Busbar manufacturing method for manufacturing a busbar of a pyrotechnical circuit breaker

Abstract

The invention is directed to a busbar manufacturing method for manufacturing a busbar (10) of a pyrotechnical circuit breaker (100), comprising the following manufacturing steps: Providing a sheet metal busbar blank (12) comprising at least two clamping sections (14, 16) and at least one displacement section (20), wherein the displacement section (20) is located between the two clamping sections (14, 16) with respect to a sheet metal plane (P). Fixation of the clamping sections (14, 16) of the sheet metal busbar blank (12) using a clamping arrangement (30), wherein the displacement section (20) remains free. Structural displacement of the displacement section (20) perpendicularly with respect to the sheet metal plane (P) such that each clamping section (14, 16) remains structurally connected to the displacement section (20) via a respective connection section (24, 26), wherein the displacement is provided by using a stamp (50) and a corresponding die (54), wherein, during the displacement process step, the stamp (50) contacts the displacement section (20) at a first sheet metal surface (17), and wherein the die (54) contacts the displacement section at a second opposite sheet metal surface (18), wherein the stamp (50) pushes the displacement section (20) into the die (54). The finished busbar (10), as a result of the busbar manufacturing method according to the invention, is provided with predetermined breaking sections (40, 42), wherein the electric resistance of the busbar (10) is relatively low.

Description

[0001] PIP24065WO / EBFS 12.11.2024

[0002] - 1 -

[0003] Busbar manufacturing method for manufacturing a busbar of a pyrotechnical circuit breaker

[0004] Description

[0005] The present invention is directed to a busbar manufacturing method for manufacturing a busbar of a pyrotechnical electric circuit breaker.

[0006] In vehicles with high-voltage applications, such as hybrid vehicles or fully electric vehicles in particular, a pyrotechnical circuit breaker is used to disconnect the power line between the battery and the users, especially the vehicle's drive system, in a few thousandts of a second in the event of an accident in order to prevent short circuits. Therefore, the pyrotechnical circuit breaker comprises a busbar which is integrated into the power line and which can be disconnected by a cutting element which is driven through the busbar using a pyrotechnical propelling charge. However, due to the high voltages, arcs occur between the free ends of the busbar, after the busbar has been cut, which can damage the pyrotechnical electric circuit breaker.

[0007] In order to provide a low electric resistance of the busbar, the cross-sectional area of the busbar should be relatively large which results in a relatively large thickness of the busbar. Thus, the large thickness of the busbar results in a relatively high structural strength, so that a relatively large kinetic energy amount is required to cut the busbar. It is therefore usual to provide predetermined breaking sections within the busbar to weaken the busbar material, so that the cutting of the busbar requires less kinetic energy. An example of a busbar with predetermined breaking sections is disclosed in DE 102019 135 591 B4.

[0008] The manufacturing of such predetermined breaking sections causes an unwanted cold work hardening within the busbar material which strengthens the busbar. Furthermore, the predetermined breaking sections cause a restriction of the cross-sectional area of the busbar over a defined length, seen in the direction of the current flow, which increases the total electrical resistance of the busbar. PIP24065WO / EBFS 12.11.2024

[0009] - 2 -

[0010] An object of the present invention is therefore to provide a busbar manufacturing method with a relatively low cold work hardening within the predetermined breaking sections and a relatively short restriction of the cross-sectional area, seen in the current flow direction.

[0011] According to the present invention, this object is achieved with a busbar manufacturing method with the features of claim 1 .

[0012] The busbar manufacturing method for manufacturing a busbar of a pyrotechnical circuit breaker according to the present invention comprises the following manufacturing steps:

[0013] In a first manufacturing step, a sheet metal busbar blank is provided within a suitable manufacturing device or manufacturing tool. The sheet metal busbar blank can be a sheet metal raw material, for example a sheet metal stripe from a sheet metal coil.

[0014] Alternatively, the sheet metal busbar blank can be a pre-manufactured busbar, which, for example, can be provided with a machined outer contour defining the final contour of the finished part. Preferably, the pre-manufactured busbar is provided with a substantially rectangular shape. The sheet metal busbar blank comprises at least two clamping sections and at least one displacement section. Preferably, the clamping sections and the displacement section are arranged adjacent to each other in a straight line which corresponds to the longitudinal extension direction and to the current flow direction of the finished busbar. The displacement section is located between the two clamping sections with respect to a sheet metal plane. If the sheet metal busbar blank is a sheet metal raw material, the clamping sections are located somewhere at the sheet metal raw material. If the sheet metal busbar blank is a pre-manufactured busbar, the clamping sections are located at both longitudinal ends of the preferably rectangular pre-manufactured busbar, wherein the displacement section is a middle section of the pre-manufactured busbar.

[0015] In a second manufacturing step, the clamping sections of the sheet metal busbar blank are fixed using at least one clamping arrangement, wherein the displacement section remains free. The clamping arrangement comprises at least two clamping devices PIP24065WO / EBFS 12.11.2024

[0016] - 3 -

[0017] wherein each clamping device is preferably defined by a first clamping element which contacts the sheet metal busbar blank at a first sheet metal surface and a second clamping element which contacts the sheet metal busbar blank at a second opposite sheet metal surface. Every clamping device fixes one of the clamping sections. The displacement section remains free, which means that no clamping device contacts the displacement section so that the displacement section is accessible.

[0018] In a third manufacturing step the displacement section is structurally displaced perpendicularly with respect to the sheet metal plane such that each clamping section remains structurally connected to the displacement section via a respective connection section. Accordingly, the displacement direction is the thickness direction of the sheet metal busbar blank. The displacement is provided by using a stamp and a corresponding die, wherein, during the displacement process step, the stamp contacts the displacement section at the first sheet metal surface, where the sheet metal busbar blank is contacted by the first clamping element of the clamping device. The stamp is arranged between the clamping devices of the clamping arrangement contacting the accessible displacement section which has been remained free of the clamping devices. The die contacts the displacement section at a second opposite sheet metal surface, where the sheet metal busbar blank is contacted by the second clamping element of the clamping device. The stamp is moved relatively to the clamping device and thereby pushes the displacement section into the die, wherein the clamping sections are fixed by the clamping arrangement.

[0019] The displacement of the displacement section creates a step between the displacement section and each clamping section, wherein the displacement section and the clamping section remain at the original thickness of the sheet metal busbar blank, whereas each connection section which structurally connects the displacement section and the adjacent clamping section is sheared such that relatively low cold work hardening effects can appear in each connection section. As a result, the material strength within the connection section is relatively low, allowing the finished busbar to be cut in a pyrotechnical electric circuit breaker with a relatively low kinetic energy. The step is also defined such that a width of the connection section seen perpendicularly to the PIP24065WO / EBFS 12.11.2024

[0020] - 4 -

[0021] displacement direction is lower than the thickness of the clamping sections or the displacement section thereby defining a predetermined breaking section.

[0022] In a preferred embodiment of the present invention, the stamp is provided with a flat contact surface. The stamp is moved in thickness direction over a length that is preferably lower than the sheet metal busbar blank thickness, thereby defining a flat displacement section.

[0023] In another preferred embodiment of the present invention, the stamp is provided with a rectangular contact surface, wherein the die is provided with a corresponding rectangular shape. The shaping of the stamp and the die results in a rectangularly shaped displacement section seen perpendicularly to the sheet metal plane. Preferably, the rectangular contact surface is flat so that a step is defined between the displacement section and each clamping section, wherein the step is provided with a linear edge. Because of the linear adjacent arrangement of the clamping sections and the displacement section, the step is arranged perpendicularly to this linear arrangement direction and therefore is arranged perpendicularly to the longitudinal extension direction and to the current flow direction of the finished busbar. As mentioned above, the width of the connection section seen perpendicularly to the displacement direction is lower than the thickness of the clamping sections or the displacement section. The low width of the connection section and the linear extension of the step result in a relatively abrupt change of the cross-sectional area at the transition between the clamping section and the connection section or at the transition between the connection section and the displacement section. With respect to the current flow direction of the finished busbar, the extension of the restriction of the cross-sectional area within the connection section is relatively short resulting in a relatively low total electric resistance of the busbar. The shorter this extension, the lower the total electric resistance of the busbar.

[0024] Preferably, an additional stamp counterpart, which is opposite to the stamp, contacts the displacement section at a second opposite sheet metal surface during the displacement process. The shape of the contact surface of the stamp counterpart corresponds to the shape of the contact surface of the stamp. The displacement PIP24065WO / EBFS 12.11.2024

[0025] - 5 -

[0026] section is thereby clamped between the stamp and the stamp counterpart during the displacement process, allowing the displacement section to substantially maintain its original shape and allowing a more precise shaping of the connection sections.

[0027] Preferably, the displacement dimension of the displacement section is at least 10% of the sheet metal busbar blank thickness. Particularly preferred, the displacement dimension of the displacement section is at least 50% of the sheet metal busbar blank thickness. Accordingly, the stamp is moved by the length of at least 10% of the sheet metal busbar blank thickness referring to the original position of the displacement section during the displacement process step. A displacement dimension of 10% of the sheet metal busbar blank thickness results in a reduction of the thickness of the connection sections which allows to cut the finished busbar within a pyrotechnical circuit breaker with a relatively low kinetic energy. The larger the displacement dimension, the lower the necessary kinetic energy for cutting the finished busbar.

[0028] Preferably, the stamp and the die are dimensioned such that the width of the connection section is smaller than 0.5 mm, seen perpendicularly to the displacement direction. In a particularly preferred embodiment, the width is smaller than 0.1 mm and is preferably as close as possible to 0.0 mm. As a result, the extension of the restriction of the cross-sectional area within the connection section is relatively short resulting in a relatively low total electric resistance of the busbar. The shorter this extension, the lower the total electric resistance of the busbar.

[0029] In another preferred embodiment, the busbar manufacturing method comprises an additional process step, wherein a cutting tool cuts the outer contour of the busbar before, during or after the displacement process step. Preferably, the displacement process step follows the cutting step so that the sheet metal busbar blank is provided with a finished outer contour before the start of displacement process step which allows a relatively precise displacement of the displacement section. The cutting tool can be defined by a separate manufacturing device / tool or can be part of a follow-on manufacturing device / tool. PIP24065WO / EBFS 12.11.2024

[0030] - 6 -

[0031] Preferably, the sheet metal busbar blank is made of copper or a copper alloy. Copperbased materials have relatively high electric conductance abilities and are therefore particularly suitable for manufacturing a busbar. Moreover, copper-based materials are easily deformable and therefore allow a relatively large displacement of the displacement section without breaking, so that a relatively low width of the connection section can be realised. Alternatively, the sheet metal busbar blank can be made of aluminum or an aluminum alloy.

[0032] The invention is further directed to a busbar manufactured according to the busbar manufacturing method as described above. The busbar is preferably used in a pyrotechnical electric circuit breaker.

[0033] The invention is further directed to a pyrotechnical electric circuit breaker with a busbar manufactured according to the busbar manufacturing method as described above. The pyrotechnical electric circuit breaker comprises a housing which is preferably sealed in a gas-tight manner. The housing comprises a guiding channel. The pyrotechnical electric circuit breaker further comprises a cutting device which is arranged within the guiding channel and which is displaceable by means of a pyrotechnical propelling device. The pyrotechnical electric circuit breaker further comprises an electric igniting device, which ignites the pyrotechnical propelling device to accelerate the cutting device within the guiding channel. The busbar extends transversally, which means perpendicularly with respect to the moving direction of the cutting device, through the guiding channel wherein the displacement section is arranged within the guiding channel. The longitudinal ends of the busbar each extend through the housing to the outside, where each end can be electrically connected to an electric line of an electric circuit of an electrically driven motor vehicle. For example, the first end of the busbar can be electrically connected to a traction battery, wherein the second end of the busbar can be electrically connected to an electric drive motor. The busbar is arranged adjacent to the cutting device opposite to the pyrotechnical propelling device, so that the cutting device is moved against the busbar after the ignition. The busbar is arranged such, that the displacement section is displaced away from the cutting device. The shape of the displacement section substantially corresponds to the shape of the cutting device, wherein the cutting device is slightly smaller than the displacement PIP24065WO / EBFS 12.11.2024

[0034] - 7 -

[0035] section. After the ignition, the cutting device is moved against the displacement section and cuts / breaks the busbar at the predetermined breaking sections which are defined by the connection sections. Because of the predetermined breaking sections, the necessary kinetic energy for breaking the busbar is relatively low. However, the busbar being manufactured according to the manufacturing method according to the invention is provided with a relatively low electric resistance.

[0036] An embodiment of the present invention is described below with reference to the enclosed figures, showing:

[0037] Figure 1 the first manufacturing step of a busbar manufacturing method according to the invention,

[0038] Figure 2 the second manufacturing step of the busbar manufacturing method of figure 1 ,

[0039] Figure 3 the third manufacturing step of the busbar manufacturing method of figure 1 ,

[0040] Figure 4 a sheet metal busbar blank for the busbar manufacturing method of figures 1-3,

[0041] Figure 5 a finished busbar manufactured according to the busbar manufacturing method of figures 1-3, and

[0042] Figure 6 a pyrotechnical electric circuit breaker with a busbar of figure 5.

[0043] Figure 1 shows the first manufacturing step of the busbar manufacturing method for manufacturing a busbar 10 of a pyrotechnical circuit breaker. In the first manufacturing step, a sheet metal busbar blank 12 made of copper is provided within a manufacturing device 1 . The sheet metal busbar blank 12 is a pre-manufactured flat busbar 11 which is shown in figure 4. The pre-manufactured busbar 11 is provided with a finished outer contour with a substantially rectangular shape comprising two clamping sections 14, 16 PIP24065WO / EBFS 12.11.2024

[0044] - 8 -

[0045] and one displacement section 20, wherein the clamping sections 14, 16 are arranged at the longitudinal ends of the pre-manufactured busbar 11 and the displacement section 20 is arranged between the clamping sections 14, 16 with respect to and seen in a sheet metal plane P. The outer contour is manufactured in a separate manufacturing process step, wherein a cutting tool, cuts the outer contour before the displacement process step (not shown). The sheet metal busbar blank 12 is placed within the manufacturing device 1 , for example, by using positioning pins or stop surfaces within the manufacturing device 1 to guarantee an exact positioning in particular of the displacement section 20.

[0046] Figure 2 shows the second manufacturing step of the busbar manufacturing method for manufacturing a busbar 10 of a pyrotechnical circuit breaker. In the second manufacturing step, the clamping sections 14, 16 of the sheet metal busbar blank 12 are fixed by using a clamping arrangement 30. The clamping arrangement 30 comprises two clamping devices 32, 34, namely an upper clamping device 32 and a lower clamping device 34. The sheet metal busbar blank 12 is placed at the lower clamping device 34, whereas the upper clamping device is moved against the sheet metal busbar blank 12 until the sheet metal busbar blank 12 is clamped between the clamping devices 32, 34. The clamping devices 32, 34, for example, each comprise an opening 33, 35, so that the clamping devices 32, 34 do not contact the displacement section 20 of the sheet metal busbar blank 12. As a result, the displacement section 20 remains free, wherein the clamping sections 14, 16 are fixed by the clamping arrangement 30.

[0047] Figure 3 shows the third manufacturing step of the busbar manufacturing method according to the invention, wherein a structural displacement of the displacement section 20 is provided. The displacement section 20 is displaced perpendicularly with respect to the sheet metal plane P such that each clamping section 14, 16 remains structurally connected to the displacement section via a respective connection section 24, 26. The first clamping section 14 is therefore connected to the displacement section 20 by a first connection section 24, whereas the second clamping section 16 is connected to the displacement section 20 by a second connection section 26. PIP24065WO / EBFS 12.11.2024

[0048] - 9 -

[0049] The displacement is provided by using a stamp 50 and a corresponding die 54, the stamp 50 being provided with a flat and rectangular contact surface 51 which contacts the displacement section 20 at a first sheet metal surface 17. The die 54 is provided with a corresponding rectangular shape is arranged concentrically with respect to the stamp 50, so that the stamp 50 is able to dive into the die, wherein a circumferential gap between the stamp 50 and the die 54 is constant. Moreover, the die 54 is defined in the lower clamping device 34 contacting the sheet metal busbar blank 12 at a second sheet metal surface 18 being opposite to the first sheet metal surface 17. As described above, the clamping devices 32, 34 each comprise an opening 33, 35. The stamp 50 extends seen perpendicularly to the sheet metal plane P through the opening 33 in the upper clamping device 32 and is pushed against the sheet metal busbar blank 12, thereby pushing the displacement section 20 into the die 54, wherein a stamp counterpart 52 contacts the second sheet metal surface 18 opposite to the stamp 50 so that the displacement section 20 becomes flat and rectangularly shaped, as shown in figure 5. The stamp counterpart 52 extends through the opening 35 in the lower clamping device 34.

[0050] The finished busbar 10, shown in figure 5 is the result of the busbar manufacturing method according to the invention. Because of the flat rectangular shape of the contact surface 51 of the stamp 50, a step-like displacement of the displacement section 20 is provided, defining a first step 13 between the first clamping section 14 and the displacement section 20, and a second step 15 between the second clamping section 16 and the displacement section 20, wherein the steps 13, 15 are provided with a linear edge respectively. The displacement dimension d of the displacement section is the length over which the stamp 50 is pushed against the sheet metal busbar blank 12 with respect to the position of contacting the first contact surface 17. The displacement dimension d is about 70% of the thickness t of the sheet metal busbar blank 12. The sheet metal busbar blank thickness t is preferably 3 mm so that the stamp 50 is pushed into the sheet metal busbar blank 12 over a length of 2.1 mm, thereby providing a displacement of the displacement section 20 of about 2.1 mm, wherein the thickness of the displacement section 20 remains at 3 mm. PIP24065WO / EBFS 12.11.2024

[0051] - 10 -

[0052] Furthermore, the width w of the connection section 24, 26 is at 0.05 mm seen perpendicularly to the displacement direction D. Therefor, the total width x of the stamp 50 is about 0.1 mm smaller than the total width y of the die 54, seen in the sheet metal plane P. As a result, two predetermined breaking sections 40, 42 are defined, where the cross-sectional area of the busbar 10 is reduced, allowing a breakage of the busbar 10 with a relatively low kinetic energy. Thus, the electric resistance within the connection sections 24, 26 is relatively low because no cold work hardening appears within the connection sections 24, 26 as a result of the shearing of the material.

[0053] Additionally, the relatively low width w of each connection section 24, 26 results in an abrupt change of the cross-sectional area of the busbar 10, wherein the reduced cross-sectional area only has an effect over width w of 0.25 mm at each connection section 24, 26, so that the busbar 10 is overall provided with a relatively low total electric resistance.

[0054] Figure 6 shows a pyrotechnical electric circuit breaker 100 which is preferably used within an electrically driven motor vehicle for cutting an electric line between a traction battery and an electric drive motor.

[0055] The pyrotechnical electric circuit breaker 100 comprises a housing 105 with a guiding channel 125 in the inside of the housing 105. The pyrotechnical electric circuit breaker 100 further comprises a piston-type cutting device 110 being provided with a rectangular cross-sectional shape. The cutting device 110 is movably arranged within the guiding channel 125 so that the cutting device 110 is linearly displaceable. The busbar 10, which is shown in figure 5, extends transversally through the guiding channel 125, wherein the displacement section 20 is arranged within the guiding channel 125. In detail, the busbar 10 extends perpendicularly with respect to the displacement direction of the cutting device 110. The busbar 10 is arranged such, that the displacement section 20 is displaced away from the cutting device 110. The two clamping sections 14, 16 each extend through the housing 105 to the outside, where the clamping sections 14, 16 are electrically connected to the electric line between the traction battery and the electric drive motor of the electrically driven motor vehicle. PIP24065WO / EBFS 12.11.2024

[0056] - 11 -

[0057] The pyrotechnical electric circuit breaker 100 comprises a pyrotechnical propelling device 120 which is arranged opposite to the cutting device 110 with respect to the busbar 10. The pyrotechnical propelling device 120 comprises an electric ignition device 122 for igniting the pyrotechnical propelling device 120. After the ignition, the pyrotechnical propelling device 120 accelerates the cutting device 110 within the guiding channel 125 and moves the cutting device 110 against the busbar 10, in particular against the displacement section 20. Because of the predetermined breaking sections 40, 42 the cutting device 110 cuts / breaks the busbar 10 at the connection sections 24, 26, shown in figure 5, and moves the cut displacement section 20 into a chamber 130 at the end of the guiding channel 125, seen in moving direction of the cutting device 110. The clamping sections 14, 16 remain within the housing, but are not electrically connected anymore, so that the electric line between the traction battery and the electric drive motor of the electrically driven motor vehicle is cut.

Claims

PIP24065WO / EBFS 12.11.2024- 12 -Claims1 . Busbar manufacturing method for manufacturing a busbar (10) of a pyrotechnical electric circuit breaker (100), comprising the following manufacturing steps: a. Providing a sheet metal busbar blank (12) comprising at least two clamping sections (14, 16) and at least one displacement section (20), wherein the displacement section (20) is located between the two clamping sections (14, 16) with respect to a sheet metal plane (P),b. Fixation of the clamping sections (14, 16) of the sheet metal busbar blank (12) using a clamping arrangement (30), wherein the displacement section (20) remains free, andc. Structural displacement of the displacement section (20) perpendicularly with respect to the sheet metal plane (P) such that each clamping section (14, 16) remains structurally connected to the displacement section (20) via a respective connection section (24, 26), wherein the displacement is provided by using a stamp (50) and a corresponding die (54), wherein, during the displacement process step, the stamp (50) contacts the displacement section (20) at a first sheet metal surface (17), and wherein the die (54) contacts the displacement section (20) at a second opposite sheet metal surface (18), wherein the stamp (50) pushes the displacement section (20) into the die (54).

2. Busbar manufacturing method according to claim 1 , wherein the stamp (50) is provided with a flat contact surface (51 ).

3. Busbar manufacturing method according to claim 1 or 2, wherein the stamp (50) is provided with a rectangular contact surface (51 ) and wherein the die (54) is provided with a corresponding rectangular shape, thereby defining a rectangular displacement section (20).

4. Busbar manufacturing method according to one of the preceding claims, wherein an additional stamp counterpart (52) being opposite to the stamp (50) contacts thePIP24065WO / EBFS 12.11.2024- 13 -displacement section (20) at a second opposite sheet metal surface (18) during the displacement process.

5. Busbar manufacturing method according to one of the preceding claims, wherein the displacement dimension (d) of the displacement section (20) is at least 10% of the sheet metal busbar blank thickness (t), and preferably is at least 50% of the sheet metal busbar blank thickness (t).

6. Busbar manufacturing method according to one of the preceding claims, wherein the stamp (50) and the die (54) are dimensioned such that the width (w) of the connection section (24, 26) is smaller than 0.5 mm, seen perpendicularly to the displacement direction (D).

7. Busbar manufacturing method according to one of the preceding claims, wherein in an additional process step, a cutting tool cuts the outer contour of the busbar (10) before, during or after the displacement process step.

8. Busbar manufacturing method according to one of the preceding claims, wherein the sheet metal busbar blank (12) is made of copper or a copper alloy.

9. Busbar (10) manufactured according to the busbar manufacturing method of one of the preceding claims.

10. Pyrotechnical electric circuit breaker (100) with a busbar (10) according to claim 9.

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