Compressor wheel with balance correction and positive piloting

Abstract

A turbocharger including, a turbine wheel (10), a shaft (111) attached to the turbine wheel (10), and a compressor wheel (132) disposed on the shaft (111) opposite the turbine wheel (10). The compressor wheel (132) includes a back wall (134) and an axial bore (137) and a pilot washer (150) is located adjacent the compressor wheel back wall (134). The pilot washer (150) has an inner diameter (162) and an outer diameter (160), and includes a conical pilot ring (154) that extends into the axial bore (137) of the compressor wheel (132). The pilot washer (150) includes a slit (164) extending from the inner diameter (162) to the outer diameter (160). A nut (113) is threaded to the shaft (111) and is operative to provide an axial clamping force on the compressor wheel (132), thereby causing the pilot washer (150) to contract onto the shaft (111) as the pilot ring (154) extends into the bore (137).

Claims

1. A turbocharger, comprising: a turbine wheel (232); a shaft (211) attached to the turbine wheel (10) and including a spherical pilot land (250); a compressor wheel (232) disposed on the shaft (211) opposite the turbine wheel (10), wherein the compressor wheel (232) includes an axial bore (237) sized to provide an interference press fit between the pilot land (250) and axial bore (237); a pilot insert (256) positioned on the shaft adjacent a nose end (236) of the compressor wheel (232); and a clamping washer (254) circumscribing the shaft (211) and located adjacent the pilot insert (256).

2. The turbocharger according to claim 1, further comprising a nut (213) threaded to the shaft (211) and operative to provide an axial clamping force on the compressor wheel (232).

3. The turbocharger according to claim 2, wherein the compressor wheel (232) is clamped between the nut (213) and a shoulder (214) disposed on the shaft (211).

4. The turbocharger according to claim 1, wherein the compressor wheel (232) includes a counter bore (238) concentric with the axial bore and sized and configured to receive the pilot insert (256) therein.

5. A turbocharger, comprising: a turbine wheel (232); a shaft (211) attached to the turbine wheel (10) and including a pilot land (250); a compressor wheel (232) disposed on the shaft (211) opposite the turbine wheel (10), wherein the compressor wheel (232) includes: an axial bore (237) sized to provide an interference press fit between the pilot land (250) and the axial bore (237); and a counter bore (238) concentric with the axial bore (237); a pilot insert (256) positioned on the shaft (211) and in the counter bore (238); and a clamping washer (254) circumscribing the shaft (211) and located adjacent the pilot insert (256).

Description

DRAWINGS

(1) Non-limiting and non-exhaustive embodiments of the disclosed technology, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

(2) FIG. 1 is a side view in cross-section of a typical turbocharger;

(3) FIG. 2 is a partial side view in cross-section illustrating a compressor wheel with balance correction and positive piloting according to a first exemplary embodiment;

(4) FIG. 3 is a top plan view of a pilot washer as shown in FIG. 2;

(5) FIG. 4 is a partial side view in cross-section illustrating an alternative construction of the pilot washer;

(6) FIG. 5 is a bottom plan view of a pilot washer illustrating cooperative indexing features of the compressor wheel and pilot washer;

(7) FIG. 6 is a partial side view in cross-section of the pilot washer shown in FIG. 5;

(8) FIG. 7 is a partial side view in cross-section illustrating the nose end of a compressor wheel with positive piloting according to a second exemplary embodiment; and

(9) FIG. 8 is a partial side view in cross-section illustrating the back wall portion of the compressor wheel with positive piloting shown in FIG. 7.

DETAILED DESCRIPTION

(10) Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense. It should be understood that not all of the components of a turbocharger are shown in the figures and that the present disclosure contemplates the use of various turbocharger components as are known in the art. Turbocharger construction is well understood in the art and a full description of every component of a turbocharger is not necessary to understand the technology of the present application, which is fully described and disclosed herein.

(11) FIG. 2 illustrates a compressor wheel with balance correction and positive piloting features according to a first exemplary embodiment. Compressor wheel 132 includes a back wall 134 and a nose end 136. Compressor wheel 132 also includes an axial bore 137 which receives shaft 111. A pilot washer 150 is located adjacent the back wall 134 and includes a conical pilot ring 154, which extends into the axial bore 137. The compressor wheel 132 may include a counter sink 138 that is sized and configured to receive the conical pilot ring 154. The compressor wheel 132 may also be mounted to the shaft 111 with a second pilot washer 150 located at the nose end 136 of the compressor wheel. A nut 113 is attached to the shaft 111 by threads 115. The nut is operative to provide an axial clamping force on the compressor wheel 132, thereby causing the pilot washer 150 to contract onto the shaft 111 as the pilot ring 154 extends into the bore 137. Because the pilot washer is slit the axial loading causes circumferential contraction such that the washer contracts to engage the shaft, thereby creating a rigid pilot. This arrangement provides positive piloting regardless of variation in bore and shaft sizes. This arrangement also helps prevent balance migration as long as the clamp load is maintained. Tolerancing can be more generous and the manufacturing processes more robust. Assembly is much easier with more clearance prior to clamping.

(12) With reference to FIG. 3, it can be appreciated that pilot washer 150 includes a washer portion 152 and a conical pilot ring 154 extending axially therefrom. The pilot washer 150 has an inner diameter 162 and an outer diameter 160 with a slit 164 extending between the inner and outer diameters. Accordingly, the pilot washer 150 includes an aperture 156 defined by the inner diameter 162. As mentioned above, the pilot washer 150 contracts to clamp against shaft 111 as a result of the conical pilot ring 154 being forced into the axial bore 137 of the compressor wheel 132. Accordingly, as the pilot ring 154 is forced into the axial bore 137, the aperture 156 contracts and slit 164 narrows.

(13) It can be appreciated from the figure that slit 164 causes the pilot washer 150 to have a non-uniform weight distribution which may be used to compensate for compressor wheel imbalance. Also shown in FIG. 3 is a material removal region 158. Material may be removed from this region in order to further compensate for imbalance in the compressor wheel 132. Accordingly, the pilot washer may be rotationally positioned with respect to the compressor wheel 132 in order to help compensate for any imbalance in the compressor wheel 132. In this case, the pilot washer is comprised of steel, which is approximately three times the density of Aluminum and approximately twice the density of Titanium.

(14) FIG. 4 illustrates an alternative construction of a pilot washer 151. In this case, pilot washer 151 includes a washer portion 153 with a conical pilot ring 155 similar to that described above with respect to FIG. 3. However, in this case, the pilot washer 151 also includes a stub ring 157 extending from the conical pilot ring 155 in an axial direction. The stub ring 157 may be pressed into the axial bore 137 of the compressor wheel 132. Thus, the pilot washer 151 is conveniently maintained in position during assembly operations.

(15) As shown in FIGS. 5 and 6, the compressor wheel and pilot washers may include cooperative indexing features. For example, in this case, the cooperative indexing features are in the form of a dowel pin 166, which is pressed into a dowel pin hole 144 formed in the compressor wheel 132. The pilot washer 151 may also include an enlarged region 168 along slit 164 that is sized to accommodate the dowel pin 166 as shown.

(16) FIGS. 7 and 8 illustrate a compressor wheel with positive piloting according to a second exemplary embodiment. In this case, the compressor wheel 232 has a back wall 234 which abuts a shoulder 214 formed on shaft 211. The assembly may also include a shoulder washer 252, which may be used for balancing compensation by removing material from the washer. In this case, shaft 211 includes a pilot land 250, which is sized to provide an interference press fit between the axial bore 237 of compressor wheel 232 and the pilot land 250. In this case, pilot land 250 is rounded or spherical in shape. Accordingly, the tolerances for the axial bore and pilot land may be relaxed when compared to traditional press fit and/or clearance fit applications.

(17) The interference fit accounts for both manufacturing tolerance and relative thermal and mechanical growth between the wheel and shaft. Further, this arrangement helps eliminate the potential for balance migration inherent with a clearance fit approach. Tight tolerances only need to be maintained on localized features, not an entire bore or shaft length. Runout tolerances are not needed. Lower cost manufacture is therefore possible. The press fit can also be tailored to the material. Since Titanium has less thermal expansion than steel, the press fit can be reduced, further reducing risk of damage.

(18) With specific reference to FIG. 7, the compressor wheel assembly may also include a pilot insert 256, which is pressed into a counter bore 238 that is formed in the nose end 236 of the compressor wheel 232. As nut 213 is threaded on the threads 215, it provides an axial clamping force against clamping washer 254, which in turn presses the pilot insert 256 into the counter bore 238. Pilot insert 256 may be split (in a similar fashion to the pilot washer described above) so that as it is forced into counter bore 238 it contracts onto shaft 211, thereby providing a positive pilot for the nose end of the compressor wheel 232. Here again, the clamping washer 254 may provide compensation for imbalance in the compressor wheel by removing material.

(19) Methods relating to the above described compressor wheel with balance correction and positive piloting are also contemplated. The methods thus encompass the steps inherent in the above described structures and assembly thereof. In an exemplary embodiment, the method may comprise determining an imbalance of a compressor wheel, positioning a washer on the shaft, wherein the washer has a non-uniform weight distribution, and positioning the compressor wheel on the shaft, adjacent the washer. The washer is rotated relative to the compressor wheel such that the non-uniform weight distribution of the washer compensates for the imbalance. The position of the washer with respect to the compressor wheel is maintained by clamping, for example. The method may further comprise removing material from the washer.

(20) Accordingly, the compressor wheel with balance correction and positive piloting has been described with some degree of particularity directed to the exemplary embodiments. It should be appreciated, however, that the present invention is defined by the following claims construed in light of the prior art so that modifications or changes may be made to the exemplary embodiments without departing from the inventive concepts contained herein.