The present invention relates generally to a housing with a mounting flange for connecting the housing to another device and, more particularly, the invention relates to a center housing with a mounting flange for connecting the center housing to a turbine housing of a turbocharger.
Turbochargers for gasoline and diesel internal combustion engines are devices known in the art that are used for pressurizing or boosting the intake air stream of the engine by using the flow of hot exhaust gas exiting the engine. The turbocharger typically includes a turbine housing with an inlet that receives exhaust gas exiting the engine such that the exhaust gas spins a turbine in the turbine housing. The turbine is mounted in the turbine housing on a shaft that is common to a radial air compressor housed in a compressor housing. Thus, rotary action of the turbine also causes the air compressor to spin within the compressor housing. The spinning action of the air compressor causes intake air to enter the compressor housing and to be pressurized or boosted a desired amount before it is mixed with fuel and combusted within a combustion chamber of the engine.
The turbine and compressor housings are typically mounted on first and second opposite sides of a center housing. The shaft extends between the turbine and the compressor through a bore in the center housing. An annular area of the first side of the center housing that extends around the shaft can be exposed to the inside of the turbine housing and, hence, the hot exhaust gas passing therethrough. The center housing also has a turbine mounting flange that extends radially outward from the first side of the center housing and is bolted to the turbine housing.
The center housing can define one or more lubricant passages for providing lubricant to the shaft and one or more coolant passages for circulating a coolant fluid such as water. The coolant passage can be an annular passage in the center housing that is proximate to the first side of the center housing and to the turbine housing. As a result of the difference in temperature between the hot exhaust gas in the turbine housing and the relatively cool lubricant and/or coolant fluid in the passages, high thermal gradients result in the center housing causing thermal stresses to develop. Thermal stress can also result from the temperature variations that occur over time during operation of the turbine. For example, the center housing is exposed to thermal transients, or variations, due to changes in the engine exhaust gas temperature over time that occur during normal engine operation. These thermal transients typically result in alternating cycles of heating and cooling of the center housing. During the heating cycles, the center housing can become hot enough to plastically deform, and stresses in the center housing that occur during the cooling cycles can be great enough to cause cracks to form. The likelihood of cracking or other stress damage is often greatest near features in the center housing, such as bolt holes that are provided in the mounting flange. Further, when liquid coolants such as water are circulated through the coolant passage, the higher cooling effect can result in even greater thermal gradients and greater or faster temperature variations in the center housing, thereby increasing the stress in the center housing and increasing the likelihood of cracking. Cracks that originate in the mounting flange can cause the housing to leak or otherwise fail.
Thus, there exists a need for an improved center housing that is characterized by reduced thermal stresses resulting from temperature variations during heating and cooling and from thermal gradients that exist between the hot exhaust gas and the relatively cooler lubricant and/or cooling fluid. The center housing design should reduce the likelihood of cracking or other failure of the center housing, for example, when cool liquid coolants are circulated through passages in close proximity to the first side of the center housing, which is exposed to the hot gas from the turbine housing.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
Referring to
As illustrated in
The center housing 40, shown individually in
As shown in
A mounting flange 70 extends in a generally radial direction from the housing body 44, e.g., from the central block portion 56, for mounting or connecting the center housing 40 to the turbine housing 20. The mounting flange 70 can be formed as an integral part of the housing body 44, and the flange 70 can include a connection portion 72 that defines one or more connection features 74 such as bolt holes or pin holes for receiving bolts, pins, or other connection devices that extend into corresponding holes or otherwise engage features in the turbine housing 20. The mounting flange 70 also defines a curved portion 76 that extends circumferentially around at least part of the housing body 44 and is disposed between the housing body 44 and the connection portion 72. At least a portion of the circumference of the flange 70 is curved or c-shaped in cross-section, with the curved portion 76 extending generally radially outward from the housing body 44, and the connection portion 72 extending further radially outward from the curved portion 76. The curved portion 76 of the mounting flange 70 has a generally c-shaped cross-section defined by c-shaped inner and outer surfaces 78, 80, such that the curved portion 76 defines a space 82 between the housing body 44 and the connection portion 72. As illustrated in
The inner surface 78 of the curved portion 76, as well as the first side 46 of the housing body 44, can be exposed to the exhaust gases in the turbine housing 20 through the aperture in the turbine housing 20. Thus, the center housing 40 is contacted and heated by the turbine housing 20 and the exhaust gas, which can reach temperatures of 1450° F. or higher. The center housing 40 is cooled by the coolant fluid circulated through the coolant passage 58, which is typically about 250° F., and by the lubricant. The center housing 40 can also be cooled, though usually to a lesser extent, through convection by air outside the center housing 40. Due to the temperature difference between the hot exhaust gas in the turbine housing 20 and the relatively cool fluid in the coolant passage 58, a spatial thermal gradient exists in the center housing 40. For example, a temperature difference of about 1200° F. can exist in the center housing 40 over a distance of 3 inches or less, though the actual thermal gradient, or temperature difference per unit length, is usually complex, having different values at different locations throughout the center housing 40.
The center housing 40 can be formed of various types of materials. In some cases, the material may have properties enabling it to resist cracking or other failure when subjected to the thermal gradient. However, in other cases the center housing 40 may be formed of a material that is susceptible to cracking when the thermal gradient is coincident with portions of the center housing 40 where stress concentrations are likely to occur, such as bolt holes. For example, the center housing 40 can be formed of cast iron, which can be strong enough to undergo repeated stresses associated with thermal gradients, especially if a large annular flange is provided for connecting the center housing 40 to the to the turbine housing 20. However, the cast iron of the center housing 40 can be susceptible to cracking by the thermal gradients if the gradients are coincident with a bolt hole or other geometric feature that concentrates stress.
The curved portion 76 of the mounting flange 70 at least partially thermally decouples the connection portion 72 of the flange 70 from the housing body 44, i.e., the curved portion 76 at least partially isolates the connection portion 72 from thermal effects in the housing body 44. Thus, although high temperatures may develop in the connection portion 72, the maximum temperature difference, and hence the maximum thermal gradient, in the connection portion 72 of the flange 70 is substantially less than that in the housing body 44. For example, if the temperature difference between the exhaust gas and the coolant fluid is about 1000° F., the temperature difference throughout the connection portion 72 of the flange 70 is typically less than about 100° F., while the temperature difference throughout the housing body 44 can be several times as great. Further, the temperature difference is typically even less in each local area that surrounds the connection features 74 in the connection portion 72. Therefore, the high stresses associated with the thermal gradient are not substantially coincident with the connection features 74 in the connection portion 72 of the flange 70, and the likelihood of failure, such as by cracking near the connection features 74, is reduced. It is understood that some thermal gradient may be present in the connection portion 72 and that the magnitude of the thermal gradient present in the connection portion 72 may vary according to such factors as the shape and dimensions of the housing body 44 and mounting flange 70, the material used to construct the housing body 44 and the mounting flange 70, the location of the coolant passage 58, the temperatures and flow rates of the exhaust gas and coolant fluid, the type of fluid coolant, and others.
The curved portion 76 of the mounting flange 70 also increases the flexibility of the flange 70, which leads to a decrease in the stresses caused by thermal variations throughout the center housing 40. During normal operation of the turbocharger, the center housing 40 can undergo repeated thermal variations, i.e., temperature changes over time. For example, when exhaust gas begins to flow through the turbine housing 20, the turbine housing 20 and the center housing 40 are heated. The temperature of all or part of the center housing 40 can fall, for example, when the temperature of the exhaust gas from the engine decreases, as typically occurs cyclically during normal operation. Such temperature variations can result in thermal expansion or contraction of the center housing 40 and/or thermal stress in the center housing 40. However, because the curved portion 76 of the flange 70 is disposed at least partially outside a radial plane defining the connection portion 72, thermal expansion and contraction of the flange 70 can occur in a non-radial direction, e.g., in an axial direction perpendicular to the plane of the connection portion 72. Thus, the shape and size of the flange 70 can change without corresponding movement of the connection portion 72 of the flange 70, and the resulting stress in the connection portion 72 of the flange 70 is reduced.
Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
This application is a continuation of U.S. application Ser. No. 10/376,048, filed Feb. 26, 2003, now U.S. Pat. No. 6,682,321 which is hereby incorporated herein in its entirety by reference.
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Number | Date | Country | |
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20040166003 A1 | Aug 2004 | US |
Number | Date | Country | |
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Parent | 10376048 | Feb 2003 | US |
Child | 10737382 | US |