CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/FR2017/050288 filed Feb. 8, 2017, claiming priority based on French Patent Application No. 1663257 filed Dec. 22, 2016.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a self-supported actuation device for an electromechanical switch, and a switch provided with such a device. It finds an application in particular for bypassing or isolating a defective cell of a battery comprising a set of electrically connected cells, for example a battery comprising one or more cells of the lithium-ion type such as the batteries used in the aeronautical or space field.

Background Art

In a battery containing one or more cells connected in series, it may happen that one of the cells becomes defective, such as through having increased resistance right up to going open circuit and/or exhibiting heavy self-discharge. In such a case, continued use of the battery is likely to damage the defective cell, and in the case of a battery comprising several cells, to negatively impact the healthy cells, and thus to quickly render the battery unusable.

In effect, overcharging occurs in the event of increased resistance of the defective cell, if the charge current of this defective cell is not sufficiently bypassed (e.g. by a balancing circuit in parallel with the cell) in order to avoid exceeding the end-of-charge voltage threshold on this defective cell while waiting for the healthy cells to arrive at their end-of-charge voltage threshold for a full charge.

Alternatively, over-discharge/in the version occurs in the event of heavy self-discharge of this defective cell, if the charge current of the healthy cells is not sufficiently bypassed (by the balancing circuit) to enable the defective cell to arrive at its end-of-charge voltage threshold for full charge.

The impact of continuation of use of the battery with a defective cell on the other healthy cells of this battery can therefore be direct (the level of charge of the healthy cells becomes increasingly incomplete) or indirect as a consequence of the behavior of the defective cell (overheating; pressure buildup, operation of the circuit breaker of one or more cells when the battery is fitted with one, setting up an open circuit in the battery's series circuit, relatively violent circuit breaking).

When such a failure of a cell is detected, the defective cell can be replaced by a healthy cell, which involves accessing the battery and interrupting use thereof for a longer or shorter period of time, together with the provision of electrical power to the circuit to which it is connected. In order to reduce the duration of the interruption of electrical power supply, the battery with the defective cell can be replaced by a battery in good condition, over the period of time needed to carry out the replacement of the defective cell.

However, this always involves accessing the battery, meaning high maintenance costs. The problem of battery access is a major problem in applications in which this battery is on-board a device or system that is difficult to access. This is the case in particular in space applications, for example for providing electrical energy for the circuits of a satellite.

It is therefore important to be able to isolate or bypass a defective cell, in order to be able to continue using the battery without risking damaging the other cells.

For this purpose, a bypass or shunting device may be used, in which an actuator activates a switching device for isolating one of the battery cells when a fault is detected on that cell.

There are known, for example, switching devices such as those described in FR 2,902,232 (=U.S. Pat. No. 8,502,636) or in FR 2,776,434 (=U.S. Pat. No. 6,249,063).

Such a device comprises an actuation device and a movable part forming contact means comprising in particular a plunger that can move inside a cylindrical body between two distinct electrical contact positions when activated by the actuation device. By suitably connecting a cell of a multi-cell battery to the electrical contacts of the switching device, the cell can be bypassed by switching the switching device from one to the other of the two electrical contact positions. Switching is obtained by the actuation device which, in the non-switched position, retains a distributor member of the contact means in the first electrical contact position. When a failure at the cell in question is detected, by auxiliary detection means, an electric current is supplied to the actuation device which releases the plunger. This is then moved to the second electrical contact position, thereby achieving the switching of the switching device and thus bypassing the defective cell.

The actuation device relies, for its part, on a coil in which movable members or jaws are mounted and held by a retaining wire wound around the coil. The retaining wire is connected to a current sensor. When a sufficiently strong current is received by the current sensor, the retaining wire melts in a manner of a fuse wire, thereby releasing the movable members or jaws which in turn free up the passage for the movement of the plunger of the switching device.

One of the problems posed by this type of device is that the movable members or jaws, once released, fall into the body of the switching device and remain free inside the switching device body. Further, these movable members or jaws and/or the coil may rotate within the device, thereby creating a risk of damage to the fuse wire.

Furthermore, there is no control of the place where the fuse wire can break. Depending on the location of the break, the release of the movable members or jaws may be less efficient, or even made impossible in particular if the breakage of the fuse wire is such that the retaining wire cannot escape.

Also, some metal parts, in particular the plunger, the retaining wire, the coil, the movable members or jaws are at a floating electric potential before and/or after activation.

SUMMARY OF THE INVENTION

One of the aims of the invention is therefore to solve in particular the above-mentioned problems. The aim of the invention is, in particular, to provide a switching device and an actuation device for such a switching device, for isolating a defective cell of a multi-cell battery, which is more efficient, robust and reliable.

According to a first aspect, the invention provides an actuation device for activating the switching in a switching device of the type having electrical contact means movable between a first and a second electrical contact position.

The actuation device comprises a current sensor, a retaining member and at least two movable members integral with a coil, and is adapted to pass, when a current is sensed by the current sensor, from a non-activation configuration in which the movable members are held by the retaining member in a first position for preventing movement of the contact means of a switching device, to an activation configuration in which the movable members are no longer held by the retaining member in said first position and are in a second position for allowing movement of the contact means of the switching device.

The coil includes a through-space for at least a part of the contact means of the switching device, and the movable members are each movable in rotation about an axis so as to open up a passage, in said second position, into said through-space, while remaining integral with the coil.

In some embodiments, the actuation device further includes one or more of the following features, taken alone or in all technically possible combinations:the coil has an abutment region for each of the movable members, and in the first position, the movable members are maintained in abutment on their respective abutment regions by the retaining member.the two axes of the two movable members are formed by pins integral with the coil.the through-space is a through-space centered on the central axis of the coil, preferably substantially cylindrical, in that the two pins are arranged parallel to said through-space and mutually symmetrically with respect to said through-space, and in that the two movable members take the form of two jaw members such that during a changeover from the first position to the second position, the respective regions of the two jaw members furthest from the respective pins move away from each other to free up access to said through-space.the current sensor comprises a current-supply wire, and in that the retaining member is of a wire type, connected by one of its ends to said coil, wound around the movable members and connected by its other end to the current-supply wire of the current sensor by a fuse wire, in the first position such that when a current is sensed by the current sensor, the fuse wire melts and releases the corresponding end of the retaining member in order to allow the passage of the movable members to adopt the second position.the fuse wire exhibits a loop configuration.the fuse wire is connected, preferably via a connecting member, to the current-supply wire of the current sensor through the coil, and an electrically isolating member is interposed between, firstly, the assembly comprising the fuse wire, optionally the connecting member, the current-supply wire of the current sensor and, secondly, the coil.

The invention also provides, according to a second aspect, a switching device comprising a body in which contact means are accommodated movable in the body between a first and a second electrical contact position.

The switching device comprises an actuation device as discussed above, housed in the body, so as to enable, when the actuation device is in the activation configuration, displacement of the contact means from the first to the second electrical contact position.

In some embodiments, the actuation device further includes one or more of the following features, taken alone or in all technically possible combinations:the body has a longitudinal axis, the contact means extending longitudinally in the body, and in that the actuation device is arranged in the body such that the through-space for the at least one part of the contact means extends longitudinally.the contact means comprise a plunger able to move longitudinally in the through-space to displace the contact means from the first to the second electrical contact position.the switching device comprises resilient return means, such as a spring, which are connected, firstly, to the body, preferably via a force distribution member such as an annular force distribution member, and, secondly, to the contact means, the resilient return means being mounted in a relaxed position when the contact means are in the second position of electrical contact and in an active position when the contact means are in the first electrical contact position, so as to allow automatic passage of the contact means from the first to the second electrical contact position under the influence of the resilient return means from the active position thereof to the relaxed position thereof.the contact means include a distributor member connected to the plunger by an electrically non-conductive base, said distributor member being in contact with a first, and a second, electrical contact terminals in the first electrical contact position, and in contact with the second, and a third, electrical contact terminals in the second electrical contact position.an end of distributor member oriented in the direction of movement of said contact means from the first to the second electrical contact position, has a radially reduced profile with respect to a longitudinal axis of the body, so as to promote engagement of said distributor member with said third terminal, in contact therewith.the switching device comprises contact elements made of electrically conductive deformable material, arranged respectively in contact with the contact terminals, and in contact with said distributor member as a function of its movement from the first to the second electrical contact position to facilitate electrical contact between said distributor member and one or the other of said contact terminals.the diameter of the portion of the electrically non-conductive base facing the contact member in contact with the contact terminal, which is not in contact with distributor member in the first contact position, is adapted to cause said contact terminal, to adopt a self-centered position on the electrically non-conductive base and perpendicular to an axis of said contact means.the actuation device is arranged at one end of the body, said end being closed by a first cover.the first cover is provided with a clearance space into which a through-space in said coil of the actuation device opens, so as to allow said at least one part of the contact means of the switching device to pass through said actuation device right up and into said clearance space.the body is closed, at its end opposite the end closed by the first cover, by a second cover provided with a cavity, and in that the said distributor member is provided at its end facing the second cover, with a centering device which can be accommodated in said cavity of the second cover.the centering device is provided with cooperation means, such as a screw thread, capable of enabling co-operation with an assembly member to enable assembly of the contact terminals, on the distributor member without damaging the said contact elements and the moving of said contact means from the second to the first electrical contact position.in the first contact position, in the second contact position, and during the changeover from the first to the second contact position, all the metal parts of said device are connected to one electrical potential.

According to a third aspect, the invention provides a device for isolating at least one determined cell of a battery which comprises a plurality of cells connected in series, said isolation device being adapted to be connected to said battery.the device for isolating comprises a switching device as discussed above, to allow the switching device to pass from a first position, in which the determined cell is connected in series with other cells, to a second position, in which the determined cell is bypassed and is no longer connected in series with the other cells.

According to a fourth aspect, the invention provides a battery comprising one or more cells connected in series, provided with the above isolation device.

In this way, the invention makes it possible to bypass a defective cell of a multi-cell battery, by means of a robust, efficient and reliable switching device.

The features and advantages of the invention will become apparent upon reading the following description, given by way of non-limiting example, with reference to the following drawings.

