SWITCHING ELEMENT

Description

[0001] The invention is based on a switching element according to the preamble of patent claim 1.

[0002] Such a switching element can be used to create a short-circuit connection, for example, in electromobility. Particularly in vehicles with a fuel cell, the switching element can be used to safely short-circuit the fuel cell, for example, for servicing the vehicle in the workshop, in a parked vehicle, in a vehicle that has been involved in an accident, or similar.

[0003] Such a switching element has two spaced-apart busbars. At least one power semiconductor is arranged between the two busbars, each of which is in contact with the busbars. The power semiconductor can be switched between an electrically non-conductive and an electrically conductive state. In the non-conductive state, the two busbars are electrically separated from each other. In the conductive state, however, an electrical short circuit is created between the two busbars. The packaged power semiconductors previously used for this purpose are attached to the busbars by means of a press connection for electrical connection. It has been found that the electrical connection is unreliable. In addition, the packaged semiconductors are expensive.

[0004] A similar switching element is known, for example, from document US 2009 / 103342 A1.

[0005] The invention is based on the object of further developing the switching element in such a way that its operational and / or functional reliability is improved. In particular, the switching element should also be more cost-effective.

[0006] This object is achieved in a generic switching element by the characterizing features of claim 1.

[0007] In the switching element according to the invention, which is defined by the features of claim 1, a means for pressing the power semiconductor against the busbars is provided. This pressing creates a secure electrical contact between the power semiconductor and the busbars, allowing the switching element to operate reliably. Further embodiments of the invention are the subject of the dependent claims.

[0008] In a simple manner, the means for pressing the power semiconductor against the busbars comprises a spring acting on one busbar. The spring can be designed, in particular, as a spring assembly consisting of disc springs, thus ensuring a high contact force on the busbars. Furthermore, the means for pressing the power semiconductor against the busbars comprises a wedge acting on the other busbar, allowing the contact force to be easily adjusted.

[0009] To switch high currents, two power semiconductors can be arranged in parallel between the busbars. The power semiconductor can be a power transistor, particularly a thyristor, as a cost-effective solution. Furthermore, the power semiconductor can be designed as a disc-shaped, unpackaged pellet. Such power semiconductor discs, also known as PUK designs, are far more cost-effective than a power semiconductor pressed into a housing.

[0010] In a further embodiment, the power semiconductor can have a control terminal in the form of a gate for switching between the non-conductive and conductive states. Furthermore, a control circuit can be provided for controlling the power semiconductor. A contact spring can expediently be provided for a reliable electrical connection between the control terminal of the power semiconductor and the control circuit, for example, to enable current triggering of the thyristor.

[0011] In a compact arrangement, the control circuit can be located on a printed circuit board. The control terminal for the power semiconductor can be located in a recess on the surface of the pellet. Conveniently, the contact spring can be held on the one hand at the control terminal of the power semiconductor, particularly in the recess, and on the other hand, be electrically connected to the control circuit. For example, the contact spring can rest against a contact surface on the printed circuit board, with the contact surface in turn establishing the electrical connection to the control circuit.

[0012] For ease of assembly, a receptacle for the spring can be provided. The receptacle can be located adjacent to one of the busbars. Furthermore, a pressure plate can be provided opposite the receptacle to support the spring. Finally, a support plate can be provided to hold the power semiconductor and, if applicable, both busbars. For ease of assembly, the receptacle, the pressure plate, and the support plate can be designed as a subassembly, with the spring, the busbars, and the power semiconductor being housed in the subassembly.

[0013] A housing may be provided for the switching element. The housing may expediently comprise a lower housing part and an upper housing part. The wedge may be adjustably mounted in the lower housing part. The lower housing part and the upper housing part may be connected to one another by means of at least one screw.

[0014] In a further embodiment, an electrical connection for a supply line can be arranged on the housing. The respective connection can also be electrically connected to the associated busbar. Finally, the subassembly and / or the control circuit and / or the printed circuit board can be located in the housing.

[0015] The following can be stated for a particularly preferred embodiment of the invention.

[0016] For safety reasons, a contactor is used in each of the FC HV + and FC HV - busbars to safely disconnect the fuel cell from the vehicle electrical system at all poles when the vehicle is idle, for example, when the vehicle is parked, in a workshop, after an accident, or similar. This is necessary because the voltage in the fuel cell can exceed the protective extra-low voltage due to residual hydrogen and / or air supply, potentially resulting in a fatal risk. The protective extra-low voltage is generally less than 60 V, but some electric vehicle manufacturers also require a high-voltage safety level, particularly less than 10 V.

[0017] Alternatively, the safe state can be achieved by short-circuiting the fuel cell. This solution has been tested and proven to be effective. Another alternative is the use of a galvanically isolated DC / DC converter, which also disconnects the fuel cell when not in operation.

[0018] Semiconductor switches are used for the short circuit, which have a short circuit as a safe state. This is currently ensured in the PUK design and by means of press connection, since all other processes, such as bonding, sintering, etc., always represent a potential disconnection point.

[0019] The construction and connection technology of the switching element according to the invention, which is designed as a semiconductor switch, comprises the contacting of the semiconductor switch and the contacting for the control connection of the semiconductor switch.

[0020] A screwed compression connection for semiconductor switches is well known and state of the art, for example, in high-voltage transmission (HV) systems, where a very large number of thyristors and / or GTOs are used in series. Defective components can remain in operation because they function 100% safely as a short circuit. Only the voltage distribution across the other components changes.

[0021] Since the switching element according to the invention is to be integrated into the fuel cell stack for safety reasons to prevent it from being torn apart in the event of an accident, the use of high-current connections (busbars) for contacting and / or heat dissipation is possible. Furthermore, in a sealed design, a pellet-shaped thyristor subassembly can also be used, which is significantly less expensive than a thyristor with a PUK housing. Both reliability and assembly can be optimized by using a wedge assembly with spring force application.

[0022] The invention creates a switching element as a reversible automatic discharger for use in a fuel cell stack.

[0023] The advantages achieved by the invention are, in particular, that the switching element can be operated reliably and can therefore be used in safety-critical applications, particularly in electromobility. Furthermore, the switching element is cost-effective.

[0024] An embodiment of the invention with various developments and refinements is shown in the drawings and is described in more detail below. Fig. 1 a switching element in exploded view, Fig. 2 Individual parts from Fig. 1 in enlarged view and Fig. 3 a sectional view of the switching element Fig. 1 .

[0025] In Fig. 1 1 shows a switching element 1 which is used in a fuel cell of an electric vehicle comprising a fuel cell stack and serves to establish a short-circuit connection in the fuel cell. The switching element 1 has a housing 2 which comprises a lower housing part 2' and a housing upper part 2", wherein the lower housing part 2' and the housing upper part 2" are connected to one another by means of at least one screw 20. An electrical connection 3, 4 for a supply line to the respective pole of the fuel cell stack is arranged on the housing 2, namely the connection 3 as a high-voltage connection HV+ to the positive pole and the connection 4 as a high-voltage connection HV- to the negative pole of the fuel cell stack. In the housing 2 there are two spaced-apart, in Fig. 2 Visible busbars 5, 6, with the respective terminals 3, 4 electrically connected to the corresponding busbar 5, 6. Specifically, busbar 5 is connected to terminal 3 as the positive busbar, and busbar 6 is connected to terminal 4 as the negative busbar.

[0026] How to proceed based on the Fig. 2 As can be seen, at least one power semiconductor 7 is arranged between the two busbars 5, 6, wherein the power semiconductor 7 is in contact with the busbars 5, 6. For the purpose of operationally and / or functionally reliable installation of the power semiconductor 7 on the busbars 5, 6, a Fig. 1 A means 8, designated in more detail, is provided for pressing the power semiconductor 7 against the busbars 5, 6. The power semiconductor 7 can be switched between an electrically non-conductive and an electrically conductive state, so that in the conductive state of the power semiconductor 7, an electrical short circuit can be created between the two busbars 5, 6 and thus for the fuel cell stack. In the non-conductive state of the power semiconductor 7, however, the fuel cell stack is in normal operation for generating electrical energy for the electric vehicle.

[0027] The design of the means 8 for pressing the power semiconductor 7 onto the busbars 5, 6 is described in more detail in the Fig. 2 and the Fig. 3 The means 8 for pressing the power semiconductor 7 onto the busbars 5, 6 comprises a spring 9 acting on one of the busbars 5. In order to generate a sufficiently high elastic force acting on the busbar 5, it is advisable for the spring 9 to be a spring assembly consisting of disc springs, such as the Fig. 2 can be removed. Furthermore, the means 8 for pressing the power semiconductor 7 onto the busbars 5, 6 comprises a wedge 10 acting on the other busbar 6. The wedge 10 is adjustably mounted in the housing base 2', as can be seen from the Fig. 1 can be seen, so that the contact pressure for the power semiconductor 7 can be adjusted by appropriate displacement of the wedge 10.

[0028] In order to avoid overloading even at high currents, two power semiconductors 7, 7' can be arranged in electrical parallel connection between the busbars 5, 6, as in Fig. 2 can be seen. The power semiconductor 7, 7' can be a power transistor, for example a thyristor. The power semiconductor 7, 7' is designed in the form of a disc-shaped, unhoused pellet, like the Fig. 2 The power semiconductor 7, 7' has a control terminal in the form of a gate for switching between the non-conductive and the conductive state, wherein the control terminal is located in a recess 11 on the surface of the pellet. Furthermore, a control circuit 12 is provided for controlling the power semiconductor 7, 7', i.e. in particular for switching the power semiconductor 7, 7' between the non-conductive and the conductive state. The control circuit 12 is arranged on a printed circuit board 13 located in the housing 2, wherein the printed circuit board 13 is according to Fig. 1 by means of screws 21 in the upper housing part 2". Finally, a contact spring 14 is provided for the electrical connection between the control terminal of the power semiconductor 7, 7' and the control circuit 12. For this purpose, the contact spring 14 is held on the one hand in the recess 11 at the control terminal of the power semiconductor 7, 7', wherein the contact spring 14 projects through a recess 15 in the busbar 5, and on the other hand has an electrical connection to the control circuit 12. For example, the contact spring 14 can on the other hand rest against a contact surface (not shown) located on the printed circuit board 13, which establishes an electrical connection to the control circuit 12. Of course, the contact spring 14 can also be electrically connected to the control circuit 12 in another way, for example via a supply line.

[0029] As in Fig. 2 As can be seen further, a receptacle 16 is provided for the spring 9. The receptacle 16 is located according to Fig. 3 on one busbar 5. Opposite the receptacle 16, a pressure plate 17 is provided in the upper housing part 2" to support the spring 9. Finally, a support plate 18 is arranged in the lower housing part 2' and acted upon by means of the wedge 10 to hold the power semiconductor 7, 7' and the two busbars 5, 6. The receptacle 16, the pressure plate 17 and the support plate 18 together with the spring 9, the power semiconductor 7, 7' and the busbars 5, 6 are pre-assembled, according to Fig. 1 designed in the form of a subassembly 19. The subassembly 19 and the printed circuit board 13 with the control circuit 12 are located in the housing 2 after assembly of the switching element 1.

[0030] The invention is not limited to the described and illustrated embodiment. Rather, it also encompasses all developments within the scope of the invention defined by the patent claims. Thus, the switching element 1 according to the invention can be used not only in a fuel cell for an electric vehicle, but can also be used in fuel cell stacks for generating energy to operate other electrical devices. Reference symbol list:

[0031] 1:Switching element 2:Housing 2':Lower housing section 2":Housing upper section 3:(Electrical) connection (HV+) 4:(Electrical) connection (HV-) 5:Busbar (positive) 6:Busbar (negative) 7, 7':Power semiconductor 8:Means of pressing (the power semiconductor) 9:Spring 10:Wedge 11:Recess (in power semiconductor for the control connection) 12:Control circuit 13:Printed circuit board 14:Contact spring (for power semiconductor) 15:Recess (in busbar) 16:Receptacle (for spring) 17:Pressure plate 18:Support plate 19:Pre-assembly 20:Screw (for housing) 21:Screw (for printed circuit board)

Claims

1. A switching element for creating a short-circuit connection with two busbars (5, 6) arranged spaced apart from one another and at least one power semiconductor (7) arranged between the two busbars (5, 6) and respectively abutting the busbars (5, 6), wherein the power semiconductor (7) is switchable between an electrically non-conducting and an electrically conducting state, wherein a means (8) for pressing the power semiconductor (7) to the busbars (5, 6) is provided and wherein the means (8) for pressing the power semiconductor (7) to the busbars (5, 6) comprises a spring (9) acting on the one busbar (5), characterised in that the means (8) for pressing the power semiconductor (7) to the busbars (5, 6) comprises a wedge (10) acting on the other busbar (6) for adjusting a contact force.

2. The switching element according to claim 1, characterised in that the spring (9) for pressing the power semiconductor (7) to the busbars (5, 6) is a spring package consisting of disc springs acting on the one busbar (5).

3. The switching element according to claim 1 or 2, characterised in that two power semiconductors (7, 7') are arranged in parallel between the busbars (5, 6).

4. The switching element according to the preceding claim, wherein the power semiconductor (7, 7') is formed in the shape of a disc-shaped pellet without a housing.

5. The switching element according to any one of the preceding claim, wherein the power semiconductor (7, 7') has a control port of the type of a gate for switching between the electrically non-conducting and the electrically conducting state.

6. The switching element according to the preceding claim, wherein a control switch (12) for controlling the power semiconductor (7, 7') is provided.

7. The switching element according to the preceding claim, wherein a contact spring (14) for electrical connection between the control port of the power semiconductor (7, 7') and the control switch (12) is provided.

8. The switching element according to any one of claims 6 or 7, wherein the control switch (12) is located on a circuit board (13) and wherein the control port for the power semiconductor (7, 7') is located in a recess (11) on the surface of the pellet.

9. The switching element according to the preceding claim, wherein the contact spring (14) is held on the control port of the power semiconductor (7, 7') and in the recess (11) on the one hand and is in electrical connection with the control switch (12) on the other hand.

10. The switching element according to any one of claims 1 to 9, wherein a receptacle (16) for the spring (9) is provided and wherein the receptacle (16) abuts the one busbar (5).

11. The switching element according to the preceding claim, wherein a pressure plate (17) for supporting the spring (9) is provided opposite the receptacle (16), wherein a support plate (18) for holding the power semiconductor (7, 7') is provided.

12. The switching element according to the preceding claim, wherein the support plate (18) is provided for holding the two busbars (5, 6).

13. The switching element according to any one of claims 10 to 12, wherein the receptacle (16), the pressure plate (17) and the support plate (18) are formed in the type of a pre-assembly group (19).

14. The switching element according to any one of claims 1 to 13, characterised in that a housing (2) is provided, the housing (2) comprises a housing lower part (2') and a housing upper part (2"), and in that the edge (10) is adjustably mounted in the housing lower part (2').

15. The switching element according to any one of claims 1 to 14, characterised in that an electrical port (3, 4) for a supply line is arranged on the housing (2), the respective port (3, 4) is in electrical connection with the associated busbar (5, 6), and in that the pre-assembly group (19) and / or the control switch (12) and / or the circuit board (13) are located in the housing (2).