DE202006004456U1 - Test device for surfaces, in particular of welding electrodes - Google Patents

Abstract

Test device for surfaces, in particular of welding electrodes (70),
with a radiation source (20) for emitting radiation,
with a transmission optics (22) for guiding the radiation onto a surface (72) to be examined, which reflects and / or scatters the radiation in a characteristic manner,
with a detector (40) for detecting the radiation reflected and / or scattered by the surface (72) and with detector optics (24) for directing the reflected and / or scattered radiation onto the detector (40),
characterized,
the transmission optics (22) and the detector optics (24) are one and the same autocollimation optics (30),
that for directing the reflected and / or scattered radiation onto the detector (40) a beam splitter means (60) is present, and
in that in order to space the radiation source (20), the autocollimation optics (30) and the detector (40) in the region of the surface (72) to be examined, there exists a beam deflection means (50) for deflecting the radiation transversely to an optical axis of the autocollimation optics (30) is.

Description

The The present invention relates to a test device for surfaces, in particular of welding electrodes, according to the preamble of claim 1.

A generic test device is for example off DE 100 23 894 C1 and has a radiation source for emitting radiation and emitting optics for guiding the radiation onto a surface to be examined, wherein the surface reflects and / or scatters the incident radiation in a characteristic manner. To detect the radiation reflected and / or scattered by the surface, the generic test device also has a detector and a detector optics is provided for guiding the radiation reflected and / or scattered by the surface onto the detector.

Such test devices are used, for example, for welding machines and welding machines in the automotive industry. In this case, metal electrodes, in particular copper electrodes, are used for electrical spot welding. After typically a few hundred spot welds, degradation of these welding electrodes occurs, necessitating milling or replacement. In order to obtain information about the state of the welding electrodes, more precisely their surface, optical test devices of the type described in US Pat DE 100 23 894 C1 used type described. The investigation can be carried out both before and after a milling operation of the welding electrodes.

optical Switches with an energetic evaluation are available for different Applications. Energetic buttons detect a detected Object, which is also called Tastgut, if this close enough to the sensor. This depends on the specific situation from the chosen ones Settings and the device type from. For such energetic push-buttons is a distance-dependence of the signal just desired and for one Evaluation necessary.

contrast Sensors are used to create a contrast mark on which the device is taught will, to recognize. These devices can with a separate transmitting and receiving optics or with a coaxial Optics be provided. To be as sharp as possible Illustration, ie a focus on a specific range, To obtain such a contrast scanner usually needs a well-defined distance of the object to be examined adhered to the device become. Sharp imaging is necessary with these devices in order to obtain an exact switching point, in view of, for example edge detection and fast response time is desired.

At the in DE 100 23 894 C1 described arrangement are arranged as transmitting and detector optics separate lenses side by side in a housing. Due to this arrangement results in a relatively high sensitivity to the distance to the welding electrode to be examined.

task The invention relates to a test device for surfaces, in particular of welding electrodes, to create, with which a dependence of an evaluable Signal as far as possible excluded with regard to range fluctuations is. The device should also be simple be built and in addition under cramped spatial Conditions can be used.

These The object is achieved by the test device having the features of the claim 1 solved.

The Test device of the type indicated above according to the invention thereby further developed that the transmitting optics and the detector optics one and the same Autocollimation optics is that for guiding the reflected off the surface and / or scattered radiation, a beam splitter means is present, and that for space-saving arrangement of the radiation source, the autocollimation optics and the detector in the area of the surface to be examined Beam deflecting means for deflecting the radiation transversely to an optical Axis of the autocollimation optics is present.

preferred Further developments of the test device according to the invention are the subject the dependent claims.

When The first basic idea of the invention can be regarded as the radiation with the same optical components on the surface to be examined and, after reflection and / or scattering on the surface to be examined, on to guide the detector. This is done with an autocollimation optics and a beam splitting means.

Another essential core idea of the present invention is that the radiation is not irradiated onto the surface to be examined on the same optical axis on which the radiation is radiated from the radiation source. Rather, a Strahlumlenkmittel is positioned between the radiation source and the surface, which deflects the radiation transversely to an optical axis of the autocollimation optics. In this way, a very space-saving arrangement of radiation source, autocollimation optics and detector in the area to be examined by simple means possible welding electrode possible.

One Another significant advantage of the invention is that the structure altogether manages with few optical components and therefore inexpensive to realize.

at a preferred variant of the test device according to the invention is the Beam deflecting a mirror. Alternatively, a prism could be used become. Due to the inventively provided deflection of the Beams across the axis of the autocollimation optics can be particularly Advantageously, two test devices according to the invention to a double test device for welding electrodes be combined, in which case a double mirror as a common Beam deflection for both test devices can be used. With such a Device can be two opposite welding electrodes be tested in pairs.

By the use of a coaxial system, that is, of a system used in the Principle with one lens or one optic per system, compared to the so-called two-eyed systems in which for stations and receiver respectively Separate optics can be used, depending on the measurement results from a possible Position inaccuracy of the surfaces to be examined and recorded clearly be reduced. In particular, in the so-called binocular Systems basically existing triangulation effects are avoided. Both a possible and unwanted page offset, so a mispositioning of object to be examined transverse to the optical axis of the incident light, as well as a scanning distance offset, so a mispositioning in Direction of the optical axis of the irradiated radiation acts Significantly lower on the measurement result than in two-eyed systems. The repeatability of the system is therefore significantly improved. In contrast to the prior art is in the test device according to the invention the distance dependence thus largely reduced.

Farther can by the special arrangement of the optical components, in particular by the Strahlumlenkmittel, the system designed depth-optimized become. By redirecting the transmit or receive beam can the depth of the case be kept particularly low. In this case, both are opto-electrical Components, so transmitter and receiver, not in the extension the optical axis of the autocollimation optics positioned. On This way will be a double sensor system allows.

Is appropriate Therefore, this double tester device can be inserted in a space between two welding electrodes casing accommodated. This is due to the inventively provided beam deflection transverse to the axis of the autocollimation optics particularly simple. With the double test device according to the invention can Also particularly closely spaced welding electrodes are examined. Therefore numerous applications, especially in the automotive industry, Parking positions of the welding machines with tight lying welding electrodes This is a particularly important advantage of the present invention Invention.

Basically you can with the test device according to the invention any surfaces, especially highly reflective surfaces with a high proportion at directed and a small amount of diffuse reflection examined become. Particularly advantageous, the test device according to the invention for Examination of the surfaces of welding electrodes, For example, be used by copper caps.

With Help inventively provided Coaxial optics in the form of an autocollimation optics can in particular an optical energy evaluation can be performed. Here are the measured intensities compared with predetermined and / or learned thresholds.

The Beam splitting means, which for guiding the of the to be examined surface reflected and / or scattered radiation to the detector necessary is, basically a mirror with a centered hole or hole to the Passage of the light coming from the radiation source his. By suitable on wide of the radiation reflected from the surface can be ensured in such a variant that sufficient radiation intensity is passed to the detector.

at a particularly preferred variant is the beam splitter means but a half-transparent mirror, which a part of the surface of the reflected and / or scatters scattered radiation in the direction of the detector. Prefers is at this semi-permeable Mirror as well a screen provided. This can be a separate component, it but can also be a coating of the beam splitter.

In order to achieve the greatest possible independence from a scanning distance, that is to say from a distance of the surface to be examined from the test device, the optical structure is preferably selected so that a transmitter-side focusing is stronger than a focusing on the surface to be examined. In this context, one also speaks of the transmitter-side focusing greater than the so-called detection ranges area to choose.

A particularly extensive scanning distance independence is achieved when the radiation in a substantially parallel beam path the surface incident.

In order to be able to compensate for an angular offset of the surface to be examined relative to the optical axis of the test device, it is expedient if the detector is arranged in the region of a focal plane of the autocollimation optics or closer to the autocollimation optics. With slight tilting of the substantially parallel beam path of this beam is then further focused in the focal plane. In view of this, the size of the detector is chosen such that a certain slight angular offset of the surface to be examined does not yet cause the focus to migrate out of the active area of the detector. On the other hand, the detector should not be so large that an obliquely milled surface of a welding electrode still leads to a nearly unchanged detection signal. As appropriate, a detector size of about 5 × 5 mm ^{2 has} proved. The reception-side focusing is therefore preferably to be designed so that the receiving element or the detector is in the range of sharp imaging, ie the smallest light beam to minimize the angular dependence of the object, that is, the surface to be examined. Due to the beam geometry, the smaller the distance between the autocollimation optics and the detector, the less the light spot on the detector moves, and the less the angular offset is, the less the effect. Preferably, therefore, the distance between the autocollimation optics, which may be a lens in a simple case, and the detector is slightly smaller than the focal length, the detector thus positioned just before the focal plane. Then you could work with a smaller area detector.

The Radiation can basically any kind of electromagnetic radiation, which is typical of used welding electrodes, most often Case copper electrodes, sufficiently characteristic reflected and / or scattered. For example, infrared or UV radiation be used. Because of the particularly easy adjustment of the Optics, in particular of the Tastguts relative to the sensor, but is preferably visible Light used. In particular conventional photodiodes can be used as detectors be used.

When Radiation source can basically all known radiation sources, in particular lasers, are used. In particularly preferred, simple and inexpensive Variants, however, LEDs are used. Is advantageous in particular an arrangement of transmitter, aperture, autocollimation optics and other optically active components, the one possible cause homogeneous light beam to the object to be examined. The surface should be as possible evenly lit. become. Therefor In particular light emitting diodes are suitable in which a bonding contact on Edge is positioned, so the usual "dips" in the angle emission characteristic of LEDs do not occur. In addition, this is for example a oval aperture on the beam splitter appropriate.

in the Regard to one as possible good signal evaluation and independence it may also be advantageous from a possible radiation background be to impose on the radiation a temporal structure, for example to use pulsed light.

Further Advantages and features of the invention will be with reference to below on the attached schematic Figures described. Herein show:

1 in a schematic view of a first embodiment of the test device according to the invention;

2 another view in the direction of arrow A of in 1 shown test device;

3 An embodiment of a double test device according to the invention with two test devices according to the invention.

A first embodiment of a test device according to the invention 10 will be related to the 1 and 2 described. 1 shows the test device 10 in the direction of arrow B off 2 , 2 shows the test device 10 in the direction of the arrow A in 1 seen. For the corresponding components are in the 1 and 2 each used the same reference numerals.

As essential components, the test device 10 a radiation source 20 , an autocollimation optics 30 , a detector 40 and a half-transparent mirror 62 as a beam splitter 60 on. A surface to be examined of a welding electrode is denoted by the reference numeral 72 Mistake. According to an essential core idea of the invention is also a mirror 52 as Strahlumlenkmittel 50 available.

The radiation source 20 , which may be, for example, a light-emitting diode, sends pulsed light first in the direction of the semi-transparent mirror 62 , The beam path and the propagation direction of the radiation are schematically indicated in the figures by arrows. From the semi-transparent mirror 62 the ge pulsed light over the mirror 52 through the autocollimation optics 30 , which in the example shown here is a simple lens 30 acts on a surface to be evaluated and examined 72 an object. This is the contact surface of a welding electrode 70 , The light beam is thereby through the autocollimation optics 30 , here both the function of a transmission optics 22 as well as that of a detector optics 24 fulfilled, if possible so guided, that a largely parallel bundle of rays on the surface 72 the welding electrode 70 incident. In this way, a substantial independence of the reflection signal with respect to a displacement of the welding electrode 70 reached in the direction of the incident radiation.

The surface to be examined and evaluated with regard to its reflectance 72 the welding electrode 70 reflects the incident light back through the lens 30 over the mirror 52 and the half-transparent mirror 62 on the detector 40 , The detector 40 may be, for example, a simple photodiode. The signals of the detector 40 are amplified and the signal level, which is substantially proportional to the intensity of the incident radiation is evaluated energetically, that is compared with predetermined thresholds. In general, the surfaces to be examined are 72 the welding electrodes 70 around highly reflective surfaces. Due to the approximately parallel incident on the object light, a substantial independence of the signal to be evaluated in terms of range fluctuations is possible. Besides that, effects can be caused by page displacement of the object by using a lens as large as possible 30 be reduced.

An example of a double test device according to the invention 100 is in 3 shown. Equivalent components here each bear the same reference numerals as in the 1 and 2 ,

Essentially, the dual test device is two identical test devices in the 1 and 2 illustrated type, wherein instead of the single mirror 52 For beam deflection, a double mirror 54 is used. The detectors 40 are in the in 3 shown each view of the semi-transparent mirrors 62 covered.

3 illustrates particularly clearly how the inventive structure and the investigation of closely spaced welding electrodes 70 made possible by the deflection of the beam transverse to the axis of the autocollimation optics. This allows in particular the investigation of welding electrodes 70 in a position of the welding gun or the welding machine with a defined, small distance between the welding electrodes 70 , Such a position is also referred to as Vorhubstellung.

Claims (9)

Test device for surfaces, in particular of welding electrodes ( 70 ), with a radiation source ( 20 ) for emitting radiation, with a transmission optics ( 22 ) for directing the radiation onto a surface to be examined ( 72 ) which characteristically reflects and / or scatters the radiation, with a detector ( 40 ) for the detection of the surface ( 72 ) reflected and / or scattered radiation and with a detector optics ( 24 ) for directing the reflected and / or scattered radiation onto the detector ( 40 ), characterized in that the transmitting optics ( 22 ) and the detector optics ( 24 ) one and the same autocollimation optics ( 30 ) is that for directing the reflected and / or scattered radiation onto the detector ( 40 ) a beam splitter means ( 60 ) is present and that for space-saving arrangement of the radiation source ( 20 ), the autocollimation optics ( 30 ) and the detector ( 40 ) in the area of the surface to be examined ( 72 ) a beam deflecting means ( 50 ) for deflecting the radiation transversely to an optical axis of the autocollimation optics ( 30 ) is available. Test device according to claim 1, characterized in that the beam deflecting means ( 50 ) a mirror ( 52 ), a double mirror ( 54 ) or a prism. Test device according to one of claims 1 or 2, characterized in that the beam splitting means ( 60 ) a semipermeable mirror ( 62 ) or a mirror with a centrally located hole. Test device according to one of claims 1 to 3, characterized in that a transmitter-side focusing is stronger than a focus on the surface to be examined ( 72 ). Test device according to one of claims 1 to 4, characterized in that the radiation in a substantially parallel beam path to the surface to be examined ( 72 ). Test device according to one of claims 1 to 5, characterized in that the detector ( 40 ) in the region of a focal plane of the autocollimation optics ( 30 ) or closer to the autocollimation optics ( 30 ) is arranged. Test device according to one of claims 1 to 6, characterized in that the radiation is visible light. Double test device for a pair of opposing welding electrodes with two test devices according to one of claims 1 to 7 and with a double mirror ( 54 ) as a common beam deflecting means for both test devices. Double test device according to claim 8, which is housed in a housing which is to be examined between two welding electrodes ( 70 ) is insertable.