JPH09171007A - Apparatus and method for determining welding state for multi-point welded product - Google Patents

Abstract

(57) [Abstract] An object of the present invention is to determine whether a spot welded part in a multi-point welded product is good or bad in a short time without increasing the size or complexity of the equipment. An object is to provide an apparatus and a determination method. SOLUTION: The determination device 1 according to the present invention has an excitation point V.
Impulsive hammer 1 for vibrating and measuring points M1 to M7
, Which detect the vibration of the robot, the vibration / vibration detection unit 3A, the FFT processing unit 3B, and the data storage unit 3
C, an OK / NG determination unit 3D, and a control / analysis unit 5 including a display unit 4. Further, the determination method of the present invention includes a step of exciting the vibration point V, a step of detecting vibration acceleration of the measurement points M1 to M7, a step of obtaining frequency characteristics of the door T, and a welding state of the door T. And a step of judging pass / fail.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for determining the quality of a welded state in a multi-point welded product.

[0002]

2. Description of the Related Art For example, a welded product such as a door, a hood, a luggage, etc., which constitutes an automobile body, which is referred to as an automobile closing body or an automobile lid, joins a plurality of panels and parts to each other by spot welding. It is assembled by that. On the other hand, as a method of judging the quality of the welded part in the welded product, a method of judging the nugget diameter based on the reflected wave of the ultrasonic wave oscillated toward the spot welded part (JP-A-62-119453) and intermittent light Method of judging the quality of the welded part by the sound wave emitted from the spot welded part with the irradiation of the laser beam (JP-A-3-2659), or based on the reflected wave of the ultrasonic wave oscillated in the spot welded part by the ultrasonic probe. We have provided a method for determining the quality of the welded part (Japanese Patent Laid-Open No. 4-265854), etc., and by further installing a transducer at the tip of the electrode of the spot welder and processing the received elastic wave from the welded part Method for inspecting a part
4-40359) etc. are provided.

[0003]

By the way, welded products such as doors, hoods, luggage, etc., which constitute the body of an automobile, are so-called multi-point products obtained by welding panels and parts at dozens of places. It is a welded product. On the other hand, since the above-described welding portion determination method is intended for a single-point welded portion, it is inevitable that an extremely long time is required when inspecting all welded portions in a multi-point welded product. However, in the case of inspecting a multi-spot welded product having an extremely large number of welding points, it is practically impossible to inspect all the welding points. On the other hand, even when the above-mentioned welding portion determination method is adopted, it is possible to shorten the welding portion inspection time for a multi-point welded product by preparing a large number of inspection devices, but this is involved in the inspection. There is an inevitable inconvenience that not only the equipment becomes large and complicated, but also the equipment cost increases. In view of the above situation, the present invention is a determination device and a determination method capable of determining in a short time the quality of a spot welded portion in a multi-point welded product without causing enlargement or complication of equipment. It is intended to be provided.

[0004]

Means for Solving the Problems In order to achieve the above object, a judging device according to the present invention is an impulse hammer for exciting a predetermined excitation point in a multi-point welded product, and a predetermined measurement point in a multi-point welded product. An acceleration pickup that detects vibration by touching the touch panel is further provided. Further, a vibration / vibration detection unit that strikes an impulse hammer and extracts an acceleration signal from the acceleration pickup, and an acceleration from the vibration / vibration detection unit An FFT processing unit that obtains frequency characteristics of a multi-point welded product by performing a fast Fourier transform process on the signal;
A data storage unit that stores the frequency characteristic of the multi-point welded product obtained in the FT processing unit and the frequency characteristic of the multi-point welded product extracted from this data storage unit are compared with the frequency characteristic of the non-defective multi-point welded product. OK / Judge the welding condition
The control / analysis means is provided with an NG determination unit and a display unit that displays the quality of the welding state of the multi-point welded product based on the determination result of the OK / NG determination unit.

Further, the determination method according to the present invention comprises a step of exciting a predetermined excitation point in a multi-point welded product, and a step of detecting the vibration acceleration at a predetermined measurement point in the multi-point welded product after this step. After this step, the process of obtaining the frequency characteristic of the multi-point welded product by performing the fast Fourier transform of the vibration acceleration at the measurement point, and the process of obtaining the frequency characteristic of the multi-point welded product after this step The frequency characteristic is compared to determine whether the welding state of the multi-point welded product is good or bad based on the change of the responsiveness at a specific frequency in which the responsiveness changes depending on the quality of the selected welding state.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment. FIGS. 1 to 7 show the determination of the welding condition of an automobile door as a multi-spot welded product by the determination device and the determination method for a multi-spot welded product according to the present invention. An example of carrying out at a spot station is shown.

As shown in FIGS. 1 and 2, the afterhem multi-spot station S (hereinafter referred to as station S) is provided with guide plates P, P and a work lifter R provided on a base B, and A plurality of support guides G, G ..., Clampers C, C ..., And electrodes (spot welding guns) E, E.

Door (front door) T which is a multi-point welded product
While being guided by the guide plates P, P, loaded into the station S from the previous process, the work lifter R is lowered to be placed on the support guides G, G ... And then locked by the clampers C, C. , Electrodes (spot welding guns) E, E ... are spot-welded to predetermined locations, and the door T, which has been spot-welded, is moved upward by the work lifter R after the clampers C, C ... Are released. Then, it is carried out for the next process.

Here, the door T of the automobile is assembled by welding a plurality of parts to each other and includes the afterhem / multi-spot welding (6 places) performed at the station S described above. As shown in (a) and (b), there are a total of 80 spot welding points w, w ... On the door T, and the multi-point welded article determination device and determination method according to the present invention are The quality of the welding state of the door T is determined for all 80 spot welding points w, w ...

In FIGS. 3 (a) and 3 (b),
The positions indicated by are the welding points w, w ...
The positions indicated by ○ are the clamp positions c, c ... By the clampers C, C, ..., The positions indicated by ◎ are the excitation points V by the impulse hammer 1 described later, and the positions indicated by ● are described later. The measurement points M1, M2, M3, M4, M5, M6, M7 by the acceleration pickups 2, 2, ...

As shown in FIG.
An impulse hammer 1 and seven acceleration pickups 2, 2, ... Are provided. The impulse hammer 1 is arranged at a position where the door T locked in the station S strikes the above-mentioned vibration point V (see FIG. 3), and the acceleration pickups 2, 2, ...
Is arranged at a position where it comes into contact with the above-mentioned measurement points M1 to M7 (see FIG. 3) with respect to the door T locked in the station S.

Incidentally, the installation position of the impulse hammer 1,
In other words, the excitation point V for the door T is set at a position where the door T as the subject can be uniformly excited, and the installation position of the acceleration pickups 2, 2, ... In other words, the measurement point M1 for the door T is set. .About.M7 are set at positions where the natural frequency can be satisfactorily measured by the vibration of the door T to the vibration point V by the impulse hammer 1.

As shown in FIG. 4, the impulse hammer 1
Are connected to the signal processing / analyzing unit 3 via the amplifier A1, and the acceleration pickups 2, 2 ... Are connected to the signal processing / analyzing unit via the electrostatic amplifiers A2, A2. It is connected to the section 3.

As shown in FIG. 5, the signal processing / analyzing unit 3 is
Excitation / vibration detection unit 3A for striking impulse hammer 1 and extracting acceleration signals from acceleration pickups 2, 2 ..., and fast Fourier transform processing of the acceleration signals from this excitation / vibration detection unit 3A for door T It has an FFT processing unit 3B for obtaining frequency characteristics.

Further, the signal processing / analyzing unit 3 stores the frequency characteristic of the door T obtained by the FFT processing unit 3B in a data storage unit 3C and the frequency characteristic of the door T taken out from the data storage unit 3C. The OK / NG determination unit 3D that determines the quality of the welding state by comparing the frequency characteristics of

Further, in the vibration / vibration detecting portion 3A, the impulse hammer 1 and the acceleration pickups 2, 2 ... Are connected via the above-mentioned amplifier A1 and electrostatic amplifiers A2, A2.
Is connected to the OK / NG judgment unit 3D,
A display unit 4 that displays the quality of the welding state of the door T based on the determination result of the / NG determination unit 3D is connected.

The signal processing / analyzing section 3 and the display section 4 constitute a control / analyzing means 5, and further the impulse hammer 1, the acceleration pickups 2 and 2 described above.
, And the control / analysis means 5 constitute a multi-point welded article determination device 10 according to the present invention.

In the determination device 10 having the above-described structure, in order to determine the quality of the welding state at the door T, the step of exciting the excitation point V on the door T and the vibration acceleration of the measurement points M1 to M7 on the door T are determined. Detecting process, measurement point M1 ~
The process of obtaining the frequency characteristic of the door T by subjecting the vibration acceleration in M7 to the fast Fourier transform process, and the response of the door T depending on the quality of the welding state. And a judgment step are required.

First, the door T carried into the station S
Are locked by the clampers C, C ... And then spot welding is performed by the electrodes (spot welding guns) E, E ... Before the releasing operation of the clampers C, C. Is struck by the impulse hammer 1, and measurement points M1 to M7 for this vibration are applied.
The response at is picked up by the acceleration pickups 2, 2, ....

After that, the clampers C, C ... Are released, and before the door T is carried out for the next process, the door T is a good product in the signal processing / analyzing unit 3 of the control / analysis means 5. It is determined whether or not the result is displayed on the display unit 4.
In this case, the operator is informed by, for example, turning on the display lamp when it is determined that the product is defective.

By the way, each of the acceleration pickups 2, 2, ...
The acceleration signal from is taken into the vibration / vibration detecting unit 3A of the signal processing / analyzing unit 3 and is then subjected to fast Fourier transform processing in the FFT processing unit 3B. The frequency of the door T obtained by this fast Fourier transform processing. The characteristics are once stored in the data storage unit 3C, and then compared with the frequency characteristics of a non-defective door in the OK / NG determination unit 3D in order to determine the quality of the welding state.

Here, in order to understand the difference in frequency characteristics between the good product and the defective product at the door T, the welding point 7 is used in the previous step.
Fig. 3 (a) with 10 sheets of good products in which all four points were welded well
One defective product not welded only at the welding point w'shown in (1) and nine more good products were sequentially passed through the judging device 1 to compare the frequency characteristic of the good product with the frequency characteristic of the defective product.

FIG. 6 is a diagram in which the horizontal axis represents frequency, and the vertical axis represents the inertance value which represents the acceleration response extracted by the acceleration pickup with respect to the excitation force. 3 (b)), the frequency characteristics in FIG.
p, 4p, 5p, and 6p show the peak frequencies of 19 non-defective products.

Similar to FIG. 6, FIG. 7 is a diagram in which the horizontal axis is the wave number and the vertical axis is the inertance value. The frequency characteristics at the measurement point M1 of 19 good products and the measurement point M1 of one defective product are shown. As is clear from this figure, there is a large difference between the frequency characteristics at the measurement point M1 of the non-defective product and the defective product at the peak frequencies 5p and 6p.

Therefore, in the OK / NG determination section 3D of the signal processing / analyzing section 3, the inertance values of the peak frequencies 5p and 6p in the frequency characteristic of the door T which is the subject are
Peak frequencies 5p and 6p in the frequency characteristics of non-defective products
It is possible to determine whether the door T is a non-defective product by comparing it with the inertance value of.

The non-defective product / defective product is discriminated by the average value x of inertance values of the peak frequencies 5p and 6p of 19 non-defective products, standard deviation u, degree of freedom N, F distribution determination value F0 (19 degrees of freedom, 5% rejection) Is obtained and is used based on the standard value determined from the critical limit method. The reference value is calculated using the following formula.

[0027] The following table shows that 73 out of the 74 welding points in the previous process were welded well, and the welding points which were consumed only at the welding points w ′ (see FIG. 3 (a)) were used to intentionally cause welding defects. The results of trying to discriminate between non-defective products and defective products by passing the sample through the determination device 1 are shown. As is clear from this table, the inertance values of the peak frequencies 5p and 6p in the sample are both well below the reference value. Therefore, the subject can be determined to be defective.

[0028] In principle, if the inertance values at all peak frequencies at a specific measurement point are not the same as the inertance values at all peak frequencies for non-defective products,
Although the object will be discriminated as a defective product, there are variations in the data in the non-defective product and often have a certain distribution. Therefore, in the actual determination device 1, the statistical rejection limit method is used as described above. It is used to discriminate good products / defective products. In addition, since the defect of the welding point acts in the direction of decreasing the rigidity of the multi-point welded product, the decrease in inertance or the shift of the peak frequency to the low frequency side is used as a judgment material as described above. is there.

By the way, it goes without saying that a multi-point welded product such as the door T will be a defective product even if there is a defect at only one welding point. In addition, the rigidity of a multi-point welded product changes even if there is a defect in even one welding point. The degree of this change in rigidity is proportional to the contribution to the multi-point welded product at each welding point, The greater the degree of failure of the welding point, the greater the change in rigidity. On the other hand, whether or not the specimen is a non-defective product is determined by comparing the frequency characteristics at the same measurement point with the non-defective product as described above, but at the welding point where the contribution is high, the welding defect is the main peak. It appears as a change in frequency, and it also appears as a change in frequency with a low peak rank at a welding point with a low contribution.For the purpose of improving detection sensitivity, select a measurement point that gives a frequency with a high peak rank. Needless to say, it is preferable.

Furthermore, as described above, when comparing the frequency characteristics at the same measurement point between the test object and the non-defective item, the contribution rate is increased by sequentially comparing the peak frequency with the peak frequency to the peak frequency with the smaller peak frequency. It is possible to detect defects at all the welding points of the object from the high welding point to the low contribution point. Also, using many measurement points,
By comparing the peak frequency at each measurement point between the test object and the non-defective product, it is possible to detect the defect at the welding point in the test object. In addition, in the early stage of the introduction of this determination device, measurement and comparison are carried out using many measurement points, and the determination is repeated, so that the required measurement points are automatically selected according to the characteristics of the welding device. It will be different.

On the other hand, the data storage section 3 of the control / analysis means 3
The frequency characteristic obtained by the fast Fourier transform processing in the FFT processing unit 3B is stored in C. The frequency characteristic stored in the data storage unit 3C is in the form of spectrum data or inertance value. May be. If the excitation to the subject is uniform, it is possible to make a determination directly using the spectrum data.If the excitation is not uniform, the inertance value can be determined from both the excitation and response spectrum data. Can be calculated, and a non-defective product / defective product can be determined based on this result. Also,
The inertance value can be used regardless of whether the vibration is uniform or not, and since it is not necessary to repeatedly perform the calculation at the time of judgment, the judgment can be speeded up.

As described above, according to the present invention, a multi-point welded product as an object is vibrated and a large number of welding points are evaluated simultaneously based on the response to the vibration. It is possible to inspect in an instant, so that it is possible to perform 100% inspection on multi-point welded products on the production line.

Further, according to the present invention, it is possible to inspect a welding point which is a shadow of another part such as an internal part, and further, at all measuring points where the natural frequency can be measured satisfactorily,
By comparing the frequency characteristics of the test object and the non-defective product, it is possible to instantly determine the defect of the welding point in any test object. Therefore, a large number of multi-point welded products and a large number of welding points Even for a welded product, it is possible to effectively determine the quality of the welded state.

Further, according to the present invention, it is possible to evaluate not only the welding point but also the multi-point welded product (welding product or welded product) itself. In addition, since it can be inspected by simply adding it to the production line, it does not require any equipment other than inspection equipment or special jigs, so it does not cause the equipment to become large or complicated and is independent from the production line. Therefore, it is possible to always perform inspection with high accuracy and accuracy without being affected by changes over time due to wear and replacement of line equipment.

Further, the present invention is not intended to judge only the door of the vehicle body, and not only the closing body for the vehicle other than the door or the lid for the vehicle, but also various steel products such as office machines and furniture, It goes without saying that the invention can be effectively applied as a determination device and determination method for various multi-spot welded products in various housings of vending machines, computers, etc., and also in manufacturing processes of various home appliances.

[0036]

As described above in detail, the apparatus for determining a multi-point welded product according to the present invention includes an impulse hammer for exciting a vibration point, an acceleration pickup for detecting a vibration at a measurement point, and a vibration / It is provided with a vibration detection unit 3A, an FFT processing unit 3B, a data storage unit 3C, an OK / NG determination unit 3D, and a control / analysis unit 5 including a display unit 4. Further, the method for determining a multi-point welded product according to the present invention includes a step of exciting a vibration point, a step of detecting a vibration acceleration at a measurement point, a step of obtaining frequency characteristics of a multi-point welded article, and a multi-point And a step of determining whether the welded state of the welded product is good or bad. In the present invention having the above-mentioned configuration, the multi-point welded article as an object is vibrated, and based on the response to the vibration, since a large number of welding points are evaluated at the same time, the multi-point welded article is instantly made. Can be inspected. Further, in the present invention having the above-mentioned configuration, it is possible to evaluate not only the individual welding points but also the multi-point welded product itself, so that the number of installed inspection devices is small, and only by adding them to the production line. Since the inspection is possible, there is no need for a device other than the inspection device or a special jig. Thus, according to the determination device and the determination method of the multi-point welded product according to the present invention, the quality of the spot welded part in the multi-point welded product is determined in a short time without causing an increase in the size and complexity of the equipment. It becomes possible to do.

[Brief description of the drawings]

FIG. 1 is a conceptual plan view showing an afterhem / multi-spot station to which a determination apparatus and a determination method for a multi-spot welded product according to the present invention are applied.

FIG. 2 is a conceptual sectional side view showing an afterhem multi-spot station.

3A and 3B are overall views showing an inner surface and an outer surface of a door as a multi-point welded product.

FIG. 4 is an overall view conceptually showing a multi-point welded article determination device according to the present invention.

FIG. 5 is a conceptual diagram showing a processing procedure in a multi-point welded product determination device according to the present invention.

FIG. 6 is a diagram showing a relationship between an inertance value and a frequency in which frequency characteristics of a plurality of non-defective products are overwritten.

FIG. 7 is a diagram showing a relationship between a frequency and an inertance value in which a frequency characteristic of a good product and a frequency characteristic of a defective product are overwritten.

[Explanation of Codes] 1 ... Impulse hammer, 2 ... Acceleration pickup, 3 ... Signal processing / analysis unit, 3A ... Excitation / vibration detection unit, 3B ... FFT processing unit, 3C ... Data storage unit, 3D ... OK / NG determination Parts, 4 ... Display part, 5 ... Control / analysis means, 10 ... Judgment device, S ... Afterhem / multi-spot station, T ... Door (multi-point welded product), V ... Excitation point, M1, M2, M3, M4, M5, M6, M7 ... Measuring points.

Claims (2)

[Claims] 1. An impulse hammer that vibrates a predetermined excitation point in a multi-point welded product by striking, and vibration of a multi-point welded product that is brought into contact with a predetermined measurement point in the multi-point welded product based on the impact of the impulse hammer. The acceleration pickup that detects the vibration, the excitation / vibration detection unit that drives the impulse hammer and extracts the acceleration signal from the acceleration pickup, and the acceleration signal from the excitation / vibration detection unit is processed by fast Fourier transform to perform multi-point welding. FFT to obtain the frequency characteristics of the product
The processing unit, the data storage unit that stores the frequency characteristics of the multi-point welded product obtained in the FFT processing unit, and the frequency characteristic of the multi-point welded product extracted from the data storage unit to the frequency of the non-defective multi-point welded product. Control with an OK / NG determination unit that determines the quality of the welding state by comparing with the characteristics and a display unit that displays the quality of the welding state of the multi-point welded product based on the determination result of this OK / NG determination unit A welding state determination device for multi-point welded articles, characterized by comprising analysis means. 2. A step of exciting a predetermined excitation point in a multi-point welded product, a step of detecting the vibration acceleration at a predetermined measurement point in the multi-point welded article, and a step of detecting the vibration acceleration of the predetermined measurement point in the multi-point welded article. A process of obtaining the frequency characteristic of a multi-point welded product by subjecting the vibration acceleration at the measurement point to a fast Fourier transform process, and following this process, in the frequency characteristic of the multi-point welded product,
Based on the change in response at a specific frequency, which was selected by comparing the frequency characteristics of multiple multi-point welded products in advance and the response changes depending on the quality of the welded state, the quality of the welded state of the multi-point welded product is determined. A method for determining a welding state for a multi-spot welded article, comprising: a determining step.