METHOD FOR PROTECTING AN ELECTRICAL CIRCUIT OF AN ELECTRICAL OR HYBRID VEHICLE COMPRISING A SCREWED ELECTRICAL CONNECTION

Abstract

The invention relates to a method for protecting an electrical circuit (10) of an electric or hybrid vehicle comprising screwed electrical connections (51, 52, 53, 54), temperature sensors (41, 42, 43, 44), and a switch (30). The method comprises the following steps: - a step of measuring the temperature values ​​of said screwed electrical connections (51, 52, 53, 54); - a step of opening the switch (30) after a predetermined time so as to protect said electrical circuit (10) if a measured temperature value of one of said screwed electrical connections (51, 52, 53, 54) exceeds a predetermined temperature threshold value for the screwed electrical connection. Figure 1

Description

Title of the invention: METHOD FOR PROTECTING AN ELECTRICAL CIRCUIT OF AN ELECTRIC OR HYBRID VEHICLE COMPRISING A SCREWED ELECTRICAL CONNECTION

[0001] The invention relates to electric vehicles, that is to say, those equipped with at least one battery for storing electrical energy intended for their propulsion. This includes vehicles with a single means of electric propulsion, as well as hybrid vehicles incorporating at least one mode of electric propulsion.

[0002] Prior art information exists for an electrical circuit comprising a first battery module having a first voltage terminal and a second battery module having a second voltage terminal. Furthermore, the electrical circuit includes a connecting bar. A first screw-type electrical connection secures the first voltage terminal to the connecting bar. A second screw-type electrical connection secures the second voltage terminal to the connecting bar.

[0003] Prior art also shows that the vehicle generates vibrations during its use, which can cause the first screwed electrical connection to loosen. In particular, two cases of failure of the screwed electrical connection can be identified. In the first case, the connecting bar tilts relative to the screwed electrical connection. In this case, part of the connecting bar is in contact with a voltage terminal. For example, the electrical resistance value of the screwed electrical connection in this second case is approximately 0.5 mOhms. In the second case, the connecting bar and the voltage terminal are no longer in contact. As a result, the electrical circuit current flows from the connecting bar to the voltage terminal via the screwed electrical connection. Consequently, the current passes through the cross-section of the screw body.For example, the electrical resistance value of the screwed electrical connection in this first case is approximately 1 mOhm.

[0004] Due to these intermittent connections, the electrical resistance of the screw connection increases. Consequently, the failure of the first screw connection results in greater Joule heating. This heating spreads from a hot spot to the battery module, reducing battery performance. As a result, a fire can start in the first module. Furthermore, in some cases of intermittent contact failure, an electric arc is generated. In short, the aforementioned failure scenarios present a risk of fire for the battery, as well as a decrease in battery performance.

[0005] To this end, patent application EP2842797 describes a device comprising a connector, disposed on the connection bar, including a first connection part and a second connection part. Furthermore, a first detection terminal is connected to the first connection part in order to measure a temperature. In addition, a second detection terminal is connected to the second connection part in order to measure a voltage. In particular, these temperature and voltage measurements are intended for the detection of a failure of the first screwed electrical connection or the second screwed electrical connection.

[0006] However, fault detection is limited to a screw-type electronic connection between the first and second modules. In practice, the electrical circuit includes other components that also use screw-type electrical connections. Thus, if such a faulty screw-type electrical connection is not detected, driver safety and vehicle integrity are compromised. Furthermore, the presence of the first and second detection terminals adds extra wiring to transmit temperature and voltage measurements. Consequently, due to the presence of cables with different potentials, the electrical circuit is exposed to additional risks of arcing and short circuits.

[0007] The objective of the present invention is to overcome the aforementioned disadvantages and to improve driver safety while ensuring the integrity and performance of the vehicle.

[0008] To achieve this objective, the invention proposes a method for protecting an electrical circuit of an electric or hybrid vehicle comprising screwed electrical connections, a battery comprising a module and a switch, each of said screwed electrical connections comprising a temperature probe, the method comprising the following steps: - a step of measuring a temperature value for each of the said screwed electrical connections; - a fault reporting step, a signal being emitted to alert the driver of the fault when the measured temperature value of one of said screwed electrical connections is greater than a predetermined temperature threshold value of the screwed electrical connection; - a step of opening the switch, after a predetermined time, so as to protect the electrical circuit, when the measured temperature value of the screwed electrical connection is greater than the predetermined temperature threshold value of the screwed electrical connection.

[0009] Such a method is adaptable to all electrical connections in the electrical circuit so as to limit the risk that a faulty screw-type electrical connection will not be detected. Furthermore, the electrical circuit wiring for such measures is simple, reducing the risk of electrical arcing. In this way, the risk of fire is prevented.

[0010] Advantageously, the predetermined temperature threshold value of each of said screwed electrical connections is between 50°C and 100°C.

[0011] Such a temperature threshold value is chosen so as to avoid triggering the interruption of the current in the electrical circuit for a functional screwed electrical connection while limiting the risk that a faulty screwed electrical connection may overheat without being detected.

[0012] Advantageously, the method also includes, between the measurement step and the reporting step, for each of said screwed electrical connections: - a first step in calculating an average temperature value Mk using the following formula: Mk _ Ti°ù n is the number of said screwed electrical connections, noted L1 for a first screwed electrical connection, L2 for a second screwed electrical connection, Li for an i-th screwed electrical connection, Lk for a k-th screwed electrical connection, up to Ln for an n-th screwed electrical connection, and Ti is the measured temperature value of the i-th screwed electrical connection Li; - a second step of calculating a standard deviation value of temperature θ using the following formula: . / / i 777. . ".2 " _ , a third calculation step .7= / / ^^^.^-^)-^1^ / (]) of a temperature threshold value Sk by the following formula: Sk = Mk + n*(where a is a predetermined positive real number. - a step of assigning the temperature threshold value Sk to the k-th screwed electrical link Lk.

[0013] The model calculates the temperature threshold value of each of said screwed electrical connections in order to detect a faulty screwed electrical connection more quickly and more reliably.

[0014] Advantageously, the predetermined parameter a is between 1 and 10.

[0015] The predetermined parameter a is chosen so as to detect a faulty screwed electrical connection more reliably.

[0016] Advantageously, the predetermined duration is between 1 second and 10 minutes.

[0017] The predetermined duration is chosen so that the driver continues to drive even in the event of a slight failure of a screwed electrical connection, while limiting the risk of further aggravating the heating of the faulty screwed electrical connection.

[0018] Advantageously, the method includes a step of regulating a value of the current intensity of the electrical circuit so as to protect the electrical circuit, the value of the current intensity of the electrical circuit being maintained below a predetermined threshold value of the current intensity of the electrical circuit, when the measured temperature value of the screwed electrical connection is greater than the predetermined temperature threshold value of the screwed electrical connection.

[0019] This allows the driver to maintain control of the vehicle for as long as possible. The current intensity is controlled so that the driver can continue driving even in the event of a minor failure of the screw-on electrical connection. In this way, the driver has the necessary time to perform maneuvers safely. At the same time, other road users are not surprised, as the vehicle can continue to move without necessarily losing traction in the event of a failure. Thus, the collective safety of road users is improved.

[0020] Advantageously, the threshold value of the predetermined current intensity of the electrical circuit is between 0 A and 500 A.

[0021] The current intensity value of the electrical circuit is chosen so as to prevent the faulty screw-type electrical connection from overheating. This improves battery performance and preserves the integrity of the vehicle.

[0022] The invention also relates to a computer program comprising program code instructions for executing the steps of the method for protecting an electrical circuit defined as above, when said program is running on a computer.

[0023] The invention also relates to an electrical circuit and an electronic control unit comprising means for acquisition, processing by software instructions stored in a memory as well as control means required for the implementation of the computer program as defined above.

[0024] In practice, the electronic control unit is a battery management system, also called a BMS. Battery management systems are already commonly used in hybrid and electric vehicles. The battery management system includes a microcontroller to process the measured temperature values.

[0025] The invention further relates to an electric or hybrid vehicle comprising an assembly including an electrical circuit and an electronic control unit as defined above.

[0026] The invention will be further detailed by describing a non-limiting embodiment, and based on the accompanying figures in which: - [Fig.l] schematically illustrates a view of an electrical circuit including a battery and a switch, according to the state of the art; - [Fig.2] illustrates a detailed view of a screwed electrical connection of the electrical circuit, illustrated in [Fig.1], the screwed electrical connection bringing into contact a first electrical termination and a second electrical termination; - [Fig.3] illustrates a flowchart representing the steps of a process for protecting the electrical circuit, illustrated in [Fig.1], according to an embodiment of the present invention.

[0027] Fig. 1 illustrates an electrical circuit 10 comprising a switch 30, screwed electrical connections 51, 52, 53, 54, temperature probes 41, 42, 43, 44 and a battery 20 comprising modules 21, 22. Each of said screwed electrical connections includes a temperature probe.

[0028] In the following, we denote n the number of screwed electrical connections 51, 52, 53, 54 in the electrical circuit 10. The screwed electrical connections 51, 52, 53, 54 are denoted as follows: a first screwed electrical connection is denoted L1, a second screwed electrical connection is denoted L2, a third screwed electrical connection is denoted L3, an i-th screwed electrical connection is denoted Li, a k-th screwed electrical connection is denoted Lk, up to an nth screwed electrical connection is denoted Ln.

[0029] A battery management unit 20 not shown includes a microcontroller.

[0030] Fig. 2 represents, in a detailed view, the electrical circuit 10 comprising a first electrical termination 61 and a second electrical termination 62.

[0031] Throughout the following, the elements which are included in the battery 20 of the electrical circuit 10 will be referred to as "internal" in relation to other elements referred to as "external", the "external" elements being included in the electrical circuit 10 and not in the battery 20.

[0032] In this case, the external screwed electrical connection 53, illustrated in [Fig.2], fixes the first electrical termination 61 to the second electrical termination 62. Generally, the screwed electrical connections 51, 52, 53, 54 include external screwed electrical connections 53, 54 to the battery 20.

[0033] Furthermore, the temperature probes 41, 42, 43, 44 include temperature probes 43, 44 external to the battery 20. In particular, the external temperature probe 43, illustrated in [Fig.2], is disposed on the first electrical termination 61. The external temperature probe 43 measures a temperature value of the external screwed electrical connection 53.

[0034] The arrangement of said external temperature probes on the battery 20 makes it possible to detect a faulty screw-type electrical connection in the entire disconnection device of the electrical circuit, contributing to a more comprehensive coverage of failure risks.

[0035] The external temperature probe 43 is electrically connected to the microcontroller. Thus, the microcontroller is able to digitally process the temperature value of the external screw-on electrical connection 53.

[0036] The electrical circuit 10, illustrated in [Fig. 1], comprises a battery 20 having modules 21, 22. In particular, module 21 includes a voltage terminal and a connecting bar. The screw-type electrical connections 51, 52, 53, 54 include internal screw-type electrical connections 51, 52 to the battery 20. In particular, the internal screw-type electrical connection 51 secures the connecting bar to the voltage terminal.

[0037] Furthermore, the temperature probes 41, 42, 43, 44 include internal temperature probes 41, 42 in the battery 20. In particular, the internal temperature probe 41 measures a temperature value of the internal screwed electrical connection 51.

[0038] Such an arrangement of said internal temperature probes in the battery 10 allows the existing measurement wiring on the module to be reused to transmit the temperature value, thus reducing the manufacturing costs of the electrical circuit.

[0039] Modules 21, 22 each comprise a cell controller electrically connected to the microcontroller. Internal temperature probes 41, 42 are electrically connected to the cell controllers. Thus, the microcontroller is able to process the measured temperature values ​​of the internal screw-connected electrical links 51, 52.

[0040] The electrical circuit 10 preferably puts the switch 30 and the screwed electrical connections 51, 52, 53, 54 in series. In this way, the same intensity of electric current I flows through the electrical circuit 10.

[0041] Advantageously, the switch 30 is connected to a first connection terminal of the electrical circuit 10. The electrical circuit 10 also includes a second connection terminal. Thus, the electrical circuit 10 supplies power to the electric or hybrid motor of the vehicle.

[0042] The external screw-type electrical connection 53, illustrated in [Fig. 2], comprises a screw and a nut 53E. The screw has a flat head 53T and a threaded body 53C. The threaded body 53C passes through the first electrical termination 61 and the second electrical termination 62. Thus, electric current is able to flow between the first electrical termination 61 and the second electrical termination 62.

[0043] Advantageously, the nut is tightened so as to be flush with a surface of the first termination 61. Thus, the nut 53E exerts a uniform pressure on the surface of the first termination 61. In this way, the risks of cracking or localized damage around the tightening point are reduced.

[0044] In addition, a clamping force is used to tighten the nut 53E. Thus, the screwed electrical connection 53 generates a compressive force so that the first electrical termination 61 and the second electrical termination 62 are kept in contact.

[0045] Figure 3 illustrates a logic diagram of a method for protecting the electrical circuit 10. According to one embodiment of the present invention, the method comprises a measurement step E1, then a signaling step E2 and then an opening step E3.

[0046] In the measurement step El, a temperature value of for each of the said screwed electrical connections 51, 52, 53, 54 is measured.

[0047] The temperature values ​​of the screwed electrical connections 51, 52, 53, 54 are noted as follows: a first temperature value, associated with the first screwed electrical connection L1, is noted T1, a second temperature value, associated with the second screwed electrical connection L2, is noted T2, a third temperature value, associated with the third screwed electrical connection L3, is noted T3, an i-th temperature value, associated with the i-th screwed electrical connection Li, is noted Ti, a k-th temperature value associated with the k-th screwed electrical connection Lk, is noted Tk, up to an nth temperature value, associated with the nth screwed electrical connection Ln, is noted Tn.

[0048] Preferably, the method also includes, between the measurement step El and the signaling step E2, for each of said screwed electrical connections 51, 52, 53, 54, a first calculation step E'1, then a second calculation step E'2 followed by a third calculation step E'3 and subsequently an assignment step E'4.

[0049] In the first calculation step E' 1, an average temperature value Mk is calculated using the following formula: Mk =

[0050] In the second calculation step E'2, a temperature standard deviation value is calculated using the following formula: a = min(ke [[ 1, «J

[0051] Advantageously, the second calculation step E'2 is pre-recorded in the microcontroller the first time the temperature standard deviation value is calculated. Thus, the protection process saves execution time.

[0052] In the third calculation step E'3, a temperature threshold value Sk is calculated using the following formula: Sk = Mk + a*o where a is a predetermined parameter. The parameter a is preferably between 1 and 10.

[0053] In the assignment step E'4, the temperature threshold value Sk is assigned to the screwed electrical connection Lk. Thus, each of said screwed electrical connections has a temperature threshold value. A first temperature threshold value is denoted SI for the first screwed electrical connection L1, a second temperature threshold value is denoted S2 for the second screwed electrical connection L2, a third temperature threshold value is denoted S3 for the third screwed electrical connection L3, up to the nth temperature threshold value denoted Sn for the nth screwed electrical connection Ln.

[0054] In the signaling step E2, a signal is emitted to alert the driver of a failure when the microcontroller determines that a measured temperature value of one of said screwed electrical links 51, 52, 53, 54 is greater than a calculated temperature threshold value of the screwed electrical link.

[0055] Preferably, the predetermined temperature threshold value of each of said screwed electrical connections 51, 52, 53, 54 is between 50°C and 100°C.

[0056] Preferably, the signal emitted is an audible and / or visual signal.

[0057] Preferably, the process includes a regulation step E' ' 1 with a value of the current intensity of the electrical circuit, the value of the current intensity of the electrical circuit being maintained below a predetermined threshold value of the current intensity of the electrical circuit, when the measured temperature value of the screwed electrical connection is greater than the predetermined temperature threshold value of the screwed electrical connection.

[0058] Advantageously, the regulation step E' ' 1 occurs between the signaling step E2 and the opening step E3. Thus, the driver is warned by a signal before the regulation of the current intensity value of the electrical circuit aimed at limiting the acceleration of the vehicle.

[0059] In the opening step E3, the switch 30 is opened, after a predetermined time, so as to protect the electrical circuit 10, when the microcontroller determines that the measured temperature value of the screwed electrical connection is greater than the calculated temperature threshold value of the screwed electrical connection.

[0060] Preferably, the predetermined duration is between 1 second and 10 minutes.

Claims

Demands

1. Method of protecting an electrical circuit (10) of an electric or hybrid vehicle comprising screwed electrical connections (51, 52, 53, 54), a battery (20) comprising a module (21, 22) and a switch (30), each of said screwed electrical connections (51, 52, 53, 54) comprising a temperature probe (41, 42, 43, 44), the method comprising the following steps: - a measurement step (El) of a temperature value for each of said screwed electrical connections (51, 52, 53, 54); - a signaling step (E2) of a failure, a signal being emitted to alert the driver of the failure when the measured temperature value of one of said screwed electrical connections (51, 52, 53, 54) is greater than a predetermined temperature threshold value of the screwed electrical connection;- an opening step (E3) of the switch (30), after a predetermined time, so as to protect the electrical circuit (10), when the measured temperature value of the screwed electrical connection is greater than the predetermined temperature threshold value of the screwed electrical connection.;

2. Method according to claim 1, characterized in that the predetermined temperature threshold value of each of said screwed electrical connections (51, 52, 53, 54) is between 50°C and 100°C.

3. A method according to claim 1 or 2, characterized in that the method also comprises, between the measurement step (E1) and the reporting step (E2), for each of said screwed electrical connections (51, 52, 53, 54): - a first calculation step (E'1) of an average temperature value Mk by the following formula: — where n is the number of said screwed electrical connections, denoted L1 for a first screwed electrical connection, L2 for a second screwed electrical connection, Li for an i-th screwed electrical connection, Lk for a k-th screwed electrical connection, up to Ln for an n-th screwed electrical connection, and Ti is the measured temperature value of the i-th screwed electrical connection Li; - a second calculation step (E'2) of a standard deviation temperature value 0 by the following formula: . / / i v1" \ - a third cr = mm 2^ m(Ti - Mk) , ke [ 1, n ] ] calculation step (E'3) of a temperature threshold value Sk by the following formula: Sk = Mk + «*<7 where a is a predetermined positive real number. - an assignment step (E'4) of the temperature threshold value Sk to the k-th screwed electrical connection Lk.

4. Method according to claim 3, characterized in that the predetermined parameter a is between 1 and 10.

5. A method according to any one of claims 1 to 4, characterized in that the predetermined duration is between 1 second and 10 minutes.

6. A method according to any one of claims 1 to 5, characterized in that the method comprises a regulating step (E” 1 ) of a value of the current intensity of the electrical circuit so as to protect the electrical circuit (10), the value of the current intensity of the electrical circuit being maintained below a predetermined threshold value of the current intensity of the electrical circuit, when the measured temperature value of the screwed electrical connection is greater than the predetermined temperature threshold value of the screwed electrical connection.

7. Method according to claim 6, characterized in that the threshold value of the predetermined current intensity of the electrical circuit is between 0 A and 500 A.

8. Computer program comprising program code instructions for performing the steps of the method for protecting an electrical circuit (10) according to any one of claims 1 to 7, when said program is running on a computer.

9. Assembly comprising an electrical circuit (10) and an electronic control unit, characterized in that the control unit comprises means for acquisition, processing by software instructions stored in memory and control means required for the implementation of the computer program according to claim 8.

10. Electric or hybrid vehicle comprising an assembly including an electrical circuit (10) and an electronic control unit according to claim 9.

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