This invention relates to engines and their associat cooling systems provided in order to cool the engine, and mo particularly to internal combustion engines for vehicle? a their cooling systems-

Internal combustion engines are known having a coola passage, or passages, at their cylinder head. When a vehicl such as a car, is driven by such an engine and the vehicle stopped, and the engine switched off, heat in the engine ten to rise and cause a localised hot spot to develop at t cylinder head. This can cause coolant in the cooling passag or passages, to boil and blow the head.

It is know to provide an electric fan to cool a radiato of a cooling system for such an engine. Cooling the radiato relies on thermal syphoning to cool the engine, and such a arrangement needs a careful design of the radiator/engin relationship to operate, properly. The fan also requires relatively high current which can drain the battery of th vehicle. A further problem is that the rotating fan can be danger to mechanics investigating the engine just after it ha been switched off.

It is also know that when a turbocharger unit i associated with an engine it too gets very hot, especially jus after the engine has been stopped. One known way of coolin the turbocharger unit is to circulate a small volume of coolin liquid through a cooling circuit passing through th turbocharger unit both whilst the engine is running an for period afterwards to prevent a hot spot developing.

According to a first aspect the invention consists in a engine and associated cooling system comprising an engin

having a passage for coolant, a cooling circuit arranged to pass coolant through the passage for coolant in the engine whilst the engine is running to cool the engine, and pump means adapted to pump the coolant through the passage for coolant in the engine after the engine has stopped running*, at least for a period of time.

Thus the coolant is pumped through the engine itself after the engine has stopped running. This prevents the build-up of a hot spot and avoids the use of a dangerous fan. A relatively large volume of coolant can be pumped through the engine.

Since most internal combustion engines have a passage for coolant, or passages for coolant, in their cylinder head it is convenient to pump coolant through these passages after the engine has stopped running.

Preferably the cooling circuit is arranged to pass coolant through the engine in a first circulation direction whilst the engine is running to cool the engine, and the pump means is adapted to pump the coolant through the engine in a second circulation direction after the engine has stopped, the first and second circulation directions through the engine being in opposite senses.

The cooling system preferably includes a one-way flow passageway leading from the pump means and provided with a one-way valve which permits coolant to flow in the one-way flow passageway when the engine has stopped in a direction complimentary to said second circulation direction, but which prevents coolant from flowing in the one-way passageway in the opposite direction. This enables the isolation of the normal, conventional, cooling system for the engine whilst the engine

is running from the cooling derived from the pump means just after the engine has stopped running. The one-way valve and one-way flow passageway can be isolated from the normal running system and so interference in the normal operation of the cooling system when the engine is running is avoided.

The engine may have first and second ports communicating with the cooling circuit, the first port comprising an inlet for coolant to enter the engine whilst the engine is running and an outlet for coolant to leave the engine when the engine has stopped, and the second port comprising an outlet for coolant to leave the engine when the engine is running and an inlet for coolant to enter the engine when the engine has stopped.

The second port may communicate with a thermostat housing in which a thermostat control of the cooling system is provided. Internal combustion engines conventionally have a fluid connection to their thermostat housing and this connection can conveniently provide the second port.

The engine and associated cooling system may have a turbocharger which is cooled by flow of coolant in a turbo- charger-cooling passageway. The coolant may flow through the turbocharger-cooling passageway in the same direction when the engine is running and when the engine has stopped and the pump means is operative.

The engine and associated cooling system may have an induction manifold cooled by coolant flowing in a manifold passageway. The coolant in the manifold passageway may flow in the same direction whether the circulation is caused by normal running of the engine or by the pump means when the engine has stopped.

According to a second aspect the invention consists in a motor vehicle incorporating an engine and associated cooling system in accordance with the first aspect of the invention.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings of which:-

Figure 1 shows a schematic representation of an engine and associated cooling system in accordance with the first aspect of the invention with the flow of coolant indicated when the engine is running; and

Figure 2 schematically shows the engine and cooling system of Figure 1 with ^" the flow of coolant indicated shortly after the engine has stopped.

The engine and associated cooling system shown in the drawings comprises an engine 1, a radiatior 2 connected to an engine water pump 3 by a bottom hose 4, and a thermostat 5 mounted in a thermostat housing 6 which is connected to the radiator 2 via a top pipe 7. The engine 1 has a conventional cylinder head having a port 8 connected via a fluid passageway to the thermostat housing 6, and a port 9 connecting the cylinder head to the water pump 3.

A heater matrix 10 is provided to heat the interior of a car and has a fluid connection to the thermostat housing 6 through fluid-communication passageway 11 which leads to a heater control 13, and thence through passageway 14 which leads from the heater control 13 to the heater matrix 10. The output from the heater matrix 10 comprises a fluid-communication passageway 15 leading to the water pump 3.

A turbo charger unit 16 is provided and is cooled vi cooling liquid supplied by fluid-communication passageway 1 leading from the thermostat housing 6 to the turbocharger unit, the cooling liquid then flowing through passageway 18 to joi passageway 15 and thence flowing to the water pump 3.

The engine 1 has an induction manifold 19 which is cooled by cooling liquid flowing from the thermostat housing 6 through an inlet passageway 20 to the induction manifold and from there through ^' an outlet passageway 21 to join the passageway 15.

A conventional header tank 22 is also provided and has the usual fluid connections comprising a pipe 23 connecting the thermostat housing 6 to the header tank and hence connecting the radiator top pipe ^* 7 to the header tank, and a pipe 24 providing a fluid connection from the header tank 22 to the bottom pipe 4 of the radiator.

The associated cooling system also has a cooling pump 25 provided to cool the engine after the engine has been switched off. The pump 25 has an input 26 connected to fluid passageway 24, and hence to the bottom pipe 4 of the radiator, and an output fluid passageway 27 connecting the output of the pump to the passageway 11 leading from the thermostat housing 6 to the heater control 13. A one-way valve 28 is provided in the fluid passageway 27 and restricts the flow of fluid in that passage to flow only towards the thermostat housing 6.

When the engine is running it is cooled using a conventional cooling system (reference numbers 1 to 24) and conventional flow of cooling liquid. Cool liquid is drawn by the water pump 3 from the radiator 2 via the bottom pipe 4 and enters the cylinder head of the engine through port 9. The

cooling liquid then passes through the cylinder head and leaves the engine through port 8 where it flows to the thermostat housing 6. From there a portion of the, by now hot, cooling liquid flows back to the radiator 2 through the top pipe 7; a portion flows to the heater matrix 10 through the connection passageway 11 to the heater control 13 and through the passageway 14, and thence back to the water pump 3 via passageway 15; a portion of the cooling fluid entering the thermostat housing 6 flows to the induction manifold via passageway 20 and from there back to the pump 3 via passageways 21 and 15; and a portion of the cooling liquid flows from the thermostat housing 6 to the turbocharger unit 16 via passageway 17 and from there back to the water pump 3 via passageways 18 and 15.

The one-way valve 28 prevents coolant flowing in passageway 11 from flowing through passageway 27 and through the pump back to the bottom pipe 4. Thus the coolant system which operates when the engine is running is isolated from the pump and effectively operates as if the pump 25 and its associated passageways 26 and 27 were not present - that is to say as a conventional cooling system. This allows the use of existing engines and radiators in their present form without the need to redesign them to allow for additional cooling when the engine is running which may otherwise occur through the additional passageways connected to the pump 25.

When the engine stops the pump 25 is activated and draws cooling liquid from the radiator 2 via the portion of the bottom pipe 4 between passageway 24 and the radiator, and from the engine 1 via port 9 and the portion of the bottom pipe 4 between port 9 and passageway 24. The output of the pump 25 pumps cooling liquid along passageway 27 through the one-way valve 28 and along passageway 11 to the thermostat housing 6.

From there the majority of cooling liquid passes into th engine 1 via port 8, and then through the engine and ou through port 9, thus cooling the engine. However, mino portions of the cooling fluid entering the thermostat housing flow to the induction manifold and turbocharger unit along th same fluid pathways 20, 21, 17, 18, and 15, as when the engin is running. A timer unit or temperature sensitive unit i provided to switch off the pump 25 either after a predetermine time or when the temperature of the cooling liquid falls to a acceptable predetermined value.

It will be appreciated that the direction of the flow o cooling liquid in the cylinder head of the engine is reverse when the pump operates after the engine has been switched off. This reversal of the flow in the engine allows the use of the one-way valve 28 so as to effectively isolate the passageways 26 and 27 from the rest of the system when the engine is running, which allows existing engines and cooling systems to be used without modification of their cooling properties during the running of the engine. A similar effect could of course be achieved by providing other valves to isolate the pump 25 and its associated passageways 26 and 27, for example solenoid control valves could be provided in passageway 26 and passageway 27. Such a solenoid control valve arrangement could enable a similar system to operate in which the cooling liquid could flow in the same direction through the engine when the engine is switched off as it does when the engine is operating. Alternatively reverse flow could still be employed. If the same - direction flow is desired the pump 25 could be incorporated with pump 3, although it may be simpler to provide two pumps.

The present invention allows existing engine and cooling systems to be improved without radically redesigning the entire cooling system, and removes the dangers of a rotating fan.