DE20300624U1 - Portable induction heating tool has a mains power unit with an oscillator connected to a transformer and hand held induction heater - Google Patents

Abstract

The power unit (1) has a rectifier (4), an inductive/capacitative connecting circuit (5) and transistorized oscillator (6) with frequency or pulse modulated output to a transformer (3) having leads to the hand tool (2) with an induction head (8) and cylindrical probe (9).

Description

01089G

IFF Prof. Dr. Habenicht
Institute for Joining Technology
Manufacturing Processes GmbH
Gutenbergstrasse 25

D-85748 Garching
10

Device for generating electrical heat

The invention relates to a particularly portable device for generating electrical heat, which operates according to the principle of induction heat generation.

From DE 20014423 A1, a heating device for the inductive heat treatment of workpieces is known, in particular for gelling or for heating flanged areas on vehicle body parts with at least one inductor, wherein the heating device has at least two stations, wherein a first station is designed for essentially selective inductive heating of the workpiece and at least one subsequent station is designed for more extensive heating of the workpiece. This is a stationary, relatively large system for heating entire components or groups of components in the manufacture of motor vehicles.

From DE 195 27 827 C2 a method for generating electrical heat with a medium or high frequency alternating heating current between approx. 50 Hz and several 100 kHz on an inductive or conductive basis is known, whereby the heat delivered to a consumer on the secondary side of a transformer

Heating current is generated on the primary side by rectification, smoothing and subsequent controllable reversal of the supply current and the heating current is generated without an oscillating circuit, whereby the reactive power generated on the secondary side is compensated for in a capacitor arrangement with the appropriate capacity connected upstream of the inverter in the direct current circuit. This device is used in particular for the inductive heating of components and component groups in the manufacture of motor vehicles, whereby very large currents are used in the area of the inductor. In particular, water cooling is necessary in such systems, so that such devices are only suitable for stationary use.

A heating device and a method for inductive heat treatment are known from EP 1 036 487 B1. This device comprises an inductor which is designed in several parts and consists of several inductor parts which can be connected to one another. The inductor parts can be arranged in close proximity to one another or positioned further away. This is intended in particular to achieve inductive heating of complex workpieces, such as vehicle body doors. This device is also very large and takes up a lot of space.

The object of the invention is to create a device for generating electrical heat which is flexible and easy to use in workshops, repair shops and in prototype production and which is inexpensive to purchase and maintain.

The problem is solved with a device for generating electrical heat, which is designed to be portable.

According to the invention, a device for generating electrical heat is designed with a portable energy supply unit and a hand-held part, the design being such that cooling of the entire system or parts of the system and in particular complex water cooling can be dispensed with. It has been shown that in most applications, simple, easy and energy-saving air cooling, for example by convection and/or a fan, is sufficient. The device according to the invention works with single-phase alternating current, using a multi-wind inductor, so that relatively low currents are required for effective induction. The device according to the invention is used, for example, for bolt bonding, whereby bolts provided with an adhesive on the front side are bonded to body parts and/or plastic parts, for example. These bolts in turn serve as a holder for, for example, interior fittings of motor vehicles. The hand-held part of the device according to the invention is designed such that a head of the hand-held part can be easily adjusted to different bolt geometries. Depending on the bolts to be glued, the voltage frequency can also be adjusted in a conventional manner using frequency or pulse width modulation. If necessary, the handpiece has air cooling, which enables cycle times to be reduced. This can be achieved using a simple fan or, for example, a compressed air connection. The cooling is designed in such a way that even a bolt that has just been glued and is still warm can be cooled down.

In an advantageous further development, a device for detecting the temperature of the bolt and/or the workpiece and/or the substrate (sheet metal) is present. This device has a feedback with the control/regulation device of the device for generating electrical heat, so that the target temperatures can be predetermined.

If a suitably designed soldering shaft is used instead of a bolt, the invention can advantageously be used as an inductively operated soldering iron.
5

Furthermore, it is possible to use the device for inductive generation of heat in a sheet metal part without a bolt or shaft. To do this, the hand part is placed on a sheet metal and then the coil of the hand inductor is supplied with electricity. In this way, sheet metal parts can be heated in a targeted manner, very quickly and, if necessary, to a very high temperature. This is advantageous, for example, in metalworking, as it means that dangerous gas burners are not required. Furthermore, the invention can create an easily controllable, safe and fast alternative to flame straightening of sheet metal parts. In conjunction with a device for detecting the temperature, however, very gentle and upper-limited amounts of heat can also be introduced. This is advantageous, for example, if the invention is to be used to weaken existing adhesive bonds by introducing heat in order to separate them without thermally overloading the sheets, or, for example, to remove dents from body panels by introducing heat in a way that protects the paint. Nevertheless, the invention can also be used to quickly remove paint from them thermally.

The advantage of the invention is that it is very compact and in particular does not require any more space than, for example, a briefcase. This makes it possible to process adhesive bolts very easily, quickly and reliably in workshops, repair shops or when producing prototypes, something that was previously not possible in such companies in such a quick and simple way. Another advantage is that the handle can be adjusted to different bolt geometries in a simple and quick way.

It is also advantageous that the device according to the invention can be used without any problems for soldering and/or heating components, e.g. in a metalworking shop, so that the dangerous handling of gas burners can be avoided.

Furthermore, the invention can be used in a simple, fast and precise manner for straightening metal components and sheets.
10

The invention is explained by way of example using a drawing. In the drawing:

Fig. 1 shows the device according to the invention in a highly schematic view;

Fig. 2 the head of a handpiece in a highly schematic, partially sectioned view;

Fig. 3 shows a further embodiment of a head of the handset in a highly schematic partially sectioned view.

The portable device according to the invention for generating electrical heat comprises an electrical energy supply unit 1 and a handset 2 connected thereto. If necessary, an isolating transformer 3 is provided in an electrically conductive connection between the electrical energy supply unit 1 and the handset 2.
30

The electrical energy supply unit 1 is accommodated in particular in a box-shaped or otherwise designed housing of small dimensions, in particular the size of a briefcase, for example, and comprises a mains rectifier 4, a DC voltage intermediate circuit 5 and a transistor inverter 6.

The electrical power supply unit can be designed as a so-called "hard chopper", i.e. without an oscillating circuit. The DC intermediate circuit 5 has two inductors Li and L2 connected in series and a capacitance C. If necessary, however, a DC intermediate circuit with only one or no inductors can also be used.

The electrical power supply unit has a control and regulating device (not shown) which controls the transistor inverter and regulates the output voltage or the output current. The regulation and control of the transistor inverter can be operated by frequency modulation or pulse width modulation.
15

The electrical energy supply unit 1 is connected on the output side to an isolating transformer 3, where the isolating transformer 3 is electrically connected on the output side to a supply line to the handset 2. In Fig. 1, the electrical supply line is shown in a simplified manner by only a single supply line.

The handpiece 2 comprises a handle 7, an inductor head 8 arranged downstream of the handle 7 and an elongated bolt receiving device 9 facing away from a workpiece to be machined.

The head of the handpiece 2 (Fig. 2) comprises a ring-shaped or cylindrical ferrite core 10. A coil 11 is arranged on the outside around the ferrite core 10. The coil 11 is electrically connected to the output of the electrical power supply unit and/or the isolating transformer 3. By applying an alternating voltage from the electrical power supply unit to the coil 11, an alternating magnetic field can be created in the core depending on the pulse width or frequency.

10 can be achieved. The core 10 is mounted in an annular, externally circumferential groove 12 on or in the bolt receiving device 9, wherein the bolt receiving device 9 is a hollow cylindrical tube which is open in the area of the core 10 5. The core 10 partially protrudes over an end face 13 of the bolt receiving device 9.

The bolt receiving device 9 is designed to receive and support a bolt 14. The bolt 14 has an elongated, cylindrical piston shaft 15 and a bolt plate 16 formed in the area of an end face. The bolt plate 16 projects radially beyond the bolt shaft 15. A suitable adhesive 17 is present on a surface of the bolt plate 16 opposite the shaft 15.

The bolt receiving device 9 has an inner diameter which corresponds to the outer diameter of the bolt shaft 15 or is slightly larger, so that the bolt shaft 15 is securely guided in the bolt receiving device 9.

In the bolt receiving device 9 there is a spring 20, at the end of which on the bolt receiving device opening side a magnet 21 is arranged. If a bolt 14 is pushed into the inductor head 9 and thus into the bolt receiving device 9, a rear end face 22 of the bolt 14 comes onto the magnet 21 and is held in the bolt receiving device 9 by the magnet and the spring 20. The outer diameter of the bolt plate 16 is dimensioned such that the bolt plate 16 rests at least partially on an end face 23 of the ferrite core 10.

In order to glue a bolt 14 at a predetermined location, the bolt 14 is inserted into the bolt receiving device 9 as already described. After the bolt 14 has been held in the bolt receiving device 9 by the magnet 21 and the spring

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which is held 20, it is placed on the assembly point, the spring 20 being compressed until the bolt 14 is completely received in the bolt receiving device 9, the bolt plate 16 resting at least partially on the end faces 23. The coil 11 is now subjected to a voltage, the voltage being applied in a pulse width and/or frequency modulated manner. The alternating current flowing in the coil 11 induces a magnetic field in the ferrite core 10. This alternating magnetic field penetrates the end faces 23 and thus the bolt plate 16, which leads to heating by inducing eddy currents in the bolt plate 16. The rest of the bolt plate 16 is also heated via heat conduction via the penetrated, heated surfaces of the bolt plate 16, so that the heat-activated or thermoplastic adhesive 17, for example, becomes liquid. After a predetermined time, for example stored via characteristic maps in the device or other control mechanisms, the coil is disconnected from the power supply or the power supply is stopped, whereby the inductor head 8 and the bolt 14 cool down and the adhesive 17 hardens.

The coil 11 is preferably formed with a plurality of turns, wherein the coil can be made from a pressed RF strand.

Instead of a bolt holder that works with a magnet 21 and a spring 20, the bolt holder can also work with a vacuum system, wherein the vacuum acts, for example, on a rear end face of the bolt 14.

In a further advantageous embodiment (Fig. 3), the bolt 14 does not have a bolt plate 16, but is essentially cylindrical. The adhesive layer 17 is applied to an outward-facing end face 24 of the bolt 14.

In this embodiment, there is no ferrite core 10 as a magnetic field concentrator. Instead, the coil 11 is formed in the area of the inductor head 8 in the circumferential L-shaped groove 12 on the bolt receiving device 9 or on the head. If this coil 11 is subjected to an alternating current, eddy currents are induced in the area enclosed by the coil 11. These eddy currents are also induced in the bolt 14 and cause the desired heating there. The coil 11 is preferably arranged in a groove (not shown) on the inside of the bolt receiving device 9.

The functional principle is otherwise identical to that of the previously described embodiment. In all embodiments, the heating can be linear or in stages. In a preferred embodiment, a detection device (not shown) for detecting the temperature of the bolt and/or the mounting point is also present and is accordingly coupled to the control or regulation of the electrical energy supply unit 1.

In the described embodiments, a cooling device (not shown) can also be present on the handle 2, which cools the bolt 14 and the assembly point again after heating, in particular by means of compressed air.

Of course, it is also possible to arrange several handpieces 2 on one electrical power supply unit.
30

Furthermore, a control system can advantageously be provided on the portable electrical power supply unit 1, which controls the process and regulates the bolts in a way that is tailored to different bolt types, bolt materials and areas of application.

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lation via frequency change and/or pulse width modulation.

The device is by no means limited to bolts; other suitable and common objects such as washers, hooks and others can also be bonded using this device, provided that inductive heating is necessary.

Furthermore, the application is not limited to the automotive industry or the bonding of bolts to sheet metal; the invention can also be used advantageously in the construction sector.

When using bolts 14 or other elements with a plate, it is expedient to keep the contact surface of the ferrite core 10 as large as possible so that the magnetic field concentrated by the ferrite core 10 acts on the plate 16 over as large an area as possible and heats it.

When using bolts 14 without a plate and thus without a ferrite core, it is expedient to keep the air gap between the external receiving device and the bolt or between the coil and the bolt as small as possible in order to reduce air gap losses.

Deviating from the embodiment described in Fig. 3, the coil 11 can also be fastened to the inductor head 8 in a different manner such that the coil 11 rests directly on the bolt 14 without any intervening elements of the bolt receiving device 9.

In addition, the invention or a handpiece 2 according to the invention can also be used as an inductively operated soldering iron. For this purpose, a soldering shaft is used instead of a bolt.

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It is also possible to use the device for inductive generation of heat in a sheet metal part without a bolt or shaft. To do this, the hand part is placed on a sheet metal and then a current is applied to the coil of the hand inductor. In this way, sheet metal parts can be heated in a targeted manner, very quickly and, if necessary, to a very high temperature. This is an advantage in the metalworking industry, for example, as it means that dangerous gas burners are no longer required.

Furthermore, the invention can be used to create an easily controlled, safe and fast alternative to flame straightening of sheet metal parts. To do this, the handpiece is placed at a predetermined location and a current is applied to the coil. By inducing currents in the sheet metal and, in the case of ferromagnetic sheets, also the magnetizations that constantly flip in accordance with the alternating field, the sheet metal heats up very quickly and yet in a spatially limited manner. This allows stresses to be introduced or reduced in a very targeted manner. Furthermore, high-strength sheets in particular can be preheated to facilitate a punch riveting, clinching or similar forming joining process that follows shortly afterwards.

In conjunction with a device for measuring the temperature, however, heat can also be introduced very gently and with a defined upper limit. This is advantageous, for example, if the invention is to be used to dissolve existing bonds by introducing heat without thermally overloading the metal sheets or, for example, to remove dents from body panels by introducing heat without damaging the paint. At the same time, the invention can also be used to quickly remove paint thermally.

Claims (26)

1. Portable device for generating electrical heat, in particular for bolt bonding, soldering, debonding, thermal straightening of e.g. metal parts, wherein at least one portable electrical energy supply unit ( 1 ) and a hand part ( 2 ) are present, which are electrically conductively connected to one another, wherein the energy supply unit ( 1 ) is designed to deliver an alternating voltage on the output side and the hand part ( 2 ) is designed as an inductor device ( 8 ) for workpieces ( 14 ) for generating heat. 2. Device according to claim 1, characterized in that the electrical energy supply unit ( 1 ) has a control device for controlling the frequency and/or pulse width (frequency modulation or pulse width modulation) of the voltage delivered on the output side. 3. Device according to claim 1 and/or 2, characterized in that the hand part ( 2 ) is designed to partially accommodate a workpiece ( 14 ) to be heated by induction. 4. Device according to one or more of the preceding claims, characterized in that an isolating transformer ( 3 ) is present between the handset ( 2 ) and the electrical power supply unit ( 1 ). 5. Device according to one or more of the preceding claims, characterized in that the regulating and control device is designed such that a continuous and/or graduated heating can be achieved. 6. Device according to one or more of the preceding claims, characterized in that a detection device for detecting the temperature of the bolt ( 14 ) and/or the assembly point is present and is correspondingly coupled to the control or regulation of the electrical energy supply unit ( 1 ). 7. Device according to one or more of the preceding claims, characterized in that a cooling device is provided on the hand-held device ( 2 ), which cools the bolt ( 14 ) and the assembly point after heating, in particular by means of compressed air. 8. Device according to one or more of the preceding claims, characterized in that the electrical energy supply unit comprises a mains rectifier ( 4 ), a DC voltage intermediate circuit ( 5 ) and a transistor inverter ( 6 ). 9. Device according to one or more of the preceding claims, characterized in that the electrical energy supply unit ( 1 ) is designed as a so-called "hard chopper", ie without an oscillating circuit. 10. Device according to one or more of the preceding claims, characterized in that the DC voltage intermediate circuit ( 5 ) comprises two series-connected inductors L1 and L2 and a capacitor C. 11. Device according to one or more of claims 1 to 10, characterized in that there is one or no inductance in the DC voltage intermediate circuit ( 5 ). 12. Device according to one or more of the preceding claims, characterized in that the hand part ( 2 ) comprises a handle ( 7 ), a downstream inductor head ( 8 ) connected to the handle ( 7 ) and a bolt receiving device ( 9 ) facing away from a workpiece ( 14 ) to be machined and extending longitudinally away from the inductor head ( 8 ). 13. Device according to one or more of the preceding claims, characterized in that the head ( 8 ) of the hand part ( 2 ) comprises an annular or cylindrical ferrite core ( 10 ), wherein a coil ( 11 ) is arranged on the outside around the ferrite core ( 10 ), wherein the coil ( 11 ) is electrically conductively connected to the output of the electrical energy supply unit ( 1 ) and/or the isolating transformer ( 3 ). 14. Device according to one or more of the preceding claims, characterized in that the core ( 10 ) is mounted in an annular, externally circumferential groove ( 12 ) on or in the bolt receiving device ( 9 ), wherein the bolt receiving device ( 9 ) is a hollow cylindrical tube which is open in the region of the core ( 10 ). 15. Device according to one or more of the preceding claims, characterized in that the core ( 10 ) partially projects beyond an end face ( 13 ) of the bolt receiving device ( 9 ). 16. Device according to one or more of the preceding claims, characterized in that the bolt receiving device ( 9 ) is designed to receive and support a bolt ( 14 ), wherein the bolt receiving device ( 9 ) has an inner diameter which corresponds to the outer diameter of a bolt shaft ( 15 ) or is slightly larger, so that the bolt shaft ( 15 ) is securely guided in the bolt receiving device ( 9 ). 17. Device according to one or more of the preceding claims, characterized in that a spring ( 20 ) is present in the bolt receiving device ( 9 ), at the end of which a magnet ( 21 ) is arranged on the bolt receiving device opening side, so that a bolt ( 14 ) inserted into the bolt receiving device ( 9 ) is held longitudinally displaceably by the magnet ( 21 ) and the spring ( 20 ) in the bolt receiving device ( 9 ). 18. Device according to one or more of the preceding claims, characterized in that the bolt receiving device ( 9 ) or the end faces ( 23 ) of the ferrite core ( 10 ) are dimensioned such that a bolt plate ( 16 ) rests at least partially on an end face ( 23 ) of the ferrite core ( 10 ) and the bolt shaft ( 15 ) can be guided securely in the bolt receiving device ( 9 ), in particular without tilting. 19. Device according to one or more of the preceding claims, characterized in that the coil ( 11 ) is formed with a plurality of turns. 20. Device according to claim 20, characterized in that the coil ( 11 ) is formed from a pressed RF strand. 21. Device according to one or more of the preceding claims, characterized in that the bolt receiving device ( 9 ) is designed with a vacuum system such that a vacuum device is formed on an end face of the bolt ( 14 ) for holding the same in the bolt receiving device ( 9 ). 22. Device according to one or more of the preceding claims, characterized in that for gluing plateless bolts ( 14 ), the coil ( 11 ) is formed in the region of the inductor head ( 8 ) in a circumferential L-shaped groove ( 12 ) on the bolt receiving device ( 9 ) or on the inductor head ( 8 ), wherein the coil ( 11 ) is arranged in a groove made on the inside of the bolt receiving device ( 9 ) with the smallest possible distance from a bolt ( 14 ) to be glued. 23. Device according to one or more of the preceding claims, characterized in that the device is a soldering iron based on the induction principle. 24. Device according to one or more of the preceding claims, characterized in that the device is a device based on the induction principle for the thermal straightening of sheet metal parts. 25. Device according to one or more of the preceding claims, characterized in that the device is a device based on the induction principle for debonding adhesive bonds. 26. Device according to one or more of the preceding claims, characterized in that the device is a device based on the induction principle for removing coatings, e.g. paint layers.