GB2360512A

GB2360512A - Pressure control valve for cooling system

Info

Publication number: GB2360512A
Application number: GB0006621A
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: 2000-03-20
Filing date: 2000-03-20
Publication date: 2001-09-26
Also published as: GB0006621D0; EP1136673A2; EP1136673A3; EP1136673B1; DE50109913D1

Abstract

A pressure control valve assembly for the cooling system of a liquid-cooled internal combustion engine comprises a housing 27 defining an orifice 36 with an annular rim, a closure member 37 which covers the orifice and is spring-biassed towards the rim and a resilient seal 42 between the closure member and the housing, the seal being compressed and arranged to react against the closure member and the housing with a resilient reaction load which is considerably less than the load of the spring bias. This arrangement avoids sticking of the valve assembly. As described the valve assembly is incorporated in a closure 25 of an expansion tank, and the valve is intended to open at a predetermined pressure. The seal 42 may extend inwardly of the member 37, as shown. Alternatively a resilient seal is carried on the inwardly directed annular surface of a separate metal or hard plastics washer located between the edge of the member 37 and the rim of the orifice 36. The assembly may also include a vacuum relief valve 45.

Description

2360512 Cooling System Pressure Control Valve Assembly This invention

relates to pressure control valve assemblies for the cooling systems of liquid cooled internal combustion engines. Such assemblies are normally incorporated in a closure cap for an expansion tank. In modern motor vehicles such expansion tanks are usually situated in a convenient underbonnet location away from a radiator of the cooling system. However, in former times such expansion tanks were normally formed as a radiator header tank and such closure caps are still frequently referred to as radiator caps.

For many years radiator caps have evolved around a design in which a spring loaded washer closes an orifice at the base of a filler neck so that at a predetermined pressure the washer lifts against the spring to limit the pressure in the cooling system. A support plate for the washer would incorporate a so-called vacuum valve (more accurately an anti-vacuum valve), to prevent the pressure falling significantly below atmospheric when the cooling system cools. An example of such a cap is shown in US 2, 164,450.

A move towards engine compartments of reduced height has resulted in cross flow radiators and a remote location for the expansion tank, as previously mentioned. Such expansion tanks are frequently made of plastics and these usually require the use of a screw threaded closure cap which incorporates the pressure control valve as an integrated assembly, i.e., these do not rely on there being a seating orifice in the expansion tank filler neck. An example of such an arrangement is shown in GB 1534 318. A problem with such valve assemblies is that there may be long periods of operation in which the pressure in the cooling system rises to that set by the spring loaded washer but there is insufficient rise in temperature or requirement to vent gasses from the cooling system to cause the washer to unseat against the spring bias. As a result, the washer tends to stick on its seat and a considerably higher pressure than was originally set by the spring bias load is required to unseat it. The older design of cap as illustrated by US 2,164,450 did not suffer this problem. Hence it was normal practice to remove the cap to inspect the coolant level so the washer and its mating surface did not remain in contact for long periods. Furthermore, imperfect sealing of the cylinder head gaskets would allow minute quantities of combustion gas to escape into the cooling system and this would be vented through the cooling system closure cap.

The present invention has as an object the provision of a valve assembly where the tendency for valve sticking and over pressure is much reduced.

In accordance with a first aspect of the invention there is provided a pressure control valve assembly for the cooling system of a liquid-cooled internal combustion engine, the valve assembly including a housing defining an orifice, an annular abutment in the housing encircling the orifice, a closure member which covers the orifice and is movable in the housing by pressure in the cooling system against a spring bias, and a resilient seal arranged to seal between the closure member and the housing such that at a predetermined pressure in the cooling system movement of the closure member against the spring bias causes the closure member to unseat from the abutment and allow venting from the cooling system through the orifice and past the resilient seal, there being a direct load path for the spring bias between the closure member and the annular abutment such that the seal is compressed to react against the closure member and the housing with a resilient reaction load which is considerably less than the load of the spring bias.

The shape of the seal may be such that the load of the seal against the closure member and the housing increases with increasing pressure in the cooling system.

The resilient seal may be carried by one of the closure member and the housing and may have a radially inwardly directed lip to seal against said other of the closure member and the housing.

The closure member may be arranged to directly abut the annular abutment at an annular interface, in which case the seal may be radially inboard of the 5 annular interface.

The seal may be carried by the closure member, e.g. by being bonded thereto.

The closure member may be hat-shaped with a cylindrical portion and an outer rim portion, the seal being on the inside of the cylindrical portion at the intersection with the outer rim portion, in which case the closure member may have an outwardly flared portion at the intersection of the cylindrical portion and the outer rim portion. The seal may be triangular in section.

The spring bias may be conveniently provided by a compression spring acting between the housing and the closure member.

The closure member may includes a non-return valve to allow flow from the passage into the cooling system. Such a non-return valve may comprise a mushroom-shaped valve member having a stem which extends through an orifice in the closure member and a head which can seal against the closure member. Where the seal is carried by the closure member, the seal may be extended radially inwards to provide a seal for the valve member.

The seal may be supported by a separate support washer which is loosely located in the housing. Such a seal may have a diamond or rhombus section and locate in a vee groove on the inner peripheral edge of the support washer.

Alternatively, such a seal may have inwardly directed lips on both its upper and lower faces where it seals against the closure member and the housing.

In accordance with a second aspect of the invention there is provided a cooling system for a liquid-cooled internal combustion engine, the cooling system including a heat exchanger, passage means for connecting the heat exchanger to the engine, an expansion tank connected to said passage means and a pressure control valve assembly according to said one aspect of the invention. Conveniently, the expansion tank has a closure cap and the pressure control valve assembly is incorporated in the closure cap.

In accordance with a third aspect of the invention there is provided a closure cap incorporating a pressure control valve assembly according to said first aspect of the invention for use in a cooling system according to said second aspect of the invention.

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 pressure control valve assembly according to the invention; Fig.2 is a cross section through a pressure control valve assembly according to the invention incorporated in a closure cap of an expansion tank shown in Fig. 1 Fig.3 is an enlarged cross-section of part of the pressure control valve assembly shown in Fig.2; Fig.4 is view similar to Fig.3 showing a first modification; Fig.5 is view similar to Fig.3 showing a second modification; Fig.6 is an enlarged view of a part of Fig.5; and Fig.7 is view similar to Fig.6 showing a further modification.

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 a 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 feed hose 22 connected to the delivery hose 13 and a return hose 23 connected to the pump return hose 16. The expansion tank 21 has a filler neck 24 closed by a closure or filler cap 25 which incorporates a pressure control valve assembly 26 as shown in detail in Fig.2. 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 16.

Referring to Fig.2, the filler cap 25 includes a main body portion 27 having internal threads 28 to engage corresponding screw threads on the expansion tank 21 and a spigot member 29 which fits over the tubular portion 31 of the main body 27 and is retained on it e.g. by solvent welding or a snap fit. Seals 32 and 33 are provided to seal against the inside of the filler neck 24. The main body portion 27 and the spigot member 29 form a housing for the pressure control valve assembly 26.

The spigot member 29 has an internal flange 34 forming on an upper surface 35 an annular abutment encircling the central orifice 36. Covering the orifice 36 is a hat-shaped closure member 37 having a cylindrical portion 38 and an outer rim portion 39. The closure member 37 is spring-biased by a preloaded compression spring 41 so that the closure member 37 directly abuts the flange 34 on the upper surface 35 at an annular interface. Radially inboard of this annular interface there is a resilient seal 42 of rubber or synthetic rubber bonded to the closure member 37 so that it seals between the closure member and the flange 34. In this condition the seal 42 is compressed to react against the flange 34 with a resilient reaction load which is considerably less than the preload from the spring 41. This is seen better in Fig.3 where the compressed form of the seal is shown in full lines and the free condition is shown dotted at 42A. It will be noted that the seal 42 is generally triangular in section whilst extending along the inner surface of the cylindrical closure member portion 38 and into a generally triangular section recess bounded by the flange upper surface 35 and an outwardly flared portion at the intersection of the cylindrical portion and the outer rim portion.

The closure member 37 also includes a non-return valve 45 which comprises a mushroom-headed valve member 46 spring loaded against the underside of the closure member 37 and including a seal 47 to close an aperture 48.

In use, liquid coolant circulates through the expansion tank 21 by means of the feed and return hoses 22 and 23. Following a cold start, the air above the level of the liquid coolant is heated and there is a rise in pressure in the cooling system. This puts a load on the closure member 37 which opposes the preload of the spring 41 such that at a predetermined pressure the outer rim portion 39 lifts away from its abutment with the flange 34 and air or vapour can escape through the orifice 36 and to atmosphere by means of radial passages 51 in the main body 27 and the spigot member 29. Thus the maximum pressure in the cooling system is limited and cannot increase significantly above the predetermined level set by the preload of the spring 41. It will be appreciated that when the closure member 37 is in abutment with the flange upper surface 35, this provides a direct load path for the spring bias between the closure member and the flange 34 such that the seal is compressed to an extent where its reaction load against the closure member and the flange upper surface 35 is considerably less than the preload of the spring 41. This means that there is less tendency for the seal 42 to stick onto the flange upper surface 35 since any stiction or breakaway load tends to be related to the normal stationary compression load.

The shape of the seal 42 is such that the load of the seal against the flange upper surface 35 increases with increasing pressure in the cooling system by virtue of the seal forming a radially inwardly directed bead 42B when in the compressed condition (Fig.3). This shape is also such that the surface of the seal 42 tends to peel away from the flange upper surface 45 as the closure member 37 moves away from the flange 34 under cooling system pressure and this also tends to prevent sticking. Furthermore, there may also be a tendency for the seal 42 to rub on the flange upper surface 45 which can also help to keep the interengaging surfaces of the interface clean and inhibit further sticking.

When the engine 11 is stopped and the cooling system cools down, the non return valve 45 acts as a conventional anti-vacuum valve to prevent the pressure in the cooling system falling significantly below atmospheric.

In the first modification shown in FigA, parts which are identical to or similar to those shown in Figs.2 and 3 carry the same reference numeral but with the addition of 100. In this modification the seal 142 has a radially inwardly directed lip 142A when in the ftee condition and this forms part of a cap-shaped diaphragm 149 of an elastomeric material which is bonded to the underside of the closure member 137. In this modification the diaphragm 149 also acts as a seal for the valve member 146 of the non-return valve 145.

In the second modification shown in Figs.5 and 6, parts which are identical to or similar to those shown in Figs.2 and 3 carry the same reference numeral but with the addition of 200. In this modification the seal 242 is supported by a separate washer 251 of metal or a relatively hard plastics material- The washer 251 is located loosely by ribs 252 in the spigot member 229. Fig.6 shows the seal 242 in the free condition where it can be seen to be of a diamond or rhombus section and is located in a vee groove on the inner peripheral edge of the support washer 251. Such washers and seals are commercially available as a complete unit, being generally known as Dowty (RT3ffl Washers.

Fig.7 shows at 242A an alternative section for the seal 242, this having inwardly directed lips 242B on both its upper and lower faces. The washer 251A 10 has an alternative U-section groove for the seal 242A.

Instead of being carried by the closure member 37, 137, the seal 42, 142 could be carried by the flange 34, 134. For example, there could be an annular recess in the flange upper surface 35 to receive an elastomeric 0 ring or lip seal which contacts the adjacent surface of the closure member outer rim portion 39.

Claims

-9CLAIMS

1. A pressure control valve assembly for the cooling system of a liquidcooled internal combustion engine, the valve assembly including a housing defining an orifice, an annular abutment in the housing encircling the orifice, a closure member which covers the orifice and is movable in the housing by pressure in the cooling system against a spring bias, and a resilient seal arranged to seal between the closure member and the housing such that at a predetermined pressure in the cooling system movement of the closure member against the spring bias causes the closure member to unseat from the abutment and allow venting from the cooling system through the orifice and past the resilient seal, there being a direct load path for the spring bias between the closure member and the annular abutment such that the seal is compressed to react against the closure member and the housing with a resilient reaction load which is considerably less than the load of the spring bias.

2. An assembly according to claim 1 wherein the shape of the seal is such that the load of the seal against the closure member and the housing increases with increasing pressure in the cooling system.

3. An assembly according to claim 1 or claim 2 wherein the resilient seal carried by one of the closure member and the housing.

4. An assembly according to claim 3 wherein the seal has a radially inwardly directed lip to seal against said other of the closure member and the housing.

5. An assembly according to any preceding claim wherein the closure member is arranged to directly abut the annular abutment at an annular interface.

6. An assembly according to claim 5 wherein the seal is radially inboard of the -10annular interface.

7. An assembly according to any of claims 3 to 6 wherein the seal is carried by the closure member and the seal is bonded thereto.

8. An assembly according to any preceding claim wherein the closure member is hat-shaped with a cylindrical portion and an outer rim portion, the seal being on the inside of the cylindrical portion at the intersection with the outer rim portion.

9. An assembly according to claim 8 wherein the closure member has an outwardly flared portion at the intersection of the cylindrical portion and the outer rim portion.

10. An assembly according to claim 8 or claim 9 wherein the seal is triangular in section.

11. An assembly according to any preceding claim wherein the spring bias is provided by a compression spring acting between the housing and the closure member.

12. An assembly according to any preceding claim wherein the closure member includes a non-return valve to allow flow from the passage into the cooling system.

13. An assembly according to claim 12 wherein the non-return valve comprises a mushroom-shaped valve member having a stem which extends, through an orifice in the closure member and a head which can seal against the closure member.

14. An assembly according to claim 13 when dependent upon claim 7 wherein the seal is extended radially inwards to provide a seal for the valve member.

15. An assembly according to claim 1 or claim 2 wherein the seal is supported by a separate support washer which is loosely located in the housing.

16. An assembly according to claim 15 wherein the seal has a diamond or rhombus section and locates in a vee groove on the inner peripheral edge of the support washer.

17. An assembly according to claim 15 wherein the seal has inwardly directed lips on both its upper and lower faces where it seals against the closure member and the housing.

18. A cooling system for a hquid-cooled internal combustion engine, the cooling system including a heat exchanger, passage means for connecting the heat exchanger to the engine, an expansion tank connected to said passage means and a pressure control valve assembly according to any preceding claim for controlling the pressure in the cooling system.

19. A cooling system according to claim 18 wherein the expansion tank has a closure cap and the pressure control valve assembly is incorporated in the closure cap.

20. A closure cap incorpo rating a pressure control valve assembly according to any of claims 1 to 17 for use in a cooling system according to claim 19.

21. A pressure control valve assembly substantially as described herein with reference to the accompanying drawings.

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22. A closure cap substantially as described herein with reference to the accompanying drawings.

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