Electronic Boom Deflector

Abstract

An electron beam deflector (32) for use in electron beam welding is provided. The deflector (32) includes a sheet (32) defining at least one path (36) through which an electron beam (14) can travel to a weld location. At least one deflection element (44) in the form of an electromagnetic coil is disposed within the at least one path (36), the electromagnetic coil (44) being configured to modify a direction of travel of the electron beam (14) to deflect the electron beam (14) so ​​that it is incident generally perpendicular to a weld location on a workpiece. The sheet (32) includes a separate base portion (40) and a lid portion (42).

Description

[Technical field]

[0001] The present invention relates to an electron beam deflector, and more particularly to a deflector used in electron beam welding. [Background technology]

[0002] Electron beam welding is used for high volume production in markets such as automotive and sensors, where high precision and low heat input welding is required to produce thousands of parts per day. Electron beam is generally the technology of choice in such high volume production environments due to the fast deflection speed of the electron beam.

[0003] A tool or fixture is generally used to hold the parts together so that they do not move or distort while the thermal energy of the electron beam is acting on them. Such tools are often large to ensure sufficient mechanical strength for the fixation, and as a result, such tools prevent the electron beam from traveling straight to the welding surface of the parts. This is particularly problematic when welding batteries for vehicles is realized, where many welds are required over a wide area and the connections between the batteries need to be sufficiently fixed to ensure high quality welds. Solutions have been tried, such as using mechanical movements to move the parts in an evacuated welding chamber or to move the electron gun away from the parts being processed, but this solution complicates the adjustment of the part position and requires a larger vacuum vessel, resulting in a significant increase in the cycle time of the process. Summary of the Invention [Means for solving the problem]

[0004] According to the present invention, there is provided an electron beam deflector for use in electron beam welding. The deflector comprises a sheet body defining at least one path through which an electron beam can pass to a weld point. At least one deflection element is disposed within the at least one path, the at least one deflection element being configured to modify the direction of travel of the electron beam. Such a deflector can be disposed within a vacuum vessel in which welding is to be performed and deflects the electron beam locally outside a gun column generating the electron beam.

[0005] Preferably, the deflection element is configured to deflect the electron beam so that the electron beam is incident substantially perpendicularly on the welding spot of the workpiece.

[0006] Preferably, the electron beam deflector is configured to be installable in a position inside the vacuum vessel near the workpieces to be welded, typically at the upper end of a jig that fixes the workpieces to be welded. Also, preferably, the electron beam deflector includes an air hole that can exhaust any air inside the planar body.

[0007] The deflector may further comprise a plurality of paths, with at least one deflection element disposed within each path.

[0008] The multiple pathways may be arranged in an array, typically in a staggered array.

[0009] Preferably, each deflection element has a magnetic field strength and direction that depends on the distance from the non-deflection axis of the electron beam generated by the electron gun.

[0010] The sheet-shaped body may include a cover portion and a separate base portion that can be connected to each other, which facilitates installation of the deflection element in the sheet-shaped body and facilitates electrical connection between the deflection element and the electronic component.

[0011] Preferably, each of the paths is formed inside the base portion, and grooves formed inside the base portion are connected to each other, which makes it easy to route electric wires throughout the base portion and enables electrical connection between the deflection elements and between the deflection elements and an external power source to be realized by using the electric wires.

[0012] Preferably, the lid portion has an opening at a portion corresponding to the position of the passage inside the base portion.

[0013] A number of deflection elements may be disposed within the path, or within each path, and each deflection element may be configured to modify different aspects of the electron beam, thereby providing deflection elements that adjust the direction, focus, and / or beam width.

[0014] Preferably, each deflection element includes an electromagnetic coil. The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram of an electron beam welding device. [Diagram 2] FIG. [Diagram 3] 3 is an exploded partial view of a deflection plate according to the first embodiment. FIG. [Figure 4] FIG. 11 is a partial cross-sectional view of a deflection plate according to the second embodiment. [Diagram 5] FIG. 11 is a partial cross-sectional view of a deflection plate according to the third embodiment. [Figure 6] FIG. 2 is a schematic diagram of a testing device for deflection plates. [Figure 7] FIG. 2 is a schematic diagram of a deflection plate provided with a beam analysis chamber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] explanation Electron beam welding apparatus 10 is shown diagrammatically in FIG. 1 and includes an electron beam gun 12 that emits an electron beam 14, and focusing elements 16, fast focusing elements 18, and fast deflection elements 24 disposed within gun 12 to modify the characteristics of electron beam 14 and adjust the position of electron beam 14 away from a central, undeflected axis that corresponds to an axial path passing through the center of gun 12. The position of beam 14 is adjusted by elements 16, 18, and 24 to allow welding at various locations, as shown by example deflected beams 20, 20', and 20''. A workpiece 26 that requires welding is disposed within container 22. An example of the workpiece 26 is an automotive battery that requires welded connections to a number of individual battery cells 28.

[0017] The cells 26 are rigidly fixed in position by a tool or fixture 30. A planar body in the form of a deflection plate 32 is placed on the fixture 30 within the vessel 22 so as to be directly above the workpiece cells 26. As shown in FIG. 2, the plate 32 is formed with a plurality of circular openings 34 that extend through the plate 32 as a plurality of paths 36 for the electron beam 14 to impinge on the weld locations associated with the cells 28 and located below the plate 32. Typically, the fixture 30 is formed with a plurality of open linear paths to access the cells 28 during welding.

[0018] 3, at least one electron beam deflection element, such as a cylindrical electromagnetic coil 44, is disposed within each path 36 of plate 32 for locally deflecting deflected beams 20, 20', 20'' as they reach plate 32. An external power source 38 is connected to plate 32 for providing power to coil 44 such that coil 44 generates a localized magnetic field.

[0019] In prior art welding where such deflection plates are not used, the electron beam 14 strikes all welds at a slight angle except for those directly below the axis coincident with the undeflected beam 14, which impairs weld quality. The deflection plates 32 locally correct the direction of electron beam travel within the vessel 22 near the batteries 26 and outside the structure of the gun 12. The plates 32 modify the direction of electron beams 20, 20', 20'' to ensure that they are directed substantially perpendicular to the welds at each battery cell 28, thereby ensuring high quality welds. If the workpiece is constructed with an irregular surface, the deflection elements within the plates 32 and adjacent the welds can be adjusted accordingly to cause the electron beam to travel slightly off-axis along path 36 so that it strikes the irregular surface substantially perpendicularly.

[0020] In FIG. 3, an exploded view of the plate 32 is shown. The plate 32 comprises a base portion 40 and a lid portion 42, typically having a thickness of the order of 10 mm to 30 mm. The base portion 40 is formed with a number of passages 36 in which the electromagnetic coils 44 are arranged. The base portion 40 is covered by the lid portion 42, which is provided with an opening, only a small portion of which is shown for clarity. The coils 44 comprise a cylindrical coil core 46 and a ferrite ring 48, typically having a diameter of 15 mm to 25 mm. An opening 52 in the lid portion 42, typically having a diameter of the order of 10 mm to 20 mm, is aligned with the passages 36 to provide a through passage for the electron beam. The passages 36 are interconnected by a groove 54 in the interior of the base portion 40, which allows a cable to pass between the coils 44 and two bypass potentiometers 56. A separate lid portion simplifies the insertion and wiring of the coils 44 inside the base portion 40. The potentiometer 56 is typically digitally responsive so that it can be easily adjusted once the lid 42 is secured to the base 40. A vent is provided in the lid 42 so that the interior region of the plate 32 can be evacuated when the vessel 22 is evacuated in preparation for welding.

[0021] Depending on the local adjustment required of the electron beam 14 as it passes through the plate 32, a single electromagnetic coil 44 may be used as the deflection element within each path 36 as shown in FIG. 3, or multiple coils may be used as the deflection elements as shown in FIGS. 4 and 5, thus allowing beam shaping and focus control with different types of coils.

[0022] As shown in Figure 4, a cylindrical deflection coil 60 is used in conjunction with a cylindrical focusing coil 62 and a cylindrical oscillating coil 64 which are connected by wires 70 to potentiometer trimmers 72 and thence to electrical inputs associated with the deflection plates 32. The position of the electromagnetic coils is fixed by a sleeve 68 which is made of a material transparent to the electron beam, for example Perspex. To reduce the amount of wiring required, the electromagnetic coils 44 are typically connected in series in one or more groups.

[0023] By having an additional beam oscillating deflection element 64 at each deflection element location, the primary high speed deflection system in gun 12 can eliminate the oscillating deflector, thereby reducing the bandwidth required for the primary electron gun deflection system, thereby improving positional accuracy and allowing more parts to be welded over a larger area without error.

[0024] In another plate configuration shown in Figure 5, a cylindrical deflection coil 60 is combined with a cylindrical stigmatism coil 80. The stigmatism beam shaping improves the beam quality and ensures that the electron beam gun 12 does not need to dynamically change the stigmation or that the electron beam gun 12 can adjust the beam focus quickly to reposition the beam 14 for each component position. By placing the deflection elements capable of beam shaping inside the plate 32 instead of inside the electron beam gun 12, the bandwidth required for the electron gun control system is reduced, and as a result the beam shaping system, which is not easy to control at high speed, generally has a higher inductance than the deflection system.

[0025] The apertures 34 and associated channels 36 are typically provided in a staggered array, as shown in Figure 2, having five rows of five apertures each, with each row offset from adjacent rows such that the apertures in every other row are horizontally aligned. It is understood that the size and shape of the plate 32 and the number of apertures therein will vary depending on the nature of the workpieces being welded and the number and spacing of weld locations on the workpiece 26 that require adjustment.

[0026] The magnetic field strength and direction generated by each electromagnetic coil 44 depends on the distance and inclination of the electron beam 14 from the central non-deflection axis to the plate opening 34. As can be seen from FIG. 1, the angles of incidence are different at three distributed locations 20, 20', 20'' of the electron beam 14 for three distributed part weld locations. Typically, the electromagnetic coil located inside the plate 32 furthest from the non-deflection axis has the most turns of the coil to generate the largest magnetic field. The remaining coils are wound to provide a magnetic field proportional to the magnetic field at the furthest location, and such that no magnetic field is typically required at the center point 90, which corresponds to the non-deflection axis of the electron beam 14 as it leaves the gun 12.

[0027] 2 shows, by way of example, the number of coil turns and resulting magnetic field strengths of the various electromagnetic coils arranged in each path, and the relative rotation of the various electromagnetic coils as indicated by the placement of the individual turns in the aperture in a view perpendicular to the page. Thus, the magnetic field strength of each deflection element 44 is set so that the magnetic field strength of the deflection element increases as the distance of the weld increases from the center of the machine and the position of the undeflected beam. Each deflection element 44 can have an adjustable fine control setting for adjusting their magnetic field rotation and magnetic field strength to ensure that the deflection is correct for the angle of the deflected electron beam, and to ensure that the electron beam passes through the fixture 30 at an angle that is most perpendicular to the part 28. Instead of electromagnetic coils, electrostatic plates or permanent magnets can be used as the deflection elements.

[0028] Fine adjustment of the magnetic field strength and rotational alignment of each deflection element may be accomplished by manual, mechanical, electrical, or electromechanical methods. The electrical wiring of the deflection elements 44, 60, 62, and 64 may be in series or parallel, as best suited for the welding equipment. The control system may use analog or digital controls, as best suited for the welding equipment.

[0029] The placement of plate 32 on top of fixture 30 within vessel 22 ensures that the electron beam is dispersed widely and rapidly to multiple weld locations on the component without any problems caused by the fixture holding the component in such a way that the electron beam is blocked or distorted by the fixture. A distributed array of electron beam deflection elements, with at least one localized deflection element disposed above each component being welded, allows the electron beam to be redirected to a weld location on the component, or redirected at a substantially perpendicular angle to a portion of the component, or redirected substantially perpendicular to the weld location, thereby limiting interference with the beam by fixture 30.

[0030] When installing or testing the deflection plate 32 for welding multiple identical parts, such as a series of vehicle batteries, a metal plate 90 with a small opening 92 may be inserted into the center of the path 36, as shown in FIG. 5. A beam collector 94 may then be placed below the path 36 where the deflection elements are located, instead of the workpiece. The control software associated with the gun 12 deflects the electron beam 14 onto each path 36 and measures the positional accuracy of each deflection element 44 as it deflects the electron beam onto the collector 94. Automated software or a manual operator can make fine corrections to the deflection elements 44 inside the plate 32 to optimize the position of the beam on the collector 94, thereby ensuring high quality welds. If the opening 92 has a small enough diameter, a power distribution analysis may be performed to assist the software or operator in making corrections to optimize the beam properties at each location.

[0031] As shown in Figure 7, beam analysis chambers 100 may be added between the deflection element positions 36 to allow for process monitoring when the system is in production. The beam analysis chambers 100 may be either an electrically isolated piece of wiring or a slit or pinhole Faraday cup type beam collector 102, which allows beam properties to be measured at multiple positions across the part for every part being processed.

[0032] Further process monitoring may be performed by an array of backscattered electron detectors positioned in the ceiling of the vacuum processing vessel 22 to analyze electrons emitted toward and reflected from the ceiling of the vacuum vessel 22 during part processing.

[0033] Further process monitoring may be performed by an array of optical cameras positioned within the surface of the vacuum vessel 22 and viewing through lead glass windows.

Claims

1. An electron beam deflector for use in electron beam welding, comprising: a planar body defining at least one path through which an electron beam can pass; At least one deflection element is disposed within the at least one path; The at least one deflection element is configured to modify a direction of travel of the electron beam.

2. 2. The electron beam deflector according to claim 1, wherein the deflection element is configured to deflect the electron beam so that the electron beam is incident on the welding point of the workpiece substantially perpendicularly.

3. 3. The electron beam deflector according to claim 1, which is configured to be installable in a vacuum.

4. Further comprising a plurality of paths; 3. The electron beam deflector according to claim 1, wherein at least one deflection element is disposed inside each of said plurality of paths.

5. 5. The electron beam deflector of claim 4, wherein each of said deflection elements has a magnetic field strength and a magnetic field direction that depend on the distance from the non-deflection axis of said electron beam.

6. 5. The electron beam deflector of claim 4, wherein the plurality of paths are arranged in an array.

7. 5. The electron beam deflector of claim 4, wherein the plurality of paths are arranged in a staggered array.

8. 3. The electron beam deflector according to claim 1, wherein the planar body comprises a cover portion and a separate base portion that can be connected to each other.

9. 9. The electron beam deflector of claim 8, wherein the paths are formed inside the base portion, and grooves formed inside the base portion are connected to each other.

10. 9. The electron beam deflector according to claim 8, wherein the lid portion has an opening at a position corresponding to the position of the path inside the base portion.

11. further comprising a plurality of deflection elements positioned within each of the paths; 3. The electron beam deflector of claim 1, wherein each of the plurality of deflection elements is configured to modify a different property of the electron beam.

12. 3. An electron beam deflector as claimed in claim 1 or 2, wherein each of the deflection elements comprises an electromagnetic coil.

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