The invention relates to an air-liquid heat exchanger for a vehicle fluid-flow circuit, and more particularly, but not exclusively, to a fuel cooler for a motor-driven vehicle.
In recent diesel-engine vehicles, it is becoming more and more common to use very high pressure injector systems. In such systems, the high pressure generated by the pump gives rise to a significant rise in the temperature of the diesel oil. However, surplus diesel oil that is not consumed by the engine is returned to the tank via a return circuit. As a result, the temperature inside the tank is raised and this can be harmful not only for the tank itself and for the return pipework, but also for the general operation of the injection system and its feed circuit.
It has therefore been found necessary, in the context of high pressure injector systems, to cool the diesel oil at some point on its path between the tank and the injector device. For reasons of convenience and bulk, the solution most generally adopted consists in placing an air cooler on the return path beneath the chassis of the vehicle between the injector device (generally situated at the front of the vehicle) and the tank (generally situated at the rear of the vehicle).
Present coolers used for this particular application are generally constituted by a tube shaped to form a sinuous xe2x80x9ccoilxe2x80x9d. Such coils are generally made of plastics material to avoid problems of corrosion, and they suffer from various drawbacks of which the main drawback lies in their lack of rigidity which makes them flexible and thus difficult to fix to the chassis of the vehicle. In addition, and for the same reason of flexibility, they require a very large number of attachment points for fixing purposes, thereby increasing the cost and the time required for installing them. Furthermore, the necessary limit on the radius of curvature of the tube forming the coil imposes relatively large size on the coil if it is desired to install a length of tube that is sufficient to provide effective cooling.
Air-liquid heat exchangers are also known for motor vehicle fluid-flow circuits, such heat exchangers comprising a plurality of tubes extending between two fixing distribution blocks to which the ends of the tubes are connected, each of the two blocks comprising:
a face facing the other block and carrying internal coupling members for coupling the corresponding ends of the tubes to the block in question;
an internal distribution channel interconnecting the internal coupling members; and
an external coupling member for coupling the block in question and its internal distribution channel to the fluid-flow circuit of the vehicle.
This provides a cooler that is compact and relatively rigid that is easy to handle and install. Manufacture is simple and above all flexible. Starting from standard fixing and distribution blocks, it suffices to fit tubes of lengths that differ as a function of the desired dimensions. In addition, the blocks provide the tubes with protection against impacts, particularly when the heat exchanger is placed horizontally beneath the chassis of a vehicle.
However, the efficiency of the cooling obtained in this way is not always sufficient. That is why it has been found useful to improve that type of heat exchanger so as to conserve its advantages while increasing its capacity for exchanging heat.
According to the invention, at least one of the two blocks has at least one ventilation nozzle passing therethrough between its face carrying the internal coupling members for coupling tubes to said block, and its opposite face.
The ventilation nozzle then contributes in two ways to the efficiency of the heat exchange performed by the heat exchanger. Firstly it improves cooling of the block itself by enabling air to flow inside the block. Secondly it channels the flow of incident air towards the tubes so as to optimize the heat dissipation they perform.
Under such circumstances, it is advantageous for the ventilation nozzle to flare from the face of the block carrying the internal coupling members for coupling tubes to said block towards the opposite face.
According to another advantageous characteristic of the invention, at least one of the two blocks is provided with cooling fins on a face opposite from its face carrying the internal coupling members for coupling tubes to said block. These fins further improve the heat dissipation of the block. They can also perform the function of deflectors for favorably directing the incident flow of air.
According to another advantageous characteristic of the invention, the external coupling member of each block is disposed on a face of said block opposite from its face carrying the internal coupling members for coupling tubes to said block.
According to another advantageous characteristic of the invention, each of the two blocks is provided on a face that is substantially perpendicular to the face carrying the internal coupling members for coupling tubes of said block with means for fixing it to a structural element of the vehicle. The blocks thus perform three functions: not only do they provide both mechanical and fluid-flow linkage between the tubes, but they also make it possible to provide fixing of the heat exchanger on the structural element of the vehicle in a manner that is fast, convenient, and standardized.
In which case, it is advantageous for the fixing means to be snap-fastening members.
Other characteristics and advantages of the invention will appear on reading the following description of a particular embodiment given by way of non-limiting example.