It is well known to provide a heating system in a vehicle to warm the cabin for the comfort of its occupants. One such heating system comprises a heat exchanger which draws off hot water exiting the engine prior to being pumped to the radiator for cooling. The hot water flows through a plurality of tubes from its entry point at a first header tank to its exit point at a second header tank. Heat dissipation means (typically a matrix of concertina fins) are provided between the tubes, such that heat from the hot water flowing in the tubes is dissipated into the surrounding air from the external surface of the tubes and fins, and relatively cools water exits the heat exchanger to be pumped back into the engine cooling system. Air is drawn through the heat exchanger, typically by a fan, and heated thereby before entering the vehicle cabin. The heater type heat exchanger can function as a heat exchanger to cool the engine coolant even where cabin heating is not required. Heated air is simply directed to external ambient air.

To further increase efficient heat dissipation, it is also known to provide turbulator means along the length of each tube, such that the water flowing through the tube is

turbulated which increases heat transfer from the tube to the heat dissipation means.

However, when the engine is first started up after a significant idle period of time, the water flowing out of the engine, and therefore the water flowing into the heat exchanger is cold. There is little or no heat dissipation for a significant period of time, during which the heating system can only pump cold air into the cabin. Particularly during cold weather conditions, the ambient temperature of the cabin at engine start-up is cold and remains so until the engine warms up sufficiently to heat the coolant being pumped through it. This is obviously uncomfortable for the occupants of the vehicle cabin, and can also be dangerous as the windscreen may mist up, reducing visibility.

Several solutions to this problem have been proposed. In one such solution, additional heating means is placed within the airflow through the heat exchanger of the vehicle heating system, to heat the air before it is pumped into the vehicle cabin. However, the provision of such additional heating means within the airflow partially impedes the flow, thereby decreasing airflow pressure and reducing both the effectiveness and the efficiency of the heating system.

In another solution, one or more combustion heaters are provided to heat the engine coolant either within the engine cooling system, or as it flows into the heat exchanger. However, there are a number of disadvantages associated with the provision of additional combustion

heaters in a vehicle, particularly the additional cost, assembly time and space required to accommodate the heater (s), especially in view of the fact that the additional heater (s) are redundant for most of the time, being required only at engine start-up. Moreover, combustion heaters require a fuel supply which further increases the additional components required as well as the overall running costs of the vehicle.

An arrangement has now been devised which seeks to overcome the problems outlined above and provides a simple, efficient means of heating coolant within an automotive system.

In accordance with a first aspect of the present invention, there is provided a coolant heater for vehicle coolant, the heater comprising a heat exchanger including an engine coolant side for coolant in an engine cooling system and an air side electrical heating means being located within said heat exchanger for heating said coolant.

Thus, at engine start-up, heating means within the heat exchanger quickly heats the coolant as it flows through the heat exchanger, so that heat is dissipated therefrom very quickly after engine start-up, which heats the air pumped into the vehicle cabin so as to quickly warm it up. Of course, the arrangement of the invention would be equally suitable for use in the engine cooling circuit to heat the coolant to its optimum operating temperature at engine start-up.

The electrical heating means within the heat exchanger beneficially comprises one or more electrical elements which heat up when an electrical current is passed therethrough. Each electrical element is held within a strip of insulating material, such as plastic.

In the case where the arrangement comprises a first header tank for receiving coolant from the engine cooling system and a second header tank, with the coolant flowing from the first header tank to the second header tank via a plurality of tubes or tubes, the heating means preferably comprises a plurality of electrical elements, one in each respective tube. Each of the electrical elements is preferably connected to a single common electrical connector to which an external power supply can be connected. The strips of insulating material in which the electrical elements are mounted or held are preferably non-uniform in cross-section or profile along their length, for example, they may be twisted into a spiral, to turbulate the coolant as it flows over them, thereby increasing heat dissipation. The electrical elements are therefore beneficially turbulator form in configuration.

The present invention extends to a vehicle heating system including a coolant heater according to the first aspect of the present invention. The vehicle heating system beneficially includes means, such as a fan or the like, for drawing or pumping air over or through the heat exchanger and into a vehicle cabin. The system preferably also includes means for monitoring the ambient temperature of the air passing over or through the heat exchanger and/or

the ambient temperature of the air in the vehicle cabin.

If the ambient air temperature is less than a first predetermined value, the power supply to the or each electrical connector is switched on to heat the elements and, therefore, the coolant. When the ambient air temperature reaches or exceeds a second predetermined value, the power supply to the or each electrical element is switched off and the heating system operates using the heated coolant from the vehicle engine cooling system.

An exemplary embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a front view of a coolant heater according to an exemplary embodiment of the present invention; Figure 2 is an end view of the coolant heater of Figure 1; Figure 3 is a schematic front view of a set of electrical elements for use in the coolant heater of Figure 1; Figure 4 is a magnified view of one of the electrical elements of Figure 3; and Figure 5 is a further magnified view of a portion of the electrical element of Figure 4.

Referring to Figures 1 and 2 of the drawings, a vehicle engine coolant heater comprises a heat exchanger 10 according to an exemplary embodiment of the invention

comprises a first header tank having an inlet in the form of a first stud tube 12 for receiving coolant from a vehicle engine, and a second header tank having an outlet in the form of a second stud tube 14. The heat exchanger core, between the two header tanks, is made up of a plurality of tubes or tubes 16 separated by heat dissipation means, such as corrugated aluminium strips (fins) 18 communicating with the outer walls of the tubes 16. A common insulated connector 20 is mounted in the upper wall of the heat exchanger 10.

Referring to Figure 3 of the drawings, an elongate spiral strip of insulating material in the form of a turbulator 22, within which is moulded an electrical element 24 is held within each tube 16. An end of each electrical element 24 is connected to the common insulated connector 20.

Referring to Figure 4 of the drawings, and as stated above, each turbulator 22 is a thin gauge high temperature insulator, with an electrical element 24 moulded therein.

The electrical element comprises an electrical conductor which enters the turbulator 22 at one end, extends along a substantial portion of its length and then doubles back on itself so as to exit the turbulator 22 at the same end as it enters. When an electrical supply voltage is connected across the two ends of the conductor via the insulated connector 20, the circuit is complete and current flows in the element 24.

Referring to Figure 5 and Figures 6A and 6B of the

drawings, the insulated connector 20 comprises a plastic housing 5 with a plurality of pairs of input apertures 26 (see Figure 6B) for receiving the ends of the electrical elements 24. For each pair of inlet apertures, the connector 20 includes therein a clenching tube 28 comprising two centrally connected tubes (Figure 6A). The ends of the electrical elements 24 are inserted through each pair of apertures 26 into the respective tubes of the clenching tube 28. The power supply (not shown) is connected to the electrical connector 20 via harness leads 30. The harness leads fit over the clenching tubes 28, compressing them so as to retain the ends of the electrical elements 24 held therein. Power is supplied via an electrical connector (not shown) located on a plastic tank.

Means for drawing air through the heat exchanger 10 into the vehicle cabin. In use, the heat exchanger 10 fits into a normal vehicle heating system and, when no power is supplied to the electrical elements 24, the insulated turbulators act in the conventional way to turbulate the coolant flowing in the tubes 16.

Control means (not shown) are provided for monitoring the ambient air temperature either in the vehicle cabin or flowing through the heat exchanger. Coolant from the engine cooling system is drawn or pumped into the first header tank via stud tube 12 and flows through the tubes 16 to the second header tank where it exits the heat exchanger via stud tube 14 and is pumped back into the engine cooling system. Air is pumped or drawn through the heat exchanger into the cabin of a vehicle and, any heat dissipated by the

heat exchanger warms the air, which in turn warms the vehicle cabin.

The ambient air temperature is monitored and, if it is below a predetermined value, the power supply to the electrical elements is switched on. The heat thus generated by the elements passes into the coolant flowing through the tubes and is dissipated and transferred to the air being drawn or pumped through the heat exchanger into the vehicle cabin. When the ambient air temperature reaches a predetermined value, the power supply to the elements is switched off and the system operates in the conventional manner.

Some of the main advantages of the invention are: 1. The heat exchanger is designed to work with any form of vehicle heating system.

2. The system eliminates the need for any additional heater i. e. PTC, Fuel Burner, etc.

3. The heater system space envelope can be reduced as no additional heater is required.

4. The heat exchanger is a lower cost option than conventional types of additional heating.

5.90% of all conventional heat exchanger components can be used, as only one new coolant tank with electrical connector is required.

6. The electrical heating element replaces a turbulator in the heat exchange tube. The pressure drop in the coolant is therefore not made adverse by the introduction of a the heater element.

An embodiment of the invention has been described above by way of example only. Modifications and variations to the described embodiment are envisaged and will be apparent to a person skilled in the art, without departing from the scope of the invention as defined by the appended claims.