Abstract:
A flow control assembly for an automatic transmission includes a valve for opening and closing communication with a source of pressurized fluid and a rotatable cam secured to a member, contact between the cam and a plunger of the valve causing said communication to open, absence of contact between the cam and the plunger causing said communication to close.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to controlling hydraulic fluid flow that lubricates a rotating clutch and discontinues the flow when the clutch is not rotating. 
         [0003]    2. Description of the Prior Art 
         [0004]    In an automatic transmission certain control elements, such as hydraulically-actuated clutches, are engaged and rotating only during operation in a few speed ratios and are non-rotating in the other speed ratios. When rotating they must be supplied with hydraulic lubricant at a flow rate of approximately 0.7 liters/minute. But if the flow rate is continuous during period of their non-rotation, energy is wasted and required pumping capacity is unnecessarily higher. Reducing pump flow demand improves fuel economy. 
         [0005]    Furthermore, supplying oil flow to the clutch when it is stationary causes oil puddling, which can cause stick-slip performance problems. 
         [0006]    A need exists in the industry for a technique that provides lubricant flow to such clutches only during periods of non-rotation without requiring computer-control or a need for an electronic solenoid for actuation. 
       SUMMARY OF THE INVENTION 
       [0007]    A flow control assembly for an automatic transmission includes a valve for opening and closing communication with a source of pressurized fluid and a rotatable cam secured to a member, contact between the cam and a plunger of the valve causing said communication to open, absence of contact between the cam and the plunger causing said communication to close. 
         [0008]    The flow control assembly is completely self-contained in the plunger, spring, and cam, and requires no computer-controlled actuation. It provides oil flow when needed, and shuts off flow when it is not needed, thereby enhancing fuel economy. 
         [0009]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0011]      FIG. 1  is a schematic diagram of a portion of an automatic transmission showing a lube cut-off valve that is actuated by rotation of the race of a OWC; 
           [0012]      FIG. 2  is side perspective view of the outer race of the OWC; 
           [0013]      FIG. 3  is a top view of a portion of the outer race; 
           [0014]      FIG. 4  is a side perspective view showing the cut-off valve open; and 
           [0015]      FIG. 5  is a side perspective view showing the cut-off valve closed. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]      FIG. 1  shows a lube cut-off valve  10  located in the inner race  12  of a OWC  14 , whose outer race  16  is formed with an axial spline  18 , which is engaged by the discs  20  of a friction clutch  22 . OWC  14  produces a one-way drive connection between the inner and outer races  12 ,  16 . 
         [0017]    The sun gear  24  of a planetary gearset  26  meshes with a set of planet pinions  28 . Sun gear  24  includes an arm  30  that extends axially and is formed with an internal axial spline, which is continually engaged with an external spline  31  formed on an arm  32  secured to outer race  16  of OWC  14 . 
         [0018]    The cut-off valve  10  includes a cylinder  38 ; a plunger  40 , located in the cylinder and contacting a cam  42  on the OWC outer race; head  46  formed on the plunger; and a coiled, helical spring, which contacts the head and continually urges the plunger into contact with the cam  42 , the position shown in  FIG. 1 . 
         [0019]    The inner race  12  of OWC  14  is formed with a radial passage  50 , which communicates with a source of automatic transmission fluid (ATF) through a passage  52 . The ATF flows radial from inner race  12 , around torque transmitting members  54 , such as rockers or rollers  54 , of the OWC  14  and through passages  56  in the outer race  16  to lubricate the discs  20  of friction clutch  22 . 
         [0020]    The cut-off valve  10  shuts-off lube flow when OWC  14  and friction clutch  22  are stationary, i.e., not rotating, and allows ATF to flow through passages  52 ,  50  and  56  when OWC  14  and friction clutch  22  are rotating. 
         [0021]    As  FIGS. 2 and 3  show the outer race  16  includes a side wall  60 , which connects external splines  18  and  31 . A tab is pierced through side wall  60  and bent axially inward to form the cam  42 , which is located in radial alignment with plunger  40 . 
         [0022]    Preferably the outer race  16  is formed with three such cams  42 , each being mutually spaced at substantial equal angular intervals. Similarly multiple cut-off valves  10  are mutually spaced at substantial equal angular intervals about the axis of rotation. 
         [0023]    As the outer race  16  rotates about its central axis, each cam  42  also rotates such that its alternately engages and disengages the plunger  40 . When a plunger  40  contacts one of the cams  42 , the head  46  is displaces axially leftward, thereby opening communication between passages  52  and  50 , as  FIG. 4  shows. When a plunger  40  is out of contact with the cams  42 , the head  46  is displaced axially rightward from the position of  FIG. 4 , to the position of  FIG. 5 , wherein communication between passages  52  and  50  is closed. 
         [0024]    The cut-off valve  10  includes a simple cam-actuated, spring-returned plunger  40 , which, when depressed by contact between the plunger and the cam  42 , allows lube oil to flow to the OWC  14  and the discs  20  of the friction clutch  22 . By selecting the spring rate of spring  48  and the profile of cam  42 , flow of lube oil can be turned on continuously after a specified rotational speed is reached. When the OWC  14  is stationary there is a high likelihood that the plunger  40  is out of contact with the ramp of cam  42  and that oil flow is stopped. 
         [0025]    The number of cams  42 , the spring rate, and the diameter of passage  50  can be sized such that the desired lube flow rate occurs when the outer race  16  is rotating and that flow stops when the outer race is stationary. 
         [0026]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.