Patent Publication Number: US-10316954-B2

Title: Oil control system and method for dual clutch transmission

Description:
CROSS-REFERENCE(S) TO RELATED APPLICATIONS 
     The present application claims priority to Korean Patent Application No. 10-2016-0168771, filed on Dec. 12, 2016, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an oil control system and an oil control method for a dual clutch transmission, and more particularly to an oil control system and an oil control method for a dual clutch transmission by which a cooling performance of a dual clutch of the dual clutch transmission may be optimized. 
     Description of Related Art 
     A dual clutch transmission is a kind of an automated manual transmission, and has two separated clutches and two separated input shafts. The two input shafts are connected to an odd number side gear set and an even number side gear set, respectively. 
     When the clutches of the dual clutch slip, the temperature of the clutch plates or a friction material may increase due to thermal energy, and the possibility of damaging the clutch plates or the frictional material is high due to the increase in temperature of the clutch plates or the frictional material. Further, as the transmission torques of the clutches may change depending on the temperature of the clutch plates or the frictional material, the shift qualities of the clutches may be influenced. 
     Meanwhile, the dual clutch is classified into a dry type and a wet type. The dry type dual clutch uses little oil and is cooled by the flow of air, which relatively deteriorates cooling efficiency and durability. 
     The wet type dual clutch uses oil, shows an excellent cooling performance, and has a high torque allowance. Accordingly, the wet type dual clutch has a cooling circuit that supplies cooling oil such as transmission fluid. 
     However, according to the conventional wet type dual clutch, the temperature of the clutch is been measured by a sensor, but it is difficult to precisely measure the temperature of the clutch due to a failure of the sensor in an extreme condition, so that the flow amount of supplied cooling fluid cannot be properly controlled. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing an oil control system and an oil control method for a dual clutch transmission, by which the flow amount of cooling oil supplied to a dual clutch may be precisely and efficiently controlled by accurately predicting the temperature of the dual clutch by use of a temperature prediction model. 
     The technical problems to be solved by the present invention are not limited to the aforementioned problems, and any other technical problems not mentioned herein will be clearly understood from the following description by those skilled in the art to which the present invention pertains. 
     According to various aspects of the present invention, an oil control system for a dual clutch transmission, which is configured to control cooling oil supplied to a dual clutch of the dual clutch transmission and lubricating oil supplied to a gearbox of the dual clutch transmission, may include an oil circuit including an oil pan in which oil is stored, an oil supply line extending from the oil pan, a cooling oil supply line branched from the oil supply line and connected to the dual clutch of the dual clutch transmission, a lubricating oil supply line branched from the oil supply line and connected to the gearbox of the dual clutch transmission, a distribution valve disposed in the oil supply line and configured to distribute the oil to the cooling oil supply line and the lubricating oil supply line, and an oil pump configured to pump the oil from the oil pan, and a control device configured to control an operation of the oil pump and to control an opening degree of the distribution valve. 
     According to various aspects of the present invention, an oil control method for a dual clutch transmission, for controlling cooling oil supplied to a dual clutch of the dual clutch transmission and lubricating oil supplied to a gearbox of the dual clutch transmission may include determining a necessary flow amount of cooling oil based on temperatures of the clutches of the dual clutch and determining a necessary flow amount of lubricating oil based on a degree of lubrication of the gears, determining a total necessary flow amount of the cooling oil and the lubricating oil of the dual clutch transmission by adding the necessary flow amount of the lubricating oil and the necessary flow amount of the cooling oil, and determining an RPM of an oil pump based on the total necessary flow amount of the oil and determining a flow amount of the supplied cooling oil and a flow amount of the supplied lubricating oil. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a dual clutch transmission controlled through an oil control system and an oil control method according to an exemplary embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating an oil control system for a dual clutch transmission according to an exemplary embodiment of the present invention; and 
         FIG. 3  is a flowchart illustrating an oil control method for a dual clutch transmission according to an exemplary embodiment of the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     Referring to  FIG. 1 , a dual clutch transmission  1  may be disposed between an engine  2  and a differential apparatus  4  to transmit power of the engine  2  to the differential apparatus  4 . 
     The dual clutch transmission  1  may include a gearbox  5 , and a dual clutch  6  disposed between the engine  2  and the gearbox  5  to transmit a torque of the engine  2  to the gearbox  5 . 
     The gearbox  5  may include gears that may be moved between a plurality of forward ratios and a plurality of reverse ratios. 
     The dual clutch  6  may have two clutches  7  and  8  that may drive the gears of the gearbox  5  through two concentric shafts  11  and  12 , and the clutches  7  and  8  may have a plurality of clutch plates and frictional materials. 
     An oil circuit  20  of the dual clutch transmission according to the exemplary embodiment of the present invention may include an oil pan  21  in which oil is stored, an oil supply line  22  extending from the oil pan  21 , a cooling oil supply line  23  branched from the oil supply line  22  and connected to the dual clutch  6 , a lubricating oil supply line  24  branched from the oil supply line  22  and connected to the gearbox  5 , and an oil pump  25  configured to pump oil from the oil pan  21 . 
     The oil supply line  22  may extend from the oil pan  21  towards the dual clutch transmission  1 . Oil for cooling and lubrication may be supplied to the dual clutch transmission  1  through the oil supply line  22 . 
     A distribution valve  26  is disposed in the oil supply line  22 , and the distribution valve  26  distributes oil to the cooling oil supply line  23  and the lubricating oil supply line  24 . 
     The distribution value  26  may have an entrance  26   a  to which the oil supply line  22  is connected, a first exit  26   b  connected to the cooling oil supply line  23 , and a second exit  26   c  to which the lubricating oil supply line  24  is connected. A portion of the oil supplied through the oil supply line  22  may be discharged through the first exit  26   b  and be supplied to the dual clutch  6  as cooling oil, and the remaining portion of the oil may be discharged through the second exit  26   c  and be supplied to the gearbox  5  as lubricating oil. 
     The distribution valve  26  may include an electronic control valve having a solenoid, and the distribution valve  26  may properly distribute a flow amount of the cooling oil supplied to the cooling oil supply line  23  and a flow amount of the lubricating oil supplied to the lubricating oil supply line  24  by relatively adjusting an opening degree of the first exit  26   b  and an opening degree of the second exit  26   c  by a control device  30 . 
     The duty of solenoid of the distribution valve  26  is controlled by the control device so that the opening degree of the first exit  26   b  and the opening degree of the second exit  26   c  may be relatively adjusted. For example, when the opening degree of the first exit  26   b  is 0%, the opening degree of the second exit  26   c  may be 100%, and accordingly, the whole oil (100%) pumped by the oil pump  25  is supplied to the gearbox  5  as lubricating oil but oil is not supplied to the dual clutch  6  at all. Further, when the opening degree of the first exit  26   b  is 30%, the opening degree of the second exit  26   c  may be 70%, and accordingly, the oil of 30% of the oil pumped by the oil pump  25  may be supplied to the dual clutch  6  as cooling oil and 70% of the oil may be supplied to the gearbox  5  as lubricating oil. 
     For example, the control device  30  may determine the necessary flow amount of the cooling oil and the necessary flow amount of the lubricating oil to determine a total necessary flow amount of the oil, and may control the opening degree of the first exit  26   b  and the opening degree of the second exit  26   c  of the distribution valve  26  based on the total necessary flow amount of the oil. 
     The cooling oil supply line  23  may be connected to the first exit  26   b  of the distribution valve  26  and the dual clutch  6 , the cooling oil, of which the flow amount has been adjusted through the opening degree of the first exit  26   b  of the distribution valve  26 , may be supplied to the dual clutch  6  through the cooling oil supply line  23 , and accordingly, the dual clutch  6  may be properly cooled. 
     The lubricating oil supply line  24  may be connected to the second exit  26   c  of the distribution valve  26  and the gearbox  5 , the lubricating oil, of which the flow amount has been adjusted through the opening degree of the second exit  26   c  of the distribution valve  26 , may be supplied to the gearbox  5  through the lubricating oil supply line  24 , and accordingly, the gears in the gearbox  5  may be properly lubricated. 
     The oil pump  25  may be an electric oil pump, and accordingly, the RPM of the oil pump  25  may be controlled by the control device  30  so that a total flow amount of the oil pumped by the oil pump  25  may be determined. 
     An oil cooler  27  may be disposed between the oil pump  25  and the distribution valve  26 , and a cooling water line extending from a cooling water circuit of an engine may pass through the internal of the oil cooler  27 . Accordingly, the oil passing through the oil cooler  27  may be cooled by engine cooling water passing through the cooling water line. 
     A housing  6   a  of the dual clutch  6  may have an oil entrance  6   b  to which the cooling oil supply line  23  is connected and an oil exit  6   c  to which a cooling oil recovery line  28  is connected. Accordingly, the cooling oil may be supplied into the dual clutch  6  through the cooling oil supply line  23 , and the cooling oil may be recovered to the oil pan  21  through the cooling oil recovery line  28 . 
     A housing  5   a  of the gearbox  5  may have an oil entrance  5   c  to which the lubricating oil supply line  24  is connected and an oil exit  5   b  to which the lubricating oil recovery line  29  is connected. Accordingly, the lubricating oil may be supplied into the gearbox  5  through the lubricating oil supply line  24 , and the lubricating oil may be recovered to the oil pan  21  through the lubricating oil recovery line  29 . 
     The control device  30  is connected to the oil pump  25  and the distribution valve  26  wherein operations of the oil pump  25  and the distribution valve  26  may be controlled by the control device  30 . 
     A temperature sensor  31  configured to measure a temperature of oil, an engine control unit (ECU)  32 , and a transmission control unit (TCU)  33  may be connected to the control device  30 . According to an embodiment, the control device  30  may be integrally integrated with the TCU  30 . 
     Referring to  FIG. 2 , the control device  30  determines a temperature of oil discharged from the oil cooler  27  by use of the temperature of oil measured by the temperature sensor  31 , an oil cooler efficiency map  41 , a flow rate of cooling water received from the ECU  32 , and cooling water data  32   a  including a temperature of cooling water ( 42 ). Here, a temperature of the oil discharged from the oil cooler  27  may be a temperature of the cooling oil supplied to the oil entrance  6   b  of the housing  6   a  of the dual clutch  6 . The oil cooler efficiency map  41  may be stored in a memory of the control device  30 . 
     In the present way, temperatures of the clutches  7  and  8  of the dual clutch  6  may be predicted by applying a temperature of the cooling oil supplied to the oil entrance  6   b  of the dual clutch  6  to a temperature model  43 . 
     According to an example, the temperature sensor  31  may be disposed adjacent to a discharge hole of the oil cooler  27 , and accordingly, may measure the temperature (i.e., the temperature of the cooling oil) of the oil discharged from the oil cooler  27 . 
     The clutch temperature model  43  may accurately determine (predict) temperatures of the clutches  7  and  8  of the dual clutch  6  by use of engine data  32   b  including an RPM and a torque of the engine, which are received from the ECU  32 , clutch data  33   a  including the number of rotations of the clutches, which are received from the TCU  33 , and coupling stages of the clutches, and a temperature equation including Equation 1. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
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     Here, {dot over (Q)} gen  denotes an amount of generated heat, {dot over (Q)} convection  denotes a convection heat, {dot over (Q)} Heatflux  denotes heat flux, C p  denotes the specific heat of oil, h denotes a heat transfer coefficient of oil, A denotes a cross-sectional area of an area through which oil is fed, m denotes a mass of oil, T i  denotes a temperature of an area that is to be measured, and T in  is a temperature of supplied oil. 
     The control device  30  determines a necessary flow amount of cooling oil by use of the temperatures of the clutches  7  and  8  of the dual clutch  6 , which was determined by the clutch temperature model  43  ( 44 ). 
     The control device  30  applies the clutch data  33   a  including the numbers of rotations of the clutches, which are received from the TCU  33 , and the coupling stages of the clutches, to a map or an equation, to predict a degree of lubrication of the gears of the gearbox  5 , and a necessary flow amount of the lubricating oil is determined based on the predicted degree of lubrication of the gears ( 45 ). 
     The control device  30  may determine a total necessary flow amount of the oil by adding the necessary flow amount of the cooling oil and the necessary flow amount of the lubricating oil, may determine an RPM of the oil pump  25  based on the total necessary flow amount of the oil, and may determine the total flow amount of the supplied oil by applying the RPM of the oil pump  25  to a specific equation ( 46 ). 
     The control device  30  controls an operation of the oil pump  25  based on the total flow amount of the supplied oil ( 47 ). The flow amount of the oil discharged from the oil pump  25  is determined based on an operation of the oil pump  25 , and the flow amount of the oil discharged from the oil pump  25  may be fed back to determine the temperature of the oil discharged from the oil cooler  27  ( 42 ) and control the opening degree of the distribution valve ( 48 ). 
     Further, the control device  30  may determine the opening degree of the first exit  26   b  and the opening degree of the second exit  26   c  of the distribution valve  26  by use of the necessary flow amount of the cooling oil and the necessary flow amount of the lubricating oil as a relative ratio, and may determine the flow amount of supplied cooling oil and the flow amount of supplied lubricating oil by applying the opening degree of the first exit  26   b  and the opening degree of the second exit  26   c  to a specific equation ( 48 ). 
     The duty of the solenoid of the distribution valve  26  is controlled based on the opening degree of the first exit  26   b  and the opening degree of the second exit  26   c  of the distribution valve  26  ( 49 ). The duty control data of the solenoid may be fed back to the clutch temperature model ( 43 ) and the prediction of the degree of lubrication of the gears ( 45 ). 
     Referring to  FIG. 3 , an oil control method for a dual clutch transmission according to an exemplary embodiment of the present invention includes determining the temperatures of clutches  7  and  8  of the dual clutch  6  (S 1 ) and determining a degree of lubrication of gears of a gearbox  5  (S 2 ), determining a necessary flow amount of cooling oil based on temperatures of the clutches  7  and  8  of the dual clutch  6  (S 3 ) and determining a necessary flow amount of lubricating oil based on the degree of lubrication of the gears (S 4 ), adding the necessary flow amount of the lubricating oil and the necessary flow amount of the cooling oil to determine a total necessary flow amount of the cooling oil and the lubricating oil of the dual clutch transmission  1  (S 5 ), and determining an RPM of an oil pump  25  based on the total necessary flow amount of the oil (S 6 ) and determining a flow amount of the supplied cooling oil and a flow amount of the supplied lubricating oil (S 7 ). 
     As described above, the control device  30  determines a temperature of oil discharged from the oil cooler  27  by use of a temperature of oil measured by the temperature sensor  31 , an oil cooler efficiency map  41 , a flow amount of cooling water received from the ECU  32 , and cooling water data  32   a  including the temperature of cooling water. Here, the temperature of the oil discharged from the oil cooler  27  may be a temperature of the cooling oil supplied to the oil entrance  6   b  of the housing  6   a  of the dual clutch  6 . 
     In the present way, the temperatures of the clutches  7  and  8  of the dual clutch  6  may be determined by applying a temperature of the cooling oil supplied to the oil entrance  6   b  of the dual clutch  6  to a temperature model  43  (S 1 ). Here, the clutch temperature model  43  may determine the temperatures of the clutches  7  and  8  by use of a temperature of the supplied cooling oil, engine data  32   b  including an RPM and a torque of an engine which are received from an ECU  32 , and clutch data  33   a  including the numbers of rotations of the clutches and the coupling stages of the clutches which are received from a TCU  33 . 
     The control device  30  applies the clutch data  33   a  including the numbers of rotations of the clutches which are received from the TCU  33 , and the coupling stages of the clutches, to a map or an equation to determine a degree of lubrication of the gears of the gearbox  5  (S 2 ). 
     A necessary flow amount of cooling oil is determined by use of the temperatures of the clutches  7  and  8  of the dual clutch  6 , which was determined by the clutch temperature model  43  (S 3 ). In addition, a necessary flow amount of the lubricating oil is determined based on the determined degree of lubrication of the gears (S 4 ). 
     A total necessary flow amount of the necessary oil is determined by adding the necessary flow amount of the cooling oil and the necessary flow amount of the lubricating oil (S 5 ). 
     A RPM of the oil pump  25  is determined based on the total necessary flow amount of the oil (S 6 ). A total flow amount of the supplied oil may be determined by applying an RPM of the oil pump  25  to a specific equation, an operation of the oil pump  25  may be controlled based on the total flow amount of the supplied oil, a flow amount of the oil discharged from the oil pump  25  may be determined based on an operation of the oil pump  25 , and the flow amount of the oil discharged from the oil pump  25  may be fed back to the determination of the temperature of the oil discharged from the oil cooler  27  ( 42 ) and the control of the opening degree of the distribution valve ( 48 ). 
     In addition, the opening degree of the first exit  26   b  and the opening degree of the second exit  26   c  of the distribution valve  26  may be determined as a relative ratio by use of the necessary flow amount of the cooling oil and the necessary flow amount of the lubricating oil, and accordingly, the flow amount of the supplied cooling oil and the flow amount of the supplied lubricating oil are determined (S 7 ). 
     According to an exemplary embodiment of the present invention, the flow amount of the cooling oil supplied to the clutches may be precisely and efficiently controlled by accurately predicting the temperatures of the clutches by use of the temperature prediction model, and accordingly, the cooling performance of the clutch may be improved. 
     In addition, oil and electrical energy may be efficiently used by properly distributing the cooling oil of the clutches and the lubricating oil of the gearbox. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “internal”, “outer”, “up”, “down”, “upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”, “inwardly”, “outwardly”, “internal”, “external”, “forwards”, and “backwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing description of specific exemplary embodiments of the present invention has been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described to explain certain principles of the invention and their practical application, to enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.