EP2924130A1 - Warming device for conductive heating of a sheet metal circuit board - Google Patents

Abstract

The present invention relates to a heating device (23) for conductive heating of a metal sheet (1) of varying cross-sectional area, wherein the sheet metal blank (1) is directly part of a circuit (16), which is characterized in that an electrically conductive compensating element (8) is provided is, which is placed on a surface of the sheet metal blank (1), wherein the cross-sectional area of the sheet metal blank (1) added to the cross-sectional area of the compensating element (8) results in a Stromleitquerschnittsfläche (17).

Description

The present invention relates to a heating device for conductive heating of a sheet metal blank according to the features in the preamble of claim 1.

From the prior art, it is known to form motor vehicle components, in particular motor vehicle exterior components or else also motor vehicle structural components from sheet metal blanks.

Here, the hot forming and press hardening for the production of high-strength or even ultrahigh-strength components made of hardenable steel alloys, especially in the field of automotive industry prevailed.

To carry out the hot forming and press hardening, a sheet metal blank is first heated at least partially above austenitizing temperature and then shaped in this state and rapidly cooled in a Hardened press tool or a downstream cooling device. This process is also known as press hardening.

Heating to over Austenitisierungstemperatur means as it were a warming to more than 900 ° C, so that an increased energy input is needed. This means high production costs and a corresponding environmental impact due to the energy consumed.

As a heating method, the prior art conductive conduction has been established in which heat is generated within the board by virtue of a current flow conducted through the board to be heated due to the electrical resistance. Such a method is for example from the DE 102 12 819 B4 known. Here, electrodes are placed on opposite ends of a sheet metal blank, so that the sheet metal blank is part of an electrical circuit. By applying a current thus a heat input is generated in the sheet metal blank. In order not to heat targeted areas of the sheet metal plate or only to a small extent, it is also provided according to current-conducting solid state applied to the board, so that a stray flux of the electric current is generated. The electric current is divided in the region of the electrically conductive solids in part on this and thus does not flow with full current density through the sheet metal plate itself, but also with parts through the solids.

Object of the present invention is to show starting from the prior art, a heating possibility for a sheet metal blank, with a rational targeted, in particular homogeneous heating of the sheet metal blank is made possible by means of conductive heating.

The aforementioned object is achieved with a heating device according to the features in claim 1.

Advantageous embodiments of the present invention are the subject of the dependent claims.

The heating device according to the invention for the conductive heating of a metal sheet with varying cross-sectional area, wherein the sheet metal plate is a direct component of a circuit is characterized according to the invention by an electrically conductive compensating body or compensating element is provided, is placed on a surface of the sheet metal blank, wherein the cross-sectional area of the sheet metal blank added to the cross-sectional area of the compensating body results in a Stromleitquerschnittsfläche.

According to the invention, a compensating element made of an electrically conductive material is thus exposed, at least on a surface preferably completely on the surface, so that divergent cross sections of the sheet metal plate with regard to the associated different heating due to a concentration of the current density are selectively influenced. In the context of the invention, it is thus possible to heat a sheet metal plate with mutually different wall thickness or alternatively also sheet metal blanks with constant wall thickness but of different widths individually partially, preferably homogeneously. In this case, the mutually different width can be influenced by a different absolute width in the respective cross section of the sheet metal blank but also by recesses, openings or openings within the sheet metal blank. If a part has a smaller wall thickness and / or a smaller width compared with the respectively adjacent cross sections, a higher current density would lead to greater heating in the case of a metal sheet without compensation element. The compensating element itself provides here by a larger cross-sectional area of the compensation element itself before a compensation of the smaller cross-sectional area of the sheet metal blank, so that a targeted adjustment of the heating of the sheet metal blank in this area is achieved by specific choice of the total resulting current flow cross-sectional area. The current flow cross-sectional area results in each case from the addition of the cross-sectional area of the sheet metal blank as well as the cross-sectional area of the compensating element. This results in an effective or effective Stromleitquerschnittsfläche. The compensating element is thus electrically conductive on the sheet metal blank, which is formed in particular of a steel material to. Conductive heating in the context of this invention is a Resistance heating in the sheet metal plate to understand due to an electrical current flow.

Preferably, the Stromleitquerschnittsfläche is constant, so that there is a homogeneous heating over the entire sheet metal blank. Scatter losses or slight deviations due to a higher cross-sectional area of the compensating element compared to a smaller cross-sectional area of the sheet metal blank are negligible within the scope of the invention.

Another essential feature of the invention is that when contacting the compensating element with corresponding electrodes, in particular the contact areas or receiving areas for the electrodes on the compensating element are formed with a high mass or relatively thick. This results in a low current density density in this area, so that it leads to the compensation element only to a slight warming. Consequently, in particular even at high utilization, heating with a corresponding compensating element according to the invention requires no separate cooling in the region of the connection of the electrodes.

The heating device according to the invention is in particular in a production line for the production of hot-formed and press-hardened or tempered sheet metal components, preferably sheet steel components integrated, with heating within a very short time, especially in the production cycle is feasible. For this purpose, the heating device is preferably attached to an industrial robot, so that it can be used as a manipulator or transport device. In particular, a heating device is used to receive the sheet metal blank from a stack or tape and to transport to a further processing device, in particular a hot forming press with simultaneous heating during transport.

In the context of the invention results as a further positive effect that sometimes the compensation element has a relation to the sheet metal plate generally larger mass, which also heats up. The compensation element then gives off at least some of the heat energy contained by heat conduction to the sheet metal blank, whereby a reduction of the production costs for purely conductive resistance heating takes place. By selective choice of the cross-sectional area of the warm compensation element and thus the compensation element during production, it is thus possible to set an optimum between heat conduction and conductive heating due to current flow through the sheet metal plate itself.

Further particularly preferably, the compensation element lies on the entire surface of the surface of the sheet metal blank. Thus, a full-surface contact is improved, in particular, the contact surface of the compensation element to the sheet metal plate is concave. So it has a curvature inwards to the compensation element out. The sheet metal plate is thus attracted to the contact surface.

Alternatively or additionally, a corresponding pressing force can furthermore be applied particularly preferably via the compensating element, so that a gap is reduced to zero in the contact surface resulting between the compensating element and the board, and thus an almost complete contact is achieved. Further particularly preferably, the compensation element is part of a pressing tool or a tempering station, so that the board is inserted into the tempering and then a corresponding contact pressure is applied.

Thus, the full-surface system continues to be reinforced, it is provided in the invention that in the compensation element vacuum channels are present, so that when applied to the vacuum channels with a negative pressure, a suction effect for tightening the sheet metal plate is used to the compensation element.

Additionally or alternatively, it is possible that the compensation element has mechanical grippers, for example as pliers, which comprise the edge side of the sheet metal blank.

In order to deposit or repel the sheet metal plate after the transport and / or heating have taken place, ejectors or pressure rams are furthermore preferably provided which repel the sheet metal blank against the holding force at the storage location.

Furthermore, it is preferably provided in the context of the invention for the introduction of the electric current that the metal sheet is contacted at each opposite ends with an electrode, either only the sheet metal blank is contacted or alternatively contacted the sheet metal blank and the compensating element at least partially by the opposite electrodes are. By appropriate choice, especially the percentage distribution, it is possible to selectively distribute the current density density at the points of introduction to sheet metal blank and compensation element such that a targeted influencing of the conductive heating is also made possible in the end regions of the sheet metal blank. Preferably, the compensation element is provided with electrodes, so that the electrical current flow is passed from the compensation elements to the board.

Furthermore, particularly preferably, the compensation element is made of scale-resistant steel material or has a scale-resistant coating, so that a scaling takes place during operation of the temperature control. Preferably, then, the contact surface of the temperature control in electrically conductive contact with the sheet metal blank. For example, the compensation element can also be formed at least partially from carbon or semiconductor materials.

The cross-sectional area of the compensating element can be adjusted by targeted variation of the height or the width of the compensating element. Further particularly preferably, two compensation elements are provided, so that the upper side but also the underside of a sheet metal blank thus the two main surfaces of the sheet metal blank are each contacted by a compensation element. The cross-sectional areas, in this case two compensating elements, added with the cross-sectional area of the sheet metal blank then in turn form the Stromleitquerschnittsfläche, which is very particularly preferably constant in the context of the invention to achieve a homogeneous heating of the sheet metal blank.

Furthermore, particularly preferably, a load distribution plate can be arranged on the side of the compensating element opposite the metal sheet, which on the one hand stabilizes the compensating element and, on the other hand, selectively influences, in particular homogenizes, the forces applied to the sheet metal plate during the recording. Again, a load distribution plate in turn with the corresponding compensation element and optionally optionally arranged therebetween insulating layer in a tempering or a press are arranged so that a uniform contact or contact pressure prevails and thus an electrical conductivity is established.

With particular preference, in the use of two compensating elements, the respectively opposite cross-sectional area of the two compensating elements can be different from one another. As a result, it is again possible to specifically set the heating to be achieved.

Figur 1a und b

eine zu erwärmende Platine in Draufsicht und Längsschnittansicht,

Figur 2a und b

ein passendes Ausgleichselement in Draufsicht und Längsschnittansicht zu der aus Figur 1a und b bekannten Platine,

Figur 3

die Platine aus Figur 1 sowie das Ausgleichselement aus Figur 2 als konduktive Erwärmungsvorrichtung,

Figur 4a bis c

ein Ausgleichselement für eine B-Säule in Draufsicht, Längsschnitt- und Querschnittsansicht,

Figur 5a und b

eine voneinander verschieden erwärmte B-Säule sowie dazugehöriges Ausgleichselement,

Figur 6a und

b ein erfindungsgemäßes Ausgleichselement in Längsschnitt- und Querschnittsansicht mit mechanischen Greifern,

Figur 7

zwei auf gegenüberliegende Seiten angeordnete Ausgleichselemente,

Figur 8

ein erfindungsgemäßes Ausgleichselement mit gegenüberliegende Isolierplatte,

Figur 9

zwei voneinander verschieden große Ausgleichelemente,

Figur 10

ein erfindungsgemäßes Ausgleichselement zur Erwärmung einer Blechplatine mit voneinander verschiedenen Wandstärken und

Figur 11

eine erfindungsgemäße Temperiervorrichtung an einem RoboterArm zur Integrierung in eine Warmformlinie.

Further advantages, features, characteristics and aspects of the present invention are the subject of the following description. Preferred embodiments are described in the following figures. These are for easy understanding of the invention. Show it:

FIGS. 1a and b

a board to be heated in plan view and longitudinal section view,

FIGS. 2a and b

a matching compensation element in plan view and longitudinal sectional view of the FIGS. 1a and b known board,

FIG. 3

the board off FIG. 1 and the compensation element FIG. 2 as a conductive heating device,

Figure 4a to c

a compensation element for a B-pillar in plan view, longitudinal section and cross-sectional view,

FIG. 5a and b

a mutually differently heated B-pillar and associated compensation element,

Figure 6a and

b shows an inventive compensation element in longitudinal section and cross-sectional view with mechanical grippers,

FIG. 7

two compensating elements arranged on opposite sides,

FIG. 8

an inventive compensation element with opposite insulating plate,

FIG. 9

two compensation elements of different sizes,

FIG. 10

an inventive compensation element for heating a metal sheet with mutually different wall thicknesses and

FIG. 11

a tempering device according to the invention on a robot arm for integration into a thermoforming line.

In the figures, the same reference numerals are used for the same or similar components, even if a repeated description is omitted for reasons of simplicity.

FIG. 1 shows a plan view and a longitudinal sectional view of a sheet metal blank to be heated 1. The sheet metal blank 1 has for this purpose two surfaces 2, 3, a surface 2 at the top and a surface 3 at the bottom.

Furthermore, the sheet metal blank 1 has a homogeneous wall thickness 4 over its entire length 5. However, the sheet metal blank 1 has a mutually different width 6, so that the width 6.1 on one side is significantly smaller than the width 6.2 on the opposite side, again in the region of a recess 7 of which a different width 6.3 composed of the widths 6.31 and 6.32 results. Each wall thickness 4 multiplied by the respective width 6 then gives a cross-sectional area of the board to the respective length section. The cross-sectional area varies here due to the mutually different width 6 and / or the recess. 7

In order to compensate for each other from the different width 6 and recess 7 different cross-sectional areas of the sheet metal blank 1, is now according to FIGS. 2a and b a compensation element 8 is provided, which according to the plan view FIG. 2a essentially corresponds to the outer dimensions of the sheet metal blank 1. This also has a length 9 which corresponds substantially to the length 5 of the sheet metal blank 1. In addition, here Stromeinleitflächen 10 are provided so that to a conductive Heating a current in the compensating element 8 and in electrical system contact with the sheet metal blank 1 in the sheet metal blank 1 is introduced. The compensation element 8 also has a recess 11, corresponding to the recess 7 in the region of the sheet metal blank 1. Further, in the compensation element 8 vacuum channels 12 are arranged to suck a sheet metal blank 1 upon application of a negative pressure to a contact surface 13 of the compensating element 8. An essential part of the invention is now over FIG. 2b clearly visible. Accordingly, the wall thickness 4 or depth 14 of the compensating element 8 at mutually different locations 14.1, 14.2, 14.3 chosen such that the mutually different widths 6 of in FIG. 1a Compensated board can be compensated. By the mutually different depths 14 of the compensating element 8 combined with the mutually different widths 15 of the compensating element 8, shown in FIG FIG. 2a , Thus, each results in a different cross-sectional area of the compensating element 8 at a longitudinal section. To the current input surface 10 then electrodes 32 can be connected for coupling to a power source.

According to the invention thus results in a closed via the compensation element 8 circuit 16 according to FIG. 3 a respective constant Stromleitquerschnittsfläche 17 (indicated by arrows), which is composed of the respective cross-sectional area of the sheet metal blank 1 and the cross-sectional area of the compensating element 8 which in turn is composed of width and wall thickness or depth. Also shown is a vacuum applied to the vacuum passages 12 for attracting the sheet metal blank 1 to the compensating element 8 in order to realize an electrical, in particular full-surface contact.

In FIGS. 4a and c a compensation element 8 is shown that in edge regions 19 according to the cross-sectional view AA in Figure 4c has an increased depth 14, just to reach in the edge region 19 of the board to be heated on the example of a B-pillar shown a softer area by a lower current flow in the board and associated with a lower heating. Also shown is a boundary 20 at which a targeted delta 21 is set in the cross-sectional area of the compensating element 8 in accordance with FIG FIG. 5a around Limit 20 on a illustrated sheet metal blank 1 for producing a B-pillar, in particular set different strength ranges from each other. In the area of the delta 21, a higher cross-sectional area of the compensating element 8 is thus recorded, so that a lower heating takes place in a lower area 22 of the sheet metal blank 1, due to a higher cross-sectional area of the compensating element 8 and thus a lower current density in the sheet metal blank 1 this area. Not shown in detail are the according to Figure 4c elevated edge regions 19, which also on the sheet metal blank 1 according to FIG. 5a would set different strengths from each other.

Furthermore shown in FIGS. 6a and b is a variant of the invention of the heating device 23, comprising the compensation element 8 and a rear load distribution plate 24 under inclusion of an insulating plate 27, wherein the compensation element 8 is arranged on the load distribution plate 24 on a gripper arm 25 of an industrial robot, not shown. Thus, in turn, in connection with the vacuum channels 12, the sheet metal blank 1 is sucked and further fixed in position on the outside arranged pliers 26, so that consequently a system contact between the surface 2 of the sheet metal blank 1 and a contact surface 13 of the compensating elements 8 is formed. In addition, an insulating plate 27 is arranged between load distribution plate 24 and compensating element 8, which prevents heat dissipation of compensating element 8 to the load distribution plate 24. Also shown at the ends of the compensation element 8 is a current input surface 10, which are coupled to electrodes 32 for application to a current.

Furthermore shown in FIG. 7 is a variant with two compensation elements 8, which are mirror-symmetrical and contact the sheet metal blank 1 from both surfaces 2, 3 forth. The compensated by the compensating element 8 cross-sectional area of the sheet metal blank 1 is thus illustrated on the image plane top and bottom of each arranged compensating element 8 compensated. In this embodiment, then the compensation elements 8 are each acted upon with electricity, alternatively, however, not shown in detail in each case only one compensation element 8 are energized.

FIG. 8 shows an alternative embodiment variant with an underlying insulating plate 27. Here, the compensation element 8, the sheet metal plate 1 press in the direction of the insulating plate 27 and thus in turn improve the contact surface contact. Again, in turn, a load distribution plate 24 is disposed behind the compensation element 8 but also behind the insulating plate 27.

FIG. 9 shows a further embodiment of a heating device 23 according to the invention, in which case again two compensating elements 8 are arranged, wherein the compensating elements 8 have mutually different cross-sectional areas. For example, this can be used as shown here for tempering a sheet metal blank 1 with a patch 28 or even for a sheet metal blank 1, not shown in detail with different wall thicknesses 4. In particular, a corresponding patch 28 is fixed to the sheet metal blank 1, for example by gluing or but a welding process or a bond or a corresponding enamel.

This is closer in FIG. 10 shown. Shown is a metal sheet 1 with longitudinally mutually different wall thicknesses 4, which is enclosed in this embodiment by an upper compensating element 8 and a lower compensating element 8. The upper compensation element in this case has vacuum channels 12, so that for example with the upper compensation element 8, the sheet metal blank 1 can be accommodated and then stored in the lower compensation element 8, in which case the temperature takes place accordingly. The sheet metal plate 1 itself has 5 different wall thicknesses 4 over their length. All the aforementioned embodiments and in particular those in the FIG. 10 illustrated variant can be incorporated into a temperature control, a press tool or a fixing tool so. For this purpose, in particular, the upper half shown on the image plane and here in particular the upper compensation element 8 is raised for inserting a board and then lowered to be placed with a corresponding press pressure in particular homogeneously distributed press pressure on the board. The load distribution plate 24 may be part of an upper tool and / or lower tool of Be tempering station or the press tool or fixing tool, wherein a gripping arm 25 according to FIGS. 6 to 10 in these cases is omitted.

A possible field of application of a heating device 23 according to the invention is shown in FIG FIG. 11 , Here, an industrial robot 29 is shown, which has received by means of the compensating element 8 according to the invention a sheet metal blank 1, wherein also shown corresponding pliers 26 which fix the sheet metal blank 1 in the received state in addition to the vacuum channels 12. However, the vacuum channels 12 or pliers 26 can also be used alone. The thus-heated sheet metal blank 1 is then transferred to a thermoforming apparatus 30, in which it can be thermoformed and optionally also press-hardened or, alternatively, transferred to a following press hardening apparatus 31 or combined pruning apparatus.

Reference numerals:

1 -

sheet metal blank

2 -

Surface top to 1

3 -

Surface bottom to 1

4 -

wall thickness

5 -

Length to 1

6 -

width

6.1 -

width

6.2 -

width

6.3 -

width

6.31 -

width

6.32 -

width

7 -

recess

8th -

compensation element

9 -

Length to 8

10 -

Stromeinleitfläche

11 -

Recess to 8

12 -

Vacuum channels

13 -

contact area

14 -

Depth to 8

14.1 -

Depth to 8

14.2 -

Depth to 8

14.3 -

Depth to 8

15 -

Width to 8

15.1 -

Width to 8

15.2 -

Width to 8

15.3 -

Width to 8

16 -

circuit

17 -

Stromleitquerschnittsfläche

17.1 -

Stromleitquerschnittsfläche

17.2 -

Stromleitquerschnittsfläche

17.3 -

Stromleitquerschnittsfläche

18 -

vacuum

19 -

Border area to 8

20 -

border

21 -

delta

22 -

lower area

23 -

heater

24 -

Load distribution plate

25 -

claw arm

26 -

tongs

27 -

insulation

28 -

patch

29 -

industrial robots

30 -

Thermoforming apparatus

31 -

Press hardening device

32 -

electrodes

Claims (12)

A heating device (23) for conductively heating a metal sheet (1) of varying cross-sectional area, the metal sheet (1) being directly part of a circuit (16), characterized in that an electrically conductive compensating element (8) is provided on one surface of the circuit Sheet metal plate (1) is placed, wherein the cross-sectional area of the sheet metal blank (1) added to the cross-sectional area of the compensating element (8) results in a Stromleitquerschnittsfläche (17). Heating device according to claim 1, characterized in that a sheet metal plate (1) with a homogeneous wall thickness (4) can be heated or that a sheet metal blank (1) with mutually different wall thickness (4) can be heated. Heating device according to one of claims 1 or 2, characterized in that the sheet metal plate (1) has recesses (7) and / or holes. Heating device according to one of claims 1 to 3, characterized in that the sheet metal blank (1) is homogeneously heated, the cross-sectional area of the sheet metal blank (1) added to the cross-sectional area of the compensating element (8) results in a constant Stromleitquerschnittsfläche (17). Heating device according to one of claims 1 to 4, characterized in that two compensating elements (8) are provided, which are placed on both surfaces (2, 3) of the sheet metal blank (1). Heating device according to one of claims 1 to 5, characterized in that the compensating element (8) at a contact surface (13) to the sheet metal blank (1) is concave shaped. Heating device according to one of claims 1 to 6, characterized in that in the compensating element (8) vacuum channels (12) are provided so that the sheet metal blank (1) is attracted by an application of negative pressure (18). Heating device according to one of claims 1 to 7, characterized in that the sheet metal blank (1) at each opposite ends with a Stromeinleitfläche (10) is contacted or sheet metal blank (1) and compensating element (8) at opposite ends in each case simultaneously with a Stromeinleitfläche ( 10) are contactable or that in each case opposite ends of the compensating element (8) are contacted with Stromeinleitflächen (10) or one end with the sheet metal blank (1) and the opposite end with the compensating element (8) are contacted. Heating device according to one of claims 1 to 8, characterized in that the compensating element (8) is formed of a scale-resistant material or that the contact surface (13) of the compensating element (8) is coated scale-resistant. Heating device according to one of claims 1 to 9, characterized in that the compensating element (8) is attached to an industrial robot (29) and can be used as a manipulator of the sheet metal blank (1). Heating device according to one of the preceding claims, characterized in that the sheet metal blank (1) can be heated with partially different temperatures, for which purpose the cross-sectional area of the sheet metal blank (1) added to the cross-sectional area of the compensating element (8) over the length of the sheet metal blank from each other Stromleitquerschnittsfläche (17) results. Heating device according to one of the preceding claims, characterized in that it is designed as a pressing tool or fixing tool or tempering, wherein in each case the sheet metal blank (1) is inserted into this and the compensation element (8) with a pressing force on the sheet metal blank (1) can be pressed.

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