GB2442489A

GB2442489A - Engine or machine condition monitoring apparatus

Info

Publication number: GB2442489A
Application number: GB0619688A
Authority: GB
Inventors: Andrew David Scarisbrick; Keith William Barter; Timothy James Bowman; Jonathan O'neill
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2006-10-05
Filing date: 2006-10-05
Publication date: 2008-04-09
Also published as: GB0619688D0

Abstract

The condition monitoring apparatus 10 makes use of sacrificial components mounted in devices 1, 20, 30, 40 and 50 (see figs 2-7) for monitoring the condition of an oil lubricated component of the engine or machine 100. The device 1, 20, 30, 40 and 50 include the camshaft, dipstick, oil filter, oil sump plug and the oil filler cap. The sacrificial component (4, 24a, 24b, 34, 44a, 44b and 54, see figs 2-7) deteriorates in an manner that mimics the actual wear of the oil lubricated component. The actual wear of the component due to deterioration of the oil can thereby be established and if required a user of the machine can be notified by means of a warning device 11.

Description

A Condition Monitoring Apparatus This invention relates to the

monitoring of the condition of an oil lubricated component in a machine and, in particular, to the measurement of wear of a component of an internal combustion engine.

The introduction of lower emission regulations such as EU Stage IV and Stage V has lead to the adoption of different approaches to combustion and exhaust treatment systems. It is known that NOx levels can be lowered by reducing the temperature of combustion which can be achieved through later injection timing and higher levels of exhaust gas recirculation. Lean NOx traps used to reduce NOx emissions have to be regularly regenerated and this is achieved by generating rich conditions in the combustion chamber. All of these techniques result in higher levels of particulate matter and in the fuel being induced past the piston and into the oil sump. Once in the oil system, this fuel and soot can have a dramatic effect on the rate at which metal contact points such as the cam followers and chain will wear.

Accurate measurement of the wear of critical components is essential in order to allow service intervals to be extended for all vehicles instead of recommending a shorter service interval based upon the worst case scenario of a vehicle driven in aggressive conditions.

The current solutions to this problem is to use a sensor that is able to detect a number of important components including soot, oil, water, acids as well as other properties that are known to effect the rate at which wear occurs.

There are two problems with such an approach, firstly, the current ability of these sensors to measure all of the important parameters accurately for different oil types does not allow an accurate indication of oil quality to be obtained and secondly, the relationship between soot levels, fuel levels in the oil and the wear rate is very complicated. The wear rate is also a function of operating conditions including temperature, load, speed, and oil type and so, even if precise measurements of soot and fuel levels in the oil can be obtained, an accurate indication of wear rate which is the parameter of interest in not easy to obtain.

An alternative technique to using a sensor of the type previously described is to use an algorithm. The algorithm is developed to estimate the level of fuel and soot in the oil and historical levels of soot and fuel determined from experimental work are then set as limits. When these limits are exceeded, the driver is warned of the danger. These algorithms are prone to the same issues described above with reference to known sensors and are calibrated using information from a range of operating conditions that is likely to be more limited than the customers will experience during normal running.

It is an object of this invention to provide a condition monitor that is more accurately able to determine the wear of a component.

According to a first aspect of the invention there is provided a condition monitoring apparatus for a machine having at least one oil lubricated component wherein the apparatus comprises a device located on the machine in the same environment as the oil lubricated component the condition of which is to be monitored and which replicates the change in condition of the oil lubricated component in a manner that can be easily measured.

The machine may be an internal combustion engine.

The device comprises of a sacrificial component urged into contact with a surface such that relative motion occurs between the sacrificial component and the surface so as to replicate the wear of the oil lubricated component.

The surface may be a moving surface formed on a component forming part of the machine.

The surface may be a moving surface formed as part of the device.

The device may include a source of motive power to move the moving surface.

The sacrificial component may be a moved relative to the surface.

The surface may be formed as part of the machine.

The device may include a source of motive power to move the sacrificial component.

The surface may be formed as part of the device.

The device may comprise a sacrificial component past which oil used to lubricate the machine may be caused to flow so as to replicate wear of the oil lubricated component.

Alternatively, the device may comprise of a sacrificial component and a jet of the oil used to lubricate the machine may be caused to impinge against the sacrificial component so as to replicate wear of the oil lubricated component.

The sacrificial component may be made from more than one material so as to replicate the wear of more than one oil lubricated component of the machine.

The device may be attached to the machine such that it can be easily removed without disassembling the machine.

The machine may be an internal combustion engine and the device may be formed as part of one of an oil filler cap, a sump plug, an oil level dipstick and an oil filter.

The apparatus may further comprise an electronic unit connected to the device to determine a change in state of the device.

The apparatus may further comprise an electronic unit connected to the device, the electronic unit being operable to provide a warning signal to a user of the machine when the wear rate of the component part as determined by the device is excessive.

According to a second aspect of the invention there is provided a method for indicating the wear of a component the method comprising using a condition monitoring apparatus in accordance with said first aspect of the invention to provide a wear value indicative of the current wear of the component, comparing the wear of the component with a predetermined wear value and, if the wear value is greater than the predetermined wear value, providing an indication to the user of the machine.

The machine may be an internal combustion engine and the method may further comprise providing the wear value whenever the engine is started.

The method may further comprise using the condition monitoring apparatus to provide an initial value before wear has commenced and subtracting the initial wear value from the current wear value to determine a total wear value, comparing the total wear value of the component with a predetermined wear value and, if the total wear value is greater than the predetermined wear value, providing an indication to the user of the machine.

The machine may be an internal combustion engine and the method further comprises providing the current wear value whenever the engine is started.

Providing an indication to the user of the machine may comprise indicating that the component requires changing.

Providing an indication to the user of the machine may comprise indicating that the actual wear of the component requires checking.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Fig.1 is a line diagram of a machine having a condition monitoring apparatus according to the invention; Fig.2 is a line diagram of a first monitoring device forming part of a first embodiment of a monitoring apparatus according to the invention Fig.3 is an outline diagram of a second embodiment of a monitoring device forming part of the monitoring apparatus shown in Fig.1; Fig.4 is an outline diagram of a third embodiment of a monitoring device forming part of the monitoring apparatus shown in Fig.1; Fig.5 is a partial cross-sectional view through a fourth embodiment of a monitoring device forming part of the monitoring apparatus shown in Fig.1; Fig.6 is a view along the line X-X on Fig.5; Fig.7 is a partial cross-sectional view through a fifth embodiment of a monitoring device forming part of the monitoring apparatus shown in Fig.l; and Fig.8 is a flow chart showing a method for indicating wear using an output from a condition monitoring device in accordance with the invention.

With reference to Fig.l there is shown a machine in the form of an internal combustion engine 100 having a cylinder block and cylinder head assembly 101, an oil reservoir in the form of a sump 103, a rocker or cam box cover 102 and an oil pump 105 to circulate oil from the sump 103 through the cylinder block and cylinder head to lubricate components associated therewith. The engine 100 is provided with a condition monitoring apparatus to monitor the condition of one or more components within the engine 100.

The condition monitoring apparatus in this case comprises of five separate monitoring devices 1, 20, 30, 40 and 50, an electronic unit 6 and a warning device in the form of a lamp 11. It will however be appreciated that the condition monitoring apparatus could have only one monitoring device and that alternative warning devices could be provided instead of or in addition to the warning lamp 11 such as an audible warning device or a display device or stored within the ECU.

All of the monitoring devices 1, 20, 30, 40 and 50 have a sacrificial component 4, 24a, 24b, 34, 44a, 44b and 54 which wears in a manner that can be measured and used as an indication of the actual wear of one or more components of the engine 100.

The first monitoring device 1 is a unique component fitted to the cam cover 102 to provide an4 indication of camshaft wear and is shown in greater detail in Fig.2.

The second monitoring device 20 is formed as part of an oil level dipstick and is used to provide an indication of the wear of a component subject to abrasive wear such as for example a piston of the engine 100 that has oil jet cooling.

The monitoring device 20 is shown in greater detail in Fig.3.

The third monitoring device 30 is formed as part of an oil filter used to filter out particulate matter from the oil and is used to monitor the corrosive effects of the oil on a soft metal bearing material such as that used in the big end bearing caps of the engine 100. The monitoring device 30 is shown in greater detail in Fig.4.

The fourth monitoring device 40 is formed as part of an oil drain or sump plug and is used to provide an indication of timing chain wear. The monitoring device 40 is shown in greater detail in Figs.5 and 6.

The fifth monitoring device 50 is formed as part of an oil filler cap and is used to provide an indication of camshaft rocker wear. The monitoring device 50 is shown in greater detail in Fig.7.

It will be appreciated that these combinations of monitoring device and engine components are only provided as examples and that other combinations could be used. The common feature of all of these monitoring devices 1, 20, 30, and 50 is that they are all attached to the engine 100 such that they can be easily removed without disassembling the engine 100. This is important because they may need to be removed at regular intervals to be replaced if they are designed to deteriorate or wear at a faster rate than the component that they are provided to mimic. That is to say it is desirable to use a material that is more sensitive to degradation of the oil than the actual component so that as soon as the oil is degraded the monitoring apparatus will be able to measure a change and warn a user of the engine 100.

With reference to Fig.2 there is shown in greater detail the first monitoring device 1 which is fitted to the cam cover 102 to provide an indication of camshaft wear.

The monitoring device 1 comprises of a sacrificial component 4 which is slidingly supported and is urged into contact with a camshaft 2 of the engine 100 by a spring 7. A sensor in the form of a piezo-electric device 5 is interposed between the spring 7 and the sacrificial component 4. A number of signals are sent to the electronic unit 6 by means of a cable 9. These signals may include a measurement of temperature of the sensor 5, an output signal from the sensor 5 and a measurement of the total acid number of the oil.

The sacrificial component 4 is made from a material that has been tested under laboratory conditions and proven to wear faster than the lobes of the camshaft 2 that it is intended to mimic when the properties of the oil used to lubricate the camshaft 2 begin to degrade. It will be appreciated that the sacrificial component 4 could be made from more than one material so as to replicate the wear of more than one oil lubricated component of the engine 100.

Therefore when the oil begins to degrade the sacrificial component 4 will begin to wear rapidly. As the sacrificial component 4 wears the load on the spring 7 reduces and this reduction in load is sensed by the piezo-electric sensor 5. The signal from the piezo-electric sensor 5 which sent to the electronic unit 6 will then indicate that rapid wear is occurring and the electronic unit 6 can either be arranged to illuminate the lamp 11 when the measured load on the piezo-electric sensor 5 falls below a predetermined value or when the rate of change of load on the piezo-electric sensor 5 increases above a pre-determined rate.

With reference to Fig.3 there is shown in greater detail the second monitoring device 20 which is used to provide an indication of piston abrasion. The monitoring device 20 comprises of a first sacrificial component 24a which is fastened to a stem 24b of the dipstick which forms a second sacrificial component. The first sacrificial component 24a is arranged such that a high pressure jet of oil from a nozzle 28a impinges directly against it. The second sacrificial component 24b is arranged such that a second jet of oil from a nozzle 28b impinges directly against it. The pressure of the jet of oil from the second nozzle 28b may be different than that from the first nozzle 28a to replicate different abrasive conditions.

Electromagnetic wave measuring devices (not shown) are directed onto the first and second sacrificial components 24a and 24b at the positions where the two jets impinge against them. The electromagnetic wave measuring devices measuring the wear of the first and second sacrificial components 24a and 24b and transmit signal to a receiver located in the upper end of the dipstick. These signals are sent to the electronic unit 6 by means of a cable 29 attached to the dipstick. Other signals such as a measurement of the temperature of the oil and a measurement of the total acid number of the oil may also be sent to the electronic unit 6 via the cable 29.

The first and second sacrificial components 24a and 24b are made from different materials that have been tested -10 -under laboratory conditions and proven to wear faster than the piston that it is intended to mimic when the properties of the oil used to cool the piston begin to degrade.

Therefore when the oil begins to degrade the sacrificial components 24a, 24b will begin to wear rapidly.

As the sacrificial components 24a, 24b wear the electromagnetic wave measuring devices will send signals to the electronic unit 6 which can be used to determine when it io is necessary to change the oil. The signals from the electromagnetic wave measuring sensors can be used by the electronic unit 6 for comparison purposes or independently to determine when rapid wear is occurring and the electronic unit 6 can either be arranged to illuminate the lamp 11 when the measured wear is greater than a predetermined value or when the rate of change of wear on one or both of the sacrificial components 24a, 24b increases above a pre-determined rate.

With reference to Fig.4 there is shown in greater detail the third monitoring device 20 which is used to monitor the corrosive effects of the oil on a soft metal bearing material such as that used in the big end bearing caps of the engine 100. The monitoring device 30 comprises of a sacrificial component 34 which is fastened in a flow of oil "OF" entering the third monitoring device 30 through a port 31. A sensor in the form of a capacitance sensor 35 is attached to one end of the sacrificial component 34.

A number of signals are sent to the electronic unit 6 by means of a cable 39. These signals may include a measurement of temperature of the sensor 35, an output signal from the sensor 35 and a measurement of the total acid number of the oil.

The first sacrificial components 34 is made from a material that has been tested under laboratory conditions -11 -and proven to corrode faster than the soft bearing material that it is intended to mimic when the properties of the oil begin to degrade and for which the capacitance changes considerably as the material corrodes.

Therefore when the oil begins to degrade the sacrificial component 34 will begin to corrode rapidly. As the sacrificial component 34 corrodes the capacitance sensor sends a signal to the electronic unit 6 which can be used to determine when it is necessary to change the oil. The signal from the capacitance sensor can be used by the electronic unit 6 to illuminate the lamp 11 when the measured corrosion is greater than a predetermined value or when the rate of change of corrosion increases above a pre-determined rate.

With reference to Figs.5 and 6 there is shown in greater detail the fourth monitoring device 40 which is used to provide an indication of timing chain wear.

The monitoring device 40 comprises of two sacrificial components 44a, 44b which are slidingly supported in a rotor 47 of an electric motor 42 fastened to a hexagonal head 41.

An outer surface of a casing of the motor 42 has a threaded form so as to permit the monitoring device 40 to be secured in an oil drain hole in the sump 103 of the engine 100.

The sacrificial components 44a, 44b are each urged into contact with a bore formed in an end portion 43 of the casing of the electric motor 42 by respective springs and a sensor in the form of a piezo-electric device 45 is interposed between each of the springs and the sacrificial component 44a, 44b with which it cooperates. A number of signals are sent to the electronic unit 6 by means of a cable 49. These signals may include a measurement of -12 -temperature of the sensor 45 for temperature compensation purposes, an output signal from the sensor 45 and a measurement of the total acid number of the oil.

The sacrificial components 44a and 44b are in this case made from the same material that has been tested under laboratory conditions and is proven to wear faster than the links of the timing chain that it is intended to mimic when the properties of the oil used to lubricate the chain begin to degrade.

Therefore when the oil begins to degrade the sacrificial components 44a and 44b will begin to wear rapidly. As the sacrificial components 44a and 44b wear the load on each spring reduces and this reduction in load is sensed by the piezo-electric sensor 45. Because the piezo-electric sensor 45 is interposed between the two springs the change in load is double that it would be if it were to be interposed between only one spring and a fixed abutment which further increases the sensitivity to wear.

The signal from the piezo-electric sensor 45 which is sent to the electronic unit 6 will then indicate that rapid wear is occurring and the electronic unit 6 can either be arranged to illuminate the lamp 11 when the measured load on the piezo-electric sensor 45 falls below a predetermined value or when the rate of change of load on the piezo-electric sensor 45 increases above a pre-determined rate.

With reference to Fig.7 there is shown a fifth monitoring device 50 which is used to provide an indication of camshaft rocker wear.

The monitoring device 50 includes an electric motor 54 having an output shaft fitted with an eccentric drive that is used to reciprocate a plate 56 having a wear surface formed thereon. The plate 56 is slidingly supported by a -13 -body 53 in which is formed a cavity defining guides for the plate 56.

A sacrificial component in the form of a wear block 54 is urged into contact with the wear surface on the plate 56 by a leaf spring 57. One end of the leaf spring 57 rests upon a piezo-electric device forming a load sensor 55. A number of signals may be sent from the sensor 55 to the electronic unit 6, these signals may include a measurement of temperature of the sensor 55 for temperature compensation purposes, an output signal from the sensor 55 and a measurement of the total acid number of the oil.

In use the electric motor 54 causes the plate 56 to be reciprocated relative to the wear block 54 causing the wear block 54 to wear. When the oil begins to degrade the sacrificial component 54 will begin to wear rapidly. As the sacrificial component 54 wears the load on the spring 57 reduces and this reduction in load is sensed by the piezo-electric sensor 55. The signal from the piezo-electric sensor 55 which is sent to the electronic unit 6 will then indicate that rapid wear is occurring and the electronic unit 6 can either be arranged to illuminate the lamp 11 when the measured load on the piezo-electric sensor 55 falls below a predetermined value or when the rate of change of load on the piezo-electric sensor 55 increases above a pre-determined rate.

Therefore in summary several new and inventive

proposals have been formulated by the inventors these can be summarised as the provision of a sacrificial sensor.

The basic implementation provides a separate wear sensor that is specifically designed to wear at a rate that is far quicker than critical engine components. In this way problems with oil quality can be identified very quickly and the driver alerted or the engine operating condition restricted. The sensor might need to be replaced regularly -14 -and would therefore ideally be located in a serviceable location such as within the oil filter, near or as part of the oil drain plug, near or as part of the oil filler cap, or as part of the oil dip stick.

In one implementation the wear sensor is constructed from a material that would be worn by the action of the sensor interacting with a component within the engine and lubricated by the engine oil supply. The sensor is designed with a known wear rate, as the lubricating oil is degraded the wear rate of the sensor will change triggering the actions described elsewhere such as sending a signal to the electronic unit 6.

Various lubrication regimes such as boundary, hydrodynamic and mixed could be simulated by different oil delivery methods to the wear interface.

Another implementation provides a wear sensor that is a self-contained unit that uses the oil flow around it, or be independently powered to mimic the wear behaviour of the critical components. Electrical signals from the electronic unit 6 could be used via actuators to reproduce the engine speed and load. The advantage of this is that it has no effect on existing components.

A further implementation uses a wear sensor that is constructed from a material that is worn by the action of the oil passing over its surface such as being placed within a high flow section of the lubrication system.

In another implementation, an oil jet is directed onto part of the sensor so that the oil jet impingement wears the sensor. By measuring wear under different flow regimes, wear due to different wear mechanisms can be identified.

-15 -An advantage of this type of sensor is that it interacts with the lubricating oil only and therefore has no direct impact on existing components.

Significant wear takes place while an engine is stationary such as corrosive or adhesive wear. Such a wear mechanism can also be simulated.

Various methods of collecting and processing the signal from the monitoring device and distributing to the required devices could be used such as a wired or wireless system.

If the monitoring device is part of the oil filter, which is a consumable item, the same wireless communication could be used to demonstrate to a customer the condition of the oil and the oil filter.

The change in dimension of the sacrificial component could be measured by many techniques including, but not limited to, Ultrasonic sensing, electromagnetic wave measuring, reluctance sensing, capacitance sensing, electrical resistance sensing and pizo-electric sensing.

The wear sensor could also include the function of other types of sensor including, but not limited to, oil temperature sensing, oil level sensing, oil acidity sensing, oil viscosity sensing, crankshaft speed sensing, camshaft speed sensing, engine Torque sensing.

The monitoring device could be designed to replicate at least one or more of the following wear mechanisms, Abrasion, Adhesion, Corrosion and Fatigue.

It is also proposed that a number of monitoring devices be designed whereby they would simulate a range of materials present in the engine. The wear of one or more of these materials could be monitored by a single monitoring device.

-16 -It will be appreciated that this could apply to relative motions including but not limited to rotating and sliding interfaces.

The electronic control unit 6 could be programmed to control a monitoring device to carry out engine load simulation by varying the speed and load on the sacrificial component by various means including but not limited to electrical actuation or hydraulic pressure to simulate the actual operating conditions of the engine.

Therefore in summary, in accordance with this invention it is proposed to use a sensor that can directly measure the wear characteristics of the oil and so provide an accurate indication of the wear of one or more components in the engine. The device allows the wear rate to be monitored accurately and continuously and, as soon as a change in wear rate is detected, a user of the machine or a driver of a vehicle could be warned, prompting an oil change or the operating conditions of the machine to be altered in order to prolong life.

This invention is novel because it proposes the use of a separate device that is designed to wear in a similar manner to a vital component but in a situation that is more accessible and does not interfere with the prime function of the component.

Although the invention has been described with respect to its applications relating to an internal combustion engine it will be appreciated that it could be applied to other types of machines having lubricated components in which it is desirable to monitor the wear of one or more components such as for example a gearbox.

With reference to Fig.8 there is shown a method for indicating the wear of the oil lubricated component to a -17 -user of the machine which in this case is an internal combustion engine.

The method starts at step 10 by initialising the system when a condition monitoring apparatus of one of the types referred to above is first fitted to the engine. That is to say an initial wear value Mi based on the signal from the sensor forming part of the apparatus is stored in the electronic unit 6 as indicated in step 20. This initial value Mi is stored in a non-volatile memory so that it remains permanently in the non-volatile memory until it is overwritten. Overwriting will only occur if the condition monitoring apparatus is replaced.

The method proper starts at step 50 when the engine is started. The electronic unit 6 then determines a current wear measurement Mc from the signal sent from the sensor of the condition monitoring apparatus as indicated in step 60.

The electronic unit 6 records in memory the current wear value Mc as indicated in step 70.

Then at step 500 the electronic unit 6 determines the total wear since the monitoring apparatus was first fitted by subtracting the current wear value Mc from the initial wear value Mi that is to say:-Total Wear (Weart0) = Mi-Mc.

Then in step 510 the electronic unit 6 determines whether the total wear W0 is greater than a pre-determined wear value W. That is to say the wear test:-Is W0 > Wmax is performed.

The pre-determined wear value Wmax is a value determined by experimental e work and corresponds to the amount of -18 -wear of the sacrificial component of the monitoring apparatus that will have occurred when the oil lubricated component reaches a state where it either requires replacing or checking. If the wear test indicates that total wear value W is not greater than

the pre-determined wear value Wtnax then the method ends as indicated in step 555.

However, if the wear test indicates that total wear value W is greater than the pre-determined wear value Winax then the method advances to step 520 which in this case is an indication that the oil lubricated component needs to be replaced.

However, it will be appreciated that by using a different calibration for the value of Wmax the indication could be one indicating that the wear of the oil lubricated component needs to be checked.

When the oil lubricated component is changed the sacrificial component of the condition monitoring apparatus or the entire condition monitoring apparatus is changed and the system is re-initialised at step 10.

If the component is checked but not replaced the value of Wmax is reset to a higher value so that a further period of engine running will be required to trigger the step 520.

This higher value may be a wear value indicative of a definite requirement to replace the oil lubricated component.

That is to say, a two stage indication is provided the first indication is one of a need to check and the second is an indication of a need to replace.

-19 -It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that one or more modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention.

Claims

-20 -Claims 1. A condition monitoring apparatus for a machine having at

least one oil lubricated component wherein the apparatus comprises a device located on the machine in the same environment as the oil lubricated component the condition of which is to be monitored and which replicates the change in condition of the oil lubricated component in a manner that can be easily measured.
2. A condition monitoring apparatus as claimed in claim 1 wherein the machine is an internal combustion engine.
3. A condition monitoring apparatus as claimed in claim 1 or in claim 2 wherein the device comprises of a sacrificial component urged into contact with a surface such that relative motion occurs between the sacrificial component and the surface so as to replicate the wear of the oil lubricated component.
4. A condition monitoring apparatus as claimed in claim 3 wherein the surface is a moving surface formed on a component forming part of the machine.
5. A condition monitoring apparatus as claimed in claim 3 wherein the surface is a moving surface formed as part of the device.
6. A condition monitoring apparatus as claimed in claim 5 wherein the device includes a source of motive power to move the moving surface.
7. A condition monitoring apparatus as claimed in claim 3 wherein the sacrificial component is a moved relative to the surface.

-21 -
8. A condition monitoring apparatus as claimed in claim 7 wherein the surface is formed as part of the machine.
9. A condition monitoring apparatus as claimed in claim 8 wherein the device includes a source of motive power to move the sacrificial component.
10. A condition monitoring apparatus as claimed in claim 7 wherein the surface is formed as part of the device.
11. A condition monitoring apparatus as claimed in claim 1 or in claim 2 wherein the device comprises a sacrificial component past which oil used to lubricate the machine is caused to flow so as to replicate wear of the oil lubricated component.
12. A condition monitoring apparatus as claimed in claim 1 or in claim 2 wherein the device comprises of a sacrificial component and a jet of the oil used to lubricate the machine is caused to impinge against the sacrificial component so as to replicate wear of the oil lubricated component.
13. A condition monitoring apparatus as claimed in any of claims 3 to 12 wherein the sacrificial component is made from more than one material so as to replicate the wear of more than one oil lubricated component of the machine.
14. A condition monitoring apparatus as claimed in any of claims 1 to 13 wherein the device is attached to the machine such that it can be easily removed without disassembling the machine.
15. A condition monitoring apparatus as claimed in claim 14 wherein the machine is an internal combustion engine and the device is formed as part of one of an oil -22 -filler cap, a sump plug, an oil level dipstick and an oil filter.
16. A condition monitoring apparatus as claimed in any of claims 1 to 15 wherein the apparatus further comprises an electronic unit connected to the device to determine a change in state of the device.
17. A condition monitoring apparatus as claimed in any of claims 1 to 15 wherein the apparatus further comprises an electronic unit connected to the device, the electronic unit being operable to provide a warning signal to a user of the machine when the wear rate of the component part as determined by the device is excessive.
18. A method for indicating the wear of a component the method comprising using a condition monitoring apparatus as claimed in any of claims 1 to 17 to provide a wear value indicative of the current wear of the component, comparing the wear of the component with a predetermined wear value and, if the wear value is greater than the predetermined wear value, providing an indication to the user of the machine.
19. A method as claimed in claim 18 wherein the machine is an internal combustion engine and the method further comprises providing the wear value whenever the engine is started.
20. A method as claimed in claim 18 wherein the method further comprises using the condition monitoring apparatus to provide an initial value before wear has commenced and subtracting the initial wear value from the current wear value to determine a total wear value, comparing the total wear value of the component with a predetermined wear value and, if the total wear value is greater than the -23 -predetermined wear value, providing an indication to the user of the machine.
21. A method as claimed in claim 20 wherein the machine is an internal combustion engine and the method further comprises providing the current wear value whenever the engine is started.
22. A method as claimed in any of claims 18 to 21 wherein providing an indication to the user of the machine comprises indicating that the component requires changing.
23. A method as claimed in any of claims 18 to 21 wherein providing an indication to the user of the machine comprises indicating that the actual wear of the component requires checking.
24. A condition monitoring apparatus for a machine substantially as described herein with reference to the accompanying drawing.
25. A method for indicating the wear of a component substantially as described herein with reference to the accompanying drawing.