Foreign object detection device

Abstract

To detect a foreign material in an object to be detected such as a lithium ion battery in a nondestructive manner with high accuracy.SOLUTION: A foreign material detection device includes a measuring instrument 10, and a transmission line 12 electrically connecting an object 200 to be measured with the measuring instrument 10. Impedance of an electric circuit including the object 200 to be measured and the transmission line 12 is measured by the measuring instrument 10, and a foreign material in the object 200 to be measured is detected from a change in the measured impedance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a foreign object detection device for lithium-ion batteries and the like. [Background technology]

[0002] A capacitive displacement sensor for detecting minute changes in the capacitance of an object under inspection with high precision has been disclosed (Patent Document 1). An RLC resonant circuit is employed in the probe facing the object under measurement to steepen the frequency characteristics of two voltages, and the resonant frequency characteristics of the RLC resonant circuit are set so that the resonance points of each voltage are slightly different. High-sensitivity capacitance detection is achieved by utilizing the fact that the intensity of the resonant current at a specific frequency changes as the capacitance component of the object under measurement changes, which causes a change in the resonant frequency.

[0003] Furthermore, a foreign object detection technique has been disclosed in which the magnetism of a structure composed of multiple components is measured, and metallic foreign objects contained in the structure are detected based on the magnetic information of the structure (Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-167143 [Patent Document 2] Japanese Patent Publication No. 2012-138318 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In a capacitance-type displacement sensor using an LC resonance circuit, the resonance frequency of the LC resonance changes due to the imaginary component of impedance such as the capacitance component and the inductance component. Therefore, it is an effective method for detecting a minute change in the imaginary component. However, this technique has no sensitivity to changes in the real component of impedance. Depending on foreign matter in the detection target object, the real component of impedance may also be affected, and it cannot be applied to the detection of foreign matter that shows only a minute change in the real component without a minute change in the imaginary component.

[0006] Also, in a technique for detecting metallic foreign matter contained in a structure based on magnetic information, it is possible to detect a foreign matter having magnetism by performing magnetization and appropriate demagnetization operations on a battery. However, there are also non-magnetic metals such as aluminum and copper as foreign matter mixed into the battery, and it is difficult to detect these foreign matters with this technique.

Means for Solving the Problem

[0007] One aspect of the present invention includes a measuring instrument, and a transmission line that electrically connects the measurement target object and the measuring instrument, and measures the impedance of an electric circuit including the measurement target object and the transmission line by the measuring instrument, and detects foreign matter in the measurement target object from the change in the measured impedance. It is a foreign matter detection device characterized by that.

[0008] Here, it is preferable to detect the change in the impedance from the change in the resonance frequency or the peak value of resonance of the electric circuit.

[0009] Also, it is preferable to provide an impedance adjustment circuit between the measuring instrument and the measurement target object, and make it possible to adjust the impedance of the electric circuit by the impedance adjustment circuit.

[0010] Also, it is preferable to detect the change in the impedance in a frequency band where the variations in the measured values of the real component and the imaginary component of the impedance are less than a predetermined accuracy threshold value.

[0011] Furthermore, it is preferable to adjust the measurement frequency by changing the electrical length of the transmission line. For example, it is preferable to change the electrical length of the transmission line by switching between multiple transmission lines. For example, it is preferable to change the electrical length of the transmission line by changing at least one of the relative permittivity and relative permeability of the transmission line.

[0012] Furthermore, the object to be measured is preferably a lithium-ion battery. [Effects of the Invention]

[0013] According to the present invention, foreign matter within an object to be measured, such as a lithium-ion battery, can be detected non-destructively and with high accuracy, even if it only affects the real part of the impedance or is non-magnetic. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows the configuration of a foreign object detection device according to an embodiment of the present invention. [Figure 2] This figure shows an example of the configuration of a transmission line in an embodiment of the present invention. [Figure 3] This figure shows an example of the configuration of a transmission line in an embodiment of the present invention. [Figure 4] This figure shows a shunt-through connection model for a foreign object detection device according to an embodiment of the present invention. [Figure 5] This figure shows the S-parameter matrix representation of the foreign object detection device in an embodiment of the present invention. [Figure 6] This figure shows the relationship between the change in the resonant frequency and the change in the real component of the load impedance of the object being measured. [Figure 7] This figure shows the relationship between the change in the resonant frequency and the change in the imaginary component of the load impedance of the object being measured. [Figure 8] This figure shows the relationship between the change in resonant frequency and the ratio of the real and imaginary components of the load impedance of the object being measured. [Figure 9]This figure shows another example of the configuration of a foreign object detection device according to an embodiment of the present invention. [Figure 10] This figure shows another example of the configuration of a foreign object detection device according to an embodiment of the present invention. [Figure 11] This figure shows another example of the configuration of a foreign object detection device according to an embodiment of the present invention. [Figure 12] This figure shows the configuration of a foreign object detection device including an impedance adjustment circuit according to an embodiment of the present invention. [Figure 13] This figure shows the configuration of the impedance adjustment circuit in this embodiment. [Figure 14] This is a flowchart showing the foreign object detection method in this embodiment. [Modes for carrying out the invention]

[0015] As shown in Figure 1, the foreign object detection device 100 in the embodiment of the present invention is configured to include a measuring instrument 10 and a transmission line 12 (12a, 12b). In the foreign object detection device 100, the measuring instrument 10 and the object to be measured 200 are electrically connected by the transmission line 12, and foreign objects present in the object to be measured 200 are detected.

[0016] The measuring instrument 10 is a measuring device capable of measuring the reflection and transmission of at least one of power, voltage, and current to the object 200 to be measured. The measuring instrument 10 can be, for example, a network analyzer.

[0017] The transmission line 12 (12a, 12b) is an electric wire that electrically connects the measuring instrument 10 and the object to be measured 200. As shown in Figure 2, the transmission line 12 can be a coaxial cable in which the signal line 14 and the return line 16 are arranged coaxially and electrically insulated between them by an insulator 18. Alternatively, as shown in Figure 3, the transmission line 12 may be a microstrip line having a structure in which the signal line 14 is arranged on the surface of a plate-shaped insulator 18 and the return line 16 is arranged on the back surface. Note that the transmission line 12 is not limited to these, and may also be a twisted pair cable, etc.

[0018] The object to be measured 200 is not particularly limited and can be, for example, a battery. Specifically, the object to be measured 200 can be, for example, a lithium-ion battery. When the object to be measured 200 is a battery, the detection of foreign matter is performed with the positive and negative electrodes of the object to be measured 200 electrically connected to the measuring instrument 10 by the transmission line 12.

[0019] In the foreign object detection device 100 shown in Figure 1, the two ports of the measuring instrument 10 are electrically connected to the object to be measured 200 via transmission lines 12a and 12b in a shunt-through connection. Specifically, one of the positive and negative electrodes of the object to be measured 200 is connected to the first port of the measuring instrument 10 via the signal line 14a of transmission line 12a. Also, the second port of the measuring instrument 10 is connected to the electrode of the object to be measured 200 that is connected to the signal line 14a, via the signal line 14b of transmission line 12b. Furthermore, the electrode of the object to be measured 200 that is not connected to the signal line 14a is connected to the first port of the measuring instrument 10 via the return line 16a of transmission line 12a. Furthermore, the positive electrode and the negative electrode of the object to be measured 200, to which the return wire 16a is connected, are connected to the second port of the measuring instrument 10 via the return wire 16b of the transmission line 12b.

[0020] The foreign object detection device 100 measures the impedance of the object to be measured 200 based on S-parameters. In the foreign object detection device 100, the measuring instrument 10 and the object to be measured 200 are connected via a transmission line 12, and resonance occurs, allowing the change in the impedance of the object to be measured 200 to be measured from the change in the resonant frequency. Furthermore, by changing at least one of the length, dielectric constant, and permeability of the transmission line 12, the electrical length of the transmission line 12 is changed, the resonant frequency is adjusted, and the change in impedance can be measured at any desired frequency.

[0021] Figures 4 and 5 show the shunt-through connection model and S-parameter matrix representation, respectively, including the transmission line 12. Here, Z0 is the characteristic impedance of the circuit, Zref is the reference impedance, Z L is the load impedance of the object 200 to be measured, l is the line length of the transmission line 12, S ZL is the S parameter matrix of the load impedance, S TL is the S parameter matrix of the transmission line 12. In this model, the load impedance Z L and the S parameter S of the transmission line 12 TL are represented by the mathematical formulas (1) and (2) respectively.

[0022]

Number

[0023]

Number

[0024] From the mathematical formulas (1) and (2), the composite S parameter is represented by the mathematical formula (3).

[0025]

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[0026] In the configuration of the shunt-through connection, the observed load impedance Z L,observed is calculated from the element S of the 2nd row and 1st column of the composite S parameter in the mathematical formula (3) as shown in the mathematical formula (4). 21 as follows.

[0027]

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[0028] When the load impedance Z L is decomposed into the real part component R and the imaginary part component X and expressed as Z L = R + jX, it becomes the mathematical formula (5).

[0029]

Number

[0030] Figures 6 and 7 show the load impedance Z in equation (5), respectively. L This shows the change in the resonant frequency when the real component R and imaginary component X of the load impedance Z are changed. L It was confirmed that the resonant frequency shifts with changes in the real component R and the imaginary component X of the function.

[0031] In other words, by detecting the change in the resonant frequency using the measuring instrument 10 of the foreign object detection device 100, the load impedance Z L Changes in the real component R and imaginary component X of the load impedance Z of the object being measured 200 can be detected. L Since the real component R and the imaginary component X of the resonance frequency change before and after a foreign object enters the object 200 being measured, the foreign object present in the object 200 can be detected from the change in the resonance frequency. In particular, by using the resonance frequency to detect foreign objects, the load impedance Z of the object 200 can be detected. L This method can detect not only the imaginary component X, but also foreign substances that affect only the real component R, as well as non-magnetic foreign substances.

[0032] Note that the load impedance Z L While the resolution of measurements detecting the real component R and imaginary component X of a function is limited to about 1% due to disturbances, the frequency-locked loop (PLL) that determines the frequency can be freely changed, and high resolution can be achieved by using a narrow-band bandpass filter.

[0033] Figure 8 shows the load impedance Z in equation (5). L This shows the rate of change of the resonant frequency with respect to the change in the ratio (R / X) of the real component R and the imaginary component X of the load impedance Z. L There is a phase relationship between the ratio of the real component R and the imaginary component X of the load impedance Z. L The rate of change of the resonant frequency reaches a maximum when the ratio of the real component R and the imaginary component X of the impedance reaches a certain value.L By keeping the ratio of the real component R and the imaginary component X close to this value, the load impedance Z L This allows us to maximize the change in the resonant frequency in response to the change in [the variable].

[0034] As described above, by capturing changes in the resonant frequency and the peak value of the resonance, the load impedance Z can be determined. L It is possible to detect minute changes in the real component R and imaginary component X by amplified sensitivity. That is, the load impedance Z can be determined from changes in the resonant frequency and the peak value of the resonance. L The presence of foreign matter within the object 200 that affects the real component R and the imaginary component X can be detected.

[0035] Note that the connection method between the measuring instrument 10 and the object to be measured 200 is not limited to the shunt-through connection shown in Figure 1.

[0036] For example, as shown in Figure 9, a foreign object detection device 102 using a reflection method connection may be used. In the foreign object detection device 102, one port of the measuring instrument 10 is electrically connected to the object to be measured 200 via a transmission line 12a. That is, one of the positive and negative electrodes of the object to be measured 200 is connected to the first port of the measuring instrument 10 via the signal line 14a of the transmission line 12a. In addition, the first port of the measuring instrument 10 is connected to the electrode of the object to be measured 200 that is not connected to the signal line 14a via the return line 16a of the transmission line 12a.

[0037] In the foreign object detection device 102, the observed load impedance Z L,observed This can be expressed by formula (6).

[0038]

number

[0039] Alternatively, for example, as shown in Figure 10, the foreign object detection device 104 may be configured as a series-through connection. In the foreign object detection device 104, the two ports of the measuring instrument 10 are electrically connected to the object to be measured 200 via transmission lines 12a and 12b. Specifically, one of the positive and negative electrodes of the object to be measured 200 is connected to the first port of the measuring instrument 10 via the signal line 14a of transmission line 12a. Also, the electrode of the positive and negative electrodes of the object to be measured 200 that is not connected to the signal line 14a is connected to the second port of the measuring instrument 10 via the signal line 14b of transmission line 12b. Furthermore, the first and second ports of the measuring instrument 10 are connected via the return line 16a of transmission line 12a and the return line 16b of transmission line 12b.

[0040] Alternatively, for example, as shown in Figure 11, the foreign object detection device 106 may be configured with a four-terminal pair connection. In the foreign object detection device 106, the measuring instrument 10 has four ports. In the foreign object detection device 106, the four ports of the measuring instrument 10 are electrically connected to the object to be measured 200 via transmission lines 12a, 12b, 12c, and 12d. Specifically, one of the positive and negative electrodes of the object to be measured 200 is connected to the first port of the measuring instrument 10 via the signal line 14a of the transmission line 12a. Also, the electrode of the positive and negative electrodes of the object to be measured 200 that is connected to the signal line 14a is connected to the second port of the measuring instrument 10 via the signal line 14b of the transmission line 12b. The electrodes of the object to be measured 200 that are not connected to the signal lines 14a and 14b of the positive and negative electrodes are connected to the third port of the measuring instrument 10 via the signal line 14c of the transmission line 12c. The electrodes of the object to be measured 200 that are connected to the signal lines 14c of the positive and negative electrodes are connected to the fourth port of the measuring instrument 10 via the signal line 14d of the transmission line 12d. Furthermore, the first port and the third port of the measuring instrument 10 are connected via the return line 16a of the transmission line 12a and the return line 16c of the transmission line 12c. In addition, the return line 16b of the transmission line 12b of the second port and the return line 16d of the transmission line 12d of the fourth port are electrically open.

[0041] In foreign object detection devices 104 and 106, the observed load impedance Z L,observed This can be expressed by formula (7).

[0042]

number

[0043] In other words, by detecting the change in the resonant frequency using the measuring instrument 10 of the foreign object detection devices 102, 104, and 106, the load impedance Z can be detected in the same way as the foreign object detection device 100. L Changes in the real component R and the imaginary component X can be detected. Therefore, foreign matter present in the object 200 can be detected from the change in the resonant frequency.

[0044] Furthermore, as shown in Figure 12, an impedance adjustment circuit 110 may be provided between the measuring instrument 10 and the object to be measured 200. The load impedance Z of the object to be measured 200 is as shown in Figure 8. L The rate of change of the resonant frequency in response to a change in the impedance is also affected by the impedance value of the object being measured. Therefore, by using the impedance adjustment circuit 110, the apparent load impedance Z of the object being measured 200 can be adjusted. L By changing this, the measurement sensitivity can be improved. The impedance adjustment circuit 110 can also be applied to the configurations of the foreign object detection devices 102, 104, and 106.

[0045] The impedance adjustment circuit 110 can be configured as shown in Figure 13, for example, by connecting impedance elements 20, 22, and 24 in a T-shape. However, the configuration of the impedance adjustment circuit 110 is such that the apparent load impedance Z of the object to be measured 200 is... L Any device that adjusts the impedance will suffice, and a circuit configuration such as one with an impedance element connected to an L-shape may also be used.

[0046] Figure 14 is a flowchart illustrating the method for detecting foreign objects within the object 200 to be measured. The method for detecting foreign objects within the object 200 using the foreign object detection device 100 will be described below with reference to the flowchart in Figure 14. Note that the foreign object detection method described below can also be applied to foreign object detection devices 102, 104, and 106.

[0047] In step S10, the load impedance Z of the object to be measured is measured using transmission lines of two or more different electrical lengths. L The reference value and accuracy are measured. Specifically, the electrical lengths of transmission lines 12a and 12b are converted to adjust the measurement frequency, and then the load impedance Z of the object to be measured 200 is measured. L The reference value and accuracy are measured. For example, multiple transmission lines with different electrical lengths are provided for each of the transmission lines 12a and 12b, and the measurement frequency can be adjusted by changing the electrical lengths of transmission lines 12a and 12b by switching between them. Alternatively, for example, the relative permittivity or relative permeability of transmission lines 12a and 12b can be changed, and the measurement frequency can be adjusted by changing the relative permittivity or relative permeability to change the electrical lengths of transmission lines 12a and 12b. Note that the load impedance Z L The accuracy refers to the load impedance Z in the measurement. L This refers to the variability of the measured values ​​of the real component R and the imaginary component X.

[0048] In step S12, the obtained load impedance Z L Based on the reference value, the impedance of the impedance adjustment circuit 110 is adjusted so that the measurement sensitivity to changes in the resonant frequency or the peak value of the resonance is maximized within the frequency range measurable by the measuring instrument 10. In other words, the load impedance Z of the object to be measured is reduced due to the intrusion of foreign matter into the object to be measured 200. L When the frequency changes, the impedance of the impedance adjustment circuit 110 is adjusted so that the change in the resonant frequency or the peak value of the resonance measured by the measuring instrument 10 is maximized.

[0049] In step S14, the measurement frequency is changed by changing the electrical length of the transmission lines 12a and 12b, while measuring the load impedance Z of the object to be measured 200. L This measures the change in the resonant frequency at various frequencies, and conversely, the load impedance Z in the frequency band where the effect of resonance is excluded. L It comprehensively detects changes in [the subject].

[0050] In step S16, the load impedance Z of the object to be measured 200, which was measured in step S14, is measured. L This determines whether the measurement is highly accurate or low accuracy. Here, high accuracy refers to the load impedance Z in the measurement. L Low accuracy means that the measurement variation of the real component R or imaginary component X is less than a predetermined accuracy threshold, and that it is above the said accuracy threshold. The threshold is preferably set appropriately according to the measurement system including the measuring device, the object to be measured, foreign matter, etc. The load impedance Z of the measured object 200 L If it is determined that the accuracy is high, the process proceeds to step S18; if it is determined that the accuracy is low, the process proceeds to step S20.

[0051] In step S18, the load impedance Z L Assuming that the measurements are taken with high precision, the presence of foreign matter within the object 200 is detected based on changes in the resonant frequency and resonance peak value. Specifically, if the measured change in the resonant frequency and resonance peak value relative to the resonant frequency and resonance peak value in a situation where no foreign matter is present within the object 200 exceeds a predetermined reference change amount, it is determined that foreign matter is present within the object 200.

[0052] On the other hand, in step S20, the load impedance Z near the resonant frequency is L Due to the large variation in measurements, the load impedance Z of the object being measured in the frequency band other than near the resonant frequency is L Based on the measured value, the presence of foreign matter in the object 200 to be measured is detected. Here, the frequency band that is not near the resonant frequency is the load impedance Z in the measurement. LThis is the frequency band in which the measurement variability of the real component R and the imaginary component X exceeds the above-mentioned precision threshold.

[0053] Specifically, the load impedance Z when no foreign matter is present in the object 200 being measured. L If the measured change in the real part component R of the real part component R exceeds a predetermined reference impedance real part change, it is determined that foreign matter is present in the object being measured 200. Alternatively, the load impedance Z in a situation where no foreign matter is present in the object being measured 200 is determined. L If the measured change in the imaginary component X of the impedance exceeds a predetermined reference impedance imaginary component change, it is determined that a foreign object is present in the object 200 being measured. In this case, the sensitivity of foreign object detection may decrease compared to the processing in step S18 when high accuracy is achieved, but the sensitivity of foreign object detection can be maintained to some extent by using a frequency band with small variations in impedance measurement due to resonance.

[0054] Furthermore, in step S20, the load impedance Z of the object to be measured is measured at a frequency that is far from the resonant frequency. L Whether it is best to measure the foreign object is preferably set appropriately depending on the configuration of the foreign object detection device 100, the properties of the object to be measured 200, and the type and characteristics of the foreign object to be detected.

[0055] As described above, by detecting foreign matter within the object 200 based on changes in the resonant frequency or the peak value of the resonance, it is possible to detect foreign matter within the object non-destructively and with high accuracy, even if it only affects the real part of the impedance or is non-magnetic. Furthermore, the load impedance Z of the object 200 L If the measurement is highly accurate, foreign objects are detected by utilizing the change in the resonant frequency, and the load impedance Z of the object being measured 200 is measured. L If the measurement is of low accuracy, the load impedance Z L By utilizing the change in the real component R or imaginary component X of the load impedance Z of the object being measured, foreign matter can be detected. LRegardless of the value or accuracy, this enables foreign object detection with higher sensitivity compared to conventional technologies.

[0056] [Configuration of the present invention] [Configuration 1] The system comprises a measuring instrument and a transmission line that electrically connects the object to be measured and the measuring instrument. A foreign object detection device characterized by measuring the impedance of an electrical circuit including the object to be measured and the transmission line using the measuring instrument, and detecting a foreign object in the object to be measured from the change in the measured impedance. [Configuration 2] The foreign object detection device described in Configuration 1, A foreign object detection device characterized in that the change in impedance is detected from a change in the resonant frequency or the peak value of the resonance of the electrical circuit. [Configuration 3] The foreign object detection device described in configuration 2, A foreign object detection device characterized by having an impedance adjustment circuit between the measuring instrument and the object to be measured, and the impedance of the electrical circuit being adjustable by the impedance adjustment circuit. [Structure 4] A foreign object detection device according to any one of configurations 1 to 3, A foreign object detection device characterized in that the change in impedance is detected in a frequency band in which the variation in the measured values ​​of the real and imaginary components of the impedance is less than a predetermined precision threshold. [Composition 5] A foreign object detection device according to any one of items 1 to 4, A foreign object detection device characterized by adjusting the measurement frequency by changing the electrical length of the transmission line. [Composition 6] The foreign object detection device described in configuration 5, A foreign object detection device characterized by changing the electrical length of a transmission line by switching between multiple transmission lines. [Composition 7] The foreign object detection device described in configuration 5, A foreign object detection device characterized by changing the electrical length of the transmission line by changing at least one of the relative permittivity and relative permeability of the transmission line. [Structure 8] A foreign object detection device according to any one of items 1 to 7, The foreign object detection device is characterized in that the object to be measured is a lithium-ion battery. [Explanation of symbols]

[0057] 10 Measuring instruments, 12 (12a, 12b, 12c, 12d) Transmission lines, 14 (14a, 14b, 14c, 14d) Signal lines, 16 (16a, 16b, 16c, 16d) Return lines, 18 Insulators, 20, 22, 24 Impedance elements, 100, 102, 104, 106 Foreign object detection devices, 110 Impedance adjustment circuits, 200 Objects to be measured.

Claims

1. The system comprises a measuring instrument and a transmission line that electrically connects the object to be measured and the measuring instrument. The impedance of the electrical circuit including the object to be measured and the transmission line is measured using the measuring instrument, and foreign matter is detected in the object to be measured from the change in the measured impedance. A foreign object detection device characterized in that the change in impedance is detected in a frequency band in which the variation in the measured values ​​of the real and imaginary components of the impedance is less than a predetermined precision threshold.

2. The system comprises a measuring instrument and a transmission line that electrically connects the object to be measured and the measuring instrument. The impedance of the electrical circuit including the object to be measured and the transmission line is measured using the measuring instrument, and foreign matter is detected in the object to be measured from the change in the measured impedance. A foreign object detection device characterized by adjusting the measurement frequency by changing the electrical length of the transmission line.

3. A foreign object detection device according to claim 1 or 2, A foreign object detection device characterized in that the change in impedance is detected from a change in the resonant frequency or the peak value of the resonance of the electrical circuit.

4. A foreign object detection device according to claim 3, A foreign object detection device characterized by having an impedance adjustment circuit between the measuring instrument and the object to be measured, and the impedance of the electrical circuit being adjustable by the impedance adjustment circuit.

5. A foreign object detection device according to claim 2, A foreign object detection device characterized by changing the electrical length of a transmission line by switching between multiple transmission lines.

6. A foreign object detection device according to claim 2, A foreign object detection device characterized by changing the electrical length of the transmission line by changing at least one of the relative permittivity and relative permeability of the transmission line.

7. A foreign object detection device according to claim 1 or 2, The foreign object detection device is characterized in that the object to be measured is a lithium-ion battery.

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