FR2489546A1 - ELECTRONIC WELDING CONTROL DEVICE - Google Patents

Abstract

THE INVENTION RELATES TO ELECTRONIC WELDING. THE CONTROL DEVICE WHICH IS THE SUBJECT OF THE INVENTION IS CHARACTERIZED IN PARTICULAR IN THAT IT INCLUDES A GENERATOR 12 OF SEARCH SIGNALS IN ELECTRICAL LINKAGE WITH THE LOCKING MECHANISMS 11, AND A SYNCHRONIZATION BLOCK 13, THE CONTROL UNIT. PROCESSING OF THE SECONDARY TRANSMISSION SIGNAL IN THE FORM OF AN IDENTIFIER BY CORRELATION 9 WHOSE INFORMATION OUTPUT IS COUPLED TO THE FIRST INPUT OF THE SAID SYNCHRONIZATION BLOCK, THE SECOND INPUT OF THE LAST IS CONNECTED TO THE OUTPUTS OF THE SAID MECHANISMS . THE INVENTION MAY FIND APPLICATIONS IN AUTOMATED ELECTRONIC WELDING SYSTEMS FOR ASSIGNING AND OR CORRECTING PROGRAMS COMMANDING THE MOVEMENT OF THE ELECTRONIC BEAM ALONG THE WELD LINE.

Description

 The present invention relates to electronic welding and in particular relates to an electronic welding control device.

 The invention can find applications in automated electronic welding systems for assigning and / or correcting programs controlling the movement of the electron beam along the weld line. Besides this, the invention can be used in automatic welders used for welding articles in series such as, for example: pistons of automobile engines, turbine blades, etc.

 An electronic welding control device is known (see U.S.A. Patent No. 3426174) comprising at least two electronic transmitters provided with electrical supply systems and electromagnetic deflection systems. One of the electronic transmitters is intended for welding (welding transmitter), the other having the role of forming control signals for continuing welding (research transmitter). The electromagnetic deflection system belonging to the research transmitter is linked to a unit controlling the contour of the scanning of the electron beam with respect to the weld. Said device further comprises a sensor of the secondary emission signal carrying the information on the relief of the surface explored. The sensor has a secondary emission electron collector associated with a measurement circuit, the latter being in the form of a resistor and an amplifier, the output of which serving as an output to said sensor. This output is connected to the input of a secondary transmission signal processing unit, this unit being connected, via a command signal forming unit to servo mechanisms ensuring the movement of the electron beam with respect to the workpiece.

The control input of the secondary emission signal processing unit is connected, via a fixing pulse generator, to an additional output of the unit controlling the contour of the scanning of the electron beam. compared to welding.

 In the known device, the unit controlling the contour of the sweep with respect to the weld consists of a basic oscillator whose output is coupled to the input of the fixing pulse generator and an amplifier whose output is coupled to the electromagnetic deflection system, the two constituent elements being joined in series. The secondary emission signal processing unit represents a time discriminator having its information input connected to the sensor of the secondary emission signal, and its control input, at the output of the fixation pulse generator. The control signal forming unit in the known device represents an integrator and an amplifier combined in series, the amplifier having its output coupled to the servo mechanisms controlling either the movement of the electronic transmitter or that of the workpiece welding. The known device also allows the coupling of this output to the electromagnetic deflection syibme which, too, ensures the movement of the electron beam relative to the part to be welded.

 The known device operates in the following manner.

Under the effect of the magnetic field of the electromagnetic deflection system, the electron beam explores the surface of the part to be welded along the contour of the scan across the weld joint. The alignment of the axis of the scan contour with the weld is done by means of the servo mechanism.

 The electron beam passing through the weld of the part to be welded, there is a modulation of the flow of secondary emission electrons. The collector perceives this flow of electrons while the measurement circuit translates the current supplied by the collector into a signal carrying information on the relief of the surface explored. Once amplified, the secondary emission signals reach the input of the time discriminator, the control inputs of the latter receiving, at the same time that the contour of the scanning is formed, two fixing pulses generated by the generator. of fixation pulses.

These pulses are located symmetrically with respect to the zero intersection of the signal supplied by the basic oscillator and fix the secondary emission signals arriving at the time discriminator. Said discriminator delivers alternating pulses at its output which are then applied to the control signal forming unit. The control signal forming unit delivers control signals which are applied to the inputs of the servo mechanisms and / or of the electromagnetic deflection system. The scanning contour of the electron beam is corrected so that the secondary emission signals obtained when the beam crosses the weld coincide with the zero intersections of the scanning signal supplied by the basic oscillator.

 After positioning the beam on the weld, the welding speed for the electronic welding transmitter is displayed. During welding, the output signal supplied by the control signal forming unit operates the mechanisms for correcting the welding and research electron beams by making them coincide with the welding.

 In real welding conditions, the background of the signal carrying the information on the relief of the surface explored makes it difficult to separate, with high reliability, the pulse obtained during the intersection of the electron beam and the solder joint. parts to be welded. Given the phase shifts inherent in the electromagnetic deflection system, the known device does not ensure a sufficiently precise orientation of the beam along the weld joint and gives rise, in addition, to distortions of the scanning contour and of the shape of the pulse of the solder joint. Thus, the time position of the pulses, the shape of which also depends on the value of the play between the parts to be welded, is only determined with a large error, which reduces the reliability of the device.

 In addition to this, the known device with given tracking error has operating speed limits since the value of the phase shifts and the non-stability of these in the electromagnetic deflection system are a function of the speed of the beam scanning movement. of electrons. All this leads to a reduction in efficiency and makes the use of two electronic transmitters compulsory. The presence of two transmitters greatly complicates the organization of the device and causes additional errors arising from the reciprocal position of these transmitters relative to the weld joint.

 The invention therefore relates to an electronic welding control device having a high reliability and a high speed of operation thanks to the treatment by correlation of the structure of the secondary emission signal during the automatic search and tracking of the weld joint.

 This problem is solved in that the electronic welding control device, of the type comprising an electronic transmitter provided with a power supply system and with an electromagnetic deflection system connected to the output of a unit controlling the contour of the scan. of the electron beam with respect to the solder joint, a secondary emission signal sensor carrying the information on the relief of the surface explored and having its output connected to the input of a signal processing unit secondary emission, the latter being connected, by means of a control signal forming unit, to servo mechanisms ensuring the movement of the electron beam with respect to the piece to be welded, is characterized, according to the invention , in that it comprises a search signal generator in electrical connection with the servo mechanisms, and a synchronization block, the unit for processing the secondary transmission signal being produced e in the form of a correlation identifier whose information output is coupled to the first input of the synchronization block, the second input of the latter being connected to the outputs of the servo mechanism, the first output of the synchronization block being connected to the first input of the unit controlling the scanning contour of the electron beam with respect to the solder joint, the second output being coupled to the control input of the search signal generator, and the third output being connected to the inputs for controlling the electrical supply system of the electronic transmitter.

 Such an embodiment of the device ensures high precision of the automatic search and of the continuation of the weld joint during electronic welding.

 It is desirable that the correlation identifier includes a body for normalizing secondary emission signals, the input of which is also that of the coorelation identifier, and at least three digital matched filters, the input of each of these. ci being connected to the output of the normalization body of the secondary emission signals, while their output constitutes the information output of the identifier by correlation.

 In addition to this, it is possible that the digital matched filters are combined in a delay line with several sockets whose input is that of the digital matched filters and whose outputs are coupled to the inputs of a decoder, the outputs of the latter being the outputs of the digital matched filters.

 It is useful that the delay line with several taps is provided with a flip-flop whose first input serves as an input to said delay line with several taps, a synchronization signal generator and a shift register , the information and control inputs of the latter being connected respectively to the outputs of the synchronization pulse generator and of the flip-flop, the second input of the latter being coupled to the setting of the first functional digit of the shift register, the output of the flip-flop and the outputs of the shift register serving as outputs to the delay line with several taps.

 Such an embodiment of the identifier by correlation based on digital elements makes it possible to eliminate the influence of phase and time distortions in various circuits of the device, which can affect the precision of the pursuit of the solder joint during electronic welding.

 It is also possible that the device is provided in addition with an adaptation unit and a switching voltage generator, the latter having its outputs connected to the control inputs of the decoder, and its inputs, via of the adapter unit, at the additional output of the unit controlling the scanning contour of the electron beam with respect to the solder joint.

 The introduction of new blocks and links makes it possible to reduce the duration of the secondary transmission signal and thus to increase the speed of operation and the efficiency of the device. It should be noted that, in the present case, the minimum duration of the secondary transmission signal is equal to the period of the scanning contour described by the harmonic function.

 It is also useful to provide the device with a device for imitating the secondary emission signal, which has its first input coupled to the output of the synchronization pulse generator, its second input, to the outputs of the voltage generator. switching, its third input, at the output of the decoder, and its output, at the input of the identifier by correlation, said imitation member being provided with a first shift register which has as inputs the first and second inputs of said member, while the outputs of the first and second shift registers are connected, via AND circuits, to the inputs of a first OR circuit whose output is also that of the signal imitation member secondary emission, the control inputs of the second register being connected, via a second OR circuit, to the output of a first generator and to the third input of the imitation member, while the outputs of this register are additionally coupled to an indicator, the output of the second generator being connected to the input of the first OR circuit.

 This is how the proposed device is adjusted without switching on the welding equipment, which contributes to increasing the reliability of the device.

 It is desirable to use a transformer as an adaptation unit.

 The adaptation unit made in the form of a transformer differentiates the signal controlling the scanning contour, which has the effect of making the establishment of the sign of the scanning speed safer and therefore increasing the tracking accuracy of the weld joint.

 It is also possible that the adaptation unit is made in the form of a frequency divider. Such an embodiment of the adaptation unit makes it possible to carry out digital processing of the signals, which makes the operation of the device more secure. It also succeeds in eliminating the influence that the transformer secondary has on the scanning contour, which has the effect of increasing the coefficient of use of the unit controlling the scanning contour of the electron beam with respect to the joint. Welding.

 It is also desirable that the proposed device contain an additional frequency divider connected between the output of the synchronization pulse generator and the second input of the unit controlling the scanning contour of the electron beam with respect to the solder joint, the fourth output of the synchronization block being connected to the control input of the synchronization pulse generator.

 Such an embodiment makes it possible to avoid errors due to the fact that the unit controlling the scanning contour of the electron beam with respect to the weld joint and the synchronization pulse generator operate asynchronously, which ensures a determination more reliable from the reciprocal position of the sweep contour and the weld joint.

 It is also possible that the synchronization unit is provided with a joint detection member, with a member for superimposing the electronic beam on the joint and with a member fixing the successive order of technological operations, the control input inputs. each of said members being joined together and serving as the second input of the synchronization unit, the information inputs of the joint detection member and of the member for superposing the electron beam on the joint being also joined together and serving as the first entry synchronization block, the first output of the electron beam superposition member at the joint serving as the first output of the synchronization block, while the second output of the electron beam superposition member at the joint is connected to the input of control of the synchronization pulse generator and serves as the fourth output of the synchronization block, the second output of the electric beam superimposition member onique at the joint serving at the same time as an input of information to the member fixing the successive order of technological operations, the output of the latter serving as a third output to the synchronization block, this having as second output ia exit from the seal detection device.

 The synchronization block according to the invention ensures the execution of the technological cycle of operation of the device during the welding of articles in series. This makes it possible to automate the entire welding process and to create, on the basis of the device according to the invention, automatic welders for the production of articles in series, for example pistons for automobile engines.

The invention will be better understood and other objects, details and advantages thereof will appear better in the light of the explanatory description which will follow of different embodiments given only by way of nonlimiting examples, with references to the drawings. nonlimiting annexed in which
- Figure 1 shows the structural diagram of the electronic welding control device according to the invention;
- Figure 2 shows an embodiment of the correlation identifier according to the invention;
- Figure 3 shows an embodiment of the digital adapted filters according to the invention;
- Figure 4 shows an embodiment of the delay line with several taps according to the invention;
- Figure 5 shows the structural diagram of the electronic welding control device according to the invention, in which a switching voltage generator and an adaptation unit have been introduced;
- Figure 6 shows an exemplary embodiment of the member for imitating the secondary transmission signal according to the invention;
- Figure 7 shows a diagram of the electronic welding control device according to the invention, provided with an additional frequency divider;
- Figure 8 shows an embodiment of the synchronization block according to the invention;
- Figure 9 shows the structural diagram of the electronic welding control device according to the invention, used in the manufacture of pistons for automobile engines;
- Figure 10 shows an example of the scanning contour of the electron beam;
- Figures II (a, b, c) represent time diagrams illustrating the structures of secondary emission signals obtained during the exploration of the surface of the parts to be welded by the electron beam along the scanning contour of Figure 10 ;
- Figure 12 shows a scanning contour of the electron beam described by the harmonic function;
FIGS. 13 (a, b, c, d) represent time diagrams of the structures of the secondary emission signals obtained during the exploration by the electron beam of the scanning contour of FIG. 12.

 The electronic welding control device as shown in FIG. 1 comprises an electronic transmitter 1 provided with an electrical supply circuit 2 and an electromagnetic deflection system 3.

The system 3 is connected to the output of a unit 4 controlling the scanning contour of an electron beam 5 with respect to a solder joint 6. The device also comprises a sensor 7 of the secondary emission signal carrying the information on the relief of the surface explored 8.

The output of the sensor 7 is coupled to the input of a secondary transmission signal processing unit which, according to the invention, is produced in the form of a correlation identifier 9. The output of said correlation identifier 9 is associated with the input of a unit 10 for forming the control signal. The output of the unit 10 is connected to servo mechanisms II ensuring the movement of the electronic beam 5 relative to the part to be treated.

 In addition to this, the device according to the invention comprises a generator 12 of search signals in electrical connection with the servo mechanisms 11 and a synchronization block 13. The first input 14 of block 13 is coupled to the information output of identifier 9. The second input 15 of block 13 is connected to the outputs of mechanisms 11. The first output 16 of block 13 is connected to the first input of the unit 4, its second output 17 is coupled to the control input of the generator 12, and its third output 18 is connected to the control inputs of the circuit 2.

The electronic transmitter I is intended to form the electronic beam 5. The transmitter 1 is provided with a barrel comprising a cathode 20, control electrodes and plates (anode) 21 and 22, respectively, and a focusing system 23. The electromagnetic deflection system 3 is a magnetic circuit with bundle deflection windings 5 in perpendicular planes
X and Y.

 The unit 4 controlling the scanning contour of the electron beam 5 with respect to the solder joint 6 comprises a basic oscillator 24 and an amplifier 25.

The output of oscillator 24 is connected, via amplifier 25, to the input of system 3.

 The function of the sensor 7 of the secondary emission signal is to transform a stream 26 of secondary emission electrons, obtained during the exploration of the surface 8 by the beam 5, into a secondary emission signal. The sensor 7 comprises a collector 27 and a measurement circuit 28 which transforms the current supplied by the collector into voltage.

 The unit 10 is a digital-analog converter of the code signal, obtained at the information output of the identifier 9, into a control signal.

 The servo mechanisms 11 have the role of ensuring the reciprocal movement of the electron beam 5 relative to the article to be welded with the solder joint 6. The movement of the beam 5 relative to the part to be welded can be carried out at using electromechanical controls in kinematic connection with the electronic transmitter 1 or else using a carriage 29 on which the part to be welded is placed. it should be noted that the electromagnetic deflection system 3 which can be used as a servo mechanism 11 is connected to the output of the unit 10 via the amplifier 25.

 The correlation identifier 9 calculates the functions of intercorrelation of the secondary emission signals with the standard signals which are formed in the correlation identifier 9 itself. According to the results of the calculation of this function, a coded signal is obtained at the output of the identifier 9 of the reciprocal position of the scanning contour and of the joint 6. The fact that there is no connection with the unit 4 excludes the influence of the phase and time distortions which take place in the circuits of the device and which can affect the accuracy of forming of the coded signal of reciprocal position of the scanning contour and the joint 6 and consequently the accuracy of tracking at during electronic welding.

 The electrical connection of the generator 12 with the mechanism 11 is ensured by means of the unit 10 (as shown in the drawing). In the given case, the generator 12 is a pulse generator. If the output of the generator 12 is connected directly to the control mechanisms II (not shown), the generator 12 is a function generator.

 The synchronization block 13 ensures synchronous operation of all the elements of the device as a function of the speed of presentation of the part to be welded under the electron beam.

 The fact of having introduced into the device the generator 12 and the block 13 makes it possible to carry out the automatic search and the "acquisition" (detection) of the joint, as well as ensuring the execution of the chosen technological cycle of operation of the device and, in this way, to automate the whole welding process and consequently to increase the reliability and the yield of the device.

 As can be seen in FIG. 2, the correlation identifier 9 according to the invention comprises a member 30 for normalizing the secondary transmission signal and at least three digital adapted filters 31, 32, 33 of standard signals.

 The input of the member 30 serves as input to the identifier 9, the output of the member 30 is coupled to the inputs of the filters 31, 32 and 33. The outputs of the filters 31, 32 and 33 are combined and constitute the information output of the identifier 9. The filter 31 delivers the standard signals identifying the displacement of the scanning contour, for example to the right of the joint 6, the filter 32 to the left of the joint, while the filter 33 records the co-incidence of the axis of the sweep contour with the seal 6.

 The member 30 ensures the invariance of the proposed device with respect to the size of the space between the active parts, that is to say with respect to the shape of the secondary emission signal appearing during the intersection of the joint 6 by the beam 5. In addition to this, it becomes possible to use digital elements to obtain suitable filtering of the standard signals. Filters 31, 32, 33 can thus be produced on a delay line 34 (FIG. 3) with several sockets, the outputs of which are coupled to the inputs of a decoder 35.

The outputs of the decoder 35 are also the outputs of the digital matched filters. it should be noted that the outputs of line 34 are adapted to the structure of the standard signal.

 According to an alternative embodiment of the correlation identifier 9, no member 30 is provided. However, in this case, there will be additional errors due to the modification of the shape of the secondary emission signal and there is a significant complication of the structure of the filters adapted to the standard signals.

 The delay line 34 with several taps, as shown in FIG. 4, contains a flip-flop 36, the first input of which serves as input to the line 34, a generator 37 of synchronization pulses and a register 38 offset. The control and information inputs of register 38 are coupled respectively to the outputs of the synchronization pulse generator 37 and of the flip-flop 36. The second input of the flip-flop 36 is coupled to the output of the first functional digit of the register 38, while its output and those of all the functional digits of register 38 serve as outputs on line 34.

 Such an embodiment of the delay line 34 with several taps makes it possible to simplify the synchronization during the processing of the secondary transmission signal and to use only one delay line 34 with several taps for all the filters adapted to identifier 9.

 there may be another version of the delay line 34, produced for example on the basis of delay LC lines. However, this leads to a considerable complication in the construction of the identifier 9.

 it should be noted that when the exploration by the electron beam is done according to the scanning contour described by the harmonic function, the device according to the invention, as shown in FIG. 5, additionally contains an adaptation unit 39 and a switching voltage generator 40. The generator 40 has its outputs coupled to the control inputs of the decoder 35, while its input is connected, via the unit 39 to the additional output 41 of the unit 4.

 The introduction of new elements 39 and 40 as well as new connections makes it possible to simplify the analysis of the standard structure, represented by trains of two pulses. The repetition period of these pulses in each of the trains, as well as their position in time with respect to the sweep contour, determine the reciprocal position of said contour and of the joint. In the case of such an analysis, the register 38 carries out the delay line 34 with several taps for a delay duration not exceeding the period of the scan, which makes it possible to reduce the number of devices and the costs as well as '' increase the speed of operation of the proposed device.

 it is possible to produce the device according to the invention so that it is provided with a member 42 (FIG. 6) for imitating the secondary emission signal.

 The first input of the member 42 is coupled to the output of the synchronization pulse generator 37, its second input to the generator 40, its third input to the output of the decoder 35, and its output to the first input of the flip-flop 36.

 In the preferred embodiment, the member 42 has a first and a second shift registers, respectively 43 and 44, a first and a second OR circuit, respectively 45 and 46, a first and a second pulse generator, respectively 47 and 48, AND circuits 49, as well as a display member 50.

The inputs of the register 43 are the first and second inputs of the member 42, while its outputs, as well as the outputs of the register 44, are connected, via the circuits 49, to the inputs of the circuit 45. The output of circuit 45 serves as an output to member 42. The control inputs of register 44 are coupled, via circuit 46, to the output of generator 47 and of decoder 35. The outputs of register 44 are also connected to the display member 50, while the output of the generator 48 is associated with one of the inputs of the circuit 45.

 The use of the member 42 makes it possible to tune the proposed device without switching on the welding equipment, which configures the generator 40.

 The transformer 51 performs the differentiation of the signal controlling the scanning contour and makes it possible to determine with great precision the scanning speed of the beam 5. It should be noted that in the case of such an embodiment of the unit 39, the generator 4C is in the form of a clipping amplifier. In this way, we manage to simplify the connection between the analog and digital parts of the device.

 it is also possible to produce the unit 39, for example, in the form of a differentiator based on operational amplifiers. However, the accuracy of determining the speed will, in this case, be insufficient, given the complexity of the formation of the signal controlling the scanning contour. In addition, the operation of such a differentiator will be much less secure than that of the transformer 51.

 In the case of an electronic welding control device produced on the basis of digital elements, the adaptation unit 39 may be in the form of a frequency divider 52 as shown in FIG. 7.

 In the case of such an embodiment of the unit 39, the basic oscillator 24 comprises a generator 53 of pulses and a conformator 54 of the scanning signal, the generator 40 of switching voltage then being a flip-flop. The input of the divider 52 is coupled to the output of the pulse generator 53. This output is connected to the input of the shaper 54 of the scanning contour signal and at the same time serves as an additional output 41 to the unit 4.

 Such an embodiment of the device makes it possible to p-access digital processing of the signals. Besides this, we manage to exclude the influence of the transformer primary on the contour of the baggage and to increase the utilization coefficient of unit 4.

 it is also possible to provide in the device according to the invention a sunrementalre frequency divider 55 connecting the output of the synchronization pulse generator 37 to the second input of the unit 4, the fourth output 56 of the block 13 being connected to the control input of the synchronization pulse generator 37.

 The errors due to the asynchronous operation of the unit 4 and of the generator 37 of synchronization pulses are thus eliminated.

An alternative embodiment of the synchronization block 13 according to the invention is given in FIG. 8. The block 13 comprises a member 57 for detecting the joint 6, a member 58 for superimposing the electron beam 5 on the
Joint 6 and a body 59 controlling the successive order of technological operations. The control inputs of organs 57, 58 and 59 are combined and constitute the second input 15 of block 13. The information inputs of organ 57 and of organ 58 are joined together and constitute the first input 14 of the block 13. The first output of member 58 is connected to the first input of unit 4 and constitutes the first output 16 of block 13, while the second output of member 58 is coupled to the control input of the synchronization pulse generator 37 and constitutes the fourth output 56 of the block 13. Besides this, the second output of the member 58 also serves as an information input to the member 59, the output of the latter being connected to the control input of the power supply circuit 2 and serving as the third output 18 to the block 13. The output of the member 57 is connected to the control input of the search signal generator 12 and constitutes the second exit 17 of block 13.

 The synchronization block 13 ensures the execution of the technological operating cycle of the device when welding articles in series. This makes it possible to automate the whole process of electronic welding and to create, on the basis of the proposed device, automatic machine tools for the manufacture of articles in series, for example pistons for automobile engines, as shown in the figure. 9.

 Lforgane 57 of such a device comprises a circuit 60 OR and a flip-flop 61, the inputs of which being connected to the output of circuit 60 and to the control mechanisms 11. The output of the flip-flop 61 constitutes the first exit 16 of block 13.

The input of circuit 60 OR serves as the first input 14 to block 13.

 The member 58 for superimposing the electronic beam on the joint is in the form of a bistable rocker 62 whose inputs serve as input 14 and input 15 to block 13. It should be noted that when it is the system 3 electromagnetic deflection which plays the role of the servo mechanism 11, the input 15 of the block 13 is connected to the input of the flip-flop 62 by means of a zero member 63.

 The member 59 fixing the successive order of the technological operations comprises a circuit 64 AND, a decoder 65 and a delay circuit 66. The inputs of circuit 64 are connected to the output of the flip-flop 62 and to the input 15 of block 13, while its output is coupled to the control input of decoder 65, whose input is also connected to the input 15. The outputs of the decoder 65 are in electrical connection with the inputs of the electrical supply circuit 2 and constitute the output 18 of the block 13.

The electrical connection of the outputs of the decoder 65 is carried out directly and / or via the circuit 66, this according to the real requirements of the welding technology.

 The electronic welding control device operates as follows. The cathode 20 (FIG. 1) of the emitter 1 produces an electronic cloud, the electrons of which are accelerated until reaching the cathode-anode potential. A potential is applied to the control electrode 21 to adjust the intensity of the generated electron beam 5, which successively crosses the magnetic fields of the electromagnetic focusing and deflection systems, respectively 23 and 3.

The system 3 makes it possible to control the position coordinates of the electron beam 5 on the surface 8 of the article to be welded.

 The unit 4 establishes the control currents to be sent to the electromagnetic deflection system 3, the magnetic flux thereof ensuring exploration by the electronic beam 5 of the scanning contour.

 FIG. 10 shows, by way of example, a scanning contour of the electron beam with respect to the joint t in the plane 8 of the part to be welded. The basic oscillator 24 (FIG. 1) establishes a voltage whose shape corresponds to the desired scanning contour, while the amplifier 25 transforms this voltage into control current of the system 3. At the times when the electron beam 5 (line of the scanning contour) crosses the joint 6, the sensor 7 delivers joint pulses 68. The electron beam 5 causes a secondary emission (flow 26 of secondary electrons) from the surface 8 of exploration. The joint 6 of the article to be welded modulates the flow 26 of secondary electrons, which is perceived by the collector 27, and the collector current in the circuit 28 is transformed into a signal reflecting the relief of the surface 8.

 Depending on the reciprocal position of the scanning contour and the joint 6, secondary emission signals of different structures are taken from the sensor 7 (their time diagrams are shown in FIG. 11 a, b, c). FIG. 11a gives the timing diagram of the secondary emission signal for the case where the axis of the scanning contour coincides with the center line of the joint 6 (as shown in line A in FIG. 10 !, in FIGS. 11b and 11c the axis is located to the left and to the right, respectively, relative to the center line of the joint 6 (in FIG. 9b, the reference letters E and C show the possible positions of the anointed with respect to the scanning contour) .

 The correlator identifier C (frngure? I, intended to identify the position of the scanning contour and of the joint, performs, according to the structure of the secondary emission signals from the sensor 7, the identification of the reciprocal position of the axis of the sweep contour and the middle of the joint. it delivers standard structures (of the kind shown for example in FIG. 11 a, b, c), from which we obtain h the output of the identifier 9 (FIG. 1) a control code which the unit 10 transforms into a control signal, said control signal acts, by means of the amplifier 25, on the position of the scanning contour relative to the seal 6 so to stabilize the structure of the secondary emission signal supplied by the sensor 7.

In order to eliminate any control errors due to the electromagnetic correction of the scanning contour with respect to the joint, the unit 10 can supply a control signal directly to the servo mechanisms II (for example, commands for moving the lem - teur 1 and of the carriage 29) which carry out the reciprocal displacement of the electronic transmitter 1 and of the part to be welded mounted on the carriage 29.

 In the case where the value of the misalignment between the scanning contour and the seal 6 does not adapt to the position sensitivity of the correlation identifier 9, the search for the seal is executed by the generator 12 of search signals. The generator 12 controls either the control mechanisms II via the unit 10, or, via the amplifier 25, the displacement current supplied by the electromagnetic deflection system 3. After the acquisition of the seal, that is to say after the appearance of the secondary emission signal delivered by the sensor 7, the generator 12 is put out of play by the signal arriving from the output 17 of the synchronization block 13 .

 The servo mechanisms 11 synchronize the operation of the block 13 which periodically switches on the unit 4 controlling the contour of the scanning and controls the speed of the electron beam by setting it either to the speed of determining the position reciprocal of the sweep contour and of the joint (tracking regime), that is to say the welding regime, as well as to the regimes of execution of other technological operations (for example, withdrawal of the electron beam from the welding zone, etc.) .

 The introduction into the electronic welding control device of the correlation identifier 9 makes it possible to eliminate the influence of phase and time distortions in the system 3 and the sensor 7.

 The identification of the reciprocal position of the scanning contour and the joint 6 according to the structure of the secondary emission signal is carried out in the identifier 9 (FIG. 2) in the following manner. The secondary emission signals carrying the information on the relief of the explored surface arrive at the member 30. In said member 30 these signals are normalized in amplitude and duration. The member 30 is generally a clipping amplifier connected in series with a pulse shaper.

 The normalized pulses supplied by the sensor 7 arrive at the inputs of the filters 31, 32, 33, at the outputs of which the function of reciprocal correlation of the secondary emission signals is formed with the standard structures recorded in each of the filters.

In this way, according to the results of calculation of this function, one obtains at the output of the identifier 9 a coded signal of the reciprocal position of the scanning contour and the joint 6. The filter 31 delivers standard signals identifying the displacement of the scanning contour, for example to the right of the seal 6, the filter 32 relates to the left side, and the filter 33 relates to the coincidence with the seal.

 The normalization of the signals to be processed ensures an invariance of the device according to the invention with respect to the magnitude of the spacing between the parts to be welded.

Besides this, one obtains the possibility of making digital adapted filters based on a single delay line 34 with several sockets (FIG. 3), coupled to the decoder 35. The inputs of the decoder 35 are coupled to the outputs of the line 34 of such that their arrangement is reversed with respect to the time structure of the standard secondary emission signal.

 In accordance with the scanning contour and with the coupling of the determined outputs (sockets) from line 34 to decoder 35, the appropriate filtering of standard pulse trains is carried out.

 By normalizing the signals supplied by the sensor 7, it becomes possible to use in line 34 the shift register 38 (FIG. 4) in which the information is shifted by means of the pulses produced by the generator 37 of synchronization pulses, while the information is introduced via the flip-flop 36. The latter is triggered by pulses coming from the member 30 for normalizing the secondary joint emission signals, and it is reset to the initial state by the signal coming from the output of the first functional digit of the shift register 38. The flip-flop 36 puts in synchronism the moments of obtaining signals, during the crossing of the joint by the beam, with the pulses supplied by the synchronization pulse generator 37. The capacity of the shift register 38 is a function of the duration of realization of the signal supplied by the sensor 7 during the scanning cycle.

 In order to increase the speed of operation of the device, it is useful to use the scanning contour described by the harmonic function. To this end, the electronic welding control device is provided with an adaptation unit 39 (FIG. 5) and with a generator 40 for switching voltage. FIG. 12 is in the form of a scanning contour of the electron beam 5 relative to the joint 6 on the surface 8 of the parts to be welded, contour which has been established by the harmonic function, FIG. 13 (a, b, c ) shows the timing diagrams of the joint pulses. FIG. 13a gives the structures noted at the coincidence of the scanning axis with the middle of the joint (line A in FIG. 12); FIG. 13b gives the same thing for the displacement of the luggage axis to the left (line B of FIG. 12); Figure 13c shows the same thing to the right of the middle of the joint of the part to be welded (line C of Figure 12). As seen in Figure 13, the standard structure represents trains of two pulses.

 The repetition period of these pulses in each of the trains, as well as their time position (FIG. 13a) relative to the sweep contour, are decisive for the reciprocal position of the contour and of the joint 6.

 The displacement of the scanning contour with respect to the joint 6 (FIG. 5) modifies the period between the pulses and the reciprocal position of these with respect to the scanning contour.

 The output signals supplied by the generator 40 and arriving at the decoder 35 control the line of the scanning speed of the electron beam 5, to which the trains composed of two pulses are attached.

où
f(1) représente la succession d'impulsions depuis
le premier chiffre fonctionnel du registre
à décalage 38;
N , le numéro du chiffre fonctionnel du registre
à décalage 38 assurant un retard d'une demi
période de balayage de la succession d'impulsions
depuis l'organe 30; le le signal fourni par le générateur 40 de tension
de commutation.As a function of the sign of the switching voltage supplied by the generator 40 and as a function of the result of determining the period between the normalized pulses, the decoder 35, with the help of the shift register 38, delivers the code (n) of the control signal

or
f (1) represents the succession of pulses from
the first functional digit of the register
offset 38;
N, the number of the functional digit of the register
offset 38 ensuring a delay of half a
pulse period scanning period
from organ 30; the signal supplied by the voltage generator 40
of commutation.

 It should be noted that to control the operation of the device, the decoder can be associated with an indicator.

où Am est l'amplitude de balayage du faisceau électronique 5.The error of the automatic superimposition of the electron beam on the joint when welding is carried out is determined by the discontinuity of the delay line 34 on the shift register 38 and by the scanning amplitude of the electron beam 5. This error , as the analysis of the device's operation shows, does not exceed the value

where Am is the scanning amplitude of the electron beam 5.

 To carry out the scanning of the electron beam 5 with respect to the joint 6 on the surface 8, the electromagnetic deflection system 3 receives the control current supplied by the amplifier 25 through the adaptation unit 39, current which varies according to the harmonic function having the period T. Said unit 39 differentiates the command and control current signal, by means of the generator 40, the decoder 35. As shown in FIG. 5, the unit 39 represents the transformer 51 whose the primary is connected, via the additional output 41 of the unit 4, in series to the winding of the electromagnetic deflection system 3, the secondary delivering the signal corresponding to the differential of the control current of the system 3, current which, via the generator 40 (clipping amplifier) controls the sign of the scanning speed.

 When the joint 6 crosses by the electron beam 5, the sensor 7 delivers secondary joint emission signals which, after having passed through normalization member 30 and the flip-flop 36, reach the shift register 38 in which the shift of the information is carried out by means of the signal supplied by the synchronization pulse generator 37. The decoder 35 delivers the code of the control signal which controls the servo mechanisms II via the unit 10. The operating modes of the unit 4, of the generator 12, of the controls of the servo-control mechanisms 11, of the electrical supply circuit 2, are fixed by the synchronization block 13.

 It is reasonable to determine the operating characteristics of the electronic welding control device without switching on the electron beam welding equipment. To this end, the proposed device has a member 42 (FIG. 6) for imitating secondary joint emission signals, the structure of which determines (imitates) the relief of the surface of the parts to be welded.

 In the first shift register 43, the sweep contour is formed in synchronism with the exploration by "unit". The synchronization pulse generator 37 adjusts the "unit" scanning speed in register 43, while the signal from generator 40 controls the scanning direction.

 In the second shift register 44, the number with "unit" determines the position of the joint with respect to the scanning contour.

 In the event of a temporal coincidence of unit coming from the output of one of the orders from register 43 with the "unit" coming from the output of the corresponding digit from register 44, the output of circuit 49 AND delivers pulses which imitate the crossing by the electronic harness of the joint 6 of the part to be welded. The pulses supplied by circuits 49 AND (FIG. 6) are joined by circuit 45 OR and arrive at the input of flip-flop 36 in the identifier by correlation 9.

 To control the position of the unit in the register 44, the member 42 comprises a first pulse generator 47 which sends its pulses, through the deudbmecircuit or 46, to the control inputs of the register 44.

 In the case where the "unit" in the register 44 is shifted compared to the average figure of the register 43, one will have at the output of the circuit 45 OR of the signals whose structure is in connection with the value of shift of the "unit" in register 44. The position of this "unit" in register 44 is determined using the indicator 50.

 From the output of the circuit 45 OR, the impulse signal arrives at the input of the flip-flop 36 of the identifier by correlation 9, at the output of which coded control signals are taken, these acting, via inputs of the OR circuit 46, on the position of the "unit" in the register 44 seeking to make the "unit" coincide with the average order of the register 43.

 During the exploration of the surface of the parts to be welded by the electron beam, there appears a parasitic modulation of the flow of secondary electrons due to scratches, oxidized films and other irregularities.

 In order to be able to deform the structure of the imitated signals, a second generator 48 has been provided in the member 42 for imitating the secondary emission signals. From the output of which the pulses reach the input of the first OR circuit 45, the output of that -ci delivering the deformed structure of the secondary emission signals.

 By tuning the electronic welding control device, the frequencies of the generators 47 and 48 are varied to determine its speed of operation and its sensitivity to interference. This gives an improvement in the characteristics of use of the device and increases the reliability of its control.

 The electronic welding control device can use digital elements. In this case, the adaptation unit 39 represents a frequency divider 52 (FIG. 7). The divider 52 also makes it possible to raise the coefficient of use of the amplifier 25.

 In the case of such an embodiment of the unit 39, the signal shaper 54, which is part of the unit 4, is controlled by the train of pulses supplied by the generator 53. The signals taken from the output 41 , which serves as an additional output to the unit 4, reach, via the frequency divider 52, the generator 40 which is in the form of a flip-flop.

The dividing coefficient of the divider 52 is chosen so that the phase shift between the scanning signal supplied by the shaper 54 and the signal supplied by the generator 40 constitutes an angle equal to
7
This makes it possible to determine with sufficient precision the sign of the speed of exploration of the electron beam 5.

 To avoid errors due to the unstable frequencies of the unit 4 of the synchronization pulse generator 37, the generator 53 is synchronized by said synchronization pulse generator 37 by means of the additional frequency divider 55. The dividing coefficient of the divider 55 is defined by the capacity of the shift register 38 and is equal to 2 N, where N is the number of the functional digit of the shift register 38 ensuring a delay of half a scanning period of the succession of pulses from the organ 30.

 The unit 4, the generator 12 of search signals and the electrical supply circuit 2 are synchronized by the block 13.

 The synchronization block 13, as shown in Figure 8, operates as follows.

With the arrival of the joint acquisition signal from the identifier 9, the output signal supplied by the member 57 puts generator 12 out of play. It should be noted that the "acquisition" signal is used "a coded signal of the control signal supplied by the identifier 9.

 Once the position of the beam 5 (FIG. 7) relative to the joint 6 has been determined, and once the control effect on the mechanisms 11 has been formed, the signal supplied by the output 56 triggers the generator 37 of synchronization pulses, while that the signal provided by the output 16 puts unit 4 out of play. The member 59 (FIG. 8) acting in synchronism with the control of unit 4 and of identifier 9 establishes control signals for circuit 2 power supply to the electronic transmitter 1. The control inputs of the members 57, 58, 59 are synchronized by the servo mechanisms 11.

 In this way, the block 13 ensures a synchronous realization of the technological cycle of operation of the device when welding articles in series.

 It is known that the joint line of the parts to be welded can have different curvatures. If the curvature of the joint is not significant, the electron beam 5 (FIG. 7) is generally displaced out of the zone of fusion of the metal and performs the exploration movement across the weld joint 6. As already mentioned, it a control effect is formed during exploration which places the electron beam 5 on the joint 6 of the edges to be welded. The rate of periodic exploration is fixed by the synchronization block 13, which is in connection with the mechanisms 11, these ensuring the advance of the article towards the welding zone.

 When welding parts whose joint line has an accentuated curvature, the commands for moving the electronic transmitter 1 and the carriage 29 relative to the articles to be welded obey an autonomous programmed digital control system, while the proposed device fulfills the function of adapting the control program for the controls of the servo mechanisms 11 to the joint line of the parts to be welded.

 To carry out repeated technological passes on the joint line of the parts to be welded, the code of the control effect is taken from the output of the correlation identifier 9 for each exploration cycle.

This code is memorized and used for the repetition of the welding technological cycle.

 Thus, on the basis of the device described, automatic machines can be created to manufacture articles in series.

 FIG. 9 shows, by way of example, the electronic welding control device used in the manufacture of pistons for automobile engines. In this device, the rattle of the servo mechanisms 11 is filled by a command 67 for advancing the pistons at the welding station, a command 68 for rotating the piston at the welding station, a command 69 for correcting the electronic transmitter. 1 relative to the seal 6 of the piston to be welded. In the given device, the decoder 45 of the correlation identifier 9 is provided with an indicator 70.

 The device operates as follows.

After switching on the device, the control 67 responds and advances the piston to the welding station. The uninterrupted loading of the pistons can be ensured either by a container transporter with lockage, or by a rotary table provided with housings for the pistons and moved by the control 67, or by another suitable device. The response of the command 67 occurs after welding of each piston to the signal from the detector 65. The flip-flop 61 delivers a control signal reaching the generator 12 of search signals and the command 69 for correcting the electronic transmitter. This signal triggers the generator 12 and acts, via the unit 10 and the amplifier 25, on the position of the electron beam 5 exploring the surface 8 of the piston to be welded. To carry out the exploration by the electron beam 5, the basic oscillator 24 is brought into synchronism by the generator 37 of synchronization pulses and delivers a harmonic signal whose frequency is multiple of the frequency of said generator 37.

The generator 37 of synchronization pulses synchronizes the generator 40 via the divider 52. The output signals delivered by the generator 40 are sent to the decoder 35.

 At the moments of coincidence of the electron beam 5 with the joint 6, there is modulation of the flux 26 of secondary emission electrons. The output of the sensor 7 receives a signal carrying the information on the relief of the explored surface 8 of the piston. When the electron beam 5 crosses the joint 6, the member 30 delivers joint pulses standardized in amplitude and in duration, which trigger the flip-flop bis

 The control 69 performs the angular displacement of the electron beam 5 (scanning contour) relative to the joint until the flip-flop 62 provides the signal preventing the formation of the scanning contour. The control signal taken from the output of the flip-flop 62 appears after the simultaneous application to the input of the latter of a "zero" control signal coming from the unit 10 via the zero element 63 and a signal from the correlation identifier 9 and corresponding to an exact coincidence of the scanning contour with the joint 6 of the part to be welded.

The flip-flop 62 deactivates the generator 37 of synchronization pulses and also the oscillator 24, and delivers a control signal to the member 59 controlling the successive order of technological operations. The coincidence circuit
ET 64 receives the output signal from the flip-flop 62, as well as a pulse sent by the welding cycle sensor installed on the piston rotation control 68 at the welding station. The output signal from circuit 64 arrives at the input of decoder 65 which controls the successive order of technological operations. At the signal from decoder 65, the power supply circuit 2 establishes the power of the electron beam necessary for welding. When the electron beam has traversed the line of the circular joint of the automobile piston, the cycle sensor installed on the control 68 provides a second pulse which, after passing through the decoder 65 and the delay circuit 66, reaches the supply circuit 2 electric and causes the speed change by ensuring a minimum number of faults in the contact area of the solder joint; it also places the electrical supply circuit 2 of the electronic transmitter in the smoothing or heat treatment regime of the solder joint.

Usually the welding of an automobile piston is done in three or four turns of the piston, after which the decoder 65 is reset, then forms the command signal to the command 67 advancing a new part to the welding station and returns the flip-flops 61 and 62 to their initial state. The search for the joint, the coincidence of the electronic harness with the joint and the display of the desired speeds of the electronic transmitter are carried out automatically without the intervention of the operator-welder.

 In order to view the control of the operation of the electronic welding control device, use is made of the indicator 70 which presents the code for shifting the sweeping contour with respect to the seal of the piston to be welded.

 The proposed device ensures a high reliability of the automatic search and tracking of the joint during electronic welding, as well as a high precision of tracking of the joint.

 The device according to the invention ensures the continuation invariance of the joint under the actual welding conditions. It is possible to make the device considered based on digital elements.

 The electronic welding control device provides for the possibility of an independent agreement without switching on the electron beam welding equipment.

 It is also possible to create based on the device which has just been described automatic machines for the manufacture of articles in series, as well as to carry out algorithms for its operation on computer.

 Of course, the invention is in no way limited to the embodiments described and shown which have been given only by way of example. In particular, it includes all the means constituting technical equivalents of the means described as well as their combinations if these are executed according to the spirit and implemented in the context of protection as claimed.

Claims (10)

 1.- Electronic welding control device, of the type comprising an electronic transmitter provided with an electrical supply system and an electromagnetic deflection system connected to the output of a control unit for the scanning contour of the electron beam relative to the weld joint, a secondary emission signal sensor carrying the information on the relief of the surface explored and having its output connected to the input of a secondary emission signal processing unit, the latter being connected by means of a control signal forming unit, to servo mechanisms ensuring the movement of the electron beam relative to the workpiece, characterized in that it comprises a search signal generator in electrical connection with the servo mechanisms, and a synchronization block, the processing unit of theSySldt <1sslonsrxndarese present in the form of an identifier by correlation whose sol rtie information is coupled to the first input of said synchronization block, the second input of the latter being connected to the outputs of said servo mechanisms, the first output of the synchronization block being connected to the first input of the unit controlling the scanning contour of the electron beam with respect to the solder joint, its second output being coupled to the control input of said search signal generator, and its third output being connected to the electrical supply system of the electronic transmitter.  2.- Device according to claim 1, characterized in that the correlation identifier comprises a member for normalizing the secondary emission signals, the input of which is also that of the correlation identifier, and at least three suitable filters digital, the input of each of which is connected to the output of said body for normalizing secondary emission signals, while the output of each of them constitutes the information output of the identifier by correlation.  3.- Device according to claim 2, characterized in that the digital matched filters are combined in a delay line with several taps whose input is that of said digital matched filters and whose outputs are coupled to the inputs of a decoder, the outputs thereof serving as outputs to the digital adapted filters.  4.- Device according to claim 3, characterized in that said delay line with several sockets is provided with a flip-flop whose first input serves as an input to said delay line with several sockets, of a signal generator synchronization and a shift register, the command and information inputs of the latter being respectively connected to the outputs of the synchronization pulse generator and of the flip-flop, the second input of the latter being coupled to the output of the first digit of said shift register, the output of the flip-flop and the outputs of the shift register serving as outputs to said delay line with several taps.  5.- Device according to claim 3, characterized in that it is further provided with an adaptation unit and a switching voltage generator whose outputs are connected to the decoder control inputs and whose inputs are connected, via the adapter unit, to an additional output of the unit controlling the scanning contour of the electron beam with respect to the weld joint.  6.- Device according to one of claims 4 and 5, characterized in that it is provided with a member for imitating the secondary emission signal, which has its first input coupled to the output of the pulse generator synchronization, its second input, to the switching voltage generator, its third input, at the output of the decoder, and its output, at the input of the identifier by correlation, said imitation member being provided with a first shift register which has the first and second inputs of said member as inputs, while the outputs of the first and second shift registers are connected, via AND circuits, to the inputs of a first OR circuit, the output of which is also that of the device for imitating the secondary transmission signal, the control inputs of the second register being connected, via a second OR circuit, to the outputs of a first generator and to the third input of the imitation organ, while the outputs of this re gistre are additionally coupled to an indicator J The output of the second generator being connected to the input of the first OR circuit.  7.- Device according to claim 5, characterized in that a transformer is used as an adaptation unit.  8.- Device according to claim 5, characterized in that a frequency divider is used as an adaptation unit.  9.- Device according to claim 4, characterized in that it contains an additional frequency divider connected between the output of the synchronization pulse generator and the second input of the unit controlling the scanning contour of the electron beam with respect to at the weld joint, the fourth output of the synchronization block being connected to the control input of the synchronization pulse generator.  10.- Device according to claim 4, characterized in that the synchronization block is provided with a joint detection member, a member for superimposing the electronic beam on the joint and a member fixing the successive order of the technological operations, the control input of each of said members serving as the second input to the synchronization block, the information inputs of the joint detection member and of the member for superposing the electronic beam on the joint being combined and serving first input to the synchronization block, the first output of the superimposition member of the electronic beam to the joint serving as the first output of the synchronization block, while the second output of the superimposition member of the electronic beam to the joint is connected to the control input of the synchronization pulse generator and serves as the fourth output to the synchronization block, the second output of the electric beam superposition member throttle at the joint serving at the same time as information input to the member fixing the successive order of technological operations, the output of the latter serving as the third output to the synchronization block, the latter having for its second output that of the seal detection device.