TECHNICAL FIELD

The present invention relates to a contra-rotating fan drive assembly and to a fan assembly comprising the contra-rotating fan drive assembly.

BACKGROUND

A conventional domestic fan assembly typically includes an impeller comprising a set of blades mounted for rotation about an axis, together with a fan drive assembly for rotating the impeller to generate an air flow. The movement and circulation of the air flow creates a breeze and, as a result, a user experiences a cooling effect as heat is dissipated through convection and evaporation. The rotation of the impeller blades exerts a tangential or rotational component on the direction of the air flowing through the impeller. This not only reduces the mass flow through the fan and increases energy losses, but also exerts torque or turning force acting on the fan. It is known that these drawbacks can be offset by using two coaxial impellers arranged to rotate in opposite directions, often termed a contra-rotating impellers. The rotation of the downstream impeller in this arrangement cancels the rotational component applied to the air flowing through the upstream impeller, maximising mass flow through the fan and minimising energy losses. The torque acting on the fan is also effectively cancelled out due contra-rotating impellers. However, contra-rotating impellers are not widely used in domestic fans, partly due to their expense, but also due to the fact that occupy more space when compared to fan comprising a single impeller.

The aim of this invention is to substantially mitigate some of the drawbacks associated with contra-rotating impellers.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided a contra-rotating fan drive assembly comprising a first impeller; a first motor comprising an inner rotor, an outer stator and a driveshaft connecting the inner rotor and the first impeller, the first motor being arranged to rotate the first impeller in a first direction; a second impeller; and, a second motor comprising an inner stator and an outer rotor connected to the second impeller, the second motor being arranged to rotate the second impeller in a second direction opposite the first direction, wherein the first and second motors are arranged coaxially and wherein the first motor is arranged concentrically within the second motor such that the second motor surrounds the periphery of the first motor.

Preferably, the inner stator of the second motor comprises an aperture for receiving the first motor such that the inner stator of the second motor is circumferentially arranged about the outer stator of the first motor. Preferably, the first impeller is arranged coaxially with both the first and second motors. Preferably, the second impeller is arranged coaxially with both the first and second motors. Preferably, the second motor is shaftless. Preferably, the second impeller is directly connected or mounted to the outer rotor of the second motor. Preferably, the blades of the second impeller extend outwardly from an outer surface of the outer rotor of the second motor.

According to another aspect of the invention, there is provided a fan assembly comprising a contra-rotating fan drive assembly according to the previous aspect.

According to another aspect of the invention, there is provided a contra-rotating drive assembly comprising: a first set of blades; an inrunner motor for rotating the first set of blades in a first direction, the inrunner motor comprising an inner rotor, an outer stator and a driveshaft connecting the inner rotor and the first set of blades; a second set of blades; and, a shaftless outrunner motor for rotating the second set of blades in a second direction opposite the first direction, the shaftless outrunner motor comprising an inner stator and an outer rotor, the second set of blades being connected to the outer rotor, wherein the inrunner motor and the shaftless outrunner motor are arranged coaxially and wherein the inrunner motor is arranged concentrically within the shaftless outrunner motor such that the outrunner motor surrounds the periphery of the inrunner motor.

Preferably, the inner stator of the shaftless outrunner motor comprises an aperture for receiving the inrunner motor such that the inner stator of the shaftless outrunner motor is circumferentially arranged about the outer stator of the inrunner motor.

According to another aspect of the invention, there is provided a contra-rotating fan drive assembly comprising a first impeller; a first motor comprising an inner rotor, an outer stator and a driveshaft connecting the inner rotor and the first impeller, the first motor being arranged to rotate the first impeller in a first direction; a second impeller; and, a second motor comprising an inner stator and an outer rotor connected to the second impeller, the second motor being arranged to rotate the second impeller in a second direction opposite the first direction, wherein the first and second motors are arranged coaxially and wherein the second motor is disposed between the first impeller and the first motor, and the inner stator of the second motor comprises an aperture through which the driveshaft of the first motor passes.

Preferably, the first and second motors are axially spaced. Preferably, the first impeller is arranged coaxially with both the first and second motors. Preferably, the second impeller is arranged coaxially with both the first and second motors.

Preferably, the second motor is shaftless. Preferably, the second impeller is directly connected or mounted to the outer rotor of the second motor. Preferably, blades of the second impeller extend outwardly from an outer surface of the outer rotor of the second motor. According to another aspect of the invention, there is provided a fan assembly comprising a contra-rotating fan drive assembly according to the previous aspect.

According to another aspect of the invention, there is provided a contra-rotating drive assembly comprising a first set of blades; an inrunner motor for rotating the first set of blades in a first direction, the inrunner motor comprising an inner rotor, an outer stator and a driveshaft connecting the inner rotor and the first set of blades; a second set of blades; and, a shaftless outrunner motor for rotating the second set of blades in a second direction opposite the first direction, the shaftless outrunner motor comprising an inner stator and an outer rotor, the second set of blades being connected to the outer rotor; wherein the inrunner motor and the shaftless outrunner motor are arranged coaxially and wherein the shaftless outrunner motor is disposed between the first set of blades and the inrunner motor, and the inner stator of the shaftless outrunner motor comprises an aperture through which the driveshaft of the inrunner motor passes.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the above and other aspects of the invention, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

FIG. 1 is a sectional view of a fan assembly comprising a contra-rotating fan drive assembly according to an embodiment of the invention; and,

FIG. 2 is a sectional view of a fan assembly comprising a contra-rotating fan drive assembly according to another embodiment of the invention.

In the drawings, like reference signs designate corresponding parts where appropriate.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the invention will now be described in which numerous features will be discussed in detail in order to provide a thorough understanding of the inventive concept as defined in the appended claims. However, it will be apparent to the reader that the invention may be put in to effect without the specific details and that, in some instances, well known methods, techniques and structures have not been described in detail in order not to obscure the inventive concept unnecessarily.

The inventive concept, as defined in the appended claims, is intended to cover contra-rotating fan drive assemblies comprising coaxial motor arrangements that enable the space occupied by the assemblies to be reduced comparative to know contra-rotating fan drive assemblies. FIG. 1 shows a fan assembly 2 comprising a contra-rotating fan drive assembly 4 according to an embodiment of the invention. The fan assembly 2 comprises a main housing 6 that forms a duct 8 defining an annular air flow path 10 that extends through the fan assembly 2. The duct 8 comprises a first end defining an annular air inlet 12, through which drive assembly 4 is configured to draw air into the duct 8, and a second end located opposite to the first end and defining an annular air outlet 16, where air that has been worked by drive assembly 4 is pumped from the duct 8. The fan drive assembly 4 then comprises a first impeller 14 disposed adjacent to the air inlet 12 and a second impeller 18 disposed adjacent to the air outlet 16. The first impeller 14 comprises a cap 19 for directing oncoming air towards the annular air inlet 12. The duct 8 is aligned with the drive assembly 4 so that its longitudinal axis is collinear with a rotational axis 20 of the contra-rotating fan drive assembly 4.

The first and second impellers 14, 18 are mixed flow impellers each comprising a generally conical hub 22, a plurality of curved impeller blades 24 connected to the conical hub 22, and an annular shroud 26 connected to the impeller blades 24 so as to surround the conical hub 22 and impeller blades 24. The impeller blades 24 are preferably integral with the conical hub 22, which is preferably formed from a plastic material.

The annular air flow path 10 is defined by an inner side of an outer wall 30 of the main housing 6 and an radially outer side 32 of the conical hubs 22, together with a radially outer side 34 of an inner wall 36 of the main housing 6 which sits adjacent the second impeller 18 and extends circumferentially about a first motor 38.

The contra-rotating fan drive assembly 4 comprises the first motor 38 and a second motor 40 coaxially mounted on a driveshaft 42 and power cable (not shown) for supplying electrical power to the first and second motors 38, 40. The first and second motors 38, 40 may be brushless DC electric motors having independently variable speeds which are controlled by a control circuit (not shown). Such electric motors and control circuits will be familiar to the person skilled in the art, and so will not be discussed in further detail. The fact that the speeds of the first and second motors 38, 40 can be independently controlled means that the quietest operating point maybe established, unlike a single motor geared contra-rotating fan drive assembly, which provides a fixed power split between impellers. The driveshaft 42 is configured to rotate about the rotational axis 20 and is rotatably supported within the main housing 6 by first, second and third bearings 44, 46, 48.

The first motor 38 is an inrunner motor comprising an outer stator assembly 50 surrounding an inner rotor assembly 52, configured to rotate relative to the outer stator assembly 50, and the driveshaft 42, which is fastened, adjacent to one of its ends, to the inner rotor assembly 52. The outer stator assembly 50 comprises a drum or bell housing 54 and a radial mounting plate 56 fastened to an open end of the bell housing. The bell housing 54 is secured to an inner side of a rear wall 55 of the main housing 6 via a circumferential coupling 57, which is concentrically aligned with the rotational axis 20. An outer side of the rear wall 55 carries a stator cap 59, which is shaped to provide a continuation of the external side 34 of the inner wall 36 of the main housing 6 so as to ensure that the air flows smoothly out from the annular air outlet 16. The first bearing 44 is position between the driveshaft 42 and the radial mounting plate 56 to rotatably isolate the outer stator assembly 50 from the driveshaft 42. The driveshaft 42 extends outwardly from the first motor 38 and connects with the first impeller 14 to transmit rotation of the inner rotor assembly 52 to the first impeller 14, which is configured to rotate about the rotational axis 20 in a first direction, for example, in the direction in which the impeller blades 24 of the first impeller 14 are curved.

The second motor 40 is an outrunner motor comprising an inner stator assembly 58 held within an outer rotor assembly 60 that is configured to rotate relative to the inner stator assembly 58. The second motor 40 is “shaftless” insofar that, unlike the first motor 38, its rotor assembly 60 is not configured to drive a driveshaft in order transmit rotation to an impeller. The inner stator assembly 58 comprises an elongate sleeve 62 defining a concentric aperture 64 through which the driveshaft 42 of the first motor 38 passes such that the second motor 40 is disposed between the first impeller 14 and the first motor 38. One end of the elongate sleeve 62, adjacent the bell housing 54 of the first motor 38, comprises a flange 66 fastened to the bell housing 54 of the first motor 38, connecting the outer stator assembly 50 of the first motor 38 and the inner stator assembly 58 of the second motor 40. This arrangement avoids the need for a separate structure supporting the outer stator assembly 50 of the first motor 38 and the inner stator assembly 58 of the second motor 40, which would increase the space occupied by the contra-rotating fan drive assembly 4. The other end of the elongate sleeve 62 comprises a narrowed ring section 68. The second and third bearings 46, 48 are provided between the driveshaft 42 and inner radial sides of the narrowed ring section 68 and the flange 66 to rotatably isolate the second motor 40 from the driveshaft 42. The outer rotor assembly 60 comprises a drum or bell housing 70 rotatably supported on an outer radial side of the narrowed ring section 68 of the inner stator assembly 58 by a fourth bearing 72. The conical hub 22 of the second impeller 18 is directly connected or mounted to the outer rotor assembly 60 via the bell housing 70 such that rotation of the outer rotor assembly 60 drives rotation of the second impeller 18 about the rotational axis 20 in a second direction, opposite the first direction in which the first impeller 14 is configured to rotate.

FIG. 2 shows a fan assembly 2 comprising a contra-rotating fan drive assembly 4 according to another embodiment of the invention. The fan assembly 2 of this embodiment is similar to the assembly shown in FIG. 1 in that it comprises a main housing 6 that forms a duct 8 defining an annular air flow path 10 that extends through the fan assembly 2. The duct 8 comprises a first end defining an annular air inlet 12, through which the drive assembly 4 is configured to draw air into the duct 8, and a second end located opposite to the first end and defining an annular air outlet 16, where air that has been worked by the drive assembly 4 is pumped from the duct 8. The fan drive assembly 4 then comprises a first impeller 14 disposed adjacent to the air inlet 12 and a second impeller 18 disposed adjacent to the air outlet 16. The first impeller 14 comprises a cap 19 for directing oncoming air towards the annular air inlet 12. The duct 8 may be aligned with the drive assembly 4 so that its longitudinal axis is collinear with a rotational axis 20 of the contrarotating fan drive assembly 4.

The first and second impellers 14, 18 are mixed flow impeller each comprising a generally conical hub 22, a plurality of curved impeller blades 24 connected to the conical hub 22, and an annular shroud 26 connected to the impeller blades 24 so as to surround the conical hub 22 and impeller blades 24. The impeller blades 24 are preferably integral with the conical hub 22, which is preferably formed from a plastic material.

The annular air flow path 10 is defined by an inner side of an outer wall 30 of the main housing 6 and a radially outer side 32 of the conical hubs 22, together with a radially outer side 34 of an inner wall 36 of the main housing 6 which sits adjacent the second impeller 18.

The contra-rotating fan drive assembly 4 comprises the first motor 38 and a second motor 40, which, in this embodiment, are coaxially mounted about a driveshaft 42 defining the rotational axis 20, and power cable (not shown) for supplying electrical power to the first and second motors 38, 40. The driveshaft 42 is supported within the main housing 6 by first, second and third bearings 44, 46, 48. As with the previous embodiment, the first and second motors 38, 40 may be brushless DC electric motors having independently variable speeds which are controlled by a control circuit (not shown).

The first motor 38 is an inrunner motor comprising an outer stator assembly 50 surrounding an inner rotor assembly 52 that is configured to rotate relative to the outer stator assembly 50, and the driveshaft 42 that is fastened to the inner rotor assembly 52. The outer stator assembly 50 comprises a drum or bell housing 54 that is rotatably isolated from the driveshaft 42 by the first and second bearings 44, 46 such that the outer stator assembly 50 is rotatably isolated from the driveshaft 42. The bell housing 54 is secured to an inner side of a rear wall 55 of the main housing 6 via a circumferential coupling 57, which is concentrically aligned with the rotational axis 20. An outer side of the rear wall 55 carries a stator cap 59, which is shaped to provide a continuation of the external side 34 of the inner wall 36 of the main housing 6 so as to ensure that the air flows smoothly out from the annular air outlet 16. The driveshaft 42 extends outwardly from the first motor 38 and connects with the first impeller 14 to transmit rotation of the inner rotor assembly 52 to the first impeller 14, which is configured to rotate about the rotational axis 20 in a first direction, for example, in the direction in which the impeller blades 24 of the first impeller 14 are curved. The second motor 40 is an outrunner motor comprising an inner stator assembly 58 held within an outer rotor assembly 60, configured to rotate relative to the inner stator assembly 58. The second motor 40 is “shaftless” insofar that, unlike the first motor 38, its rotor assembly 60 is not configured to drive a driveshaft in order transmit rotation to an impeller. In this embodiment, the inner stator assembly 58 defines a concentric aperture in which the first motor 38 is held such that the first motor 38 is arranged concentrically within the second motor 40. That is, the second motor 40 surrounds a circumference/periphery of the first motor 38. Specifically, the inner stator assembly 58 of the second motor 40 is circumferentially arranged about the outer stator assembly 50 of the first motor 38. In this arrangement, the inner stator assembly 58 of the second motor 40 may be connected, either directly or indirectly, to an outer radial surface of the bell housing 54 of the first motor 38. The outer rotor assembly 60 comprises a drum or bell housing 70 which is supported on the driveshaft 42 by the third bearing 48 to rotatably isolate the second motor 40 from the driveshaft 42. The conical hub 22 of the second impeller 18 is directly connected or mounted to the outer rotor assembly 60 via the bell housing 70 such that rotation of the outer rotor assembly 60 drives rotation of the second impeller 18 about the rotational axis 20 in a second direction, opposite the first direction in which the first impeller 14 rotates. By concentrically arranging the first motor 38 within the second motor 40 means that the second motor 40 does not need to be directly supported on the driveshaft 42. This, in turn, means that the length of the driveshaft 42 can shortened, when compared to the embodiment of FIG. 1 , meaning that the contra-rotating fan drive assembly 4 occupies comparatively less space within the fan assembly 2.

It will be appreciated by those skilled in the art that the invention has been described by way of example only, and that a variety of alternative approaches or modifications may be adopted without departing from the scope of the invention as defined by the appended claims. For example, in both of the embodiments described above, the conical hub 22 of the second impeller 18 is connected to the outer rotor assembly 60 of the second motor 40 via the bell housing 70. However, embodiments are envisioned in which the conical hub 22 is not required and the plurality of impeller blades 24 of the second impeller 18 extend outwards directly from an outer radial surface the outer rotor assembly 60. In such an embodiment, the outer radial surface may be defined by the bell housing 70 of the outer rotor assembly 60. Moreover, in the embodiments described above, the contra-rotating first and second impellers 14, 18 function to pump air through the annular air flow path 10, but those skilled in the art will appreciate that this function, of pumping air through the annular air flow path 10, could also be carried out by contra-rotating propellers each having a plurality of blades.

In all embodiments the first motor 38, which is an inrunner motor, is arranged to drive the rotation of the first impeller 14, which is the front impeller of the contra-rotating fan drive assembly 4. This arrangement is advantageous as, from an aerodynamic standpoint, the front impeller in a contrarotating fan arrangement requires more power and rotational speed when compared to the rear impeller, and inrunner motors are capable of producing higher rotational speeds, and are thus more efficient, comparative to outrunner motors.

Furthermore, the above described embodiments each relate to a contra-rotating drive assembly for driving a fan and therefore comprise first and second contra-rotating impellers, wherein an impeller is a rotating part of a machine that is designed to move a fluid. However, those skilled in the art will appreciate that the above-described contra-rotating drive assembly could equally be used to drive contra-rotating propellers for generating thrust. Fan drive assemblies in accordance with the present invention have been described with reference to particular embodiments thereof in order to illustrate the principles of operation. The above description is thus by way of illustration and directional references (including: upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, side, above, below, front, middle, back, vertical, horizontal, height, depth width, and so forth) and any other terms having an implied orientation refer only to the orientation of the features as shown in the accompanying drawings. They should not be read to be requirements or limitations, particularly as to the position, orientation, or use of the invention unless specifically set forth in the appended claims. Connection references (e.g., attached, coupled, connected, joined, secured and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other, unless specifically set forth in the appended claims.