METHOD AND DEVICE FOR DETECTING AN EXCEEDING OF A PREDEFINED TEMPERATURE THRESHOLD

Description

FIELD OF INVENTION

[0001] The invention relates to temperature monitoring devices for heat sources, and more particularly to monitoring devices comprising electronic components exhibiting a resistance that varies with the operating temperature. CONTEXT OF THE INVENTION

[0002] The present invention proposes a device for detecting temperature exceedances of one or more heat sources, allowing adjustment of the monitored temperature threshold.

[0003] A device for monitoring the temperature of several heat sources, consisting of battery cells, is known from document CN102195270. The device comprises a plate whose volume varies with temperature. The plate is placed against a wall of the cell being monitored. In case of overheating, the plate expands and mechanically actuates a switch located opposite it; opening the switch interrupts the flow of charging current through the cell.

[0004] However, this solution offers only one parameter for adjusting the overheating temperature threshold: the distance between the plate and the switch. This parameter can therefore only be set during the manufacturing of the module containing the cell(s) to be monitored, and is then fixed. The monitored temperature threshold value cannot be adjusted. Furthermore, it causes the cells to disconnect abruptly, and no other corrective measures are possible.

[0005] Another example of a temperature overshoot detection device can be found in document US2011 / 210703A1.

[0006] Therefore, there is a need for a temperature monitoring device for one or more heat sources, allowing adjustment of the monitored temperature threshold.

[0007] To this end, the invention aims to provide a device for detecting when a first predefined temperature threshold is exceeded by at least one heat source, the detection device comprising: at least one component exhibiting variable electrical resistance depending on the component's operating temperature, and an electrical power source capable of supplying an electric current flowing through said component, said component being capable of being thermally coupled to said heat source, such that the operating temperature varies according to: the temperature of the heat source and the heat released by Joule effect in the component when the electric current flows through it, the variable electrical resistance having a high value if the operating temperature is above a second predefined temperature threshold, called the trigger threshold, the electrical energy source being configured to generate the electric current such that the operating temperature is greater than or equal to the trigger threshold as soon as the temperature of said heat source is greater than or equal to the first predefined temperature threshold, the variable electrical resistance then having the high value, in which the electrical energy source is a current source,and in which the electric current is supplied in the form of periodic pulses, with a fixed or variable duty cycle.

[0008] In preferred embodiments, the device according to the invention may advantageously have the following characteristics, alone or in combination: The device may be electrically isolated from the heat source, it may be configured to detect the exceeding of the first temperature threshold by one heat source among a plurality of heat sources, and may include a plurality of components in the form of a plurality of resettable fuses, each resettable fuse being able to be thermally coupled to at least one heat source, the fuses being able to be connected in series, it may further include a plurality of resistors, each being able to have a distinct ohmic value, a resistor being able to be connected in parallel across the terminals of each fuse, at least one heat source may be a battery cell, the device may further include a monitoring module configured to trigger a corrective or signaling action when the variable electrical resistance of one of said components has the high value.

[0009] Another object of the invention is a method for monitoring the exceeding of a first temperature threshold by at least one heat source, the method being carried out by a detection device (D) comprising: at least one component exhibiting variable electrical resistance depending on the component's operating temperature, the variable electrical resistance having a high value if the operating temperature exceeds a second predefined temperature threshold, called the trigger threshold, and an electrical power source capable of supplying an electric current flowing through said component, the process comprising: a thermal coupling step of at least one heat source to at least one component, such that the operating temperature varies according to: ▪ the temperature of the heat source and, ▪ the heat released by Joule effect in the component when an electric current flows through it; a connection step of the electrical energy source to at least one component; a configuration step of the electrical energy source to generate the electric current such that the operating temperature is greater than or equal to the trigger threshold as soon as the temperature of said heat source is greater than or equal to the first predefined temperature threshold, the variable electrical resistance then exhibiting the high value, in which the source of electrical energy is a current source, and in which the electric current is supplied in the form of periodic pulses, with a fixed or variable duty cycle.

[0010] In preferred embodiments, the method according to the invention may advantageously have the following characteristics, alone or in combination, provided that the detection device may include: a plurality of components connected in series, each exhibiting a variable electrical resistance depending on the respective operating temperature, and a plurality of resistors exhibiting distinct ohmic values, one resistor being connected in parallel across the terminals of each component, such that when the electrical resistance of a component has the high value, the equivalent resistance of the electrical chain formed by the components and the resistors has a distinct value for each component and the resistor connected to it in parallel, The process may then include: during the thermal coupling step, each component is thermally coupled to at least one heat source; during the connection step, the power supply is connected to the electrical chain formed by the components and resistors; the process may then further include: a step of generating a power supply signal from the power supply; a step of detecting a response signal at the terminals of the power supply; a step of determining an equivalent resistance of the electrical chain formed by the components and resistors; a step of identifying the component whose resistance has the highest value, based on the equivalent resistance.

[0011] The configuration step may then include a sub-step for sizing the detection device, including determining an initial duty cycle of the periodic current pulses, based on: of the first temperature threshold to be monitored, the electrical characteristics of at least one component, and the characteristics of the thermal coupling achieved between at least one heat source and at least one component.

[0012] After an initial detection of exceeding the first temperature threshold, the configuration step may also include: a substep of sending current pulses having a second duty cycle, lower than the first duty cycle; a substep of confirming detection of the first overshoot detection.

[0013] Another object of the invention relates to a vehicle comprising a temperature overshoot detection device as previously described. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] THE figures 1 And 2 These schematically represent two embodiments of a temperature overshoot detection device arranged to monitor the respective temperatures of a plurality of battery cells. figures 3 And 4 represent two temperature overshoot detection devices according to two embodiments of the invention. figure 5 represents the steps of the process of identifying a heat source that has exceeded a predefined temperature threshold, according to an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] In figure 1 A detection device according to an embodiment of the invention is schematically represented. The device D is installed in a vehicle V to monitor the temperature of a plurality of heat sources S1, S2, Sj,... Sn consisting of battery cells grouped in modules M1, ... Mm. The battery cells are of the flexible type, known by the English term "soft-shell".

[0016] The device comprises a plurality of components C1, C2, Ci, Ck, having a variable electrical resistance R_PTC depending on an operating temperature Tf of the component C1, C2, Ci, Ck. In a preferred embodiment, the components C1, C2, Ci, Ck are in the form of a plurality of resettable fuses.

[0017] Each resettable fuse C1, C2, Ci, Ck is thermally coupled to at least one heat source S1, S2, Sj, Sn. In the example illustrated in figure 1 The heat sources are battery cells, and thermal coupling is achieved by wrapping each resettable fuse C1, C2, Ci, Ck in a thermal sleeve, which is then attached to the battery cells. Each resettable fuse C1, C2, Ci, Ck is coupled to two battery cells, with the connection achieved by compression and / or gluing.

[0018] The device also includes an electrical power source E capable of supplying an electric current Is flowing through the resettable fuses C1, C2, Ci, Ck, which are thermally coupled to the battery cells S1, S2, Sj, Sn, such that the respective operating temperatures of components C1, C2, Ci, Ck vary according to of the temperature T of the heat source(s) S to which they are thermally coupled, and of the heat released by Joule effect in the component C1, C2, Ci, Ck when it is traversed by the electric current Is.

[0019] The variable electrical resistance of a component, in this example a resettable fuse, has a high value Rd if the operating temperature Tf of the component is greater than a second predefined temperature threshold, called the tripping threshold Td.

[0020] The electrical power source is configured to generate the electric current Is so that the operating temperature Tf is greater than or equal to the trigger threshold Td as soon as the temperature T of said heat source S is greater than or equal to the first predefined temperature threshold TS, the variable electrical resistance then exhibiting the high value Rd.

[0021] Device D is electrically isolated from the heat source S. In this way the operating characteristics of the detection device D are independent of the electrical characteristics of the heat sources to be monitored: the current Is flowing through the resettable fuses has a value varying between 100 mA and 800 mA, for a voltage delivered by the power source E of a typical value of 12 V, while the operating voltage delivered by the battery cell assembly is typically 400 V.

[0022] In the illustrated example, the energy source E is a current source, and the components C1, C2, Ci, and Ck are connected in series. In this way, the electric current Is does not depend on the number k of components in the device D, nor on the number n of heat sources to be monitored, which simplifies the adjustment of the first temperature threshold TS. Simply by decreasing the current Is delivered by the current source E, the first temperature threshold TS is increased, and vice versa.

[0023] As already mentioned, the operating temperature of a component, in this example a resettable fuse, depends on the temperature T of the heat source S to which the component is thermally coupled, and on the heat released by Joule heating within the component when an electric current Is flows through it. Thus, for a component characterized by a given trip temperature threshold Td, the adjustment of the first temperature threshold TS reached by the monitored heat sources S1, S2, Sj, Sn, can be achieved by varying the heat released by Joule heating within the component.

[0024] In a preferred embodiment, the electric current Is is supplied in the form of periodic pulses, with a fixed or variable duty cycle.

[0025] The amount of heat released by Joule effect in the component can thus be adjusted by changing the time the electric current passes through the component, which can be achieved simply by varying the duty cycle of the periodic pulses.

[0026] In figure 3 is illustrated an embodiment of the detection device incorporating an electrical energy source E configured to deliver an electrical current Is in the form of electrical pulses.

[0027] During the E32 sizing phase of the detection device D, a fixed duty cycle can be determined for each application, based on the first temperature threshold TS to be monitored, the electrical characteristics of components C1, C2, Ci, Ck, and the characteristics of the thermal coupling between the heat sources to be monitored and these components. This duty cycle, and consequently the first temperature threshold TS to be monitored, can thus be adjusted according to the specific requirements of each application.

[0028] During the operation of the detection device D, the ability to vary the duty cycle allows the first temperature threshold TS to be adjusted without intervening on the installation of the device D and its thermal coupling to the heat sources.

[0029] A point variation in the duty cycle, after a first detection of exceeding the first temperature threshold TS, allows confirmation in a phase E36 of this first detection, and therefore makes the result of the detection more reliable, by sending pulses of lower duty cycle in a phase E34.

[0030] In a preferred embodiment, the detection device D further includes a monitoring module M configured to trigger a corrective or signaling action when the variable electrical resistance of one of said components C1, C2, Ci, Cn exhibits a high value Rd. This module M is configured to detect the change in the resistance value of a component Ci, for example, by measuring both the voltage and / or the current across the terminals of the electrical power source.

[0031] Next, the monitoring module M can trigger a cooling action, which will lower the temperature of the heat sources and components C1, C2, Ci, and Cn. This configuration is particularly advantageous for detection devices D equipped with components C1, C2, Ci, and Cn in the form of resettable fuses. Indeed, the variable resistance of this type of component returns to a low value, known as the holding resistance Rm, once the operating temperature has dropped, thus allowing the heat source temperature monitoring process to restart.

[0032] In a preferred embodiment, illustrated in figure 2 , device D further includes a plurality of resistors R1, R2, Ri, Rk, each having a distinct ohmic value, one resistor being connected in parallel across the terminals of each component C1, C2, Ci, Ck.

[0033] This arrangement allows for the identification of a resettable fuse Ci thermally coupled to a heat source Sj, in this example a battery cell, which has exceeded the first temperature threshold TS, as will be explained later. Thus, targeted cooling strategies at the heat source level can be implemented.

[0034] Such a detection device D can be configured to identify, among a plurality of heat sources S1, S2, Sj, Sn, a heat source Sj that has exceeded a first predefined temperature threshold TS. The device D comprises a plurality of components C1, C2, Ci, Ck connected in series, each having a variable electrical resistance depending on a respective operating temperature. The variable electrical resistance has a high value Rd, called the trigger resistance, if the operating temperature Tfj is above the second predefined temperature threshold, called the trigger threshold Td, and a low value Rm, called the holding resistance, otherwise.

[0035] It should be noted that depending on the embodiment, the holding resistance Rm of a component C1, C2, Ci, Ck, can correspond to a value close to 0Ω, and the tripping resistance Rd to an open circuit; this is the case for fuse or switch type components.

[0036] In the embodiment using resettable fuses, the holding resistance Rm has a typical resistance of 0Ω, and the tripping resistance Rd has a typical resistance of a few kΩ.

[0037] In all cases, the value of the holding resistance Rm is negligible compared to the value of the triggering resistance Rd, so that Rd + (k-1)*Rm ≈ Rd, k being the number of components of the detection device D. The use of this characteristic will be explained later.

[0038] Each component C1, C2, Ci, Ck is suitable for being thermally coupled to at least one of the heat sources S1, S2, Sj, Sn, so that its operating temperature is greater than or equal to the triggering threshold Td as soon as the temperature of said at least one heat source Si, Sk, Sn is greater than or equal to the first predefined temperature threshold TS, the variable electrical resistance then exhibiting the high value Rd.

[0039] The device D further includes a plurality of resistors R1, R2, Ri, Rk, having distinct ohmic values, one resistor being connected in parallel across the terminals of each component C1, C2, Ci, Ck, so that when the electrical resistance of a component Ci has the high value Rd, the equivalent resistance Re of the electrical chain formed by the components C1, C2, Ci, Ck and the resistors R1, R2, Ri, Rk, has a value characteristic of that component Ci and the resistance Ri which is connected to it in parallel.

[0040] Alternatively, a resistor Ri can be connected in parallel with a group of series-connected components Ci-1, Ci, Ci+1, each coupled to at least one respective heat source. This arrangement is particularly advantageous if the heat sources are grouped together. An example of an application of this embodiment of the invention is the temperature monitoring of flexible battery cells grouped in battery modules M1, M2,... Mm, as illustrated in figure 4 If one of the monitored battery cells Sj exceeds the first predefined temperature threshold TS, the component Ci thermally coupled to that cell Sj will exhibit the high resistance value Rd. If the other battery cells do not exceed the first temperature threshold TS, the entire series of components will exhibit an equivalent resistance Rd + (k-1)*Rm, where k is the number of components connected in series; the entire series of these resistances connected in parallel with the resistance Ri will exhibit an equivalent resistance Re = Ri * Rd + k − 1 * Rm / Ri + Rd + k − 1 * Rm .

[0041] The choice of components Ci and resistors Ri is made such that 1) the value of the resistance Rm is negligible compared to that of Rd; Rd + k − 1 * Rm ≈ Rd . Therefore, as Re = Ri * Rd + k − 1 * Rm / Ri + Rd + k − 1 * Rm , its value is approximately equal to Re ≈ Ri * Rd / Ri + Rd . 2) Ri is negligible compared to Rd, so that Ri * Rd / Ri + Rd ≈ Ri .

[0042] Therefore, the equivalent resistance Re of a resistor Ri, connected in parallel with a component Ci thermally coupled to a battery cell Sj that has exceeded the first temperature threshold TS, or with a group of components Ci-1, Ci, Ci+1, connected in series, one of which is thermally coupled to a battery cell Sj that has exceeded the first temperature threshold TS, is approximately equal to Ri. By judiciously choosing distinct ohmic values ​​for the resistors R1, R2, ... Ri, Rk, the equivalent resistance of the electrical chain under consideration has a characteristic value of component Ci thermally coupled to battery cell Sj having exceeded the first temperature threshold TS, or of the group of components Ci-1, Ci, Ci+1, connected in series, of which a component Ci thermally coupled to a battery cell Sk has exceeded the first temperature threshold TS and the resistance Ri which is connected to it in parallel.

[0043] A method for identifying a heat source Sj that has exceeded a predefined first threshold TS of a temperature T, among a plurality of heat sources S1, S2, Sj, Sn, will now be described with reference to the figure 5 .

[0044] The method can be implemented using a detection device as described above, i.e. comprising a plurality of components C1, C2, Ci, Ck which can have, depending on their operating temperature, a low value, called holding resistance Rm, or a high value called triggering resistance Rd, and a plurality of resistors R1, R2, Ri, Rk, having distinct ohmic values ​​and connected in parallel with a component Ci or a group of components Ci-1, Ci, Ci+1 connected in series.

[0045] The process includes a thermal coupling step E10 of the plurality of heat sources S1, S2, Sj, Sn, to components C1, C2, Ci, Ck, each component being thermally coupled to at least one heat source Si, such that its operating temperature is greater than or equal to the trigger threshold Td as soon as the temperature of said at least one heat source is greater than or equal to the first predefined temperature threshold TS, the variable electrical resistance of the component then having the high value Rd, a connection step E20 of the electrical chain formed by the components C1, C2, Ci, Ck and the resistors R1, R2, Ri, Rk, to an electrical energy source E, a generation step E30 of a supply signal U, I by the electrical energy source E, a detection step E40 of a response signal i, u across the terminals of the electrical energy source E,a step E50 of determining an equivalent resistance Re of the electrical chain formed by the components C1, C2, Ci, Ck and the resistors R1, R2, Ri, Rk; a step E60 of identifying the component Ci whose resistance has the high value Rd, as a function of the equivalent resistance Re.

[0046] In the illustrated example, the power supply signal generated at generation stage E30 is an electric current Is, and the response signal detected at detection stage E40 is a voltage across the current source E.

[0047] Knowing the value of the generated current Is and the value of the detected voltage, the equivalent resistance Re of the electrical circuit is determined during the execution of the determination step E50. As explained previously, this equivalent resistance is characteristic of the component Ci, or the group of components where one has a high resistance value Rd, and of the resistance Ri connected to it in parallel. This allows the identification of this component Ci during the identification step E60.

[0048] Of course, the present invention is not limited to the examples and embodiments described and represented, but is susceptible to many variations accessible to a person skilled in the art.

[0049] For example, other arrangements are possible, depending on the configuration of the heat sources. In particular, the invention is applicable to monitoring the surfaces of heat sources by creating grids covering the surface to be monitored and placing components as described, thermally coupled to the surface to be monitored, at the nodes of the grid.

Claims

1. Device (D) for detecting exceedance of a first predefined threshold (TS) of a temperature (T) by at least one heat source (S), the detecting device (D) comprising - at least one component (C1, C2, Ci, Ck) having an electrical resistance that is variable depending on an operating temperature of the component (C1, C2, Ci, Ck), - an electrical power source able to deliver an electrical current (Is) that flows through said component (C1, C2, Ci, Ck), said component (C1, C2, Ci, Ck) being able to be thermally coupled to said heat source (S), so that the operating temperature (Tf) varies depending on - the temperature (T) of the heat source (S) and - the heat given off by Joule heating in the component (C1, C2, Ci, Ck) when the electrical current (Is) flows therethrough, the variable electrical resistance having a high value (Rd) if the operating temperature (Tf) is higher than a second predefined temperature threshold, called the trip threshold (Td), the electrical power source being configured to generate the electrical current (Is) so that the operating temperature (Tf) is higher than or equal to the trip threshold (Td) if the temperature (T) of said heat source (S) is higher than or equal to the first predefined temperature threshold (TS), the variable electrical resistance then having the high value (Rd), and characterized in that the electrical power source is a current source, and wherein the electrical current (Is) is delivered in the form of periodic pulses, of fixed or variable duty cycle, so that the amount of heat generated by Joule heating may be adjusted by modifying the time for which electrical current passes through the component.

2. Device (D) according to the preceding claim, wherein the device (D) is electrically isolated from the heat source (S).

3. Device (D) according to either one of the preceding claims, characterized in that it is configured to detect the exceedance of the first temperature threshold (TS) by one heat source among a plurality of heat sources (S1, S2, Sj, Sn), and in that it comprises a plurality of components (C1, C2, Ci, Ck) taking the form of a plurality of resettable fuses, each resettable fuse (C1, C2, Ci, Ck) being thermally coupled to at least one heat source (S1, S2, Sj), the fuses (C1, C2, Ci, Ck) being connected in series.

4. Device (D) according to the preceding claim, furthermore comprising a plurality of resistors (R1, R2, Ri, Rk), each having a different resistance, one resistor being connected in parallel across the terminals of each fuse (C1, C2, Ci, Ck).

5. Device (D) according to any one of the preceding claims, wherein the at least one heat source is a battery cell.

6. Device according to any one of the preceding claims, furthermore comprising a monitoring module (M) configured to trigger a correcting or flagging action when the variable electrical resistance of one of said components (C1, C2, Ci, Ck) has the high value (Rd).

7. Method for monitoring exceedance of a first threshold (TS) of a temperature (T) by at least one heat source (S, S1, Si, Sk, Sn), the method being executed by a detecting device (D) comprising - at least one component (C1, C2, Ci, Ck) having an electrical resistance that is variable depending on an operating temperature (Tf) of the component, the variable electrical resistance having a high value (Rd) if the operating temperature (Tf) is higher than a second predefined temperature threshold, called the trip threshold (Td), - an electrical power source able to deliver an electrical current (Is) that flows through said component (C1, C2, Ci, Ck), the method comprising: - a step (E10) of thermally coupling the at least one heat source (S, S1, Si, Sk, Sn) to the at least one component (C1, C2, Ci, Ck), so that the operating temperature (Tf) varies depending on ∘ the temperature (T) of the heat source (S) and ∘ the heat given off by Joule heating in the component (C1, C2, Ci, Ck) when the electrical current (Is) flows therethrough, - a step (E20) of connecting the electrical power source (E) to the at least one component (C1, C2, Ci, Ck); - a step (E30) of configuring the electrical power source to generate the electrical current (Is) so that the operating temperature (Tf) is higher than or equal to the trip threshold (Td) if the temperature (T) of said heat source (S) is higher than or equal to the first predefined temperature threshold (TS), the variable electrical resistance then having the high value (Rd), wherein the electrical power source is a current source, and wherein the electrical current (Is) is delivered in the form of periodic pulses, of fixed or variable duty cycle, so that the amount of heat generated by Joule heating may be adjusted by modifying the time for which electrical current passes through the component.

8. Monitoring method according to the preceding claim, wherein the detecting device (D) comprises a plurality of components (Cj) connected in series and each having an electrical resistance that is variable depending on the respective operating temperature (Tfj), and a plurality of resistors (Rj) that have different resistances, one resistor being connected in parallel across the terminals of each component (Cj), so that, when the electrical resistance of a component (Ck) has the high value (Rd), the equivalent resistance (Re) of the electrical chain formed by the components (Cj) and the resistors (Rj) has a different value for each component (Ck) and the resistor (Rk) that is connected thereto in parallel, and wherein - during the thermal coupling step (E10), each component (Cj) is thermally coupled to at least one heat source (Si, Sk), - during the connecting step (E20), the electrical power source (E) is connected to the electrical chain formed by the components (Cj) and the resistors (Rj), the method furthermore comprising - a step (E30) of generating a supply signal (I) with the electrical power source (E), - a step (E40) of detecting a response signal (u) across the terminals of the electrical power source (E), - a step (E50) of determining an equivalent resistance (Re) of the electrical chain formed by the components (Cj) and the resistors (Rj); - a step (E60) of identifying the component (Ck) the resistance of which has the high value (Rd), depending on the equivalent resistance (Re).

9. Monitoring method according to either of Claims 7 and 8, wherein the configuring step (E30) comprises a sub-step (E32) of dimensioning the detecting device (D) comprising determining a first duty cycle of the periodic current pulses, depending on: - the first temperature threshold (TS) to be monitored, - the electrical characteristics of the at least one component (C1, C2, Ci, Ck), and - the characteristics of the thermal coupling between the at least one heat source (S) and the at least one component (C1, C2, Ci, Ck).

10. Monitoring method according to the preceding claim, wherein, after a first detection of exceedance of the first temperature threshold (TS), the configuring step (E30) furthermore comprises: - a sub-step (E34) of transmitting current pulses having a second duty cycle lower than the first duty cycle; - a sub-step (E36) of confirming detection of the first exceedance detection.

11. Vehicle (V) comprising a device (D) for detecting exceedance of a predefined temperature threshold (TS) according to one of Claims 1 to 6.