it is shown in figure 5, magnetic flux is used as the magnetic characteristic value of evaluation objective, and magnetization is confirmed
After magnetic flux and under magnetic virgin state electromagnetic induction measurement result between there is good correlation.But, as
The replacement of magnetic flux, it is possible to use the various magnetic that magnet material after magnetization is had by the magnetic characteristic evaluation method according to the present invention
Characteristic value is estimated.In this case, during the measurement of (3) magnetic characteristic value, with the mark after the obtained magnetization of measurement
The desired magnetic characteristic value of quasi-sample substitutes magnetic flux, and this measured value is used for follow-up during.Valuable magnetic
The example of characteristic value also includes permeability, magnetic coercive force, residual magnetic flux density etc. in addition to magnetic flux.
In the explanation of above-mentioned electromagnetic induction measurement, based on the conduct in each information including in synchronous detection signal
The value of real part of index, evaluates to the magnetic characteristic after magnetization, and synchronous detection signal is based on the alternation flowing through magnet exciting coil 11
The waveform of electric current detects from the electric current flowing through detection coil 12.But, the information being used as index is not limited to value of real part
(x), but can be by such as imaginary values (y), absolute value ((z=x2+y2)1/2) or the out of Memory such as phase difference (θ) be used as index.
Table 1 below illustrates the square value R of coefficient R2, square value R2It is that the value of magnetic flux is being obtained with by the measurement of single electromagnetic induction
The relation between one in corresponding value of real part x, imaginary values y and the absolute value z that obtain obtains after carrying out linear approximation.Here
The measurement result of the magnetic flux after the result of the electromagnetic induction measurement being used and magnetization is by using and the sample shown in Fig. 5
Different samples and obtain.
[table 1]
| Synchronization detected value | Value of real part x | Imaginary values y | Absolute value z |
| R2 | 0.89 | 0.86 | 0.87 |
According to table 1, it is to be understood that compared to using imaginary values y, in the situation using value of real part x and absolute value z
Under, it is thus achieved that and the good correlation between the magnetic flux after magnetization.Specifically, obtain in the case of using value of real part x
Obtained more preferable correlation.This is because, compared with real part, imaginary part may be affected by the fluctuation of measuring condition, such as phase
Impact etc. for the measurement position checking coil 10.Owing to absolute value includes imaginary, so absolute value is likely to meeting and exists
Affected by measurement position in a way.So, when electricity uses the real part of magnetic induction measurement as index, can be accurately
Estimate to evaluate sample magnetic characteristic after magnetization.
As described above, the magnetic characteristic evaluation method according to the present invention go for any kind of by magnetization become
The magnet material of permanent magnet.In other words, this method go for such as heat distortion magnet magnet material or for
Any magnet material such as the magnet material of sintered magnet.But, in the case of sintered magnet, the surface of magnet material is at sintering
When be easy to occur the changes such as oxidation.The change on this surface causes carrying out electromagnetic induction in use synchronization detection and measures when institute
The signal detecting exists big modulation degree (modulation).Therefore, after by impact magnetization such as the size differences of crystal grain
The signal that the factor of magnetic characteristic is caused may be buried in modulation product, thus is difficult to signal be detected.In contrast, exist
In the case of heat distortion magnet, form homogeneous magnet material easily by heat treatment and magnet material is susceptible to such as oxygen
The surface modifications such as change.Therefore, it is applied to heat distortion magnet rather than sintering magnetic in the magnetic characteristic evaluation method according to the present invention
In the case of body, can with high accuracy evaluate and be subjected to magnetized expected magnetic characteristic.Additionally, the scraping of the surface of magnet material
Also the result that the electromagnetic induction that impact uses synchronization to detect to a great extent such as trace is measured.Therefore, in addition to heat treatment, excellent
Selection of land does not carry out the machining of grinding etc. to magnet material.
As described above, the magnetic characteristic evaluation method according to the present invention can especially preferably be applicable to evaluate thermal deformation magnetic
The situation of the magnet material of body magnetic characteristic after magnetization, the magnet material of heat distortion magnet preferably transports and nothing after inspection
Need to magnetize, after magnetization, very big residual magnetic flux density can be applied on the magnet material of heat distortion magnet.This magnetic characteristic
The example of excellent heat distortion magnet includes the magnet described in patent document 1, specifically, has into and is grouped into R-T-
B (R is rare earth metal, R:28wt.% to 30wt.%, B:0.85wt.% to 1.10wt.%, T: the transition metal of iron group) is (all
As become be grouped into Nd-Fe-B etc.) anisotropic hot extrusion deformation magnet.
Although based on embodiment, the present invention will be described, but the invention is not restricted to the present embodiment, can without departing substantially from
Various modification is made within the scope of idea of the invention.
The Japanese patent application No.2015-058989 that the application submitted to based on March 23rd, 2015, and this Japan is special
The full content of profit application is hereby incorporated herein by.
Reference and the explanation of symbol
1 electromagnetic induction measurement apparatus
10 inspection coils
11 magnet exciting coils
12 detection coils
13 positioning fixtures
14 magnets release fixture
15 lifting units
S sample
Claims (7)
1. a magnetic characteristic evaluation method, comprising:
Evaluating sample measurement process, it performs electromagnetic induction measurement to the evaluation sample being formed by unmagnetized magnet material,
In the measurement of described electromagnetic induction, by alternating magnetic field being applied on sample produce induced-current in described sample and leading to
Cross synchronization detection to detect described induced-current, thus obtain synchronous detection signal；
Process measured by standard specimen, and it performs the measurement of described electromagnetic induction, the plurality of mark to multiple unmagnetized standard specimens
Quasi-sample is all formed in the way of roughly the same with described evaluation sample；
Magnetic characteristic value measures process, and it carries out magnetizing and measuring the magnetic of the plurality of standard specimen to the plurality of standard specimen
Characteristic value；
Corresponding process, it is to the synchronization detection with regard to the plurality of standard specimen obtaining during the measurement of described standard specimen
Between signal and the described magnetic characteristic value with regard to the plurality of standard specimen obtaining during the measurement of described magnetic characteristic value
Relation is estimated；And
Evaluation procedure, it is based on the described relation estimating in described corresponding process, according in described evaluation sample measurement mistake
The synchronous detection signal with regard to described evaluation sample obtaining in journey estimates the magnetic characteristic value of described evaluation sample.
2. magnetic characteristic evaluation method according to claim 1, wherein, described magnetic characteristic value is magnetic flux.
3. magnetic characteristic evaluation method according to claim 1, wherein,
Described alternating magnetic field is produced by making alternating current flow through magnet exciting coil；
Described induced-current is as benchmark by the described alternating current to flow through described magnet exciting coil, to because of described electromagnetism sense
Should and produces and flow through detection coil electric current be synchronized detection and detect, described detect coil also serve as described excitation
Coil or arrange independently relative to described magnet exciting coil；And
All used in described corresponding process and described evaluation procedure by the value of real part of the signal detected by described synchronization detection
Make described synchronous detection signal.
4. magnetic characteristic evaluation method according to claim 2, wherein,
Described alternating magnetic field is produced by making alternating current flow through magnet exciting coil；
Described induced-current is as benchmark by the described alternating current to flow through described magnet exciting coil, to because of described electromagnetism sense
Should and produces and flow through detection coil electric current be synchronized detection and detect, described detect coil also serve as described excitation
Coil or arrange independently relative to described magnet exciting coil；And
All used in described corresponding process and described evaluation procedure by the value of real part of the signal detected by described synchronization detection
Make described synchronous detection signal.
5. magnetic characteristic evaluation method according to any one of claim 1 to 4, wherein,
In described corresponding process, by the range set of the synchronous detection signal corresponding with the magnetic characteristic value in predetermined scope
For excellent product scope；And
In described evaluation procedure, if the synchronous detection signal of described evaluation sample is within described excellent product scope, then
Described evaluation sample is evaluated as excellent product.
6. magnetic characteristic evaluation method according to any one of claim 1 to 4, wherein, described magnet material is thermal deformation
The magnet material of magnet.
7. a magnetic characteristic valuator device, comprising:
Magnetic field generation unit, it produces alternating magnetic field and be applied to described alternating magnetic field on sample, and
Induced-current detector unit, it detects, by synchronization, the induced-current producing in described sample, wherein
Described equipment performs magnetic characteristic evaluation method according to any one of claim 1 to 6.
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| JP2015058989A JP6446304B2 (en) | 2015-03-23 | 2015-03-23 | Magnetic characteristic evaluation method and magnetic characteristic evaluation apparatus |
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|---|---|---|---|---|
| CN109142508A (en) * | 2018-08-09 | 2019-01-04 | 西红柿科技（武汉）有限公司 | A kind of magnetic conductivity instrument for Magnetic Flux Leakage Inspecting |
| CN117607244A (en) * | 2024-01-22 | 2024-02-27 | 河南工学院 | Multi-sensitive-array crane steel wire rope flux weakening on-line monitoring method and system |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP6288894B1 (en) * | 2017-07-27 | 2018-03-07 | 株式会社テクレコ | Magnetic ink detection device |
| JP2020056704A (en) * | 2018-10-03 | 2020-04-09 | 株式会社玉川製作所 | Automatic sample exchange device for vibrating sample magnetometer |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102132155A (en) * | 2008-08-27 | 2011-07-20 | 杰富意钢铁株式会社 | Magnetic measuring method and device |
| CN202770984U (en) * | 2012-09-20 | 2013-03-06 | 上海市计量测试技术研究院 | Magnetic material shielding property self-evaluating device |
| CN103119432A (en) * | 2010-12-21 | 2013-05-22 | 新东工业株式会社 | Surface property magnetic evaluation device and method |
| CN103930775A (en) * | 2011-11-07 | 2014-07-16 | 日产自动车株式会社 | Magnetic body evaluation device and method |
| JP2014203872A (en) * | 2013-04-02 | 2014-10-27 | 株式会社ダイドー電子 | Method for regenerating scrap magnet |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4342962A (en) * | 1980-04-21 | 1982-08-03 | Bell Telephone Laboratories, Incorporated | Method for measuring coercivity in magnetic materials |
| JPH05119138A (en) * | 1991-08-19 | 1993-05-18 | Daido Steel Co Ltd | Method and apparatus for estimating magnetic characteristics after magnetization of raw material |
| JP3985695B2 (en) * | 2003-02-27 | 2007-10-03 | 株式会社ジェイテクト | Method for evaluating the degree of orientation of anisotropic magnetic materials |
| JP2013245958A (en) * | 2012-05-23 | 2013-12-09 | Hitachi Industrial Equipment Systems Co Ltd | Magnetic flux density distribution measurement apparatus and magnetic flux density measurement method |
| EP2960669B1 (en) * | 2013-02-25 | 2022-04-06 | Nissan Motor Co., Ltd. | Magnet evaluating device and method |
-
2015
- 2015-03-23 JP JP2015058989A patent/JP6446304B2/en active Active
-
2016
- 2016-03-23 CN CN201610170128.1A patent/CN105988093B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102132155A (en) * | 2008-08-27 | 2011-07-20 | 杰富意钢铁株式会社 | Magnetic measuring method and device |
| CN103119432A (en) * | 2010-12-21 | 2013-05-22 | 新东工业株式会社 | Surface property magnetic evaluation device and method |
| CN103930775A (en) * | 2011-11-07 | 2014-07-16 | 日产自动车株式会社 | Magnetic body evaluation device and method |
| CN202770984U (en) * | 2012-09-20 | 2013-03-06 | 上海市计量测试技术研究院 | Magnetic material shielding property self-evaluating device |
| JP2014203872A (en) * | 2013-04-02 | 2014-10-27 | 株式会社ダイドー電子 | Method for regenerating scrap magnet |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109142508A (en) * | 2018-08-09 | 2019-01-04 | 西红柿科技（武汉）有限公司 | A kind of magnetic conductivity instrument for Magnetic Flux Leakage Inspecting |
| CN117607244A (en) * | 2024-01-22 | 2024-02-27 | 河南工学院 | Multi-sensitive-array crane steel wire rope flux weakening on-line monitoring method and system |
| CN117607244B (en) * | 2024-01-22 | 2024-04-30 | 河南工学院 | Multi-sensitive-array crane steel wire rope flux weakening on-line monitoring method and system |
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| CN105988093B (en) | 2019-05-03 |
| JP2016176885A (en) | 2016-10-06 |
| JP6446304B2 (en) | 2018-12-26 |
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