Patent Application
20140178188
The present disclosure relates to a turbocharger for engines, and more particularly, to a turbo wheel and shaft assembly for improved turbocharger performance.
This section provides background information related to the present disclosure which is not necessarily prior art.
Turbo charged engines utilize compressed air which results in a larger quantity of air being forced into the engine, creating more power. The energy used to drive the turbo compressor is extracted from waste exhaust gases. As the exhaust gases leave the engine, they are directed through a turbine wheel placed in the exhaust flow. The gases drive the turbine wheel, which is directly connected via a shaft to a compressor wheel. Increased exhaust gas flow drives the turbine wheel faster, providing the engine more air, thereby producing more power. Therefore, the turbocharger uses the extraction of energy from the exhaust gas to improve the engine efficiency.
Turbochargers are usually seen as power enhancement on performance cars, but today, turbochargers are becoming more regularly used to provide greater torque on small capacity engines. The advantages of using a turbocharged engine include improved fuel efficiency and reduced exhaust emissions. The components of the turbocharger generally include a housing defining a compressor chamber and a turbine chamber, a compressor wheel is disposed in the compressor chamber, and a turbine wheel is disposed in the turbine chamber. A turbine shaft is provided for connecting between the turbine wheel and the compressor wheel.
With reference to
It has been a discovery of the present invention, however, that as the seam between the turbine wheel and turbine shaft is welded, residual stresses are formed in the turbine wheel and shaft. These residual stresses are directly related to the heat put into the components during the welding process. The weld operation is performed utilizing a focused beam such as via electron beam welding, although laser welding or friction welding could also be used. After the weld process is completed, a defocused beam can be utilized to broaden the heating operation to relieve some of the residual stresses imparted to the turbine wheel and shaft. However, the turbine wheels and shaft assemblies that have been properly balanced after the welding process are placed in use in a turbocharger in which the temperatures can exceed 600° C. The heating of the turbine wheel and shaft assembly can cause the residual stresses from the welding process to relax that can result in wheel distortion. According to the theory of the discovery of the present application, because the weld location 118 is so close to the turbine wheel, a large amount of heat is required to adequately relieve the residual stresses in the large mass of the turbine wheel.
Accordingly, it is the intent of the present application to move the weld location further away from the mass of the turbine wheel body so that the weld is moved away from the large mass of the turbine wheel and a defocused beam can more easily relieve the residual stresses in the weld location. In addition, by moving the weld location away from the body of the turbine wheel, the weld can be placed in a lower operation temperature location to minimize the effects of weld residual stress relaxation on the wheel imbalance mitigation. Accordingly, the present disclosure provides a turbine wheel and shaft assembly for a turbocharger including a turbine wheel including a body portion supporting a plurality of blades on a first axial face thereof. A hub extends from the body portion on the second axial face. The hub has a predetermined diameter and a length. A shaft is welded to the hub at a weld location spaced from the axial face. The weld location is spaced axially from the second axial face of the body portion by a distance that is at least 50 percent, and more preferably, at least 75 percent of the diameter of the hub.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments will now be described more fully with reference to the accompanying drawings.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
With reference to
According to the principles of the present disclosure, the turbine wheel 40 and shaft 44 are assembled in a unique manner that eliminates the imbalance problem of welded turbo wheel and shaft assemblies. In particular, as shown in
To further reduce the residual stresses, it is advantageous to also reduce the mass of the shaft 44 by providing a hollow cylindrical shaft. In addition, the hub 58 can also be hollowed out in order to reduce the mass in the weld region to thereby eliminate distortion of the parts. It is noted that the removal of the additional mass by providing a hollow shaft 44 and a hollow region within the hub 58 is optional, although it can increase the cooling rates of the parts while also reducing the residual stresses that are generated during the welding process. In the embodiment shown in
According to an alternative embodiment as illustrated in
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
