DE2713874C2 - Calorimeter for quickly measuring the welding energy of a laser beam - Google Patents

Description

characterized,

- That the measuring system (M) is equipped with an energy receiver (DK) , in the area of which the first temperature sensor (Hi) is arranged.

- that an electrical storage device (C) is provided,

in which the start temperature determined by the first temperature sensor (H 1) immediately before the start of the energy supply can be stored.

- That the electrical memory (C) for simulating the cooling process can be discharged with the aid of the second temperature sensor (f / 2), which scans the ambient temperature,

- That a differentiating element (D) is provided for determining the time point corresponding to the maximum temperature of the measuring system (M).

- that the measuring device (V) calibrated in energy units has an inverting (-), a non-inverting (+) and a trigger input (0-equipped voltmeter (V) ki,

- that the first temperature sensor (H \) is permanently connected to the non-inverting input (+) of the voltmeter ( ! ^.

- That the electrical memory (C) is connected to the inverting fungang (-). The voltmeter (V) is only influenced via the inverting input (-) when the trigger input '^ is activated.

- and that the differential element (D) is connected to the trigger input (t) Ac \ voltmeter (V) . so that the differentiator (D) bc \ reaching the maximum temperature delivers a trigger pulse (i'3) / ur activation of the voltmeter (V) , through which this / ur formation of the difference / between maximum temperature and start temperature and / ur display of the result in-Hnergieemheiten is caused.

2. Calorimeter according to claim 1 characterized in that a highly thermally conductive double cone (DK) serves as an energy absorber in the measuring system, around 4en a heating coil (HW) is wound to calibrate the measuring system (M) with a calibration pulse.

3-calorimeter according to claim 2, characterized in that a device is provided for monitoring the anvil cone (DK) for overload.

4. Calorimeter according to claim 2, characterized in that a device for monitoring the double cone (DK) for insulation faults (5) is provided.

The invention relates to a calorimeter as described in the preamble of claim 1 Art.

Automatic welding machines are used to weld metal sheets, for example contact sheets for relays used that work with a laser beam. Since the energy of the laser beam must be precisely metered, it is necessary to review them and correct them if necessary.

Two methods are common for measuring the energy of laser welding pulses, namely the calorimetric one and the photometric method. The former works more precisely, so that it is used to calibrate the Photometric devices are used, but the large ones interfere with its operational use Waiting times (several minutes) between the individual measurements, during which the measuring system (receiver) must cool down again to ambient temperature. The photometric method, on the other hand, has a lot short waiting times, but requires aging of the cal lead elements used for occasional recalibration.

The invention is concerned with the calorimetric method. It is based on a calorimeter im The generic term of claim 1 described for example by DE-OS 22 56 372 is known. and has set itself the task of developing such a calorimeter in such a way that the long waiting times between the individual measurements do not have to be observed, but that the Measurements follow one another at short intervals without having to forego the greatest possible accuracy can.

This problem is solved by a calorimeter with the features of patent claims * · i.

The fact that the measuring system determines the start temperature / u The beginning of the energy supply measures and at the end of the measurement a difference between the maximum temperature and Starting temperature is formed, it is not necessary wait until the measuring system has cooled down to the ambient temperature.

The measuring system also gives off heat to the environment while the energy is being supplied. To this too Take into account heat dissipation / u, the cooling process is simulated during a renewed supply of energy, '• o that the / u previously determined start temperature corresponds is corrected accordingly. In this way you can Obtain measured values with the desired accuracy without the measuring system cooling down - You have to wait for the ambient temperature. .

The example of the invention is explained in more detail with reference to the drawing. In

F- ig. 1 the interconnection of one berm made devices, in

F i g. 2 the execution of the measuring system in which

F ί gi 3 and 4 the temperature measurement curves and in the

F i g. 5 and 6 show the control pulses.

The calorimeter is shown in FIG. I consisting essentially of a measuring head, which is shown in detail in Figure 2, a differentiator D, a clamping * riungsspeicher SS, a calibration generator EG and

The digital voltmeter V, which displays the measurement result and is calibrated in energy units. The laser welding pulses / to be measured are generated in a device L.

To measure the laser beam energy, the sheets to be welded are replaced by an adapter on which the measuring system M is located. As a result, the measuring system Μ is fixed in exactly the right position.

According to FIG. 2, the measuring system M consists of a double cone DK made of copper, the temperature of which is measured by a thermistor H 1. This thermistor is connected to the voltage storage device SS via plugs 2 and 3.

A second thermistor H2 measures the ambient temperature in the measuring system M in order to control the electrical cooling simulation. This thermistor is connected to plugs 1 and 2.

To calibrate the measuring system, a heating coil WlV is wound around the double cone DK , with which a defined amount of electrical energy can be fed to this double cone in order to then read it off on the measuring device V. This heating coil is connected to plugs 4 and 6.

In addition, the double cone DK is connected via the plug 5 to an Isolatior.smeßgerät not shown here in order to signal possible damage to the insulation due to the action of heat.

The six connectors described above are connected to the measuring system M via a shielded line, the shielding being connected to ground via a connector 7.

The temperature of the double cone DK ascertained by the temperature sensor H 1 reaches the voltage store 55, the differentiating element D and the non-inverting input + of the measuring device V as an electrical voltage. This voltage UX is shown, for example, in FIG. 3 shown.

A voltage t / 2 is applied to the inverting input - of the measuring device V. as shown in FIG. There'. Differentiator D sends trigger pulses t / 3 according to FIG. 3 to the input t of the measuring device V at times ti and t5. 5 from. It also controls the voltage store SS with a potential t / 4 according to FIG. 6.

As already described, the voltage t / l is continuously applied to the differentiating element D. to the voltage memory 55 and to the measuring device V. At the beginning of the measurement, the differentiating element D., whose task it is to determine voltage changes in the voltage i'J, removes the control voltage t / 4 from the voltage store 55 via the input s (FIG. 6). Since at this point in time the double cone DK has the temperature of its surroundings, the temperature to be stored by the voltage storage device SS has the initial value O. as in FIG. 4 is shown. Because the temperature value is stored electrically in the capacitor C in the voltage memory 55, it is consequently also not charged.

After this initial temperature has been saved, the Cierät / is switched on. The La "erstrahl meets in Meßsvstem M to the double cone DK and absorbieruDieütrahlenenergieerhöhidie there double cone is temperature and thus the Ausgängsspannung UU During the temperature rise maintains the voltage memory 55 the initial value Ui firmly. As soon as the temperature maximum is reached, the difference

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65 decorative element D determines the direction of the temperature reduction and transmits a trigger pulse Vl (FIG. 5) to the measuring device V at time ti . This measuring device then records the energy-proportional difference between the initial t / 2) and maximum value (i'l) and displays it in energy units.

After this measurement result is fixed, this differentiator D sets the time 1 3 delay after the trigger pulse at the time the control voltage f2 t / 4 (Fig. 6) back to the voltage memory 55 at. At this moment, the maximum temperature determined by the sensor H 1 can be applied as a voltage to the capacitor C in the voltage store SS . Since the access to the voltage store SS is now open, the subsequent cooling of the double cone DK is noticeable at both input voltages of the voltmeter K (curves Ul and U 2).

At the beginning of the new measurement, which takes place before the double cone DK has cooled down to the ambient temperature, the voltage store 55 is blocked again at time i4. The voltage t / 2 is not 0 this time, like τ at the beginning of the first measurement, but it has a bc-sJirTite value which is expressed in a corresponding charge of the capacitor C. Since the double cone DK also abkür'i during the renewed heating by the laser beam, the capacitor C is discharged proportionally to the cooling process in a replica of this cooling process, which consists of the resistance wound to the thermistor H 2. The discharge speed is determined by the ambient temperature measured by the thermistor H 2; as a result, the electrical Abkwhlnachbildung reduced the stored initial value by a certain amount, so that the display remains unaffected by the Märkeren cooling of the double cone DK.

The time for a measurement is therefore determined by the time in which the amount of heat in the copper body of the double cone DK and in the thermistor lending. A measurement is r. The others are possible as long as the limit / temperatm determined by the non-linear temperature measurement circuit is not exceeded. A signal lamp, not shown here, serves to monitor it. controlled by the sensor H 1, responds when the highest permissible temperature is reached.

One with the MeUsystcm \ / thermally tightly coupled Hei / spiral HH 'Si will soon CTgedruckt the calibration button lcgi the Eichgenei, itor Id used for quick and easy function and calibration control. As already stated, a heat pulse to the heating coil // VK with the the double cone DK is supplied with a definite surge of electrical energy.

As described above, a double cone OK is used to absorb the laser energy. It has been deshalh chosen so designed receiver, because the laser beam does not strike spotted on him what damage m führe'n koVinte. In this way, you will eventually be more evenly distributed over a larger area. Thus, an inclined surface or a simple cone could also be used; a double cone, however, still has the advantage that the construction can be made flatter and the measuring system can consequently be attached to the correct location without additional modification of the welding machine.

For this purpose 2 sheets of drawing sheets

Claims (1)

Patent claims: 1, Calorimeter for quickly measuring the welding energy of a laser beam, especially for an automatic welding machine for welding sheet metal, - With a measuring system that can be heated by the laser beam and its heating can be displayed by means of a measuring device calibrated in energy units, - With a first temperature sensor to measure the temperature caused by the laser beam warming - as well as with a second temperature sensor to determine a comparison value,