Abstract:
An active electromechanical armature assembly for a transmission is provided. The active electromechanical armature assembly improves fuel economy by storing transmission fluid in areas away from rotating components during hot operation. During other conditions the transmission fluid is kept in the sump. The active electromechanical armature assembly includes a moveable armature or plunger. Movement of the plunger controls the opening and closing of an opening that communicates between the sump and the side or front cover of the transmission.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/045,928 filed Sep. 4, 2014. The disclosure of the above application is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to an active electromechanical hydraulic fluid level control system for an automatic transmission, and more particularly to an assembly for actively controlling hydraulic fluid level between a sump and a side or front cover in an automatic transmission using an electromechanical device. 
       BACKGROUND 
       [0003]    A typical automatic transmission includes a hydraulic control system that is employed to provide cooling and lubrication to components within the transmission and to actuate a plurality of torque transmitting devices such as clutches and brakes. The hydraulic control system typically includes a sump located at a bottom of the transmission that collects the hydraulic fluid from the remainder of the hydraulic control system. The sump stores the hydraulic fluid to be suctioned back into the hydraulic control system by a pump. A minimum level of hydraulic fluid is required in the sump in order to feed the hydraulic control system for all ranges of transmission operation and to account for dynamic movement of the hydraulic fluid within the sump. It is desirable to keep the amount of hydraulic stored in the sump to this minimum level since hydraulic fluid in the sump interferes with the rotating components of the transmission. The rotating components, including for example gears, clutch plates, and interconnecting members, traveling through the stored hydraulic fluid within the sump experience increased drag, thus increasing spin losses and in turn decreasing the efficiency of the transmission. 
         [0004]    The minimum level of hydraulic fluid that must be stored in the sump varies based on various factors including the operating temperature of the hydraulic fluid. Therefore it is desirable to store excess hydraulic fluid out of the sump and in a separate area that does not interfere with rotating components. One solution is to actively control the level of hydraulic fluid between the sump and a front or side cover of the transmission using a passive thermal valve. These passive thermal valves allow hydraulic fluid to flow between the sump and the front cover based on the temperature of the hydraulic fluid. While these systems are useful for their intended purpose, there is a need in the art for an active control system that minimizes cost and mass and that allows excess hydraulic fluid to be stored out of the sump during normal operating conditions but not during certain other conditions, such as end-of-line testing or transportation of the transmission. 
       SUMMARY 
       [0005]    An active electromechanical armature assembly for a transmission is provided. The active electromechanical armature assembly improves fuel economy by storing transmission fluid in areas away from rotating components during hot operation. However, during other conditions the transmission fluid is kept in the sump. The active electromechanical armature assembly is a device which converts electrical energy into mechanical movement of an armature or plunger. Movement of the plunger seals and unseals an opening that communicates between the sump and the side or front cover of the transmission. The present invention improves fuel economy by as much as 0.5% by storing excess hydraulic fluid away from rotating components. 
         [0006]    In one example, an assembly for use in a transmission of a motor vehicle includes a first fluid reservoir, a second fluid reservoir having a hole that communicates with the first fluid reservoir; and an electromechanical assembly disposed in the second fluid reservoir. The electromechanical assembly includes a coil, an armature disposed within the coil and moveable between a first position and a second position, and a plunger head connected to an end of the armature for sealing the hole between the first and second fluid reservoirs when the armature is in the first position. 
         [0007]    In another example, the first fluid reservoir is located in a sump of the transmission and the second fluid reservoir is located in a side cover of the transmission. 
         [0008]    In another example, the control valve further includes a biasing member that biases the armature to the second position. 
         [0009]    In another example, the control valve further includes a coil housing connected to an end cap, and the coil is disposed within the coil housing and the armature extends out from the end cap. 
         [0010]    In another example, the coil is disposed around an inner sleeve and the armature is slidable within the inner sleeve. 
         [0011]    In another example, the coil is interconnected to an electronic control module. 
         [0012]    In another example, the armature includes a base portion slidably disposed within the inner sleeve and a neck portion connected to the plunger head, and the neck portion is extended out from a bore in the end cap. 
         [0013]    In another example, the plunger head includes an angled front surface that complements an angled surface surrounding the hole. 
         [0014]    In another example, the biasing member is disposed partially within the inner sleeve and partially within an enlarged section of the bore of the end cap. 
         [0015]    In another example, the biasing member is disposed around the neck portion of the armature and is in contact with an inner surface of the end cap and with the end surface of the base portion of the armature. 
         [0016]    In another example, the first reservoir is separated from the second reservoir by a separator wall, and the hole is disposed through the separator wall. 
         [0017]    In another example, the control valve is connected to the separator wall. 
         [0018]    In another example, the second reservoir is disposed in a bottom portion of a side cover of the transmission. 
         [0019]    In another example, the second reservoir is not in direct communication with rotating components of the transmission. 
         [0020]    Further features and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0022]      FIG. 1  is a schematic diagram of an exemplary front wheel drive transmission according to the principles of the present invention; 
           [0023]      FIG. 2  is an enlarged cross section of a portion of the exemplary front wheel drive transmission shown in  FIG. 1 ; 
           [0024]      FIG. 3  is a front or side view of the exemplary front wheel drive transmission of  FIG. 1  with a side or front cover removed; 
           [0025]      FIG. 4  is a side view of an electromechanical armature assembly used in the exemplary front wheel drive transmission according to the principles of the present invention; 
           [0026]      FIG. 5A  is a cross-sectional view taken in the direction of arrows  5 - 5  in  FIG. 4  of the electromechanical armature assembly in a first position; and 
           [0027]      FIG. 5B  is a cross-sectional view taken in the direction of arrows  5 - 5  in  FIG. 4  of the electromechanical armature assembly in a second position. 
       
    
    
     DESCRIPTION 
       [0028]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0029]    With reference to  FIG. 1 , a schematic diagram of an exemplary transmission is generally indicated by reference number  10 . The transmission  10  is an automatic, front wheel drive, multiple speed transmission. However it should be appreciated that the transmission may be a manual transmission or any other type of transmission without departing from the scope of the present invention. The transmission  10  includes a typically cast, metal housing  12  which encloses and protects the various components of the transmission  10 . The housing  12  includes a variety of apertures, passageways, shoulders and flanges which position and support these components. The transmission generally  10  includes an input shaft  14 , an output shaft  16 , a starting device  18 , and a gear arrangement  20 . The input shaft  14  is connected with a prime mover (not shown) such as an engine. The prime mover may be an internal combustion gas or Diesel engine or a hybrid power plant. The input shaft  14  receives input torque or power from the prime mover. The output shaft  16  is preferably connected with a final drive unit (not shown) which may include, for example, propshafts, differential assemblies, and drive axles. The input shaft  14  is coupled to and drives the gear arrangement  20  through the starting device  18 . The starting device  18  is illustrated as a torque converter in the example provided, though various other hydrodynamic and mechanical devices may be used without departing from the scope of the present invention. 
         [0030]    The gear arrangement  20  generally provides multiple forward and reverse speed or gear ratios between the input shaft  14  and the output shaft  16 . The gear arrangement  20  may have various forms and configurations but generally includes a plurality of gear sets or a continuously variable unit having a chain or belt and movable pulley pairs, a plurality of shafts or interconnecting members, and at least one torque transmitting mechanism. The gear sets may include intermeshing gear pairs, planetary gear sets, or any other type of gear set. The plurality of shafts may include layshafts, countershafts, sleeve or center shafts, reverse or idle shafts, or combinations thereof. The torque transmitting mechanisms may include clutches, brakes, synchronizer assemblies or dog clutches, or combinations thereof, without departing from the scope of the present invention. 
         [0031]    Operation of the starting device  18  and gear arrangement  20 , including selection of gear ratios via clutch and brake engagement, is controlled by an electronic transmission control module (ETCM)  22  and a hydraulic control system  24 . The ETCM  22  is preferably an electronic control device having a preprogrammed digital computer or processor, control logic, memory used to store data, and at least one I/O peripheral. The control logic includes a plurality of logic routines for monitoring, manipulating, and generating data. The ETCM  22  controls the actuation of the torque transmitting mechanisms in the gear arrangement  20  via the hydraulic control system  24 . The hydraulic control system  24  generally includes electrically controlled solenoids and valves that selectively communicate hydraulic fluid throughout the transmission  10  in order to control, lubricate, and cool the various components of the transmission  10 . 
         [0032]    The hydraulic fluid used by the hydraulic control system  24  is primarily stored in a sump or reservoir  26 . The sump  26  is preferably located at a bottom of the transmission  10 . A pump (not shown) produces a suction that draws the hydraulic fluid from the sump  26  and into the hydraulic control system  24  where the hydraulic fluid is used to engage torque transmitting mechanisms and to cool and lubricate the transmission  10 . 
         [0033]    The transmission  10  further includes a front or side cover  28  attached to a side or front of the transmission  10 . The side cover  28  protects components of the hydraulic control system  24  within the transmission  10  and functions as a secondary transmission oil storage reservoir, as will be described in greater detail below. 
         [0034]    Turning to  FIGS. 2 and 3 , the transmission housing  12  includes a separator wall  12   a  that extends vertically from a bottom of the housing  12  to a top of the housing  12 . A rim or flange  12   b  extends perpendicularly out from the separator wall  12   a.  The flange  12   b  is disposed around the entire outer periphery of the separator wall  12   a,  forming a pocket or cavity  32 . Various components of the transmission  10  are disposed within the cavity  32 , for example a transmission valve body  34  of the hydraulic control system  24 . The transmission valve body  34  contains many of the pressure regulation valves, directional valves and solenoids that control the transmission  10 . 
         [0035]    The side cover  28  is configured to connect and seal to the flange  12   b,  thus enclosing the cavity  32 . For example, the side cover  28  includes a wall or rim  28   a  that extends perpendicularly out from a main portion  28   b.  The rim  28   a  is disposed around the entire outer periphery of the side cover  28 . The rim  28   a  includes a plurality of bolt holes  36  that align with a plurality of bolt holes  38  formed on the flange  12   b.  A plurality of bolts  40  or other fasteners connect the side cover  28  to the housing  12  overtop the cavity  32 . A seal (not shown) is disposed on or radially inward of the rim  28   a  in order to seal the side cover  28  to the flange  12   b  of the housing  12 . 
         [0036]    A lower portion or secondary reservoir  32   a  of the cavity  32  acts as a secondary hydraulic fluid reservoir to the sump  26 . The secondary reservoir  32   a  is not in communication with any rotating components of the transmission  10 . Communication of the hydraulic fluid from the secondary reservoir  32   a  to the sump  26  is controlled via an active electromechanical armature assembly or control valve  50 . The electromechanical armature assembly  50  is disposed within the secondary reservoir  32   a  of the cavity  32  near a bottom of the transmission housing  12 . The electromechanical armature assembly  50  opens and closes a drain hole or sump drain-back  51  disposed in the separator wall  12   a.  The drain hole  51  allows fluid communication between the sump  26  and the secondary reservoir  32   a.    
         [0037]    Turning to  FIG. 4 , the electromechanical armature assembly  50  generally includes a coil housing  52  connected to an end cap  54 . A moveable plunger or armature  56  extends out from the end cap  54 . The armature  56  is moveable between a first position, shown in  FIG. 5A , and a second position shown in  FIG. 5B . Movement of the armature  56  selectively seals the drain hole  51 , as will be described in greater detail below. 
         [0038]    With reference to  FIGS. 5A and 5B  and continued reference to  FIG. 4 , an electrical coil or other resistance element  60  is disposed about or wrapped around an inner sleeve  62  disposed within the coil housing  52 . The coil  60  is connected to a connector port  64  disposed on an outside of the coil housing  52 . The connector port  64  is interconnected to the ETCM  22  or to another power source. The coil  60  is enclosed and protected by the coil housing  52 . 
         [0039]    The armature  56  includes a base portion  66  slidably disposed within the inner sleeve  54 . The base portion  66  is preferably made from steel, iron or another ferro-magnetic material. A neck portion  68  extends out from an end surface  66   a  of the base portion  66 . The neck portion  68  is disposed through a bore  54   a  formed in the end cap  54 . A distal or end portion  68   a  of the neck portion  68  terminates in a plunger head  70 . The plunger head  70  is disposed outside the coil housing  52  and the end cap  54 . The plunger head  70  has an angled front surface  72  that complements an angled surface  74  in the separating wall  12   a  surrounding the drain hole  51 . 
         [0040]    A biasing member  76 , such as a spring, is disposed partially within the sleeve  62  and partially within an enlarged section  54   b  of the bore  54   a  of the end cap  54 . It should be appreciated that other types of biasing members may be employed without departing form the scope of the present invention. In the example provided, the biasing member  76  is disposed around the neck portion  68  of the armature and is in contact with an inner surface  78  of the end cap  54  and with the end surface  66   a  of the base portion  66  of the armature  56 . The biasing member  76  biases the armature  56  to the second (i.e. open) position. In the second position, shown in  FIG. 5B , the plunger head  70  is not seated in the drain hole  51 . 
         [0041]    To move the armature to the first position (i.e. closed) position, the ETCM  22  commands an electric current through the coil  60 . The electrical current flowing through the coil  60  generates a magnetic field, and the direction of this magnetic field with regards to its North and South Poles is determined by the direction of the current flow within the coil  60 . The strength of this magnetic field can be increased or decreased by controlling the amount of current flowing through the coil  60 . The armature  56  disposed within the coil  60  is attracted towards the center of the coil  60  by a magnetic flux. Thus the armature  56  moves or strokes within the inner sleeve  62  and compresses the biasing member  76  as the armature  56  moves towards the drain hole  51 . When the armature  56  is fully extended and in the closed position, the angled front surface  72  fully contacts the angled surface  74  and seals the drain hole  51 . 
         [0042]    Returning to  FIGS. 2 and 4 , the electromechanical armature assembly  50  is connected to the separator wall  12   a  of the housing  12  by a bracket  80  and pin or case boss  82 . The bracket  80  and case boss  82  position the electromechanical armature assembly  50  above the drain hole  51  within the secondary reservoir  32   a  at a predetermined, fixed height relative to the drain hole  51 . Communication between the sump  26  and the secondary reservoir  32   a  is controlled by activation of the electromechanical armature assembly  50 . For example, the fluid level in the sump may be kept reduced by storing fluid within the secondary reservoir  32   a  by commanding a current in the coil  60 , thus creating a magnetic flux and moving the armature  56  against the biasing member  76  to seal the drain hole  51  with the plunger head  70 . Closing of the electromechanical armature assembly  50  hydraulically isolates the secondary reservoir  32   a  from the sump  26  thereby keeping the fluid level within the sump  26  to a predefined minimum. This predefined minimum is controlled by a distance of the electromechanical armature assembly  50  from a bottom of the sump  26 . When the transmission cools and the current in the coil  60  is reduced, the biasing member  76  moves the armature  56  to the open position, thus unsealing the drain hole  51 . Transmission fluid can then communicate from the secondary reservoir  32   a  through the drain hole  51  and into the sump  26 . 
         [0043]    Keeping the level of hydraulic fluid in the sump  26  to a minimum enables components of the gear arrangement  20  such as planetary gear sets, shafts or members, and clutches or brakes to rotate with a minimum of spin losses. The result is a more efficient transmission providing improved fuel economy. 
         [0044]    The description of the invention is merely exemplary in nature and variations that do not depart from the general essence 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.