US20160228934A1

US20160228934A1 - Two-blow heating and forming tool and method for producing hot-formed and press-hardened motor vehicle components

Info

Publication number: US20160228934A1
Application number: US15/016,499
Authority: US
Inventors: Georg Frost; Max NIESSE; Oliver LUETKEMEYER; Jan Lackmann; Stefan Konrad; Ulrich Huschen; Josef Koester
Original assignee: Benteler Automobiltechnik GmbH
Current assignee: Benteler Automobiltechnik GmbH
Priority date: 2015-02-05
Filing date: 2016-02-05
Publication date: 2016-08-11
Also published as: DE102015101668A1; CN105855380A; CN113145745A

Abstract

A two-blow heating and forming tool for the simultaneous production of two hot-formed and press-hardened motor vehicle components is provided. The tool includes a heating device and a forming device, with at least two contact heating tools and at least two hot-forming and press-hardening tools being arranged next to one another in parallel in a press such that, during a closing movement, two blanks are heated and two heated blanks are hot-formed and press-hardened to form two motor vehicle components. A method for producing hot-formed and press-hardened motor vehicle components using a two-blow heating and forming tool is also provided, the method including producing two mirror-inverted motor vehicle components simultaneously in one press cycle.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a two-blow heating and forming tool for the simultaneous production of two hot-formed and press-hardened motor vehicle components and a method for producing motor vehicle components.
2. Description of the Prior Art
It is known from the prior art to produce motor vehicle components as formed sheet-metal components made from steel materials. For this purpose, steel blanks are provided and are placed into a press-forming tool and, by closing of the press-forming tool, are shaped three-dimensionally and then form the motor vehicle component.
Furthermore, the hot-forming and press-hardening technology is established in the prior art. It is possible in this case to increase the strength of motor vehicle components with the same or even reduced wall thicknesses by thermal treatment. To this end, the blanks are austenitized, consequently heated to a temperature above the AC3 point and hot-formed in said austenitized condition. This immediately affords the advantage that the degrees of freedom in terms of shaping are also increased because of the heated blank. After the shaping has ended, the motor vehicle component produced in this manner is quenched and the initially austenitic material structure is converted into an at least partial, in particular complete high-strength martensitic material structure. In particular, this takes place in the press tool preferably after the press-forming operation has finished, and therefore this operation is also referred to as press-hardening.
EP 2 014 777 B1 discloses a method and an apparatus for tempering a steel sheet body, in which a metal blank is heatable by contact heating by means of two contact plates. A rapid and targeted admission of heat into the blank can take place here and therefore, for example, a blank can be austenitized for subsequent hot forming.
Furthermore, DE 10 2012 021 031 A1 discloses a method for producing press-hardened sheet-metal components, in which at least one steel sheet is heated without a furnace by means of an inductor or a pressed-on contact plate and is then transferred into one or more press steps connected one behind another.

SUMMARY OF THE INVENTION

It is the object of the present invention, starting from the abovementioned prior art, to demonstrate a possibility of efficiently reducing the production costs, the required production area and the production time for producing hot-formed and press-hardened components.
The abovementioned object is achieved by a two-blow combined heating and forming tool for the simultaneous production of two hot-formed and press-hardened motor vehicle components including at least two contact heating tools and at least two hot-forming and press-hardening tools which are arranged in parallel next to one another in a press such that, during a closing movement, two blanks are heated and two heated blanks are hot-formed and press-hardened to form two motor vehicle components. The method part of the object is furthermore achieved by a method for producing hot-formed and press-hardened motor vehicle components using a two-blow heating and forming tool having at least two contact heating tools and at least two hot-forming and press-hardening tools which are arranged in parallel next to one another in a press such that, during a closing movement, two blanks are heated and two heated blanks are hot-formed and press-hardened to form two motor vehicle components. According to the method and using the tool, two mirror-inverted motor vehicle components are simultaneously produced in one press cycle.
Advantageous variant refinements of the present invention include: 1) mounting the two contact heating tools and/or the two hot-forming and press-hardening tools resiliently, in particular on a top die; 2) designing the two hot-forming and press-hardening tools as combined hot-cutting and/or hot-perforating tools; 3) providing a conveyor which transfers the heated blanks from the contact heating tools into the hot-forming and press-hardening tools, in particular in a time less than or equal to the press cycle, preferably in a part of the press cycle; 4) using a mechanical press, in particular a servopress, or using a hydraulic press; 5) providing the contact heating tools with at least one contact plate, wherein the contact plate is preferably heated by an inductor, or wherein the contact plate is formed by an electrically heatable conductor; 6) providing the contact heating tools with one electric compensating element each, wherein a current-conducting cross-sectional area of the compensating element added to the current-conducting cross-sectional area of the blank to be heated forms an overall current-conducting cross-sectional area, wherein, by configuration of the overall current-conducting cross-sectional area, a homogeneous heating of the blank takes place or a partially differing heating takes place in a targeted manner; 7) resiliently mounting the contact heating tools and/or the hot-forming and press-hardening tools so as to be relatively movable on a support plate of the press; 8) providing the contact heating tools and/or the hot-forming and press-hardening tools with an additional trimming tool and/or perforating tool; 9) arranging an elastic adjusting element between a hot-forming and press-hardening tool and press, as a result of which the hot forming is already completed before the press is completely closed, and the remaining closing distance of the press leads to compression of the elastic adjusting element; incorporating an elastic element between contact heating tool and press table, the elastic element compensating for a thermal expansion of the contact heating tool, in particular of a segmented contact heating tool; 10) providing a linear conveyor system, formed from at least two rails lying opposite in parallel, along heating and forming tool, the rails being shiftable in at least one translatory direction and gripping elements being arranged on the rails, the gripping elements being shiftable in the axial direction of the rails, and wherein the gripping elements are raisable and lowerable in the vertical direction (V) orthogonally to the axial direction of the rails; and/or 11) enabling the rails to be shiftable orthogonally to the axial direction thereof and outward or inward with respect to the heating and forming tool, and/or wherein the rails are shiftable in the axial direction thereof for transporting the blanks and motor vehicle components. These and other advantageous embodiments will be discussed in greater detail hereinafter.
The two-blow heating and forming tool for producing two hot-formed and press-hardened motor vehicle components has a region with a heating device and a region with a forming device. The heating and forming tool is distinguished in that at least two contact heating tools and at least two hot-forming and press-hardening tools are arranged next to one another in parallel in a press, such that, during a closing movement, two blanks are heated and two motor vehicle components are hot-formed and press-hardened, consequently in one press cycle. The tools are preferably activated via a press drive or with a plurality of press drives, which are, however driven synchronously, and therefore the heating device and the forming device are closable at least overlapping in time or simultaneously.
“Two-blow” within the context of the present invention means that the at least two hot-forming and press-hardening tools drop simultaneously and therefore two components are produced simultaneously. The two contact heating tools likewise drop parallel thereto and heat two blanks, the two heated blanks then being transferred into the hot-forming and press-hardening tools after opening and then being correspondingly formed upon renewed closing. Two new cold blanks are then placed here into the contact heating tools and heated. Within the context of the present invention, the heating and forming tool may also be of three-blow design by which three components are then produced simultaneously in one press cycle. It is also possible for the heating and forming tool to be of four-blow design; consequently, four components are produced simultaneously.
The heating and forming tool according to the present invention for the simultaneous production of two hot-formed and press-hardened components is suitable in particular for producing left/right components. For example, in the event of the production of motor vehicle bodies, a left motor vehicle pillar and a right motor vehicle pillar can be produced. For example, door impact supports or hot-formed and press-hardened reinforcing patches can also be produced simultaneously.
A significant space saving in a production factory turns out to be a particular advantage since the two heating stations, two transfer devices and two forming presses that are otherwise required for producing two different components are integrated into a combined heating and forming tool in a space-saving manner.
In a preferred variant embodiment, a conveyor is furthermore provided, the conveyor replacing the transfer devices between separate heating station and separate forming device. The space required by such a transfer device for the handling, for example the pivoting space of an industrial robot, can therefore also be omitted in a space-saving manner in the apparatus according to the present invention. Furthermore, it is also not necessary to separately operate four presses which are movable up and down, but rather all of the functions can be integrated in one press. By eliminating the handling time which a transfer device would require for transferring the blank from the separate heating device to the separate forming device, the production time can simultaneously be reduced and, overall, the production costs of the components can be reduced because of lower operating costs. A further resulting advantage is that, with the supply of one batch of sheet-metal blanks, it is ensured that, in particular when producing left/right components, production differences between different deliveries of semi-finished products or starting materials are avoided. The left/right components produced simultaneously in each case are therefore equivalent, based on the delivered batch of sheet-metal blanks to be processed. The number of rejects is, in turn, reduced, as a result of which the production costs drop overall. The range of fluctuation of the strength profile in the components is reduced by means of short transfer distances/times and therefore the product quality is increased.
In order to compensate for tolerances which differ from one another and/or due to distortion of the respective press table, the two contact heating tools and/or the two hot-forming and press-hardening tools are mounted resiliently, in particular on a top die of the press. The resilient mounting or the mounting with a different compensating element makes it possible to compensate for the thermal distortion during operation. Also, by means of different coordination of the compensating elements or springs, in particular the length thereof, and/or before the compensating elements or springs are configured, the absolute contact during the closing movement of the press can be temporally determined. For example, the hot-forming and press-hardening tools can be mounted with a compensating element or spring element which is longer than the compensating element or spring element of the contact heating tools. During the closing movement of the press, the hot-forming and press-hardening tools therefore first of all come into contact with the metal blank and, during the further closing movement, the forming operation is sometimes completed before the bottom dead center is reached. By further lowering of the press, the contact pressure via the compensating element and/or the spring is then increased, thus ensuring optimum fitting of the formed blank in the forming cavity. The bottom dead center position can then be particularly effectively maintained while the quenching operation for press hardening is carried out since a particularly advantageous conduction of heat is ensured because of the contact with increased surface pressure of formed blank with the inner side of the respective forming tool halves of the hot-forming and press-hardening tools. During the press-hardening time, the contact heating can then take place simultaneously at the contact heating tools. It is also possible to configure the springs or compensating elements of the contact heating tools in such a manner that the contact heating tools have reached full contact of the blanks to be heated without the press already being at the bottom dead center. A further closing of the press then ensures that the contact pressure of the contact heating tools with the blank to be heated is increased, which has a positive influence on the transfer of heat because of heat conduction owing to the increased surface pressure and the thus improved contact.
The relative mounting can be designed as described below.
The contact heating tools and the hot-forming and press-hardening tools can each be mounted in a floating manner individually or together on the top die or on the bottom die by means of a hydraulic compensating cushion. In the event of individual mounting, each tool part, consequently each contact heating tool and each hot-forming and press-hardening tool, is then assigned to a compensating cushion on the top die and/or on the bottom die. In the event of a combined mounting, it is possible, for example, for the two contact heating tools to be mounted via a common compensating cushion and for the two hot-forming and press-hardening tools each to be mounted on the top die and/or bottom die likewise via a common compensating cushion. All of the tools can also be mounted on the top die and/or on the bottom die of the press via a respective central common cushion. The mounting takes place in a floating manner such that a relative movement with respect to the press stroke direction in a translatory and/or rotatory manner is possible. The hydraulic compensating cushion is designed in such a manner that a cushion cover, in particular a metallic cushion cover, is formed between the rear side or back side of the respective tool and punch of the top die and/or press table of the bottom die. Said cushion cover is then filled with a hydraulic medium, in particular a fluid. The pressure in the hydraulic cushion can be preset here or else is actively readjustable or settable as the closing movement is being carried out and/or in the closed state.
If the press is now closed, the contact heating tools and/or the hot-forming and press-hardening tools can carry out a relative compensating movement with the press closed, and therefore tilting is eliminated by means of the floating mounting with the hydraulic compensating cushion, and the contact heating tools and hot-forming and press-hardening tools, which are each suspended on the top die and bottom die of the press, can be optimally aligned with one another, and the press force can be transmitted to the blanks to be heated and/or to the formed blanks and can therefore ensure a uniform contact. The compensating cushion itself is designed in such a manner that it withstands the compressive forces occurring during the pressing.
In particular, the advantage is afforded here that sliding blocks can be formed on the top die or on the punch of the top die or on a press table of the bottom die, on which sliding blocks contact heating tools and/or hot-forming and press-hardening tools, which are interchangeable for changing over the production line, are then mounted with the incorporation of the compensating cushion. A simple change of tools can therefore take place and, because of the floating mounting, a complicated readjustment or remachining, in particular of the hot-forming and press-hardening tools, can be dispensed with since a relative inherent centering with respect to one another takes place because of the floating mounting. For example, it is also conceivable for the compensating cushion to be controlled actively and therefore for the pressure in the compensating cushion to be increasable via a hydraulic cylinder. When the press is completely closed, a high pressure can therefore be introduced into the compensating cushion, as a result of which the contact pressure at contact heating tool and/or the hot-forming and press-hardening tools is increased,
In a further preferred variant embodiment of the mounting, the contact heating tools and/or the hot-forming and press-hardening tools are mounted in a manner so as to be relatively movable on the top die and/or on the bottom die with the incorporation of a plurality of spring elements. When the press is closed, the contact heating tools and/or hot-forming and press-hardening tools moving toward one another can therefore execute a relative movement because of the spring elements, and therefore a virtually complete contact is ensured for the contact heating or for the contact cooling during press hardening. Also in this case, it is possible, in turn, for the contact heating tools and/or for the hot-forming and press-hardening tools to be mounted in a floating manner on the top and/or on the bottom die of the press, in particular via sliding blocks, such that, specifically during a change of tools for changing of the production line to other products, short set-up times arise and complicated readjustment work is dispensed with. It is also possible for the springs to be blockable.
Guides, in particular linear guides, are furthermore particularly preferably provided such that, in the case of a floating mounting of the contact heating tools and/or of the hot-forming and press-hardening tools, centering transversely with respect to the vertical direction takes place because of the linear guide in the press closing direction, By this means, a lateral unintentional offset of hot-forming and press-hardening tool and/or of the contact heating tools is avoided,
In a further preferred variant refinement, the two hot-forming and press-hardening tools are in each case designed as combined hot-cutting and hot-perforating tools. The blanks can therefore first of all be heated by the contact heating tools and subsequently transferred into the hot-forming and press-hardening tools by means of a conveyor. In the hot-forming and press-hardening tools, the blanks can then be formed and trimmed and/or perforated in the still hot state. After the forming operation has finished, the formed components can then be press-hardened by means of quenching. A further remachining can then advantageously be dispensed with, as a result of which, in turn, the production time and therefore the production costs are lowered. Also, only a small amount of tool wear should be noted here since the hot cutting or hot perforating is carried out on the relatively soft, heated metal blank and not subsequently on the already hardened motor vehicle component. Within the scope of the present invention, the contact heating tools can be designed in such a manner that they completely heat the blanks and in particular completely heat the same up over the austenitizing temperature.
However, it is also possible within the context of the present invention for the contact heating tools to carry out only partial temperings. Consequently, blank regions are not heated at all or are heated lower than the AC3 temperature, whereas other regions are heated up over the austenitizing temperature. It is also conceivable within the context of the invention for the blanks placed into the contact heating tools to be first of all preheated, for example homogeneously to a temperature lower than or equal to the AC1 temperature or a temperature lower than the AC3 temperature. In the contact heating tools, regions are then heated up in a targeted manner above the AC3 temperature, whereas the regions below the AC3 temperature are either kept at said temperature or are not tempered at all, but also do not cool down severely.
It is also conceivable within the context of the invention for the hot-forming and press-hardening tools to be of segmented design such that, for example in the case of the blank being heated up completely homogeneously to over the AC3 temperature, a partially different cooling takes place. It is also possible for a partially different tempering to take place in the contact heating tools and a partially different quench hardening to take place in the hot-forming and press-hardening tools. By this means, components can be produced with strength regions which are partially different from one another.
Within the context of the present invention, it is also conceivable for the contact heating tools and/or the hot-forming and press-hardening tools to be of segmented design in each case. By means of the individual segments, regions which are partially different from one another can then be tempered and/or quenched, with only a low conduction of heat within the tool and the blank or within the hot-formed and press-hardened component arising, in particular through separating gaps between the segments. The different segments of the contact heating tools and/or of the hot-forming and press-hardening tools can also be formed from materials which differ from one another, and therefore different temperings take place because of the different heat conductivities of each material.
Furthermore, a conveyor is provided which transfers the heated blanks from the contact heating tools into the hot-forming and press-hardening tools. The conveyor is designed in particular as a linear conveyor which transfers the heated blanks within the press into the hot-forming and press-hardening tools. The conveyor is preferably designed as a rack drive or 2-axle or 3-axle drive. However, the conveyor may also be designed in such a manner that it already supplies the cold blanks to the contact heating tools and removes the finished, hot-formed and press-hardened components from the press. However, the supplying of the cold blanks and removal of the components produced can also take place by means of a respective manipulator, for example by means of an industrial robot. A plurality of isochronously movable linear conveyors which are arranged one behind another in the conveying direction offset by the width of a heating and/or press-hardening tool are also possible.
The time required by the conveyor in order to transfer the heated blanks from the contact heating tools into the hot-forming and press-hardening tools is less than or equal to the press cycle, preferably less than half the press cycle, and, in particular, the time is less than one third of the press cycle. An opening movement can be carried out until the top dead center is reached and at the same time, in turn, then a closing movement of the press, wherein, for example, with the press already half or three quarters open, the transport of the heated blanks to the hot-forming and press-hardening tools begins, the press reaches the top dead center and, in turn, carries out the closing movement. Before the middle closing distance is reached, the conveyor has already placed the heated blanks into the hot-forming and press-hardening tools. This affords the advantage according to the present invention of rationalizing the production time, in particular if the contact heating already begins because of contact before the bottom dead center is reached. The same is true for the hot-forming and press-hardening tool. In so far as the forming is already finished before the bottom dead center is reached, the press hardening can already start. By means of the two previously described measures, the time for keeping the press closed is in turn reduced, preferably to zero, and therefore so is the production time as a whole.
A servopress or else a hydraulic press is particularly preferably used as the press itself. The two presses permit, in particular, the targeted control possibility with regard to opening and closing movements and, in the closed position, permit the contact pressure to be readjusted once again, and therefore it is possible to meet the contact heating requirements and the hot-forming and press-hardening requirements simultaneously in one press.
In a further preferred variant refinement, the contact heating tool is designed in such a manner that the latter has at least one contact plate, preferably two contact plates, consequently one contact plate on the top die and one on the bottom die, which then enclose a blank between them when the press is closed. The at least one contact plate is preferably heatable by induction.
In an alternative variant refinement, it is also possible for the contact plate itself to be designed as a conductor, wherein the conductor is heated on the basis of electrical resistance heating when a current is conducted therethrough, wherein the current flow is interrupted before contact with the blank in order to avoid a short circuit. The contact of the heated conductor then in turn ensures that heat is transferred from conductor to the blank to be heated.
Within the context of the present invention, it is also possible to use segmented contact plates such that regions of the blank which partially differ from one another are heated in a targeted manner.
In the event of the use of a conductor, a flat conductor is preferably formed, the conductor having one and/or more gaps, wherein the parts which are separated by the slot or gap then produce a conductor or a current path through which an electric current then flows when the poles are connected and heats the conductor in the process. It is also conceivable to form a contact plate by means of a plurality of conductors, wherein the individual conductors are then in each case tempered differently from one another such that regions differing from one another are formed in the blank. In order to avoid an electrical short circuit, the current flow is then interrupted in each case at the latest shortly before contact with the blank. The remaining heat is then output by means of heat conduction.
It is also possible to heat the contact plates by other heat sources, for example by heat radiation or other heat conduction. Preferably, however, in the case of contact plates, the latter are heated via an inductor. The contact plates themselves then in turn output the sensible heat by means of heat conduction to the blank to be heated.
In a further preferred variant refinement, the contact heating tool is designed in such a manner that an electric compensating element is formed. A current-conducting cross-sectional area is formed, and therefore the one contact heating tool is designed as an electric compensating element. The latter is placed onto the blank to be heated, with the current-conducting cross-sectional area of the compensating element added to the current-conducting cross-sectional area of the blank to be heated then forming an overall current-conducting cross-sectional area, wherein, by configuration of the overall current-conducting cross-sectional area, a homogeneous heating of the blank takes place or a partially differing heating takes place in a targeted manner. The contact heating tool is formed here as a combined heating tool from heat transferring and from the compensating element by means of heat conduction because of contact and heat produced directly in the blank because of an electrical current flow. In particular, a varying width and/or thickness of a previously trimmed blank can be compensated for in a targeted manner with the electric compensating element, and/or by varying the current cross-sectional area of the compensating element itself, a more substantial influencing of the heating in the blank can be brought about in a targeted manner, in particular with a homogeneous cross-sectional profile because of the conduction of electrical energy.
In a further preferred variant refinement, either the contact heating tools themselves or alternatively also the hot-forming and press-hardening tools can each have an additional trimming tool and/or perforating tool. It is thereby possible to integrate cutting out operations and/or edge trimming into the production process.
In a further advantageous variant refinement, an elastic adjusting element is arranged between the hot-forming and press-hardening tool and the press or the top die or bottom die of the press, as a result of which the hot forming is already completed before the press is completely closed, and the residual closing distance of the press leads to compression of the elastic adjusting element. It is also conceivable to arrange such an elastic adjusting element between press and contact heating tools. It is preferable that a plurality of elastic adjusting elements be usable per tool. This means that the hot forming is completed and keeping the press shut begins before the press itself reaches the bottom dead center or reversing point. Furthermore, keeping the press shut is ended only upon the upward movement thereof after the latter has completely traversed the bottom reversing point or the bottom dead center and the top die is in turn raised. By means of this measure, the cycle time of hot forming and press hardening of the sheet-metal component is in turn reduced in such a manner in that the forming already begins at a very early point and is completed before the other dead center is reached, and the holding time is maximally used for the quenching hardening of the formed sheet-metal component.
As a positive secondary effect, the adjusting elements, which are in turn elastic, can be used for compensating for tilted contact heating tools and/or hot-forming and press-hardening tools. At the same time, differences in the press dropping together between contact heating tool and hot-forming and press-hardening tool because of different required press forces can be compensated for with the elastic adjusting elements. The elastic adjusting elements are decisively designed as passive adjusting elements, in particular as compression springs. However, the elastic adjusting elements may also be, for example, of active design by means of an electric, hydraulic or pneumatic actuator. The advantage arising therewith is that the time for keeping the press closed at the bottom dead center can be reduced to zero.
Furthermore, an elastic element is particularly preferably incorporated between contact heating tool and press table, wherein the elastic element compensates for a thermal expansion of the contact heating tool, in particular of a segment of a segmented contact heating tool. Precisely in the case of partially differing contact heating in conjunction with a segmented contact heating tool, the individual elements expand to different degrees from one another because of thermal action. Due to the different temperatures and/or different coefficients of thermal expansion, individual segments expand to differing degrees from one another. Even the deviation of a few tenths of a millimeter may already partially lead to no more contact with the blank to be heated, and therefore poorer heating and/or heating which is not clearly demarcated is carried out.
By means of the elastic elements on the contact heating tools, in particular on the segments of the contact heating tools, the present invention is able to compensate for thermal expansions which differ from one another.
The previously mentioned object is furthermore achieved according to the present invention by a method for producing hot-formed and press-hardened motor vehicle components using a two-blow heating and forming tool according to the previously mentioned features in that two mirror-inverted motor vehicle components are produced simultaneously in one press cycle. Two blanks are likewise heated and are machined by forming in the following press cycle.
It is therefore possible in particular for left/right components, for example a left B pillar and a right B pillar with respect to the direction of travel, to be produced. The advantage is in particular afforded here of shortening the production time and using effects of synergy since it is not necessary for four individual heating and forming devices to be operated, but rather all of the components can be produced simultaneously on one press.
Within the context of the invention, it is possible in particular to carry out the heating on the contact heating tool in a time of 3 to 20 seconds, in particular 4 to 10 seconds. The forming is carried out isochronously in a time of preferably 0.1 to 3 seconds, in particular 1 to 2 seconds, wherein the quench hardening is carried out directly following the forming in a time of 4 to 20 seconds, particularly preferably of 5 to 10 seconds.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features, properties and aspects of the present invention are the subject matter of the description below. Preferred variant refinements are illustrated in the schematic figures as summarized below.

FIG. 1 shows the two-blow heating and forming tool according to the present invention in a side view.

FIG. 2 shows the tool from FIG. 1 with additional compensating elements.

FIG. 3 shows a cross-sectional view through a hot-forming and press-hardening tool with resilient mounting.

FIG. 4 shows an alternative variant in a partial sectional view.

FIG. 5 shows a schematic top view of the heating and forming tool according to the invention.

FIG. 6 shows a contact plate designed as conductor, in a top view.

FIG. 7 shows a cross section through a contact heating tool according to the invention with compensating element.

FIG. 8 shows a variant refinement of the heating and forming tool according to the invention in a detailed view with respect to the hot-forming and press-hardening tools.

FIG. 9 shows a cross-sectional view of a contact heating tool according to the invention.

FIG. 10 shows an exemplary embodiment of a three-blow tool.

FIG. 11 shows an exemplary embodiment of a four-blow tool.

FIGS. 12 to 14 show the process sequence of a hot-forming line according to the invention with a combined heating and forming tool.

FIGS. 15a and b show a raising function of a linear conveyor system with fixed gripping elements.

FIGS. 16a and b show a raising function of a linear conveyor system with relatively movable gripping elements.

FIGS. 17a to c show active grippers according to the invention.

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

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
FIG. 1 shows the two-blow heating and forming tool 1 according to the invention in a side view. The heating and forming tool 1 has a central press 2, wherein two contact heating tools 3 and, following the latter, two hot-forming and press-hardening tools 4 are arranged within the press 2. Blanks 5 from a stack of blanks are placed into the heating and forming tool 1, and heated and pre-shaped to form motor vehicle components 6 and press-hardened. According to the present invention, two motor vehicle components 6 are simultaneously produced with the two-blow heating and forming tool. Two blanks 5 are placed into the contact heating tools 3. The blanks 5 which are located to this point in the contact heating tools 3 and which have been heated are both simultaneously transferred by a conveyor 7, illustrated here as a linear conveyor, into the hot-forming and press-hardening tools 4. When the press 2 of the heating and forming tool 1 is closed, the two blanks 5 placed into the contact heating tools 3 are therefore heated, and the heated blanks transferred into the hot-forming and press-hardening tools 4 are formed to give a respective motor vehicle component 6.
The distance to be covered between contact heating tool 3 and hot-forming and press-hardening tool 4 is constant for each blank 5, and therefore a uniform temperature drop arises in each component because of the transfer time.
The hot-forming and press-hardening tools 4 can be additionally designed as hot-perforating and/or hot-cutting tools, and therefore perforating and/or trimming is also carried out simultaneously with the forming.
FIG. 2 shows the two-blow heating and forming tool 1 from FIG. 1 with additionally arranged spring bearings 8. In this variant refinement, the hot-forming and press-hardening tools 4 and the contact heating tools 3 are mounted resiliently. This affords the advantage that, when the press 2 is closed by upper part 9 and lower part 10 of the contact heating tools 3 and/or upper part 11 and lower part 12 of the hot-forming and press-hardening tools 4 relative movements can be compensated for via the spring bearings 8. This relates in particular to thermally different expansions, but also to distortion which may occur between the top die 13 and the bottom die 14 during operation of the press 2,
FIG. 3 shows a cutout of the press 2 according to the invention with respect to a hot-forming and press-hardening tool 4 with upper part 11 and lower part 12. Moreover, the upper part 11 of the hot-forming and press-hardening tool 4 is mounted on the top die 13 and the lower part 12 of the hot-forming and press-hardening tool 4 is mounted on the bottom die 14, more precisely on a press table 15 of the bottom die 14. For this purpose, the hot-forming and press-hardening tool 4 firstly has cooling ducts 16 and secondly a forming cavity 17 is produced between a forming surface 18 of the upper part 11 and a forming surface 19 of the lower part 12 of the hot-forming and press-hardening tool 4. As illustrated here, it is possible by means of tilting, in particular by means of rotation with respect to the press stroke direction 20, for an erroneous position of the upper part 11 and lower part 12 of the hot-forming and press-hardening tool 4 to occur. To compensate for said erroneous position, spring elements 21 are arranged between press table 15 and lower part 12 of the hot-forming and press-hardening tool 4, said spring elements, upon further carrying out of the closing movement, compensating for the position of the lower part 12 of the hot-forming and press-hardening tool 4 in such a manner that an approximately uniform contact of the formed blank 5 (not illustrated specifically) and the respective forming surface 18 of the hot-forming and press-hardening tool 4 occurs in the forming cavity 17. By means of the virtually complete contact, very good removal of heat is noted. Also illustrated is a control line 22 via which, for example, the spring elements 21 would be blockable. The spring elements 21 themselves may be designed as mechanical springs, in particular spiral springs or helical compression springs, but also as hydraulic or pneumatic spring elements.
FIG. 4 shows an alternative variant of the hot-forming and press-hardening tool 4 in a partial sectional view, wherein a hydraulic cushion 23 is arranged here between top die 13 and upper part 11 of the hot-forming and press-hardening tool 4. For this purpose, the hydraulic cushion 23 has a cushion cover 24 which is coupled in a fluid-tight manner to the top die 13 of the press 2 at a frame 25 encircling the outside. A corresponding fluid is then arranged in an arising interior space 26, and therefore the upper part 11 of the hot-forming and press-hardening tool 4 can move relative to the top die 13 of the press 2. In order to basicly ensure contact and transition of the entire press force in the press stroke direction 20, contact bars 27 are furthermore arranged, and therefore, in the event of reaching the bottom dead center of the press 2, a backside 28 of the upper part 11 of the hot-forming and press-hardening tool 4 comes into form-fitting contact with the top die 13 of the press 2 because of the contact bar 27 and therefore at the latest then transmits the entire press force. However, it is possible beforehand to ensure optimum self-centering of upper part 11 and lower part (not illustrated specifically) of the hot-forming and press-hardening tool 4 by carrying out the relative movement because of the hydraulic cushion 23.
The respective floating mounting of FIG. 3 or FIG. 4 is alternatively or additionally also applicable to the contact heating tools 3.
FIG. 5 shows a schematic top view of the heating and forming tool 1. A conveyor 7 in the form of a linear conveyor 29 is illustrated. After heating, the blanks 5 are transferred in the conveying direction 30 to the press-hardening tools (not illustrated specifically). For this purpose, the conveyor 29 is provided with receptacles 31 which then grasp the blanks 5 by means of a contact or gripping device (not illustrated specifically) and convey said blanks in the conveying direction 30. It is furthermore illustrated that a left region of the blank 5 with respect to the plane of the figure is heated to a temperature of AC1 and a region of the blank 5 with respect to the right plane of the figure is heated to a temperature of AC3. Consequently, temperature regions which are different from one another are produced on the blanks 5 and then, after the press-hardening operation is completed, said temperature regions produce two regions 33, 34 which are different from each other on the motor vehicle components 32 produced, wherein a first region 33 has a lower strength than a second region 34. The two motor vehicle components 32 produced can then be, for example, a left B pillar and a right B pillar for a motor vehicle body, said B pillars being produced simultaneously in one press cycle.
FIG. 6 shows a contact plate 35 designed as a conductor, in a top view. The contact plate 35 itself has a rectangular configuration, wherein various slots 36 which extend from an upper side as far as a lower side of the contact plate 35, with respect to into the direction of the figure, are formed within the contact plate 35. By this means, the contact plate 35 is separated electrically from the slots 36 in such a manner that a current path 37 is produced through the contact plate 35. If two electric poles 38 are then connected and a current is applied to the contact plate 35, an electric current flows through the current path 37 and heats the contact plate 35 because of resistance heating. When the closing movement is being carried out and/or a blank 5 to be heated is deposited on the contact plate 35, the current flow is interrupted shortly before the surface contact in order to avoid an electrical short circuit. The heat located in the contact plate 35 is then output to the blank to be heated because of contact by the contact plate 35.
FIG. 7 shows a cross section through a contact heating tool 3 according to the invention. It is readily apparent here that, firstly, the blank 5 to be heated has been inserted, but a compensating element 39 is arranged on the upper part 9 of the contact heating tool 3. Electric poles 38 are arranged in each case on the outer side of the compensating element 39, and therefore, when in the state of a closed contact heating tool 3, in particular with contact, preferably electrical, conductive contact, of compensating element 39 and blank 5 and application of an electric current, a resistance heating both of the compensating element 39 and optionally of the blank 5 is produced. At the same time, however, the compensating element 39 has a residual heat, and therefore, in addition, by means of heat conduction, an application of heat to the blank 5 to be heated likewise takes place because of the contact. It can be seen that, in the transverse direction Q, the compensating element 39 has a differing cross-sectional area, wherein the entire compensating element 39 is formed from a conductive material. The differing cross-sectional area results in a differing current-conducting cross-sectional area and therefore in heating, which partially differs in intensity, because of the current flow density. In particular, more intense heating arises at the left and right end, at both of which a smaller cross section should be noted, than in a central region because of a higher current flow density. Owing to the fact that the blank 5 has a constant cross section, firstly, when a current is applied to the electric poles 38, more current flows in the outer regions through the blank 5, and therefore more intense heating can be noted here. The current-conducting cross-sectional area of the compensating element 39 and the current-conducting cross-sectional area of the blank 5 then produce an overall current-conducting cross-sectional area. Also illustrated is an insulating counterlayer 40 on the lower part 10 of the contact heating tool 3 and also an insulating counterlayer 40 between upper part 9 of the contact heating tool 3 and the compensating element 39.
FIG. 8 furthermore shows a variant refinement of the heating and forming tool 1 according to the invention in a detailed view with respect to the hot-forming and press-hardening tools 4. It is illustrated here in turn that the upper part 11 and the lower part 12 of the respective hot-forming and press-hardening tool 4 are arranged on the top die 13 and the bottom die 14, respectively, of the press 2. The lower parts 12 of the hot-forming and press-hardening tool 4 are mounted here spaced apart at a distance a from a press table 15 of the bottom die 14 in the press stroke direction 20. When the closing movement is carried out, the upper part 11 and the lower part 12 of the respective hot-forming and press-hardening tool 4 therefore already come into contact, incorporating the blank 5, and therefore the forming operation is completed even before the bottom dead center is reached. A further lowering then leads to compression of the respective elastic adjusting element 41, and therefore the lower parts 12 of the hot-forming and press-hardening tools 4 move in the direction of the press table 15 of the bottom die 14. During this period of time, the press-hardening operation can already begin because of the cooling ducts 16, and it is ensured in turn that a virtually full contact of upper tool 11 with the formed blank 5 and lower part 12 and formed blank 5 of the hot-forming and press-hardening tool 4 and associated good heat conduction are produced. Furthermore, there are centering means 42 in the form of centering pins which are formed protruding in relation to the lower parts 12 of the hot-forming and press-hardening tools 4 and come into engagement with centering grooves 43 formed on the upper parts 11 of the hot-forming and press-hardening tools 4 when the closing movement is carried out in the press stroke direction 20. By this means, a linear guidance is performed in the press stroke direction 20, said guidance in particular avoiding a lateral offset of upper part 11 and lower part 12 of the hot-forming and press-hardening tool 4 specifically because of the elastic mounting by means of the adjusting elements 41, This design can also be implemented on the contact heating tools 3.
FIG. 9 shows a cross-sectional view of a contact heating tool 3 according to the invention, wherein the contact heating tool 3 has a plurality of individual segments 44, 45. The segments 44 here are in particular non-tempered segments and the segments 45, by contrast, are actively heated segments tempered to a higher temperature in relation to the temperature of the segments 44. All of the segments 44, 45 are formed in a manner thermally insulated from one another via a respective separating gap 46. Consequently, the actively heated segments 45 expand more greatly than the segments 44, and therefore it is provided according to the invention that elastic elements 47 are arranged on the lower segment 45 in a manner suspended on the press table 15 of the bottom die 14 such that a thermal expansion, in particular in the press stroke direction 20, is compensated for by the elastic elements 47. Within the context of the invention, each individual segment 44, 45 of the contact heating tool 3 can therefore also be mounted on its own per se, in particular in a manner so as to be relatively movable by means of elastic elements 47, and therefore a differing thermal expansion is compensated for by the elastic elements 47 and hence the individual segments 44, 45 are each approximately in contact over the full area thereof with the blank 5 to be heated. This variant refinement may also be transferred to the hot-forming and press-hardening tool 4. Furthermore, a linear guide 48 is provided which permits linear guidance in the press stroke direction 20 and reduces shearing off transversely with respect to the press stroke direction.
FIG. 10 shows a top view of a combined heating and forming tool 1 according to the invention which is of three-blow design. For this purpose, individual blanks 5 are placed in the conveying direction 30 into the heating and forming tool 1 and first of all three blanks 5.1 are simultaneously heated on one contact heating tool 3 each and, in the subsequent press cycle, the three heated blanks 5.2 are simultaneously formed in three hot-forming and press-hardening tools 4 such that three motor vehicle components 6 are produced simultaneously in one press cycle. In this case, a three-blow heating and forming tool 1 is described.
FIG. 11 shows a variant refinement of the heating and forming tool 1 according to the invention as a four-blow variant. In this case, blanks 5 from two stacks of blanks are first of all again placed in the conveying direction 30 into the heating and forming tool 1. However, there are now only two contact heating tools 3 here, wherein each contact heating tool simultaneously heats two blanks 5.1 to be heated. Each heated blank 5.2 is then brought onto a separate hot-forming and press-hardening tool 4, and, during a press closing movement, consequently a press cycle, four motor vehicle components 6 are simultaneously produced. These are in particular smaller motor vehicle components 6, for example reinforcing patches or the like. In this case, the heating and forming tool 1 is of four-blow design. It is also conceivable for the contact heating tools 3 to be arranged next to one another in the conveying direction 30 and also for the four hot-forming and press-hardening tools 4 to be arranged next to one another in the conveying direction 30.
FIG. 12 shows a heating and forming tool 1 according to the invention, having a contact heating tool 3 and a hot-forming and press-hardening tool 4 and also a linear conveyor system 49 arranged thereon. The contact heating tool 3 is a two-blow tool. This means, two blanks 5.1, 5.2 can be simultaneously heated in one contact heating tool 3. The hot-forming and press-hardening tool 4 is likewise a two-blow tool. This means, two heated blanks are simultaneously hot-formed and subsequently press-hardened in one hot-forming and press-hardening tool 4. The gripping elements are preferably designed as blank grippers 51 and/or tempering grippers 52 and/or product grippers 53. The linear conveyor system 49 has two rails 50 arranged parallel to each other, wherein gripping elements are arranged on the rails 50. Two blank grippers 51 are arranged from the left to the right, with respect to the plane of the figure. Two tempering grippers 52 are arranged in the center, with respect to the plane of the figure, and two product grippers 53 are arranged on the right side, with respect to the plane of the figure. The heating and forming tool 1 is therefore a two-blow tool. It can also be of single-blow, three-blow, four-blow or multi-blow design. Furthermore, an overall displacement distance G is illustrated.
According to the variant illustrated here, the gripping elements are positionally fixed with respect to the rails 50 in the axial direction 54 of the rails 50, wherein the rails 50 are movable in the axial direction 54 thereof. Alternatively, it would also be conceivable for the gripping elements to be shiftable in the axial direction 54 with respect to the rails 50.
Furthermore, it is illustrated that the rails 50 have carried out a relative movement 55 with respect to the axial direction 54 thereof orthogonally inward. The respective gripping elements have therefore been brought into engagement with the blanks 5.1, the heated blanks 5.2 or motor vehicle components 6.
The linear conveyor system 49 then carries out a transport movement in the axial direction 54 of the rails 50. The end position is illustrated in FIG. 13. The formed motor vehicle components 6 are deposited on a schematically illustrated depositing stack 56. The heated sheet-metal blanks 5.2 are deposited on the hot-forming and press-hardening tool 4. The newly received sheet-metal blanks 5.1 are deposited on the contact heating tool 3, and, in turn, new sheet-metal blanks 5.1 are ready for heating. Subsequently, a movement is carried out outward by the rails 50, and therefore the entire rails 50 with the respective gripping elements are moved outward with respect to the axial direction 54 of the rails 50 and are no longer in engagement with the sheet-metal blanks 5.1, 5.2 and motor vehicle components 6.
A reversing movement 57 is then carried out in the axial direction 54 of the rails 50, in particular said reversing movement 57 is carried out synchronously with the two rails 50, as shown in FIG. 14. Subsequently, the operation begins again, as illustrated in FIG. 12. The returned rails 50 are moved toward each other, and therefore the gripping elements come into engagement with the heated sheet-metal blanks 5.2 and the motor vehicle components 6.
FIGS. 15a and 15b show a raising operation of the blanks with the blank grippers 51. The rails 50 have carried out a relative movement 55 toward each other orthogonally with respect to the axial direction 54 thereof, and therefore the blank grippers 51 are located below the sheet-metal blank 5.1 with respect to the vertical direction V. Subsequently, a raising movement, illustrated in FIG. 15b , is carried out by the rails 50. This means that the entire rails 50 are moved upward in the vertical direction V. The sheet-metal blank 5.1 then rests, as it were, on the blank grippers 51 and is likewise raised.
FIGS. 16a and 16b show an alternative variant refinement thereto. Here, it is not the rails 50 which are raised with respect to the vertical direction V, but rather only the blank grippers 51. The latter are therefore mounted in a manner so as to be relatively movable on the rails 50 with respect to the vertical direction and can also be raised or lowered.
FIGS. 17a, 17b and 17c show a relative movement analogous to FIGS. 16a and 16b , with the difference that the blank grippers 51 here are depicted as active grippers. The latter are illustrated in an open position according to FIG. 17a , and therefore the rails 50 have carried out a relative movement 55 directed toward each other. According to FIG. 17b , the blank grippers 51 as active grippers are then closed and, according to FIG. 17c , are raised again in the vertical direction V.
The invention being thus described, it will be apparent that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be recognized by one skilled in the art are intended to be included within the scope of the following claims.

REFERENCE SIGNS

1—heating and forming tool
2—press
3—contact heating tool
4—hot-forming and press-hardening tool
5—blank
5.1—blank to be heated
5.2—heated blank
6—motor vehicle component
7—conveyor
8—spring bearing
9—upper part to 3
10—lower part to 3
11—upper part to 4
12—lower part to 4
13—top die to 2
14—bottom die to 2
15—press table to 14
16—cooling ducts
17—forming cavity
18—forming surface to 11
19—forming surface to 12
20—press stroke direction
21—spring element
22—control line
23—hydraulic cushion 24—cushion cover
25—frame
26—interior space
27—contact bar
28—backside to 11
29—linear conveyor
30—conveying direction
31—receptacle
32—motor vehicle component
33—first region to 32
34—second region to 32
35—contact plate
36—slot
37—current path
38—electric pole
39—compensating element
40—insulating counterlayer
41—adjusting element
42—centering means
43—centering grooves
44—segment
45—segment
46—separating gap
47—elastic elements
48—linear guide
49—linear conveyor system
50—rails
51—blank gripper
52—tempering gripper
53—product gripper
54—axial direction
55—relative movement
56—depositing stack
57—reversing movement
a—distance
G—overall displacement distance
Q—transverse direction
V—vertical direction

Claims

What is claimed is:

1. A two-blow heating and forming tool for the simultaneous production of two hot-formed and press-hardened motor vehicle components, comprising at least two contact heating tools and at least two hot-forming and press-hardening tools which are arranged in parallel next to one another in a press, such that, during a closing movement, two blanks are heated and two heated blanks are hot-formed and press-hardened to form two motor vehicle components.

2. The heating and forming tool as claimed in claim 1, wherein the two contact heating tools and/or the two hot-forming and press-hardening tools are mounted resiliently.

3. The heating and forming tool as claimed in claim 1, wherein the two contact heating tools and/or the two hot-forming and press-hardening tools are mounted resiliently on a top die.

4. The heating and forming tool as claimed in claim 1, wherein the two hot-forming and press-hardening tools are designed as combined hot-cutting and/or hot-perforating tools.

5. The heating and forming tool as claimed in claim 1, wherein a conveyor is provided which transfers the heated blanks from the contact heating tools into the hot-forming and press-hardening tools.

6. The heating and forming tool as claimed in claim 5, wherein the heated blanks are transferred by the conveyor from the contact heating tools into the hot-forming and press-hardening tools in a time less than or equal to the press cycle.

7. The heating and forming tool as claimed in claim 5, wherein the heated blanks are transferred by the conveyor from the contact heating tools into the hot-forming and press-hardening tools in a time that is a part of the press cycle.

8. The heating and forming tool as claimed in claim 1, wherein a mechanical press or a hydraulic press is used.

9. The heating and forming tool as claimed in claim 1, wherein a servopress is used.

10. The heating and forming tool as claimed in claim 1, wherein the contact heating tools have at least one contact plate heated by an inductor.

11. The heating and forming tool as claimed in claim 1, wherein the contact heating tools have at least one contact plate that is formed by an electrically heatable conductor.

12. The heating and forming tool as claimed in claim 1, wherein the contact heating tools have one electric compensating element each, wherein a current-conducting cross-sectional area of the compensating element added to the current-conducting cross-sectional area of the blank to be heated form an overall current-conducting cross-sectional area, wherein, by configuration of the overall current-conducting cross-sectional area, a homogeneous heating of the blank takes place in a targeted manner.

13. The heating and forming tool as claimed in claim 1, wherein the contact heating tools have one electric compensating element each, wherein a current-conducting cross-sectional area of the compensating element added to the current-conducting cross-sectional area of the blank to be heated form an overall current-conducting cross-sectional area, wherein, by configuration of the overall current-conducting cross-sectional area, a partially differing heating takes place in a targeted manner.

14. The heating and forming tool as claimed in claim 1, wherein the contact heating tools and/or the hot-forming and press-hardening tools are resiliently mounted so as to be relatively movable on a support plate of the press.

15. The heating and forming tool as claimed in claim 1, wherein the contact heating tools and/or the hot-forming and press-hardening tools each have an additional trimming tool and/or perforating tool.

16. The heating and forming tool as claimed in claim 1, wherein an elastic adjusting element is arranged between hot-forming and press-hardening tool and press, as a result of which the hot forming is already completed before the press is completely closed, and the remaining closing distance of the press leads to compression of the elastic adjusting element.

17. The heating and forming tool as claimed in claim 1, wherein an elastic element is incorporated between contact heating tool and press table, the elastic element compensating for a thermal expansion of the contact heating tool.

18. The heating and forming tool as claimed in claim 1 wherein a linear conveyor system which is formed from at least two rails lying opposite in parallel is provided along heating and forming tool, the rails being shiftable in at least one translatory direction and gripping elements being arranged on the rails, the gripping elements being shiftable in the axial direction of the rails, and wherein the gripping elements are raisable and lowerable in the vertical direction (V) orthogonally to the axial direction of the rails.

19. The heating and forming tool as claimed in claim 18, wherein the rails are shiftable orthogonally to the axial direction thereof and outward or inward with respect to the heating and forming tool, and/or wherein the rails are shiftable in the axial direction thereof for transporting the blanks and motor vehicle components.

20. A method for producing hot-formed and press-hardened motor vehicle components using a two-blow heating and forming tool comprising:

providing a two-blow heating and forming tool for the simultaneous production of two hot-formed and press-hardened motor vehicle components, said tool including at least two contact heating tools and at least two hot-forming and press-hardening tools which are arranged in parallel next to one another in a press, such that, during a closing movement, two blanks are heated and two heated blanks are hot-formed and press-hardened to form two motor vehicle components; and

simultaneously producing two mirror-inverted motor vehicle components in one press cycle.