System and method for determining whether to start an engine

Abstract

The present disclosure provides a system and method for determining whether to start an engine. The system includes an engine configured to provide driving force to a vehicle by combustion of fuel; an electric motor configured to provide driving force to the vehicle using electric power; an engine clutch connecting the engine and a drive shaft; and a controller configured to control engagement of the engine clutch and start of the engine. The controller calculates a predicted vehicle speed at the time of engagement of the engine clutch based on a current vehicle speed at a request for passive running drive of the vehicle. The controller determines whether to start the engine by comparing the predicted vehicle speed with a reference vehicle speed.

Description

Technical Field

[0001] This disclosure relates to a system and method for determining whether to start an engine, and more specifically, to a system and method for determining whether to start an engine based on the vehicle speed when the engine clutch is engaged when passive driving is requested. Background Technology

[0002] Recently, with increasing attention to environmental issues and the global trend towards increasingly stringent vehicle emission regulations, there has been a growing interest in environmentally friendly vehicles. In a narrow sense, hybrid vehicles can differ from fuel cell vehicles and electric vehicles; however, in this specification, a hybrid vehicle refers to a vehicle that uses both an engine and an electric motor as its power source. That is, a hybrid vehicle includes a hybrid drive mode as the engine's driving mode and an electric vehicle (EV) drive mode as the electric motor's driving mode to reduce fuel consumption. Furthermore, the driving mode of a hybrid vehicle can switch between hybrid drive mode and EV drive mode.

[0003] When the driving mode is switched to EV driving mode, the vehicle is driven by the electric motor. Therefore, it is necessary to disconnect the engine and drive unit that are not providing driving force. That is, the engine clutch connecting the engine and drive unit is disengaged. Conversely, when the hybrid vehicle enters a passive driving state during EV driving mode, the engine is started, and the engine clutch is engaged with the engine.

[0004] However, there is a certain time interval between the hybrid control unit instructing the engine clutch to engage and the engine clutch actually engaging. During this time interval, the vehicle speed may decrease. After the hybrid vehicle enters passive driving mode, due to the sudden deceleration of the vehicle, passive driving may not be needed when the engine clutch and engine actually engage. In this case, the engine starts when the hybrid vehicle enters passive driving mode and shuts off when the engine clutch and engine actually engage. That is, the engine starts / stops in a short period of time, which causes discomfort to the driver and wastes fuel due to the unnecessary engine starting.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the background of this disclosure, and therefore may contain information that does not constitute prior art known to a person skilled in the art in this country. Summary of the Invention

[0006] This disclosure aims to solve the aforementioned problems related to the prior art, and the purpose of this disclosure is to provide a system and method for determining whether to start the engine of a vehicle when passive driving is requested, so as to prevent unnecessary engine start / stop operations.

[0007] In one aspect, this disclosure provides a system for determining whether to start an engine, the system comprising an engine configured to provide driving force to a vehicle by fuel combustion; an electric motor configured to provide driving force to the vehicle using electrical energy; an engine clutch connecting the engine and a drive shaft; and a controller configured to control the engagement of the engine clutch and the starting of the engine, wherein the controller can calculate a predicted vehicle speed at which the engine clutch engages based on the current vehicle speed at the time of a request for passive driving drive of the vehicle, and the controller can determine whether to start the engine by comparing the predicted vehicle speed with a reference vehicle speed.

[0008] In a preferred embodiment, the predicted vehicle speed can be the sum of the current vehicle speed and the value obtained by multiplying the vehicle's deceleration by the time it takes for the engine clutch to engage.

[0009] In another preferred embodiment, the controller can predict the rate of increase of the engine's RPM when the engine clutch engages based on the current revolutions per minute (RPM) of the motor, and the time taken for the engine clutch to engage can be a value obtained by dividing the current RPM of the motor by the rate of increase of the engine's RPM.

[0010] In yet another preferred embodiment, the reference vehicle speed can be a preset vehicle speed for each gear of the vehicle, and the reference vehicle speed can be preset to a low speed for low gears.

[0011] In another preferred embodiment, the controller can calculate the vehicle speed error value based on changes in vehicle deceleration, changes in braking amount, or changes in the degree of brake pedal operation, and the controller can set the reference vehicle speed to a value obtained by adding the preset vehicle speed for each gear of the vehicle to the vehicle speed error value.

[0012] In another preferred embodiment, the controller can calculate a vehicle speed error value that is proportional to the absolute value of the deceleration, and the vehicle speed error value can be positive when the deceleration has a negative value.

[0013] In another preferred embodiment, the controller can calculate a vehicle speed error value that is proportional to the degree of brake pedal operation or the amount of braking.

[0014] In another preferred embodiment, the controller may determine whether the passive driving conditions of the vehicle are met based on at least one of the following: the state of charge (SOC) of the vehicle's battery, the result of determining whether the battery charging is limited, and the downshift request.

[0015] In yet another preferred embodiment, the controller can calculate the target gear to engage when the driver requests a downshift, and the controller can compare a preset reference speed and a predicted speed corresponding to the target gear.

[0016] In another preferred embodiment, when the battery's SOC is fully charged or when the battery's charging is limited, the controller can compare a preset reference speed and a predicted speed corresponding to the vehicle's current gear.

[0017] In yet another preferred embodiment, passive driving can be a driving state in which deceleration is generated by the engine, and when passive driving continues, deceleration of the vehicle is generated by the engagement of the engine clutch.

[0018] In another preferred embodiment, when the predicted vehicle speed is less than or equal to the reference vehicle speed, the controller can determine that passive driving is unnecessary and may not start the engine.

[0019] In another aspect, this disclosure provides a method for determining whether to start the engine, the method comprising the steps of: determining passive driving conditions of the vehicle; predicting the expected time of engine clutch and engine engagement in response to a request for passive driving; calculating a predicted vehicle speed at the expected engine clutch and engine engagement based on the current vehicle speed at the time of the request for passive driving; and determining whether to start the engine by comparing the predicted vehicle speed with a reference vehicle speed.

[0020] In a preferred embodiment, determining passive driving conditions may include: determining whether passive driving conditions are met based on at least one of the following: the vehicle's battery state of charge (SOC), a result of determining whether battery charging is limited, and a downshift request.

[0021] In another preferred embodiment, predicting the expected engine clutch and engine engagement time in response to a passive driving drive request may include: predicting the rate of increase of the engine's RPM at engine clutch engagement based on the current RPM of the electric motor, and calculating the time taken for engine clutch engagement by dividing the current RPM of the electric motor by the rate of increase of the engine's RPM.

[0022] In yet another preferred embodiment, calculating the predicted vehicle speed may include adding the current vehicle speed to a value obtained by multiplying the vehicle's deceleration by the time it takes for the engine clutch to engage.

[0023] In yet another preferred embodiment, in controlling whether to start the engine, when the predicted vehicle speed is less than or equal to the reference vehicle speed, it can be determined that passive driving is unnecessary and the engine can be not started.

[0024] In another preferred embodiment, the reference speed can be a value obtained by adding the speed error value calculated based on changes in vehicle deceleration, changes in braking amount, or changes in the degree of brake pedal operation to the preset speed of each gear of the vehicle.

[0025] In another preferred embodiment, the gear for calculating the reference vehicle speed can be the target gear to be engaged when the driver requests a downshift.

[0026] In another preferred embodiment, when a request for passive driving is made due to the vehicle's battery being fully charged or the battery being under-charged, the reference speed can be a preset speed based on the vehicle's current gear.

[0027] Other aspects and preferred embodiments of this disclosure are discussed below.

[0028] It should be understood that the term "vehicle" or "of a vehicle" or other similar terms used herein generally include motor vehicles, such as passenger cars including sport utility vehicles (SUVs), public vehicles, trucks, various commercial vehicles, ships including various vessels, aircraft, etc., and includes hybrid vehicles, electric vehicles, internal combustion engine vehicles, plug-in hybrid vehicles, hydrogen-powered vehicles, and other vehicles powered by alternative fuels (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle with two or more power sources, such as a gasoline-powered and electric-powered vehicle. Attached Figure Description

[0029] The above and other features of this disclosure will now be described with reference to specific exemplary embodiments shown in the accompanying drawings. These drawings are merely illustrative and therefore do not limit the scope of this disclosure.

[0030] Figure 1 This is a diagram illustrating the construction of a power system for a hybrid vehicle according to one embodiment of the present disclosure;

[0031] Figure 2 This is a block diagram illustrating a system for determining whether to start an engine according to one embodiment of the present disclosure;

[0032] Figure 3 This is a diagram illustrating a method for determining whether to start the engine according to one embodiment of the present disclosure; and

[0033] Figure 4This is a flowchart illustrating a method for determining whether to start the engine according to one embodiment of the present disclosure.

[0034] It should be understood that the accompanying drawings are not necessarily drawn to scale, but rather present a slightly simplified representation of various preferred features illustrating the basic principles of this disclosure. Specific design features of the disclosure herein (e.g., including specific dimensions, orientations, positions, and shapes) will depend in part on the specific application and usage environment.

[0035] In the accompanying drawings, reference numerals denote portions that are identical or equivalent to the contents of this disclosure. Detailed Implementation

[0036] The advantages and features of this disclosure, as well as the methods for implementing them, will become clear from the following detailed description of embodiments with reference to the accompanying drawings. However, this disclosure may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be sufficient and complete, and will fully convey the scope of this disclosure to those skilled in the art. This disclosure is defined by the scope of the claims. Throughout the specification, the same reference numerals denote the same parts.

[0037] The terms “-part,” “-unit,” and “-module” described in the specification refer to a unit for performing at least one function or operation, and can be implemented as a hardware component, a software component, or a combination of hardware and software components.

[0038] Furthermore, in the following description, the terms "first" and "second" are used only to avoid confusion of the specified components and do not indicate the order or importance of the components or the relationship between the components.

[0039] The above description is an illustration of this disclosure. Furthermore, the above disclosure is intended to illustrate and explain preferred embodiments of this disclosure, and this disclosure can be used in various other combinations, modifications, and environments. In other words, the content of this disclosure can be changed or modified within the scope of the concepts disclosed herein, within the equivalent scope of this disclosure, and / or within the scope of the technology and knowledge in the relevant art. The described embodiments demonstrate the optimal technical state for implementing the technical ideas of this disclosure and can be modified in various ways according to the specific application and the needs of using this disclosure. Therefore, the above description is not intended to limit this disclosure to the embodiments. Moreover, the appended claims should be construed as including such other embodiments.

[0040] Figure 1 This is a diagram illustrating the construction of a power system for a hybrid vehicle according to one embodiment of the present disclosure.

[0041] refer to Figure 1The power system of a hybrid vehicle may include an engine 10, an electric motor 20, an engine clutch 30, a hybrid starter generator 40, and a transmission 50.

[0042] In the case of a hybrid vehicle, engine 10 and electric motor 20 can be connected in series and used simultaneously to generate driving force. Engine 10 can consume fuel to provide driving force for the vehicle. Electric motor 20 can use electrical energy to provide driving force for the vehicle. In hybrid drive mode, fuel is consumed to drive the vehicle, while in electric vehicle (EV) drive mode, electric motor 20 is used to drive the vehicle. An engine clutch 30 for selectively enabling or discontinuing power transmission can be arranged between engine 10 and electric motor 20. Engine clutch 30 can be hydraulically engaged (locked) or disengaged (opened), thereby connecting or disconnecting engine 10 from the drive shaft. When engine clutch 30 and engine 10 are engaged, the driving force generated from engine 10 and electric motor 20 can be transmitted to the wheels via transmission 50. Transmission 50 is connected to the output side of electric motor 20 to transmit driving force from engine 10 and electric motor 20 to drive shaft.

[0043] The hybrid starter generator 40 can function as a motor when the engine 10 starts and as a generator when power generation is needed. The hybrid starter generator 40 can be connected to a pulley (not shown) of the engine 10. Furthermore, the hybrid starter generator 40 can set the torque of the engine 10. The hybrid starter generator 40 can measure the real-time torque of the engine 10 and control the torque of the engine 10 using the pulley (not shown) connected to the engine 10.

[0044] Battery 60 can supply electrical energy to motor 20. When the vehicle is coasting, battery 60 can be charged by motor 20 according to its state of charge (SOC). The term "coasting" means that the driver uses the vehicle's inertia to drive the vehicle without applying any pressure to the accelerator pedal or the brake pedal. During coasting, an inverter (not shown) connected to motor 20 can charge battery 60.

[0045] When driving the hybrid vehicle in hybrid drive mode, the engine clutch 30 can engage with the engine 10. When driving the hybrid vehicle in EV drive mode, the engine clutch 30 can disengage from the engine 10. That is, in EV drive mode, the engine clutch 30, located between the engine 10 and the electric motor 20, can disengage, and the drive shaft can be connected only to the electric motor 20. For reference, when the vehicle is driven in EV drive mode with the engine clutch disengaged (open), the vehicle can coast due to the inertia of the vehicle with the brake pedal and accelerator pedal closed, and the regenerative power (charging power) from the electric motor 20 can be stored in the battery 60 via an inverter (not shown). At this time, the motor torque (coasting torque) can be controlled based on the engine friction torque corresponding to the current speed of the input shaft of the transmission (transmission input speed).

[0046] For example, when driving in EV drive mode, the vehicle can enter a passive driving state when the driver requests a downshift, when the battery 60 is fully charged (SOC), or when the charging of the battery 60 is limited. The term "passive driving" can refer to a driving state in which deceleration is generated by the engine 10. In other words, "passive driving" can refer to a driving state in which the engine 10 and engine clutch 30 engage during EV drive mode, thus initiating engine braking. While passive driving continues, the vehicle can decelerate due to the engagement of the engine clutch 30, and fuel cut-off control can be implemented to stop the fuel supply to the engine 10.

[0047] Figure 2 This is a block diagram illustrating a system for determining whether to start an engine according to one embodiment of the present disclosure.

[0048] refer to Figure 1 and Figure 2 Hybrid vehicles may include a controller 200 for setting the vehicle's hybrid drive mode or EV drive mode. For example, the controller 200 may be a hybrid power control unit (HCU). The controller 200 may calculate a predicted vehicle speed based on the current vehicle speed when the engine clutch 30 engages, in response to a request for passive driving, and may control the starting of the engine 10 by comparing the predicted vehicle speed with a reference vehicle speed. Various information about the vehicle may be sent to the controller 200 for this purpose.

[0049] Brake pedal sensor (BPS) 110 can detect the degree to which the brake pedal is depressed. The degree of brake pedal operation measured by BPS 110 can be transmitted to controller 200. Controller 200 can calculate the braking amount based on the degree of brake pedal operation.

[0050] Vehicle speed sensor 120 can be a sensor that measures vehicle speed. For example, vehicle speed sensor 120 may include a sensor that measures the speed of the vehicle's wheels. The vehicle speed measured by vehicle speed sensor 120 can be sent to controller 200. Controller 200 can calculate the vehicle's deceleration based on the change in vehicle speed.

[0051] Motor 20 can send information about its revolutions per minute (RPM) to controller 200. As an example, controller 200 can calculate the time period from the occurrence of a passive driving request until the engine clutch 30 and engine 10 engage, based on the RPM information of motor 20. As another example, controller 200 can calculate the torque of motor 20 based on the current RPM information, and can calculate the vehicle deceleration based on information about the torque of motor 20, the rotational inertia of engine 10, the rotational inertia of motor 20, the rotational inertia of the transmission system, the rotational inertia of the vehicle, the frictional torque of engine 10, the frictional torque of the transmission system, and the vehicle's driving load. Furthermore, when motor 20 is in a state of limited regenerative braking, motor 20 can send this information to controller 200.

[0052] Battery 60 can send information about its state of charge (SOC) to controller 200. Controller 200 can determine whether battery 60 is fully charged based on its SOC. When it is determined that battery 60 is fully charged, controller 200 can determine that regenerative braking of motor 20 is limited and charging of battery 60 is limited.

[0053] The shift request unit 150 can send a downshift request from the driver to the controller 200. For example, the downshift request may include a manual downshift request via the gear lever or a downshift request via paddle shifters. That is, the shift request unit 150 may include a gear lever and paddle shifters installed in the vehicle.

[0054] In addition, the controller 200 can receive information about the torque of the engine 10 and the real-time rate of change of the torque of the engine 10 through the hybrid starter generator 40 connected to the engine 10.

[0055] The controller 200 may include a passive driving determination unit 210, an engine start determination unit 220, and a drive controller 230. The passive driving determination unit 210, the engine start determination unit 220, and the drive controller 230 may be components classified according to the functions of the controller 200.

[0056] The passive driving determination unit 210 can determine whether the passive driving conditions of the vehicle are met based on at least one of the following: the state of charge (SOC) of the battery 60, the result of determining whether the charging of the battery 60 is limited, and a downshift request. As an example, when the SOC of the battery 60 is fully charged or when the charging of the battery 60 is limited, the motor 20 will not generate a drag sensation. Therefore, the controller 200 generates a drag sensation by engaging the engine clutch 30 and the engine 10. As another example, when the vehicle is driving in EV drive mode and there is a downshift request from the driver, the controller 200 can engage the engine clutch 30 and the engine 10 to generate a drag sensation through engine braking.

[0057] The engine start determination unit 220 can calculate the predicted vehicle speed when the engine clutch 30 engages based on the current vehicle speed in response to the vehicle's passive driving drive request, and can determine whether to start the engine 10 by comparing the predicted vehicle speed with the reference vehicle speed.

[0058] For example, Formula 1 below shows that the predicted vehicle speed can be the sum of the current vehicle speed and the value obtained by multiplying the vehicle's deceleration by the time it takes for the engine clutch to engage (hereinafter referred to as "clutch engagement time").

[0059] Formula 1: Predicted vehicle speed (V) new = Current vehicle speed (V0) + deceleration (a) × clutch engagement time (Δt)

[0060] The clutch engagement time can be obtained by dividing the current RPM of the motor 20 by the rate of increase of the RPM of the engine 10. The rate of increase of the RPM of the engine 10 can be the rate of increase of the RPM of the engine 10 at a preset engagement of the engine clutch based on the current RPM of the motor 20. That is, the rate of increase of the RPM of the engine 10 can be determined based on a preset table of the current RPM of the motor 20.

[0061] As an example, the reference vehicle speed can be a preset speed for each gear of the vehicle. In this case, the reference vehicle speed can be preset to a low speed for lower gears. Thus, the reference vehicle speed changes according to the gear of the vehicle. However, when the driver requests a downshift, the reference vehicle speed can change according to the target gear. The engine start determination unit 220 can calculate the target gear to engage in response to the driver's downshift request and can compare the preset reference speed and the predicted speed corresponding to the target gear. For example, even if the driver requests a downshift through two gears, it can downshift through only one gear to protect the transmission 50. Therefore, the engine start determination unit 220 can predict the target gear to engage in response to a downshift request, rather than based on the gear requested by the driver, and can calculate the reference vehicle speed corresponding to the target gear.

[0062] The engine start determination unit 220 can calculate a reference vehicle speed, which varies based on changes in vehicle deceleration, braking amount, or brake pedal operation. The engine start determination unit 220 can also calculate a vehicle speed error value based on these changes. Furthermore, the engine start determination unit 220 can set the reference vehicle speed to a value obtained by adding the preset vehicle speed for each gear to the vehicle speed error value.

[0063] As an example, the vehicle speed error value can increase with the increase of the absolute value of deceleration. The vehicle speed error value and the absolute value of deceleration can have a proportional relationship. When the deceleration is negative, the vehicle speed error value can be positive. Furthermore, when the deceleration is 0, the vehicle speed error value can be 0. That is, when the vehicle deceleration is high, the vehicle speed can decrease rapidly until the engine clutch 30 and engine 10 engage. As the vehicle speed decreases more rapidly, since the passive driving drive conditions are not met before the engine clutch 30 and engine 10 engage, the possibility of engine 10 shutting down for a short period after engine 10 is engaged is higher. Therefore, the engine start determination unit 220 can set a larger reference vehicle speed as the absolute value of deceleration increases.

[0064] As an example, the braking amount or degree of operation of the brake pedal can be proportional to the vehicle speed error value. The engine start determination unit 220 can determine the change in the degree of brake pedal operation based on information received from the BPS 110, and can calculate the braking amount based on the change in the degree of brake pedal operation. As the braking amount and degree of operation of the brake pedal increase, the vehicle speed decreases more quickly. Therefore, since the passive driving drive conditions are not met before the engine clutch 30 and engine 10 are engaged, the possibility of engine 10 shutting off for a short period of time after engine 10 is engaged is high. Therefore, the engine start determination unit 220 can set a larger reference vehicle speed as the braking amount and degree of brake pedal operation increase.

[0065] When the predicted vehicle speed is less than or equal to the reference vehicle speed, the engine start determination unit 220 can determine that passive driving drive is not required and can choose not to start the engine 10. In other words, when the predicted vehicle speed is greater than the reference vehicle speed, the engine start determination unit 220 can start the engine 10. Traditionally, the engine 10 starts upon a request for passive driving drive. However, in the prior art, there is a problem that the passive driving drive conditions are not met when the engine clutch 30 and engine 10 are engaged due to a decrease in vehicle speed, leading to frequent engine shutdowns of the engine 10. When the vehicle speed suddenly decreases, there is no need to generate a dragging sensation, which may result in the failure to meet the passive driving drive conditions. The controller 200 can start the engine 10 only when the passive driving drive conditions at which the engine clutch 30 and engine 10 are expected to be met, by comparing the predicted vehicle speed (which is the vehicle speed at which the engine clutch 30 and engine 10 are engaged) with the reference vehicle speed, instead of comparing the current vehicle speed with the reference speed. For this purpose, the engine start determination unit 220 can compare the predicted vehicle speed with the reference vehicle speed.

[0066] When the engine start determination unit 220 determines that the predicted vehicle speed is greater than the reference vehicle speed, the drive controller 230 can start the engine 10 and engage the engine clutch 30 and the engine 10. The drive controller 230 can control the hybrid starter generator 40 to start the engine 10. When starting the engine 10, the drive controller 230 can control the fuel supply device 300 to perform fuel cut-off control, thereby stopping the fuel supply to the engine 10. However, when the engine start determination unit 220 determines that the predicted vehicle speed is less than the reference vehicle speed, the drive controller 230 may not start the engine 10. In this case, the drive controller 230 may not start the engine 10 and may not operate the hybrid starter generator 40.

[0067] Unlike the example above, in response to a request for passive driving, controller 200 can output a command to engage engine clutch 30 and engine 10. However, during the engagement of engine clutch 30 and engine 10, controller 200 can determine whether to start engine 10 by comparing the predicted vehicle speed with a reference vehicle speed. When the predicted vehicle speed is less than or equal to the reference vehicle speed, controller 200 may not start engine 10. With engine 10 off, even if engine clutch 30 and engine 10 are engaged, the vehicle will not experience unnecessary drag.

[0068] According to embodiments of this disclosure, by comparing the predicted vehicle speed when the engine clutch 30 and engine 10 are engaged with a reference vehicle speed that varies according to the target gear, the engagement of the engine clutch 30 and the starting of the engine 10 can be controlled. Therefore, before the engine clutch 30 and engine 10 are engaged, it is possible to prevent the engine 10 from shutting off for a short period after being engaged due to failure to meet passive driving conditions. Consequently, unnecessary on / off operations of the engine 10 are prevented, thus preventing driver discomfort and saving fuel used to start the engine 10 and energy used to operate the hybrid starter generator 40, thereby improving the vehicle's fuel efficiency.

[0069] According to embodiments of this disclosure, since the target gear, vehicle deceleration, braking amount, and brake pedal operation are considered when setting the reference vehicle speed as a factor for determining whether to start the engine 10, the reference vehicle speed can be calculated based on the predicted change in vehicle speed. If the reference vehicle speed is calculated based on the vehicle's current gear when the vehicle speed is rapidly decreasing and therefore engine braking is not required, the reference vehicle speed will be less than the predicted vehicle speed, which may lead to unnecessary starting of the engine 10. To prevent this, when the absolute value of the vehicle deceleration, braking amount, and brake pedal operation are large, the controller 200 can set the reference vehicle speed to a large value, such that even when the vehicle speed is rapidly decreasing, the reference vehicle speed is greater than or equal to the predicted vehicle speed. As a result, unnecessary frequent start / stop operations of the engine 10 can be prevented.

[0070] Figure 3 This is a diagram illustrating a method for determining whether to start the engine according to one embodiment of the present disclosure. For simplicity, descriptions identical to those described above will be omitted.

[0071] refer to Figures 1 to 3 The controller 200 can calculate the time period from the occurrence of a passive driving drive request until the engine clutch 30 and engine 10 engage, based on information about the RPM of the motor 20. Specifically, the time spent engaging the engine clutch 30 can be calculated based on the current RPM of the motor 20 and a preset increase rate of the RPM of the engine 10 based on the current RPM of the motor 20. Figure 3 In the diagram, t1 represents the time when the passive driving drive request is made, t2 represents the expected time when the engine clutch 30 and engine 10 are engaged, and Δt represents the time period from the occurrence of the passive driving drive request until the engine clutch 30 and engine 10 are engaged.

[0072] When it is determined that the driver has requested a downshift, the controller 200 determines whether the vehicle is operating in passive driving mode. The controller 200 can calculate the predicted vehicle speed V at the expected engagement time t2 of the engine clutch 30 and engine 10 based on the current vehicle speed V0 at the time the passive driving request was made, the vehicle's deceleration, and the time Δt taken for the engine clutch 30 and engine 10 to engage. new Additionally, the controller 200 can calculate the reference vehicle speed V based on the target gear. Ref With predicted vehicle speed V new Compare them.

[0073] As an example, in the prior art, the current vehicle speed V0 is compared with the reference vehicle speed V... Ref A comparison is made to determine whether to start engine 10. Therefore, engine 10 is started immediately after a passive driving drive request is made. However, as the vehicle speed continues to decrease, the current vehicle speed V0 decreases to the reference vehicle speed V during the expected engagement time t2 of engine clutch 30 and engine 10. Ref The following (V0 decreases to a value similar to V) new (speed), thereby shutting off engine 10. This short-term on / off operation of engine 10 causes discomfort to the driver, wastes fuel due to the starting of engine 10, and wastes energy due to the operation of hybrid starter generator 40.

[0074] As another example, according to an embodiment of this disclosure, by predicting the vehicle speed V new Instead of the current vehicle speed V0 and the reference vehicle speed V Ref A comparison is made to determine whether to start the engine 10. Therefore, it is possible to prevent the engine 10 from starting unnecessarily. This is because the predicted vehicle speed V is calculated by the controller 200 at the time t1 when the passive driving drive request is made. new Less than the reference vehicle speed V Ref Therefore, controller 200 does not start engine 10.

[0075] Figure 4 This is a flowchart illustrating a method for determining whether to start the engine according to one embodiment of the present disclosure. For simplicity, descriptions identical to those described above will be omitted.

[0076] refer to Figure 4 The controller can determine the passive driving conditions of the vehicle. Based on the battery's SOC, the controller can determine whether the battery's charging is limited, and at least one piece of information from the downshift request in S100, determine whether the passive driving conditions of the vehicle are met.

[0077] The controller can determine the target gear. Since the driver requests a downshift, the gear can be lowered to a level below the gear required for passive driving. Simultaneously with determining the target gear, the controller can predict the expected engine clutch and engine engagement time in response to the request for passive driving. To predict the expected engine clutch and engine engagement time, the controller can predict the rate of increase in engine RPM at clutch engagement based on the current RPM of the electric motor, and can calculate the clutch engagement time by dividing the current RPM of the electric motor by the rate of increase in engine RPM in S200.

[0078] The controller can calculate the predicted vehicle speed at the expected engine clutch and engine engagement based on the current vehicle speed in response to a request for passive driving. The predicted vehicle speed can be the sum of the current vehicle speed and a value obtained by multiplying the vehicle's deceleration by the time taken for the S300 engine clutch 30 and engine 10 to engage.

[0079] The controller can calculate the reference vehicle speed in the target gear and can control whether to start the engine in S400 by comparing the predicted vehicle speed with the reference vehicle speed.

[0080] When the predicted vehicle speed is greater than the reference vehicle speed, the controller can start the engine. When the predicted vehicle speed is greater than the reference vehicle speed, the controller needs to generate a drag sensation through engine braking. The controller can operate the hybrid starter generator to start the engine and can engage the engine clutch and engine after starting the engine. At this time, the controller can perform fuel cut-off control in the S500 to improve the vehicle's fuel efficiency.

[0081] When the predicted vehicle speed is less than or equal to the reference vehicle speed, the controller may not start the engine. Keeping the engine off may be advantageous in terms of vehicle fuel efficiency and driver performance when the predicted vehicle speed is less than or equal to the reference vehicle speed. Therefore, in the S600, the controller can keep the engine off.

[0082] As is apparent from the above description, according to embodiments of this disclosure, the engagement of the engine clutch and the starting of the engine can be controlled by comparing a predicted vehicle speed at engine clutch and engine engagement with a reference vehicle speed, the reference vehicle speed varying according to the target gear. Therefore, it is possible to prevent engine shutdown for a short period after engine engagement due to the failure to meet passive driving conditions before engine clutch and engine engagement. Consequently, unnecessary engine start / stop operations are prevented, thus preventing driver discomfort and saving fuel used for starting the engine and energy used for operating the hybrid starter generator, thereby improving vehicle fuel efficiency.

[0083] According to embodiments of this disclosure, since the target gear, vehicle deceleration, braking amount, and brake pedal operation are considered when setting a reference vehicle speed as a factor for determining whether to start the engine, the reference vehicle speed can be calculated based on the predicted change in vehicle speed. If the reference vehicle speed is calculated based on the vehicle's current gear when the vehicle speed is rapidly decreasing and therefore engine braking is not required, the reference vehicle speed will be less than the predicted vehicle speed, which may lead to unnecessary engine starting. This disclosure prevents this problem.

[0084] This disclosure has been described in detail with reference to preferred embodiments. However, those skilled in the art will understand that any changes may be made to these embodiments without departing from the principles and spirit of this disclosure, and the appended claims and their equivalents define the scope of this disclosure.

Claims

1. A system for determining whether to start an engine, the system comprising: An engine is configured to provide driving force to a vehicle through fuel combustion; An electric motor is configured to provide driving force to the vehicle using electrical energy; An engine clutch connects the engine and the drive shaft; as well as The controller is configured to control the engagement of the engine clutch and the starting of the engine. The controller calculates the predicted vehicle speed at which the engine clutch engages based on the current vehicle speed at the time of the passive driving drive request. The controller determines whether to start the engine by comparing the predicted vehicle speed with the reference vehicle speed. The controller predicts the rate of increase in engine speed per minute when the engine clutch engages, based on the current speed per minute of the motor. The time taken for the clutch to engage is a value obtained by dividing the current revolutions per minute of the motor by the rate of increase of the revolutions per minute of the engine.

2. The system according to claim 1, wherein, The predicted vehicle speed is the sum of the current vehicle speed and the value obtained by multiplying the vehicle's deceleration by the time it takes for the engine clutch to engage.

3. The system according to claim 1, wherein, The reference vehicle speed is a preset vehicle speed for each gear of the vehicle, and The reference vehicle speed is preset to a low speed for low gears.

4. The system according to claim 1, wherein, The controller calculates the vehicle speed error value based on changes in the vehicle's deceleration, braking amount, or brake pedal operation. The controller sets the reference vehicle speed to a value obtained by adding the preset vehicle speed for each gear of the vehicle to the vehicle speed error value.

5. The system according to claim 4, wherein, The controller calculates a vehicle speed error value that is proportional to the absolute value of the deceleration, and Wherein, when the deceleration has a negative value, the vehicle speed error value has a positive value.

6. The system according to claim 4, wherein, The controller calculates a vehicle speed error value that is proportional to the degree of operation of the brake pedal or the amount of braking.

7. The system according to claim 1, wherein, The controller determines whether the passive driving conditions of the vehicle are met based on at least one of the following: the charging status of the vehicle's battery, the result of determining whether the battery charging is limited, and the downshift request.

8. The system according to claim 7, wherein, The controller calculates the target gear to engage when the driver requests a downshift, and The controller compares the preset reference speed corresponding to the target gear with the predicted speed.

9. The system according to claim 7, wherein, When the battery is fully charged or when the battery charging is limited, the controller will compare the preset reference speed corresponding to the current gear of the vehicle with the predicted speed.

10. The system according to claim 1, wherein, The passive driving drive is a driving state in which deceleration is generated by the engine, and When the passive driving continues, the vehicle decelerates by engaging the engine clutch.

11. The system according to claim 1, wherein, When the predicted vehicle speed is less than or equal to the reference vehicle speed, the controller determines that the passive driving drive is unnecessary and does not start the engine.

12. A method for determining whether to start an engine, the method comprising the steps of: The passive driving conditions of the vehicle are determined by the controller; In response to a request for passive driving, the expected engagement time of the engine clutch and engine is predicted. The predicted vehicle speed when the engine clutch engages with the engine is calculated based on the current vehicle speed at the time of the passive driving request. as well as The predicted vehicle speed is compared with the reference vehicle speed to determine whether to start the engine; The prediction of the expected engagement time of the engine clutch with the engine in response to the request of the passive driving drive includes: Based on the current revolutions per minute (RPM) of the motor, predict the rate of increase in the engine's RPM when the engine clutch engages, and The time taken for the clutch to engage is calculated by dividing the current revolutions per minute of the motor by the rate of increase in the revolutions per minute of the engine.

13. The method according to claim 12, wherein, Determining the passive driving conditions includes: determining whether the passive driving conditions are met based on at least one of the following: the charging state of the vehicle's battery, the result of determining whether the battery charging is limited, and a downshift request.

14. The method according to claim 12, wherein, Calculating the predicted vehicle speed includes adding the value obtained by multiplying the vehicle's deceleration by the time it takes for the engine clutch to engage to the current vehicle speed.

15. The method according to claim 12, wherein, In controlling whether to start the engine, when the predicted vehicle speed is less than or equal to the reference vehicle speed, it is determined that the passive driving drive is unnecessary, and the engine is not started.

16. The method according to claim 15, wherein, The reference speed is a value obtained by adding the speed error value calculated based on the changes in the vehicle's deceleration, braking amount, or brake pedal operation to the preset speed of each gear of the vehicle.

17. The method according to claim 16, wherein, The gear for calculating the reference vehicle speed is the target gear to be engaged when the driver requests a downshift.

18. The method according to claim 16, wherein, When the passive driving request is generated due to the vehicle's battery being fully charged or the battery being under-charged, the reference speed is a preset speed based on the vehicle's current gear.

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