JP2022067667A - Electric compressor - Google Patents

Abstract

To reduce a gas flow passing a bearing while making a hole diameter of a communication hole smaller, in an electric compressor.SOLUTION: An electric compressor 1 comprises: a housing 2 having a compressor chamber 7 and a motor chamber 9 which are partitioned by a partitioning wall 11; an impeller 3 accommodated in the compressor chamber 7; a shaft 13 having the impeller 3, penetrating the partitioning seal 11, and extending over the compressor chamber 7 and the motor chamber 9; a motor part 5 accommodated in the motor chamber 9, and rotating the shaft 13; a bearing 33 interposed between the shaft 13 and the partitioning wall 11; and a communication hole 39 penetrating the partitioning wall 11 in a position facing an impeller back face 31, and making the compressor chamber 7 and the motor chamber 9 communicate with each other. There is formed a labyrinth seal part 41 which is arranged between the impeller back face 31 and the partitioning seal 11, and seals a clearance between the communication hole 39 and the bearing 33.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an electric compressor.

Conventionally, the centrifugal compressor described in Patent Document 1 below is known. In this centrifugal compressor, the impeller housed in the compressor room is rotated by the motor housed in the motor room. The shaft to which the impeller is attached extends through the partition wall that separates the compressor chamber and the motor chamber, and is pivotally supported by a bearing installed in the partition wall. Here, when a pressure difference between the compressor chamber and the motor chamber is generated, a gas air flow is generated between the compressor chamber and the motor chamber. This gas air flow may pass through the bearing and cause the grease of the bearing to flow out, deteriorating the performance of the bearing. Therefore, in order to balance the pressure between the compressor chamber and the motor chamber as described above, the partition wall is formed with a communication hole for communicating the compressor chamber and the motor chamber at the position on the back surface of the impeller.

International Publication WO 2017/057482 Gazette International Publication WO2014 / 096786 Jitsukaihei 05-012693 Gazette Japanese Unexamined Patent Publication No. 2014-169699

However, since there is a risk of water entering the motor chamber from the compressor chamber, it is not preferable to make the pore diameter of the communication hole extremely large. Therefore, there is a limit to the speed of pressure equilibration between the compressor chamber and the motor chamber by the communication holes. Therefore, when sudden pressure fluctuations in the compressor chamber occur, such as when the impeller is accelerating, the pressure equilibration by the communication holes may not be in time, and as a result, the air flow of the gas passing through the bearing may not be sufficiently suppressed.

The present disclosure describes an electric compressor that reduces the airflow of gas passing through a bearing while suppressing the hole diameter of the communication hole.

The electric compressor according to one aspect of the present disclosure is provided with a housing having a compressor chamber and a motor chamber partitioned by a partition wall, an impeller housed in the compressor chamber, and an impeller, and the compressor penetrates the partition wall. A shaft extending between the chamber and the motor chamber, a motor portion housed in the motor chamber to rotate the shaft, a bearing interposed between the shaft and the partition wall, and penetrating the partition wall at a position facing the back surface of the impeller. A communication hole for communicating the compressor chamber and the motor chamber is provided, and a labyrinth seal portion is provided between the back surface of the impeller and the partition wall and seals between the communication hole and the bearing. It is an electric compressor.

The labyrinth seal portion may have a portion formed on the back surface of the impeller. The impeller may be made of resin. The labyrinth seal portion may have a plurality of ribs formed on the back surface of the impeller so as to form a concentric circle centered on the rotation axis of the impeller and to extend in the direction of the rotation axis toward the partition wall.

According to the electric compressor of the present disclosure, it is possible to reduce the air flow of gas passing through the bearing while suppressing the hole diameter of the communication hole.

It is sectional drawing of the electric compressor of an embodiment. It is sectional drawing which enlarges and shows the vicinity of the bearing of the electric compressor of an embodiment. It is a figure which looked at the impeller of the electric compressor of an embodiment from the back side.

The electric compressor 1 according to the embodiment will be described with reference to FIG. The electric compressor 1 is a centrifugal compressor including an impeller 3 that rotates around a rotation axis X and a motor unit 5 as a power source, and supplies compressed air to an internal combustion engine of a vehicle or a ship, for example. In the following description, the terms "axial direction", "diameter direction", and "circumferential direction" mean the axial direction, radial direction, and circumferential direction of the rotation of the impeller 3.

The housing 2 of the electric compressor 1 has a compressor chamber 7 in which the impeller 3 is housed and a motor room 9 in which the motor unit 5 is housed. The housing 2 has a partition wall 11 that divides the compressor chamber 7 and the motor chamber 9 in the axial direction and partitions the housing 2. In the example of FIG. 1, the housing 2 is mainly composed of three parts connected in the axial direction, but the housing 2 is not limited to this form, and the parts constituting the housing 2 and the combination method can be freely designed. It is possible. As the material of the housing 2, aluminum is preferable because it is advantageous for weight reduction, but for example, stainless steel or carbon steel can also be adopted.

The electric compressor 1 includes a shaft 13 extending on the rotation axis X. The shaft 13 penetrates the partition wall 11 and extends to the compressor chamber 7 and the motor chamber 9. The impeller 3 is attached to one end of the shaft 13. The rotor 15 of the motor unit 5 is attached to the other end of the shaft 13. The motor unit 5 has the rotor 15 and a stator 17 arranged around the rotor 15. The stator 17 is fixed to the inner wall surface of the housing 2 in the motor chamber 9. The motor unit 5 is housed in a motor chamber 9, which is a substantially closed space.

The compressor chamber 7 has a diffuser 19 provided on the outer peripheral side of the impeller 3 and a scroll 21 provided on the outer peripheral side of the diffuser 19. Further, the compressor chamber 7 is opened to the outside through an intake port 23 provided on the rotation axis X and a discharge port 27 which is an outlet of the scroll 21.

When electric power is supplied to the motor unit 5, the rotor 15 and the shaft 13 rotate around the rotation axis X with respect to the stator 17. As a result, when the impeller 3 in the compressor chamber 7 rotates, the external gas is sucked into the impeller 3 in the axial direction through the intake port 23 and discharged in the radial direction from the impeller 3. After that, the gas is compressed through the diffuser 19 and the scroll 21, and is discharged to the outside as compressed air through the discharge port 27. This compressed air is supplied to the internal combustion engine as described above.

The electric compressor 1 includes bearings 33 and 35 that rotatably support the shaft 13 with respect to the housing 2. The bearings 33 and 35 are arranged so as to sandwich the motor portion 5 in the axial direction, and support the shaft 13 with both sides. One bearing 33 on the side close to the impeller 3 is installed so as to be embedded in the partition wall 11 and is interposed between the shaft 13 and the partition wall 11. The other bearing 35 is fixed to the support portion 36 protruding from the inner wall surface of the motor chamber 9.

The bearing 33 is a grease-filled ball bearing. In the bearing 33, a plurality of balls arranged in the circumferential direction are interposed between the outer ring and the inner ring. The space between the outer ring and the inner ring is filled with grease so as to immerse the ball. Seals are provided on both ends of the space in which the grease is sealed to prevent grease from leaking or foreign matter from entering. The seal may be a contact type seal or a non-contact type seal. 1 and 2 schematically show each element such as a bearing 33, and the seal and grease are not shown. Since the configuration of this type of ball bearing is known, further detailed description will be omitted. Since the outer ring of the bearing 33 is fixed to the partition wall 11 and the inner ring of the bearing 33 is fixed to the shaft 13, the shaft 13 rotates smoothly with respect to the partition wall 11.

Subsequently, with reference to FIG. 2, the structure in the vicinity of the compressor chamber 7 and the bearing 33 will be further described. The compressor chamber 7 is a space on the intake port 23 side of the partition wall 11 in the internal space of the housing 2, and refers to the space from the intake port 23 to the discharge port 27. The compressor chamber 7 includes a narrow space sandwiched in the axial direction between the impeller 3 and the partition wall 11. Hereinafter, the space sandwiched between the impeller 3 and the partition wall 11 in the axial direction is referred to as a back space 37. Further, the surface of the impeller 3 that faces the partition wall 11 in the axial direction is called the impeller back surface 31.

The partition wall 11 is provided with a communication hole 39 for balancing the pressure between the compressor chamber 7 and the motor chamber 9. The communication hole 39 is formed so as to penetrate the partition wall 11 in the axial direction, and communicates the compressor chamber 7 and the motor chamber 9. The communication hole 39 is provided at a position facing the back surface 31 of the impeller in the axial direction. A plurality of communication holes 39 may be formed in the partition wall 11. Gas flows back and forth between the compressor chamber 7 and the motor chamber 9 through the communication hole 39, so that the pressure between the compressor chamber 7 and the motor chamber 9 is equilibrated.

If there is no communication hole 39, when a pressure difference between the compressor chamber 7 and the motor chamber 9 occurs, an air flow in the rotation axis X direction penetrating the inside of the bearing 33 (hereinafter referred to as “through airflow”) may be generated. .. Then, there is a possibility that the grease of the bearing 33 will flow out due to such a through air flow and the bearing function of the bearing 33 will be deteriorated. According to the communication hole 39 described above, such a through-air flow of the bearing 33 is reduced, and deterioration of the bearing 33 is suppressed.

However, since there is a risk of water entering the motor chamber 9 from the compressor chamber 7, it is not preferable to make the hole diameter of the communication hole 39 extremely large. Therefore, there is a limit to the speed of pressure equilibration between the compressor chamber 7 and the motor chamber 9 by the communication hole 39. Therefore, when a sudden pressure fluctuation in the compressor chamber 7 occurs, such as when the impeller 3 is accelerating, there is a possibility that the through-air flow of the bearing 33 cannot be sufficiently suppressed.

Therefore, as a countermeasure, a labyrinth seal portion 41 is provided in the back space 37. The labyrinth seal portion 41 is provided in an annular shape in the region between the communication hole 39 and the bearing 33. FIG. 3 is a view of the impeller 3 as viewed from the back surface 31 side of the impeller. As shown in FIGS. 2 and 3, the labyrinth seal portion 41 has a plurality of (five in the case of the present embodiment) ribs 43. The ribs 43 are concentrically provided on the back surface 31 of the impeller with the rotation axis X as the center. Each rib 43 is formed on the back surface 31 of the impeller, has a cylindrical shape with the rotation axis X as a cylinder axis, and extends in the axial direction toward the partition wall 11. Each rib 43 extends to the immediate vicinity of the partition wall 11 and narrows the axial width of the back space 37.

Further, of the back space 37, the space 37a on the inner peripheral side of the labyrinth seal portion 41 is formed in a space having a relatively large volume. In the following, the space on the inner peripheral side of the labyrinth seal portion 41 of the back space 37 is referred to as the inner peripheral back space 37a, and the space on the outer peripheral side of the back space 37 on the outer peripheral side of the labyrinth seal portion 41 is referred to as the outer peripheral back space 37b. .. The impeller 3 is made of resin and is manufactured by injection molding. The rib 43 is also integrally formed as one part of the impeller 3 at the time of injection molding.

Such a labyrinth seal portion 41 seals between the communication hole 39 and the bearing 33, and the gas flow between the communication hole 39 and the bearing 33 is obstructed and reduced. That is, the flow of gas between the inner peripheral back space 37a and the outer peripheral back space 37b is obstructed and reduced.

The action and effect of the labyrinth seal portion 41 as described above will be described. Consider a case where a sudden increase in pressure in the compressor chamber 7 occurs when the labyrinth seal portion 41 does not exist. In this case, the pressure increase in the back space 37 causes the gas to move to the motor chamber 9 through the communication hole 39. If the hole diameter of the communication hole 39 is not sufficient, it takes a certain amount of time to increase the pressure in the motor chamber 9 as described above. Then, immediately after the pressure rise in the compressor chamber 7, the pressure in the rear space 37 becomes higher than that in the motor chamber 9, and a through air flow of the bearing 33 may be generated from the rear space 37 toward the motor chamber 9.

On the other hand, when the labyrinth seal portion 41 is present, the gas flow from the outer peripheral back space 37b to the inner peripheral back space 37a is obstructed by the labyrinth seal portion 41, so that the pressure of the inner peripheral back space 37a rises. It also takes some time. Further, as described above, the relatively large volume of the inner peripheral back space 37a also causes the pressure increase of the inner peripheral back space 37a to take time. On the other hand, since the labyrinth seal portion 41 is located on the inner peripheral side of the communication hole 39, the gas flow from the outer peripheral back space 37b to the communication hole 39 is not obstructed.

Then, the speed of the pressure rise in the inner peripheral back space 37a and the speed of the pressure rise in the motor chamber 9 become close to each other. As a result, the pressure difference between the motor chamber 9 and the inner peripheral rear space 37a immediately after the pressure rise in the compressor chamber 7 is relaxed, so that the through-air flow of the bearing 33 from the inner peripheral rear space 37a toward the motor chamber 9 flows. It will be reduced. Therefore, according to the electric compressor 1, the through-air flow of the bearing 33 can be reduced without extremely increasing the hole diameter of the communication hole 39.

Further, since the labyrinth seal portion 41 is provided at a position between the impeller back surface 31 and the partition wall 11, it is easy to secure the volume of the inner peripheral back space 37a, and the pressure increase of the inner peripheral back space 37a can be appropriately delayed. can. On the other hand, for example, instead of the labyrinth seal portion 41, it is conceivable to seal between the shaft 13 and the partition wall 11 at a position between the bearing 33 and the impeller 3 by a seal ring or the like. However, in this case, it is difficult to secure a large volume in the space between the seal and the bearing 33, and as a result, it is difficult to appropriately delay the pressure rise in the space.

Further, if the seal ring as described above is adopted, the flow of gas passing through the seal ring is extremely obstructed due to the high sealing property of the seal ring. Therefore, immediately after the pressure rise in the compressor chamber 7, the pressure in the motor chamber 9 rises faster than the space between the seal ring and the bearing 33. Then, it is conceivable that a through-air flow of the bearing 33 is generated so as to flow backward from the motor chamber 9 toward the seal ring. Therefore, the configuration in which the labyrinth seal portion 41 is provided as in the present embodiment is preferable to the configuration in which the seal ring is provided between the shaft 13 and the partition wall 11.

Further, since the labyrinth seal portion 41 is formed by integrally forming the plurality of ribs 43 on the impeller 3 by injection molding, the number of parts of the electric compressor 1 is increased and the labor for manufacturing the impeller 3 is also increased. It can be avoided. Further, the labyrinth seal portion 41 may be any as long as it obstructs the flow of gas between the outer peripheral back space 37b and the inner peripheral back space 37a to some extent, and high sealing performance is not required. Therefore, the strict dimensional accuracy of the rib 43 is not required, and the impeller 3 can be manufactured with the dimensional accuracy by injection molding.

Further, in the case of the resin impeller 3 by injection molding, it is preferable to suppress the wall thickness of the impeller 3 as much as possible to make it uniform in order to suppress defects in injection molding. On the other hand, it is also necessary to secure the mechanical strength of the impeller 3. According to the impeller 3 of the present embodiment, since a plurality of concentric ribs 43 are provided on the back surface 31 of the impeller, it is easy to reduce the wall thickness of the impeller 3 and to achieve both mechanical strength. Further, since each rib 43 has a cylindrical shape extending in the axial direction, it is possible to release the mold on the back surface 31 side of the impeller in the axial direction at the time of injection molding, and it is relatively easy to manufacture by injection molding. ..

The present disclosure can be carried out in various forms having various changes and improvements based on the knowledge of those skilled in the art, including the above-described embodiment. It is also possible to construct a modified example by utilizing the technical matters described in the embodiment. The configurations of the respective embodiments may be combined and used as appropriate.

In the above-described embodiment, the rib 43 that narrows the back space 37 is provided on the back surface 31 of the impeller, but the uneven shape portion for narrowing the back space 37 may be provided on the partition wall 11. Further, it is not essential that such an uneven shape portion is integrally formed with the impeller 3, and a separate component having the uneven shape portion may be joined to the back surface 31 of the impeller. Similarly, a separate component having the uneven shape portion as described above may be joined to the partition wall 11. Further, in the above-described embodiment, the impeller 3 is made of resin and is manufactured by injection molding, but the present invention is not limited to this, and the material and manufacturing method of the impeller 3 can be appropriately changed.

1 Electric compressor 2 Housing 3 Impeller 5 Motor part 7 Compressor room 9 Motor room 11 Partition wall 13 Shaft 31 Impeller back 33 Bearing 39 Communication hole 41 Labyrinth seal part 43 Rib X Rotating axis

Claims (4)

A housing having a compressor chamber and a motor chamber partitioned by a partition wall,
The impeller housed in the compressor chamber and
A shaft provided with the impeller and extending through the partition wall to the compressor chamber and the motor chamber.
A motor unit housed in the motor chamber and rotating the shaft,
A bearing interposed between the shaft and the partition wall,
A communication hole that penetrates the partition wall at a position facing the back surface of the impeller and communicates the compressor chamber and the motor chamber is provided.
An electric compressor provided between the back surface of the impeller and the partition wall and formed with a labyrinth seal portion for sealing between the communication hole and the bearing. The electric compressor according to claim 1, wherein the labyrinth seal portion has a portion formed on the back surface of the impeller. The electric compressor according to claim 1 or 2, wherein the impeller is made of resin. The labyrinth seal portion is
1. The electric compressor described in the section.

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