CENTRIFUGAL FAN

Abstract

A centrifugal fan includes a centrifugal impeller rotatable around an axis of rotation; a drive motor of the centrifugal impeller; a casing including a central portion for housing the motor and the centrifugal impeller and a tangential outlet channel in communication with the central portion. The casing has an inlet opening in the central portion and an outlet opening in the tangential outlet channel. The fan includes a system for cooling the motor including the impeller, a ventilation channel operating between the tangential outlet channel and the central portion for generating a flow of cooling air, a collar integral with the centrifugal impeller extending axially from the centrifugal impeller around the motor and a plurality of blades of the motor for generating a tangential cooling component which combines with the flow of cooling air and generating as a resultant, a helical vortex around the motor.

Description

TECHNICAL FIELD

This invention relates to a centrifugal fan and in particular a centrifugal fan comprising a system of cooling the motor of the fan.

BACKGROUND ART

In the automotive field (for coach, truck and similar applications) the use of centrifugal fans driven by DC motors of the open type is widespread.

These fans are conveniently provided with systems for cooling the relative drive motors based on a forced circulation of cooling air.

FIG. 1 illustrates a prior art centrifugal fan, in a schematic view partly in cross-section.

This type of fan comprises a scroll-shaped outer casing 100, formed by a central portion 101 and an outlet channel 102 in communication with the central portion 101.

The casing 100 has an inlet opening 103 formed in the central portion 101 and an outlet opening 104 formed at the end of the channel 102.

A motor 105, generally of the “open” type and equipped with aeration holes 105a, is mounted inside the scroll for driving a centrifugal impeller 106, rotating around its axis R, which sucks air at the inlet opening 103 and introduces the blown air into the channel 102 of the scroll 2.

After being placed in rotation, the impeller 106 generates a pressure difference between the inlet opening 103 and the outlet opening 104 so as to generate a flow F of air along the channel 102. Generically, it is indicated that there is a high pressure at the outlet, or outside, of the fan whilst there is a negative pressure (compared with the outlet) at the inlet, or inside.

The cooling system of the motor 105 comprises a recirculation duct 107 having inlet in communication with the channel 102 and outlet in communication with the central portion 101. The duct 107 collects pressurised air at the outlet of the casing 100 so as to form a flow RF of cooling air which is pushed, from the over-pressure coming from the impeller 106, to the central portion 101 at the rear part of the motor 105. In this way, the flow RF of cooling air passes through the aeration holes 105a of the motor 105 removing the heat directly from the windings of the motor 105 and again reaching the inside of the impeller 106 and from there reintroduced into the channel 102.

The reference markets for these fans require more advanced solutions from a point of view of the electronic drive of the motor, which must be integrated in the motor whether it is of the brushless type or the DC type, and at the same time from a point of view of the lifetime and reliability of the motor under harsh operational conditions.

The main obstacle to the adoption of these solutions is due to the relatively poor performance of the cooling systems of the prior art motor which cannot guarantee the optimum operational conditions of the fans operated.

Consider, for example, that in the case of drive electronics integrated in the motor the limit operating temperature must be up to 50° C. less than the temperature of the windings and a cooling system of the motor is therefore essential which can remove large quantities of heat in order not to exceed the limit operational conditions.

It should be noted that both the lifetime of the product and the possibility of operating under harsh operational conditions are closely linked to the possibility of guaranteeing an adequate and efficient cooling of the motor and the relative electronics.

DISCLOSURE OF THE INVENTION

In this context, the main technical purpose of this invention is to provide a centrifugal fan which is free of the above-mentioned drawbacks.

One aim of this invention is to provide a centrifugal fan equipped with a highly efficient cooling system.

Another aim of this invention is to provide a fan equipped with a cooling system which is able to remove large quantities of heat from the motor driving the impeller, also, for example, in the case of adoption of a closed motor in which the cooling components may not be directly exposed to a forced flow of cooling air.

The technical purpose indicated and the aims specified are substantially achieved by a centrifugal fan according to independent claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention are more apparent in the non-limiting description which follows of a preferred embodiment of a centrifugal fan as illustrated in the accompanying drawings, in which:

FIG. 1 illustrates a schematic view of a prior art centrifugal fan.

FIG. 2 illustrates a cross-sectional schematic view of a first embodiment of a centrifugal fan according to this invention;

FIG. 3 illustrates a top plan view of a second embodiment of a centrifugal fan according to this invention;

FIG. 4 illustrates a schematic cross-section according to the line IV-IV of the fan of FIG. 3;

FIG. 5 illustrates a conveniently scaled-up portion of the fan of FIG. 4;

FIG. 6 illustrates a top plan view of the fan of FIG. 3, with some parts cut away to better illustrate others;

FIG. 7 illustrates a first perspective view of a first embodiment of a impeller of a centrifugal fan according to this invention;

FIG. 8 illustrates a second perspective view of the impeller of FIG. 7;

FIG. 9 illustrates a partly schematic cross-section of a portion of a third embodiment of a fan according to this invention;

FIG. 10 illustrates schematic perspective view of a detail of the centrifugal impeller of the fan of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

With reference to the accompanying drawings, with particular reference to the FIG. 2, the numeral 1 denotes a centrifugal fan according to this invention.

The fan 1, which has an axis of rotation R, comprises a casing, or volute or scroll 2, an electric motor 3, preferably of the closed or “sealed” type, having a corresponding shaft 3a, located inside the casing 2 and supported by it and a centrifugal impeller 4, illustrated in particular in FIGS. 7 and 8, driven by the motor 3.

The impeller 4, rotatable around the axis R, comprises a plurality of centrifugal blades 5, having main extension according to the axis R, and a first and a second support ring 6, 7 between which the blades 5 extend.

The impeller 4 has a first inlet 8, formed by the opening delimited by the support ring 7, coaxial to the axis R, and a tangential outlet 9 defined, in practice, by the spaces between the blades 5.

The impeller 4 comprises a hub 10, connected to the first support ring 6, for coupling with the motor 3.

The hub 10 has a sleeve 11, for coupling with the shaft 3a, from which a plurality of arms 12 extend for connecting with the ring 6.

The hub 10 also comprises a central portion 13 which extends from the sleeve 11 between the arms 12 and delimits, with the arms 12 and the support ring 6, a plurality of openings 14.

As illustrated, for example, in FIGS. 2, 3 and 4, the motor 3 is partially inserted inside the hub 10 whilst in alternative embodiments not illustrated the motor 3 is outside the hub 10.

The aforesaid casing 2 has an axial inlet opening 15, that is, coaxial with the axis of rotation R (and therefore coaxial with the inlet 8 of the impeller 4), and a tangential outlet opening 16, located in a known manner with respect to the impeller 4, for circulating the air moved by the impeller 4.

The casing 2 comprises a main body which has a central portion 17 in which is formed the inlet opening 15 and an outlet channel 18, which extends tangentially from the central portion 17 and is in fluid communication with it, and at the free end of which is located the outlet opening 16.

The fan 1 comprises a cover 19 for closing the casing 2 to which, preferably, the motor 3 is anchored.

In practice, the cover 19 is located, relative to the motor 3, from the opposite part of the impeller 4 and it is coupled to the central portion 17 of the main body.

The cover 19 forms a housing 20 for the motor 3 in which the motor 3 is partially located.

More specifically, the cover 19 has an inner cylindrical side wall 21 and an inner rear wall 22 joined with the side wall 21 delimiting the housing 20 and the motor 3 is located in a coaxial fashion inside the housing 20.

More specifically, with reference to the FIG. 5, the upper portion 3b of the motor 3 is the portion of the motor 3 which is housed in the housing 20 and the lower portion 3c of the motor 3 is the portion partly inserted in the hub 10.

An air circulation zone 32 is defined between the motor 3, specifically between its upper portion 3b, and the cover 19.

The fan 1 comprises a cooling system for removing heat from the motor 3 by means of a flow RF of cooling air directed from the inside of the casing 2 towards the outside of it.

According to this invention, as will be clarified below, the flow RF of cooling air consists of a tangential component and an axial component, directed according to the axis of rotation R.

The tangential component and the axial component are added vectorially generating, as the resultant, a helical vortex RF around the motor 3.

With reference to FIG. 2, in a first embodiment, the cooling system of the motor 3 comprises, for generating the aforesaid axial component, the impeller 4 and a duct 30 having inlet 26 in the outlet channel 18 and outlet 27 in the central portion 17, substantially at the motor 3.

In use, an over-pressure is created at the outlet 9 of the impeller 4, in particular also at the inlet 26 of the duct 30.

This over-pressure pushes air along the duct 30 from the inlet 26 towards the outlet 27; the flow of air exiting from the duct 30 forms the aforesaid axial component.

For generating, in use, the aforesaid tangential component of the cooling flow RF, the cooling system comprises a collar 28 integral with the impeller 4 and extending axially from the impeller 4 towards the motor 3, outside of it, and a plurality of radial blades 29, supported by the collar 28 and facing the motor 3.

The collar 28 is made in a single body with the impeller 4 and extends from the support ring 6 on the opposite side with respect to the blades 5.

The radial blades 29 extend between the support ring 6 and the outer collar 28 and they extend from the latter towards the motor 3.

The outer collar 28 together with the blades 29 surround the motor 3 and in particular the upper portion 3b of the motor.

The aforesaid housing 20 is designed to accommodate, in addition to the motor 3, also the collar 28 and therefore the blades 29.

The blading constituted by the blades 29, together with the outer collar 28, placed in rotation with the impeller 4, being a single body with the impeller, generates a contribution to the cooling flow RE which forms the aforesaid tangential component.

The effect of the rotation of the blades 29 is, in other words, that of dragging the air contained in the hollow space between the blades 29 and the motor 3, generating the tangential component of the cooling flow RF.

The aforesaid axial component is advantageously directed from the upper portion 3b of the motor towards the lower portion 3c of the motor, inside the casing 2, in such a way that the cooling flow RF, resultant from the combination between the tangential component and the axial component moves, through the openings 14 of the hub 10, to the inside of the impeller 4, from where it is expelled outside the casing 2 through the outlet opening 16.

In a second embodiment, illustrated in FIGS. 4 and 5, the cooling system comprises a hollow space 31, or annular channel 31, formed between the cylindrical outer wall of the collar 28 and the cylindrical side wall 21 of the housing 20.

The annular channel 31 places the channel 18 in fluid communication with the central portion 17 of the casing 2 at the upper part 3b of the motor 3.

More specifically, the cover 19 is shaped in such a way that the annular hollow space 31 is in fluid communication with the channel 18.

With reference in particular to FIG. 5, reference numeral 31a indicates the inlet of the annular channel 31 and reference numeral 31b indicates the outlet of the channel 31.

The cooling system comprises, similarly to the first embodiment, the collar 28 integral with the impeller 4 and extending axially from the impeller 4 towards the motor 3, outside of it, and the radial blades 29 supported by the collar 28 and facing the motor 3.

The collar 28 is made in a single body with the impeller 4 and extends from the support ring 6 on the opposite side with respect to the blades 5.

The radial blades 29 extend between the support ring 6 and the outer collar 28 and they extend from the latter towards the motor 3.

The outer collar 28 together with the blades 29 surround the motor 3 and in particular the upper portion 3b of the motor.

The aforesaid housing 20 is designed to accommodate, in addition to the motor 3, also the collar 28 and therefore the blades 29.

The blading constituted by the blades 29, together with the outer collar 28, placed in rotation with the impeller 4, being a single body with the impeller, generates the contribution to the cooling flow RF which forms the aforesaid tangential component.

The effect of the rotation of the blades 29 is, in other words, that of dragging the air contained in the hollow space between the blades 29 and the motor 3, generating the tangential component of the cooling flow RF.

In use, the impeller 4 pushes air at high speed along the canal 8.

The high speed air generates a Venturi effect which generates, in turn, a negative pressure at the outlet 31b of the channel 31.

The negative pressure causes a suction effect along the hollow space 31 of the flow of cooling air.

In other words, a suction flow is generated in the annular channel 31 directed from the inlet 31a to the outlet 31b.

In practice, the suction along the hollow space 31 generates, inside the central portion 17 of the casing 2, the so-called axial component substantially directed according to the axis of rotation R of the motor 3 inside the casing 2.

This axial component is sucked inside the impeller 4 through the inlet 8.

The axial component is advantageously directed from the lower portion 3c of the motor towards the upper portion 3b of the motor, inside the casing 2, in such a way that the helical cooling flow RF, resultant from the combination between the tangential component and the axial component moves, through the openings 14 of the hub 10, through the impeller 4, to the zone 32 from where it is expelled outside the casing 2 through the hollow space 31 and the channel 18.

The axial component combines with the tangential flow due to the blades 29 generating the aforesaid helical vortex RF which is carried from inside the casing 2 to the outside of the casing 2 through the hollow space 31 and the channel 18.

In the preferred embodiment illustrated, the annular channel 31 has the outlet 31b delimited between the cover 19 and the impeller 4, having dimension “h” of the same order of magnitude as the dimension “h1” of the channel 31 between the collar 28 and the cylindrical side wall 21 delimiting the housing 20.

In other words, the cover 19 is shaped in such a way as to delimit the outlet 31b with the first support ring 6 and/or with the blades 5.

In the embodiment illustrated, the outlet 31b of the annular channel 31 is advantageously formed by the support ring 6 and specifically by an annular rim 60 of it which faces a corresponding annular portion 19a of the cover 19.

The annular hollow space 31 is in communication with the air circulation zone 32, where the inlet 31a is formed.

In this way, in use, the flow drawn along the hollow space 31 combines in the zone 32 with the tangential flow due to the blades 29, generating the aforesaid vortex RF around the motor 3 which is sucked into the channel 18.

In the aforesaid air circulation zone 32 the flow of cooling air RF touches the cover of the motor 3 removing heat from it.

The air circulation zone 32 is defined between the rear wall 22 of the housing 20 and the rear surface 33 of the motor 3 to which it faces.

In practice, the inside of the housing 20 is provided with the space for the circulation of the air both between the side wall and between the base wall of the motor 3 and the cover 19.

A third embodiment of a fan according to this invention is illustrated in FIG. 9.

In this solution, compared with the second embodiment, the suction of the cooling flow across the hollow space 31 is assisted by a series of centrifugal blades 40 positioned on the outside of the collar 28 for forcing the air from the hollow space 31 towards the outlet opening of the channel 18.

The centrifugal blades 40 extend from the opposite side with respect to the motor 3 and form a second auxiliary centrifugal fan 41 which further pushes the cooling flow, resultant from the combination of the tangential component with the axial component, from the hollow space 31 towards the outside of the casing 2.

The blades 40 are advantageously made in a single body with the collar 28 and extend outside the collar, as also shown in FIG. 10.

In the preferred embodiment illustrated by way of example, each blade 40 is formed as an extension of a corresponding blade 5 of the impeller 4, as shown in FIG. 10.

Preferably, the cooling system, and the blades 29 in particular, are designed in such a way that the tangential component is of an order of magnitude greater than the axial component for effectively removing heat from the motor 3.

The duct 30 external to the casing 2 in the first embodiment and the hollow space or annular channel 31 in the second and in the third embodiment define a ventilation channel forming part of the cooling system of the fan 1 thanks to which the cooling flow RF defined as a helical vortex removes heat from the motor 3.

The motor 3 is therefore touched by high speed air on the external skin which is particularly effective in the removal of heat.

The effect of the rotation of the blades 29 is in other words, that of dragging the air contained in the hollow space between the blades 29 and the motor 3, generating the aforesaid tangential component.

The motor is enveloped by a helical vortex which is very effective for forced cooling without using an axial component that is detrimental for the efficiency and the noise level of the fan.

The axial component is necessary for transporting the quantity of heat collected by the aforesaid vortex RF outside the “motor zone”.

The centrifugal fan provided with the cooling system as described allows the adoption of closed or sealed motors, which work well in harsh ambient conditions, also with drive electronics integrated inside.

The cooling system as described allows the lifetime of the fan to be extended by up to more than 30,000 working hours compared with prior art fans.

The proposed solutions allow maximisation of the cooling of the motor driving the impeller, minimisation of the sources of fluid dynamic noise and, at the same time, minimisation of the costs for equal performance levels by avoiding adoption of the connecting duct between fan outlet and housing of the motor.

The adoption of the annular suction channel inside the casing of the fan (axial component) allows both the noise of the air due to the fluid dynamics and the vibrations to be reduced compared with prior art solutions,

Claims

1. A centrifugal fan comprising

a centrifugal impeller rotatable around an axis of rotation;

a drive motor of the centrifugal impeller;

a casing comprising a central portion for housing the motor and the centrifugal impeller and a tangential outlet channel in communication with the central portion, the casing having an inlet opening in the central portion and an outlet opening in the tangential outlet channel,

a system for cooling the motor comprising the impeller and a ventilation channel operating between the tangential outlet channel and the central portion for generating a flow of cooling air, the fan characterised in that the cooling system comprises a collar integral with the centrifugal impeller extending axially from the centrifugal impeller around the motor and a plurality of radial blades supported by the collar and facing the motor for generating a tangential cooling component which combines with the flow of cooling air generating as a resultant a helical vortex RF around the motor.

2. The fan according to claim 1, wherein the casing comprises a cover closing the central portion positioned coaxially to the motor on the opposite side with respect to the centrifugal impeller, the ventilation channel being at least partly formed between the outer surface of the collar and the cover.

3. The fan according to claim 2, wherein the ventilation channel has an annular outlet, delimited between the cover and the centrifugal impeller, having dimension of the same order of magnitude as the dimension of the ventilation channel between the collar and the cover.

4. The fan according to claim 1, wherein the cooling system comprises a plurality of centrifugal blades extending from the opposite side of the motor with respect to the collar, for forcing the cooling flow along the tangential outlet channel.

5. The fan according to claim 4, wherein the centrifugal blades extend from the collar and form a single body with the collar.

6. The fan according to claim 1, wherein the collar and the first radial blades are made in a single body with the centrifugal impeller.

7. The fan according to claim 1, wherein the motor is at least partly inserted in the centrifugal impeller.

8. The fan according to claim 1, wherein the casing comprises a cover closing the central portion positioned coaxially to the motor on the opposite side with respect to the centrifugal impeller, the cover having a cylindrical inner side wall and an inner rear wall delimiting a housing in which the motor is inserted, the ventilation channel being formed between the collar and the cylindrical inner side wall, an air circulation zone being formed between the inner rear wall and a rear surface of the motor, the ventilation channel and the circulation zone being in fluid communication with each other.

9. The fan according to claim 1, wherein the ventilation channel is formed by a recirculation duct outside the casing having inlet in the tangential outlet channel and outlet in the central portion.