JPH0515658U - Magnetic bearing motor - Google Patents

Abstract

(57) [Summary] [Structure] Both sides of the rotor 5 fitted to the rotating shaft 6A are supported by the radial magnetic bearings 3A and 3B, and the axial displacement is adjusted by the thrust magnetic bearings 4.
A and 6B are made of low-expansion high tensile strength alloy steel, and the small diameter portion of the rotating shaft 6A on one side and the hollow portion 63 of the rotating shaft 6B on the other side are combined to form a small diameter portion 62 of the rotating shaft 6A. The rotor 5 is fitted and both end faces of the rotor 5 are brought into contact with the stepped portion of the rotary shaft 6A and the end face of the rotary shaft 6B. [Effect] Since the rotor is fitted to the rotary shaft of low tensile expansive high tensile strength alloy steel to transmit torque to the load, axial expansion due to temperature rise of the rotor causes axial end of the rotary shaft. It is possible to provide a magnetic bearing motor in which the axial displacement of the rotating shaft is small even when the temperature of the rotor rises, without significantly affecting the displacement of the magnetic bearing.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnetic bearing motor used in a high speed rotating device such as a turbo machine, and more particularly to a magnetic bearing motor having a load connected to both ends of a rotating shaft.

[0002]

[Prior Art]

 Conventionally, magnetic bearing motors used in high-speed rotating devices such as turbomachines maintain radial air bearings on both sides of the rotor, which is fixed approximately at the center of the rotating shaft, to maintain the air gap between the rotor and the stator. There is. A thrust magnetic bearing that controls the axial position is provided on the anti-load side of the motor, and a shaft end position sensor that detects the axial position of the rotor is provided at the load side shaft end. The thrust magnetic bearing is controlled by the output of the shaft end position sensor so that the axial position of the load side shaft end comes to a predetermined position.

[0003]

[Problems to be solved by the device]

 However, in the above configuration, when the load increases at high speed rotation, heat is concentrated on the rotor portion due to iron loss of the motor, etc., the temperature of the rotating shaft rises, and thermal expansion expands the entire rotating shaft in the axial direction. The antiload side shaft end is displaced the most, but if the displacement is too large, the thrust magnetic bearing cannot control the axial position of the antiload side shaft end. For example, when attaching the first and second stage turbo blowers to both shaft ends of a magnetic bearing motor and rotating the impeller, axial displacement is required to maintain a constant gap between the impeller and the casing. However, there is a risk of the impeller and casing coming into contact with each other and being damaged due to the large axial displacement of the rotating shaft due to thermal expansion. In order to avoid this, if the gap is enlarged in consideration of thermal expansion, the discharge amount may be significantly reduced and the operating efficiency may be reduced. An object of the present invention is to provide a magnetic bearing motor in which the axial displacement of the rotating shaft is small even when the temperature of the rotor rises.

[0004]

[Means for Solving the Problems]

 The present invention is a magnetic bearing motor in which both sides of a rotor fitted to a rotary shaft are supported by radial magnetic bearings, and axial displacement is adjusted by thrust magnetic bearings. The small diameter part of the rotating shaft on one side made of high tensile strength alloy steel and the hollow part of the rotating shaft on the other side made of low expansion high tensile strength alloy steel are connected to each other, and the small diameter part of the rotating shaft on the one side is formed. The rotor is fitted in the above, and both end faces of the rotor are brought into contact with the stepped portion of the rotating shaft on one side and the end face of the rotating shaft on the other side. As a second method, the rotor and the rotary shaft on the one side are fitted so as to transmit torque and slide in the axial direction, and both end surfaces of the rotor and the one side are fitted. A gap is provided between the stepped portion of the rotary shaft and the end face of the rotary shaft on the other side.

[0005]

[Action]

 The small diameter part of the rotating shaft on one side made of low expansion high tensile strength alloy steel and the hollow part of the rotating shaft on the other side made of high expansion tensile strength alloy steel of the same low expansion are combined to form a small diameter part of the rotating shaft on one side. Since the rotor is fitted in the part, when a load is applied to the rotor, the temperature of the rotor rises and the rotor tries to expand in the axial direction. However, since both sides of the rotor come into contact with the stepped portion of the rotating shaft on the one side and the end surface of the rotating shaft on the other side, and the rotating shaft on the one side is connected by the hollow part of the rotating shaft on the other side, The space between the two ends of the child hardly expands due to the temperature rise. Therefore, the rotor cannot be compressed and expanded in the axial direction, and the axial displacement due to the temperature rise of the rotor becomes very small.

[0006]

【Example】

 The present invention will be described with reference to the embodiments shown in the drawings. FIG. 1 is a side sectional view showing an embodiment of the present invention, in which a hollow cylindrical stator 2 around which an electric coil 21 is wound is provided inside a hollow cylindrical frame 1, and a radial radiator is provided on both sides of the stator 2. Al magnetic bearings 3A and 3B are provided, and a thrust magnetic bearing 4 is provided between one radial bearing 3B and the stator 2. Inside the stator 2, there is provided a rotor 5 formed of a steel solid rotor facing each other with a gap. A plurality of rotor bars 51 extending in the axial direction and equidistantly in the circumferential direction and a short-circuit ring 52 connected to the rotor bars 51 at both end surfaces of the rotor 5 are die-cast into the rotor 5. Reinforcing rings 53 are fitted onto the outer circumferences of the short-circuit rings on both sides of the rotor 5 by shrink fitting. The rotor 5 is made of low-expansion high tensile strength alloy steel such as Invar, and is fitted and fixed to the small diameter portion 62 of the rotary shaft 6A having the stepped portion 61. One end of the rotary shaft 6A is fixed to the rotor 5. The impeller 71 of the first-stage turbo blower 7 provided at one end of the frame 1 is connected. The rotor 5 and the impeller 71 of the rotary shaft 6A are formed to have an outer diameter substantially the same as that of the rotor 5, the radial magnetic bearings 3A are opposed to each other through a gap, and the rotary shaft 6A is levitated. The other end of the small diameter portion 62 of the rotating shaft 6A is fitted into the hollow portion 63 provided at one end of the rotating shaft 6B, which is also concentrically made of the same low expansion high tensile strength alloy steel, and is fitted into the rotating shaft 6A. And the rotary shaft 6B are connected to each other so that the stepped portion 61 of the rotary shaft 6A and the end face 64 of the rotary shaft 6B come into contact with the end face of the reinforcing ring 53, respectively. An impeller 81 of a second stage turbo blower 8 provided at the other end of the frame 1 is connected to the other end of the rotary shaft 6B. A thrust disk 65 is provided between the rotor 5 of the rotary shaft 6B and the impeller 81, and the thrust disk 65 is opposed to the thrust magnetic bearing 4 via a gap to detect the axial displacement of the impellers 71 and 81. Thus, the axial displacement of the rotating shaft 6A and the rotating shaft 6B is adjusted. Further, the rotating shaft 6B is formed to have substantially the same outer diameter as that of the rotor 5, the radial magnetic bearings 3B are opposed to each other through a gap, and the rotating shaft 6B is levitated together with the rotating shaft 6A.

When a load is applied to the rotor 5, the temperature of the rotor 5 rises and tries to expand in the axial direction. However, the reinforcing ring 53 is formed on the stepped portion 61 of the rotary shaft 6A and the end surface 64 of the rotary shaft 6B. In contact with each other, the rotary shaft 6A is connected by the hollow portion 63 of the rotary shaft 6B, so that the space between the both ends of the rotor 5 hardly expands due to the temperature rise. Therefore, the rotor 5 cannot be compressed and expanded in the axial direction, and the axial displacement due to the temperature rise of the rotor 5 becomes very small. In addition, the expansion coefficient of low tensile strength high tensile strength alloy steel such as Invar is 1.0 × 10 ⁻⁶ / ° C., and the expansion ratio of maraging steel used for the rotor 5 is 10. Since the coefficient of expansion is extremely low compared to 1 × 10 ^-6 / ° C, the axial displacement due to temperature rise is very small. Further, as shown in FIGS. 2 and 3, spline teeth 66 are provided on the outer circumference of the rotary shaft 6A, and spline grooves 54 that mesh with the spline teeth 66 are provided on the inner circumference of the rotor 5 to connect the rotary shaft 6A and the rotary shaft 5 to each other. It is fitted so as to be able to transmit torque and slide in the axial direction, and a gap is provided between the reinforcing ring 53 and the stepped portion 61 and the end surface 64 so that the rotor 5 transmits torque to the rotating shaft 6A. However, even if it freely expands in the axial direction, the displacement of the shaft ends of the rotary shaft 6A and the rotary shaft 6B may not be affected.

[0008]

[Effect of the device]

 As described above, according to the present invention, the rotor is fitted to the rotating shaft of low tensile strength high tensile strength alloy steel to transmit the torque to the load. Axial expansion does not significantly affect the displacement of the shaft end of the rotating shaft. For example, high efficiency can be achieved without significantly changing the axial gap of a two-stage turbo blower with loads on both ends of the rotating shaft. It is possible to provide a magnetic bearing motor in which the axial displacement of the rotating shaft is small even when the temperature of the rotor rises due to such operations as above.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a side sectional view showing another embodiment of the present invention.

FIG. 3 is a front sectional view showing another embodiment of the present invention.

[Explanation of symbols]

1 frame 2 stator 3A, 3B radial magnetic bearing 4 thrust magnetic bearing 5 rotor 51 rotor bar 52 short-circuit ring 53 reinforcing ring 54 spline groove 6A, 6B rotary shaft 61 stepped portion 62 small diameter portion 63 hollow portion 64 end face 65 thrust disk 66 Spline teeth 7, 8 Turbo blower 71, 81 Impeller

Claims (2)

[Scope of utility model registration request] 1. A magnetic bearing motor in which both sides of a rotor fitted to a rotary shaft are supported by radial magnetic bearings, and axial displacement is adjusted by thrust magnetic bearings.
The rotating shaft is configured by connecting a small diameter portion of the rotating shaft on one side made of low expansion high tensile strength alloy steel and a hollow portion of the rotating shaft on the other side made of low expansion high tensile strength alloy steel, The rotor is fitted to the small diameter portion of the rotary shaft on one side, and both end faces of the rotor are in contact with the stepped portion of the rotary shaft on the one side and the end face of the rotary shaft on the other side. Magnetic bearing motor characterized by. 2. The rotor and the rotary shaft on the one side are fitted so as to transmit torque and slide in the axial direction,
2. The magnetic bearing motor according to claim 1, wherein a gap is provided between each side end surface of the rotor and the stepped portion of the one rotation shaft and the end surface of the other rotation shaft.