Control method and system for protecting the clutch friction elements of an automatic transmission and vehicle with automatic transmission having this system

Abstract

A method for controlling clutch friction elements of an automatic transmission, the method comprising: (a) retrieving information about clutches from a data storage unit (10) and acquiring information necessary to predict a temperature of a friction element for each clutch; (b) deriving a predicted temperature value of a friction element for each clutch using the information about the clutches and the information required to predict the temperature of the friction element; (c) predicting for each clutch whether or not overheating will occur by comparing the derived predicted temperature value of the friction element for each clutch with a permissible temperature specified for each clutch; and (d) determining a target gear stage while avoiding the overheating clutch with a predicted temperature value exceeding the allowable temperature by switching to an avoidance gear mode, characterized in that the method further comprises: (e) determining whether additional protective measures are to be taken by comparing the predicted temperature value of the friction element with a reference temperature obtained by adding a specific value to the current oil temperature in a state in which the avoidance switching mode is switched; and (f) Determining a final target hydraulic pressure for the target gear stage.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Korean Patent Application No. 10-2021-0047306, filed on April 12, 2021, the entire contents of which are incorporated herein by reference for all purposes. AREA

[0002] The present disclosure relates to a control method and system for protecting clutch friction elements of an automatic transmission, and more particularly, to a control method and system that predict overheating of shift clutches constituting an automatic transmission and protect the shift clutches from overheating and resulting damage or breakage through predetermined control, and to a vehicle having an automatic transmission including the system. BACKGROUND

[0003] In general, an automatic transmission is a mechanical device that automatically achieves optimal gear shifting in response to a vehicle's driving speed and load. Such an automatic transmission is designed to change gears by operating a shift solenoid and a shift clutch (hereinafter referred to as the "clutch") under the control of a transmission control unit (TCU), which outputs a shift control command according to the driver's request or the vehicle's driving condition.

[0004] A transmission control unit for controlling an automatic transmission uses a shift map (shift pattern) created from the relationship between the accelerator pedal depression and vehicle speed to find an optimal shift stage that corresponds to the pedal depression and vehicle speed. Then, the shift stage is set as the target shift stage, and a target oil pressure (solenoid duty value) for shifting to the target shift stage is determined, and a shift solenoid is controlled based on this.

[0005] When oil is supplied to the clutch involved in the target shift speed according to the operation of the shift solenoid, the clutch is shifted to the engaged side, thus achieving the target shift. In situations where the amount of oil supplied to the clutch is below the required level or the torque fluctuation is large, such as during a sharp kick-down shift, excessive slippage occurs between the clutch friction elements (disk and plate), causing the clutch to overheat or be severely damaged.

[0006] However, since the state of the art does not know any technology to prevent overheating and the resulting damage of the clutch friction elements (disk and plate) that occurs due to excessive slippage between the clutch friction elements in situations where the amount of oil supplied to the clutch is below the required level or the torque fluctuation is large, e.g. during a sharp kick-down shift, there is a need to address this issue.

[0007] The foregoing statements are intended only to contribute to an understanding of the background of the present disclosure and should not be construed as falling within the scope of the prior art that is already known to those skilled in the art.

[0008] From US 2017 / 0 043 779 A1, a method and a system for controlling clutch friction elements of an automatic transmission are known, in which, among other things, a predicted temperature value of a friction element is derived in order to make a prediction for each clutch as to whether overheating will occur or not. SUMMARY

[0009] In one aspect, a control method and system for protecting clutch friction elements of an automatic transmission are provided, wherein overheating of shift clutches is predicted in real time based on various information detected from various parts of a vehicle, and when overheating of a particular shift clutch is predicted, predetermined control (shift avoidance, engine torque limiting, etc.) is performed to protect the shift clutch from overheating and resulting damage, and a vehicle with an automatic transmission is provided that includes the control system.

[0010] In one aspect of the present disclosure, a method for controlling clutch friction elements of an automatic transmission is provided, the method comprising: (a) retrieving information about clutches from a data storage unit and collecting information necessary to predict a temperature of a friction element for each clutch; (b) deriving a predicted temperature value of a friction element for each clutch using the information about the clutches and the information required to predict the temperature of the friction element; (c) predicting for each clutch whether or not overheating will occur by comparing the derived predicted temperature value of the friction element for each clutch with a permissible temperature specified for each clutch; and (d) determining a target shift stage while avoiding the overheating clutch with a predicted temperature value exceeding the allowable temperature by switching to an avoidance shift mode.

[0011] The control procedure also includes the following: (e) determining whether additional protective measures are to be taken by comparing the predicted temperature value of the friction element with a reference temperature obtained by adding a specific value to the current oil temperature in a state in which the avoidance switching mode is switched; and (f) Determining a final target hydraulic pressure for the target gear stage.

[0012] In certain preferred aspects, the information required to predict the friction element temperature for each clutch may include the rotational speed of an oil pump or a torque converter turbine and / or an oil temperature and / or a current gear ratio and / or an oil supply flow rate for each clutch and / or the rotational speeds of a clutch hub and a clutch drum for each clutch corresponding to the rotational speed of the turbine and / or a target hydraulic pressure for each clutch.

[0013] Preferably, in step (b), the predicted temperature value of the friction element for each clutch can be derived by determining the rotational speed and the relative speed of the clutch hub and the clutch drum for each clutch corresponding to the current turbine rotational speed from the clutch speed map determined by the relationship between the rotational speed of the turbine and the clutch hub and the clutch drum for each clutch, determining the current rotational speed of the oil pump or the turbine rotational speed and the oil temperature and the oil supply flow rate for each clutch corresponding to the current gear stage using an oil flow rate map, determining an estimated transmission torque for each clutch using a clutch torque map,which uses the piston acting pressure derived from the target hydraulic pressure for each clutch and the rotational inertia of the friction element as factors, and deriving a heating value of the friction element for each clutch using a heating value map determined by the relationship between the estimated transmission torque for each clutch and the relative speed between a clutch hub and the clutch drum, and finally determining the predicted temperature value of the friction element for each clutch according to the oil supply flow rate for each clutch and the heating value of the friction element for each clutch using a friction element temperature map determined by the relationship between the heating value of the friction element for each clutch and the oil supply flow rate for each clutch.

[0014] In certain preferred aspects, when switching the mode to the avoidance shift mode upon input of a shift command, the target shift stage may be determined while avoiding the shift clutch detected as an overheating clutch.

[0015] If, as a result of the comparison in step (e), the predicted temperature value of the friction element is equal to or greater than the reference temperature, the final target hydraulic pressure for the target gear stage can preferably be derived in step (f) after the protective measure for additionally limiting engine torque to protect the friction element has been taken. Furthermore, if the predicted temperature value of the friction element is less than the reference temperature, the final target hydraulic pressure for the target gear stage is directly derived in step (f) without taking the protective measure for additionally limiting engine torque to protect the friction element.

[0016] In certain aspects, the additional engine torque limit for protecting the friction element may be realized by the process of determining the limited torque corresponding to the predicted temperature value of the friction element for each clutch and the current oil temperature using a torque limit map in which different torque limit values ​​are stored according to the predicted temperature value of the friction element and the oil temperature, and controlling the engine power so that the determined limited torque is not exceeded.

[0017] In addition, the final target hydraulic pressure can be derived by adding a hydraulic pressure compensation value determined in a hydraulic compensation map with an oil temperature, a throttle opening rate (%), a coolant temperature, and a load as factors to a base hydraulic pressure value determined according to the engine torque.

[0018] In another aspect, a system for controlling clutch friction elements of an automatic transmission is provided, the system comprising: a data storage unit configured to store information about clutches; a data acquisition unit configured to acquire information necessary to predict a temperature of a friction element for each clutch; and a transmission control unit (TCU) configured to perform transmission control using the information about the clutches and the information required to predict the friction element temperature, the TCU comprising: a plurality of processors programmed to predict friction element overheating for each clutch by predicting the friction element temperature for each clutch using the information about the clutches and the information necessary to predict the friction element temperature, and to control shifting while avoiding the clutch for which overheating is predicted.

[0019] The plurality of processors include: a predicted temperature deriving part configured to derive a predicted temperature value of a friction element for each clutch by using the information about the clutches and the information required to predict the temperature of the friction element; an overheating determining part configured to predict, for each clutch, whether or not overheating will occur by comparing the derived predicted temperature value of the friction element for each clutch with an allowable temperature set for each clutch; a protection logic operating part having avoidance switching logic configured to detect the clutch for which overheating is predicted as an overheating clutch and determine a shift stage while avoiding the clutch detected as an overheating clutch;and a hydraulic pressure control part configured to derive a final target hydraulic pressure for shifting to a target gear stage and perform transmission control based on the derived final target hydraulic pressure;

[0020] The predicted temperature deriving part derives the predicted temperature value of the friction element for each clutch by determining the rotational speed and the relative speed of the clutch hub and the clutch drum for each clutch according to the current turbine rotational speed from the clutch speed map defined by the relationship between the rotational speed of the turbine and the clutch hub and the clutch drum for each clutch; determining the current rotational speed of the oil pump or the turbine rotational speed and the oil temperature and the oil supply flow rate for each clutch according to the current gear stage using an oil flow rate map; determining an estimated transmission torque for each clutch using a clutch torque map;which uses the piston acting pressure derived from the target hydraulic pressure for each switching clutch and the rotational inertia of the friction element as factors, and deriving a heating value of the friction element for each switching clutch using a heating value map determined by the relationship between the estimated transmission torque for each switching clutch and the relative speed between a clutch hub and the clutch drum, and finally determining the predicted temperature value of the friction element for each switching clutch according to the oil supply flow rate for each switching clutch and the heating value of the friction element for each switching clutch using a friction element temperature map determined by the relationship between the heating value of the friction element for each switching clutch and the oil supply flow rate for each switching clutch.

[0021] In addition, the protection logic operation part may further include a torque limiting logic configured to compare the predicted temperature value of the friction element with a reference temperature obtained by adding a specific value to the current oil temperature, and when the predicted temperature value of the friction element is equal to or greater than the reference temperature, further limit an engine torque to protect the friction element.

[0022] One or more of the above steps and embodiments may be performed using a processor or a control unit.

[0023] In another aspect of the present disclosure, an automatic transmission vehicle is provided that includes the control system for protecting a clutch friction element of an automatic transmission according to the aspect of the present disclosure.

[0024] In certain additional aspects, overheating of the clutches, or more specifically, the overheating of the clutch friction elements, is predicted in real time based on various information collected from each part of a vehicle. Then, if overheating in the friction element of a specific clutch is predicted, the overheating and resulting damage to the specific clutch can be reliably prevented by implementing predetermined control (avoiding shifting, limiting engine torque, etc.).

[0025] Further aspects are revealed below. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram schematically illustrating a system configuration of a control system for protecting a clutch friction element of an automatic transmission according to an embodiment of the present disclosure; Fig. 2 is a flowchart schematically illustrating a control process for protecting a clutch friction element of an automatic transmission; and Fig. 3 is a control flowchart specifically illustrating a control process for protecting a clutch friction element of an automatic transmission. DETAILED DESCRIPTION

[0026] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0027] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present disclosure. As used herein, an element expressed in the singular includes multiple elements unless the context clearly indicates otherwise.

[0028] It is further understood that the term "comprising" or "including" indicates the presence of a stated feature, number, step, operation, element, part, or combination thereof, but does not preclude the presence or addition of one or more additional features, numbers, steps, operations, elements, parts, or combinations thereof.

[0029] Terms such as "first," "second," etc., may also be used to describe different elements, but the elements should not be limited by these terms. The above terms are used only to distinguish the individual components.

[0030] In addition, terms such as "...part", "...unit", "...module", etc., described in the specification refer to a unit that performs at least one function or operation that can be implemented by hardware or software or a combination of hardware and software.

[0031] Furthermore, the control logic of the present disclosure may be implemented as a non-transitory computer-readable medium on a computer-readable medium containing executable program instructions executed by a processor, a controller, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable medium may also be distributed in network-coupled computer systems such that the computer-readable medium is stored and executed in a distributed manner, e.g., through a telematics server or a controller area network (CAN).

[0032] It is understood that the term "vehicle" or "vehicular" or a similar term, as used herein, encompasses motor vehicles in general, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and also hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle with two or more power sources, e.g., a gasoline-powered and electric-powered vehicle.

[0033] In the description with reference to the accompanying drawings, it should be noted that identical elements in the drawings are designated by the same reference numerals, and repeated descriptions for the same configuration are omitted. Furthermore, detailed descriptions of well-known functions and configurations that might obscure the gist of the present disclosure are omitted.

[0034] The present disclosure is intended to predict the overheating of shift clutches in real time based on various information acquired from each component of a vehicle, and to protect against overheating and the resulting damage to the specific shift clutch when overheating is predicted in a specific shift clutch by performing a predetermined control (avoiding shifts, limiting engine torque, etc.). The design of a control system for protecting a clutch friction element of an automatic transmission is described based on Fig. 1 described.

[0035] Fig. 1 is a block diagram schematically showing a system configuration of a control system for protecting a clutch friction element of an automatic transmission according to an embodiment of the present disclosure.

[0036] With reference to Fig. 1, a clutch friction element protection control system 1 according to an embodiment of the present disclosure includes a data storage unit 10 configured to store information about a plurality of shift clutches constituting an automatic transmission, a data acquisition unit 20 configured to acquire information required for predicting a temperature of a friction element for each shift clutch, and a transmission control unit (TCU) 30 configured to control the transmission using the information about the shift clutches and the information required for predicting the temperature of the friction element.

[0037] Here, the information about the clutches stored in the data storage unit 10 may be information about the overall specification of the clutch, such as the number of clutch friction elements (the number of clutch discs and clutch plates) and the diameter of the friction elements of each clutch, and about an overlap area of ​​adjacent friction elements (the clutch disc and clutch plate), ie, an actual friction area between adjacent friction elements.

[0038] Furthermore, the information acquired by the data acquisition unit 20 for predicting the friction element temperature for each clutch may include the rotational speed of an oil pump or a torque converter turbine, an oil temperature, a current gear stage, an oil supply flow rate for each clutch, and / or the rotational speeds of a clutch hub and a clutch drum for each clutch corresponding to the rotational speed of the turbine, and / or a target hydraulic pressure for each clutch.

[0039] The transmission control unit 30 is configured to predict friction element overheating for each clutch by predicting the friction element temperature for each clutch using the information about the clutches and the information required to predict the friction element temperature provided by the data storage unit 10 and the data acquisition unit 20, respectively. The transmission control unit includes a plurality of processors programmed to sequentially perform a series of shift control processes while avoiding the clutch for which overheating is predicted.

[0040] The plurality of processors constituting the TCU 30 of the control system preferably include a predicted temperature deriving part 32 configured to derive a predicted temperature value of a friction element for each clutch, and an overheat determining part 34 configured to predict, for each clutch, whether or not overheating will occur by comparing the predicted temperature value of the friction element for each clutch with an allowable temperature set for each clutch.

[0041] In addition, the processors include a protection logic operation part 36 having an avoidance switching logic, which is configured to detect the switching clutch for which overheating is predicted as an overheating clutch and determine a shift speed while avoiding the switching clutch detected as an overheating clutch, and a hydraulic pressure control part 38 configured to derive a final target hydraulic pressure for switching to a target shift speed and perform transmission control based on the derived final target hydraulic pressure.

[0042] The predicted temperature deriving part 32 derives the predicted temperature value of the friction element for each clutch using the information about the clutches and the information required for predicting the temperature of the friction element. In the predicted temperature deriving part 32, the process of deriving the predicted temperature value of the friction element for each clutch using the information about the clutches and the information required for predicting the temperature of the friction element is performed as follows. PROCESS FOR DERIVING THE PREDICTED FRICTION ELEMENT TEMPERATURE FOR EACH CLUTCH 1. Determining the rotational speed and the relative speed of the clutch hub and the clutch drum for each switching clutch according to the current turbine rotational speed from the clutch speed map determined by the relationship between the rotational speed of the turbine and the clutch hub and the clutch drum for each switching clutch; 2. Determining the current rotational speed of the oil pump or the turbine rotational speed and the oil temperature and the oil supply flow rate for each shift clutch according to the current shift stage using an oil flow map; 3. Determining an estimated transmission torque for each switching clutch using a clutch torque map that uses the piston acting pressure derived from the target hydraulic pressure for each switching clutch and the rotational inertia of the friction element as factors, and deriving a heating value of the friction element for each switching clutch using a heating value map determined by the relationship between the estimated transmission torque for each switching clutch and the relative speed between a clutch hub and the clutch drum; and 4. Finally, determining the predicted temperature value of the friction element for each clutch according to the oil supply flow rate for each clutch and the heating value of the friction element for each clutch using a friction element temperature map determined by the relationship between the heating value of the friction element for each clutch and the oil supply flow rate for each clutch.

[0043] The information on the predicted temperature value of the friction element for each clutch derived by the predicted temperature deriving part 32 through the above series of processes is supplied to the overheat determining unit 34, which determines whether or not overheating occurs by comparing the predicted temperature value of the friction element for each clutch provided by the predicted temperature deriving part 32 with the allowable temperature set for each clutch (reference value for determining the overheating of the friction element for each clutch).

[0044] Specifically, when the predicted temperature value of the friction element for each clutch exceeds the correspondingly set allowable temperature (the reference value for determining friction element overheating for each clutch), the overheating determination part 34 determines (predicts) that the clutch having the predicted temperature value has overheated. Specifically, when the predicted temperature value of the friction element exceeds the allowable temperature, it is predicted that excessive slippage will occur in the corresponding clutch during shifting, resulting in overheating.

[0045] The determination information from the overheat determination section 34 is forwarded to the protection logic operation section 36. Based on the determination information provided by the overheat determination section 34, the protection logic operation section 36 identifies the clutch predicted to be overheated due to excessive slippage during shifting as an overheating clutch. Further, upon receiving a shift request, the protection logic operation section determines a target shift speed while avoiding the clutch identified as an overheating clutch, thereby preventing the clutch from overheating.

[0046] For example, in a situation where a kick-down shift is required due to a sudden operation of an accelerator pedal while driving in the 8th stage, and the target shift stage determined on a special shift map from the current accelerator pedal operation amount and the vehicle speed is the 5th stage (8th stage → 5th stage), the temperature of the shift clutch which is used when the shift stage is changed to the 5th stage

[0047] stage exceeds the allowable temperature, the target shift stage is changed to the 6th stage instead of the 5th stage to prevent overheating of the corresponding shift clutch.

[0048] The protection logic operating section 36 also includes torque limiting logic for additionally limiting engine torque to protect a friction element. Here, the torque limiting logic can be programmed to compare the predicted temperature value of the friction element for each clutch with a reference temperature (e.g., oil temperature + 5°C) obtained by adding a specific value to the current oil temperature, and limit the engine torque to the set range when the predicted temperature value of the friction element is equal to or greater than the reference temperature.

[0049] On the other hand, when the target shift stage is finally determined by the dedicated shift map set by the relationship between the pedal operation amount of the accelerator pedal and the vehicle speed, or the final destination to be avoided by the protective logic operation part 36 is determined, the hydraulic pressure control part 38 derives the final target hydraulic pressure for shifting to the target shift stage and controls the shift solenoid based on the derived final target hydraulic pressure to perform the shifting.

[0050] Here, the final target hydraulic pressure can be derived by adding a hydraulic pressure compensation value determined in a hydraulic compensation map with an oil temperature, a throttle opening rate (%), a coolant temperature, and a load as factors to a base hydraulic pressure value determined according to the engine torque. That is, the final target hydraulic pressure for shifting to the target gear can be determined as a value obtained by adding the hydraulic pressure compensation value to the base hydraulic pressure value.

[0051] A sequential control process for protecting a clutch friction element using the control system for protecting a clutch friction element of an automatic transmission according to an embodiment of the present disclosure will be described with reference to the control flowchart of Fig. 2. To simplify the description, the Fig. 1 is described using the corresponding reference numerals.

[0052] Fig. 2 is a flowchart schematically illustrating a control process for protecting a clutch friction element of an automatic transmission, and Fig. 3 is a control flowchart specifically illustrating a control process for protecting a clutch friction element of an automatic transmission.

[0053] With reference to Fig. 2 and Fig.3, the control method for protecting the clutch friction element of the automatic transmission according to the embodiment of the present disclosure mainly includes step S100 for information acquisition, step S200 for deriving the predicted temperature, step S300 for overheat prediction, and step S400 for controlling the protection logic. Furthermore, the control method may also include an additional step S500 for determining a protection logic control, an additional step S600 for controlling the protection logic, and a step S700 for determining the final target hydraulic pressure.

[0054] In the information acquisition step S100, information about the clutches is retrieved from the data storage unit 10, and information required for predicting the temperature of the friction element for each clutch is acquired.

[0055] The information about the clutches may include information about the overall specification of the clutch, such as the number of clutch friction elements (the number of clutch discs and clutch plates) and the diameter of the friction elements of each clutch, and about an overlap area of ​​adjacent friction elements (the clutch disc and clutch plate), i.e. an actual friction area between adjacent friction elements.

[0056] Furthermore, the information required to predict the friction element temperature for each clutch may include the rotational speed of an oil pump or a torque converter turbine and / or an oil temperature and / or a current gear stage and / or an oil supply flow rate for each clutch and / or the rotational speeds of a clutch hub and a clutch drum for each clutch corresponding to the rotational speed of the turbine and / or a target hydraulic pressure for each clutch.

[0057] In predicted temperature derivation step S200, the predicted temperature value of the friction element for each clutch is derived using the information about the clutches and the information required for predicting the temperature of the friction element obtained in information acquisition step S100. Since the detailed process for deriving the predicted temperature value of the friction element for each clutch in predicted temperature derivation step S200 has already been described above, redundant description will be omitted below.

[0058] In overheat prediction step S300, whether overheating will occur for each clutch is predicted by comparing the predicted temperature value of the friction element for each clutch, which was derived by the predicted temperature deriving step S200, with the allowable temperature (the reference value for determining friction element overheating for each clutch) set for each clutch. In overheat prediction step S300, if the predicted temperature value exceeds the allowable temperature, it is predicted that the corresponding clutch will overheat during the shifting operation.

[0059] When overheating is not predicted for any of the shift clutches in the overheat prediction step S300, that is, when the predicted temperature value is below the allowable temperature, the shift operation is performed by executing hydraulic pressure control depending on the target shift stage determined on the shift map according to the pedal operation amount of the accelerator pedal and the vehicle speed without any additional operation, and when overheating is predicted for a specific shift clutch, a process proceeds to the protection logic control step S400.

[0060] In the protection logic control step S400, the operation mode switches to an avoidance shift mode in which an overheating clutch for which the predicted temperature value exceeds the allowable temperature is avoided. Specifically, when switching to the avoidance shift mode, when a shift command is input, the target shift speed is determined by avoiding the shift clutch detected as an overheating clutch, thereby preventing overheating of the corresponding clutch (the clutch detected as an overheating clutch) in advance.

[0061] For example, in a situation where a kick-down shift is required due to a sudden operation of an accelerator pedal during driving in the 8th stage and the target shift stage determined on a special shift map from the current accelerator pedal operation amount and the vehicle speed is the 5th stage (8th stage → 5th stage), the temperature of the shift clutch applied when changing the shift stage to the 5th stage exceeds the allowable temperature, the target shift stage is changed to the 6th stage instead of the 5th stage in order to prevent overheating of the corresponding shift clutch.

[0062] In the additional step S500 for determining a protective logic operation, it is determined whether additional protective measures should be taken by comparing the predicted temperature value of the friction element with the reference temperature obtained by adding a certain value to the current oil temperature in the state where the mode changes to the avoidance shift mode in the previous step S400. The additional protective measures may be measures for protecting a friction element of the clutch involved in switching to the changed target shift speed by limiting engine torque.

[0063] As a result of the comparison by the additional protection logic control determination step S500, when the predicted temperature value of the friction element is equal to or greater than the reference temperature after taking protective measures to further limit the engine torque to protect the friction element (additional protection logic control step S600), a process proceeds to the final target hydraulic pressure determination step S700, in which the final target hydraulic pressure for the target gear stage is derived.

[0064] At this time, in the additional limit of the engine torque for protecting the friction element in the additional protection logic control step S600, the limit torque is determined according to the predicted temperature value of the friction element for each switching clutch and the current oil temperature using a torque limit map in which various torque limits are stored according to the predicted temperature value of the friction element and the oil temperature, and the engine output is controlled in cooperation with an ECU so that the determined limit torque is not exceeded.

[0065] In contrast, if the predicted temperature value of the friction element is lower than the reference temperature as a result of the comparison by the additional step S500 for the protection logic operation, the final target hydraulic pressure for shifting to the target gear speed is derived directly, without additional protective measures for limiting the engine torque to protect the friction element. That is, step S600 is skipped, and the process proceeds directly from step S500 to step S700.

[0066] At this time, in step S600, when the target shift stage is finally determined by the dedicated shift map or the final target shift stage to be avoided by the above-described protection logic operation part 36 is determined, the final target hydraulic pressure for shifting to the target shift stage is derived to determine the final target hydraulic pressure.

[0067] Here, the final target hydraulic pressure can be derived by adding a hydraulic pressure compensation value determined in a hydraulic compensation map with an oil temperature, throttle opening rate (%), coolant temperature, and load as factors to a base hydraulic pressure value determined according to the engine torque. That is, the final target hydraulic pressure for shifting to the target gear stage can be determined as a value obtained by adding the hydraulic pressure compensation value to the base hydraulic pressure value.

[0068] According to the embodiments of the present disclosure, overheating of the clutches, more specifically, overheating of the clutch friction elements, is predicted in real time based on various information acquired from each part of a vehicle. Then, if overheating in the friction element of a specific clutch is predicted, overheating and resulting damage to the specific clutch can be reliably prevented by implementing predetermined control (avoiding shifting, limiting engine torque, etc.).

[0069] In the above detailed description of the present disclosure, only certain embodiments have been described. However, it is to be understood that the present disclosure is not limited to the particular form recited in the detailed description, but rather includes all modifications, equivalents, and substitutions falling within the spirit and scope of the present disclosure as defined by the appended claims.

Claims

[1] A method for controlling clutch friction elements of an automatic transmission, the method comprising: (a) retrieving information about clutches from a data storage unit (10) and acquiring information necessary to predict a temperature of a friction element for each clutch; (b) deriving a predicted temperature value of a friction element for each clutch using the information about the clutches and the information required to predict the temperature of the friction element; (c) predicting for each clutch whether or not overheating will occur by comparing the derived predicted temperature value of the friction element for each clutch with a permissible temperature specified for each clutch; and (d) determining a target gear stage while avoiding the overheating clutch with a predicted temperature value exceeding the permissible temperature by switching to an avoidance gear mode, characterized by that the procedure further comprises: (e) determining whether additional protective measures are to be taken by comparing the predicted temperature value of the friction element with a reference temperature obtained by adding a specific value to the current oil temperature in a state in which the avoidance switching mode is switched; and (f) Determining a final target hydraulic pressure for the target gear stage. [2] The method according to claim 1, wherein the information required for predicting the friction element temperature for each clutch comprises at least one of the rotational speed of an oil pump or a torque converter turbine, an oil temperature, a current gear stage, an oil supply flow rate for each clutch, and / or the rotational speeds of a clutch hub and a clutch drum for each clutch corresponding to the rotational speed of the turbine, and / or a target hydraulic pressure for each clutch. [3] A method according to claim 1 or 2, wherein in step (b) the predicted temperature value of the friction element for each clutch is derived by: Determining the rotational speed and the relative speed of the clutch hub and the clutch drum for each switching clutch according to the current turbine rotational speed from the clutch speed map determined by the relationship between the rotational speed of the turbine and the clutch hub and the clutch drum for each switching clutch; Determining the current rotational speed of the oil pump or the turbine rotational speed and the oil temperature and the oil supply flow rate for each shift clutch according to the current shift stage using an oil flow map; Determining an estimated transmission torque for each switching clutch using a clutch torque map that uses the piston acting pressure derived from the target hydraulic pressure for each switching clutch and the rotational inertia of the friction element as factors, and deriving a heating value of the friction element for each switching clutch using a heating value map determined by the relationship between the estimated transmission torque for each switching clutch and the relative speed between a clutch hub and the clutch drum; and finally determining the predicted temperature value of the friction element for each clutch according to the oil supply flow rate for each clutch and the heating value of the friction element for each clutch using a friction element temperature map defined by the relationship between the heating value of the friction element for each clutch and the oil supply flow rate for each clutch. [4] Method according to one of the preceding claims, wherein when switching the mode to the avoidance shift mode upon input of a shift command, the target shift stage is determined while avoiding the shift clutch detected as an overheating clutch. [5] A method according to any one of the preceding claims, wherein, when the predicted temperature value of the friction element is equal to or greater than the reference temperature, the final target hydraulic pressure for the target gear stage is derived after the protective measure for additionally limiting an engine torque for protecting the friction element has been taken, and when the predicted temperature value of the friction element is lower than the reference temperature, the final target hydraulic pressure for the target gear stage is directly derived without taking the protective measure of additionally limiting an engine torque to protect the friction element. [6] A method according to claim 5, wherein the additional engine torque limitation for protecting the friction element is realized by determining the limited torque according to the predicted temperature value of the friction element for each clutch and the current oil temperature using a torque limit map in which different torque limit values ​​are stored according to the predicted temperature value of the friction element and the oil temperature, and controlling the engine power so that the determined limited torque is not exceeded. [7] A method according to claim 5 or 6, wherein the final target hydraulic pressure is derived by adding a hydraulic pressure compensation value determined in a hydraulic compensation map with an oil temperature, a throttle opening rate (%), a coolant temperature and a load as factors to a base hydraulic pressure value determined in accordance with the engine torque. [8] System for controlling clutch friction elements of an automatic transmission, the system comprising: a data storage unit (10) designed to store information about clutches; a data acquisition unit (20) configured to acquire information necessary to predict a temperature of a friction element for each clutch; and a transmission control unit, TCU, (30) adapted to perform the transmission control using the information about the clutches and the information required to predict the friction element temperature, the TCU (30) comprising: a plurality of processors programmed to predict overheating of the friction element for each clutch by predicting the temperature of the friction element for each clutch using the information about the clutches and the information required to predict the temperature of the friction element, and to control the shifting while avoiding the clutch for which overheating is predicted, characterized by , that the multiple processors include: a predicted temperature deriving part (32) configured to derive a predicted temperature value of a friction element for each clutch by using the information about the clutches and the information required to predict the temperature of the friction element; an overheat determination part (34) configured to predict for each clutch whether or not overheating will occur by comparing the derived predicted temperature value of the friction element for each clutch with an allowable temperature set for each clutch; a protection logic operating part (36) having an avoidance switching logic, which is designed to recognize the clutch for which overheating is predicted as an overheating clutch and to determine a switching stage while avoiding the clutch recognized as an overheating clutch; and a hydraulic pressure control part (38) configured to derive a final target hydraulic pressure for shifting to a target gear stage and to perform transmission control based on the derived final target hydraulic pressure, and wherein the predicted temperature deriving part (32) derives the predicted temperature value of the friction element for each clutch by: Determining the rotational speed and the relative speed of the clutch hub and the clutch drum for each switching clutch according to the current turbine rotational speed from the clutch speed map determined by the relationship between the rotational speed of the turbine and the clutch hub and the clutch drum for each switching clutch; Determining the current rotational speed of the oil pump or the turbine rotational speed and the oil temperature and the oil supply flow rate for each shift clutch according to the current shift stage using an oil flow map; Determining an estimated transmission torque for each switching clutch using a clutch torque map that uses the piston acting pressure derived from the target hydraulic pressure for each switching clutch and the rotational inertia of the friction element as factors, and deriving a heating value of the friction element for each switching clutch using a heating value map determined by the relationship between the estimated transmission torque for each switching clutch and the relative speed between a clutch hub and the clutch drum; and finally determining the predicted temperature value of the friction element for each clutch according to the oil supply flow rate for each clutch and the heating value of the friction element for each clutch using a friction element temperature map defined by the relationship between the heating value of the friction element for each clutch and the oil supply flow rate for each clutch. [9] The system according to claim 8, wherein the protection logic operation part (36) further comprises a torque limiting logic configured to compare the predicted temperature value of the friction element with a reference temperature obtained by adding a specific value to the current oil temperature, and when the predicted temperature value of the friction element is equal to or greater than the reference temperature, further limit an engine torque to protect the friction element. [10] A vehicle with an automatic transmission comprising the system for protecting a clutch friction element of an automatic transmission according to claim 8 or 9.

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