GB2442742A

GB2442742A - Cooling system for an internal combustion engine comprising an exhaust gas cooler

Info

Publication number: GB2442742A
Application number: GB0620165A
Authority: GB
Inventors: Ian Graham Pegg; Les William Routledge
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2006-10-12
Filing date: 2006-10-12
Publication date: 2008-04-16
Also published as: DE102007048503A1; GB0620165D0; GB0718254D0; GB2442839A; JP2008095694A; GB2442839B; JP5490987B2

Abstract

A cooling system for an internal combustion engine 1 comprises a coolant circuit through which coolant is circulated by a pump 4, an electronically controlled flow control valve 2 to control the flow of coolant flowing through the engine, and an exhaust gas cooler 5 forming part of an exhaust recirculation system provided to recirculate exhaust gas from an exhaust outlet of the engine to an air inlet of the engine. The exhaust gas cooler is arranged to receive a supply of coolant from a position located upstream of the electronically controlled flow control valve such that, when the electronically controlled flow control valve is operated to restrict the flow of coolant through the engine, the flow through the exhaust gas cooler is automatically increased. Preferably, the electronically controlled flow control valve is able to control the cooling of the engine irrespective of the speed at which the pump used to urge coolant to flow into the engine is rotated. The electronically controlled flow control valve may either be located at an outlet from the engine or between the pump and the engine. Preferably, the engine comprises a cylinder block and a cylinder head which include coolant passages. The engine cylinder block and engine cylinder head may each have an independent coolant flow path therethrough.

Description

A Cooling System for an Engine This invention relates to a cooling

system for an internal combustion engine and in particular to a cooling system for an engine having an exhaust gas recirculation system including an exhaust gas cooler.

A typical motor vehicle or automobile engine cooling system includes an engine coolant jacket, a radiator, a o cabin heater matrix, a degas system, a radiator bypass, a fan for drawing air through the radiator, a circulatory pump for circulating the coolant from the engine through the radiator and returning it to the engine.

Such a system typically includes a thermostat, which opens to allow the circulation of the coolant to the radiator when the engine reaches a minimum desired operating temperature. The coolant flow is driven conventionally by a pump rotated by a belt driven by the crankshaft pulley and the flow rate is dependant upon engine speed.

Local combustion chamber wall and the oil film temperatures seen by the piston skirt and rings are controlled predominantly by the engine speed and operating load (heat release rate), charge temperature, pressure and composition and coolant temperature and coolant flow rate.

A major function of the coolant within an engine, besides heat removal, is to ensure acceptable temperature gradients are achieved around each cylinder and across the whole engine. This avoids excessive thermal distortion and stresses induced due to the temperature differences. These stresses, especially during warm-up, can lead to low cycle fatigue issues. For this reason, the coolant flow rate requirement will depend on the heat input rate as much as it does on the actual local metal or coolant temperatures.

Local boiling and degas requirements also need to be taken into account. Some coolant flow is therefore always needed.

For different vehicle operating conditions and engine speeds and loads there are different considerations to take into account, such as cabin heater performance, fuel economy, emissions, oil film temperature, etc. Adding an additional control to the coolant system on top of a thermostatically controlled valve will help to optimise the local operating temperatures within the engine which will improve the efficiency of the engine and reduce CO emissions particularly when the engine is running under part load conditions.

It is also well known in order to improve emission performance of an engine to provide the engine with an exhaust gas recirculation system in which exhaust gas from an exhaust outlet of the engine is passed through an exhaust gas cooler in order to cool the exhaust gas before returning the cooled exhaust gas to an air inlet of the engine.

Cooling of the exhaust gas is very important as the temperature of the exhaust gas returning to the engine will have a significant effect on the NOx emissions from the engine. In order to maximise efficiency and minimise emissions from the engine the exhaust gas recirculation system is normally arranged to maximise the recirculation of exhaust gasses when the engine is operating under part load conditions and so this is when the maximum demand for the removal of heat from the exhaust gas has to be met by the exhaust gas cooler.

It is an object of this invention to provide a cooling system for an engine that maximises the efficiency of an engine by controlling the temperature of the engine and cooling recirculated exhaust gas in an economical manner.

According to the invention there is provided a cooling system for an internal combustion engine having a coolant circuit through which coolant is circulated by a pump, an electronically controlled flow control valve to control the flow of coolant flowing through the engine and an exhaust gas cooler forming part of an exhaust recirculation system provided to recirculate exhaust gas from an exhaust outlet of the engine to an air inlet of the engine wherein the exhaust gas cooler is arranged to receive a supply of ic coolant from a position located upstream of the electronically controlled flow valve such that, when the electronically controlled flow valve is operated to restrict the flow of coolant through the engine, the flow through the exhaust gas cooler is automatically increased.

The electronically controlled control valve may be located at an outlet from the engine and the supply of coolant for the exhaust gas cooler may be taken from a position located between the electronically controlled flow valve and an outlet from the engine.

Alternatively, the electronically controlled control valve is located at an outlet from the engine, the pump is located upstream from the engine and the supply of coolant for the exhaust gas cooler may be taken from a position located upstream from the electronically controlled flow valve between the engine and the pump.

As a further alternative, the pump may be located upstream from the engine, the electronically controlled control valve may be located between the pump and the engine and the supply of coolant for the exhaust gas cooler is taken from a position located between the electronically controlled flow valve and the pump.

As a further alternative, the engine may include passages formed in a cylinder head of the engine and in a cylinder block of the engine, the coolant passages in the cylinder block may be connected by a first coolant supply conduit to an outlet from the pump, the coo].ant passages in the cylinder head may be connected by a second coolant supply conduit to an outlet from the pump and the flow through the first coolant supply passage may be controlled by the electronically controlled flow control valve so as to allow the flow through the cylinder block to be independently controlled wherein the supply of coolant for the exhaust gas cooler may be taken from a position located upstream from the electronically controlled flow valve and downstream from the pump.

As a further alternative, the engine may include i5 passages formed in a cylinder head of the engine and in a cylinder block of the engine, the coolant passages in the cylinder block may be connected by a first coolant supply conduit to an outlet from the pump, the coolant passages in the cylinder head may be connected by a second coolant supply conduit to an outlet from the pump and the flow through the second coolant supply passage may be controlled by the electronically controlled flow control valve so as to allow the flow through the cylinder head to be independently controlled wherein the supply of coolant for the exhaust gas cooler may be taken from a position located upstream from the electronically controlled flow valve and downstream from the pump.

As yet a further alternative, the engine may have a cylinder block and a cylinder head each having an independent coolant flow path therethrough, a first electronically controlled flow control valve may be positioned at a coolant outlet from the cylinder block to control the flow of coolant through the cylinder block and a second electronically controlled flow control valve may be positioned at a coolant outlet from the cylinder head to control the flow of coolant through the cylinder head wherein the supply of coolant for the exhaust gas cooler may be taken from a position located upstream from the first electronically controlled flow valve and downstream from the cylinder block.

Alternatively, the engine may have a cylinder block and a cylinder head each having an independent coolant flow path therethrough, a first electronically controlled flow control valve may be positioned at a coolant outiet from the cylinder block to control the flow of coolant through the cylinder block and a second electronically controlled flow control valve may be positioned at a coolant outlet from the cylinder head to control the flow of coolant through the cylinder head wherein the supply of coolant for the exhaust gas cooler may be taken from a position located upstream from the second electronically controlled flow valve and downstream from the cylinder head.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Fig.1 is a line diagram of a first embodiment of a cooling system for an engine according to the invention; Fig.2 is a line diagram of a second embodiment of a cooling system for an engine according to the invention; Fig.3 is a line diagram of a third embodiment of a cooling system for an engine according to the invention; Fig.4 is a line diagram of a fourth embodiment of a cooling system for an engine according to the invention; Fig.5 is a line diagram of a fifth embodiment of a cooling system for an engine according to the invention; Fig.6 is a line diagram of a sixth embodiment of a cooling system for an engine according to the invention; and Fig.7 is a line diagram of a seventh embodiment of a cooling system for an engine according to the invention.

With reference to Fig.l there is shown an engine 1 having a supply of coolant supplied from a pump 4 through a supply conduit SL. The coolant flows from the supply conduit SL through conduits (not shown) in the engine 1 to an outlet. The outlet from the engine 1 is connected to an electronically controlled flow control valve 2 which is used to control the flow of coolant through the engine 1. The electronically controlled flow valve 2 is controlled by an electronic controller (not shown) in order to maintain the temperature of the engine 1 within predetermined limits.

The electronically controlled flow valve 2 can be actuated directly by an electrical actuator or may be actuated by other types of actuator such as a vacuum actuator controlled by the electronic control unit.

The electronically controlled flow valve 2 has an outlet connected to a radiator supply conduit RSL. The radiator supply conduit RSL transfers the coolant to an inlet to a radiator 9 and also to an inlet to a bypass control valve 3. The radiator 9 has an outlet connected to a radiator return conduit RR which returns coolant that has passed through the radiator 9 to an outlet side of the bypass control valve 3 where it flows back to an inlet side of the pump 4 via a bypass return conduit BRL.

A degas chamber 10 is connected to an upper end of the radiator 9 by a degas conduit DSL. The degas chamber 10 is used to remove gas from the coolant flowing through the cooling system and can be of any known type. The degassed coolant is returned to a position upstream from an inlet to the pump 4 via a degas return conduit DRL.

At a position upstream from the electronically controlled flow valve 2 but downstream from the engine 1 a supply of coolant is tapped off to supply an exhaust gas cooler 5 through an exhaust gas coolant supply conduit EGRI.

The exhaust gas cooler 5 forms part of an exhaust gas recirculation system in which exhaust gas is drawn off from an exhaust outlet such as an exhaust manifold (not shown) of the engine 1 and is passed through the exhaust gas cooler 5 and is then returned to an air inlet to the engine such as an inlet manifold (not shown) . One or more exhaust gas flow control valves (EGE valves) may be provided to control the flow of exhaust gas through the exhaust gas cooler 5 based upon the operating conditions of the engine 1. The EGR valves may be controlled by the same electronic control unit used to control the operation of the electronically controlled flow valve 2 or may be independently controlled.

An exhaust gas coolant bypass control valve 6 is provided to control the flow of coolant through a bypass passage EGRB. If the flow of coolant through the exhaust gas cooler 5 becomes excessive then the exhaust gas bypass control valve 6 can be opened to allow the coolant to bypass the exhaust gas cooler 5. The exhaust gas bypass control valve 6 may be controlled by the same electronic control unit used to control the operation of the electronically controlled flow valve 2 or may be independently controlled.

After passing through the exhaust gas cooler 5 or through the bypass passage EGRB the coolant flows through an exhaust gas coolant return conduit EGRR to a cabin heater 8 and then from the cabin heater 8 to an inlet side of the pump 4 via a coolant return conduit RL.

A heater bypass control valve 7 is provided to control the flow of coolant through a heater bypass passage HE. If the flow of coolant through the heater 8 becomes excessive then the heater bypass control valve 7 can he opened to allow the coolant to bypass the heater 8. The heater bypass control valve 7 may be controlled by the same electronic control unit used to control the operation of the electronically controlled flow valve 2 or may be independently controlled.

Basic operation of the cooling system is as follows, when the engine 1 is started from cold the electronic control unit opens the electronically controlled flow valve 2 so as to permit the coolant from the pump 4 to pass freely through the engine 1 to the inlet to the radiator 9 through the radiator supply conduit RSL and also to the bypass control valve 3. Because the temperature of the coolant is below one or more predetermined temperatures the bypass control valve 3 is open allowing the majority of the coolant to flow back to the pump 4 without passing through the radiator 9 so as to facilitate a rapid warm up of the coolant circulating through the cooling system. Because the electronically controlled flow valve 2 is open and the bypass control valve 3 is open there is very little flow thorough the exhaust gas coolant supply conduit EGRI to the exhaust gas cooler 5 due to the relative resistances to flow through the alternative flow paths. That is to say, the resistance to flow through the exhaust gas cooler 5 and the heater 8 is greater than the resistance to flow through the bypass control valve 3.

When the temperature of the coolant reaches a predetermined temperature the bypass control valve 3 will close so that all of the coolant passing though the radiator supply conduit RSL will flow through the radiator 9 before being returned to an inlet or upstream side of the pump 4 via the radiator return conduit RR and the bypass return conduit BRL.

L\Jsj -The electronically controlled flow valve 2 is then controlled by the electronic control unit to control the temperature of the engine 1 by opening and closing the electronically controlled flow valve 2 to increase or reduce the flow of coolant through the engine 1. The electronic control unit is arranged to receive one or more temperature inputs from temperature sensors (riot shown) located on the engine 1.

The cooling system has to be able to prevent overheating of the engine 1 when the engine 1 is operating at maximum load and therefore the flow of coolant through the engine 1 is too great when the engine 1 is operating under part load conditions with the electronically controlled flow valve 2 fully open. This will result in overcooling of the engine 1 which is undesirable as it has a detrimental effect on engine efficiency and emission performance.

Therefore, when the electronic control unit determines that the temperature of the engine is below that required to operate the engine 1 at maximum efficiency and with minimum CO2 emissions it will control the electronically controlled flow valve 2 so as to restrict the flow exiting from the engine 1. The closing of the electronically controlled flow valve 2 has the effect of increasing the pressure upstream which causes an increase in flow through the exhaust gas coolant supply conduit EGRI to the exhaust gas cooler 5.

One of the advantages of the invention is that the flow through the exhaust gas cooler 5 is automatically increased when the engine 1 is operating at part load which is the operating condition where the maximum cooling effect is required from the exhaust gas cooler 5 to cool the exhaust gas passing through it.

-10 -When the engine 1 is operating at high load the flow of coolant through the engine 1 must be increased in order to maintain the temperature of the engine 1 within a preferred range where both emission and engine performance are at or near to their optimum. Therefore, when the engine 1 is operating at high load, the electronically controlled flow valve 2 is opened under the control of the electronic control unit to permit more coolant to flow through the engine 1. Although the opening of the electronically controlled flow valve 2 will reduce the amount of flow through the exhaust gas cooler 5 this is not so important at high engine load because the volume of exhaust gas recirculated is less than it is during part load conditions.

In addition, if the pump 4 is directly driven by the engine 1 then, when the engine 1 is operating at high load, the engine 1 is often operating at high speed and so the flow of the coolant from the pump 4 will be higher than it would be at the lower engine speeds often associated with part load running.

With reference to Fig.2 there is shown a second embodiment of the invention which in most respects is identical to that previously described with respect to Fig.1 and for which the same nomenclature is used. The second embodiment will not be described again in detail with respect to the common features only in respect to the differences.

The only significant difference between the embodiment shown in Fig.2 and that shown in Fig.1 is that the exhaust coolant supply conduit EGRI connects to the main cooling circuit at a position between the outlet from the pump 4 and the inlet to the engine 1 and in this case at a position located in the supply conduit SL. That is to say, the supply of coolant for the exhaust gas cooler 5 is taken from a position located upstream from the electronically -11 -controlled flow valve 2 and the engine 1 and downstream from the pump 4.

It will be appreciated that, as with the first embodiment the flow of coolant through the engine 1 is controlled by the electronically controlled flow valve 2 which is located downstream from the engine 1.

One advantage of this second embodiment over the first io embodiment shown in Fig.1 is that the flow of coolant to the exhaust gas cooler 5 is likely to be cooler because it is drawn off at a position upstream from the engine 1 and therefore before it has been heated by the engine 1.

is it will be appreciated that, when the engine 1 is operating at a normal running temperature, cooled water will be returned to the pump 4 from the radiator 9 through the bypass return conduit BRL and so the temperature of the coolant is at its lowest in the bypass return conduit ERL.

Operation of the cooling system is as previously described and will not be described again.

As for the first embodiment, it is an advantage of the second embodiment that the flow through the exhaust gas cooler 5 is automatically increased when the engine 1 is operating at part load. This is when the maximum cooling effect is required from the exhaust gas cooler 5 to cool the exhaust gas passing through it because this is when the maximum exhaust gas recirculation is required to control emissions from the engine 1.

With reference to Fig.3 there is shown a third embodiment of the invention which is in many respects the same as that shown and described with respect to Figs.l and 2.

-12 -The engine 1 receives a supply of coolant supplied from a pump 4 through a supply conduit SL. The coolant flows from a pump 4 to an electronically controlled flow control valve 20 which is used to control the flow of coolant through the supply conduit SL to the engine 1. The electronically controlled flow valve 20 is controlled by an electronic controller (not shown) in order to maintain the Lemperature of the engine within predetermined limits. The electronically controlled flow valve 20 can be actuated directly by an electrical actuator or may be actuated by other types of actuator such as a vacuum actuator controlled by the electronic control unit.

The coolant from the supply conduit SL passes through conduits (not shown) in the engine 1 to an outlet.

The outlet from the engine is connected to a radiator supply conduit RSL. The radiator supply conduit RSL transfers the coolant to an inlet to a radiator 9 and also to an inlet to a bypass control valve 3. The radiator 9 has an outlet connected to a radiator return conduit RR which returns coolant that has passed through the radiator 9 to an outlet side of the bypass control valve 3 where it flows back to an inlet side of the pump 4 via a bypass return conduit BRL.

A degas chamber 10 is connected to an upper end of the radiator 9 by a degas conduit DSL. The degas chamber is used to remove gas from the coolant flowing through the cooling system and can be of any known type. The degassed coolant is returned to a position upstream from an inlet to the pump 4 via a degas return conduit DRL.

At a position upstream from the electronically controlled flow valve 20 but downstream from the pump 4 a supply of coolant is tapped off to supply the exhaust gas cooler 5 through an exhaust gas coolant supply conduit EGRI.

-13 -The exhaust gas cooler 5 forms part of an exhaust gas recirculation system in which exhaust gas is drawn off from an exhaust outlet such as an exhaust manifold (not shown) of the engine 1 is passed through the exhaust gas cooler 5 and then is returned to an air inlet to the engine such as an inlet manifold (not shown) One or more exhaust gas flow control valves (EGR valves) may he provided to control the flow of exhaust gas through the exhaust gas cooler 5 based upon the operating conditions of the engine 1. The EGR valves may be controlled by the same electronic control unit used to control the operation of the electronically controlled flow valve 20 or may be independently controlled.

A heater bypass control valve 7 is provided to control the flow of coolant through a heater bypass passage HB. If the flow of coolant through the heater 8 becomes excessive then the heater bypass control valve 7 can be opened to allow the coolant to bypass the heater 8. The heater bypass control valve 7 may be controlled by the same electronic control unit used to control the operation of the -14 -electronically controlled flow valve 2 or may be independently controlled.

Basic operation of the cooling system is as follows, when the engine is started from cold the electronic control unit opens the electronically controlled flow valve 20 so as to permit the coolant from the pump 4 to pass freely through the engine 1 to the inlet to the radiator 9 through the radiator supply conduit RSL and also to the bypass control valve 3. Because the temperature of the coolant is below a predetermined temperature the bypass control valve 3 is open allowing the majority of the coolant to flow back to the pump 4 without passing through the radiator 9 so as to facilitate a rapid warm up of the coolant circulating through the cooling system. Because the electronically controlled flow valve 20 is open there is very little flow through the exhaust gas coolant supply conduit EGRI to the exhaust gas cooler 5 due to the relative resistances to flow through the alternative flow paths. That is to say, the resistance to flow through the exhaust gas cooler 5 and the heater 8 is greater than the resistance to flow through the electronically controlled flow valve 2.

When the temperature of the coolant reaches a predetermined temperature the bypass control valve 3 will close so that all of the coolant passing though the radiator supply conduit RSL will flow through the radiator 9 before being returned to an inlet or upstream side of the pump via the radiator return conduit RR and the bypass return conduit BRL.

The electronically controlled flow valve 20 is then controlled by the electronic control unit to control the temperature of the engine 1 by opening and closing the electronically controlled flow valve 20 to increase or reduce the flow of coolant through the engine 1. The electronic control unit is arranged to receive one or more -15 -temperature inputs from temperature sensors (not shown) located on the engine 1 which are used by the electronic control unit to control the opening position of the electronically controlled flow valve 20.

The cooling system has to be able to prevent overheating of the engine 1 when the engine 1 is operating at maximum load and therefore the flow of coolant through the engine 1 is too great when the engine 1 is operating under part load conditions with the electronically controlled flow valve 20 fully open.

Therefore, when the electronic control unit determines that the temperature of the engine is below that required to operate the engine 1 at maximum efficiency and with minimum CO emissions, the electronic control unit operates the electronically controlled flow valve 20 so as to restrict the flow of coolant entering the engine 1 from the pump 4.

The closing of the electronically controlled flow valve 20 has the effect of increasing the pressure upstream which causes an increase in flow through the exhaust gas coolant supply conduit EGRI to the exhaust gas cooler 5.

One of the advantage of this embodiment is that the flow through the exhaust gas cooler 5 is automatically increased when the engine 1 is operating at part load when the maximum cooling effect is required from the exhaust gas cooler 5 to cool the exhaust gas passing through it.

When the engine 1 is operating at high load the flow of coolant through the engine 1 must be increased in order to maintain the temperature of the engine 1 within a preferred range where both emission and engine performance are at or near to their optimum. Under such conditions the electronically controlled flow valve 20 is opened under the control of the electronic control unit to permit more coolant to flow through the engine 1. Although the opening -16 -of the electronically controlled flow valve 20 will reduce the amount of flow through the exhaust gas cooler 5 this is not so important at high engine load because the volume of exhaust gas recfrculated is less than it is durnq part load conditions.

With reference to Fig.4 there is shown part of a cooling system according to a fourth embodiment of the invention. It will he appreciated that as with the first three embodiments the cooling system would in practice also include a radiator to cool the coolant, a degas circuit to remove entrained gas from the coolant and in most cases a cabin heater. These are not shown on Fig.4 as they are not key features of the invention.

The engine 1 has a cylinder block 100 and a cylinder head 200 each of which is provided with an independent supply of coolant from the pump 4.

The supply of coolant from the pump 4 to the cylinder head 200 passes through a flow restrictor 122 sized to prevent overcooling of the cylinder head 200. After passing through the cylinder head 200 the coolant returns to the pump 4 through a return conduit RL.

The supply of coolant from the pump 4 to the cylinder block 100 passes through a electronically controlled flow valve 121 which has an outlet connected to an inlet of the cylinder block 100 by means of a supply conduit SL. The coolant from the supply conduit SL passes through conduits (not shown) in the cylinder block 100 to an outlet and then returns to an inlet side of the pump through the return conduit RL.

The electronically controlled flow control valve 121 is used to controlthe flow of coolant through the cylinder block 100. The electronically controlled flow valve 121 is -17 -controlled by an electronic controller (not shown) in order to maintain the temperature of the cylinder block 100 within predetermined limits. The electronically controlled flow valve 121 can be actuated directly by an electrical actuator or may be actuated by other types of actuator such as a vacuum actuator controlled by the electronic control unit.

At a position upstream from the electronically controlled flow valve 121 but downstream from the pump 4 a supply of coolant is tapped off to supply the exhaust gas cooler 5 through an exhaust gas coolant supply conduit EGRI.

The exhaust gas cooler 5 forms part of an exhaust gas recirculation system in which exhaust gas is drawn off from an exhaust outlet such as an exhaust manifold (not shown) of the engine 1 is passed through the exhaust gas cooler 5 and then is returned to an air inlet to the engine such as an inlet manifold (not shown) . One or more exhaust gas flow control valves (EGR valves) may be provided to control the flow of exhaust gas through the exhaust gas cooler 5 based upon the operating conditions of the engine 1. The EGR valves may be controlled by the same electronic control unit used to control the operation of the electronically controlled flow valve 20 or may be independently controlled.

After passing through the exhaust gas cooler 5 the coolant flows through an exhaust gas coolant return conduit EGRR to the coolant return conduit RL and then back to an inlet side of the pump.

Basic operation of the cooling system is as follows, when the engine 1 is started from cold the electronic control unit opens the electronically controlled flow valve 121 so as to permit the coolant from the pump 4 to pass freely through the cylinder block 100 and will return to the pump 4 without having been cooled by a radiator in order to speed up the warming of the engine 1. At the same time -18 -coolant flows through the cylinder head 200 back to the pump 4.

Because the electronically controlled flow valve 121 is open there is very little flow through the exhaust gas coolant supply conduit EGRI to the exhaust gas cooler 5 due to the relative resistances to flow through the alternative flow paths. That is to say, the resistance to flow through the exhaust gas cooler 5 is greater than the resistance to flow through the electronically controlled flow valve 121 and the cylinder block 100.

When the temperature of the coolant reaches a predetermined temperature the electronically controlled flow valve 121 is then controlled by the electronic control unit to vary the temperature of the cylinder block 100 by opening and closing the electronically controlled flow valve 121 to increase or reduce the flow of coolant through the cylinder block 100 and maintain the temperature of the cylinder block 100 within a preferred temperature range. The electronic control unit is arranged to receive one or more temperature inputs from temperature sensors (not shown) located on the cylinder block 100 in order to control the operation of the electronically controlled flow valve 121.

The cooling system has to be able to prevent overheating of the cylinder block 100 when the engine 1 is operating at maximum load and so the flow of coolant through the cylinder block 100 is too great when the engine 1 is operating under part load conditions and the electronically controlled flow valve 121 is fully open. Under such part load conditions over cooling of the engine 1 will occur unless the flow through the cylinder block 100 is restricted. Therefore when the electronic control unit determines that the temperature of the cylinder block 100 is below that required to operate the engine 1 at maximum efficiency and with minimum CO emissions it will control the -19 -electronically controlled flow valve 121 so as to restrict the flow of coolant entering the cylinder block 100 from the pump 4 and increase the temperature of the cylinder block 100. This closing of the electronically controlled flow valve 121 has the effect of increasing the pressure upstream which causes an increase in flow through the exhaust gas coolant supply conduit EGRI to the exhaust gas cooler 5.

Therefore as with the previous embodiments one of the advantages of this embodiment is that the flow through the exhaust gas cooler 5 is automatically increased when the engine 1 is operating at part load and this is when the maximum cooling effect from the exhaust gas cooler 5 is required to cool the exhaust gas passing through it.

When the engine 1 is operating at high load the flow of coolant through the cylinder block 100 must be increased in order to maintain the temperature of the cylinder block 100 within the preferred range where both emission and engine performance are at or near to their optimum, the electronically controlled flow valve 121 is therefore opened under the control of the electronic control unit to permit more coolant to flow through cylinder block 100. Although the opening of the electronically controlled flow valve 121 will reduce the amount of flow through the exhaust gas cooler 5 this is not so important at high engine load because the volume of exhaust gas recirculated is less than it is during part load conditions.

With reference to Fig.5 there is shown part of a cooling system according to a fifth embodiment of the invention. It will be appreciated that, as with the first three embodiments, the cooling system would in practice also include a radiator to cool the coolant, a degas circuit to remove entrained gas from the coolant and in most cases a cabin heater. These are not shown on Fig.5 as they are not key features of the invention.

-20 -The engine 1 has a cylinder block 100 and a cylinder head 200 each of which is provided with an independent supply of coolant from the pump 4.

The supply of coolant from the pump 4 to the cylinder head 200 passes through a second supply conduit SL2 to an electronically controlled flow valve 222 used to control the flow of coolant through the cylinder head 200. After passing through the cylinder head 200 the coolant returns to the pump 4 through a return conduit RL.

The supply of coolant from the pump 4 passes through a first supply conduit SL to a first electronically controlled flow valve 221 which has an outlet connected to an inlet of the cylinder block 100. The coolant from the first electronically controlled flow valve 221 passes through conduits (not shown) in the cylinder block 100 to an outlet and then returns to an inlet side of the pump through the return conduit RL. The electronically controlled flow control valve 221 is used to control the flow of coolant through the cylinder block 100.

The first and second electronically controlled flow valves 221 and 222 are controlled by an electronic controller (not shown) based upon temperature signals produced by temperature sensors on the engine 1 in order to maintain the temperature of the cylinder block 100 and the cylinder head 200 within predetermined limits. The first and second electronically controlled flow valve 221 and 222 can be actuated directly by an electrical actuator or may be actuated by other types of actuator such as a vacuum actuator controlled by the electronic control unit.

At a position upstream from the second electronically controlled flow valve 222 but downstream from the pump 4 a -21 -supply of coolant is tapped off to supply the exhaust gas cooler 5 through an exhaust gas coolant supply conduit EGRI.

The exhaust gas cooler 5 forms part of an exhaust gas s recirculation system in which exhaust gas is drawn off from an exhaust outlet such as an exhaust manifold (not shown) of the engine 1 is passed through the exhaust gas cooler 5 and then is returned to an air inlet to the engine such as an inlet manifold (not shown) . After passing through the o exhaust gas cooler 5 the coolant flows through an exhaust gas coolant return conduit EGRR to the coolant return conduit RL and then back to an inlet side of the pump.

One advantage of this embodiment is that the flow through the exhaust gas cooler 5 is automatically increased when the engine 1 is operating at part load by closing of the second electronically controlled flow valve 222 which is required in order to maintain the temperature of the cylinder head 200 within a preferred temperature operating range.

When the engine 1 is operating at high load, the flow of coolant through the cylinder head 200 must be increased and the electronically controlled flow valve 222 is therefore opened under the control of the electronic control unit. Although the opening of the electronically controlled flow valve 222 will reduce the amount of flow through the exhaust gas cooler 5 this is not so important at high engine load because the volume of exhaust gas recirculated through the exhaust gas cooler 5 is less then than it is during part load conditions.

With reference to Fig.6 there is shown part of a cooling system according to a sixth embodiment of the invention. It will be appreciated that as with the first three embodiments the cooling system would in practice also include a radiator to cool the coolant, a degas circuit to -22 -remove entrained gas from the coolant and in most cases a cabin heater. These are not shown on Fig.6 as they are not key features of the invention.

The supply of coolant from the pump 4 to the cylinder head 200 passes through a second supply conduit SL2. After passing through the cylinder head 200 the coolant returns to the pump 4 through to a second electronically controlled flow valve 322 used to control the flow of coolant through the cylinder head 200 and through a return conduit RL.

The supply of coolant from the pump 4 passes through a first supply conduit SL1 to an inlet of the cylinder block 100. The coolant passes through conduits (not shown) in the cylinder block 100 to an outlet and then to a first electronically controlled flow valve 321 used to control the flow of coolant through the cylinder block 100 before returning to an inlet side of the pump through the return conduit RL.

The first and second electronically controlled flow valves 321 and 322 are controlled by an electronic controller (not shown) based upon temperature signals produced by temperature sensors on the engine 1 in order to maintain the temperature of the cylinder block 100 and the cylinder head 200 within predetermined limits. The first and second electronically controlled flow valve 321 and 322 can be actuated directly by an electrical actuator or may be actuated by other types of actuator such as a vacuum actuator controlled by the electronic control unit.

At a position upstream from the first electronically controlled flow valve 321 but downstream from the pump 4 a -23 -supply of coolant is tapped off to supply the exhaust gas cooler 5 through an exhaust gas coolant supply conduit EGRI.

That is to say, at a position downstream from the cylinder block 100 but upstream from the first electronically controlled flow valve 321 a supply of coolant is tapped off for the exhaust gas cooler 5.

The exhaust gas cooler 5 forms part of an exhaust gas recirculation system in which exhaust gas is drawn off from an exhaust outlet such as an exhaust manifold (not shown) of the engine 1 is passed through the exhaust gas cooler 5 and then is returned to an air inlet to the engine such as an inlet manifold (not shown) . After passing through the exhaust gas cooler 5 the coolant flows through an exhaust gas coolant return conduit EGRR to the coolant return conduit RL and then back to an inlet side of the pump 4.

As with the previous embodiments one advantage of this embodiment is that the flow through the exhaust gas cooler 5 is automatically increased when the engine 1 is operating at part load by closing of the first electronically controlled flow valve 321 which is required in order to maintain the temperature of the cylinder block 100 within a preferred temperature operating range.

When the engine 1 is operating at high load the flow of coolant through the cylinder block 100 must be increased and the first electronically controlled flow valve 321 is therefore opened under the control of the electronic control unit. Although the opening of the first electronically controlled flow valve 321 will reduce the amount of flow through the exhaust gas cooler 5 this is not so important at high engine loads because the volume of exhaust gas recirculated through the exhaust gas cooler 5 is less then than it is during part load conditions.

-24 -With reference to Fig.7 there is shown part of a cooling system according to a seventh embodiment of the invention. It will be appreciated that, as with the first three embodiments, the cooling system would in practice also include a radiator to cool the coolant, a degas circuit to remove entrained gas from the coolant arid in most cases a cabin heater. These are not shown on Fig. 7 as they are not key features of the invention.

The supply of coolant from the pump 4 to the cylinder iS head 200 passes through a second supply conduit SL2. After passing through the cylinder head 200 the coolant returns to the pump 4 through to a second electronically controlled flow valve 322 used to control the flow of coolant through the cylinder head 200 and through a return conduit RL.

The first and second electronically controlled flow valves 321 and 322 are controlled by an electronic controller (not shown) based upon temperature signals produced by temperature sensors on the engine 1 in order to maintain the temperature of the cylinder block 100 and the cylinder head 200 within predetermined limits. The first and second electronically controlled flow valve 321 and 322 can be actuated directly by an electrical actuator or may be -25 -actuated by other types of actuator such as a vacuum actuator controlled by the electronic control unit.

At a position upstream from the second electronically controlled flow valve 322 but downstream from the pump 4 a supply of coolant is tapped off to supply the exhaust gas cooler 5 through an exhaust gas coolant supply conduit EGRI.

That is to say, at a position downstream from the cylinder head 200 but upstream from the second electronically o controlled flow valve 322 a supply of coolant is tapped off for the exhaust gas cooler 5.

As with the previous embodiments one of the advantages of this embodiment is that the flow through the exhaust gas cooler 5 is automatically increased when the engine 1 is operating at part load by closing of the second electronically controlled flow valve 322 which is required in order to maintain the temperature of the cylinder head within a preferred temperature operating range. :30

When the engine 1 is operating at high load, the flow of coolant through the cylinder head 200 must be increased and the second electronically controlled flow valve 322 is therefore opened under the control of the electronic control unit. Although the opening of the second electronically controlled flow valve 322 will reduce the amount of flow through the exhaust gas cooler 5 this is not so important at -26 -high engine loads because the volume of exhaust gas recirculated through the exhaust gas cooler 5 is less then than it is during part load conditions.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to a number of specific embodiments it is not limited to these embodiments and that various alternative embodiments or modifications to the disclosed embodiments could be made without departing from the scope of the invention.

Claims

-27 -Claims 1. A cooling system for an internal combustion engine

having a coolant circuit through which coolant is circulated by a pump, an electronically controlled flow control valve to control the flow of coolant flowing through the engine and an exhaust gas cooler forming part of an exhaust recirculation system provided to recirculate exhaust gas from an exhaust outlet of the engine to an air inlet of the engine wherein the exhaust gas cooler is arranged to receive a supply of coolant from a position located upstream of the electronically controlled flow valve such that, when the electronically controlled flow valve is operated to restrict the flow of coolant through the engine, the flow through the is exhaust gas cooler is automatically increased.
2. A cooling system as claimed in claim 1 wherein the electronically controlled control valve is located at an outlet from the engine and the supply of coolant for the exhaust gas cooler is taken from a position located between the electronically controlled flow valve and an outlet from the engine.
3. A cooling system as claimed in claim 1 wherein the electronically controlled control valve is located at an outlet from the engine, the pump is located upstream from the engine and the supply of coolant for the exhaust gas cooler is taken from a position located upstream from the electronically controlled flow valve between the engine and the pump.
4. A cooling system as claimed in claim 1 wherein the pump is located upstream from the engine, the electronically controlled control valve is located between the pump and the engine and the supply of coolant for the exhaust gas cooler is taken from a position located between the electronically controlled flow valve and the pump.

-28 -
5. A cooling system as claimed in claim 1 wherein the engine includes passages formed in a cylinder head of the engine and in a cylinder block of the engine, the coolant passages in the cylinder block are connected by a first coolant supply conduit to an outlet from the pump, the coolant passages in the cylinder head are connected by a second coolant supply conduit to an outlet from the pump and the flow through the first coolant supply passage is controlled by the electronically controlled flow control valve so as to allow the flow through the cylinder block to be independently controlled wherein the supply of coolant for the exhaust gas cooler is taken from a position located upstream from the electronically controlled flow valve and downstream from the pump.
6. A cooling system as claimed in claim 1 wherein the engine includes passages formed in a cylinder head of the engine and in a cylinder block of the engine, the coolant passages in the cylinder block are connected by a first coolant supply conduit to an outlet from the pump, the coolant passages in the cylinder head are connected by a second coolant supply conduit to an outlet from the pump and the flow through the second coolant supply passage is controlled by the electronically controlled flow control valve so as to allow the flow through the cylinder head to be independently controlled wherein the supply of coolant for the exhaust gas cooler is taken from a position located upstream from the electronically controlled flow valve and downstream from the pump.
7. A cooling system as claimed in claim 1 in which the engine has a cylinder block and a cylinder head each having an independent coolant flow path therethrough, a first electronically controlled flow control valve positioned at a coolant outlet from the cylinder block to control the flow of coolant through the cylinder block and a -29 -second electronically controlled flow control valve positioned at a coolant outlet from the cylinder head to control the flow of coolant through the cylinder head wherein the supply of coolant for the exhaust gas cooler is taken from a position located upstream from the first electronically controlled flow valve arid downstream from the cylinder block.
8. A cooling system as claimed in claim 1 in which the engine has a cylinder block and a cylinder head each having an independent coolant flow path therethrough, a first electronically controlled flow control valve positioned at a coolant outlet from the cylinder block to control the flow of coolant through the cylinder block and a second electronically controlled flow control valve positioned at a coolant outlet from the cylinder head to control the flow of coolant through the cylinder head wherein the supply of coolant for the exhaust gas cooler is taken from a position located upstream from the second electronically controlled flow valve and downstream from the cylinder head.
9. A cooling system for an internal combustion engine substantially as described herein with reference to the accompanying drawing.