JP2011220264A - Centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a high resonance frequency of a rotary shaft by reducing a separation distance between an impeller and a bearing along an axial direction of a rotary shaft.SOLUTION: A centrifugal compressor includes: a bearing 30 including a bearing inner race 32 and a bearing outer race 34 and axially supporting a rotary shaft 18 rotatably; a collar member 40 attached to the rotary shaft 18 and fixing the bearing inner race 32; and a bolt member 42 attached to a housing 14 and fixing the bearing outer race 34. An outer circumferential surface of the collar member 40 and an inner circumferential surface of the bolt member 42 are disposed opposite each other in a separated state in a radial direction. A labyrinth seal 48 is formed between an annular groove 46 formed on the outer circumferential surface of the collar member 40 and the inner circumferential surface of the bolt member 42.

Description

  The present invention relates to a centrifugal compressor that compresses gas by rotating an impeller with a rotational driving force of a motor.

  Conventionally, a centrifugal compressor including a centrifugal compressor and an axial compressor has been used as an air supply source in factories and the like. As this type of centrifugal compressor, for example, Patent Document 1 includes a rotor shaft penetrating both ends in a housing, and an impeller attached to an end portion of the rotor shaft. A high-speed rotating electric motor in which a labyrinth seal is provided between a shaft and a through-hole of a housing is disclosed.

  In the high-speed rotary electric motor disclosed in Patent Document 1, a bearing (bearing) that rotatably supports the rotor shaft is disposed in the vicinity of the rotor that rotates together with the rotor shaft.

JP 2002-64956 A

  By the way, when the separation distance between the bearing along the axial direction of the rotating shaft and the center of gravity of the impeller is large, the resonance frequency of the rotating shaft is lowered, and it is difficult to rotate the impeller at high speed. In this regard, in the high-speed rotary electric motor disclosed in Patent Document 1, the relationship of the separation distance between the bearing and the center of gravity of the impeller is not specifically disclosed and is unknown.

  Further, in the high-speed rotary electric motor disclosed in Patent Document 1, in order to fix the bearing to the rotating shaft, the bearing inner ring fixing member and the bearing outer ring fixing member are temporarily arranged between the labyrinth seal and the bearing. If it is arranged along the axial direction, the distance between the bearing and the center of gravity of the impeller is increased by the width dimension of the bearing inner ring fixing member and the bearing outer ring fixing member, and the impeller can be rotated at high speed. It becomes even more difficult.

  The present invention has been made in view of the above points, and it is possible to set the resonance frequency of the rotating shaft high by shortening the separation distance between the bearing and the impeller along the axial direction of the rotating shaft as compared with the conventional one. An object is to provide a possible centrifugal compressor.

  In order to achieve the above object, the present invention provides a centrifugal compressor that compresses gas by rotating an impeller with a rotational driving force of a motor. The centrifugal compressor has a bearing inner ring and a bearing outer ring, and the rotation shaft is rotatable. A supporting bearing, provided between the impeller and the bearing, and provided between the impeller and the bearing, a first fixing member mounted on the rotating shaft and fixing the bearing inner ring, A second fixing member that is mounted on the housing and fixes the bearing outer ring, and an outer peripheral surface of the first fixing member and an inner peripheral surface of the second fixing member are opposed to each other in a state of being radially separated from each other. In any one of the outer peripheral surface and the inner peripheral surface, a groove portion extending in the circumferential direction is provided. In this case, the bearing may be constituted by a grease seal type bearing.

  In the present invention, since the outer peripheral surface of the first fixing member and the inner peripheral surface of the second fixing member are opposed to each other in a state of being radially separated from each other, the first fixing member in which the groove portion is formed in either one of them. A labyrinth seal is formed between the outer peripheral surface and the inner peripheral surface of the second fixing member, while the bearing outer ring is fixed by the second fixing member.

  Therefore, according to the present invention, the second fixing member is provided with a member having a sealing function and a member having a fixing function individually by combining the sealing function and the fixing function to achieve multi-function. Thus, the number of parts is reduced, and the distance from the center of the bearing to the center of gravity of the impeller can be shortened as compared with the prior art. As a result, it is possible to set the resonance frequency of the rotating shaft to be higher than that in the prior art, the rotating shaft can be driven to rotate at a higher speed, and the overall size of the apparatus can be reduced.

  Further, according to the present invention, the second fixing member extends along the radial direction the escape passage for the gas flowing out from the gap between the outer peripheral surface of the first fixing member and the inner peripheral surface of the second fixing member. By providing in this way, the gas flowing out from the gap between the outer peripheral surface of the first fixing member and the inner peripheral surface of the second fixing member can be smoothly discharged through the escape passage.

  Further, according to the present invention, the rotary shaft is fastened in the axial direction by the tension shaft, and the first fixing member is sandwiched between the impeller and the bearing inner ring, thereby separating the bearing from the center of the impeller to the center of gravity of the impeller. The distance can be shortened compared to the conventional case.

  Furthermore, according to the present invention, the second fixing member is provided with an inclined surface that is inclined from the inner peripheral surface of the second fixing member toward one surface on the bearing outer ring side, so that gas (air) is made into the inclined surface. Can flow smoothly along.

  Still further, according to the present invention, the second fixing member is fixed to the housing by an inlay structure, so that the gap between the outer peripheral surface of the first fixing member and the inner peripheral surface of the second fixing member is accurately set. can do.

  According to the present invention, it is possible to obtain a centrifugal compressor capable of setting the resonance frequency of the rotating shaft higher by reducing the distance between the bearing and the impeller along the axial direction of the rotating shaft than the conventional one. it can.

It is a partially omitted vertical sectional view of a centrifugal compressor according to an embodiment of the present invention. It is a principal part expanded longitudinal cross-sectional view of FIG. (A) is an enlarged vertical sectional view of a state in which the bearing is fixed to the rotating shaft in the present embodiment, and (b) is an enlarged vertical sectional view showing another example of a member for fixing the bearing. (A) is a disassembled perspective view of the collar member and bolt member which fix a bearing, (b) is a perspective view which shows the state in which the said collar member and bolt member were assembled | attached. It is a longitudinal cross-sectional view which shows the flow path of the air which flowed out from the labyrinth seal part. (A) is a partially omitted vertical sectional view showing a separation distance from the bearing center to the impeller center of gravity in the present embodiment, and (b) is a part showing a separation distance from the bearing center to the impeller center of gravity in the comparative example. FIG.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a partially omitted longitudinal sectional view of a centrifugal compressor according to an embodiment of the present invention, and FIG. 2 is an enlarged longitudinal sectional view of a main part of FIG.

The centrifugal compressor 10 according to the embodiment of the present invention is incorporated in, for example, a fuel cell system and supplies compressed air to a fuel cell (stack) (not shown).
As shown in FIG. 1, the centrifugal compressor 10 includes a first housing 14a having an inlet port 12a through which air is introduced and an outlet port 12b through which compressed air is led out, and a second motor 26 in which a motor 26 to be described later is housed. A housing 14 including a housing 14b is provided.

  The housing 14 has a rotating shaft 18 that is rotatably supported through a through hole, and an impeller 20 is fixed to one end portion along the axial direction of the rotating shaft 18. The housing 14 houses a motor 26 having a magnet color rotor 22 that rotates integrally with the rotary shaft 18 and a stator 24 that is fixed to the housing 14 side.

  As shown in FIG. 2, a tension shaft 28 having a head portion 28 a engaged with the impeller 20 and extending to a tension shaft nut fastening portion (not shown) is fitted inside the rotary shaft 18. The impeller 20, the rotary shaft 18, the magnet color rotor 22, and the like that are respectively mounted along the axial direction of the tension shaft 28, and The tension shaft 28 is clamped between a tension shaft nut fastening portion (not shown) that is screwed to the other end side along the axial direction of the tension shaft 28, and is integrated with the tension shaft 28 by the axial force (tensile force). Retained. Therefore, the rotating shaft 18 is fastened in the axial direction of the tension shaft 28.

  FIG. 3A is an enlarged longitudinal sectional view showing a state in which the bearing is fixed to the rotating shaft in the present embodiment, and FIG. 3B is an enlarged longitudinal sectional view showing another example of a member for fixing the bearing. 4 (a) is an exploded perspective view of the collar member and the bolt member for fixing the bearing, and FIG. 4 (b) is a perspective view showing a state in which the collar member and the bolt member are assembled.

  An annular step portion 29 having a plurality of steps is formed on the outer peripheral surface of the central portion along the axial direction of the rotating shaft 18. A bearing 30 that rotatably supports the rotary shaft 18 is disposed on the large diameter portion of the annular step portion 29. The bearing 30 is an angular contact bearing and is constituted by a grease seal type bearing. The bearing 30 includes a bearing inner ring 32 that is in contact with the rotating shaft 18 side, a bearing outer ring 34 that is in contact with the housing 14 side, and a ball 36 that is interposed between the bearing inner ring 32 and the bearing outer ring 34 in a freely rolling manner. And have. A thrust washer 38 is mounted on the rear side along the axial direction of the bearing 30 at a position where it abuts against the flange of the housing 14.

  In the axial direction of the tension shaft 28, between the impeller 20 and the bearing 30, a ring-shaped collar member (first shaft) that is press-fitted into the rotary shaft 18 (small diameter portion of the annular step portion 29) and fixes the bearing inner ring 32. (Fixing member) 40 is provided. The collar member 40 is sandwiched between the impeller 20 and the bearing inner ring 32 along the axial direction. The collar member 40 may be fixed by an axial force along the axial direction of the tension shaft 28. Further, between the impeller 20 and the bearing 30, a ring-shaped bolt member (second fixing member) 42 that is mounted in the hole 41 of the housing 14 and fixes the bearing outer ring 34 is provided. On the outer peripheral surface of the bolt member 42, a screw portion 42 a that is fastened to a screw groove in the hole portion 41 of the housing 14 is provided.

  The ring-shaped collar member 40 and the bolt member 42 are disposed so as to overlap in the axial direction, and are opposed to each other in a state of being separated by a gap 44 in the radial direction.

  A plurality of annular grooves (grooves) 46 extending along the circumferential direction are formed on the outer peripheral surface of the collar member 40. The plurality of annular groove portions 46 are arranged side by side with substantially the same groove depth along the thickness direction substantially orthogonal to the circumferential direction. On the other hand, the inner peripheral surface of the bolt member 42 is formed by a curved surface having a band shape and a constant radius of curvature. Therefore, a non-contact labyrinth seal portion 48 is configured by the annular groove portion 46 formed on the outer peripheral surface of the collar member 40 and the inner peripheral surface of the bolt member 42 that are opposed to each other in the radial direction in a separated state.

  In the present embodiment, as shown in FIG. 3A, a plurality of annular grooves 46 are formed on the outer peripheral surface of the collar member 40, and a non-contact labyrinth seal is formed between the inner peripheral surface of the bolt member 42. Although the portion 48 is formed, the present invention is not limited to this, and a plurality of annular groove portions 46 are formed on the inner peripheral surface of the bolt member 42 as shown in another example of FIG. You may make it form the non-contact rabbling seal part 48 between the outer peripheral surfaces of the member 40. FIG. In the present embodiment, the number of stages of the annular groove 46 is set to four, but the present invention is not limited to this and may be a plurality of stages.

  As shown in FIG. 4, an annular bulging portion 49 that bulges toward the bearing 30 is formed on one side surface between the inner diameter and the outer diameter of the ring-shaped bolt member 42. The annular bulging portion 49 is provided with a relief passage 50 that is formed by a notch portion that is formed apart by a predetermined angle and extends along the radial direction of the bolt member 42.

  The escape passage 50 is for smoothly letting out air (gas) flowing out (leaking) from the gap 44 between the outer peripheral surface of the collar member 40 and the inner peripheral surface of the bolt member 42 toward the housing 14 side. In the present embodiment, four escape passages 50 are formed at a separation angle of 90 degrees along the circumferential direction. However, the present invention is not limited to this, and one or more escape passages 50 are formed. Good.

  Further, the annular bulging portion 49 of the bolt member 42 is provided with an inclined surface 52 that extends from the inner peripheral surface of the bolt member 42 and inclines toward the one surface 34a on the bearing outer ring 34 side. By forming such an inclined surface 52, it is possible to improve the flow of air that has passed through the labyrinth seal portion 48 and to easily flow out to the housing 14 side.

  Further, the bolt member 42 is provided with an inlay structure 54 for providing concentricity (centering) with the collar member 40 when the bolt member 42 is fixed to the housing 14 (FIG. 3A). )reference). The inlay structure 54 is formed on the outer peripheral surface of the bolt member 42, and includes an annular step surface 56 including a small-diameter outer diameter surface that is reduced in diameter from the screw portion 42a. An annular step surface corresponding to the annular step surface 56 on the bolt member 42 side is formed.

  In this case, the collar member provided with the annular groove portion 46 by fitting the annular step surface 56 formed on the outer peripheral surface of the bolt member 42 into the annular step surface formed on the hole 41 side of the housing 14. The dimension of the gap 44 between the outer peripheral surface of 40 and the inner peripheral surface of the bolt member 42 can be set with high accuracy.

  On the other side surface of the bolt member 42 located on the back surface of the impeller 20, a plurality of mounting hole portions 58 (four are illustrated in FIG. 4A) are formed along the circumferential direction. By using a mounting jig (not shown) provided with a plurality of pins inserted into the mounting hole 58, the bolt member 42 is securely fastened to the hole 41 of the housing 14 with a prescribed (predetermined) tightening torque. The deformation amount of the inner peripheral surface of the bolt member 42 can be suppressed.

  Referring back to FIGS. 1 and 2, a back space communicating with a gap 44 formed between the inner peripheral surface of the bolt member 42 and the outer peripheral surface of the collar member 40 is provided on the rear surface of the impeller 20 adjacent to the bearing 30 side. A portion 60 is provided, and compressed air compressed by the impeller 20 flows out through the back space portion 60.

  Further, as shown in FIGS. 1 and 2, a cooling passage 62 is provided around the housing 14 so as to circulate cooling water and cool the bearing outer ring 34. Further, as shown in FIG. 5, the housing 14 is provided with an air outlet passage 64 for leading out the air that flows out (leaks out) from the labyrinth seal portion 48 and passes through the escape passage 50 to the outside. . The air outlet passage 64 is arranged and configured so as not to interfere with the cooling passage 62, and has an inlet portion 64a in which an opening facing the bearing outer ring 34 is formed, and a radial passage portion 64b extending along the radial direction. The thrust passage portion 64c extends substantially parallel to the axial direction of the rotary shaft 18.

  In other words, in the portion where the air outlet passage 64 is formed, the inner diameter of the cooling passage 62 is narrowed to be offset (offset) toward the inner diameter side of the housing 14, and the air outlet passage 64 is not formed. In the part, the cooling passage 62 is formed with an enlarged diameter as compared with the above, and has an arrangement structure that does not interfere with each other (see FIG. 2 and FIG. 5 in comparison).

  The centrifugal compressor 10 according to the present embodiment is basically configured as described above. Next, the function and effect will be described.

  When a power supply (not shown) is turned on and the motor 26 is driven to rotate, the rotary shaft 18 and the tension shaft 28, the impeller 20 attached to the tip of the tension shaft 28, and the axis of the tension shaft 28 A tension shaft nut (not shown) attached to the rear side along the direction rotates integrally. The impeller 20 rotates, the air introduced from the inlet port 12a is compressed according to the rotational speed, and the compressed air led out from the outlet port 12b is supplied to a fuel cell (not shown).

  At that time, a part of the compressed air passes through a back space 60 formed on the back surface of the impeller 20 and a plurality of annular grooves 46 formed on the outer peripheral surface of the collar member 40 and an inner peripheral surface of the bolt member 42. It flows out (leaks) to the non-contact labyrinth seal part 48 comprised between. In the labyrinth seal portion 48, the leaked pressure of the compressed air that has flowed out is gradually reduced for each groove portion of the plurality of annular groove portions 46. Further, the air leaking from the labyrinth seal portion 48 is discharged to the outside via the inlet portion 64a, the radial passage portion 64b, and the thrust passage portion 64c of the air outlet passage 64 formed in the housing 14. As a result, in this embodiment, the air that has flowed out (leaked out) from the labyrinth seal portion 48 can be discharged smoothly.

  In this embodiment, the inner peripheral surface of the bolt member 42 forms a predetermined gap 44 with the annular groove portion 46 of the collar member 40 to form the labyrinth seal portion 48, while the annular side portion of the bolt member 42 is formed. The bearing outer ring 34 is fixed.

  Therefore, in the present embodiment, the bolt member 42 can be provided with a member having a sealing function and a member having a fixing function individually by combining the sealing function and the fixing function to achieve multiple functions. This eliminates the need for the number of parts, and the distance D1 from the center of the bearing 30 to the center of gravity of the impeller 20 can be shortened as compared with the prior art (see FIG. 6A). As a result, the resonance frequency of the rotating shaft 18 can be lowered and driven to rotate at a higher speed, and downsizing of the entire apparatus can be achieved.

  For example, in the comparative example shown in FIG. 6B, a member A for forming a labyrinth seal portion between the annular groove portion and a member B for fixing the bearing outer ring are separately required. The distance D2 from the center of the impeller to the center of gravity of the impeller is longer than the distance D1 of the present embodiment (D1 <D2).

  In this case, the resonance frequency in the comparative example is about 1300 Hz (78000 rpm) in the actually measured value by hammering, whereas the resonance frequency in this embodiment is about 1700 Hz (102000 rpm) in the actually measured value by hammering. I was able to.

  Thus, in this embodiment, since the resonance frequency of the rotating shaft 18 can be set higher than in the prior art, the rotating speed of the rotating shaft 18 (impeller 20) can be made even faster and more stable ( It can be rotated (suppressing abnormal vibration).

  Further, in the present embodiment, the annular step surface 56 is formed on the outer peripheral surface of the bolt member 42, and the inlay structure 54 is formed between the hole portion 41 of the housing 14, so that the bolt member 42 with respect to the center line of the housing 14. These axes can be made to coincide with each other so that a good coaxiality (concentricity) can be obtained. As a result, the dimension of the gap 44 between the inner peripheral surface of the bolt member 42 and the outer peripheral surface of the collar member 40 can be set with high accuracy.

  Further, in the present embodiment, a non-contact labyrinth seal portion 48 is configured between the inner peripheral surface of the bolt member 42 and the annular groove portion 46 of the collar member 40. As a result, in a mechanism that seals compressed air with a known contact seal (not shown), the generation of wear powder and the like that would occur from the contact seal and its contact sliding portion is prevented, and a specified amount (place) (Quantitative determination) Since it becomes unnecessary to replace a contact seal (not shown) that has caused the above wear, maintenance work becomes unnecessary and durability can be improved.

DESCRIPTION OF SYMBOLS 10 Centrifugal compressor 14 Housing 16 Motor 18 Rotating shaft 20 Impeller 28 Tension shaft 30 Bearing 32 Bearing inner ring 34 Bearing outer ring 40 Collar member (first fixed member)
42 Bolt member (second fixing member)
46 Annular groove (groove)
48 Labyrinth seal 50 Relief passage 52 Inclined surface 54 Inner structure

Claims (6)

In the centrifugal compressor that compresses gas by rotating the impeller with the rotational driving force of the motor,
A bearing having a bearing inner ring and a bearing outer ring and rotatably supporting a rotating shaft;
A first fixing member that is provided between the impeller and the bearing and that is mounted on the rotating shaft and fixes the bearing inner ring;
A second fixing member provided between the impeller and the bearing and mounted on a housing to fix the bearing outer ring;
With
The outer peripheral surface of the first fixing member and the inner peripheral surface of the second fixing member are disposed to face each other in a radially separated state, and either the outer peripheral surface or the inner peripheral surface is disposed in the circumferential direction. A centrifugal compressor characterized in that a groove extending along the groove is provided. The centrifugal compressor according to claim 1, wherein
The centrifugal compressor is characterized in that the bearing comprises a grease seal type bearing. The centrifugal compressor according to claim 1 or 2,
The second fixing member is provided with an escape passage for gas flowing out from a gap between the outer peripheral surface of the first fixing member and the inner peripheral surface of the second fixing member so as to extend along the radial direction. A centrifugal compressor characterized by having The centrifugal compressor according to any one of claims 1 to 3,
The centrifugal compressor is characterized in that the rotating shaft is fastened in an axial direction by a tension shaft, and the first fixing member is sandwiched between the impeller and the bearing inner ring. The centrifugal compressor according to any one of claims 1 to 4,
The centrifugal compressor, wherein the second fixing member is provided with an inclined surface that is inclined from an inner peripheral surface of the second fixing member toward one surface on the bearing outer ring side. The centrifugal compressor according to any one of claims 1 to 5,
The centrifugal compressor is characterized in that the second fixing member is fixed to the housing by an inlay structure.

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