METHOD AND DEVICE FOR CONTROLLING REGENERATION WHEN COLLAPSING A VEHICLE WITH AN ENGINE WITH CONTINUOUSLY ADJUSTABLE VALVE OPENING TIME

Abstract

Method for controlling regeneration during coasting of a vehicle equipped with a continuously variable valve timing (CVVD) engine, wherein an engine control unit (ECU) controls regenerative braking in the vehicle, the method comprising the following steps: Determine, via the ECU, whether the current state of the vehicle meets coasting regeneration conditions; and The ECU enters a coasting regeneration mode and performs regenerative braking when the current state of the vehicle meets the coasting regeneration conditions. Continuous monitoring to ensure that the coast-down regeneration conditions are met when the vehicle is driven in coast-down regeneration mode, where it is determined that the coasting regeneration conditions are met when the current state of the vehicle is a coasting state, and Ending the coast-down regeneration mode when the thrust state is cleared as a result of monitoring, wherein upon entering coast-down regeneration mode a throttle valve is fully opened so that an intake air quantity of the engine is maximized and a CVVD target duration is controlled so that it is maximized, so that a current generating torque of a belt-driven motor (BDM) is controlled so that it is increased, wherein in the step of entering the coast-down regeneration mode, a valve overlap, in which both an exhaust valve and an intake valve are open, is controlled to maximize it within a controllable range, with a closing time of the intake valve being delayed after a start time of a compression stroke, thereby reducing pumping loss and increasing the current-generating torque of the belt-driven engine.

Description

BACKGROUND(a) Technical field

[0001] The present disclosure relates to a method and a device for controlling regeneration during coasting of a vehicle, in particular to the method and the device for controlling regeneration during coasting of a mild hybrid electric vehicle (MHEV) equipped with a motor with continuously variable valve duration (CVVD). (b) Description of the state of the art

[0002] Vehicle emissions regulations have recently become stricter to improve the environment. However, existing powertrains based on gasoline engines have limited capacity to meet these emissions standards. To comply with the increasingly stringent emissions regulations, research and development of new powertrain systems are actively underway.

[0003] One of several technologies for meeting stricter emissions regulations is a mild hybrid electric vehicle (MHEV) system, designed so that a belt-driven motor (BDM) can assist engine power. An MHEV system equipped with a belt-driven motor offers a cost advantage compared to a full hybrid system.

[0004] By using an MHEV system with a belt-driven engine, it is particularly possible to achieve the advantages of a hybrid system and to increase the fuel efficiency of a powertrain without significant changes to the powertrain, e.g. by simply replacing a three-phase generator (power generator) of existing internal combustion engines with a belt-driven engine.

[0005] However, since in a conventional MHEV system the engine (i.e., the belt-driven motor) is always connected to the crankshaft of a power unit via a belt, the problem arises that the power unit acts as a resistance during regenerative braking (i.e., including frictional resistance, load, etc. of the power unit). Consequently, it is a drawback that the efficiency of regenerative braking decreases compared to other hybrid vehicles.

[0006] In conventional hybrid systems, the motor is separate from the power unit and performs regenerative braking independently by controlling power generation. Since the power unit is switched off in this case, it has no influence on driving. However, in a MHEV, because a belt-driven motor is connected to the crankshaft of the power unit, the frictional torque and the load of the power unit act simultaneously during regenerative braking, so the efficiency of regenerative braking can only be increased to a limited extent.

[0007] Furthermore, during regeneration while coasting (where a motor generates electricity while the vehicle is coasting without the accelerator or brake pedal being pressed), the power-generating torque of a belt-driven motor and the drag torque of a power unit are simultaneously applied to a drive shaft. Consequently, when the power-generating torque of the belt-driven motor increases due to relatively strong deceleration, the driver will notice a difference in driving compared to conventional internal combustion engine vehicles.

[0008] Since regulations such as UNECE WP29 stipulate that brake lights should be switched on when a vehicle decelerates by 1.3 m / s² or more, the increase in the amount of electricity generated by a belt-driven motor during regenerative braking is limited. Consequently, a problem arises with a system where the energy recovery ratio during coasting regeneration is inevitably low.

[0009] DE 100 63 751 A1 discloses a method for operating an internal combustion engine installed in a motor vehicle with controlled inlet and outlet valves, which is rigidly coupled to an electric machine charging an electrical energy storage device and which is used to generate recuperation power during coasting or braking operation of the internal combustion engine.

[0010] In DE 10 2013 013 541 B3 a motor vehicle with an internal combustion engine and with an air conditioning system comprising an electric motor designed to drive a compressor of the air conditioning system for compressing a cooling fluid is shown.

[0011] From US 2012 / 0 304 962 A1 a method for estimating a combustion torque acting on the crankshaft of an internal combustion engine is known.

[0012] US Patent 5,899,828 A discloses an engine control device for a hybrid vehicle that reduces shocks and improves fuel economy when the engine is subject to fuel cut-off control at the time of speed reduction by applying the brake pedal.

[0013] DE 698 16 387 T2 discloses a control system for controlling a hybrid vehicle which has an internal combustion engine and an electric motor that can operate in recuperation mode. SUMMARY

[0014] One object of the present disclosure is to provide a method and a device for controlling the regeneration during coasting of a vehicle equipped with a continuously variable valve timing (CVVD) engine, wherein the method and the device can reduce the influence of the engine's drag torque on the vehicle's deceleration during coasting regeneration and thereby increase the amount of energy recovered by the engine's power generation, even without adding a specific mechanical device.

[0015] According to one aspect of the present disclosure, a method for controlling regeneration during coasting of a vehicle equipped with a continuously variable valve timing (CVVD) engine comprises the following to solve the problems: (a) determining, by means of an engine control unit (ECU), whether a current state of the vehicle meets coasting regeneration conditions; (b) entering a coasting regeneration mode by means of the ECU and performing regenerative braking when the current state of the vehicle meets the coasting regeneration conditions; (c) continuously monitoring whether the coasting regeneration conditions are met when the vehicle is driven in a coasting regeneration mode;and (d) termination of the coast-down regeneration mode when a thrust condition which is one of the coast-down regeneration conditions is cleared as a result of monitoring, wherein upon entry into the coast-down regeneration mode a throttle valve is fully opened so that an intake air quantity of the engine is maximized and a CVVD target duration is controlled to maximize it, thereby controlling the current-generating torque of a belt-driven motor (BDM) to increase it.

[0016] In step (a) it is determined that the coast-down regeneration conditions are met if the current state of the vehicle is a coasting state.

[0017] In step (b), valve overlap, in which both an exhaust and an intake valve are open, is controlled to maximize it within a controllable range. The closing time of the intake valve can be delayed after the start of a compression stroke (late intake valve closure - LIVC), thereby reducing pumping losses and increasing the power-generating torque of the belt-driven engine.

[0018] If an accelerator pedal and a brake pedal are not pressed, so that the output signals from an accelerator position sensor (APS) and a brake position sensor (BPS) are zero, and a vehicle speed and engine speed are above the corresponding set vehicle speed and engine speed, the current state of the vehicle can be determined as a coasting state.

[0019] A condition in which a gearshift lever is positioned in a D range may also be included in the thrust state.

[0020] To solve the problems, according to a further aspect of the present disclosure, a device for controlling regeneration during coasting of a vehicle equipped with a continuously variable valve timing (CVVD) engine comprises the following: a data detector that acquires information in real time to determine whether entry into coasting regeneration mode has occurred; an ECU that determines whether entry into coasting regeneration mode has occurred by analyzing the information supplied by the data detector;and a CVVD controller that controls a valve opening duration in coast-down regeneration mode under control of the ECU, wherein entry into coast-down regeneration mode under control of the ECU occurs when a current state of the vehicle, as a result of the analysis of the information supplied by the data detector, meets coast-down regeneration conditions, and wherein in coast-down regeneration mode a throttle valve is fully opened so that an intake air quantity of the engine under control of the ECU is maximized, and the CVVD controller controls a target CVVD duration to maximize it, thereby controlling the current-generating torque of a belt-driven motor (BDM) to increase it.

[0021] When the coast-down regeneration mode is activated, the CVVD controller controls valve overlap, where both an exhaust valve and an intake valve are open, thus maximizing it within a controllable range, and delays the intake valve closing time after the start of a compression stroke (late intake valve closure - LIVC), thereby reducing pumping losses and increasing the current-generating torque of the belt-driven engine.

[0022] The ECU continuously monitors, based on information supplied in real time by the data detector, whether the coast-down regeneration conditions are met, while controlling the target CCVD duration to be maximized by the CVVD controller, and the CVVD controller can control a valve opening duration of an intake valve so that it is set to a target value output from mapping data in accordance with a current driving condition under the control of the ECU when a coast-down regeneration condition, which is one of the coast-down regeneration conditions, is lifted as a result of the monitoring.

[0023] The information acquired by the data detector for entering coasting regeneration mode may include information from an accelerator position sensor (APS) and / or information from a brake position sensor (BPS) and / or vehicle speed information and / or engine speed information and / or gear shift information.

[0024] In a coasting state where neither the accelerator nor the brake pedal is pressed, so that the output signals from the accelerator position sensor (APS) and the brake position sensor (BPS) are zero, and the vehicle speed and engine speed are above the corresponding set vehicle speed and engine speed, the ECU can determine that the current state of the vehicle meets the coasting regeneration conditions.

[0025] According to the method and device for controlling regeneration during coasting of a MHEV equipped with a CVVD engine, as described in this disclosure, pumping losses are reduced by controlling the valve opening duration during coasting regeneration. This reduces the drag torque of a power unit and increases the power output of a belt-driven engine. Consequently, it is possible to improve fuel efficiency.

[0026] According to the present disclosure, it is therefore possible to reduce pumping losses by controlling the valve direction during coasting regeneration, thereby reducing the influence of the engine's drag torque on vehicle deceleration during coasting regeneration. It is also possible to increase the amount of energy recovered through the engine's power generation without adding any special mechanical device. Therefore, it is possible to significantly improve a vehicle's fuel efficiency even without adding any special mechanical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and further tasks, features and other advantages of the present disclosure will be better understood from the following detailed description in conjunction with the accompanying drawings. These show: Fig. 1 a graphic representation which schematically shows the design of a device for controlling the regeneration during the coasting of a vehicle equipped with an engine with continuously variable valve duration (CVVD) according to an embodiment of the present disclosure; Fig. 2 a curve showing a change in an inlet valve upon entering a coasting regeneration mode; and Fig. 3 a flowchart showing a method for controlling regeneration during coasting of a vehicle equipped with a continuously variable valve timing (CVVD) engine according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE REVELATION

[0028] It is understood that the term "vehicle" or "vehicle-related" or a similar term as used herein includes motor vehicles in general, 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, and also includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other vehicles powered by alternative fuels (e.g., fuels derived from resources other than petroleum). As used herein, a hybrid vehicle is a vehicle with two or more energy sources, e.g., vehicles powered by both gasoline and electric power.

[0029] As used herein, singular forms "ein, eine" and "der, die, das" are intended to include the plural forms unless the context clearly indicates otherwise. It is further understood that the terms "umbandt" and / or "umfassend," when used in this description, specify the presence of the named features, integers, steps, processes, elements, and / or components, but do not exclude the presence or addition of one or more further features, integers, steps, processes, elements, components, and / or groups thereof. As used herein, the term "and / or" includes all combinations of one or more of the related listed elements.Unless explicitly stated otherwise, the term "include" and variants such as "includes" or "comprehensive" throughout this description are to be understood as meaning the inclusion of the elements mentioned, but not the exclusion of other elements. Furthermore, the terms "unit," "-er," "-or," and "module" used in this description refer to units for processing at least one function and one operation and can be implemented by hardware components or software components and combinations thereof.

[0030] Furthermore, the control logic of the present disclosure can be embodied as non-volatile, computer-readable media on a computer-readable medium containing executable program instructions that are executed by a processor, a controller, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable medium can also be distributed across networked computer systems, such that the computer-readable media is stored and executed in a distributed manner, for example, by a telematics server or a controller area network (CAN).

[0031] Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0032] The terminology used here serves only to describe certain embodiments and is not intended to limit the present disclosure. Singular forms are intended to include plural forms unless the context clearly indicates otherwise.

[0033] The terms "first," "second," "second," etc., used in the description can be used to describe different components, but the components should not be interpreted as being limited to these terms. The terms are used only to distinguish one component from another.

[0034] In the following description, which refers to the accompanying drawings, the same components are identified with the same reference numerals and are not described repeatedly. However, detailed descriptions of well-known technologies are omitted from the description of this disclosure in order to avoid obscuring the disclosure with unnecessary details.

[0035] Fig. Figure 1 is a graphic representation that schematically shows the design of a device for controlling regeneration during coasting of a vehicle equipped with a continuously variable valve timing (CVVD) engine (e.g. a mild hybrid electric vehicle or MHEV) according to an embodiment of the present disclosure.

[0036] Referring to Fig. 1 comprises a device for controlling coasting regeneration according to an embodiment of the present disclosure, which is applied to a mild hybrid electric vehicle comprising a CVVD system and a belt-driven motor (BDM) connected to a motor output shaft to transmit power to and receive power from the motor, a data detector 10, a motor control unit (ECU) 20 and a CVVD controller 30.

[0037] The data detector 10 acquires information in real time to determine whether the coasting regeneration mode has been entered. The information acquired by the data detector 10 to determine whether the coasting regeneration mode has been entered can include information from an accelerator pedal position sensor (APS) and / or a brake position sensor (BPS) and / or vehicle speed information and / or engine speed information and / or gear selection information.

[0038] The information acquired by data detector 10 is fed to ECU 20, and ECU 20 analyzes the information supplied by data detector 10. In particular, ECU 20 determines, by analyzing the information supplied by data detector 10, whether entry into coasting regeneration mode has occurred, and determines that entry into coasting regeneration mode has occurred if the current vehicle state, as determined based on the information transmitted by data detector 10, is a coasting state.

[0039] "Engine braking" refers to a situation in which a vehicle is driven solely by inertia, without the accelerator and brake pedals being used. Specifically, engine braking can be a coasting situation where the outputs of the accelerator and brake position sensors are zero, and the vehicle speed and engine speed exceed a certain set value.

[0040] Depending on the specific case, the overrun state may include a condition where the gear selector is in the D range; however, the conditions for determining whether entry into coasting regeneration mode has occurred are not limited to those described above. Depending on the vehicle specifications, new conditions may be added to those described above, and some of the conditions described above may be excluded in specific cases.

[0041] The CVVD controller 30 controls the valve opening duration under the control of the ECU 20. The CVVD controller 30 can consist of a drive motor that generates and outputs a suitable torque for controlling the valve opening duration under the control of the ECU 20, and a variable controller that is operated in such a way that it changes the center of rotation of a camshaft via the drive motor. The CVVD controller 30 is well known in the prior art, so a detailed description is omitted.

[0042] It should be noted that CVVD (Continuous Variable Valve Duration) is a technology for increasing overall performance by freely controlling the duration for which an intake valve is open. In other words, CVVD controls the duration for which a valve is open by using a difference in the speed at which a cam lobe pushes the valve when the center of rotation of a camshaft moves.

[0043] As described above, the ECU 20 determines, based on the acquisition information supplied by the data detector 10, whether entry into coast-down regeneration mode has occurred. If the vehicle state is the coast-down state described above, the ECU 20 determines that the conditions for coast-down regeneration are met, determines that entry into coast-down regeneration mode has occurred, and executes a series of controls for coast-down regeneration.

[0044] The control sequence performed by the ECU 20 in coasting regeneration mode, which is a control to increase the power-generating torque of the belt-driven motor, includes the control of the engine throttle valve and the control of the valve opening duration by the CVVD controller 30. For this purpose, the ECU 20 simultaneously transmits a control signal to the engine throttle valve and the CVVD controller 30 upon entering coasting regeneration mode, in order to increase the power-generating torque of the belt-driven motor during regenerative braking.

[0045] Specifically, ECU 20 fully opens a throttle valve simultaneously with entering coast-down regeneration mode, thus maximizing the engine's intake air volume. ECU 20 also issues a command to the variable controller of CVVD controller 30 to maximize the target CVVD duration within a permissible duration range.

[0046] For this purpose, the ECU 20 can be equipped with one or more processors that are operated according to defined programs. In particular, the ECU 20 can be equipped with one or more processors that are operated by programs designed to perform the steps of the method for controlling regeneration during the coasting of a vehicle equipped with a CVVD engine (e.g., an MHEV) according to an embodiment of the present disclosure described below.

[0047] The CVVD controller 30 delays the closing time of the intake valve after the start of a compression stroke, according to the instruction from the ECU 20, when entering coast-down regeneration mode (LIVC, Late Intake Valve Closure). Furthermore, the valve overlap, where both an exhaust and an intake valve are open, is controlled to maximize it within a controllable range (controlled as shown by curve ① in [reference to diagram]). Fig. 2).

[0048] This is with reference to Fig. 2 described.

[0049] Fig. Figure 2 is a curve showing the change of an inlet valve when entering the coasting regeneration mode.

[0050] As in Fig. As shown in Figure 2, the CVVD controller 30 simultaneously controls the valve overlap (area marked by an ellipse) upon entering the coast-down regeneration mode, in which both the exhaust and intake valves are open, so that it is maximized within the controllable range according to the instruction from the ECU 20. Additionally, the closing time of the intake valve is delayed after the start of a compression stroke (which typically corresponds to bottom dead center).

[0051] It should be noted that valve overlap refers to a condition in which both the exhaust and intake valves are open to improve intake / exhaust efficiency in the high-speed range of the engine, thus preventing engine malfunction. In other words, valve overlap allows an engine to operate smoothly and deliver high power at high speeds.

[0052] If, as in Fig. Figure 2 shows that if the closing time of the intake valve is delayed after the start of a compression stroke, some of the intake air flowing into the combustion chamber during the intake stroke is forcibly expelled from the combustion chamber during the compression stroke. A slight reduction in power is unavoidable, but the effective compression start point is correspondingly delayed. Consequently, the expansion-to-compression ratio increases, and the heat of combustion performs more work. Furthermore, the negative work during the compression stroke decreases, thus reducing pumping losses.

[0053] The braking torque applied to the drive shaft during coasting regeneration (when the belt-driven motor generates electricity while the vehicle is coasting with the accelerator and brake pedals released) is the sum of the electricity-generating torque of the belt-driven vehicle and the drag torque of the motor. If the drag torque of the motor is reduced, the vehicle's deceleration can be maintained even if the electricity-generating torque of the belt-driven motor is increased by the amount of the reduced torque.

[0054] The drag torque of the engine consists of the friction torque of the engine and the pumping loss. The pumping loss, which is a pressure loss due to the vacuum generated in the intake manifold of an engine, can be reduced, as described above, by controlling the opening duration of the intake valve, for example by increasing the period during which both the exhaust and intake valves are open and the degree of opening of the intake valve.

[0055] Increasing the duration of opening of both the exhaust and intake valves, and the degree of intake valve opening, allows more air to flow into the cylinder, thus raising the cylinder's internal pressure. This also reduces the pressure differential between the intake and exhaust manifolds, thereby reducing pumping losses. Consequently, the engine's drag torque (the load applied to the engine) can be actively reduced.

[0056] In the present disclosure, it was assumed that the drag torque of one of the power machines can be controlled by the CVVD control, wherein the ECU 20, upon entering the coast-down regeneration mode, controls the CVVD controller 30 in such a way that the opening duration of the inlet valve increases, thereby reducing the pumping loss and decreasing the drag torque of the power machine in order to increase the level of power generation of the belt-driven engine.

[0057] As described above, if the intake valve opening duration is increased and more air flows into a cylinder, the intake air cannot flow smoothly if the engine's throttle valve is even slightly closed, thus potentially affecting the valve opening duration control. Therefore, the throttle valve is fully closed simultaneously with the entry into coast-down regeneration mode to prevent the intake air from influencing the valve opening duration control.

[0058] It should be noted that the in Fig. 2. Curve ① shown is the curve illustrating the change of an intake valve upon entering a coasting regeneration mode proposed in the present disclosure, and other curves (intake valve curves) are curves illustrating changes of various types of intake values ​​that can be shown in accordance with the driving conditions of vehicles. The greater the width between the starting point and the endpoint (the left-right width in 2. ... Fig. 2) The longer the curve, the longer the time the valve is open.

[0059] The ECU 20 continuously monitors, based on the information provided in real time by the data detector 10, whether the coast-down regeneration conditions are met, while controlling a CVVD target duration (the duration of the intake valve to be increased) to be maximized by the CVVD controller 30, and changes the CVVD to a normal control mode when it determines that the overrun condition, which is one of the conditions for coast-down regeneration, has been eliminated as a monitoring result.

[0060] For example, if the actuation of an accelerator pedal or a brake pedal is detected (when the output signal of the accelerator pedal position sensor or the brake pedal position sensor is not equal to 0) while a vehicle is being driven in coasting regeneration mode (when the throttle valve is fully open or the CVVD target duration is controlled to maximize it), the ECU 20 instructs the CVVD controller to enter a normal CVVD control mode in which the intake valve opening duration is set to a target value output from the mapping data according to the current driving state of the vehicle.

[0061] However, if it is determined that the thrust condition, which is one of the coast-down regeneration conditions, is maintained, the pump loss is reduced by controlling the CVVD target duration to maximize it, thereby maintaining the coast-down regeneration mode, which increases the level of power generation from the belt-driven motor.

[0062] A regeneration control method, which is carried out by the device for controlling the regeneration during the coasting of an MHEV with a CVVD engine according to an embodiment of the present disclosure described above, is described with reference to Fig. 3 described.

[0063] Fig. Figure 3 is a flowchart showing a method for controlling regeneration during coasting of a vehicle equipped with a CVVD engine according to an embodiment of the present disclosure.

[0064] With reference to Fig.3. The method for controlling regeneration during coasting of an MHEV with a CVVD engine according to an embodiment of the present disclosure can at its broadest extent include determining whether the current state of a vehicle meets the coasting regeneration conditions (S100) and entering the coasting regeneration mode and performing regenerative braking when the current state of the vehicle meets the coasting regeneration conditions (S200).

[0065] If the vehicle's current state is coasting, step S100 can determine that the coasting regeneration conditions are met. Coasting is a state in which neither the accelerator nor the brake pedal is depressed, so the output signals from the accelerator position sensor (APS) and the brake position sensor (BPS) are zero, and the vehicle speed and engine speed are above the corresponding set vehicle speed and engine speed.

[0066] Depending on the specific case, the overrun state may include a condition where the gear selector is in the D range; however, the conditions for determining whether entry into coasting regeneration mode has occurred are not limited to those described above. Depending on the vehicle specifications, new conditions may be added to those described above, and some of the conditions described above may be excluded in specific cases.

[0067] If the current state of a vehicle meets the coast-down regeneration conditions and entry into coast-down regeneration mode occurs, in step S200 the throttle valve is fully opened so that the engine's intake air volume is maximized and the CVVD target duration is controlled to maximize it, thereby increasing the current-generating torque of the belt-driven motor (BDM).

[0068] Controlling the CVVD target duration to maximize it means controlling the valve overlap, where both the exhaust and intake valves are open, to maximize it within the controllable range, and delaying the intake valve closing time after the start of a compression stroke (LIVC, Late Intake Valve Closure), thereby reducing pumping loss.

[0069] As described above, the braking torque applied to the drive shaft during coasting regeneration (when the belt-driven motor generates electricity while the vehicle is coasting with the accelerator and brake pedals released) is the sum of the power-generating torque of the belt-driven motor and the drag torque of the engine. Therefore, if the drag torque of the engine is reduced, the vehicle's deceleration can be maintained even if the power-generating torque of the belt-driven motor is increased by the amount of the reduced torque.

[0070] The drag torque of the engine consists of the friction torque of the engine and the pumping loss. The pumping loss, which is a pressure loss due to the vacuum generated in the intake manifold of an engine, can be reduced, as described above, by controlling the opening duration of the intake valve (e.g., by increasing the period during which both the exhaust and intake valves are open, and by increasing the opening degree of the intake valve).

[0071] Increasing the duration of opening of both the exhaust and intake valves, and the degree of intake valve opening, allows more air to flow into the cylinder, thus raising the cylinder's internal pressure. This also reduces the pressure differential between the intake and exhaust manifolds, thereby reducing pumping losses. Consequently, the engine's drag torque (the load applied to the engine) can be actively reduced.

[0072] In the present disclosure, it was assumed that the drag torque of a power machine can be controlled by the CVVD control, wherein the ECU 20, upon entering the coast-down regeneration mode, controls the CVVD controller 30 in such a way that the opening duration of the inlet valve increases, thereby reducing the pumping loss and decreasing the drag torque of the power machine in order to increase the level of power generation of the belt-driven engine.

[0073] As described above, if the intake valve opening duration is increased and more air flows into a cylinder, the intake air cannot flow smoothly if the engine's throttle valve is even slightly closed, thus potentially affecting the valve opening duration control. Therefore, the throttle valve is fully closed simultaneously with the entry into coast-down regeneration mode to prevent the intake air from influencing the valve opening duration control.

[0074] The control method described in this disclosure continuously monitors whether the coast-down regeneration conditions are met when a vehicle is driven in coast-down regeneration mode (S300). If it is determined that the coast-down regeneration condition, which is one of the coast-down regeneration conditions, has been eliminated as a result of the monitoring, the coast-down regeneration mode is terminated and the CVVD control mode is changed to the normal control mode (S400).

[0075] For example, if the actuation of an accelerator pedal or a brake pedal is detected (when the output signal of the accelerator pedal position sensor or the brake position sensor is not equal to 0) while a vehicle is being driven in coasting regeneration mode (when the throttle valve is fully open or the CVVD target duration is controlled to maximize it), a control procedure is initiated in which the valve opening duration of the intake valve is set to a target value output from the mapping data, according to the current driving state of the vehicle.

[0076] However, if it is determined that the thrust condition, which is one of the coast-down regeneration conditions, is maintained, the pump loss is reduced by controlling the CVVD target duration to maximize it, thereby maintaining the coast-down regeneration mode, which increases the level of power generation from the belt-driven motor.

[0077] In general, in a mild hybrid electric vehicle (MHEV) system, the engine is connected to the crankshaft of a power unit via a belt, so the engine's drive shaft cannot be disconnected from the power unit during coasting regeneration. Consequently, both the engine's power-generating torque and the power unit's drag torque are applied to the drive shaft, meaning that an increase in the engine's power-generating torque results in a corresponding increase in deceleration, which the driver can perceive as a difference in driving dynamics.

[0078] Therefore, the amount of power generated by an engine during coasting regeneration in the MEHV system is necessarily limited by the prior art. However, according to the present disclosure, the pumping loss during coasting regeneration is reduced by controlling the valve opening duration, thereby reducing the drag torque of a power unit. Furthermore, it is possible to increase the amount of power generated by the belt-driven engine due to the reduced drag torque, thus improving fuel efficiency.

[0079] According to the present disclosure, it is therefore possible to reduce pumping losses by controlling the valve direction during coasting regeneration, thereby reducing the influence of the engine's drag torque on vehicle deceleration during coasting regeneration. It is also possible to increase the amount of energy recovered through the engine's power generation without adding any special mechanical device. Therefore, it is possible to significantly improve a vehicle's fuel efficiency even without adding any special mechanical device.

Claims

[1] Method for controlling regeneration during coasting of a vehicle equipped with a continuously variable valve timing (CVVD) engine, wherein an engine control unit (ECU) controls regenerative braking in the vehicle, the method comprising the following steps: Determine, via the ECU, whether the current state of the vehicle meets coasting regeneration conditions; and The ECU enters a coasting regeneration mode and performs regenerative braking when the current state of the vehicle meets the coasting regeneration conditions. Continuous monitoring to ensure that the coast-down regeneration conditions are met when the vehicle is driven in coast-down regeneration mode, where it is determined that the coasting regeneration conditions are met when the current state of the vehicle is a coasting state, and Ending the coast-down regeneration mode when the thrust state is cleared as a result of monitoring, wherein upon entering coast-down regeneration mode a throttle valve is fully opened so that an intake air quantity of the engine is maximized and a CVVD target duration is controlled so that it is maximized, so that a current generating torque of a belt-driven motor (BDM) is controlled so that it is increased, wherein in the step of entering the coast-down regeneration mode, a valve overlap, in which both an exhaust valve and an intake valve are open, is controlled to maximize it within a controllable range, with a closing time of the intake valve being delayed after a start time of a compression stroke, thereby reducing pumping loss and increasing the current-generating torque of the belt-driven engine. [2] Method according to claim 1, wherein the current state of the vehicle is determined as a push state when output signals of an accelerator pedal position sensor and a brake position sensor are zero and a vehicle speed and an engine speed are above a corresponding set vehicle speed and a set engine speed. [3] Method according to claim 2, wherein a condition in which a shift lever is positioned in a D-area is further included in the thrust state. [4] Device for controlling regeneration during coasting of a vehicle equipped with a continuously variable valve timing (CVVD) engine, the device comprising: a data detector that captures information in real time to determine whether an entry into a roll-out regeneration mode has occurred; an engine control unit (ECU) that determines, by analyzing the information supplied by the data detector, whether entry into coasting regeneration mode has occurred; and a CVVD controller that controls the valve opening duration in the coast-down regeneration mode under the control of the ECU, where entry into coast-down regeneration mode under the control of the ECU occurs when a current state of the vehicle, as a result of the analysis of the information supplied by the data detector, meets coast-down regeneration conditions, wherein in the coast-down regeneration mode a throttle valve is fully opened so that an intake air quantity of the engine is maximized under the control of the ECU, and the CVVD controller controls a CVVD target duration so that it is maximized so that a current-generating torque of a belt-driven motor (BDM) is controlled so that it is increased, where, upon entering the coast-down regeneration mode, the CVVD controller controls valve overlap, in which both an exhaust valve and an intake valve are open, to maximize it within a controllable range, and delays the closing time of the intake valve after a compression stroke start time, thereby reducing pumping losses and increasing the power-generating torque of the belt-driven engine, and wherein the ECU continuously monitors, based on the information supplied in real time by the data detector, whether the coast-down regeneration conditions are met, while controlling the CCVD target duration to be maximized by the CVVD controller, and the CVVD controller controls a valve opening duration of an inlet valve so that it is set to a target value output from mapping data in accordance with a current driving condition under the control of the ECU when a coast-down regeneration condition, which is one of the coast-down regeneration conditions, is lifted as a result of the monitoring. [5] Device according to claim 4, wherein the information acquired by the data detector for entering the coasting regeneration mode includes accelerator pedal position sensor information and / or brake position sensor information and / or vehicle speed information and / or engine speed information and / or gear shift information. [6] Device according to claim 4, wherein in a coasting state in which the output signals of an accelerator pedal position sensor and a brake position sensor are zero and a vehicle speed and an engine speed are above a corresponding set vehicle speed and a set engine speed, the ECU determines that the current state of the vehicle meets the coasting regeneration conditions.

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