Electrical switching device and method for switching thereof with contact separation in the event of protection

Abstract

The present invention relates to a switching device for opening and closing a load circuit, in particular in an electric vehicle, having at least one switch contact which can be moved from an open position into a closed position and which is held at a distance from a counter-contact in the open position and is in electrically conductive abutment with the counter-contact in the closed position. The invention further relates to a method for switching a load circuit, in particular in an electric vehicle, at least one switch contact being moved from an open position into a closed position and thereby being brought into electrically conductive contact with a counter-contact. In order to provide the most compact, light, cost-effective and reliable switching and separation unit for load currents, it is provided according to the invention that, in a safety position, the at least one switch contact is held separated from the counter-contact in order to protect the load circuit.

Claims

1. A switching device for opening and closing a load circuit, in particular in an electric vehicle, having at least one switch contact which can be moved from an open position (A) into a closed position (B) and which is held at a distance from a counter-contact in the open position (A) and is in electrically conductive abutment with the counter-contact in the closed position (B), wherein, in a safety position (C), the at least one switch contact is held separated from the counter-contact in order to protect the load circuit from overload, and wherein the switching device is retained by a retention force in a normal operating state (N) in which the switching device can be moved from the open position into the closed position, and when under electrical voltage in the closed position, at least in the event of an overload, an actuating magnetic field produced by a load current path has a weakening effect on a retaining magnetic field which acts on the retention force.

2. The switching device according to claim 1, wherein, in the open position (A), the at least one switch contact is retained at a distance from the counter-contact over a switching path (K) and in that the switching path (K) is increased by a safety distance (S) in the safety position (C).

3. The switching device according to claim 2, wherein the safety distance (S) is greater than the switching path (K).

4. The switching device according to claim 1, wherein a distance between the at least one switch contact and the counter-contact is greater in the safety position (C) than a distance between the at least one switch contact and the counter-contact necessary for extinguishing an electric arc in the event of a maximum possible overload current in the closed position (B).

5. The switching device according to claim 1, wherein it comprises a safety stop which limits movements of the at least one switch contact in the direction of the counter-contact in the safety position (C).

6. The switching device according to claim 1, further comprising a separation drive, whose separation force (F.sub.31) in the safety position (C) acts counter to a closure force (F.sub.20) for moving the at least one switch contact from the open position (A) into the closed position (B).

7. The switching device according to claim 6, wherein the separation force (F.sub.31) is greater than the closure force (F.sub.20).

8. The switching device according to claim 6, wherein the separation drive comprises a resilient separation element which at least partially produces the separation force (F.sub.31).

9. The switching device according to claim 1, further comprising a switching unit for switching between the open position (A) and the closed position (B) and by a safety unit for moving into the safety position (C).

10. The switching device according to claim 9, wherein the safety unit is retained by a magnetic clamp/spring system and/or an electromagnetic coil in a release position (X), in which the switching device can be moved from the open position (A) into the closed position (B).

11. The switching device according to claim 1, wherein a contact member carries the at least one switch contact and a retention stop, the contact member being blocked in the safety position (C) on the retention stop.

12. The switching device according to claim 11, wherein it is constructed at least partially concentrically relative to the contact member.

13. A method for switching a load circuit, in particular in an electric vehicle, at least one switch contact being moved from an open position (A) into a closed position (B) and thereby being brought into electrically conductive contact with a counter-contact, wherein, in the event of an overload of the load circuit, the switch contact is automatically separated from the counter-contact and moved into a safety position (C), and wherein the switching device is retained by a retention force in a normal operation state (N) in which the switching device can be moved from the open position into the closed position, and, when under electrical voltage in the closed position, at least in the event of an overload, an actuating magnetic field produced by a load current path has a weakening effect on a retaining magnetic field which acts on the retention force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic cross-section of a switching device according to the invention in the normal operating state in the open position;

(3) FIG. 2 is a schematic cross-section of the switching device in the normal operating state in the closed position; and

(4) FIG. 3 is a schematic cross-section of the switching device in the safety position.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) The structure and the operation of a switching device 1 according to the invention are first explained with reference to FIG. 1, which shows the switching device in a normal operating state N in an open position A in a schematic cross-sectional view along the centre axis M thereof. The switching device 1 comprises a switching unit 2 and a safety unit 3 which act on a switching member 4 in the form of a contact bridge. The switching member 4 is constructed so as to be able to be joined together with a counter-contact 5 in a switching direction T.

(6) The switching unit 2 is constructed as a monostable relay or contactor and comprises a coil 20a which is arranged concentrically about the centre axis M and which, together with a coil core 20b which can be displaced parallel with the switching direction T and which is also arranged concentrically relative to the centre axis M and a yoke 20c which predominantly surrounds the coil 20a in cross-section externally at the peripheral side, form a switch drive 20 of the switching unit 2. The core 20b is arranged so as to be able to be displaced parallel with the switching direction T, supported on the yoke 20c in the switching direction T by means of a restoring member 21 in the form of a helical spring which is arranged concentrically about the centre axis M and connected so as to transmit movement or in a rigid manner to a shaft 40 of the switch member 4 at a rear end of the shaft 40. When a control voltage (not shown) is applied to the coil 20a, the switch drive 20 produces a switching force or closure force F.sub.20 which is directed in the switching direction T and attempts to move the core 20b together with the switch member 40 counter to a restoring force F.sub.21 applied by the restoring member 21 in a switching direction T.

(7) The safety unit 3 contains a first yoke 30a with a support portion 30b and a first magnet closure portion 30c. Another yoke 30d of the safety device 3 comprises another magnet closure portion 30e and a safety stop 32 which is constructed as a movable yoke portion 30f or armature. The safety stop 32 is constructed so as to be able to be displaced counter to the switching direction T and is retained in the normal operating state N by a retention force F.sub.33 which is applied by a retention magnet 33 and which is directed in the switching direction T in the form of a movable yoke portion 30f as part of the other yoke 30d in a release position X. The yoke 30a, the other yoke 30d and the retention magnet 33 form a retention member 30 which produces the retention force F.sub.33. In the release position X, the retention force F.sub.33 of the retention magnet 33 exceeds a separation force F.sub.31 applied by a separation drive 31 in the form of a helical spring which is arranged concentrically relative to the centre axis M so that the safety unit 3 remains in the release position X. The separation drive 31 in the form of the helical spring is clamped between the support portion 30b and the movable yoke portion 30f or safety stop 32.

(8) The switching member 4 has a switch contact 4a which is constructed to be in electrically conductive abutment by means of a switch contact face 4b with a counter-switch contact face 5b of the counter-contact 5. The switch contact 4a is arranged at a distal end of a switch contact arm 4c, which is supported displaceably parallel with the switching direction T on the shaft 40 of the switch member 4. The switch contact arm 4c abuts in the open position A a switch stop 40a, which is secured to the shaft 40 and/or is formed thereon. The switch contact 4a is clamped between the switch stop 40a and a resilient element 41 in the form of a helical spring which is arranged concentrically relative to the shaft 40 or the centre axis M. Counter to the switching direction T, the resilient element 41 rests on an abutment 40b which is fitted to the shaft 40 and/or formed thereon in the form of another stop so that the resilient element 41 applies a damping force F.sub.41 directed in the switching direction T to the switch contact arm 4c and presses it against the switch stop 40a. There is further formed on the switch member 4 a retention stop 42 which may be constructed in the same manner as the switch stop 40a and the abutment 40b as a disc which is formed in an annular or concentric manner on the shaft 40 or secured thereto.

(9) In the normal operating state N shown in FIG. 1 in the open position A of the switching device 1, a switching path K between the switch member 4 and counter-contact 5 or switch contact face 4b of the switch contact 4a and the counter-switch contact face 5b is smaller than a travel H of the switch member 4, which is measured between the safety stop 32 and the retention stop 42 and the travel H of the switch drive 20. The travel H is generally greater than a drive travel H of the switch drive 20 in order to avoid a situation in which the core 20b does not strike the yoke 20c when moving from the open position O into a closed position B and consequently the magnetic retention force is reduced by the remaining air gap. A safety distance S is created between the retention stop 42 and the yoke 20c. The switching path K, the drive travel H, the travel H and the safety distance S are all measured in parallel to the switching direction T.

(10) FIG. 2 is a schematic cross-section of the switching device 1 in the normal operating state N in the closed position B. The coil 20a is excited with a control voltage and has moved the core 20b together with the switch member 4 secured thereto in the switching direction T so that the switch contact 4a is in abutment with the counter-contact 5. Since the limited travel H or a limited travel H, respectively, is greater than the switching path K, the switch contact arm 4c has been raised off the switch stop 40a and moved counter to the resilient force F.sub.41 in the direction of the abutment 40b so that, parallel with the switch direction, there is an excess travel G between the switch contact arm 4c and the switch stop 40a. The closure force F.sub.20 exceeds the total of the restoring force F.sub.21 and resilient force F.sub.41.

(11) Owing to the switch contact 4a and counter-contact 5 being brought into contact, a load circuit is closed. As a part of the load circuit, a load current path 6 is formed and may comprise, for example, at least one electrical line. The load current path 6 is partially guided along the first magnet closure portion 30c of the safety unit 3 and consequently along the retention magnet 33 and forms an actuating magnetic field 7.

(12) The actuating magnetic field 7 comprises magnetic flux lines 7a and 7b. The magnetic flux lines 7a and in particular the magnetic flux lines 7b extend perpendicularly relative to a retaining magnetic field 8 which acts on the retention force F.sub.33 and which flows from the retention magnet 33 in a first magnetic field portion 8a through the other magnet closure portion 30e and subsequently the movable yoke portion 30f or the safety stop 32 and consequently produces the magnetic retention force F.sub.33 which retains the safety unit 3 in the release position X. A second magnetic field portion 8b flows through the first yoke 30a and extends perpendicularly relative to the actuating magnetic field 7 and in particular to the magnetic flux lines 7b which consequently have a tendency to weaken the retaining magnetic field 8.

(13) This weakening of the retaining magnetic field 8 is used to weaken the retention force F.sub.33 in the event of an overload. The retention magnet 33 is constructed in such a manner that the retaining magnetic field 8 and consequently the retention force F.sub.33 is disrupted in the event of an overload by the actuating magnetic field 7 in such a manner that the separation force F.sub.31 applied by the separation drive 31 exceeds the sum of the closure force F.sub.20 and retention force F.sub.33 (minus the resilient force F.sub.41 and restoring force F.sub.21) in order to release the switch contact 4a from the counter-contact 5 in an abrupt manner.

(14) FIG. 3 is a schematic cross-section of the switching device 1 after the occurrence of an overload O in the safety position C. In the event of an overload O, the separation force F.sub.31 (in addition to the restoring force F.sub.21 and the resilient force F.sub.41) had initially exceeded the total of the closure force F.sub.20 and retention force F.sub.33. Consequently, the safety stop 32 has been released from the other yoke 30d and completely interrupted the first magnetic field portion 8a, whereby all the retention force F.sub.33 abruptly fell away and the safety stop 32 was thrown counter to the switching direction T. The retention stop 42 which is arranged in the closed position B in the normal operating state N in the switching direction T shortly in front of the safety stop 32 was carried by the retention stop 42 when the stop 42 was thrown out and consequently moved the entire contact member 4 and the switch contact 4b which is arranged thereon and separated them abruptly from the counter-contact 5.

(15) By opening the additional yoke 30d, the magnetic retention force F.sub.33 is reduced. In the event of short-term excessive currents or current peaks, the movable yoke portion 30f or safety stop 32 may be raised briefly from the other magnet closure portion 30e. This applies in particular to currents slightly below an actuation threshold of the safety device 3. The retaining magnetic force F.sub.33 generally decreases more rapidly than the separation force F.sub.31 when the additional yoke portion 30d is opened. A point for irreversible opening of the additional yoke 30d or an actuation point of the safety unit 3 is generally located shortly behind the contact position of the additional magnet closure portion 30e and movable yoke portion 30d or safety stop 32 in the release position X. The actuation point is exceeded as soon as a sum of the restoring force F.sub.21, separation force F.sub.31 and resilient force F.sub.41 exceeds the retention force F.sub.33. The safety stop 32 is then moved in an irreversible manner counter to the switching direction T. If the actuation point is not exceeded, the movable yoke portion 30d or safety stop 32 again moves back to the additional yoke portion 30e.

(16) The switch contact 4b is retained with spacing from the counter-contact 5 with a separation spacing L which is measured parallel with the switching direction T and which substantially corresponds to a sum of the switching path K and safety spacing S. The separation force F.sub.31 (in addition to the restoring force F.sub.21) is greater than the closure force F.sub.20 so that only a mechanical intervention from outside the switching device 1 can move the switching device 1 back into the normal operating state N, for example, by the switch member 40 and/or the core 20b being moved manually with a resetting force F.sub.R in the switching direction T and the separation force F.sub.33 (in addition to the restoring force F.sub.21) being overcome and the safety stop 32 again being brought into contact with the additional magnet closure portion 30e in order to close the retaining magnetic field 8 and to move the safety unit 3 back into the release position X.

(17) Within the notion of the invention, variations from the embodiment described above of a switching device 1 according to the invention are possible. Thus, the switching unit 2 and the safety unit 3 can be freely combined with each other in any number in order to switch a desired load current and to bring about an actuation of the safety unit 3 in the event of an overload. To this end, the switching unit may be freely provided with coils 20a, cores 20b and yokes 20c in order to form a switch drive 20, but which may also be constructed as a pneumatic and/or hydraulic drive. The restoring member 21 may be constructed as a spring in accordance with respective requirements, but may also be constructed differently.

(18) The safety unit 3 may be freely provided with a first yoke 30a, a support portion 30b, a first magnet closure portion 30c, another yoke 30d, another magnet closure portion 30e and a movable yoke portion 30f in order to form a retention member 30 with a separation drive member 31. The separation drive member 31 does not necessarily have to be constructed as a resilient element but may instead also be constructed differently in accordance with respective requirements, as long as it is capable of producing a sufficiently large and constantly available separation force F.sub.31 in order to move the safety device 1 into the safety position C as rapidly as possible and with the shortest possible delay. Accordingly, the safety stop 32 and the retention magnet 33 may be constructed and arranged in accordance with respective requirements. The retention magnet 33 does not necessarily have to be constructed as a magnetic clamp as shown here, but may, for example, also be constructed as an electromagnet.

(19) The switch member 4 may be constructed in accordance with respective requirements with a switch contact 4a and the switch contact face 4b thereof and a switch contact arm 4c on a shaft, for example, as shown here, as a type of tension armature, but may equally well be constructed as a tilting armature. Accordingly, the switch stop 40a and abutment 40b may be constructed in accordance with respective requirements in order, with the aid of a damping element 41, to damp a striking of the contact member 4 or switch contact 4a on the counter-contact 5. The damping element 41 does not necessarily have to be formed as a helical spring as shown herein, but instead may be selected in accordance with respective requirements. The retention stop 42 is intended to be constructed in such a manner that it can ensure a reliable throwing action of the contact member 4 or reliable cooperation with a safety stop 32.

LIST OF REFERENCE NUMERALS

(20) 1 Switching unit 2 Switching unit 3 Safety device 4 Switch member (contact bridge) 5 Counter-contact 5a Counter-contact face 6 Load current path 7 Actuating magnetic field 7a, 7b Magnetic flux line 8 Retaining magnetic field 8a First magnetic field portion 8b Second magnetic field portion 20 Switch drive 20a Coil 20b Core 20c Yoke 30 Restoring member (spring) 30 Retention member 30a First yoke 30b Support portion 30c First magnet closure portion 30d Additional yoke 30e Additional magnet closure portion 30f Movable yoke portion 31 Separation drive member 32 Safety stop 33 Retention magnet 4a Switch contact 4b Switch contact face 4c Switch contact arm 40 Shaft 40a Switch stop 40b Abutment 41 Damping element 42 Retention stop F.sub.20 Switching force/closure force F.sub.21 Restoring force F.sub.31 Separation force F.sub.33 Retention force F.sub.41 Damping force F.sub.R Resetting force A Open position B Closed position C Safety position G Damping path/excess travel H Drive travel (maximum) H Travel (limited) K Switching path L Separation distance M Centre axis N Normal operating state O Occurrence of overload S Safety distance T Switching direction X Release position