GB2420845A

GB2420845A - A coolant system for an engine featuring coolant injector nozzles

Info

Publication number: GB2420845A
Application number: GB0426645A
Authority: GB
Inventors: Ian Graham Pegg; Les William Routledge
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2004-12-04
Filing date: 2004-12-04
Publication date: 2006-06-07
Anticipated expiration: 2024-12-04
Also published as: DE102005057760B4; GB0426645D0; DE102005057760A1; GB2420845B

Abstract

A cooling system for an engine comprises a cooling circuit through which coolant is circulated by a pump 5, the coolant circuit featuring at least one coolant injector 8 comprising a hollow body 30 defining a flow passage through which coolant can flow, the hollow body 30 having a convergent nozzle portion 33 at one end to provide a jet of coolant 34 and one or more apertures 31 formed so as to permit coolant to escape 32 from the hollow body 30 in a different direction to the direction in which the coolant flows from the nozzle portion 33. The cooling system may in use cool a cylinder block 10, having at least one cylinder 11 and a cooling passage 12 encircling the cylinder 11. The cooling passage 12 may include an interbore passage 12a located between adjacent cylinders 11. There may be provided at least one coolant injector 8 aligned with a respective inter-bore cooling passage 12a. There may be a number of coolant injectors 8 located on opposite sides of the cylinder block 10. The coolant may exit the apertures 31 at substantially 90 degrees to the direction of flow from the nozzle portion 33. There may be two apertures 31 formed on opposite sides of the hollow body 30. The hollow body 30 may be cylindrical.

Description

A Cooling System for an Engine This invention relates to the cooling of an

internal combustion engine and in particular to a cooling system for providing improved cooling without requiring the use of more energy to provide the cooling effect.

It is well known to provide a cooling system for an internal combustion engine in which coolant is circulated through a cylinder block and cylinder head of the engine in order to remove heat from these components.

To improve cooling and reduce parasitic losses, primarily that of the coolant pump, engine designers have deployed cross flow cooling strategies where the coolant flows across the block normally from the intake side to the exhaust side and then up into the cylinder head exhaust side and across to the intake side. Although this is a major step forward in terms of effective cooling it does not utilise the coolant in the most efficient manner. For example, the flow through the inter-bore region in Lhe engine block is limited as it is flow restrictive and is dependant on a pressure differential from ne side of the cylinder block to the other side being established. These inter-bore regions tend to be hot spots within the cylinder block and higher temperatures often exist in the inter-bore regions due to the low flow rates that can be achieved resulting in poorer cooling in these regions.

The disadvantages of the increased temperature in this zone relative to the rest of the cylinder bore include:- * thermal bore distortion, leading to higher oil consumption and blow by which require the use of higher load rings which then lead to higher friction and wear; * higher stresses within the engine especially during warm-up, leading to the use of larger structural components or components made from more expensive materials; * the production of uneven local oil film temperatures which lead to uneven friction characteristics; * high local oil film temperatures leading to local oil degradation before excessive temperatures have been reached in the rest of the engine, which will result in reduced oil service life, the need to use higher oil viscosity grades which increase friction and parasitic losses when the oil is cold and which are often more expensive to purchase; and * reduced power rating capability due to thermal load restrictions.

It is therefore desirable to improve the cooling of an engine in this region to minimise or eliminate these disadvantages.

In addition, the cooling of the cylinder head is not ideal in that, although a large flow of coolant may be supplied to the cylinder head, the supplied coolant is not necessarily used in an efficient manner. This is because there is a large variation in the amount of cooling required between different areas of the cylinder head and some hot spots always exist. For example, the cylinder head in the region of the valve bridges will become very hot unless adequate cooling is provided. It is important to provide adequate cooling to the cylinder head in order to control the emissions produced by the engine and to maintain the structural integrity of the various cylinder head components.

With a conventional cooling system arrangement a large flow of coolant is passed through the cylinder block and the cylinder head in order to ensure that the hot spots in the cylinder block and cylinder head are adequately cooled but for many regions of the cylinder block and the cylinder head such a large coolant flow is not required and so, in effect, energy is being wasted by circulating more coolant than is actually required and this results in reduce engine fuel economy.

Ideally, the cylinder block should be maintained at a sufficiently high temperature to produce low friction with minimal oil degradation and the minimum of temperature variation using the minimum coolant flow and the cylinder head temperature should be controlled to produce low cylinder head temperatures and hence reduced NOx emissions.

It is an object of this invention to provide an improved cooling system for an internal combustion engine.

According to a first aspect of the invention there is provided a cooling system for an engine comprising a cooling circuit through which coolant is circulated by a pump wherein the coolant is supplied to the engine so as to provided a directed flow of coolant and a general flow of coolant within the engine.

Advantageously, at least a proportion of the coolant may be supplied to the engine from the pump through one or more coolant injectors.

Each of the coolant injectors may include a convergent nozzle portion to provide a directed flow of coolant.

Each of the coolant injectors may further comprise one or more outlets arranged to permit coolant to flow in a different direction to the direction of coolant flow through the nozzle portion so as to provide a general flow of coolant to the engine.

The engine may include a cylinder block having at least one cylinder and a cooling passage encircling at least a part of each cylinder wherein the directed flow to the cylinder block may be aligned so as to promote a circulatory flow through each respective cooling passages around each cylinder.

The cylinder block may have at least two cylinders and a part of the cooling passage for each cylinder may include an inter-bore cooling passage located between the cylinder and an adjacent cylinder and at least a part of the directed flow may be aligned so as to specifically promote increased flow through the or each inter-bore cooling passage.

Preferably, at least one coolant injector is aligned with a respective inter-bore cooling passage in the cylinder block.

There may be number of coolant injectors located on one side of the cylinder block and at least one of the coolant injectors may be aligned with a corresponding inter-bore cooling passage.

There may be a first coolant injector located on one side of the cylinder block aligned with a first inter-bore cooling passage associated with a cylinder and there may be a second coolant injector located on an opposite side of the cylinder block aligned with a second inter-bore cooling passage associated with the same cylinder so as to promote the circulation of coolant flow around the cylinder.

There may be several coolant injectors on one side of the cylinder block at least some of which may be aligned with first inter-bore cooling passages associated with some of the cylinders of the engine and there may be several coolant injectors on the opposite side of the cylinder block at least some of which are aligned with second inter-bore cooling passages associated with the same cylinders of the engine so as to promote the circulation of coolant around the cylinders of the engine.

The or each coolant injector on one side of the cylinder block may be located on a common plane as the or each coolant injector on the opposite side of the cylinder block. The common plane may be located towards a lower end of the or all of the cylinder coolant jackets.

The or all of the coolant injectors on one side of the cylinder block may be located on a first common plane and the or all of the coolant injectors on the opposite side of the cylinder block may be located on a second common plane that is offset with respect to the first common plane.

The first common plane may be located towards a lower end of the or all of the cylinder coolant jackets and the second common plane is located towards an upper end of the or all of the cylinder coolant jackets.

Preferably, the second common plane may be located at a position where it will maximise circulatory flow through the inter-bore regions.

There may be a least one coolant injector positioned so as to promote the flow of coolant through an end cooling passage defined between a respective cylinder and an end wall of the cylinder block.

The engine may have a cylinder head and a least a portion of the coolant supplied to the cylinder head may be supplied through one or more coolant injectors.

The or each of the coolant injectors may provide a directed flow of coolant which is directed towards a portion of the cylinder head requiring supplementary cooling.

The or each portion of the cylinder head requiring supplementary cooling may comprises one of a portion of the cylinder head in close proximity to one or more exhaust valves supported by the cylinder head and at least one support for a fuel injector. The or each portion of the cylinder requiring supplementary cooling may be a valve bridge joining two exhaust valve supports.

The cylinder head may be connected to a cylinder block of the engine and a portion of the coolant may be supplied to cooling passages formed in the cylinder head from the cylinder block.

The coolant supplied to the cylinder head from the cylinder block may form a general coolant flow to the cylinder head and the coolant injectors may provide at least a directed coolant flow. The coolant injectors may provide both a directed coolant flow and a supplementary general coolant flow.

According to a second aspect of the invention there is provided a coolant injector for supplying coolant to an engine comprising a hollow body defining a flow passage through which coolant can flow, the hollow body having a convergent nozzle portion at one end to provide a jet of coolant and one or more apertures formed so as to permit coolant to escape from the hollow body in a different direction to the direction in which coolant flows from the nozzle portion.

The cross-sectional area of the hollow body may be larger than the crosssectional area of the nozzle portion at the position where the jet issues from the nozzle portion.

The coolant may exit the or each aperture substantially at 90 degrees to the direction of flow from the nozzle portion.

There may be at least one aperture formed in the hollow body on opposite sides of the hollow body.

The hollow body may be cylindrical.

According to a third aspect of the invention there is provided a method for cooling an engine comprising providing a source of coolant to cool the engine using a pump to circulate the coolant through a cooling circuit, providing a first directed flow of coolant to cool specific regions of the engine and providing a second general flow of coolant to cool the remaining regions of the engine.

The method may further comprise using a common coolant injector to supply the first and second coolant flows to the engine.

The specific regions may be known hot regions within the engine.

The specific regions may include inter-bore cooling passages formed in a cylinder block of the engine between adjacent cylinders of the engine, valve bridges formed in a cylinder head of the engine or supports for fuel injectors formed in a cylinder head of the engine.

The method may further comprise using the first directed coolant flow to promote circulation of coolant around the cylinders of the engine.

The invention will now be described by way of example with reference to the accompanying drawing of which:- Fig.1 is a schematic diagram of a first embodiment of a cooling system according to a first aspect of the invention; Fig.2a is a scrap cross- section through part of the cylinder block shown in Fig.1 showing how directed cooling provided by a coolant injector is used to improve the cooling in the inter-bore regions of the engine; Fig.2b is a cross- section similar to that shown in Fig.2a but showing the use of an alternative type of coolant injector; Fig.3a is an enlarged view of the coolant injector shown in Fig.2a according to a second aspect of the invention; Fig.3b is an enlarged view of the coolant injector shown in Fig.2b according to a second aspect of the invention; Fig.4 is a line diagram showing the use of multiple coolant injection to promote circulatory flow aroung cylinders of an engine; Fig.5a is a schematic diagram of a second embodiment of a cooling system according to the first aspect of the invention as applied to a four cylinder inline engine and utilising multiple coolant injection as shown in Fig.4; Fig.5b is a schematic diagram similar to Fig.5a but showing a third embodiment of a cooling system according to the first aspect of the invention; Fig.6a is a schematic diagram of a fourth embodiment of a cooling system according to the first aspect of the invention as applied to a three cylinder inline engine and utilising multiple coolant injection as shown in Fig.4; Fig.6b is a schematic diagram similar to Fig.6a but showing a fifth embodiment of a cooling system according to the first aspect of the invention; Fig.7a is a schematic diagram of a sixth embodiment of a cooling system according to the first aspect of the invention as applied to a five cylinder inline engine and utilising multiple coolant injection as shown in Fig.4; Fig.7b is a schematic diagram similar to Fig.7a but showing a seventh embodiment of a cooling system according to the first aspect of the invention; Fig.8a is a schematic diagram of a eighth embodiment of a cooling system according to the first aspect of the invention as applied to a six cylinder inline engine and utilising multiple coolant injection as shown in Fig.4; Fig.8b is a schematic diagram similar to Fig.8a but showing a ninth embodiment of a cooling system according to the first aspect of the invention; Fig.9 is a partial cross-section through a cylinder head using a cooling system according to the invention; and Fig.lO is a schematic diagram of a cylinder head having a cooling system according to the invention.

With reference to Fig. 1 there is shown a cylinder block 10 forming part of an internal combustion engine. The cylinder block 10 in this case supports four cylinders 11.

A coolant pump 5 which in this case is a variable flow rate - 10 - pump is used to circulate coolant through a cooling circuit (not shown) . The cooling circuit includes a radiator to cool the coolant and will also typically include a degas reservoir to permit gasses entrained in the coolant to be removed and a cabin heater to provide heat for a cabin of a motor vehicle to which the engine is fitted. The radiator and any of the other components referred to constitute a return circuit of the cooling circuit.

The coolant exiting the pump 5 passes through a coolant supply conduit 6 to a distribution manifold 7 connected to the cylinder block 10. The distribution manifold 7 is used to supply the coolant to a number of coolant injectors 8 used to supply coolant to the cylinder block 10.

The cylinder block 10 has a number of coolant passages 12 formed therein to guide the coolant through the cylinder block 10. These coolant passages 12 include inter-bore passages 12a formed between adjacent cylinders 11 and end passages formed between the outermost cylinders 11 and respective end walls of the cylinder block 10 so that each of the cylinders 11 is encircled by a coolant passage for most of its length. It will be appreciated that each of the cylinders is attached at its upper and lower portions to the cylinder block 10 so that these end portions define the upper and lower extents of the cooling passage around each cylinder 11, the portion of each cooling passage around each cylinder is often called the cylinder coolant jacket.

After passing through the passages in the cylinder block 10 the coolant exits the cylinder block and returns to the return circuit through one or more return conduits indicated by the reference number 20. The coolant passes through the return circuit and is then returned to the pump 5 through a pump supply conduit 21.

- 11 - In this case all of the coolant injectors are located on one side of the cylinder block 10 but as will be described hereinafter this need not be the case.

The coolant injectors 8 are all aligned with either one of the inter-bore passages 12a or one of the end passages and different types of coolant injector 8 can be used depending upon the flow required. Two types of coolant injector are shown in Figs 2a to 3b but other types could also be used.

Referring to figs 2a and 3a a coolant injector according to a second aspect of the invention is shown which is suitable for use as the coolant injector 8 or for any other use where directed and general coolant flows are required. The coolant injector comprises a hollow body 30 having two opposed apertures 31 formed therein part way along the hollow body 30 and terminates at one end in a convergent nozzle portion 33. Coolant enters the hollow body 30 of the coolant injector 8 from the distribution manifold 7, as indicated by the arrows "F" and 25, and flows through the hollow body 30 to the nozzle portion 33 and issues from the nozzle portion 33 as a fast flowing jet, as indicated by the arrow 34. It will be appreciated that the cross-sectional area of the hollow body 30 is larger than the cross-sectional area of the nozzle portion 33 at the position where the jet issues from it.

Some of the coolant entering the hollow body 30 also escapes through the apertures 31 which provide a general unfocussed flow of coolant to the cylinder block 10.

The nozzle portion 33 on the other hand provides a directed flow of coolant with considerable momentum that can be aligned with or aimed at regions of the cylinder block 10 or other engine components requiring the maximum cooling.

- 12 - One such region is the inter-bore passages 12a through which in a conventional engine it is difficult to obtain much flow. By aligning a coolant injector 8 with one of these passages 12a a fast moving flow of coolant is produced which improves the transfer of heat from the adjacent cylinders 11. It will also be appreciated that the coolant injectors will act as jet pumps and will tend to entrain the coolant surrounding the coolant injector 8 so that the bulk of coolant will begin to move and not just the coolant injected.

With particular reference to Figs 2b and 3b a second embodiment of coolant injector is shown which is suitable for use as the coolant injector 8 or in any situation where both directed and general coolant flow is required.

The coolant injector 8 comprises of a hollow cylindrical body 130 and terminates at one end in a convergent nozzle portion 133. Coolant enters the hollow body 130 of the coolant injector 8 from the distribution manifold 7, as indicated by the arrow 25, and flows through the hollow body 130 to the nozzle portion 133 and issues from the nozzle 133 as a fast flowing jet, as indicated by the arrow 34.

In this case only one side aperture 131 is formed in the hollow body 130 through which coolant may exit, as indicated by the arrow 32.

As before the jet of coolant from the nozzle portion 133 is aligned with a region that requires enhanced cooling such as the inter-bore passages 12a and will promote improved cooling in this region. The side aperture 131 will tend to cause the coolant to circulate around the cylinder 11 located on the same side as the aperture 131 as indicated by the arrow "CF" on Fig.2b. It will also be appreciated that the coolant injectors will act as jet pumps and will - 13 - tend to entrain the coolant surrounding the coolant injector 8 so that the bulk of coolant will begin to move and not just the coolant injected.

By increasing the flow rate of coolant through the inter bore passages the heat transfer rate in these areas will be increased and so a more uniform temperature around the circumference of each bore will be produced.

Referring now to Fig. 5a there is shown an alternative arrangement of coolant injectors to that shown in Fig.1.

The cylinder block 110 as before supports four cylinders 111. A coolant pump 5 is used to circulate coolant through a cooling circuit (not shown) . The cooling circuit as before includes a radiator to cool the coolant and will also typically include a degas reservoir to permit gasses entrained in the coolant to be removed and a cabin heater to provide heat for a cabin of a motor vehicle to which the engine is fitted. The radiator and any of the other components referred to constitute a return circuit of the cooling circuit.

The coolant exiting the pump 5 passes through a coolant supply conduit 106 to a first manifold 107 connected to the cylinder block 110. The manifold 107 is used to supply the coolant to a number of coolant injectors 108 used to supply coolant to one side of the cylinder block 110. A second supply conduit 109 is used to supply coolant to a second manifold 103 located on the opposite side of the cylinder block 110 to the first manifold 107. The second manifold 103 supplies coolant to two coolant injectors 104.

The cylinder block 110 has a number of coolant passages formed therein to guide the coolant through the cylinder block 110. These coolant passages include inter-bore passages formed between adjacent cylinders 111 and end - 14 - passages formed between the outermost cylinders 111 and respective end walls of the cylinder block 110.

The arrangement of the passages is such that each of the cylinders is encircled by a coolant passage that is to say cylinder coolant jacket for some of its length. In practice the cylinder coolant jacket is likely to extend for 70% to 120% of the distance travelled by the piston rings fitted to a piston slidingly supported by the cylinder.

After passing through the passages in the cylinder block 110 the coolant exits the cylinder block 110 and returns to the return circuit through one or more return conduits indicated by the reference number 20. The coolant passes through the return circuit and then is returned to the pump 5 through a pump supply conduit 21.

The coolant injectors 108 are all located on a common plane located towards a lower end of all of the cylinder coolant jackets and the coolant injectors 104 are all located on a common plane vertically offset to the common plane upon which all of the coolant injector 108 are located and in this case the plane is positioned at a position where the maximum improvement to the flow can be produced. This is likely to be somewhere between the top of each cylinder coolant jacket and a point midway between the top and bottom of each cylinder coolant jacket that is to say near to the top of each cylinder coolant jacket.

One of the injectors 108 is aligned with the inter-bore passage between the second and third cylinders as counted from the left hand side of the cylinder block 110 shown in Fig.5a and two of the coolant injectors 108 are aligned with the end passages between the first and fourth cylinders and the end walls of the cylinder block 110.

- 15 - The two coolant injectors 104 are aligned with the inter-bore passages between the first and second and the third and fourth cylinders as counted from the left hand side of the cylinder block 110. The inter-bore passages of an engine are known hot spots or hot regions due to the difficulty of cooling these areas using conventional methods. it will be appreciated that in these areas the coolant is heated simultaneously by two sources of heat as it passes between two cylinders 111.

In all cases the coolant injectors 108, 104 on opposite sides of the cylinder block 110 are not aligned with the same inter-bore passages because, if they are so aligned, the directed flows from the two coolant injectors 108, 104 would react against one another and prevent a circulatory flow of coolant through the inter-bore passages from being established. In addition a further significant advantage of using the coolant injector arrangement shown is that a strong circulation around each of the cylinders 110 is set up by having the coolant injectors 108 on opposite sides of the cylinder block 110 and only having one coolant injector 108, 104 aligned with each inter-bore passage. Each of the cylinders 111 has in effect two passages connecting one side of the cylinder block to the other side of the cylinder block 110 in the case of the first cylinder, the first of these is the end passage between the first cylinder and the left hand end of the cylinder block 110 and the second is the inter-bore passage between the first and second cylinders, in the case of the second cylinder, the first passage is the inter-bore passage between the second and third cylinders and the second is the inter-bore passage between the first and second cylinders, in the case of the third cylinder, the first passage is the inter-bore passage between the second and third cylinders and the second is the inter-bore passage between the third and fourth cylinders and in the case of the fourth cylinder the first passage is the end passage between the fourth cylinder and the right - 16 - hand end wall of the cylinder block and the second is the inter-bore passage between the fourth and third cylinders.

Therefore it can be seen that all of the coolant injectors 108 on the first side of the cylinder block 110 are aligned with the first passages and all of the coolant injectors 104 on the second side of the cylinder block 110 are aligned with the second passages. In this way the jets of coolant from the coolant injectors 104 on the second side of the cylinder block 110 reinforce and assist the coolant injectors 108 on the first side of the cylinder block 110 in producing a strong circulation around each of the cylinders 111. This circulation is advantageous in that it reduces temperature differentials around the circumference of each cylinder 111 and improves the cooling of the inter-bore regions. It will be appreciated that the invention makes use of the momentum of the incoming flow of coolant from the coolant injectors to generate a circulatory flow and also to promote flow through the inter-bore passages rather than relying on pressure differences to produce the flow in this region. This means that a smaller pump can be used to produce cooling that is as good as or better than that previously produced because lees pressure differential has to be produced. It will be appreciated that the pressure differential in a prior art arrangement is produced by supplying a large flow of coolant to the cylinder block which then ahs to pass through the restrictive inter- bore passages so generating a pressure differential across this region.

As can best been seen with reference to Fig.4 by locating the coolant injectors 108, 104 on the opposite sides of the cylinder block 110 at different heights a secondary boost is given to the circulating flow and a helical or spiral circulating flow is produced.

- 17 - In this case the first coolant injectors 108 are aligned near to a lower end of the cylinder coolant jackets and produce a number of jets 34 and the second coolant injectors 104 are positioned higher up the cylinder coolant jackets and produce jets 134. By aligning some of the coolant injectors 104 higher the flow of coolant in the region of the cylinders 111 where the most heat is likely to be transferred is vigorous so as to maximise the transfer of heat away from the cylinders 111 and produces the maximum circulatory effect. It will be appreciated that the position where the maximum circulatory effect is produced is likely to be somewhere between half way up each cylinder coolant jacket and an upper end of each cylinder coolant jacket. Due to the fact that combustion will occur in this area, the maximum cylinder temperatures are likely to also occur there and so this will also improve the transfer of heat from the cylinders 111.

Although it is desirable to locate the coolant injectors 108, 104 on different planes it will be appreciated that all of the coolant injectors could be located on a common plane near to the lower end of the cylinder coolant jackets. Although this will still promote a circulation around the cylinders 111 the strength of the circulation will not be so vigorous near to the top of the cylinder coolant jackets as it is near to the bottom where it is injected.

It will be appreciated that the volume of coolant circulating around each cylinder is not only that entering via the jets but is the entire volume of coolant surrounding each cylinder 111 and that the jets act as jet or impulse pumps urging all of the coolant surrounding each cylinder 111 tocirculate. This means that a lower flow rate of coolant can be used to produce the same heat transfer and so a smaller pump can potentially be used to produce the same cooling effect.

- 18 - With reference to Fig.5b there is shown a cooling system which is in most respects the same as that previously described with respect to Fig.5a except that the number of first coolant injectors 108 has been reduced from three to one. The coolant injector 108 is connected directly to the coolant supply conduit 106 without the need for a manifold.

This arrangement is less expensive to produce but will produce slightly reduced thermal performance compared to that previously described particularly in the end passages between the first and fourth cylinders and the respective end walls of the cylinder block 110. However these end passages are not so critical as the inter-bore passages.

As before a strong circulation is generated by the coolant injectors 108, 104 around the cylinders 111 to promote good heat transfer from the cylinders 111 and the coolant injectors 108, 104 are aligned with the inter-bore passages to ensure that the flow in these regions is vigorous so as to ensure good cooling in these regions.

With reference to Fig.6a there is shown a cylinder block 210 which supports three cylinders 211. A coolant pump 5 is used to circulate coolant through a cooling circuit (not shown) . The cooling circuit as before includes a radiator to cool the coolant and will also typically include a degas reservoir to permit gasses entrained in the coolant to be removed and a cabin heater to provide heat for a cabin of a motor vehicle to which the engine is fitted.

The radiator and any of the other components referred to constitute a return circuit of the cooling circuit.

The coolant exiting the pump 5 passes through a coolant supply conduit 206 to a first manifold 207 connected to the cylinder block 210. The manifold 207 is used to supply the coolant to two coolant injectors 208 used to supply coolant - 19 - to one side of the cylinder block 210. A second supply conduit 209 is used to supply coolant to a second manifold 203 located on the opposite side of the cylinder block 210 to the first manifold 207. The second manifold 203 supplies coolant to two coolant injectors 204.

The cylinder block 210 has a number of coolant passages formed therein to guide the coolant through the cylinder block 210. These coolant passages include inter-bore passages formed between adjacent cylinders 211 and end passages formed between the outermost cylinders 211 and respective end walls of the cylinder block 210.

The arrangement of the passages is such that each of the cylinders 211 is encircled by a coolant passage for some of its length to form a cylinder coolant jacket.

After passing through the passages in the cylinder block 210 the coolant exits the cylinder block 210 and returns to the return circuit through one or more return conduits indicated by the reference number 20. The coolant passes through the return circuit to be cooled and is then returned to the pump 5 through a pump supply conduit 21.

The coolant injectors 208 are both located on a common plane located towards a lower end of the cylinder coolant jackets and the coolant injectors 204 are all located on a common plane vertically offset to the common plane upon which all of the coolant injector 208 are located and in this case the plane is positioned at a position where the maximum coolant circulation will be produced by their positioning which is towards and upper end of each of the cylinder coolant jacket. That is to say above a midpoint of each cylinder 211.

One of the injectors 208 is aligned with the inter-bore passage between the second and third cylinders as counted - 20 - from the left hand side of the cylinder block 210 shown in Fig.6a and the other coolant injector 208 is aligned with the end passage between the first cylinder and the left hand end wall of the cylinder block 210.

One of the injectors 204 is aligned with the inter-bore passage between the first and second cylinders as counted from the left hand side of the cylinder block 210 and the other is aligned with the end passage between the third cylinder and the right hand end wall of the cylinder block 210.

The coolant injectors 208, 204 on opposite sides of the cylinder block are not aligned with the same inter-bore passages because, if they are so aligned, the directed flows from the two coolant injectors 208, 204 would react against one another and prevent a fast moving circulatory flow of coolant from being established. As before a strong circulation around each of the cylinders 210 is set up by having the coolant injectors 208 on opposite sides of the cylinder block 210 and only having one coolant injector 208, 204 aligned with each inter-bore passage. Each of the cylinders 211 has in effect two passages connecting one side of the cylinder block to the other side of the cylinder block 210.

In the case of the first cylinder, the first of these passages is the end passage between the first cylinder and the left hand end of the cylinder block 210 and the second is the inter-bore passage between the first and second cylinders, in the case of the second cylinder, the first passage is the inter-bore passage between the second and third cylinders and the second is the inter-bore passage between the first and second cylinders and in the case of the third cylinder, the first passage is the interbore passage between the second and third cylinders and the - 21 - second is the end passage between the third cylinder and the right hand end wall of the cylinder block.

Therefore it can be seen that all of the coolant injectors 208 on the first side of the cylinder block 210 are aligned with the first passages and all of the coolant injectors 204 on the second side of the cylinder block 210 are aligned with the second passages. In this way the jets of coolant from the coolant injectors 204 on the second side of the cylinder block 210 reinforces and assists the coolant injectors 208 on the first side of the cylinder block 210 in producing a strong circulation around each of the cylinders 211.

As before, by aligning some of the coolant injectors 204 higher it is ensured that the flow of coolant in the region of the cylinders 211 where the most heat is likely to be transferred is particularly vigorous so as to increase the transfer of heat away from the cylinders 211 in this region.

Although it is desirable to locate the coolant injectors 208, 204 on different planes it will be appreciated that all of the coolant injectors could be located on a common plane near to the lower end of the cylinder coolant jackets. Although this will still promote a circulation around the cylinders 211 the strength of the circulation will not be so strong or vigorous near to the top of the cylinder coolant jackets as it is near to the bottom where it is injected.

As before the volume of coolant circulating around each cylinder is not only that entering via the jets but is the entire volume of coolant surrounding each cylinder 211 and the jets from the coolant injectors 208, 204 act as impulse pumps urging all of the coolant in the coolant passage surrounding each cylinder 211 to circulate.

- 22 - With reference to Fig.6b there is shown a cooling system which is in most respects the same as that previously described with respect to Fig.6a except that the number of first coolant injectors 208 has been reduced from two to one and the number of coolant injectors 204 on the opposite side of the cylinder block 210 has also been reduced from two to one.

This allows the coolant injectors 208, 204 to be directly connected to their respective coolant supply conduits 206, 209 without the need for a manifold.

This arrangement is less expensive to produce but will produce slightly reduced thermal performance compared to that previously described in the end passages between the first and third cylinders and the respective end walls of the cylinder block 210. However a circulatory flow will still be produced by the two coolant injectors 208, 204.

With reference to Fig.7a there is shown a cylinder block 310 which supports five cylinders 311. A coolant pump is used to circulate coolant through a cooling circuit (not shown) . The cooling circuit as before includes a radiator to cool the coolant and will also typically include a degas reservoir to permit gasses entrained in the coolant to be removed and a cabin heater to provide heat for a cabin of a motor vehicle to which the engine is fitted. The radiator and any of the other components referred to constitute a return circuit of the cooling circuit.

The coolant exiting the pump 5 passes through a coolant supply conduit 306 to a first manifold 307 connected to the cylinder block 310. The manifold 307 is used to supply the coolant to three coolant injectors 308 used to supply coolant to one side of the cylinder block 310. A second supply conduit 309 is used to supply coolant to a second - 23 - manifold 303 located on the opposite side of the cylinder block 310 to the first manifold 307. The second manifold 303 supplies coolant to three coolant injectors 304.

The cylinder block 310 has a number of coolant passages formed therein to guide the coolant through the cylinder block 310. These coolant passages include inter-bore passages formed between adjacent cylinders 311 and end passages formed between the outermost cylinders 311 and respective end walls of the cylinder block 310.

The arrangement of the passages is such that each of the cylinders 311 is encircled by a coolant passage for most of its length which is often referred to as a cylinder coolant jacket.

After passing through the passages in the cylinder block 310 the coolant exits the cylinder block 310 and returns to the return circuit through one or more return conduits indicated by the reference number 20. The coolant passes through the return circuit and then is returned to the pump 5 through a pump supply conduit 21.

The coolant injectors 308 are all located on a common plane located towards a lower end of the cylinder coolant jackets and the coolant injectors 304 are all located on a second common plane vertically offset above the common plane upon which all of the coolant injector 308 are located. In this case the second common plane is positioned at a position where the maximum circulatory effect can be produced by their positioning although this need not be the case.

The coolant injectors 308, 304 on opposite sides of the cylinder block are not aligned with the same inter-bore passages because if they are the directed flows from the two coolant injectors 308, 304 would react against one another - 24 - and prevent a fast moving circulating flow of coolant from being established. As before a strong circulation around each of the cylinders 310 is set up by having the coolant injectors 308, 304 on opposite sides of the cylinder block 310 and only having one coolant injector 308, 304 aligned with each inter- bore passage. Each of the cylinders 311 has in effect two passages connecting one side of the cylinder block 310 to the other side of the cylinder block 310. In the case of the first cylinder, the first of these is the end passage between the first cylinder and the left hand end of the cylinder block 310 and the second is the inter-bore passage between the first and second cylinders, in the case of the second cylinder, the first passage is the inter-bore passage between the second and third cylinders and the second is the inter-bore passage between the first and second cylinders, in the case of the third cylinder, the first passage is the inter-bore passage between the second and third cylinders and the second is the inter-bore passage between the third and fourth cylinders, in the case of the fourth cylinder, the first passage is the inter-bore passage between the fourth and fifth cylinders and the second is the inter-bore passage between the fourth and third cylinders and, in the case of the fifth cylinder, the first passage is the inter-bore passage between the fifth and fourth cylinders and the second is the end passage between the fifth cylinder and the right hand end wall of the cylinder block 310.

Therefore it can be seen that all of the coolant injectors 308 on the first side of the cylinder block 310 are aligned with the first passages and all of the coolant injectors 304 on the second side of the cylinder block 310 are aligned with the second passages. In this way the jets of coolant from the coolant injectors 304 on the second side of the cylinder block 310 reinforce and assist the coolant injectors 308 on the first side of the cylinder block 310 in - 25 - producing a strong circulation around each of the cylinders 311.

As before, by aligning some of the coolant injectors 304 higher it is ensured that the flow of coolant in the region of the cylinders 311 where the most heat is likely to be transferred is vigorous so as to maximise the transfer of heat away from the cylinders.

Although it is desirable to locate the coolant injectors 308, 304 on different planes it will be appreciated that all of the coolant injectors could be located on a common plane near to the lower end of the cylinder coolant jackets. Although this will still promote a circulation around the cylinders 311 the strength of the circulation will not be as strong near to the top of the cylinder coolant jackets as it is near to the bottom where it is injected.

As before the volume of coolant circulating around each cylinder is not only that entering via the jets but is the entire volume of coolant surrounding each cylinder 311 and the jets from the coolant injectors 308, 304 act as jet or impulse pumps urging all of this coolant to circulate.

With reference to Fig.7b there is shown a cooling system which is in most respects the same as that previously described with respect to Fig.7a except that the number of first coolant injectors 308 has been reduced from three to two and the number of coolant injectors 304 on the opposite side of the cylinder block 210 has also been reduced from three to two.

The arrangement of the coolant injectors 308, 304 is as previously described so as to promote a circulating flow around each of the cylinders 311 and to promote the flow of coolant through the inter-bore passages.

- 26 - This arrangement is less expensive to produce but will produce slightly reduced thermal performance compared to that previously described with respect to Fig.7a particularly in the end passages between the first and fifth cylinders and the respective end walls of the cylinder block 310. However a circulatory flow will still be produced by the two coolant injectors 308, 304 and cooling in the end passages is not as critical as it is between cylinders. l0

With reference to Fig.8a there is shown a cylinder block 410 which supports six cylinders 411. A coolant pump is used to circulate coolant through a cooling circuit (not shown) . The cooling circuit as before includes a radiator to cool the coolant and will also typically include a degas reservoir to permit gasses entrained in the coolant to be removed and a cabin heater to provide heat for a cabin of a motor vehicle to which the engine is fitted. The radiator and any of the other components referred to constitute a return circuit of the cooling circuit.

The coolant exiting the pump 5 passes through a coolant supply conduit 406 to a first manifold 407 connected to the cylinder block 410. The manifold 407 is used to supply the coolant to four coolant injectors 408 used to supply coolant to one side of the cylinder block 410. A second supply conduit 409 is used to supply coolant to a second manifold 403 located on the opposite side of the cylinder block 410 to the first manifold 407. The second manifold 403 supplies coolant to three coolant injectors 404.

The cylinder block 410 has a number of coolant passages formed therein to guide the coolant through the cylinder block 410. These coolant passages include inter-bore passages formed between adjacent cylinders 411 and end passages formed between the outermost cylinders 411 and respective end walls of the cylinder block 410.

- 27 - The arrangement of the passages is such that each of the cylinders 411 is encircled by a coolant passage for most of its length which is often referred to as a cylinder coolant jacket.

After passing through the passages in the cylinder block 410 the coolant exits the cylinder block 410 and returns to the return circuit through one or more return conduits indicated by the reference number 20. The coolant passes through the return circuit where it is cooled and then is returned to the pump 5 through a pump supply conduit 21.

The coolant injectors 408 are all located on a common plane located towards a lower end of the cylinder coolant jackets and the coolant injectors 404 are all located on a common second plane vertically offset to the common plane upon which all of the coolant injector 408 are located. In this case the second common plane is positioned at a position higher up on each cylinder coolant jacket where the maximum heat transfer from the cylinders 411 is required.

The coolant injectors 408, 404 on opposite sides of the cylinder block are not aligned with the same inter-bore passages because, if they are, the directed flows from the two coolant injectors 408, 404 would react against one another and prevent a fast moving flow of circulating coolant from being established. As before a strong circulation around each of the cylinders 410 is set up by having the coolant injectors 408, 404 on opposite sides of the cylinder block 410 and only having one coolant injector 408, 404 aligned with each inter-bore passage. Each of the cylinders 411 has in effect two passages connecting one side of the cylinder block 410 to the other side of the cylinder block 410. In the case of the first cylinder, the first of these is the end passage between the first cylinder and the - 28 - left hand end of the cylinder block 410 and the second is the inter-bore passage between the first and second cylinders, in the case of the second cylinder, the first passage is the inter-bore passage between the second and third cylinders and the second is the inter-bore passage between the first and second cylinders, in the case of the third cylinder, the first passage is the inter-bore passage between the second and third cylinders and the second is the inter-bore passage between the third and fourth cylinders, in the case of the fourth cylinder, the first passage is the inter-bore passage between the fourth and fifth cylinders and the second is the inter-bore passage between the fourth and third cylinders and, in the case of the fifth cylinder, the first passage is the inter-bore passage between the fifth and fourth cylinders and the second is the inter-bore passage between the fifth and sixth cylinders and in the case of the sixth cylinder the first is the end passage between the sixth cylinder and the right hand end wall of the cylinder block 410 and the second is the inter-bore passage between the sixth and fifth cylinders.

Therefore it can be seen that all of the coolant injectors 408 on the first side of the cylinder block 410 are aligned with the first passages and all of the coolant injectors 404 on the second side of the cylinder block 410 are aligned with the second passages. In this way the jets of coolant from the coolant injectors 404 on the second side of the cylinder block 410 reinforce and assist the coolant injectors 408 on the first side of the cylinder block 410 in producing a strong circulation around each of the cylinders 411.

As before, by aligning some of the coolant injectors 404 higher up on the cylinders 411 it is ensured that the flow of coolant in the region of the cylinders 411 where the most heat is likely to be transferred is vigorous so as to maximise the transfer of heat away from the cylinders 411.

- 29 - Although it is desirable to locate the coolant injectors 408, 404 on different planes it will be appreciated that all of the coolant injectors could be located on a conm-ion plane near to the lower end of the cylinder coolant jackets or could be positioned so that none of them lie on a cormnon plane or only some of them lie on a common plane.

As before the volume of cqolant circulating around each cylinder is not only that entering via the jets but is the entire volume of coolant surrounding each cylinder 411 and the jets from the coolant injectors 408, 404 act as jet or impulse pumps urging all of this coolant to circulate by using the momentum of the coolant issuing from the nozzles.

With reference to Fig.8b there is shown a cooling system which is in most respects the same as that previously described with respect to Fig.8a except that the number of first coolant injectors 408 has been reduced from four to two.

The arrangement of the coolant injectors 408, 404 is as previously described such as to promote a circulating flow around each of the cylinders 411 and to promote the flow of coolant through the inter-bore passages.

This arrangement is less expensive to produce but will produce slightly reduced thermal performance compared to that previously described with respect to Fig.8a particularly in the end passages between the first and sixth cylinders and the respective end walls of the cylinder block 410. However a circulatory flow will still be produced by the two coolant injectors 408, 404 and cooling in these end passages is not as critical as it is between cylinders.

- 30 - It will be appreciated that the coolant injectors referred to in Figs.5a to 8b could by of one of the types shown in Figs.3a or 3b or could be some other type of device able to promote a high speed coolant flow into the cylinder block to improve inter-bore cooling and promote a circulating flow around the cylinders of the engine. It will however be appreciated that the coolant injectors shown in Figs. 3a and 3b are particularly advantageous as they are able to provide both a directed and a general flow from a single coolant supply.

It will be appreciated that in each case the return from the cylinder block to the return circuit can be either directly from the cylinder block or, as more commonly is the case, the return from the cylinder block is to a cylinder head of the engine where the coolant is used to provide cooling to the cylinder head before being returned to the return circuit. Although the invention has bee described thus far with respect to inline engines it will be appreciated that it could be equally applied to other forms of engine such as "V" or horizontally opposed engines.

With particular reference to Figs. 9 and 10 there is shown a cylinder head 50 for a diesel engine in which is formed a cooling passage 52 used to transport coolant to various parts of the cylinder head 50. Fig.9 shows a portion of the cylinder head 50 in the region of one combustion chamber 55 (see Fig.10) and in this case six cylinder head bolts 56 are used to secure the cylinder head 50 to a cylinder block (not shown) around each combustion chamber 55.

A boss 65 is provided to support a fuel injector (not shown), an aperture 59 is formed to locate a glow plug and the cylinder head defines two exhaust valve ports 53 and two inlet valve ports 54 in which, in use, respective exhaust and inlet valves are located.

- 31 - A general supply of coolant 20 is provided to the cylinder head 50 through a number of passages which are connected to passageways formed in the cylinder block to which the cylinder head 50 is fastened.

In addition to this general supply of coolant a separate supply of coolant is supplied to the cylinder head through one of a number of coolant injectors 58. In this case the engine is a four cylinder engine and so four coolant injectors 58 are used. The coolant injectors are connected to a source of pressurised coolant in the form of a pump 40 by means of a supply pipe 60 and manifold 59.

Each of the coolant injectors 58 is arranged to supply a directed flow of coolant, as indicated by the arrow J" on Fig.9, and also a general flow of coolant, as indicated by the arrows "G" on Fig.9 to the cylinder head 50.

The pump 40 is preferably of a variable flow type the output from which is controlled by an electronic control unit 41. This enables the cooling of the cylinder head 56 to be adjusted by varying the flow to the coolant injectors 58. It will be appreciated that this cooling is independent of any cooling provided by the coolant passing through the cooling passage 52 from the cylinder block.

The coolant injectors 58 are positioned so as to direct coolant at regions of the cylinder head 50 that require additional cooling compared to the rest of the cylinder head 50. These regions are sometimes called hot spots and in most cases the material forming the valve bridges on the exhaust side of a cylinder head are one of such hot spots and another is the supports or bosses 65 supporting the fuel injectors as by cooling these the fuel injectors will also be cool-ed.

- 32 - By being able to specifically cool the valve bridge regions the thermal stresses formed in the cylinder head 50 are reduced as the thermal gradient between different regions is reduced by lowering the temperature of the valve bridges. In addition, these regions often limit the power rating of the engine because if the temperature is not controlled in these regions the material may locally weaken and fail even though in general terms the remaining material of the cylinder head 50 is sufficiently strong to withstand the forces of combustion.

One of the advantages of using a coolant injector of the type shown in Figs. 3a and 3b is that not only a directed flow but also a general flow is provided. This is important because if the flow of coolant from the coolant injectors 58 is greatly increased and only directed flow was provided this would in itself produce a thermal gradient in the region where it is injected. However when additional general flow is also flowing in from the coolant injector 58 at the same time it will tend to cool the area surrounding the region to which directed cooling is applied thereby reducing any thermal gradients that might otherwise exist.

A further advantage is that by using such a coolant injector both directed and general coolant flow can be provided to the cylinder head if the cylinder block and the cylinder head are independently cooled. In this case coolant from the cylinder block will not pass through the cylinder head and so a general flow of coolant to the cylinder head will be required.

Therefore in summary the invention provides a cooling system for an engine in which both a directed and general coolant supply is provided. This is advantageous because the general coolant flow can be used to provide an overall cooling effect and the directed flow can be used to cool areas or regions that would otherwise run too hot unless a - 33 - very much higher flow of coolant is supplied. This allows the use of a smaller pump than would otherwise be required and also reduces the thermal stresses induced in the engine by reducing thermal gradients that would otherwise exist in the region of localised hot spots.

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

- 34 - Claims 1. A cooling system for an engine comprising a cooling

circuit through which coolant is circulated by a pump wherein the coolant is supplied to the engine so as to provided a directed flow of coolant and a general flow of coolant within the engine.
2. A cooling system as claimed in claim 1 wherein at least a proportion of the coolant is supplied to the engine from the pump through one or more coolant injectors.
3. A cooling system as claimed in claim 2 wherein each of the coolant injectors includes a convergent nozzle portion to provide a directed flow of coolant.
4. A cooling system as claimed in claim 3 wherein each of the coolant injectors further comprises one or more outlets arranged to permit coolant to flow in a different direction to the direction of coolant flow through the nozzle portion so as to provide a general flow of coolant to the engine.
5. A cooling system as claimed in any of claims 1 to 4 in which the engine includes a cylinder block having at least one cylinder and a cooling passage encircling at least a part of each cylinder wherein the directed flow to the cylinder block is aligned so as to promote a circulatory flow through each respective cooling passages around each cylinder.
6. A cooling system as claimed in claim 5 wherein the cylinder block has at least two cylinders and a part of the cooling passage for each cylinder includes an inter-bore cooling passage located between the cylinder and an adjacent cylinder and at least a part of the directed flow is aligned - so as to specifically promote increased flow through the or each interbore cooling passage.
7. A cooling system as claimed in claim 6 when claim 5 is dependent upon any of claims 2 to 4 wherein at least one coolant injector is aligned with a respective inter-bore cooling passage in the cylinder block.
8. A cooling system as claimed in claim 7 wherein there are number of coolant injectors located on one side of the cylinder block and at least one of the coolant injectors is aligned with a corresponding inter-bore cooling passage.
9. A cooling system as claimed in claim 7 wherein there is a first coolant injector located on one side of the cylinder block aligned with a first inter-bore cooling passage associated with a cylinder and there is a second coolant injector located on an opposite side of the cylinder block aligned with a second inter-bore cooling passage associated with the same cylinder so as to promote the circulation of coolant flow around the cylinder.
10. A cooling system as claimed in claim 7 or in claim 8 wherein there are several coolant injectors on one side of the cylinder block at least some of which are aligned with first inter-bore cooling passages associated with some of the cylinders of the engine and there are several coolant injectors on the opposite side of the cylinder block at least some of which are aligned with second inter-bore cooling passages associated with the same cylinders of the engine so as to promote the circulation of coolant around the cylinders of the engine.
11. A cooling system substantially as described herein with reference to the accompanying drawings.

11. A cooling system as claimed in claim 9 or in claim 10 wherein the or each coolant injector on one side of the cylinder block is located on a common plane as the or each coolant injector on the opposite side of the cylinder block.

- 36 -
12. A cooling system as claimed in claim 11 wherein the common plane is located towards a lower end of the or all of the cylinder coolant jackets.

13. A cooling system as claimed in claim 9 or in claim wherein the or all of the coolant injectors on one side of the cylinder block are located on a first common plane and the or all of the coolant injectors on the opposite side of the cylinder block are located on a second common plane that is offset with respect to the first common plane.

14. A cooling system as claimed in claim 13 wherein the first common plane is located towards a lower end of the or all of the cylinder coolant jackets and the second common plane is located towards an upper end of the or all of the cylinder coolant jackets.

15. A cooling system as claimed in claim 14 wherein the second common plane is located at a position where it will maximise circulatory flow through the inter-bore regions.

16. A cooling system as claimed in any of claims 5 to 15 wherein there is a least one coolant injector positioned so as to promote the flow of coolant through an end cooling passage defined between a respective cylinder and an end wall of the cylinder block.

17. A cooling system as claimed in any of claims 1 to 16 wherein the engine has a cylinder head and a least a portion of the coolant supplied to the cylinder head is supplied through one or more coolant injectors.

18. A cooling system as claimed in claim 17 wherein the or each of the coolant injectors provides a directed - 37 - flow of coolant which is directed towards a portion of the cylinder head requiring supplementary cooling.

19. A cooling system as claimed in claim 18 wherein the or each portion of the cylinder head requiring supplementary cooling comprises one of a portion of the cylinder head in close proximity to one or more exhaust valves supported by the cylinder head and at least one support for a fuel injector.

20. A cooling system as claimed in claim 19 wherein the or each portion of the cylinder requiring supplementary cooling is a valve bridge joining two exhaust valve supports.

21. A cooling system as claimed in any of claims 17 to wherein the cylinder head is connected to a cylinder block of the engine and a portion of the coolant is supplied to cooling passages formed in the cylinder head from the cylinder block.

22. A cooling system as claimed in claim 21 wherein the coolant supplied to the cylinder head from the cylinder block forms a general coolant flow to the cylinder head and the coolant injectors provide at least a directed coolant flow.

23. A coolant injector for supplying coolant to an engine comprising a hollow body defining a flow passage through which coolant can flow, the hollow body having a convergent nozzle portion at one end to provide a jet of coolant and one or more apertures formed so as to permit coolant to escape from the hollow body in a different direction to the direction in which coolant flows from the nozzle portion.

- 38 - 24. A coolant injector as claimed in claim 23 wherein the cross-sectional area of the hollow body is larger than the cross-sectional area of the nozzle portion at the position where the jet issues from the nozzle portion.

25. A coolant injector as claimed in claim 23 or in claim 24 wherein the coolant exits the or each aperture substantially at 90 degrees to the direction of flow from the nozzle portion.

26. A coolant injector as claimed in any of claims 23 to 25 wherein there are two apertures formed in the hollow body on opposite sides of the hollow body.

27. A coolant injector as claimed in any of claims 23 to 26 wherein the hollow body is cylindrical.

28. A method for cooling an engine comprising providing a source of coolant to cool the engine using a pump to circulate the coolant through a cooling circuit, providing a first directed flow of coolant to cool specific regions of the engine and providing a second general flow of coolant to cool the remaining regions of the engine.

29. A method as claimed in claim 28 wherein the method further comprises using a common coolant injector to supply the first and second coolant flows to the engine.

30. A method as claimed in claim 28 or in claim 29 wherein the specific regions are known hot regions within the engine.

31. A method as claimed in any of claims 28 to 30 wherein the specific regions include inter-bore cooling passages formed in a cylinder block of the engine between adjacent cylinders of the engine.

- 39 - 32. A method as claimed in any of claims 28 to 31 wherein the specific regions include valve bridges formed in a cylinder head of the engine.

33. A method as claimed in any of claims 28 to 32 wherein the method further comprises using the first directed coolant flow to promote circulation of coolant around the cylinders of the engine.

34. A cooling system substantially as described herein with reference to the accompanying drawing.

35. A coolant injector substantially as described herein with reference to the accompanying drawing.

36. A method for cooling an engine substantially as described herein with reference to the accompanying drawing.

Amendments to the claims have been filed as follows -4t0- Claims 1. A cooling system for an engine comprising a cooling circuit through which coolant is circulated by a pump wherein the coolant is supplied to the engine so as to provided a directed flow of coolant and a general flow of coolant within the engine wherein the engine includes a cylinder block defining at least three cylinders, each of the cylinders having a cooling passage encircling at least a part of each cylinder which includes an inter-bore cooling passage located between the cylinder and an adjacent cylinder, a first coolant injector located on one side of the cylinder block aligned with a first inter-bore cooling passage associated with one of the cylinders and a second coolant injector located on an opposite side of the cylinder block aligned with a second inter-bore cooling passage associated with the same cylinder so as to promote the circulation of coolant flow around the respective cylinder.

2. A cooling system as claimed in claim 1 wherein there are several coolant injectors on one side of the cylinder block at least some of which are aligned with first inter-bore cooling passages associated with some of the cylinders of the engine and there are several coolant injectors on the opposite side of the cylinder block at least some of which are aligned with second inter-bore cooling passages associated with the same cylinders of the engine so as to promote the circulation of coolant around the cylinders of the engine.

3. A cooling system as claimed in claim 1 or in claim 2 wherein the or all of the coolant injectors on one side of the cylinder block are located on a first common plane and the or all of the coolant injectors on the opposite side of the cylinder block are located on a second common plane that is offset with respect to the first common plane. -4)-

4. A cooling system as claimed in claim 13 wherein the first coi-nrnon plane is located towards a lower end of the inter-bore cooling passages and the second common plane is located towards an upper end of the interbore cooling passages.

5. A cooling system as claimed in claim 4 wherein the second common plane is located at a position where it will maximise circulatory flow through the inter-bore regions.

6. A cooling system as claimed in any of claims 1 to wherein there is a least one coolant injector positioned so as to promote the flow of coolant through an end cooling passage defined between a respective cylinder and an end wall of the cylinder block.

7. A cooling system as claimed in any of claims 1 to 6 wherein each of the coolant injectors includes a convergent nozzle portion to provide a directed flow of coolant and one or more outlets arranged to permit coolant to flow in a different direction to the direction of coolant flow through the nozzle portion so as to provide a general flow of coolant to the engine.

8. A cooling system as claimed in any of claims 1 to 7 wherein the engine further comprises a cylinder head and a least a portion of the coolant supplied to the cylinder head is supplied through a separate supply line to one or more coolant injectors each of which provides a flow of coolant which is directed towards a portion of the cylinder head requiring supplementary cooling.

9. A cooling system as claimed in claim 8 wherein the cylinder head is connected to the cylinder block of the engine and a portion of the coolant is supplied to cooling passages formed in the cylinder head from the cooling passages in the cylinder block such that the coolant supplied to the cylinder head from the cylinder block forms a general coolant flow to the cylinder head and the coolant supplied from the coolant injectors provide a directed coolant flow.

10. A cooling system as claimed in claim 8 or in claim 9 wherein the or each portion of the cylinder head requiring supplementary cooling comprises one of a portion of the cylinder head in close proximity to one or more exhaust valves supported by the cylinder head, at least one support for a fuel injector and a valve bridge joining two exhaust valve supports.