JPS5939975B2 - rotor shaft - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating shaft of a cylindrical rotor such as a turbine generator.

The shaft material of the rotating shaft of a large cylindrical rotor such as a turbine generator is forged, but non-metallic inclusions exist in the shaft center and material discontinuities tend to concentrate. A circular center hole is drilled in the shaft center to remove defects and to non-destructively inspect the shaft material for defects.

Thus, like the rotating shaft of a cylindrical rotor of a two-pole turbine generator, two magnetic pole parts are formed in the outer circumferential direction, and a slot part is formed in which a plurality of slots are arranged between the magnetic pole parts. In such cases, due to unbalanced centrifugal force loads generated during rotation, high stress is locally generated on the surface of the central hole provided in the axis, or an elliptical stress distribution state occurs.

Generally, the stress value is proportional to the product of the square of the rotational speed and the square of the shaft diameter.

Since high stress on the surface of the center hole is directly related to failure of the shaft material, the stress value must be kept below the allowable stress of the shaft material.

FIG. 1 shows a cross-section of the rotating shaft of a cylindrical rotor of a two-pole turbine generator.

In the figure, a rotating shaft 1 is provided with a slot portion 3 in which a plurality of slots for inserting field windings are arranged between magnetic pole portions 2 and 20 in the outer circumferential direction, had a circular hole 4 with radius r.

The center line of the slot portion 3 passing through the center O is the y-axis, and the center line of the magnetic pole portion 2 is the y-axis.

3a is the bottom of the slot of the slot portion 3, and R is the radius of this slot bottom.

2a is the bottom of the magnetic pole part 2 having the same radius as the bottom 3a of the slot, P is the average surface force of the bottom 2a of the magnetic pole part 2, and Q is the average surface force of the bottom 3a of the slot.

FIG. 2 shows a calculation example of the stress distribution on the surface of the center hole 40 during rotation using the finite element method.

In Figure 2, the horizontal axis is the y-axis in Figure 1 OR the y-axis at 90°
The central angle θ is the central angle θ, and the vertical axis is the stress θ− generated at the central angle θ.
This is the stress ratio to the stress at 45°, that is, the stress ratio when the stress at θ=450 is set to 1.

Curve 6 is shown in Figure 1 with P=15Q and R=8.57.
The stress distribution on the surface of the center hole 40 when r is shown.

The maximum stress distribution has an elliptical shape with the short axis being the centerline y-axis of the magnetic pole part 2, and the maximum stress value is approximately 1.3 near θ-00, and the shaft diameter is limited by this maximum stress value. .

Therefore, if the stress in this localized stress concentration area can be reduced to a lower stress value, the same shaft material can be applied to even larger capacity turbine generators.

The present invention reduces the local stress concentration on the surface of the hole by making the hole provided in the shaft center into an elliptical shape, and makes the stress distribution on the surface almost uniform, thereby preventing breakage accidents during rotation and further increasing the stress concentration. The object of the present invention is to provide a rotating shaft of a cylindrical rotor that can be applied to large-capacity machines.

An embodiment of the present invention shown in the drawings will be described below.

In FIG. 3, the same parts as in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted.

An elliptical hole 5 is provided at the axis of the rotating shaft 1. is in the y-axis direction, which is the center line of the magnetic pole part 2.

The stress distribution on the surface of the elliptical hole 5 is shown in FIG.

Curve 7 has a ratio a of major axis to minor axis d of 1.2, and curve 8 has a
This is a curve showing the stress distribution when L5 is taken as L5.

Even if the external force conditions acting on the rotating shaft 1 are the same as those for the conventional circular hole 4, stress concentration on the center hole surface is alleviated by changing the axial length ratio a between the long axis and the short axis d. Appropriate selection can result in a nearly uniform stress distribution.

There is an elliptical shape, that is, an axial length ratio a where the maximum stress value on the surface of the center hole is minimum, and the axial length ratio a between the major axis and the minor axis d in FIG. 2 is 1.35 to 1.45.

Note that the hole at the center of the rotating shaft may be not only elliptical but also an elliptical elongated hole with a short straight portion that approximates an ellipse, to achieve a substantially uniform stress distribution.

As described above, according to the present invention, an elliptical long hole is provided in the axis of the rotating shaft of the cylindrical rotor, with the center line of the magnetic pole part being the long axis and the center line of the slot part being the short axis. It is possible to alleviate the local stress concentration that occurs on the surface of the center hole of the shaft, which has the excellent effect of preventing breakage accidents during rotation and making it possible to apply it to large-scale machines with a large capacity.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the rotation axis of a conventional cylindrical rotor.
FIG. 2 is a curve diagram showing the stress distribution on the surface of the center hole of the rotating shaft, and FIG. 3 is a cross-sectional view showing one embodiment of the rotating shaft of the cylindrical rotor of the present invention. DESCRIPTION OF SYMBOLS 1...Rotating shaft, 2...Magnetic pole part, 3...Slot part, 4...Circular hole, 5...Oval hole.

Claims (1)

[Claims] 1. In a rotating shaft of a cylindrical rotor that has two magnetic pole parts and a slot part in which a plurality of slots are arranged between the magnetic pole parts in the circumferential direction, the center line of the magnetic pole parts is located at the axis. A rotating shaft of a cylindrical rotor, characterized in that it is provided with an elliptical elongated hole whose long axis is the center line of the slot portion and whose short axis is the center line of the slot portion.