Splittable cooling circuit for a fuel cell installed in an automobile

Abstract

The invention relates to a cooling circuit (0) for a fuel cell installed in a motor vehicle, comprising: - a first branch comprising a cell assembly (1) and a pump (9), - a second branch comprising at least one radiator (2) to which is associated at least one motor-fan assembly (2a), - a third branch comprising a liquid / liquid type heat exchanger (3a) between the coolant of the cell assembly (1) and another coolant from at least one other fluid loop (3), and a device configured to generate a flow of coolant in a first direction of circulation and to allow flow in a second direction of coolant circulation, and - a fourth branch (4) providing a possible bypass of the radiator(s) (2) by the coolant from the cell assembly (1) via the pump (9). Figure 1

Description

Title of the invention: Splittable cooling circuit for a fuel cell installed in a motor vehicle

[0001] The present invention relates to a splittable cooling circuit for a fuel cell embedded in a motor vehicle.

[0002] Engine braking is a braking method by which a vehicle is slowed down by the resistance its engine offers to its operation. This technique is associated with piston engines, which then incur significant losses due to pumping (fuel injection being cut off) and friction between the mechanical parts of the drivetrain. The term is also used for vehicles powered by electric motors when these operate as generators and recharge, for example, a battery through regenerative braking.

[0003] Engine braking is an important feature for vehicles towing and / or transporting heavy loads on steep roads because it significantly reduces the vehicle's braking work on descents. Intensive use of the friction braking system on long, steep descents quickly (within minutes) reaches its limits of effectiveness due to excessive heating, and can even lead to its destruction. Under the influence of temperature, the brake pads and drum linings can melt, while the brake fluid can vaporize. Very long descents are therefore common accident sites.

[0004] A diesel powertrain generates significant braking power: for a given engine, up to 160 kW at 3500 rpm, approximately 100 kW at 2500 rpm, and up to 50 kW at 1500 rpm. A spark-ignition powertrain of equivalent engine power delivers approximately 100 kW less at 5500 rpm and less than 20 kW at 2500 rpm.

[0005] The braking power of electric vehicles is significantly lower than that of vehicles with internal combustion engines. Electric vehicles, however, have highly efficient regenerative braking systems that can generate high braking performance, provided that the state of charge of the electrochemical energy storage system is sufficiently low, at the top of a descent, to store all the energy accumulated during braking.

[0006] Over long distances downhill, and especially on steep gradients, the state of charge of the electrochemical energy storage system can quickly reach 100%, inhibiting any opportunity for further energy storage. In this case, the vehicle's friction braking system must dissipate the energy required to braking the vehicle. At the maximum authorized total weight known as "PTRA", if the trailer brakes are limited, overheating of the vehicle's friction braking system occurs rapidly, leading to its destruction and therefore the loss of the vehicle's braking function.

[0007] The fuel cell of an electrified vehicle, on the other hand, has no intrinsic braking power. The fuel cell vehicle thus has a significant deficit compared to a vehicle with self-ignition or even spark-ignition engines, and can therefore only rely on regenerative braking and the storage of recovered energy in the electrochemical energy storage unit it carries, which is itself of much smaller size, power, capacity and energy than the electrochemical energy storage unit of an equivalent electric vehicle.

[0008] All subsystems and components of the vehicle and its powertrain are used to dissipate excess electrical power: electric heaters (electrochemical storage of motor power, fuel cell, passenger compartment), motor-fan groups of the vehicle's thermal systems (including the one or those dedicated to cooling the fuel cell), electric air conditioning compressor, electric air compressor of the fuel cell, deliberate degradation of the efficiency of the electric motor(s) and its inverter(s), etc., as well as a system dedicated to the thermal management of the fuel cell.

[0009] The fuel cell thermal management system is also used to dissipate some of the excess electrical power as thermal power, for example by activating at least one electric heater in one of the vehicle's fluid loops and bringing said fluid loop into thermal contact, via a heat exchanger between their two heat transfer fluids, with the fuel cell cooling circuit. It is therefore essential, whether the fuel cell is operational (idling) or deactivated, not to degrade the fuel cell's durability in the short or medium term by: - excessively high (or even excessively low) coolant temperatures at the inlet and / or outlet of the fuel cell, - and / or an excessively large temperature gradient between the inlet and outlet of the fuel cell coolant, - and / or an excessive flow of coolant within the stack, - and / or a level of humidity inside the stack outside the permissible limits, leading to irreversible deterioration and / or degradation, by excessive drying or humidification, of the assembly formed by the membrane and the electrodes of each cell of the stack.

[0010] These conditions reduce the availability of the fuel cell thermal management system to fuel to dissipate some of the excess electrical power. Furthermore, state-of-the-art systems do not offer optimal thermal power dissipation functionality for some of the excess electrical power.

[0011] To overcome these drawbacks, the fuel cell cooling circuit according to the invention is separable and allows the cell to be isolated from any internal heat transfer fluid passage. The fuel cell cooling circuit includes additional devices to increase the cell's cooling capacity.

[0012] When it is necessary to dissipate excess electrical power into thermal power via the fuel cell's thermal management system, the fuel cell's cooling circuit is configured such that the heat transfer fluid used in it bypasses the cell without passing through it. Under these conditions, the fuel cell, deactivated and disconnected from its cooling circuit, no longer presents constraints to the dissipation of very high thermal power through its thermal management system, which is then fully mobilized to dissipate the excess electrical power into thermal power. A hydraulic distributor is located within the cooling circuit of the fuel cell assembly and manages the distribution of flow rates (including their cancellation) in the different branches of the circuit.

[0013] A hydraulic distributor, located within the cooling circuit of the fuel cell assembly, distributes the coolant flow rates among the different branches of this circuit. In particular, this distributor prevents the simultaneous flow of coolant through several branches of this circuit and, specifically, isolates the cell assembly from any internal coolant circulation that would otherwise dissipate excess electrical power as heat in the fuel cell cooling circuit. The fuel cell thermal management system is thus freed from the constraints imposed by the cell and can dissipate a significantly larger amount of excess electrical heat to the environment outside the vehicle.

[0014] Thus, any safety risk of overheating, degradation, ignition, or boiling of the vehicle's conventional friction braking system, and of an accident, is eliminated. The vehicle therefore has the potential to travel long distances or to travel downhill without risk.

[0015] More specifically, the invention relates to a cooling circuit for a fuel cell installed in a motor vehicle, said fuel cell comprising an assembly of cells, said cooling circuit comprising: - a first branch comprising the cell assembly, and a coolant circulation pump, - a second branch comprising at least one radiator to which is associated the less a motor-fan unit to ensure dissipation to the outside air of the heat from a coolant circulating in the cooling circuit, - a third branch comprising a liquid / liquid type heat exchanger between the coolant of the cell assembly and another coolant from at least one other fluid loop of the motor vehicle chosen from: a fluid loop providing heating for a passenger compartment and a fluid loop providing heating and cooling for an electrochemical drive storage unit, and a device configured to generate a flow of coolant in a first direction of coolant circulation and to be passing in a second direction of coolant circulation opposite to the first direction of circulation, - a fourth branch providing a possible bypass of the radiator(s) by the coolant from the cell assembly via the pump, a first pressure-suppressor valve being placed at the inlet of the fourth branch in fluidic communication with a pump discharge.

[0016] According to one embodiment of the invention, the first branch further comprises a particle filter.

[0017] According to one embodiment of the invention, the device configured to generate a flow of coolant in a first direction of coolant circulation and to be conductive in a second direction of coolant circulation comprises: - a first non-return valve advantageously actuated against a return spring preferably located downstream of the heat exchanger, - a second non-return valve mounted on a branch off the first valve in a manner antagonistic to the first valve, said second valve being coupled to an auxiliary pump, - the first valve being hydraulically designed to be able to open under the action of the pump, whereas any activation of the auxiliary pump is insufficient to open the first valve, - the second valve being designed to have characteristics inferior to those of the valve and the auxiliary pump is chosen for its pressure and flow characteristics being inferior to those of the pump.

[0018] According to one embodiment of the invention, the device configured to generate a flow of coolant in a first direction of coolant circulation and to be passing in a second direction of coolant circulation includes an auxiliary pump configured to be passing against the current in the second direction of circulation when not flowing, without generating excessive pressure loss or hydraulic or electrical disturbances.

[0019] According to one embodiment of the invention, a hydraulic distributor disposed at the interface between the four branches of the cooling circuit includes a movable shutter along an axis according to a translational movement within the distributor, so that an evolution of the shutter within the distributor makes it possible to close or open the passage of the coolant through the distributor to the different branches of the cooling circuit.

[0020] According to one embodiment of the invention, the hydraulic distributor comprises: - an inlet, in fluidic communication with a main coolant outlet of the cooling circuit, - a first outlet in fluidic communication via a pipe with the second branch of the cooling circuit and at least one radiator, - a second outlet in fluidic communication with the liquid / liquid heat exchanger, and - a third outlet in fluidic communication with the fourth branch via the first pressure-sensing valve integrated into the hydraulic distributor downstream of the obturator, a second pressure-sensing valve assembled solidly to the shaft driven against a return spring being able to selectively close or open the second outlet of the distributor.

[0021] According to one embodiment of the invention, said cooling circuit includes a coolant reservoir for the cell assembly ensuring the functions of degassing the cooling circuit, thermal expansion of the liquid and pressurization of the cooling circuit at the pump inlet.

[0022] According to one embodiment of the invention, the tank includes a coolant inlet opening into the tank from an auxiliary coolant outlet of the cell assembly by way of an auxiliary branch comprising an ion exchanger or deionizer.

[0023] According to one embodiment of the invention, the reservoir has a coolant inlet opening underwater into the reservoir from an auxiliary coolant outlet of the radiator so that this portion of the liquid flow from it has not exchanged heat through the radiator with outside air.

[0024] According to one embodiment of the invention, the reservoir has a coolant outlet leading to a pump suction inlet.

[0025] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given only by way of illustration and in no way limit the invention.

[0026] [Fig. 1] The [Fig. 1] is a schematic representation of a cooling circuit for a fuel cell on board a motor vehicle according to the invention;

[0027] [Fig.2] [Fig.2] is a schematic representation illustrating in bold the circulation of the coolant circuit of the [Fig.l] when the ambient temperature is below a cold start temperature of the fuel cell or when the fuel cell is active at low load in the warm-up phase or in steady thermal regime;

[0028] [Fig.3] The [Fig.3] is a schematic representation illustrating in bold the circulation of the coolant of the circuit of the [Fig.1] when the battery is stressed under a load greater than that of the operating case of the [Fig.2];

[0029] [Fig.4] [Fig.4] is a schematic representation illustrating in bold the circulation of the coolant from the circuit of the [Fig.l] during thermal regulation of the fuel cell;

[0030] [Fig.5] The [Fig.5] is a schematic representation illustrating in bold the circulation of the coolant of the circuit of the [Fig.1] during a high need for cooling of the fuel cell;

[0031] [Fig.6] The [Fig.6] is a schematic representation illustrating in bold the circulation of the coolant of the circuit of the [Fig.1] during an exceptional need for cooling of the fuel cell;

[0032] [Fig.7] Fig.7 is a schematic representation illustrating in bold the circulation of the coolant from the circuit of the [Fig.l] when it is necessary to dissipate some of the excess electrical power of the vehicle in thermal form within the cooling circuit while the fuel cell is inactive or deactivated;

[0033] [Fig.8a][Fig.8b][Fig.8c] Figures 8a, 8b and 8c illustrate an alternative embodiment in which the translation of the pressure-static valve is carried out against a return spring assembled within the distributor around the second outlet to the third branch of the cooling circuit;

[0034] [Fig.9] Fig.9 illustrates an alternative embodiment in which a hy chamber The emergency hydraulic valve with thermostatic temperature control is located under or behind the hydraulic distributor.

[0035] Identical, similar, or analogous elements retain the same reference from one figure to another.

[0036] Figure 1 details the cooling architecture implemented to ensure the thermal management of the fuel cell consisting of a stack of cells (1) and other components necessary for its operation, not shown here. The coolant is moved within the cooling circuit (0) of the cell stack (1) by a pump (9), preferably electric. Immediately upstream of the cell stack (1), a particulate filter (11) is located within the cooling circuit (0) to protect the constituent parts of the cell assembly (1).

[0037] The cooling circuit (0) has four branches. A first branch includes the cell assembly (1), the particulate filter (11) and the pump (9).

[0038] A second branch includes at least one radiator (2) to which is attached at least one motor-fan unit or GMV (2a), the assembly ensuring the dissipation to the outside air of the heat by the coolant throughout the circuit (0).

[0039] A third branch includes a liquid / liquid type heat exchanger (3a) between the (specific) coolant of the cell assembly (1) and the coolant of at least one other fluid loop (3) of the vehicle selected from: a fluid loop providing passenger compartment heating and comprising at least one electric heater (3d) and a liquid / air type heat exchanger (3b) between this coolant and the air entering the passenger compartment and a pump (3c), and a fluid loop providing heating and cooling of the electrochemical energy storage system. The fluid loop associated with the electrochemical energy storage system includes an electric heater (3d'), a heat exchanger (3b1) between this coolant and components of the electrochemical energy storage system (in particular electrochemical cells) and a pump (3c1).The passenger compartment heating loop and the electrochemical storage loop can be arranged in parallel. Thus, the heat exchanger (3a) allows heat exchange between the coolant of the cell assembly (1) circulating in the cooling circuit (0), and the coolant of one of the at least two other fluid loops (3). A first check valve (5), advantageously actuated against a return spring, is located on this third branch, preferably downstream of the heat exchanger (3a). A second check valve (7), mounted on the branch of the valve (5) opposite the valve (5), and coupled to a second auxiliary pump (6), is located in parallel with this first check valve.The valve (5) is hydraulically designed to open under the action (pressure differential) of the pump (9), whereas any activation of the auxiliary pump (6) is insufficient to open it. The valve (7) is designed to have lower characteristics (full-opening flow rate, return spring set pressure) than the valve (5), and the pump (6) is chosen for its lower characteristics (pressure jump and flow rate) than the pump (9). As an alternative to placing the valve (5) on the third branch, and the valve (7) and pump (6) in a bypass of the valve (5), the pump (6) is placed on the third branch in the same orientation as in [Fig. 1] and so as to allow counter-current flow when not in operation, without generating excessive pressure loss or hydraulic or electrical disturbances.

[0040] A fourth branch (4) provides a possible bypass of the radiator(s) (2) by the coolant from the cell assembly (1). At the inlet of the fourth branch in fluidic communication with the discharge of the pump (9) is disposed a pressure-static valve (105) integrated into a hydraulic distributor (100) and moved for example against a return spring by the pressure exerted at the outlet of the cell assembly (1) by the pump (9) in operation.

[0041] A hydraulic distributor (100) is located at the interface between these four branches of the cooling circuit (0). The hydraulic distributor includes a shutter (101) driven, for example, by a stepper motor (102) along an axis (103) in a translational movement within the distributor (100). The movement of the shutter (101) within the distributor (100) allows the passage of coolant through the distributor (100) to the different branches of the circuit (0) to be closed or opened. Thus, the hydraulic distributor (100) comprises: an inlet, in fluidic communication with the main coolant outlet of the circuit (0), a first outlet, in fluidic communication via a pipe (8) with the second branch of the circuit (0) and at least one radiator (2), a second outlet, in fluidic communication with the liquid / liquid heat exchanger (3a); a third outlet, in fluidic communication with the fourth branch (4) via the pressure-controlled valve (105) integrated into the hydraulic distributor (100) downstream of the obturator (101), a pressure-static valve (104) assembled securely to the shaft (103), moved for example against a return spring and able, under certain operating conditions explained later, to close or open the second outlet of the distributor (100).

[0042] The cooling circuit (0) also includes a coolant reservoir (14) for the cell assembly (1) which performs the functions of degassing the circuit (0), thermally expanding the liquid, and pressurizing the circuit (0) at the inlet of the pump (9). The reservoir (14) provides two inlets for the coolant: one opening into the tank (14) (above the maximum liquid level in the tank (14)), coming from an auxiliary coolant outlet of the cell assembly (1) by an auxiliary branch (12) of the circuit (0) carrying an ion exchanger or deionizer (13) in order to preserve a very low electrical conductivity of the coolant within the circuit (0) and passing through the cell assembly (1); the other opening underwater into the reservoir (14) (below the minimum liquid level in the reservoir (14)), coming from an auxiliary coolant outlet of the radiator (2) located within the radiator (2) so that this portion of liquid flow that originates from it has not exchanged calories through the radiator (2) with the outside air moved through the radiator (2) by the forward movement of the vehicle and / or the activation of the GMV(s) (2a).

[0043] The reservoir (14) has a coolant outlet leading to a suction inlet of the pump (9).

[0044] Figure 2 illustrates the configuration taken by the circuit (0) when: either the fuel cell is inactive, the ambient temperature (T°amb) is negative and lower than the cold start temperature of the cell (T°fcs for "freeze cold start" according to Anglo-Saxon terminology), therefore T°amb < T°fcs, such that it is necessary to heat the cell and in particular the assembly of cells (1) by an external source namely the heater (3d); either the fuel cell is active under low load, in the temperature rise phase or in a steady thermal regime, such that the heat transfer fluid pump (9) is under low stress (requirement of a small flow of coolant within the cell assembly (1)).

[0045] In both cases, the pump (9) is activated with a set coolant flow rate within the cell assembly (1) in order to optimize heat exchange: on the one hand, within the liquid / liquid exchanger (3a) from on the one hand the fluid of the fluidic loop (3) heated by the electric heater (3d) to raise the temperature of the passenger compartment and / or the electrochemical storage of the drive and of the cell assembly (1), to on the other hand the coolant of the cell assembly (1) or, within the liquid / liquid exchanger (3a) from the coolant of the cell assembly (1) to the fluid of the fluidic loop (3) to at least contribute to raising the temperature of the passenger compartment and / or the electrochemical drive storage, the electric heater (3d) being inactive or under low load in order to reduce its electrical consumption; and on the other hand, within the cell assembly (1), between the coolant of the cell assembly heated through the exchanger (3a) and the constituent elements of the cell assembly (1).

[0046] The hydraulic distributor (100) is configured such that its first outlet is closed by the valve (101) and its second outlet is open. The set pressure of the valve (105) (for example, of its spring) is defined and adjusted so that in this configuration (in particular, once the setpoint coolant flow rate is established within the cell assembly (1)) the pressure exerted at the outlet of the cell assembly (1) by the pump (9) in the hydraulic distributor (100) upstream of the valve (105) is insufficient to cause Even partial opening means that the valve (105) is closed and prevents the coolant from the cell assembly (1) from passing through the distributor (100) to and through the branch (4). The valve (105) set pressure is also chosen to protect the heat exchanger (3a) from excessive flow through it and / or excessive pressure at its inlet, generated according to the operating point of the pump (9). This case is addressed by the configuration shown in [Fig. 3]. The closed position of the valve (105) essentially forces the coolant from the cell assembly (1) through the third branch of the circuit (0) when the obturator (101) blocks the passage through the distributor (100) to its first outlet.

[0047] Furthermore, the pressure differential across the valve (5) is sufficient to cause it to open, due to the upstream coolant pressure at the outlet of the heat exchanger (3a) and the vacuum and suction exerted by the pump (9). Thus, the entire flow of coolant from the pump (9) and the cell assembly (1) passes through the hydraulic distributor (100) from its inlet to its second outlet, exclusively through the third branch of the circuit (0) and the heat exchanger (3a) thanks to the open position of the valve (5). The auxiliary pump (6) is inactive and the valve (7) is closed, held against its seat by the pressure exerted by the coolant from the heat exchanger (3a) and secondarily by the vacuum exerted by the pump (9) through the pump (6).Following the valve (5), the coolant is drawn in by the pump (9) and discharged to the inlet of the cell assembly (1) via the particulate filter (11). Finally, a small portion of the coolant flow passing through the cell assembly (1) exits through the branch (12) and enters the reservoir (14), the outlet of which is also located at the inlet, at the suction of the pump (9).

[0048] The circuit (0) occupies the configuration described in [Fig. 3] if the fuel cell is subjected to a higher load requiring a greater flow rate of coolant within the cell assembly (1). The pump (9) is then activated with a correspondingly higher setpoint, opening the valve (105) and allowing access for the coolant from the cell assembly (1) through the branch (4). This reduces the flow rate of coolant through and the liquid pressure at the inlet of the heat exchanger (3a), protecting the latter from any degradation and any risk of internal or external leakage.

[0049] Figure 4 describes the configuration taken by the circuit (0) when it is necessary to regulate to a given temperature setpoint (for a low or medium load applied to the fuel cell) the temperatures of the coolant at the inlet and outlet of the cell assembly (1) as well as the temperature difference across the cell assembly (1), so that then the full cooling requirement, The coolant supplied by the radiator(s) (2), whether or not assisted by a GMV (2a), is not required. In this case, the obturator (101) occupies an intermediate position within the hydraulic distributor (100), partially opening the passage of the coolant admitted into the distributor (100) to the first and third outlets, i.e., to the radiator(s) (2) via the pipe (8), and to branch (4) respectively, the second outlet to the third branch and the heat exchanger (3a) of circuit (0) remaining open. Even a partial opening of the first outlet of the distributor (100) allows the entry (2b) of coolant from the radiator(s) (2), without having exchanged heat with the outside air, into the reservoir (14).

[0050] The coolant flow in the pipe (15), upstream of the outlet of the third branch of the circuit (0), is then a mixture between a portion of coolant flow from branch (4), modulo the position of the valve (105), without having undergone heat exchange with the external environment, and a portion of coolant flow from the second branch after having undergone heat exchange with the external environment through the radiator(s) (2).Thus, the coolant flow rate in the pipe (15), upstream of the outlet of the third branch of the circuit (0), is, for a given position of the valve (105), independent of the position of the internal shutter (101) of the hydraulic distributor (100): the position of the shutter (101) between the first and third outlets only changes its composition (distribution between the portions of flow from branch (4) and flow from the radiator(s) (2)) and therefore its temperature. Thus, the shutter (101) occupies a position within the hydraulic distributor (100) that opens the first outlet more and closes the third outlet more (even to 100% open and 100% closed respectively, as illustrated in Figures 5 or 6) as the temperatures of the coolant at the inlet and outlet of the cell assembly (1) are high and increase.Conversely, the obturator (101) occupies within the hydraulic distributor (100) a position which closes the first outlet more and opens the third outlet more (or even 100% closed and 100% open respectively, as illustrated in figures 2 or 3) as the temperatures of the coolant at the inlet and outlet of the cell assembly (1) are low and decrease.

[0051] Furthermore, the temperature difference across the cell assembly (1), between the inlet and outlet of the cell assembly (1), directly influences the coolant flow rate setpoint across the cell assembly (1) applied to the pump (9). In this configuration, the third branch remains active (for example, if it is necessary to heat the passenger compartment using the heat dissipated in its coolant by the cell assembly (1)) and the valve (5) is open, so that The flow rate of coolant admitted into the inlet of the pump (9) (and therefore into the inlet of the cell assembly (1) via the filter (11)) is the sum of the flow rates from the branch (4) modulo the position of the valve (105), the radiator(s) (2)) and the third branch via the valve (5).

[0052] In case of a significant need for cooling, the circuit (0) adopts the configuration described in [Fig.5] where the obturator (101) in the hydraulic distributor (100) occupies a position closing any passage of coolant flow via the bypass branch (4) of the radiator(s) (2), and fully freeing the first outlet in fluidic communication via a pipe (8) with the second branch of the circuit (0) and at least one radiator (2), so that the coolant flow through the pipe (15) is 100% from the radiator(s) (2). With the branch (4) closed by the obturator (101), the valve (105) located in the distributor (100) immediately downstream of the obturator (101) is no longer subjected to the pressure of the coolant prevailing in the distributor (100), resulting from the assembly of cells (1) and the pump (9), and adopts its rest position resting on its seat.However, with the third branch remaining active (for example, if it is necessary to heat the passenger compartment using the heat dissipated in its coolant by the cell assembly (1)) and the valve (5) being open, the flow rate of coolant admitted into the inlet of the pump (9) (and therefore into the inlet of the cell assembly (1) via the filter (11)) is the sum of the flow rate from the radiator(s) (2) and the flow rate from the third branch carrying the heat exchanger (3a) via the valve (5).

[0053] In case of very high or exceptional cooling requirements, the circuit (0) adopts the configuration described in [Fig.6] where the shutter (101) occupies the same position as in [Fig.5], completely blocking the third outlet in fluidic communication with the fourth branch (4) and totally freeing the first outlet in fluidic communication by a pipe (8) with the second branch and at least one radiator (2), and where the third branch is also blocked by the closure of the second outlet of the distributor (100) by the pressure-static valve (104) integral with the shaft (103) driven by the stepper motor (102) of the distributor (100), for example if it is no longer necessary to heat the passenger compartment by the calories dissipated in its coolant by the assembly of cells (1), for example by an ambient temperature above a predetermined threshold, and / or if it is no longer necessary to heat the electrochemical motor storage by the same means, for example in the case where its temperature has reached and exceeded a predetermined threshold.In this configuration, the flow of coolant admitted into the inlet of the hydraulic distributor (100) is entirely directed through the radiator(s) (2) and the liquid admitted into the inlet of the pump (9) (and therefore into the inlet of the cell assembly (1) via the filter (11)) is entirely and solely the flow from the radiator(s) (2).

[0054] In the case where it is necessary to dissipate at least part of the excess electrical power of the vehicle by dissipating it as thermal power within the thermal management system of the fuel cell and while the fuel cell is inactive or deactivated, [Fig. 7] shows the configuration then assumed by the circuit (0). In this state, the excess electrical power is dissipated as heat by the heater (3d) in the coolant of the fluidic loop (3) driven by the pump (3c), and the associated heat is transferred through the liquid / liquid heat exchanger (3a) to the coolant of the fuel cell, driven within the circuit (0) by the activation of the pump (6) and the open position of the non-return valve (7).

[0055] However, in this operating mode, when the fuel cell is inactive or deactivated, it is advisable that this coolant not pass through the cell assembly (1) of the fuel cell, so as not to degrade its constituents or impair their durability, or that of the fuel cell, in the short or medium term, due to excessively high or low coolant temperature conditions at the inlet and / or outlet of the fuel cell and the cell assembly (1) and / or excessively high temperature gradients between the inlet and outlet of the coolant of the cell assembly (1) and / or excessive coolant flow within the cell assembly (1) and / or humidity outside the permissible limits internally of the cell assembly (1), these conditions leading to irreversible deterioration and / or degradation,by excessive drying or wetting of the assembly formed by the membrane and electrodes of each cell in the fuel cell cell assembly (1).

[0056] As a result, the pump (9) is inactive and the obturator (101) in the hydraulic distributor (100) occupies a position completely closing the inlet in the distributor (100) to the coolant, completely closing the third outlet in fluidic communication with the fourth branch (4) and totally freeing the first outlet in fluidic communication through the pipe (8) with the second branch and at least one radiator (2).At the same time, with the pump (9) inactive, the check valve (5) is in its rest position, closed, but the activation of the pump (6) is sufficient to cause the check valve (7) positioned in parallel with the valve (5) to open, and to cause the pressure-sensing valve (104) to open. This valve is then moved against its return spring and, under these conditions and thanks to the activation of the pump (6), releases the second outlet of the distributor (100) through which the coolant, propelled into the circuit (0) by the activation of the pump (6) and the opening of the valve (7), enters the hydraulic distributor (100). The position of the obturator (101) allows the coolant to pass only through the first outlet of the distributor (100), through the second branch of the circuit (0) and the... at least one radiator (2). The pump (6) then draws the coolant from the radiator(s) (2) and the reservoir (14) via the branch (2b) from the radiator(s) (2), and discharges it through the open valve (7) into the third branch of the circuit (0), against the direction of flow illustrated in Figures 2 to 5, through the liquid / liquid heat exchanger (3a), the valve (5) being closed and the activation of the pump (6) being insufficient to cause it to open. Thus, the position then taken by the obturator (101) in the hydraulic distributor (100) and the deactivation of the pump (9) allow the coolant from the circuit (0) to bypass the cell assembly (1). The first branch is then disconnected from the circuit (0) and in particular no flow of coolant then passes through the cell assembly (1).

[0057] Thus in this configuration, the thermal power from the excess electrical power via the heater (3d) is transferred via the exchanger (3a) as heat into the coolant of the circuit (0), the configuration of which in this operating mode allows a very large amount of thermal power from excess electrical power to be dissipated to the environment outside the vehicle, since this thermal management system has been sized (radiators (2), GMV (2a)) to dissipate, taking into account the efficiency of the fuel cell subsystem, a thermal power greater than the maximum electrical power delivered by the cell (for example, 180 to 200kW of thermal power in severe ambient conditions, for an electrical power of 150kW supplied by the fuel cell subsystem).A large amount of heat and thermal power can thus be dissipated through the exchanger (3a) in the circuit (0) and therefore a large amount of electrical power can be dissipated, since the configuration of the circuit (0) shown in [Fig.7] makes it possible to overcome the constraints imposed by the assembly of cells (1) of the fuel cell, which the coolant of the circuit (0) then bypasses without passing through it.

[0058] In the case, similar to that explained in [Fig. 7], where it is necessary to dissipate at least part of the vehicle's excess electrical power by dissipating it as thermal power within the fuel cell's thermal management system, and while the fuel cell is active at idle (so as not to deactivate it and have to reactivate it quickly, as deactivation / activation cycles damage the internal components of the cell assembly (1)), it is then imperative that the coolant from circuit (0) flow through the cell assembly (1). It is then no longer possible for the coolant from circuit (0) to bypass the cell assembly (1) via the configuration shown in [Fig. 7], and circuit (0) adopts a configuration similar to that described in [Fig. 5]. In this operating mode, where, analogously to what was presented in the context of the [Fig.7], at least part of the excess electrical power of the vehicle is dissipated as thermal power through the exchanger (3a) within the thermal management system of the fuel cell and more particularly to the coolant of the circuit (0), the hot coolant having passed through the third branch and charged with calories dissipated by the fluid loop (3) through the exchanger (3a) is mixed, upstream of the inlet of the pump (9), with the cold coolant from the radiator(s) (2).The position setpoint of the shutter (101) in the hydraulic distributor (100) and the coolant flow setpoint of the pump (9), defined by criteria of coolant temperature at the inlet of the cell assembly (1) and of coolant temperature difference between the outlet and inlet of the cell assembly (1), are then greater than those which would have been required by the thermal management of the fuel cell alone and in particular the cell assembly (1), in order: that a coolant at an already mixed temperature, resulting from the mixing of the hot coolant from the exchanger (3a) with the cold coolant from the radiator(s) (2), is introduced at the inlet of the cell assembly (1) to take into account the additional heat dissipation which constitutes, via the exchanger (3a), the fluidic loop (3) of the vehicle.The assembly (1) is therefore not the only source of heat that must be dissipated to the outside environment via the radiator(s) (2) and the GMV (2a).

[0059] Conversely, if the cooling provided to the circuit coolant (0) by the implementation of the radiator(s) (2) and / or the GMV(s) (2a) is greater (in absolute value) than the heat dissipation in this liquid by the cell assembly (1) and by the fluidic loop (3) through the exchanger (3a), the position setpoints of the shutter (101) in the distributor (100) and of the liquid flow rate of the pump (9) will be adapted (and in particular reduced) so as to respect the criteria of liquid temperature at the inlet of the cell assembly (1) and of liquid temperature difference between the outlet and inlet of the cell assembly (1).

[0060] Thus, it is possible to dissipate a significant amount of thermal power in the circuit (0) without disconnecting the fuel cell which is then active at idle.

[0061] Figures 8a-8c and 9 illustrate two complementary variants enabling the functionality of the fuel cell cooling circuit (0) to be maintained in the event of failure of the hydraulic distributor (100).

[0062] Thus, [Fig. 8a] shows that within the hydraulic distributor (100), the translation of the pressure-seal valve (104) along the axis (103) by the action of the stepper motor (102) is carried out against a return spring (106) assembled within the distributor (100) around the second outlet to the third branch of the circuit (0), of so that: in the configurations illustrated in figures 2 to 5, the pressure-static valve (104) is not in contact with the return spring (106) which is then relaxed and free, in accordance with [Fig.8a]; in the configuration described in [Fig.8b], the pressure-static valve (104) is in the process of translation between the positions respectively illustrated in figures 5 and 6 or 7 and comes into contact without yet exerting pressure against the return spring (106); in the mode of operation described in figures 6 or 7 and in accordance with [Fig.8c], the pressure-static valve (104) then completely closing the second outlet of the hydraulic distributor (100) to the third branch of the circuit (0) is totally in contact against and puts under maximum pressure (without it being in contiguous coils) the return spring (106); In the event of failure of the hydraulic distributor (100), for example of the electrical control of the stepper motor (102) or of the motor (2) itself, while the pressure-sensing valve (104) occupies the position illustrated in [Fig.8c], the return spring (106) relaxes the pressure then exerted by the valve (104) and pushes it back along the axis (103) without changing the position of the obturator (101), in accordance with the position taken in [Fig.8b] by the valve (104), so as to free access to the second outlet to the third branch of the circuit (0).

[0063] Figure 9 illustrates the implementation of an emergency hydraulic chamber (130), located below or behind the hydraulic distributor (100), operated by a double-acting thermostatic valve (120) with two valves (121, 128), and whose access from the distributor (100) is controlled by a single-acting thermostatic valve (110) with one valve (111), the temperature-sensitive element (112) of which is irrigated by the coolant from the cell assembly (1) and entering the distributor (100) through its inlet. In particular, the temperature-sensitive element (112) is located inside the distributor (100) so as to: be thermosensitized by the coolant from the cell assembly (1) and heading towards the second outlet and the third branch of the circuit (0); never obstruct in its travel the shaft (103) and the pressure-sensing valve (104) within the hydraulic distributor (100), regardless of the position of the valve (111) which, when the thermostatic valve (110) is opened, moves against a return spring (115) which bears, at the other end, against the bracket (116) of the thermostatic valve (110) whose progressive opening is achieved by lifting, against the flange (114) of the bracket (116), its shaft (113) which is integral with the thermosensitive element (112) whose internal material expands under the effect of the temperature of the coolant flowing through it.

[0064] The diameter of the valve (111) of the thermostatic valve (110) is greater than the equivalent hydraulic diameter of the coolant passage, for compensate for the pressure loss across the valve (110).

[0065] The opening temperature of the thermostatic valve (110) is chosen so as to remain closed during the nominal operation of the hydraulic distributor (100) and to open passively only when the coolant temperature from the cell assembly (1) is abnormally high for the nominal operation of the thermal management system and the fuel cell, but so as to open at a coolant temperature from the cell assembly (1) lower than that associated with the occurrence of abnormal operation or degradation of the cell assembly (1). For example, the initial opening temperature of the thermostatic valve (110) is set at a value greater than or equal to 85°C.

[0066] When access is granted by opening the thermostatic valve (110), the valve (111) ordinarily blocking this access having then lifted from its seat under the action of the shaft (113) against the spring (115), the coolant flows into the hydraulic chamber (130) in which the double-acting thermostatic valve (120) is located. This valve and the configuration of the chamber (130) are designed so that, at rest, the main valve (121) of the valve (120) blocks the passage of the coolant to a conduit (131) in fluidic communication with the pipe (8), while the secondary valve (128) allows the passage of the coolant to a conduit (132) in fluidic communication with the branch (4) of the circuit (0).

[0067] The thermostatic valve (120) comprises a temperature-sensitive element (122) irrigated by the coolant from the thermostatic valve (110): the internal material of the element (122), upon expansion, causes a shaft (123) to translate against a flange (124) of a bracket (126), against which a return spring (125) bears, thus regulating the stroke of the main valve (121) under the effect of the temperature of the coolant irrigating the temperature-sensitive element (122). A shaft (127) is integral with the temperature-sensitive element (122) or the valve (121) and carries the secondary valve (128), against which a return spring (129) is fixed, also resting against one end of the shaft (127). As the valve (120) is progressively opened, the valve (121) gradually releases the passage of coolant from the thermostatic valve (110) to the conduit (131) and the secondary valve (128) gradually closes the passage to the conduit (132).When the valve (120) is fully open, the valve (121) completely opens the passage to the conduit (131) and the valve (128) completely closes the passage to the conduit (132) by pressing against the inner wall of the part of the chamber (130) opening into the conduit (132).

[0068] As with the thermostatic valve (110), the diameters of the valves (121) and (128) of the valve (120) are respectively larger than the hydraulic diameters equivalents of the coolant passages, to compensate for the pressure drop of the valve (120).

[0069] The full opening temperature of the thermostatic valve (120) is chosen to be lower than the opening temperature of the valve (110) so as to cause the rapid and wide opening (modulo the response time of the thermosensitive element (122)) of the valve (120) as soon as the coolant from the thermostatic valve (110) arrives in the chamber (130).

[0070] Thus, in the event of a proven failure (given the then high temperature of the coolant from the cell assembly (1), capable of causing the opening of the thermostatic valve (110)) of the hydraulic distributor (100), the thermostatic valve (120), located in the emergency hydraulic chamber (130) arranged hydraulically in bypass of the distributor (100), takes over from the distributor (100) and ensures in its place the thermoregulation of the cell assembly (1) of the fuel cell.

Claims

Claims

1. Cooling circuit (0) for a fuel cell installed in a motor vehicle, said fuel cell comprising an assembly of cells (1), characterized in that said cooling circuit (0) comprises: - a first branch comprising the assembly of cells (1), and a pump (9) for circulating coolant, - a second branch comprising at least one radiator (2) with which at least one motor-fan unit (2a) is associated to ensure dissipation to the outside air of the calories of a coolant circulating in the cooling circuit (0),- a third branch comprising a liquid / liquid type heat exchanger (3a) between the coolant of the cell assembly (1) and another coolant of at least one other fluid loop (3) of the motor vehicle chosen from: a fluid loop ensuring the heating of a passenger compartment and a fluid loop ensuring the heating and cooling of an electrochemical motor storage device, and a device configured to generate a flow of coolant in a first direction of circulation of the coolant and to be passing in a second direction of circulation of the coolant opposite to the first direction of circulation, - a fourth branch (4) providing a possible bypass of the radiator(s) (2) by the coolant coming from the cell assembly (1) via the pump (9),a first pressure-static valve (105) being arranged at the inlet of the fourth branch in fluid communication with a discharge of the pump (9).,

2. Cooling circuit according to claim 1, characterized in that the first branch further comprises a particle filter (11).

3. Cooling circuit according to claim 1 or 2, characterized in that the device configured to generate a flow of coolant in a first direction of circulation of the coolant and to be passing in a second direction of circulation of the coolant comprises: - a first non-return valve (5) advantageously moved against a return spring preferably downstream of the heat exchanger (3a), - a second non-return valve (7) mounted on a bypass branch of the first valve (5) antagonistically to the first valve (5), said second valve being coupled to an auxiliary pump (6), - the first valve (5) being hydraulically designed to be able to open under the action of the pump (9) while any activation of the auxiliary pump (6) is insufficient to open the first valve (5), - the second valve (7) being designed to have characteristics lower than those of the valve (5) and the auxiliary pump (6) is chosen for its pressure and flow characteristics lower than those of the pump (9).

4. Cooling circuit according to claim 1 or 2, characterized in that the device configured to generate a flow of coolant in a first direction of circulation of the coolant and to be passing in a second direction of circulation of the coolant comprises an auxiliary pump (6) configured to be passing counter-current in the second direction of circulation when not delivering, without generating excessive pressure drop or hydraulic or electrical disturbances.

5. Cooling circuit according to any one of claims 1 to 4, characterized in that a hydraulic distributor (100) arranged at the interface between the four branches of the cooling circuit (0) comprises a shutter (101) movable along an axis (103) according to a translational movement within the distributor (100), so that an evolution of the shutter (101) within the distributor (100) makes it possible to close or release the passage of the coolant through the distributor (100) towards the different branches of the cooling circuit (0).

6. Cooling circuit according to claim 5, characterized in that the hydraulic distributor (100) comprises: - an inlet, in fluid communication with a main coolant outlet of the cooling circuit (0), - a first outlet in fluid communication via a pipe (8) with the second branch of the cooling circuit (0) and the at least one radiator (2), - a second outlet in fluid communication with the liquid / liquid heat exchanger (3a), and - a third outlet in fluid communication with the fourth branch (4) via the first pressure-activated valve (105) integrated in the hydraulic distributor (100) downstream of the shutter (101), a second pressure-activated valve (104) securely assembled to the axis (103) moved against a return spring capable of selectively closing or releasing the second outlet of the distributor (100).

7. Cooling circuit according to any one of claims 1 to 6, characterized in that it comprises a reservoir (14) of cooling liquid for the assembly of cells (1) ensuring the functions of degassing the cooling circuit (0), thermal expansion of the liquid and pressurization of the cooling circuit (0) at the inlet of the pump (9).

8. Cooling circuit according to claim 7, characterized in that the reservoir (14) comprises a coolant inlet opening into the air into the reservoir (14) from an auxiliary coolant outlet of the cell assembly (1) via an auxiliary branch (12) comprising an ion exchanger or deionizer (13).

9. Cooling circuit according to claim 7 or 8, characterized in that the tank (14) comprises a coolant inlet opening underwater into the tank (14) from an auxiliary coolant outlet of the radiator (2) so that this portion of the liquid flow which comes from it has not exchanged calories through the radiator (2) with outside air.

10. Cooling circuit according to any one of claims 7 to 9, characterized in that the reservoir (14) comprises a coolant outlet opening towards a suction inlet of the pump (9).

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