Hybrid electric vehicle and methods for controlling it

Abstract

Methods for controlling a hybrid electric vehicle, comprising the following: Receiving traffic light information, including signal information and distance information of an upcoming traffic light, by a controller under an entry condition for an electric vehicle (EV) mode; Prediction of the duration of an EV mode based on the traffic light information received by the controller; Prediction of a coolant temperature in EV mode by the controller depending on the predicted duration of the EV mode; Comparing the predicted coolant temperature with a reference temperature at which a fully automatic temperature control unit (FATC) requests the start of an internal combustion engine by the control unit; and The controller enters EV mode when the predicted coolant temperature is higher than the reference temperature.

Description

BACKGROUND Area of ​​the invention

[0001] The present invention relates to a hybrid electric vehicle and a method for controlling the same, and in particular to a hybrid electric vehicle and a method for controlling the same, which are able to predict the duration of an electric vehicle (EV) mode based on traffic light information and to estimate the temperature of a coolant accordingly, thereby minimizing the entry into a series hybrid electric vehicle (HEV) mode for interior heating. Discussion of the state of the art

[0002] In general, a hybrid electric vehicle (HEV) is a vehicle that uses two types of energy sources, namely an internal combustion engine and an electric motor. Such a hybrid electric vehicle generates optimal power and torque through the harmonious operation of the two power sources, namely the internal combustion engine and the electric motor. Specifically, in a hybrid electric vehicle that uses a parallel-type or transmission-mounted electric drive (TMED) system, where an electric motor and an internal combustion engine clutch (EC) are mounted between an internal combustion engine and a transmission, the power of the internal combustion engine and the power of the electric motor can be transmitted simultaneously to a single drive shaft.

[0003] Under normal conditions, the hybrid electric vehicle initially operates in electric vehicle (EV) mode during acceleration, relying solely on the electric motor. If greater driving power is subsequently required, the driving mode switches to hybrid electric vehicle (HEV) mode, where power is generated by both the electric motor and the combustion engine. Depending on the primary power source, the HEV mode, in which the electric motor and combustion engine work together, can be further subdivided into parallel HEV mode and series HEV mode.

[0004] In parallel HEV mode, the combustion engine's power serves as the driving force. In series HEV mode, however, the motor operates at a low load, thus using the combustion engine's power to generate electricity. Parallel HEV mode is more efficient than series HEV mode. However, since the TMED hybrid electric vehicle is generally not equipped with a torque converter, it is difficult, unlike a vehicle with a combustion engine, to maintain the motor's engagement below a certain vehicle speed. Therefore, the TMED hybrid electric vehicle operates in series HEV mode when traveling at low speeds below a predetermined speed.

[0005] In newly developed vehicles, a fully automatic temperature control (FATC) system is responsible for climate control operation. In hybrid electric vehicles, the FATC unit, when necessary, controls the heating of the interior air using the engine coolant, which is heated by the engine. Specifically, if the engine coolant temperature falls below the temperature required by the FATC unit to heat the interior air, the FATC unit requests a hybrid control unit (HCU) to start the engine. The HCU then starts the engine, selecting either parallel or series operation depending on the situation.

[0006] Fig. Figure 1 shows diagrams to illustrate problems of the HEV mode switching control when the vehicle stops due to a traffic light under driving conditions that require interior heating. Fig. Figure 1 shows a vehicle speed graph, a graph showing a change in the value of an accelerator pedal position sensor (APS), a driving mode graph, and a coolant temperature graph. The horizontal axis of each of these graphs represents time.

[0007] The first section, S1, is a section in which the vehicle travels at a speed that allows it to operate in parallel mode. In parallel mode, the power of the internal combustion engine acts as the driving force, and therefore the temperature of the engine coolant can rise due to the engine's heat. As the driving time in parallel mode increases, the coolant temperature rises, and the engine coolant, whose temperature is higher than a reference temperature, can be used as an energy source for heating the passenger compartment.

[0008] A second section, S2, is a section in which the vehicle decelerates to a standstill due to a stop signal from a traffic light, such as a red light. Since the accelerator pedal is no longer used for deceleration and the vehicle speed decreases, the driving mode switches to EV mode. Consequently, the combustion engine stops running, and the coolant temperature drops.

[0009] A third section, S3, is a section in which the engine for interior heating operates when the vehicle is stationary or traveling at low speed. When the vehicle is stationary or traveling at low speed, the internal combustion engine stops, and consequently, the coolant temperature drops. If the coolant temperature is equal to or lower than a preset value, the heating output requested by the driver may not be guaranteed. Accordingly, the FATC unit requests the HCU to start the internal combustion engine when the coolant temperature drops to a first reference value (FATC On Temp.). The HCU then starts the internal combustion engine to raise the coolant temperature at the request of the FATC unit. When the engine is started, either parallel or series mode can be selected. However, when the vehicle is in the third section, S3, i.e.,When driving at low speed or when stopped, the vehicle switches to serial HEV mode.

[0010] A fourth section, S4, is a section in which the serial HEV mode for cabin heating is terminated, and the vehicle remains ready until the traffic light signal changes to a go signal, such as a green light. If the coolant temperature rises and reaches a second reference value (FATC Off Temp.) at which cabin heating is possible due to the serial HEV mode, the FATC unit requests the HCU to shut off the engine. The HCU stops the combustion engine to terminate the serial HEV mode at the FATC unit's request. With the combustion engine off, the coolant temperature drops. A fifth section, S5, is a section in which the vehicle resumes driving in response to the traffic light's "go" signal and travels at a speed that allows the vehicle to operate in parallel mode.

[0011] As described above, the combustion engine must be run for cabin heating when the coolant temperature drops under driving conditions that require cabin heating. When the combustion engine is started for cabin heating, it is advantageous to drive the vehicle in parallel HEV mode to improve fuel efficiency and increase the coolant temperature. However, when the vehicle is traveling at low speeds or stopped, for example, at a traffic light, it is difficult to reach the vehicle speed at which the vehicle can switch to parallel HEV mode, so the vehicle must be driven in series HEV mode.

[0012] Particularly in extremely cold environments, the FATC unit may repeatedly request the combustion engine to start for extended periods or frequently. Consequently, the vehicle operates in series HEV mode to regulate coolant temperature, rather than in EV mode, resulting in reduced fuel efficiency.

[0013] Furthermore, DE 10 2028 121 700 A1 provides methods and systems for controlling an internal combustion engine idling stop based on upcoming traffic and road conditions. For example, a method can include: receiving data, including traffic information and road characteristics immediately in front of a vehicle from one or more remote sources, and adjusting one or more vehicle thresholds based on the received data. The duration of the future idling stop of the internal combustion engine can be estimated based on the received data, and an idling stop of the internal combustion engine can be initiated based on the duration of the future idling stop and the adjusted one or more vehicle thresholds.

[0014] Furthermore, US patent 2019 / 0100193A1 discloses a method for controlling the engine operation of a hybrid vehicle to minimize non-driving fuel consumption when stopped, comprising the steps of receiving traffic information, including signal information from a traffic light ahead; determining whether a forward signal change condition is met based on the received signal information when stopped; setting one of the various engine operating conditions according to the result of the determination; and comparing the set engine operating condition with a current vehicle state to determine whether the engine is running or not. OVERVIEW

[0015] Accordingly, the present invention relates to a hybrid electric vehicle and a method for controlling it, which substantially eliminate one or more problems arising from limitations and disadvantages of the prior art. One object of the present invention is to provide a hybrid electric vehicle and a method for controlling it that are capable of minimizing driving in a series HEV mode for interior heating under driving conditions that require interior heating, thereby minimizing any deterioration in fuel efficiency. However, the objectives to be achieved by the exemplary embodiments are not limited to the objects mentioned above, and other objects not mentioned here will be clearly understood by those skilled in the art, to whom the exemplary embodiments are addressed, from the following description.

[0016] The problems are solved by a method having the features of claim 1 and a hybrid electric vehicle having the features of claim 11. Advantageous further developments can be found in the dependent claims.To solve the above and other problems, a method for controlling a hybrid electric vehicle according to an exemplary embodiment of the invention comprises the following: receiving traffic light information, including signal information and distance information of an upcoming traffic light under an EV mode entry condition; predicting the duration of the EV mode based on the received traffic light information; predicting the temperature of a coolant in the EV mode according to the predicted duration of the EV mode; comparing the predicted temperature of the coolant with a reference temperature at which a fully automatic temperature control unit (FATC) requests the starting of an internal combustion engine; and entering the EV mode when the predicted temperature of the coolant is greater than the reference temperature.

[0017] Furthermore, a hybrid electric vehicle according to an exemplary embodiment of the invention comprises a first controller configured to receive traffic light information, including signal information and distance information from an upcoming traffic light, and a second controller configured to predict the duration of an EV mode based on the received traffic light information, to predict the temperature of a coolant in the EV mode according to the predicted duration of the EV mode, to compare the predicted temperature of the coolant with a reference temperature at which a fully automatic temperature control unit (FATC) requests the starting of an internal combustion engine, and to enter the EV mode when the predicted temperature of the coolant is greater than the reference temperature. BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0018] The accompanying drawings, which are included for a better understanding of the invention and form part of this application, show exemplary embodiments of the invention and, together with the description, serve to explain the principle of the invention. The drawings include: shows Fig. 1. Instructions for explaining problems with the HEV mode switching for interior heating in a conventional hybrid electric vehicle according to the state of the art; Fig. Figure 2 shows an example of the construction of a powertrain of a hybrid electric vehicle, as it occurs in exemplary embodiments according to the invention; Fig. Figure 3 is a block diagram showing an example of a control system for a hybrid electric vehicle, as applicable in exemplary embodiments according to the invention; Fig. 4 is a flowchart that schematically shows a control process of a hybrid electric vehicle according to an exemplary embodiment of the invention; Fig. Figure 5 is a diagram illustrating a method for predicting the duration of an EV mode based on traffic light information in a hybrid electric vehicle according to an exemplary embodiment of the invention; Fig. Figure 6 is a diagram illustrating a method for predicting the temperature of a coolant in a hybrid electric vehicle according to an exemplary embodiment of the invention; Fig. Figure 7 is a flowchart showing a control process of a hybrid electric vehicle according to a first exemplary embodiment of the present disclosure; Fig. Figure 8 is a flowchart showing a control process of a hybrid electric vehicle according to a second exemplary embodiment of the invention; and Fig. Figure 9 shows diagrams illustrating the effects of the HEV mode switching on interior heating in a hybrid electric vehicle according to the invention. DETAILED DESCRIPTION

[0019] It is understood that the term "vehicle" or "vehicle-like" or a similar term as used herein encompasses 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 hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other vehicles using alternative fuels (e.g., fuels derived from resources other than petroleum). As described herein, a hybrid vehicle is a vehicle that has two or more sources of propulsion, e.g., both gasoline-powered and electric-powered vehicles.

[0020] Although the exemplary embodiment is described as using a plurality of units to execute the exemplary process, the exemplary processes can also be executed by one or more modules. Furthermore, it is understood that the term controller / control unit refers to a hardware device comprising memory and a processor, specifically programmed to execute the processes described herein. The memory is configured to store the modules, and the processor is specifically configured to execute the modules to perform one or more processes, which are further described below.

[0021] Furthermore, the control logic according to the invention can be embodied as a non-volatile, computer-readable medium on a computer-readable medium containing executable program instructions that are executed by a processor, a controller / control unit, or the like. Examples of computer-readable data carriers 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 recording medium can also be distributed across networked computer systems, allowing the computer-readable medium to be stored and executed in a distributed manner, for example, by a telematics server or a controller area network (CAN).

[0022] The terminology used herein serves only to describe certain embodiments and is not to be understood as limiting the invention. The singular forms "a," "an," and "the" used herein also include the plural forms unless the context clearly indicates otherwise. Furthermore, it is understood that the terms "comprises" and / or "comprehensive," as used in this description, describe the presence of specified features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes all combinations of one or more of the related listed items.

[0023] Unless explicitly stated or evident from the context, the term "approximately" is used here to mean within a normal tolerance range in engineering, i.e., within about two standard deviations from the mean. "Approximately" can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise indicated by the context, all numerical values ​​given herein are to be considered modified by the term "approximately".

[0024] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily carry out the exemplary embodiments. However, the present invention can be embodied in many different forms and should not be understood as limited to the exemplary embodiments shown here. For the sake of clarity, parts of the drawings that are irrelevant to the description of the present invention have been omitted. The same reference numerals refer to the same elements throughout the description.

[0025] If, throughout the description, a particular part "includes" or "comprises" a specific component, this means that other components, unless otherwise specified, are not excluded and may also be included. The same reference numbers used throughout the description refer to the same components.

[0026] Fig. Figure 2 shows an example of the construction of a powertrain of a hybrid electric vehicle, in which exemplary embodiments of the invention can be used. Fig. Figure 2 shows a powertrain of a hybrid electric vehicle that uses a parallel hybrid system in which an electric motor (or drive motor) 140 and an engine coupling (EC) 130 are arranged between an internal combustion engine (ICE) 110 and a transmission 150.

[0027] If, in such a vehicle, a driver presses an accelerator pedal after starting the vehicle, the electric motor 140 can initially be driven by the energy of a battery in the state in which the motor clutch 130 is open, and then the motor's power can be transmitted via the transmission 150 and an axle drive (FD) 160 to the wheels to turn them (i.e., in EV mode). If greater driving force is required when accelerating the vehicle, an auxiliary motor (or a starter / generator motor) 120 can be used to drive the motor 110.

[0028] When the rotational speeds of the combustion engine 110 and the electric motor 140 are equal, the engine clutch 130 is engaged, so that both the combustion engine 110 and the electric motor 140, or only the combustion engine 110, propel the vehicle (i.e., transition from EV mode to HEV mode). If a predetermined engine-off condition is met, e.g., when the vehicle is decelerating, the engine clutch 130 is disengaged and the combustion engine 110 is switched off (i.e., transition from HEV mode to EV mode). Furthermore, when the hybrid electric vehicle decelerates, the driving force of the wheels is converted into electrical energy and the battery is charged with this electrical energy; this is known as regenerative braking or brake energy recuperation.

[0029] The starter / generator motor 120 functions as a starter when the internal combustion engine is started and as a generator when the rotational energy of the internal combustion engine is being stored after starting or when the internal combustion engine is switched off. Therefore, the starter / generator motor 120 can be referred to as a "hybrid starter generator (HSG)" or, in some cases, as an "auxiliary motor".

[0030] The relationships between the control systems in the vehicle using the powertrain described above are in Fig. 3 shown. Fig. Figure 3 is a block diagram showing an example of a control system for a hybrid electric vehicle in which exemplary embodiments of the invention can be used.

[0031] Referring to Fig. 3 In a hybrid electric vehicle, in which exemplary embodiments of the invention are applicable, the internal combustion engine 110 can be operated by an engine control unit 210, and the torque of the starter / generator motor 120 and the electric motor 140 can be controlled by an engine control unit (MCU) 220. The engine clutch 130 can be controlled by a clutch control unit 230. In particular, the engine control unit 210 can be referred to as an engine management system (EMS). Furthermore, the transmission 150 can be controlled by a transmission control unit 250. In some cases, a control unit configured for the operation of the starter / generator motor 120 and a control unit configured for the operation of the electric motor 140 can be provided separately.

[0032] Each of the controllers can be connected to a Hybrid Control Unit (HCU) 240, which is a higher-level controller configured to execute the overall mode switching process. It can provide the Hybrid Control Unit 240 with information required for engine clutch control at the time of switching driving modes or gear changes, and / or information required for engine stop control, or it can perform an operation in response to a control signal while the Hybrid Control Unit 240 is operating. More specifically, the Hybrid Control Unit 240 can be configured to determine, depending on the vehicle's driving state, whether the mode switching process should be performed.

[0033] For example, the hybrid control unit can be configured to determine the point in time at which the engine clutch 130 should be opened. Once the engine clutch 130 is open, the hybrid control unit can be configured to perform hydraulic pressure control (in the case of a wet engine clutch) or torque capacity control (in the case of a dry engine clutch). Furthermore, the hybrid control unit 240 can be configured to determine the state of the engine clutch (e.g., engaged, slipped, open, etc.) and to set the time at which fuel injection into the internal combustion engine 110 should be stopped. In addition, the hybrid control unit can be configured to transmit a torque command to the engine control unit 220 to adjust the torque of the starter / generator motor 120 in order to control the engine stop, thereby controlling the recovery of the engine's rotational energy.Furthermore, the hybrid control 240 can be configured to determine the mode switching condition and to operate the subordinate controls in order to carry out the mode switching at the time of the mode switching control according to the exemplary embodiments of the invention, which will be described later.

[0034] Of course, it is clear to those skilled in the art that the connection relationships between the controllers and the functions / division of the controllers described above are exemplary and are not limited by their designations. For example, the hybrid controller 240 can be implemented in such a way that its function is provided by any other controller besides the hybrid controller 240, or in such a way that its function is distributed and provided by two or more of the other controllers.

[0035] Furthermore, although above with reference to Fig. 2 and Fig. 3, a parallel hybrid electric vehicle of the type gear-mounted electric drive (TMED), is described only by way of example, and the exemplary embodiments of the invention are not limited to a specific type of hybrid electric vehicle. The exemplary embodiments of the invention can be used in any type of hybrid electric vehicle as long as it is possible to implement interior heating using the heat generated by the operation of the motor.

[0036] A more efficient control method according to an exemplary embodiment of the invention is described below, based on the vehicle structure described above. Fig. Figure 4 is a flowchart that schematically illustrates a control process of a hybrid electric vehicle according to an exemplary embodiment of the invention. Referring to Fig. 4 In an exemplary embodiment of the invention, the duration of the EV mode can be predicted based on traffic light information (S10), and a reduction in the coolant temperature can be estimated (S20). If the occurrence of the serial HEV mode is expected based on the estimated coolant temperature, the occurrence of the serial HEV mode can be prevented or minimized (S30).

[0037] If the duration of EV mode is predicted based on traffic light information in step S10, the traffic light information may include at least one of the following: the signal change interval of an upcoming traffic light, the currently displayed signal ahead on the current route, the remaining distance to an upcoming traffic light, the remaining time of the currently displayed signal, information about the display of the next signal, or information about the location of the traffic light. In addition to the traffic light information, further traffic information may be included, such as information about the route to an upcoming traffic light, congestion in each segment, and an average speed in each segment. It can be assumed that the traffic light information and the traffic information are received via an audio / video / navigation (AVN) system, but this is only an example.

[0038] The exemplary embodiments of the invention are not limited to a specific controller or system, as long as it is possible to establish wireless communication with a unit that provides the traffic information. For example, traffic light information can be acquired from a telematics center via a telematics modem or via a data center / server / cloud connection using a wireless communication module, and vehicle speed information can be acquired via various sensors installed in the vehicle. The duration of EV mode can be predicted based on the traffic light information.

[0039] Fig. Figure 5 is a diagram illustrating a method for predicting the duration of EV mode based on traffic light information according to an exemplary embodiment of the invention. Referring to Fig. 5. The duration of EV mode can be calculated using a time interval t1 that the vehicle needs to reach a traffic light and a signal waiting time interval t2 that remains until a release signal from the traffic light, e.g. a green light, is switched on.

[0040] The time interval t1 required to reach the traffic light can be calculated by inserting the remaining distance d1 to the traffic light and the vehicle speed into the following equation 1. t1=d1 / vehicle speed where t1 represents the time required to reach the traffic light, and d1 represents the remaining distance to the traffic light.

[0041] The signal waiting time t2 can be calculated by inserting the remaining time of the current signal and the remaining time of the next signal into the following logical formula 1. Logical Formula 1: If t1 > t_now, Predicted Signal = Next Signal, t2 = t_next - t_now. Otherwise, Predicted Signal = Current Signal, t2 = t_now - t1 where t_now represents the remaining time of the current signal and t_next represents the remaining time of the next signal.

[0042] If the predicted signal is 'stop' according to the above logical formula 1, then the duration of the EV mode t_EV can be calculated as follows: t_EV = t1 + t2, and if the predicted signal is 'go', then the duration of the EV mode t_EV can be calculated as follows: t_EV = 0. If the duration of the EV mode is predicted, then step S20, i.e., the process of estimating the coolant temperature, can be carried out.

[0043] Fig. Figure 6 is a diagram illustrating a method for predicting the coolant temperature in a hybrid electric vehicle according to an exemplary embodiment of the invention. With reference to Fig. 6. A change in the temperature of the engine coolant can be achieved using the amount of heat Q absorbed by the engine. engine , the amount of heat Q released into the atmosphere Out and the amount of heat Q used for interior heating Fatc This can be calculated. This is expressed using equation 2 below. ΔT=Qengine−(QOut+QFatc)CM where Q engine represents the amount of heat absorbed by the engine, Q Out represents the amount of heat released into the atmosphere (Q Out = f(Outside air temperature, engine coolant temperature), Q Fatc represents the amount of heat used for interior heating (Q Fatc= f(target temperature, internal temperature), C represents the heat capacity of the engine coolant and M represents the mass of the engine coolant.

[0044] The predicted coolant temperature T Final Using ΔT calculated by equation 2 above, it can be calculated by the following equation 3, in which a change in the amount of heat during EV mode in the initial coolant temperature T initial is reflected. TFinal=Tinitial+∫0tEVΔT dt

[0045] Will the predicted coolant temperature T Final Obtained through the above calculation process, it can be determined whether the FATC unit requests engine drive at the time of entry into EV mode. In other words, the predicted coolant temperature T FinalIf the temperature is equal to or less than the first reference value (FATC An Temp.) required by the FATC unit to perform interior heating, it can be predicted that the FATC unit will request the motor to drive at the time of entering EV mode, and thus it is possible to perform control to minimize operation in series HEV mode.

[0046] As a control method to minimize operation in series HEV mode, when the FATC unit requests motor operation, the motor stop time before entering EV mode can be delayed as much as possible, or the heating power of the FATC unit can be reduced. Alternatively, these two methods can also be used together.

[0047] Fig. Figure 7 is a flowchart illustrating a control method for a hybrid electric vehicle according to a first exemplary embodiment of the invention. In particular, it shows Fig. 7 an embodiment in which a motor stop time is delayed as much as possible to minimize operation in serial HEV mode.

[0048] Referring to Fig. 7. When switching to EV mode is requested (S110), the duration of EV mode can be predicted based on traffic light information (S120). The duration of EV mode can be predicted by calculating the time interval t1 that the vehicle needs to decelerate and reach a traffic light, and the signal waiting interval t2 that remains until a green light signal is activated.

[0049] If the duration of EV mode is predicted, a change in coolant temperature can be predicted (S130). The predicted coolant temperature T Final can be calculated by changing the amount of heat during EV mode in the initial coolant temperature T initialis taken into account. Subsequently, it can be determined whether the calculated predicted coolant temperature T Final a low coolant temperature that is equal to or lower than the first reference value (FATC An Temp.) required by the FATC unit to perform interior heating (S140).

[0050] In response to the finding that the predicted coolant temperature T Final Since there is no low coolant temperature, the engine coolant temperature is sufficient to maintain interior heating, even when EV mode is activated. Accordingly, the engine can be stopped and EV mode activated (S150). In response to the determination in step S140 that the predicted coolant temperature T FinalIf the coolant temperature is low, the entry into EV mode can be delayed, and it can be determined whether the vehicle is capable of being driven in parallel HEV mode (S160). Generally, the vehicle can be driven in parallel HEV mode if it is traveling at a predetermined speed or higher.

[0051] If the vehicle is capable of operating in parallel HEV mode, the parallel HEV mode can be maintained (S170). The process returns to step S120 to predict the duration of the EV mode. If the vehicle is not capable of operating in parallel HEV mode, the serial HEV mode can be maintained (S180). The process returns to step S120 to predict the duration of the EV mode.

[0052] As described above, in the first exemplary embodiment according to the invention, when switching to EV mode is requested, a predicted coolant temperature T can be used. Final calculated using traffic light information before the engine is switched off, and it can be determined whether the predicted coolant temperature T Final a low coolant temperature. In response to the finding that the predicted coolant temperature T Final If the coolant temperature is low, the HEV mode can be maintained, and in response to the finding that the predicted coolant temperature T FinalIf the temperature is sufficiently high, the driving mode can be switched to EV mode. Accordingly, when the vehicle stops at a traffic light or travels at a low speed, it is possible to prevent a deterioration in fuel efficiency by entering the HEV mode to regulate the coolant temperature at the request of the FATC unit.

[0053] Fig. Figure 8 is a flowchart showing a control process of a hybrid electric vehicle according to a second exemplary embodiment of the invention. In particular, it shows Fig. 8 An exemplary embodiment with reduced heating power to minimize operation in series HEV mode. Referring to Fig. 8. When switching to EV mode is requested (S210), the duration of EV mode can be predicted based on traffic light information (S220). The duration of EV mode can be predicted by calculating the time interval t1 that the vehicle needs to decelerate and reach a traffic light, and the signal waiting interval t2 that remains until a green light signal is activated.

[0054] If the duration of EV mode is predicted, a change in coolant temperature can be predicted (S230). The predicted coolant temperature T Final can be calculated by changing the amount of heat during EV mode in the initial coolant temperature T initial is taken into account. Subsequently, it can be determined whether the calculated predicted coolant temperature T Finala low coolant temperature that is equal to or lower than the first reference value (FATC An Temp.) required by the FATC unit to perform interior heating (S240).

[0055] In response to the finding that the predicted coolant temperature T Final Since there is no low coolant temperature, the engine coolant temperature is sufficient to maintain interior heating, even when EV mode is activated. Accordingly, the engine can be stopped and EV mode can be activated (S250). In response to the finding in step S240 that the predicted coolant temperature T FinalIf the coolant temperature is low, the entry into EV mode can be delayed, and a reduction in heating power can be requested from the FATC unit (S250). In other words, a request can be made to reduce the target coolant temperature required for interior heating or to reduce the heating temperature.

[0056] If reducing the heating power of the FATC unit is not possible, the engine can be switched off and EV mode activated (S280). If reducing the heating power of the FATC unit is possible (S260), the coolant reference temperature or the heating temperature can be adjusted to reduce the heating power (S270). The process then returns to step S220 to predict the duration of EV mode.

[0057] As described above, in the second exemplary embodiment of the invention, when switching to EV mode is requested, a predicted coolant temperature T can be used. Final calculated based on traffic light information before the engine is switched off, and it can be determined whether the predicted coolant temperature T Final a low coolant temperature. In response to the finding that the predicted coolant temperature T Final If the coolant temperature is low, the heating power can be reduced, thus preventing a deterioration in fuel efficiency due to entering serial HEV mode to adjust the coolant temperature at the request of the FATC unit.

[0058] The control process according to the exemplary embodiments of the invention can be implemented such that the hybrid control unit receives traffic light information from the AVN system and executes a pre-stored program in internal memory to predict the duration of the EV mode or to estimate the coolant temperature. Furthermore, the heating setting can be received from the climate control unit (e.g., the FATC unit). In addition, information about the current coolant temperature can be received from the engine control unit, and a request to start the engine can be made by transmitting a command to the engine control unit. According to another aspect of this exemplary embodiment, the engine control unit can be configured to execute the control logic described above, or a separate control unit can be provided for executing the control logic.

[0059] Fig. Figure 9 shows diagrams to illustrate the effects of the HEV mode switching on the interior heating in the hybrid electric vehicle according to the invention. Fig. Figure 9 shows a vehicle speed graph, a graph showing a change in the value of an accelerator pedal position sensor (APS), a driving mode graph, and a coolant temperature graph. The horizontal axis of each of these graphs represents time.

[0060] The first section, S1, is a section where the vehicle travels at a speed that allows it to operate in parallel mode. In parallel mode, the combustion engine's power acts as the driving force, therefore the engine coolant temperature can rise due to the engine's heat. As the driving time in parallel mode increases, the coolant temperature rises, and the engine coolant, now at a temperature higher than a reference temperature, can be used as an energy source for heating the passenger compartment.

[0061] A second section, S2, is a deceleration section in which the vehicle slows down and approaches a traffic light. When the driver releases the accelerator pedal to decelerate, the vehicle's speed decreases. Conventionally, as the vehicle's speed decreases, the engine is switched off to enter EV mode, and the coolant temperature drops from the moment EV mode is activated. However, the present invention predicts the duration of EV mode based on traffic light information and forecasts a change in coolant temperature based on the duration of EV mode.

[0062] In response to the finding that the predicted coolant temperature T FinalIf the coolant temperature is low, equal to or lower than the first reference value (FATC An Temp.) required by the FATC unit to perform interior heating, the entry into EV mode can be postponed, and the parallel HEV mode can be maintained. Accordingly, the coolant temperature rises continuously. According to the invention, the duration of the EV mode and a resulting change in the coolant temperature can be predicted in the state where the parallel HEV mode is maintained. In response to the finding that the predicted coolant temperature T Final If the coolant temperature is not low, the engine can be stopped and EV mode can be activated. The coolant temperature will decrease from the moment EV mode is activated.

[0063] A third section S3 and a fourth section S4 are sections in which the vehicle waits for the traffic light signal to change to a go signal. Since the coolant temperature drops to a low level while the vehicle waits for a traffic signal, the FATC unit typically requests the combustion engine to start. Accordingly, the HCU enters series HEV mode to increase the coolant temperature. In contrast, according to the invention, the parallel HEV mode can be maintained until the coolant temperature rises sufficiently based on the signal waiting time, and then the EV mode can be activated, preventing the coolant temperature from dropping to a low level while the vehicle waits for a traffic signal. Consequently, it is possible to maintain the EV mode while the vehicle waits for a traffic signal.

[0064] A fifth section, S5, is a section in which the vehicle resumes driving in response to the traffic light's green light signal and travels at a speed at which the vehicle can operate in parallel mode. As described above, the present invention is able to minimize operation in series HEV mode for interior heating when a vehicle is traveling at a low speed or is stopped, for example, due to a traffic light.

[0065] The present invention can be implemented as code that can be written to a non-volatile, computer-readable recording medium and thus read by a computer system. The non-volatile, computer-readable recording medium includes all types of recording devices on which data is stored that can be read by a computer system. Examples of computer-readable recording media are a hard disk drive (HDD), a solid-state drive (SSD), a silicon disk drive (SDD), a ROM, a RAM, a compact disk ROM (CD-ROM), a magnetic tape, a floppy disk, and an optical data storage device.

[0066] As can be seen from the above description, a hybrid electric vehicle according to at least one exemplary embodiment of the invention, configured as described above, can minimize driving in series HEV mode under driving conditions that require interior heating, thereby improving fuel efficiency. In particular, the duration of EV mode and changes in coolant temperature are predicted using traffic light information. Based on this prediction, the time a vehicle is driven in parallel HEV mode is increased, or the heating power of the FATC unit is reduced, thus minimizing driving in series HEV mode.

Claims

[1] Method for controlling a hybrid electric vehicle comprising: Receiving traffic light information, including signal information and distance information of an upcoming traffic light, by a controller under an entry condition for an electric vehicle (EV) mode; Prediction of the duration of an EV mode based on the traffic light information received by the controller; Prediction of a coolant temperature in EV mode by the controller depending on the predicted duration of the EV mode; Comparing the predicted coolant temperature with a reference temperature at which a fully automatic temperature control unit (FATC) requests the start of an internal combustion engine by the control unit; and The controller enters EV mode when the predicted coolant temperature is higher than the reference temperature. [2] Method according to claim 1, further comprising: Determine, through the control system, whether entry into a first hybrid electric vehicle (HEV) mode, which uses the power of the internal combustion engine as propulsion, is possible when the predicted coolant temperature is equal to or less than the reference temperature; and Entry into the first HEV mode by the control unit in response to the determination that entry into the first HEV mode is possible. [3] Method according to claim 2, further comprising: Entry into a second HEV mode by the control system, using the power of the internal combustion engine to generate electricity, in response to the finding that entry into the first HEV mode is impossible. [4] Method according to claim 3, wherein the first HEV mode comprises a parallel mode and wherein the second HEV mode comprises a serial mode. [5] The method of claim 1, further comprising: Requesting the FATC unit by the controller to reduce the reference temperature and / or a heater setting temperature when it is determined that the predicted coolant temperature is equal to or lower than the reference temperature. [6] Method according to claim 1, wherein receiving the traffic light information comprises receiving at least one of the following information: a signal change interval of an upcoming traffic light, a currently displayed signal ahead of a current route, a remaining distance to an upcoming traffic light, a remaining time interval of a currently displayed signal, information to display the next signal or information on the location of the traffic light. [7] Method according to claim 1, wherein the prediction of the duration of the EV mode based on the received traffic light information comprises calculating a sum of a time period required by a vehicle to decelerate and reach a traffic light based on the traffic light information and a signal waiting period remaining until a traffic light enable signal is switched on. [8] Method according to claim 7, wherein the prediction of the duration of the EV mode based on the received traffic light information comprises the calculation of the signal waiting time using a current signal, a remaining time of the current signal, a next signal and a remaining time of the next signal. [9] Method according to claim 1, wherein the prediction of the coolant temperature in EV mode comprises adding a coolant temperature, which is to be reduced by heating when the internal combustion engine is not operated during the duration of the EV mode, to a reference coolant temperature when the internal combustion engine is operated. [10] Non-volatile, computer-readable recording medium on which a program for carrying out the method according to claim 1 is recorded. [11] Hybrid electric vehicle, comprising: a first control system that is set up to receive traffic light information, including signal information and distance information from an upcoming traffic light; and a second control unit is set up to predict the duration of an electric vehicle (EV) mode based on the received traffic light information, to predict the temperature of a coolant in the EV mode according to the predicted duration of the EV mode, to compare the predicted coolant temperature with a reference temperature at which a fully automatic temperature control unit (FATC) requests the starting of an engine, and to enter EV mode when the predicted coolant temperature is greater than the reference temperature. [12] Hybrid electric vehicle according to claim 11, wherein the second control is configured to determine, in response to the finding that the predicted temperature of the coolant is equal to or less than the reference temperature, whether entry into a first hybrid electric vehicle (HEV) mode using power from the internal combustion engine as a driving force is possible, and to enter the first HEV mode in response to the finding that entry into the first HEV mode is possible. [13] Hybrid electric vehicle according to claim 12, wherein the second control is configured, in response to the finding that entry into the first HEV mode is impossible, to enter a second HEV mode in which the power of the internal combustion engine is used to generate electricity. [14] Hybrid electric vehicle according to claim 11, wherein the FATC unit is configured to perform interior heating using the coolant and to request the second controller to start the engine in response to the detection that the temperature of the coolant is equal to or lower than the reference temperature. [15] Hybrid electric vehicle according to claim 14, wherein the second controller is configured to request the FATC unit to reduce the reference temperature and / or a heating set temperature when it is determined that the predicted coolant temperature is equal to or lower than the reference temperature. [16] Hybrid electric vehicle according to claim 11, wherein the traffic light information includes at least one of the following: a signal change interval of an upcoming traffic light, a currently displayed signal ahead of a current route, a remaining distance to an upcoming traffic light, a remaining time interval of a currently displayed signal, information for displaying the next signal or information on the location of the traffic light. [17] Hybrid electric vehicle according to claim 11, wherein the second controller is configured to predict the duration of the EV mode by calculating a sum of a time period required for a vehicle to decelerate based on the traffic light information and to reach a traffic light, and a signal waiting period remaining until a traffic light enable signal is switched on. [18] Hybrid electric vehicle according to claim 17, wherein the second controller is configured to calculate the signal waiting time using a current signal, a remaining time of the current signal, a next signal and a remaining time of the next signal. [19] Hybrid electric vehicle according to claim 11, wherein the second control is configured to predict the coolant temperature in EV mode by adding a coolant temperature to a reference coolant temperature when the internal combustion engine is operating, which is to be reduced by heating when the internal combustion engine is not operating during the EV mode.

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