Launch control method for hybrid vehicle

Abstract

The present invention relates to a method for controlling the launch of a hybrid vehicle, and its main purpose is to provide a method for controlling the launch of a hybrid vehicle that can improve the limitations of engine idle speed control and torque output securing by a conventional engine controller, thereby ensuring drivability during slip launch and improving the vehicle's driving performance in uphill and restricted situations. To achieve the above objective, the method comprises the steps of: determining whether a predetermined control entry condition is satisfied from information collected from the vehicle upon detection of a driver's acceleration request; if it is determined that the control entry condition is satisfied, initiating integrated control of slip launch and series launch and determining the charging power of a starter generator connected to transmit power to the engine; determining an integrated engine load based on the determined starter generator charging power and determining an engine target driving torque based on the determined integrated engine load; performing engine torque control to control the engine torque to the determined engine target driving torque and performing battery charging using the starter generator; and performing engine speed control using the starter generator. A method for controlling the start of a hybrid vehicle is disclosed, comprising the step of applying a controlled hydraulic pressure to the engine clutch to perform engine clutch slip control.

Description

Technology Field

[0001] The present invention relates to a method for controlling the launch of a hybrid vehicle, and more specifically, to a method for controlling the launch of a hybrid vehicle that can improve the limitations of controlling the idle speed of the engine itself and securing torque output by a conventional engine controller, thereby ensuring drivability during slip launch and improving the driving performance of the vehicle in uphill and restricted situations. Background Technology

[0003] A hybrid vehicle refers to a vehicle that uses two or more different types of power sources, and generally refers to a vehicle driven by an internal combustion engine (ICE) and an electric motor. Depending on how the engine and motor are operated in harmony during driving, a hybrid vehicle can not only output optimal torque but also maximize fuel efficiency.

[0004] Hybrid vehicles can have their drivetrains configured in various structures, and a TMED (Transmission Mounted Electric Device) hybrid system is known in which the engine and the motor are connected via an engine clutch and the transmission is connected to the motor output side. FIG. 1 is a diagram illustrating the powertrain configuration of a hybrid vehicle, illustrating the configuration of a TMED hybrid system in which the motor (3) and the transmission (4) are connected.

[0005] As described, in the TMED hybrid system, an engine clutch (2) and a motor (3) are positioned between the engine (1) and the transmission (4). Here, the engine clutch (2) is positioned between the engine (1) and the motor (3), which are the two driving sources of the vehicle. Additionally, the transmission (4) is mounted on the output side of the motor (3), and the transmission input shaft is connected to the motor output shaft, so that the motor speed becomes the rotational speed of the transmission input shaft (i.e., the transmission input speed).

[0006] Looking at the configuration, the TMED hybrid system comprises an engine (1) and a motor (3) that are driving sources for driving the vehicle, an engine clutch (2) interposed between the engine (1) and the motor (3), a transmission (4) connected to the output side of the motor (3), an inverter (5) for driving and controlling the motor (3), and a battery (6) connected to the motor (3) so as to be chargeable / dischargeable through the inverter (5).

[0007] The engine clutch (2) selectively engages or disengages to connect or disconnect the engine (1) and the motor (3) to enable power transmission. The inverter (5) converts the direct current from the battery (6) into a three-phase alternating current and applies it to the motor (3) to drive the motor (3).

[0008] The transmission (4) transmits the rotational power of the motor (3) or the combined rotational power of the engine (1) and the motor (3) to the drive wheels through the drive shaft, and the transmission (4) may be an automatic transmission (AT) or a dual clutch transmission (DCT).

[0009] In addition, the TMED hybrid system may further include a starter generator, namely an HSG (Hybrid Starter and Generator) (7), which is connected to the engine (1) to transmit power and starts the engine or generates power using the rotational force transmitted from the engine. The HSG (7) is a motor directly connected to the engine (1) via a power transmission mechanism, and pulleys and belts are mainly used as the power transmission mechanism.

[0010] The above HSG (7) is also connected to the battery (6) via the inverter (5) to enable charging and discharging. Additionally, the HSG (7) receives power from the battery (6) and operates as a motor or as a generator that converts and recovers the rotational power of the engine (1) into electrical energy. When operating as a motor, it is mainly used to start the engine (1), and since it is connected to the engine (1) to transmit power at all times, it may also be used to control the engine speed.

[0011] In addition, hybrid vehicles are equipped with a Hybrid Control Unit (HCU) as the top-level controller that controls the overall operation of the vehicle, and are also equipped with various controllers to control the vehicle's various devices.

[0012] For example, an engine control unit (ECU) that controls the operation of the engine (1), a motor control unit (MCU) that controls the operation of the drive motor (3) and the HSG (7), a transmission control unit (TCU) that controls the operation of the transmission (4), a brake control unit (BCU) that performs braking control of the vehicle, and a battery management system (BMS) that collects battery status information and performs control for managing the battery (6) are provided.

[0013] And, the hybrid vehicle can be driven in an EV (Electric Vehicle) mode, which is a pure electric vehicle mode that uses only the power of the motor (3), or in an HEV (Hybrid Electric Vehicle) mode that uses a combination of the power of the engine (1) and the power of the motor (3).

[0014] Additionally, during braking or coasting, a regenerative mode can be performed to recover the vehicle's kinetic energy through the motor (3) and charge the battery (6). In the regenerative mode, the motor (3) receives the rotational force of the drive wheel, and at this time, the motor (3) operates as a generator to charge the battery (6) through the inverter (5).

[0015] Furthermore, in hybrid vehicles, switching between the two aforementioned modes occurs depending on driving conditions during operation, and vehicle starting is generally performed in EV mode. However, if the State of Charge (SOC) of the battery supplying power to the motor drops below a certain level or the battery temperature falls to an extremely low state (e.g., below -20°C), vehicle starting via motor drive becomes impossible due to insufficient battery discharge. In such cases, the engine is driven to start the vehicle, after which a portion of the engine power is used for HSG generation and battery charging, and the remaining power is transmitted to the engine clutch.

[0016] At this time, if the engine clutch engages when the engine torque is insufficient (i.e., at a low engine speed), problems such as the engine stalling may occur because the engine's inertia is far less than the rotational inertia of the shaft extending from the output stage of the engine clutch through the motor to the transmission. Therefore, in such a state, it is common to control the engine clutch to a slip state through hydraulic control, and this method of starting can be called "slip starting."

[0017] When engine speed (RPM) is low, the engine may stall, and if the engine speed is too high during a slip state, it can lead to issues such as noise generation. Ultimately, the key to slip-starting is controlling the hydraulic pressure of the engine clutch to allow the vehicle to launch while maintaining an appropriate engine speed. Typically, to maintain engine speed, the Engine Control Unit (ECU) provides a margin in the torque for speed control.

[0018] Meanwhile, in TMED-type hybrid vehicles, switching from EV mode to HEV mode requires a process of engaging the engine clutch between the engine and the motor to enable engine power to be transmitted to the drive shaft. Additionally, engaging the engine clutch requires synchronizing the engine speed with the motor speed, and forcibly engaging the engine clutch without speed synchronization results in a shock.

[0019] When the available power of the motor is sufficient, it is possible to increase the motor speed in EV mode to the minimum engine speed at which the driving state can be maintained, and to engage the engine clutch when speed synchronization is achieved. However, as mentioned above, if the available power of the motor is limited due to factors such as battery temperature or charge status, or if driving resistance is high due to factors such as increased road gradient, making it difficult to secure a sense of acceleration using only the motor's power, the motor speed cannot be increased to the minimum engine speed at which the driving state can be maintained solely through EV driving.

[0020] Therefore, under the above conditions, slip-start driving is required to utilize engine torque transmitted to the drive shaft via engine clutch slip, in addition to EV driving using motor torque. In conventional hybrid vehicles (HEV, PHEV), during slip-starting utilizing the engine clutch slip state, the engine clutch is controlled to a slip state through hydraulic pressure application to transmit engine torque to the drive shaft, and the transmitted torque is used as the driving torque. At the same time, as the engine load increases during the engine clutch slip section, the engine control unit (ECU) independently performs engine speed control to prevent engine stall and ensure stable engine torque output and transmission, thereby preventing speed fluctuations.

[0021] During such engine speed control, the load amount (engine clutch slip load + HSG charging load) is calculated by the higher-level controller, the hybrid controller (HCU), and transmitted to the engine controller (ECU). The engine controller then performs control to additionally output the torque of the load amount transmitted from the hybrid controller, in addition to the torque required to maintain the engine at idle speed.

[0022] In addition, since the situation in which slip oscillation control is used is one where the available power of the motor is limited or insufficient, control is required to secure additional motor power. Conventionally, the HSG is operated as a generator using engine rotational force to charge the battery, and the charged power is used as power for driving the motor. Control for this purpose can be called "series oscillation control."

[0023] Since engine torque is utilized even during the aforementioned series oscillation control, the additional power acts as a load on the engine; to control engine speed, the hybrid controller calculates the corresponding load amount and transmits it to the engine controller, which then controls the engine to secure additional torque.

[0024] Meanwhile, the acceleration control of hybrid vehicles according to conventional technology has the following problems.

[0025] First, it is difficult to ensure control robustness when the engine controller controls the engine at idle speed. The control is significantly affected by environmental factors that influence engine torque, such as sudden changes in engine load or high altitudes and extremely low temperatures, which occur during conventional idle speed control and engine clutch slip start-up control. Furthermore, due to the engine's characteristics, there is often a lack of responsiveness to the aforementioned load changes during idle speed control, making it difficult to maintain the engine speed. In such cases, various problems may arise, including insufficient power output due to speed drop, engine stall, deterioration of NVH performance due to speed changes, worsening drivability, and ultimately, a decline in vehicle marketability.

[0026] Next, there are difficulties in securing stable torque output during idle speed control by the engine controller. Specifically, while feedback control is performed based on changes in engine speed during idle speed control, if additional engine torque output is required for slip oscillation during speed control, simultaneous control for speed and driving torque is necessary. This not only degrades controllability but also makes it difficult to secure stable torque output.

[0027] In particular, when using an engine equipped with a turbocharger, there are limitations in securing speed control robustness and torque output because idle speed control and turbo boosting control for torque acquisition must be performed simultaneously. If turbo boosting control is not used to secure the robustness of engine idle speed control, output can only be secured up to the turbo non-operation torque level at an engine speed of 1200 rpm as shown in Table 1 below. Consequently, only about 76% of the output relative to the turbo operating torque can be delivered as driving torque, resulting in a loss in terms of performance.

[0028]

[0029] Furthermore, conventional technology suffers from a problem where the number of control elements increases significantly due to the dualization of motor drive power securing control using the HSG (Hydraulic Starter Generator) and engine clutch slip oscillation control. Due to the dualization of entry conditions and control structures for the aforementioned series oscillation control using the HSG and engine clutch slip oscillation control, the control process is structurally very complex; consequently, although both controls aim for performance improvement, cooperative control is difficult.

[0030] Furthermore, since calibration of the control elements for the two aforementioned controls is required separately, it is disadvantageous in terms of labor costs. It is advantageous to implement the engine clutch slip oscillation control so that it is applied simultaneously with the HSG series oscillation control, which is intended to secure motor driving power and minimize battery charge depletion caused by continuous motor power usage. The problem to be solved

[0032] Accordingly, the present invention was created to solve the aforementioned problems, and aims to provide a launch control method for a hybrid vehicle that can improve the limitations of engine idle speed control and torque output securing by conventional engine controllers, thereby ensuring drivability during slip launch and improving the vehicle's driving performance in uphill and restricted situations.

[0033] The objectives of the present invention are not limited to those mentioned above, and other unmentioned objectives will be clearly understood by those skilled in the art to which the present invention pertains (hereinafter referred to as "skilled in the art") from the description below. means of solving the problem

[0035] To achieve the above objective, according to an embodiment of the present invention, a method for controlling the launch of a hybrid vehicle is provided, comprising: a step in which a controller determines whether a predetermined control entry condition is satisfied from information collected from a vehicle when a driver’s acceleration request is detected; a step in which, if it is determined that the control entry condition is satisfied, slip launch and series launch integrated control is initiated by the controller and the charging power of a starter generator connected to transmit power to the engine is determined; a step in which an integrated engine load is determined by the controller based on the determined starter generator charging power and an engine target driving torque is determined based on the determined integrated engine load; a step in which engine torque control is performed by the controller to control the engine torque to the determined engine target driving torque and battery charging is performed using the starter generator; a step in which engine speed control is performed by the controller using the starter generator; and a step in which engine clutch slip control is performed by applying a hydraulic pressure regulated to the engine clutch by the controller. Effects of the invention

[0037] Thus, according to the launch control method of a hybrid vehicle according to the present invention, the limitations of engine idle speed control and torque output securing by a conventional engine controller can be improved, and thereby, not only can drivability during slip launch be secured, but the driving performance of the vehicle can also be improved in uphill and restricted situations. Brief explanation of the drawing

[0039] Figure 1 is a diagram illustrating the powertrain configuration of a hybrid vehicle. Figure 2 is a diagram showing the configuration of the controller and main devices of a hybrid vehicle. FIG. 3 is a flowchart showing the entire process of oscillation control according to an embodiment of the present invention. FIG. 4 is a flowchart showing the entry conditions for slip oscillation and series oscillation control and the speed control process using HSG according to an embodiment of the present invention. FIG. 5 is a flowchart illustrating the process of calculating the integrated engine load and determining the target engine operating torque in the oscillation control process according to an embodiment of the present invention. Specific details for implementing the invention

[0040] The specific structural or functional descriptions presented in the embodiments of the invention are merely illustrative for the purpose of explaining embodiments according to the concept of the invention, and embodiments according to the concept of the invention may be implemented in various forms. Furthermore, it should not be interpreted as being limited to the embodiments described herein, but should be understood to include all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0041] Meanwhile, in the present invention, terms such as "first" and / or "second" may be used to describe various components, but said components are not limited to said terms. For the sole purpose of distinguishing one component from other components, for example, without departing from the scope of rights according to the concept of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0042] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. Conversely, when it is stated that one component is "directly connected" or "directly in contact" with another component, it should be understood that there are no other components in between. Other expressions used to describe the relationship between components, such as "between" and "exactly between," or "adjacent to" and "directly adjacent to," should be interpreted in the same way.

[0043] Throughout the specification, identical reference numbers denote identical components. The terms used in this specification are for describing embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used in this specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0045] FIG. 2 is a diagram showing the configuration of a controller and main devices of a hybrid vehicle. In describing embodiments of the present invention below, reference will be made to FIG. 1 and FIG. 2 regarding the configuration of the controller and devices of a hybrid vehicle.

[0046] The present invention aims to provide a launch control method for a hybrid vehicle that can improve the limitations of engine idle speed control and torque output securing by conventional engine controllers, thereby ensuring drivability during slip launch and improving the vehicle's driving performance in uphill and restricted situations.

[0047] The control process of the present invention can be performed by cooperative control between a plurality of in-vehicle controllers. That is, as shown in FIG. 2, a hybrid vehicle is equipped with a hybrid controller (hereinafter referred to as 'HCU') (20), which is a top-level controller that controls the overall operation of the vehicle based on vehicle driving information detected by a driving information detection unit (10), and additionally, various controllers are provided to control various devices of the vehicle.

[0048] For example, together with the hybrid controller (20), the engine controller (hereinafter referred to as 'ECU') (30) that controls the operation of the engine (1), the motor controller (hereinafter referred to as 'MCU') (40) that controls the operation of the drive motor (3) and HSG (7), the transmission controller (hereinafter referred to as 'TCU') (50) that controls the operation of the transmission (4), and the battery controller (hereinafter referred to as 'BMS') (60) that collects battery status information and performs control to manage the battery (6) can perform cooperative control for vehicle launch by exchanging information with each other through the vehicle network.

[0049] Among the device configurations of Fig. 2, the engine clutch (2) can be controlled by the HCU (20), and the hydraulic pressure applied to the engine clutch (2) is controlled according to the control command output by the HCU (20).

[0050] In addition, among the device configurations of FIG. 2, the driving information detection unit (10) includes an engine speed detection unit that detects engine speed (RPM), an HSG speed detection unit that detects HSG (starter generator) speed, and an accelerator pedal detection unit that detects the driver's accelerator pedal input value (APS value). The HSG speed detection unit may be a conventional resolver installed in the HSG (7), and the accelerator pedal detection unit may be a conventional accelerator pedal sensor (Accelerator Position Sensor, APS) installed in the accelerator pedal that outputs an electrical signal according to the driver's accelerator pedal operation state.

[0051] In the following description, the control entities for each stage or process are described as the controllers mentioned above; however, the oscillation control process according to the present invention may also be performed by a single integrated control element instead of multiple controllers. Both the multiple controllers and the single integrated control element may be collectively referred to as controllers, and it can be said that the oscillation control process of the present invention is performed by these controllers. In the following description, the term "controller" may refer to the controller collectively referred to above or to one of the controllers mentioned above.

[0052] Table 2 below illustrates the subject of engine speed control during slip oscillation in the oscillation control process according to the conventional and the present invention.

[0053]

[0054] The control entities and responsible controls shown in Table 2 are exemplary and the present invention is not limited thereto, and the control entities and responsible controls can be appropriately modified to a extent that does not deviate significantly from the control functions normally performed by the controller.

[0055] In the present invention, a control configuration is applied that integrates slip oscillation control using an engine clutch (2) and series oscillation control using an HSG (7). That is, in the present invention, integrated control of slip oscillation and series oscillation is performed. In the prior art, entry conditions were set and judged, and engine load was calculated and transmitted separately for slip oscillation control and series oscillation control. In the present invention, this is changed to simultaneous entry of slip oscillation control and series oscillation control and calculation of the integrated engine load. To this end, control entry conditions for starting integrated control of slip oscillation and series oscillation are set in the controller (HCU).

[0056] In addition, in the oscillation control method according to the present invention, an engine speed control process using an HSG (7) is added during slip oscillation and series oscillation. That is, in the past, the ECU (30) independently performed idle speed control for the engine, but in the present invention, as exemplified in Table 2, the HCU (20) and MCU (40) perform cooperative control for engine speed control using a starter generator, i.e., an HSG (7), which is an engine-connected motor. At this time, feedback and feedforward control for the HSG (7) and engine torque intervention (torque limiting) control during speed divergence can be performed.

[0057] In addition, the oscillation control method according to the present invention includes a process for determining and calculating the operating point of engine torque during slip oscillation and series oscillation, and the HCU (20) determines the torque and operating point that the engine (1) must output by considering the series charge amount (battery charge amount by HSG) by the HSG (7) and the slip amount of the engine clutch (2).

[0058] In addition, in the oscillation control method according to the present invention, when engine speed control using HSG (7) cannot be performed or control fails due to insufficient HSG output or a failure situation, the conventional engine speed control, that is, the self-engine idle speed control process by the ECU, is performed.

[0059] FIG. 3 is a flowchart showing the entire process of oscillation control according to an embodiment of the present invention, and FIG. 4 is a flowchart showing the entry conditions for integrated control of slip oscillation and series oscillation and the speed control process using HSG according to an embodiment of the present invention.

[0060] In addition, FIG. 5 is a flowchart illustrating the process of calculating the integrated engine load and determining the target engine operating torque in the oscillation control process according to an embodiment of the present invention. The control process will be described in more detail with reference to FIGS. 3 to 5.

[0061] In the present invention, as described above, the entry conditions for slip oscillation control and series oscillation control are identical, and when the predetermined entry conditions are satisfied, both slip oscillation control and series oscillation control are performed. That is, after the driver's intention to accelerate is detected and the predetermined entry conditions are satisfied, the series oscillation control is started and performed together with the slip oscillation, and the HSG (7) is driven as a generator by the rotational force of the engine (1) to charge the battery by the HSG and thereby secure the available power and driving torque of the motor (1). In this way, in the present invention, since the slip oscillation control using the engine clutch (2) and the series oscillation control using the HSG (7) are integrated, control simplification becomes possible.

[0062] As shown in FIGS. 3 and 4, basically, when there is a driver's intention to accelerate, the vehicle's starting (starting) control is initiated (S20), and the controller (HCU) determines that there is a driver's intention to accelerate from the signal of the accelerator pedal detection unit among the driving information detection units (10) (driver acceleration request detection) (S10).

[0063] Additionally, when vehicle launch control begins after detecting a driver acceleration request (S20), the controller (HCU) determines whether the current vehicle state satisfies a predetermined control entry condition based on information collected from the vehicle. Here, if it is determined that the control entry condition is satisfied, the controller starts integrated control for slip launch and series launch, i.e., integrated control for slip launch and series launch (S30).

[0064] Referring to FIG. 4, the control entry condition is a first threshold value (P) where the battery charging / discharging power (absolute value) is preset. th A condition (S22) exceeding ) and a second threshold value (Tq) in which the HSG charge / discharge torque limit value (absolute value) is preset thIt may include a condition (S23) that exceeds ). In addition, it may further include a condition (S21) in which no failure, such as a failure of the MCU (including the inverter) controlling the operation of the HSG, has occurred as a result of the fault diagnosis (MCU normal state).

[0065] When all of the above control entry conditions are satisfied, an integrated control that performs slip oscillation control and series oscillation control together as described above, i.e., the slip oscillation and series oscillation integrated control presented in the present invention, is initiated (S30, S31). On the other hand, when none of the above control entry conditions are satisfied, a conventional slip oscillation control including an engine idle speed control process by the ECU (30) is performed (S24).

[0066] Under the above control entry condition, the first threshold value (P th ) is set as a power threshold at which engine speed control using the HSG (7) becomes impossible due to the battery charging / discharging power limit, and is then input and stored in the HCU (20) for use. In order to prevent a situation where minimum engine speed control by the HSG (7) is impossible due to the battery charging / discharging power limit, making it impossible to maintain the target speed and consequently unable to start the vehicle, the battery charging / discharging power is set to a first threshold (P th If it is less than ) it transitions to conventional slip oscillation control (S24).

[0067] The above first threshold value (P th ) is not a fixed value but a value that can be varied according to the power consumption of the air conditioning system or other in-vehicle electronic components, and the controller (HCU) determines a corresponding first threshold value (P) from the power consumption of the in-vehicle electronic components. th ) can be determined by setting information. Here, the setting information consists of power consumption and a first threshold value (P th As data with a predefined correlation of ), the first threshold value (P) based on power consumption th ) can be a map, table, formula, etc. that is set.

[0068] In addition, under the above control entry condition, a second threshold value (Tq th ) is set as a torque threshold at which engine speed control using the HSG (7) becomes impossible due to the HSG charge / discharge torque limit, and is then input and stored in the HCU (20) for use. Since speed control is impossible when the torque is limited due to a failure of the MCU (40) and inverter or a low SOC state of the battery (6), the HSG charge / discharge torque is monitored to set a second threshold (Tq th If it is less than ) it transitions to conventional slip oscillation control (S24).

[0069] The second threshold value (Tq) which is the threshold value for the HSG charge / discharge torque limit value th ) can be varied according to the accelerator pedal input value (APS value) or the driver's requested torque detected by the accelerator pedal detection unit among the driving information detection units (10). As the accelerator pedal input value or the driver's requested torque value increases, the amount of slip used by the engine clutch (2) increases and the amount of speed control fluctuation due to the large load increases, so the second threshold value (Tq th This allows the accelerator pedal threshold or the driver's requested torque to be variable.

[0070] Since the above driver-requested torque is a control variable already used and determined from vehicle driving information, such as accelerator pedal input values, in the conventional hybrid vehicle control process, the description of its calculation method, etc., will be omitted in this specification.

[0071] In this way, the second threshold value (Tq) in the controller (HCU) th When ) is determined by setting information, the setting information is data that predefines the correlation between the accelerator pedal input value or the driver's requested torque and the second threshold value, and the second threshold value (Tq) is a value according to the accelerator pedal input value or the driver's requested torque. th ) can be a map, table, formula, etc. that is set.

[0072] Meanwhile, when all of the above control entry conditions are satisfied and integrated control of slip oscillation and series oscillation begins (S30, S31), the HCU (20) and MCU (40) perform cooperative control for series oscillation. At this time, the HCU (20) and MCU (40) determine the HSG charging power (S32), and then use the determined HSG charging power to perform the engine integrated load calculation process (S40) and the engine target driving torque determination process (S50), and in addition, perform engine speed control using the HSG (S70). Furthermore, the ECU (30) performs engine torque control for slip oscillation.

[0073] To explain the integrated control process for slip oscillation and series oscillation in more detail, first, the HSG charging power is determined by the controller (HCU) (S32), where 'charging' means battery charging by the HSG. In an embodiment of the present invention, the HSG charging power can be determined as a power value obtained by subtracting the HSG speed control margin power from the maximum power capable of continuous charging according to the HSG Spec.

[0074] The HSG charging power is a value that can be varied by the engine target speed or other external conditions, taking into account control stability and launch performance. Since the maximum charging power is limited by the HSG specifications, it is determined and used as a value smaller than the corresponding value by the margin power, based on the continuous charging rating of the HSG specifications. The margin power for the above HSG speed control may also be a value that varies according to vehicle conditions (e.g., 1 kW based on the HSG power). As the HSG charging power is one of the control variables already used in hybrid vehicle control, and various methods for determining it are known, further explanation is omitted in this specification.

[0075] When the HSG charging power is determined as described above, the engine integrated load amount during slip oscillation and series oscillation is calculated using this (S40). In an embodiment of the present invention, the process of calculating the engine integrated load amount is as shown in FIG. 5.

[0076] To calculate the integrated engine load, the HSG target charging torque is determined using the determined HSG charging power and HSG target speed (S41). Here, the HSG target speed can be set to a value proportional to the engine target speed when the engine clutch is engaged, that is, a value obtained by multiplying the engine target speed by a preset factor value. Here, the factor value may be the pulley ratio of the HSG power transmission mechanism.

[0077] Specifically, since the engine (1) and the HSG (7) are connected by a power transmission mechanism including a belt and a pulley, the HSG target speed can be calculated by the formula 'HSG target speed = engine target speed × pulley ratio of the HSG power transmission mechanism'.

[0078] At this time, the engine target speed is set to the lowest engine speed (RPM) at which the driving state can be maintained when the engine clutch is engaged, and the HSG target speed can be set to the value obtained by multiplying the engine target speed by the pulley ratio.

[0079] In an embodiment of the present invention, the HSG target speed is preset in the controller (HCU) and used to determine the HSG target charging torque, or the engine target speed and pulley ratio are preset and input into the controller (the product of the engine target speed and the pulley ratio is the HSG target speed) and used to determine the HSG target charging torque.

[0080] In the controller (HCU), the HSG target charging torque can be calculated by a formula from the determined HSG charging power and HSG target speed, and the formula for calculating the HSG target charging torque is as follows: Equation 1.

[0082] [Mathematical Formula 1]

[0083] HSG Target Charging Torque = [HSG Charging Power / (HSG Target Speed ​​× 2π / 60)] - C

[0085] In the above mathematical formula 1, 'C' is a value of compensation torque for engine speed error compensation (hereinafter referred to as 'engine speed error compensation torque'), and the engine speed error compensation torque used to calculate the HSG target charging torque is a value determined in the previous control cycle (a value determined at step S45 of the previous control cycle, see FIG. 5).

[0086] Here, the engine speed error is the difference between the actual engine speed and the target engine speed, and the actual engine speed is the current engine speed detected by the engine speed detection unit among the driving information detection units. Also, in the above mathematical formula 1, '2π / 60' is a constant for converting RPM into a Radius value.

[0087] Subsequently, once the HSG target charging torque is obtained as described above, the controller (HCU) can determine the engine-side HSG charging load by multiplying it by a value proportional to the HSG target charging torque, that is, a predetermined factor value. Here, the factor value may be the pulley ratio of the HSG power transmission mechanism. Specifically, as shown in Equation 2 below, the engine-side HSG charging load can be determined by multiplying the HSG target charging torque by the pulley ratio of the HSG power transmission mechanism (S42). Here, the load is the torque value.

[0088] Next, the engine integrated load amount is determined by the sum of the engine-side HSG charging load and the engine clutch transmission torque in the controller (HCU) as shown in Equation 3 below (S43).

[0090] [Mathematical Formula 2]

[0091] Engine-side HSG charging load = HSG target charging torque × Pulley ratio

[0093] [Mathematical Formula 3]

[0094] Integrated Engine Load = Engine-side HSG Charging Load + Engine Clutch Transmission Torque

[0096] In mathematical formula 3, engine clutch transmitted torque (T CLT ) is, for example, 'T CLT It can be calculated by the formula = μ×A×P'. Here, 'μ' represents the clutch friction coefficient, 'A' represents the effective area of ​​the clutch, and 'P' represents the clutch hydraulic pressure. The formula for calculating the engine clutch transmission torque may be modified depending on the specifications and structure of the clutch applied to the actual vehicle. As the engine clutch transmission torque is one of the control variables already used in hybrid vehicle control, and various methods for determining it are known, further explanation is omitted in this specification.

[0097] In addition, the HSG output torque can be calculated using the engine-side HSG charging load and speed control feedback torque determined by the above mathematical formula 2 in the controller (HCU), and the formula for calculating the HSG output torque is as follows mathematical formula 4.

[0099] [Mathematical Formula 4]

[0100] HSG Output Torque = (Engine-side HSG Charging Load / Pulley Ratio) + Speed ​​Control Feedback Torque

[0102] Referring to the above mathematical formula 4, it can be seen that the HSG output torque is calculated from the engine-side HSG charging load and the speed control feedback torque, and that the pulley ratio of the HSG power transmission mechanism is used together. Here, the speed control feedback torque can be an HSG torque value that causes the HSG speed detected by the HSG speed detection unit to follow the HSG target speed, as described later in the engine speed control process (S70) using the HSG (7). The above speed control feedback torque refers to the HSG torque output to provide feedback control by referencing the error between the current HSG speed and the target speed so that the HSG speed can follow the HSG target speed.

[0103] Next, the controller (HCU) determines the engine speed error compensation torque using the calculated HSG output torque (S44). The engine speed error compensation torque (C) calculated at this time is used to determine the HSG target charging torque in step S41 of the next control cycle.

[0104] To explain in more detail the process of determining the engine speed error compensation torque (S44), the engine speed error compensation torque is determined by the controller (HCU) using setting information from the HSG charging limit torque, HSG output torque, and HSG target charging torque. At this time, the setting information may be a map or table in which the engine speed error compensation torque corresponding to the HSG charging limit torque, HSG output torque, and HSG target charging torque is set. Alternatively, the setting information may be a formula capable of calculating the engine speed error compensation torque from the HSG charging limit torque, the HSG output torque determined in the previous control cycle, and the HSG target charging torque.

[0105] The above HSG charging limiting torque is a value based on the HSG's hardware specifications (H / W Spec.), and it may be a value determined from a map by the controller using the available battery power and HSG speed as input variables. It is a value determined to output and limit the HSG charging power continuous rating specification (Spec.) to the maximum torque available at that time, based on the current available battery power and HSG speed, in order to prevent the HSG from being used beyond its allowable rating.

[0106] Table 3 below illustrates a map in which the corresponding engine speed error compensation torque (C) can be determined from the HSG charging limit torque (①), HSG output torque (②), and HSG target charging torque (③).

[0108]

[0110] Specifically, Table 3 above illustrates a map in which the engine speed error compensation torque (C) is set to a value corresponding to the difference between the HSG target charging torque (③) and the HSG output torque (②) (③-②), and the difference between the HSG charging limit torque (①) and the HSG output torque (②) (①-②).

[0111] In Table 3, the values ​​of ③-② are related to the determination of engine speed error, and the values ​​of ①-② are considered to secure an additional control margin for engine speed error by taking into account charging limits. In the map above, the engine speed error compensation torque value corresponding to the value between ③-② and ①-② can be determined by interpolation.

[0112] As shown in the map of Table 3 in an embodiment of the present invention, the larger the value of ③-② and the larger the value of (①-②), the larger the value of the engine speed error compensation torque (C) can be set.

[0113] And, when the engine integrated load amount is determined by mathematical formula 3 as described above, the controller (HCU) determines the engine target operating torque using the determined engine integrated load amount information as shown in FIG. 3 (S50).

[0114] Referring to FIG. 5, the controller (HCU) first calculates the engine speed error, which is the difference between the actual engine speed and the target engine speed (S51), and then determines the engine torque limit value (D) using setting information from the engine speed error and the driver accelerator pedal input value (APS value) or the driver requested torque (S52). The actual engine speed is vehicle driving information detected by the engine speed detection unit among the driving information detection units (10), and the accelerator pedal input value is vehicle driving information detected by the accelerator pedal detection unit among the driving information detection units.

[0115] The above engine torque limit value is a value intended to prevent engine speed divergence and varies according to the engine speed error, accelerator pedal input value, or driver-requested torque. In the present invention, setting information is used in which the engine torque limit value (D) is set according to the engine speed error, accelerator pedal input value, or driver-requested torque, and this setting information may be a map, a table, or a formula.

[0116] Table 4 below is an example of a map in which the engine torque limit value can be determined from the engine speed error and the driver's requested torque. By referring to this, it can be seen that the engine torque limit value corresponding to the engine speed error and the driver's requested torque is set.

[0118]

[0120] As shown in Table 4 of the embodiments of the present invention, the larger the engine speed error and the larger the driver's requested torque value, the larger the engine torque limit value for preventing engine speed divergence can be set.

[0121] When the engine torque limit value is determined as described above, the controller, specifically the HCU (20), finally determines the smaller value between the engine integrated load and the engine torque limit value as the engine target driving torque (S53). Then, the HCU (20) transmits the finally determined engine target driving torque to the ECU (30), and the ECU (30) controls the engine torque using the final engine target driving torque transmitted from the HCU (20) as the target value (S60).

[0122] In this way, when the engine target driving torque is finally determined in the HCU (20), the engine torque can be controlled in the ECU (30) using the engine target driving torque transmitted from the HCU (20) as the target value, but alternatively, the final engine target driving torque can be determined in the ECU (30).

[0123] That is, the HCU (20) transmits the determined engine integrated load amount to the ECU (30) as the engine target driving torque value, and simultaneously transmits the determined engine torque limit value to the ECU (30). Accordingly, the ECU (30) finally determines the engine target driving torque from the engine target driving torque and engine torque limit value transmitted from the HCU (20), and controls the engine torque using the finally determined engine target driving torque as the target value. In the ECU (30), the final engine target driving torque value is determined as the smaller value between the engine integrated load amount and the engine torque limit value.

[0124] In this way, the engine integrated load amount in the ECU (30) is used as the engine target driving torque value, but if the engine integrated load amount is greater than the engine torque limit value for preventing engine speed divergence, the engine target driving torque value is limited to the engine torque limit value.

[0125] Thus, the ECU (30) can control the engine torque by using the final determined target engine driving torque value as the target value. Consequently, while engine speed control was performed in the ECU in the conventional method, engine torque control is performed in the ECU in the present invention. Therefore, in the present invention, engine speed control in the ECU becomes unnecessary, and maximum engine torque output control becomes possible.

[0126] In the engine torque control process by the ECU (30) in the present invention, the existing reserve torque required for pure engine torque control is unnecessary, so the change in engine output is minimized, allowing the current maximum engine output to be fully utilized as driving torque. In addition, control robustness and fast responsiveness can be secured through motor speed control. Furthermore, the engine integrated load calculation process and the engine target driving torque determination process are integrated within the controller, thereby enabling simplification of control.

[0127] Meanwhile, as shown in FIG. 3, engine speed control using HSG (7) is performed by cooperative control of HCU (20) and MCU (40) during slip oscillation and series oscillation control (S70). Although there is a speed difference corresponding to the pulley ratio between the engine (1) and HSG (7), since HSG (7) is connected to the engine (1) in a way that allows power transmission by means of a power transmission mechanism including a belt and a pulley, it is possible to feedback control the engine speed to the target speed using HSG.

[0128] In the present invention, a controller utilizes an HSG (7) to control the engine speed when a vehicle starts, and controls the engine speed to follow the target engine speed using the HSG (7). At this time, rather than controlling the actual engine speed to control the engine speed to the target engine speed, the controller (HCU and MCU) controls the speed of the HSG (7) which is connected to the engine (1) to enable power transmission. That is, the driving of the HSG is feedback-controlled so that the HSG speed reaches the target HSG speed, thereby maintaining the engine speed at the target engine speed, and the target HSG speed is obtained from the target engine speed.

[0129] As described above, since the HSG (7) is connected to the engine (1) so as to be able to continuously transmit power, the HSG target speed is related to the engine target speed and has the relationship 'HSG target speed = engine target speed × pulley ratio of the HSG power transmission mechanism'. At this time, the engine target speed is set to the lowest engine speed (RPM) at which the driving state can be maintained when the engine clutch is engaged, and the HSG target speed is set to the value obtained by multiplying the engine target speed by the pulley ratio.

[0130] In an embodiment of the present invention, the controller (HCU and MCU) can control the HSG torque so that the HSG speed reaches the HSG target speed by using the actual HSG speed as a feedback value during the engine speed control process. Here, the actual HSG speed is the speed detected by the HSG speed detection unit among the driving information detection units (10).

[0131] In the feedback control process described above, the controller calculates the HSG speed error value, which is the difference between the actual speed of the HSG and the target speed of the HSG, and controls the HSG torque by reducing this HSG speed error value. In this way, PI control, which reduces the HSG speed error by applying a P gain to the HSG speed error, can be applied. As such, in the present invention, by controlling the engine speed by feedback controlling the speed of the HSG, which is an engine-connected motor, it is possible to secure superior responsiveness and accuracy compared to the engine speed control method by the existing ECU.

[0132] In the engine speed control process using the above HSG, the HSG torque value (torque command value) for feedback-controlling the HSG speed to the HSG target speed can be used as the speed control feedback torque value when calculating the engine integrated load amount in step S43.

[0133] Meanwhile, after engine speed control using HSG (7) is performed, the controller (HCU) applies the controlled hydraulic pressure to the engine clutch (2) to control the engine clutch slip (S81). When applying hydraulic pressure for slipping the engine clutch, the slope of the hydraulic pressure application is varied according to the driver's demand torque, which is a value representing the driver's intention to accelerate. At this time, control responsiveness can be ensured by using a larger hydraulic pressure application slope as the driver's demand torque increases.

[0134] In the present invention, the engine speed is controlled by controlling the HSG speed to the HSG target speed, thereby ensuring robustness of the engine control and, compared to conventional technology, being able to respond sensitively to engine load, it is possible to increase the hydraulic application slope further, and thereby improve acceleration response performance and climbing performance.

[0135] In addition, regarding the method of determining engine clutch slip hydraulic pressure for slip control of the engine clutch in the present invention, a conventional hydraulic pressure determination method can be applied as is. For example, after determining a corresponding slip torque from the battery SOC value provided by the BMS (60) and the driver accelerator pedal input value (APS value) or driver requested torque, the slip hydraulic pressure can be determined using a predetermined formula from the determined slip torque.

[0136] Ultimately, the slip hydraulic pressure determined as above is applied to the engine clutch to control the engine clutch to a slip state, and at the same time, the HSG (7) is operated as a generator by the engine rotational force so that the battery is charged by the HSG (7) (S81).

[0137] Afterwards, the available power of the drive motor increases due to battery charging, and eventually, after the speed synchronization of the engine (1) and the drive motor (3), a torque is transmitted from the engine to the drive shaft (S81), and slip launch and series launch driving of the vehicle becomes possible (slip launch and increased EV driving range possible) (S83).

[0138] In this way, according to the method for controlling the launch of a hybrid vehicle according to the present invention, integrated control of engine clutch slip launch and series launch is applied, thereby improving the limitations of engine idle speed control and torque output securing by the existing ECU. Through this, not only can drivability during slip launch be secured, but the driving performance and marketability of the vehicle can also be improved in uphill and restricted situations.

[0139] To explain in more detail, first, according to the present invention, the robustness of speed control is ensured, thereby improving vehicle marketability. Conventionally, during engine clutch slip launch and series launch, speed control of the engine itself by the ECU was performed, resulting in problems such as insufficient target speed tracking and engine stall. However, the present invention utilizes speed control using an HSG, which is an engine-linked motor, thereby minimizing the influence of external environmental conditions. Furthermore, since the engine speed is controlled through the motor (HSG), a fast control response is possible, and there are advantages in improving target speed tracking and robustness. Additionally, since it is possible to secure maximum engine performance without issues such as engine stall or degradation of slip / series launch performance, launch performance can be improved.

[0140] Next, the vehicle's marketability can be improved by enabling the use of maximum engine torque during vehicle acceleration. Conventionally, it was necessary to secure reserve torque for control response during engine speed control, and there was a problem of output loss due to securing reserve torque that could not be used for vehicle propulsion. On the other hand, in the present invention, there is no need to secure reserve torque from the engine during speed control by the HSG (motor), and the engine's maximum torque can be fully and stably utilized by minimizing engine torque variability. Ultimately, by making it possible to utilize the engine's maximum output, improvements in acceleration and climbing performance become possible.

[0141] Next, control integration enables the simplification of the HCU logic structure and the minimization of development effort. Conventionally, since the determination of control entry conditions and the calculation of engine torque operating points were performed separately for slip oscillation and series oscillation, there were issues of excessive control complexity and development effort for logic. In contrast, the present invention enables integrated control of slip oscillation and series oscillation, thereby allowing for the elimination of unnecessary logic and simplification, as well as the minimization of development effort and the assurance of robustness.

[0143] Although embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also included within the scope of the present invention. Explanation of the symbols

[0145] 1 : Engine 2: Engine Clutch 3 : Motor 4 : Transmission 5 : Inverter 6 : Battery 7 : HSG 10: Driving information detection unit 20 : Hybrid Controller (HCU) 30 : Engine Control Unit (ECU) 40 : Motor Controller (MCU) 50 : Transmission Control Unit (TCU) 60 : Battery Management System (BMS)

Claims

Claim 1 A method for controlling the launch of a hybrid vehicle, comprising: a step in which a controller determines whether a predetermined control entry condition is satisfied from information collected from the vehicle when the driver's acceleration request is detected; a step in which, if it is determined that the control entry condition is satisfied, slip launch and series launch integrated control is initiated by the controller and the charging power of a starter generator connected to transmit power to the engine is determined; a step in which an integrated engine load is determined by the controller based on the determined starter generator charging power and an engine target driving torque is determined based on the determined integrated engine load; a step in which engine torque control is performed by the controller to control the engine torque to the determined engine target driving torque and battery charging is performed using the starter generator; a step in which engine speed control using the starter generator is performed by the controller; and a step in which engine clutch slip control is performed by applying a hydraulic pressure regulated to the engine clutch by the controller. Claim 2 A method for controlling the launch of a hybrid vehicle according to claim 1, wherein the control entry condition comprises: a condition in which the battery charging / discharging power exceeds a preset first threshold value; and a condition in which the charging / discharging torque limit value of the starter generator exceeds a preset second threshold value. Claim 3 A method for controlling the oscillation of a hybrid vehicle according to claim 2, wherein the control entry condition further includes a condition in which no failure has occurred in the inverter and motor controller for driving and controlling the starter generator as a result of fault diagnosis. Claim 4 A method for controlling the oscillation of a hybrid vehicle according to claim 2, wherein the first threshold value is determined by a controller as a variable value corresponding to the power consumption of an electrical component within the vehicle based on setting information. Claim 5 A method for controlling the launch of a hybrid vehicle according to claim 2, wherein the second threshold value is determined by setting information in the controller as a variable value corresponding to the driver's accelerator pedal input value or the driver's requested torque. Claim 6 A method for controlling the launch of a hybrid vehicle, characterized in that, in any one of claims 1 to 3, when it is determined that the control entry condition is not satisfied, slip launch control is performed by the controller to transmit engine torque to the drive shaft through engine clutch slip, and engine idle speed control is performed to control the engine speed to the idle speed by controlling the engine torque during the slip launch control. Claim 7 A method for controlling the launch of a hybrid vehicle according to claim 1, wherein, in the step of determining the starter generator charging power, the starter generator charging power is determined as a value obtained by subtracting a predetermined starter generator speed control margin power from the maximum power capable of continuous charging of the starter generator. Claim 8 A method for controlling the launch of a hybrid vehicle according to claim 1, wherein the step of determining the engine integrated load comprises: a step of determining the starter generator target charging torque based on the determined starter generator charging power and the starter generator target speed; a step of determining the engine-side starter generator charging load from the determined starter generator target charging torque; and a step of determining the engine integrated load by summing the determined engine-side starter generator charging load and the engine clutch transmission torque. Claim 9 A method for controlling the launch of a hybrid vehicle according to claim 8, wherein the target charging torque of the starter generator is determined by the following mathematical formula 1. Mathematical formula 1: Target charging torque of the starter generator = [Starter generator charging power / (Starter generator target speed × 2π / 60)] - C, where C is a value determined in the previous control cycle and is a compensation torque for compensating for the engine speed error, which is the difference between the engine speed detected by the engine speed detection unit and the target engine speed. Claim 10 A method for controlling the launch of a hybrid vehicle according to claim 8 or claim 9, wherein the target speed of the starter generator is determined by multiplying the target speed of the engine by a predetermined factor value, and the target speed of the engine is the lowest engine speed at which the driving state can be maintained when the engine clutch is engaged. Claim 11 A method for controlling the launch of a hybrid vehicle according to claim 9, wherein the compensation torque is determined by setting information within the controller as a value corresponding to the determined starter generator output torque, the starter generator charging limit torque, and the starter generator target charging torque, when the starter generator output torque is determined by a predetermined formula from the engine-side starter generator charging load and speed control feedback torque. Claim 12 A method for controlling the launch of a hybrid vehicle according to claim 11, wherein the setting information for determining the compensation torque is a map in which the compensation torque is set to a value corresponding to the difference value (③-②) between the starter generator target charging torque (③) and the starter generator output torque (②), and the difference value (①-②) between the starter generator charging limit torque (①) and the starter generator output torque (②). Claim 13 A method for controlling the launch of a hybrid vehicle according to claim 11, wherein the speed control feedback torque is a starter generator torque value that causes the starter generator speed detected by the starter generator speed detection unit to follow the starter generator target speed while engine speed control using the starter generator is performed. Claim 14 A method for controlling the launch of a hybrid vehicle according to claim 8, wherein the charging load of the engine-side starter generator is determined by multiplying the determined target charging torque of the starter generator by a predetermined factor value. Claim 15 A method for controlling the launch of a hybrid vehicle according to claim 1, wherein the step of determining the engine target driving torque comprises: a step of determining an engine speed error, which is the difference between the engine speed detected by an engine speed detection unit and the engine target speed; a step of determining an engine torque limit value based on setting information from the engine speed error and the driver accelerator pedal input value or the driver requested torque; and a step of determining the smaller value between the determined engine integrated load amount and the engine torque limit value as the engine target driving torque. Claim 16 A method for controlling the launch of a hybrid vehicle according to claim 1, wherein, in the step of performing engine speed control using the starter generator, torque control for the starter generator is performed using the starter generator speed detected by the starter generator speed detection unit as a feedback value so that the starter generator speed follows a predetermined starter generator target speed.

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