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The invention relates to a compressor housing, a turbocharger comprising such a compressor housing, the use of such a turbocharger and a method of manufacturing such a compressor housing.
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A turbocharger compressor and a plastic compressor housing are known from
US2010/0232955 . This compressor is a radial or centrifugal compressor. The plastic compressor housing defines at least a part of a compressor wheel compartment for a compressor wheel, a spiral shaped compressor passage, and a diffuser. With the rotational speed of the compressor wheel, fresh air is drawn in axially, wherein the fresh air is accelerated by means of the wheel to high velocity and then expelled in a radial direction. The diffuser's function is to slow down the high-velocity air, with minimal losses, so that both pressure and temperature rise. The spiral shaped compressor passage collects the air and slows it down further before it reaches the compressor passage outlet.
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A turbocharger should be reliable and preferably lowers the overall emissions of the engine. With the mass production of turbochargers it is important that the turbocharger comprises of a minimum number of parts. Further, those parts should be easy to manufacture and easy to assemble, in order to provide a cost effective turbocharger.
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It is an object of the present invention to provide a plastic compressor housing improving the performance of a compressor.
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This object is achieved by a compressor housing according to claim 1.
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An advantage of plastic compressor housings compared to conventional aluminum compressor housings is the greater freedom in design for cost efficiently manufacturing the compressor housing and improving the performance of the compressor as well. An additional advantage of plastic is that it is possible to manufacture a lightweight compressor housing. In the manufacturing process of a plastic compressor housing it is possible to reduce the material to be used by providing hollow spaces or thinner parts in less strength-critical areas of the compressor housing. In the strength critical areas of the plastic compressor housing, it is relatively simple to provide plastic supporting ribs or the like. Further, it is possible in a cost effective way to include in the manufacturing process different functions in the plastic compressor housing. In other words, it is relatively easy to provide openings for positioning reinforcing elements and/or a screw thread or other connecting shapes in the plastic design for connecting the compressor housing for example to a center hub rotating assembly of a turbocharger.
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An important feature of plastic is its relatively low thermal conductivity, i.e. plastic is a thermal insulator. The insulating plastic walls of the diffuser and the spiral shaped compressor passage provide a good insulating shield to protect the air being compressed inside the compressor against the external heat produced by external components such as for example the combustion engine. The shielding effect has the result that the air temperature inside the compressor is less heated by external influences such that in relative terms compared to aluminum more compression with the compressor can be achieved.
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By using plastic it is further possible to design without complex manufacturing steps an arched or bent design of a diffuser channel for deflecting air tangentially and/or axially in the diffusor channel between the inlet and the outlet. The plastic inner walls of the diffuser channel are arch-shaped or bent between the inlet and the outlet. The arched diffuser optimizes flow patterns of the air to be compressed thereby increasing the performance of the compressor. The inner walls of the arched diffuser channel have a radius of curvature over more than 75% of the complete distance between diffuser inlet and diffuser outlet. In a diffuser channel having at least two radii of curvature, the centers of the at least two radii of curvature are located on one side of the diffuser only. In this way the diffuser defines a smooth arched flow path without any opposing bents, such as a first bend having a radius of curvature on a first side of the diffuser and a second bend having a radius of curvature on a second opposing side of the diffuser. By providing the centers of the at least two radii of curvature on one side of the diffuser only an optimal air flow is provided through the diffuser to the spiral shaped compressor passage increasing the performance of the compressor.
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In an embodiment, the compressor housing is made as one-piece plastic compressor housing. The one-piece plastic compressor housing does not require any joining steps in the manufacturing process. As a result, the inner walls of the diffuser and/or the spiral shaped compressor passage do not have any joining seams. A seam-free compressor housing optimizes air flow and further increases the performance of the compressor housing.
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In another embodiment, the spiral shaped compressor passage comprises an outlet for supplying compressed air to at least one cylinder for combustion, wherein an end of the spiral shaped compressor passage opposing the outlet is closed. In other words this end is a dead end located at the start of the passage preventing air to enter directly in a wider diverged part of the passage located closer to the outlet of the passage near the cylinder. In this way the air collected in the passage near the closed end is forced to flow through the spiral shaped passage to the cylinder. By providing a closed end or a closed scroll, the airflow in the wider diverged part of the passage near the closed end is no longer disturbed, such that airflow and compression of the air are optimized in the compressor housing.
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In a further embodiment, the housing comprises a hollow space between the compressor wheel compartment and the spiral shaped compressor passage. This hollow space or spaces reduce the weight and material to be used for manufacturing the compressor housing. The hollow space or spaces can be in fluid connection with the diffuser channel and the compressor compartment for recirculating air. It is also possible that the hollow space(s) is in fluid connection with different parts of the compressor compartment for recirculating air only in the compressor compartment. These fluid connections for recirculating air widen the compressor performance map by moving the surge line to the left in the compressor performance map by allowing a small amount of airflow to bleed off the low-velocity portion of the wheel and recirculate, to ward off blade stall. The main advantage of a compressor housing made from plastic is that these fluid connections can be established in an uncomplicated manner and in a cost-effective way.
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In another embodiment the compressor housing comprises a center axis, which coincides in an assembled compressor with the axial axis of the compressor wheel, wherein the distance measured in a axial direction parallel to the axial axis of the compressor wheel between the center of the spiral shaped compressor passage and the center of the diffuser inlet is at least two times the distance measured in the axial direction between the center of the spiral shaped compressor passage and the inner wall of the spiral shaped compressor passage. This design of the arched diffusor in relation to the spiral passage provides a compressor housing improving the compression performance of the compressor.
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To explain the invention in more detail, exemplary embodiments thereof will hereinafter be described with reference to the accompanying drawings, wherein:
- Figure 1 shows a section of a turbocharger according to the present invention;
- Figure 2 shows a section of a compressor having a compressor housing according to the present invention;
- Figure 3 shows a schematic view of a part of a compressor housing according to the present invention;
- Figure 4 shows a section of another embodiment of a compressor housing according to the present invention.
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In this description, identical or corresponding parts have identical of corresponding reference numerals.
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Figure 1 shows a section of a turbocharger 10 according to the present invention. Turbochargers 10 have become more and more popular for use in connection with passenger car engines, because the use of a turbocharger 10 permits selection of a smaller engine that develops the same amount of horsepower. Using a smaller and a lower mass engine together with a turbocharger 10 has the desired effect of decreasing the overall weight of the car, decreasing fuel consumption and reducing the overall emissions of the engine, which contributes to a cleaner environment.
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The turbocharger 10 includes a turbine 3 operatively connected to the engine exhaust manifold (not shown), a centrifugal compressor 1 operatively connected to the engine air intake manifold (not shown), and a center hub rotating assembly 5 housing a shaft 7 that connects the compressor wheel 9 with the turbine wheel 11.
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The turbine wheel 11 is driven to rotate by the exhaust gas flowing in the exhaust manifold. Rotation of the turbine wheel 11 causes by means of the shaft 7 rotation of the compressor wheel 9. As the compressor wheel 9 rotates in the compressor housing 15, it increases the air mass flow rate, airflow density and air pressure delivered to the engine cylinders (not shown).
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The compressor housing 15 is shown in greater detail in figure 2. The compressor housing 15 is adapted to receive air from an air intake 17 and distribute the air to a compressor wheel 9 rotatable disposed around an axial axis 19 within the compressor housing 15 and coupled to an end of the shaft 7. The compressor housing 15 provides a compressor wheel compartment 21 for the compressor wheel 9, a spiral shaped compressor passage 23, and a diffuser 25 interposed between the compressor wheel 9 and the spiral shaped compressor passage 23. The spiral shaped compressor passage 23 is formed along an outer region and radially remote from the compressor wheel 9.
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The diffuser 25 has inner walls 26, 28 defining a diffuser channel 30, an inlet 31 in fluid communication with the compressor wheel compartment 21 for radially receiving high-velocity fresh air axially drawn in by means of the compressor wheel 9 and an outlet 33 in fluid communication with the spiral shaped compressor passage 23. The distance between the inlet 31 of the diffuser channel 30 and the radially most remote compressor wheel tip 39 is smaller than 10 mm. In addition, the distance d between the opposing inner walls 26, 28 in the middle section of the diffuser is about 4 mm. As shown in figures 1 and 2 the distance between the opposing inner walls 26, 28 near the inlet 31 and/or near the outlet 33 may be somewhat larger than the distance d, but this distance is smaller than 2 times the distance d.
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The plastic inner walls 26, 28 of the diffuser channel are curved providing an arched designed diffuser channel 30 between the inlet and the outlet for deflecting air tangentially and/or axially in the diffusor channel between the inlet and the outlet. Using the thermal insulating properties of plastic and the optimized airflow by means of the arched design of the diffuser channel 30 a significant increase of the compressor performance is achieved. By means of the arched design of the diffuser it is also possible without increasing the outer dimensions of the compressor housing to provide a longer diffuser channel. The longer diffuser channel improves the compressor performance further. It is also possible to provide a more compact compressor housing by means of an arched diffuser 25. With the arched diffuser 25 the passage 23 can be moved closer to the compressor wheel 9 thereby providing a reduction in the outer dimensions of the compressor housing 15.
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The compressor housing 15 shown in figures 1 and 2 is made as one-piece plastic compressor housing 15. Such a one-piece plastic compressor housing 15 has no joining seams, which has a beneficial effect on the air flowing through the seam-free diffuser 25 and seam-free spiral shaped compressor passage 23. Compressor 15 can be manufactured by additive manufacturing such as laser sintering and/or by subtractive manufacturing. It is also possible to use lost core technology to manufacture the compressor housing 15.
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The compressor housing 15 comprises a center axis 41, which as shown in figures 1 and 2 coincides in an assembled compressor 1 with the axial axis 19 of the compressor wheel 9.
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The distance A1 measured only in a axial direction parallel to the axial axis 19 between the center 45 of the spiral shaped compressor passage 23 and the center 47 of the diffuser inlet 31 is about two times the distance A2 measured in the axial direction only between the center 45 of the spiral shaped compressor passage 23 and the inner wall 49 of the spiral shaped compressor passage 23. The position to measure these distances is preferably where the diameter of the passage reaches or has reached its maximum diameter. A preferred area is about 270°-360° measured from the start of the passage. In this preferred area of the spiral shaped compressor passage 23 the maximum distance A1 is preferably sixth times the distance A2. By means of such a design it is possible to achieve more performance within a restricted radial volume.
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Figure 3 shows a schematic view of a spiral shaped compressor passage 23 of a compressor housing 15 according to the present invention. The spiral shaped compressor passage 23 comprises a passage outlet 51 for supplying compressed air to at least one cylinder (not shown) for combustion. The passage 23 diverges in the direction of the outlet 51, such that the cross sectional area of the passage 23 smoothly increases. An end 53 of the spiral shaped compressor passage 23 opposing the outlet 51 is closed. By providing a closed end 53 in the passage 23, the airflow in the wider diverged part Z of the passage 23 near the closed end 53 is no longer disturbed, such that airflow and compression of the air in the passage 23 are further optimized. The closed end is located at a distance smaller than 3 cm of the outer wall of the spiral shaped compressor passage.
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In figure 4 a section of another embodiment of a compressor housing 115 according to the present invention is shown. The compressor housing 115 is made of four plastic components 2, 4, 6, 8 defining the compressor wheel compartment 121, the passage 123, the diffuser 125, and the air intake 117. These plastic components 2, 4, 6, 8 can be joined together by means of hot gas welding. The advantage of hot gas welding two plastic components is high-quality seams. Such high-quality seams reduce the impact of a seam to the air flow. Other joining techniques like ultrasonic welding or adhering can also be used to join the components. The position of a seam can be chosen such that the influence of the seam of the air flow is negligible. By using plastic it also possible in an uncomplicated manner to shape each component to integrate various functions therein such as complementary shapes of the component parts to be connected together for providing a stronger connection. It is also possible to use different types of plastic for each component. For example, component 8 can be manufactured from a plastic type having a lower quality than the plastic type of the other components 2, 4, 6.
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Though not shown, it is preferred to provide a housing 115 in which the components 2, 4, 6, 8 are joined such that the passage 23 is seam-free. It is also possible to reduce the number of plastic components 2, 4, 6, 8, if desired.
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The compressor housing 115 comprises a hollow space 122 between the compressor wheel compartment 121 and the spiral shaped compressor passage 123. The dimensions of the spiral-shaped hollow space 122 change over 360 degrees and preferably these dimensions change inversely proportional with the dimensions of the spiral shaped compressor passage 123. The hollow space may comprise various compartments or multiple spaces separated by reinforcing ribs or the like. This hollow space 122 reduces the weight and material to be used for manufacturing the compressor housing 115.
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The hollow space 122 can be in fluid connection (not shown) with the diffuser channel 125 and the compressor compartment 121 for recirculating air. It is also possible that the hollow space 122 is in fluid connection (not shown) with different parts of the compressor compartment 121 only for recirculating air.
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The turbocharger 10 shown in the figures comprising a plastic compressor housing 15 preferably manufactured of polyphenylene sulfide.
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The compressor housing according to the present invention can be made from any suitable thermosetting polymers such as for example phenol formaldehyde resin or any suitable high temperature thermoplastic polymers such as for example polyphenylene sulfide.
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It is possible that the closed end 53 is located against the outer wall of the spiral shaped compressor passage 23.
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The plastic turbocharger compressor housing 115 can be manufactured by injection molding and assembling e.g. welding and/or screwing.
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The compressor housing according to the present invention can also be used in an electrically driven or supported flow compressor or a secondary air charger.
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It is also possible to provide a turbocharger compressor housing manufactured of plastic material, wherein the housing comprises at least a part of a compressor wheel compartment for a compressor wheel, and a spiral shaped compressor passage the spiral passage comprises an outlet for supplying compressed air to at least one cylinder for combustion, wherein an end opposing the outlet is closed. Such a compressor housing can be combined with any of the above features and it is further possible to use this housing having a closed end without an arched diffuser.
