Method for forming metal composite films for battery cells

Abstract

A method for forming a metal composite film for battery cells includes at least the following steps: (a) inserting the metal composite film into a forming apparatus having a recess; (b) fixing the metal composite film in place by closing a film holder; (c) preforming the metal composite film within the recess in a first direction; and (d) final forming of the metal composite film within the recess in a second direction.

Claims

1. A method for forming a metal composite film for battery cells, comprising at least the following steps: a) inserting the metal composite film into a forming apparatus having a first section and a second section that together define a recess, wherein a part of the recess defines a final form, and wherein on at least one side of the recess is mounted an electrical coil configured to emit an electromagnetic pulse; b) fixing the metal composite film in place within the recess by closing a film holder; c) using at least a first electromagnetic pulse, preforming the metal composite film within the recess in a first direction; and d) using at least a second electromagnetic pulse, final forming of the metal composite film within the recess in a second direction that is selected to be opposite to the first direction.

2. The method as recited in claim 1, further comprising removing air from the forming apparatus at least during the preforming or final forming of at least an area of the recess which is disposed behind the metal composite film in the respective deformation direction.

3. The method as recited in claim 1, wherein the metal composite film comprises an aluminum composite film.

4. The method as recited in claim 1, wherein the metal composite film has a wall thickness of between 120 m and 180 m.

5. The method as recited in claim 1, wherein an electrical coil configured to emit an electromagnetic pulse is mounted on only one side of the recess, such that the electrical coil emits both the first and the second electromagnetic pulses, wherein the polarity of the second electromagnetic pulse is reversed as compared to the polarity of the first electromagnetic pulse.

6. The method as recited in claim 1, wherein an electrical coil configured to emit an electromagnetic pulse is mounted on both sides of the recess, such that a first electrical coil mounted on a first side of the recess emits the first electromagnetic pulse, and a second electrical coil mounted on a second side of the recess emits the second electromagnetic pulse.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention, as well as the technical field are explained in greater detail in the following with reference to the enclosed figures. It should be noted that the present invention is not to be limited by the cited exemplary embodiments. In particular, unless explicitly described otherwise, it is also possible to extract partial aspects of the subject matter explained in the figures and combine them with other elements and realizations from the present description. It should be noted, in particular that the figures and, in particular the illustrated relative sizes are only schematic. In the drawing:

(2) FIG. 1: shows a cross-sectional side view of first design variant of a forming apparatus;

(3) FIG. 2: shows a cross-sectional side view of second design variant of a forming apparatus;

(4) FIG. 3: shows a cross-sectional side view of third design variant of a forming apparatus;

(5) FIG. 4: shows a cross-sectional side view of fourth design variant of a forming apparatus;

(6) FIG. 5 shows a motor vehicle having battery cells; and

(7) FIG. 6 shows a cross-sectional side view of fifth design variant of a forming apparatus.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 shows a forming apparatus 1 in a cross-sectional side view. Forming apparatus 1 is composed of a first section 2, which is configured as a die and forms the lower part, as well as of a second section 3, which acts as a film holder 20 and forms an upper part of forming apparatus 1. At the outer rim of forming apparatus 1, a metal composite film 4 is securely clamped in place between first section 2 and second section 3. To that end, first section 2 and second section 3 are pressed securely against each other. Metal composite film 4 is an aluminum composite film, for example, which, as is known, is also referred to as a pouch film. The two sections 2, 3, jointly enclose a recess 5, in which the pouch film is formed into a finished film pocket, a pouch. First section 2 defines that part of recess 5 which forms a final, finished form 6. This means that first section 2 is formed as an exact negative form for the final state of fully formed metal composite film 4. In recess 5 in FIG. 1, the up arrows indicate a first direction 18 and the down arrows a second direction 19.

(9) In response to a deformation in first direction 18, the metal composite film is initially deformed into a preform 7 and, subsequently thereto, in response to a deformation in (opposite) second direction 19, brought to a final, finished form 6.

(10) The dashed line illustrated inside of recess 5 shows the contour profile of metal composite film 4 having preform 7. This means that the dashed line indicates the contour profile of the metal composite film 4 upon completed preforming. Both first section 2 and second section 3 are each equipped with air ducts 8 which ensure that air is removed from recess 5 both during preforming and during final forming. First section 2 also has a first coil 9 which is designed to emit an electromagnetic pulse as soon as the illustrated conductor of first coil 9 is traversed by a current. First coil 9 is able to generate an electromagnetic pulse, which forms metal composite film 4 upwardly in first direction 18 by the thereby produced Lorentz force that acts on metal composite film 4. There, metal composite film 4 then comes in contact with that section of recess 5 which belongs to second section 3 of forming apparatus 1. To achieve final form 6 of metal composite film 4, second section 3 has a second coil 10, which is likewise designed to emit an electromagnetic pulse, however, in the opposite direction. That is, the Lorentz force produced by coil 10 is transferred at this stage in second direction 19. Once the preforming is carried out, another electromagnetic pulse may be emitted by now above disposed second coil 10, which, in turn, effects the forming into final, finished form 6. During the process of forming into final, finished form 6, metal composite film 4 is pressed downward into recess 5 of first section 2 configured as a die. Reversing the polarity of the current flow makes it likewise possible for only one coil to be used, as shown in the embodiment depicted in FIG. 6. Thus, the direction of the Lorentz force is controllable.

(11) In many respects, there are advantages to the forming by an electromagnetic pulse. Thus, in this manner, a very high process speed of more than 100 m/s, for example, may be reached. This significantly improves the formability of the material used since, for the deformation, it may be brought into a viscoplastic state. Furthermore, the friction that otherwise normally occurs between the punch and the die of a forming tool and the workpiece is avoided by the metal composite film 7 at hand, which is to be formed, being formed without contact. This also makes it possible to considerably lower the energy consumption since there is no need for mechanical drives nor for the energy-consuming generation of compressed air for a pressure-driven forming process. Thus, using compressed air for the forming requires a relatively cost-intensive generation of compressed air, particularly when working with large sizes, which is reflected in higher process costs. Also, the use of controllable valves negatively affects the process times, for example, since they operate relatively slowly. Another advantage of the electromagnetic forming is the shaping of sharp contours. Thus, it is not only possible to produce vertical edges, but also to create undercuts.

(12) The present invention is also able to substantially reduce the wear that forming apparatus 1 is subject to and make possible greater drawing depths than in the related art heretofore. Moreover, an especially uniform distribution of material on formed metal composite film 4 may be achieved by the present invention and, in particular, by the forming by electromagnetic pulses. Other positive secondary effects of the present invention are that it is possible to appreciably shorten the cycle times required for production and substantially reduce the spring-back of the component to be formed that regularly occurs during a forming process.

(13) After this step, the shaping part of the production process is completed, and the finish-formed metal composite film 4 may be removed. The metal composite film, respectively the pouch film is thereby separated during the production process or also subsequently thereto to ensure that the desired final dimensions are adjustable.

(14) FIG. 2 shows another possible specific embodiment of the present invention. This forming apparatus 1 features coil 10 only in second section 3 that forms the upper part. In this specific embodiment, second section 3 acts as a film holder 20, as it is pressed firmly against underlying first section 2 and thereby securely clamps metal composite film 3 in place in forming apparatus 1. To form metal composite film 4 into preform 7 following the clamping, compressed air is fed through air duct 8, configured at the bottom left, into recess 5, so that, inside of recess 5, metal composite film 4 is initially preformed upwardly in first direction 18. In the subsequent process step, metal composite film 4 located in preform 7, is formed at an especially high speed in second direction 19, downwards into final, finished form 7 by an electromagnetic pulse generated by coil 10 due to the thereby produced Lorentz force. In this specific embodiment, the preforming process is carried out using compressed air, and the final forming process is carried out via an electromagnetic pulse.

(15) In the specific embodiments shown in FIGS. 1 and 2, preform 7, thus the geometry of preformed metal composite film 4, may be precisely defined by the inner contour of second section 3 in the area of recess 5.

(16) FIG. 3 illustrates another possible specific embodiment of the present invention where first section 2 is again formed as a die and is part of recess 5. Air is supplied to recess 5 and removed therefrom via air duct 8. In this specific embodiment as well, metal composite film 4 is first securely clamped in place within the forming apparatus 1 by second section 3 acting as film holder 20. The special feature of this specific embodiment is that, on the top side, recess 5 no longer has a shaping area, rather is merely covered by coil 10. To place composite film 4 at this stage in preform 7, compressed air is directed via air duct 8, configured at the bottom left, into recess 5, whereby metal composite film 4 is preformed in preform 7 indicated by the dashed line. In this specific embodiment, metal composite film 4 does not come into contact with a shaping area of second section 3. To subsequently place metal composite film 4, preformed in this manner, in preform 6, an electromagnetic pulse is again generated by coil 10. This electromagnetic pulse induces a Lorentz force to act downwardly in second direction 19 on metal composite film 4. Metal composite foil 4 is hereby formed at high speed in the direction of the die of first section 2, thereby assuming the contour of final, finished form 6. Combining preforming and final forming at high speed makes it possible to form metal composite film 4 to a much greater extent than was heretofore the case, without producing damage, such as cracks, for example, on metal composite film 4.

(17) FIG. 4 shows another possible specific embodiment of a forming apparatus 1 which is largely constructed in the same way as forming apparatus 1 according to FIG. 3. However, in place of previously used coil 10 in second section 3, this specific embodiment provides a mechanically acting punch 11, which may be moved downwards in the direction of arrow 12. The purpose of this punch 11 is to form metal composite film 4 in final, finished form 6 by mechanical forming, after it has been placed in preform 7 by compressed air fed via air channel 8 in first direction 18. For that purpose, punch 11 is moved downwards into the die of first section 2 by a driving device (not shown) in the direction of arrow 12. The direction of arrow 12 thereby corresponds to second direction 19. In this specific embodiment as well, the combination of preforming and final forming makes it possible to achieve an especially effective deep drawability without damaging metal composite film 4.

(18) In the specific embodiments in accordance with FIGS. 3 and 4, preform 7 is not defined by second section 3. Rather, in these specific embodiments, metal composite film 4 may assume a free contour during the preforming process.

(19) Finally, also shown in FIG. 5 is a specific embodiment where a motor vehicle 13 is operated by an electric drive. For that purpose, a schematically illustrated electric motor 14 is powered by a battery 15. The power supply is controlled by a control 16. Disposed within battery 15 are a multiplicity of battery cells 17, which may be produced in accordance with the present invention. A thus designed motor vehicle 13 has the advantage that battery cells 17 located therein are especially reliable as the encasing thereof using metal composite films 4 may be realized without damage and, therefore, extremely reliably and, at the same time, very efficient and reliably encased battery cells may be used.

LIST OF REFERENCE NUMERALS

(20) 1 forming apparatus 2 first section 3 second section 4 metal composite film 5 recess 6 final, finished form 7 preform 8 air duct 9 first coil 10 second coil 11 punch 12 arrow 13 motor vehicle 14 electric motor 15 battery 16 control 17 battery cell 18 first direction 19 second direction 20 film holder