JP2013140122A - Air-coupled ultrasonic test equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide air-coupled ultrasonic test equipment that ensures high ultrasonic testing accuracy even if an inspection object is a multi-layer structure where no transverse wave is generated due to mode change.SOLUTION: A multi-layer structure is employed as an inspection object (3). An air- coupled ultrasonic test equipment includes: a longitudinal ultrasonic wave transmitter (5) that transmits toward a measurement point on the inspection object (3) in the air atmosphere a longitudinal ultrasonic wave in an open-tube resonance frequency band including a center frequency f which satisfies a condition of f≒V*N/(2 t) (N is a positive integer), provided that the thickness of the inspection object is t, and the sonic speed of a longitudinal ultrasonic wave propagating in the inspection object is V; and a longitudinal ultrasonic wave receiver (6) that receives the longitudinal ultrasonic wave transmitting through the inspection object (3).

Description

  The present invention relates to an airborne ultrasonic flaw detector.

  An object to be inspected placed in an atmosphere in the air, an ultrasonic transmitter for transmitting longitudinal ultrasonic waves to the object to be inspected, and an ultrasonic reception for receiving ultrasonic waves transmitted through the object to be inspected Some have a child and obliquely enter longitudinal ultrasonic waves propagating in the air with respect to the object to be inspected (see Patent Document 1). In this device, a transverse wave is generated by mode conversion at the incident point of the ultrasonic wave to the object to be inspected, and this transverse wave is used to improve the transmittance of the ultrasonic wave in the object to be inspected and to improve the S / N ratio. ing.

JP 2009-63372 A

By the way, there is a laminate type battery in which a power generation element in which an electrode and a separator are laminated is covered with a laminate film as an exterior material and an electrolyte is filled in the exterior material.
In this laminate type battery, an electrolytic solution exists immediately below the laminate sheet. Since a transverse wave due to mode conversion does not occur inside the electrolyte, the technique of Patent Document 1 cannot be applied in the first place.

  Therefore, an object of the present invention is to provide an aerial ultrasonic apparatus capable of realizing high ultrasonic flaw detection accuracy even for an inspection object such as a multilayer structure in which a transverse wave due to mode conversion does not occur.

The airborne ultrasonic inspection apparatus of the present invention uses a multilayer structure as an object to be inspected. When the thickness of the object to be inspected is t and the sound velocity of the longitudinal wave ultrasonic wave propagating through the object to be inspected is V, f≈V · N / (2t) (where N is a positive integer) (1)
A longitudinal wave ultrasonic transmitter for transmitting a longitudinal wave ultrasonic wave in an open tube resonance frequency band including a center frequency f that satisfies the above condition toward a measurement point on an object to be inspected placed in an atmosphere in air; A longitudinal wave ultrasonic wave receiver for receiving longitudinal wave ultrasonic waves transmitted through the object to be inspected.

  According to the present invention, longitudinal wave ultrasonic waves in the open tube resonance frequency band including the center frequency satisfying the condition of the above expression (1) are irradiated toward the measurement point on the inspection object placed in the atmosphere in the air. Therefore, the transmission intensity of longitudinal wave ultrasonic waves increases. As a result, the S / N ratio is increased, and high ultrasonic flaw detection accuracy can be realized even in a multilayer structure such as a laminate type electric device such as a laminate type battery.

1 is a schematic configuration diagram of an airborne ultrasonic flaw detector according to a first embodiment of the present invention. It is explanatory drawing of the open tube resonance phenomenon of the longitudinal wave ultrasonic wave which arises inside a to-be-inspected object. It is a flowchart of 1st Embodiment for demonstrating calculation of the center frequency of the longitudinal wave ultrasonic wave of the open tube resonance frequency band which propagates to a to-be-inspected object. It is a characteristic figure of the transmission intensity of the longitudinal wave ultrasonic wave with respect to an acrylic board thickness. It is explanatory drawing which shows the mode of a standing wave on the conditions which the transmission intensity of a longitudinal wave ultrasonic wave becomes the maximum and the minimum. It is a characteristic figure of the transmission intensity of the longitudinal wave ultrasonic wave with respect to the gap | deviation from a positive integer. It is a flowchart of 2nd Embodiment for demonstrating calculation of the center frequency of the longitudinal wave ultrasonic wave of the open tube resonance frequency band which propagates to a to-be-inspected object. It is explanatory drawing which shows the influence of the length of the wavelength of the longitudinal wave ultrasonic wave which resonates inside to-be-inspected object, and the thickness fluctuation amount of to-be-inspected object. FIG. 6 is a characteristic diagram of transmission intensity of longitudinal ultrasonic waves with respect to the center frequency of Example 1. 4 is a characteristic diagram of transmission intensity of longitudinal ultrasonic waves with respect to a deviation from a positive integer 1 in Example 1. FIG. It is a schematic perspective view of a laminate type battery. It is a disassembled perspective view of an electric power generation element. 6 is a schematic perspective view of a sample battery of Example 2. FIG. 3 is a longitudinal sectional view of a sample battery of Example 2. FIG. 6 is a characteristic diagram of transmission intensity of longitudinal wave ultrasonic waves according to Example 2. FIG. 6 is a schematic perspective view of a sample battery of Example 3. FIG. 6 is a longitudinal sectional view of a sample battery of Example 3. FIG. 6 is a characteristic diagram of transmission intensity of longitudinal wave ultrasonic waves according to Example 3. FIG. It is a characteristic view of the change rate of the transmission intensity of the longitudinal wave ultrasonic wave of Examples 2 and 3.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an airborne ultrasonic flaw detector 1 according to a first embodiment of the present invention. The aerial ultrasonic flaw detector 1 includes an object to be inspected 3, longitudinal wave ultrasonic transmission / reception sensors 5 and 6, a Z axis moving mechanism 11, an X axis / Y axis moving mechanism 13, a longitudinal wave ultrasonic pulsar receiver 15, and a data collecting apparatus. 19, data processing device 20 and the like.

  In FIG. 1, a device under test 3 is attached to a support mechanism 4 and placed in the air. The support mechanism 4 is fixed to the base 14. Here, the object to be inspected 3 is a so-called laminate type battery (multi-layer structure) comprising an electrode and a separator, and covering a power generation element having a square flat shape as a whole with an aluminum laminate film, and joining and sealing a peripheral portion by heat fusion. Body).

  A longitudinal wave ultrasonic wave transmission sensor (longitudinal wave ultrasonic wave transmitter) 5 that irradiates longitudinal wave ultrasonic waves 7 toward the object to be inspected 3 is passed above the object to be inspected 3, and the object to be inspected is transmitted through the object to be examined 3 below A longitudinal wave ultrasonic wave reception sensor (longitudinal wave ultrasonic wave receiver) 6 for receiving the incoming longitudinal wave ultrasonic wave 8 is provided. Here, the “longitudinal wave ultrasonic wave” is an ultrasonic wave that propagates in the thickness direction (vertical direction in FIG. 1) of the inspection object 3.

  These transmission / reception sensors 5 and 6 are attached to one ends of a pair of support bodies 9 and 10 extending so as to sandwich the object 3 to be inspected, and the other ends of the support bodies 9 and 10 move the support bodies 9 and 10 in the vertical direction. The movable body 12 is connected via a Z-axis moving mechanism 11 that can be used. The Z-axis moving mechanism 11 moves in the height direction (vertical direction in FIG. 1) of the longitudinal wave ultrasonic transmission / reception sensors 5 and 6 with respect to the surface of the object to be inspected according to an instruction from the sensor traverse controller 22.

  The moving body 12 is connected to the base 14 via an X-axis / Y-axis moving mechanism 13 that can move the moving body 12 in the surface direction of the object 3 to be inspected (the horizontal direction in FIG. 1 and the direction orthogonal to the paper surface). ing. The X-axis and Y-axis moving mechanism 13 moves (scans) each measurement point on the surface of the inspection object 3 to an arbitrary point on the surface of the inspection object 3 in accordance with an instruction from the sensor traverse controller 22. . The X-axis / Y-axis moving mechanism 13 and the Z-axis moving mechanism 11 output each measurement point on the surface of the inspection object 3 as three-dimensional position data (X, Y, Z).

  15 transmits a longitudinal wave ultrasonic wave as an input signal to the inspection object 3 toward the longitudinal wave ultrasonic wave transmission sensor 5 and receives a transmission signal of the longitudinal wave ultrasonic wave from the longitudinal wave ultrasonic wave reception sensor 6. Thus, the longitudinal wave ultrasonic pulsar receiver obtains the transmission intensity of longitudinal wave ultrasonic waves.

  The transmission intensity of the longitudinal wave ultrasonic wave from the longitudinal wave ultrasonic pulser receiver 15 and the position data from the X-axis / Y-axis moving mechanism 13 and the Z-axis moving mechanism 11 are input to the data collecting device 19. The data collection device 19 associates these position data with longitudinal wave transmission intensity data.

  The data processing device 20 that receives a signal from the data collection device 19 performs data processing such as two-dimensional imaging of longitudinal intensity transmission data. This two-dimensional image is displayed on the monitor 21. With the two-dimensional image displayed on the monitor 21, it is possible to visually check whether or not there is a defect inside the inspection object 3.

  Further, the data processing device 20 sets a scanning condition (movement condition) in the surface direction of the inspection object 3. The scanning conditions set by the data processing device 20 are sent to the sensor traverse controller 22. In the sensor traverse controller 22, the longitudinal wave ultrasonic transmission / reception sensors 5, 6 are connected via the X-axis / Y-axis movement mechanism 13 and the Z-axis movement mechanism 11 so as to coincide with the scanning conditions in the surface direction of the inspection object 3. It moves in the surface direction of the inspection object 3.

  In the present embodiment, air exists in a part of the propagation path of the longitudinal wave ultrasonic waves (from the longitudinal wave ultrasonic transmission sensor 5 to the subject 3 and from the subject 3 to the longitudinal wave ultrasonic reception sensor 6). Therefore, the ultrasonic wave attenuates in the process of propagating in the air (in the air). In this case, an object to be inspected placed in an atmosphere in the air, an ultrasonic transmitter for transmitting longitudinal ultrasonic waves to the object to be inspected, and an ultrasonic wave transmitted through the object to be inspected are received. 2. Description of the Related Art There is a conventional apparatus that includes an ultrasonic receiver and that makes longitudinal wave ultrasonic waves obliquely incident on an object to be inspected. In this conventional apparatus, a transverse wave is generated by mode conversion at the point of incidence of longitudinal ultrasonic waves on the object to be inspected, and this transverse wave is used to improve the transmittance of ultrasonic waves inside the object to be inspected (transmittance). : Transverse wave> longitudinal wave), S / N (signal intensity against noise) ratio is improved.

  However, when the object to be inspected is a laminated battery in which a power generation element in which an electrode and a separator are laminated is covered with a laminate film as an exterior material and the interior of the exterior material is filled with an electrolyte, There is a problem that it cannot be applied. In a laminate type battery, an electrolytic solution exists immediately below a laminate sheet, and a transverse wave due to mode conversion does not occur inside the electrolytic solution. Therefore, the conventional device cannot be applied in the first place. In addition, since the laminate type battery has an ultrasonic wave propagation path in which electrolyte and thin electrodes are arranged alternately, transverse waves that can improve the S / N ratio are generated even in laminates (solids) such as thin electrodes. do not do.

  Therefore, in the first embodiment of the present invention, open tube resonance is generated in the inspection object 3 by longitudinal wave ultrasonic waves. Here, “open tube resonance” applies open tube resonance in air column vibration. When open tube resonance is generated in the inspection object 3 by the longitudinal wave ultrasonic wave, the transmission intensity of the longitudinal wave ultrasonic wave is increased and the longitudinal wave ultrasonic wave is not attenuated inside the inspection object 3.

  The longitudinal wave has the same vibration direction at each point in the medium and the traveling direction of the wave and cannot be shown as it is, so it is a transverse wave (for example, the displacement in the traveling direction of the wave is positive and the displacement in the reverse direction is negative). In FIG. 2, the state of longitudinal wave ultrasonic waves when open tube resonance is generated inside the inspection object 3 is as shown in FIG. That is, a standing wave is generated when open tube resonance occurs. The standing wave here means that the longitudinal wave ultrasonic wave incident from one end (the upper end in FIG. 2) of the object 3 is reflected at the other end (the lower end in FIG. 2) at the free end, and again at the original end at the free end. It is a wave that repeatedly interferes with reflection and makes both ends belly.

  In FIG. 2, when the thickness of the object to be inspected 3 is t and the sound velocity of the longitudinal wave ultrasonic wave propagating through the object to be inspected 3 is V, the center frequency f of the longitudinal wave ultrasonic wave in the open tube resonance frequency band. Satisfies the following equation (1). Here, N in the formula (1) is a positive integer (1, 2, 3,...).

f≈V · N / (2t) (1)
When the inspection object 3 is irradiated with longitudinal wave ultrasonic waves in the open tube resonance frequency band including the center frequency f that satisfies the condition of the expression (1), a standing wave is generated in the inspection object 3. Fig. 2 shows five types of standing waves, the first standing wave, the second standing wave, the third standing wave, the fourth standing wave, and the fifth standing wave from the left side. Yes.

  In the present embodiment, as shown in FIG. 1, the thickness t of the inspection object 3 and the sound velocity V of the longitudinal wave ultrasonic wave propagating through the inspection object 3 in the thickness direction can be dealt with as shown in FIG. A transmission wave frequency variable device 16 and an input device 17 are attached to the ultrasonic wave pulser receiver 15. That is, when the representative thickness t of the object to be inspected 3 and the sound velocity V of the longitudinal wave ultrasonic wave are input by the input device 17, the transmission wave frequency varying device 16 calculates the center frequency f of the longitudinal wave ultrasonic wave by the above equation (1). To do. In the longitudinal wave ultrasonic pulsar receiver 15, longitudinal wave ultrasonic waves in the open tube resonance frequency band including the center frequency component calculated by the transmission wave frequency varying device 16 are generated, and this is used as an input signal to the device under test 3. This is given to the ultrasonic wave transmission sensor 5. As the input signal, for example, a sine wave signal, a random waveform signal, a chirp signal, or the like may be used.

  The flowchart of FIG. 3 is for calculating the center frequency f of the longitudinal ultrasonic wave in the open tube resonance frequency band that propagates through the device under test 3, and is executed by the transmission wave frequency variable device 16. In steps 1 and 2, the representative thickness t of the object to be inspected 3 and the sound velocity V of the longitudinal ultrasonic wave propagating through the object to be inspected 3 are read. Here, the representative thickness t of the device under test 3 is measured in advance. The sound velocity V of the longitudinal ultrasonic wave propagating through the inspection object 3 is also obtained in advance by conformance. The sound velocity V may be a constant value simply, but it is conceivable to use a value corresponding to the temperature when affected by the temperature.

  In step 3, the center frequency f of the longitudinal wave ultrasonic wave in the open tube resonance frequency band is calculated by the same equation as the above equation (1), and the center frequency f calculated in step 4 is output to the longitudinal wave ultrasonic pulser receiver 15. .

  The longitudinal wave ultrasonic pulsar receiver 15 to which the center frequency f is given generates longitudinal wave ultrasonic waves in the open tube resonance frequency band including the center frequency f, and the generated longitudinal wave ultrasonic waves in the open tube resonance frequency band are inspected. It transmits to the longitudinal wave ultrasonic transmission sensor 5 as an input signal to the body 3. The ultrasonic transmission sensor 5 irradiates the inspection object 3 with the longitudinal wave ultrasonic wave, and the longitudinal wave ultrasonic reception sensor 6 receives the longitudinal wave ultrasonic wave transmitted through the inspection object 5.

  When configured in this manner, longitudinal wave ultrasonic waves resonate inside the device under test 3 as shown in FIG. 2 according to the same principle as open tube resonance of air column vibration. As a result, the transmission intensity of the longitudinal wave ultrasonic wave transmitted through the inside of the inspection object 3 and received by the longitudinal wave ultrasonic wave reception sensor 6 is increased.

  FIG. 4 shows the variation of the thickness of an acrylic plate using longitudinal wave ultrasonic waves in an open tube resonance frequency band including a center frequency f = 333 [kHz] and the sound velocity V of the longitudinal wave ultrasonic waves is 2731 [m / sec]. An example is shown in which open tube resonance occurs at a specific plate thickness and the transmission intensity of longitudinal ultrasonic waves is increased. As shown in FIG. 4, the transmission intensity of longitudinal ultrasonic waves is close to 1 [V] at the two acrylic plate thicknesses where the peak is generated, whereas 0.8 [V] at other acrylic plate thicknesses. You can see that it has not reached.

  Further details will be described. When the above equation (1) is arranged by the thickness t of the object to be inspected on the left side and the wavelength λ of the ultrasonic wave propagating through the object to be inspected on the right side, the following equation (2) is obtained.

t≈ (V / f) / 2 · N = λ / 2 · N (2)
Furthermore, when formula (2) is organized by N,
N = t / (λ / 2) = 2t / λ (3)
The following equation is obtained.

  When the value of N calculated by the equation (3) is infinitely equal to a positive integer (1, 2, 3,...), The longitudinal wave ultrasonic wave transmission intensity is maximized and the S / N ratio is improved. To do. On the other hand, as the value of N becomes equal to 0.5, 1.5, 2.5, which is farthest from a positive integer, the transmission intensity of longitudinal ultrasonic waves decreases, and the S / N ratio decreases. For example, the upper part of FIG. 5 shows how the longitudinal wave ultrasonic wave propagates through the object under the condition that the transmission intensity of the longitudinal wave ultrasonic wave is maximized, and the lower part of FIG. 5 shows the transmission intensity of the longitudinal wave ultrasonic wave is minimized. It shows a state in which longitudinal wave ultrasonic waves propagate through the test object under conditions. As can be seen by comparing the two, the upper part of FIG. 5 shows the state of longitudinal wave ultrasonic waves when open tube resonance occurs.

  FIG. 6 shows an example in which the conditions under which the transmission intensity of longitudinal ultrasonic waves propagating through the acrylic plate is maximized and minimized are confirmed. That is, in FIG. 6, the thickness t of the acrylic plate is set under the condition that the sound velocity V of the longitudinal wave ultrasonic wave propagating through the acrylic plate is 2731 [m / sec] and the center frequency f of the longitudinal wave ultrasonic wave is 333 [kHz]. The value of a positive integer N (1, 2, 3,...) Is changed by shaking from 1 [mm] to 11.5 [mm]. From FIG. 6, when the value of N is equal to a positive integer, for example, when N = 0.96 (deviation 0.04 from the positive integer 1), the transmission intensity of longitudinal ultrasonic waves is 0.92 [V]. It is getting bigger. Similarly, when N = 1.94 (deviation 0.06 from positive integer 1), the transmission intensity of longitudinal ultrasonic waves is relatively high at 0.91 [V]. On the other hand, when N = 0.5 (deviation 0.5 from the positive integer 1), the transmission intensity of longitudinal ultrasonic waves is relatively small, 0.30 [V]. Thus, when the value of N is infinitely equal to a positive integer (1, 2, 3,...), The value of N is farthest from the positive integer. 0.5, 1.5, 2.5. An increase in transmission intensity of about 10 [dB] and an effect of improving the S / N ratio were observed compared to when equal to.

  Further, taking a large positive integer N means that the order of the resonance frequency inside the object to be inspected is increased from the relationship of the above equation (1). As the order of the resonance frequency increases, the inside of the inspection object can be detected with high accuracy and high resolution. Therefore, by using the high-frequency (MHz order) longitudinal wave ultrasonic transmission / reception sensors 5 and 6, it is possible to detect the inside of the inspection object (internal flaw detection) with high-accuracy and high-resolution longitudinal wave ultrasonic waves. Specifically. In laminated batteries, the power generation element is covered with an exterior material and then filled with an electrolyte. At that time, the air inside the power generation element is not replaced with the electrolyte, and air may remain in the interior of the power generation element. is there. When air remains inside the power generation element, no reaction occurs in that portion, and the battery performance is lowered. In this case, if the aerial ultrasonic flaw detector 1 shown in FIG. 1 is used, it can be visually confirmed by the monitor 21 whether or not air particles are generated inside the power generation element. As the air particle becomes smaller, it cannot be detected unless the wavelength is shortened. However, by using the high-frequency longitudinal wave ultrasonic wave as described above, it becomes possible to detect even when the air particle is small.

  Here, the function and effect of the first embodiment will be described.

In the first embodiment, when the multilayer structure is an object to be inspected 3, the thickness of the object to be inspected 3 is t, and the velocity of longitudinal wave ultrasonic waves propagating through the object to be inspected 3 is V. f≈V · N / (2t) (where N is a positive integer) (1)
The longitudinal wave ultrasonic wave transmission sensor 5 that transmits the longitudinal wave ultrasonic wave in the open tube resonance frequency band including the center frequency f that satisfies the above condition toward the measurement point on the inspection object 3 placed in the atmosphere in the air. (Longitudinal wave ultrasonic transmitter) and a longitudinal wave ultrasonic wave reception sensor 6 (longitudinal wave ultrasonic wave receiver) that receives the longitudinal wave ultrasonic wave transmitted through the object 3 to be inspected. According to the first embodiment, the measurement points on the inspected object 3 in which longitudinal wave ultrasonic waves in the open tube resonance frequency band including the center frequency f satisfying the condition of the above expression (1) are placed in the atmosphere in the air. As a result, the transmission intensity of longitudinal ultrasonic waves increases. As a result, the S / N ratio is increased, and high ultrasonic flaw detection accuracy can be realized even in a multilayer structure such as a laminate type battery (laminate type electrical device).

  According to the first embodiment, longitudinal wave ultrasonic waves in the open tube resonance frequency band including the component of the center frequency f are input from the longitudinal wave ultrasonic transmission sensor 5 (longitudinal wave ultrasonic transmitter) to the inspection object 3. A longitudinal wave ultrasonic pulser receiver 15 that receives a signal from a longitudinal wave ultrasonic wave reception sensor 6 (longitudinal wave ultrasonic wave receiver), a longitudinal wave ultrasonic wave transmission sensor 5, and a longitudinal wave ultrasonic wave reception A Z-axis moving mechanism 11 (thickness direction moving mechanism) that can move the position of the sensor 6 relative to the measurement point on the inspection object 3 in the thickness direction of the inspection object 3, and the measurement point on the inspection object 3 The X-axis / Y-axis moving mechanism 13 (surface direction moving mechanism) that can move in the surface direction of the inspection object 3, the position data of the measurement points on the inspection object 3, and the longitudinal wave output from the longitudinal wave ultrasonic pulser receiver 15. Data collected in association with ultrasonic wave transmission intensity data A data collection device 19; a data processing device 20 that receives output data of transmission intensity of longitudinal wave ultrasonic waves from the data collection device 19 to form a two-dimensional image; a monitor 21 that displays the two-dimensional image; Surface direction movement condition setting device (20) for setting movement conditions in the surface direction of the acoustic wave transmission / reception sensors 5 and 6 (longitudinal ultrasonic transducers), and movement conditions set by the surface direction movement condition setting device (20) Since the sensor traverse controller 22 (traverse controller) for controlling the X-axis / Y-axis moving mechanism 13 is provided so that the ultrasonic wave inside the inspected object 3 can be easily obtained at any measurement point on the inspected object 3. Can perform flaw detection.

    According to the first embodiment, the input device 17 that can input the thickness t of the inspection object 3 and the speed of sound V of the longitudinal wave propagating through the inspection object 3, and the thickness input from the input device 17. Since the center frequency f is calculated from t and the sound velocity V, and the transmission wave frequency variable device 16 that transmits the calculated center frequency f to the longitudinal wave pulse pulsar receiver 15 is provided, the thickness t of the object to be inspected 3 and the object to be inspected are included. 3, the center frequency f of the longitudinal wave ultrasonic wave in the open tube resonance frequency band can be easily changed even if the sound velocity V of the longitudinal wave ultrasonic wave propagating through 3 is different.

(Second Embodiment)
The flowchart of FIG. 7 is for calculating the center frequency f of the longitudinal ultrasonic wave in the open tube resonance frequency band that propagates through the device under test 3, and is executed by the transmission wave frequency variable device 16. This replaces FIG. 3 of the first embodiment. The same steps as those in FIG.

  In the first embodiment, the thickness of the laminated battery as the object to be inspected 3 is considered to be substantially constant. Actually, the surface of the laminated battery is not necessarily flat and the thickness is not strictly constant. Therefore, if there is a slight unevenness or wrinkled slope on the surface of the laminated battery, it reaches the longitudinal ultrasonic wave reception sensor 6 due to variations in the incident angle of the longitudinal ultrasonic wave incident on the surface of the laminated battery from the air. The transmission intensity level of longitudinal wave ultrasonic waves that fluctuate varies. In response to this change, if the level falls below the “threshold for determining the detection target”, a slight unevenness or wrinkle on the surface of the laminated battery is erroneously determined as “detection target”. There's a problem.

  Therefore, in the second embodiment, the thickness variation Δt of the inspected object 3 is seen, and when the thickness variation Δt exceeds a predetermined value, it is determined that an erroneous determination occurs, and a positive integer in the above equation (1). Longitudinal ultrasonic waves in an open tube resonance frequency band including the center frequency f where N is 1 are used.

  When the difference from the first embodiment is mainly described, steps 11 to 13 are newly added in the flow of FIG.

  First, in step 11, the thickness variation Δt of the inspection object 3 is read. The thickness variation amount Δt of the object to be inspected 3 is obtained in advance and is input by the input device 17 of the transmission wave frequency variable device 16.

  In step 12, the thickness variation Δt is compared with a predetermined value. The predetermined value is a determination value for determining whether an erroneous determination occurs, and is determined in advance. When the thickness variation amount Δt is equal to or greater than a predetermined value, it is determined that an erroneous determination occurs, and the process proceeds to step 13 where a center frequency f having a positive integer of 1 is calculated by the following equation (4). As can be seen by comparing the equation (4) with the above equation (1), the equation (4) is N = 1 in the equation (1).

f≈V / (2t) (4)
In step 4, the center frequency f calculated in step 13 is output to the longitudinal wave ultrasonic pulsar receiver 15.

  On the other hand, when the thickness variation amount Δt is less than the predetermined value in step 12, it is determined that no erroneous determination occurs, and the process proceeds to step 3 to calculate the center frequency f of the longitudinal ultrasonic wave by the same equation as the above equation (1). . In step 4, the center frequency f calculated in step 3 is output to the longitudinal wave ultrasonic pulsar receiver 15.

  The longitudinal wave ultrasonic pulsar receiver 15 to which the center frequency f is given generates longitudinal wave ultrasonic waves in the open tube resonance frequency band including the center frequency f, and the generated longitudinal wave ultrasonic waves in the open tube resonance frequency band are inspected. It transmits to the longitudinal wave ultrasonic transmission sensor 5 as an input signal to the body 3. The longitudinal wave ultrasonic wave transmission sensor 5 irradiates the inspection object 3 with longitudinal wave ultrasonic waves in the open tube resonance frequency band, and the longitudinal wave ultrasonic wave reception sensor 6 receives the longitudinal wave ultrasonic wave transmitted through the inspection object 5. .

  Next, the reason why the center frequency f is calculated by the above equation (4) in which the positive integer N is 1 when the thickness fluctuation amount Δt is equal to or greater than a predetermined value will be described.

  When the above equation (1) is modified and arranged by the thickness t of the object to be inspected on the left side and the wavelength λ of the longitudinal ultrasonic wave propagating through the object to be inspected on the right side, the following equation (2) is obtained.

t≈ (V / f) / 2 · N = λ / 2 · N (2)
When N = 1, that is, by determining the center frequency of longitudinal ultrasonic waves in the open tube resonance frequency band so that a primary standing wave is generated in the thickness direction of the object to be inspected, equation (2) is (5).

t = λ / 2 (5)
From equation (5) λ = 2t (6)
Thus, the wavelength λ of the longitudinal ultrasonic wave propagating through the inside of the inspection object 3 becomes the longest.

  Here, assuming that the thickness t of the object to be inspected 3 has a thickness variation amount of ± Δt, the value of N is affected by the thickness variation. Substituting t ± Δt in place of t in the above equation (3) yields the following equation (7).

N = t / (λ / 2)
= 2 (t ± Δt) / λ = 2t / λ ± 2Δt / λ (7)
As can be seen by comparing equation (7) with equation (3), the value of N varies by the amount of the second term on the right side of equation (7), that is, ± 2Δt / λ with respect to a positive integer value. .

  Here, if the wavelength λ of the longitudinal ultrasonic wave propagating inside the object to be inspected is as large as possible with respect to the thickness fluctuation amount Δt, ± 2Δt / λ≈0, and the value of N is unlimitedly a positive integer ( 1, 2, 3 ...). At this time, the transmission intensity of the longitudinal wave ultrasonic wave received by the longitudinal wave ultrasonic wave reception sensor 6 does not substantially change even if a thickness variation amount of ± Δt exists in the object to be inspected. There is almost no impact on the fluctuations. On the other hand, when the frequency of longitudinal ultrasonic waves propagating inside the object to be inspected is high (wavelength λ is short), ± 2Δt / λ approaches ± 0.5. That is, since the value of N approaches a positive integer ± 0.5, the transmission intensity of the longitudinal wave ultrasonic wave received by the longitudinal wave ultrasonic wave reception sensor 6 decreases (the transmission intensity of the longitudinal wave ultrasonic wave fluctuates). .

  FIG. 8 shows the influence of the length of the longitudinal ultrasonic wave resonating inside the inspection object and the thickness variation Δt of the inspection object. As can be seen from FIG. 8, when the same thickness variation Δt exists, when the wavelength λ is the longest, N = 1, the influence is greater than when N = 2, 3, where the wavelength λ is relatively short. I understand that there are few. As described above, the longer the wavelength λ, the less the influence of the thickness variation Δt of the object to be inspected. Therefore, when the thickness variation Δt is equal to or greater than a predetermined value, the transmission intensity of longitudinal wave ultrasonic waves is reduced. The center frequency when N is 1 is selected so that the longitudinal ultrasonic wave having the longest wavelength λ propagates through the object to be inspected. As a result, the primary standing wave having the longest wavelength λ in the thickness direction is generated in the object to be inspected (see the left side of FIG. 8). Therefore, when a laminated battery is used as the object to be inspected, Even if there is a thickness variation such as an inclined portion due to a slight unevenness or wrinkle, the influence can be remarkably reduced.

In the second embodiment, an electric device in which a power generation element composed of an electrode and an electrolyte is covered with a flat film as an exterior material is an inspection object 3, and the thickness of the inspection object is t, and the inspection object When the velocity of longitudinal ultrasonic wave propagating in the wave is V, f≈V / (2t) (4)
The longitudinal wave ultrasonic wave transmission sensor 5 that transmits the longitudinal wave ultrasonic wave in the open tube resonance frequency band including the center frequency f that satisfies the above condition toward the measurement point on the inspection object 3 placed in the atmosphere in the air. (Longitudinal wave ultrasonic transmitter) and a longitudinal wave ultrasonic wave reception sensor 6 (longitudinal wave ultrasonic wave receiver) that receives the longitudinal wave ultrasonic wave transmitted through the object 3 to be inspected. According to the second embodiment, longitudinal wave ultrasonic waves in the open tube resonance frequency band including the center frequency f satisfying the condition of the above expression (4) are measured on the inspected object 3 placed in the atmosphere in the air. Irradiating to a point. That is, since the longitudinal wave ultrasonic wave having the longest wavelength λ in the open tube resonance frequency band is adopted, the attenuation of the longitudinal wave ultrasonic wave due to the influence of the variation Δt in the thickness direction of the laminated battery can be further reduced. it can. Thereby, even if the surface of the laminate film, which is an exterior material of the laminate type battery, has an inclined portion due to unevenness or wrinkles, high ultrasonic flaw detection accuracy can be realized.

Example 1
Example 1 is an example of the first embodiment. An acrylic plate having a representative thickness of 4 [mm] and a sound velocity of 2731 [m / sec] when longitudinal wave ultrasonic waves propagate was used as an object to be inspected. The acrylic plate was irradiated with longitudinal ultrasonic waves in an open tube resonance frequency band including center frequencies of 175 [kHz], 333 [kHz], and 741 [kHz]. That is, when the longitudinal wave ultrasonic wave of the open tube resonance frequency band including the center frequency of 333 [kHz] is irradiated, the transmission intensity of the longitudinal wave ultrasonic wave becomes 0.92 [V]. Similarly, when the longitudinal wave ultrasonic wave in the open tube resonance frequency band including the center frequency of 175 [kHz] is irradiated, the transmission intensity of the longitudinal wave ultrasonic wave is 0.44 [V]. Similarly, when the longitudinal wave ultrasonic wave in the open tube resonance frequency band including the center frequency of 741 [kHz] is irradiated, the transmission intensity of the longitudinal wave ultrasonic wave is 0.19 [V]. FIG. 9 shows a summary of these results.

  Here, when N is calculated when the center frequency is 333 [kHz], N = 0.96, that is, the deviation from the positive integer 1 is 0.04. Similarly, when N is calculated when the center frequency is 175 [kHz], N = 0.52, that is, the deviation from the positive integer 1 is 0.48. Similarly, when N is calculated when the center frequency is 741 [kHz], N = 2.20, that is, the deviation from the positive integer 1 is 0.20.

  Therefore, when the result of FIG. 9 is re-examined with the deviation from the positive integer 1 as the horizontal axis, the result of FIG. 10 is obtained. From FIG. 10, when the center frequency is 333 [kHz], the condition of the center frequency f≈V · N / (2t) is best satisfied, and the transmission intensity of longitudinal ultrasonic waves is maximized.

(Example 2)
Example 2 is an example of the second embodiment. Here, first, the laminate type battery 31 will be outlined with reference to FIGS.

  FIG. 11 is a schematic perspective view of a laminated battery 31 such as a lithium ion secondary battery, and FIG. 12 is an exploded perspective view of the power generation element 32.

  As shown in FIG. 11, in the laminate type battery 31, a substantially square flat power generation element 32 in which a charge / discharge reaction actually proceeds is sealed inside a laminate film 44 (flat film) that is a battery exterior material. Has a structured. Specifically, the polymer-metal composite laminate film is used as a battery exterior material, and its peripheral portions 44a, 44b, 44c, and 44d are joined by thermal fusion, so that the power generating element 32 is housed and sealed. doing.

  As shown in FIG. 12, the power generation element 32 has a configuration in which a negative electrode 34, a separator 32, and a positive electrode 38 are stacked in this order. Here, the negative electrode 34 is obtained by disposing negative electrode active material layers 36 and 36 on both surfaces of a rectangular thin plate-like negative electrode current collector 35. Similarly, the positive electrode 38 is obtained by disposing positive electrode active material layers 40 and 40 on both surfaces of a rectangular thin plate-shaped positive electrode current collector 39. The separator 42 is mainly formed from a porous thermoplastic resin. Since the separator 42 holds the electrolytic solution, an electrolyte layer is formed integrally with the separator 42. In other words, an electrolyte layer having a function as a Li ion transfer medium between two electrodes is composed of a liquid electrolyte and a microporous membrane separator 42 containing a resin.

  Thus, the adjacent negative electrode 34, separator 42 (including the electrolytic solution), and positive electrode 38 constitute one unit cell layer 43 (unit cell). In the single cell layer 43, electrons and ions move between the two electrodes to perform a charge / discharge reaction (electrochemical reaction) of the battery. Therefore, it can be said that the laminated battery 31 has a configuration in which the single battery layers 43 are stacked to be electrically connected in parallel. Further, a seal portion (insulating layer) for insulating between the adjacent negative electrode current collector 35 and positive electrode current collector 39 may be provided on the outer periphery of the unit cell layer 43. All of the outermost negative electrode current collectors 35 located on both outermost layers of the power generation element 32 are only on one side (in FIG. 12, the uppermost negative electrode current collector 35 has only the lower surface, and the lowermost negative electrode current collector 35 has Is disposed on the upper surface only).

  The negative electrode current collector 35 and the positive electrode current collector 39 are attached with two high voltage tabs, a negative electrode tab 45 and a positive electrode tab 46, which take out electrons entering and exiting each electrode (negative electrode or positive electrode) to the outside. It is led out of the laminate film 44 so as to be sandwiched between the two. Since the power generation element 32 is formed in a square flat shape having four sides as a whole, the two high-power tabs 45 and 46 are collectively led to the outside only from one side of the four sides (see FIG. 11). In FIG. 12, it goes without saying that the negative electrode tabs 45 and the positive electrode tabs 46 are electrically connected. This completes the outline of the laminate-type battery 31.

  Now, the sample laminate type battery (hereinafter referred to as “sample battery”) 31 used as the object to be inspected in Example 2 has a representative thickness of 7 [mm] and is 0.73 [mm] due to the influence of wrinkles or the like. A thickness variation occurred. In the following description, it is assumed that the sample battery 31 of Example 2 was as shown in FIG.

  FIG. 14 is a longitudinal sectional view of the sample battery 31 of Example 2 along the alternate long and short dash line on the surface in FIG. As shown in FIG. 14, the sample battery 31 of Example 2 has two convex portions 51 and 52 on the surface (upper surface) due to thickness variation.

  In this case, first, as shown in FIGS. 13 and 14, the longitudinal wave ultrasonic transmission / reception sensors 5 and 6 were set at the first measurement position (referred to as “measurement position A”) (see the solid line). And after irradiating the longitudinal wave ultrasonic wave of the open tube resonance frequency band containing the center frequency 180 [kHz] and calculating | requiring the transmission intensity of the longitudinal wave ultrasonic wave, the open tube resonance frequency band containing the center frequency 746 [kHz] The longitudinal wave ultrasonic wave was irradiated, and the transmission intensity of the longitudinal wave ultrasonic wave was obtained.

  Next, as shown in FIGS. 13 and 14, the longitudinal ultrasonic transmission / reception sensors 5 and 6 (referred to as “measurement position B”) shifted slightly from the measurement position A along the alternate long and short dash line. Set (see broken line). In the same manner as described above, longitudinal wave ultrasonic waves in an open tube resonance frequency band including a center frequency of 180 [kHz] are irradiated, the transmission intensity of the longitudinal wave ultrasonic waves is obtained, and an open wave including a center frequency of 746 [kHz] is then obtained. Longitudinal ultrasonic waves in the tube resonance frequency band were irradiated, and the transmission intensity of the longitudinal wave ultrasonic waves was obtained.

  FIG. 15 summarizes the relationship between the transmission intensity of the longitudinal wave ultrasonic wave thus obtained and the measurement position. The horizontal axis represents the measurement position, and the vertical axis represents the transmission intensity of the longitudinal wave ultrasonic wave. Here, the wavelength λ of longitudinal wave ultrasonic waves having a center frequency of 180 [kHz] is 9.1 [mm], and the wavelength λ of longitudinal wave ultrasonic waves having a center frequency of 746 [kHz] is 2.2 [mm]. From FIG. 15, the longitudinal wave ultrasonic wave of 9.1 [mm] having a relatively long wavelength λ has a transmission intensity variation of 0.09 [V], whereas the wavelength λ is relatively short. In longitudinal wave ultrasonic waves of 2.2 [mm], the amount of change in transmission intensity is as large as 0.53 [V].

  As described above, according to the second embodiment, the longitudinal wave ultrasonic wave having a relatively long wavelength λ of 9.1 [mm] is caused by a slight unevenness (thickness variation) on the battery surface of the sample battery 31. It can be seen that the amount of change in ultrasonic transmission intensity can be reduced.

(Example 3)
Example 3 is also an example of the second embodiment. Here again, the sample battery 31 of Example 3 is described as shown in FIG. FIG. 17 is a longitudinal sectional view of the sample battery 31 of Example 3 along the two-dot chain line on the surface in FIG. As shown in FIG. 17, the laminate type battery 31 of Example 3 has a convex portion 53 on one surface (upper surface) due to thickness variation.

  In this case, first, as shown in FIGS. 16 and 17, the longitudinal wave ultrasonic transmission / reception sensors 5 and 6 were set at the third measurement position (referred to as “measurement position C”) (see the solid line). And after irradiating the longitudinal wave ultrasonic wave of the open tube resonance frequency band containing the center frequency 180 [kHz], and determining the transmission intensity of the longitudinal wave ultrasonic wave, the open tube resonance frequency including the center frequency of 746 [kHz]. The longitudinal ultrasonic wave of the band was irradiated and the transmission intensity of the longitudinal ultrasonic wave was determined.

  Next, as shown in FIGS. 16 and 17, the longitudinal wave ultrasonic transmission / reception sensors 5 and 6 are moved to the fourth measurement position (referred to as “measurement position D”) slightly shifted from the measurement position C along the two-dot chain line. Was set (see long dashed line). In the same manner as described above, longitudinal wave ultrasonic waves in an open tube resonance frequency band including a center frequency of 180 [kHz] are irradiated, the transmission intensity of the longitudinal wave ultrasonic waves is obtained, and an open wave including a center frequency of 746 [kHz] is then obtained. Longitudinal ultrasonic waves in the tube resonance frequency band were irradiated, and the transmission intensity of the longitudinal wave ultrasonic waves was obtained.

  Next, as shown in FIGS. 16 and 17, longitudinal wave ultrasonic transmission / reception sensors 5 and 6 are moved to a fifth measurement position (referred to as “measurement position E”) further shifted along the two-dot chain line from the measurement position D. Was set (see short dashed line). Then, as described above, after irradiating longitudinal wave ultrasonic waves in an open tube resonance frequency band including the center frequency 180 [kHz], and determining the transmission intensity of the longitudinal wave ultrasonic waves, the center frequency includes 746 [kHz]. Longitudinal ultrasonic waves in the open tube resonance frequency band were irradiated, and the transmission intensity of the longitudinal wave ultrasonic waves was obtained.

  FIG. 18 summarizes the relationship between the transmission intensity of the longitudinal wave ultrasonic wave thus obtained and the measurement position. The measurement position is plotted on the horizontal axis, and the transmission intensity of the longitudinal wave ultrasonic wave is plotted on the vertical axis. Here, the wavelength λ of longitudinal wave ultrasonic waves having a center frequency of 180 [kHz] is 9.1 [mm], and the wavelength λ of longitudinal wave ultrasonic waves having a center frequency of 746 [kHz] is 2.2 [mm]. As shown in FIG. 18, in the longitudinal wave ultrasonic wave of 9.1 [mm] having a relatively long wavelength λ, the transmission intensity change amount is 0.21 [V], whereas the wavelength λ is relatively short. In longitudinal wave ultrasonic waves of 2.2 [mm], the amount of change in transmission intensity is as large as 0.53 [V].

  Thus, according to the third embodiment, as in the second embodiment, the longitudinal wave ultrasonic wave having a relatively long wavelength λ of 9.1 [mm] is slightly more uneven on the battery surface of the sample battery 31. It can be seen that the amount of change in the transmission intensity of longitudinal ultrasonic waves due to (thickness variation) can be reduced.

(Summary of Examples 2 and 3)
FIG. 19 is a table summarizing the rate of change in the transmission intensity of longitudinal wave ultrasonic waves from the amount of change in the transmission intensity of longitudinal wave ultrasound obtained in Examples 2 and 3. In FIG. 19, the horizontal axis is arranged by thickness variation / (λ / 4) [%]. From FIG. 19, the longitudinal frequency ultrasonic wave with a relatively low center frequency of 180 [kHz] has a relatively high frequency longitudinal wave with a ratio of the thickness variation to the wavelength λ of 746 [kHz]. It is smaller than ultrasound. From this, it can be seen that the deviation from the resonance condition is small, and the rate of change of the transmission intensity of the longitudinal wave ultrasonic wave is relatively small. N = 1, 2, and 3 are data obtained by theory and experiment.

  In the embodiment, the longitudinal wave ultrasonic transmission / reception sensors 5 and 6 are described as a set, but the present invention is not limited to this. Two or more sets of longitudinal wave ultrasonic transmission / reception sensors 5 and 6 may be provided.

  In the embodiment, the laminated battery is exemplified as the electric device, but the electric device is not limited thereto. As long as it is a multilayer structure, it can be applied to other types of secondary batteries and even primary batteries. Moreover, it is applicable not only to batteries but also to electrochemical capacitors such as electric double layer capacitors.

1 Longitudinal Wave Ultrasonic Flaw Detector 3 Inspected Object 5 Longitudinal Wave Ultrasonic Transmitter Sensor (Longitudinal Wave Ultrasonic Transmitter)
6 Longitudinal wave ultrasonic sensor (longitudinal wave ultrasonic receiver)
11 Z-axis movement mechanism (thickness direction movement mechanism)
13 X-axis / Y-axis moving mechanism (plane direction moving mechanism)
15 Longitudinal wave ultrasonic pulser receiver (longitudinal wave ultrasonic pulser receiver)
16 Transmission Wave Frequency Variable Device 19 Data Collection Device 20 Data Processing Device 21 Monitor 22 Sensor Traverse Controller (Traverse Controller)
31 Laminated battery (multilayer structure)

Claims (4)

When the multilayer structure is an object to be inspected, the thickness of the object to be inspected is t, and the velocity of longitudinal wave ultrasonic waves propagating through the object to be inspected is V. f≈V · N / (2t) (where N is Positive integer)
An ultrasonic transmitter for transmitting longitudinal wave ultrasonic waves in an open tube resonance frequency band including a center frequency f satisfying the above condition toward a measurement point on an object to be inspected placed in an atmosphere in air; An aerial ultrasonic flaw detector comprising: a receiver that receives longitudinal ultrasonic waves that pass through a body. An electrical device in which a power generation element composed of an electrode and an electrolyte is covered with a flat film as an exterior material is an object to be inspected. The thickness of the object to be inspected is t, and longitudinal wave ultrasonic waves that propagate through the object to be inspected. When the speed of sound is V, f ≒ V / (2t)
A longitudinal wave ultrasonic transmitter for transmitting a longitudinal wave ultrasonic wave in an open tube resonance frequency band including a center frequency f that satisfies the above condition toward a measurement point on an object to be inspected placed in an atmosphere in air; An aerial ultrasonic flaw detector comprising: a longitudinal wave ultrasonic wave receiver that receives a longitudinal wave ultrasonic wave transmitted through an object to be inspected. A longitudinal wave ultrasonic wave in an open tube resonance frequency band including the center frequency component is generated as an input signal input from the longitudinal wave ultrasonic transmitter to the object to be inspected, and from the longitudinal wave ultrasonic receiver. A longitudinal ultrasonic pulsar receiver that receives the signal;
A thickness direction moving mechanism capable of moving a position of the longitudinal wave ultrasonic transmitter and the longitudinal wave ultrasonic receiver with respect to a measurement point on the inspection object in a thickness direction of the inspection object;
A surface direction moving mechanism capable of moving a measurement point on the inspection object in a surface direction of the inspection object; and
A data collection device that collects positional data of measurement points on the object to be inspected and data of transmission intensity of longitudinal wave ultrasonic waves output from the longitudinal wave ultrasonic pulser receiver;
A data processing device that receives the output data of the transmission intensity of the longitudinal ultrasonic waves from the data collection device to form a two-dimensional image;
A monitor that displays this two-dimensional image;
A plane direction movement condition setting device for setting a plane direction movement condition of the longitudinal wave ultrasonic transceiver; and
The aerial ultrasonic flaw detector according to claim 1, further comprising: a traverse controller that controls the surface direction moving mechanism so as to satisfy the movement condition set by the surface direction movement condition setting device.   An input device that can input the thickness of the object to be inspected and the sound velocity of longitudinal ultrasonic waves propagating through the object to be inspected, and the center frequency calculated from the thickness and sound velocity input from the input device, 4. The airborne ultrasonic flaw detector according to claim 3, further comprising a transmission wave frequency variable device that transmits a frequency to the longitudinal ultrasonic pulser / receiver.

Images