Method for protecting an electrical circuit branch of a motor vehicle

Abstract

The invention relates to a method for protecting a circuit branch arranged between an electric battery and a piece of equipment, comprising - a step (E2) comprising i. comparing the temperature measured at a given point on the branch with a maximum temperature threshold, ii. then, when the measured temperature is above the threshold, actuating the opening of the branch and / or actuating deactivation of the piece of equipment, and - a step (E3) comprising i. measuring an intensity of an electric current passing through the branch of the electrical circuit, ii. then, calculating an estimated temperature at the given point, and comparing the estimated temperature with the maximum temperature threshold, iii. then, when the estimated temperature is above the maximum temperature threshold, actuating the opening of the branch and / or actuating deactivation of the piece of equipment.

Description

Description Title of the invention: Method for protecting a branch of an electrical circuit of a motor vehicle.

[0001] The invention relates to a method for protecting a branch of an electrical circuit in a motor vehicle.

[0002] Strict regulations are in place to prevent incidents related to high-voltage electrical circuits in motor vehicles. Currently, to ensure a level of safety compliant with regulations, when excessive electrical consumption is detected in an electrical circuit, the circuit is interrupted by at least one protective component, such as fuses, located at various points in the circuit.

[0003] However, the use of fuses has drawbacks. In particular, the characteristics of equipment connected to a circuit branch must be defined not only according to the vehicle's functional requirements, but also according to the characteristics of the fuse placed on that circuit branch and intended to protect it. Indeed, for a fuse to protect equipment, the equipment must withstand at least the same stresses as the fuse protecting it. However, to avoid unwanted interruptions in the electrical circuit, it is necessary to oversize the fuses, which leads to oversizing the equipment and therefore additional costs.

[0004] Furthermore, a fuse is a destructive means of protection, as the fuse is not reusable and can potentially cause a breakdown immobilizing the vehicle.

[0005] The object of the invention is to provide a device and a method for protecting a branch of an electrical circuit in a motor vehicle, overcoming the aforementioned drawbacks and improving upon known prior art protection devices and methods. In particular, the invention makes it possible to create a simple and reliable device and method that reduces manufacturing costs while complying with regulations concerning high-voltage electrical circuits in electric vehicles.

[0006] To this end, the invention relates to a method for protecting a branch of an electrical circuit in a motor vehicle, the branch of the electrical circuit being located between an electric battery and a power supply unit, the unit being capable of being controlled for its deactivation, and the branch of the circuit being equipped with a means for opening the branch of the circuit. Furthermore, the method includes - a first step of determining a given temperature measurement point and a maximum temperature threshold associated with that point, the given point being located on the branch, -a second step comprising i. measuring a temperature at a given point on the branch and comparing the measured temperature to the maximum temperature threshold, ii. then, when the measured temperature is greater than or equal to the maximum temperature threshold, commanding the opening means to open the branch and / or commanding the equipment to deactivate, and - a third step comprising i. a measurement of the intensity of an electric current passing through the branch of the electrical circuit, ii. then, depending on the measured intensity, a calculation of an estimated temperature at the given point of the branch of the electrical circuit, and a comparison of the estimated temperature to the maximum temperature threshold, iii. then when the estimated temperature is greater than or equal to the maximum temperature threshold, a command of the opening means to open the branch and / or a command to deactivate the equipment.

[0007] In one embodiment, the second and third steps are executed simultaneously or successively.

[0008] In one embodiment, at least one piece of equipment is an electric motor and / or a charger and / or a compressor and / or a current converter.

[0009] In one embodiment, the given point and the maximum temperature threshold are determined according to the physical characteristics of the components constituting the branch of the electrical circuit and / or arranged on the branch of the electrical circuit.

[0010] In one embodiment, the given point is determined to be - a point on the branch with the highest temperature when the intensity of a current flowing through the branch exceeds a given initial intensity threshold, and / or - a point on the branch that deteriorates first when the intensity of a current flowing through the branch exceeds a second intensity threshold.

[0011] In one embodiment, the means for opening the branch is a relay or a fuse or a pyroelectric switch or a transistor.

[0012] In one embodiment, the branch of the electrical circuit is arranged between an electric battery and a piece of equipment for its power supply, the equipment being capable of being controlled for its deactivation, and the device includes (i) a temperature sensor disposed on the branch of the electrical circuit, (ii) a means for measuring the intensity of a current flowing through the branch of the electrical circuit, (iii) a means for opening the branch of the circuit, and (iv) a memory, the device comprising hardware and / or software elements implementing the process according to the invention.

[0013] The invention further relates to a computer program product comprising program code instructions recorded on a computer-readable medium to implement the steps of the process according to the invention when said program is running on a computer or a computer program product downloadable from a communication network and / or recorded on a computer-readable and / or computer-executable data medium, comprising instructions which, when the program is executed by the computer, cause the computer to implement the steps of the process according to the invention.

[0014] The invention also relates to a computer-readable data recording medium on which is recorded a computer program comprising program code instructions for implementing the process according to the invention, or a computer-readable recording medium comprising instructions which, when executed by a computer, lead the computer to implement the steps of the process according to the invention.

[0015] The invention ultimately relates to a signal from a data carrier, carrying the computer program product according to the invention.

[0016] The attached drawing represents, by way of example, an embodiment of a protection device according to the invention and an execution of a protection method according to the invention.

[0017] Figure [1] illustrates a high-level architecture of a protection device according to the invention.

[0018] Figure [Fig. 2] is a flowchart of one execution method of an opening method according to the invention.

[0019] An example of an embodiment of a motor vehicle 100 equipped with a protection device 10 according to the invention is described below with reference to [Fig.1].

[0020] Figure 1 illustrates an overall architecture of a motor vehicle 100 equipped with a protection device 10 according to the invention.

[0021] The motor vehicle 100 according to the invention is equipped with a battery 1, an electrical circuit 2, and at least one piece of equipment 3 connected to the battery 1 by a branch 21 of the electrical circuit 2.

[0022] In the described embodiment, battery 1 is a high-voltage battery intended to power, in particular, an electric motor of the motor vehicle 100. In one embodiment, battery 1 is a 48-volt battery, meaning it is designed to provide a nominal voltage of 48 volts. Alternatively, the nominal voltage of battery 1 could be between 48 volts and 800 volts. Furthermore, battery 1 could be a lithium-ion battery with a nominal voltage of around 12 volts.

[0023] Equipment 3 can be, for example, an electric motor, a charger, a compressor, or a power converter. In the embodiment of the invention, equipment 3 is capable of being controlled to deactivate itself.

[0024] Branch 21 of the electrical circuit 2 includes means 22 for connecting the equipment 3 to the battery 1. An opening means 25 for branch 21 is also arranged on branch 21, between the battery 1 and the equipment 3.

[0025] The connecting means 22 are conductive parts. They can be copper plates, also called "busbars," or copper wires protected by a layer of electrical insulation; alternatively, busbars can be electrical plates made of aluminum. The term "electrical plate" refers to electrical connection plates.

[0026] The connecting means 22 are ohmic conductors. They are made of a material that heats up when an electric current passes through it.

[0027] Thus, an electrical overload or a short circuit occurring in branch 21 of electrical circuit 2 can be detected either by measuring the intensity of an electric current flowing through branch 21, or by measuring the temperature at a given point 23, this point 23 being the hottest point of branch 21 of electrical circuit 2. Alternatively, the given point 23 could correspond to a point on branch 21 of electrical circuit 2 that is not necessarily the hottest, but is the most susceptible to damage from heat. In one embodiment of the invention, a maximum temperature threshold is defined that must not be exceeded at the given point 23. Beyond this threshold, there is a risk of damage to electrical circuit 2.

[0028] The protection device 10 further includes at least one temperature sensor 24 disposed at the given point 23. In addition, the protection device 10 includes at least one means for measuring the intensity of a current flowing in the branch 21 of the electrical circuit 2.

[0029] The opening of branch 21 can be implemented by a relay, an electrical contactor, a transistor, or a pyroelectric switch. Other means of opening branch 21 25 can be considered. The opening means 25 of branch 21 is advantageously controllable by a control unit 41 of a microprocessor 4 of the protection device 10.

[0030] The opening means 25 of branch 21 can advantageously be reversible, i.e., non-destructive, as is the case for a contactor or a relay. Alternatively, destructive opening means can be considered, such as a fuse or a pyroelectric switch.

[0031] The protection device 10 includes a microprocessor 4 containing a control unit 41 for controlling components of the electrical circuit 2; in particular, the control unit 41 is capable of controlling the opening of branch 21 of the electrical circuit 2 by means of the opening means 25. In addition, the control unit 41 is capable of controlling the deactivation of the equipment 3. In one embodiment, the term "deactivation" of the equipment 3 may refer to a shutdown of the equipment 3 controlled by the control unit 41, or to an opening of an electrical circuit supplying the equipment 3.

[0032] The protection device 10, and more specifically the microprocessor 4, also includes a memory 42 capable of containing the maximum temperature threshold.

[0033] The protection device 10 also includes a microprocessor 4. The protection device 10, and particularly the microprocessor 4, enables the implementation of a method for protecting a branch 21 of an electrical circuit 2 connecting an electric battery 1 of a motor vehicle 100 to at least one piece of equipment 3, the method mainly comprising the following modules: - a first module 411 for determining a given point 23 for measuring a temperature and a maximum temperature threshold associated with the given point 23, the first module collaborating with the memory 42, - a second module 412 for measuring a temperature at a given point 23 of the branch 21, comparing the measured temperature to the maximum temperature threshold, and controlling the opening means 25 and / or deactivating the equipment 3, the second module collaborating with a temperature sensor 24, the memory 42, the opening means 25 and the equipment 3, - a third module 413 for measuring the intensity of an electric current flowing through branch 21, and for calculating an estimated temperature at a given point 23 of the branch 21 of the electrical circuit 2, for comparing the estimated temperature to the maximum temperature threshold, and for controlling the opening means 25 and / or deactivating the equipment 3, the third module collaborating with the current intensity measurement means 26, the memory 42, the opening means 25 and the equipment 3.

[0034] The motor vehicle 100, in particular the control device, preferably includes all the hardware and / or software elements configured to implement the method defined in the object of the invention or the method described below.

[0035] One execution method of the control process is described below with reference to [Fig.2]. The process comprises three steps E1 to E3. After execution of the first step E1, the process includes a loop through the second and third steps E2, E3, which can be executed successively or in parallel.

[0036] In one embodiment, the first step of the process takes place during the design of the motor vehicle 100.

[0037] In a first step El, we determine - a given point 23 for measuring the temperature of branch 21, - a maximum temperature threshold associated with the given point 23, the given point 23 being located on branch 21

[0038] The given point 23 may correspond to the point on branch 21 that reaches the highest temperature. Alternatively, the given point 23 may correspond to a point on branch 21 of the electrical circuit 2 that is not necessarily a point that reaches the highest temperatures, but which is the most likely to deteriorate under the effect of heat.

[0039] In other words, the given point 23 can be determined as being - a point on branch 21 whose temperature is highest when the intensity of a current flowing through branch 21 exceeds a first given intensity threshold, and / or - a point on branch 21 which deteriorates first when the intensity of a current flowing through branch 21 exceeds a second given intensity threshold.

[0040] The given point 23 is advantageously determined by taking into account all the components of branch 21 of the electrical circuit 2, whether they are the equipment 3 supplied by branch 21 of the electrical circuit 2 (for example a motor, a charger, etc...), or the opening means 25 (transistor, relay...), or the components which connect the different elements together.

[0041] Once the given point 23 is determined, a maximum temperature is determined which must not be reached at this point of the electrical circuit 2.

[0042] A temperature sensor 24 is then installed at the given point 23 of the branch 21 of the electrical circuit 2. In addition, a means 26 for measuring a current intensity is also disposed in the branch 21 of the electrical circuit 2, in particular at the given point 23.

[0043] Then we move on to the second and third steps E2, E3, which are executed simultaneously or successively.

[0044] In the second step E2, a temperature is measured at a given point 23 on branch 21 and compared to the previously calculated maximum temperature threshold. As long as the measured temperature remains below the maximum temperature threshold, the temperature at point 23 continues to be monitored periodically.

[0045] If the measured temperature reaches the maximum temperature threshold, the opening means 25 of branch 21 is activated. No current then flows in branch 21 of the electrical circuit 2.

[0046] Thus, in the second step, we monitor the proper functioning of branch 21 of the electrical circuit 2 by verifying that the temperature measured at the given point 23 remains below a maximum temperature threshold.

[0047] In parallel with the second step E2, or consecutively to the second step E2, in the third step E3 - we measure the intensity of the current flowing through branch 21 then - We calculate, based on the measured intensity, an estimated temperature at the given point 23 of branch 21 of the electrical circuit 2, and we compare the estimated temperature to the maximum temperature threshold.

[0048] If the estimated temperature reaches the maximum temperature threshold, equipment 3 is deactivated.

[0049] In one embodiment, several branches of the electrical circuit 2 can each be protected by a device according to the invention.

[0050] Thanks to the invention, an electrical overconsumption or a short circuit affecting branch 21 of the electrical circuit 2 can be detected by two independent measures implemented respectively in step E2 and step E3.

[0051] Furthermore, the protection of branch 21 of electrical circuit 2 is achieved by two independent technical means, an opening of branch 21 of electrical circuit 2 and / or a deactivation of the equipment 3 connected to branch 21 of electrical circuit 2.

[0052] The device according to the invention can be described as a virtual fuse implementing simultaneously - on the one hand, two independent monitoring methods: monitoring a temperature measured by a sensor, and monitoring a temperature calculated from a current intensity measurement in branch 21 of electrical circuit 2, and - on the other hand, two independent means of protection, that is to say an opening of branch 21 of electrical circuit 2, and a deactivation of equipment 3 located on branch 21 of electrical circuit 2.

[0053] Thus, independently, - the implementation of step E2 alone makes it possible to achieve a level of security corresponding to the ASIL B level of the ISO26262 standard, and - the implementation of step E3 alone makes it possible to achieve a level of security corresponding to the ASIL B level of the ISO26262 standard.

[0054] Implementing a combination of steps E2 and E3 thus makes it possible to achieve, without using a physical fuse, a level of safety corresponding to the ASIL D level of the ISO26262 standard.

[0055] The multiplicity of monitoring and protection methods, as well as the elimination of physical fuses, also makes it possible to reduce the margins applied for the sizing of the equipment of the motor vehicle, thus reducing the cost of manufacturing the motor vehicle.

[0056] Furthermore, the invention implements a non-destructive interruption of branch 21 of the electrical circuit, which reduces the cost of restoring the vehicle after opening a branch 21 of the circuit or deactivation of equipment by the protection device according to the invention.

Claims

Demands

1. A method for protecting a branch (21) of an electrical circuit (2) of a motor vehicle (100), the branch (21) of the electrical circuit (2) being disposed between an electric battery (1) and equipment (3) for its power supply, the equipment (3) being capable of being controlled for its deactivation, and the branch (21) of the circuit being equipped with a means for opening the branch (21) of the circuit, characterized in that it comprises: - a first step of determining a given point (23) for measuring a temperature and a maximum temperature threshold associated with the given point (23), the given point (23) being located on the branch (21), - a second step comprising i. measuring a temperature at a given point (23) of the branch (21) and comparing the measured temperature to the maximum temperature threshold, ii. then, when the measured temperature is greater than or equal to the maximum temperature threshold, commanding the opening means (25) to open the branch (21) and / or commanding the deactivation of the equipment (3), and - a third step comprising i. a measurement of the intensity of an electric current passing through the branch (21) of the electrical circuit (2), ii. then, depending on the measured intensity, a calculation of an estimated temperature at the given point (23) of the branch (21) of the electrical circuit (2), and a comparison of the estimated temperature to the maximum temperature threshold, iii. then when the estimated temperature is greater than or equal to the maximum temperature threshold, a command of the opening means (25) to open the branch (21) and / or a command to deactivate the equipment (3).

2. A protection method according to the preceding claim, characterized in that the second and third steps are carried out simultaneously or successively.

3. A protection method according to any one of the preceding claims, characterized in that at least one piece of equipment (3) is an electric motor and / or a charger and / or a compressor and / or a current converter.

4. A protection method according to any one of the preceding claims, characterized in that the given point (23) and the maximum temperature threshold are determined according to the physical characteristics of the components constituting the branch (21) of the electrical circuit (2) and / or arranged on the branch (21) of the electrical circuit (2).

5. A protection method according to any one of the preceding claims, characterized in that the given point (23) is determined to be - a point on branch (21) whose temperature is highest when the intensity of a current flowing through branch (21) exceeds a first given intensity threshold, and / or - a point on branch (21) which deteriorates first when an intensity of a current through branch (21) exceeds a second intensity threshold.

6. A protection method according to any one of the preceding claims, characterized in that the opening means (25) of the branch (21) is a relay or a fuse or a pyroelectric switch or a transistor.

7. A device (10) for protecting a branch (21) of an electrical circuit (2) of a motor vehicle (100), the branch (21) of the electrical circuit (2) being disposed between an electric battery (1) and a power supply device (3), the device (3) being capable of being controlled for its deactivation, the device comprising a temperature sensor (24) disposed on the branch (21) of the electrical circuit (2), a means for measuring the intensity of a current flowing through the branch (21) of the electrical circuit (2), a means for opening (25) the branch (21) of the circuit, and a memory (42), the device comprising hardware and / or software elements (2, 4, 21, 22, 23, 24, 25, 26, 41, 42, 411, 412, 413) implementing the method according to any one of claims 1 to 6.

8. Product computer program comprising program code instructions recorded on a computer-readable medium to carry out the steps of the process according to any one of claims 1 to 6 when said program is run on a computer.

9. A computer-readable data recording medium on which is recorded a computer program comprising program code instructions for implementing the method according to any one of claims 1 to 6 or according to claim 8.

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