GB2523980A

GB2523980A - Method of identifying a fault

Info

Publication number: GB2523980A
Application number: GB1320642.0A
Authority: GB
Inventors: Stuart Briscoe
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2013-11-22
Filing date: 2013-11-22
Publication date: 2015-09-16
Anticipated expiration: 2033-11-22
Also published as: WO2015075219A1; GB2523980B; EP3071810A1; GB201320642D0

Abstract

A method of identifying the condition of a temperature responsive valve, eg mechanical thermostat 107, which controls the flow of coolant in an engine cooling system 101 having a radiator 103 comprises (i) measuring t1, the temperature of coolant fluid as it exits the engine; (ii) measuring t2, the temperature of coolant fluid as it exits the radiator; and (iii) diagnosing the condition of the temperature responsive valve, eg whether it stuck, dependent upon the measured values of t1 and t2. The thermostat 107 may be identified as stuck open if t1 and t2 meet a first criterion or as stuck closed if they meet a second criterion. The method may also involve calculating a radiator cooling factor tr = (t2 t3)/(t1 t3) where t3 is ambient temperature. A fault in the thermostat may be reported if the fault occurs more than a predetermined number of times.

Description

Method of Identifying a Fault

TECHNICAL FIELD

This invention relates to a method of identifying the state of or a fault in a temperature responsive valve, a cooling system for use in an engine, and an engine comprising same.

BACKGROUND

Internal combustion engines typically have an ideal operating temperature. At or near this temperature the components of the engine will function most effectively. In particular, lubricants within the engine will be at their most efficient, reducing wear on engine components. In addition, if the engine becomes too hot, this may damage the components of the engine. Therefore it is often necessary to manage the temperature of an engine while it is operating.

For this reason, internal combustion engines are typically provided with a radiator. Coolant may be pumped through the engine, absorbing heat from the components of the engine, and then passed into the radiator. In the radiator, the heat from the coolant is allowed to dissipate, typically into an air stream which may be blown over the radiator by a fan. In this way the engine is cooled, preventing the engine from becoming overheated and so preventing damage to the components of the engine.

However, it is not always desirable to remove heat from the engine. In particular, when the engine is beneath its ideal operating temperature, for example when the engine has just been started, it may be desirable to allow the engine to heat up as quickly as possible.

Therefore many internal combustion engines use a temperature responsive valve, often called a thermostat, to control the flow of coolant to the radiator.

The thermostat is typically a mechanical device which is arranged to allow coolant to flow to the radiator once a predetermined temperature is reached. Mechanical thermostats are inexpensive and reliable. However, without the addition of other components, they do not provide feedback as to their status to the engine management systems. It would be useful to know this in order to better manage other aspects of the engine's functions.

In addition, thermostats are subject to sticking, and the thermostat may be stuck open, allowing coolant to flow to the radiator even at low temperatures, or stuck closed, preventing coolant from flowing to the radiator even at high temperatures.

In such circumstances the vehicle will run either hotter or colder than is necessary or desirable. This decreases the efficiency of the engine, and may cause damage to the engine's components. Therefore it would be desirable to be able to diagnose a stuck thermostat without needing to inspect the component.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention there is provided a method of identifying the condition of a temperature responsive valve when the temperature responsive valve is part of an engine cooling system which further comprises a fluid circulation system to circulate coolant fluid through the engine and a heat-dissipating radiator, and wherein the temperature responsive valve is arranged to control the amount of fluid which flows through the radiator. The method comprises: measuring t1, the temperature of coolant fluid as it exits the engine; measuring t2, the temperature of coolant fluid as it exits the radiator; and identifying the condition of the temperature responsive valve dependent upon the measured values of t and t2.

In this way the invention provides a method of identifying the condition of a temperature responsive valve without having to measure the state of the valve directly. This information can then be used to manage the behaviour of other valve and pumps within the coolant system, as well as other aspects of the engine, more efficiently. The temperature responsive valve may be a mechanical valve. The temperature responsive valve may comprise wax.

The temperature responsive valve may comprise a wax valve. Alternatively, the temperature responsive valve may comprise an electronic temperature sensor, an electrically driven valve or any other suitable components.

Typically the operating condition of the valve is determined by comparing t1 and t2. The method may comprise comparing t1 and t2 to predefined criteria. The method may further comprise: identifying that the temperature responsive valve is open if the measured values of ti and t2 meet a first set of predefined criteria; and identifying that the temperature responsive valve is closed if the measured values of ti and t2 meet a second set of predefined criteria.

The valve is open when it is in a position typically associated with a high temperature fluid passing through the valve. Where the valve comprises wax, the wax would then expand and cause the valve to "open". The valve is closed when it is in a position typically associated with a low temperature fluid passing through the valve.

The method may comprise: measuring t3, an ambient temperature; and identifying the condition of the temperature responsive valve dependent upon the measured values of t1, t2 and t3.

Where t3 is measured, it may be that the method comprises calculating a radiator cooling factor t1, wherein: t1 = (t2 -t3) / (t1 -t3) the method further comprising identifying the condition of the temperature responsive valve dependent upon the measured value of ti..

In accordance with a second aspect of the present invention there is provided a method of identifying a fault in a temperature responsive valve when the temperature responsive valve is part of an engine cooling system which further comprises a fluid circulation system to circulate coolant fluid through the engine and a heat dissipating radiator, and wherein the temperature responsive valve is arranged to control the amount of fluid which flows through the radiator. The method comprises: measuring t1, the temperature of coolant fluid as it exits the engine; measuring t2, the temperature of coolant fluid as it exits the radiator; and identifying a fault in the temperature responsive valve if the measured values of t1 and t2 meet predefined criteria.

In this way the invention provides a method of identifying a fault without having to inspect the temperature responsive valve directly. The temperature responsive valve may be a mechanical valve. The temperature responsive valve may comprise wax. The temperature responsive valve may comprise a wax valve. Alternatively, the temperature responsive valve may comprise an electronic temperature sensor, an electrically driven valve or any other

suitable components.

It may be that the method further comprises: identifying a Stuck Open fault in the temperature responsive valve if the measured values of t1 and t2 meet a first set of predefined criteria; or identifying a stuck-closed fault in the temperature responsive valve if the measured values ofti and t2 meet a second set of predefined criteria.

A Stuck Open fault indicates that the temperature responsive valve is stuck in an open position, for example because a wax component has shrunk but the valve has not closed. A Stuck Closed fault indicates that the temperature responsive valve is stuck in a closed position, for example because the wax has expanded or attempted to expand, but the valve has not opened.

Often, a Stuck Closed fault is associated with a high value of t1 and a low value of t2. In contrast, a Stuck Open fault is generally associated with a low value of t1 and a value of t2 close to t1.

It may be that the method further comprises: measuring t3, an ambient temperature; and identifying a fault in the temperature responsive valve if the measured values of t1, t2 and t3 meet predefined criteria.

Typically, t3 will be a temperature outside the engine. However t3 may also comprise a temperature taken from a component within the engine, for example the temperature of air flow within a duct.

Where t3 is measured, it may be that the method comprises calculating a radiator cooling factor t1, wherein: t1 = (t -t3) I (t -t3) the method further comprising identifying a fault in the temperature responsive valve if the measured value oft1 meets a predefined criteria.

It may be that the method comprises identifying a Stuck Open fault in the temperature responsive valve if t1 is greater than a first predefined value. It may be that the method comprises identifying a Stuck Closed fault in the temperature responsive valve if t1 is less than a second predefined value. It may be that at least one of the first and second predefined values depends at least in part upon t1. It may be that at least one of the first and second predefined values depends at least in part upon t2. It may be that at least one of the first and second predefined values depends at least in part upon t3.

The invention further provides a method of reporting a fault, the method comprising: identifying a fault a plurality of times; increasing a first counter whenever a fault is identified; and reporting a fault in the temperature responsive valve if the first counter exceeds a first predetermined threshold.

Reporting a fault may comprise producing an audible or visual cue such as an alarm or a display on a vehicle dashboard. Reporting the fault need not necessarily happen immediately. For example, reporting a fault may comprise storing data in a memory for later retrieval by an engineer during a vehicle service.

It may be that the method further comprises: decreasing the first counter whenever a method of identifying a fault is performed and a fault is not identified.

Alternatively the method of reporting a fault may comprise decreasing the counter when a fault is identified, and increasing the counter when a fault is not identified.

The method of reporting a fault may comprise: increasing a first counter whenever a Stuck Open fault is identified; increasing a second counter whenever a Stuck Closed fault is identified; reporting a Stuck Open fault in the temperature responsive valve if the first counter reaches a first predefined threshold; and reporting a Stuck Closed fault in the temperature responsive valve if the second counter reaches a second predefined threshold.

The invention further provides a cooling system for use in an engine having a radiator to dissipate excess heat, the system comprising: a controller; a fluid circulation system to circulate coolant fluid through the engine and radiator; a temperature responsive valve; a first temperature sensor arranged to measure t1, the temperature of the coolant fluid in the fluid circulation system as the fluid exits the engine; and a second temperature sensor arranged to measure t2, the temperature of the coolant fluid in the fluid circulation system as the fluid exits the radiator, the controller being arranged to carry out any method as described above.

The invention further provides an engine for use in a vehicle, the engine comprising a cooling system as described above.

Lastly, the invention provides a vehicle comprising an engine as described above and a radiator.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 shows a diagram of a temperature regulation system according to the invention; and Figures 2 to 6 show tables in a database for the temperature regulation system of Figure 1.

DETAILED DESCRIPTION

Figure 1 shows a diagram of a temperature regulation system 101 suitable for use in a vehicle. The temperature regulation system 101 is intended to dissipate heat produced by the vehicle's internal combustion engine 102 through a radiator 103. The flow of coolant through the temperature regulation system 101 is indicated by lines and arrows 104.

When the temperature regulation system 101 is in use, a pump 105 pumps the coolant.

From the pump, the coolant first passes through the engine 102. The engine 102 is an internal combustion engine, and as such it comprises pistons (not shown) into which fuel is injected and then ignited, in order to drive the vehicle. The ignition of the fuel creates heat, raising the temperature of the pistons. The heat is then absorbed in part by the coolant as it passes through the engine 102.

As the coolant leaves the engine, it passes through an Engine Out temperature sensor 106, which measures t1, the temperature of the coolant as it leaves the engine. The coolant then passes through a thermostat 107. The thermostat 107 comprises a mechanical valve. The mechanical valve in turn comprises a volume of wax which expands and contracts as it heats and cools, operating the valve. The valve is arranged such that when the wax is cool, all of the coolant is directed by the thermostat to the pump 105 and from there back into the engine 102. This ensures that, while the engine is cool, the heat absorbed by the coolant is largely kept within the engine, allowing the engine to heat up quickly.

As the wax heats and expands, the valve operates, directing first some and then all of the coolant to a radiator 103. The radiator comprises a network of ducts through which the coolant flows, the outer surface of the ducts in the radiator being exposed to an air flow so that heat from the coolant can be conducted to the atmosphere. As such, the coolant decreases in temperature as it passes through the radiator 103.

As the coolant leaves the radiator 103, it passes through a Radiator Out temperature sensor 108, which measures t2, the temperature of the coolant as it leaves the radiator. The coolant then passes on to the pump 105 and from there back into the engine 102. The newly cooled coolant can then absorb more heat from the engine 102. This ensures that, when the engine is hot, it may be cooled by losing heat to the coolant.

As such, the action of the thermostat 107 helps to regulate the temperature of the engine, cooling the engine only once the engine has reached a desired temperature.

The temperature regulation system 101 also comprises an Ambient Temperature sensor 109, which measures t3, the ambient temperature of air surrounding the vehicle.

Lastly, the temperature regulation system 101 comprises a control unit 110, which is connected to the temperature sensors 106, 108, 109. The temperature sensors 106, 108, 109 report the measured temperatures t1, t2 and t3 to the control unit 110.

The control unit 110 is arranged to monitor the measured temperatures t1, t2 and t3 in order to determine or diagnose the condition of the thermostat 107, as well as diagnosing any faults in the thermostat 107, should one occur. Turning to fault condition first, if the thermostat becomes stuck, then the coolant will be misdirected and this may cause the engine to be over or under cooled. For example, if the thermostat is stuck so too much coolant passes through the radiator, then the engine will drop in temperature, causing the engine to operate inefficiently. Alternatively, if the thermostat is stuck so that too little coolant passes through the radiator, then the engine will rise in temperature. This may also cause the engine to operate inefficiently, and may also cause damage to the engine components.

The control unit 110 is arranged to periodically calculate a radiator cooling factor t1 using the equation: t1 = (t -t3) / (t1 -t3).

The control unit 110 further comprises a database, and example tables from the database are shown in Figures 2. The control unit also maintains a Stuck Open counter, c1 and a Stuck Closed counter, c2. Initially, both c1 and c2 are set to zero, and neither c1 nor c2 can drop below zero.

Whenever the control unit 110 calculates a value of t1, it compares t1 and the corresponding t1 temperature to the tables in the database. Figure 2 shows a table 201 intended to help diagnose a Stuck Open valve in the thermostat 107, in which the thermostat 107 becomes stuck such that too much coolant flows to the radiator. In these circumstances, the temperature of the engine, as indicated by t1, drops. The temperature t1 may also be low in cold atmospheric conditions, or when the engine has just started, and ordinarily this causes the valve in the thermostat 107 to close such that t1 remains high with respect to t2. However if the valve is stuck open then t1 will approach t2 such that tr approaches 1. Therefore if the valve is stuck open the values of t1 and t1 will tend to occupy the lower left portion of the thermostat Stuck Open regime table 201 shown in Figure 2.

Therefore the control unit 110 checks the thermostat Stuck Open regime table 201 and adds the value indicated by the table to c1. If the values correspond to the lower left portion of the table, then c1 increases by 1. Alternatively, if the values correspond to another location on the table then c1 is unchanged following the comparison with the thermostat Stuck Open

regime table 201.

Similarly, Figure 3 shows a table 202 intended to help diagnose a Stuck Closed valve in the thermostat 107, in which the thermostat 107 becomes stuck such that too little coolant flows to the radiator. In these circumstances, the temperature of the engine, as indicated by t1, rises. The temperature t1 may also be high in hot atmospheric conditions, or when the engine has been working hard, and ordinarily this causes the valve in the thermostat 107 to open such that t1 drops and t2 rises. However if the valve is stuck closed then t1 will remain high with respect to t2, such that t1 approaches 0. Therefore if the valve is stuck the values of t1 and t1 will tend to occupy the upper right portion of the thermostat stuck shut regime table 202 shown in Figure 3.

Therefore the control unit 110 checks the thermostat stuck shut regime table 202 and adds the value indicated by the table to c2. If the values correspond to the upper right portion of the table then c2 increases by 1. Alternatively, if the values correspond to another location on the table then c2 is unchanged following the comparison with the thermostat stuck shut

regime table 202.

It may be that the control unit 110 is arranged to immediately report an error if c1 or c2 increase by 1. However it is often advantageous to arrange for the control unit 110 to carry out multiple checks of t before reporting an error in order to ensure greater statistical rigour, since it is possible for the engine to enter into a Stuck Open or Stuck Closed regime when it is transitioning between states. For example, the engine may warm up enough to cause the valve to open, but then continue to warm for a brief while before the coolant has a chance to counteract this, causing the engine to briefly enter a state in which c2 would increase by 1.

Therefore typically the control unit 110 will only report an error if c1 or c2 pass a predetermined threshold. Separate thresholds may be provided for c1 and c2.

In addition, when the control unit 110 performs a check of t, it may be that everything is operating normally. In this case the radiator cooling factor t1 should approach 1 as the temperature of the vehicle rises. For this reason the control unit also compares tr and t1 to the thermostat normal open regime table 203 shown in Figure 4. The control unit 110 then subtracts the value in the table 203 from both c1 and c2. Therefore if the values of t1 and t1 occupy the lower right portion of the thermostat normal open regime table 203, then both c1 and c2 decrease by 1.

As such, c1 tends to increase when the valve in the thermostat 107 is stuck open, c2 tends to decrease when the valve in the thermostat 107 is stuck shut, and both c1 and c2 tend to decrease when the valve in the thermostat 107 is operating normally.

When c1 passes the threshold value for c1, the control unit 110 diagnoses a Stuck Open fault and reports this fault. Similarly, when c2 passes the threshold value for c2, the control unit diagnoses a Stuck Closed fault and reports this fault. Reporting the fault comprises displaying a message to the driver on their dashboard and logging the fault in a memory provided for such faults within the control unit 110. The message for the driver may be accompanied by an audible tone or similar.

When the vehicle is serviced, an engineer can then access the control unit 110 to download records indicating the nature of the fault, the time it was diagnosed, the values of c1 and c2 and any other relevant information.

In a further embodiment of the invention, the control unit is also arranged to trigger an intervention by a mechanical override provided as part of the valve in the thermostat 107.

The mechanical override may be arranged to move the thermostat to a particular position, either open, closed or in between depending upon the needs of the engine.

In a still further embodiment of the invention, a second thermostat stuck shut regime table 301 and a second thermostat Stuck Open regime table 302 are used. Examples of the second tables 301, 302 are shown in Figures 5 and 6. The tables are largely the same except that the values added to c1 and c2 are weighted according to how far the engine is from its expected operating regime. In this particular example, as the engine approaches extremes oft1 and t1, c1 and c2 may be increased by two instead of just one following a single check oft1 by the control unit 110.

Even when no fault is occurring, the control unit 110 shown in Figure 1 can still make use of the measurements of t1, t2 and t3 to determine the state of the thermostat 107. Figure 7 is a graph of the temperature readings received by the control unit during normal operation over time. Line 401 indicates t1, line 402 indicates t2 and line 403 indicates t3. Line 404 is the temperature recorded by a further temperature sensor (not shown in Figure 1) which is located close to the engine out temperature sensor 106 which measures t1.

As can be seen in the graph shown in Figure 7, over time the changing workload of the engine results in significant changes in t2, as measured by the radiator out temperature sensor 108. By watching for changes in this and other temperatures, the control unit 110 can diagnose changes in the thermostat 107. By way of an example, four dotted lines 405, 406, 407 and 408 have been added to the graph in Figure 7 to indicate when the thermostat 107 opens or closes. At lines 405 and 407, the thermostat 107 is opened, and this is associated with a sharp rise in t2. At lines 406 and 408 the thermostat 107 is closed, and this is associated with a sharp drop in t2. In operation, the control unit 110 diagnoses whether the thermostat is opened or closed by monitoring t1, t2 and t3. This information can then be used in the management of other engine control systems.

One example of where knowledge of the thermostat/valve state could be useful is in an engine with a variable flow coolant pump control. In such an engine, if the thermostat is open then it may be advantageous to increase the coolant flow by varying the amount of coolant pumped by the pump. Similarly, when the thermostat is closed it may be advantageous to reduce the coolant flow.

In the examples given above a cooling system according to the invention is used with an internal combustion engine, however a cooling system according to the invention can be used with any sort of engine, for example the electrical engine in an electrical vehicle or a hybrid electrical vehicle. A cooling system according to the invention could also be used to cool engines which are not in vehicles, and to cool devices other than engines.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Further aspects of the present invention are outlined in the following series of numbered paragraphs: 1. A method of identifying the condition of a temperature responsive valve when the temperature responsive valve is part of an engine cooling system which further comprises a fluid circulation system to circulate coolant fluid through the engine and a heat-dissipating radiator, and wherein the temperature responsive valve is arranged to control the amount of fluid which flows through the radiator, the method comprising: measuring t1, the temperature of coolant fluid as it exits the engine; measuring t2, the temperature of coolant fluid as it exits the radiator; and identifying the condition of the temperature responsive valve dependent upon the measured values oft1 and t2.

2. A method of identifying the condition of a temperature responsive valve as described in the preceding numbered paragraph, the method further comprising: identifying that the temperature responsive valve is open if the measured values of ti and t2 meet a first set of predefined criteria; and identifying that the temperature responsive valve is closed if the measured values of ti and t2 meet a second set of predefined criteria.

3. A method of identifying the condition of a temperature responsive valve as described in any preceding numbered paragraph, the method further comprising: measuring t3, an ambient temperature; and identifying the condition of the temperature responsive valve dependent upon the measured values of t1, t2and t3.

4. A method of identifying the condition of a temperature responsive valve as described in the preceding numbered paragraph, wherein the method comprises calculating a radiator cooling factor t1, wherein: t1 = (t2 -t3) / (t1 -t3) the method further comprising identifying the condition of the temperature responsive valve dependent upon the measured value of I. 5. A method of identifying a fault in a temperature responsive valve when the temperature responsive valve is part of an engine cooling system which further comprises a fluid circulation system to circulate coolant fluid through the engine and a heat-dissipating radiator, and wherein the temperature responsive valve is arranged to control the amount of fluid which flows through the radiator, the method comprising: measuring t1, the temperature of coolant fluid as it exits the engine; measuring t2, the temperature of coolant fluid as it exits the radiator; and identifying a fault in the temperature responsive valve if the measured values of t1 and t2 meet predefined criteria.

6. A method of identifying a fault as described in paragraph 5, the method further comprising: identifying a Stuck Open fault in the temperature responsive valve if the measured values oft1 and t2 meet a first set of predefined criteria; and identifying a Stuck Closed fault in the temperature responsive valve if the measured values ofti and t2 meet a second set of predefined criteria.

7. A method of identifying a fault as described in paragraph 5 or 6, the method further comprising: measuring t3, an ambient temperature; and identifying a fault in the temperature responsive valve if the measured values of t1, t2 and t3 meet predefined criteria.

8. A method of identifying a fault as described in paragraph 7, wherein the method comprises calculating a radiator cooling factor t1, wherein: t1 = (t2 -t3) / (t1 -t3) the method further comprising identifying a fault in the temperature responsive valve if the measured value oft1 meets predefined criteria.

9. A method of identifying a fault as described in paragraph 8, wherein the method comprises identifying a Stuck Open fault in the temperature responsive valve if t1 is greater than a first predefined value.

10. A method of identifying a fault as described in paragraph 8 or 9, wherein the method comprises identifying a Stuck Closed fault in the temperature responsive valve if t1 is less than a second predefined value.

11. A method of identifying a fault as described in paragraph 9 or 10, wherein at least one of the first and second predefined values depends at least in part upon the value oft1.

12. A method of reporting a fault, the method comprising: performing a method of identifying a fault according to any of paragraphs 5 to 11 a plurality of times; increasing a first counter whenever a fault is identified; and reporting a fault in the temperature responsive valve if the first counter exceeds a first predetermined threshold.

13. A method of reporting a fault according to paragraph 12, the method further comprising: decreasing the first counter whenever a method of identifying a fault is performed and a fault is not identified.

14. A method of identifying a fault according to paragraph 12 or 13 when dependent upon claim 6, the method comprising: increasing a first counter whenever a Stuck Open fault is identified; increasing a second counter whenever a Stuck Closed fault is identified; reporting a Stuck Open fault in the temperature responsive valve if the first counter reaches a first predefined threshold; and reporting a Stuck Closed fault in the temperature responsive valve if the second counter reaches a second predefined threshold.

15. A cooling system for use in an engine having a radiator to dissipate excess heat, the system comprising: a controller; a fluid circulation system to circulate coolant fluid through the engine and radiator; a temperature responsive valve; a first temperature sensor arranged to measure t1, the temperature of the coolant fluid in the fluid circulation system as the fluid exits the engine; and a second temperature sensor arranged to measure t2, the temperature of the coolant fluid in the fluid circulation system as the fluid exits the radiator, the controller being arranged to carry out the method according to any preceding numbered paragraph.

16. An engine for use in a vehicle, the engine comprising a cooling system according to paragraph 15.

17. A vehicle comprising an engine according to paragraph 16.

Claims

CLAIMS1. A method of identifying the condition of a temperature responsive valve when the temperature responsive valve is part of an engine cooling system which further comprises a fluid circulation system to circulate coolant fluid through the engine and a heat-dissipating radiator, and wherein the temperature responsive valve is arranged to control the amount of fluid which flows through the radiator, the method comprising: measuring t1, the temperature of coolant fluid as it exits the engine; measuring t2, the temperature of coolant fluid as it exits the radiator; and identifying the condition of the temperature responsive valve dependent upon the measured values of t1 and t2.
2. A method of identifying the condition of a temperature responsive valve as claimed in claim 1, the method further comprising: identifying that the temperature responsive valve is open if the measured values of tl and t2 meet a first set of predefined criteria; and identifying that the temperature responsive valve is closed if the measured values of ti and t2 meet a second set of predefined criteria.
3. A method of identifying the condition of a temperature responsive valve as claimed in claim 1 or 2, the method further comprising: measuring t3, an ambient temperature; and identifying the condition of the temperature responsive valve dependent upon the measured values of t1, t2 and t3.
4. A method of identifying the condition of a temperature responsive valve as claimed in claim 3, wherein the method comprises calculating a radiator cooling factor t1, wherein: = (t -t3) I (t -t3) the method further comprising identifying the condition of the temperature responsive valve dependent upon the measured value of t.
5. A method of identifying a fault in a temperature responsive valve when the temperature responsive valve is part of an engine cooling system which further comprises a fluid circulation system to circulate coolant fluid through the engine and a heat-dissipating radiator, and wherein the temperature responsive valve is arranged to control the amount of fluid which flows through the radiator, the method comprising: measuring t1, the temperature of coolant fluid as it exits the engine; measuring t2, the temperature of coolant fluid as it exits the radiator; and identifying a fault in the temperature responsive valve if the measured values of t1 and t2 meet predefined criteria.
6. A method of identifying a fault as claimed in claim 5, the method further comprising: identifying a Stuck Open fault in the temperature responsive valve if the measured values ofti and t2 meet a first set of predefined criteria; and identifying a Stuck Closed fault in the temperature responsive valve if the measured values oft1 and t2 meet a second set of predefined criteria.
7. A method of identifying a fault as claimed in claim 5 or 6, the method further comprising: measuring t3, an ambient temperature; and identifying a fault in the temperature responsive valve if the measured values of t1, t2 and t3 meet predefined criteria.
8. A method of identifying a fault as claimed in claim 7, wherein the method comprises calculating a radiator cooling factor tr, wherein: t1 = (t2 -t3) / (t1 -t3) the method further comprising identifying a fault in the temperature responsive valve if the measured value of tr meets predefined criteria.
9. A method of identifying a fault as claimed in claim 8, wherein the method comprises identifying a Stuck Open fault in the temperature responsive valve if t1 is greater than a first predefined value.
10. A method of identifying a fault as claimed in claim 8 or claim 9, wherein the method comprises identifying a Stuck Closed fault in the temperature responsive valve if t1 is less than a second predefined value.
11. A method of identifying a fault as claimed in claim 9 or claim 10, wherein at least one of the first and second predefined values depends at least in part upon the value oft1.
12. A method of reporting a fault, the method comprising: performing a method of identifying a fault according to any of claims 5 to 11 a plurality of times; increasing a first counter whenever a fault is identified; and reporting a fault in the temperature responsive valve if the first counter exceeds a first predetermined threshold.
13. A method of reporting a fault according to claim 12, the method further comprising: decreasing the first counter whenever a method of identifying a fault is performed and a fault is not identified.
14. A method of identifying a fault according to claim 12 or claim 13 when dependent upon claim 6, the method comprising: increasing a first counter whenever a Stuck Open fault is identified; increasing a second counter whenever a Stuck Closed fault is identified; reporting a Stuck Open fault in the temperature responsive valve if the first counter reaches a first predefined threshold; and reporting a Stuck Closed fault in the temperature responsive valve if the second counter reaches a second predefined threshold.
15. A cooling system for use in an engine having a radiator to dissipate excess heat, the system comprising: a controller; a fluid circulation system to circulate coolant fluid through the engine and radiator; a temperature responsive valve; a first temperature sensor arranged to measure t1, the temperature of the coolant fluid in the fluid circulation system as the fluid exits the engine; and a second temperature sensor arranged to measure t2, the temperature of the coolant fluid in the fluid circulation system as the fluid exits the radiator, the controller being arranged to carry out the method according to any preceding claim.
16. An engine for use in a vehicle, the engine comprising a cooling system according to claim 15.
17. A vehicle comprising an engine according to claim 16.