Power plants – Pressure fluid source and motor – Coaxial impeller and turbine unit
Reexamination Certificate
2001-03-27
2003-05-20
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Coaxial impeller and turbine unit
C137S312000, C137S625640
Reexamination Certificate
active
06564546
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a system which hydraulically alters and varies the preset revolutions per minute (RPM) stall range of a torque converter associated with an automatic transmission of an engine while maintaining or improving its coupling efficiency.
BACKGROUND OF THE INVENTION
The torque converter is used in all automobiles that have an automatic transmission. It is physically connected to an engine's crankshaft on one side, and both mechanically and hydraulically to the transmission on the other. The basic function of the torque converter is to effectively couple the engine's power to the transmission and remaining drive train during each phase of a vehicle's operation and movement. It serves two primary functions: It acts as a fluid coupling that smoothly transfers engine torque to the transmission, and it also multiplies this torque when additional performance is desirable. To make the converter an efficient driveline component, Its size and configuration must be determined to meet the requirements of each automotive application.
During operation it must first permit a certain amount of slippage (stall speed) in order to assist engine in getting into its power (torque) range. This will allow for smooth engine operation each time the vehicle starts from rest and begins to accelerate. All torque converters are manufactured with a preset RPM stall (slip) range. The proper stall setting is predetermined by a number of automotive application factors. These include the following: A) How the vehicle is used and how much it weighs, B) The amount of torque the engine produces and it's RPM torque (power) curve, and C) The vehicle's rear axle ratio and tire size. Changes to any of these factors will likewise affect the operation of the torque converter, and hence on the performance of the vehicle. When any of these factors are permanently changed the torque converter must be mechanically reworked to achieve the desired RPM stall speed, particularly in high performance vehicles.
Once a vehicle is in motion the initial slippage (stall speed) is nearly eliminated through the inherent fluid dynamics of the torque converter. The engine and transmission are considered to be “fluid coupled” at that point. Any remaining slippage is viewed as the torque converter's coupling inefficiency. This is typical for any type of “non-lockup” type converter.
When a torque converter slips during any phase of vehicle operation, the engine's energy used to cause the slippage is converted to heat. This heat is transferred to the transmission fluid and subsequently to the transmission itself.
Converter Assembly
The torque converter is designed with three basic circular components: 1) the impeller or pump (driving component), 2) the turbine (driven or output component), and 3) the stator (reaction component). The stator allows the converter to multiply torque. Without this component the converter would be just a fluid coupling. It would only be capable of transferring an engine's torque and not multiply it.
These components are assembled in a specific position relative to each other and enclosed in a fluid filled circular steel housing. The impeller is secured to the “transmission side” of the converter housing. The turbine is located opposite the impeller and can rotate freely before being splined to the input shaft of the transmission. The stator is positioned between each of these components. It is mounted on a one-way roller clutch that is splined to the stationary stator support that projects from the front of the transmission. Each of these components incorporates a series of radial fins or blades that permit continuous fluid flow between them. One side of the converter housing is bolted to the flex plate that rotates with the crankshaft of the engine. The other side has an open hub that is indexed into the front pump of the transmission.
Normal Torque Converter Operation
Whenever an engine is run, the converter housing rotates and spins the front pump of the transmission. This action causes the entire transmission hydraulic system to become pressurized. This includes keeping the torque converter full and pressurized (50 to 80 psi). The transmission hydraulic system also provides a continuous flow of fluid in and out of the converter, and directs the existing heated fluid to the transmission oil cooler. However, this fluid transfer and flow do not provide the necessary force to turn the transmission's input shaft. The fluid flow through the action of the converter's three main internal components provides the torque transfer through the converter. This fluid movement is known as “rotary flow” and “vortex flow”.
Since these components form a closed unit, the fluid flow is a varying but continuous process. Rotary flow describes the fluid movement in the direction of the converter rotation around the centerline of the transmission input shaft. When the impeller and turbine components are rotating at nearly the same speed the fluid movement is considered to be at nearly 100% rotary flow and the converter at its maximum “coupling phase”. Conversely, when the fluid is circulating through all three components in a spiral path and there's great difference in rotational speed between the impeller and turbine, the fluid movement is considered to be nearly all vortex flow and the converter is at or near it's “stall phase”. This flow causes the engine's input torque to become multiplied.
Acting as a centrifugal oil pump, the impeller component initiates and maintains fluid flow as it rotates. The fluid is pumped from the impeller into the turbine. It travels in a circular motion in the direction of engine rotation. As the high velocity oil flow strikes the turbine, it's force tries to make it rotate in the same direction. When an engine is idling, the force of this oil flow is not great enough to turn the turbine. If it were, the engine would stall with the vehicle stopped in gear. As the engine speed is increased from idle, the impeller speed also increases. Subsequently, the fluid flow and force to the turbine are also increased. This allows the turbine to transmit greater engine torque to the transmission. When the oil leaves the turbine it flows through the stator component. The stator redirects and accelerates the oil back into the impeller. This action increases both the velocity and force of the oil against the turbine fins, thereby multiplying (converting) the torque of the engine.
When a vehicle is standing still, with the transmission in gear, and the brakes applied, the torque converter is capable of multiplying engine torque by two-to-one or more when the engine's throttle is applied. This is considered the “turbine stall”, or more commonly known as “converter stall”. The maximum engine speed at which the turbine can be held stationary is known as the “rated stall RPM”. The stator component is designed in such a way that it redirects the flow of oil back to the impeller in different ways depending on the speed and direction of the oil after it leaves the turbine. When the turbine is stalled, the oil leaves at a high angle striking the broad portion of the stator's blades. This locks the one way roller clutch in the stator and prevents it from rotating. This causes an increase in the force and velocity of the oil (vortex flow) as it approaches the impeller. When the vehicle and turbine speed increases, the centrifugal force of the oil leaving the turbine also increases until it approaches the speed of the impeller. This also causes a change in the direction of oil flow leaving the turbine, so that it now strikes the back of the stator's blades. As this occurs, the roller clutch automatically releases and the stator is able to freewheel. At this point (the converter's coupling phase), the stator will rotate in conjunction with the speed of the impeller, turbine and oil (rotary flow). When all the torque converter's components (including the fluid) rotate as a single unit, th
FB Performance Transmission Inc.
Kershteyn Igor
Look Edward K.
Walker Alfred M.
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