GB2311843A

GB2311843A - Air flow system for a vehicle heat exchanger

Info

Publication number: GB2311843A
Application number: GB9606568A
Authority: GB
Inventors: Craig Alexander Perrie
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1996-03-28
Filing date: 1996-03-28
Publication date: 1997-10-08
Also published as: GB9606568D0

Abstract

In a heat exchanger air flow system for a motor vehicle cooling system coolant passes through the core 111 of a heat exchanger 110 and is cooled by fan 114 and ram air 30, 32. At standstill or at slow speeds, flaps 20, 21, 22, 23 are biased against the core 111 by spring loaded members 201, 211, 221, 231 and prevent air recirculation (115, 116, figure 2) through the core 111. When the vehicle moves forwards and ram air 30, 32 overcomes the biasing of the spring loaded members 201, 211, 221, 231 the flaps 20, 21, 22, 23 pivot about the sides 200, 210, 220, 230 of the heat exchanger. The whole face of the core 111 is exposed to the passage of ram air 30, 32 for maximum available cooling effect.

Description

A Heat Exchanger Air Flow System For A Motor Vehicle This invention relates to heat exchanger air flow systems for motor vehicles and in particular to heat exchanger air flow systems for motor vehicle cooling systems.

It is known to provide a motor vehicle with a liquid cooled engine and to provide a heat exchanger as part of the cooling system for that engine in order to reduce the temperature of the cooling liquid.

It is common to fit these heat exchangers to the front of the vehicle and to provide an associated air flow system. The air flow system takes advantage of the forward motion of the vehicle and is arranged to direct air through the core of the heat exchanger. This provides a cooling air flow for the liquid passing through the core and this effect is known in the art as "ram air" cooling.

It is an object of this invention to provide an improved heat exchanger air flow system.

According to the invention there is provided a heat exchanger air flow system for a motor vehicle comprising a heat exchanger including a cooling core with an air .- .

through it, a fan in close proximity to the heåt exchanger and having air ducting means associated with the heat' exchanger which is moveable from a first position in which it covers part of the cooling core to a second position in which said part of the cooling core is uncovered wherein said ducting means is in said first position when the vehicle is stationary and is progressively moved towards said second position as the vehicle moves forward with increasing speed such that above a predetermined speed the ducting means is in said second position.

The ducting means may be urged towards said first position by a biasing means.

The biasing means may be of sufficient strength to hold the ducting means in said first position while the vehicle is stationary or travelling at a very slow speed but is overcome by the pressure of air impinging upon the heat exchanger as the vehicle moves forward with increased speed such that beyond a predetermined speed the biasing means is overcome and the full surface area of the heat exchanger is uncovered.

The ducting means may be in the form of flaps, in which case the flaps may be made of an elastomeric material.

Preferably, the ducting means may be attached directly to part of said heat exchanger.

The ducting means may be pivotally attached to said heat exchanger.

The invention will now be described by way of example with reference to the accompanying drawings in which: figure 1 shows a prior art heat exchanger air flow system; figure 2 shows part of a heat exchanger air flow system in accordance with the invention in a first "closed" position; and figure 3 shows the part of the heat exchanger air flow system described with reference to figure 2 in a second "open" position.

The prior art arrangement in figure 1 includes a heat exchanger 10 which has a serpentine core 11 through which cooling liquid passes. A fan 14 is provided, which is positioned behind the heat exchanger 10 in close proximity to it and is used to draw air through a cooling core 11.

A proportion of the cooling liquid (not shown) is diverted from the rest of the cooling system (not shown) and passed through the core 11. It enters the core 11 through an entry point 12 in a hot state and leaves by an exit point 13 after cooling. As the coolant passes through the core 11, it is cooled by air passing through the core 11 either as ram air or drawn through by the fan 14.

The fan 14 is arranged to operate if the temperature of the cooling liquid rises above a predetermined temperature, typically in the region of 1000C. Such an increase in temperature occurs if there is an insufficient cooling effect produced by the ram air, as happens for example when the vehicle (not shown) is stationary or moving very slowly.

The under-bonnet space behind the heat exchanger 10 in many vehicles is confined and often takes the form of an engine compartment with the engine (not shown) very close to the heat exchanger 10.

As the fan 14 draws air through the core 11, pressure builds up in the under-bonnet space between the heat exchanger 10 and the engine with the result that a pressure differential can be created across the heat exchanger 10.

The air behind the heat exchanger 10 can then be pushed back through the core 10 in the direction of the arrows 15, 16 by the pressure differential and this effect is known in the art as "air recirculation".

The air behind the heat exchanger 10 is at a raised temperature, having passed through the core 11 and also having been heated further by heat radiated by the engine.

The raised temperature of the air recirculation 15, 16 means it has reduced capacity to absorb heat from the core 11, thus reducing the cooling efficiency of the heat exchanger 10.

When the vehicle is travelling forwards above a certain speed, the high volume of cooler ram air passing through the core 11 causes the air exiting the core 11 to be forced away under the vehicle and air recirculation 15, 16 is thereby eliminated.

With reference to figure 2, a heat exchanger 110 of the same basic construction as the prior art heat exchanger 10 of figure 1 is shown in a first or closed position and the same features have corresponding reference numerals with 100 added.

Ducting means in the form of rubber flaps 20, 21, 22, 23 are pivotally attached to the sides 200, 210, 220, 230 of the heat exchanger 110 and are typically lmm thick. The flaps 20, 21, 22, 23 are biased into a closed position to cover an area of the core 111 by biasing means in the form of spring loaded members 201, 211, 221, 231.

Referring now to figure 3, the heat exchanger arrangement of figure 2 is shown in a second or open position with the vehicle moving forward and reference numerals corresponding to figure 2 are used. Air passing through the core 111 is represented by the arrows 30, 31, 32.

When the vehicle is stationary or travelling very slowly, the spring loaded members 201, 211, 221, 231 urge the rubber flaps 20, 21, 22, 23 into the closed position to cover the sections of the core 111 through which hot air would normally pass due to air recirculation 115, 116. The air recirculation 115, 116 is therefore blocked by the flaps 20, 21, 22, 23 when they are in the closed position.

In such situations, the fan 114 switches on and draws cooling air through the uncovered area of the core 111.

The area of the core 111 which remains uncovered can be reduced to as little as 60% of the full area available.

The uncovered area is still sufficient to provide enough cooling to satisfy the vehicle requirements at low loads.

As the vehicle moves forwards it compresses the air directly in its path which impinges on the core 111 and gives rise to a ram air flow which prevents the air recirculation 115, 116 from occurring.

As the vehicle speed increases further, the ram air 30, 32 progressively overcomes the biasing of the spring loaded members 201, 211, 221, 231 and progressively moves the flaps 20, 21, 22, 23 into their open position as shown in figure 3. In the open position, ram air 30, 32 can pass through the whole of the core 111 and its full cooling effect can be used.

Further ram air combines with the air drawn through by the fan 114 to provide the cooling air 31, which passes through the area of the core 111 not affected by the flaps 20, 21, 22, 23, which is the whole of the core 111 when the flaps 20, 21, 22, 23 are fully open. As the temperature of the coolant drops, the fan 114 switches off and the cooling air 31 drops in level to match the ram air 30, 32 thereby providing substantially even cooling across che whole of the core 111, within the restrictions imposed by the configuration of the vehicle forward end and components upstream of the core 111 (neither shown).

The embodiment of the invention described above provides an air flow system particularly suited to heat exchanger installations in motor vehicle where there is not enough space to provide a conventional cowl.

It will be appreciated that the fan 114 could equally well be mounted in front of the heat exchanger 110, in which case it would propel air through the core 111 instead of drawing it in. As the passage for cooling air propelled through the core 111 would be substantially the same for both front and rear mounted fans 114, the flaps would be installed behind the heat exchanger 100 in the same way for both options.

The heat exchanger installation is not limited to a mounting arrangement across the front of the vehicle, but may be mounted elsewhere subject to the provision of suitable ducting for ram air.

Claims

1. A heat exchanger air flow system for a motor vehicle comprising a heat exchanger including a cooling core with an air passage through it, a fan in close proximity to the heat exchanger and having air ducting means associated with the heat exchanger which is moveable from a first position in which it covers part of the cooling core to a second position in which said part of the cooling core is uncovered wherein said ducting means is in said first position when the vehicle is stationary and is progressively moved towards said second position as the vehicle moves forward with increasing speed such that above a predetermined speed the ducting means is in said second position.

2. A heat exchanger air flow system according to claim 1 wherein said ducting means is urged towards said first position by a biasing means.

3. A heat exchanger air flow system according to claim 1 or claim 2 wherein said biasing means is of sufficient strength to hold the ducting means in said first position while the vehicle is stationary or travelling at very slow speed but is overcome by the pressure of air impinging upon the heat exchanger as the vehicle moves forward with increased speed such that beyond a predetermined speed the biasing means is overcome and the full surface area of the heat exchanger is uncovered.

4. A heat exchanger air flow system according to any one of claims 1 to 3 wherein said ducting means are in the form of flaps.

5. A heat exchanger air flow system according to any one of claims 1 to 4, wherein said ducting means are made of an elastomeric material.

6. A heat exchanger for a heat exchanger air flow system according to any preceding claim wherein said ducting means are attached directly to part of said heat exchanger.

7. A heat exchanger for a heat exchanger air flow system according to claim 6 wherein said ducting means are pivotally attached to said heat exchanger.

8. A heat exchanger air flow system substantially as described herein with reference to the accompanying drawings.

9. A heat exchanger for a heat exchanger air flow system substantially as described herein with reference to figures 2 and 3 of the accompanying drawings.