GB2360838A

GB2360838A - An expansion tank for an engine cooling system

Info

Publication number: GB2360838A
Application number: GB0007699A
Authority: GB
Inventors: William Richard Hutchins
Original assignee: Bayerische Motoren Werke AG; MG Rover Group Ltd
Current assignee: Bayerische Motoren Werke AG; MG Rover Group Ltd
Priority date: 2000-03-31
Filing date: 2000-03-31
Publication date: 2001-10-03
Anticipated expiration: 2020-03-31
Also published as: GB0007699D0; GB2360838B

Abstract

An expansion tank for an engine cooling system comprises a housing 24 defining an enclosed chamber 25 and having a coolant inlet connection 35 for coolant discharged from the engine, a coolant collector 41 and a coolant outlet connection 37. The coolant inlet 35 may direct the coolant tangentially towards a wall of the housing 24 to help trapped air and vapour to escape from the coolant. The collector 41 may comprise a gutter arranged on the housing wall below the stream of incoming coolant from the inlet 35 and a funnel 43 may then direct the coolant from the gutter 41 to the outlet 37. One side of the gutter 41 may have a weir (51) which extends to a height which is less that of the walls of the gutter 41 and the walls of the funnel 43. At low coolant flow rates all the coolant collected in the gutter 41 flows in to the funnel 43 and is delivered back to the engine without substantial mixing with a mass of coolant in the chamber 25. At higher coolant flow rates, coolant spills over the weir (51) to mix with the main body of coolant in the chamber 25. This flow of coolant returns to the engine through the outlet connection 37 by way of an outlet 38.

Description

2360838 Cooling System Expansion Tank This invention relates to expansion

tanks for the cooling systems of liquid cooled internal combustion engines.

A typical cooling system expansion tank is a closed vessel which, when the engine is at rest, is only partially filled with liquid coolant, the remainder of the space above the liquid being available for the volumetric expansion of the coolant due to heat. Coolant discharged from the engine flows into the tank above the level of liquid coolant and returns from the bottom of the tank to join the flow of coolant returned to the engine. Such an expansion tank also serves as a means of enabling gasses dissolved or trapped in the coolant to rise to the liquid surface and escape. Furthermore, air above the liquid surface becomes heated by the incoming coolant, thereby further helping to pressurise the cooling system and prevent cavitation in a circulation pump.

One problem in the design of such expansion tanks is that at low pump flows, particularly when the engine is cold,. it is undesirable that heat be lost from the liquid coolant into the mass of coolant already in the tank and it is an object of the invention to provide an expansion tank for the cooling system of a liquid cooled internal combustion engine which can provide a more direct path for coolant from an inlet to the outlet of the tank.

According to the present invention there is provided an expansion tank for the cooling system of a liquid-cooled internal combustion engine, the tank comprising a housing forming an enclosed chamber, an inlet connection on the housing for connection to a supply of coolant discharged from the engine and an outlet connection on the housing for the return of coolant to the engine, the inlet connection discharging into an inlet orifice located at or towards the top of the chamber and the outlet connection connecting to a main outlet located at or towards the bottom of the chamber, wherein a coRector is arranged in the housing to collect coolant discharged from the inlet orifice to duct the collected coolant into the outlet connection and discharge it through a collector outlet adjacent the main outlet such that coolant flowing from the collector outlet can exit from the outlet 5 connection with little or no mixing with coolant in the chamber.

The inlet orifice may be arranged to direct incoming coolant onto a deflector, the deflector preferably being at an oblique angle to incoming coolant. The deflector is preferably concave and may comprise a wall portion of the housing. Conveniently, the inlet orifice is arranged so that the flow therefrom is substantially tangential to the adjacent outer wall of the housing.

The collector may comprise a gutter arranged on the housing wall below the stream of incoming coolant, in which case a funnel may be arranged to duct coolant from the gutter into the collector outlet. The gutter may be arranged on both sides of the funnel. At least one side of the gutter may terminate in a weir, in which case an inclined channel may be arranged to collect coolant spilling over the weir and discharge it towards the bottom of the tank. The inclined channel may be on an outer wall of the housing.

Conveniently the funnel extends substantially perpendicularly from the gutter, e.g. towards the main outlet.

Conveniently, the housing comprises two housing portions joined at a substantially horizontal joint face, the inlet connection and the inlet orifice being formed in the upper housing portion and the outlet connection, the collector and the collector outlet being formed in the lower housing portion, in which case the collector may be formed by the outer wall of the lower housing portion and at least one wall extending substantially vertically therefrom.

The gutter may extend circumferentially around at least part of the upper rim of the lower housing portion.

The gutter may have weirs to restrict the flow of coolant along the gutter.

Baffles may be provided in the lower housing portion to restrict the pendulum action of the mass of coolant in the chamber.

Preferably, the housing has a substantially spherical outer wall.

The collector outlet may discharge into the outlet connection downstream of the flow from the main outlet. Alternatively, it may discharge into the camber upstream of the flow into the main outlet. In such an arrangement, the collector outlet may comprises a vertical slit in the or one of the walls of the collector.

The invention will now be described by way of example and with reference to the accompanying drawings, of which:

Fig. 1 is a diagrammatic representation of the cooling system of a liquid cooled internal combustion engine incorporating a first embodiment of an expansion tank according to the invention; Fig.2 is a plan view of the expansion tank shown in Fig.1; Fig. 3 is a section on the line III-III in Fig. 2; Fig.4 is a plan view on arrow B in Fig.3 with the upper portion of the expansion tank housing removed; Fig.5 is a developed cross-section on the line V-V in Fig.4; Fig.6 is perspective view of the lower housing part as seen on the arrow C in Fig.3; Fig.7 is a cross-section on the line VII-VII in Fig.4; Fig.8 is perspective view of a lower housing part of a second embodiment of the invention; Fig.9 is perspective view of a lower housing part of a third embodiment of the invention; and Fig. 10 is a cross-section on the line X-X in Fig.9.

Referring to Fig. 1, an internal combustion engine 11 has a pump 12 which can deliver liquid coolant (e.g., a water/antifreeze mix) through the engine to an engine delivery hose 13 and a heat exchanger in the form of a conventional air cooled radiator 14. Flow from the radiator 14 to the pump 12 is through a radiator return hose 15 and a pump return hose 16. A thermostat and bypass control valve 17 operates to control flow in the radiator return hose 15 and in a bypass hose 18 such that until the coolant reaches higher temperatures most of the flow of coolant from the engine 11 is through the bypass hose 18 and there is no flow through the radiator 14. At higher coolant temperatures, most of the flow is through the radiator 14 and not through the bypass hose 18. An expansion tank 21 has a tank feed hose 22 connected to the engine delivery hose 13 and a tank return hose 23 connected to the pump return hose 16. A heater matrix 19 for the heating the vehicle passenger compartment is also connected between the engine delivery hose 13 and the pump return hose.

With further reference to Figs.2 to 7, it can be seen that the expansion tank 21 comprises a housing 24 forming an enclosed chamber 25. The housing 24 is generally spherical in shape, being formed by upper and lower moulded portions 26, 27 joined at a substantially horizontal equatorial joint face 28. The housing 24 may be conveniently made of engineering plastics material, e.g. polyamide, and the equatorial joint may be made by hot plate welding. It may be convenient to form the moulded housing portions 26, 27 together and join these by an integral hinge at an axis depicted by the line X-X in Fig.2. At the equatorial joint face 28, each moulded portion 26, 27 incorporates a small flange 31, 32 to enable jointing pressure t o be applied and these flanges are extended towards the hinge axis X-X to provide a mounting bracket 33.

The upper housing portion 26 incorporates a filler neck 34 for closure by a filler cap (not shown) which incorporates the normal pressure control valve and anti-vacuum valve. The upper housing portion 26 also has an inlet connection 35 for connection to the tank feed hose 22 and this discharges into an inlet orifice 36 located at the top of the chamber 25. - The housing lower portion 27 has an outlet connection 37 for connection to the tank return hose 23 and this connects to a main outlet 38 located at the bottom of the chamber 25.

A collector in the form of a V-section gutter 41 of variable width and depth extends circumferentially around part of the upper rim (i.e. flange 32) of the lower housing portion 27, the gutter being formed by a substantially vertical wall 42 and the adjacent housing outer wall, the wall 42 extending inwardly into the chamber to a height substantially equal to that of the joint face 28 and chordally of the flange, as can be best seen from Fig.4. The gutter 41 is intersected substantially perpendicularly by a funnel 43 which extends towards the main outlet 38 and which is formed by two generally radial walls 44 and 45, an end wall 46 and by the adjacent housing outer wall. The walls 44, 45 and 46 extend substantially vertically into the chamber 25 to a height substantially equal to that of the joint face 28. The funnel 43 provides a duct for coolant collected in the gutter 41 to flow into a funnel outlet 47 which connects to the outlet connection 37 adjacent to and downstream of the main outlet 38.

At one end of the gutter 41 there is an upstanding weir 51 which extends to a height which is somewhat less than that of the walls 42, 44, 45 and 46 forming the gutter 41 and the funnel 43. On the far side of the weir 51, i.e. the opposite side to the gutter 41, there is an upstanding arcuate wall 52 which, with the adjacent 5 outer wall of the lower housing portion 27, forms a generally V-shaped inclined channe153.

In use, with a cold engine 11 and cooling system, the level of liquid coolant in the expansion tank 21 will be between the H and L marks shown for reference on Fig. 3, i.e. the chamber 25 will be approximately 40% to 48% full of liquid coolant.

Coolant is pumped by the pump 12 out of the engine 11 into the delivery hose 13 through the tank feed hose 22 and into the expansion tank 21 through the inlet orifice 36. From the inlet orifice 36 the coolan t is directed as a stream onto the adjacent spherical wall surface to be collected in the gutter 41. At relatively low flow rates all the coolant collected in the gutter 41 flows from the gutter 41 into the funnel 43 and is delivered back to the pump 12 through the tank return hose 23 and the pump return hose 16 by way of the outlet connection 37 and the funnel outlet 47. In this way the hot coolant delivered by the engine undergoes no substantial mixing with the mass of liquid coolant in the chamber 25 outside of the funnel 43 and the gutter 41. At higher flow rates, the funnel 43 and the gutter 41 will tend to fill so that liquid coolant spills over the weir 51 and down the inclined channel 53 to mix with the main body of coolant outside of the funnel 43 and gutter 41, this flow of coolant returning to the engine through the outlet connection 37 by way of the main outlet 38, It will be noted that the inlet orifice 36 (and hence the incoming jet of coolant) is tangential to the adjacent spherical wall portion of the housing 24 so that the jet impacts onto the housing wall at an oblique angle and will therefore attach to it.

By minimising the volumetric capacity of the gutter 41 and the funnel 43 and preventing mixing with the main volume of coolant in the chamber 25, the heat lost from the coolant between entering at the inlet connection 35 and exiting at the outlet connection 37 is greatly reduced compared to a conventional expansion tank, particularly in the period immediately following a cold engine start. Hence there can be an improved warm-up of the engine, reducing exhaust emissions and improving heater performance. By directing the incoming stream of coolant over the spherical wall portion adjacent the inlet orifice 36, there is a substantial area of hot coolant exposed to the air in the chamber 25 above the level of coolant enabling this air to expand as a result of heating so that the design pressure of the cooling system can be achieved under normal operating conditions. This is an advantage in helping to avoid cavitation of the pump 12.

It will be appreciated that the gutter 41 and the funnel 43 can be incorporated in the housing lower portion 27 without additional components, the vertical walls 42, 44, 45 and 46 making for relatively simple mould tools. The generally spherical shape of the expansion tank housing 24 is an aid to strength, although other shapes are possible and may be required to suit particular vehicle installations. The incorporation of a generally curved wall portion immediately adjacent the inlet orifice 36 helps to direct the flow of incoming coolant into the gutter 41 and helps to allow the escape of trapped air and vapour. If for any reason such a wall portion cannot be conveniently incorporated into the wall of the housing, a separate deflector may be mounted inside the tank for this purpose.

Instead of being at the very top of the chamber 25, the inlet orifice 36 may be closer to the gutter to reduce the area of housing wall wetted by the incoming stream of coolant. If required, there may be a deflector plate under the inlet orifice to direct any dribbles at very low flow rates directly into the gutter or funnel. The position of the outlet orifice at the bottom of the chamber 25 maximises the reserve volume of coolant in the tank 21 but this may be varied to be slightly above the bottom if manufacturing considerations dictate or to provide a sludge trap.

If required, a weir may be provided at each end of the gutter with an additional inclined channel. The inclined channel 53 helps to further promote the escape of trapped air and vapour under the higher flow conditions so that an additional weir and channel may well be beneficial in this respect, particularly where the inclination of the vehicle can change due to loading and it is subjected to acceleration, deceleration and cornering forces.

In the second embodiment of the invention shown in Fig. 8, parts which are identical to or similar to those shown in Figs.2 to 7 carry the same reference numeral but with the addition of 100. Again, the housing is generally spherical in shape, being formed by an upper moulded portion (not shown) which is substantially identical to the upper moulded portion 26 of the first embodiment and a lower moulded portion 127, these being joined at a substantially horizontal equatorial joint face 128 formed by flange 132.

The housing lower portion 127 has an outlet connection 137 for connection to the tank return hose and this connects to a main outlet 138 located at the bottom of the chamber 125. A V-section gutter 141 of generally constant depth is formed by a vertical wall 142 and the adjacent outer wall of the lower housing portion 127, the wall 142 extending to a height substantially equal to that of the joint face 128.

The gutter 141 extends circumferentially around the upper rim of the lower housing portion 127 and is intersected by a funnel 143 formed by two vertical radial walls 144 and 145, a curved (i.e. part- cylindrical) end wall 146 and by the adjacent housing.outer wall, the walls 144, 145 and 146 extending to a height substantially equal to that of the joint face 128. The funnel 143 provides a duct for coolant collected in the gutter 141 to flow into a funnel outlet 147 which connects to the outlet connection 137 adjacent to and downstream of the main outlet 138. Spaced along the gutter 141 there are four weirs 151A, 151B, 151C, 1511), each of which extends to a height which is somewhat less than that of the gutter wall 142.

In the centre of the lower housing portion 127 there is a float type level sensor assembly 155 for providing a signal which indicates a low level of coolant. On the far side of this from the funnel 143 is an L-shaped baffle 156. Between the L-shaped baffle 156 and the funnel 143 in one circumferential direction there is an S-shaped baffle 158 and opposite this there is a G-shaped baffle 157. Each baffle 156, 157, 158 extends generally vertically to the height of the gutter wall 142 and 10includes a respective generally radial portion 161, 162, 163 which is joined to the gutter wall 142. In the case of baffle 156, the free end of portion 164 is curved inwards towards the funnel 143. Extending chordally from each radial portion 161, 162, 163 is a respective further baffle portion 164, 165, 166. The S-shaped baffle 158 includes a further portion 169 extending perpendicularly of the portion 166 between the portion 164 of the L shaped baffle 156 and the level sensor assembly 155. Similarly, the G-shaped baffle 157 includes a further portion 171 extending directly between the funnel 143 and the level sensor assembly 155 and perpendicularly of the portion 165. A further portion 172 extends perpendicularly of the portion 171 between the portion 166 of the S-shaped baffle 158 and the level sensor assembly 155.

As for the first embodiment, in use with a cold engine and cooling system, the expansion tank will be approximately 40% to 48% full of liquid coolant. Coolant is pumped out of the engine, into the expansion tank through the inlet orifice and is directed as a stream onto the adjacent spherical wall surface to be collected in the gutter 141. At relatively low flow rates all the coolant collected in the gutter 141 flows into the funnel 143 to be delivered back to the pump by way of the outlet connection 137 and the funnel outlet 147. In this way the hot coolant delivered by the engine undergoes no substantial mixing with the mass of liquid coolant in the chamber outside of the funnel 143 and the gutter 141. At higher flow rates, the funnel 143 and the gutter 141 will tend to fill so that liquid coolant spills over the gutter 141 and into the chamber to mix with the main body of coolant in the chamber 125, this flow of coolant returning to the engine through the outlet connection 137 by way of the main outlet 138. The weirs 151A, 151B, 151C and 151D restrict the flow of coolant along and around the gutter, particularly when the expansion tank is installed in a motor vehicle performing extremes of acceleration, braking or cornering. The baffles 156, 157 and 158 act under the same circumstances to help prevent spurious operation of the level sensor 155 by diverting away from it and restricting the pendulum action of the mass of coolant.

In a modification (not shown), the gutter 141 extends only part way in each circumferential direction from the funnel 143, e.g. as far as the first weirs 151A and 15 1D. This arrangement is substantially the same as the first embodiment in that the inlet orifice needs to be arranged so that the flow from it is directed towards the gutter 141.

In the third embodiment of the invention shown in Figs.9 and 10, parts which are identical to or similar to those shown in Fig.8 carry the same reference numeral but with the addition of a further 100. This embodiment is based on the level sensor omitted for clarity. One essential difference is that the outlet connection 237 extends vertically downwards from the centre of the lower housing portion 227 so making the expansion tank more adaptable to different vehicle installations. The other essential difference is that the funnel 243 has a slot 247 in the end wall 246 to form an funnel outlet adjacent the main tank outlet 238.

At the relatively low flow rates previously referred to the coolant collected in the gutter 241 flows into the funnel 243 and out into the chamber in the immediate vicinity of the main outlet 238. Because the expansion tank is sealed, the flow of coolant returned to the outlet connection 237 is equal to the incoming flow from the inlet orifice so that hot coolant flowing from the funnel 143 through the slot 247 is drawn back into the main outlet 238 with a minimum of mixing with the colder coolant in the chamber. At higher flow rates, the funnel 243 and the gutter 241 will tend to fill as before so that liquid coolant spills over the gutter 241 and into the chamber to mix with the main body of coolant outside of the funnel and gutter.

The arrangement shown in Fig. 9 and 10 may not be quite so advantageous as 10 in the first and second embodiments in terms of the extent to which the hot coolant can mix with the cold coolant. However, it is a simpler design to manufacture and retains the advantage if the gutter and funnel promoting the rise of trapped air and vapours so that relatively gas-free coolant passes from the slot 147 to the main outlet 238.

In a first modification to the arrangement shown in Fig. 9 and 10, the slot 247 is replaced by a hole in the funnel end wall 246. In a further modification, the funnel 243 is omitted, the gutter having a slot or hole formed as in the end wall of the tunnel.

i i 1 1

Claims

-12CLAIMS

1. An expansion tank for the cooling system of a liquid-cooled internal combustion engine, the tank comprising a housing forming an enclosed chamber, an inlet connection on the housing for connection to a supply of coolant discharged from the engine and an outlet connection on the housing for the return of coolant to the engine, the inlet connection discharging into an inlet orifice located at or towards the top of the chamber and the outlet connection connecting to a main outlet located at or towards the bottom of the chamber, wherein a collector is arranged in the housing to collect coolant discharged from the inlet orifice to duct the collected coolant into the outlet connection and discharge it through a collector outlet adjacent the main outlet such that coolant flowing from the collector outlet can exit from the outlet connection with little or no mixing with coolant in the chamber.

2. A tank according to claim 1 wherein the inlet orifice is arranged to direct incoming coolant onto a deflector.

3. A tank according to claim 2 wherein the deflector is at an oblique angle to incoming coolant.

4. A tank according to claim 2 or claim 3 wherein the deflector is concave.

5. A tank according to any of claims 2 to 4 wherein the deflector comprises a wall portion of the housing.

6. A tank according to claim 5 wherein the inlet orifice is arranged so that the flow therefrom is substantially tangential to the adjacent outer wall of the housing.

7. A tank according to claim 5 or claim 6 wherein the collector comprises a gutter arranged on the housing wall below the stream of incoming coolant.

8. A tank according to claim 7 wherein a funnel is arranged to duct coolant from the gutter into the collector outlet.

9. A tank according to claim 8 wherein the gutter is arranged on both sides of the funnel.

10. A tank according to claim 9 wherein at least one side of the gutter terminates in a weir.

11. A tank according to claim 10 wherein an inclined channel is arranged to collect coolant spilling over the weir and discharge it towards the bottom of the tank.

12. A tank according to claim 11 wherein the inclined channel is on an outer wall of the housing.

13. A tank according to any of claims 7 to 12 wherein the funnel extends substantially perpendicularly from the gutter.

14. A tank according to any preceding claim wherein the housing comprises two housing portions joined at a substantially horizontal joint face, the inlet connection and the inlet orifice being formed in the upper housing portion and the outlet connection, the collector and the collector outlet being formed in the lower housing portion.

15. A tank according to claim 14 wherein the collector is formed by the outer wall of the lower housing portion and at least one wall extending substantially -14vertically therefrom.

16. A tank according to claim 14 or claim 15 when dependent on claim 7 wherein the gutter extends circumferentially around at least part of the upper rim of the lower housing portion.

17. A tank according to claim 7 or any claim dependent thereon wherein the gutter has weirs to restrict the flow of coolant along the gutter.

18. A tank according to claim 14 or any claim dependent therefom. wherein baffles are provided in the lower housing portion to restrict the pendulum action of the mass of coolant in the chamber.

19. A tank according to any preceding claim wherein the housing has a substantially spherical outer wall.

20. A tank according to any preceding claim wherein the collector outlet discharges into the outlet connection downstream of the flow from the main outlet.

21. A tank according to any of claims 1 to 19 wherein the collector outlet discharges into the camber upstream of the flow into the main outlet.

22. A tank according to claim 21 when dependent on claim 15 wherein the collector outlet comprises a vertical slit in the or one of the walls of the collector.

23. An expansion tank for the cooling system of a liquid-cooled internal combustion engine and substantially as described herein with reference to the accompanying drawings.