GB2321957A

GB2321957A - Cooling I.C. engines

Info

Publication number: GB2321957A
Application number: GB9702244A
Authority: GB
Inventors: William Robert English
Original assignee: Perkins Ltd
Current assignee: Perkins Ltd
Priority date: 1997-02-04
Filing date: 1997-02-04
Publication date: 1998-08-12
Anticipated expiration: 2017-02-04
Also published as: GB9702244D0; GB2321957B

Abstract

A cooling system for an i.c. engine includes a radiator for cooling liquid coolant pumped through a coolant jacket carried by the engine. The coolant is conveyed to the radiator by a circulating means comprising various inlet and outlet lines. The system includes a thermostatically operated valve (24) which operates in a known manner to return coolant directly to the coolant jacket when its temperature is below a predetermined working level. The system also includes a vent passage/channel (48) integrally formed with or in association with the valve which allows entrapped air to pass to the radiator during an initial period of engine operation. The air venting line/channel includes a valve/tap (50 and 52) means which is actuable to close it.

Description

A COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE The present invention relates to a cooling system for an internal combustion (i.c.) engine of the type including a radiator for cooling liquid coolant circulated through a coolant jacket carried by the engine, a thermostatically operated valve for preventing circulated coolant from passing to the radiator during a period when the temperature of said coolant is below a predetermined working level and a radiator by-pass line for returning coolant directly to the coolant jacket during this period.

In particular, the present invention relates to a cooling system for an i.c. engine including a means for allowing air entrapped in the system to pass to the radiator during an initial engine operating period.

When an i.c. engine cooling system is initially filled, or is subsequently topped-up, with liquid coolant, air may become entrapped in parts of the system such as the coolant jacket, for example. Entrapped air can reduce the ability of the circulating liquid coolant to remove thermal energy from the engine cylinder head and/or cylinder block which can lead to local variations in the degree of cooling of engine components. It is particularly important that thermal energy is efficiently transferred away from components such as exhaust valves, for example, which require cooling immediately the engine is started. Also, the entrapped air can accumulate in the coolant pump causing an airlock therein which may seriously reduce coolant pumping efficiency which is undesirable.

In order to obviate the problems caused by air entrapped in the cooling system, a bleed or vent hole may be provided in, or in association with, a valve member of the thermostatically operated valve. The bleed hole allows air entrapped in a housing of the valve to pass to the radiator whilst the thermostatically operated valve remains in a closed position preventing circulated coolant from passing to the radiator prior to engine start-up from cold. The bleed or vent hole may be fitted with a jiggle pin to allow easy passage of air therethrough whilst impeding the flow of liquid coolant in cases where a permanent bleed is not required. Thus, air becoming entrapped in the cooling system when the system is being filled or subsequently topped-up, or dislodged during an initial period of engine operation whilst the thermostatically operated valve is closed, can escape via the bleed or vent hole to the radiator where coolant/air separation can more readily take place.

It has been found, however, that a coolant/air mix may not readily pass through the bleed hole during engine operation even in the case where the bleed hole is designed to allow a permanent flow. This problem has been found to be particularly severe where the central axis of the bleed hole lies generally horizontal, but it may be caused by other factors such as a negative pressure exerted on the hole by the suction side of the coolant pump, turbulence in the coolant/air mixture or even the physical arrangement of the cooling system components.

The result is that coolant/air separation and air venting may be unsatisfactory until the thermostatically operated valve opens to allow the coolant/air mix to flow directly to the radiator where the conditions for separation are more favourable.

US 4 144 849 discloses a cooling system for an i.c.

engine which, rather than utilising a bleed or vent hole in the valve member of a thermostatically operated valve, employs a venting channel in the housing of the thermostatically operated valve which by-passes a valve member of the valve for closing an outlet line of the radiator. The by-pass channel communicates between a chamber of the housing on the radiator outlet line side of the valve member and an inlet line to the radiator. Thus, when the cooling system is filled with coolant, air entering the system can escape via the venting channel to the radiator inlet line and hence to the radiator filling opening.

Similarly, US 4 147 139 utilises a venting line connected between the housing of the thermostatically operated valve and the radiator. The venting line communicates between a chamber located on a radiator outlet line side of the valve member for closing said line and an upper part of the radiator. On filling the cooling system with coolant, air entering the system can escape via the venting line to exit via the radiator filling opening.

The cooling systems of US 4 144 849 and US 4 147 139, however, each rely on an upper end of the venting channel/line being continuously supplied with coolant during engine operation to prevent air in an upper part of the radiator being sucked by the coolant pump into the coolant line supplying coolant to the coolant jacket of the engine. Consequently, a proportion of the heated coolant flowing from the engine coolant jacket to the radiator passes to the coolant jacket inlet line before it can pass through the radiator for cooling thus reducing the thermal dissipation efficiency of the cooling system.

It is an object of the present invention to obviate or mitigate the abovementioned problem of the prior art cooling systems.

It is another object of the present invention to provide a means for allowing air entrapped in the cooling system of an engine to pass to an upper part of the radiator during an initial engine operating period.

It is yet a further object of the invention to provide a means for enabling the entrapped air passage means to be made non-effective during normal engine operation.

It is a still further object of the invention to provide a means which not only allows the entrapped air passage means to be made non-effective during normal engine operation, but which also allows a known method of releasing entrapped air during coolant filling of a nonoperating engine to be utilised.

According to a first aspect of the present invention, there is provided a coolant system for an internal combustion engine, comprising: a pumping means for circulating liquid coolant through a coolant jacket carried by the engine; a radiator means for cooling coolant circulated through said coolant jacket; circulating means communicating between the coolant jacket and the radiator means for conveying coolant therebetween, said circulating means including a thermostatically operated valve means for substantially preventing circulated coolant from passing to the radiator means and a means for returning said circulated coolant prevented from passing to the radiator means to the coolant jacket when the temperature of said circulated coolant is below a predetermined level, wherein said circulating means also includes a means for allowing air entrapped in the system to pass from a first location situated on a first side of a valve member of the thermostatically operated valve means to a second location situated on a second side of said valve member.

Preferably, said air passage means includes a valve/tap means which is actuable to close said passage means, According to a second aspect of the present invention, there is provided a method of releasing air entrapped in a cooling system of an i.c. engine, comprising the steps of: pumping liquid coolant through a coolant jacket carried by the engine; conveying coolant pumped through the coolant jacket to a radiator means for cooling therein via a circulating means communicating between the coolant jacket and the radiator means; returning cooled coolant exiting said radiator means to said coolant jacket via said circulating means; using a thermostatically operated valve means comprising part of the circulating means to substantially prevent coolant pumped through the coolant jacket from passing to the radiator means when the temperature of said pumped coolant is below a predetermined working level; returning said pumped coolant prevented from passing to the radiator means to the coolant jacket; and allowing air entrapped in the system to pass from a first location situated on a first side of a valve member of the valve means to a second location situated on a second side of said valve member.

Preferably, the method includes closing said entrapped air passage means after an initial engine operating period.

According to a third aspect of the present invention, there is provided an i.c. engine incorporating a cooling system in accordance with the first aspect of the invention.

According to a fourth aspect of the present invention, there is provided a thermostatically operated valve means capable of being incorporated in a cooling system for an i.c. engine, said valve means comprising a housing accommodating a valve member, said valve member being actuable in response to the temperature of fluid passing through the housing between a first position where it closes a first outlet port to allow fluid communication between an inlet port and a second outlet port to a second position where it closes said second outlet port and simultaneously opens said first outlet port allowing fluid communication between said inlet port and first outlet port, wherein the valve means includes a channel or passage by-passing the valve member and allowing fluid communication between a first location on an inlet port side of the valve member for closing the first outlet port and a second location on an outlet port side of said valve member, the diameter of said by-pass channel or passage being considerably smaller than the diameter of the outlet port.

Preferably, said by-pass channel or passage includes a valve/tap means actuable to close said channel or passage.

Further features of the cooling system, method, i.c.

engine and thermostatically operated valve means in accordance with the various aspects of the present invention are as defined in the appended claims.

The foregoing and further features of the present invention will be more readily understood from the following description of preferred embodiments, by way of example thereof, with reference to the accompanying drawings, of which; Figure 1 is a schematic side view of a known cooling system for an i.c. engine with a thermostatically operated valve means in a closed position during an initial engine operating period; Figure 2 is a further schematic side view of the known engine cooling system with the thermostatically operated valve means in an open position allowing coolant to flow through the radiator means of the system; Figure 3 is a cross-sectional side view of a thermostatically operated valve means in a closed position comprising part of a cooling system in accordance with a first embodiment of the invention; Figure 3a is an enlarged view of the circled portion of figure 3; Figure 4 is a cross-sectional side view of the valve means of Figure 3 with the valve means shown in an open position; Figure 4a is an enlarged view of the circled portion of figure 4; Figure 5 is a cross-sectional side view of a thermostatically operated valve means in a closed position comprising part of a cooling system in accordance with a second embodiment of the present invention; and Figure 5a is an enlarged view of the circled portion of figure 5.

Figures 1 and 2 schematically illustrate a typical cooling system arrangement for an i.c. engine. The system 10 comprises a pump 12 for circulating liquid coolant through a coolant jacket (symbolically indicated by arrows 14) carried by the engine cylinder block 16 and cylinder head 18, a coolant jacket outlet line 20 for carrying circulated coolant to a radiator inlet line 22 via a thermostatically operated valve 24, a radiator 26 for cooling circulated coolant and a radiator outlet line 28 for conveying cooled coolant back to the pump 12.

In this known system, the coolant is caused to circulate up through the coolant jacket of the engine during which the coolant absorbs thermal energy generated by the operating engine through contact with the surfaces of the coolant jacket. The heated coolant is then conveyed to the radiator 26 and flows downwardly through the radiator 26 dissipating thermal energy through contact with the surfaces of the elements (not shown) comprising the radiator 26. The thermostatically operated valve 24 connects the coolant jacket outlet line 20 with the radiator inlet line 22 and is connected to the pump 12 via a radiator by-pass line 30. On engine start-up from cold, the valve 24 is in a closed position substantially closing off the radiator inlet line 22, but leaving open the radiator by-pass line 30. Consequently, coolant is caused to circulate around a primary circuit comprising the coolant jacket 14, the coolant jacket outlet line 20, -the valve 24, the radiator by-pass line 30, the pump 12 and a coolant jacket inlet line 32. The primary circuit allows the temperature of the circulating coolant to increase more rapidly than would be the case if the coolant were to be allowed to flow via the radiator 26 prior to being returned to the coolant jacket 14. The valve 24 remains closed until such time as the temperature of the coolant circulating in the primary circuit reaches a predetermined working level at which the valve 24 is actuated to open the radiator inlet line 22 and simultaneously close the radiator by-pass line 30. Coolant is now circulated around a secondary circuit comprising the coolant jacket 14, the coolant jacket outlet line 20, the valve 24, the radiator inlet line 22, the radiator 26, the radiator outlet line 28, the pump 12 and the coolant jacket inlet 32. This circuit comprises the coolant circulation circuit for normal engine operation, whereby thermal energy carried by the coolant away from the engine cylinder block 16 and cylinder head 18 is dissipated to atmosphere by the radiator 26.

The purpose of the thermostatically operated valve 24 is, therefore, to allow engine coolant to be heated to its working temperature level as quickly as possible during an initial period of following engine start up from cold.

This is particularly important where the circulating engine coolant is employed for other purposes such as a means for heating the cab of a vehicle, for example.

It can be seen from Figure 1 that a valve member 34 of the thermostatically operated valve 24 for closing the radiator inlet line 22 includes a bleed or vent hole 36.

This hole 36 is of small diameter when compared to the diameter of the radiator inlet line 22. When the thermostatically operated valve 24 is in its closed position prior to engine start-up from cold, the bleed hole 36 allows air that has become entrapped in a housing 38 of the valve 24 when the system was being filled or topped-up with coolant to escape to the radiator inlet line 22 and thereafter to pass to an upper part of the radiator 26. However, on engine start-up, entrapped air remaining in the system becomes dislodged and mixes with the circulating coolant and is carried in the form of a coolant/air mixture around the primary circuit. A small proportion of the coolant/air mix may pass to the radiator inlet line 22 via the bleed hole 36, but it will take a considerable period of engine operation for all of the coolant/air mix to escape this way. Consequently, during an initial period of engine operation when it is necessary to increase coolant temperature as rapidly as possible, heat energy is dissipated as coolant is circulated in the secondary circuit.

Reference is now made to figures 3 and 4 of the drawings which provide cross-sectional side views of a thermostatically operated valve in both its closed and open positions. The valve illustrated in these figures is intended to be incorporated in a cooling system for an i.c. engine of known or suitable type in replacement of the existing thermostatically operated valve thus providing a cooling system for an i.c. engine in accordance with a first embodiment of the present invention. Like numerals to those employed in the description of the known system illustrated by figures 1 and 2 will be utilised in the following description.

The valve 24 to be incorporated in the cooling system 10 in accordance with a first embodiment of the invention comprises a housing 38 which accommodates a valve member 40. The valve member 40 in this embodiment is absent a bleed or vent hole and is actuable in response to coolant temperature in a known manner. In a first position, the valve member 40 closes a first outlet port 42 leaving open a second outlet port 44 and when it moves to a second position it closes said second outlet port 44 and simultaneously opens said first outlet port 42. Each of the outlet ports (42, 44) can separately communicate with an inlet port 46 depending on the position occupied by the valve member 40. In use, the first outlet port 42 is connected to the radiator inlet line 22 of the cooling system 10, the second outlet port 44 is connected to a radiator by-pass line 30 and the inlet port 46 is connected to a coolant jacket outlet line 20. Thus, the valve 24 operates in a conventional manner to prevent coolant flowing to the radiator 26 when the temperature of said coolant is not sufficiently high to cause the valve member 40 to move to its second position, i.e. when the temperature of the coolant is below a predetermined working level.

In the context of the present invention, the significant feature of the valve 24 is the inclusion of a channel or passage 48 by-passing the valve member 40, or that part 40t thereof, which closes the first outlet port 42. The by-pass channel or passage 48 is of sufficient diameter to allow a turbulent coolant/air mix to flow therethrough during an initial engine operating period from cold start-up following a coolant fill or top-up.

During this period, the valve 24 has closed the radiator inlet line 22 thus preventing coolant flowing from the engine coolant jacket 14 to the radiator 26.

The by-pass channel or passage 48 is preferably positioned at a relatively high level in the cooling system 10, on or adjacent to the valve housing 38. The by-pass channel or passage 48 carries a tubular insert 50 which has a transverse hole 52 to permit coolant to flow through both the passage 48 and the insert 50. The insert 50 carries an internal screw thread (not shown) into which a plug 54 is able to be screwed. Preferably, the plug 54 or the insert 50 has a locking means (not shown) which may, for example, be in the form of a plastic insert in the shank or oversized screw threads to hold the plug 54 in a first position as is more clearly shown in figure 3a.

The valve 24 and its housing 38 together with the bypass passage 48, the insert 50 and the plug 54 may be configured as a unitary apparatus for fitting on the engine or connecting into the external conduits (lines) of the cooling system 10. Alternatively, the assembly of bypass passage 48, insert 50 and plug 54 may be configured to be separate from the valve housing 38 and connected thereto by conduit means (not shown). It will be appreciated that, depending on the material forming the channel or passage wall, the plug 54 may screw-threadedly locate in a threaded hole in the wall, there being no need for an insert.

When the engine is started from cold, the plug 54 in its first position permits the coolant/air mix to by-pass the closed valve member 40 and hence reach the radiator inlet line 22 for passage to the radiator 26 where conditions are more conducive to coolant/air separation.

The engine is run under these conditions for a length of time sufficient for the entrapped air to be substantially dislodged by circulating coolant and to collect in an upper part of the radiator 26.

After the set time of engine running, the plug 54 is fully screwed down to a second position to close the bypass passage 48 as shown in Figures 4 and 4a. The closing of the by-pass passage enables the engine and any associated cab heater device (not shown) to reach operating temperature in the fastest possible time.

Preferably, the plug 54 has a sealing means (not shown) such that when the plug is fully engaged with the insert 50 it prevents any loss of coolant during normal engine operation. The plug sealing means may be incorporated with the above mentioned plug locking means. The plug 54 therefore is screwed to its second "closed" position for all engine operating periods except for a short initial period on start up from cold after the cooling system has been filled or topped-up after maintenance, for example.

In a second embodiment of a cooling system 10 for an i.c. engine, a valve 24 as shown in Figure 5 is incorporated in replacement of the existing thermostatically operated valve. This embodiment is similar to that of the first embodiment but is provided with means for allowing entrapped air to escape during filling of the coolant system when the engine is not operating. Specifically, the threaded plug 54 is provided with one or more slots or flats 56 extending axially along approximately half the length of the shank of the plug 54.

The slots or flats 56 extend in depth to approximately the root diameter of the screw thread.

In operation, the plug 54 is unscrewed prior to filling of the cooling system to the extent that the slots 56 communicate with atmosphere. As coolant is introduced into the engine, air entering the system can flow though the by-pass passage 48 and vent to atmosphere by flowing along the slots 56 in the plug 54. When coolant starts to emerge from the slots 56, the plug 54 is screwed into the insert 50 to prevent further coolant loss.

The slotted plug 54 may be screwed from its position allowing the passage to communicate with atmosphere to an end position at which the passage is closed. However, the plug 54 can occupy a position intermediate the position at which air can escape to atmosphere and its "closed" position. In its intermediate position, the plug 54, in a similar manner to the first embodiment, allows air or a coolant/air mix to flow through the passage 48.

It is therefore possible with the arrangement according to the second embodiment of the invention to allow air entering the system on coolant filling or top-up to exhaust to atmosphere via the plug 54 and thereafter, during an initial period of engine operation, to allow remaining air entrapped in the system to be dislodged and vent to the upper part of the radiator 26 in a manner as aforesaid. In this way, air becoming entrapped in the cooling system of an engine on coolant filling or toppingup can be removed from critical parts of the system after a short period of engine operation and thereafter the cooling system of the engine, whilst the thermostatically operated valve is in its closed position, operate normally without the disadvantage that the coolant circulating in the primary circuit contains entrapped air mixed therein.

Claims

1. A cooling system for an internal combustion engine, comprising: a pumping means for circulating liquid coolant through a coolant jacket carried by the engine; a radiator means for cooling coolant circulated through said coolant jacket; circulating means communicating between the coolant jacket and the radiator means for conveying coolant therebetween, said circulating means including a thermostatically operated valve means for substantially preventing circulated coolant from passing to the radiator means and a means for returning said circulated coolant prevented from passing to the radiator means to the coolant jacket when the temperature of said circulated coolant is below a predetermined level, wherein said circulating means also includes a means for allowing air entrapped in the system to pass from a first location situated on a first side of a valve member of the thermostatically operated valve means to a second location situated on a second side of said valve member.

2. A system as claimed in claim 1, wherein said valve member, in use, closes a radiator means inlet line.

3. A system as claimed in claim 2, wherein said first location is situated in the circulating means on a coolant jacket side of said valve member.

4. A system as claimed in any preceding claim, wherein said first location is situated in a housing of the thermostatically operated valve means.

5. A system as claimed in any preceding claim, wherein the air passage means comprises a conduit means connecting said first location to said second location

6. A system as claimed in any one of claims 1 to 4, wherein the air passage means is formed integrally with the housing of the thermostatically operated valve means.

7. A system as claimed any preceding claim, wherein said air passage means includes a valve/tap means which is actuable to close said passage means.

8. A system as claimed in claim 7, wherein said valve/tap means is actuable to allow said air passage means to communicate directly with atmosphere.

9. A method of releasing air entrapped in a cooling system of an i.c. engine comprising the steps of: pumping liquid coolant through a coolant jacket carried by the engine; conveying coolant pumped through the coolant jacket to a radiator means for cooling therein via a circulating means communicating between the coolant jacket and the radiator means; returning cooled coolant exiting said radiator means to said coolant jacket via said circulating means; using a thermostatically operated valve means comprising part of the circulating means to substantially prevent coolant pumped through the coolant jacket from passing to the radiator means when the temperature of said pumped coolant is below a predetermined working level; returning said pumped coolant prevented from passing to the radiator means to the coolant jacket; and allowing air entrapped in the system to pass from a first location situated on a first side of a valve member of the valve means to a second location situated on a second side of said valve member.

10. A method as claimed in claim 9, wherein it includes the step of allowing entrapped air to pass via said air passage means from a first location situated on a coolant jacket side of a valve member for closing a radiator means inlet line to a second location situated on a radiator means side of said valve member.

11. A method as claimed in claim 9 or 10, wherein a valve/tap means of said air passage means is actuated to close said passage means.

12. A method as claimed in any one claims 9 to 11, wherein it comprises actuating said valve/tap means of the air passage means to allow said passage means to communicate directly with atmosphere when the cooling system is being filled or topped-up with coolant.

13. An i.c engine incorporating a cooling system in accordance with any one of claims 1 to 8.

14. A thermostatically operated valve means capable of being incorporated in a cooling system for an i.c.

engine, said valve means comprising a housing accommodating a valve member, said valve member being actuable in response to the temperature of fluid passing through the housing between a first position where it closes a first outlet port to allow fluid communication between an inlet port and a second outlet port to a second position where it closes said second outlet port and simultaneously opens said first outlet port allowing fluid communication between said inlet port and first outlet port, wherein the valve means includes a channel or passage by-passing the valve member and allowing fluid communication between a first location on an inlet port side of the valve member for closing the first outlet port and a second location on an outlet port side of said valve member, the diameter of said by-pass channel or passage being considerably smaller than the diameter of the outlet port.

15. A valve means as claimed in claim 14, wherein said channel is formed integrally with the housing.

16. A valve means as claimed in claim 14, wherein the passage comprises a conduit connected to the exterior of the housing with respective by-pass passage inlet and outlet ports.

17. A valve means as claimed in any one of claims 14 to 16, wherein the by-pass channel or passage includes a valve/tap means actuable to close said passage.

18. A valve means as claimed in claim 17, wherein said valve/tap means is actuable to allow said by-pass channel or passage to communicate with atmosphere.

19. A cooling system substantially as hereinbefore described with reference to figures 3 and 4 of the drawings.

20. A cooling system substantially as hereinbefore described with reference to figures 5 of the drawings.

21. A method substantially as hereinbefore described with reference to figures 3 and 4 of the drawings.

22. A method substantially as hereinbefore described with reference to figure 5 of the drawings.

23. An i.c. engine substantially as hereinbefore described with reference to figures 3 and 4 of the drawings.

24. An i.c. engine substantially as hereinbefore described with reference to figure 5 of the drawings.

25. A thermostatically operated valve means substantially as hereinbefore described with reference to figures 3 and 4 of the drawings.

26. A thermostatically operated valve means substantially as hereinbefore described with reference to figure 5 of the drawings.