GB2540401A

GB2540401A - A cooling assembly

Info

Publication number: GB2540401A
Application number: GB1512442.3A
Authority: GB
Inventors: Swithun Hale Thomas
Original assignee: Chongqing Changan Automobile Co Ltd; Changan UK R&D Centre Ltd
Current assignee: Chongqing Changan Automobile Co Ltd; Changan UK R&D Centre Ltd
Priority date: 2015-07-16
Filing date: 2015-07-16
Publication date: 2017-01-18
Anticipated expiration: 2035-07-16
Also published as: GB2540401B; GB201512442D0

Abstract

The assembly 10 is for controlling the temperature of a vehicle engine and includes a coolant fluid control element 20 selectively operable in a first series mode (figure 2) and a second parallel mode (figures 3 and 4). In the series mode the control element directs coolant in series through one of a cylinder head 16 and engine block 18 of the engine and subsequently through the other of the cylinder head and engine block. In the parallel mode the control element directs coolant through the cylinder head and engine block simultaneously. Ideally the control element comprises a first valve element 26 that closes when the coolant temperature is below a first threshold to enable the series mode and opens when the coolant temperature is above a second threshold to enable the parallel mode. A second valve element 30 may be included to selectively open a heat discharge flow path 32 during the parallel mode to pass coolant from the engine to a heat removal unit 34 such as a radiator 36. A third valve element 38 may be provided that closes a bypass flow path 40 circumventing the radiator when the control element is in the series mode.

Description

A COOLING ASSEMBLY

This invention relates to a cooling assembly for controlling the temperature of a vehicle engine.

It is desirable to control the temperature of a vehicle engine so as to prevent components of the vehicle engine overheating during operation of the vehicle engine, which could lead to damage of the components and therefore prevent the vehicle engine from working properly.

According to a first aspect of the invention there is provided a cooling assembly, for controlling the temperature of a vehicle engine, comprising an engine coolant circuit around which a coolant fluid flows, the engine coolant circuit including an engine cylinder head and an engine block arranged in fluid communication with one another and a coolant fluid control element selectively operable in a first series mode and a second parallel mode, the coolant fluid control element in the first series mode directing the coolant fluid in series through one of the engine cylinder head and the engine block and then the other of the engine cylinder head and the engine block, and the coolant fluid control element in the second parallel mode directing the coolant fluid in parallel through both the engine cylinder head and the engine block simultaneously.

The inclusion of a coolant fluid control element that is operable in a first series mode in which coolant fluid is directed in series through one of the engine cylinder head and the engine block and then the other of the engine cylinder head and the engine block enables a maximum amount of heat to be transferred from each of the engine cylinder head and the engine block to the coolant fluid, and so increases the temperature of the coolant fluid as quickly as possible.

This is particularly desirable when starting a vehicle engine from cold as having the temperature of the coolant fluid rise as quickly as possible allows it to be used to warm quickly a lubricant fluid, e.g. an engine oil, within the engine. Warming the lubricant fluid is, in turn, especially advantageous because it improves the efficiency with which the engine is able to operate and so reduces fuel consumption and harmful emissions during such start-up of the engine.

Meanwhile, having a coolant fluid control element that is operable in a second parallel mode in which coolant fluid is directed in parallel through both the engine cylinder head and the engine block simultaneously provides for the efficient removal of heat from the engine cylinder head and engine block and consequently control of the engine temperature, e.g. when the engine has warmed to its normal operating temperature, in a manner that is best-suited to minimising the degree of knocking combustion taking place, i.e. minimising the amount of air/fuel mixture which spontaneously ignites within the engine cylinder head rather than burning progressively.

Preferably the coolant fluid control element operates in the first series mode when the temperature of the vehicle engine is below a first threshold and the coolant fluid control element operates in the second parallel mode when the temperature of the vehicle engine is above a second threshold.

Such an arrangement permits the temperature of the coolant fluid to be increased as quickly as possible when the vehicle engine is cold, i.e. when the temperature of the vehicle engine is below the first threshold, such as during start-up of the engine. Moreover, the arrangement allows subsequent control of the vehicle engine temperature once the engine has warmed to its normal operating temperature, i.e. when the temperature of the engine is above the second threshold.

The first and second thresholds may differ from one another.

Having first and second thresholds that are different to one another accommodates a gradual switching of the coolant fluid control element between the first series mode and the second parallel mode which may be desirable depending on how in practice the fluid control element is embodied.

In some embodiments of the invention the coolant fluid control element is operable in the first series mode to direct the coolant fluid in series through the engine cylinder head and then through the engine block.

Directing the coolant fluid through the engine cylinder head first increases the temperature of the coolant fluid in the quickest manner possible because the engine cylinder head is usually warmer than the engine block.

Optionally the coolant fluid control element in the first series mode directs the coolant fluid through the engine cylinder head in a first direction and through the engine block in a second direction opposite to the first direction.

The inclusion of a coolant fluid control element which provides the aforementioned functionality obviates the need for additional fluid conduits within the engine coolant circuit to selectively permit the directing of coolant fluid through the engine cylinder head and engine block in both series and parallel.

The coolant fluid control element may include a first valve element operable to selectively open a parallel flow path extending between the engine block and the engine cylinder head to permit the flow of coolant fluid through the said parallel flow path.

Such an arrangement selectively permits the flow of coolant fluid through the engine cylinder head and the engine block in parallel, as well as selectively forcing the coolant fluid to flow in series through the engine cylinder head and the engine block, and so desirably facilitates switching between the first series mode and the second parallel mode.

In other embodiments of the invention the engine coolant circuit includes a second valve element operable to selectively open a heat discharge flow path to permit the flow of coolant fluid through a heat removal unit.

The selective provision of such a heat discharge flow path permits regulation of the coolant fluid temperature by selectively transferring heat from the coolant fluid to another medium, e.g. the air outside the vehicle in which the engine is located, via the heat removal unit.

The second valve element may close the heat discharge flow path when the coolant fluid control element is operating in the first series mode.

Closing the heat discharge flow path when the coolant fluid control element is operating in the first series mode helps to ensure quick and efficient heating of the coolant fluid by preventing the removal of heat from the coolant fluid by the heat removal unit. As a result, prompt warming of a lubricant fluid can likewise be achieved.

Optionally the second valve element selectively opens the heat discharge flow path when the coolant fluid control element is operating in the second parallel mode.

Selectively opening the heat discharge flow path in this manner permits heat from the coolant fluid to be removed via the heat removal unit, as needed, and thereby maintains a desired temperature of the coolant fluid when the engine has warmed to its normal operating temperature. The coolant fluid is therefore able to regulate the engine temperature.

The first and second valve elements may be integrated within a single valve module.

The integration of the first and second valve elements within a single valve module reduces the number of moving parts required in the engine coolant circuit, and so leads to an even more reliable invention.

The engine coolant circuit may include a third valve element operable to provide a bypass flow path to permit the coolant fluid to bypass the heat removal unit.

The provision of such a bypass flow path and the option thereafter of allowing the coolant fluid to bypass the heat removal unit allows for regulation of the temperature of the coolant fluid.

Optionally the third valve element maintains the bypass flow path closed while the coolant fluid control element is in the first series mode.

Maintaining such a bypass flow path closed during this period helps to ensure all of the coolant fluid passes through the engine cylinder head and engine block, and so assists in ensuring the coolant fluid is heated as quickly as possible.

Preferably operation of the third valve element at least is dependent on the temperature of the engine block.

Such an arrangement means that the opening of the bypass flow path is determined by the temperature of the engine block which helps to ensure that the bypass flow path remains closed until the vehicle engine is sufficiently warm, i.e. the coolant fluid is warmed as quickly as possible until the vehicle engine is sufficiently warm.

Optionally the third valve element is positioned in direct contact with the engine block.

Positioning the third valve element in direct contact with the engine block allows the third valve element to react quickly to changes in the temperature of the engine block, and hence permit accurate opening of the bypass flow path.

There now follows a brief description of preferred embodiments of the invention, by way of non-limiting examples, with reference being made to the following drawings in which:

Figure 1 schematically shows a cooling assembly according to a first embodiment of the invention;

Figure 2 shows a configuration of the cooling assembly of Figure 1 when operating in a first series mode;

Figure 3 shows a first configuration of the cooling assembly of Figure 1 when operating in a second parallel mode;

Figure 4 shows a second configuration of the cooling assembly of Figure 1 when operating in the second parallel mode; and

Figure 5 schematically shows a cooling assembly according to a second embodiment of the invention. A cooling assembly according to a first embodiment of the invention is designated generally by reference numeral 10 and is shown in Figure 1.

The first cooling assembly 10 includes an engine coolant circuit 12 around which flows a coolant fluid 14 (not shown in Figure 1), that typically is a mixture of water and antifreeze.

The engine coolant circuit 12 includes an engine cylinder head 16 and an engine block 18 that are arranged in fluid communication with one another.

The engine coolant circuit 12 also includes a coolant fluid control element 20 that is selectively operable in a first series mode and a second parallel mode. In the embodiment shown, in the first series mode the coolant fluid control element 20 directs the coolant fluid 14 in series through the engine cylinder head 16 and then through the engine block 18 while, in the second parallel mode, the coolant fluid control element 20 directs the coolant fluid 14 in parallel through both the engine cylinder head 16 and the engine block 18 simultaneously. In other embodiments of the invention (not shown) the coolant fluid control element 20 may first direct coolant fluid 14 through the engine block 18 and then through the engine cylinder head 16 when operating in the first series mode.

The coolant fluid control element 20 operates in the first series mode when the temperature of a vehicle engine (not shown) in which the first cooling assembly 10 is located is below a first threshold and the coolant fluid control element 20 operates in the second parallel mode when the temperature of the said vehicle engine is above a second threshold.

In the embodiment shown, the first threshold differs from the second threshold and, by way of example, the first threshold is approximately 70°C and the second threshold is approximately 75°C. In other embodiments of the invention the first threshold may be higher than or lower than 70°C and the second threshold may similarly be different to 75°C. In still further embodiments of the invention the first and second thresholds may be the same as one another, and/or may vary according to engine speed and/or engine load.

In each instance such operation of the coolant fluid control element 20 is achieved by way of a thermostatic actuator. More particularly, the coolant fluid control element 20 includes a first valve element 26 that is operable to selectively open a parallel flow path 28 that extends between the engine block 18 and the engine cylinder head 16 so as to permit the flow of coolant fluid 14 through the said parallel flow path 28. One suitable type of first valve element 26 is a wax thermostatic element, although other valve elements are also possible, such as valve elements operated by an electric motor or gear, a pneumatic or hydraulic actuator or an electronic solenoid (which may, for example, utilise an existing or specially installed vacuum system or lubrication system), or a bi-metallic strip.

The first valve element 26 closes the parallel flow path 28 when the coolant fluid control element 20 is operating in the first series mode, as shown in Figure 2, whilst the first valve element 26 opens the parallel flow path 28 when the coolant fluid control element 20 is operating in the second parallel mode, as shown in Figures 3 and 4. In this manner the coolant fluid control element 20 is able in the first series mode to direct the coolant fluid 14 in series through the engine cylinder head 16 and then through the engine block 18, and more particularly direct the coolant fluid 14 through the engine cylinder head 16 in a first direction 22 and then through the engine block 18 in a second direction 24 opposite to the first direction 22.

The engine coolant circuit 12 further includes a second valve element 30 that is operable to selectively open a heat discharge flow path 32 so as to permit the flow of coolant fluid 14 through a heat removal unit 34. In the embodiment shown the second valve element 30 is also a wax thermostatic element, although other types of valve element may also be used.

The heat removal unit 34 in the embodiment shown is a radiator 36, but it may be any type of unit which permits the transfer of heat from one medium to another, i.e. any type of heat exchanger.

The second valve element 30 closes the heat discharge flow path 32 when the coolant fluid control element 20 is operating in the first series mode, and selectively opens the heat discharge flow path 32 when the coolant fluid control element 20 is operating in the second parallel mode. More particularly, the second valve element 30 progressively opens the heat discharge flow path 32 when the temperature of the coolant fluid 14 reaches a third threshold, which by way of example extends across the approximate range of 85°C to 100°C.

The engine coolant circuit 12 further includes a third valve element 38 that is operable to provide a bypass flow path 40 to permit the coolant fluid 14 to bypass the heat removal unit 34.

When the coolant fluid control element 20 is operating in the first series mode the third valve element 38 ensures that the bypass flow path 40 is closed.

Meanwhile, when the coolant fluid control element 20 is operating in the second parallel mode, the third valve element 38 ensures that the bypass flow path 40 is open, as shown in Figures 3 and 4. Thereafter, operation of the second valve element 30 to open the heat discharge flow path 32 and simultaneously close the bypass flow path 40 (as shown in Figure 3), i.e. when the temperature of the coolant fluid 14 is above the coolant fluid threshold, causes the coolant fluid 14 to pass through the heat removal unit 34 whereby the temperature of the coolant fluid 14 is reduced. In the meantime, operation of the second valve element 30 to close the heat discharge flow path 32 and at the same time open the bypass flow path 40 (as shown in Figure 4), i.e. when the temperature of the coolant fluid 14 is below the coolant fluid threshold, prevents the coolant fluid from flowing through the heat removal unit 34 such that it continues to flow around the engine coolant circuit 12 via the said open bypass flow path 40.

As shown in Figures 2 to 4, the first and third valve elements 26, 38 are coupled with one another such that they operate in unison with one another. As a result, the third valve element 38 begins to open the bypass flow path 40 only when the coolant fluid control element 20 switches from the first series mode to the second parallel mode, i.e. only when the first valve element 26 moves from a closed position (as shown in Figure 2) to an open position (as shown in Figure 3). In this manner the combined operation of the first and third valve elements 26, 38 maintains the bypass flow path 40 closed in the first series mode while in the second parallel mode allowing the second valve element 30 to selectively open and close the bypass flow path 40 according to whether the heat discharge flow path 32 is correspondingly closed or open.

Operation of both the first and third valve elements 26, 38 is dependent on the temperature of the engine block 18 and indeed the first and third valve elements 26, 38 are both positioned in direct contact with the engine block. The third valve element 38 is similarly a wax thermostatic element, but a different type of valve element could be used.

The engine coolant circuit 12 also includes a heat exchange flow path 42 which permits the flow of coolant fluid 14 through a heat exchanger 44. The heat exchanger 44 is arranged in thermal communication with an engine lubricant circuit (not shown), and so permits the transfer of heat between the coolant fluid 14 flowing in the engine coolant circuit 12 and a lubricant fluid, e.g. an engine oil, that is flowing through the engine lubricant circuit.

In addition to the foregoing, the first cooling assembly 10 further includes a pump 46 which is in fluid communication with the engine coolant circuit 12 to drive the coolant fluid 14 around the engine coolant circuit 12. In particular, the pump 46 is arranged in the engine coolant circuit 12 so as to drive the coolant fluid 14 towards the engine cylinder head 16.

The first cooling assembly 10 also includes a header tank 48 that is similarly in fluid communication with the engine coolant circuit 12 which helps to ensure the engine coolant circuit 12 remains full of coolant fluid 14. In other embodiments of the invention (not shown) the header tank 46 may instead be an expansion tank to accommodate expansion of the coolant fluid 14 during use of the invention.

The engine coolant circuit 12 shown further includes an optional cabin heater flow path 50 which permits the flow of coolant fluid 14 through a cabin heater unit 52 upon switching of a cabin heater valve 54. The cabin heater unit 52 includes a heat transfer element (not shown) to transfer heat from the coolant fluid 14 flowing through the heater flow path 50 into a vehicle cabin (not shown) via the cabin heater unit 52. Optionally the cabin heater unit 52 could instead be arranged in series with the oil heat exchanger 44.

Operation of the first cooling assembly 10 will now be described, with the vehicle engine in which the first cooling assembly 10 is located being initially in a cold state, i.e. with the vehicle having been switched off for some time, e.g. overnight.

When the vehicle engine is started up, the pump 46 begins to drive the coolant fluid 14 towards the engine cylinder head 16. The temperature of the vehicle engine is below the first threshold, and so the coolant fluid control element 20 operates in the first series mode, i.e. the first valve element 26 is closed whereby the parallel flow path 28 is similarly closed, and so the first valve element 26 prevents the flow of coolant fluid 14 between the engine cylinder head 16 and the engine block 18 via such a path 28.

As a result, the coolant fluid 14 is forced through the engine cylinder head 16 in the first direction 22 and then through the engine block 18 in the second direction 24.

The coolant fluid 14 leaves the engine block 18 and flows through the heat exchange path 42 into the heat exchanger 44. After the heat exchange path 42, the coolant fluid 14 returns, via the second valve element 30, to the pump 46 to begin the aforementioned flow cycle again.

Each of the engine cylinder head 16 and engine block 18 heats up as operation of the vehicle engine is underway. As a result, heat from the engine cylinder head 16 and engine block 18 is transferred to the coolant fluid 14 flowing therethrough and the temperature of the coolant fluid 14 begins to rise.

The now heated coolant fluid 14 flows through the heat exchange path 42 and heat from the coolant fluid 14 is transferred via the heat exchanger 44 to the engine lubricant circuit, which in turn heats a lubricant fluid flowing through the engine lubricant circuit. In this way, the lubricant fluid is heated quickly during start-up of the vehicle engine.

During this time the heat discharge flow path 32 is closed by the second valve element 30 and the bypass flow path 40 is closed by the corresponding third valve element 38. As a result, all of the coolant fluid 14 is forced through the engine cylinder head 16 and engine block 18 in the manner set out above.

As the vehicle engine continues to warm its temperature moves between the first and second thresholds, i.e. between 70°C and 75°C. More specifically, as the temperature of the engine block 18 reaches the first threshold of 70°C the third valve element 38 begins to open the bypass flow path 40 at the same time as the first valve element 26 begins to open the parallel flow path 28. During this temporary transition, i.e. as the temperature of the engine block rises from 70°C to 75°C, coolant fluid 14 may be unable to flow through the parallel flow path 28 but able to flow through the bypass flow path 40 and towards the pump 46, and so in this transitional switching period coolant fluid 14 may not be able to flow through the engine block 18.

The temporary lack of coolant fluid 14 through the engine block 18 causes its temperature to increase rapidly, and so the first and third valve elements 26, 38 operate quickly to open the parallel flow path 28 and close the bypass flow path 40, respectively. Consequently, as the vehicle engine temperature reaches and exceeds the second threshold of 75°C, the first valve element 26 is fully open (as shown in Figures 3 and 4) and the engine coolant fluid control element 20 is operating in the second parallel mode, i.e. the parallel flow path 28 is open and coolant fluid 14 is directed to flow in parallel through both the engine cylinder head 16 and the engine block 18 simultaneously.

In other embodiments in which the first and third valve elements 26, 38 open and close instantaneously, e.g. if they are part of a thermal management system controlled by an electronic control unit, such a transitional switching period may not arise.

Moreover, as mentioned above, when the temperature of the coolant fluid 14 lies towards the upper end of the third threshold, the second valve element 30 progressively opens the heat discharge flow path 32 and simultaneously progressively closes the bypass flow path 40 (as shown in Figure 3) so as to permit the flow of some or all of the coolant fluid 14 leaving the engine cylinder head 16 and the engine block 18 through the heat removal unit 34. The heat removal unit 34 then transfers heat from the said some or all of the coolant fluid 14 to the air outside the vehicle in which the engine is located, and so the coolant fluid 14 is cooled.

The now cooled coolant fluid 14 leaves the heat removal unit 34 and returns to the pump 46.

As and when the temperature of the coolant fluid 14 falls towards the lower end of the third threshold the second valve element 30 progressively closes the heat discharge flow path 32 while simultaneously progressively opening the bypass flow path 40 (as shown in Figure 4) and use of the heat removal unit 34 by some or all of the coolant fluid 14 is suspended.

In the foregoing manner the second valve element 30 operates to regulate the temperature of the coolant fluid 14, and more particularly operates to progressively blend cooled coolant fluid 14 flowing through the heat discharge flow path 32 with uncooled coolant fluid flowing in the bypass flow path 40.

In each instance coolant fluid 14 circulates through the engine cylinder head 16 and the engine block 18 and heat from the engine cylinder head 16 and the engine block 18 is transferred to the coolant fluid 14.

In addition to the foregoing, the coolant fluid 14 flows through the heat exchanger 44 which permits the transfer of heat from the engine lubricant flowing through the engine lubricant circuit to the coolant fluid 14.

During operation of the vehicle engine and while the coolant fluid control element 20 is operating in the second parallel mode, the cabin heater flow path 50 may be selectively opened by the cabin heater valve 54 so as to permit the flow of coolant fluid 14 through the cabin heater unit 52. The heat transfer element present in the cabin heater unit 52 is then able to transfer heat from the coolant fluid 14 into a vehicle interior. A cooling assembly according to a second embodiment of the invention is designated generally by the reference numeral 100 and is shown in Figure 5.

The second cooling assembly 100 includes identical features to the first cooling assembly 10 and such like features share the same reference numerals.

The second cooling assembly 100 differs from the first cooling assembly 10 in that it includes a second engine coolant circuit 212 in which the first, second and third valve elements 26, 30, 38 are integrated within a single valve module 110. In other embodiments of the invention (not shown) only the first and third valve elements 26, 38 may be integrated within a single valve module.

The valve module 110 is a rotating valve 112 which is driven by an electric motor (not shown). The second cooling assembly 100 may optionally include a control unit, such as a programmable microcontroller, to control the electric motor or the valve module 110 directly if some other actuator is used. Such a control unit may also, in other embodiments of the invention, control one or more of the first, second and third valve elements 26, 30, 38 in the first engine coolant circuit 12.

The valve module 110 has five ports 114a, 114b, 114c, 116a, 116b which consist of first, second and third inlet ports 114a, 114b, 114c and first and second outlet ports 116a, 116b.

The first inlet port 114a is in fluid communication with the parallel flow path 28, the second inlet port 114b is in fluid communication with the bypass flow path 40, and the third inlet port 114c is in fluid communication with the heat discharge flow path 32.

Meanwhile the first outlet port 116a lies in fluid communication with the parallel flow path 28 and cooperates with the first inlet port 114a to selectively permit the flow of coolant fluid 14 through the parallel flow path 28.

The second outlet port 116b selectively cooperates with each of the second and third inlet ports 114b, 114c so as to permit either the flow of coolant fluid 14 through the bypass flow path 40 (via the second inlet port 114b) or through the heat discharge flow path 32 (via the third inlet port 114c).

The second cooling assembly 100 operates in a similar manner to that described hereinabove in relation to the first cooling assembly 10.

In particular, when the coolant fluid control element 20 is operating in the first series mode and the coolant fluid 14 is therefore to be prevented from flowing through the parallel flow path 28, no fluid conduit is provided within the valve module 110 between the first inlet port 114a and the first outlet port 116a such that both are effectively closed so as to prevent such flow.

In the meantime, when the coolant fluid control element 20 is operating in the second parallel mode, and the flow of the coolant fluid 14 is to be permitted through the parallel flow path 28, a fluid conduit is provided between the first inlet port 114a and the first outlet port 116a such that both are effectively open so as to permit such flow.

Moreover, flow of the coolant fluid 14 is prevented through both of the heat discharge flow path 32 and the bypass flow path 40 when the coolant fluid control element 20 is operating in the first series mode by failing to provide a fluid conduit between each of the second and third inlet ports 114b, 114c and the second outlet port 116, i.e. by effectively closing at least the second and third inlet ports 114b, 114c.

Meanwhile, as desired during the second parallel mode, flow of the coolant fluid 14 is progressively switched between the heat discharge flow path 32 and the bypass flow path 40 by selectively providing one or both of a fluid conduit between the second inlet port 114b and the second outlet port 116b (to allow flow through the bypass flow path 40), and a fluid conduit between the third inlet port 114c and the second outlet port 116b (to allow flow through the discharge flow path 32). Such switching allows control of the coolant fluid temperature by mixing, i.e. progressively blending, cooled coolant fluid 14 flowing through the heat discharge flow path 32 with uncooled coolant fluid flowing in the bypass flow path 40.

Claims

CLAIMS:

1. A cooling assembly, for controlling the temperature of a vehicle engine, comprising an engine coolant circuit around which a coolant fluid flows, the engine coolant circuit including an engine cylinder head and an engine block arranged in fluid communication with one another and a coolant fluid control element selectively operable in a first series mode and a second parallel mode, the coolant fluid control element in the first series mode directing the coolant fluid in series through one of the engine cylinder head and the engine block and then the other of the engine cylinder head and the engine block, and the coolant fluid control element in the second parallel mode directing the coolant fluid in parallel through both the engine cylinder head and the engine block simultaneously.

2. A cooling assembly according to Claim 1 wherein the coolant fluid control element operates in the first series mode when the temperature of the vehicle engine is below a first threshold and the coolant fluid control element operates in the second parallel mode when the temperature of the vehicle engine is above a second threshold.

3. A cooling assembly according to Claim 2 wherein the first and second thresholds differ from one another.

4. A cooling assembly according to any preceding claim wherein the coolant fluid control element is operable in the first series mode to direct the coolant fluid in series through the engine cylinder head and then through the engine block.

5. A cooling assembly according to any preceding claim wherein the coolant fluid control element in the first series mode directs the coolant fluid through the engine cylinder head in a first direction and through the engine block in a second direction opposite to the first direction.

6. A cooling assembly according to any preceding claim wherein the coolant fluid control element includes a first valve element operable to selectively open a parallel flow path extending between the engine block and the engine cylinder head to permit the flow of coolant fluid through the said parallel flow path.

7. A cooling assembly according to any preceding claim wherein the engine coolant circuit includes a second valve element operable to selectively open a heat discharge flow path to permit the flow of coolant fluid through a heat removal unit.

8. A cooling assembly according to Claim 7 wherein the second valve element closes the heat discharge flow path when the coolant fluid control element is operating in the first series mode.

9. A cooling assembly according to Claim 7 or Claim 8 wherein the second valve element selectively opens the heat discharge flow path when the coolant fluid control element is operating in the second parallel mode.

10. A cooling assembly according to any one of Claims 7 to 9 wherein the first and second valve elements are integrated within a single valve module.

11. A cooling assembly according to any one of Claims 7 to 10 wherein the engine coolant circuit includes a third valve element operable to provide a bypass flow path to permit the coolant fluid to bypass the heat removal unit.

12. A cooling assembly according to Claim 11 wherein the third valve element maintains the bypass flow path closed while the coolant fluid control element is in the first series mode.

13. A cooling assembly according to Claim 11 or Claim 12 wherein operation of the third valve element at least is dependent on the temperature of the engine block.

14. A cooling assembly according to Claim 13 wherein the third valve element is positioned in direct contact with the engine block.

15. A cooling assembly as herein described with reference to and/or as illustrated in the accompanying drawings.