Patent Grant
10546705
The invention relates to DC voltage power sources, and in particular the electrical equipment items intended to ensure the safety of such DC voltage sources.
DC voltage power sources are commonly based on the use of electrochemical accumulators. These voltage sources can for example be used in the field of electrical and hybrid transport systems or embedded systems.
An electrochemical accumulator usually has a nominal voltage of the following order of magnitude:
1.2 V for batteries of NiMH type,
3.3 V for a lithium-ion iron phosphate LiFePO4 technology,
4.2 V for a cobalt oxide based lithium-ion type technology.
These nominal voltages are too low in relation to the requirements of most of the systems to be powered. To obtain the appropriate voltage level, a number of accumulators are placed in series. To obtain high powers and capacities, a number of accumulators are placed in parallel. The number of stages (number of accumulators in series) and the number of accumulators in parallel in each stage vary as a function of the voltage, of the current and of the capacity desired for the battery. The combination of a number of accumulators is called an accumulator battery.
Such batteries are for example used in vehicles to drive an alternating current electric motor via an inverter. Such batteries also have a high capacity in order to favor the range of the vehicle in electric mode. Typically, an electric vehicle uses an accumulator battery with a nominal voltage of the order of 400V, with a peak current of 200 A and a capacity of 20 kWh.
The electrochemical accumulators used for such vehicles are generally of the lithium-ion type for their capacity to store a significant energy with a weight and a volume that are contained. The lithium-ion iron phosphate LiFePO4 type battery technologies are the subject of significant developments by virtue of a high intrinsic safety level, at the cost of a slightly reduced energy storage density.
The document WO2012171917 describes battery elements comprising electrochemical accumulators, such elements being intended to be connected in series to form a DC voltage power source. Each battery element is provided with a protection device intended to isolate the battery of this element from other elements, or to ensure the continuity of service of the DC voltage source, or to allow maintenance operations on this DC voltage source. Each battery element comprises two branches in parallel connected between its two terminals. In a first branch, the battery is connected in series with a MOSFET switch of normally-open type. In a second branch, the two terminals are connected via a normally-closed switch. When the element is used, the normally-closed switch is kept open and the normally-open switch is kept closed. In the absence of control due to a malfunction or maintenance, the normally-closed switch remains closed and the normally-open switch remains open, such that the voltage of the battery is not applied to the terminals of the element.
In practice, such an element presents drawbacks. The MOSFET switches and their controls come at a relatively high cost, notably because of the need to add a heat sink to them. Furthermore, these switches are the source of spurious energy losses and overheating even when they are open. In particular, the normally-closed switch causes permanent losses upon the operation of the element (when this switch is therefore open) although the probability of the occurrence of a fault is reduced.
The document FR1605493 describes a switch for firing missiles. The switch is temporarily closed for the firing time, then destroyed, which is not an inconvenience since the missile also ends up being destroyed. Such a switch is therefore unsuitable for guaranteeing a closed state in the absence of control.
The document U.S. Pat. No. 2,721,240 describes a switch, comprising two electrodes and a conductive element propelled by a pyrotechnic charge. Upon its propulsion, the conductive element is passed through by the electrodes and forms an electrical contact between them. The reliability of such a contact is insufficient to guarantee that a closed state of the switch will be maintained.
The invention aims to resolve one or more of these drawbacks. The invention thus relates to a switch, as defined in the attached claims.
The invention further relates to a DC voltage power supply system, as defined in the attached claims.
Other features and advantages of the invention will emerge clearly from the description which is given thereof hereinbelow, in an indicative and nonlimiting manner, with reference to the attached drawings, in which:
The invention proposes a safety switch for a DC voltage power supply. Such a switch comprises first and second electrically conductive electrodes and an electrically conductive element. Initially, an electrically insulating medium separates these electrodes from one another, and also separates at least the electrically conductive element from the second electrode. The switch further comprises a pyrotechnic element including an explosive, the explosion of which causes the electrically conductive element to be driven into contact with the second electrode and the conductive element to be welded with the second electrode to form a solid and durable electrically conductive link between the first and second electrodes. “Solid and durable” should be understood to mean that the electrically conductive link remains after the explosion. The weld is therefore not destroyed by this same explosion.
In the presence of a malfunction, the connection between the two electrodes can thus be closed solidly, reliably and durably, in order to short-circuit an electrical system connected to the terminals of the switch, notably when demanded by safety considerations. Because of the energy applied by the explosion onto the electrically conductive element, the latter is welded to the second electrode, which makes it possible to ensure an electrical contact between the conductive element and the second electrode allowing current of high intensity to pass between the first and second electrodes with reduced losses. The conduction between the first and second electrodes can for example be guaranteed without break, even for short-circuit currents of a DC voltage power supply.
Such a switch therefore proves particularly advantageous, particularly for securing a DC voltage power supply, even though a person skilled in the art generally would not consider the use of pyrotechnic elements in proximity to a component considered to be dangerous (for example a DC voltage power supply based on electrochemical cells of the lithium-ion type). In practice, the risk associated with the explosion of a pyrotechnic element is well controlled, by virtue of the mass production of such components, in particular for manufacturing airbags. Thus, the quantity of energy released by an explosion and the guarantee of the explosion are parameters that are perfectly controlled in pyrotechnic elements.
The electrodes 11 and 12 are here housed in a chamber 16. The electrodes 11 and 12 are fixed against an internal wall 161 of the chamber 16, in order to ensure that they are mechanically secured. The switch 1 further comprises an electrically conductive element 15. The element 15 is housed inside the chamber 16. The element 15 is separated from the electrodes 11 and 12 via an electrically insulating medium 162 present in the chamber 16. The medium 162 is, for example, an inert gas. To this end, the element 15 is kept separated from the electrodes 11 and 12. The element 15 is here held against a wall of the chamber 16 opposite the wall 161. The electrically insulating medium 162 also separates the electrodes 11 and 12 to electrically insulate them inside the chamber 16. The internal surface of the chamber 16 is electrically insulating to guarantee the electrical insulation between the electrode 11, the electrode 12 and the conductive element 15. The switch 1 thus has a configuration of normally-open type between the electrodes 11 and 12, illustrated in
The element 15 has a part directly above the first electrode 11, and a part directly above the second electrode 12. The switch 1 further comprises a pyrotechnic element 17. The pyrotechnic element 17 includes an explosive 171 attached to the conductive element 15, and a detonator 172 configured to initiate the explosion of the explosive 171. The explosion of the explosive 171 can be controlled by any appropriate means, for example by the application of an electrical signal to the detonator 172 via a control circuit 9 or via an overall heating up of the explosive 171.
The explosive 171 is configured for the gases generated by its explosion to propel the element 15 through the chamber 16 toward the electrodes 11 and 12. Upon the explosion, the gases generated by the explosive 171 apply a pressure onto the element 15 to detach it from the chamber 16, to propel the element 15 into contact both with the electrode 11 and with the electrode 12, and to heat up this element 15. The element 15 is propelled with a sufficient energy to be welded to the electrode 11 on the one hand and to the electrode 12 on the other hand, according to the configuration illustrated in
The switch 1 then has a reliable and durable closed configuration between the electrodes 11 and 12. The electrodes 11 and 12 and the element 15 advantageously comprise metallic materials. The metallic material of the element 15 enters into contact with the metallic materials of the electrodes 11 and 12 to form welds upon the explosion of the explosive 171.
Whereas a brazed joint consists in assembling two parts with an addition of intermediate material between these two parts, a weld secures the element 15 directly with each electrode 11 and 12 by fusion between their own materials, at the interface between these materials. The weld is here produced in a solid and durable manner, such that a brief fusion occurs at the interface between the element 15 and each electrode 11 and 12. This weld at the interface, of very brief duration, is reflected in an almost immediate return to the solid state of the surfaces in contact during the weld. Such a return to the solid state makes it possible to avoid a bounce effect.
Moreover, the element 15 is driven by the explosion in a direction at right angles to the contact surface of each electrode, the contact surface to which it has to be welded. Thus, the quality of the weld is maximized between the element 15 and each electrode, which also favors an absence of bounce. Advantageously, the contact surfaces of the electrodes 11 and 12 are substantially flat.
A direct pressure of the gases from the explosion onto the element 15 favors the heating up thereof (and therefore a weld at the interface upon a contact with the electrode 12), its deformation on contact with the electrode 12 and its propulsion at a supersonic speed. Such a propulsion also favors the welding between two different metals, for example when copper is used to form the element 15 and aluminum is used to form the electrode 12 (or vice-versa). Such a direct pressure of the gases also makes it possible to reduce the quantity of material to be moved and thus makes it possible to use a lesser quantity of explosive material.
A rapid explosion explosive can propel the element 15 at a speed of the order of 7500 m/s, a slow explosion explosive being able to propel the element 15 at a speed typically lying between 1500 and 2000 m/s. Such a type of welding is notably detailed in the U.S. Pat. No. 3,590,877 in order to repair heat exchange tubes. The patent EP0381880 also provides dimensioning rules for a quantity of explosive to be used as a function of the weight of the element to be welded by projection, in particular for a nitroguanidine-based explosive.
By using pyrotechnic elements marketed for airbag manufacture, tests have shown that 25 to 30% of the energy of the explosion was transferred as kinetic energy onto the element 15. By determining the energy necessary to produce a weld between the element 15 and the electrode 12, it will be possible to easily determine the quantity of explosive 171 to be included in the pyrotechnic element 17.
The explosive 171 is configured for the gases generated by its explosion to propel an end of the element 15 through the chamber 16 toward the electrode 12. This end is initially directly above the electrode 12. Upon the explosion, the gases generated by the explosive 171 apply a pressure onto this end of the element 15 to propel it into contact with the electrode 12 and to heat up this element 15. The element 15 is propelled with a sufficient energy to be welded to the electrode 12, according to the configuration illustrated in
The electrodes 11 and 12 are electrically conductive. The electrode 11 is for example electrically connected to a connector 111. The electrode 12 is for example electrically connected to a connector 112. The electrode 13 is for example electrically connected to a connector 113.
The electrodes 11 to 13 are here housed in a chamber 16. The electrodes 11 and 12 are fixed against an internal wall 161 of the chamber 16, in order to ensure that they are mechanically secured. The electrode 13 is fixed against an internal wall of the chamber 16, opposite the wall 161. The switch 1 further comprises an electrically conductive element 15. The element 15 is housed inside the chamber 16. The element 15 is separated from the electrode 12 via an electrically insulating medium 162 present in the chamber 16. To this end, the element 15 is kept separated from the electrode 12. The element 15 is here held against the wall of the chamber 16 opposite the wall 161. The electrically insulating medium 162 also separates the electrodes 11 and 12 to electrically insulate them inside the chamber 16. The internal surface of the chamber 16 is electrically insulating to guarantee the electrical insulation between the electrode 11 and the electrode 12, between the electrode 13 and the electrode 12, and between the conductive element 15 and the electrode 12. The switch 1 thus has a configuration of normally-open type between the electrodes 11 and 12, illustrated in
The element 15 is electrically linked to the electrode 11 and is mechanically fixed to this electrode 11. To favor the electrical contact between the element 15 and the electrode 11 and the mechanical strength of their link, the electrode 11 and the element 15 are advantageously formed of a single piece. The element 15 is further electrically linked to the electrode 13 and is mechanically fixed to this electrode 13. The switch 1 thus has a configuration of normally-closed type between the electrodes 11 and 13, illustrated in
The element 15 has an end directly above the electrode 12. The switch 1 further comprises a pyrotechnic element 17. The pyrotechnic element 17 includes an explosive 171 attached to the conductive element 15, and a detonator 172 configured to initiate the explosion of the explosive 171. The explosion of the explosive 171 can be controlled by any appropriate means, for example by the application of an electrical signal to the detonator 172 via a control circuit 9.
The explosive 171 is configured for the gases generated by its explosion to break the link between an end of the element 15 and the electrode 13. Consequently, the connection between the electrode 11 and the electrode 13 is open. The connection between the electrodes 12 and 13 also remains open. The gases generated by the explosion of the explosive 171 further propel this end of the element 15 through the chamber 16 toward the electrode 12. Upon the explosion, the gases generated by the explosive 171 apply a pressure onto this end of the element 15 to propel it into contact with the electrode 12 and to heat up this element 15. The element 15 is propelled with a sufficient energy to be welded to the electrode 12, according to the configuration illustrated in
The electrodes 11 to 14 are housed in a chamber 16. The electrodes 11 and 12 are fixed against an internal wall 161 of the chamber 16, in order to ensure that they are mechanically held. The electrodes 13 and 14 are fixed against an internal wall of the chamber 16, in order to ensure that they are mechanically held, this wall being opposite the wall 161.
The switch 1 further comprises an electrically conductive element 15. The element 15 is housed inside the chamber 16. The element 15 is separated from the electrodes 11 and 12 via an electrically insulating medium 162 present in the chamber 16. To this end, the element 15 is kept separated from the electrodes 11 and 12. The element 15 is here fixed to the electrodes 13 and 14 and electrically connects the electrodes 13 and 14. The switch 1 thus has a configuration of normally-closed type between the electrodes 13 and 14, illustrated in
The electrically insulating medium 162 also separates the electrodes 11 and 12 to electrically insulate them inside the chamber 16. The insulating medium 162 also separates the electrodes 11 and 12 from the electrodes 13 and 14. The internal surface of the chamber 16 is electrically insulating to guarantee the electrical insulation between the electrode 11 and the electrode 12 relative to one another, and to the conductive element 15, the electrode 13 and the electrode 14. The switch 1 thus has a configuration of normally-open type between the electrodes 11 and 12, illustrated in
The element 15 has a part directly above the first electrode 11, and a part directly above the second electrode 12. The switch 1 further comprises a pyrotechnic element 17. The pyrotechnic element 17 includes an explosive 171 attached to the conductive element 15, and a detonator 172 configured to initiate the explosion of the explosive 171. The explosion of the explosive 171 can be controlled by any appropriate means, for example by the application of an electrical signal to the detonator 172 via a control circuit 9.
The explosive 171 is configured for the gases generated by its explosion to detach the element 15 from the electrodes 13 and 14, and propel the element 15 through the chamber 16 toward the electrodes 11 and 12. Upon the explosion, the gases generated by the explosive 171 apply a pressure onto the element 15 to detach it from the electrodes 13 and 14, to propel the element 15 into contact both with the electrode 11 and with the electrode 12, and to heat up this element 15. The element 15 is propelled with a sufficient energy to be welded to the electrode 11 on the one hand and to the electrode 12 on the other hand, according to the configuration illustrated in
The switch 1 then has a reliable and durable closed configuration between the electrodes 11 and 12. The switch 1 then has an open configuration between the electrodes 13 and 14 (then separated by the medium 162), between the electrodes 11 and 13, between the electrodes 11 and 14, between the electrodes 12 and 13 and between the electrodes 12 and 14.
To facilitate the pivoting of the element 15 relative to the electrode 11 upon the explosion:
To facilitate the break between the element 15 and the electrode 13 upon the explosion:
To facilitate the break between the element 15 and the electrode 14 upon the explosion:
The electrode 12 includes an electrically conductive sleeve surrounding the element 15. The sleeve of the electrode 12 is separated from the element 15 by an annular space. The annular space also forms a separation between the electrodes 11 and 13. The electrodes 11 and 13 are advantageously fixed inside insulating blocks 18. The insulating blocks 18 electrically insulate the electrodes 11 and 13 relative to the electrode 12.
Upon the explosion of the explosive 171, a break is produced between the element 15 and the electrode 13 to open the connection between the electrode 11 and the electrode 13. The element 15 is deformed in the annular space until it comes into contact with the sleeve of the electrode 12. The electrical connection between the electrode 11 and the electrode 12 is thus closed. The electrode 12 and the electrode 13 then remain electrically insulated via a block 18 and an insulating medium 162 present in the annular space.
For a nominal current of 200 A, metal copper cables will be able to have a section of 70 mm2. The element 15 will be able to be dimensioned to guarantee an equivalent welding surface area with the sleeve of the electrode 12.
The switch 41 is of the normally-open type. The switch 42 can be selectively opened or closed via a control circuit that is not illustrated.
In normal operation, when the voltage from the source 2 is to be applied between the terminals 31 and 32, the switch 41 is kept open and the switch 42 is kept closed, as illustrated in
In case of a malfunction, for example if an excessive temperature is measured at the source 2 (for example a temperature close to the thermal runaway temperature of an electrochemical accumulator) or at the connections, the explosion of the explosive of the pyrotechnic element of the switch 41 is controlled. Thus, the switch 41 is closed and a short-circuit is thus formed between the terminals 31 and 32, which makes it possible to maintain a conduction between these terminals. Moreover, the switch 42 is open and the link between the terminal 31 and the pole 21 is therefore broken, such that the source 2 can no longer output current.
Since the switch 41 is of the normally-open type, in normal operation, the voltage between the poles 21 and 22 of the source 2 is applied between the terminals 31 and 32.
Upon a malfunction causing an excessive current to be output by the source 2, the closure of the switch 41 is controlled by an explosion of the explosive 171 and the fuse 43 melts to open the connection between the pole 21 and the terminal 31.
To obtain such automatic triggering, the fuse 43 is advantageously dimensioned as follows. If Iccmax is used to designate the maximum short-circuit current output by the DC voltage source 2, the fuse 43 is dimensioned to remain closed when it is passed through by this current Iccmax for a time sufficient for its heating up to initiate the explosion of the explosive 171.
A power supply system 31 is illustrated in
An identical continuity of service is obtained by connecting the systems 3 as detailed with reference to
| Number | Date | Country | Kind |
|---|---|---|---|
| 13 58869 | Sep 2013 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/069329 | 9/10/2014 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/036455 | 3/19/2015 | WO | A |
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| Number | Date | Country | |
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