JP2023111002A - Composite bearings and compressor - Google Patents

Abstract

To restrain loss of a function of protecting a rotating body.SOLUTION: A first composite bearing 10A and a second composite bearing 10B each comprise a magnetic bearing 20 rotatably supporting a rotating shaft 2 in a non-contact manner by a magnetic force, and a double row ball bearing 30 having an internal diameter in non-contact with the rotating shaft 2 supported by the magnetic bearing 20. The double row ball bearing 30 comprises an inner ring 31, a first outer ring 32 and a second outer ring 33 arranged in parallel along a rotation axis A of the rotating shaft 2, first rolling elements 34 arranged between the first outer ring 32 and the inner ring 31, and second rolling elements 35 arranged between the second outer ring 33 and the inner ring 31. When relative motion does not occur between the inner ring 31 and the first outer ring 32 and between the inner ring 31 and the second outer ring 33, a second preload is larger than a first preload.SELECTED DRAWING: Figure 2

Description

The present invention relates to composite bearings and compressors with composite bearings.

Patent Literature 1 discloses a technique related to a touchdown bearing. Touchdown bearings are employed in rotating machinery along with magnetic bearings. A magnetic bearing supports the rotating shaft in a non-contact manner. When this magnetic bearing loses its supporting function for some reason, the touchdown bearing takes over the supporting function.

JP 2019-138333 A

A ball bearing employing a plurality of rolling elements is used as a touchdown bearing. The rotating shaft is usually supported by magnetic bearings. Therefore the ball bearing is not working. When the support function of the magnetic bearing is lost and the ball bearing takes over the support function, the movement of the inner ring of the ball bearing transitions from rest to a predetermined rotational speed. Furthermore, when ball bearings take over the supporting function, the ball bearings are subjected to transient axial loads at the moment contact with the rotating shaft occurs. If a transient axial load acts on the ball bearing while the ball bearing is moving from a stationary state to a predetermined rotational speed, there is a risk of slippage of the rolling elements relative to the inner and outer rings. Slippage of the rolling elements damages the rolling elements. As a result, the supporting function of the ball bearing may be impaired. In other words, a situation arises in which the function of protecting the rotating body by the ball bearing is not reliably exhibited.

SUMMARY OF THE INVENTION The present invention provides a composite bearing capable of suppressing loss of a function to protect a rotating body, and a compressor equipped with the composite bearing.

A composite bearing, which is one embodiment of the present invention, includes a magnetic bearing that rotatably supports a rotating shaft by magnetic force without contact, and a double-row ball that has an inner diameter that does not come into contact with the rotating shaft supported by the magnetic bearing. a bearing, wherein the double-row ball bearing comprises an inner ring, a first outer ring and a second outer ring juxtaposed along the axis of the rotating shaft, and a first rolling element arranged between the first outer ring and the inner ring. and a second rolling element disposed between the second outer ring and the inner ring, and in a state where no relative motion occurs between the inner ring and the first outer ring and between the inner ring and the second outer ring, Either one of the first preload acting on the first rolling element and the second preload acting on the second rolling element is greater than the other.

In the composite bearing, the rotating shaft is supported by the magnetic bearing in the normal state. When the support function of the magnetic bearing is lost, the rotary shaft is supported by the double-row ball bearing. When the support of the rotary shaft is switched from the magnetic bearing to the double-row ball bearing, an axial load acts on the double-row ball bearing. This axial load changes the state of the first preload acting on the first rolling element or the second preload acting on the second rolling element. Changes in these preload conditions can result in slippage of the rolling elements relative to the inner or outer ring. In the double-row ball bearing, one of the first preload and the second preload is set larger than the other. As a result, the initial states of the first preload and the second preload of the double-row ball bearing can be set so that the difference between the first preload and the second preload becomes small when an axial load acts. As a result, the rolling elements are prevented from slipping on the inner ring or the outer ring, so that the supporting function of the double-row ball bearing can be ensured. Therefore, in the composite bearing, when the magnetic bearing loses its supporting function, the double-row ball bearing can replace the supporting function of the rotating body, so loss of the function of protecting the rotating body can be suppressed. .

In one form of composite bearing, the inner ring receives an external force directed from the second outer ring toward the first outer ring, and the second preload may be greater than the first preload. According to this configuration, it is possible to suppress a decrease in the second preload due to the axial load.

In one form of the composite bearing, the inner ring may receive an external force directed from the second outer ring toward the first outer ring, and the second contact angle of the second rolling element may be greater than the first contact angle of the first rolling element. Even with this configuration, it is possible to suppress a decrease in the second preload due to the axial load.

A compressor according to another aspect of the present invention includes the above-described composite bearing, a rotating shaft rotatably supported by the composite bearing, a power section for providing power to drive the rotating shaft, and a an impeller; This compressor has a composite bearing that can suppress the loss of the function to protect the rotating body. Therefore, the compressor can continue to exhibit its function stably.

In another form of compressor, only one impeller is provided at one end of the rotating shaft, and the composite bearing rotates so that the second outer ring is closer to the impeller than the first outer ring. It may be arranged with respect to the axis. With this configuration as well, loss of the function of protecting the rotating body by the composite bearing is suppressed, so that the compressor can stably continue to exhibit its function.

In another form of compressor, the impellers are provided on both ends of the rotating shaft, respectively, and the composite bearing is arranged on the side of the two impellers closer to the impeller located on the high pressure side. , may be arranged with respect to the axis of rotation. With this configuration as well, loss of the function of protecting the rotating body by the composite bearing is suppressed, so that the compressor can stably continue to exhibit its function.

ADVANTAGE OF THE INVENTION According to this invention, the compressor provided with the composite bearing which can suppress the loss of the function which protects a rotating body, and the said composite bearing is provided.

FIG. 1 is a diagram showing the overall configuration of a compressor provided with composite bearings. FIG. 2 is a cross-sectional view showing an enlarged part of the structure of a double-row ball bearing that constitutes a composite bearing.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted.

As shown in FIG. 1, the compressor 1 has a rotating shaft 2, a motor 3 (power section), a first composite bearing 10A, and a second composite bearing 10B. A first compressor impeller 4 is provided at a first end of the rotating shaft 2 , and a second compressor impeller 5 is provided at a second end of the rotating shaft 2 . The first compressor impeller 4, the second compressor impeller 5, and the rotary shaft 2 constitute a rotor 7 supported by a first composite bearing 10A and a second composite bearing 10B. Therefore, this compressor 1 is a two-stage compressor driven by the motor 3 . For example, gas compressed by the first compressor impeller 4 is sent to the second compressor impeller 5 for further compression. Note that the compressor 1 may be a single-stage compressor by omitting the second compressor impeller 5 .

The rotating shaft 2, the motor 3, the first composite bearing 10A, the second composite bearing 10B, the first compressor impeller 4 and the second compressor impeller 5 are housed in a housing (not shown) of the compressor 1. . The motor 3 has a rotor 8 provided on the rotary shaft 2 and a stator 9 arranged around the rotor 8 . The motor 3 rotates the rotary shaft 2 by rotating the rotor 8 .

A first composite bearing 10A and a second composite bearing 10B are arranged in the compressor 1 . The first composite bearing 10A and the second composite bearing 10B are spaced apart in the longitudinal direction of the rotating shaft 2 . A first composite bearing 10A is arranged between the motor 3 and the first compressor impeller 4 . A second composite bearing 10B is arranged between the motor 3 and the second compressor impeller 5 . That is, the motor 3 is sandwiched between the first composite bearing 10A and the second composite bearing 10B. The first composite bearing 10A and the second composite bearing 10B rotatably support the rotary shaft 2 . The first composite bearing 10A and the second composite bearing 10B receive an external force (radial load) in the radial direction of the rotating shaft 2 . Note that the first composite bearing 10A and the second composite bearing 10B may have a structure that receives an axial load (thrust load).

The first composite bearing 10A and the second composite bearing 10B each have a magnetic bearing 20 and a double row ball bearing 30. As shown in FIG. As an example, the magnetic bearing 20 is arranged on the motor 3 side, and the double-row ball bearing 30 is arranged on the first compressor impeller 4 side. The arrangement of the magnetic bearing 20 and the double row ball bearing 30 may be reversed. That is, the magnetic bearing 20 may be arranged on the first compressor impeller 4 side, and the double-row ball bearing 30 may be arranged on the motor 3 side.

The magnetic bearing 20 rotatably supports the rotating shaft 2 in a non-contact manner. The magnetic bearing 20 controls the support position of the rotating shaft 2 by a well-known structure. The magnetic bearing 20 generates a restoring force that returns the rotating shaft 2 to the reference position when the rotating shaft 2 deviates from the reference position. The magnetic bearing 20 has a magnetic bearing hole 20H that is a through hole. The inner diameter of the magnetic bearing hole 20H is larger than the outer diameter of the rotating shaft 2 . A predetermined gap is provided between the inner peripheral surface of the magnetic bearing 20 and the outer peripheral surface of the rotating shaft 2 . The inner peripheral surface of the magnetic bearing 20 may be defined, for example, by an electromagnet that produces an electromagnetic force. The inner peripheral surface of the magnetic bearing 20 may be defined, for example, by a position sensor that measures the position of the rotating shaft 2 with respect to the electromagnet.

The double row ball bearing 30 supports the rotating shaft 2 in a situation where the magnetic bearing 20 cannot support the rotating shaft 2 . That is, it can be said that the double-row ball bearing 30 is a touchdown bearing. For example, when the magnetic bearing 20 is exerting its support function, a disturbance force that cannot be tolerated by the magnetic bearing 20 acts. It may also be used to avoid contact between the magnetic bearing 20 and the rotating shaft 2 before the rotation of the rotating shaft 2 starts or when the rotation ends.

The double row ball bearing 30 has a ball bearing hole 30H which is a through hole. The inner diameter of the double row ball bearing 30 is larger than the outer diameter of the rotating shaft 2 . In other words, the double-row ball bearing 30 has an inner diameter that does not come into contact with the rotating shaft 2 supported by the magnetic bearing 20 . A predetermined gap is provided between the inner peripheral surface of the double-row ball bearing 30 and the outer peripheral surface of the rotating shaft 2 . The gap between the inner peripheral surface of double-row ball bearing 30 and the outer peripheral surface of rotating shaft 2 is smaller than the gap between the inner peripheral surface of magnetic bearing 20 and the outer peripheral surface of rotating shaft 2 . As a result, when the rotating shaft 2 moves in the radial direction, the rotating shaft 2 contacts the inner peripheral surface of the double-row ball bearing 30 earlier than the inner peripheral surface of the magnetic bearing 20 .

FIG. 2 shows an enlarged cross section of the double-row ball bearing 30 . The double row ball bearing 30 has an inner ring 31 , a first outer ring 32 , a second outer ring 33 , a first rolling element 34 and a second rolling element 35 .

The inner ring 31 has a ring-like shape. A surface on the inner peripheral side of the inner ring 31 is referred to as an inner diameter surface 31a. The inner diameter surface 31a constitutes a ball bearing hole 30H through which the rotating shaft 2 is inserted. The inner diameter of the inner diameter surface 31 a is larger than the outer diameter of the rotating shaft 2 . Therefore, a gap is formed between the inner diameter surface 31 a and the outer peripheral surface of the rotating shaft 2 . The outer peripheral surface of the inner ring 31 includes a first inner ring raceway surface 31b and a second inner ring raceway surface 31c. The inner ring raceway surface is also called a raceway groove. The first inner ring raceway surface 31b is separated in the direction of the rotation axis A from the second inner ring raceway surface 31c.

The first outer ring 32 also has a ring-like shape. The inner peripheral surface of the first outer ring 32 includes a first outer ring raceway surface 32a. The first outer ring raceway surface 32a faces the first inner ring raceway surface 31b. A plurality of first rolling elements 34 are arranged between the first outer ring raceway surface 32a and the first inner ring raceway surface 31b. The first rolling element 34 is a metal sphere. The first rolling element 34 may be configured to be held by a retainer. Therefore, the inner diameter of the first outer ring raceway surface 32a is larger than the outer diameter of the first inner ring raceway surface 31b, and the first rolling elements 34 are provided between the first outer ring raceway surface 32a and the first inner ring raceway surface 31b. Positionable gaps are provided. Further, in the first outer ring 32 , the outer ring thickness in the direction along the rotation axis A is smaller than the inner ring thickness in the direction along the rotation axis A. As an example, the outer ring thickness is slightly less than half the inner ring thickness.

A surface on the outer peripheral side of the first outer ring 32 is referred to as an outer diameter surface 32b. Outer diameter surface 32 b may contact housing 51 . The first outer ring 32 has a first outer end face 32c and a first inner end face 32d in the direction of outer ring thickness. The first outer end surface 32c faces outward. For example, the first outer end face 32c may be pressed against the fixing portion 52. As shown in FIG. A first pressurization is generated by this pressing. The first inner end face 32d faces inward. The inner side is the direction facing the second outer ring 33 . Therefore, the first inner end face 32d contacts the second outer ring 33. As shown in FIG.

The second outer ring 33 is adjacent to the first outer ring 32 in the direction of the rotation axis A. As shown in FIG. The second outer ring 33 has a configuration similar to that of the first outer ring 32 . That is, the second outer ring 33 also has a second outer ring raceway surface 33a, a second outer diameter surface 33b, a second outer end surface 33c, and a second inner end surface 33d. Since these configurations are the same as those of the first outer ring 32, detailed description thereof will be omitted.

Here, a characteristic configuration of the double-row ball bearings 30 included in the first composite bearing 10A and the second composite bearing 10B will be described. A first preload acting on the first rolling element 34 and a second preload acting on the second rolling element 35 in a state where there is no relative motion between the inner ring 31 and the first outer ring 32 and between the inner ring 31 and the second outer ring 33 Either one of the second preloads is greater than the other.

For example, in FIG. 2, the second preload of the second rolling element 35 is made larger than the first preload of the first rolling element 34 in advance. Differential preload is achieved by several means. For example, the magnitude of the preload can be achieved by the shape of the second inner ring raceway surface 31c with which the second rolling elements 35 contact and the shape of the second outer ring raceway surface 33a with which the second rolling elements 35 contact. In other words, the first contact angle T1 defined on the first rolling element 34 and the second contact angle T2 defined on the second rolling element 35 are made different from each other. In the example of FIG. 2 , the second contact angle T2 on the second rolling element 35 is made larger than the first contact angle T1 on the first rolling element 34 . According to such a configuration, even when an axial load directed from the second outer ring 33 to the first outer ring 32 acts on the inner ring 31 from the rotating shaft 2, the second preload acting on the second rolling elements 35 does not become too small. . As a result, the slippage of the second rolling elements 35 is suppressed, and heat generation is also suppressed. The occurrence of slippage of the second rolling elements 35 can be defined by the minimum preload at which slippage does not occur. That is, even if the axial load acts and the second preload acting on the second rolling elements 35 becomes small, the second preload may be set to be greater than the minimum preload.

Note that the means for setting the magnitude of the preload is not limited to the configuration of the second inner ring raceway surface 31c and the second outer ring raceway surface 33a. For example, the ball diameter of the second rolling element 35 may be different from the ball diameter of the first rolling element 34 .

In the example of FIG. 1, the gas compressed by the first compressor impeller 4 is sent to the second compressor impeller 5 and further compressed. That is, the first compressor impeller 4 is on the low pressure side and the second compressor impeller 5 is on the high pressure side. Then, a force acting from the high pressure side to the low pressure side acts on the rotating shaft 2 . In other words, a force acts from the second compressor impeller 5 toward the first compressor impeller 4 . When the rotary shaft 2 contacts the double-row ball bearing 30, a force directed from the second compressor impeller 5 toward the first compressor impeller 4 acts on the inner ring 31 as an axial load.

In such a case, the second preload of the second outer ring 33 arranged on the high pressure side is set to be greater than the first preload of the first outer ring 32 arranged on the low pressure side. As a result, the force directed from the second compressor impeller 5 to the first compressor impeller 4 can appropriately cope with the axial load.

The first composite bearing 10A and the second composite bearing 10B are provided with a magnetic bearing 20 that rotatably supports the rotating shaft 2 without contact by magnetic force, and with respect to the rotating shaft 2 supported by the magnetic bearing 20. a double row ball bearing 30 having a non-contacting inner diameter. The double-row ball bearing 30 includes an inner ring 31, a first outer ring 32 and a second outer ring 33 arranged side by side along the rotation axis A of the rotating shaft 2, and a first outer ring 32 and the inner ring 31 arranged between the first outer ring 32 and the inner ring 31. It has one rolling element 34 and a second rolling element 35 arranged between the second outer ring 33 and the inner ring 31 . The second preload acting on the second rolling elements acts on the first rolling elements 34 in a state where there is no relative motion between the inner ring 31 and the first outer ring 32 and between the inner ring 31 and the second outer ring 33. greater than the first preload.

Rotating shaft 2 is supported by magnetic bearing 20 when first composite bearing 10A and second composite bearing 10B are in a normal state. When the support function of the magnetic bearing 20 is lost, the rotary shaft 2 is supported by the double-row ball bearing 30 . When the support of the rotary shaft 2 is switched from the magnetic bearing 20 to the double-row ball bearing 30 , an axial load acts on the double-row ball bearing 30 . This axial load changes the state of the first preload acting on the first rolling element 34 or the second preload acting on the second rolling element 35 . If the state of these preloads changes, slippage of the first rolling element 34 or the second rolling element 35 may occur. In the double-row ball bearing 30, one of the first preload and the second preload is set larger than the other. As a result, the initial states of the first preload and the second preload of the double-row ball bearing 30 can be set so that the difference between the first preload and the second preload becomes small when an axial load acts. As a result, the occurrence of slippage of the first rolling element 34 or the second rolling element 35 is suppressed, so the function of supporting the double-row ball bearing 30 can be ensured. Therefore, in the first composite bearing 10A and the second composite bearing 10B, when the magnetic bearing 20 loses its supporting function, the double-row ball bearing 30 can replace the supporting function of the rotor 7. Loss of the function to protect the rotating body 7 can be suppressed.

The compressor 1 drives the first composite bearing 10A and the second composite bearing 10B, the rotating shaft 2 rotatably supported by the first composite bearing 10A and the second composite bearing 10B, and the rotating shaft 2. and a first compressor impeller 4 and a second compressor impeller 5 fixed to the rotary shaft 2. This compressor 1 has a first composite bearing 10A and a second composite bearing 10A that can suppress the loss of the function of protecting the rotating body 7 in which the first compressor impeller 4, the second compressor impeller 5 and the rotating shaft 2 are integrated. It has a composite bearing 10B. Therefore, the compressor 1 can stably continue to exhibit its function.

A first compressor impeller 4 is provided at a first end of the rotating shaft 2 and a second compressor impeller 5 is provided at a second end of the rotating shaft 2 . The first composite bearing 10A and the second composite bearing 10B are arranged with respect to the rotating shaft 2 so as to be on the side closer to the second compressor impeller 5 arranged on the high pressure side of the two impellers. It is This configuration also suppresses the loss of the function of protecting the rotating body 7 by the first composite bearing 10A and the second composite bearing 10B, so that the compressor 1 can stably continue to exhibit its function. can.

The present invention has been described in detail based on its embodiments. However, the present invention is not limited to the above embodiments. Various modifications are possible for the present invention without departing from the gist thereof.

Devices to which the first composite bearing 10A and the second composite bearing 10B are applied are not limited to compressors. The first composite bearing 10A and the second composite bearing 10B may be employed in a rotating machine having a rotating shaft.

Only one second compressor impeller 5 is provided at one end of the rotary shaft 2 . The first composite bearing 10A and the second composite bearing 10B are arranged with respect to the rotating shaft so that the second outer ring 33 is closer to the second compressor impeller 5 than the first outer ring 32 is. This configuration also suppresses the loss of the function of protecting the rotating body by the first composite bearing 10A and the second composite bearing 10B, so that the compressor 1 can stably continue to exhibit its function. .

1 compressor 2 rotating shaft 3 motor (power unit)
4 First compressor impeller 5 Second compressor impeller 7 Rotating body 8 Rotor 9 Stator 10A First composite bearing 10B Second composite bearing 20 Magnetic bearing 30 Double-row ball bearing 31 Inner ring 31a Inner diameter surface 31b First inner ring raceway surface 31c Second inner ring raceway surface 32 First outer ring 32a First outer ring raceway surface 32b Outer diameter surface 32c First outer end surface 32d First inner end surface 33 Second outer ring 33a Second outer ring raceway surface 33b Second outer diameter surface 33c Second outer side End surface 33d Second inner end surface 34 First rolling element 35 Second rolling element 51 Housing 52 Fixed portion A Rotational axis T1 First contact angle T2 Second contact angle

Claims (6)

a magnetic bearing that rotatably supports the rotating shaft without contact by magnetic force;
a double-row ball bearing having an inner diameter that does not come into contact with the rotating shaft supported by the magnetic bearing;
The double-row ball bearing,
inner ring;
a first outer ring and a second outer ring juxtaposed along the axis of the rotating shaft;
a first rolling element arranged between the first outer ring and the inner ring;
a second rolling element disposed between the second outer ring and the inner ring;
A first preload acting on the first rolling element and a second preload acting on the second rolling element in a state where no relative motion occurs between the inner ring and the first outer ring and between the inner ring and the second outer ring. 2. Composite bearings, one of which is greater than the other. the inner ring receives an external force from the second outer ring toward the first outer ring;
2. The composite bearing of claim 1, wherein said second preload is greater than said first preload. the inner ring receives an external force from the second outer ring toward the first outer ring;
3. A composite bearing according to claim 1 or 2, wherein the second contact angle of said second rolling element is greater than the first contact angle of said first rolling element. A composite bearing according to any one of claims 1 to 3;
a rotating shaft rotatably supported by the composite bearing;
a power unit that provides power to drive the rotating shaft;
and an impeller fixed to the rotating shaft. Only one impeller is provided at one end of the rotating shaft,
The compressor according to claim 4, wherein the composite bearing is arranged with respect to the rotating shaft so that the second outer ring is closer to the impeller than the first outer ring. The impellers are provided at both ends of the rotating shaft,
6. The compressor according to claim 5, wherein said composite bearing is arranged with respect to said rotating shaft so as to be on the side closer to said impeller arranged on the high pressure side of said two impellers.

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