EP0652375A1

EP0652375A1 - A blower assembly

Info

Publication number: EP0652375A1
Application number: EP94203055A
Authority: EP
Inventors: Ronald Joseph Goubeaux; James Joseph Christen
Original assignee: General Motors Corp
Current assignee: Motors Liquidation Co
Priority date: 1993-11-05
Filing date: 1994-10-20
Publication date: 1995-05-10

Abstract

A blower assembly (10) for a vehicle heating and cooling system has a particularly compact and efficient arrangement of components. A blower housing (12) has a planar back wall (18) and spiral side wall (20), with an electric motor (16) mounted to and through the back wall. A cylindrical blower (14) is mounted to the drive shaft (34) through a central, dome shaped hub (26) that covers the protruding end of the motor and runs parallel to the back wall. An electrical controller (36) with significant cooling demand is mounted to the back wall, close to and concentric to both the motor and the blower. A heat sink (38) conductively connected through the back wall to the controller is located entirely beneath and behind the dome shaped blower hub. The rest of the air flow space inside the housing is therefore unobstructed.

Description

This invention relates to blower assemblies and blower housing designs in general for air conditioning systems, and specifically to such a design with an improved, compact design for a cooling means used in conjunction with the blower motor and associated speed controller.
Vehicle heating and cooling systems have a blower assembly with an electric motor driven blower enclosed in a housing, often called a scroll housing. The blower, typically called a squirrel cage blower, has a cylindrical array of axially extending blades arranged so as to pull outside air axially in and send it radially outwardly in a circular, pressurised flow. The scroll housing side wall that surrounds the vanes is not concentric, but follows a spiral pattern from a narrow point to a widest point near a tangentially located outlet opening. The scroll housing wall stands out from a planar back wall, to which the electric motor is mounted and through which the end of the motor and the drive shaft protrude. The blower has a hub secured at its centre to the motor drive shaft. The blower hub is dome shaped, so as to clear the protruding end of the motor. The circular perimeter edge of the hub runs parallel to the housing back wall, with a small gap.
There are cooling demands associated with the motor and with the motor speed controller. The motor is cooled, in some designs, with an air tube that picks up moving air out of the scroll housing outlet and ducts it back to the motor housing. Another approach is to provide vents or vane like structures in the blower hub to circulate air behind the hub, where it can impact on the protruding end of the motor, which is vented. Yet another approach is to provide separate vanes on the back of the perimeter of the hub to pull air beneath the blower hub. Another cooling demand is created by mechanisms that control the motor speed. Direct current motor speed control mechanisms may use a resister to dump extra power, which needs to be cooled. This is usually accomplished by placing the resistor downstream in the blower outlet air flow. Obviously, this represents somewhat of a flow obstruction. Another cooling demand is created by motor speed control mechanisms, such as those using so called pulse width modulation, which incorporate heat producing power transistors. Such speed controllers would, ideally, be located as close as possible to the motor, so as to minimise circuit wire lengths. The precipitous switching effect of the transistors creates voltage spikes which, acting through long wires, can create RF interference. Heat sinks to cool the power transistors, of course, must conductively contact the transistors, and must be exposed to a cooling air stream. There is not a great deal of room available between the blower and scroll housing wall for such a heat sink, which also represents an obstruction to air flow. Nevertheless, that is where transistor heat sinks have been placed, so as to achieve proximity to the blower motor and its controller, and because it was thought that only there could enough cooling air flow be obtained.
A blower assembly in accordance with the present invention is characterised by the features specified in the characterising portion of Claim 1.
The present invention provides a heat sink arrangement that is much more compact, and which represents no obstruction to blower air flow, while maintaining maximum proximity to the blower motor and its controller.
In the preferred embodiment disclosed, the blower hub, contrary to general practice, is left uninterrupted, without vents or holes. No structure is provided to deliberately move air beneath or behind the hub. In spite of the lack of openings through the hub surface, a good deal of air flow behind the hub is found to exist. The behind the hub air flow also has a detectable velocity pattern, and has been found to be greatest at a location just upstream from the narrow point of the blower-scroll wall clearance. A heat sink is mounted to the housing back wall or blower motor mounting flange in the maximum air speed location, entirely beneath the blower hub. Adequate cooling is obtained with no obstruction of other air flow, and the heat sink is contained and protected within otherwise unused space. In addition, in the embodiment disclosed, the motor controller is mounted outside the back wall, just beneath the heat sink, and close to the motor and blower. Circuit wire length and RF interference are thereby minimised.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

Figure 1 is a view looking axially down into a scroll housing and blower, with part of the blower broken away to show the heat sink location;
Figure 2 is a cross section of the housing taken along the line 2-2 of Figure 1; and
Figure 3 is a velocity profile of air flow behind the hub of the blower.

Referring first to Figures 1 and 2, a vehicle heating and cooling system includes a blower assembly 10 comprised of a scroll housing, indicated generally at 12, a squirrel cage type blower, indicated generally at 14, and electric motor, indicated generally at 16. Scroll housing 12 is adapted to be mounted to a non illustrated vehicle dash panel, which includes a fresh air inlet. The housing 12 has a generally flat back wall 18 and a spiral shaped side wall 20 with an outlet opening 22 that feeds air into the rest of the heating and cooling system. The blower 14 has a conventional cylindrical array of blades or vanes 24 at its perimeter. In the centre of the blower 14 is a dome shaped hub 26, which bulges upwardly considerably from an annular perimeter edge 28. The upward bulge is provided primarily to clear the protruding end of the motor 16, which is secured to the housing back wall 18 and extends axially through it to a considerable degree. The motor 16 is secured through housing back wall by a mounting flange 30 that is fixed to the back wall 18 with a sealing gasket 32. The centre of the hub 26 is attached to the end of motor drive shaft 34, which serves to locate the hub perimeter edge 28 parallel to and very close to the inner surface of the housing back wall 18, surrounding the end of the motor 16. It will be noted that the hub 26 is uninterrupted by any vent holes or other openings.
Referring next to Figures 1 and 3, the operation of the blower 14, in so far as supplying air to the heating and cooling system is concerned, is conventional. The blades 24 are designed to pull air axially inwardly as the hub 26 is spun counter clockwise and sling it radially outwardly and into a counter clockwise vortex that ultimately exits through the tangentially located outlet 22. What was unexpected was the airflow that was discovered beneath and behind the hub 26. While the blower 14 operated, a series of fifteen generally evenly spaced locations behind the hub 26 were probed to detect and measure air flow speed. The velocities of air flow discovered are graphed in Figure 3. The exact location of each velocity point around the circumference of the hub 26 is not so significant as the fact that a peak area of air flow speed exists, as shown by the dotted line in Figure 3. This corresponds roughly with the arcuate area between the lines A and B shown in Figure 1. Even more significant, of course, is the fact that air flow was found at all, when it had been thought that the only way to create such flow was to ventilate the hub 26, or provide separate vanes below the hub perimeter edge 28 to pull it in. The physical mechanism causing this flow is not perfectly understood, though there is an apparent rough correlation between the velocity and the narrowness of the radial clearance between the array of blades 24 and the scroll housing side wall 20. The A to B area corresponds to the narrowest clearance. There may or may not be causality along with the correlation. The air flow beneath the hub 26 may have something to do with pressure differentials on opposite sides of the blower 14. It is also thought that the fact that the hub 26 is uninterrupted and unvented may be significant. At any rate, it is now clear that moving air does get under and through the small clearance between the hub edge 28 and the housing back wall 18, through whatever means.
Referring again to Figures 1 and 2, the discovered air flow described above is put to good use. The motor 16 is run by an electronic controller, the location of which is indicated by the dotted line 36. The controller 36 is contained within an arcuate housing secured to the back of the motor flange 30, proximate to and concentric with both the blower 14 and the motor 16. The total package is thus compact and space efficient. The details of the controller 36 are not important to the invention, but it is significant that it contains components, in this case, power transistors, which run quite hot. In addition, the power transistors create voltage spikes which can translate into RF interference if they run through lengthy circuit wires. Because of the proximity of the controller 36 to the motor 16, the circuit wires can be short, minimising RF noise. In order to handle the cooling load, a heat sink, indicated generally at 38, is located behind the hub 26. Specifically, the heat sink 38 is a cast, extruded or machined aluminium or other heat conducting material piece, with a flat base 40 and three fins 42. The base 40 fits beneath the hub perimeter edge 28, and the three fins 42 are profiled so as to fit in the sloped space available between the end of the motor 16 and the hub 26. The heat sink 38 is not directly secured to the housing back wall 18, but is basically co-planar with it, since it is secured to the motor housing flange 30 and moves into place when the motor 16 is installed. It is also deliberately located in the area noted above where the air velocity is the highest. The heat sink 38 is conductively connected to those elements of the controller 36, such as power transistors, that require cooling. The ability to place the heat sink 38 in the otherwise unused space beneath the blower hub 26 lends itself to the compact arrangement of the housing 12, the blower 14 and the controller 36 described above. The heat sink 38 can provide cooling while providing no obstruction whatsoever to air flow around the blower 14 or through the outlet 22. It is also protected and enclosed by the hub 26.
Variations in the embodiment disclosed could be made. The heat sink 38 could be lengthened considerably into an arcuate shape, so as to fill more of the empty available volume behind hub the 26. Should it be necessary, because of the location of the controller 36, the heat sink 38 could be placed in a location other than right in the peak air velocity location shown. While it would not operate as efficiently, increasing its size as noted could compensate. It is thought that some voids in the surface of the hub 26 could be tolerated without significantly affecting the air flow beneath it. For example, a small opening might be provided for tool access, or to allow visual inspection of the heat sink after installation.
The disclosures in United States patent application no. 147,517, from which this application claims priority, and the abstract accompanying this application, are incorporated herein by reference.

Claims

A blower assembly comprising a blower housing (12); an electric blower drive motor (16) with a shaft (34) extending through a back wall (18) of the housing; an electronic controller (36) for operating the motor; and a generally cylindrical blower (14) having blades (24) in a cylindrical perimeter array and a central hub (26) secured at its centre to the shaft in close, parallel proximity to the back wall, the hub having a dome shape; characterised by a heat sink (38) connected through the back wall to the controller and located substantially entirely beneath the dome of the hub, whereby air flow from the blower is substantially unobstructed.
A blower assembly as claimed in Claim 1, wherein the housing (12) has a spiral shaped side wall (20) extending from the back wall (18); wherein the array of blades (24) defines a radial clearance relative to the side wall that has a narrowest point corresponding to an area of maximum air flow behind the hub (26) when the blower (14) operates; and wherein the heat sink is located in the area of maximum air flow.
A blower assembly as claimed in Claim 1 or Claim 2, wherein the electronic controller (36) is located behind the back wall (18) proximate to and concentric with the motor (16).