초록 ▼

Device for controlling the speed of a turbosupercharger in an internal-combustion engine comprising: a compressor, a turbine, a wastegate valve; the control device comprising: a calculating unit, which receives at input a set of parameters comprising a pre-set limit speed of rotation of the turbosup

Device for controlling the speed of a turbosupercharger in an internal-combustion engine comprising: a compressor, a turbine, a wastegate valve; the control device comprising: a calculating unit, which receives at input a set of parameters comprising a pre-set limit speed of rotation of the turbosupercharger, the air pressure measured at input to the compressor, and the mass flow rate of the compressor, and is designed to process the parameters for determining, through a predetermined map that characterizes operation of the compressor, a limit supercharging pressure correlated to the air pressure obtainable at output from the compressor in a condition of rotation of the turbine at a speed substantially equal to the preset limit speed of rotation; a comparison unit designed to verify whether a required objective supercharging pressure satisfies a preset relation with the calculated limit supercharging pressure; and a driving unit, which, in the case where the preset relation is satisfied, is designed to govern the wastegate valve for controlling the speed of the turbine as a function of the limit supercharging pressure so as to limit the speed of rotation of the turbosupercharger to a value substantially equal to the limit speed of rotation.

대표청구항 ▼

The invention claimed is: 1. A method (1) for controlling the speed of rotation of a turbosupercharger (7) in an internal-combustion engine (2) of a motor vehicle comprising: a compressor (9), a turbine (8) for driving the compressor (9) in rotation under the action of the exhaust gases of the engi

The invention claimed is: 1. A method (1) for controlling the speed of rotation of a turbosupercharger (7) in an internal-combustion engine (2) of a motor vehicle comprising: a compressor (9), a turbine (8) for driving the compressor (9) in rotation under the action of the exhaust gases of the engine (2); and a wastegate valve (12) for regulating the flow rate of the exhaust gases provided at input to the turbine (8) for controlling the speed of rotation of the turbine (8) itself as a function of an objective supercharging pressure (POB) which indicates the value of the supercharging pressure that, on the basis of an objective map of the engine and of a set of parameters of engine is required at output from said compressor (9); said method being characterized in that it comprises the steps of: establishing a limit speed of rotation (Ntc) of the turbosupercharger (7); and during control of the speed of rotation of the turbine (8) performed through said wastegate valve (12), implementing the following steps: measuring the pressure (PAMB) of the air taken in at input by the compressor (9); determining the mass flow rate (QAH) of the compressor (9); calculating, through a predetermined map (15a) that characterizes operation of the compressor (9) and as a function of the preset limit speed of rotation (Ntc), of the measured air pressure (PAMB), and of the mass flow rate (QAH), a limit supercharging pressure (SP1), which is correlated to the air pressure obtainable at output from the compressor (9) when the turbine (8) turns at a speed substantially equal to said pre-set limit speed (Ntc); verifying whether the required objective supercharging pressure (POB) satisfies a pre-set relation with said calculated limit supercharging pressure (SP1), said preset relation being satisfied when said required objective pressure (POB) is higher than said limit supercharging pressure (SP1); and in the case where said relation is satisfied, actuating said wastegate valve (12) for controlling the speed of rotation of the turbine (8) as a function of the limit supercharging pressure (SP1) so as to limit the speed of rotation of said turbosupercharger (7) to a value substantially equal to said preset limit speed (Ntc): in the case where said relation is not satisfied, actuating said wastegate valve (12) for controlling the speed of rotation of the turbine (8) as a function of the objective supercharging pressure (POB) so as to achieve a supercharging corresponding to the objective pressure (POB)itself. 2. The method according to claim 1,characterized in that said predetermined map (15a) comprises a plurality of characteristic curves of operation (Ci), each of which is associated to a respective speed (Vtc) of rotation of the compressor (9) and is designed to yield a maximum compression ratio (RM) of the compressor (9) itself as a function of its mass flow rate (QAH) and of the preset limit speed (Ntc); said step of calculating the limit supercharging pressure (SP1) comprises the step of identifying, on said pre-determined map (15a), the characteristic curve of operation (Ci) associated to a value of speed (Vtc) corresponding to the preset limit speed (Ntc). 3. The method according to claim , characterized in that said predetermined map (15a) comprises a plurality of characteristic curves of operation (Ci), which are associated to one and the same speed (Vtc) of rotation of the compressor (9), are each correlated to a respective temperature (T) of the air at input to the compressor (9), and are designed to yield a maximum compression ratio (RM) of the compressor (9) itself as a function of its mass flow rate (QAH)and of the temperature (TAMB) of the air measured at input to the compressor (9); said step of calculating the limit supercharging pressure (SP1) comprises the step of identifying a characteristic curve of operation (Ci) associated to a temperature (T) corresponding to the ambient temperature (TAmB) measured upstream of said compressor (9). 4. The method according to claim 2, characterized in that said step of calculating the limit supercharging pressure (SP1) comprises the steps of determining a maximum compression ratio (RM) by means of the characteristic curve of operation (Ci) identified, and as a function of said mass flow rate (QAH); and calculating said limit supercharging pressure (SP1) as a function of said maximum compression ratio (RM) and of said measured pressure (PAMB) of the air. 5. The method according to claim 1, characterized in that it comprises the step of establishing a first safety threshold (ΔC1), and in that said step of determining a maximum compression ratio (RM) comprises the step of determining a limit compression ratio (RPL) by making a difference between said maximum compression ratio (RM) and said first safety threshold (ΔC1); said limit supercharging pressure (SP1) being determined as a function of the limit compression ratio (RPL) and of the air pressure (PAMB) measured at input to the compressor (9). 6. The method according to claim 1, characterized in that it comprises the steps of establishing a second safety threshold (ΔC2), measuring the air pressure (PUTH) supplied at output from the compressor (9), determining an effective compression ratio (RE) between the pressures measured at output (PUTH) from and, respectively, at input to the compressor (9), determining a deactivation compression ratio (RD) as a function of the difference between said maximum compression ratio (RM) and said second safety threshold (ΔC2), verifying whether said effective compression ratio (RE) satisfies or not a preset relation of comparison with the deactivation compression ratio (RD), and disabling or not control of said wastegate valve (12) according to the result of said verification. 7. The method according to claim 6, characterized in that said first and/or second safety thresholds (ΔC1, ΔC2) can each assume a preset constant value, or else can be varied each as a function of one or more parameters (TAMB, QAH, PAMB, PUTH) correlated to the air taken in by the compressor (9), and/or as a function of one or more engine operating parameters (2). 8. The method according claim 4, characterized in that the characteristic curves (Ci) of the predetermined map of operation (15a) and the corresponding parameters (Vtcr, QAHR) that characterize said curves are normalized with respect to a reference pressure (PRIF) and/or reference temperature (TRIF); said step of calculating the limit supercharging pressure (SP1) comprises the steps of identifying the curve of operation (Ci) corresponding to a preset normalized limit speed (Ntcr), and determining, on the basis of the curve (Ci) identified, a maximum compression ratio (RM) as a function of a normalized mass flow rate (QAHR). 9. A device (10) for controlling the speed in an internal-combustion engine of a motor vehicle comprising: a compressor (9); a turbine (8), designed to drive said compressor (9) in rotation under the action of the exhaust gases of the engine (2); and a wastegate valve (12), designed to regulate the flow rate of the exhaust gases provided at input to the turbine (8); said control device (10) comprising a control unit (14) designed to govern said wastegate valve (12) for controlling the speed of rotation of the turbine (8) as a function of an objective supercharging pressure (POB) which indicates the value of the supercharging pressure that, on the basis of an objective map of the engine and of a set of parameters of engine is required at output from said compressor (9); said control device (10) being characterized in that it comprises: first sensor means (20a) for measuring the air pressure (PAMB) at input to said compressor (9); and in that said control unit (14) comprises: a calculating unit (15), which receives at input a set of parameters comprising a pre-set limit speed (Ntc), said air pressure (PAMB) measured at input to the compressor (9), and the mass flow rate (QAH) of said compressor (9), and is designed to process said parameters for determining, through a predetermined map (15a) that characterizes operation of the compressor (9), a limit supercharging pressure (SP1) correlated to the air pressure obtainable at output from the compressor (9) in a condition in which the turbine (8) turns at a speed substantially equal to the preset maximum limit speed (Ntc); a comparison unit (16), designed to verify whether the required objective supercharging pressure (POB) satisfies a pre-set relation with said calculated limit supercharging pressure (SP1), said pre-set relation being satisfied when said required objective pressure (POB) is higher than said limit supercharging pressure (SP1);and a driving unit (17), which, in the case where said pre-set relation is satisfied, is designed to govern said wastegate valve (12) for controlling the speed of rotation of the turbine (8) as a function of the limit supercharging pressure (SP1) so as to limit the speed of rotation of said turbosupercharger (7) to a value substantially equal to said pre-set limit speed (Ntc), and in the case where said pre-set relation is not satisfied, said driving unit (17) being able to actuate said wastegate valve (12) for controlling the speed of rotation of the turbine (8) as a function of the objective supercharging pressure (POB) so as to achieve a supercharging corresponding to the objective pressure (POB) itself. 10. The device according to claim 9,characterized in that said calculating unit (15) comprises first calculation means (24) containing said pre-determined map (15a), which in turn comprises a plurality of curves of operation (Ci), each of which is associated to a pre-set speed (Vtc) and is designed to yield a maximum compression ratio (RM) of the compressor (9) as a function of its given mass flow rate (QAH) and as a function of said limit speed (Ntc); said first calculation means (24) being designed to identify the curve of operation (Ci) associated to a pre-set speed (Vtc) corresponding to the pre-set limit speed (Ntc). 11. The device according to claim 9, characterized in that said calculating unit (15) comprises first calculation means (24) containing said pre-determined map (15a), which in turn comprises a plurality of curves of operation (Ci), which are associated to one and the same speed (Vtc) of rotation of the compressor (9), are each correlated to a respective temperature (T) of the air at input to the compressor (9), and are designed to yield a maximum compression ratio (RM) of the compressor (9) itself as a function of its mass flow rate (QAH) and of the temperature of the air (TAMB) measured upstream of said compressor (9); said first calculation means (24) being designed to identify the curve of operation (Ci) associated to a temperature (T) corresponding to the ambient temperature (TAMB) measured upstream of said compressor (9). 12. The device according to claim 10, characterized in that said first calculation means (28) are designed to determine, on the basis of the curve (Ci) identified, a maximum compression ratio (RM) as a function of said mass flow rate (QAH)so as to calculate said limit supercharging pressure (SP1) as a function of said maximum compression ratio (RM) and said measured air pressure (PAMB). 13. The device according to claim 12, characterized in that said calculating unit (15) comprises second calculation means (26), which receive at input a first preset safety threshold (ΔC1) and are designed to determine a limit compression ratio (RPL) as a function of the difference between said maximum safety ratio (RM) and said first safety threshold (ΔC1); and third calculation means (27) designed to determine said limit supercharging pressure (SP1) as a function of said limit compression ratio (RPL) and of said measured pressure (PAMB) of the air at input to the compressor (9). 14. The device according to claim 9, characterized in that it comprises: second sensor means (29), designed to measure an air pressure (PUTH) present at output from the compressor (9); deactivation means (28) receiving at input a set of parameters containing a second preset safety threshold (ΔC2) and said air pressure (PUTH), measured at output from the compressor (9); said deactivation means (28) being designed to: determine an effective compression ratio (RE) between the air pressure (PUTH) measured at output from said compressor (9) and the air pressure (PAMB) measured at input to said compressor (9); determine a deactivation compression ratio (RD) as a function of the difference between said maximum compression ratio (RM) and said second safety threshold (ΔC2); and verify whether said effective compression ratio (RE) satisfies or not a preset relation of comparison with the deactivation compression ratio (RD) so as to disable or not control of said wastegate valve (12) according to the result of said verification.