Power plants – Pressure fluid source and motor – Coaxial impeller and turbine unit
Reexamination Certificate
1999-10-01
2001-07-31
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Coaxial impeller and turbine unit
C060S365000, C416S180000, C416S19700C, C416S19300A, C416S19600R, C416S22300B, C416S243000, C416SDIG005
Reexamination Certificate
active
06266958
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a stator wheel for a hydrodynamic torque converter comprising a stator wheel hub arrangement and a plurality of stator wheel blades arranged successively in the circumferential direction on the stator wheel hub arrangement. Each stator wheel blade has a radial inner flow-around profile area and a radial outer flow-around profile area and the flow-around profile in the radial outer flow-around profile area differs from the flow-around profile in the radial inner flow-around profile area.
2. Description of the Related Art
Hydrodynamic torque converters are generally used for transmitting torque in drivetrains of motor vehicles, especially motor vehicles with an automatic transmission, and use the fluid circulating within the torque converter to transmit torque between an impeller wheel and a turbine wheel of the torque converter. The flow of fluid exiting the turbine wheel is conducted into the impeller wheel via a stator wheel. This type of torque converter must be capable of performing the torque transmission coupling function or converter function over a wide range of operating states of a drive system. A high starting conversion is required particularly in the starting range in which the turbine wheel is initially at a standstill and only the impeller wheel is driven by the engine. However, a very high efficiency is required in the normal driving state in which the ratio of the turbine speed to the impeller speed is in a range of greater than 0.8. The different components used in a torque converter, in particular the turbine, impeller and stator, may have configurations which are adapted to the respective requirements, especially in the area of their respective blades. However, since the torque conversion on the one hand and the torque transmission without conversion on the other hand require different blade geometries to achieve optimum function in each particular case, compromises must be made so that the blades in torque converters have acceptable characteristics for both the starting range and normal driving operation. Accordingly, it is known, for example, to construct the stator wheel blades in such a way that they have a blade flow-around profile designed for the starting range in a radial inner area and a flow-around profile designed for normal driving operation or continuous operation in the radial outer area. A continuous transition of the profile takes place between the radial inside and radial outside of the stator wheel. The final result of this compromise is that the torque converter has no optimum characteristic for virtually any operating state.
A prior art torque converter is disclosed in EP 0 846 894 A2 in which the stator wheel blades are divided into a radial inner area and a radial outer area. In the radial inner area, the blades have an inner profile which is optimized essentially for the starting operation requirements. This inner profile extends approximately up to the radial longitudinal center of the blades and passes, via a step, into an outer flow-around profile which is designed for continuous operation in the radial outer area. However, unwanted flow mixtures occur at the step between the inner profile and the outer profile.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a stator wheel for a hydrodynamic torque converter that is further optimized for different operating states.
According to an embodiment of the invention, this object is met by a stator wheel for a hydrodynamic torque converter comprising a stator wheel hub arrangement and a plurality of stator wheel blades arranged successively in the circumferential direction at the stator wheel hub arrangement. Each of the plural stator wheel blades has a radial inner flow-around profile area and a radial outer flow-around profile area and the profile of the radial outer flow-around profile area differs from a profile of the radial inner flow-around profile area.
It is further provided in the stator wheel according to the invention that a first cover ring surrounding the stator wheel hub arrangement and connected with the stator wheel blades is provided in a radial transition area between the radial inner flow-around profile area and the radial outer flow-around profile area.
The separation of the two flow-around profile areas by the first cover ring divides the stator blade into two flow areas. A first flow area, i.e., the radial inner flow area, is optimized for a different operating state than the second flow area, i.e., the radial outer flow area. The cover ring prevents unwanted flow mixtures which occur in the transition area between the radial inner flow-around profile area and the radial outer flow-around profile area in the prior art devices because of the step-like change in the profile that exists in the prior art devices. The efficiency of a torque converter is increased through the integration of a stator wheel according to the invention.
When a second cover ring connected with the stator wheel blades is further provided at a radial outer end area of the stator wheel blades, a virtually completely closed flow channel system is provided for the radial outer flow-around profile area as well as for the radial inner flow-around profile area. This embodiment further improves flow characteristics and consequently improves the efficiency of the stator wheel.
A first stator wheel blade portion comprising the radial inner flow-around profile area may be formed between the stator wheel hub arrangement and the first cover ring, and a second stator wheel blade portion comprising the radial outer flow-around profile area may be provided between the first and second cover rings.
Different configurations may be realized by using the first cover ring and by dividing the individual blades into first, i.e., inner blade portions and second, i.e., outer blade portions which is possible because of the first cover ring. For example, a second stator wheel blade portion may adjoin at least a first stator wheel blade portion in a radially flush manner. Alternatively, the first stator wheel blade portions and the second stator wheel blade portions may be at least partially offset relative to one another in the circumferential direction.
Furthermore, the separation of the inner flow-around profile area from the outer flow-around profile area by the first cover ring enables a free selection of the quantity of respective blade portions in each of these areas. More specifically, a larger quantity of blade portions may be provided in the outer area than in the inner area.
Many embodiments are possible for the cover ring. The choice of the various possible embodiments of the first cover ring to be used depends among other things on the manufacturing method to be selected for producing the stator wheel. In particular, the production of a stator wheel by an axial drawing method makes it possible to construct the stator wheel integral with the fist cover ring. However, a disadvantage in this respect consists in that blades which overlap one another in the circumferential direction cannot be produced by the axial drawing method. However, this configuration may be realized by using a radial drawing method. To ensure in this case also, for example, that the flow turbulence which compulsorily occurs due to the stepped transition in the prior art is prevented in the transition area between the radial inner flow-around profile area and the radial outer flow-around profile area, it is suggested according to another feature of the present invention that a profile transition area with an essentially continuous transition between the flow-around profile of the radial inner flow-around profile area and the flow-around profile of the radial outer flow-around profile area is provided between the radial inner flow-around profile area and the radial outer flow-around profile area.
Since the effect of the radial outer area of the flow circuit is generally strengthened in torque converters when there is a relati
Sasse Christoph
Wienholt Hans-Wilhelm
Cohen & Pontani, Lieberman & Pavane
Leslie Michael
Look Edward K.
Mannesmann Sachs AG
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