GB2423572A

GB2423572A - IC engine cooling system

Info

Publication number: GB2423572A
Application number: GB0526195A
Authority: GB
Inventors: Timothy Bishop
Original assignee: Connaught Motor Co Ltd
Current assignee: Connaught Motor Co Ltd
Priority date: 2004-12-22
Filing date: 2005-12-22
Publication date: 2006-08-30
Anticipated expiration: 2025-12-22
Also published as: GB0526195D0; GB2423572B; GB2421547A; GB0428089D0; GB0526196D0

Abstract

An internal combustion engine has valves for selectively restricting fluid circulation through one of the two regions. The regions are the head 104 and block 102, which may be supplied by a pump 118 and reservoir 138, with flow in vertical risers being through valves 152. The valves may be spring loaded to stay closed at a low pump power, but open at a high pump power, or the valves my be electromagnetic. In an embodiment the pump 118 is electrically driven in response to thermistors 144,145, and may receive pulse-width modulated signals, or no signal when the engine temperature is low. Also claimed and described are an engine with coolant channels in the block parallel to the top face and riser channels in the head parallel to the central axis; and an engine with the reservoir 138 disposed to define a maximum coolant level in the engine when the cooling system is inactive (e.g. with the head 104 dry and coolant drained to the lowest areas of the system). Stud bores may be used as the risers.

Description

3071 56.GB

INTERNAL COMBUSTION ENGINE COOLING

The present invention relates to an engine having a cooling system which can operate in various modes to cool various regions of the engine. The invention also relates to an arrangement of cooling channels in an engine and an arrangement of a cooling system in an engine.

Conventional internal combustion engine cooling is achieved by a mechanical fluid pump feeding cooled fluid into the cylinder block and thence through the cylinder head to return to the radiator A thermostat is incorporated somewhere in the system. Thus cooling of the cylinder block and the cylinder head is carried out using a single coolant circuit.

There are fuel economy gains and an improvement in emissions levels to be made by separating the cooling of some regions of the engine from other regions and sometimes temporarily removing the coolant altogether from particular regions of the engine. For example, it would be beneficial to separate the block cooling from the head cooling. In particular, from cold start it is important to cause the engine to warm up rapidly. Therefore, ideally, no coolant would be supplied to the cylinder block or head or both at start-up until after the engine had been running for long enough that the critical components had warmed up to operating temperature. Air-cooled engines suffer bore wear at one-tenth of the rate of liquid-cooled engines entirely because the bores warm up faster, as well as having relatively better fuel economy and lower emissions levels at start-up. The cylinder head, however, requires cooling (particularly near the exhaust ports) even before the block has reached operating temperature, although it would be beneficial to run the engine for some time after start-up without cooling the cylinder head. Due to the high temperatures involved in the combustion process, noise and packaging issues, there are practical problems with air cooling, therefore liquid coolants are used for most applications.

3071 56.GB Thus with a liquid-cooled engine it would be preferable to split the cooling into two circuits, one for cooling the block and one for cooling the head, and to have separate control of the circuits. Prior art systems that have attempted this are complicated and/or expensive. Examples include spray cooling on to certain zones of the engine and nuclear boiling. One reason for this is that conventional engines have a coolant system which uses a pump forming part of the engine and which is run directly by the engine. In a conventional engine it is not possible to run the engine without running the pump because the two are intrinsically linked by a fixed drive, usually a belt. Consequently there can be no time at start-up when coolant is not supplied to the engine, hence the coolant fluid prevents fast warm-up of the engine. Another reason is the arrangement of coolant channels within the engine.

Therefore there is a need for an engine in which cooling of various regions of the engine can be controlled separately and in which in certain circumstances cooling can be avoided.

According to a first aspect of the present invention there is provided an engine comprising an engine block having first and second regions and a cooling system defining a circuit for coolant fluid, the circuit passing through the first and second regions and the engine comprising restriction means for selectively restricting circulation of coolant fluid through the first region.

According to a second aspect of the present invention, there is provided an engine comprising first and second regions and a cooling system, wherein the cooling system is controllable to operate in any of the following operating modes when the engine is running: (i) cooling of the first region alone; (ii) cooling of both regions simultaneously; (iii) no cooling action.

According to a third aspect of the present invention, there is provided an engine comprising. a cylinder block having a central axis and a top face substantially 3071 56.GB perpendicular to the central axis; and a cylinder head disposed on the top face of the cylinder block, wherein the cylinder block comprises one or more coolant channels for transporting coolant around the block, the coolant channels running in a direction generally parallel to the top face, and the cylinder head comprises one or more riser channels connected to the coolant channels and extending substantially parallel to the central axis According to a fourth aspect of the present invention, there is provided an engine comprising: a cylinder block having a central axis, a top face substantially perpendicular to the central axis and at least one channel in which coolant can flow to cool the cylinder block; a cylinder head disposed on the top face of the cylinder block and having at least one channel in which coolant can flow to cool the cylinder head; and a cooling system comprising a reservoir for holding coolant and from which coolant can be supplied to the channels of the cylinder block and cylinder head, the reservoir being disposed such that in use it defines a maximum coolant level in the engine when the cooling system is inactive.

Further preferred features of the invention are set out in the accompanying claims The invention will now be described, by way of example only, with reference to the accompanying drawings in which Figure 1 is a schematic view of part of an internal combustion engine of the prior art including its coolant circuit; Figure 2 is a simplified schematic view of part of an internal combustion engine and coolant system in accordance with the invention; 3071 56.GB Figure 3 is a simplified schematic view of a cross-section through the engine of figure 2; Figures 4 and 5 are a partial schematic views of an internal combustion and coolant system in accordance with the invention; and Figure 6 shows the flow paths in an example engine block.

Figure 1 shows, in accordance with the prior art, part of an engine 1. The engine has a cylinder block 2, and a cylinder head 4 disposed on the block 2. The block 2 and head 4 has four bores (although there could, of course, be any number) spaced along its length machined from top to bottom in the figure, in which cylinders run and combustion takes place. These are labelled with reference numerals 6, 7, 8, 9 from left to right in the figure and they are sized such that each bore extends across a substantial part of the width of the head 4, and the four bores together extend along a substantial part of the length of the head 4. In practice the top of the head 4 includes an intricately-shaped combustion chamber at the top of each of the bores 6-9, including finish-machined holes for inlet and exhaust valves and fuel injectors. The bores would not be visible from the top as shown because they would be obscured by the valve train and a cover. However, these components are anyway omitted in the figure for clarity, although the position of the inlet and exhaust valves is shown by four circles 10 on the bore 6.

Also visible on the cylinder head are much smaller bored holes 12 and 14 The holes 12 are for coolant to cool the cylinder head Their exact position can be varied from engine to engine, but it is particularly important to provide coolant in the region of the exhaust valves as exhaust gases reach extremely high temperatures and therefore some protection from overheating is required for the valves and cylinder head in that region. The coolant used is fluid-based. The holes 14 are for oil, and their exact position is chosen to ensure lubrication of 3071 56.GB other components, however it is important that no oil is present in the combustion chamber.

Although not shown in the figure, the bores 6-9 run downwards through the head 4 where they meet similar bores in the block 2. . Also the bores can be confined to the cylinder block 2 with the combustion chamber is confined to the head. In each of the bores 6-9 runs a piston, the bottom of which attaches to a connecting rod, which in turn is attached to a crankshaft running along the lower end of the block 2 (left to right in the figure). One end of the crankshaft is shown labelled with reference numeral 16. A fluid pump 18 is incorporated in the block 2 and is disposed such that it is powered directly from the crankshaft 16 by means of a belt that also runs around the crankshaft 16. The belt 20 is shown schematically in the figure connecting the fluid pump 18 and the crankshaft 16, but in practice it could drive additional components too. Thus the fluid pump 18 operates to pump coolant around the entire engine from start-up. It can be seen in figure 1 that the coolant holes 12 extend downwards through the head 4 and the block 2 such that coolant can be pumped through them from the fluid pump 18. The front holes only are shown with dotted lines. The holes 12 are on a single circuit fed by chilled coolant from the pump 18. Coolant exits the pump 18 at the point labelled 22 (the right hand end of the pump in the figure), is pumped along the block 2 and up through all the bores in parallel, past all the combustion chambers, along the upper region of the head 4 and exits the cylinder head at a point 24 towards the top of the head 4. The circuit is a closed circuit and prior to start-up the static coolant level is towards the top of the head 4. In operation, the exit temperature is measured by a thermistor circuit 26, and the hot coolant is then passed through a radiator (heat exchanger) 28 and then back to the pump 18. The operation of the radiator 28 is controlled in dependence on the measured coolant temperature by use of a thermostat (electrically enhanced or otherwise).

The actual position of the components can vary in practice from that shown in the figure. For example; within the cylinder block roughly around the top 30% has 3071 56.GB fluid channelling, and this would be by an open area roughly around the top 50% of the bores. The top area of the block is either open (where the whole area of fluid way is open to the underneath of the head) or closed (where the connection is made via holes in the top surface of the block). The head has the combustion chambers in it, and not any part of the bore. In this arrangement the pump releases fluid into the open area within the block and the fluid is forced upward through the head to the exit.

It can be understood from figure 1 that block and head cooling is achieved by use of a single coolant circuit and that consequently it is not possible to cool the block and the head at different rates. It is also not possible to run the engine without pumping coolant around it, although the thermostat generally switches out the radiator, leaving the coolant to recycle around the engine until such time it gets hot enough to be released.

Figures 2 and 3 illustrate one arrangement for cooling, in which the cylinder head and cylinder block are cooled in series. Figures 4 and 5 illustrate an alternative embodiment in which the cooling paths for the head and the block are in parallel.

The embodiment of figures 4 and 5 has the advantage that different cooling rates can more readily be applied to the head and the block.

In another example the pump exit is split within the block 2. The fluid flows down the longitudinal channel and some flows through the vertical slots and around the bores. This coolant rises through the engine via the stud-bores. The majority of the fluid flows vertically from its block channel directly into the head 4, around the valves and combustion chamber and upward to the point where it meets the block coolant exiting the stud-bores and leaves the head at the highest point. The stud- bores may be controlled by valves, for example a simple spring loaded valve may suffice to adjust the flow between the head and the block.

3071 56.GB In the case of downwards draining cooling, the pump will be feeding the block in the conventional manner and will be drawing fluid from the base of the reservoir.

The top of the reservoir will be level with the base of the cylinder head. Thus the fluid will flow from the pump into the block, rise by whatever route to the highest point, spill over the "weir" which may in fact have to be a differential pressure valve, and return to the reservoir via the radiator.

Turning now to figure 2, part of an engine 100 embodying the invention is shown The engine 100 has a cylinder block 102 and a cylinder head 104. There are four bores 106, 107, 108, 109 machined through the block 102 and the head 104 in a similar manner to those of the engine 1. Although a set of holes 112 can be seen in the top of the head 102 in a similar position to the holes 12 of the engine 1, the extension of these holes into the head 102 differs. The cooling system of the engine 100 will now be described.

A fluid pump 118 is provided as a stand-alone electric fluid pump. The system can work with a conventional mechanical fluid pump and strategically placed thermostat but improved control by use of a standalone pump makes this a preferred embodiment as the pump can be controlled independently of the engine 100.

Other components of the cooling system are a reservoir 138 connected to the entry to the pump 118, the reservoir being used for feeding coolant into the engine as will be described below There is a weir 140 at a position higher than the highest point of coolant in the cylinder head which is used to manage overflow of coolant from the engine 100 and which connects to a radiator 128. The return from the radiator feeds back into the reservoir, transpose reservoir and pump.

There is also a thermistor circuit 142 including thermistors 144 and 145, this circuit being used to control the pump 118 as will be described below.

3071 56.GB The pump 118 feeds one or two pairs of channels 130. One channel of a pair runs along the length of the cylinder block 102 at the front, and the other at the back. Two channels 130 are shown running in parallel along the front of the block 102; the equivalent other channels of the pairs are also present in the rear of the block 102. In fact the channels can be positioned wherever is most appropriate for the engine design.

In one example of a configuration for the channels 130, they could be shaped strategically to allow intimate coolant access around the cylinders. An example of such a configuration is shown in figure 3, which is a cross-sectional view through the block 102 at the level of one of the pairs of channels 130. In this example the channels 130 become wider in between cylinders so that coolant can be transported closer to the centre (widthwise) of the block 102. Another example configuration is illustrated in figures 4 and 5 and will be described below.

Turning back to figure 2, it can be seen that in this example the upper pair of the two pairs of channels 130 has a number of vertical channels 132 emanating from it, which extend to the top face of the block 102 where they connect into strategically placed drillings 134 (risers) in the cylinder head 104. Thus coolant can flow upwards from the block 102 into the cylinder head 104. The risers 134 are located in the head 104 such that coolant flows directly up and around the combustion chamber jackets. In the embodiment stud bores (the bore holes through the cylinder head that accommodate the threaded studs that attach the head to the block) are used as the risers. There are eight risers, two spaced around each of the bores 106-109. The risers 134 extend near to the top of the head 104, where they feed into a manifold 136. The manifold 136 connects back to the radiator 128 (via the weir 140) such that hot coolant from the cylinder head returns to the radiator 128.

In order to operate the cooling system effectively, the coolant reservoir 138 is provided externally to the engine 100 (similar to a radiator header tank). The 3071 56.GB reservoir 138 has an input connection 146 from the pump 118 at its base (left- hand side in the figure) and two output connections at its top (right- hand or engine side in the figure). A first output connection 148 feeds into the block 102 and is split to feed into the two pairs of channels 130. A second output connection 150 feeds into the bottom of the head 104. Thus it can be understood that the block 102 and the head 104 can be separately supplied with coolant. However, without control coolant flows from the block 102 upwards into the risers 134 as previously described, thus cooling the block 102 and the head 104 simultaneously. This is desirable if the entire engine 100 is to be cooled. However, the case in which it is desired only to cool the head 104 and not the block 102 will now be described.

The top of the reservoir 138 is substantially level with the base of the cylinder head 104. or it could be mounted even lower, allowing both block and head to be "dry" until pump run. Thus it is lower than the coolant channels within the head 104. The coolant system is designed such that it can only be filled to the maximum reservoir level, but the reservoir 138 has sufficient capacity to fill the head coolant channels above it upon request from the pump 118.

Thus, with the pump 118 turned off, coolant settles to the level of the top of the reservoir 138, leaving the head 102 "dry" and ready for near instant warm-up.

Although there is coolant present in the block 102 since it is below the top of the reservoir 138, the coolant is not being pumped or cooled and therefore has minimal cooling impact. From engine start-up, the thermistor circuit 142 operates to control the pump 118. Temperature readings are taken by thermistors 144 situated near the combustion chamber in the cylinder head 104 and thermistors situated in the region of the bores in the block 102. Only two thermistors 144 and two thermistors 145 are shown in the figure. It would be possible to use one only in the head, but if it failed then full cooling would have to be instigated as default. So it is preferred to have two thermistors monitoring temperatures in the combustion zone and two monitoring temperatures in the block (although these would normally be needed principally for high-speed monitoring rather than low- 3071 56.GB speed due to the complex thermal map of an IC engine). The thermistor readings are received and processed by the thermistor circuit 142 so that temperatures in the block 102 and head 104 are monitored.

After start-up, the head 104 will warm up more quickly than the block 102 because of the combustion process. At the appropriate time after starting the engine 100, temperature monitoring by readings from the thermistors 144 indicate that the head 104 has reached a temperature at which cooling is required. This temperature is predetermined based on experience of engine running and cooling requirements. Therefore, the thermistor circuit 142 sends an instruction to the pump 118 to switch on at a first power level to pump coolant into the head 104 via the input connection 150, and fill the upper reaches of the engine 100 by drawing fluid from the base of the reservoir 138. Thus the head 104 is filled to the highest point of the engine, thereby cooling the head 104 including around the combustion chambers Hot coolant flows from the top of the head 104 into the manifold 136 and onto the weir 140. Thus excess coolant is allowed to spill over, to flow through the radiator 128 and back to the reservoir 138.

During the above-described process, the pumping action of the pump 118 does also initially cause a pumping effect on coolant into the block 102 through the input connection 148. However, there is provided a springloaded valve cap 152 at the top of each vertical channel 132. At the first power level (i.e. below a given fluid flow-rate) of the pump 118 the fluid pressure is insufficient to open valve caps 152. Therefore there is no flow circuit through or out of the block 102 because there is nowhere for the coolant to go to. Thus the block 102 is effectively sealed from the head 104 whilst the head cooling continues to flow. There is, however, a general thermo-syphon action of coolant around the block which balances its own internal temperatures and stresses After a further time, temperature monitoring from the thermistors 145 indicates that the block 102 has reached a temperature at which cooling is required. Again, 3071 56.GB -Il - this temperature is predetermined based on experience of the cooling requirements of engines and perhaps the specific engine in use. At this point, the thermistor circuit 142 sends a signal to the pump 118 to increase its power to a second, higher power level. The pump could operate at effectively variable power levels by being signalled to operate at variable levels or by pulse-width modulation. This increases the fluid pressure sufficiently to lift the spring caps 152 from their seats, thereby enabling coolant to flow upwards through the vertical channels 132 and into the risers 134, thus allowing block cooling flow as a percentage of the total flow. Coolant still continues to flow directly into the head 104 as well, as it flows through both the connections 148 and 150. The spring caps are basically designed such that they lift from their seats at a fluid pressure which allows a desired percentage of flow through the block 102.

In order to avoid aeration the system is preferably designed as a closed system to run under differential pressure rather than atmospheric pressure by the use of appropriate valves and/or controls.

It can now be understood that none of the engine or only the cylinder head or the whole engine can be cooled as appropriate in dependence on the measured temperatures.

The "rail" design of the block cooling channels 130 is used to a further advantage.

There can be seen in figure 2 two further channels 154, each disposed adjacent to a coolant channel 130 such that it runs around the block 102 directly below its respective coolant channel 130. The channels 154 are used for pumping oil around the engine 100. The entire oil flow is pumped the length of the block 102 and back again in the channel 154. Thus significant heat transfer is obtained in either direction, warm coolant to cold oil and hot oil to warm coolant.

Frictional losses are reduced and external oil coolers and pipe-work eliminated or reduced.

307156GB - 12- Any suitable liquid coolant could be used. Examples include fluid, oil and glycol.

Different coolants could be used for the block and the head. for instance oil could be used for the block and fluid for the head.

Figures 4 and 5 show in more detail one configuration for the coolant channels in part of a V-design internal combustion engine. The figures show one cylinder 160, the oil supply channel 161 and the fluid channels for coolant. The coolant is introduced through a rail 162 which interconnects the cooling channels for all the cylinders. From the rail 162 coolant flows to a cavity 163 at the cylinder head, and from there up a channel 164 to a collector 165. From the rail 162 the coolant can also flow to a jacket 166 that surrounds the cylinder, and from there up the stud bore 167 to the exit manifold. From the exit manifold the coolant can flow over a weir to the radiator. In accordance with the principles described above, the relative flow to the cavity 163 and the jacket 166 can be controlled to achieve improved performance.

So, block coolant flows horizontally from the rail 162 and through cutouts into the cavity 163 near the cylinder head and the jacket 166 around the cylinder. It then passes upwards through channels 164, 167 to the top of the engine. In this example, the flow path for the cylinder head coolant is in parallel with the flow path for the cylinder block coolant The stud bore 167 is enclosed at the top by a valve which can be spring loaded or otherwise controlled Only when this valve is opened can the coolant flow onwards to the collector 165 allowing the two flows to be reunited When the engine and pump are turned off the coolant in the system drains down to a reservoir level around the bottom of the rail 162. When the engine is turned on and warms up the pump begins to run, gently at first, and the flow of coolant initiates through the hottest parts such as the cavity 163 As more heat is 307156 GB produced by the engine more coolant is caused to flow around the system. The valve at the top of the stud bore 167 then opens to allow the block coolant to flow It will be appreciated by those skilled in the art that modifications can be made to the embodiment described above without departing from the scope of the invention. For example, as an alternative to the spring caps 152 the manifold 136 could have an electronically or thermostatically controlled valve that modulates the flow differential between block and head. The arrangement of channels and risers could be varied to distribute coolant to particular areas of the engine as desired, and in particular more or less channels and risers could be used. The split of coolant flow does not have to be exactly block-head, but could be split across other regions of the engine depending on the cooling needs of a particular engine. The level of the reservoir could also be varied to achieve a different static coolant level.

When the flow of coolant through a part of the coolant circuit is stopped, for example when a valve is closed between the rail so that coolant cannot flow from the rail 162 to the jacket 166, there could still be convective circulation of fluid within the jacket 166. Furthermore, whether the valves are open or not, there could be convective flow through the cooling circuit itself without the pump operating.

The control regime is preferably arranged to avoid over-cooling of the head. This could occur if after the engine has been run for an extended period of time the head is cooler than the block due to ever-rising oil temperature due to friction and the slow leaching of heat into the cylinder liners through piston crown temperature. There is therefore a scenario to be avoided in which the block temperature sensor becomes the controlling sensor, possibly resulting in over- cooling of the head.

3071 56.GB - 14 - Figure 6 shows an example of an engine block in which the invention can be implemented. An unrestricted flow path extends from the inlet, around the region in the immediate vicinity of the cylinders' heads and back to the outlet. A second flow path extends around another region of the engine, including the zone below the cylinder head region and also including the upper part of the head section of the block. The second flow path can be restricted by a controllable flow restrictor.

The flow restrictor operates so as lo limit flow in the second circuit when the engine is warming up. To achieve this the flow restrictor could be a temperature- sensitive valve, or it could operate under the control of a remote temperature sensor. In this figure reference 50 denotes an oil gallery located adjacent to the water flow to promote heat transfer between the two. This oil gallery is located immediately below the water gallery.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

3071 56.GB - 15- CLAIMS

1. An engine comprising an engine block having first and second regions and a cooling system defining a circuit for coolant fluid, the circuit passing through the first and second regions and the engine comprising restriction means for selectively restricting circulation of coolant fluid through the first region.

2. An engine as claimed in claim 1, wherein the engine is capable of operating in a first mode in which coolant fluid can circulate through the first region but not through the second region whilst the engine is running.

3 An engine as claimed in claim 1 or 2, wherein the engine is capable of operating in a second mode in which coolant fluid can circulate through both regions simultaneously whilst the engine is running.

4. An engine as claimed in any preceding claim, wherein the engine comprises means for preventing flow of coolant fluid to both the first and second regions whist the engine is running, and the engine is capable of operating in a third mode in which coolant fluid can circulate through neither of the first and second regions whist the engine is running.

5. An engine according to any preceding claim, wherein the restriction means is operable in dependence on sensed temperature.

6. An engine according to claim 5, wherein the restriction means is arranged such that if the temperature of the first region is sensed to be below a first predetermined temperature, and the temperature of the second region is sensed to be above a second predetermined temperature, flow of coolant fluid to the first region is relatively restricted.

3071 56.GB - 16-

7. An engine according to claim 5 or 6, wherein the restriction means is arranged such that if the temperature of the first region is sensed to be above the first predetermined temperature, and the temperature of the second region is sensed to be above the second predetermined temperature, flow of coolant fluid to the second region is relatively unrestricted.

8. An engine according to any of claims 5 to 7 as dependent on claim 4, wherein if the temperature of the first region is below the first predetermined temperature, and the temperature of the second region is below the second predetermined temperature, the cooling system is arranged to operate in the third mode.

9. An engine according to any preceding claim, wherein the cooling system comprises means for measuring the temperatures of the first and second regions.

An engine according to claim 9, wherein the cooling system further comprises one or more measuring devices in each of the first and second regions and a controller arranged to interpret temperature measurements received from the measuring devices to determine whether the first region is above or below the first predetermined temperature and to determine whether the second region is above or below the second predetermined temperature.

11. An engine according to claim 4 as dependent on claims 2 and 3, wherein the cooling system comprises a pump arranged to pump coolant to the first and second regions and which pump is controllable to operate at a first power level when the cooling system is operating in the first mode, to operate at a second, higher power level when the cooling system is operating in the second mode and to be inoperable when the cooling system is operating in the third mode.

3071 56.GB

12. An engine according to claim 11, as dependent on claim 10, wherein the controller is further arranged to control the power level of the pump in dependence on the interpreted temperature measurements.

13. An engine according to claim 11 or claim 12, wherein the cooling system is arranged such that at the first power level, the pump operates to supply coolant only to the second region and at the second power level the pump operates to supply coolant to both the first and second regions

14. An engine according to any preceding claim, wherein cooling of the second region is carried out using a first channel configuration in the second region arranged to allow coolant to flow into, through and out of the second region substantially independently of coolant flow in the first region, and wherein cooling of the first region is carried out using a second channel configuration in the first region arranged to allow coolant to flow into and through the first region but to only allow coolant to flow out of the first region through the second region.

15. An engine according to claim 14 as dependent on claims 2 and 3, arranged such that the first and second channel configurations are separated when the cooling system is operating in the first mode, and are interconnected when the cooling system is operating in the second mode.

16. An engine according to claim 15 as dependent on claim 4, wherein the first and second channel configurations are further separated when the cooling system is operating in the third mode

17. An engine according to claim 15 or claim 16, wherein the first and second channel configurations are separated by mechanical means which are activatable in dependence on the operating mode of the cooling system to separate or allow interconnection of the first and second channel configurations and to thereby vary the relative cooling in the first and second regions.

3071 56.GB

18 An engine according to claim 17, wherein the mechanical means are spring- loaded valves which are activatable to move in dependence on coolant pressure and to thereby separate or not separate the first and second regions.

19. An engine according to claim 15 or claim 16, wherein the relative cooling in the first and second regions is controllably variable by means of one of electronic control and thermostatic control to thereby vary the relative coolant flow rates in the first and second channel configurations.

20. An engine according to any preceding claim, wherein in use the second region is disposed above the first region

21. An engine according to claim 20 as dependent on claim 4, wherein the cooling system further comprises a coolant supply reservoir, the reservoir defining a maximum coolant level in the engine when the cooling system is operating in the third mode and being disposed in use below the first region to thereby substantially eliminate coolant from the first region when the cooling system is operating in the third mode

22. An engine according to any of claims 11 to 21, wherein the pump is stand- alone with respect to the engine

23. An engine according to any preceding claim, wherein the cooling system comprises a radiator for cooling hot coolant from the first and second regions.

24. An engine according to any preceding claim, wherein the second region is a combustion region in which fuel combustion takes place.

3071 56.GB - 19-

25. An engine according to claim 24, wherein the first region is an energy transfer region in which energy produced by the fuel combustion is mechanically transferred.

26. An engine according to claim 25, wherein the energy transfer region is disposed adjacent to the combustion region.

27. An engine according to any of claims 24 to 25, wherein the combustion region comprises a cylinder head.

28. An engine according to claim 27 as dependent on claim 14, wherein the cylinder head comprises at least one channel disposed substantially vertically in use into which coolant can flow from the energy transfer region.

29. An engine according to any of claims 25 to 28, wherein the energy transfer region comprises a cylinder block.

30. An engine according to claim 29 as dependent on claim 14, wherein the cylinder block comprises one or more channels disposed substantially horizontally in use.

31. An engine according to claim 30, wherein the said channels are shaped to facilitate cooling of the cylinders.

32 An engine according to claim 30 or claim 31, wherein the cylinder block further comprises one or more further channels emanating from at least one of the substantially horizontal channels and disposed substantially vertically in use, from which channels coolant can flow out of the cylinder block.

3071 56.GB - 20 -

33. An engine according to claim 32, wherein each substantially vertical channel in the cylinder block is substantially aligned with a respective substantially vertical channel in the cylinder head

34 An engine according to any of claims 30 to 33, wherein the cylinder block further comprises channels through which oil can flow, these oil channels being disposed adjacent to the substantially horizontal coolant channels thus facilitating mutual heat transfer between fluids in the oil and coolant channels.

35. An engine substantially as herein described with reference to figures 2 and 3 of the accompanying drawings.

36. An engine comprising: a cylinder block having a central axis and a top face substantially perpendicular to the central axis; and a cylinder head disposed on the top face of the cylinder block, wherein the cylinder block comprises one or more coolant channels for transporting coolant around the block, the coolant channels running in a direction generally parallel to the top face, and the cylinder head comprises one or more riser channels connected to the coolant channels and extending substantially parallel to the central axis

37. An engine according to claim 36, wherein the coolant channels are shaped to facilitate cooling of the cylinders.

38. An engine comprising: a cylinder block having a central axis, a top face perpendicular to the central axis and at least one channel in which coolant can flow to cool the cylinder block, a cylinder head disposed on the top face of the cylinder block and having at least one channel in which coolant can flow to cool the cylinder head; and 3071 56.GB - 21 - a cooling system comprising a reservoir for holding coolant and from which coolant can be supplied to the channels of the cylinder block and cylinder head, the reservoir being disposed such that in use it defines a maximum coolant level in the engine when the cooling system is inactive.

39. An engine according to claim 38, wherein the reservoir has an upper surface defining the maximum coolant level in the reservoir and the upper surface is disposed substantially level with the top face of the cylinder block and substantially parallel thereto.