Abstract:
An electro-hydraulic clutch system for a motor vehicle includes a clutch mechanism that selectively engages an engine of the motor vehicle with a gear box, an actuator that pumps and retrieves hydraulic fluid to and from the clutch mechanism to activate the clutch mechanism, and a solenoid with a valve and/or a check ball that is disposed in the path of the hydraulic fluid between the actuator and the clutch mechanism. The solenoid has a normally closed position to prevent flow of the hydraulic fluid back to the actuator in the event of a system failure. The solenoid can also be used to reduce energy consumption in steady state conditions.

Description:
FIELD 
       [0001]    The present disclosure relates to a motor vehicle transmission. More specifically, the present disclosure relates to an electro hydraulic clutch by wire motor vehicle transmission. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    A typical motor vehicle transmission includes a hydraulic control system that is employed to actuate torque transmitting devices. These torque transmitting devices may be, for example, friction clutches that when engaged couple an engine with a gearbox. The conventional hydraulic control system typically includes a main pump or actuator that provides a pressurized fluid, such as oil, that activates the clutch to engage or disengage the torque transmitting devices in order to obtain different gear ratios. 
         [0004]    While previous hydraulic control systems are useful for their intended purpose, the need for new and improved hydraulic control system configurations within transmissions which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness, is essentially constant. Accordingly, there is a need for an improved, cost-effective hydraulic control system for use in a hydraulically actuated automatic transmission. 
       SUMMARY 
       [0005]    An electro-hydraulic clutch system for a motor vehicle includes a clutch mechanism that selectively engages an engine of the motor vehicle with a gear box, an actuator that pumps and retrieves hydraulic fluid to and from the clutch mechanism to activate the clutch mechanism, and a solenoid with a valve and/or a check ball that is disposed in the path of the hydraulic fluid between the actuator and the clutch mechanism. The solenoid has a normally closed position to prevent flow of the hydraulic fluid back to the actuator in the event of a fault in the electro-hydraulic clutch system. The solenoid can also be used to reduce energy consumption in steady state conditions. 
         [0006]    Further features, advantages, and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0007]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the views. In the drawings: 
           [0008]      FIG. 1  is a schematic drawing of an electro-hydraulic clutch for a motor vehicle transmission in accordance with the principles of the present invention; and 
           [0009]      FIG. 2  is a flow diagram of a process for operating the electro-hydraulic clutch shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0011]    Referring now to  FIG. 1 , an electro-hydraulic clutch system embodying the principles of the present invention is designated at  10 . The electro-hydraulic clutch system  10  includes a clutch mechanism  12  that selectively engages an engine  14  with a gearbox  16  through a drive shaft  17 . The electro-hydraulic clutch system  10  also includes an actuator  18  that pumps a hydraulic fluid  24 , such as, for example oil through a conduit  26  to and from the clutch mechanism  12 . The flow of the hydraulic fluid results in the opening and closing of the clutch mechanism  12 . Note, that the present invention is not limited to any particular type of normally open or closed clutch system. For example, in a normally open clutch system, the flow of hydraulic fluid to the clutch mechanism  12  causes a set of actuation devices  24  to engage a clutch  36 , thereby coupling the engine  14  to the gearbox  16  and the remainder of the drivetrain through the drive shaft  17 . As the hydraulic fluid flows away from the clutch mechanism  12 , the actuation devices  24  disengage the clutch, thereby de-coupling the engine from the gearbox  16  and the remainder of the drivetrain. 
         [0012]    Alternatively, in a normally closed clutch system, the flow of hydraulic fluid away from the clutch mechanism  12  causes the set of actuation devices  24  to engage the clutch  36 , thereby coupling the engine  14  to the gearbox  16  and the remainder of the drivetrain through the drive shaft  17 . Further, in the normally closed clutch system, as the hydraulic fluid flows to the clutch mechanism  12 , the actuation devices  24  disengage the clutch, thereby de-coupling the engine from the gearbox  16  and the remainder of the drivetrain. 
         [0013]    The actuator  18  includes a piston  20  that reciprocates in a bore  21 . The piston  20  can be driven by any suitable electronic, mechanical, or electro-mechanical mechanism  22 . As the piston  20  reciprocates in the bore  21 , the hydraulic fluid  24  is pumped out of and retrieved back into the actuator  18 . The actuator  18  may be operated under the direction of any suitable controller associated with the motor vehicle. The actuator  18  may pump hydraulic fluid to other various devices or parts that may require fluid flow for hydraulic control functions, lubrications, or cooling, such as, for example, rotatable shafts, gearing arrangements, and/or or other torque transmitting devices. 
         [0014]    The electro-hydraulic clutch system  10  further includes a solenoid  28  disposed in the path of the flow of hydraulic fluid  24 . The solenoid  28  includes a valve that is normally closed to prevent oil from flowing in the reverse direction during any failure of the electro-hydraulic control system  10 , including, but not limited to, a power failure or a failure of any control unit associated with the electro-hydraulic control system  10 . This feature prevents the unintended application of the clutch  36 . As shown in  FIG. 1 , the solenoid  28  is operated by electronic controller  30 . The electronic controller  30  may include software algorithm, such as, for example, described below, stored in a non-transitory computer readable mechanism. Note that the present invention is not limited to a normally closed solenoid. For example, the solenoid  28  can include a check ball  32  that is actuated by the solenoid  28 . Specifically, the solenoid  28  under the direction of the controller  30  opens and closes the check ball  32  to open and close off the flow of hydraulic fluid  24  between the actuator  18  and the clutch mechanism  12 . The check ball  32  itself is normally closed. That is, when power is cut off from the solenoid  28 , the check ball closes to prevent flow of hydraulic fluid in the reverse direction back to the actuator. 
         [0015]    Turning now to  FIG. 2 , there is shown a process  100  for operating the electro-hydraulic clutch system  10 . The process  100  can be, for example, implemented as software algorithm in the controller  30 . 
         [0016]    In a particular, arrangement the process  100  begins in a step  102 . Next the process  100  proceeds to a decision step  104 , which may be a safety algorithm, where the process determines if there has been a fault in the controller  30 , or a fault such as, for example, a system failure of the electro-hydraulic clutch system  10 , a failure of any control unit associated with the electro-hydraulic clutch system  10 , or a failure of a diagnostic event. If the decision step  104  determines that there has been a fault, the process proceeds to a step  105 , which de-energizes the solenoid  28 . This results in closing the valve in the solenoid  28 , or the check ball  32 , if the solenoid  28  includes a check ball. In any case, the flow of hydraulic fluid  24  is stopped, such that, the clutch mechanism  12  remains open (i.e. dis-engaged), for example, if the motor vehicle is at an intersection, or remains closed (i.e. engaged), for example, if the motor vehicle is moving along a highway. 
         [0017]    If, however, the decision step  104  determines that there has not been a system fault, then the process proceeds to a decision step  106 . Here, the process determines, with the use of a clutch control algorithm, if the clutch pedal is actuated. If the clutch pedal is not actuated, that is, the answer to the decision step  106  is no, then the process again proceeds to the step  105  where the solenoid  28  is de-energized to close the flow of hydraulic fluid  24  by closing the solenoid  28  such that the clutch mechanism  12  remains engaged to maintain the coupling between the engine  14  and the gearbox  16 . 
         [0018]    In the event that the clutch pedal is actuated, that is, the answer to the decision step  106  is yes, then the process  100  proceeds to a decision step  108 . At this step  108 , the process  100  determines with the use of an energy saving algorithm if the clutch mechanism  12  is fully opened. If the answer is yes, then the process  100  again proceeds to step  105  to de-energize the solenoid  28 , which closes off the flow of fluid  24 . As such, the clutch mechanism remains fully open, that is, not engaged. Note that in these circumstances, this is the situation where conventional clutch systems consume a significant amount of energy. With the electro-hydraulic clutch system  10 , however, energy consumption is minimized since both the solenoid  28  and the actuator  18  can be de-energized while keeping the clutch fully opened. Accordingly, when the motor vehicle is stopped, for example, at a red light, then the electro-hydraulic clutch system  10  does not need energy to hold the clutch mechanism  12  opened. 
         [0019]    Finally, if the decision step  108  determines that the clutch mechanism  12  is not fully opened, that is, the answer to the decision step  108  is no, then the process  100  proceeds to a step  110 , where the process  100  energizes the solenoid  28  to enable control of the clutch mechanism  12  to open or close the clutch mechanism  12  as the driver desires. Finally, the process  100  proceeds to a step  112  where the process  100  ends. 
         [0020]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.