Abstract:
A torque converter stator for improved fluid coupling and acceleration is provided. The stator includes a plurality of circumferential long and short blades for increasing torque to an automatic transmission by employing reaction force produced when a flow transmission oil within the torque converter impinges an exterior surface of the blades. The stator utilizes the plurality of circumferential short blades for increasing torque during times a vehicle starting or accelerating and for permitting an obstructed fluid coupling in the turbine and impeller are a coupling point.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a torque converter stator used in a motor vehicle transmission. A torque converter is principally constructed to have three wheels, namely an impeller or pump, a turbine and a stator. These three components are joined together and its interior is filled with transmission oil. The impeller is connected to an input shaft of the torque converter and converts rotary force from the engine into flow of the oil through centrifugal force. The turbine that is connected to an output shaft of the converter receives the flow of the oil from the impeller and converts it into torque. The stator changes the direction of the flow of the oil leaving the turbine before the oil returned to the impeller, so as to perform a function of increasing the transmitted torque. 
   The oil is a transmitting medium that circulates between the input side and output side of the torque converter. The impeller and turbine are connected to the input and output shafts of the converter and are allowed to slide relative to each other. These two parts function as a clutch so as to make it easy for the vehicle to be started and absorbs shocks. These advantages promote torque converters for wide use in passenger cars and other types of motor vehicles. 
   The stator is an important part of the torque converter and various designs have been utilized in the prior art to improve engine economy during coasting, anti-creep idling, and for improved acceleration. 
   The stator is designed with two considerations in mind. First, when the car is just starting or accelerating, the stator takes the fluid flow from the turbine and redirects fluid so that it will not slow down the impeller and work against the engine. Second, when the car is running with high operational transmission oil flow, the stator&#39;s job is to get out of the way and let the fluid flow naturally and unobstructed. 
   Prior art stator designs have attempted to improve upon stator blade design by providing for variable pitch stator blades. However, the prior art stators with variable pitch are complicated and subject to wear. Accordingly, it is an objective of the current invention to utilize a stator which provides the benefits of variable pitch stators but in a unit or member, preferably cast in one-piece. 
   Moreover, conventional hydraulic torque converters include a stator having a one-way clutch which, when it is locked to deflect oil back to the impeller from the turbine. When a sufficient speed ratio between the turbine and impeller is achieved (i.e., the turbine and the impeller are turning at almost the same speed), the one-way clutch of the stator assembly free-wheels because fluid coming from the turbine strikes the back side of the stator blades. Accordingly, an objective of the present invention is to utilize the benefits of a free-wheeling stator during both low and high transmission oil flow. 
   Stator blades encounter varying transmission oil centrifugal forces during operation. For example, during low speed operation the oil is relatively uniform throughout the entire expanse of the stator but during high transmission oil flow, the oil is directed to the outside of the stator by centrifugal force. Accordingly, it is a still further objective of the present invention to provide a stator design which utilizes the centrifugal forces encountered by a stator. 
   It is a further objective of the present invention to provide a torque converter which overcomes the disadvantages of the prior art. 
   It is a still further objective of the present invention to provide a stator which is a simplified form, and is therefore less costly in production and use. 
   These and other objectives will become apparent from the following description of the invention. 
   SUMMARY OF THE INVENTION 
   The foregoing objectives may be achieved using a stator with long and short blades that increase torque to an automatic transmission by employing reaction force produced when a flow of transmission oil within the torque converter impinges an exterior surface of the blades. The plurality of circumferential short blades are for increasing torque during times a vehicle is starting or accelerating and for permitting unobstructed fluid coupling when the turbine and the impeller are at a coupling point. 
   According to another feature of the present invention, the stator has a bossed portion and a circumferential ring portion, the long blades attached to the boss portion and the circumferential ring portion and the short blades only attached to the boss portion. 
   According to another feature of the present invention, the short stator is approximately 30%–60% of the long length of the long blade. 
   According to a still further feature of the present invention, the long and short blades are in close proximity to the impeller blades and extend beyond a stator plane defined by the impeller facing side of the circumferential ring. 
   According to a still further feature of the present invention, a stator has a one-way clutch that prevents movement from the stator during times of increasing torque and permits idling at the coupling point. 
   According to a still further feature of the present invention, a stator is produced in a one-piece configuration. 
   According to a still further feature of the present invention, the stator has an equal number of long and short blades and alternates them around the perimeter of the stator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of the stator in use showing the fluid flow between the impeller, turbine, and stator. 
       FIG. 2  is an exploded view of the turbine, impeller, and stator in between. This Figure illustrates the flow of the transmission oil through these three parts and illustrates the rotational direction of the parts. 
       FIG. 3  is a top view of the stator of the present invention. 
       FIG. 4  is a cross-sectional view taking along line  4 — 4  of  FIG. 3 . 
       FIG. 5  is a side view of the stator as illustrated in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference to the drawings, reference numeral  10  generally designates a torque converter stator. In  FIG. 1 , the torque converter stator  10  is shown in use in a torque converter  12  used in an automatic transmission. 
   Within the torque converter  12 , a turbine  16  is provided having blades or vanes  18 . A converter shell  20  is rotatably attached to an input shaft  22  and an impeller or pump  24  is fixed to the converter shell  20 . The impeller has blades or vanes  26 . The output of an engine (not shown) is transmitted to the input shaft  22 . 
   The turbine  16  is disposed in the converter shell  20  such that its oil inlet side faces the oil outlet side of the impeller  24 . The turbine  16  is coupled to an output shaft  28  of the torque converter  12  that serves as an input into the transmission  14 . 
   The stator  10  is disposed between the turbine  16  and the impeller  24 . The stator  10  is attached to a hollow stationary shaft  27  via a one-way clutch  30 . The output shaft  28  slides up through the hollow stationary shaft  27  and is attached to the turbine. A circulation path is formed through which an oil flows in the direction of arrows in  FIG. 1  when the impeller  24  is rotated. The impeller  24  and turbine  16  have cores  32 ,  34  so as to increase the rigidity with which each blade array is mounted and to partially define the oil circulation path. 
   As seen in  FIG. 2 , fluid moves through the torque converter along path F. The rotation of the turbine and impeller are illustrated by arrows Rt and Ri, respectively. The rotation of the stator  10  is indicated by Sf which stands for stator free-wheeling direction and S 1  stands for stator locked position. 
   As seen in  FIG. 3 , the stator  10  has a plurality of long blades  40  and short blades  42 . These blades  40 ,  42  cooperate to increase torque which is input to the automatic transmission by employing reaction force which is produced when a flow of oil within the torque converter impinges an exterior surface of the blades. The long blades  40  are provided radially on the circumference of a boss portion  44  and extend to an outer circumferential ring portion  46  so as to become integral with both the boss portion  44  and the circumferential ring portion  46 . 
   The short blades  42  are provided radially on the circumference of the boss portion  44  and terminate short of the circumferential ring portion  46 . 
   The distance between the boss portion  44  and the circumferential ring  46  is approximately 4.2 centimeters (cm). The long blades  40  extends the entire 4.2 cm. In contrast, the short vane  42  extends approximately 1.9 cm from the boss portion  44  or approximately 45% the length of the long blade. The short blade may be sized to be between 30%–60% the length of the long blade. Alternatively the short blade may be any percentage of length of the long blade. 
   As seen in  FIGS. 2 and 4 , the stator blades  40 ,  42  have a front side  50  and a back side  52 . The one-way clutch  30  prevents movement of the stator  10  when oil impinges the front side  50  and permits movement (i.e., idling) when oil impinges the back side  52  when at a coupling point as described below. 
   The stator  10  has blades  40 ,  42  in close proximity to the blades  26  of the impeller  24 . In this position, the blades  40 ,  42  improve acceleration by changing the direction of transmission oil better so that it does not hit the impeller at an incorrect angle. As seen in  FIGS. 1 and 5 , the stator blades  40 ,  42  extend beyond a stator plane defined by the impeller facing side  56 . Opposite the impeller facing side  56  is the turbine facing side  54 . 
   The stator  10  is constructed as one-piece. A shown in the figures, the stator  10  has eighteen blades  40 ,  42  with nine long blades  40  and nine short blades  42 . The blades  40 ,  42  alternate between long blade  40  and short blade  42 . It is to be understood that any number of short and long blades  40 , 42  may be used. 
   The long and short blades  40 ,  42  cooperate to redirect oil when there is a large speed ratio between the impeller and turbine. As the speed ratio between the impeller and turbine approaches 1:1, the windows that are created by having a short vane  42  permit better coupling of the impeller  24  and the turbine  16  such that oil flows better. In operation, the stator  10  serves to change the direction of flow of oil. As the speed ratio approaches 1:1 where the impeller  24  and turbine  16  are rotated at substantially the same speed, the direction of flow of the oil into the stator  10  is changed and causes a reverse affect as oil strikes a back side of the blades  40 ,  42 . In this case, therefore, the stator  10  is brought into an idling condition by means of a one-way clutch  30  where the stator  10  free-wheels. As a result, the oil flows into and out of the stator  10  in substantially the same direction and the stator  10  does not exert a force to change the flow direction of oil. At this point of operation, the stator is at a “coupling point”. At the coupling point, the predominant amount of oil is thrown to the outside of the stator thereby the blades  40 ,  42  do not inhibit the flow of oil. 
   Changes in the direction of flow of the oil toward each blade  40 ,  42  of the stator will now be described. When a vehicle is just starting or accelerating, the oil strikes the front side  50  (concave side) of a blade  40 ,  42  of the stator  10  and the direction is changed by the maximum angle because the one-way clutch  30  prevents the stator  10  from rotating. When the speed ratio changes until it reaches the coupling point, the oil flows into and out of the stator  10  by substantially the same angle. The speed ratio is further increased to be close to one, the flow of oil hits the rear face  52  (convex face) of the blade  40 ,  42  and the stator is brought into an idling position. 
   The oil striking the rear face of the blades  40 ,  42  interrupts the smooth flow of oil between the impeller  24  and turbine  16 . The windows provided by using short blades  42  increases the flow rate of the circulating oil as compared to a stator only having long blades  40 . 
   The invention has been shown and described above with the preferred embodiments, and it is understood that many modifications, substitutions, and additions may be made which are within the intended spirit and scope of the invention. In the foregoing, it can be seen that the present invention accomplishes all of the stated objectives.