Method and system for controlling an engine clutch of a vehicle

Abstract

A method and system for controlling an engine clutch of a vehicle, comprising the following steps: determining whether a learning mode entry condition is satisfied based on whether a forced downshift occurs during execution of variable hydraulic control of the engine clutch and based on the degree of slippage of the engine clutch; when a vehicle state satisfies a predetermined learning mode entry condition, deriving and storing a learning hydraulic value, the learning hydraulic value being used to suppress slippage that would occur when a forced downshift occurs during execution of the variable hydraulic control so that slippage does not occur; and when the same forced downshift situation occurs, calculating a final hydraulic pressure by adding a hydraulic compensation value to a target hydraulic pressure, and using the calculated final hydraulic pressure to control the engine clutch.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0016954, filed on February 5, 2021, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present disclosure relates to a method and system for controlling an engine clutch of a vehicle, and more specifically, to a method and system for controlling an engine clutch of a P2-type parallel hybrid vehicle, wherein the P2-type parallel hybrid vehicle is configured such that an engine, an electric motor, and a transmission constituting a power system are arranged in a row, wherein an engine clutch is interposed between the engine and the electric motor to regulate the transfer of power in the direction from the engine to the electric motor. Background Art

[0004] Generally, a hybrid vehicle is a vehicle that is driven by effectively combining two or more different types of power sources. In most cases, a hybrid vehicle is driven by power provided by an engine running on a compressed fuel-air mixture and an electric motor powered by a battery. Such a vehicle is called a hybrid electric vehicle (HEV).

[0005] Hybrid electric vehicles have been widely researched due to the increasing demand for improving fuel efficiency and developing more environmentally friendly vehicles. As is known to all, hybrid electric vehicles can be configured to adopt various power transmission structures, including an engine and an electric motor as a power source. Most of the hybrid electric vehicles currently being developed adopt two power transmission structures: parallel type and series type.

[0006] In the parallel type power transmission structure, the engine is only used for power generation, and the motor is only used for driving the vehicle. The advantage of the series type power transmission structure over the parallel type power transmission structure is that it has a relatively simple structure and simple control logic. However, in the series type power transmission structure, the mechanical energy from the engine is converted into electrical energy stored in the battery, and the vehicle is driven by the motor powered by the battery. Therefore, the series type power transmission structure has disadvantages in terms of energy conversion efficiency.

[0007] In contrast, the disadvantage of the parallel power transmission structure relative to the series power transmission structure is that it has a relatively complex structure and complex control logic. However, in the parallel power transmission structure, the mechanical energy from the engine and the electrical energy from the battery can be used at the same time. Therefore, the parallel power transmission structure has an advantage in the efficient use of energy. In addition, hybrid electric vehicles can be designed without making major changes to the drive system of the existing internal combustion engine, thereby reducing manufacturing costs. This advantage has led to the recent increase in the development of parallel hybrid electric vehicles.

[0008] A typical example of a parallel hybrid electric vehicle is a mild hybrid vehicle in which an electric motor assists the engine to provide power. Mild hybrid types are divided into P0, P1, P2, P3, P4, etc. according to the position of the electric motor (called a mild hybrid starter and generator (MHSG) in a mild hybrid vehicle) in the vehicle power system.

[0009] In these types of hybrid vehicles, such as Figure 1 As shown in (Prior Art), a P2 type mild hybrid vehicle refers to a vehicle configured such that an engine 10, a motor 40, and a transmission 50 constituting a power system are arranged in a row, and an engine clutch 30 is interposed between the engine 10 and the motor 40 to regulate the transmission of power from the engine 10 to the motor 40. Therefore, the vehicle is equipped with a system for transmitting the output of the motor 40 and the output of the engine 10 to the axles.

[0010] For reference, Figure 1 The power transmission type shown is applicable not only to P2 type mild hybrid vehicles but also to general parallel type hybrid vehicles.

[0011] Reference numeral 20 denotes a starter motor. The starter motor 20 is an electric motor capable of generating power and electricity. The starter motor 20 provides driving power for starting the engine 10. Depending on the situation, the starter motor 20 is driven by the power of the engine 10, thereby generating electricity. The starter motor 20 may be coupled to the engine 10 using a mechanical power transmission device such as a belt, a chain, or a gear. The coupling ratio between the starter motor 20 and the engine 10 is determined differently according to needs.

[0012] The engine clutch 30 regulating power transmission between the engine 10 and the motor 40 is a hydraulic clutch operated using hydraulic pressure. The engine clutch 30 allows or prevents transmission power between the engine 10 and the motor 40 through opening, slipping, closing or locking operation of a hydraulic control actuator (HCA).

[0013] In the prior art, the P2 type parallel hybrid system configured as described above controls the torque generated from the engine 10, which is hydraulically transmitted to the engine clutch 30 so as to be transmitted to the axle. At this time, after accurately determining the current state of the engine clutch 30, such as the open state, slip stage, closed state or locked state, the control of the engine clutch 30, such as slip and synchronization control, must be performed.

[0014] However, in the P2 type parallel hybrid system in the prior art, during the execution of the variable hydraulic control of the engine clutch 30, when the load on the vehicle suddenly increases (for example, when the vehicle is traveling along an upwardly inclined road), or when a forced downshift occurs (for example, when an operation for sudden acceleration is performed), the engine clutch 30 may slip. The slip in the engine clutch 30 is caused by the sudden change in the number of engine resolutions and the engine torque. Therefore, the acceleration is reduced, and the feeling of the gear shift cannot be properly produced.

[0015] For reference, "variable hydraulic control" is hydraulic control performed on the engine clutch 30. During variable hydraulic control, the engine clutch is controlled with maximum pressure to suppress slippage and power loss due to slippage at the end of shifting. Then, when the engine torque is kept constant, such as in a fixed speed driving situation where the change in engine torque is small, the pressure used to control the engine clutch is gradually reduced. Therefore, energy loss due to the application of unnecessary excessive hydraulic pressure is prevented.

[0016] The above content is only intended to help understanding the background of the present disclosure, but does not mean that the present disclosure belongs to the scope of the relevant fields known to those skilled in the art. Summary of the invention

[0017] An object of the present disclosure is to provide a method and system for controlling an engine clutch of a P2 type parallel hybrid vehicle, which method and system are capable of preventing slippage of the engine clutch when a forced downshift occurs during execution of variable hydraulic control of the engine clutch of the P2 type parallel hybrid vehicle.

[0018] According to one aspect of the present disclosure, a method for controlling an engine clutch of a P2-type parallel hybrid vehicle is provided, the method comprising: (a) determining whether a learning mode entry condition is satisfied based on whether a forced downshift occurs during execution of a variable hydraulic control of the engine clutch of the P2-type parallel hybrid vehicle and based on the degree of slippage of the engine clutch, (b) when a vehicle state satisfies a predetermined learning mode entry condition, deriving and storing a learning hydraulic value, the learning hydraulic value being used to suppress slippage that would occur when a forced downshift occurs during execution of a variable hydraulic control of the engine clutch so that slippage does not occur in the next same forced downshift situation, and (c) when the same forced downshift situation occurs during the next variable hydraulic control of the engine clutch, calculating a final hydraulic pressure by adding a hydraulic compensation value obtained by multiplying the learning hydraulic value by a compensation coefficient to a target hydraulic pressure, and using the calculated final hydraulic pressure to control the engine clutch.

[0019] In the method, in step (a), during execution of variable hydraulic control of an engine clutch of the vehicle, when a forced downshift occurs and when a slip amount of the engine clutch is at or above a first set value, it may be determined that the learning mode entry condition is satisfied.

[0020] In the method, step (b) may also include: (b-1) capturing the engine torque and the shift progress step at the learning entry time point; (b-2) when the slip amount of the engine clutch calculated based on the difference between the resolution number of the engine and the resolution number of the P2 motor is greater than the maximum slip amount previously during the forced downshift, updating the maximum slip amount and storing the updated value as the engine clutch slip learning value; (b-3) capturing the shift progress step at the learning end time point, at which time point the slip amount of the engine clutch drops below the second set value; and (b-4) determining the learning hydraulic value corresponding to the engine clutch slip learning value in step (b-2) from a dedicated mapping.

[0021] In this method, in step (b-3), when the slip amount of the engine clutch does not drop below the second set value, it is possible to return to the immediately previous step (b-2), and step (b-2) and the steps after step (b-2) can be repeated.

[0022] In the method, when the same forced downshift occurs during the next execution of variable hydraulic control of the engine clutch, in step (c), the final hydraulic pressure can be applied in a shift interval that is the same as the shift interval from the shift progress step at the previous learning entry time point to the shift progress step at the learning end time point, so that the engine clutch can be controlled.

[0023] In the method, the compensation coefficient may include an engine torque coefficient and an oil temperature coefficient.

[0024] In the method, the engine torque coefficient can be the ratio between the current engine torque and the engine torque at the learning entry time point (current engine torque to the engine torque at the learning entry time point), and the oil temperature coefficient can be determined from the oil temperature map, in which the compensation coefficient as a coefficient for compensating for the delay in the response speed of the engine clutch caused by the oil temperature is stored as a value that varies with the oil temperature range.

[0025] According to another aspect of the present disclosure, there is provided a system for controlling an engine clutch of a P2-type parallel hybrid vehicle in which an engine, an electric motor, and a transmission are arranged in a row and in which an engine clutch is installed between the engine and the electric motor, the system comprising: a clutch actuator that provides hydraulic pressure required to drive the engine clutch; a torque measuring unit that measures the torque of the engine; an oil temperature measuring unit that measures the oil temperature inside the engine clutch; and a controller that calculates a target hydraulic pressure to be applied to the engine clutch based on information provided by the torque measuring unit and the oil temperature measuring unit of the engine, and controlling the operation of the clutch actuator based on the calculated target hydraulic pressure, wherein, when a forced downshift occurs during the execution of variable hydraulic control of the engine clutch and when the amount of slippage occurring in the engine clutch is a predetermined value (a first set value) or higher than a predetermined value, the controller derives a learned hydraulic pressure value for suppressing slippage through learning, and stores the derived learned hydraulic pressure value, and when the same forced downshift occurs during the next execution of variable hydraulic control of the engine clutch, the controller calculates a final hydraulic pressure by adding a hydraulic compensation value obtained by multiplying the learned hydraulic pressure value by a compensation coefficient to the target hydraulic pressure, and uses the calculated final hydraulic pressure to control the engine clutch.

[0026] In this system, the controller can capture the shift progress step at a time point when a forced downshift occurs and when the amount of slip occurring in the engine clutch is a predetermined value (a first set value) or higher than a predetermined value during the execution of variable hydraulic control of the engine clutch, and capture the engine torque; when the slip amount of the engine clutch calculated based on the difference between the resolution number of the engine and the resolution number of the P2 motor is greater than the maximum slip amount previously during the forced downshift, the controller can update the maximum slip amount, and can store the value obtained by the update as an engine clutch slip learning value; the controller can capture the shift progress step at the learning end time point, at which time point the slip amount of the engine clutch drops below a predetermined value (a second set value); and the controller can retrieve a hydraulic value corresponding to the engine clutch slip learning value from a dedicated mapping, and can determine the retrieved hydraulic value as a learning hydraulic value.

[0027] In this system, the controller may repeat a process in which, when the slip amount of the engine clutch does not drop below a predetermined value (a second set value), the slip amount of the engine clutch is recalculated, and in which, when the calculated slip amount of the engine clutch is greater than a previous maximum slip amount, the maximum slip amount is updated and the value obtained by the update is stored as an engine clutch slip learning value.

[0028] In this system, when the same forced downshift situation occurs during the next execution of variable hydraulic control of the engine clutch, the controller can apply the final hydraulic pressure in the shift interval that is the same as the shift progress step from the time point when the amount of slip that occurs has a predetermined value (first set value) or higher than the predetermined value to the shift progress step at the learning end time point, thereby controlling the engine clutch.

[0029] In this system, the compensation coefficients may include an engine torque coefficient and an oil temperature coefficient.

[0030] In this system, the engine torque coefficient can be the ratio of the current engine torque to the engine torque at the learning entry time point (current engine torque to the engine torque at the learning entry time point), and the oil temperature coefficient can be determined from the oil temperature map, in which the compensation coefficient is stored as a value that varies with the oil temperature range as a coefficient for compensating for the delay in the response speed of the engine clutch caused by the oil temperature.

[0031] According to the present disclosure, during the execution of the variable hydraulic control of the engine clutch, when a forced downshift occurs and when the engine clutch slips, a compensation value (hydraulic pressure compensation value of the engine clutch) for preventing slipping in the next same gear shifting situation is derived through learning, and the compensation value is applied to the engine clutch control in the next same gear shifting situation. Therefore, slipping can be effectively prevented or pre-processed.

[0032] Therefore, based on the slippage in the previous gear shifting situation, the method and system for controlling the engine clutch of the P2 type parallel hybrid vehicle according to the embodiment of the present disclosure pre-processes the engine clutch slippage that will occur when the forced downshift occurs during the execution of the variable hydraulic control. Therefore, the reduction of acceleration and driving performance due to the slippage of the engine clutch can be prevented, and the gear shift quality can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other objects, features and other advantages of the present disclosure will be more clearly understood through the following detailed description in conjunction with the accompanying drawings, in which:

[0034] Figure 1 (Prior Art) is a schematic diagram showing a power transmission structure of a P2 type parallel hybrid vehicle in the prior art;

[0035] Figure 2 is a schematic diagram showing a configuration of basic components of a P2-type parallel hybrid vehicle including a system for controlling an engine clutch according to an embodiment of the present disclosure;

[0036] Figure 3is a view schematically showing a controller for engine clutch control and its adjacent constituent elements;

[0037] Figure 4 is a graph showing changes over time in the number of resolutions of the engine and the number of resolutions of the P2 motor, which are generated when a kick-down occurs during execution of the variable hydraulic control; and

[0038] Figure 5 is a control flowchart for illustrating a method of controlling an engine clutch of a P2 parallel hybrid vehicle according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0039] It should be understood that the term "vehicle" or "vehicular" or other similar terms used herein include general motor vehicles, such as passenger cars, including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including various ships and boats, aircraft, etc., and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As described herein, a hybrid vehicle is a vehicle having two or more power sources, such as a gasoline-powered vehicle and an electric-powered vehicle.

[0040] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "one", "an", "the" are also intended to include plural forms. It will be further understood that when used in this specification, the terms "include" and / or "include" specify the presence of the features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their combinations. As used herein, the term "and / or" includes any and all combinations of one or more related listed items. Throughout the specification, unless clearly described to the contrary, the term "include" and variants such as "include" or "include" will be understood to imply the inclusion of the elements, but do not exclude any other elements. In addition, the terms "unit", "part (-er)", "device (-or)" and "module" described in the specification refer to units for processing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof.

[0041] In addition, the control logic of the present disclosure may be embodied as a non-transitory computer-readable medium on a computer-readable medium containing executable program instructions executed by a processor, a controller, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disk (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium may also be distributed in a network-coupled computer system so that the computer-readable medium is stored and executed in a distributed manner, such as by a telematics server or a controller area network (CAN).

[0042] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings so that those skilled in the art to which the present disclosure pertains can practice the embodiments without excessive experiments.

[0043] The terminology used hereinafter throughout this specification is for describing particular embodiments only and is not intended to be limiting of the present disclosure.The indefinite articles "a" and "an" are used to mean one or more, not just one, unless the context clearly indicates otherwise.

[0044] In addition, the terms first, second, etc. are used to describe various constituent elements, but should not be interpreted as imposing any limitation on their meanings. These terms are only used to distinguish one element from another.

[0045] The same constituent elements have the same reference numerals, and descriptions thereof are not repeated. Detailed descriptions of related arts known in the art will be omitted when it is determined to unnecessarily obscure the essence and gist of the present disclosure.

[0046] Fundamentally, the method and system for controlling the engine clutch of a P2-type parallel hybrid vehicle according to an embodiment of the present disclosure are configured in such a manner that when a forced downshift occurs during the execution of variable hydraulic control of the engine clutch in the P2-type parallel hybrid vehicle, a compensation value for preventing the engine clutch from slipping is derived through learning, and the derived compensation value is reflected in the next gear shift situation under the same conditions.

[0047] Therefore, the system for controlling the engine clutch of a P2 type parallel hybrid vehicle according to an embodiment of the present disclosure pre-processes the slip of the engine clutch that will occur when a forced downshift occurs under certain circumstances, especially during the execution of variable hydraulic control. Therefore, the reduction in acceleration and driving performance due to the slip of the engine clutch is prevented, and the shift quality is improved.

[0048] For reference, "variable hydraulic control" is hydraulic control performed on the engine clutch. During variable hydraulic control, the engine clutch is controlled using the maximum pressure to suppress slippage and power loss due to slippage at the end time point of the shift. Then, when the engine torque changes less due to the constant engine torque in a fixed speed driving situation, the pressure used to control the engine clutch is gradually reduced. Therefore, energy loss due to the application of unnecessary excessive hydraulic pressure is prevented.

[0049] First, a system for controlling an engine clutch of a P2 type parallel hybrid vehicle according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

[0050] Figure 2 is a schematic diagram showing a configuration of basic components of a P2-type parallel hybrid vehicle including a system for controlling an engine clutch according to an embodiment of the present disclosure. Figure 3 is a view schematically showing a controller for engine clutch control and its adjacent constituent elements.

[0051] refer to Figure 2 and Figure 3 Fundamentally, a P2 type parallel hybrid vehicle in which a system for controlling an engine clutch according to one aspect of the present disclosure is applied is configured in such a manner that an engine 110, an electric motor 140 and a transmission constituting a power system are arranged in a row, and an engine clutch 130 is interposed between the engine 110 and the electric motor 140 to regulate the transmission of power in a direction from the engine 110 to the electric motor 140.

[0052] An integrated starter and generator (ISG) 120 is coupled to the engine 110. The ISG 120 is an electric motor capable of generating power and generating electricity. The ISG 120 provides driving power for starting the engine 110. According to circumstances, the ISG 120 is driven by the power of the engine 110, thereby generating electricity. The ISG 120 may be coupled to the engine 110 using a mechanical power transmission device such as a belt, a chain, or a gear. The coupling ratio between the ISG 120 and the engine 110 may be variously determined as needed.

[0053] The system for controlling a clutch according to an embodiment of the present disclosure is applied to a P2 type parallel hybrid vehicle, and includes an engine torque measuring unit 112 that measures the torque of a clutch actuator 160 and an engine 110, and an oil temperature measuring unit 132 that measures the oil temperature in an engine clutch 130. In addition, the system for controlling the engine clutch includes a controller 170 that calculates a target hydraulic pressure to be applied to the engine clutch 130 based on information provided by the engine torque measuring unit 112 and the oil temperature measuring unit 132.

[0054] For reference, the above-mentioned "controller" is a term collectively referring to control-related components equipped with one or more processors. The control-related components are programmed in a manner in which a sequence of steps for at least one function or processing operation is performed step by step. According to the present disclosure, it is desired that the term "controller" is understood to collectively perform the functions of an engine control unit (ECU), a hydraulic control unit (HCU), and a transmission control unit (TCU) known in the art.

[0055] Under the control of the controller 170, the clutch actuator 160 provides the hydraulic pressure required to drive the engine clutch 130. To this end, based on the above-mentioned engine torque, oil temperature information, etc., the controller 170 calculates the target hydraulic pressure of the optimal level to be applied to the engine clutch 130. The controller 170 adjusts or controls the operation of the clutch actuator 160 in such a manner that the calculated target hydraulic pressure can be applied to the engine clutch 130.

[0056] When the vehicle is running under a low load, for example, in a fixed speed driving situation, the variation of the engine torque becomes small due to the constant engine torque. Therefore, it is not necessary to use the maximum pressure (target hydraulic pressure) to control the engine clutch 130. The reason for this is that in a situation where the variation of the engine torque becomes small due to the constant engine torque, the load on the engine clutch 130 is lower than during high load driving such as when driving on an upward sloping road.

[0057] Therefore, the controller 170 determines whether the vehicle is running under a low load (whether a driving range in which the change in the engine torque is small) based on the output information (engine torque information) of the engine torque measuring unit 112 and the time when the output information is continuously output. When the result of the determination is that the vehicle is running under a low load, the control unit 170 gradually reduces the hydraulic pressure applied to the engine clutch 130. Therefore, the control unit 170 performs variable hydraulic pressure control that prevents energy loss due to unnecessary excessive hydraulic pressure.

[0058] However, during the execution of the variable hydraulic control, when the load on the vehicle suddenly increases (for example, when the vehicle is traveling along an upwardly inclined road), or when a forced downshift is performed (for example, when an operation for sudden acceleration is performed), slippage may occur in the engine clutch 130. The reason for this is that when a downshift is performed while gradually reducing the hydraulic pressure applied to the engine clutch 130 by means of the variable hydraulic control, the number of engine revolutions and the engine torque causing the slippage increase sharply.

[0059] Therefore, during the execution of the variable hydraulic control of the engine clutch 130, when a forced downshift occurs, and when the amount of slip occurring in the engine clutch 130 is a predetermined value (hereinafter referred to as the "first set value") or higher than a predetermined value, the controller 170 performs a series of control steps, wherein a learned hydraulic value for suppressing slip is derived and stored through learning, and wherein the stored learning compensation value is reflected in the hydraulic pressure of the engine clutch 130 in the next same gear shift situation.

[0060] To this end, the controller 170 may be equipped with one or more processors that operate according to a preset program to gradually execute the sequence of control method steps described below.

[0061] The program may be a program written in such a manner as to control the engine clutch 130. According to the preset program, when a forced downshift occurs during the execution of the variable hydraulic control, and when the amount of slippage occurring in the engine clutch 130 is a first set value or higher, a learning hydraulic pressure value is derived through a series of learning steps described below, a hydraulic pressure compensation value is obtained by multiplying the derived learning hydraulic pressure value by a predetermined compensation coefficient, and a final hydraulic pressure is calculated by adding the obtained hydraulic pressure compensation value to the target hydraulic pressure. Thus, the engine clutch 130 is controlled.

[0062] In the program executed by the processor equipped with the controller 170, the following sequence of processing steps may be performed according to the program for deriving the learned hydraulic pressure value.

[0063] ① During the execution of the variable hydraulic control of the engine clutch 130, when a forced downshift occurs and when the amount of slip occurring in the engine clutch 130 is at or above a first set value, the shift progress step and the engine torque at the time point when the slip occurs (the amount of slip is at or above the first set value) are captured.

[0064] ② During forced downshifting, when the slip amount of the engine clutch 130 calculated from the difference between the resolution number of the engine and the resolution number of the P2 motor 140 (desirably, the absolute value of the difference between the resolution number of the engine and the resolution number of the P2 motor 140 (|resolution number of the engine-resolution number of the P2 motor 140|)) is higher than the previous maximum slip amount, the maximum slip amount is updated and the value obtained by the update is stored as the engine clutch slip learning value.

[0065] ③ When the slip amount of the engine clutch drops below a predetermined value (hereinafter referred to as a "second set value"), the shift step at the learning end time point is captured.

[0066] ④ Retrieve a hydraulic pressure value corresponding to the engine clutch slip learning value from a dedicated map (hydraulic pressure compensation map), and determine the hydraulic pressure value as the learning hydraulic pressure value.

[0067] The program may be written in such a manner that the following steps are repeated. If the slip amount of the engine clutch 130 does not drop below the second set value in the third step while learning is performed through the above-described sequence of processing steps (learning step), the slip amount of the engine clutch 130 is recalculated. When the calculated slip amount of the engine clutch 130 is greater than the previous maximum slip amount, the maximum slip amount is updated, and the value obtained by the update is stored as the slip learning value of the engine clutch 130.

[0068] When the same kick-down situation occurs during the next variable hydraulic control execution of the engine clutch 130, the learned hydraulic pressure value derived through the sequence of processing steps (learning steps) as described above is reflected as a compensation value (hydraulic pressure compensation value) when determining the final hydraulic pressure applied to the engine clutch 130 through the clutch actuator 160. The hydraulic pressure compensation value here may be a value obtained by multiplying the learned hydraulic pressure value by a compensation coefficient.

[0069] The compensation coefficient may include an engine torque coefficient and an oil temperature coefficient. The engine torque coefficient may be a ratio between the current engine torque and the engine torque at the learning entry time point (a value captured as current engine torque / engine torque at the learning entry time point). The oil temperature coefficient may be a value retrieved from an oil temperature map in which the compensation coefficient is stored as a coefficient for compensating for a response speed delay of the engine clutch 130 due to the oil temperature as a value varying with an oil temperature interval.

[0070] Specifically, when a kick-down situation identical to the immediately preceding kick-down situation occurs during the execution of the variable hydraulic control, the controller 170 retrieves the learning hydraulic pressure value derived through the above-mentioned sequence of processing steps (learning steps) and records it in the storage device. In addition, the compensation coefficient (engine torque coefficient and oil temperature coefficient) is derived from the current engine torque and oil temperature. The derived compensation coefficient is reflected in the retrieved learning hydraulic pressure value, thereby calculating the final hydraulic pressure.

[0071] The calculated final hydraulic pressure is applied to the same shift interval as the shift interval at the time point of the learned hydraulic pressure value (a portion from the shift progress step at the time point when the amount of slippage occurring is the first set value or higher to the shift progress step at the time point when the amount of slippage decreases to or lower than the second set value), thereby controlling the engine clutch 130. Therefore, slippage that would occur when a kick-down occurs during execution of the variable hydraulic pressure control is prevented.

[0072] For reference, "shift progress steps" refers to shift stages assigned by the controller 170 in such a manner that when a shift is performed at the request of a user or due to a change in load on the vehicle during driving, it is represented in a digital form according to the shift progress state. In the case of a general automatic transmission, although the steps vary depending on the transmission specifications, the shift stages are set in such a manner that once a shift command is issued, the shift is performed over 15 steps from when the shift is prepared to when the shift is completed.

[0073] It is assumed that, among the 15 steps, learning is entered in the third step (a time point when the amount of slippage occurring in the engine clutch 130 is a first set value or higher), and the learning end time point (a time point when the amount of slippage of the engine clutch 130 drops to a second set value or lower) is set in the 13th step. Under this assumption, due to the reasons described above, the system for controlling the engine clutch according to the present disclosure controls the engine clutch 130 using the final hydraulic pressure, wherein, when the next same shifting situation (forced downshift during execution of the variable hydraulic pressure control) occurs, the final hydraulic pressure controls the engine clutch 130 reflecting the immediately previous learning hydraulic pressure value in the shifting interval from the third step to the 13th step.

[0074] Figure 4 is a graph showing changes in the resolution number of the engine and the resolution number of the P2 motor 140 over time, which is generated when a kick-down occurs during execution of the variable hydraulic control, and is necessary for describing the embodiment of the present disclosure.

[0075] Figure 4 The portion (indicated by the oblique lines) where the difference between the resolution number of the engine 140 and the resolution number of the P2 motor 140 occurs is the portion where the engine clutch 130 slips during the forced downshift. The time point at which the difference between the two resolution numbers starts to rise to a predetermined value (first set value) or higher is the learning entry time point for deriving the learning hydraulic pressure value described above. The time point when the difference between the two resolution numbers drops to a predetermined value (second set value) or lower is the learning end time point.

[0076] At this time, the system for controlling the engine clutch according to the present disclosure captures the gear shift progress step (gear shift period) at each of the learning entry time point and the learning end time point. Then, when a gear shift situation occurs under the same conditions (a situation in which a forced downshift occurs during the execution of the variable hydraulic pressure control), the system for controlling the engine clutch performs a gear shift in the same gear shift interval ( Figure 3 The above-mentioned learning hydraulic pressure value for engine clutch control is reflected in the learning part in the above-mentioned learning part). Therefore, slip is processed in advance.

[0077] The following will refer to Figure 5 The control flow chart in the figure is used to describe the engine clutch control process performed by the system for controlling the engine clutch of the above-mentioned P2 type parallel hybrid vehicle. For ease of description, refer to Figure 1 and Figure 2 The description will be made using the reference numerals of the constituent elements shown in FIG.

[0078] refer to Figure 5 The engine clutch control process performed by the system for controlling the engine clutch of the above-mentioned P2 type parallel hybrid vehicle starts from a condition determination step S100. In this step, it is determined whether the learning mode entry condition is satisfied according to whether a forced downshift occurs during the execution of the variable hydraulic pressure control of the clutch of the P2 type parallel hybrid vehicle and based on the information about the slip of the engine clutch 130.

[0079] In the condition determination step S100, ideally, during the execution of variable hydraulic control (control of gradually reducing the hydraulic pressure applied to the engine clutch 130) of the P2 type parallel hybrid vehicle, when a forced downshift occurs, and when the slip amount of the engine clutch 130 caused by the forced downshift rises to a first set value or higher than the first set value, it can be determined that the learning entry condition is met.

[0080] When it is determined in the condition determination step S100 that the predetermined learning entry condition (variable hydraulic control, kick-down, and the amount of slip occurring is the first set value or more) is satisfied, the learning step S200 is performed. In the learning step S200, the learning hydraulic value is used to suppress the slip that will occur when the kick-down occurs so that slip does not occur in the next same shifting situation.

[0081] Specifically, the learning step S200 includes step S210: capturing the gear shift progress step (gear shift period) and the engine torque at the learning entry time point; and step S220: when the slip amount of the engine clutch 130 calculated based on the difference between the resolution number of the engine 110 and the resolution number of the P2 motor 140 is greater than the maximum slip amount previously during the forced downshift, updating the maximum slip amount and storing the value obtained by the update as the engine clutch slip learning value.

[0082] In addition, the learning step S200 includes a step S230: when the slip amount of the engine clutch 130 drops below the second set value (S230-1), capturing the shift progress step (shift phase) at the learning end time point (S230-2); and a step S240: determining a learning hydraulic pressure value corresponding to the engine clutch slip learning value using a dedicated map (hydraulic compensation map). When the slip amount does not drop below the second set value in step S230-1, return to step S220, and repeatedly execute step S220 and subsequent steps.

[0083] After learning is performed through steps S210 and S240, when the same forced downshift situation occurs during the variable hydraulic pressure control of the engine clutch 130, the engine clutch control step S300 is performed. In the engine clutch control step S300, a final hydraulic pressure is calculated by adding a hydraulic pressure compensation value obtained by multiplying a learning hydraulic pressure value learned in the learning process from step S210 to step S240 by a compensation coefficient to the target hydraulic pressure, and the engine clutch is controlled using the calculated final hydraulic pressure.

[0084] Specifically, in step S300, the final hydraulic pressure reflecting the hydraulic pressure compensation value is applied to the shifting interval (expressed as Figure 3 The engine clutch is controlled in the same shift range as the learning part).

[0085] The compensation coefficient here may be configured to include an engine torque coefficient and an oil temperature coefficient. In this case, the engine torque coefficient is a ratio between the current engine torque and the engine torque at the learning entry time point (current engine torque / engine torque at the learning entry time point), and the oil temperature coefficient is a coefficient for compensating for the engine clutch response speed delay. The oil temperature coefficient may be a value retrieved from an oil temperature map in which the compensation coefficient is stored as a coefficient for compensating for the response speed delay of the engine clutch 130 due to the oil temperature as a value that varies with the oil temperature interval.

[0086] In a P2 type parallel hybrid vehicle in the prior art, during the execution of variable hydraulic control of the engine clutch 130, when the load on the vehicle suddenly increases (for example, when the vehicle is traveling along an upwardly inclined road), or when a forced downshift occurs (for example, when an operation for sudden acceleration is performed), the engine clutch 130 may slip. The slip in the engine clutch 130 is caused by the number of engine resolutions and the sudden change in engine torque. Therefore, the acceleration is reduced, and the feeling of shifting cannot be properly produced.

[0087] In contrast, according to the present disclosure, during the execution of the variable hydraulic control of the engine clutch 130, when a forced downshift occurs and when the engine clutch 130 slips, a compensation value (hydraulic pressure compensation value of the engine clutch 130) for preventing slip in the next same gear shifting situation is derived through learning, and the compensation value is applied to the engine clutch control in the next same gear shifting situation. Therefore, slip can be effectively prevented or pre-processed.

[0088] Therefore, based on the slippage in the previous gear shifting situation, the method and system for controlling the engine clutch of the P2 type parallel hybrid vehicle according to the embodiment of the present disclosure pre-processes the engine clutch slippage that will occur when the forced downshift occurs during the execution of the variable hydraulic control. Therefore, the reduction of acceleration and driving performance due to the slippage of the engine clutch can be prevented, and the gear shift quality can be improved.

[0089] Only specific embodiments of the present disclosure are described above. However, it should be understood that the present disclosure is not limited to the above specific embodiments, and all changes, equivalents and replacements falling within the essence and spirit of the present disclosure are included in the scope of the present disclosure.

Claims

1. A method for controlling an engine clutch of a P2 type parallel hybrid vehicle, the method comprising: (a) determining whether a learning mode entry condition is satisfied based on whether a forced downshift occurs during execution of variable hydraulic pressure control of the engine clutch of the P2 type parallel hybrid vehicle and based on the degree to which slippage of the engine clutch occurs; (b) when the vehicle state satisfies a predetermined learning mode entry condition, deriving and storing a learning hydraulic pressure value for suppressing slip that would occur when the kick-down occurs during execution of the variable hydraulic pressure control of the engine clutch so that slip does not occur in the next same kick-down situation; as well as (c) when the same forced downshift situation occurs during the next execution of variable hydraulic control of the engine clutch, a final hydraulic pressure is calculated by adding a hydraulic pressure compensation value obtained by multiplying the learned hydraulic pressure value by a compensation coefficient to a target hydraulic pressure, and the engine clutch is controlled using the calculated final hydraulic pressure.

2. The method according to claim 1, wherein: In step (a), during execution of the variable hydraulic pressure control of the engine clutch of the vehicle, when the kick-down occurs and when the slip amount of the engine clutch is at or above a first set value, it is determined that the learning mode entry condition is satisfied.

3. The method according to claim 1, wherein: Step (b) further comprises: (b-1) capturing engine torque and learning the shift schedule step at the entry time point; (b-2) when the slip amount of the engine clutch calculated from the difference between the resolution number of the engine and the resolution number of the P2 motor is larger than the maximum slip amount previously during the kick-down, updating the maximum slip amount and storing the value obtained by the update as the engine clutch slip learning value; (b-3) capturing a shift progress step at a learning end time point at which the slip amount of the engine clutch decreases below a second set value; and (b-4) Determining a learning hydraulic pressure value corresponding to the engine clutch slip learning value described in step (b-2) from a dedicated map.

4. The method according to claim 3, wherein: In step (b-3), when the slip amount of the engine clutch does not drop below the second set value, the process returns to the immediately preceding step (b-2), and step (b-2) and steps after step (b-2) are repeatedly executed.

5. The method according to claim 3, wherein: When the same forced downshift occurs during the next execution of the variable hydraulic control of the engine clutch, in step (c), the final hydraulic pressure is applied in a shift interval that is the same as the shift interval from the shift progress step at the previous learning entry time point to the shift progress step at the learning end time point, thereby controlling the engine clutch.

6. The method according to claim 1, wherein: The compensation coefficients include: Engine torque coefficient; and Oil temperature coefficient.

7. The method according to claim 6, wherein: The engine torque coefficient is a ratio between a current engine torque and an engine torque at a learning entry time point, and the oil temperature coefficient is determined from an oil temperature map, in which the compensation coefficient is stored as a value that varies with an oil temperature range as a coefficient for compensating for a delay in a response speed of the engine clutch due to oil temperature.

8. A system for controlling an engine clutch of a P2 type parallel hybrid vehicle, in which an engine, an electric motor and a transmission are arranged in a row, and in which the engine clutch is installed between the engine and the electric motor, the system comprising: a clutch actuator providing the hydraulic pressure required to actuate the engine clutch; A torque measuring unit, measuring the torque of the engine; An oil temperature measuring unit, for measuring the oil temperature inside the engine clutch; as well as a controller that calculates a target hydraulic pressure to be applied to the engine clutch from information provided by the torque measuring unit and the oil temperature measuring unit of the engine, and controls the operation of the clutch actuator based on the calculated target hydraulic pressure, Wherein, when a forced downshift occurs during the execution of the variable hydraulic control of the engine clutch and when the slip occurring in the engine clutch is a predetermined value or higher than a predetermined value, the controller derives a learned hydraulic value for suppressing the slip by learning and stores the derived learned hydraulic value, and when the same forced downshift occurs during the next execution of the variable hydraulic control of the engine clutch, the controller calculates a final hydraulic pressure by adding a hydraulic compensation value obtained by multiplying the learned hydraulic value by a compensation coefficient to the target hydraulic pressure, and uses the calculated final hydraulic pressure to control the engine clutch.

9. The system according to claim 8, wherein: The controller captures a shift progress step at a time point when the forced downshift occurs during execution of the variable hydraulic control of the engine clutch and the slip occurring in the engine clutch is a predetermined value or higher than a predetermined value, and captures the engine torque; when the slip amount of the engine clutch calculated from the difference between the resolution number of the engine and the resolution number of the P2 motor is greater than the maximum slip amount previously during the forced downshift, the controller updates the maximum slip amount and stores the value obtained by the update as an engine clutch slip learning value; the controller captures a shift progress step at a learning end time point, at which the slip amount of the engine clutch drops below a predetermined value; and the controller retrieves a hydraulic value corresponding to the engine clutch slip learning value from a dedicated map and determines the retrieved hydraulic value as the learning hydraulic value.

10. The system according to claim 9, wherein: The controller repeats a process in which, when the slip amount of the engine clutch does not drop below a predetermined value, the slip amount of the engine clutch is recalculated, and in which, when the calculated slip amount of the engine clutch is greater than the previous maximum slip amount, the maximum slip amount is updated, and the value obtained by the update is stored as an engine clutch slip learning value.

11. The system according to claim 9, wherein: When the same forced downshift situation occurs during the next execution of the variable hydraulic control of the engine clutch, the controller applies the final hydraulic pressure in a shift interval that is the same as the shift interval from the shift progress step at a time point when the slip occurs to a predetermined value or more to the shift progress step at the learning end time point, thereby controlling the engine clutch.

12. The system according to claim 8, wherein: The compensation coefficients include: Engine torque coefficient; and Oil temperature coefficient.

13. The system according to claim 12, wherein: The engine torque coefficient is a ratio between a current engine torque and an engine torque at a learning entry time point, and the oil temperature coefficient is determined from an oil temperature map, in which the compensation coefficient is stored as a value that varies with an oil temperature range as a coefficient for compensating for a delay in a response speed of the engine clutch due to oil temperature.

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