Abstract:
A method for stabilizing an engine clutch control includes transmitting an engine clutch operation start command from a controller to an engine clutch system, the engine clutch system including an engine clutch, detecting a hydraulic pressure generated during the operation of the engine clutch system, carrying out an oil leakage judgment mode using the controller so as to judge whether the hydraulic pressure is a normal hydraulic pressure where the operation of the engine clutch is available or if the hydraulic pressure an abnormal hydraulic pressure where the operation of the engine clutch is unavailable, and changing an operation mode to an emergency operation mode wherein the operation of the engine clutch is stopped in case of abnormal hydraulic pressure, and carrying out an operation mode change by operating the engine clutch in a case of normal hydraulic pressure, based on a control by the controller.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority to Korean Patent Application No. 10-2015-0175688, filed on Dec. 10, 2016 with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    Exemplary embodiments of the present disclosure relate to an engine clutch control and, particularly to a method and engine clutch system for stabilizing a Dual Clutch Transmission (DCT)-based dry type engine clutch control, and an engine employing the same. 
       BACKGROUND 
       [0003]    In general, a hybrid electronic vehicle (hereinafter referred to “HEV”) is configured to use, as a power source, an internal combustion engine and an electric motor. HEVs can be categorized into parallel, serial and mild types in terms of power transfer structure. The HEV uses, as a transmission system, a Dual Clutch Transmission (DCT), wherein an even number gear input shaft and an odd number gear input shaft are used in conjunction with two clutches. 
         [0004]    In particular, the HEV in general is operated in either the EV mode (Electric Vehicle Mode) wherein only the motor is used as a power source, and the HEV mode (Hybrid electric Vehicle Mode) wherein the engine and the motor are used together as a power source. An engine clutch system is employed to connect or disconnect the engine and the motor when changing the operation mode between the EV mode and the HEV mode. 
         [0005]    For example, the engine clutch system may be formed of a NC (Normally Close) type engine clutch and a motored hydraulic actuator. If the motored hydraulic actuator does not operate, the engine clutch will maintain a connection between the engine and the motor, whereby the power connection between the engine and the motor can be maintained. If the motored hydraulic actuator operates, the engine clutch will disconnect the connection between the engine and the motor, thus disconnecting the power connection between the engine and the motor. 
         [0006]    In this way, the HEV can be selectively operated in the EV mode or the HEV mode depending on the operation state of the engine clutch system. 
         [0007]    The engine clutch system, however, may be configured to form a flow passage by connecting the motored hydraulic actuator and the engine clutch via a hydraulic line, whereby it may be impossible to control the engine clutch based on the motored hydraulic actuator if oil leaks. Repeated oil leakage may result in a failure in the normal operation of the engine clutch based on the motored hydraulic actuator. 
       SUMMARY 
       [0008]    An embodiment of the present disclosure is directed to a method and engine clutch system for stabilizing an engine clutch control and an engine employing the same, wherein any oil leakage can be quickly detected in such a way to change an abnormal change in the hydraulic pressure of a motored hydraulic actuator due to an actuator stroke into an oil leakage data, and in particular, any clutch slip and clutch burning in an engine clutch control section due to an abnormal actuator stroke can be prevented by recovering the motored hydraulic actuator to a non-operation state in case of an oil leakage. 
         [0009]    Other objects and advantages of the present disclosure can be understood by the following description, and become apparent with reference to the embodiments of the present disclosure. Also, it is obvious to those skilled in the art to which the present disclosure pertains that the objects and advantages of the present disclosure can be realized by the means as claimed and combinations thereof. 
         [0010]    According to one embodiment of the present disclosure, a method for stabilizing an engine clutch control, includes transmitting an engine clutch operation start command from a controller to an engine clutch system, the engine clutch system including an engine clutch provided to connect and disconnect an engine and a motor; detecting a hydraulic pressure generated during the operation of the engine clutch system; carrying out an oil leakage judgment mode using the controller so as to judge whether the hydraulic pressure is a normal hydraulic pressure where the operation of the engine clutch is available or if the hydraulic pressure an abnormal hydraulic pressure where the operation of the engine clutch is unavailable; and changing an operation mode to an emergency operation mode wherein the operation of the engine clutch is stopped in case of abnormal hydraulic pressure, and carrying out an operation mode change by operating the engine clutch in a case of normal hydraulic pressure, based on a control by the controller. 
         [0011]    The hydraulic pressure may be generated by the actuator stroke of the motored hydraulic actuator of the engine clutch system. 
         [0012]    The oil leakage judgment mode may be carried out in such a way that the motored hydraulic actuator of the engine clutch system is operated by the controller, the hydraulic pressure is detected as the current hydraulic pressure P current  due to the increase in the actuator stroke, and the current hydraulic pressure P current  is compared to the set limit hydraulic pressure P limit , thus judging the normal hydraulic pressure and the abnormal hydraulic pressure. 
         [0013]    The increase of the actuator stroke may be carried out from the initial stroke X 0  to the maximum stroke X max , and the current hydraulic pressure P current  is detected at the position of the maximum stroke X max . 
         [0014]    The limit hydraulic pressure P limit  may be defined as a minimum hydraulic pressure among the hydraulic pressures which are generated when the motored hydraulic actuator normally operates without any oil leakage. 
         [0015]    The normal hydraulic pressure may be a pressure in a case where the current hydraulic pressure P current  is a pressure which is over the limit hydraulic pressure P limit , and the abnormal hydraulic pressure may be a pressure in a case where the current hydraulic pressure P current  is smaller than the limit hydraulic pressure P limit  or is equal thereto. 
         [0016]    The emergency operation mode may be carried out in such a way that the abnormal hydraulic pressure is created as an engine clutch system oil leakage code, the motored hydraulic actuator reversely operates in accordance with a control of the controller for the actuator stroke to be recovered to the initial state, the operation of the engine clutch is stopped after the actuator stroke is recovered to the initial state, and the control is changed to the limp home control after the operation of the engine clutch is stopped. 
         [0017]    The initial state recovery of the actuator stroke may mean the position of the initial stroke X 0 . 
         [0018]    The limp home control may be carried out in such a way that the engine is driven by the controller, the motor is controlled in sync with the engine by the controller, and the DCT carries out an oscillation control by means of the controller. 
         [0019]    The operation mode change may be carried out between a Hybrid Electric Vehicle (HEV) mode and an Electric Vehicle (EV) mode. 
         [0020]    The engine clutch may be a dry type engine clutch which operates based on the Normally Close (NC) type engine clutch. 
         [0021]    According to another embodiment of the present disclosure, an engine clutch system, includes a controller including an oil leakage detection map wherein the data to judge a system hydraulic pressure as a normal hydraulic pressure in the absence of an oil leakage and as an abnormal hydraulic pressure in the presence of an oil leakage is formed in the form of a map; a motored hydraulic actuator which includes an actuator motor controlled by a Local Control Unit (LCU) connected via a high speed Controller Area Network (CAN) communication line to the controller, a lead screw provided to change the rotation of the actuator motor into a straight line motion, a piston rod provided for generating an actuator stroke in cooperation with the lead screw, and a master cylinder which forms or removes a hydraulic pressure based on an oil supply or recovery of the oil reservoir in response to a motion of the piston rod; a pressure sensor for detecting the hydraulic pressure of the master cylinder and supplying the detection to the controller; a Concentric Slave Cylinder (SCS) which is connected to the master cylinder via a hydraulic line and generates a hydraulic pressure stroke based on the supplied hydraulic pressure; and an engine clutch connected to the CSC and a spring and configured to receive the hydraulic pressure stroke. 
         [0022]    According to another embodiment of the present disclosure, a vehicle includes an engine clutch system including a controller having an oil leakage detection map wherein the data to judge a system hydraulic pressure as a normal hydraulic pressure in the absence of an oil leakage and an abnormal hydraulic pressure in the presence of an oil leakage is formed in the form of a map, a motored hydraulic actuator controlled by the controller and generating a hydraulic pressure based on the actuator stroke, a pressure sensor for detecting a hydraulic pressure and supplying the detection to the controller, a Concentric Slave Cylinder (CSC) for receiving the hydraulic pressure and generating a hydraulic pressure stroke, and an engine clutch connected to the CSC and a spring and receiving the hydraulic pressure stroke; an engine connected to a Hybrid Starter &amp; Generator (HSG); a motor which employs a Hybrid Electric Vehicle (HEV) mode when is connected to the engine by the engine clutch system and employs an Electric Vehicle (EV) mode when disconnected from the engine; and a Dual Clutch Transmission (DCT) connected to the motor. 
         [0023]    According to the present disclosure, the following advantages and effects can be obtained in such a way that an engine clutch system which is able to normally control an engine clutch in case of an oil leakage is provided at a vehicle. First, a control structure of an engine clutch system can be provided, which is able to control a DCT-based engine clutch using a motored hydraulic. Second, a HEV mode control logic can be provided, which is able to detect any oil leakage at the engine clutch system. Third, any clutch burning which may cause a clutch slip due to an abnormal actuator stroke in an engine clutch control section can be prevented. Fourth, the engine clutch system may be developed into a DCT-based dry type engine clutch system. Fifth, an oil leakage detection limp home control technology in a future DCT-based dry engine clutch system-employed hybrid vehicle can be preoccupied. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIGS. 1A and 1B  are flowcharts for describing a method for stabilizing an engine clutch control according to embodiments of the present disclosure. 
           [0025]      FIG. 2  is a view illustrating an example of a vehicle which is employing a method for stabilizing an engine clutch control according to embodiments of the present disclosure. 
           [0026]      FIG. 3  is a view illustrating a detailed configuration of an engine clutch system according to embodiments of the present disclosure. 
           [0027]      FIG. 4  is a view illustrating an operation state of an engine clutch system according to embodiments of the present disclosure. 
           [0028]      FIG. 5  is a graph illustrating an example of a hydraulic pressure curve of a motored hydraulic actuator according to embodiments of the present disclosure. 
           [0029]      FIG. 6  is a clutch control curve of an engine clutch which is associated with a motored hydraulic actuator according to embodiments of the present disclosure. 
           [0030]      FIG. 7  is a graph illustrating an operation state of an engine clutch system in an EV mode of a vehicle according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    The terms and words used in the specification and claims should not be construed as their ordinary or dictionary meanings. On the basis of the principle that the inventor can define the appropriate concept of a term in order to describe his/her own disclosure in the best way, meanings should be construed as meaning and concepts for complying with the technical idea of the present disclosure. Accordingly, the embodiments described in the present specification and the construction shown in the drawings are merely one preferred embodiment of the present disclosure, and the detailed description section does not cover all the technical ideas of the disclosure. Thus, it should be understood that various changes and modifications may be made at the time of filing the present application. In addition, detailed descriptions of functions and constructions well known in the art may be omitted to avoid unnecessarily obscuring the concepts of the present disclosure. Exemplary embodiments of the present disclosure will be described below in more detail with reference to the accompanying drawings. 
         [0032]      FIGS. 1A and 1B  are flowcharts for describing a method for stabilizing an engine clutch control according to embodiments of the present disclosure. As illustrated therein, a method for stabilizing an engine clutch control according to the present disclosure is provided, wherein any oil leakage at a hydraulic line can be detected based on a limit pressure value with respect to a hydraulic pressure area of an actuator stroke in such a way to recognize an occasion wherein the hydraulic pressure is abnormally generated due to the actuator stroke at an engine clutch system in a case of an oil leakage at the hydraulic line. Accordingly, the vehicle can then be changed to a limp home (a minimum driving state of the vehicle due to a hardware error) as an emergency operation mode in case of an oil leakage. As a result, the vehicle is able to obtain a HEV mode control logic without any clutch slip and burning due to an abnormal actuator stroke in the clutch control section. 
         [0033]      FIG. 2  and  FIG. 3  are views illustrating a vehicle and an engine clutch to which the method for stabilizing an engine clutch control is employed according to embodiments of the present disclosure. 
         [0034]    Referring to  FIG. 2 , the vehicle  100  may include, but is not limited to, an internal combustion type engine  200 , an electric motor type motor  300 , a HSG (Hybrid Starter &amp; Generator)  400  which is connected to a crank shaft of the engine  200  and is provided to drive the engine  200  when the engine is started, a DCT (Dual Clutch Transmission)  500  which is connected to the motor  300  and is configured to operate as a transmission system, and an engine clutch system  1  which is able to change the driving mode between the HEV mode and the EV mode in response to a connection and disconnection control of the engine  200  and the motor  300 . 
         [0035]    Referring to  FIG. 3 , the engine clutch system  1  may include, but is not limited to, a controller  10 , an oil leakage detection map  10 - 1 , a motored hydraulic actuator  20 , a pressure sensor  30 , a hydraulic line  40 , a CSC (Concentric Slave Cylinder)  50  and an engine clutch  60 . 
         [0036]    More specifically, the controller  10  may be configured to operate as an upper level controller which is connected, via a high speed CAN (Controller Area Network) communication line, to each lower level controller of the vehicle  100  which may include a LCU (Local Control Unit)  21 - 1  of the motored hydraulic actuator  20 . The controller  10 , therefore, may be the same as an HCU (Hybrid Control Unit) which is provided to control the HEV/EV modes and the limp home. In particular, the controller  10  may be connected to, or may include, an oil leakage detection map  10 - 1  so as to read the data of the oil leakage detection map  10 - 1 . The oil leakage detection map  10 - 1  may be formed into a map which may include a limit hydraulic pressure to judge a normal hydraulic pressure and an oil leakage due to the actuator stroke of the motored hydraulic actuator  20 , and an engine clutch system oil leakage code, etc. related with the oil leakage. Moreover, the controller  10  may be configured to supply any instruction or command to the PWM (Pulse Width Modulation) DUTY. 
         [0037]    More specifically, the motored hydraulic actuator  20  may include, but is not limited to, an actuator motor  21  which is controlled by an LCU (Local Control Unit)  21 - 1  connected to the controller  10  via a high speed CAN communication line, a lead screw  23  which converts the rotation of the actuator motor  21  into a straight movement, a piston rod  25  which generates an actuator stroke in sync with the lead screw  23 , and a master cylinder  27  which is able to form a hydraulic pressure or remove the hydraulic pressure in accordance with an oil supply or recovery of an oil reservoir based on the motion of the piston rod  25 . 
         [0038]    More specifically, the pressure sensor  30  detects the hydraulic pressure which is generate at the master cylinder  27  and transmits the detection to the oil leakage detection map  10 - 1  (or the controller connected via a high speed CAN communication line). 
         [0039]    More specifically, the hydraulic line  40  connects the master cylinder  27  and the CSC  50 , thus supplying the hydraulic pressure which has generated at the master cylinder  27  to the CSC  50 . In particular, the hydraulic line  40  may be formed of a hose or a pipe. 
         [0040]    More specifically, the CSC  50  is connected to the spring of the engine clutch  60  and is provided to supply, to the engine clutch  60 , the stroke generated by the hydraulic pressure from the hydraulic line  40 . In particular, the CSC  50  may be formed of the type of a module which is equipped with the functions of a clutch release cylinder, a release lever, a release fork, a release bearing, a pivot and an input shaft sleeve. 
         [0041]    More specifically, the engine clutch  60  may be formed of a dry type engine clutch which can operate by way of the NC (Normally Close) and is provided to disconnect the engine  200  and the motor  300  which have been connected by the operation of the CSC  50 . The engine clutch  60 , therefore, will change the operation mode of the vehicle  100  from the HEV mode to the EV mode in such a way to disconnect the engine  200  and the motor  300 . 
         [0042]    The embodiment of the method for stabilizing an engine clutch control of the present disclosure will be described with reference to  FIG. 4  to  FIG. 7 . In this case, the main control component may be a controller  10 , and the controller  10  may employ the HCU. 
         [0043]    The step S 10  is a step wherein the start key on of the vehicle is recognized by the controller  10 . In this case, the start key on of the vehicle means a state before the engine  200  is started. 
         [0044]    The step S 20  is a step wherein an engine clutch operation start command is transmitted from the controller  10 . Referring to  FIG. 4 , the controller  10  will transmit a motor rotation command to the LCU  21 - 1 , and the LCU  21 - 1  will allow rotation of the actuator motor  21  in response to a motor rotation command. It will be, hereinafter, assumed that the rotation direction of the actuator motor is a direction wherein the actuator stroke can be increased. 
         [0045]    The step S 30  is a step wherein the actuator hydraulic pressure supply control is carried out by the controller  10 . Referring to  FIG. 4 , the controller  10  may keep transmitting a command to the LCU  21 - 1  for the actuator motor  21  to continuously rotate. As a result, the rotation of the actuator motor  21  is converted into a forward straight movement of the lead screw  23 , thus allowing the piston rod  25  to forwardly move toward the master cylinder  27 , and the forward movement of the piston rod  25  may result in the increase in the actuator stroke. Thereafter, the oil in the chamber of the master cylinder  27  is pressurized by the piston rod  25 . For this reason, a hydraulic pressure can be formed at the master cylinder  27  thanks to the increase in the actuator stroke. 
         [0046]    The step S 40  is a step wherein the actuator hydraulic pressure supply control is finished with an actuator stroke increase control of the controller  10 . Referring to  FIG. 4 , the controller  10  will stop the actuator hydraulic pressure supply control when the actuator stroke (X actuator stroke ) is changed into a maximum actuator stroke (X max ) (namely, the disconnection of the engine clutch) at the initial actuator stroke (X 0 ) (namely, the connection of the engine clutch). For this, the controller  10  may use the sensor installed at the master cylinder  27  to detect X actuator stroke  or may use the oil leakage detection map  10 - 1 , wherein X 0  and X max  of the motored hydraulic actuator  20  are stored in the form of a data. 
         [0047]    The step S 50  is a step wherein the hydraulic pressure generated at the motored hydraulic actuator  20  is recognized by the controller  10 . In this case, the controller  10  receives the hydraulic pressure detected by the pressure sensor  30  and recognizes the received hydraulic pressure as the current hydraulic pressure of the motored hydraulic actuator  20 , and defines it as P current . Here, P current  means a hydraulic pressure that the pressure sensor  30  generates at the master cylinder  27  at the maximum forward position (namely, X max ) of the piston rod  25 . 
         [0048]    The step S 60  is a step wherein the oil leakage at the motored hydraulic actuator  20  is judged by the controller  10 . In this case, the controller  10  will employ P limit  which is in contrast with P current . P limit  means the minimum normal hydraulic pressure in the normal hydraulic pressure area which is detected as the position of X max  wherein the motored hydraulic actuator  20  is in the normal operation state where there is not any oil leakage, and P limit  may be defined as a limit hydraulic pressure. P limit  will be stored in the oil leakage detection map  10 - 1  in the form of a data. The controller  10 , therefore, is able to judge the oil leakage state of the motored hydraulic actuator  20  in such a way as to use P current  detected by the pressure sensor  30  and P limit  stored at the oil leakage detection map  10 - 1 . For this, the controller  10  may employ a relational formula of P current ≦P limit , wherein “≦” means a sign of inequality which shows a size relationship between two values and means that P limit  is larger than or equal to P current . Referring to  FIG. 5 , there is shown a pressure characteristic with respect to the actuator stroke of the motored hydraulic actuator  20 . Since the abnormal hydraulic pressure judgment range is formed below the normal hydraulic pressure curve, it is possible to judge any oil leakage by using P limit . 
         [0049]    As a result of the check in the step S 60 , if the controller  10  goes to the emergency operation mode of a step S 70  if the current hydraulic pressure P current  is smaller than the limit hydraulic pressure P limit , and if the current hydraulic pressure P current  is larger than or equal to the limit hydraulic pressure P limit , the controller  10  will go to the mode change (HEV-&gt;EV) in a step S 100 . Referring to  FIG. 6 , shown is an operation relationship between the motored hydraulic actuator  20  and the engine clutch  60 . As illustrated therein, the controller  10  will judge the normal state of the hydraulic pressure with respect to the actuator stroke section (X 0 &lt;-&gt;X max ), by means of which the engine clutch  60  cannot be operated with the abnormal hydraulic pressure in the clutch control section which matches with the actuator stroke section (X 0 &lt;-&gt;X max ). As a result, the engine clutch  60  will prevent any clutch burning which may occur due to clutch slip in the clutch control section. 
         [0050]    The emergency operation mode in the step S 70  may be classified into an initial state recovery control of the engine clutch system in the steps S 71  to S 74 , and a limp home control of the steps S 75  and S 76 . Therefore, if the actuator stroke does not automatically recover the close state of the engine clutch  60  to the initial state when the oil is leaking, the vehicle  100  will be driven only in the EV mode, thus preventing a SOC (State Of Charge) depletion of the high voltage battery which might occur if the vehicle  100  is driven only in the EV mode. 
         [0051]    The step S 71  is a step wherein an error code is generated by the controller  10 . Referring to  FIG. 4 , the controller  10  will read the oil leakage code of the engine clutch system stored in the oil leakage detection map  10 - 1  and store a corresponding oil leakage code or display the oil leakage code on a screen or use it as an alarm lamp turning-on signal. 
         [0052]    The step S 72  is a step wherein the actuator hydraulic pressure recovery control is carried out by the controller  10 . Referring to  FIG. 4 , the controller  10  will transmit a motor reverse rotation command to the LCU  21 - 1 , and the LCU  21 - 1  will reversely rotate the actuator motor  21  in response to a motor reverse rotation command. The reverse rotation of the actuator motor  21  will be converted into a backward straight line movement of the lead screw  23 , thus moving backward the piston rod  25  so that it can separate from the master cylinder  27 , and the movement of the piston rod will cause a decrease in the actuator stroke. Since the piston rod  25  separates from the master cylinder  27 , a hydraulic pressure may decrease at the master cylinder  27  due to the decrease in the actuator stroke. 
         [0053]    The step S 73  is a step where the actuator hydraulic pressure recovery control is finished with the aid of the actuator stroke recovery control of the controller  10 . Referring to  FIG. 4 , the controller  10  will stop the actuator hydraulic recovery control when X actuator stroke  has changed from X max  to X 0 . 
         [0054]    The step S 74  is a step wherein the engine clutch operation stop command is transmitted from the controller  10 . Referring to  FIG. 4 , the controller  10  transmits a motor control command to the LCU  21 - 1 , and the LCU  21 - 1  stops the actuator motor  21  in response to a motor stop command. As a result, the initial state recovery control of the engine clutch system  1  due to the oil leakage is finished. 
         [0055]    The step S 75  is a step wherein the limp home control entry is carried out by the controller  10 . Referring to  FIG. 2 , the controller  10  will transmit a control command to the HSG  400  based on an engine start on event, thus starting the engine  200  and controlling the motor in sync with the resolution per minute of the engine  200 . As a result, the vehicle  100  will carry out a sync control of the engine  200  and the motor  300  in the HEV mode wherein the engine clutch  60  is in the close state. 
         [0056]    The step S 76  is a step wherein the limp home control is carried out by the controller  10 . Referring to  FIG. 2 , the controller  10  will carry out an oscillation control using the slip-possible DCT clutch of the DCT  500 , whereupon the vehicle  100  can be, or enter, a limp home driving state. 
         [0057]    Meanwhile, the step S 100  is a step wherein the mode change will be carried out if the current hydraulic pressure P current  is larger than or equal to the limit pressure P limit , and the step S 110  is a step wherein the vehicle will be driven with the motor after the operation move is changed from the HEV mode to the EV mode. Referring to  FIG. 1  and  FIG. 7 , the CSC  50  may cause a CSC release travel with a motion which is in proportion to the actuator stroke of the motored hydraulic actuator  20  and may generate a hydraulic pressure which is in proportion to the release load based on a change in the actuator stroke and may transfer it to the engine clutch. Thereafter, the engine clutch  60  will be opened due to the increase in the actuator stroke in the close state which corresponds to the initial state, and the change from the close state to the opening state of the engine clutch may mean, or cause, a change from the HEV mode to the EV mode, so the vehicle can be driven in the EV mode. 
         [0058]    The steps S 100  and S 110  are related to the normal driving state of the vehicle. 
         [0059]    As described above, in the method for stabilizing the engine clutch control according to the embodiment of the present disclosure, the engine clutch system  1  having the engine clutch  60  which is able to connect and disconnect the engine  200  and the motor  300  receives an engine clutch operation start command by the controller  10 , and the current hydraulic pressure P current  detected based on the stroke of the motored hydraulic actuator of the engine clutch system  1  is compared to the limit hydraulic pressure P limit , whereby the normal hydraulic pressure due to the absence of the oil leakage is judged, and the abnormal hydraulic pressure due to the presence of the oil leakage is judged. Since the dry type engine clutch  60  which operates in the NC (Normally Close) of the engine clutch system  1  can be operated only in case where the hydraulic oil is in the normal state in order to prevent any clutch slip and clutch burning in the engine clutch control section, stability of the HEV mode logic of the vehicle  100  can be obtained. 
         [0060]    While the present disclosure has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the disclosure as defined in the following claims.