System and method for managing a clutch device of a mechanical air compressor intended to supercharge an internal combustion engine of a motor vehicle

Abstract

This method for managing a clutch device (19) of a mechanical air compressor (13) intended to supercharge an internal combustion engine (1) of a motor vehicle comprises steps of: determining a state of the clutch device corresponding either to a heating phase if the clutch device is in a slipping phase, or to a cooling phase otherwise; calculating a variation in the energy accumulated in a lining of the clutch device during a time step of predetermined value, from at least one predetermined map representative of the variation in energy accumulated in the lining as a function of the state of the clutch device; updating a stored value of the energy accumulated in the lining as a function of the calculated variation in the accumulated energy; and, managing the clutch device as a function of the updated value of the energy accumulated in the lining. Figure for the abstract: Figure 1

Description

Title of the invention: System and method for managing a clutch device of a mechanical air compressor intended to supercharge an internal combustion engine of a motor vehicle Technical field

[0001] The present invention relates to a method for managing a clutch device of a mechanical air compressor intended to supercharge an internal combustion engine of a motor vehicle. The invention also relates to a system for managing such a clutch device. Previous techniques

[0002] To drastically limit polluting emissions of the nitrogen oxide (NOx) type, internal combustion engines will have to operate in the future with very lean fuel mixtures.

[0003] Such operation requires the ability to ensure very high air flow rates for which it is necessary to adopt engine supercharging systems, most often dual-stage.

[0004] Dual-stage supercharging systems generally comprise a mechanical compressor associated with a turbocharger. The mechanical compressor is driven by the engine crankshaft to assist the turbocharger, i.e. to provide additional compression.

[0005] Since the mechanical compressor is very energy-intensive, its use is reserved for operating ranges where the turbocharger cannot provide supercharging alone. Furthermore, the mechanical compressor is limited in speed and must not be driven beyond a predetermined threshold engine speed. It is then necessary to use a clutch device to couple or decouple the compressor and the engine.

[0006] Such a clutch device ensures a progressive coupling between the crankshaft and the mechanical compressor. The progressiveness of the coupling is ensured by a slipping phase generating a significant quantity of heat.

[0007] This heat can lead to damage to the clutch device, particularly at the level of the linings. Statement of the invention

[0008] The invention aims to prevent damage by overheating of the linings of the clutch devices.

[0009] The subject of the invention is a method for managing a clutch device of a mechanical air compressor intended to supercharge an internal combustion engine. of a motor vehicle.

[0010] The method comprises steps of: - determination of a state of the clutch device corresponding either to a heating phase if the clutch device is in the slipping phase, or to a cooling phase otherwise; - calculation of a variation in the energy accumulated in a lining of the clutch device during a time step of predetermined value, from at least one predetermined map representative of the variation in energy accumulated in the lining as a function of the state of the clutch device; - updating a stored value of the energy accumulated in the lining of the clutch device as a function of the calculated variation of the accumulated energy; and - management of the clutch device based on the updated value of the energy accumulated in the clutch device lining.

[0011] Such a method aims to prevent damage by overheating of the lining of the clutch device.

[0012] For example, in the clutch device management step, coupling of the compressor and the engine is only permitted on condition that the value of the energy accumulated in the lining of the clutch device is less than or equal to a predetermined energy threshold value.

[0013] Advantageously, the calculation of the variation in energy during the heating phase is carried out using a first map and a second map representative of the energy accumulated in the lining as a function respectively of a compression ratio of the mechanical compressor and a slip ratio of the clutch device. Such maps make it possible to estimate simply and with good precision the increase in the energy accumulated in the lining during the heating phase.

[0014] According to one characteristic, the energy variation in the heating phase is calculated by integrating the sum of a first contribution and a second contribution resulting respectively from the first mapping and the second mapping.

[0015] According to another characteristic, the calculation of the energy variation in the cooling phase is carried out using a first-order filter, representative of the cooling of the lining as a function of time, in the absence of any energy input. Such a first-order filter represents an inexpensive means in terms of computing power which makes it possible to estimate simply and with good precision the reduction in the energy accumulated in the lining in the cooling phase.

[0016] For example, the filter is initialized to an initial value corresponding to the value

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[0023] of energy accumulated in the lining and converges towards a zero value as a function of a time constant calibrated in advance and representative of a value corresponding to the time necessary for the temperature of the lining to drop to a predetermined level representative of an energy level of the lining allowing coupling of the clutch device and the engine without risk of damage to the lining. According to another aspect, the invention relates to a system for managing a clutch device of a mechanical air compressor intended to supercharge an internal combustion engine of a motor vehicle. The management system includes means of: - determination of a state of the clutch device corresponding either to a heating phase if the clutch device is in the slipping phase, or to a cooling phase otherwise; - calculation of a variation in the energy accumulated in a lining of the clutch device during a time step of predetermined value, from at least one predetermined map representative of the variation in energy of the lining as a function of the state of the clutch device; - updating a stored value of the energy accumulated in the lining of the clutch device as a function of the calculated variation of the accumulated energy; - management of the clutch device based on the updated value of the energy accumulated in the clutch device lining. According to another aspect, the invention also relates to an internal combustion engine of a motor vehicle comprising a mechanical air compressor for supercharging the engine, and a system for managing a clutch device of the compressor as described above and implementing a management method as described above. Brief description of the drawings Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which: [Fig.l] illustrates the architecture of an internal combustion engine associated with a clutch device management system according to the invention; [Fig.2] is a flowchart of a method for managing a clutch device according to the invention; Detailed description of at least one embodiment In the example illustrated in [Fig.l], the internal combustion engine 1 of a vehicle automobile is of the spark-ignition type and includes, but is not limited to, four cylinders 2 in line, a fresh air intake manifold 3, or distributor 3, an exhaust manifold 4 and a turbo-compression system or turbocharger 5.

[0024] The engine 1 is associated with an air intake circuit, a burnt gas exhaust circuit and a fuel supply circuit (not shown).

[0025] The air intake circuit comprises from upstream to downstream in the direction of air circulation: an air filter 6, a flow meter 7, an air intake valve 8, a first 9 and a second 10 branches mounted in parallel, a throttle body 11 and the distributor 3 which can integrate a heat exchanger 12, for example an air-water exchanger. The first branch 9 leads the intake air to a mechanical compressor 13 driven by a crankshaft 14 of the engine 1 via a belt 15. The mechanical compressor 9 is mounted upstream of the compressor 5a of the turbocharger 5. The second branch 10 is provided with a bypass valve 16 and leads the air directly to the compressor 5a of the turbocharger 5 without passing through the mechanical compressor 13.

[0026] The exhaust circuit comprises from upstream to downstream in the direction of circulation of the burnt gases: the exhaust manifold 4, a turbine 5b of the turbocharger 5, a pollution control system 17 comprising for example a three-way catalyst, and a silencer 18.

[0027] In the example illustrated in [Fig.l], the mechanical compressor 13 is associated with a turbocharger 5. Alternatively, it remains possible for the supercharging of the engine 1 to be carried out solely by a mechanical compressor 13 without a turbocharger 5.

[0028] The invention finds a possible application to any combustion engine associated with a mechanical compressor driven by a clutch device, in particular electronically controlled, whether the mechanical compressor is alone or associated in a double-stage supercharging with a turbocharger.

[0029] The invention finds a particularly advantageous application in the case of hydrogen spark-ignition engines.

[0030] In the preferred embodiment illustrated in [Fig.l], the turbocharger 5 usefully reuses the energy contained in the exhaust gases to increase the mass flow rate of fresh air entering the engine: the turbine takes energy from the burnt gases passing through it and restores this energy to the compressor which compresses the intake air and increases its density. The operation of the mechanical compressor 13 uses the mechanical energy of the crankshaft 14 which degrades the efficiency of the engine 1.

[0031] It is therefore preferable to reserve the use of the mechanical compressor 13 for operating ranges where the turbocharger 5 cannot provide supercharging alone. engine management 1.

[0032] In order to be able to be activated and deactivated, the mechanical compressor 13 is provided with a clutch device 19 which makes it possible to couple and uncouple the mechanical compressor 13 and the engine 1, as required. A part of the clutch device 19 is integral with the compressor 13, and another part is integral with a pulley 20 which is coaxial with the axis of rotation of the compressor 13. This pulley 20 is driven by the crankshaft 14 of the engine by means of drive means 15, for example a belt 15 which connects the pulley 20 to a second pulley mounted at the end of the crankshaft. Thus the speed ratio between the crankshaft 14 and the pulley 20 is fixed, and the rotation of the compressor until the speed of the pulley 20 is gradually reached is ensured by closing the clutch device 19.

[0033] Conventionally, a mechanical compressor is activated when the engine speed N is lower than a first predetermined fixed speed threshold NI and when the engine setpoint torque Tq is higher than a first torque threshold Cl which depends on the engine speed N. After activation of the compressor, the speed N and the setpoint torque Tq are continuously measured. The compressor is deactivated if the speed N becomes higher than a second predetermined fixed speed threshold N2 which is strictly higher than NI, or if the setpoint torque Tq becomes lower than a second torque threshold C2 which depends on the speed N and which is strictly lower than Cl for an identical speed value N.

[0034] Thus, the activation or deactivation of the mechanical compressor in the prior art takes no account of the state of the clutch device. However, each time the compressor is coupled to the engine, the slipping phase of the clutch device causes a significant release of heat likely to damage the clutch device in the long term, when these coupling phases are repeated.

[0035] A management strategy for the clutch device 19 is defined in order to protect a lining of the clutch device 19 against a risk of damage linked to overheating.

[0036] During the slipping phase, the clutch device 19 is in a heating phase.

[0037] The heat released during the heating phase is proportional to the drive torque of the compressor 13 and to a speed ratio of the compressor 13, or slippage rate, i.e. to a ratio between the rotation speed of the compressor 13 and that of the pulley 20.

[0038] The drive torque is shared between an inertia torque of the compressor 13, which must be accelerated from zero speed to the rotation speed of the pulley 20, and a compression torque proportional to the compression ratio of the mechanical compressor 13. The compression ratio is equal to the ratio between the value of the pressure measured downstream of the compressor, divided by the value of the pressure measured upstream of the compressor, these values ​​being for example measured by pressure sensors at the terminals of the compressor 13.

[0039] The speed ratio or slip rate of the clutch device 19 is the ratio between the speed of the compressor 13 and the speed of the pulley 20. This ratio is zero at the start of the slip phase and gradually converges towards 1 when the slip phase is finished.

[0040] Outside the slipping phase, the clutch device 19 is considered to be in a cooling phase, because it releases to its environment the heat accumulated in the slipping phase. The release of accumulated heat is mainly done by conduction with the components in direct contact with the clutch device 19 and by convection with the surrounding air. It should be noted that the heat provided by the control current which passes through a solenoid which controls the movement of an armature of the clutch device 19 is neglected.

[0041] It is understood from the above that, if the slip phases are too close together, the cooling phases between two compressor clutch phases are not long enough to allow the heat accumulated in the clutch to be evacuated. If the accumulated energy continues to increase, it eventually reaches a threshold which endangers the proper functioning of the clutch.

[0042] Furthermore, the engine 1 comprises a management system 21 of the clutch device 19 comprising a memory 22, a calculation module 23, a communication module 24, a measurement module 25 and a control module 26.

[0043] The communication module 24 of the management system 21 is capable of communicating with a high-level electronic control unit (not shown) configured to control the various elements of the internal combustion engine from data collected by sensors at different locations in the engine. Preferably, the electronic control unit transmits to the management system 21 data representative of the speed of the pulley 20, the speed of the compressor 13, the pressures at the terminals of the compressor 13 which make it possible to determine the compression ratio.

[0044] The measuring module 25 is configured to determine whether or not the clutch device 19 is in the slipping phase.

[0045] The control module 26 of the management system 21 is configured to control the coupling and uncoupling of the mechanical compressor 13 and the engine 1, in particular as a function of a value of the energy accumulated in the lining of the clutch device 19.

[0046] The calculation module 23 is configured to calculate a variation of the energy accumulated in a lining of the clutch device during a time step of predetermined value and as a function of at least one predetermined map, stored in memory 22 and representative of the variation in energy of the lining as a function of the state of the clutch device.

[0047] For example, the control module 26 only authorizes coupling of the compressor 13 and the engine 1 on the condition that the value of the energy accumulated in the lining of the clutch device is less than or equal to a predetermined energy threshold value El. Alternatively, it remains possible to issue an alert message concerning the overheating of the clutch device 19 when the value of the energy accumulated in the lining of the clutch device exceeds El.

[0048] [Fig.2] is a flowchart of a method for managing a clutch device 19 according to an embodiment of the invention.

[0049] The method begins with a step 30 of determining a state of the clutch device corresponding either to a heating phase if the clutch device is in a slipping phase, or to a cooling phase otherwise.

[0050] The method continues with a step 31 of calculating a variation in the energy accumulated in a lining of the clutch device 19 during a time step of predetermined value. The calculation of the variation in the energy accumulated in the lining uses at least one predetermined map, contained in the memory 22 and representative of the variation in energy accumulated in the lining as a function of the state of the clutch device 19 determined in step 30.

[0051] Preferably, the calculation of the energy variation in the heating phase is carried out using a first map and a second map representative of the energy accumulated in the lining as a function respectively of the compression ratio of the mechanical compressor and the slip ratio of the clutch device 19.

[0052] For example, the energy variation in the heating phase is calculated by integrating the sum of a first contribution and a second contribution resulting respectively from the first mapping and the second mapping.

[0053] For example, the energy variation in the cooling phase is calculated using a first-order filter representative of the cooling of the lining as a function of time, in the absence of any energy input. This filter is in particular initialized to an initial value corresponding to the stored value of energy accumulated in the lining and converges towards a zero value as a function of a time constant calibrated in advance and representative of a value corresponding to the time necessary for the temperature of the lining to drop to a predetermined level representative of an energy level of the lining allowing coupling of the clutch device 19 and the motor 1 without risk of damage to the lining.

[0054] The management system 21 then updates a stored value of the energy accumulated in the lining of the clutch device 19 as a function of the calculated variation of the accumulated energy (step 32). The value of the energy accumulated in the lining is stored in the memory 22 of the management system 21. For example, during the first start (which excludes restarts after an engine stop controlled by a Stop & Start function) of the engine 1, the stored value of the energy accumulated in the lining is initialized to 0.

[0055] The method continues with a step 33 of managing the clutch device 19 as a function of the value updated in step 32 of the energy accumulated in the lining of the clutch device 19.

[0056] For example, during management step 33, the management system 21 only authorizes the coupling of the compressor 13 and the engine 1 on the condition that the stored value of the energy accumulated in the lining of the clutch device 19 is less than or equal to the energy threshold value EL

Claims

Claims

1. Method for managing a clutch device (19) of a mechanical air compressor (13) intended to supercharge an internal combustion engine (1) of a motor vehicle, characterized in that it comprises steps of: - determining a state of the clutch device (19) corresponding either to a heating phase if the clutch device (19) is in a slipping phase, or to a cooling phase in the opposite case; - calculating a variation in the energy accumulated in a lining of the clutch device (19) during a time step of predetermined value, from at least one predetermined map representative of the variation in energy accumulated in the lining as a function of the state of the clutch device (19); - updating a stored value of the energy accumulated in the lining of the clutch device (19) as a function of the calculated variation in the accumulated energy;and, - management of the clutch device (19) as a function of the updated value of the energy accumulated in the lining of the clutch device (19).;

2. Method according to claim 1, wherein in the step of managing the clutch device (19), a coupling of the compressor (13) and the engine (1) is only authorized on condition that the value of the energy accumulated in the lining of the clutch device (19) is less than or equal to a predetermined energy threshold value (El).

3. Method according to claim 1 or 2, in which the calculation of the energy variation in the heating phase is carried out using a first map and a second map representative of the energy accumulated in the lining as a function respectively of a compression rate of the mechanical compressor (13) and a slippage rate of the clutch device (19).

4. Method according to claim 3, in which the energy variation in the heating phase is calculated by an integration of the sum of a first contribution and a second contribution from respec- tively from the first mapping and the second mapping.

5. Method according to any one of claims 1 to 4, in which the calculation of the energy variation in the cooling phase is carried out using a first-order filter, representative of the cooling of the lining as a function of time, in the absence of any energy input.

6. Method according to claim 5 in which said filter is initialized to an initial value corresponding to the energy value accumulated in the lining and converges towards a zero value as a function of a time constant calibrated in advance and representative of a value corresponding to the time necessary for the temperature of the lining to drop to a predetermined level representative of an energy level of the lining allowing coupling of the clutch device (19) and the engine (1) without risk of damage to the lining.

7. Management system (21) of a clutch device (19) of a mechanical air compressor (13) intended to supercharge an internal combustion engine (1) of a motor vehicle, characterized in that it comprises means for: - determining a state of the clutch device corresponding either to a heating phase if the clutch device is in a slipping phase, or to a cooling phase in the opposite case; - calculating a variation in the energy accumulated in a lining of the clutch device during a time step of predetermined value, from at least one predetermined map representative of the variation in energy of the lining as a function of the state of the clutch device; - updating a stored value of the energy accumulated in the lining of the clutch device as a function of the calculated variation in the accumulated energy;- management of the clutch device based on the updated value of the energy accumulated in the lining of the clutch device.;

8. Internal combustion engine (1) of a motor vehicle comprising a mechanical air compressor (13) for supercharging the engine, and a management system (21) of a clutch device (19) of the com- presser (13) according to claim 7 and implementing a management method according to any one of claims 1 to 6.

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