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

Abstract

This method of managing a clutch device (19) of a mechanical air compressor (13) for supercharging an internal combustion engine (1) of a motor vehicle comprises the steps of: - determining 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; - calculating a variation of the energy accumulated in a lining of the clutch device during a time step of predetermined value, from at least one predetermined mapping representative of the variation of 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 according to the calculated variation of the accumulated energy; and, - managing the clutch device according to the updated value of the energy accumulated in the lining.

Description

DescriptionTitle of the invention: System and method for managing a clutch device of a mechanical air compressor for supercharging an internal combustion engine of a motor vehicleTechnical field

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

[0002] To drastically limit polluting emissions such as nitrogen oxides (NOx), internal combustion engines will have to operate in the future with very poor fuel mixtures.

[0003] Such an operating mode requires being able to ensure very high air flows for which it is necessary to adopt engine supercharging systems, most often double-stage.

[0004] Double- stage supercharging systems typically include 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] As the mechanical compressor is very energy intensive, its use is reserved for operating modes where the turbocharger cannot ensure supercharging alone. Furthermore, the mechanical compressor is speed-limited and must not be driven beyond a predetermined engine threshold speed. It is then necessary to use a clutch device allowing the compressor and the engine to be coupled or uncoupled.

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

[0007] This heat can lead to damage to the clutch device, especially in the area of the linings.Explanation of the invention

[0008] The invention relates to the prevention of overheating damage to the linings of clutch devices.

[0009] The invention relates to a method for managing a clutch device of a mechanical air compressor for supercharging an internal combustion engine of a motor vehicle.

[0010] The method comprises the steps of:- determining 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;- calculating a variation of the energy accumulated in a lining of the clutch device during a time step of predetermined value, from at least one predetermined mapping representative of the variation of 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 according to the calculated variation of the accumulated energy; and- managing the clutch device according to the updated value of the energy accumulated in the clutch device lining.

[0011] Such a method is intended to prevent overheating damage to the clutch device lining.

[0012] For example, in the clutch device management step, coupling of the compressor and the engine is allowed only if the value of the energy accumulated in the clutch device lining 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 mapping and a second mapping representative of the energy accumulated in the lining as a function respectively of a compression ratio of the mechanical compressor and a slipping ratio of the clutch device. Such mappings make it possible to estimate in a simple manner and with good precision the increase in the energy accumulated in the lining during the heating phase.

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

[0015] According to another feature, the calculation of the energy variation in the cooling phase is carried out using a filter of order 1, 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 that makes it possible to estimate in a simplemanner and with good accuracy the decrease in the energy accumulated in the lining during the cooling phase.

[0016] For example, the filter is initialised to an initial value corresponding to the value of energy accumulated in the lining and converges to a zero value as a function of a time constant calibrated in advance and representative of a value corresponding to the time required for the temperature of the lining to drop to a predetermined level representative of a level of energy of the lining allowing coupling of the clutch device and the engine without risk of damage to the lining.

[0017] According to another aspect, the invention relates to a system for managing a clutch device of a mechanical air compressor for supercharging an internal combustion engine of a motor vehicle.

[0018] The management system comprises means for:- determining 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;- calculating a variation of the energy accumulated in a lining of the clutch device during a time step of predetermined value, from at least one predetermined mapping representative of the variation of energy 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 according to the calculated variation of the accumulated energy;- managing the clutch device according to the updated value of the energy accumulated in the clutch device lining.

[0019] According to another aspect, the invention also relates to a motor vehicle internal combustion engine comprising a mechanical air compressor for supercharging the engine, and a system for managing a compressor clutch device as described above and implementing a management method as described above.Brief description of the drawings

[0020] Other aims, characteristics and advantages of the invention will become apparent on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings wherein:

[0021] [Fig.1] illustrates the architecture of an internal combustion engine associated with a system for managing a clutch device according to the invention;

[0022] [Fig.2] is a flow chart of a method for managing a clutch device according to the invention;Detailed description of at least one embodiment

[0023] In the example shown in Figure 1, the internal combustion engine 1 of a motor vehicle is of the spark- ignition type and comprises, by way of example, four cylinders 2 in line, a fresh air intake manifold 3, or distributor 3, an exhaust manifold 4 and a turbo-compression system or turbo-compressor 5.

[0024] The engine 1 is associated with an air intake circuit, a burnt gases 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 branch mounted in parallel, a throttle box 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 through a belt 15. The mechanical compressor 9 is mounted upstream the compressor 5a of the turbocharger 5. The second branch 10 is provided with a bypass valve 16 and leads 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 flow of the burnt gases: the exhaust manifold 4, a turbine 5b of the turbocharger 5, an emission control system 17 comprising, for example, a three-way catalyst, and a silencer 18.

[0027] In the example illustrated in Figure 1, the mechanical compressor 13 is associated with a turbocharger 5. Alternatively, it remains possible that the supercharging of the engine 1 is carried out only by a mechanical compressor 13 without a turbocharger 5.

[0028] The invention can be applied to any combustion engine associated with a mechanical compressor driven by a clutch device, in particular an electronically controlled clutch, whether the mechanical compressor is alone or associated in a double-stage supercharger with a turbocharger.

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

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

[0031] It is therefore preferable to reserve the use of the mechanical compressor 13 for operating modes where the turbocharger 5 alone cannot ensure supercharging of the engine 1 on its own.

[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. 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 speed N of the engine is less than a first predetermined fixed speed threshold N1 and when the setpoint torque Tq of the engine is greater than a first torque threshold Cl which depends on the speed N of the engine. After the compressor is activated, the speed N and the setpoint torque Tq are continuously measured. The compressor is deactivated if the speed N becomes greater than a second predetermined fixed speed threshold N2 and which is stringently greater than Nl, or if the setpoint torque Tq becomes less than a second torque threshold C2 dependent on the speed N and which is stringently less than Cl for an identical speed value N.

[0034] Thus, the activation or deactivation of the mechanical compressor in the prior art does not take into account 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 strong release of heat likely to damage the clutch device in the long term, when these coupling phases are repeated.

[0035] A strategy for managing the clutch device 19 is defined in order to protect a lining of the clutch device 19 against a risk of damage related 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 driving torque of the compressor 13 and to a speed ratio of the compressor 13, or slipping rate, that is to say to aratio between the rotational speed of the compressor 13 and that of the pulley 20.

[0038] The drive torque is divided between an inertia torque of the compressor 13, which must be accelerated from a 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 slipping 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 beginning of the slipping phase and gradually converges to 1 when the slipping phase is completed.

[0040] Outside the slipping phase, it is considered that the clutch device 19 is in a cooling phase, because it restores to its environment the heat accumulated in the slipping phase. The return of accumulated heat is mainly 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 that passes through a solenoid that controls the movement of an armature of the clutch device 19 is neglected.

[0041] It is understood from the above that, if the slipping phases are too close together, the cooling phases between two clutch phases of the compressor are not long enough to allow the heat accumulated in the clutch to be discharged. If the accumulated energy continues to increase, it eventually reaches a threshold that puts the proper operation mode of the clutch at risk.

[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 able to communicate with a high-level electronic control unit (not shown) configured to control the various components of the internal combustion engine from data collected by sensors at different locations of 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 and the pressures at the terminals of the compressor 13, which make it possible to determine the compression ratio.

[0044] The measurement 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 according to 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 mapping, stored in the memory 22 and representative of the variation of energy of the lining as a function of the state of the clutch device.

[0047] For example, the control module 26 allows coupling of the compressor 13 and the motor 1 only if 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] Figure 2 is a flow chart 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 the slipping phase, or to a cooling phase otherwise.

[0050] The method continues with a step 31 of calculating a variation of the energy accumulated in a lining of the clutch device 19 during a time step of predetermined value. The calculation of the variation of the energy accumulated in the lining uses at least one predetermined mapping, contained in the memory 22 and representative of the variation of 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 variation in energy during the heating phase is carried out using a first mapping and a second mapping representative of the energy accumulated in the lining as a function respectively of the compression ratio of the mechanical compressor and the slipping rate of the clutch device 19.

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

[0053] For example, the energy variation in the cooling phase is calculated using a filter of order 1, representative of the cooling of the lining as a function of time, in the absence of any energy input, to an initial value corresponding to the value of energy accumulated in the liningand converges to a zero value as a function of a time constant calibrated in advance and representative of a value corresponding to the time required for the temperature of the lining to drop to a predetermined level representative of a level of energy of the lining allowing coupling of the clutch device 19 and the engine 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 according to 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 gasket is initialised to 0.

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

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

Claims

Claims1.- Method of managing a clutch device (19) of a mechanical air compressor (13) intended to supercharge an internal combustion engine (1) of a motor vehicle, characterised in that it comprises the steps of:- determining a state of the clutch device (19) corresponding either to a heating phase if the clutch device (19) is in the slipping phase, or to a cooling phase otherwise;- calculating a variation of the energy accumulated in a lining of the clutch device (19) during a time step of predetermined value, from at least one predetermined mapping representative of the variation of 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) according to the calculated variation of the accumulated energy; and- managing the clutch device (19) according to the updated value of the energy accumulated in the clutch device (19) lining.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 allowed only if the value of the energy accumulated in the clutch device (19) lining is less than or equal to a predetermined energy threshold value (El).3.- Method according to claim 1 or 2, wherein the calculation of the variation in energy during the heating phase is carried out using a first mapping and a second mapping representative of the energy accumulated in the lining as a function respectively of a compression ratio of the mechanical compressor (13) and a slipping ratio of the clutch device (19).4.- Method according to claim 3, wherein the variation in energy during the heating phase is calculated by integrating the sum of a first contribution and a second contribution from the first mapping and the second mapping, respectively.5.- Method according to any one of Claims 1 to 4, wherein the calculation of the energy variation in the cooling phase is carried out using a filter of order 1, 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 wherein the filter is initialised to an initial value corresponding to the value of energy accumulated in the lining and converges to a zero value as a function of a time constant calibrated in advance and representative of a value corresponding to the time required for the temperature of the lining to drop to a predetermined level representative of alevel of energy of the lining allowing coupling of the clutch device (19) and the engine (1) without risk of damage to the lining.7.- System of managing (21) a clutch device (19) of a mechanical air compressor (13) intended to supercharge an internal combustion engine (1) of a motor vehicle, characterised in that it comprises means of:- determining 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;- calculating a variation of the energy accumulated in a lining of the clutch device during a time step of predetermined value, from at least one predetermined mapping representative of the variation of energy 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 according to the calculated variation of the accumulated energy;- managing the clutch device according to the updated value of the energy accumulated in the clutch device lining. 8.- A motor vehicle internal combustion engine (1) comprising a mechanical air compressor(13) for supercharging the engine, and a system (21) for managing a clutch device (19) of the compressor (13) according to claim 7 and implementing a management method according to any one of claims 1 to 6.

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