EP2446978A1 - Method and device for producing hardened moulded components - Google Patents

Abstract

The method for the production of hardened mold components (5) such as structural- or body making parts of motor cars, comprises heating a metal printed circuit board, subsequently transforming in mold cavity (4) of a thermoforming tool (1) to mold component and then hardening through contact with a coolant in the mold cavity of the thermoforming tool, where the coolant is guided through flow channels (7, 8) into the mold cavity. The aggregate condition of the coolant is adjustable. The coolant is supplied with a pressure of up to 25 MPa into mold cavity. The method for the production of hardened mold components (5) such as structural- or body making parts of motor cars, comprises heating a metal printed circuit board, subsequently transforming in mold cavity (4) of a thermoforming tool (1) to mold component and then hardening through contact with a coolant in the mold cavity of the thermoforming tool, where the coolant is guided through flow channels (7, 8) into the mold cavity. The aggregate condition of the coolant is adjustable. The coolant is supplied with a pressure of up to 25 MPa into mold cavity. The mold component is partially cooled with the coolant, whose pressure lies above the vapor pressure of the coolant. The time duration of the coolant supply and/or the height of the pressure are varied. The component temperature of the mold component is measured in the mold cavity and the tool temperature is measured in the area of the contact surface (9) of the mold cavity. The starting time and end time of the coolant supply is controlled in dependent upon the component temperature and/or the tool temperature. The coolant distribution is variably controllable in the mold cavity. The first area of the mold component is subjected with the coolant and the second area of the mold component is not subjected with the coolant or the first area or the second area is subjected with the coolant. The mold component is fixedly held after the reception from the thermoforming tool in a cooling station. The coolant is supplied with a pressure in the mold cavity, and the pressure is adapted during the cooling phase at the vapor pressure of the coolant in control-technical manner. The pressure and/or temperature control is adjusted in dependent upon a temperature measurement on mold component in the thermoforming tool and/or temperature measurement on the thermoforming tool. The coolant is intermittently sprayed in the mold cavity. An independent claim is included for a thermoforming tool for transforming and hardening of metal sheet.

Description

The invention relates to a method and an apparatus for producing hardened molded components, in particular of structural or body parts of motor vehicles.

To reduce weight and increase crash resistance, high-strength steel sheets are used in the automotive industry, which are hot-formed to form components and press-hardened. The hot working and press hardening of metal sheets as such is known, for example, by the DE 24 524 86 A1 , Here, a metal plate is heated to a temperature in the specific Austenitisierungstemperaturbereich the erkstoffs, that is, to a temperature above the transition temperature AC1, preferably greater than AC3, in a heat treatment plant, then placed in a press tool and reshaped. Clamped in the press tool, the molded components are hardened by cooling.

The cooling required for curing is divided into indirect cooling and direct cooling.

The indirect cooling takes place via cooling channels, which are introduced in the form of holes or slots (shaft cooling) at a defined distance from the forming surface in the tool. Through these channels flows a coolant, usually water, which dissipates the heat given off by the warm mold component to the tool to the outside.

In direct cooling, the mold component in the thermoforming mold is brought into direct contact with the cooling medium. In the from the DE 10 2005 028 010 B3 known thermoforming tool is the lower tool of the press within a liquid bath. Both parts of the mold geometry and the entire mold geometry can be below the liquid level. The sheet metal profile to be molded and hardened is placed above the liquid level and immersed in the liquid bath when the press is moved by the upper tool and deep-drawn into the lower tool.

A direct cooling in a thermoforming tool is still from the DE 26 03 618 A1 known. In the forming surface of the lower and upper tool concentric annular grooves are introduced, lead into the guided through the tools channels. Through these channels, a cooling liquid is fed into the annular grooves for direct contact with a sheet metal profile to be hardened. This direct cooling can be at least theoretically expect improved cooling, since the cooling liquid comes into direct contact with the mold component.

In practice, the contact pressure or the contact conditions between the molded component and the thermoforming tool have a significant influence on the heat transfer and heat dissipation. The tools are manufactured with CNC machines to the nearest hundredth of a millimeter and then inked to keep the gaps between the mold and the tool as small as possible. Despite all efforts it comes in areas In which component stretches are made or in areas of steep frames to air gaps between the component and tool, which act strongly insulating, so that the heat transfer suffers here. Also due to wear, air gaps between the component and tool can not be avoided.

The coolant or liquid used is predominantly water whose high enthalpy of evaporation promotes the cooling process. Depending on the height of the surface temperature on the molded component, different boiling phenomena occur on contact between the coolant and the molded component. At the high surface temperatures, the water evaporates and it forms on the mold component surface of a vapor film, which acts insulating due to the opposite to the liquid significantly lower thermal conductivity. In the field of film boiling, the molded component therefore cools only slowly. If the surface to be cooled falls below the so-called Leidenfrost temperature, locally and irregularly distributed over the mold component surface there is direct contact between the liquid and the mold component. The dissipated heat flow increases in these areas. As soon as the temperature of the coolant falls below the boiling temperature, evaporation no longer takes place and the heat is transferred convectively when the mold component surface is completely wetted. The pre-established boiling phenomena or phase states of the coolant during cooling can lead to locally and temporally different and uncontrollable cooling processes on the molded component. This affects the component properties and ultimately the product quality.

The invention is, starting from the prior art, the object of further developing a method and apparatus for producing cured mold components to increase the efficiency of heat transfer and thus improve the cooling effect and differentiated by the material characteristics of the mold components and process reliable and reproducible to be able to adjust. Furthermore, the invention aims to improve an apparatus for the production of cured molded components plant technology.

A first solution of the procedural part of the task according to claim 1 in a method in which the mold components are cured in the thermoforming mold by direct cooling by means of a coolant. According to the invention, the mold component is at least partially cooled with a coolant whose pressure is above the vapor pressure of the coolant, wherein the coolant is introduced into the mold space at a pressure of up to 25 MPa.

Unwanted air cushions or air gaps in the thermoforming tool can be caused for example by wear on the mold or as a result of manufacturing tolerances in tool making. In order to improve the contact and thus the heat dissipation from the mold component to the thermoforming mold, the unwanted air gap between mold component and tool or the contact surfaces in the mold cavity of the tool is closed by coolant at a pressure above the vapor pressure of the coolant in the mold space or in the tool gap between upper tool and lower tool is introduced. This aspect of the invention thus aims at obtaining a stable liquid phase of the refrigerant during the cooling process. The evaporation of the coolant is prevented by working in an elevated pressure range above the steam curve. By introduced into the mold space or the gap between the mold component and the contact surfaces of the tool coolant, the heat transfer in contrast to the otherwise existing air cushions is extremely increased. The heat transfer now ideally corresponds to the case of good tool contact.

The loading of the mold component with coolant in the mold space in order to cool and harden it can take place over the entire surface of the component or partially restricted to certain areas of the mold component. This gives a completely press-hardened molded component or a partially cured or partially differently hardened molded component. It is also possible different areas of the mold component to cool differently and to give these areas mutually different hardness values and strength properties.

The coolant is introduced into the mold cavity at a pressure of up to 25 MPa, with very high volume flows. Also, the duration of the coolant supply and / or the amount of pressure can be varied. In practice, it can be assumed that the minimum pressure should be 6 MPa. It has been shown that at a pre-pressure of less than 6 MPa incomplete heat transfer leads to a significant reduction in the cooling of the workpiece and thus the strength of the finished mold member.

In an advantageous development, the component temperature of the molded component is measured in the mold space. Furthermore, the tool temperature in the region of the contact surfaces of the mold cavity can also be measured. Depending on the component temperature and / or the tool temperature, the starting time and the end time of the coolant supply are controlled.

Furthermore, it is provided in a method modification that the coolant distribution in the mold space is variably controllable. In this case, certain (first) regions of the molded component can be acted upon with coolant and other (second) regions of the molded component not. It is also possible for different areas to be acted upon by coolant from one another at different times, in order to adjust the material properties in these areas in a targeted manner or differentiated.

In particular, when the component is cooled differently in areas, it is advantageous if the mold component is held fixed after removal from the thermoforming mold in a cooling station. As a result, a distortion of the mold component due to thermal stresses can be avoided.

For targeted adjustment of the state of aggregation of the coolant, the pressure with which the coolant is introduced or injected into the mold space during the cooling phase is adjusted in terms of control technology to the vapor pressure of the coolant. Depending on the injection pressure, it is possible to produce a water layer with good heat conduction or a wet steam with a different heat conductivity in the tool gap.

The pressure can - as already stated above - time-controlled and / or temperature-controlled, in particular depending on a temperature measurement on the mold component in the thermoforming mold and / or on the thermoforming tool itself.

The coolant may also be injected intermittently into the mold cavity. As a result, two parameters which can also be rationally implemented within the context of mass production - pulse duration and frequency - are available. By targeted control of the amount of coolant per pulse and their timing high heat flows can be dissipated. The control is particularly advantageous in such a way that one pulse per press-pressure or tool stroke is realized.

A first solution of the objective part of the object consists in a thermoforming tool having the features of claim 5.

The thermoforming tool comprises an upper tool and a lower tool. In the upper and / or lower tool inflow channels are provided, via which a cooling medium in the formed between the upper tool and lower tool mold space and the tool gap of the closed mold space is conductive. The state of aggregation of the coolant is adjustable. This is done by controlling the amount of pressure with which the coolant is injected or pressed into the mold space during the cooling process. For this purpose, all the necessary control and regulating technical apparatuses and units are assigned to the thermoforming tool, in particular a high-pressure pump, a pressure booster, a High-pressure accumulator, an injection control and / or a coolant quantity control.

The coolant can be injected with a pressure in the mold space, wherein the height of the pressure and / or the injection duration of the coolant can be controlled.

In the upper tool and / or in the lower tool supply lines for the coolant are provided. From the supply lines branch off injection lines, which open in the mold space. On the outlet side, the injection lines may have nozzles, preferably the injection lines open with thin openings without integrated nozzles in the mold space.

In a modification of the thermoforming tool means for influencing the heat transfer are arranged in the contact surfaces of the mold space. Such means may in particular be heating elements, clearances, air gaps, inserts of materials with lower or higher thermal conductivity or ceramic inserts. This embodiment is particularly suitable for the production of partially differently cured molded components, either targeted air transfer in the air cushion with minimal heat transfer or just the greatest possible heat transfer can be realized by injecting the coolant.

An advantageous development of the thermoforming tool provides that a measuring and evaluation unit is provided, by means of which the state of wear of the thermoforming tool or the upper tool and / or the lower tool can be determined. The state of wear can in particular be determined by evaluating the operating pressures, the coolant volume and / or the discharge quantities of the coolant measured at pressure relief valves. The wear or state determination of the thermoforming tool allows tool maintenance planning.

The objective part of the object is further achieved by a thermoforming tool according to the features of claim 12.

The thermoforming tool has an upper tool and a lower tool. The coolant is provided via a cooling system and introduced via inflow channels, which are provided in the upper tool and / or lower tool, in the mold space formed between the upper tool and the lower tool. The cooling system comprises at least one pressure generator, wherein the pressure generator is at least indirectly driven by the thermoforming tool, so the upper tool and / or the lower tool. Particularly preferably, the pressure generator is an energy converter in the form of a piston-cylinder unit.

As a volume buffer and energy storage, a pressure accumulator is integrated into the cooling system. In particular, a hydropneumatic pressure accumulator in the form of a bladder accumulator, a membrane accumulator or a piston accumulator is used.

The hydropneumatic accumulator is a hydraulic component that utilizes the compressibility of gas, typically nitrogen, to store the pressure and volume of the incompressible coolant in the cooling system. The pressure accumulator consists of a high-strength steel container. The liquid and the gas part are separated by a gas-tight separating element (bubble or membrane). The fluid space of the pressure accumulator is in communication with the cooling system. As the pressure increases, coolant flows into the liquid space, compressing the gas (nitrogen) in the gas space. As the pressure drops, the compressed gas expands, thus providing the stored energy to the cooling system.

The basic supply of the cooling system with coolant takes place via a priming pump. The priming pump leads coolant to the pressure generator. For this purpose, the Vorfüllpumpe and the pressure generator are connected via a line in which a check valve is integrated.

The pressure generator fills the accumulator during the closing movement of the thermoforming tool. For this purpose, the or pressure generator is preferably mechanically coupled to the upper tool of the thermoforming tool. For cooling At the end of the closing movement of the thermoforming tool or the upper tool, the coolant supply is opened and coolant is removed from the pressure accumulator. The pressure accumulator thus ensures the supply of coolant under high pressure of up to 25 MPa into the thermoforming tool.

The pressure generation within the cooling system is thus completely or at least partially by the thermoforming tool itself. For this purpose, the movement of the upper tool and / or the lower tool is used when closing and opening to drive or to actuate the pressure generator.

Of course, it is also conceivable that the cooling system is additionally lifted by the Vorfüllpumpe itself to a minimum pressure, which would entail a high-pressure pump with low volume throughput and correspondingly high losses in continuous operation.

It is also possible that the piston-cylinder unit is positioned instead of the tool-integrated design below the press or the thermoforming tool but is nevertheless actuated indirectly by the press pressure.

A further embodiment variant is represented by the fact that a high-pressure pump which takes over the function of the pressure generator is positioned between the fore pump and the pressure accumulator.

It is also possible that a Vorfüllpumpe positioned outside the tool and operated independently controlled by the press stroke.

Preferably, two or more pressure generators are provided. The coolant supply to the upper tool and the lower tool is preferably carried out separately, so that two partial cooling systems are provided. In this way, the upper tool and the lower tool are independently supplied with coolant, so that no high-pressure lines must be laid directly between the upper tool and the lower tool.

In a particularly advantageous for practice thermoforming tool, the pressure generator and the pressure accumulator are connected to each other coolant-conducting, wherein in the connecting line between the pressure generator and pressure accumulator, a pressure relief valve and preferably another check valve are integrated.

In practice, it is advantageous if a filter device is integrated into the cooling system and the coolant circuit. Furthermore, a heat exchanger and / or a cooler can be provided in the cooling system. This is switched before or after the filter device or arranged in a filter tank.

Used coolant exits the thermoforming tool and is collected in a collection system and sent for reuse.

Figur 1

schematisch eine erste Ausführungsform eines Warmformwerkzeuges in einer vertikalen Schnittdarstellung;

Figur 2

schematisch eine zweite Ausführungsform eines Warmformwerkzeuges in einer vertikalen Schnittdarstellung;

Figur 3

die Dampfdruckkurve von Wasser;

Figur 4

die Dampfdruckkurve von Wasser mit der Darstellung von zwei Punkten unterschiedlicher Druckhöhe bei denen unterschiedliche Aggregatzustände des Wassers vorliegen;

Figur 5

ein Warmformwerkzeug entsprechend der Figur 2 in der Offenstellung mit der Darstellung des Kühlsystems;

Figur 6

das Warmformwerkzeug entsprechend der Figur 5 in der Schließstellung und

Figur 7

eine Variante des Warmformwerkzeugs wie in der Figur 5 dargestellt.

The invention is described below with reference to the figures and by explanation of various embodiments. The figures show:

FIG. 1

schematically a first embodiment of a thermoforming tool in a vertical sectional view;

FIG. 2

schematically a second embodiment of a thermoforming tool in a vertical sectional view;

FIG. 3

the vapor pressure curve of water;

FIG. 4

the vapor pressure curve of water with the representation of two points of different pressure levels where different states of aggregation of the water are present;

FIG. 5

a thermoforming tool according to FIG. 2 in the open position with the representation of the cooling system;

FIG. 6

the thermoforming tool according to the FIG. 5 in the closed position and

FIG. 7

a variant of the thermoforming tool as in the FIG. 5 shown.

FIG. 1 shows a thermoforming tool 1. The thermoforming tool 1 essentially comprises an upper tool 2 and a lower tool 3, which are displaceable relative to each other and between which a mold space 4 is formed.

Clamped in the mold space 4 can be seen a deformed mold component 5 made of steel. The mold gap formed between the upper tool 2 and the lower tool 3 in the closed mold space 4 is designated by 6. For the production of the molded component 5, a board of hardenable steel has been heated to a hardening temperature above the austenitizing temperature, then transferred to the thermoforming tool 1 and formed. Clamped in the mold space 4, the mold component 5 is cooled and cured by a rapid cooling below the martensite start temperature.

Supply lines 7 are provided in the upper tool 2 and in the lower tool 3, of which injection lines 8 depart for the mold space 4. For cooling the mold component 5, coolant KM, as a rule water, is injected from the supply lines 7 via the injection lines 8 into the forming space 4 or the tool gap 6 and air gaps 10 present between the forming element 5 and the contact surfaces 9 of the forming space 4. The thermoforming tool 1 further includes here not shown pressure generator and / or a pressure accumulator and control and regulating devices for adjusting the coolant pressure and the coolant quantity, the duration of the coolant supply and temperature sensing elements.

In the mold space 4 is a direct cooling by injecting or pressing of coolant KM and the contact of the coolant KM with the mold component 5. The coolant supply including the supply line 7, the injection line 8 and the associated printing apparatus and equipment belong to a first cooling system. The first cooling system works in the High pressure range, whereby the pressure and the aggregate state of the coolant KM are adjustable.

In the upper tool 2 and in the lower tool 3 can also be seen cooling channels 11. These belong to a second cooling system, via which an indirect cooling of the mold component 5 takes place. Through the cooling channels 11, a coolant is passed, which receives the heat emitted by the warm mold component 5 to the thermoforming tool 1 and the upper tool 2 and the lower tool 3 and dissipates heat to the outside. As coolant, water is also preferably used here. Preferably, the coolant is guided in the second cooling system in a cooling circuit with recooling. While the coolant KM in the first cooling system is under high pressure, the coolant is present in the second cooling system with operating pressures of up to 0.6 MPa.

That in the FIG. 2 illustrated thermoforming tool 12 corresponds to the basic structure with upper tool 2 and lower tool 3 the previously based FIG. 1 explained thermoforming tool 1. Accordingly, corresponding components or component component are provided with the same reference numerals. A further explanation is omitted.

The thermoforming tool 12 differs from the thermoforming tool 1 in that indirect cooling is eliminated and no separate cooling channels are provided in the upper tool 2 and in the lower tool 3, via which heat is removed from the thermoforming tool 12.

The FIGS. 5 and 6 show a thermoforming tool 12 - as well as from the FIG. 2 explained - together with a cooling system KS. The FIG. 5 shows the thermoforming tool 12 in the open position. The FIG. 6 shows the thermoforming tool 12 in the closed position with deformed and clamped mold component. 5

As described above, the thermoforming tool 12 has an upper tool 2 and a lower tool 3, which are displaceable relative to one another and between which a molding space 4 is formed.

In the upper tool 2 and in the lower tool 3 supply lines 7 are provided, of which branch off the injection lines 8, which open into the mold space 4. The coolant KM is provided via a cooling system KS. For cooling system KS include pressure generator 13 and a pressure accumulator 14 together with control and regulating equipment and devices as well as shut-off valves and a Vorfüllpumpe 15th

In the exemplary embodiment illustrated here, the cooling system KS has two pressure generators 13 in the form of piston-cylinder units 16, 17. These are drive-coupled with the thermoforming tool 12 and are actuated by the upper tool 2. Each of the piston-cylinder units 16, 17 consists essentially of a cylinder 18 with a displaceable piston 19 guided therein and a piston rod 20 which is mechanically connected to the upper tool 2. The piston-cylinder units 16, 17 are synchronized with each other, wherein the cylinder chambers 21 communicate coolant-conducting. Due to the communication of the printing systems on all sides, a wedging of the press can be prevented, in particular in the case of a malfunction, such as, for example, a leak in one of the pressure-retaining systems.

The Vorfüllpumpe 15 supplies the cooling system KS with coolant KM and provides the necessary form. The coolant KM is transferred via the feed pump 22 into the cylinder space 21 of the piston-cylinder unit 16 (arrow P1) A check valve 23 is integrated into the supply line 22. The check valve 23 permits the free flow of the coolant KM in the direction to the pressure generator 13 and the piston-cylinder unit 16 and blocks it in the reverse direction. In the supply line 22 between the priming pump 15 and the check valve 23, a pressure relief valve 30 is further integrated.

The pre-filling pump 15 continuously supplies coolant KM into the pressure generator 13. The pre-filling pump 15 can run continuously, which increases the service life because the startup and shutdown operations can be minimized.

From the piston-cylinder unit 16, the coolant KM is transferred via a main supply line 24 into the supply lines 7 in the upper tool 2 and in the lower tool 3. In the main supply line 24, a closing valve 25 is arranged, via which the supply of coolant KM to the hot mold 12 can be opened or closed.

The pressure accumulator 14 is connected to the main supply line 24. In the main supply line 24 is connected between the pressure generator 13 and the piston-cylinder unit 16 and the pressure accumulator 14 upstream of a pressure relief valve 26 and a check valve 27 integrated.

The accumulator 14 is designed as a bubble store and acts as a volume buffer and energy storage. The pressure accumulator 14 consists of a high-strength steel container 28. In the steel container 28, a closed, elastic reservoir bladder 29 is integrated. The storage bladder 29 is filled with gas, usually nitrogen. By the storage bladder 29, the gas and the coolant KM are separated from each other.

Although only one pressure accumulator 14 together with control and valve members is shown in the embodiment explained here, a symmetrical design of the cooling system KS is expedient in practice. Accordingly, the pressure generator 13 shown on the left in the image plane in the form of the piston-cylinder unit 17 with the vorerläuterten valves and a pressure accumulator 14 and equipped with lines for transferring the coolant KM in the supply lines. 7

The mode of operation and the operating principle for the production of hardened molded components are described below.

The FIG. 5 shows the thermoforming tool 12 in the open position. In the FIG. 6 one recognizes the closed position of the thermoforming tool 12. When Starting up of the upper tool 2, coolant KM is pumped via the pre-filling pump 15 into the pressure generator 13 (arrow P1) or sucked in via the feed line 22 from a coolant container, not shown here. Gravity can also be utilized to fill the cooling system KS with coolant KM if the coolant tank is arranged above the thermoforming tool 12. A combination between the utilization of the geodetic pressure and the suction of the coolant KM via the piston-cylinder units 16, 17 is possible. During this phase, the accumulator 14 is relaxed. The closing valve 25 is closed.

A metal plate, in particular a plate made of hardenable steel, is heated to a temperature in the specific austenitizing temperature range of the material and then placed in the mold cavity 4 of the thermoforming mold 12 on the lower tool 3.

The thermoforming tool 12 is closed. For this purpose, the upper tool 2 is moved downward in the direction of the lower tool 3. During the closing movement, the pistons 19 of the piston-cylinder units 16, 17 in the cylinder 18 are moved downward. In this case, force is exerted on the coolant KM in the cylinder chambers 21 of the piston-cylinder units 16, 17, which leads to an increase in pressure. The coolant KM is pressed from the cylinders 18 via the main supply line 24 in the direction of the thermoforming tool 12 in the pressure accumulator 14 (arrow P2). In practice, the bubble pressure may be up to 25 MPa, for example 13 MPa. The pressure in accumulators 14 may vary as they are not always completely drained during the coolant supply cycle. To prevent overpressure in the accumulator 14, the pressure relief valve 26 is provided. The check valve 27 prevents a return flow from the pressure accumulator 14 in the direction of the upstream pressure generator 13.

It has been found that incomplete heat transfer at a pre-pressure of less than 6 MPa leads to a significant reduction in the Cooling of the workpiece and thus the strength of the finished mold component 5 leads.

By closing the thermoforming tool 12, the board is formed in the warm state. After completion of the closing movement, the mold component 5 is finished, so completed the forming process. Upon completion of the closing movement, the closing valve 25 is opened and coolant KM is transferred by relaxing the pressure accumulator 14 via the main supply line 24 and the supply lines 7 and the injection lines 8 in the mold space 4 (arrow P3).

The coolant KM flows through the air gaps 10 between the mold component 5 and the contact surfaces 9 of the mold space 4. It comes to the direct contact of the coolant KM with the mold component 5 and the upper tool 2 and the lower tool 3 and the contact surfaces 9, whereby a direct cooling of the Molded component 5 and the associated curing takes place. This leads to a partial evaporation of the coolant. The pressure accumulator 14 ensures a back pressure of at least 0.5 MPa, preferably higher, to ensure further injection and maintenance of the pressure of the coolant KM.

The used coolant KM runs out of the thermoforming tool 12 and is taken up in a drip pan and / or discharged via a collecting channel.

After forming, the thermoforming tool 12 remains briefly closed for the required holding time to ensure the structural transformation for curing. Subsequently, the closing valve 25 is closed and the thermoforming tool 12 moves apart, so that the cycle can start anew.

The inventively provided cooling system KS allows a very fast injection of coolant KM without delay in pressure build-up. Advantageous for this purpose are, in particular, the short coolant paths, because the cooling system KS in the hot forming tool 12 or directly in spatial proximity of the thermoforming tool 12 is arranged. The integration of the cooling system KS in the thermoforming tool 12 leads to a significantly reduced space requirements. The integration of the cooling system KS in the thermoforming tool 12, a mobility of the thermoforming tool 12 is possible. The thermoforming tool 12 can be used in various presses. A conversion of the thermoforming tool 12 from one press to another press is complete with upper tool 2 and lower tool 3 including cooling system KS.

In terms of plant technology, the cooling system KS continues to be characterized by the fact that there are hardly any pressure fluctuations in the system.

The thermoforming tool 12, as in the FIG. 7 represented corresponds to the basic structure of the armformwerkzeug 12 according to the FIGS. 5 and 6 , The components or component components are therefore provided with the same reference numerals to a repeated description is omitted. The modification consists in the arrangement of a measuring and evaluation unit ME, which serves to determine the state of wear of the upper tool 2 and / or the lower tool 3. The blow-off amount of the relief valve 26 can be measured and used as a wear indicator for tool maintenance planning. For this purpose, the discharge side of the pressure relief valve 26 is connected to a measuring and evaluation unit ME. The blow-off quantity decreases with increasing tool wear or increasing volume of the air cushion between the tool and the workpiece. This means that the greater the wear, the more water gets into the air gaps and the less is blown out as a surplus per stroke of the tool. By monitoring and evaluating the blow-off quantity, conclusions can be drawn about the tool wear and thus a tool diagnosis can be carried out.

The basic principle and four possible exemplary embodiments of the cooling of the molded component in a thermoforming tool 1 or 12 are explained below.

Rationale:

The apparatus configuration of the thermoforming tool 1 or 12 allows the coolant KM is introduced with a pressure p _KM above the vapor pressure p _{D of} the coolant KM in the mold space 4 and in the tool gap 6. This ensures a stable liquid phase of the coolant KM. This ensures a high heat transfer and a high heat dissipation and thus a very good cooling. Manufacturing and / or wear-related air gaps 10 between the contact surface 9 of the mold space 4 and the mold component 5 are closed by the coolant KM. Since the coolant KM, in the present case water, is above the vapor pressure p _D under a high pressure p _KM , evaporation upon contact with the hot component surface of the molded component 5 is prevented. The cooling takes place uniformly over the entire mold component surface. Zones of poor heat conduction through vapor formation are avoided. FIG. 3 shows the curve of the vapor pressure p _D of water. In the basic principle of the invention, a liquid state of matter of the coolant KM is set by adjusting the pressure p _{KM of} the coolant KM during the cooling phase in a range above the vapor pressure p _D. The water is controlled in time with pressures p _KM up to 25 MPa at very high volume flows in the mold space 4 of the closed thermoforming tool 1, 12 and pressed into the air gaps 10. By injected into the mold space 4 and the tool gap 6 and in the air gaps 10, under high pressure water, a very good heat transfer and thus a high cooling effect is ensured. The evaporation of the water and an adversely affecting the heat dissipation, insulating vapor film is avoided. The heat transfer corresponds at least almost to the heat transfer at full-surface tool contact.

Embodiment 1

By controlling the timing of injection start and end of injection and the pressure level, the component hardness can be controlled specifically. The minimum hardness in this case forms the hardness that is achieved in the mold component at a certain holding time without injection cooling, up to the maximum hardness, which depends on the material properties and the alloy concept of the component material. The control of injection start and end of injection is also possible by an online measurement of the mold component temperature in or comparatively on the tool. For this purpose, the component temperature T _{B of} the mold component 5 in the mold space 4 is measured. Furthermore, the tool temperature T _W in the region of the contact surfaces 9 of the mold space 4 can be measured. The starting time T _A (injection start) and the end time T _E (injection end) of the coolant supply is controlled as a function of the component temperature T _B and / or the tool temperature T _W.

Embodiment 2:

Due to the possible extremely short closing times of the thermoforming tool 1 or 12, partially cured mold components 5 can be produced, in which only certain regions of the mold component 5 in the mold space 4 are exposed to coolant KM. There is a sectional coolant injection into controllable areas of the mold space 4 and corresponding thereto on the areas of the mold component 5, which should be hard after removal. In the areas of the mold component 5, which should have a lower strength after the thermoforming and press-hardening process, the cooling can be additionally delayed by the use of means for influencing the heat transfer, which are arranged in the contact surfaces 9 of the mold space 4. Such means may be, for example, heating elements, clearances, air gaps, inserts of materials with lower or higher thermal conductivity or ceramic inserts.

From the thermoforming tool 1 or 12, a mold component 5 is removed, which has at least two zones or areas which have different temperatures from each other. This mold component 5 is held fixed for further cooling in a separate cooling station. This measure has an advantageous effect on the defined cooling of the soft, non-hardened or less strongly hardened regions and prevents warping of the molded component 5.

Embodiment 3

By varying the injection duration in conjunction with a variation of the injection pressure p _KM , freely different heat transfer coefficients can be set distributed over a mold component 5. Depending on the injection pressure, it is possible in the mold space 4 or in the tool gap 6 between the upper tool 2 and lower tool 3 to produce a water layer with a good heat conduction and a wet steam with a different, poorer thermal conductivity. The two operating points of the refrigerant pressure are in the FIG. 4 characterized. Point 1 is in the range of a stable liquid phase above the curve of the vapor pressure p _D. Point 2 lies in the wet steam area below the curve of the vapor pressure p _D. As a result, there is another way to set the component properties targeted.

Embodiment 4

By operating the high pressure injection cooling in the wet steam region, hot forming tools can be conveniently constructed without conventional cooling. It can thus be a thermoforming tool 12 as in FIG. 2 as well as the FIGS. 5 and 6 shown used in which is dispensed with an indirect cooling system.

When operating in the wet steam region, the heat energy from the mold component is used in a planar manner to transfer the water from the liquid phase into the gaseous phase. In order not to produce a closed water film in the tool gap 6, the injection pressure p _{KM is} timed or adapted via a temperature measurement on the mold component 5. Alternatively, the tool temperature T _W is measured comparatively on the hot forming tool 1 or in the area of the contact surfaces 9 of the forming space 4 and is constantly adapted to the vapor pressure p _D.

In the above-described embodiments 1 to 4 can be provided to use the pressure relief valve 26 in addition to indirect wear indicator of the thermoforming tool 1 and 12 respectively. For this purpose, the discharge amount on Relief valve 26 metrologically detected and evaluated by the measurement and evaluation unit ME. Thus, a statement about the wear of the mold 1, 12 can be taken during operation over time to plan and perform timely tool overhauls or -instandhaltungen.

Reference numerals:

1 -

Thermoforming tool

2 -

upper tool

3 -

lower tool

4 -

cavity

5 -

mold component

6 -

tool gap

7 -

supply line

8th -

Injection line

9 -

contact area

10 -

air gap

11 -

cooling channel

12-

Thermoforming tool

13 -

pressure generator

14 -

accumulator

15 -

priming pump

16 -

Piston-cylinder unit

17 -

Piston-cylinder unit

18 -

cylinder

19 -

piston

20 -

piston rod

21 -

cylinder space

22 -

feed

23 -

check valve

24 -

Main supply line

25 -

closing valve

26 -

Pressure relief valve

27 -

check valve

28 -

steel containers

29 -

bladder

30 -

Pressure relief valve

KM -

coolant

KS -

cooling system

p _KM -

Coolant pressure

p _D -

vapor pressure

T _B -

component temperature

T _W -

mold temperature

T _A -

Start time (start of injection)

T _E -

End time (end of injection)

P1 -

arrow

P2 -

arrow

P3 -

arrow

ME -

Measuring and evaluation unit

Claims (13)

Method for producing hardened molded components, in particular structural or body components of motor vehicles, wherein a metal plate is heated, then hot-formed in the mold space (4) of a thermoforming tool (1; 12) to form the molded component (5) and contacted by a coolant (KM) in the mold space (4) of the thermoforming tool (1; 12) is hardened, for which the coolant (KM) is passed through inlet channels (7, 8) in the mold space (4), and the mold component (5) at least partially with a coolant (KM ) is cooled, the pressure (p _KM ) above the vapor pressure (P _D ) of the coolant (KM), characterized in that the coolant (KM) is introduced at a pressure of up to 25 MPa in the mold space (4). A method according to claim 1, characterized in that the coolant distribution in the mold space (4) is variably controllable, in particular the first regions of the mold component (5) with coolant (KM) are acted upon and second areas of the mold component (5) not with coolant (KM) be acted upon or a first area and a second area temporally offset with coolant (KM) are applied. Method according to at least one of claims 1 or 2, characterized in that the coolant (KM) with a pressure (p _KM ) in the mold space (4) is introduced and the pressure (p _KM ) during the cooling phase control technology to the vapor pressure (p _D ) of the coolant is adjusted. Method according to at least one of Claims 1 to 3, characterized in that the pressure (p _KM ) is time-controlled and / or temperature-controlled, in particular as a function of a temperature measurement on the mold component (5) in the thermoforming mold (1; 12) and / or a temperature measurement on the thermoforming mold (1; 12). A thermoforming tool for forming and hardening metal sheets with an upper tool (2) and a lower tool (3), wherein at least one of the tools (2, 3) has inflow channels (7, 8) via which a coolant (KM) flows into the between upper tool ( 2) and lower tool (3) formed mold space (4) is conductive, characterized in that the physical state of the coolant (KM) is adjustable. Thermoforming tool for forming and hardening metal sheets with an upper tool (2) and a lower tool (3) and a cooling system (KS), wherein at least one of the tools (2, 3) inflow channels (7, 8), via which a coolant (KM ) can be conducted in the mold space (4) formed between the upper tool (2) and lower tool (3), characterized in that the cooling system (KS) comprises at least one pressure generator (13), in particular in the form of a piston-cylinder unit (16, 17), wherein the pressure generator (13) is actuated at least indirectly by the upper tool (2) and / or the lower tool (3). Thermoforming tool according to claim 5 or 6, characterized in that the coolant (KM) with a pressure (p _KM ) in the mold space (4) can be injected and the height of the pressure (p _KM ) and / or the injection duration (T _E ) controllable are. Thermoforming tool according to one of claims 5 to 7, characterized in that in the upper tool (2) and / or in the lower tool (3) supply lines (7) for the coolant (KM) and from the supply lines (7) branches off and in the mold space (4 ) are provided injection lines (8). Thermoforming tool according to at least one of claims 5 to 8, characterized in that in the contact surfaces (9) of the mold space (4) means for influencing the heat transfer are arranged. Thermoforming tool according to at least one of claims 5 to 9, characterized in that a measuring and evaluation unit (ME) is provided for determining the state of wear of the upper tool (2) and / or the lower tool (3). Thermoforming tool according to claim 6, characterized in that in the cooling system (KS) at least one pressure accumulator (14) is integrated. A thermoforming tool according to at least one of claims 6 or 11, characterized in that the pressure generator (13) and the pressure accumulator (14) are connected to one another by incorporation of a pressure relief valve (26). Thermoforming tool according to at least one of claims 6 or 11 to 12, characterized in that the pressure generator (13) downstream, in particular between the pressure generator (13) and the pressure accumulator (14), a pressure relief valve (26) is provided and the pressure relief valve (26) is coupled with a measuring and evaluation unit (ME), wherein by the measuring and evaluation unit (ME) of the wear state of the upper tool (2) and / or the lower tool (3) can be determined.

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