JP2012083117A - Inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inspection device capable of inspecting a conductivity distribution of a conductive layer of a lithium ion secondary battery in the state protective sheets such as a polyethylene are stuck together.SOLUTION: The inspection device is equipped with: first and second planar electrodes (2a, 2b) confronted each other with an interposed sheet material (1) to be inspected; an oscillation circuit (4) connected between the first planar electrode and second planar electrode, and provided with a reactance element and a capacitance element; means (5) connected to the oscillation circuit to detect an oscillation frequency of the oscillation circuit; and scanning means for two-dimensionally making a relative displacement for the sheet material and first and second planar electrodes. As for this invention, a conductivity change of the conductive sheet of the sheet material is detected as a change of the oscillation frequency.

Description

The present invention relates to an inspection apparatus for detecting a conductivity distribution of a sheet material in which a conductive sheet and an insulating protective sheet are bonded together.
The present invention also relates to an inspection apparatus for inspecting a sheet-like electrode material used as an anode or a cathode of a lithium ion secondary battery.

  With the development of electric vehicles, there is a strong demand for the development of lithium ion secondary batteries. A lithium ion secondary battery includes an anode, a cathode, a separator disposed between the anode and the cathode, and an electrolyte. The anode has an aluminum sheet member functioning as a current collector and an active material layer, and the active material layer is bonded onto the surface of the aluminum sheet member through a conductive layer (conductive film) having a thickness of about 20 μm. Has been. Similarly, the cathode has a copper sheet member functioning as a current collector and an active material layer, and the active material layer is bonded onto the surface of the copper sheet member via a conductive layer (Patent Document). 1).

The active material layer of the anode has an active material such as lithium cobaltate or lithium manganate having a diameter of about 10 μm, and the surface of the active material is covered with a conductive aid that is a carbon-based fine powder such as carbon black. Yes. The cathode active material layer includes a graphite active material having a diameter of about 10 μm, and the surface of the active material is similarly covered with a carbon-based fine conductive additive.
JP 2010-153140 A

  In a lithium ion secondary battery, a conductive layer for bonding an active material layer is formed on the surface of an aluminum or copper sheet member that functions as a current collector. This conductive layer functions as a binding material for binding the active material layer to an aluminum or copper sheet-shaped current collector and also as a current collector. Therefore, it is necessary to strictly manage the conductivity or resistance value of the conductive layer. For example, when a portion having a high conductivity is partially formed in the conductive layer, local current concentration occurs, and metallic lithium is deposited, causing thermal runaway. In addition, if there is a part with a low electrical conductivity (a part where the resistance value is locally high), the current flowing through the part around the part with a low electrical conductivity increases locally, as well as uneven current distribution. The problem of forming is generated. Such local current concentration causes a reduction in battery life. Therefore, measuring the conductivity distribution of the conductive layer for bonding the active material layer to the current collector and checking whether it is within the allowable conductivity range is the life of the lithium ion secondary battery. It is extremely important to improve

  On the other hand, the conductive layer is an adhesive conductive sheet, and is transported in a structure in which an insulating protective sheet such as polyethylene or resin-coated paper is bonded to both sides of the conductive layer. The conductivity distribution must be measured in the combined state, which hinders quality control of the conductive layer.

  In addition, regarding the sheet-like electrode material constituting the anode or cathode of the lithium ion secondary battery, when the distribution of the conductive auxiliary agent having a diameter of about 1 μm dispersed on the surface of the lithium manganate or graphite active material is not uniform, Current concentration tends to occur, causing a reduction in the life of the lithium ion battery. That is, when there is a location where the distribution amount of the conductive assistant is locally small, the current density at the location is locally low. In addition, when a portion where the distribution amount of the conductive auxiliary agent is partially generated is generated, local current concentration occurs, which causes a problem that adversely affects the life of the battery. Therefore, in the lithium ion secondary battery, inspecting the conductivity distribution of the sheet-like electrode material constituting the anode or the cathode is extremely useful for quality control of the lithium ion secondary battery.

An object of the present invention is to realize an inspection apparatus that can inspect the conductivity distribution of a conductive layer of a lithium ion secondary battery in a state where a protective sheet such as polyethylene or resin-coated paper is bonded.
Another object of the present invention is to provide an inspection apparatus for measuring the conductivity distribution of a sheet-like electrode material constituting the anode and cathode of a lithium ion secondary battery.

The inspection apparatus according to the present invention is an inspection apparatus for measuring the conductivity distribution in the thickness direction of the conductive layer whose both surfaces are covered with an insulating protective sheet,
First and second flat plate electrodes arranged to face each other with a sheet material including a conductive layer and an insulating protective sheet interposed therebetween;
An oscillation circuit connected between the first plate electrode and the second plate electrode and having a reactance element and a capacitor element;
Means for detecting an oscillation frequency of the oscillation circuit connected to the oscillation circuit;
Scanning means for two-dimensionally moving the sheet material and the first and second flat plate electrodes;
A change in conductivity of the conductive layer is detected as a change in oscillation frequency.

  The composite capacity of the sheet-like material in which the conductive layer and the insulating protective sheet are bonded to each other changes according to the conductivity of the conductive layer, and the composite capacity increases as the conductivity of the conductive layer increases. Therefore, in the present invention, a change in the combined capacitance caused by a change in the conductivity of the conductive layer is detected as a change in the oscillation frequency of the oscillation circuit. That is, in an oscillation circuit including a reactance element and a capacitive element, if a sheet-like material is connected in parallel to the reactance element, the oscillation frequency also changes in accordance with the change in the composite capacity of the sheet-like material. The change in conductivity of the conductive layer to be detected can be detected as a change in oscillation frequency. Moreover, the electrical conductivity distribution of the sheet-like material can be measured by two-dimensionally scanning the two plate electrodes connected to the oscillation circuit with respect to the sheet-like material. And it is possible to judge the quality of a sheet-like material by whether the measured electrical conductivity distribution exceeds a predetermined threshold value. Therefore, an inspection apparatus useful for quality control of the conductive layer used for the anode or cathode of the lithium ion secondary battery is realized.

An inspection apparatus according to the present invention is an inspection apparatus for detecting a conductivity distribution in a thickness direction of an active material layer of a sheet-like electrode material having a metal sheet and an active material layer formed on the surface thereof,
An inspection head having an air injection nozzle and a flat plate electrode facing the sheet-like electrode material through an air gap and ejecting an air flow toward the sheet-like electrode material;
An oscillation circuit electrically connected between the flat plate electrode and the metal sheet, and having a reactance element and a capacitor element;
Means for detecting an oscillation frequency of the oscillation circuit connected to the oscillation circuit;
Scanning means for relatively moving the sheet material and the inspection head two-dimensionally;
A change in conductivity in the thickness direction of the active material layer included in the sheet-like electrode material is detected as a change in oscillation frequency.

  When the sheet-like electrode material constituting the anode or cathode of the lithium ion secondary battery and the flat plate electrode are arranged to face each other through an air gap, when viewed as an equivalent circuit, a capacitor Cg is formed by the air gap, and the active material layer Is regarded as a parallel circuit of a resistor Re and a capacitor Ce. Accordingly, a combined capacitance of the capacitors Cg and Ce is formed between the metal sheet and the flat plate electrode. On the other hand, when the resistance value (conductivity) of the active material layer changes, the capacitor Ce changes, so the combined capacitance also changes. Therefore, for example, if an oscillation circuit is connected between the flat plate electrode and the metal sheet, the oscillation frequency of the oscillation circuit also changes in accordance with the change in the combined capacitance. Therefore, the conductivity distribution of the active material layer can be measured based on the change in the oscillation frequency of the oscillation circuit.

  Furthermore, if a DC voltage source is connected between the aluminum or copper metal sheet constituting the anode or cathode and the flat plate electrode, the combined capacitance of the capacitors Cg and Ce changes according to the change in the conductivity of the active material. In addition, the voltage generated at the plate electrode also changes corresponding to the change in the combined capacitance. Or if the alternating voltage of a predetermined frequency is applied between a flat electrode and a metal sheet, the gain and phase of the electric current which flow corresponding to the change of the electrical conductivity of an active material layer will change. Accordingly, it is possible to detect a change in the conductivity of the active material layer based not only on the change in the oscillation frequency but also on the change in the gain and phase of the current and the change in the DC voltage.

  By measuring the conductivity distribution of the sheet-like electrode material used in the lithium ion secondary battery, during the manufacturing process of the sheet-like electrode material, the stirring state of the coating solution in which the active material, the conductive additive and the binder are mixed Pass / fail judgment is possible. That is, during the production process of the anode or cathode sheet-like electrode material, a mixed liquid in which an active material, a conductive additive and a binder are mixed is created, and the mixed liquid is applied to the surface of an aluminum or copper sheet to form a sheet. An electrode material is produced. In this case, it is possible to adjust the stirring time of the mixed solution from the measured conductivity distribution by applying the mixed solution in the manufacturing process onto the metal sheet and measuring the conductivity distribution. For example, when the deviation of the measured conductivity distribution is large, it can be determined that the distribution state of the conductive auxiliary agent is uneven and the stirring time is insufficient. In this case, the stirring time added based on the deviation of the conductive layer distribution can be set. Thus, by measuring the electrical conductivity distribution of the sheet-like electrode material, it is possible to obtain information useful for quality control of the sheet-like electrode material, and to further improve the production yield of lithium ion secondary batteries. it can.

In the present invention, even if both sides of the conductive layer to be inspected are covered with an insulating protective sheet, the change in the composite capacitance caused by the change in conductivity can be measured as the change in oscillation frequency. . As a result, the conductivity distribution of the adhesive conductive layer can be easily detected.
Furthermore, in the present invention, the sheet electrode material used as the anode or cathode of the lithium ion secondary battery has a plate electrode opposed to each other through an air gap, which is caused by a change in conductivity of the active material layer. The combined capacity of the measurement unit changes. As a result, a change in the conductivity of the active material layer can be detected as a change in the oscillation frequency of the oscillation circuit, as a change in phase between voltage and current, or as a change in DC voltage.

It is a figure which shows the basic composition of the inspection apparatus by this invention. It is a figure which shows the test | inspection state of the sheet material containing a conductive layer. It is a figure which shows the equivalent circuit of a sheet material. It is a figure which shows the specific structure of the test | inspection apparatus by this invention. It is a figure which shows the structure of another test | inspection apparatus by this invention. It is a figure which shows the structure of another test | inspection apparatus by this invention. It is a figure which shows the electric circuit of the test | inspection apparatus shown in FIG.

  FIG. 1 is a diagram showing a basic configuration of an inspection apparatus according to the present invention. First and second plate electrodes 2a and 2b are arranged on both sides of the sheet material 1 to be inspected. These 1st and 2nd flat plate electrodes are arrange | positioned so that the sheet material 1 containing a conductive layer may be pinched | interposed, and it may comprise it so that both surfaces of a sheet material may be pressed lightly. The flat plate electrodes 2 a and 2 b are, for example, circular or rectangular metal electrodes having a diameter of 2 mm, and these metal electrodes are arranged so as to be accurately overlapped when viewed in a direction perpendicular to the sheet material 1. The first flat plate electrode 2a is connected to the oscillation circuit 4 via the coaxial cable 3a. The second plate electrode 2a is also connected to the oscillation circuit 4 via the coaxial cable 3b. The two coaxial cables 3a and 3b have the same length and the same capacitance, and their outer skins are grounded.

  In this example, the oscillation circuit 4 uses a Colpitts type oscillation circuit. The oscillation circuit 4 includes a reactance element L and two capacitors C1 and C2 connected in series, and connects the reactance element and the two capacitors in parallel. The coupling point between the reactance element L and the capacitor C1 is connected to the base of the transistor Tr via the capacitor C3. The collector of the transistor Tr is connected to the frequency counter 5, and the oscillation frequency is output from the frequency counter 5. The emitter of the transistor Tr is connected to the connection point between the capacitors C1 and C2. The first coaxial cable 3a is connected to the connection point between the reactance element L and the capacitor C1, and the second coaxial cable 3b is connected to the connection point between the reactance element and the capacitor C2.

  FIG. 2 is a diagrammatic sectional view showing the configuration of the sheet-like material 1 to be inspected. The sheet-like material 1 is a three-layer structure, and includes a conductive layer 10 having a thickness of about 20 μm, and dielectric first and second protective sheets 11 and 12 bonded to both surfaces thereof. Since the conductive layer of the lithium ion secondary battery is an adhesive conductive sheet material, both surfaces of the conductive layer 10 are covered with insulating protective sheets 11 and 12 such as polyethylene. In this example, the conductivity distribution in the thickness direction of the conductive layer 10 is measured in a state where two protective sheets are bonded.

  FIG. 3 shows an equivalent circuit of the sheet-like material 1 including a conductive layer. Since the conductive layer 10 is regarded as a resistor having a dielectric property, it is replaced by a parallel connection of a capacitance C10 and a resistor R. The first and second polyethylene protective sheets 11 and 12 that protect the conductive layer 10 can be regarded as capacitors having capacitances C11 and C12, respectively. Therefore, the sheet-like material 1 to be inspected is represented by the equivalent circuit shown in FIG. 3, and Cs is the entire capacitor of the sheet material including the conductive layer.

Here, the total synthetic capacitance Cs of the sheet material including the conductive layer is expressed by the following equation.
1 / Cs = 1 / C11 + 1 / C10 + 1 / C12 (1) Formula

Further, the capacitance C of a plate capacitor having an area of S, a thickness of d, and a dielectric constant of ε is expressed by the following equation.
C = εS / d (2) Formula

  An increase in the conductivity in the bulk direction of the conductive layer 10 located in the middle of the sheet-like material 1 means that the thickness of the conductive layer 10 is equivalently reduced. In actual measurement, when the thickness of the conductive layer 10 is reduced, the resistance value of the conductive layer 10 is measured to be small. Further, when the thickness of the conductive layer is reduced, the capacitance component of the conductive layer 10 changes according to the conductivity of the conductive layer 10 according to the equation (2), and the conductivity increases (the resistance value decreases). ) And the capacitance increases and the conductivity decreases (the bulk resistance increases), the capacitance decreases.

  Furthermore, when the capacitance of the conductive layer 10 changes, the combined capacitance Cs also changes. That is, since the capacitances of the two protective sheets 11 and 12 take a constant value, from the equation (1), when the capacitance of the conductive layer 10 increases, the combined capacitance Cs increases, and the capacitance of the conductive layer increases. As it decreases, the combined capacity decreases. Therefore, the combined capacitance changes in accordance with the change in the conductivity of the conductive layer 10, and the combined capacitance Cs increases when the conductivity of the conductive layer 10 increases, and the combined capacitance decreases when the conductivity of the conductive layer decreases. .

Next, the oscillation frequency of the oscillation circuit 4 shown in FIG. 1 will be described. When the capacitance of the sheet material is Cs, the capacitance of the two capacitors of the oscillation circuit is Cosc, and the capacitance of the coaxial cable is Ccable, the combined capacitance C0 of the oscillation circuit is expressed by the following equation.
C0 = Cs + Cosc + Ccable (3) Expression The oscillation frequency f of the oscillation circuit is expressed by the following expression where L is the reactance of the reactance element.
f = 1 / (2π√LC0) Equation (4)

  Here, since the electrostatic capacitance Cosc of the two capacitors of the oscillation circuit and the electrostatic capacitance Ccable of the coaxial cable are set to a constant value, according to the change in the conductivity of the conductive layer included in the sheet-like material to be inspected. Thus, the oscillation frequency f of the oscillation circuit 4 changes, the oscillation frequency decreases as the conductivity of the conductive layer 10 increases, and the oscillation frequency increases as the conductivity decreases. As a result, it becomes possible to measure a change in conductivity of the conductive layer included in the sheet-like material as a change in oscillation frequency.

  In the inspection apparatus according to the present invention, the frequency counter 5 detects the oscillation frequency of the oscillation circuit 4. The oscillation frequency is measured in advance using a sheet-like material whose conductivity of the conductive layer 10 is known, and the relationship between the conductivity and the oscillation frequency is measured in advance. In the actual inspection, the conductivity is measured by detecting the oscillation frequency from the frequency counter and collating the detected oscillation frequency with respect to the correspondence relationship between the frequency and the conductivity. When used as an inspection device, an oscillation frequency that prescribes an allowable limit is set in advance, and it is determined whether or not the detected oscillation frequency is within a predetermined allowable range. Can be judged.

  FIG. 4 is a diagram showing a specific example of the inspection apparatus according to the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to the member same as the member used in FIG. The sheet material 1 whose conductivity distribution is to be inspected is intermittently conveyed in the first direction by the first conveying roller pair 20 and the second conveying roller pair 21. As shown in FIG. 4B, the first and second flat plate electrodes 2a and 2b are connected to a ball screw mechanism 22 and are orthogonal to the first direction which is the moving direction of the sheet-like material 1 by the ball screw mechanism. It is continuously moved in the direction of 2 at a constant speed. For the sake of clarity, only the ball screw for moving the plate electrode 2a is shown. In this example, the flat plate electrode is a rectangular electrode. The first and second transport roller pairs intermittently move the sheet material by a distance equal to the width of the plate electrode. Then, every time the sheet-like material 1 is intermittently moved once, the two flat plate electrodes 2a and 2b are moved continuously in the second direction in synchronization with each other, and the movement of the sheet-like material 1 in the first direction and the flat plate The movement of the electrode in the second direction is repeated alternately. Therefore, the sheet-like material 1 is scanned two-dimensionally by the pair of flat plate electrodes 2a and 2b.

  The first and second plate electrodes 2a and 2b are connected to the inspection circuit 23 via coaxial cables 3a and 3b. The inspection circuit 23 includes an oscillation circuit, a frequency counter, and a table that defines the relationship between frequency and conductivity. The inspection circuit 23 detects the oscillation frequency in synchronization with the movement of the sheet material 1 and the movement of the plate electrode. The address in the first direction is detected from the rotation amount of the motor driving the pair of conveying rollers, supplied to the inspection circuit 23, and the second direction is determined by address information from an encoder (not shown) connected to the ball screw 22. The address information is output and supplied to the inspection circuit 23. Therefore, the inspection circuit 23 can detect the conductivity distribution of the sheet-like material 1 from the address information in the first and second directions and the detected oscillation frequency. And about the site | part which exceeded the electric conductivity of tolerance, the value and address of the electric conductivity are memorize | stored in memory.

  FIG. 5 is a diagram showing another inspection apparatus according to the present invention. In this example, an inspection apparatus for inspecting the conductivity distribution of the sheet-like electrode material constituting the anode or cathode of a lithium ion battery will be described. In the anode or cathode sheet-like electrode material, a conductive layer is formed on an aluminum or copper sheet functioning as a current collector, and an active material layer is formed through the conductive layer. In this active material layer, if the carbon-based fine conductive additive is not uniformly distributed on the surface of the active material, for example, a large amount of the conductive additive is locally distributed or the distribution amount of the conductive additive is partial. When the amount is small, the electrical conductivity in the thickness direction of the active material layer changes. On the other hand, when the distribution state of the conductive auxiliary agent is not uniform, local current concentration is likely to occur, which causes a reduction in battery life. The cause of the non-uniform distribution of the conductive auxiliary agent is due to insufficient mixing treatment in the mixing step of mixing the active material, the conductive auxiliary agent and the binder during production. Therefore, the quality control in the manufacturing process of the active material layer can be further improved by measuring the electrical conductivity distribution of the sheet electrode material including the current collector and the active material layer during the manufacturing process of the sheet electrode material. It becomes possible.

  Referring to FIG. 5, the first and second inspection heads 40a and 40b are arranged to face each other in a non-contact state through an air gap with respect to the sheet-like electrode material 30 to be inspected. The sheet-like electrode material 30 has an aluminum sheet 31, and active material layers 32a and 32b are formed on both sides of the sheet material via conductive layers. In this example, the conductivity distribution between the aluminum sheet 31 and the active material layers 32a and 32b, that is, the conductivity distribution in the thickness direction of the active material layer including the conductive layer is measured, and the conductivity distribution is within a predetermined range. Inspect whether or not.

  The first inspection head 40a includes a flat plate electrode 41a and two air injection nozzles 42a. The air injection nozzle is connected to the air source 43a. The flat plate electrode 41a faces the sheet electrode material 30 through an air gap. The air injection nozzle 42 a injects air toward the sheet-like electrode material 30. The plate electrode 41a is connected to the positive electrode of the DC power supply 44a. The negative electrode of the DC power supply is electrically connected to the aluminum sheet 31 via the connection member 45a.

  Similarly, the second inspection head 40b includes a flat plate electrode 41b and two air injection nozzles 42b. The air injection nozzle is connected to the air source 43b. The flat plate electrode 41b faces the sheet-like electrode material 30 through an air gap. The air injection nozzle 42 b injects air toward the sheet electrode material 30. The plate electrode 41b is connected to the positive electrode of the DC voltage source 44b. The negative electrode of the DC voltage source is electrically connected to the aluminum sheet 31 via the connection member 45b.

  During the inspection, air is injected at the same injection pressure from the two air nozzles 42a and 42b facing each other with the sheet-like electrode material 30 therebetween. Thereby, the distance between the 1st flat plate electrode 41a and the sheet-like electrode material 30 is maintained by the substantially constant value, and the distance between the 2nd flat plate electrode 41b and the sheet-like electrode material 30 is also the same. It is maintained at a constant value. Therefore, a series connection of the capacitance due to the air gap and the capacitance component and resistance component due to the active material layer is formed between the first flat plate electrode 41a and the aluminum sheet member 31. Similarly, a series connection of a capacitance due to an air gap and a capacitance component and a resistance component due to the active material layer is formed between the second flat plate electrode 41 b and the aluminum sheet member 31.

Here, the combined capacitance C formed between the aluminum sheet 31 and the flat plate electrode 41 is regarded as a series connection of the capacitance component due to the air gap and the capacitance component of the active material layer. Therefore, when the DC voltage V is applied between the aluminum sheet 31 and the flat plate electrode 41, the charge Q is accumulated in the composite capacitor C. Here, the relationship between the DC voltage V, the combined capacitance C, and the accumulated charge Q is defined by the following equation.
Q = CV

  While maintaining this state, the two plate electrodes 41 a and 41 b are scanned two-dimensionally with respect to the sheet-like electrode material 30. As a scanning method, the two-dimensional scanning method shown in FIG. 4 can be used. When the conductivity of the active material layer at the scanned position changes during the scanning of the plate electrode, the combined capacitance between the aluminum sheet 31 and the plate electrode 41 changes corresponding to the change in the conductivity of the active material layer. To do. On the other hand, since the electric charge Q is accumulated between the aluminum sheet 31 and the flat plate electrode 41, the voltage of the flat plate electrodes 41a and 41b abruptly changes in accordance with the change in the composite capacitance accompanying the change in the conductivity of the active material layer. The voltage value that changes and occurs in the plate electrode corresponds to the change in the conductivity of the active material layer. Therefore, a change in the conductivity of the active material layer is detected by detecting a voltage change generated in the flat plate electrode. The voltage generated in the plate electrode 41a is amplified by the amplifier 46a and input to the inspection circuit 48a via the high pass filter 47a. The inspection circuit 48a measures the conductivity distribution based on the detected voltage value and the address information of the scanning position. At this time, the relationship between the conductivity and the voltage value is obtained in advance using a sheet material having a known conductivity, stored in the memory, and the conductivity distribution is obtained by comparing the corresponding relationship with the detected voltage. Can do.

  The inspection circuits 48a and 48b perform pass / fail determination based on the measured conductivity distribution. For example, the electrical conductivity is measured in advance for the same type of sheet-like electrode material, the average value is obtained, and set as a threshold value. Then, using the change from the threshold set for the measured conductivity distribution, if the change exceeding the threshold exceeds a predetermined range, it can be determined to be defective. For example, by grasping the distribution state of the area determined to be defective, it is possible to take a manufacturing measure such as feeding back to the process of mixing the active material and the conductive additive and further extending the mixing time.

  In the inspection apparatus of this example, the method for detecting the conductivity distribution can be replaced with the method for detecting the conductivity distribution based on the change of the oscillation frequency shown in FIG. In this case, the oscillation circuit 4 and the frequency counter 5 for detecting the oscillation frequency shown in FIG. 1 are used, and the first and second plate electrodes 41a and 41b are connected to the oscillation circuit via the coaxial cables 3a and 3b. In this case, a series connection of a capacitive component by two air layers and a capacitive component and a resistance component of two active material layers is configured between the first flat plate electrode and the second flat plate electrode. When the conductivity of the active material layer changes, the combined capacitance of the series connection changes accordingly, so that the oscillation frequency changes according to the change of the combined capacitance. Therefore, if the two inspection heads 40a and 40b are synchronously two-dimensionally scanned, the conductivity distribution is detected from the change in the oscillation frequency.

  FIG. 6 is a view showing another modification of the inspection apparatus according to the present invention. In this example, a multi-head inspection apparatus in which a plurality of plate electrodes are arranged in a line will be described. Referring to FIG. 6, the conductivity distribution in the thickness direction of the active material layer of the sheet-like electrode material 52 in which the active material layer 51 is formed on the surface of the aluminum sheet 50 is detected. Of course, the present invention is also applied to inspection of a sheet electrode material in which an active material layer is formed on a copper sheet. The inspection head 53 is disposed so as to face the sheet electrode material 52 through an air gap. The inspection head 53 has a plurality of plate electrodes 54a to 54n (only the reference numerals 54a and 54n are shown in the drawing) arranged in a line. An insulating member (not shown) is interposed between adjacent plate electrodes to electrically insulate each other. The inspection head 53 has an air nozzle (not shown) for jetting air toward the sheet-like electrode material, and the distance between the flat plate electrode and the sheet-like electrode material is made constant by the jetted air flow. maintain. The plate electrodes 54a to 54n are connected to gain / phase detectors 55a to 55n (only the reference numerals 55a and 55n are shown) for detecting current gain and phase, respectively. The other ends of the gain / phase detectors 55 a to 55 n are connected to the oscillator 56. The oscillator 56 outputs an AC voltage having a frequency of, for example, about several hundred MHz. The other end of the oscillator 56 is electrically connected to the aluminum sheet 50.

  FIG. 7 is a diagram showing an electric circuit of the above-described embodiment. FIG. 7A shows an equivalent circuit of the inspection head and the sheet-like electrode material. An air gap exists between the plate electrode 54 and the active material layer 51, and this air gap is represented as a capacitor Cg. The active material layer 51 is expressed as a parallel circuit of a capacitor Ce and a resistor Re. Therefore, the measurement part of each flat electrode and sheet-like electrode material is displayed as an equivalent circuit shown in FIG. Here, the capacitor Cg is defined by the distance between the flat plate electrode and the sheet-like electrode material, and takes a substantially constant value. Further, the capacitance of the active material layer also takes a substantially constant value. On the other hand, when the electrical conductivity (resistance value) in the thickness direction of the active material layer 51 changes, the combined capacitance and resistance value of the measurement unit change. In this case, when an AC voltage having a predetermined frequency is applied between each flat plate electrode and the metal sheet, a phase is formed in the flowing current, and this phase corresponds to the combined capacitance of the measurement unit. Therefore, the gain and phase of the current flowing through the measurement unit change according to the change in the combined capacitance of the measurement unit due to the change in the conductivity of the active material layer. In this example, a change in conductivity of the active material layer 51 is detected as a change in gain and phase. In the case of this method, since interference between the plate electrodes does not occur, it is possible to measure the phase distribution by simultaneously applying an inspection voltage to each plate electrode.

  FIG. 7B is a measurement circuit diagram of the entire inspection apparatus. This example is a multi-channel type inspection apparatus, and measures simultaneously using n measurement channels. A parallel circuit of a phase detector for measuring the phase and gain of voltage and current and a resistor R is connected to each plate electrode. Amplifiers A-1 to An are connected to this parallel circuit. That is, the measurement channels ch-1 to ch-n including the amplifier A, the phase detector, and the plate electrode are connected in parallel. Then, the oscillator 56 is connected to the n measurement channels.

  When a voltage having a predetermined frequency is applied to each measurement channel from the oscillator 56, a current is generated in each measurement channel, and the gain and phase of the current are detected by the gain / phase detector. The detected gain and phase are output for each detector and input to an inspection circuit (not shown). In the inspection circuit, the gain and phase are detected for each measurement channel, that is, for each line. Further, the sheet-like electrode material to be inspected is transferred at a constant speed in a direction perpendicular to the extending direction of the inspection head, or in a direction perpendicular to the paper surface of FIG. Detected. In addition, the relationship between the gain and phase and the conductivity is measured in advance using a sheet-like material having a known conductivity, and stored in a memory. Then, the conductivity distribution of the sheet-like electrode material is measured based on the relationship between the detected gain and phase values and the phase and conductivity measured in advance.

1 Sheet material 2a, 2b Flat plate electrode
3a, 3b coaxial cable
4 Oscillating circuit 5 Frequency counter 10 Conductive layer 11, 12 Protective sheet 20, 21 Conveying roller pair 22 Ball screw mechanism 23 Inspection circuit 30 Sheet electrode material 31 Aluminum sheet 32a, 32b Active material layer 40a, 40b Inspection head 41a, 41b Flat plate electrode 42a, 42b Air injection nozzles 43a, 43b Air sources 44a, 44b DC voltage sources 45a, 45b Connection members 46a, 46b Amplifiers 47a, 47b High-pass filters 48a, 48b Inspection circuit

Claims (7)

An inspection device for measuring the conductivity distribution of a conductive layer whose both surfaces are covered with an insulating protective sheet,
First and second flat plate electrodes arranged to face each other with a sheet material including a conductive layer and an insulating protective sheet interposed therebetween;
An oscillation circuit connected between the first plate electrode and the second plate electrode and having a reactance element and a capacitor element;
Means for detecting an oscillation frequency of the oscillation circuit connected to the oscillation circuit;
Scanning means for two-dimensionally moving the sheet material and the first and second flat plate electrodes;
An inspection apparatus for detecting a change in conductivity of the conductive layer as a change in oscillation frequency.   The inspection apparatus according to claim 1, wherein a synthetic capacitance formed between the first plate electrode and the second plate electrode and a capacitor element of the oscillation circuit are connected in parallel, and during the inspection, An inspection apparatus characterized in that a combined capacitance between the plate electrodes changes in accordance with a change in conductivity of the conductive layer, and the change in the combined capacitance is detected as a change in oscillation frequency.   3. The inspection apparatus according to claim 1, wherein the scanning unit includes a first driving unit that intermittently moves the sheet material in a first direction, and a first driving unit and a second plate electrode. And a second driving means for continuously moving in a second direction orthogonal to the direction of the first and second plates of the sheet material to be inspected are two-dimensionally scanned by the first and second plate electrodes. Inspection apparatus characterized by that. An inspection apparatus for detecting a conductivity distribution in a thickness direction of an active material layer of a sheet-like electrode material having a metal sheet and an active material layer formed on a surface thereof,
An inspection head having an air injection nozzle and a flat plate electrode facing the sheet-like electrode material through an air gap and ejecting an air flow toward the sheet-like electrode material;
An oscillation circuit electrically connected between the flat plate electrode and the metal sheet, and having a reactance element and a capacitor element;
Means for detecting an oscillation frequency of the oscillation circuit connected to the oscillation circuit;
Scanning means for relatively moving the sheet material and the inspection head two-dimensionally;
An inspection apparatus for detecting a change in conductivity in a thickness direction of an active material layer included in the sheet-like electrode material as a change in oscillation frequency. An inspection apparatus for detecting a conductivity distribution in the thickness direction of an active material layer of a sheet-like electrode material having a metal sheet and an active material layer formed on both surfaces thereof,
A first inspection head having an air injection nozzle and a first flat plate electrode facing the first surface of the sheet-like electrode material through an air gap and ejecting an air flow toward the sheet-like electrode material; and air A second inspection head having an air injection nozzle and a second flat plate electrode facing the second surface of the sheet-like electrode material through a gap and ejecting an air flow toward the sheet-like electrode material;
An oscillation circuit electrically connected between the first plate electrode and the second plate electrode and having a reactance element and a capacitor element;
Means for detecting an oscillation frequency of the oscillation circuit connected to the oscillation circuit;
A scanning means for two-dimensionally moving the sheet material and the first and second inspection heads;
An inspection apparatus for detecting a change in conductivity in a thickness direction of an active material layer included in the sheet-like electrode material as a change in oscillation frequency. An inspection apparatus for detecting a conductivity distribution in a thickness direction of an active material layer of a sheet-like electrode material having a metal sheet and an active material layer formed on a surface thereof,
An inspection head having an air injection nozzle and a flat plate electrode facing the sheet-like electrode material through an air gap and ejecting an air flow toward the sheet-like electrode material;
A DC voltage source connected between the metal sheet and the plate electrode;
A voltage detecting means connected to the flat plate electrode for detecting a voltage change generated in accordance with a change in conductivity of the active material layer of the sheet-like electrode material;
Scanning means for relatively moving the sheet-like electrode material and the plate electrode in a two-dimensional manner,
An inspection apparatus for detecting an electrical conductivity distribution in a thickness direction of an active material layer of the sheet-like electrode material as a voltage change. An inspection apparatus for inspecting the conductivity distribution in the thickness direction of an active material layer of a sheet-like electrode material having a metal sheet and an active material layer formed on the surface thereof,
An inspection head having a plurality of flat plate electrodes arranged to face the sheet electrode material via an air gap and having an air injection nozzle that jets an air flow toward the sheet electrode material,
An oscillator that applies an alternating voltage of a predetermined frequency to each plate electrode;
A phase detector connected to each plate electrode of the inspection head and detecting a phase between a current and a voltage generated between the plate electrode and the metal sheet;
An inspection apparatus that detects an electrical conductivity distribution of an active material layer of the sheet-like electrode material based on phase information output from the phase detector.

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