Method for controlling an internal combustion engine system equipped with a charger

Abstract

A method for controlling an internal combustion engine system equipped with a charger (300), wherein the charger (300) is driven by an electric motor and is arranged upstream of a turbocharger (500), comprising: an operating range determination (S100) of determining a target value of a boost pressure as a function of a rotational speed of an internal combustion engine (100), which is detected and transmitted by detection means, and then determining whether the charger (300) is in an operable range by means of a control device (900) based on an air volume introduced into the charger (300) and an operable maximum rotational speed of the charger (300), characterized in that the method further comprises: a target speed derivation (S300) of deriving at least one or more target speeds of the charger (300) based on a comparison of a reference value previously input to the control device (900) and an actual state value of a vehicle input to the control device (900) by the control device (900), with at least one of an opening degree of an accelerator pedal (200), a rotational speed of the internal combustion engine, a fuel level, an actual pressure of an intake manifold (110), a rate of change of the opening degree of the accelerator pedal (200) as a function of time, the target value of the boost pressure, a boost ratio of the charger (300) and the turbocharger (500), and the introduced air volume while the charger (300) is in an operable range; a drive speed setting (S500) of setting a largest value among the at least one or more target speeds of the loader (300) that have been derived as a drive speed of the loader (300), and determining whether the drive speed thus set is equal to or greater than a predetermined reference value that is previously input to the control device (900) by means of the control device (900); and a charger driving (S700) of driving the charger (300) at the set drive speed by closing a bypass valve (700) to open a charger path (310) when the drive speed of the charger is equal to or greater than the reference value, by means of the control device (900).

Description

The invention relates to a method for controlling a supercharger-equipped internal combustion engine system, which is intended to control the supercharger depending on a driving mode of an internal combustion engine in an internal combustion engine system equipped with a mechanical supercharger (supercharger) and a turbocharger.In order to increase a boost ratio of intake air in the case of a diesel engine, an engine system equipped with a turbocharger or both a mechanical supercharger and a turbocharger is used in the diesel engine. Specifically, an engine-driven supercharger driven not by a driving force of an internal combustion engine but by a driving force of an electric motor may be used. In general, since a compressor of the engine-driven supercharger has an inversely proportional relationship between a flow rate and a compression ratio, the compression ratio is low in a high flow rate region and high in a low flow rate region. That is, the supercharger is operated only as a flow resistance in a region outside an operation range.Further, the turbocharger has a problem of troublesome turbo lag and adjustment of the size of the turbocharger, so that the emission (EM) and the fuel efficiency may be deteriorated due to inefficient turbo operation.From US 2006 / 0 207 252 A1, post-published DE 10 2015 121 986 A1, DE 11 2005 000 534 T5 and US 2013 / 0 074 495 A1, a method for controlling an internal combustion engine system equipped with a supercharger according to the preamble of claim 1 is known.An object of the present invention is to provide a method of controlling an engine system equipped with a supercharger, which is capable of increasing the efficiency of the engine system by appropriately controlling the supercharger.This object is achieved by a method for controlling an internal combustion engine system equipped with a supercharger according to claim 1.In the operating range determination, a target value of the boost pressure may be determined (or determined) based on the rotational speed of the internal combustion engine and a fuel level.The operating range determination may further include a boost pressure comparison of comparing, by the controller, the target value of the boost pressure determined in the controller with an actual value of the boost pressure input to the controller.When it is determined (or determined) in the operation range determination that the supercharger is not in the operable range, the bypass valve is opened to close the supercharger path.In the target rotation speed derivation, the controller may determine (or determine) that an opening degree of an accelerator pedal is equal to or greater than a predetermined reference value that is previously input to the controller.In the target rotation speed derivation, when the opening degree of the accelerator pedal is equal to or greater than the predetermined reference value that has been input to the controller beforehand, the target rotation speed of the supercharger is derived based on the opening degree of the accelerator pedal, the rotation speed of the engine, a fuel level, and an actual pressure of an intake manifold.In the target rotation speed derivation, the controller may confirm (or verify or check) whether a change rate of the opening degree of the accelerator pedal as a function of time is equal to or greater than the predetermined reference value that has been previously input to the controller.In the target rotation speed derivation, when the change rate of the opening degree of the accelerator pedal as a function of time is equal to or greater than the predetermined reference value that has been previously input to the controller, the target rotation speed of the supercharger may be derived based on the change rate of the opening degree of the accelerator pedal as a function of time, on the rotation speed of the engine, a fuel level, and an actual pressure of the intake manifold.In the target rotation speed derivation, the controller may derive a driving power based on an intake pressure, an exhaust pressure, and an introduced air volume of the supercharger.The target speed derivative may further include a duty cycle derivative of deriving (or dedurating) a duty cycle of the supercharger and a turbocharger via the controller.In the duty derivation, the controller may derive (or deduce) the duty based on the intake pressure and the exhaust pressure of the supercharger, the target value of the boost pressure, and the atmospheric pressure.In the duty cycle derivation, the controller may derive (or deduce) a variance between the intake pressure and the exhaust pressure of the supercharger.In the duty derivation, the controller may derive (or deduce) an opening degree of a turbocharger vane.In the duty cycle derivation, the controller may derive (or deduce) an improved level of fuel efficiency.In the boost ratio derivation, the controller may derive (or deduce) the boost ratio of the supercharger and the turbocharger by comparing the drive power of the supercharger with the improved amount of fuel efficiency.In the target speed derivation, the target speed of the supercharger may be derived (or deduced) based on the target value of the boost pressure, the boost ratio of the supercharger and the turbocharger, and the introduced air volume.It may be confirmed (or verified) at the target rotation speed derivation whether a difference between the target value of the boost pressure and an actual value of the boost pressure derived at the operation range determination is equal to or greater than the predetermined reference value input to the controller beforehand.In the target rotation speed derivation, when the difference between the target value of the boost pressure and the actual value of the boost pressure is equal to or greater than the predetermined reference value that is input to the controller beforehand, the target rotation speed of the supercharger may be derived based on a difference value between the target value of the boost pressure and the actual value of the boost pressure, the intake pressure, and the introduced air volume of the supercharger.When the input speed set in the input speed setting is less than the reference value, the operation range determination may be repeatedly performed.The method for controlling the engine system equipped with the supercharger is advantageous in that the bypass valve is provided in the supercharger path through which air flows into the supercharger, and the supercharger path is controlled so as to be openable or closable as the bypass valve opens or closes, so that the low and medium speed torque is improved, and thus the driving performance and the acceleration performance can be improved. Moreover, by determining (or determining) and controlling the duty ratio of the supercharger and the turbocharger, fuel efficiency is improved, defects in turbo lag and characteristics following the control are improved, and thereby, emission (EM) improvement is enabled.It is understood that the term "vehicle" or "vehicular" or other similar term as used herein includes general motor vehicles such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, as well as hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle having two or more sources of power, for example both gasoline propulsion and electric propulsion.The invention will be explained in more detail with reference to the drawings. In the drawing, the following are shown: FIG. 1 is a flowchart of a method for controlling a supercharger-equipped internal combustion engine system according to an exemplary embodiment of the invention; and FIG. 2 is a block diagram illustrating the configuration of an engine system for performing the method of FIG. 1.It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.Although various embodiments are shown and described in which a motor-driven supercharger 300 driven by an electric motor is mounted, the driving manner of the supercharger 300 is not limited thereto and may be changed as desired.According to the invention, a supercharger 300 is driven after a driving range of an internal combustion engine 100 is divided into a driving power mode, a fuel efficiency mode, and an emission (EM) mode, and then a target rotational speed of the supercharger 300 is derived for each mode. Therefore, the method for controlling the supercharger-equipped engine system according to various embodiments of the invention includes an operating range determination step S 100 of calculating (or determining) a target value of the supercharging pressure in a controller 900 depending on a rotational speed of an engine, and then determining whether the supercharger 300 is in an operable range, a target rotational speed derivation step S 300 of deriving, in the controller 900, a target rotational speed of the supercharger 300 based on a reference value previously input to the controller 900 and an actual state value of a vehicle input to the controller 900 when it is determined in the operating range determination step S 100 that the supercharger 300 is in the operable range, a driving speed setting step S 500 of setting a maximum value of the target speed, which is derived in the target speed deriving step S 300, to a driving speed of the supercharger 300 and confirming whether the set driving speed is equal to or greater than a predetermined reference value, which is previously input to the controller 900, and a supercharger driving step S 700 of driving the supercharger 300 at the set driving speed by closing a bypass valve 700 to open a supercharger path 310 when the driving speed set in the driving speed setting step S 500 is equal to or greater than the reference value.When the engine 100 of the vehicle starts running, the operation range determination step S 100 is performed in the controller 900 to calculate a target value of the boost pressure based on the rotation speed of the engine and a fuel level or the rotation speed of the engine and a load detected and transmitted by detection means. The operating range determining step S100 further includes a boost pressure comparing step S200 of comparing the target value of the boost pressure calculated in this manner with an actual value of the boost pressure input to the controller 900. In the boost pressure comparison step S 200, it is preferable to perform the boost pressure comparison by subtracting the actual value of the boost pressure from the target value of the boost pressure. Thereafter, in the operation range determination step S 100, it is determined whether the supercharger 300 is in the operable range based on an air volume introduced into the supercharger 300 and an operable maximum rotational speed of the supercharger 300.When it is determined in the operation range determination step S 100 that the supercharger 300 is not in the operable range, the bypass valve 700 is opened to close the supercharger path 310, and the operation range determination step S 100 is repeatedly performed. Therefore, when the supercharger 300 is not in the operable range, the supercharger 300 is not driven.When it is determined in the operation range determination step S 100 that the supercharger 300 is in the operable range, the target rotation speed derivation step S 300 is performed in the controller 900 to derive the target rotation speed of the supercharger 300 based on the reference value previously input to the controller 900 and the actual state value of the vehicle input to the controller 900. In the target rotation speed deriving step S300, the driving range of the engine 100 is divided into modes, and then the target rotation speed is derived depending on an associated driving mode.In detail, the driving range of the internal combustion engine 100 is classified into a driving power mode, a fuel efficiency mode, and an emission (EM) mode, and the purpose of driving the supercharger 300 varies depending on each mode. First, in the driving power mode, the purpose is to improve the acceleration performance by increasing the low-speed torque. In the fuel economy mode, the purpose is to operate the supercharger 300 at points where the efficiency of the mechanical supercharger 300 and the efficiency of a turbocharger 500 are maximum. Finally, in the EM mode, the purpose is to improve defects in turbo lag or the characteristics following control, and thereby operate the supercharger 300 in a direction of preventing CO, HC, and PM from being increased and discharged.First, a case where the driving mode of the engine 100 is determined as the driving power mode and the target rotational speed of the supercharger 300 is derived will be described. In order to operate the supercharger 300 for the purpose of improving the low-speed torque and the acceleration performance, the intention of a driver should be reflected. The driver's intention may be detected depending on an opening degree (engine load) of an accelerator pedal 200 with respect to a depression amount of the accelerator pedal 200 that is depressed by the driver and a change rate of the opening degree as a function of time. Therefore, the target rotation speed in the controller 900 is derived based on a reference value related to the accelerator pedal 200 that is previously input to the controller 900 and a change (actual state value) of the accelerator pedal 200 transmitted from the detecting means.That is, in the target rotation speed deriving step S 300, the controller 900 confirms that the opening degree of the accelerator pedal 200 is equal to or greater than a predetermined reference value that is previously input to the controller 900. When the opening degree of the accelerator pedal 200 is equal to or greater than the predetermined reference value that is previously input to the controller 900, it is determined that the driving of the engine 100 is in the driving power mode. Therefore, the target rotation speed of the supercharger 300 is derived in the controller 900 based on the opening degree of the accelerator pedal 200, the rotation speed of the engine, the fuel level, and the actual pressure of an intake manifold 110. In this regard, the inferred target speed is referred to as a first target speed of the drive power mode.In addition, in the target rotation speed deriving step S 300, the controller 900 confirms that a change rate of the opening degree of the accelerator pedal 200 as a function of time is equal to or greater than the predetermined reference value that is previously input to the controller 900. When the change rate of the opening degree of the accelerator pedal 200 as a function of time is equal to or greater than the predetermined reference value that is previously input to the controller 900, it is determined that the driving of the engine 100 is also in the driving power mode. Therefore, the target rotational speed of the supercharger 300 is derived in the controller 900 based on the change rate of the opening degree of the accelerator pedal 200 as a function of time, the rotational speed of the engine, the fuel level, and the pressure of the intake manifold 110. In this regard, the inferred target speed is referred to as a second target speed of the drive power mode.Second, a case will be described in which the drive mode of the engine 100 is determined as the fuel efficiency mode and the target rotational speed of the supercharger 300 is derived. In order to operate the supercharger 300 for the purpose of causing the engine 100 to enter the fuel efficiency mode, overall determination based on the driving performance of the supercharger 300, an increase in pressure during driving of the supercharger 300, and an opening degree of the turbocharger vane corresponding to the increase in pressure is required. By means of an equation input to the control device 900, the target rotational speed of the supercharger 300 can be derived based on these contents.First, in the target rotation speed deriving step S 300, the controller 900 derives the driving power of the supercharger 300 based on the intake pressure, the exhaust pressure, and the introduced air volume of the supercharger 300. After the driving power of the supercharger 300 is derived, a duty deriving step S 400 of deriving the duty of the supercharger 300 and the turbocharger 500 may be further performed.In the boost ratio deriving step S 400, the controller 900 derives the boost ratio based on the intake pressure and the exhaust pressure of the supercharger 300, the target value of the boost pressure, and the atmospheric pressure, which can be represented by the following Equation 1.In the duty deriving step S 400, an improved fuel efficiency measure for each duty is calculated from Equation 1.At the same time, in order to derive the duty in the duty deriving step S 400, the controller 900 derives a variance between the intake pressure and the exhaust pressure of the supercharger 300 based on the intake pressure, the introduced air volume, and the duty of the supercharger 300. Further, in the boost ratio deriving step S 400, the controller 900 derives the opening degree of the turbocharger blade based on the target value of the boost pressure, the variance between the intake pressure and the exhaust pressure of the supercharger 300, and the actual position of the turbocharger blade. In the boost ratio deriving step S 400, the controller 900 derives the improved amount of fuel efficiency based on the opening degree of the turbocharger blade, such as the boost ratio is set, the actual position of the turbocharger blade, the rotational speed of the internal combustion engine, and the fuel level or the load.The charge ratio is determined based on the driving power of the supercharger 300, the fuel efficiency, the improved degree of fuel efficiency, and the rotation speed of the internal combustion engine, each derived as described above.Here, when the improvement in fuel efficiency is compared with the drive power of the supercharger 300 by Equation 2 and then the drive power is low, it is determined that the engine 100 is in the fuel efficiency mode, and the charge ratio of the supercharger 300 and the turbocharger 500 is derived. Therefore, in the target rotation speed deriving step S 300, the target rotation speed of the supercharger 300 is derived based on the target value of the boost pressure, the charge ratio of the supercharger 300 and the turbocharger 500, and the introduced air volume, and the derived target rotation speed is referred to as a third target rotation speed.Third, a case will be described in which the drive mode of the engine 100 is determined as the EM mode and the target rotational speed of the supercharger 300 is derived. In the EM mode, improvement in fuel efficiency by driving electric power of the supercharger 300 cannot be expected. However, the EM mode is performed to reduce the deterioration of CO, HC and PM generated due to defects of turbo lag or control following characteristics resulting from insufficient charge, and can be detected by a difference between the target value of the boost pressure and the actual value of the boost pressure and by an increase of the boost pressure. Therefore, the controller 900 derives the target rotational speed based on the target value of the boost pressure that is previously input to the controller 900 and the actual value of the boost pressure through the operation range determination step S 100 and the boost pressure comparison step S 200.That is, in the target rotation speed deriving step S 300, it is confirmed that the difference between the target value of the boost pressure and the actual value of the boost pressure derived in the operation range determining step S 100 is equal to or greater than the predetermined reference value that is previously input to the controller 900. When the difference between the target value of the boost pressure and the actual value of the boost pressure is equal to or greater than the predetermined reference value that is previously input to the controller 900, this is determined as the EM mode. Therefore, based on a difference value between the target value of the boost pressure and the actual value of the boost pressure, an intake pressure of the supercharger 300, and an introduced air volume, the target rotation speed of the supercharger 300 is derived, and the derived target rotation speed is referred to as a fourth target rotation speed.In the target rotation speed deriving step S 300, only a target rotation speed or up to four target rotation speeds may be derived depending on the driving state of the engine 100. Therefore, in the target rotation speed deriving step S 300, a maximum value among the derived first to fourth target rotation speeds is set as the input rotation speed of the supercharger 300. As a result, the input rotation speed setting step S 500 is performed to confirm that the set input rotation speed is equal to or greater than the predetermined reference value that is previously input to the controller 900. When the input speed set in the input speed setting step S 500 is less than the reference value, the operation range determination step S 100 is repeatedly performed.In contrast, when the input speed set in the input speed setting step S 500 is equal to or greater than the reference value, the supercharger driving step S 700 is performed to open the supercharger path 310 by closing the bypass valve 700, and then the supercharger 300 is driven at the set input speed. Thereafter, the operation range determination step S 100 is repeatedly performed.The process of deriving the first target rotational speed, the second target rotational speed, the third target rotational speed, and the fourth target rotational speed may be previously input to the controller 900 based on a map derived by physical contents and actual experiments. These contents may be changed in various ways depending on a design or environment.As described above, according to the invention, there is provided a method of controlling a supercharger-equipped internal combustion engine system, in which a bypass valve is provided in a supercharger path through which air flows into the supercharger, and the supercharger path is controlled so as to be openable or closable as the bypass valve opens or closes, so that the low- and medium-speed torque is improved, and thereby the driving performance and the acceleration performance can be improved. Moreover, by obtaining and controlling a charge ratio of the supercharger and a turbocharger, fuel efficiency is improved, defects in turbo lag and characteristics following the control are improved, and thereby, emission is enabled to be improved.

Claims

A method for controlling an engine system equipped with a supercharger (300), the supercharger (300) being operated by an electric motor and being disposed upstream of a turbocharger (500), comprising: an operation range determination (S100) of determining a target value of a supercharging pressure depending on a rotational speed of an engine (100) detected and transmitted by detection means, and then determining whether the supercharger (300) is in an operable range by means of a controller (900) based on an air volume introduced into the supercharger (300) and an operable maximum rotational speed of the supercharger (300), characterized in that the method further comprises: a target rotational speed derivation (S300) of deriving at least one or more target rotational speeds of the supercharger (300) based on a comparison of a reference value, which is previously input to the controller (900), and an actual state value of a vehicle input to the controller (900), by the controller (900), having at least one of an opening degree of an accelerator pedal (200), a rotational speed of the internal combustion engine, a fuel level, an actual pressure of an intake manifold (110), a change rate of the opening degree of the accelerator pedal (200) as a function of time, the target value of the boost pressure, a charge ratio of the supercharger (300) and the turbocharger (500), and the introduced air volume during the supercharger (300) is in an operable range; setting (S 500), by the controller (900), a largest value among the at least one or more target speeds of the supercharger (300) derived as a driving speed of the supercharger (300), and determining whether the thus set driving speed is equal to or greater than a predetermined reference value previously input to the controller (900); and supercharger driving (S 700), by the controller (900), driving the supercharger (300) at the set driving speed by closing a bypass valve (700) to open a supercharger path (310) when the driving speed of the supercharger is equal to or greater than the reference value.The method according to claim 1, wherein in the operating range determination (S100), a target value of the boost pressure is determined based on the rotational speed of the internal combustion engine (100) and the fuel level, the fuel level being detected and transmitted by the detection means.The method according to claim 1 or 2, wherein the operating range determination (S100) further comprises: a boost pressure comparison (S200) of comparing the target value of the boost pressure determined in the controller (900) with an actual value of the boost pressure input to the controller (900) by the controller (900).The method according to any one of claims 1 to 3, wherein when it is determined in the operation range determination (S100) that the supercharger (300) is not in the operable range, the bypass valve (700) is opened to close the supercharger path (310).The method according to any one of claims 1 to 4, wherein in the target rotation speed derivation (S300), the controller (900) determines whether an opening degree of an accelerator pedal (200) is equal to or greater than a predetermined reference value that is previously input to the controller (900).The method according to claim 5, wherein in the target rotation speed derivation (S300), when the opening degree of the accelerator pedal (200) is equal to or greater than the predetermined reference value that has been previously input to the controller (900), the target rotation speed of the supercharger (300) is derived based on the opening degree of the accelerator pedal (200), the rotation speed of the engine (100), a fuel level, and an actual pressure of an intake manifold (110).The method according to claim 5 or 6, wherein in the target rotation speed derivation (S300), the controller (900) determines whether a change rate of the opening degree of the accelerator pedal (200) as a function of time is equal to or greater than the predetermined reference value previously input to the controller (900).The method according to claim 7, wherein in the target rotation speed derivation (S300), when the change rate of the opening degree of the accelerator pedal (200) as a function of time is equal to or greater than the predetermined reference value that has been previously input to the controller (900), the target rotation speed of the supercharger (300) is derived based on the change rate of the opening degree of the accelerator pedal (200) as a function of time, the rotation speed of the engine (100), a fuel level, and an actual pressure of the intake manifold (110).The method according to any one of claims 1 to 8, wherein in the target rotation speed derivation (S300), the controller (900) derives a driving power based on an intake pressure, an exhaust pressure, and an introduced air volume of the supercharger (300).The method according to claim 9, wherein the target rotation speed derivation (S300) further comprises: a duty derivation (S400) of deriving the duty of the supercharger (300) and the turbocharger (500) by the controller (900).The method according to claim 10, wherein in the boost ratio derivation (S400), the controller (900) derives the boost ratio based on the intake pressure and the exhaust pressure of the supercharger (300), the target value of the boost pressure, and the atmospheric pressure.The method according to claim 10 or 11, wherein in the duty deriving (S400), the controller (900) derives a difference between the intake pressure and the exhaust pressure of the supercharger (300).The method according to any one of claims 10 to 12, wherein in the duty derivation (S400), the controller (900) derives an opening degree of a turbocharger blade.The method according to any one of claims 10 to 13, wherein in the duty deriving (S400), the controller (900) derives an improved amount of fuel efficiency.The method according to claim 14, wherein in the boost ratio derivation (S400), the controller (900) derives the boost ratio of the supercharger (300) and the turbocharger (500) when the controller (900) determines that the driving power of the supercharger (300) is less than the improvement of the fuel efficiency by comparing the driving power of the supercharger (300) with the improved amount of the fuel efficiency.The method according to any one of claims 10 to 15, wherein in the target rotation speed derivation (S300), the target rotation speed of the supercharger (300) is derived based on the target value of the boost pressure, the charge ratio of the supercharger (300) and the turbocharger (500), and the introduced air volume.The method according to any one of claims 1 to 16, wherein at the target rotation speed derivation (S300), it is determined whether a difference between the target value of the boost pressure and an actual value of the boost pressure derived at the operation range determination (S100) is equal to or greater than the predetermined reference value that is previously input to the controller (900).The method according to claim 17, wherein in the target rotation speed derivation (S300), when the difference between the target value of the boost pressure and the actual value of the boost pressure is equal to or greater than the predetermined reference value that is previously input to the controller (900), the target rotation speed of the supercharger (300) is derived based on a difference value between the target value of the boost pressure and the actual value of the boost pressure, the intake pressure, and the introduced air volume of the supercharger (300).The method according to any one of claims 1 to 18, wherein when the input rotational speed set at the input rotational speed setting (S500) is less than the reference value, the operation range determination (S100) is repeatedly performed.

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