JP2760095B2 - Centrifugal compressor impeller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a light weight and high strength centrifugal compressor wheel.

[Prior Art] As disclosed in JP-A-56-13499, in a centrifugal compressor impeller of a type in which the blades are covered by side plates, the suction port side end of the side plates is separated from the blades. Therefore, the centrifugal stress burden on this portion is high, and fatigue fracture is likely to occur.
Therefore, a reinforcing ring is fitted around the outer periphery of the suction port side end of the side plate. However, in the centrifugal compressor wheel having no side plate, the above-described problem does not occur.

In the impeller of the conventional centrifugal compressor shown in FIGS. 3 and 4, the blade 5 defines a groove passage curved in an arc shape from the axial suction port 18 at the front end of the shaft to the radially outward discharge port 19 at the rear end of the shaft. The main body 6 to be fitted is fitted to the shaft 2 and a seal member 8 is provided between the rear end wall 7 of the main body 6 and the step 9 of the shaft 2 to prevent the lubricating oil of the bearing 10 from being sucked into the impeller. The main body 6 is connected to the shaft 2 by screwing the nut 3 to the front end of the shaft 2. Shaft 2 is a bearing at the rear end
10 supports the housing (not shown).

[Problems to be Solved by the Invention] As described above, in an impeller of a type in which the shaft 2 is supported by the housing only on the rear end side (for example, incorporated in an exhaust turbocharger), the center of gravity of the main body 6 The longer the distance B between G and the bearing 10, the greater the load on the bearing 10. In addition, the axially-facing portion of the rear end wall 7 of the main body 6 greatly affects the weight of the impeller.

SUMMARY OF THE INVENTION In view of the above-described problems, an object of the present invention is to provide a centrifugal compressor impeller that does not lose its strength against centrifugal stress and thermal stress even when the weight is reduced by removing the rear end axial side of the main body. Is to provide.

[Means for Solving the Problem] In order to achieve the above object, in the configuration of the present invention, a groove passage curved in an arc shape from an axial suction port at a front end of a shaft to a radially outward discharge port at a rear end of a shaft by a blade is provided. A conical cavity is formed on the axis of the rear end of the impeller to be sectioned, and a ring made of a high-strength material with a smaller coefficient of thermal expansion than the impeller is fitted on the outer peripheral surface of the rear end. is there.

[Action] If the rear end of the impeller is partially removed on the axial center side, the main body is significantly reduced in weight, but the rear end of the impeller expands radially outward due to centrifugal stress and thermal stress. Deformation force is received, but deformation due to centrifugal stress and thermal stress is suppressed by the reinforcing ring fitted to the outer peripheral surface of the rear end of the impeller.

[Embodiment of the Invention] Fig. 1 is a side sectional view showing a schematic configuration of an impeller of a centrifugal compressor according to the present invention. According to the present invention, a hollow portion 17 defined by the conical surface 14 and the end wall surface 15 is formed on the axial center side of the rear end of the main body 6, whereby the weight of the main body 6 is significantly reduced. A seal member 8 is interposed between the end wall surface 15 and the step 9 of the shaft 2 and fastened by a nut 3 screwed to the front end of the shaft 2.

In order to suppress deformation of the rear end of the main body 6, an annular body 16 made of a material having a smaller coefficient of thermal expansion than the main body 6, for example, carbon fiber strength plastic (CSRP), is fitted to the outer peripheral surface of the rear end. .

As shown in FIG. 3, an annular groove is formed on the outer peripheral surface of the rear end of the main body 6.
13 may be formed, and a carbon long fiber, a ceramic long fiber called Kevlar, or the like may be wound inside the annular groove 13 and filled with an epoxy resin or the like to be fixed.

Next, the operation of the impeller of the centrifugal compressor according to the present invention will be described. As shown by a chain line in FIG. 2, when the body 6 of the impeller is heated due to a rise in temperature accompanying the compression of air, the impeller is deformed by thermal expansion and centrifugal stress (the figure is expanded). Such deformation is suppressed by the annular body 16 having a smaller coefficient of thermal expansion than the main body 6 and a high strength. That is, aluminum alloy, magnesium alloy,
Compared to engineering plastics, carbon long fibers and ceramic long fibers have a low coefficient of thermal expansion,
Since the strength is high, deformation of the main body 6 due to thermal stress or centrifugal stress can be suppressed.

[Effects of the Invention] As described above, the present invention provides a rear end portion of an impeller in which a blade path defines an arc-shaped curved groove passage from an axial suction port at a front end of a shaft to a radially outward discharge port at a rear end of a shaft. A conical cavity is formed on the axis side, and a ring made of a high-strength material having a smaller coefficient of thermal expansion than the impeller is fitted on the outer peripheral surface of the rear end. The provision of the conical hollow portion on the side significantly reduces the weight of the main body and reduces the load on the bearing at high speed rotation.

By providing the conical hollow portion on the axial center side of the rear end of the main body, the distance between the main body and the bearing is reduced, and in this sense, the load on the bearing is also reduced.

Since the weight of the main body is reduced, the natural frequency (second order) of the rotating system is higher than a commonly used rotation range, and safety against vibration destruction is improved.

[Brief description of the drawings]

1 is a side view of a wheel of a centrifugal compressor according to the present invention, FIG. 2 is a side cross-sectional view showing thermal deformation of the wheel, and FIG. 3 is a side cross-sectional view showing a modified embodiment of a ring body. FIG. 4 is a side sectional view of a conventional impeller of a centrifugal compressor. 2: shaft, 4: impeller, 5: blade, 16: ring, 17: empty, 18: suction port, 19: discharge port

Claims (1)

(57) [Claims] 1. A blade-shaped conical cavity at the rear end of the impeller, wherein a groove passage curved in an arc shape is defined from the axial suction port at the front end of the shaft to the radially outward discharge port at the rear end of the shaft. A centrifugal compressor impeller characterized in that an annular body made of a high-strength material having a smaller coefficient of thermal expansion than the impeller is fitted to the outer peripheral surface of the rear end portion.