阅读说明：本技术 轴流风扇 (Axial flow fan ) 是由 井内一博 松山纯也 于 2019-06-13 设计创作，主要内容包括：提供一种轴流风扇,其具有配置于壳体的轴向上部的上侧叶轮和配置于所述上侧叶轮的轴向下侧的上侧电路板。上侧叶轮的上侧叶轮杯具有上侧筒部和上侧盖部。另外,轴流风扇具有配置于壳体的轴向下部的下侧叶轮和配置于所述下侧叶轮的轴向上侧的下侧电路板。下侧叶轮的下侧叶轮杯具有下侧筒部和下侧盖部。所述上侧筒部的轴向上端外径小于所述上侧筒部的轴向下端外径。所述下侧筒部的轴向下端外径小于所述下侧筒部的轴向上端外径。所述下侧筒部的轴向下端外径小于所述上侧筒部的轴向下端外径。(An axial fan is provided with an upper impeller disposed at an upper portion in an axial direction of a casing and an upper circuit board disposed at a lower portion in the axial direction of the upper impeller. The upper impeller cup of the upper impeller has an upper cylinder portion and an upper cover portion. The axial flow fan includes a lower impeller disposed at a lower portion in an axial direction of the casing and a lower circuit board disposed at an upper portion in the axial direction of the lower impeller. The lower impeller cup of the lower impeller has a lower cylinder portion and a lower cover portion. The outer diameter of the upper end of the upper side cylinder part in the axial direction is smaller than the outer diameter of the lower end of the upper side cylinder part in the axial direction. The outer diameter of the axial lower end of the lower side cylinder part is smaller than the outer diameter of the axial upper end of the lower side cylinder part. The axial lower end outer diameter of the lower side cylinder part is smaller than the axial lower end outer diameter of the upper side cylinder part.)

1. An axial flow fan, comprising:

a casing extending along a central axis extending up and down and including an air supply flow path having an air inlet at an upper end and an air outlet at a lower end;

an upper impeller disposed at an axially upper portion of the casing and rotating around the central axis;

an upper motor that rotates the upper impeller about the central axis; and

an upper circuit board disposed axially below the upper impeller,

the upper impeller has:

an upper impeller cup fixed to the upper motor; and

a plurality of upper side blades arranged in a circumferential direction on an outer surface of the upper side impeller cup,

the upper impeller cup has:

an upper cylinder portion that is radially opposed to the upper motor and extends along the central axis; and

an upper cover portion radially expanding at an axially upper end of the upper cylinder portion,

further, the axial flow fan includes:

a lower impeller disposed at an axially lower portion of the casing and rotating around the central axis;

a lower motor that rotates the lower impeller about the central axis; and

a lower circuit board disposed axially above the lower impeller,

the lower impeller has:

a lower impeller cup fixed to the lower motor; and

a plurality of lower side blades arranged in a circumferential direction on an outer surface of the lower side impeller cup,

the lower impeller cup has:

a lower cylinder portion that is radially opposed to the lower motor and extends along the central axis; and

a lower cover portion radially expanding at an axial lower end of the lower cylinder portion,

the outer diameter of the upper end of the upper side cylinder part in the axial direction is smaller than the outer diameter of the lower end of the upper side cylinder part in the axial direction,

the outer diameter of the lower axial end of the lower side cylinder part is smaller than the outer diameter of the upper axial end of the lower side cylinder part,

the axial lower end outer diameter of the lower side cylinder part is smaller than the axial lower end outer diameter of the upper side cylinder part.

2. The axial flow fan according to claim 1,

the upper tube portion has a 1 st upper inclined portion having a conical shape whose outer diameter increases toward the lower side in the axial direction.

3. The axial flow fan according to claim 1 or 2,

the lower cylinder portion has a 1 st lower inclined portion having a conical shape whose outer diameter increases toward the axially upper side.

4. The axial flow fan according to any one of claims 1 to 3,

the outer diameter of the upper end of the lower side cylinder part in the axial direction is the same as the outer diameter of the lower end of the upper side cylinder part in the axial direction.

5. The axial flow fan according to any one of claims 1 to 4,

the upper cover portion has a conical 2 nd upper inclined portion extending axially downward toward the radially outer side.

6. The axial flow fan according to any one of claims 1 to 5,

the lower cover portion has a conical 2 nd lower inclined portion extending upward in the axial direction as it goes radially outward.

7. The axial flow fan according to any one of claims 1 to 6,

the radially outer ends of the axially upper portions of the plurality of upper blades are curved axially upward as they go axially upward.

8. The axial flow fan according to any one of claims 1 to 7,

the radially outer ends of the axially lower portions of the plurality of upper blades are curved toward the axially lower side as they go toward the axially lower side.

9. The axial flow fan according to any one of claims 1 to 8,

the radially outer ends of the axially upper portions of the plurality of lower blades are curved axially upward as they go axially upward.

10. The axial flow fan according to any one of claims 1 to 9,

the radially outer ends of the axially lower portions of the plurality of lower blades are curved toward the axially lower side as they go toward the axially lower side.

11. The axial flow fan according to any one of claims 1 to 10,

the upper impeller and the lower impeller are housed in the air supply flow path.

12. The axial flow fan according to any one of claims 1 to 11,

the outer diameter of the upper side circuit board is smaller than that of the upper side impeller.

13. The axial flow fan according to any one of claims 1 to 12,

the outer diameter of the lower side circuit board is smaller than that of the lower side impeller.

Technical Field

The present invention relates to an axial fan.

Background

Patent document 1 discloses a double counter-rotating axial flow fan as a conventional axial flow fan. The double counter-rotating axial flow fan disclosed in patent document 1 includes: a housing having a wind tunnel; a preceding stage impeller that rotates in the wind tunnel; and a rear-stage impeller that rotates in the wind tunnel in the direction opposite to the front-stage impeller. This improves the characteristics of the air volume and the static pressure, and reduces power consumption and noise.

Patent document 1: japanese patent laid-open No. 2012 and 219712

In the double counter-rotating axial-flow fan disclosed in patent document 1, the circuit board for controlling the rotation of the impeller is not considered to be a large circuit board. Thus, there are the following problems: the hub of the impeller is enlarged and the wind tunnel is narrowed, so that the pressure-air volume characteristic of air is reduced.

Disclosure of Invention

In view of the above-described problems, an object of the present invention is to provide an axial fan capable of securing an installation space for a circuit board and appropriately maintaining pressure-air volume characteristics of air even when the circuit board is large-sized.

An exemplary axial flow fan of the present invention includes: a casing extending along a central axis extending up and down and including an air supply flow path having an air inlet at an upper end and an air outlet at a lower end; an upper impeller disposed at an axially upper portion of the casing and rotating around the central axis; an upper motor that rotates the upper impeller about the central axis; and an upper circuit board disposed axially below the upper impeller. The upper impeller has: an upper impeller cup fixed to the upper motor; and a plurality of upper side blades arranged in a circumferential direction on an outer surface of the upper side impeller cup. The upper impeller cup has: an upper cylinder portion that is radially opposed to the upper motor and extends along the central axis; and an upper cover portion that expands in a radial direction at an axial upper end of the upper cylinder portion. The axial flow fan further includes: a lower impeller disposed at an axially lower portion of the casing and rotating around the central axis; a lower motor that rotates the lower impeller about the central axis; and a lower circuit board disposed axially above the lower impeller. The lower impeller has: a lower impeller cup fixed to the lower motor; and a plurality of lower side blades arranged in a circumferential direction on an outer surface of the lower side impeller cup. The lower impeller cup has: a lower cylinder portion that is radially opposed to the lower motor and extends along the central axis; and a lower cover portion that expands in a radial direction at an axial lower end of the lower cylinder portion. The outer diameter of the upper end of the upper side cylinder part in the axial direction is smaller than the outer diameter of the lower end of the upper side cylinder part in the axial direction. The outer diameter of the axial lower end of the lower side cylinder part is smaller than the outer diameter of the axial upper end of the lower side cylinder part. The axial lower end outer diameter of the lower side cylinder part is smaller than the axial lower end outer diameter of the upper side cylinder part.

According to the exemplary axial flow fan of the present invention, even when the circuit board is large in size, the pressure-air volume characteristic of air can be appropriately maintained while ensuring the installation space of the circuit board.

Drawings

Fig. 1 is an overall perspective view of an example of an axial flow fan according to an embodiment of the present invention.

Fig. 2 is a longitudinal sectional view of the axial flow fan.

Fig. 3 is an overall perspective view of the axial flow fan in a case where the casing is not shown.

Fig. 4 is a side view of the axial flow fan without showing the casing.

Description of the reference symbols

1: an axial flow fan; 2: a housing; 3: an air supply flow path; 4: an upside fan; 5: a lower fan; 31: an air suction port; 32: an exhaust port; 41: an upper housing; 42: an upper side impeller; 43: an upper motor; 44: an upper side circuit board; 51: a lower housing; 52: a lower side impeller; 53: a lower motor; 54: a lower side circuit board; 411: an upper motor base part; 412: an upper peripheral wall; 413: an upper side rib; 421: an upper side impeller cup; 422: an upper side blade; 431: an upper shaft; 432: an upper side bearing; 433: an upper stator; 434: an upper rotor; 511: a lower motor base part; 512: a lower peripheral wall; 513: a lower rib; 521: a lower impeller cup; 522: a lower side blade; 531: a lower shaft; 532: a lower bearing; 533: a lower stator; 534: a lower rotor; 4111: a base; 4112: a bearing holding portion; 4211: an upper side cylinder part; 4211 a: 1 st upper inclined part; 4212: an upper side cover portion; 4212 a: 2 nd upper inclined part; 4331: a stator core; 4332: an insulating member; 4333: a coil; 4341: a rotor yoke; 4342: a magnet; 5111: a base; 5112: a bearing holding portion; 5211: a lower side cylinder part; 5211 a: 1 st lower inclined part; 5212: a lower side cover portion; 5212 a: 2 nd lower inclined part; 5331: a stator core; 5332: an insulating member; 5333: a coil; 5341: a rotor yoke; 5342: a magnet; c: a central axis.

Detailed Description

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification, a direction in which the central axis of the axial flow fan extends is simply referred to as "axial direction", a direction perpendicular to the central axis with the central axis of the axial flow fan as a center is simply referred to as "radial direction", and a direction along an arc with the central axis of the axial flow fan as a center is simply referred to as "circumferential direction". In this specification, for convenience of explanation, the shape and positional relationship of the respective portions will be described with the axial direction as the vertical direction and the vertical direction in fig. 2 as the vertical direction of the axial flow fan. The upper side of the axial flow fan is the air suction side, and the lower side of the axial flow fan is the air exhaust side. The vertical direction is not limited to the orientation and positional relationship when the axial flow fan is used. In the present specification, a cross section parallel to the axial direction is referred to as a "longitudinal cross section". In addition, "parallel" used in the present specification does not mean parallel in a strict sense, and includes substantially parallel.

< 1. integral structure of axial fan >

Fig. 1 is an overall perspective view of an example of an axial flow fan according to an embodiment of the present invention. Fig. 2 is a longitudinal sectional view of the axial flow fan. The axial flow fan 1 has a casing 2. The casing 2 extends along a central axis C extending vertically, and has an air flow passage 3 therein. The air blowing flow path 3 has an air inlet 31 at an upper end and an air outlet 32 at a lower end. That is, the casing 2 extends along a central axis C extending vertically, and includes the air flow path 3 having the air inlet 31 at an upper end and the air outlet 32 at a lower end.

The axial flow fan 1 includes an upper fan 4 and a lower fan 5. The upper fan 4 includes an upper casing 41, an upper impeller 42, an upper motor 43, and an upper circuit board 44. The lower fan 5 includes a lower housing 51, a lower impeller 52, a lower motor 53, and a lower circuit board 54. That is, the axial flow fan 1 includes a casing 2, an upper impeller 42, an upper motor 43, an upper circuit board 44, a lower impeller 52, a lower motor 53, and a lower circuit board 54. The housing 2 includes an upper housing 41 and a lower housing 51.

< 1-1. Structure of upside fan

The upper casing 41 is disposed outside the upper impeller 42, the upper motor 43, and the upper circuit board 44. The upper case 41 has an upper motor base 411, an upper peripheral wall 412, and an upper rib 413.

The upper motor base 411 is disposed axially below the upper motor 43. The upper motor base part 411 has a base part 4111 and a bearing holding part 4112. The base portion 4111 is disposed axially below the upper motor 43, and has a disk shape extending radially about the central axis C. The bearing holding portion 4112 protrudes from the upper surface of the base portion 4111 toward the axial upper side. The bearing holding portion 4112 is cylindrical with the center axis C as the center. A pair of upper bearings 432 arranged in an axially upward and downward direction are housed and held inside the bearing holding portion 4112. An upper motor 43 is fixed to a radially outer surface of the bearing holder 4112.

The upper peripheral wall 412 is disposed radially outward of the upper impeller 42. The upper peripheral wall 412 is cylindrical and extends axially upward and downward. The air flow passage 3 is disposed radially inward of the upper peripheral wall 412. That is, the inlet port 31, which is a circular opening, is disposed at the axial upper end of the upper peripheral wall 412.

The upper rib 413 is disposed radially outward of the base 4111 of the upper motor base 411 and radially inward of the upper peripheral wall 412. The upper rib 413 extends in the radial direction, and connects the base 4111 and the upper peripheral wall 412. The upper ribs 413 are arranged in plurality in the circumferential direction. The air flowing through the air blowing flow path 3 passes between the adjacent upper ribs 413.

The upper impeller 42 is disposed radially inward of the upper housing 41 and axially upward and radially outward of the upper motor 43. The upper impeller 42 is rotated about the center axis C by an upper motor 43. That is, the upper impeller 42 is disposed at an axially upper portion of the casing 2 and rotates about the center axis C. The upper impeller 42 has an upper impeller cup 421 and a plurality of upper blades 422.

The upper impeller cup 421 is fixed to the upper motor 43. The upper impeller cup 421 is a substantially cylindrical member having a cover on the upper side in the axial direction. A rotor yoke 4341 of the upper motor 43 is fixed to the inside of the upper impeller cup 421. The plurality of upper blades 422 are arranged in the circumferential direction on the outer surface of the upper impeller cup 421. The detailed structure of the upper impeller 42 will be described later.

The upper motor 43 is disposed radially inward of the upper housing 41. The upper motor 43 is supported by an upper motor base portion 411 of the upper housing 41. The upper motor 43 rotates the upper impeller 42 about the center axis C. The upper motor 43 includes an upper shaft 431, an upper bearing 432, an upper stator 433, and an upper rotor 434.

The upper shaft 431 is disposed along the center axis C. The upper shaft 431 is a columnar member made of metal such as stainless steel, and extends upward and downward along the shaft. The upper shaft 431 is supported by an upper bearing 432 to be rotatable about the center axis C.

The upper bearings 432 are at least axially arranged in pairs up and down. The upper bearing 432 is held inside a cylindrical bearing holding portion 4112 of the upper motor base portion 411. The upper bearing 432 is formed of, for example, a ball bearing, but may be formed of a sleeve bearing or the like. A pair of upper bearings 432, which are axially upper and lower, rotatably support the upper shaft 431 around the center axis C with respect to the upper housing 41.

The upper stator 433 is fixed to the outer peripheral surface of the bearing holding portion 4112 of the upper motor base portion 411. The upper stator 433 includes a stator core 4331, an insulator 4332, and a coil 4333.

The stator core 4331 is formed by stacking electromagnetic steel plates such as silicon steel plates vertically. The insulating member 4332 is made of resin having insulating properties. The insulator 4332 is provided to surround an outer surface of the stator core 4331. Coil 4333 is made of a conductive wire wound around stator core 4331 with insulator 4332 interposed therebetween.

The upper rotor 434 is disposed axially above and radially outside the upper stator 433. The upper rotor 434 rotates about the center axis C relative to the upper stator 433. The upper rotor 434 has a rotor yoke 4341 and a magnet 4342.

The rotor yoke 4341 is a substantially cylindrical member made of a magnetic material and having a cover on the upper side in the axial direction. The rotor yoke 4341 is fixed to the upper shaft 431. The magnet 4342 is cylindrical and fixed to the inner circumferential surface of the rotor yoke 4341. The magnet 4342 is disposed radially outward of the upper stator 433.

The upper circuit board 44 is disposed axially below the upper impeller 42. More specifically, the upper circuit board 44 is disposed axially below the upper impeller 42 and the upper motor 43 and axially above the base 4111 of the upper motor base 411. The upper circuit board 44 has a circular plate shape extending in the radial direction with the center axis C as a center, for example. An outlet of the coil 4333 is electrically connected to the upper circuit board 44. An electronic circuit for supplying a driving current to the coil 4333 is mounted on the upper side circuit board 44.

In the upper fan 4 of the above structure, when a drive current is supplied to the coil 4333 of the upper motor 43 via the upper circuit board 44, a magnetic flux in the radial direction is generated in the stator core 4331. A magnetic field generated by the magnetic flux of stator core 4331 acts on a magnetic field generated by magnet 4342, and torque is generated in the circumferential direction of upper rotor 434. By this torque, the upper rotor 434 and the upper impeller 42 rotate about the central axis C. When the upper impeller 42 rotates, an air flow is generated by the plurality of upper blades 422. That is, the upper fan 4 generates an air flow having an upper side as an intake side and a lower side as an exhaust side, and can blow air.

< 1-2. Structure of lower side fan

The lower housing 51 is disposed outside the lower impeller 52, the lower motor 53, and the lower circuit board 54. The lower housing 51 has a lower motor base 511, a lower peripheral wall 512, and a lower rib 513.

The lower motor base 511 is disposed axially above the lower motor 53. The lower motor base portion 511 has a base portion 5111 and a bearing holding portion 5112. The base 5111 is disposed axially above the lower motor 53 and has a disk shape extending radially about the center axis C. The bearing holding portion 5112 protrudes toward the axial lower side from the lower surface of the base portion 5111. The bearing holding portion 5112 is cylindrical with the center axis C as the center. A pair of lower bearings 532 arranged in an axially upward and downward direction are housed and held inside the bearing holding portion 5112. A lower motor 53 is fixed to a radially outer surface of the bearing holding portion 5112.

The lower peripheral wall 512 is disposed radially outward of the lower impeller 52. The lower peripheral wall 512 is cylindrical and extends axially upward and downward. The air flow passage 3 is disposed radially inward of the lower peripheral wall 512. That is, the exhaust port 32, which is a circular opening, is disposed at the axial lower end of the lower peripheral wall 512.

The lower rib 513 is disposed radially outward of the base 5111 of the lower motor base portion 511 and radially inward of the lower peripheral wall 512. The lower rib 513 extends in the radial direction, connecting the base 5111 and the lower peripheral wall 512. The lower ribs 513 are arranged in plurality in the circumferential direction. The air flowing through the air blowing flow path 3 passes between the adjacent lower ribs 513.

The lower impeller 52 is disposed radially inside the lower housing 51 and axially below and radially outside the lower motor 53. The lower impeller 52 is rotated about the center axis C by a lower motor 53. That is, the lower impeller 52 is disposed at the lower portion in the axial direction of the casing 2 and rotates about the center axis C. The lower impeller 52 has a lower impeller cup 521 and a plurality of lower blades 522.

The lower impeller cup 521 is fixed to the lower motor 53. The lower impeller cup 521 is a substantially cylindrical member having a cover on the lower side in the axial direction. A rotor yoke 5341 of the lower motor 53 is fixed to the inside of the lower impeller cup 521. The plurality of lower blades 522 are arranged in the circumferential direction on the outer surface of the lower impeller cup 521. The detailed structure of the lower impeller 52 will be described later.

The lower motor 53 is disposed radially inward of the lower housing 51. The lower motor 53 is supported by a lower motor base portion 511 of the lower housing 51. The lower motor 53 rotates the lower impeller 52 about the central axis C. The lower motor 53 has a lower shaft 531, a lower bearing 532, a lower stator 533, and a lower rotor 534.

The lower shaft 531 is disposed along the center axis C. The lower shaft 531 is a columnar member made of metal such as stainless steel, and extends upward and downward along the shaft. The lower shaft 531 is supported by a lower bearing 532 to be rotatable about the center axis C.

The lower bearings 532 are at least one pair arranged vertically along the axial direction. The lower bearing 532 is held inside a cylindrical bearing holding portion 5112 of the lower motor base portion 511. The lower bearing 532 is formed of, for example, a ball bearing, but may be formed of a sleeve bearing or the like. A pair of axially upper and lower bearings 532 rotatably support the lower shaft 531 about the center axis C with respect to the lower housing 51.

The lower stator 533 is fixed to the outer peripheral surface of the bearing holding portion 5112 of the lower motor base portion 511. The lower stator 533 has a stator core 5331, an insulator 5332, and a coil 5333.

The stator core 5331 is formed by stacking electromagnetic steel plates such as silicon steel plates vertically. The insulating material 5332 is made of resin having insulating properties. The insulator 5332 is provided to surround the outer surface of the stator core 5331. The coil 5333 is formed of a wire wound around the stator core 5331 with an insulator 5332 interposed therebetween.

The lower rotor 534 is disposed axially below and radially outside the lower stator 533. The lower rotor 534 rotates about the central axis C with respect to the lower stator 533. The lower rotor 534 has a rotor yoke 5341 and a magnet 5342.

The rotor yoke 5341 is a substantially cylindrical member made of a magnetic material and having a cover on the lower side in the axial direction. The rotor yoke 5341 is fixed to the lower shaft 531. The magnet 5342 is cylindrical and fixed to the inner circumferential surface of the rotor yoke 5341. The magnet 5342 is disposed radially outward of the lower stator 533.

The lower circuit board 54 is disposed axially above the lower impeller 52. More specifically, the lower circuit board 54 is disposed axially above the lower impeller 52 and the lower motor 53 and axially below the base 5111 of the lower motor base 511. The lower circuit board 54 has a circular plate shape extending in the radial direction around the center axis C, for example. Lead wires of the coil 5333 are electrically connected to the lower circuit board 54. An electronic circuit for supplying a driving current to the coil 5333 is mounted on the lower side circuit board 54.

In the lower fan 5 configured as described above, when a drive current is supplied to the coil 5333 of the lower motor 53 via the lower circuit board 54, a magnetic flux in the radial direction is generated in the stator core 5331. The magnetic field generated by the magnetic flux of stator core 5331 acts on the magnetic field generated by magnet 5342 to generate a torque in the circumferential direction of lower rotor 534. By this torque, the lower rotor 534 and the lower impeller 52 rotate about the central axis C. As the lower impeller 52 rotates, an airflow is generated by the plurality of lower blades 522. That is, the lower fan 5 generates an air flow having an upper side as an air suction side and a lower side as an air discharge side, and can blow air.

< 2. detailed Structure of upper side impeller and lower side impeller

Next, the detailed structure of the upper impeller 42 and the lower impeller 52 will be described with reference to fig. 3 and 4 in addition to fig. 1 and 2. Fig. 3 is an overall perspective view of the axial flow fan 1 in a case where the casing 2 is not shown. Fig. 4 is a side view of the axial flow fan 1 without showing the casing 2. For convenience of explanation, in fig. 4, the axial lower end outer diameter D422 of the upper cylinder 4211 and the axial upper end outer diameter D522 of the lower cylinder 5211 are shown in the upper and lower positions of the upper impeller 42 and the lower impeller 52, respectively.

The upper impeller cup 421 has an upper cylinder 4211 and an upper cover 4212. The upper cylinder 4211 and the upper cover 4212 are one member.

The upper cylinder 4211 is disposed radially outward of the upper motor 43, and radially encloses the upper motor 43. The upper tube 4211 extends vertically along the central axis C. That is, the upper cylinder 4211 radially faces the upper motor 43 and extends along the central axis C.

The upper cover 4212 is disposed at an axially upper end of the upper tube 4211. The upper cover 4212 has a circular plate shape extending in the radial direction about the central axis C. The outer edge portion of the upper cover 4212 is connected to the axial upper end portion of the upper tube 4211. That is, the upper cover 4212 is radially expanded at the axial upper end of the upper tube 4211.

The lower impeller cup 521 has a lower cylinder portion 5211 and a lower cover portion 5212. The lower barrel portion 5211 and the lower cap portion 5212 are one component.

The lower cylinder portion 5211 is disposed radially outward of the lower motor 53, and radially inwardly encloses the lower motor 53. The lower tube portion 5211 extends vertically along the central axis C. That is, the lower cylindrical portion 5211 radially faces the lower motor 53 and extends along the central axis C.

The lower cover 5212 is disposed at the axial lower end of the lower barrel 5211. The lower cap portion 5212 is shaped like a circular plate extending radially about the center axis C. The outer edge of the lower cover 5212 is connected to the axial lower end of the lower barrel 5211. That is, the lower cap portion 5212 radially expands at the axial lower end of the lower barrel portion 5211.

As shown in fig. 4, the axial upper end outer diameter D421 of the upper cylinder portion 4211 is smaller than the axial lower end outer diameter D422 of the upper cylinder portion 4211. The axial lower end outer diameter D521 of the lower cylinder portion 5211 is smaller than the axial upper end outer diameter D522 of the lower cylinder portion 5211. The axial lower end outer diameter D521 of the lower cylinder portion 5211 is smaller than the axial lower end outer diameter D422 of the upper cylinder portion 4211.

According to the configuration of the above embodiment, the air flow space in the vicinity of the upper end in the axial direction of the upper cylinder 4211 of the upper impeller 42 is larger than the air flow space in the vicinity of the lower end in the axial direction of the upper cylinder 4211. Therefore, the increase in turbulence of the air flow can be suppressed or reduced radially outside the upper cylinder portion 4211, and the air can be efficiently sent to the exhaust side. The air flow space in the vicinity of the lower end of the lower cylinder portion 5211 of the lower impeller 52 in the axial direction is larger than the air flow space in the vicinity of the upper end of the lower cylinder portion 5211 in the axial direction. Therefore, an increase in air pressure can be suppressed or reduced radially outward of the lower cylindrical portion 5211, and air can be efficiently delivered to the exhaust side. This ensures a space for installing the upper circuit board 44 and the lower circuit board 54 in the radial direction, and appropriately maintains the pressure-air volume characteristic of air.

The axial upper end outer diameter D522 of the lower cylinder portion 5211 is the same as the axial lower end outer diameter D422 of the upper cylinder portion 4211. With this configuration, the air on the upper impeller 42 side, in which the pressure increase is suppressed, can be smoothly transmitted to the lower impeller 52 side. Therefore, air can be efficiently blown.

The upper cylinder 4211 has a 1 st upper inclined portion 4211 a. The 1 st upper inclined portion 4211a is disposed on the outer peripheral portion of the upper tube portion 4211. The 1 st upper inclined portion 4211a has a conical shape whose outer diameter increases toward the axially lower side. With this structure, the outer shape of the upper cylinder portion 4211 is tapered in the axial direction. That is, the radially outer air flow space of the upper cylinder 4211 gradually narrows from the axially upper side toward the axially lower side. Therefore, the installation space of the upper circuit board 44 can be increased below the upper cylinder portion 4211 in the axial direction while suppressing a sudden increase in air pressure radially outside the upper cylinder portion 4211.

The lower tube portion 5211 has a 1 st lower inclined portion 5211 a. The 1 st lower inclined portion 5211a is disposed on the outer peripheral portion of the lower cylindrical portion 5211. The 1 st lower inclined portion 5211a has a conical shape with an outer diameter increasing toward the axially upper side. With this structure, the outer shape of the lower tube portion 5211 is tapered in the axial direction. That is, the radially outer air flow space of the lower cylindrical portion 5211 gradually increases from the axially upper side toward the axially lower side. Therefore, the air pressure can be gradually reduced radially outward of the lower tubular portion 5211, and the installation space of the lower circuit board 54 can be increased axially upward of the lower tubular portion 5211.

The upper cover 4212 has a 2 nd upper inclined portion 4212 a. The 2 nd upper inclined portion 4212a is disposed on the outer peripheral portion of the upper cover 4212. The 2 nd upper inclined portion 4212a has a conical shape extending axially downward as it goes radially outward. According to this configuration, when the air on the upper side in the axial direction with respect to the upper impeller cup 421 is guided to the outside in the radial direction of the upper cylinder portion 4211, the air flow space gradually becomes narrower from the axial direction side to the axial direction side. Therefore, the air can be sent to the lower side in the axial direction of the upper impeller cup 421 while suppressing resistance of the air sucked through the air inlet 31.

The lower cap 5212 has a 2 nd lower inclined portion 5212 a. The 2 nd lower inclined portion 5212a is disposed on the outer peripheral portion of the lower cap portion 5212. The 2 nd lower inclined portion 5212a has a conical shape extending upward in the axial direction as it goes radially outward. According to this configuration, when the air on the radially outer side of the lower cylinder portion 5211 is guided to the axially lower side than the lower impeller cup 521, the air flow space gradually increases from the axially upper side to the axially lower side. Therefore, the air can be discharged from the exhaust port 32 to the outside while suppressing turbulence of the air directed axially downward of the lower impeller cup 521.

The upper and lower axial portions of the upper blades 422 are curved in different directions from each other toward the upper or lower axial side. In detail, radially outer ends of axially upper portions of the plurality of upper blades 422 are bent axially upward as going toward the axially upper side. Further, radially outer ends of axially lower portions of the plurality of upper blades 422 are curved axially downward as they go axially downward. With these configurations, the flow velocity on the radial inner side can be suppressed, and the air resistance on the downstream side of the air blowing flow path 3 can be reduced. Therefore, the pressure-air volume characteristics of the air can be improved.

The axially upper and lower portions of the plurality of lower blades 522 are curved in different directions from each other as they extend toward the axially upper side or the axially lower side, respectively. In detail, radially outer ends of axially upper portions of the plurality of lower blades 522 are bent axially upward as going toward the axially upper side. Further, radially outer ends of axially lower portions of the plurality of lower blades 522 are bent axially downward as they go axially downward. With these configurations, the flow velocity on the radial inner side can be suppressed, and the air resistance on the downstream side of the air blowing flow path 3 can be reduced. Therefore, the pressure-air volume characteristics of the air can be improved.

The upper impeller 42 is disposed axially below the air inlet 31. That is, the upper impeller 42 does not protrude outside the air flow path 3. The lower impeller 52 is disposed axially above the exhaust port 32. That is, the lower impeller 52 does not protrude outside the air flow path 3. That is, the upper impeller 42 and the lower impeller 52 are housed in the air flow path 3. With this configuration, the pressure-air volume characteristic of the air can be improved. Further, since the upper impeller 42 and the lower impeller 52 do not protrude outside the casing 2, the axial flow fan 1 can be easily attached to a device or the like. Moreover, the upper impeller 42 and the lower impeller 52 can be protected.

As shown in fig. 4, the outer diameter D44 of the upper circuit board 44 is smaller than the axial lower end outer diameter D422 of the upper tube 4211 of the upper impeller 42. That is, the outer diameter of the upper circuit board 44 is smaller than the outer diameter of the upper impeller 42. With this configuration, the upper circuit board 44 can suppress disturbance of the air in the air flow passage 3 due to the upper impeller 42 protruding radially outward.

As shown in fig. 4, the outer diameter D54 of the lower circuit board 54 is smaller than the axial upper end outer diameter D522 of the lower cylindrical portion 5211 of the lower impeller 52. That is, the outer diameter of the lower circuit board 54 is smaller than the outer diameter of the lower impeller 52. With this configuration, the turbulence of the air in the air flow path 3 caused by the lower circuit board 54 protruding radially outward from the lower impeller 52 can be suppressed.

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While the embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and various modifications can be made without departing from the scope of the present invention. The above embodiments and modifications thereof can be combined as appropriate.

Industrial applicability

The present invention can be used for an axial fan, for example.