Automatic ultrasonic examination device, automatic ultrasonic examination method and production method using the examination method

An automatic ultrasonic examination device includes an ultrasonic test instrument, a robot arm, and a control device. The ultrasonic test instrument includes an ultrasonic probe to send ultrasonic and detecting reflected waves while being in contact with the spot-welded portion, and an ultrasonic test instrument main device connected to the ultrasonic probe to convert the reflected wave detection signals received from the ultrasonic probe into test information. The control device includes a real center location computing unit to identify a real center location of the spot-welded portion with reference to pieces of test information obtained around a preset tentative center location of the spot-welded portion, and a determination unit to check quality of the spot-welded portion with reference to test information obtained at the real center location.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to automatic ultrasonic examination devices, automatic ultrasonic examination methods and production methods using the examination method. The invention particularly relates to automatic ones using robots.

2. Background Art

It has been conventionally known that there is a method using ultrasonic test instruments as nondestructive examination methods for inspecting spot-welded portions. The ultrasonic test instrument includes, for example, an ultrasonic probe for sending ultrasonic waves and detecting the reflected waves while being in contact with spot-welded portions, and an ultrasonic test instrument main device connected to the ultrasonic probe for receiving reflected wave detection signals from the ultrasonic probe and converting them into test data. In the ultrasonic test instrument, since ultrasonic waves are attenuated through a nugget formed inside of the spot-welded portion, it is possible to check quality of the welded portions, as shown in Japanese Unexamined Patent Publication H11-326287

PROBLEMS TO BE SOLVED BY THE INVENTION

In order to test precisely the spot-welded portions, it is necessary for the ultrasonic probe to contact the center location of the nugget for an ultrasonic test. However, the precise center location of the nugget is different from the apparent center location of weld scars in many cases, so that it is difficult to identify the precise center location from the appearance. Even if the precise center location is identified, since levels of the reflected waves relative to the nugget are different depending on incident angles of the ultrasonic waves, it is difficult to check precisely the quality of the spot-welded portions and troublesome to adjust the angle of the ultrasonic probe. Especially if the spot-welded portion is formed on a curved surface, it consumes a lot of working hours. Accordingly, if an operator performs a test operation, the accuracy of the quality check and the operation efficiency are extremely deteriorated.

Alternatively, although an apparatus has been proposed that performs the test operation by robots, no method of the operation has been proposed to identify the center location of the nugget in the spot-welded portions or to adjust the optimum incident angle of the ultrasonic waves efficiently and highly accurately.

SUMMARY OF THE INVENTION

It is an object of the present invention to check quality of spot-welded portions using an ultrasonic test instrument highly accurately and at high speed.

Unit for Solving Problems

An automatic ultrasonic examination device according to a first aspect of the present invention is provided to test automatically a spot-welded portion of a test object. The device includes an ultrasonic test instrument, a robot arm, and a control device. The ultrasonic test instrument includes an ultrasonic probe to send ultrasonic waves and detecting reflected waves while being in contact with the spot-welded portion and an ultrasonic test instrument main device connected to the ultrasonic probe to convert the reflected wave detection signals received from the ultrasonic probe into test information. The robot arm includes a plurality of joints to adjust three-dimensionally the posture and location of the ultrasonic probe relative to the spot-welded portion. The control device is connected to the ultrasonic test instrument and robot arm to communicate data and signals with the ultrasonic test instrument and robot arm. The control device includes a real center location identifying unit to identify a real center location of the spot-welded portion with reference to pieces of test information obtained around a preset tentative center location of the spot-welded portion, and a determination unit to check quality of the spot-welded portion with reference to the test information obtained at the real center location.

In the automatic ultrasonic examination device, since the real center location identifying unit can identify the real center location of the spot-welded portion, i.e., the center location of a nugget that cannot be judged from the appearance, it is possible to check quality of the spot-welded portions with a high degree of accuracy compared to the operation by the operator. In addition, the automatic operation by the control device and robot arm makes it possible to perform the operation at high speed compared to the operation by the operator.

An automatic ultrasonic examination device according to a second aspect of the present invention is the device of the first aspect, wherein the control device further includes an optimum test information unit to obtain test information optimum to check quality of the spot-welded portion with reference to pieces of test information obtained around the central axis of the real center location while pivoting on a contact point between the ultrasonic probe and the real center location. The determination unit checks the quality of the spot-welded portion with reference to the optimum test information.

In the automatic ultrasonic examination device, since the determination unit checks the quality with reference to the optimum test information, it is possible for the determination unit to check the quality with a high degree of accuracy.

An automatic ultrasonic examination device according to a third aspect of the present invention is the device of the first or second aspect, wherein the location and number of the test points can be preset by the control device.

In the automatic ultrasonic examination device, since locations and number of the test points can be preset, it is possible to deal with various spot-welded portions in size.

An automatic ultrasonic examination device according to a fourth aspect of the present invention is the device of any of the first to third aspects, wherein a space between the adjacent test points can be preset by the control device.

In the automatic ultrasonic examination device, since a space between the adjacent test points can be preset, it is possible to deal with various spot-welded portions in size.

An automatic ultrasonic examination device according to a fifth aspect of the present invention is the device of any of the first to fourth aspects, wherein the test points are located around the tentative center location in a lattice arrangement.

In the automatic ultrasonic examination device, since the test points are located in a lattice arrangement, it is possible to identify more precisely the real center location.

An automatic ultrasonic examination device according to a sixth aspect of the present invention is the device of any of the first to fifth aspects. The device further includes a tentative center location identifying unit connected to the control device to identify a tentative center location by taking in and image processing the image data of the spot-welded portion.

In the automatic ultrasonic examination device, since the tentative center location identifying unit identifies the tentative center location judged from the appearance, it is possible to identify the tentative center location close to the real center location, thereby reducing the number of pieces of the test information obtained by the real center location identifying unit. As a result, it is possible to check quality of the spot-welded portion with a high degree of accuracy at high speed.

An automatic ultrasonic examination method according to a seventh aspect of the present invention to test automatically a spot-welded portion of a test object, in an automatic ultrasonic examination device including an ultrasonic test instrument to obtain test information from the test object, and a robot arm to adjust three-dimensionally the posture and position of the ultrasonic test instrument relative to the test object, is provided. The method includes a real center location identifying step to identify a real center location of the spot-welded portion with reference to pieces of the test information around a tentative center location of the spot-welded portion obtained by the ultrasonic test instrument, and a determination step to check the quality of the spot-welded portion with reference to the test information obtained at the real center location.

In the automatic ultrasonic test method, since the real center location identifying step is included, it is possible to check the quality of the spot-welded portion with a high degree of accuracy compared to the operation by the operator.

An automatic ultrasonic examination method according to an eighth aspect of the present invention is the method of seventh aspect, and further includes an optimum test information detection step to obtain test information optimum to check the quality of the spot-welded portion with reference to pieces of test information obtained around the central axis of the real center location while pivoting on a contact point between the ultrasonic probe and the real center location. In the determination step, the quality of the spot-welded portion is checked with reference to the optimum test information.

In the automatic ultrasonic test method, since the quality is checked with reference to the optimum test information, it is possible to check the quality of the spot-welded portion with a high degree of accuracy.

An automatic ultrasonic examination method according to a ninth aspect of the present invention is the method according to the seventh or eighth aspect is provided. The method further includes a tentative center location identifying step to identify the tentative center location by image-processing the image data of the spot-welded portion.

In the automatic ultrasonic test method, since the tentative center location can be identified according to the appearance of the spot-welded portion, it is possible to reduce the number of pieces of the test information obtained at the real center location identifying step. As a result, it is possible to check the quality of the spot-welded portion with a high degree of accuracy and to perform the operation at high speed.

A method of producing spot-welded products according to a tenth aspect includes a spot welding step to spot-weld a plurality of metal materials, and an ultrasonic test step to check the quality of the welded portion of the spot-welded product using an ultrasonic examination method according to any of the seventh to ninth aspects.

In the production method, since quality of the welded portion is checked using the automatic ultrasonic examination method as recited in any of the seventh to ninth aspects, it is possible to check the quality of the welded portion with a high degree of accuracy at high speed, as well as improving quality and productivity of the spot-welded product, compared to the operation by the operator.

Effect of the Invention

In the automatic ultrasonic examination device and the examination method according to the present invention, the identification of the center location of the nugget and the estimate of the test points performed as described above make it possible to perform the test with a high degree of accuracy at high speed.

In the production method according to the present invention, use of the automatic ultrasonic examination method makes it possible to improve quality and productivity of the spot-welded product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed description will be made on one embodiment of the present invention referring to the figures.

Structure of the Automatic Ultrasonic Examination Device

FIG. 1shows a view of an entire arrangement of an automatic ultrasonic examination device of one embodiment of the present invention, andFIG. 2shows a detailed structure view of an automatic ultrasonic examination device of the one embodiment of the present invention. An automatic ultrasonic examination device1serves to test automatically spot-welded portions of a test object7, and includes an ultrasonic test instrument2, robot arms4, a tentative center location identifying device6(tentative center location identifying unit), a fixed base8, and a control deice5.

The ultrasonic test instrument2serves to test the spot-welded portions by ultrasonic waves, and includes an ultrasonic probe2aand an ultrasonic test instrument main device2b. The ultrasonic probe2aserves to send ultrasonic waves and to detect reflected waves while being in contact with the spot-welded portions, and is attached to the tip of the robot arm4. The ultrasonic probe2ais connected to the ultrasonic test instrument main device2bso that it can send reflected wave detection signals to the ultrasonic test instrument main device2b. The ultrasonic test instrument main device2bserves to receive the reflected wave detection signals from the ultrasonic probe2a, and to convert the reflected wave detection signals into test data. The device2bis connected to the ultrasonic probe2a.

As an example of the ultrasonic test instrument main device2b, a personal computer or the like can be employed that is provided with a CPU, RAM, and ROM. As shown inFIG. 2, software applications that are pre-installed in the ultrasonic test instrument main device2brealize a test data conversion unit21and a first communication unit22. The test data conversion unit21has a function of receiving the reflected wave detection signals from the ultrasonic probe2aand converting them into the test data. The first communication unit22has a function of communicating with the control device5(described later). It should be noted that “the test data” unit data are composed of the travel of the ultrasonic waves and the level of the reflected waves.

The robot arm4serves to adjust three-dimensionally the posture and location of the ultrasonic probe2arelative to the spot-welded portions. The robot arm4is provided with a plurality of joints so that it can move the ultrasonic probe2ato any location according to instructions from a robot control unit50(described later) of the control device5.

(3) Tentative Center Location Identifying Device6

The tentative center location identifying device6serves to identify the tentative center location according to the appearance of the spot-welded portion, and includes a camera6aand an image processing device6b. The camera6ais attached to the tip of the robot arm4where it does not interfere with the ultrasonic probe2a. Additionally, the attachment location and angle of the camera6aare adjusted so that the spot-welded portions can be shot when the tip of the ultrasonic probe2ais in contact with the spot-welded portion.

One example of the image processing device6bis a personal computer as in the case of the ultrasonic test instrument main device2b. As shown inFIG. 2, software applications pre-installed in the image processing device6brealize an image processing unit61and a second communication unit62. The image processing unit61has a function of identifying the tentative center location of the spot-welded portion by image process. The second communication unit62has a function of communicating with the control device5(later described). The detail of functions of the image processing unit61will be described later.

The fixed base8serves to fix the test object7thereto, and is provided with positioning pins or the like depending on the test object7. The fixed base8is configured to rotate and to move horizontally, the movements being controlled by the fixed base control unit51(described later) of the control device5. In the control device5, coordinates in three axial directions (X axis, Y axis, Z axis) are preset using the center coordinate and the center of the fixed base8. Accordingly, if the location of the spot-welded portion in the test object7is known, the control device5can set position coordinates of the spot-welded portions from the center of the fixed base8, thereby moving the ultrasonic probe2ato a rough center location (an initial center location) of the spot-welded portion.

In the present embodiment, as the test object7, a turbine shell73for a torque converter will be described.FIG. 3shows a cross-sectional view of the turbine shell73. O-O inFIG. 3represents the rotational axis of the torque converter. The turbine shell73is constituted by an annular shell body74and a driven plate75. The driven plate75is constituted by an annular portion76and a plurality of projections77projecting in an axial direction from a radially inner portion of the annular portion76. The annular portion76is fixed to the surface of the radially outer portion of the shell body74by spot welding so that the turbine shell73is formed with a plurality of spot-welded portions70. The automatic ultrasonic examination device1of the present embodiment tests the spot-welded portions70by ultrasonic waves.

The control device5serves to control the automatic ultrasonic examination device1so as to perform automatically the test operation, and can send and receive data and signals between itself and peripheral devices. One example of the control device5is a personal computer as in the case of the ultrasonic test instrument main device2b. As shown inFIG. 2, software applications preinstalled in the control device5realize a robot control unit50, a fixed base control unit51, an estimated value computing unit52, a tentative center location computing unit53, a real center location computing unit54, an optimum estimated value computing unit55, a determination unit56, an initial setting unit57, a third communication unit58, and an image processing device control unit59.

The robot control unit50has a function of controlling the movement of the robot arm4. The fixed base control unit51has a function of controlling the movement of the fixed base8. The estimated value computing unit52has a function of converting the test data obtained by the ultrasonic test instrument2into estimated values. The tentative center location computing unit53has a function of calculating the coordinate of the tentative center location data, the data being obtained by the tentative center location identifying device6.

The real center location computing unit54(a real center location identifying unit) has a function of identifying the real center location of the spot-welded portion according to a plurality of estimated values around the tentative center location. The optimum estimated value computing unit55has a function of obtaining an estimated value to check the quality according to a plurality of estimated values gained by changing angles of the ultrasonic probe2aat the real center location. The determination unit56has a function of checking the quality of the spot-welded portions according to the optimum estimated value gained by the optimum estimated value computing unit55.

The initial setting unit57has a function of presetting numerical values to be necessitated by each of the computing units. The third communication unit58connects the units with each other, and has a function of communicating with the peripheral devices. The image processing device control unit59has a function of sending an image processing instruction to the image processing unit61. Detail of functions of each unit will be described later.

2. Operation Flow of the Automatic Ultrasonic Examination Device

FIG. 4shows one example of the operation flow of the automatic ultrasonic examination device1of one embodiment of the present invention. As shown inFIG. 4, the operation flow of the automatic ultrasonic examination device1is mainly made of steps from first step S1to ninth step S9.

At first step S1, the turbine shell73is attached to the fixed base8by the robot arm4, while the ultrasonic probe2ais not attached to the tip of the robot arm4. This step needs not to be performed by the robot arm4of the automatic ultrasonic examination device1in a case that a robot of adjacent apparatus performs the operation.

The optimum diameter of the ultrasonic probe2avaries depending on the diameter of spot-welded portions. At the second step S2, the robot arm4selects the optimum ultrasonic probe2a. This is preset by the initial setting unit57of the control device5depending on types of the test object7. If first step S1is implemented by the robot of the adjacent apparatus, this step can be omitted except for a case in which types of the test object7is changed.

(3) Third Step S3(Tentative Center Location Identifying Step)

At the third step S3, the tentative center location is identified by the tentative center location identifying device6according to the appearance of the spot-welded portion. The center location of the spot-welded portions will be described herein.

FIG. 5shows a cross sectional view and plan view of the spot-welded portion70. As shown inFIG. 5, the spot-welded portion70is formed with a distorted circular scar such as a weld scar71. Meanwhile, a nugget72is formed between the driven plate75and the annular portion76by spot welding. The nugget72is a portion where the driven plate75and the annular portion76are welded to each other.

The weld scar71and the nugget72have a circular shape with a small amount of distortion in the plan view. If it is assumed that the center location of the weld scar71is an appearance center location71aand the center location of the nugget72is an inner center location72a, both the center locations71aand72ado not generally correspond to each other as shown inFIG. 5. Meanwhile, in order to check precisely the quality of the spot-welded portion70, it is preferable to test the inner center location72aof the nugget72.

At this step, according the flow diagram shown inFIG. 6, first, the tentative center location equivalent to the appearance center location71ais identified by the tentative center location identifying device6according to the appearance. This will makes it easier to identify the inner center location72a.

First, the robot control unit50sends an instruction to the robot arm4, and then the robot arm4moves the ultrasonic probe2ato the initial center location of the spot-welded portion (step S31). Then, the tip of the ultrasonic probe2ais brought into contact with the initial center location. As a result, the camera6a, which is attached to the tip of the robot arm4, makes it possible to shoot the spot-welded portion.

Next, the image processing device control unit59of the control device5sends a shooting instruction to the image processing device6b, and the image data of the spot-welded portions70are obtained by the image processing unit61(step S32). Then, the obtained image data are subjected to image processing such that the shape of the weld scar71of the spot-welded portions70becomes clearer (step S33). Specifically, the image processing device6bperforms the image processing by making use of the differences in brightness and color between the weld scar71and the peripheral portion such that the coordinate of the outside shape can be calculated, thereby figuring out the shape of the weld scar71.

Finally, the coordinate of the outer periphery of the weld scar71on the image data are calculated (step S34), the coordinate of the tentative center location on the image data are calculated using the coordinate of the outer periphery (step S35). After that, the tentative center location data are sent to the control device5(step S36).

The tentative center location computing unit53of the control device5calculates the coordinate data of the tentative center location on the coordinate provided on the fixed base8, using the initial center location on the image data that is preset by the initial setting unit57and the obtained tentative center location data. The coordinate of the calculated tentative center location is stored into the control device5.

As mentioned above, at third step S3, it is possible to obtain the coordinate data of the tentative center location of the spot-welded portions70in the coordinate provided on the fixed base8.

(4) Fourth Step S4(Real Center Location Identifying Step)

At the fourth step S4, a plurality of test data is obtained with reference to the tentative center location identified at the third step S3, and the real center location, which corresponds to the inner center location72aof the spot-welded portions70, is identified.

The method to identify the real center location will be described herein. As mentioned before, inside of the spot-welded portions70is formed the nugget72(refer toFIG. 5), which generally has the thickest portion in the center where the ultrasonic waves are most attenuated. Accordingly, as a way to identify the inner center location72aof the nugget72, it is assumed that among a plurality of points around a tentative center location71bthe point where the ultrasonic waves are most attenuated is the inner center location72a(more precisely, the point closest to the inner center location72a). At fifth step S5, as described above, the ultrasonic tests performed at a plurality of test points make it possible to identify the real center location.

A more detailed description will be made on a plurality of test points.FIG. 7shows one example of positioning of the test points at the fifth step.FIG. 7is an enlarged view of a plan view of the spot-welded portion inFIG. 5. InFIG. 7, for convenience, the tentative center location71bis represented as a point same as the point of the appearance center location71a. As shown inFIG. 7, a flat surface is preset that includes the spot-welded portion70and P axis and Q axis intersecting with each other at right angles on the flat surface. The ultrasonic tests are performed at a plurality of test points Andisposed in a lattice-like arrangement along the directions of P axis and Q axis, where the number of points in the directions of P axis and Q axis are the number of the test points Npand NQ, in this embodiment, a total of twenty five points (test points A1to A25) are set by the control device5, where NP=5 and NQ=5. In addition, a space between the adjacent test points in the directions of P axis and Q axis are preset by the control device5as test spaces δPand δQ. At each of the test points set as described above, an ultrasonic test is carried out according to the flow diagram shown inFIG. 8.

First, the ultrasonic probe2ais moved by the robot arm4to the test point A1, so that the tip of the ultrasonic probe2ais brought into contact with the test point A1(step S41). Next, the ultrasonic test instrument main device2bobtains the test data with reference to the reflected wave detection signals sent from the ultrasonic probe2a(step S42).

The test data B1at the test point A1which is obtained by the ultrasonic test instrument main device2bare taken into the control device5(step S43). Then, the estimated value computing unit of the control device5calculates estimated value C1using the test data B1(step S44). In this embodiment, although “estimated value C=2*N*t” is employed that is calculated using the number of reflection echoes N and the measured plate thickness t, an estimated value that is calculated in another way can be employed. The calculated estimated value C1is stored into the control device5by the real center location computing unit of the control device5as first test data group as well as the coordinate data of the test point A1(step S45). Until the estimated value C1to C25at the test points A1to A25are obtained, the steps S41to S45are repeated (step S46). During this operation, angles of the ultrasonic probe2aat each of the test points Anare the same as each other relative to the flat surface including P axis and Q axis, e.g., in perpendicular.

From among all of estimated values C1to C25, the minimum estimated value is selected (step S47). Then, the coordinate data of the test points Anwhich correspond to the minimum estimated value Cnare stored into the control device5as real center location data (step S48).

As described above, at the fourth step S4, it is possible to obtain the coordinate data of the real center location of the spot-welded portion.

(5) Fifth Step S5(Optimum Test Information Detection Step)

At the fifth step S5, while the ultrasonic probe2ais brought into contact with the real center location that is identified at the fifth step S5, a plurality of test data is obtained by changing the angle of the ultrasonic probe2a, thereby to select test data that are optimum to check the quality of the spot-welded portion from among the test data.

A description will be made on a way to obtain the optimum estimated value herein.FIG. 9shows angle setting of the ultrasonic probe2aat the fifth step S5. The angle of the ultrasonic probe2arelative to the spot-welded portion at the initial state is perpendicular to the flat surface defined by the P axis and Q axis. Around the locations of the axes, the tests are performed along a plurality of test axes Dnthat have different angles against the directions of the P axis and Q axis. In the present embodiment, the number of the test axes Mp, MQas the number of axes that are set in the directions of P axis and Q axis is set to be a total of twenty five points by the initial setting unit57, where MP=5 and MQ=5. In addition, the angle between the adjacent test axes Dnin the directions of P axis and Q axis is preset by the initial setting unit57as test angles αPand αQ. Along each of test axes Dnset as described above, the ultrasonic test is performed as described hereinafter.

As shown in a flow diagram inFIG. 10, first, the ultrasonic probe2ais moved by the robot arm4to the real center location, the tip of the ultrasonic probe2ais brought into contact with the real center location (step S51). Next, the ultrasonic test instrument main device2bobtains the test data with reference to the reflected wave detection signals sent from the ultrasonic probe2a(step S52).

The test data E1at the test axis D1obtained by the ultrasonic test instrument main device2bare taken into the control device5(step S53). Then, the estimated value computing unit of the control device5computes the estimated value F1using the test data E1(step S54). As an estimated value, one computed with the same calculating formula at the fifth step S5is used. The calculated estimated value F1is stored by the optimum estimated value computing unit of the control device5into the control device5as a second group of the test data as well as the angle data of the test axis D1(step S55). Until the estimated values F1to F25of the test axes D1to D25are obtained, the steps S51to S55are repeated (step S56).

From among all of estimated values F1to F25, the minimum estimated value Fnis selected (step S57). Then, the selected minimum estimated value is stored into the control device5as an optimum estimated value (step S58).

As described above, at the fifth step S5, it is possible to obtain the optimum estimated value to check quality of the spot-welded portion.

At the sixth step S6, the quality of the spot-welded portion is checked by comparing the optimum estimated value obtained at the fifth step S5and a criterion value gained by experiments. Specifically, if the optimum estimated value is equal to or less than the criterion value, it is determined that the quality of the welding of the spot-welded portion is good. If the optimum estimated value is larger than the criterion value, it is determined that the quality of the welding of the spot-welded portion is not good.

At the seventh step S7, test steps from the third step S3to the sixth steps S6are implemented on a plurality of spot-welded portions on one turbine shell73. After the test is performed on all of the spot-welded portions at the seventh step S7, and at the eighth step S8, the ultrasonic probe2ais removed so that the robot arm4can return the ultrasonic probe2ato storage. Then, at the ninth step S9, the robot arm4discharges the turbine shell73to a corresponding position according to the judgment result at sixth step S6.

As described above, in the automatic ultrasonic examination device1, unit provided in the tentative center location identifying device6and the control device5make it possible to check the quality of the spot-welded portions at high speed and with a high degree of accuracy compared to the operation by the operator.

The advantageous effect gained by the automatic ultrasonic examination device1and the examination method according to the present invention is summarized hereinafter.

In the automatic ultrasonic examination device1, the real center location computing unit54of the control device5can identify the real center location of the spot-welded portion, i.e., the center location of the nugget72, which cannot be judged from the appearance. The identifying of the center location which cannot be judged from the appearance makes it possible to check the quality of the spot-welded portion70with a high degree of accuracy at high speed compared to the test operation by the operator. Furthermore, the lattice arrangement of the test points Anmakes it possible to identify precisely the real center location. Moreover, since the number of the test points NPand NQor the spaces between the test points δPand δQin the directions of P axis and Q axis are set by the initial setting unit57, it is possible to deal with various spot-welded portions in size.

Furthermore, in the automatic ultrasonic examination device1, the optimum estimated value computing unit55of the control device5selects an optimum estimated value from the second group of the test data along the test axes Dn. As a result, it is possible to obtain the better optimum estimated value to check the quality and to check the quality of the spot-welded portions with a high degree of accuracy compared to the operation by the operator.

In the automatic ultrasonic examination device1, the tentative center location identifying device6can identify the tentative center location judging from the appearance. Accordingly, a range where the real center location computing unit54of the control device5obtains the first group of the test data can be set smaller, thereby making it possible to check the quality of the spot-welded portion with a high degree of accuracy at high speed.

Since the quality of the welded portion is checked by the above-described automatic ultrasonic examination device1and examination method, it is possible to check the quality of the welded portion with a high degree of accuracy at high speed, thereby improving the quality and productivity of the spot-welded products compared to the operation by the operator.

4. Other Embodiments

The present invention is not limited to the above-described embodiments, and it is possible to change or modify them variously without departing from a scope of the present invention. Hereinafter, a description will be made on other embodiments.

(1) Tentative Center Location Identifying Device6

In the above-described embodiment, the tentative center location identifying device6identifies the center of the weld scar71in plane on the image. It is possible to identify three-dimensionally the tentative center location by an image processing software application that three-dimensionally performs an image processing, so that it is possible to identify more precisely the tentative center location (especially, in a direction perpendicular to the flat surface defined so as to include the spot-welded portions70). In this case, the number of the camera6ais not limited to one, i.e., a plurality of cameras6amay be used.

In the above-described embodiment, the tentative center location identifying device6identifies the tentative center location. If the preset initial center location is very close to the tentative center location or setting of the number of the test points Npand NQor the test spaces δpand δQis adjusted so as to expand the test range at fifth step S5, it is unnecessary to use the tentative center location identifying device6, making use of the initial center location as a tentative center location.

In the above-described embodiment, the ultrasonic test instrument main device2b, the control device5, and the image processing device6bare different apparatuses. These functions are realized by a personal computer or the like into which software applications are installed that are provided with all functions of these apparatuses.

(3) Real Center Location Computing Unit54

In the above-described embodiment, at the fourth step S4, the real center location computing unit54sets a plurality of test points into a lattice arrangement. It is possible not to employ the lattice arrangement but to set various positionings of the test points depending on other conditions such as size of the spot-welded portion.

(4) Optimum Estimated Value Computing Unit55

In the above-described embodiment, the optimum estimated value computing unit55sets a plurality of test axes at the fifth step S5. It is possible to set the axes in different ways. For example, various settings of the test axes can be performed depending on accuracy or time, e.g., swinging the slanted ultrasonic probe2aaround the central axis at an angle to obtain estimated values. Depending on the product, the number of axes that are set can be decreased.

INDUSTRIAL APPLICABILITY

In the automatic ultrasonic examination device and the examination method according to the present invention, the above-described identification of the center location of the nugget and the estimate of the test points makes it possible to perform the test with a high degree of accuracy at high speed. Furthermore, in the production method according to the present invention, the use of the automatic ultrasonic examination method makes it possible to improve quality and productivity of the spot-welded products. Accordingly, the automatic ultrasonic examination device, the examination method, and the production method according to the present invention are useful in fields where it is required to perform the test with a high degree of accuracy at high speed or to improve quality and productivity of the spot-welded products.