Method for controlling an engine with a continuously variable valve duration device

Abstract

Method for controlling an engine (2) with a continuously variable valve duration (CVVD) device (40), the method comprising: Correcting a torque requested by a driver; Transmitting a start signal by a hybrid control unit (Hybrid Control Unit - HCU) (8) to an engine control unit (ECU) (5) when the corrected required torque for driving the engine (2) meets required conditions; Determining a CVVD setpoint for operation of a CVVD intake device (45) according to the corrected required torque; Determining a target current value corresponding to the CVVD target value; and Changing the CVVD setpoint to a CVVD synchronization value when a current state of the engine (2) is in a starting interval, wherein the CVVD synchronization value is configured to synchronize a starting speed (revolutions per minute) of the engine (2) with a speed of an automatic transmission (4) or a speed of a motor generator (3); where the CVVD synchronization value is set to a higher value than the CVVD setpoint.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of Korean Patent Application No. 10-2018-0140079 (KR 10 2020 056 130 A), filed on November 14, 2018, which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates to a method of controlling an engine having a continuously variable valve duration (CVVD) device, and more particularly to a method of controlling an engine having a CVVD device that varies a CVVD setpoint to relatively lower an engine starting speed in a cranking interval (full explosion) of the engine. BACKGROUND

[0003] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0004] An internal combustion engine burns a mixture of fuel and air in a predetermined ratio using a predetermined ignition method to generate power using explosion pressure. Typically, a camshaft is driven by a timing belt connected to a crankshaft, which converts linear motion of a cylinder due to explosion pressure into rotary motion to actuate an intake valve and an exhaust valve. While the intake valve is open, air is drawn into a combustion chamber, and while the exhaust valve is open, gas burned in the combustion chamber is expelled.

[0005] The opening / closing timing and opening duration of the intake and exhaust valves should be adjusted depending on engine operating conditions such as engine speed and load to ensure optimal engine performance. In this context, a continuously variable valve duration (CVVD) device has been developed to adjust the opening duration of the intake and exhaust valves.

[0006] Recently, a motor with a CVVD device has been applied to various hybrid vehicles such as hybrid electric vehicles (HEV) or plug-in hybrid electric vehicles (PHEV).

[0007] A hybrid vehicle can operate in one of the following driving modes: EV mode, in which the hybrid vehicle is powered only by motor-generator power; HEV mode, in which the hybrid vehicle is powered by engine power and motor-generator power; and motor-drive mode, in which the hybrid vehicle is powered only by engine power. Under operating conditions (HEV mode or motor-drive mode) where the motor needs to be driven, a CVVD value corresponding to a torque requested by a driver can be determined, and the CVVD device can be driven according to the determined CVVD value to start the engine.

[0008] However, while the engine is started depending on the CVVD value corresponding to the torque requested by the driver, the engine starting speed may become relatively high, which may make it difficult to synchronize a speed of the engine with a speed of an automatic transmission and / or a speed of the motor-generator.

[0009] From JP 2014 - 58 259 A, a method for controlling an engine with a continuously variable valve duration device is known1, the method comprising: correcting a torque required by a driver; transmitting a start signal by a hybrid control unit to an engine control unit when the corrected required torque for driving the engine meets conditions required; determining a CVVD target value for operating a CVVD intake device according to the corrected required torque; determining a target current value corresponding to the CVVD target value; and changing the CVVD target value into a CVVD synchronization value when a current state of the engine is in a cranking interval, wherein the CVVD synchronization value is configured to synchronize a starting speed of the engine with a speed of an automatic transmission or a speed of a motor-generator.

[0010] The above information described in this background section is intended to facilitate understanding of the background of the inventive concept and may include any technical concept not considered to be prior art that is already known to a person skilled in the art. OVERVIEW

[0011] It is therefore an object of the present disclosure to provide a method for controlling an engine having a continuously variable valve duration (CVVD) device that varies a CVVD setpoint to reduce an engine starting speed in a cranking interval of the engine, thereby improving fuel efficiency and the state of charge (SOC) of a battery.

[0012] The problem is solved by a method having the features of claim 1. Advantageous further developments can be found in the subclaims.

[0013] In one aspect of the present disclosure, a method for controlling an engine having a continuously variable valve duration (CVVD) device may include: correcting a driver-required torque; transmitting / sending a start signal through a hybrid control unit (HCU) to an engine control unit (ECU) when the corrected required torque for driving the engine satisfies required conditions; determining a CVVD target value for operating a CVVD intake device according to the corrected required torque; determining a target current value corresponding to the CVVD target value;and changing the CVVD setpoint to a CVVD synchronization value when a current state of the engine is in a cranking interval, wherein the CVVD synchronization value is set to enable a starting speed of the engine to be synchronized with the speed of an automatic transmission and / or the speed of a motor-generator. The CVVD synchronization value is set to a higher value than the CVVD setpoint.;

[0014] The method may further comprise: changing to a current synchronization value corresponding to the CVVD synchronization value; and applying the current synchronization value to a drive motor of the CVVD aspirator.

[0015] The target current value corresponding to the CVVD target value can be applied to a drive motor of the CVVD intake device when the current state of the engine is outside the cranking interval.

[0016] The required torque can be corrected using a vehicle's drive mode, gear position, engine oil temperature, coolant temperature, and intake air quantity.

[0017] The CVVD target value may be determined by inputting the corrected required torque into a CVVD map, and the CVVD map may include CVVD target values ​​mapped according to an engine speed and an engine torque.

[0018] The target current value may be determined by entering the CVVD target value into an (electrical) current map, and the (electrical) current map may include current values ​​mapped according to the CVVD target values.

[0019] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure. DRAWINGS

[0020] In order that the disclosure may be well understood, various forms thereof will now be described, by way of example, with reference to the accompanying drawings: Fig. 1 illustrates the arrangement / configuration of a hybrid vehicle in one form of the present disclosure; Fig. 2 illustrates the arrangement / configuration of an engine control system in one form of the present disclosure; Fig. 3 illustrates a flowchart of a method of controlling an engine having a continuously variable valve duration device in one form of the present disclosure; Fig. 4 shows a graph of fuel quantity and engine speed when an engine starts according to the CVVD setpoint; Fig. 5 shows a graph of fuel quantity and engine speed when an engine starts according to a CVVD synchronization value; and Fig. 6 illustrates a graph of a valve profile through a CVVD device in one form of the present disclosure.

[0021] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0022] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference characters designate like or corresponding parts and features.

[0023] Some forms of the present disclosure will be described below with reference to the accompanying drawings. Throughout the drawings, the same reference numerals are used to designate the same or equivalent elements. Furthermore, a detailed description of known techniques related to the present disclosure is omitted in order not to unnecessarily obscure the gist of the present disclosure.

[0024] Terms such as first, second, "A", "B", (a), and (b) may be used to describe the elements in some forms of the present disclosure. These terms are used merely to distinguish one element from another, and the core / intrinsic features, sequences or orders, and the like of the respective features are not limited by the terms. Furthermore, unless otherwise specified, all terms used herein, including technical or scientific terms, have the same meanings as those commonly understood by one of ordinary skill in the art or the field to which the present disclosure relates.Such terms / expressions, as defined in a commonly used dictionary, should be interpreted to have meanings corresponding to the context-dependent meanings in the relevant field of prior art and should not be interpreted as having ideal or overly formal meanings unless clearly defined as such in the present application.

[0025] Control methods in some forms of the present disclosure may be performed by at least one controller. The term "controller" refers to a hardware device having a memory and a processor configured to perform one or more steps interpreted as its algorithmic structure. The memory stores algorithmic steps, and the processor is specifically configured to execute the algorithmic steps to perform one or more of the processes described below.

[0026] Furthermore, the control logic of the present disclosure may be embodied in a non-transitory computer-readable medium on a computer-readable medium comprising program instructions executable by a processor, controller, or the like. Examples of computer-readable medium include, but are not limited to, ROM, RAM, CD (compact disc) ROM, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable medium may be distributed in networked computer systems so that it can be stored and executed in a distributed manner, e.g., by a telematics server or a controller area network (CAN).

[0027] With reference to Fig. 1, in some forms of the present disclosure, a hybrid powertrain may include an engine 2, a motor-generator 3, and an automatic transmission 4.

[0028] The hybrid vehicle may be a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or the like.

[0029] As described below, a CVVD (Continuous Variable Valve Duration) device 40 and CVVT (Continuous Variable Valve Timing) devices 45 and 55 may be connected to the engine 2, and the engine 2 may be controlled by an engine control unit (ECU) 5. The ECU 5 may transmit commands to a throttle valve (not shown), a fuel injector (not shown), the CVVT devices 45 and 55, the CVVD device 40, and the like, thereby controlling the operation of the engine 2.

[0030] The motor-generator 3 may be a synchronous motor-generator in which a permanent magnet is embedded in a rotor and a stator coil is wound on a stator. The motor-generator 3 may be controlled by an electric motor control unit (MCU) 6. The MCU 6 may transmit commands / instructions to the motor-generator 3 to thereby control the operation of the motor-generator 3.

[0031] A clutch may be mounted between the engine 2 and the motor-generator 3. By engaging and disengaging the clutch 9, the engine 2 can be engaged and disengaged from the motor-generator 3.

[0032] The automatic transmission 4 may be configured to shift gears according to the driver's intention (vehicle speed, degree of operation of an accelerator pedal, and the like). The automatic transmission 4 may be controlled by a transmission control unit (TCU).

[0033] The ECU 5, the MCU 6 and the TCU 7 may be connected to a hybrid control unit (Hybrid Control Unit) 8, and the HCU 8 may be configured to manage energy consumption of the vehicle and to drive the vehicle with the highest efficiency.

[0034] The HCU 8 may be configured to control the operation of the CVVD motor 2 by the control instructions of the ECU 5, the operation of the motor generator 3 by the control instructions of the MCU 6, the engagement and disengagement of the clutch 9 and gear changes of the transmission 4 by the control instructions of the TCU 7, and the like.

[0035] Meanwhile, Fig. 1 shows the configuration / arrangement of a TMED (Transmission Mounted Electric Device) hybrid vehicle in which the engine 2 and the motor-generator 3 are connected via the clutch 9. However, the present inventive concept is not limited thereto and can be applied to various hybrid vehicles, such as an FMED (Flywheel Mounted Electric Device) hybrid vehicle and a power-split hybrid vehicle.

[0036] With reference to Fig. 2, a control system of the engine 2 may include a data detector 10, a camshaft position sensor 20, the ECU 5, the CVVD intake device 40, a CVVT intake device 45, and a CVVT exhaust device 55.

[0037] The data detector 10 can detect data related to a current driving state of the vehicle in order to control the CVVD intake device 40, the CVVT intake device 45 and the CVVT exhaust device 55.

[0038] The data detector 10 may include a vehicle speed sensor 11, an engine speed sensor 12, an oil temperature sensor 13, a coolant temperature sensor 16, an air flow sensor 14, and an accelerator position sensor (APS) 15.

[0039] The vehicle speed sensor 11 can detect the speed of the vehicle, transmit a corresponding signal to the ECU 5 and be attached to a wheel of the vehicle.

[0040] The engine speed sensor 12 can detect the speed of the engine according to changes in the phase of a crankshaft or phase of a camshaft and transmit a corresponding signal to the ECU 5.

[0041] The oil temperature sensor 13 can detect the temperature of engine oil and transmit a corresponding signal to the ECU 5.

[0042] The coolant temperature sensor 16 can detect the temperature of the engine cooling coolant and transmit a corresponding signal to the ECU 5.

[0043] The air flow sensor 14 can detect the amount of air sucked into an intake manifold and transmit a corresponding signal to the ECU 5.

[0044] The APS 15 can detect the degree to which the driver depresses the accelerator pedal, so that an accelerator pedal position value can be determined by the APS 15. For example, when the accelerator pedal is fully depressed, the accelerator pedal position value is 100 percent, and when the accelerator pedal is not depressed, the accelerator pedal position value is 0 percent.

[0045] In some forms of the present disclosure, a throttle position sensor (TPS) mounted on an intake port may be used instead of the APS 15. In this case, the position value of the accelerator pedal may be determined by the degree of opening of the throttle valve.

[0046] The camshaft position sensor 20 can detect an angle change of the camshaft and transmit a corresponding signal to the ECU 5.

[0047] In some forms of this disclosure, which are Fig. 2, the CVVD intake device 40 and the CVVT intake device 45 may be mounted on an intake side of the engine 2, and the CVVT exhaust device 55 may be mounted on the exhaust side or exhaust side of the engine 2.

[0048] The CVVD intake device 40 can adjust an opening duration of an intake valve of the engine according to the signal from the ECU 5, and the CVVD intake device 40 can be driven by a drive motor 41. The CVVT intake device 45 can adjust an opening / closing timing of the intake valve of the engine according to the signal from the ECU 5.

[0049] The ECU 5 may classify a plurality of control areas according to the engine speed and the engine load based on the signals from the data detector 10 and the camshaft position sensor 20, and control the CVVD intake device 40, the CVVT intake device 45, and the CVVT exhaust device 55 according to the plurality of control areas.

[0050] The ECU 5 may be at least one processor operated by a created program, and the created program may be programmed to control the engine with the CVVD device in some forms of the present disclosure.

[0051] Some of the forms of the present disclosure described herein may be embodied in a recording medium readable by a computer or similar device using software, hardware, or a combination thereof.

[0052] In a hardware implementation, some forms of the present disclosure set forth herein may be realized using at least one of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and electrical devices for performing other functions.

[0053] In software implementation, some forms of the present disclosure relating to procedures / methods and functions set forth herein may be implemented by separate software modules. Each of the software modules may perform one or more functions and operations described in this disclosure. Software code may be implemented in software applications written in suitable programming languages.

[0054] With reference to Fig. 3, a method for controlling an engine with a CVVD device in some forms of the present disclosure is described in detail. When a driver-requested torque is input to the HCU 8, the HCU 8 may correct the requested torque using a vehicle drive mode, gear position, engine oil temperature, engine coolant temperature, intake air amount, and the like in step S1.

[0055] The HCU 8 may be configured to select one of an EV mode, HEV mode, and motor drive mode, and the hybrid vehicle may run in one of the drive modes: the EV mode in which the hybrid vehicle is powered only by power from the motor generator; the HEV mode in which the hybrid vehicle is powered by power from the engine and power from the motor generator; and the motor drive mode in which the hybrid vehicle is powered only by power from the engine.

[0056] The HCU 8 may determine in step S2 whether the required torque for driving the motor 2 corrected by a mode selection map satisfies required conditions. The HCU 8 may store the mode selection map in a memory thereof, and the mode selection map refers to a map in which the EV mode range, the HEV mode range, and the motor drive mode range are divided according to an engine torque and an engine speed.

[0057] If the corrected required torque does not satisfy the conditions required to drive the motor 2 in step S2, the ECU 5 may stop the engine 2 in step S11, and the MCU 6 may control the motor generator 3 to perform the EV mode in step S12.

[0058] If the corrected required torque satisfies the conditions required to drive the engine 2 in step S2, the HCU 8 may transmit a start signal to start the engine 2 to the ECU 5 in step S3.

[0059] The HCU 8 may determine a CVVD target value for determining an intake valve duration by operating the CVVD intake device 40 according to the corrected required torque in step S4. The memory of the HCU 8 may store a CVVD map, and the CVVD map may include CVVD target values ​​mapped according to an engine speed and an engine load (torque). Thus, the HCU 8 may determine the CVVD target value by inputting the corrected required torque to the CVVD map.

[0060] The ECU 5 may determine a target current value corresponding to the determined CVVD target value in step S5. When the target current value is applied to the drive motor 41 of the CVVD intake device 40, the CVVD intake device 40 may be driven at the CVVD target value. The ECU 5 may store an (electrical) current map in a memory thereof, and the (electrical) current map may include current values ​​mapped according to CVVD target values. Thus, the ECU 5 may determine the target current value by inputting the CVVD target value into the current map.

[0061] The ECU 5 may determine in step S6 whether a current state of the engine 2 is within a cranking interval (full explosion) for restarting after the engine 2 is turned on / off. For example, if a rotational speed of the engine 2 detected by the engine rotational speed sensor is lower than a set rotational speed for full explosion, it may be determined that the current state of the engine 2 is within the cranking interval (that is, the starting of the engine 2 is not completed), and if a rotational speed of the engine 2 detected by the engine rotational speed sensor is higher than or equal to the set rotational speed for full explosion, it may be determined that the current state of the engine 2 is outside the cranking interval (that is, the starting of the engine 2 is completed).

[0062] If it is determined in step S6 that the current state of the engine 2 is in the cranking interval (that is, when the starting of the engine 2 is not completed), the ECU 5 may change the CVVD target value to a predetermined range for synchronizing CVVD values ​​(for example, 0-55) in step S7. The CVVD synchronization values ​​refer to CVVD values ​​set to enable the engine starting speed to be suitable for synchronization with a speed of the automatic transmission 4 and / or a speed of the motor generator 3.

[0063] When the CVVD target value is changed to the CVVD synchronization value, the ECU 5 may change to a current synchronization value corresponding to the CVVD synchronization value in step S8, so that the ECU 5 can apply the current synchronization value to the drive motor 41 of the CVVD intake device 40 to drive the CVVD intake device 40 according to the CVVD synchronization value in step S9. When the current synchronization value is applied to the drive motor 41 of the CVVD intake device 40, the starting speed of the engine 2 can be set to a speed suitable for synchronization. When the hybrid vehicle is running in the HEV mode, the starting speed of the engine 2 can be accurately synchronized with the speed of the automatic transmission 4 and the speed of the motor generator, and when the hybrid vehicle is running in the motor drive mode, the starting speed of the engine 2 can be accurately synchronized with the speed of the automatic transmission 4.

[0064] Meanwhile, when the starting speed of the engine 2 becomes relatively lower, the starting speed of the engine 2 can be more accurately synchronized with the speed of the automatic transmission 4 and / or the speed of the motor generator 3.

[0065] In some forms of the present disclosure, the CVVD synchronization value may be greater than the CVVD setpoint so that the starting speed of the engine 2 in the cranking interval may be lowered relative to the prior art starting speed, thereby facilitating its synchronization, increasing starting torque, and improving fuel efficiency. For example, as in Fig. 4, in a case where a CVVD target value is 226, when the engine 2 starts in a state where a target current value corresponding to the CVVD target value is applied to the drive motor 41 of the CVVD intake device 40, a starting speed can become 1280. In comparison to, as shown in Fig. 5, in a case where a CVVD value is increased to 236 (CVVD synchronization value), a starting speed can be lowered to 1220, and thus the synchronization can be performed accurately and easily, and the fuel efficiency can be improved.

[0066] If it is determined in step S6 that the current state of the engine 2 is outside the cranking interval (that is, when the starting of the engine 2 is completed), the ECU 5 may apply the target current value corresponding to the CVVD target value to the drive motor 41 of the CVVD application device 40 to drive the CVVD intake device 40 according to the CVVD target value in step S10. As in Fig. 6, when the CVVD intake device 40 operates according to the CVVD setpoint, the intake valve duration can be determined.

[0067] As set forth above, in some forms of the present disclosure, the method for controlling an engine having a CVVD device may vary a CVVD setpoint to relatively lower an engine starting speed in the cranking interval (full explosion) of the engine, thereby enabling the engine starting speed to be accurately synchronized with a speed of the automatic transmission and / or a speed of the motor-generator, and thus increasing starting torque and improving fuel efficiency and the state of charge (SOC) of a battery. 1 hybrid powertrain 2 engines 3 Motor-Generator 4 automatic transmissions 5 Engine control unit 6 Electric motor control unit 7 Transmission control unit 8 Hybrid control 9 Clutch 10 Data detector 11 Vehicle speed sensor 12 Engine speed sensor 13 Oil temperature sensor 14 Air flow sensor 15 Accelerator pedal position sensor 16 Coolant temperature sensor 20 Camshaft position sensor 40 CVVD suction device 45 CVVT intake device 55 CVVT exhaust device

Claims

[1] Method for controlling an engine (2) having a continuously variable valve duration (CVVD) device (40), the method comprising: Correcting a torque requested by a driver; Transmitting a start signal by a hybrid control unit (Hybrid Control Unit - HCU) (8) to an engine control unit (ECU) (5) when the corrected required torque for driving the engine (2) meets required conditions; Determining a CVVD setpoint for operation of a CVVD intake device (45) according to the corrected required torque; Determining a target current value corresponding to the CVVD target value; and Changing the CVVD setpoint to a CVVD synchronization value when a current state of the engine (2) is in a starting interval, wherein the CVVD synchronization value is configured to synchronize a starting speed (revolutions per minute) of the engine (2) with a speed of an automatic transmission (4) or a speed of a motor generator (3); where the CVVD synchronization value is set to a higher value than the CVVD setpoint. [2] The method of claim 1, wherein the method further comprises: Change to a current synchronization value corresponding to the CVVD synchronization value; and Applying the current synchronization value to a drive motor (41) of the CVVD suction device (45). [3] The method of claim 1, wherein the method comprises: Applying the target current value corresponding to the CVVD target value to the drive motor (41) of the CVVD intake device (45) when the current state of the engine (2) is not in the starting interval. [4] The method of claim 1, wherein the method comprises: Correcting the required torque using a vehicle drive mode, gear position, engine oil temperature, coolant temperature, and intake air flow. [5] The method of claim 1, wherein the method comprises: Determining the CVVD setpoint by entering the corrected required torque into a CVVD map, wherein the CVVD map includes the CVVD setpoint mapped according to the speed of the engine (2) and an engine torque. [6] The method of claim 1, wherein the method comprises: Determining the target current value by entering the CVVD target value into a current map, wherein the current map includes a current value that is mapped according to the CVVD target value.

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