JP5381623B2 - Physical property value detection method for measurement object and physical property value detection system for measurement object - Google Patents

Description

  The present invention relates to a physical property value detection method and a physical property value detection system for detecting a physical property value of an object to be measured from the intensity of an ultrasonic beam received after passing through the object to be measured.

When measuring the thickness of a thin plate-shaped measurement object, it is possible to measure by directly sandwiching the measurement object with a micrometer, dial gauge, etc., or the transmission intensity of radiation, ultrasonic waves, etc. transmitted through the measurement object. Based on this, a technique for detecting the thickness of a measurement object is known.
Among the methods for measuring the thickness of a measurement object using such a technique, Patent Document 1 discloses a measurement method using ultrasonic waves, that is, transmitting ultrasonic waves to an object and transmitting transmitted ultrasonic waves. An ultrasonic thickness measurement method is described in which the thickness of an object is measured based on received intensity. In the ultrasonic thickness measurement method of Patent Document 1, even if the wavelength of the ultrasonic wave radiated to the object changes with the change in the sound speed due to temperature, the frequency at which the ultrasonic measurement conditions related to the wavelength are the same is used. The frequency setting range is determined so as to include the frequency, and the frequency is continuously changed over the setting range.

Japanese Patent Application Laid-Open No. 2004-156917

  In this Patent Document 1, the frequency of the ultrasonic wave (ultrasonic beam) is continuously changed within the set range, but this is for correcting the measurement conditions that have changed along with the change in the sound speed, It can be said that the thickness (physical property value) of the object (measurement object) is actually measured using a single frequency (for example, around 40 kHz) as the frequency of the ultrasonic wave (ultrasound beam). However, there is a possibility that sufficient measurement accuracy cannot be obtained when ultrasonic waves (ultrasonic beams) having a single frequency are used.

  The present invention has been made in view of the current situation, and provides a physical property value detection method for a measurement object and a physical property value detection system for the measurement object that can accurately detect the physical property value using an ultrasonic beam. The purpose is to provide.

In one embodiment of the present invention, an ultrasonic beam radiated into the air is transmitted through a measurement object and then received, and a physical property value of the measurement object is detected from the intensity of the received ultrasonic beam. A method for detecting a physical property value of an object to be measured, wherein the ultrasonic beams having different frequencies are obtained in advance based on the correlation between the intensity and the physical property value of the object to be measured. From the intensity of the ultrasonic beam, a physical property value for each frequency of the measurement object is obtained, the physical property value of the measurement object is specified based on each physical property value for each frequency , and the measurement object is An electrode plate for a battery, in which an active material layer is formed on a current collector foil, and the physical property value is a physical property value detection method for an object to be measured, which is a basis weight of the active material layer .

  In the above-described physical property value detection method of the measurement object, based on the correlation between the intensity of the ultrasonic beam and the physical property value of the measurement object, the physical property by frequency of the measurement object is determined from the intensity of the ultrasonic beam of each frequency. Get the value. And the physical property value is specified based on the physical property value for each frequency. For this reason, the physical property value of the measurement object can be detected more accurately than the physical property value based on one ultrasonic beam having a single frequency.

  Examples of the physical property value include the thickness and density of the measurement object, and the basis weight (weight per unit area) of the coating film applied to the substrate.

By the way, in measuring the basis weight (weight per unit area) of the active material layer in the electrode plate (positive electrode plate and negative electrode plate) in which the active material layer is formed on the current collector foil, for example, a micrometer or dial It is also conceivable to use a measuring tool such as a gauge that measures the object by contacting it. However, it is difficult to measure with an electrode plate having a thin current collector foil or active material layer (for example, about 100 μm), and the measurement takes time.
On the other hand, according to the above-described physical property value detection method of the measurement object, since the basis weight of the active material layer is detected in a non-contact manner, it can be easily detected in a short time without damaging the electrode plate. Can do.

According to another aspect of the present invention, there is provided an ultrasonic wave receiving means having a radiation unit that radiates an ultrasonic beam in the air and a wave receiving unit that receives the ultrasonic beam and converts it into an electrical signal. Wave measurement means, and from the intensity of the ultrasonic beam transmitted through the measurement object disposed between the radiation part and the wave reception part received by the ultrasonic wave reception means, the measurement object A physical property value detection system for a measurement object for detecting a physical property value of a physical object, wherein the ultrasonic radiation means is configured to be capable of emitting the ultrasonic beams having different frequencies from the radiation unit, and the measurement target The ultrasonic beam of each frequency is obtained based on the correlation between the intensity and the physical property value of the measurement object obtained in advance for the ultrasonic beam of each frequency transmitted through the object. From the strength of A frequency different thing of value obtaining means for obtaining respective frequency different things of value, based on each of said frequency different thing of value, and a physical property value specifying means for specifying the physical properties of the measurement object, the measurement object Is an electrode plate for a battery formed by forming an active material layer on a current collector foil, and the physical property value is a physical property value detection system for an object to be measured, which is the basis weight of the active material layer .

  In the above-described physical property value detection system for an object to be measured, since the above-described physical property value acquisition unit by frequency and physical property value specifying unit are provided, a plurality of physical property values by frequency based on ultrasonic beams having different frequencies are used. The physical property value of the measurement object can be specified. Therefore, the physical property value of the measurement object can be detected with higher accuracy than the physical property value obtained based on the ultrasonic beam having a single frequency.

  In the above-described physical property value detection system of the measurement object, the basis weight of the active material layer is detected in a non-contact manner, so that it is easy to damage without damaging the electrode plate as compared with measurement using a measurement tool such as a micrometer. And it can detect in a short time.

It is a perspective view of the battery of an embodiment. It is a perspective view of the electrode plate (positive electrode plate, negative electrode plate) of an embodiment. It is explanatory drawing of the physical-property value detection apparatus concerning embodiment. It is a calibration curve showing the correlation between the intensity of ultrasonic beams having different frequencies and the basis weight of the measurement object (positive electrode plate, negative electrode plate). It is a flowchart of the physical-property value detection method of the measuring object of embodiment.

(Embodiment)
Next, embodiments of the present invention will be described with reference to the drawings.
In addition, in the physical property value detection apparatus 100 of the measurement object according to the present embodiment and the physical property detection method using the same, an electrode plate for the battery 1 (a positive electrode plate 30 and a negative electrode plate 40 described later) is used as the measurement object. ) Is used. First, the battery 1 will be described with reference to FIGS.
The battery 1 is a lithium ion secondary battery that includes a belt-like positive electrode plate 30, a negative electrode plate 40, and a separator 20 that extend in the longitudinal direction DA, and forms a wound power generation element 10 that is wound around these. (See FIG. 1). In addition, the battery 1 accommodates the electric power generation element 10 in the battery case 80, as shown in FIG.

  The battery case 80 has a battery case body 81 and a sealing lid 82 both made of aluminum. Among these, the battery case main body 81 has a bottomed rectangular box shape, and an insulating film (not shown) made of resin and bent into a box shape is interposed between the battery case 80 and the power generation element 10. The sealing lid 82 has a rectangular plate shape, closes the opening of the battery case body 81, and is welded to the battery case body 81. Of the positive electrode current collecting member 91 and the negative electrode current collecting member 92 connected to the power generation element 10, the positive electrode terminal portion 91 </ b> A and the negative electrode terminal portion 92 </ b> A located at the tips of the sealing lid 82 pass through, respectively. 1 protrudes from the lid surface 82a facing upward. Insulating members 95 made of insulating resin are interposed between the positive electrode terminal portion 91A and the negative electrode terminal portion 92A and the sealing lid 82 to insulate each other. Further, a rectangular plate-shaped safety valve 97 is also sealed on the sealing lid 82.

The power generation element 10 is a wound type in which a strip-like positive electrode plate 30 and a negative electrode plate 40 are wound into a flat shape via a strip-like separator 20 (see FIG. 1). Only the separator 20 is wound on the outermost and innermost sides of the power generation element 10. The positive electrode plate 30 and the negative electrode plate 40 of the power generation element 10 are joined to a plate-like positive current collector 91 or negative current collector 92 bent in a crank shape, respectively (see FIG. 1). Among these, the separator 20 made of polyethylene is impregnated with an electrolytic solution (not shown) obtained by adding a solute (LiPF ₆ ) to a mixed organic solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC). .

Further, as shown in the perspective view of FIG. 2, the thin plate-shaped positive electrode plate 30 has a belt-like shape extending in the longitudinal direction DA, and the aluminum foil 38 made of aluminum and the main surfaces of the aluminum foil 38 are respectively long. It has two positive electrode active material layers 31 and 31 formed and arranged in a strip shape extending in the direction DA.
The positive electrode active material layer 31 includes positive electrode active material particles (not shown) made of LiCoO ₂ , a conductive material (not shown) made of acetylene black, and a binder (not shown) made of polyvinylidene fluoride (PVDF). including.

On the other hand, as shown in FIG. 2, the thin negative electrode plate 40 also has a strip shape extending in the longitudinal direction DA and a copper foil 48 made of copper, and strips extending in the longitudinal direction DA on both main surfaces of the copper foil 48. And two negative electrode active material layers 41, 41 formed and arranged on the substrate.
Among these, the negative electrode active material layer 41 includes negative electrode active material particles (not shown) made of graphite and a binder (not shown) made of PVDF.

Next, the physical property value detection apparatus 100 according to the present embodiment will be described with reference to FIG.
The physical property detection device 100 receives an ultrasonic wave radiation unit 110 that radiates an ultrasonic beam US and the ultrasonic beam US, and outputs the received electric signal (specifically, depending on the size of the ultrasonic beam US). And an ultrasonic wave receiving portion 120 that converts the amplitude into an AC signal having the same frequency as the frequency of the ultrasonic beam US, and a U-shape that holds the ultrasonic wave radiating portion 110 and the ultrasonic wave receiving portion 120. Arm 130 and a control unit 150 that controls the ultrasonic radiation unit 110 and the ultrasonic wave reception unit 120 and processes an electrical signal.

Among these, the control unit 150 includes a known microcomputer (not shown) including a CPU, a ROM, and a RAM, and controls the ultrasonic radiation unit 110 and the ultrasonic wave reception unit 120 according to a stored program. Perform the process.
The ultrasonic radiation unit 110 includes an ultrasonic transducer, and includes a radiation unit 111 that emits an ultrasonic beam US, and a drive circuit 116 that drives the ultrasonic transducer at a predetermined frequency. Note that the ultrasonic beam US is a convergent ultrasonic beam whose beam diameter decreases as it progresses. For this reason, the intensity | strength of the ultrasonic beam US received by the ultrasonic receiving part 120 can be made higher, and the physical property value (among these, the positive electrode plate 30, the negative electrode plate 40) The basis weight of the positive electrode active material layer 31 and the negative electrode active material layer 41) can be detected more reliably. Further, the drive circuit 116 of the ultrasonic radiation unit 110 sequentially switches the frequencies f1, f2, and f3 of the drive voltage for driving the radiation unit 111 at predetermined time intervals (for example, every second) in accordance with an instruction from the control unit 150. From the radiation unit 111, ultrasonic beams US having frequencies f1, f2, and f3 are sequentially emitted.

  On the other hand, the ultrasonic wave receiving unit 120 is disposed opposite to the radiation unit 111, and when receiving the ultrasonic beam US, the ultrasonic wave receiving unit 121 includes an ultrasonic transducer that generates an electric signal having an amplitude corresponding to the intensity. And a wave receiving circuit 126 for converting the output (electric signal) of the ultrasonic transducer into a DC voltage signal having a voltage value corresponding to the magnitude.

  Further, as described above, the control unit 150 instructs the ultrasonic radiation unit 110 (drive circuit 116) to switch the frequency, and also receives the received ultrasonic beam US output from the ultrasonic reception unit 120. The voltage value of the DC voltage signal corresponding to the intensity of the signal is A / D converted and captured. Based on the magnitude of the voltage value of this signal, the physical property value (the weight per unit area of the positive electrode active material layer 31 and the negative electrode active material layer 41) of the measurement object (positive electrode plate 30, negative electrode plate 40) is detected.

The control unit 150 includes an intensity UC (a magnitude of the DC voltage signal) of the ultrasonic beam US received by the wave receiving unit 121 and a measurement object (positive electrode) for each frequency f1, f2, and f3. The data of the calibration curve (see FIG. 4) indicating the correlation with the physical properties by frequency of the plate 30 and the negative electrode plate 40 (the basis weight AP of the positive electrode active material layer 31 and the negative electrode active material layer 41) are respectively stored. Yes. For this reason, by using this calibration curve, from the intensity obtained for each frequency f1, f2, f3 (intensities UC1, UC2, UC3 described later), the physical property values for each frequency (frequency basis weights AP1, AP2, AP3 described later). ) Can be obtained.
This calibration curve was obtained in advance using samples with known physical property values, and obtaining the relationship between this physical property value and the intensity UC of the transmitted ultrasonic beam for samples with various physical property values. It is.

However, in this embodiment, the calibration curve was obtained as follows.
By the way, it is difficult to prepare a large number of active material layers with different basis weights (thicknesses and densities) on the current collector foil, and obtaining the relationship between the basis weight and the intensity of the transmitted ultrasonic beam is difficult. difficult. The intensity of the transmitted ultrasonic beam varies depending on the weight per unit area, regardless of the substance, in a substance having a thickness or density similar to that of an electrode plate. Therefore, metal foils having different thicknesses were used as samples instead of using an electrode plate, that is, a current collector foil having an active material layer formed thereon. This is because it is easier to obtain the relationship between the weight per unit area and the intensity of the transmitted ultrasonic beam.

As a sample, a metal foil having a thickness of 10 to 100 μm made of the same material as the aluminum foil 38 used as a current collector foil of the positive electrode plate 30 was prepared at intervals of 5 μm. And about the metal foil of each thickness, the ultrasonic beam of 1st frequency f1 (100 kHz) is radiated | emitted and the relationship between the intensity | strength UC of the transmitted ultrasonic beam and the weight per unit area is obtained. Since the thickness of aluminum foil 38 used for positive electrode plate 30 (and hence the weight per unit area) is constant, the relationship between strength UC and basis weight AP of positive electrode active material layer 31 is obtained by subtracting this thickness. I got.
Specifically, the points given by the intensity and the basis weight are plotted for each sample (metal foil) on a graph in which the horizontal axis is the intensity UC1 of the ultrasonic beam and the vertical axis is the basis weight AP1. Then, based on the plotted points, for the first frequency f1, a quadratic expression (y = ax ² + bx + c (a, b, and c are constants) that obtains the basis weight y when the intensity of the ultrasonic beam is x. )) In the form of an approximate expression (calibration curve G1).
Further, similarly, calibration curves G2 and G3 represented by quadratic expressions are respectively obtained for the ultrasonic beams having the second frequency f2 (200 kHz) and the third frequency f3 (400 kHz) (see FIG. 4).
Similarly, for the metal foil made of the same material as the copper foil 48 used for the negative electrode plate 40, the ultrasonic beam having the first frequency f1, the second frequency f2, and the third frequency f3 is in the form of a quadratic expression. Obtain a calibration curve for each.

A physical property value detection method for detecting the basis weight AP of the positive electrode active material layer 31 of the positive electrode plate 30 in the battery 1 using the physical property value detection device 100 described above will be described with reference to the flowchart shown in FIG.
In addition, the positive electrode active material layer 31 of the positive electrode plate 30 serving as a measurement object is in a state of being completed by coating and compression in the manufacturing process of the battery 1.

First, as shown in FIG. 3, the positive electrode plate 30 is disposed between the ultrasonic radiation unit 110 and the ultrasonic wave reception unit 120. Then, in step S <b> 1 of the flowchart shown in FIG. 5, the ultrasonic beam US having the first frequency f <b> 1 (100 kHz) is radiated from the radiation unit 111 to the positive electrode plate 30.
Subsequently, from the intensity (first frequency intensity UC1) of the ultrasonic beam US received by the wave receiving unit 121, the control unit 150 uses the calibration amount G1 shown in FIG. First frequency basis weight AP1) is calculated (step S2).

Next, in step S <b> 3, an ultrasonic beam US having a second frequency f <b> 2 (200 kHz) is emitted from the radiation unit 111 to the positive electrode plate 30 instead of the first frequency f <b> 1.
In step S4, the basis weight of the positive electrode active material layer 31 (second frequency) is calculated based on the calibration curve G2 shown in FIG. 4 from the intensity (second frequency intensity UC2) of the ultrasonic beam US received by the wave receiver 121. The frequency basis weight AP2) is calculated.

Subsequently, in step S5, instead of the second frequency f2, the ultrasonic beam US having the third frequency f3 (400 kHz) is emitted from the radiation unit 111 to the positive electrode plate 30.
In step S6, the basis weight of the positive electrode active material layer 31 (third value) is calculated based on the calibration curve G3 shown in FIG. 4 from the intensity (third frequency intensity UC3) of the ultrasonic beam US received by the wave receiver 121. The frequency basis weight AP3) is calculated.

  Subsequently, in step S7, the basis weight AP of the positive electrode active material layer 31 is calculated based on the first frequency basis weight AP1, the second frequency basis weight AP2, and the third frequency basis weight AP3. Specifically, the average value of the first frequency basis weight AP1, the second frequency basis weight AP2, and the third frequency basis weight AP3 is calculated as the basis weight AP.

In the present embodiment, steps S2, S4, and S6 correspond to frequency-specific property value acquisition means, and step S7 corresponds to property value specification means.
In addition, the physical property value detection method for detecting the basis weight AP of the negative electrode active material layer 41 of the negative electrode plate 40 in the battery 1 is the same as that of the positive electrode active material layer 31 using the physical property value detection device 100 described above. Since this is done, the description is omitted.

  As described above, in the physical property value detection method for the positive electrode plate 30 (negative electrode plate 40) according to the present embodiment, the intensity of the ultrasonic beam US having the frequencies f1, f2, and f3 based on the calibration curves G1, G2, and G3. From UC1, UC2, and UC3, the frequency basis weights AP1, AP2, and AP3 of the positive electrode active material layer 31 (negative electrode active material layer 41) are obtained, respectively. Based on these frequency basis weights AP1, AP2, AP3, the basis weight AP of the positive electrode active material layer 31 (the negative electrode active material layer 41) is specified. Therefore, the basis weight AP of the positive electrode active material layer 31 (the negative electrode active material layer 41) can be detected with higher accuracy than the basis weight based on one ultrasonic beam having a single frequency.

Further, in the positive electrode plate 30 (negative electrode plate 40) in which the positive electrode active material layer 31 (negative electrode active material layer 41) is formed on the aluminum foil 38 (copper foil 48), the positive electrode active material layer 31 (negative electrode active material layer 41). In measuring the basis weight AP, for example, it is also conceivable to use a measuring tool such as a micrometer or a dial gauge that is measured in contact with an object to be measured. However, it is difficult to measure with the positive electrode plate 30 (negative electrode plate 40) in which the thickness of the aluminum foil 38 (copper foil 48) and the positive electrode active material layer 31 (negative electrode active material layer 41) is thin (for example, about 100 μm), Moreover, it takes time to measure.
On the other hand, according to the physical property value detection method of the positive electrode plate 30 (negative electrode plate 40) according to the present embodiment, the basis weight AP of the positive electrode active material layer 31 (negative electrode active material layer 41) is detected in a non-contact manner. Therefore, the positive electrode plate 30 (negative electrode plate 40) can be detected easily and in a short time without damaging the positive electrode plate 30 (negative electrode plate 40).

  Further, in the physical property value detection device 100 of the positive electrode plate 30 (negative electrode plate 40) according to the present embodiment, the above-described physical property value acquisition means (steps S2, S4, S6) and physical property value specifying means (step S7). Therefore, the basis weight AP of the positive electrode active material layer 31 (negative electrode active material layer 41) is specified using a plurality of physical property values AP1, AP2, AP3 by frequency based on ultrasonic beams US having different frequencies. be able to. Therefore, the basis weight AP of the positive electrode active material layer 31 (the negative electrode active material layer 41) can be detected with higher accuracy than that in which the basis weight is obtained based on an ultrasonic beam having a single frequency.

  Further, if the physical property value detection device 100 is used, the basis weight AP of the positive electrode active material layer 31 (negative electrode active material layer 41) is detected in a non-contact manner, compared with measurement using a measurement tool such as a micrometer. Detection can be performed easily and in a short time without damaging the positive electrode plate 30 (negative electrode plate 40).

In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.
For example, in the embodiment, the physical property value by frequency (AP1 or the like) based on the intensity (UC1 or the like) of the ultrasonic beam of each frequency is calculated and obtained from the calibration curve formula obtained in advance. However, for example, by using a look-up table in which the value of the intensity (UC1 or the like) of each frequency is associated with the value of the physical property value (AP1 or the like) for each frequency, A sex value may be acquired. In the embodiment, the physical property value of the measurement object is obtained by obtaining the basis weight of the active material layer in the electrode plate. However, as the physical property values, for example, the thickness and density of the measurement object can be measured.

1 Battery 30 Positive electrode plate (electrode plate, measurement object)
31 Positive electrode active material layer (active material layer)
38 Aluminum foil (current collector foil)
40 Negative electrode plate (electrode plate, measurement object)
41 Negative electrode active material layer (active material layer)
48 Copper foil (current collector foil)
100 Physical property value detector (physical property value detection system for measurement object)
110 Ultrasonic radiation part (ultrasonic radiation means)
111 Radiation unit 120 Ultrasonic wave receiving unit (Ultrasonic wave receiving means)
121 Wave receiver AP (active material layer) basis weight (property value)
AP1 first frequency basis weight (property value by frequency)
AP2 Second frequency basis weight (property value by frequency)
AP3 Third frequency basis weight (property value by frequency)
f1 First frequency (frequency)
f2 Second frequency (frequency)
f3 Third frequency (frequency)
G1, G2, G3 calibration curve (correlation)
UC intensity UC1 first frequency intensity (intensity)
UC2 Second frequency intensity (intensity)
UC3 Third frequency intensity (strength)
US ultrasonic beam

Claims (4)

Detecting the physical property value of the measurement object, detecting the physical property value of the measurement object from the intensity of the ultrasonic beam received after the ultrasonic beam emitted in the air is transmitted through the measurement object A method,
Based on the correlation between the intensity and the physical property value of the measurement object obtained in advance for the ultrasonic beams having different frequencies, the intensity of the ultrasonic beam of each frequency Obtain the physical property value by frequency of the measurement object, and specify the physical property value of the measurement object based on each physical property value by frequency ,
The measurement object is
An electrode plate for a battery, in which an active material layer is formed on a current collector foil,
The physical property values are
A method for detecting a physical property value of an object to be measured, which is a basis weight of the active material layer . A method for detecting a physical property value of a measurement object according to claim 1,
  The ultrasonic beam is
    It is a convergent ultrasonic beam whose beam diameter decreases as it progresses
A method for detecting physical properties of a measurement object. An ultrasonic radiation means having a radiation part for emitting an ultrasonic beam in the air;
An ultrasonic wave receiving means having a wave receiving portion for receiving the ultrasonic beam and converting it into an electrical signal;
The physical property value of the measurement object is detected from the intensity of the ultrasonic beam received by the ultrasonic wave receiving means and transmitted through the measurement object disposed between the radiation part and the wave reception part. A physical property value detection system for a measurement object,
The ultrasonic radiation means is
From the radiation part, it is possible to radiate the ultrasonic beams having different frequencies from each other,
Based on the correlation between the intensity and the physical property value of the measurement object obtained in advance for the ultrasonic beam of each frequency transmitted through the measurement object and received, From the intensity of the ultrasonic beam, the physical property value acquisition means by frequency for obtaining the physical property value by frequency of the measurement object,
Physical property value specifying means for specifying the physical property value of the measurement object based on each physical property value by frequency , and
The measurement object is
An electrode plate for a battery, in which an active material layer is formed on a current collector foil,
The physical property values are
A physical property value detection system for an object to be measured which is a basis weight of the active material layer . A physical property value detection system for a measurement object according to claim 3,
  The ultrasonic beam is
    It is a convergent ultrasonic beam whose beam diameter decreases as it progresses
Physical property value detection system for measurement objects.

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