JP2013127204A - Electric pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric pump which prevents a decrease in pump efficiency while preventing an impeller from contacting with a casing.SOLUTION: A vortex chamber 24 in which a fluid flows is formed between an outer periphery surface 28a of the impeller 28 and an inner periphery surface 14a of the casing in the electrical pump. In the vortex chamber 24, an interval between the outer periphery surface 28a and the inner periphery surface 14a is the narrowest at a position 24a. A low rigidity part which has lower rigidity than the other parts is provided in a shaft 44. The low rigidity part is formed such that upon actuation of the electric pump, a center point 44c of the shaft 44 when the shaft 44 is viewed from above moves on a line L2 which is parallel to a tangent L1 of the outer periphery surface 28a at the position 24a and which passes the center point 44c of the shaft 44 or a region S1 at the opposite side of the position 24a out of two regions divided by the line L2.

Description

  The present specification discloses an electric pump.

  Patent Document 1 discloses a pump including a shaft, an impeller, and a pulley. The impeller is attached to one end of the shaft. The pulley is attached to the other end of the shaft. The shaft is rotatably supported by a bearing. The shaft is provided with a low-rigidity flexible portion having a smaller cross-sectional area than other portions of the shaft between the pulley and the bearing. In this pump, the pulley is rotated by applying a tension to the belt wound around the pulley. As the pulley rotates, the shaft rotates relative to the bearing, and as a result, the impeller rotates.

  When tension is applied to the belt, a bending moment acts on the shaft. At this time, the bending moment of the shaft in the vicinity of the bearing is relieved by bending the flexible portion.

JP-A-8-261194

  When the pump is operated, the shaft bends by receiving external force such as fluid pressure or vibration. As a result, the impeller attached to the shaft moves following the deformation of the shaft. Thereby, an impeller may contact the casing which accommodates the impeller. When the impeller comes into contact with the casing, the impeller rotation is impeded by the frictional force between the impeller and the casing, and the pump efficiency decreases. On the other hand, if the gap between the impeller and the casing is increased in order to prevent contact between the impeller and the casing, the pressure increase of the fluid is hindered and the pump efficiency is lowered. In this specification, the electric pump which suppresses the fall of pump efficiency by suppressing that an impeller and a casing contact is provided.

  The electric pump disclosed by this specification is provided with a casing, a shaft, a rotor, an impeller, and a stator. The casing forms a motor chamber and a pump chamber. The lower end side of the shaft is supported by a support portion provided in the casing. The rotor rotates around the shaft. The impeller is attached to the upper end side of the rotor and is rotatably accommodated in the pump chamber. The stator is disposed on the outer peripheral side of the rotor in the motor chamber. In the pump chamber, a vortex chamber through which fluid flows is formed between the outer peripheral surface of the impeller and the inner peripheral surface of the casing. In the vortex chamber, the gap between the outer peripheral surface of the impeller and the inner peripheral surface of the casing is the narrowest at a specific position in the circumferential direction of the impeller. At least one member of the support portion and the shaft is provided with a low-rigidity portion having lower rigidity than other portions of the member. The low-rigidity part is a specific point where the shaft center point when the shaft is viewed from above is parallel to the tangent to the outer peripheral surface of the impeller at the above specific position and passes through the shaft center point when the electric pump is operated. Or two regions divided by the specific straight line, so as to move to a region opposite to the specific position.

  If the shaft receives an external force such as fluid pressure or vibration during operation of the electric pump, the shaft deforms while being supported by the support portion. In the above electric pump, since the low rigidity portion is provided, when the shaft is viewed from above, the center point of the shaft moves to the specific straight line or the region opposite to the specific position. The shaft is deformed. As a result, the impeller moves following the deformation of the shaft. That is, the impeller does not move in a direction in which the distance between the outer peripheral surface of the impeller and the inner peripheral surface of the casing is reduced at the specific position. As a result, it is possible to prevent contact between the outer peripheral surface of the impeller and the inner peripheral surface of the casing at the specific position, that is, the position where the distance between the outer peripheral surface of the impeller and the inner peripheral surface of the casing is the smallest. it can. According to this configuration, in consideration of the deformation of the shaft, the distance between the outer peripheral surface of the impeller and the inner peripheral surface of the casing at the specific position does not need to be increased. Thereby, the fall of pump efficiency can be suppressed.

  The low rigidity portion may be formed on the lower end side of the shaft. The other part may be formed on the upper end side of the shaft. According to this configuration, when the shaft receives an external force, the lower end side of the shaft, which is a low-rigidity portion, bends, thereby preventing other portions of the shaft from bending. As a result, it is possible to suppress the portion of the shaft passing through the rotor from being bent. Thereby, it can suppress that a shaft and a rotor contact | win strongly.

  In the low-rigidity portion, the cross-sectional area in the direction perpendicular to the axial direction of the shaft may be smaller than other portions of the shaft. Alternatively, the low-rigidity part may have an elastic member formed of a material having a lower elastic coefficient than other parts of the shaft.

  The low rigidity portion may be formed in a part of the support portion. According to this configuration, when the shaft receives an external force, the low rigidity portion provided in the support portion is deformed, so that the shaft bends compared to the configuration in which the support portion firmly supports the shaft. Can be suppressed.

The schematic longitudinal cross-sectional view of the electric pump of 1st Example is shown. The schematic diagram showing the state which the shaft bent is shown. The figure for demonstrating the state of the movement of the center point of a shaft is shown. The schematic longitudinal cross-sectional view of the electric pump of 2nd Example is shown. The cross-sectional shape of the thin diameter part of 2nd Example is shown. The schematic longitudinal cross-sectional view of the electric pump of 3rd Example is shown. The schematic longitudinal cross-sectional view of the electric pump of 4th Example is shown. The cross-sectional shape of the low-rigidity part of 4th Example is shown. The cross-sectional shape of the space | gap of a modification is shown. The cross-sectional shape of the space | gap of a modification is shown. The cross-sectional shape of the small diameter part of a modification is shown.

(First embodiment)
The electric pump 10 according to the present embodiment is installed in an engine room of an automobile and is used for circulating cooling water that cools an engine, an inverter, and the like. As shown in FIG. 1, the electric pump 10 includes a pump unit 20 and a motor unit 40. The outer wall of the electric pump 10 is constituted by a casing 12.

  The pump unit 20 is formed in the upper casing 14 of the casing 12. The pump unit 20 has a pump chamber 26 formed by the upper casing 14. A suction port 22 and a discharge port (not shown) formed in the casing 12 are connected to the pump chamber 26. The suction port 22 is connected to the upper end of the pump chamber 26. The discharge port extends in the tangential direction of the outer periphery of the pump chamber 26. An impeller 28 of the rotating body 30 is disposed in the pump chamber 26. The impeller 28 has a circular shape when viewed from above, and the top surface is inclined upward from the outer periphery toward the center when viewed from the side. A plurality of blades are formed on the upper surface of the impeller 28 at regular intervals.

  The outer peripheral surface 28 a of the impeller 28 faces the inner peripheral surface 14 a of the upper casing 14. A vortex chamber 24 is formed between the outer peripheral surface 28a and the inner peripheral surface 14a. FIG. 3 is a schematic diagram when the inner peripheral surface 14a of the upper casing 14 is viewed from above. As shown in FIG. 3, the width of the vortex chamber 24 (the distance between the outer peripheral surface 28a and the inner peripheral surface 14a) is the smallest at the position 24a. The width of the vortex chamber 24 is gradually increased as it advances in the rotation direction R of the impeller 28. The vortex chamber 24 is connected to the discharge port at a position where the width of the vortex chamber 24 is maximized.

  As shown in FIG. 1, the motor unit 40 is disposed below the pump unit 20. The motor unit 40 is formed in the lower casing 16 of the casing 12. The motor unit 40 has a motor chamber 48 formed by the lower casing 16. The motor unit 40 includes a shaft 44, a rotor 42, and a stator 46. The lower end portion of the shaft 44 is fixed to the support portion 52 of the lower casing 16. The support portion 52 supports the shaft 44 by making a round of the lower end portion of the shaft 44 in the circumferential direction of the shaft 44. The shaft 44 extends in the vertical direction in the casing 12, and the tip thereof reaches the pump chamber 26.

  A gap 44 a extending upward from the lower end is formed in the shaft 44. The cross section of the air gap 44a (the cross section in the direction perpendicular to the axial direction of the shaft 44) is circular. The length range 44b in which the air gap 44a is formed is less rigid than the other part of the shaft 44. Hereinafter, the portion of the shaft 44 in the length range 44b is referred to as a low-rigidity portion 44b.

  As shown in FIG. 3, when the cross section in the direction perpendicular to the axial direction of the shaft 44 is viewed in the low-rigidity portion 44b, the center X1 of the cross section of the gap 44a (shown by a broken line) is on the straight line L2. To position. The center X1 is offset to the right from the center point 44c of the shaft 44. In the modification, the center X1 may be located in the region S1. The region S1 is a straight line L2 that is parallel to the tangent L1 of the impeller 28 at the position 24a (the position where the width of the vortex chamber 24 is minimum) and passes through the center point 44c of the shaft 44 when the electric pump 10 is stopped. Of the two regions divided by the above, the region does not include the position 24a. The region S2 is a region including the position 24a of the two regions divided by the straight line L2.

  A rotating body 30 is rotatably attached to the shaft 44. The rotating body 30 includes an impeller 28 and a rotor 42. The cylindrical rotor 42 is provided below the impeller 28 and is disposed in the motor chamber 48. The rotor 42 is made of a magnetic material, and is magnetized so as to have a plurality of magnetic poles in the circumferential direction. The impeller 28 and the rotor 42 are integrally connected. For this reason, when the rotor 42 rotates, the impeller 28 also rotates. The stator 46 is disposed on the outer peripheral side of the rotor 42 and faces the rotor 42. The stator 46 is connected to an external power source (not shown) (for example, a battery mounted on the vehicle) via a drive circuit (not shown).

  Next, the operation of the electric pump 10 will be described. When electric power is supplied from the drive circuit to the stator 46, the rotor 42 rotates around the shaft 44. As a result, the impeller 28 rotates and the cooling water is sucked into the pump chamber 26 from the suction port 22. The cooling water sucked into the pump chamber 26 is increased in pressure by the rotation of the impeller 28 and discharged from the discharge port to the outside of the casing 12.

  During the operation of the electric pump 10, an external force is applied to the shaft 44 due to coolant pressure, vibration, eccentricity of the rotor 42, and the like. The shaft 44 is in a cantilever state where the lower end is supported by the support portion 52. For this reason, when the shaft 44 receives an external force, the portion supported by the support portion 52 becomes the fixed end of the cantilever and the shaft 44 bends.

  The shaft 44 has a low rigidity portion 44b. When the cross section perpendicular to the axial direction of the shaft 44 is viewed, the center X1 of the air gap 44a of the low-rigidity portion 44b is formed on the straight line L2 (see FIG. 3) at a position offset from the center point 44c. Yes. For this reason, the shaft 44 bends so that the center point 44c moves on the straight line L2 (in the modified example, in the region S1). As a result, the impeller 28 moves as the center point 44c moves. The impeller 28 moves in a direction not approaching the inner peripheral surface 14a of the upper casing 14 at the position 24a (that is, a direction parallel to the tangent L1 (a direction away from the position 24a in the modified example)). According to this configuration, it is not necessary to set a large width of the vortex chamber 24 at the position 24a in consideration of the bending of the shaft 44. Since the minimum width of the vortex chamber 24 can be kept small, the pump efficiency can be improved compared to the case where the width of the vortex chamber 24 is set large.

  As shown in FIG. 2, when the shaft 44 is bent, the shaft 44 comes into contact with the rotating body 30 at the contact positions CP1 and CP2. Since the low-rigidity portion 44 b is formed at the lower end portion of the shaft 44, the shaft 44 is greatly bent by the low-rigidity portion 44 b near the support portion 52. As a result, the bending moment of the shaft 44 located in the through hole 30a of the rotating body 30 is relaxed. According to this structure, the bending amount of the shaft 44 located in the through-hole 30a can be suppressed.

  If the amount of bending of the shaft 44 located in the through hole 30a increases, the shaft 44 and the rotating body 30 come into contact with each other at the contact positions CP1 and CP2 and the opposite side of the shaft 44. As a result, there is a possibility that the sliding resistance between the shaft 44 and the rotating body 30 becomes high and the rotation of the rotating body 30 is hindered. In the electric pump 10, occurrence of such a situation can be suppressed.

(Second embodiment)
Differences from the first embodiment will be described. As shown in FIG. 4, in the electric pump 100 of the second embodiment, the shape of the shaft 144 is different from that of the shaft 44. The shaft 144 is not formed with a gap 44a, but has a small diameter portion 144a. The small diameter portion 144a is disposed above the support portion 52 and on the lower end side of the through hole 30a. The small diameter portion 144a is a cylinder smaller than the diameter of the other portion of the shaft 144.

  As shown in FIG. 5, the center X2 of the small diameter portion 144a is located in the region S2 (region on the position 24a side). The center X2 is offset so as to approach the left side (that is, the side where the width of the vortex chamber 24 is narrower) than the center point 144c of the shaft 144. In the modification, the center X2 may be on the straight line L2. However, the center X2 and the center point 144c may not coincide with each other. The portion where the small diameter portion 144a is located has lower rigidity than the other portions of the shaft 144 (hereinafter referred to as “low-rigidity portion 144b”).

  When an external force is applied to the shaft 144 during the operation of the electric pump 100, the shaft 144 is greatly bent at the low rigidity portion 144b. Since the center X2 of the small-diameter portion 144a is located on the region S2 side (on the straight line L2 in the modified example), when the shaft 144 is viewed from above, the center point 144c of the shaft 144 is on the straight line L2 or the region S1. Bend to move in. Therefore, the electric pump 100 can achieve the same effect as the electric pump 10.

(Third embodiment)
Differences from the second embodiment will be described. As shown in FIG. 6, the electric pump 200 of the third embodiment is different from the shaft 144 in the shape of the shaft 244. A small diameter portion 244a similar to the small diameter portion 144a is formed on the shaft 244. An elastic member 244b is disposed around the small diameter portion 244a. The elastic member 244b is formed of a material having an elastic coefficient smaller than that of the shaft 244 such as elastically deformable rubber or aluminum. The portion constituted by the small-diameter portion 244a and the low-rigidity member 244b has lower rigidity than other portions of the shaft 244 (hereinafter referred to as “low-rigidity portion 244c”). The electric pump 200 can achieve the same effects as the electric pump 100.

(Fourth embodiment)
Differences from the first embodiment will be described. As shown in FIG. 7, in the electric pump 300 of the fourth embodiment, the shaft 344 and the support portion 352 are different from the shaft 44 and the support portion 52, respectively. No gap is formed at the lower end of the shaft 344. That is, the shaft 44 has a solid cylindrical shape.

  The support portion 352 is formed with a low-rigidity portion 352a when a cross section in a direction perpendicular to the axial direction of the shaft 344 is viewed. As shown in FIG. 8, the low-rigidity portion 352a is formed in the region S1. In FIG. 8, only the low-rigidity portion 352a is extracted from the support portion 352. The low rigidity portion 352a is in contact with the outer peripheral surface of the shaft 344. The low-rigidity part 352a is formed of a material having a smaller elastic coefficient than other parts of the support part 352 such as elastically deformable rubber. The electric pump 300 can achieve the same effects as the electric pump 100.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

(1) The gap 44 a of the shaft 44 of the first embodiment may be filled with a material having a smaller elastic coefficient than the shaft 44.

(2) In each of the above embodiments, the low-rigidity portion 44b or the like is formed only in one of the shaft 44 and the support portion 52 and the like. However, for example, a low-rigidity portion may be provided on both the shaft 44 and the support portion 52 and the like like an electric pump including the shaft 44 and the support portion 352.

(3) In the second and third embodiments, the narrow diameter portions 144a and 244b are made of the same material as the other portions of the shafts 144 and 244. However, the small diameter portions 144a and 244b may be made of a material having a lower elastic coefficient than other portions of the shafts 144 and 244. In this case, the low-rigidity member 244b is

(4) In the first embodiment, when the cross section in the direction perpendicular to the axial direction of the shaft 44 is viewed in the low-rigidity portion 44b, the center of the cross section of the gap 44a is located in the region S1 shown in FIG. To do. However, the gap 44a may be formed so that the rigidity of the portion located in the region S1 is smaller than the stiffness of the portion located in the region S2 in the low-rigidity portion 44b. Similarly, in the configurations of the second and third embodiments, the low-rigidity portions 144b and 244c may be formed so that the rigidity of the portion located in the region S1 is lower than the rigidity of the portion located in the region S2. Good.

(5) In the first embodiment, the gap 44a has a circular cross section. However, the cross section of the gap 44a is not limited to a circle. The cross section of the gap 44a may be a polygon such as a quadrangle. Alternatively, as shown in FIG. 9, the cross section of the gap 44a may be oval.

(6) In the first embodiment, the center X1 of the gap 44a is located on the straight line L2. However, as shown in FIG. 10, the center X1 may be located within the region S1.

(7) The small diameter portion 144a of the second embodiment may not be a cylinder. For example, as illustrated in FIG. 11, the narrow-diameter portion 144a may have a shape in which a cutout is formed in a part of the region S1 as compared with other portions of the shaft 144. Generally speaking, the small-diameter portion 144a may have a shorter outer peripheral length than other portions of the shaft 144. The small diameter portion 144a may be formed in the region S2 when a cross section in a direction perpendicular to the axial direction of the shaft 144 is viewed. The same applies to the narrow diameter portion 244a.

(8) When a cross section in a direction perpendicular to the axial direction of the shaft 344 is viewed, a part of the low-rigidity portion 352a may be formed in the region S2 of FIG. When a pressing force acts on the support portion 352 from the shaft 344 due to an external force applied to the shaft 344 and the low-rigidity portion 352a is elastically deformed, the center point of the shaft 344 when the shaft 344 is viewed from above is The low-rigidity portion 352a may be formed so as to move along the straight line L2 or to the region S1.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

10, 100, 200, 300: electric pump, 12: casing, 24: vortex chamber, 24a: position, 26: pump chamber, 28: impeller, 42: rotor, 44, 144, 244, 344: shaft, 44a: gap , 44b, 144b, 244c: low rigidity portion, 44c: center point, 46: stator, 48: motor chamber, 52, 352: support portion

Claims (5)

A casing forming a motor chamber and a pump chamber;
A shaft whose lower end is supported by a support provided in the casing;
A rotor rotating about the shaft;
An impeller attached to the upper end side of the rotor, and rotatably accommodated in the pump chamber;
In the motor chamber, an electric pump comprising a stator disposed on the outer peripheral side of the rotor,
In the pump chamber, a vortex chamber through which a fluid flows is formed between the outer peripheral surface of the impeller and the inner peripheral surface of the casing,
The vortex chamber has a narrowest interval between the outer peripheral surface of the impeller and the inner peripheral surface of the casing at a specific position in the circumferential direction of the impeller.
At least one member of the support portion and the shaft is provided with a low rigidity portion having lower rigidity than the other portion of the member,
The low-rigidity portion is configured such that, when the electric pump is operated, a center point of the shaft when the shaft is viewed from above is parallel to a tangent to the outer peripheral surface of the impeller at the specific position. An electric pump configured to move to a region on a side opposite to the specific position among two regions divided by the specific line or on a specific straight line passing through the point. The low rigidity portion is formed on the lower end side of the shaft,
The electric pump according to claim 1, wherein the other portion is formed on the upper end side of the shaft.   3. The electric pump according to claim 2, wherein the low-rigidity portion has a smaller cross-sectional area in a direction perpendicular to the axial direction of the shaft than that of the other portion of the shaft.   The electric pump according to claim 2 or 3, wherein the low-rigidity portion includes an elastic member made of a material having an elastic coefficient smaller than that of the other portion of the shaft.   The electric pump according to any one of claims 1 to 4, wherein the low-rigidity portion is formed in a part of the support portion.

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