GB2476073A

GB2476073A - Thermostatic valve assembly

Info

Publication number: GB2476073A
Application number: GB0921623A
Authority: GB
Inventors: Remy Fontaine; Oliver Maier
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2009-12-10
Filing date: 2009-12-10
Publication date: 2011-06-15
Anticipated expiration: 2029-12-10
Also published as: GB2476073B; GB0921623D0

Abstract

A thermostatic valve assembly for an engine cooling system has an inlet port 50, an outlet port 52 and at least one moveable sealing element 60, 62 for selectively closing or opening a pathway of coolant circulating in the engine, and is characterized by at least a first and a second thermal expansion element 54, 56, 55, 58. To open the pathway, the first thermal expansion element 54, 56 stretches to an extended configuration in response to the coolant having a first temperature. To close the pathway, the second thermal expansion element 55, 58 stretches to an extended configuration in response to the coolant having a second temperature that is above the first temperature.

Description

S Thermostatic Valve Assembly for Use in Engine Cooling Systems

Description

The present invention relates to the field of

thermostatic valve assemblies for use in an engine cooling systems, in particular for cooling systems of motorized vehicles. The invention further relates to a respective engine cooling system, to a motorized vehicle equipped with such a cooling system as well as to a method of operating of an engine cooling system.

Background and Prior Art

Thermostatic valve assemblies for use in engine cooling systems are commonly used in order to manipulate the flow of a liquid coolant circulating in the engine cooling system. In particular with cooling systems for motorized vehicles, the coolant heated by an engine, e.g. combustion engine, flows to a radiator providing heat exchange with the environment, typically with an ambient air flow. The coolant being cooled down then returns to the engine in order to provide continuous heat dissipation.

In typical engine cooling systems, thermostatic valve assemblies provide temperature-dependent manipulation of the flow of the coolant. In particular, during a warm-up phase of the engine, just after engine start, it is beneficial, to reduce the cooling capacity of the cooling system. For this purpose, the thermostatic valve assembly blocks a fluid-flow communication between the engine and the radiator as long as the coolant temperature is below a predefined threshold temperature.

When the operating temperature has been reached, the thermostatic valve assembly establishes a fluid-flow communication between the engine and the radiator for providing increased cooling capacity.

Such a conventional thermostatic valve is for instance disclosed in US 6,761,321 Bi. This thermostatic device comprises a valve driving section which opens and closes a first and a second valve body by means of expansion of a wax element. Said wax element is adapted to sense the temperature of the cooling water. As the cooling water reaches a predetermined temperature, the wax gradually expands, a piston extends and a first valve body supported on a shaft falls against the urging force of a spring element. Consequently, a channel which was in a blocked state opens and cooling water from a radiator can be emitted from the engine.

Typically, engine cooling systems are further coupled to a heating or air-conditioning unit of a motorized vehicle. Such heating and/or air conditioning systems also comprise heat exchanging means for supplying the vehicle interior with cooled air. The cooling capacity of such passenger heating and/or air conditioning systems is substantially smaller than the cooling capacity of the main radiator.

In situations, in which the vehicle's engine is driven in an upper power-regime, a maximum of cooling capacity is required. Here, it would be beneficial to decouple a passenger heating and/or air conditioning system from the engine cooling system, such that the entire coolant flows through the main radiator in order to provide maximum cooling capacity for the engine.

Otherwise, the branch-off from the cooling system that comprises the passenger heating and/or air conditioning system serves as a bypass for the coolant. Due to its limited cooling capacity of the interior related heat exchanger, the coolant would not optimally be cooled down.

Objects of the Invention It is therefore an object of the present invention to provide an improved thermostatic valve assembly and an improved engine cooling system, in particular for motorized vehicles, which is enabled to selectively block a fluid-flow communication between a passenger heating and/or air conditioning system (HVAC) and a main radiator of the cooling circuit in situations, where maximum cooling capacity is required for engine operation. The invention further aims to provide a thermostatic valve assembly being simple and robust in construction as well as easy to implement in existing engine cooling system configurations.

Summary of the Invention

The thermostatic valve assembly according to the present invention is adapted for use in an engine cooling system, in particular in cooling systems of motorized vehicles, wherein the engine is either designed as combustion engine or as hybrid-engine or even as a fuel-cell stack. The valve assembly comprises an inlet port and at least one outlet port and further has at least one moveable sealing element disposed therein for selectively blocking or opening a pathway for a coolant circulating in the engine cooling system. By way of a thermally triggered displacement of the sealing element, a fluid-flow communication between the inlet port and the outlet port can either be established or blocked. The thermostatic valve assembly is preferably designed as two-way valve but may also be designed as three-way or generally as more-way valve assembly.

The thermostatic valve assembly further comprises at least a first and a second thermal expansion element, each of which being adapted to stretch to an extended configuration in response to the temperature rising above a predefined threshold. Typically, the valve assembly comprises a housing in which the coolant flows in direct vicinity and in thermal contact with the at least first and second thermal expansion elements.

First and second thermal expansion elements are mechanically coupled or mechanically engaged with the at least one sealing element in such a way, that for opening of the pathway, the first thermal expansion element is adapted to stretch to an extended configuration in response to the coolant having a first temperature.

Furthermore, for blocking of the pathway, the second thermal expansion element is adapted to stretch to its extended configuration in response to the coolant having a second temperature, which is above the first temperature.

In this way, the thermostatic valve assembly provides a fluid-flow communication between inlet port and outlet port only within a predefined temperature range, which is governed by first and second predefined temperatures of the coolant. This functionality is of particular benefit in engine cooling systems, since a passenger heating and/or air conditioning system can be disconnected from a main cooling circuit in order to enforce, that the entire coolant flows through the main radiator of the engine cooling system for providing a maximum cooling capacity.

The thermal expansion element typically comprises a moveable piston being driven by a thermal expansion medium, such like a wax that melts at a predefined temperature. Preferably, first and second thermal expansion elements are provided with waxes of different composition, respectively, such that a thermally-induced stretching of first and second thermal expansion elements occurs at different temperatures.

According to a preferred embodiment of the invention, the first and the second expansion elements are mounted on a support structure with a first end portion. With an opposite end portion, hence with their second end portion, first and second expansion elements are mechanically or operably engaged with the sealing element or components thereof. In this way, the sealing element or its particular component can be displaced relative to the housing of the valve assembly when the coolant temperature substantially matches or rises above first and/or second predefined temperature ranges.

In another embodiment, the valve assembly comprises first and second sealing elements, wherein the first sealing element is mechanically engaged with the first expansion element and wherein the second sealing element is mechanically engaged with the second thermal expansion element. In this way, relative position and/or orientation of first and second sealing elements may vary according to the respective configuration of first and second thermal expansion elements.

Here, it is conceivable, that each sealing element is separately adapted to block or to open the pathway for the coolant. Alternatively, first and second sealing element may constitute a sealing assembly which is closed when both thermal expansion elements feature a common configuration, i.e. an initial, hence retracted or a final, hence stretched or expanded configuration. In all other setups, in which first and second thermal expansion elements feature different configurations, the pathway for the coolant is open.

According to another preferred embodiment, the second thermal expansion element is mechanically engaged with the second end portion of the first thermal expansion element. In this configuration, first and second thermal expansion elements are mechanically coupled in series. Hence, first expansion element is arranged between a support structure of the thermostatic valve assembly and the first sealing element, whereas the second thermal expansion element is coupled between first and second sealing elements.

In this way, the second thermal expansion element is adapted to displace the second sealing element with respect to the first sealing element. In other words, the second thermal expansion element is designed to modify the distance between first and second sealing elements.

Consequently, the first thermal expansion element is exclusively adapted to displace first and second sealing elements in unison with respect to the housing of the valve assembly. By way of a thermally-induced stretching of the first thermal expansion element, both sealing elements are displaced together with respect to the housing of the valve assembly.

In a further preferred embodiment, first and second expansion elements are spring-loaded with respect to the housing of the valve assembly by way of a corrimon and single spring element. Hence, thermally induced stretching of first and/or second expansion elements works against the action of said spring element. If the temperature of the coolant drops below the predefined first and/or second temperature, the respective expansion elements retract to their initial configuration accompanied by a returning of first and/or second sealing elements to their initial or medium position.

In an alternative embodiment, first and second sealing elements constitute a sealing assembly and directly form a sealing seat. Here, first and second sealing elements are coupled to a common support structure by first and second thermal expansion elements, respectively. In this embodiment, first and second thermal expansion elements are arranged in parallel, such that a thermally induced displacement of the first expansion element leads to a displacement of the first sealing element relative to the second sealing element.

This relative movement in turn leads to a release of the sealing seat, such that the pathway for the coolant between inlet and outlet port is opened.

When the coolant temperature further rises to the second temperature, the second sealing element is displaced in the same direction towards the first sealing element in order to re-establish the sealing seat and to block the fluid communication between inlet port and outlet port.

In this embodiment it is of particular benefit, when the first sealing element is spring-loaded by a first spring element and when the second sealing element is spring-loaded by a second spring element. In this way, first and second sealing elements can be independently displaced in the housing against the action of the respective first and second spring elements. Displacement of the first sealing element therefore has no influence on the position of the second sealing element and vice versa.

In a further preferred embodiment, the first sealing element comprises a sealing cone forming a sealing seat with the second sealing element comprising a corresponding orifice adapted to receive the sealing cone. As soon as the sealing cone enters the orifice, a liquid tight sealing seat is established and a fluid-flow communication between inlet port and outlet port is substantially blocked.

In a further preferred embodiment universally applicable to all conceivable thermostatic valve assemblies according to the present invention, an electrically driven heating unit is provided for manually triggering a thermally induced stretching of first and/or the second thermal expansion elements. By way of the heating unit, opening and closing temperatures of the thermostatic valve assembly can be individually manipulated. For instance, the heating unit is adapted to provide a temperature offset to the thermostatic valve assembly, such that the first thermal expansion element can even be displaced in a temperature range of the coolant being below the first temperature.

Similarly, the heating unit may also affect the thermal response of the second thermal expansion element.

Having such a supplemental heating unit, the thermal response of the thermostatic valve assembly can be easily and individually adapted to predefined specifications.

Moreover, by means of the heating unit, also the temperature interval in which the valve assembly provides fluid-flow communication between inlet port and outlet port can be modified either by lowering the first temperature and/or by lowering the second temperature.

In a further aspect, the invention also refers to an engine cooling system that comprises a cooling circuit having at least one bypass and a main cooling circuit, wherein the bypass is branched-off from said main cooling circuit. The bypass is thermally coupled with a passenger heating and/or air conditioning system, whereas the main cooling circuit provides a fluid-flow communication between the heat-generating engine and a radiator.

The engine cooling system also comprises at least one valve assembly according to the present invention for thermally connecting the bypass and the passenger heating and/or air conditioning system with the main cooling circuit only if the coolant temperature is between or equal to the first temperature and the second temperature, wherein the second temperature is above the first temperature. Preferably, the inventive thermostatic valve assembly controls the bypass branched off from the main cooling circuit.

In a further independent aspect, the invention also relates to a motorized vehicle comprising an engine, such as a combustion engine or a fuel cell stack and further comprises an engine cooling system according to the present invention.

In still another aspect, the invention also relates to a method of operating an engine cooling system that comprises a main cooling circuit and a bypass, wherein the bypass is thermally coupled with a passenger heating and/or air conditioning system. The cooling system comprises a valve assembly according to the present invention and the method of operating the engine cooling system is governed by two steps of selectively opening and/or blocking a pathway in the valve assembly for thermally coupling or decoupling the heating and/or air conditioning system with the main cooling circuit.

Said method of operating the engine cooling system is characterized by opening a pathway in the valve assembly for providing a fluid-flow communication between the heating and/or air conditioning system with the main cooling circuit as the coolant temperature reaches a first predefined temperature. In a subsequent step, the method of operating the engine cooling system is adapted to block the pathway in the valve assembly as soon as the coolant temperature exceeds a second predefined temperature, which is above the first temperature.

Therefore, a temperature selective opening and blocking of a fluid-flow communication is easily achievable by the above described thermostatic valve assembly comprising first and second thermal expansion elements that provide temperature-triggered displacement of at least one moveable sealing element at two different coolant temperatures.

Brief Description of the Drawings

Various features, benefits and embodiments of the present invention are explained in greater detail below in connection with the drawings, in which: Figure 1 shows a block diagram of an engine cooling system, Figure 2 shows a diagram being illustrative on the opening and closing behavior of a valve assembly, Figure 3 shows a first embodiment of the valve assembly according to the present invention in an initial configuration below the first temperature, Figure 4 shows the valve assembly according to Figure 3 in opened configuration and Figure 5 shows the valve assembly according to Figures 3 and 4 above the second temperature, Figure 6 shows another embodiment of the valve assembly in a configuration below the first temperature, Figure 7 depicts the valve assembly according to Figure 6 in a temperature range between first and second temperatures, and Figure 8 illustrates the valve assembly according to Figures 6 and 7 in a block configuration above the second temperature.

Detailed description

The engine cooling system 10 as illustrated in Figure 1 comprises an engine module 26 having an engine 18, a pump 20 and a three-way valve 22. Depending on the configuration of the three-way valve 22 a main cooling circuit 30 can be thermally coupled to the engine module 26. The main cooling circuit 30 further comprises a radiator 12 that provides heat dissipation to ambient air. On demand, a rotating fan assembly 14 can be supplementally activated in order to generate sufficient airflow.

In a starting phase, i.e. just after an engine startup, the three-way valve 22 is substantially configured in such a way, that the coolant heated by the engine 18 exclusively flows via a bypass 32. In this way, heat dissipation is kept on a minimum level so as to accelerate engine heat up.

When a predefined temperature level has been reached, the three-way valve 22, which may be implemented as thermostatic valve assembly, is reconfigured so as to provide a fluid-flow communication between the main cooling circuit 30 and the engine 18.

Furthermore, the cooling system 10 comprises a bypass 28 branched-off from the main cooling circuit 30 by way of a two-way valve assembly 24, 74. By way of said bypass 28, a passenger heating and/or air conditioning system (HVAC) 16 can be coupled with the main cooling circuit 30, wherein the bypass 28 independently enters the engine module 26. Since the three-way valve 22 is arranged downstream the two-way valve 24, 74, the bypass 28 can be brought in fluid-flow communication with the engine module 26 irrespective on the configuration of the three-way valve 22.

The two-way valve 24, 74 is particularly adapted to provide fluid-flow communication between the passenger heating unit 16 and the main cooling circuit 30 only within a predefined temperature range. During the startup phase below a predefined first temperature Topen it is intended, that the pathway through the thermostatic valve assembly 24, 74 is blocked. When the coolant is heated to the first temperature, the thermostatic valve assembly 24 opens and provides fluid-flow communication between the heating and/or air conditioning system 16 and the main cooling circuit and/or the engine module 26.

Depending on the heat produced by the engine 18 also the three-way valve 22 may open so as to provide a thermal coupling between the radiator 12 and the engine module 26.

The passenger heating system 16 provides heat exchange with the interior of a not further illustrated vehicle but its cooling capacity is substantially smaller than that of the radiator 12. When driven in A/C-mode, the HVAC 16 even generates additonal heat.

In situations, where a maximum cooling capacity is required for dissipating heat produced by the engine 18 it is beneficial to block the two-way valve assembly 24 in order to enforce, that the entire coolant of the engine cooling system circulates through the radiator 12.

For this purpose, the thermostatic valve assembly 24 is adapted to block fluid flow therethrough as soon as the coolant temperature rises above a second predefined temperature Tciose. In this way a further heating of the coolant can be counteracted by providing a maximum of cooling capacity by making exclusive use of the radiator 12.

The diagram in Figure 2 shows the opening behavior of the thermostatic valve assembly 24, 74 versus temperature 42. In vertical direction 44, the degree of opening of the valve assembly 24, 74 is illustrated in percent from 0 to 100, whereas the rising temperature reflects in horizontal direction 42. As apparent from the diagram 40, the valve remains 24, 74 substantially closed as the temperature rises. It abruptly opens with the temperature approaching a first temperature Topen.

Already slightly above Topen, the valve 24, 74 is opened to a degree of 75 to 80 percent. As the temperature further rises, opening of the valve approaches 100 percent. As soon as the coolant temperature approaches the second predefined temperature Tciose, the pathway for the coolant is abruptly blocked and the opening of the valve approaches 0 percent.

In the series of sketches according to Figures 3 to 5, a first embodiment of the thermostatic valve assembly 24 is illustrated. Said valve assembly 24 comprises a housing 48, an inlet port 50 as well as an outlet port 52. Inside the housing 48 there is provided a chamber 53 in which a first sealing element 60 and a second sealing element 62 are movably disposed. In the initial configuration according to Figure 3, which reflects a situation, wherein the coolant temperature is below Topen, a first sealing element 60 abuts with a circumferential sealing member 64 against an inner sidewall of the chamber 53.

In this setup, the sealing element 60 blocks a pathway through the valve assembly 24. Coolant approaching the valve assembly 24 via the inlet port 50 can therefore not enter the chamber 53. In order to provide at least a minimum of coolant circulation, the inlet port 50 is provided with a bypass line 68, so that the coolant being present at the inlet port 50 is representative of the coolant circulating in the engine cooling system 10.

In or between the inlet ports 50 there is further provided a support structure 51 for a first thermal expansion element 54, 56. This thermal expansion element 54, 56 comprises a piston 56 being mechanically engaged with the sealing disc 60. The thermal expansion element 54 is further filled with a temperature sensitive medium, such as a wax component featuring a well-defined melting point, which for instance matches with the first temperature Topen.

VJhen the coolant heats up to the first temperature, the wax component inside the thermal expansion element 54 melts and expands, which leads to a respective displacement of the piston 56' of the thermal expansion element 54' as depicted in Figure 4. As a consequence, the sealing disc 60' is shifted upwards and coolant may enter the chamber 53 via the inlet port 50.

Since the oppositely disposed second sealing element 62' is not yet in contact with an upper wall of the chamber 53, inlet port 50 and outlet port 52 are in fluid-flow communication and the liquid coolant is allowed to pass through the valve assembly 24' as depicted in Figure 4. The second sealing element 62 is almost identical to the first sealing element 60. Its orientation is rotated by 1800 with respect to the first sealing element 60, such that the sealing member 64 of the second sealing element 62 faces towards an upper wall of the chamber 53.

In the embodiment according to Figures 3 to 5, first and second sealing members 60, 62 are mechanically engaged by means a second thermal expansion element 55, 58 arranged between the sealing disc 60 and the second sealing element 62. As becomes apparent from a comparison of Figures 4 and 5, the second thermal expansion element 55' will stretch with its piston 58'' to its extended configuration as soon as the coolant temperature approaches the second predefined temperature Tciose.

Generally, the second thermal expansion element 55, 58 is similarly designed compared to the first thermal expansion element 54, 56 but may only be provided with a different wax composition. As the second expansion element 55', 58'' stretches to its final and extended configuration as depicted in Figure 5, the second sealing element 62" approaches the upper wall of the chamber 53 until it abuts with said wall with its sealing member 64.

In the configuration according to Figure 5, which refers to a temperature range above Tciose, a pathway between inlet port 50 and outlet port 52 is blocked again. In this setup, coolant may circulate through the chamber 53 by way of the bypass line 68 so as to maintain a minimal coolant flow allowing to keep the temperature of the coolant inside the chamber 53 close to the temperature of the coolant circulating in the main cooling circuit 30.

In the embodiment according to Figures 3 and 5, the upper second sealing element 62 is spring-loaded with respect to the housing 48 of the thermostatic valve assembly 24. Hence, a compression spring element 66 extends between an upper sidewall of the chamber 53 and the upper second sealing element 62. Since the thermal expansion element 54, 56, 55, 58 and the corresponding sealing elements or sealing discs 60, 62 are arranged in series, a restoring force for returning first and second sealing elements 60, 62 as well as first and second thermal expansion elements 54, 56, 55, 58 can be provided by a single and common spring element 66.

In Figures 6 through 8, another embodiment of a thermostatic valve assembly 74 is illustrated in three different configurations representing three different coolant temperatures, namely below between Topen and Tciose and above Tcioe, respectively. In an initial configuration according to Figure 6, inlet port 76 and outlet port 78 of the thermostatic valve assembly 74 are not in a fluid-flow communication. Here, a sealing element 90, 88 is in its closed configuration. The sealing element 90 comprises a sealing cone matching with an orifice provided in a sealing disc 88. Both components of the sealing element 88, 90 are coupled to a common support structure 92, 94 via first and second thermal expansion elements 80, 82, respectively.

The second thermal expansion element 82 is supported on a support structure 94 whereas the first thermal expansion element 80 is connected to a support structure 92. In contrast to the embodiment according to Figures 3 to 5, both support structures 92, 94 are immobile with respect to the housing of the thermostatic valve assembly 74. It is even conceivable, that support structure 92 and support structure 94 are integrally formed, e.g. with the housing of the valve assembly 74. I0

The disc like sealing element 88 is supported by two symmetrically arranged pistons 80 that act as thermal expansion elements being sensitive to a first lower temperature Topen. In response to the coolant being heated to said first temperature, the thermal expansion element stretches in direction of the main coolant flow and the sealing element 88 becomes displaced with respect to the sealing cone 90. Hence, the sealing seat formed by sealing cone 90 and corresponding orifice of the sealing element 88 is annihilated. Consequently, coolant entering the valve assembly 74' via the inlet port 76 may flow through the chamber 77 and may leave the thermostatic valve assembly 74' via the outlet port 78.

When the coolant temperature further rises, the second thermal expansion element 82 is activated and starts to stretch in the same direction as the first thermal expansion element 80' did before. Consequently, the sealing cone 90' approaches the sealing element 88' and a sealing seat between sealing cone 90' and sealing element 88' is reestablished.

In the illustrated configurations according to Figures 7 and 8, the thermally induced displacement provided by first and second thermal expansion elements 80' and 82' is limited by a stopper element 96 radially inwardly protruding from the housing of the thermostatic valve assembly 74.

In contrast to the embodiment according to Figures 3 to 5, the valve assembly 74 is provided with two spring elements 84, 86, each of which being individually engaged with the first or with the second sealing element 88, 90. In this way, first and second sealing elements 88, 90 can be displaced independent of another.

Even though not explicitly illustrated, also the thermostatic valve assembly 74 according to Figures 6 through 8 is provided with a bypass line in order to provide a minimum exchange of coolant even if the pathway through the thermostatic valve assembly 74 is blocked.

Li St of reference nume ra is engine cooling system 12 radiator 14 fan 16 passenger heating and/or air conditioning (HVAC) 18 engine pump 22 valve assembly 24 valve assembly 26 engine module 28 bypass main cooling circuit 32 bypass 40 diagram 42 temperature 44 opening degree 48 housing inlet port 51 support structure 52 outlet port 53 chamber 54 thermal expansion element thermal expansion element 56 piston 58 piston sealing element 62 sealing element 64 sealing member 66 spring element 68 bypass line 74 thermostatic valve assembly 76 inlet port 78 outlet port thermal expansion element 82 thermal expansion element 84 spring element 86 spring element 88 sealing element sealing element 92 support structure 94 support structure 96 stopper

Claims

Cia ims 1. A thermostatic valve assembly for use in an engine cooling system having an inlet port (50; 76) and an outlet port (52; 78) and comprising at least one moveabie sealing element (60, 62; 88, 90) for selectively blocking or opening a pathway for a coolant circulating in the engine cooling system, characterized by at least a first and a second thermal expansion element (54, 56, 55, 58; 80, 82), wherein for opening of the pathway the first thermal expansion element (54, 56; 80) is adapted to stretch to an extended configuration in response to the coolant having a first temperature and wherein for blocking of the pathway, the second thermal expansion element (55, 58; 82) is adapted to stretch to an extended configuration in response to the coolant having a second temperature, which is above the first temperature.
2. The valve assembly according to claim 1, wherein the first and second expansion elements (54, 56, 55, 58; 80, 82) are mounted on a support structure (51, 60; 92, 94) with a first end portion and being mechanically engaged with the sealing element (60, 62; 88, 90) with a second, opposite end portion.
3. The valve assembly according to any one of the preceding claims, further comprising a first sealing element (60; 88) mechanically engaged with the first expansion element (54, 56; 80) and further comprising a second sealing element (62, 90) mechanically engaged with the second expansion element (62; 90)
4. The valve assembly according to claim 2 or 3, wherein the second thermal expansion element (55, 58) is mechanically engaged with the second end portion of the first thermal expansion element (54, 56)
5. The valve assembly according to any one of the preceding claims, wherein the second thermal expansion element (55, 58) is adapted to displace the second sealing element (62) with respect to the first sealing element (60)
6. The valve assembly according to any one of the preceding claims, wherein the first thermal expansion element (54, 56) is adapted to displace first and second sealing elements (60, 62) with respect to a housing of the valve assembly in unison.
7. The valve assembly according to any one of the preceding claims, wherein first and second expansion elements (54, 56, 55, 58) and/or first and second sealing elements (60, 62) are loaded by a common spring element (66)
8. The valve assembly according to any one of the preceding claims 1 to 3, wherein the first and the second sealing element (88, 90) form a sealing seat and wherein first and second sealing elements (88, 90) are coupled to a common support structure (92, 94) via first and second thermal expansion elements (80, 82), respectively.
9. The valve assembly according to any one of the preceding claims, wherein the first sealing element (88) is spring loaded by a first spring element (84) and wherein the second sealing element (90) is spring loaded by a second spring element (86)
10. The valve assembly according to any one of the preceding claims, wherein the first sealing element comprises a sealing cone (90) forming a sealing seat with the second sealing element (88) comprising an orifice adapted to receive the sealing cone (90)
11. The valve assembly according to any one of the preceding claims, further comprising an electrically driven heating unit for manually triggering a thermally induced stretching of the first and/or the second thermal expansion element (54, 56, 55, 58; 80, 82)
12. An engine cooling system comprising a cooling circuit having at least one bypass (28) branched-off from a main cooling circuit (30), wherein the bypass (28) is thermally coupled with a passenger heating and/or air conditioning system (16) and further comprising at least one valve assembly (24) according to any one of the preceding claims, for thermally connecting the bypass (28) with the main cooling circuit (30) only if the coolant temperature is between the first temperature and the second temperature.
13. A motorized vehicle comprising an engine and an engine cooling system according to claim 12.
14. A method of operating an engine cooling system comprising a main cooling circuit (30) and a bypass (28) being thermally coupled with a passenger heating and/or air conditioning system (16) and comprising a valve assembly (24) according to any one of the preceding claims 1 to 11, the method comprises the steps of: -opening a pathway in the valve assembly (24) for thermally coupling the heating and/or air conditioning system (16) with the main cooling circuit (30) as the coolant temperature reaches a first predefined temperature, and -blocking the pathway in the valve assembly (24) as soon as the coolant temperature exceeds a second predefined temperature which is above the first temperature.