GB2418988A

GB2418988A - A soot management system for an engine

Info

Publication number: GB2418988A
Application number: GB0422141A
Authority: GB
Inventors: Michael James Watts; Michael Willcock; Keith William Barter; Ian Pegg
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2004-10-06
Filing date: 2004-10-06
Publication date: 2006-04-12
Anticipated expiration: 2024-10-06
Also published as: GB2418988B; GB0422141D0; JP2006105153A; CN1807851A; DE102005047139A1; CN100564820C

Abstract

A system and method are disclosed which enable a more accurate estimate of the soot concentration in the oil of an engine 5 to be established. This estimate can be used to alert a user of the engine 5 when the oil needs to be changed and to control removal of soot from the oil. The invention also provides a method for alerting an operator of the engine 5 when a soot removal filter 16 needs to be changed. Soot production is determined by sensors which measure the engine speed and the load. The condition of the oil can also be inferred from the oil temperature and level.

Description

24 1 8988

A SOOT MANAGEMENT SYSTEM FOR AN ENGINE

This invention relates to internal combustion engines and in particular to a system and method for estimating the accumulation of soot In the oil used to lubricate the engine so as to enable a more accurate determination to be made of when the oil needs to be changed.

It is well known that soot accumulates in the oil of an internal combustion engine under certain operating conditions and in particular in the oil of a diesel engine. As the soot level builds up it can have a detrimental effect on engine durability. To prevent excessive wear of the engine, the oil must be changed before the concentration of the soot in the oil reaches a critical predetermined limit. The soot build up rate varies depending upon several factors including vehicle usage and engine age. In order to prevent excessive levels of soot occurring and subsequent risk of engine damage it is usual for the oil change interval to be set based on soot build up in the oil for the worst case. This means that for many engines the oil is changed earlier than is necessary which has the disadvantage of unnecessary down time for the engine. This can be significant if the engine Is used in a commercial environment and, in addition, unnecessary oil changes increase the cost of operating the engine.

It is an object of this invention to provide a system and method that provides a more accurate estimate of soot in oil concentration and so enables the oil to be changed only when required.

According to a first aspect of the invention there is provided a system for monitoring the operation of an oil lubricated internal combustion engine, the system comprising at least one filter to remove soot from the lubricating oil, a controller operatively connected to one or more sensors used to supply signals indicative of soot production and soot removal to the controller, wherein the controller is operable to calculate an estimate of soot produced by the engine and deposited in the oil from the soot production sensor or sensors, estimate the soot removed from the oil by the or each filter from the soot removal sensor or sensors and estimate a soot in oil concentration based upon the estimates of soot deposited and soot removed from the oil If the concentration of soot in the oil is above a maximum permitted soot in oil concentration limit, the controller may be further operable to activate an operator warning device to indicate that the oil needs to be changed.

The controller may be further operable to receive at least one signal indicative of engine service history.

The engine service history may include data relating to the oil change history and the controller may be operable to refine the estimate of soot in oil concentration based upon the oil change history.

The engine service history may include data regarding when the soot removal filter was fitted The controller may be operable to receive one or more signals from an oil temperature and level sensor.

The controller may be operable to refine the soot in oil concentration based upon the oil level signal received from the oil temperature and level sensor.

The filter used to remove soot from the oil may be a bypass filter and the controller may be further operable to control usage of the bypass filter such that oil Is only passed through the bypass filter when the soot in oil concentration exceeds a predetermined soot in oil limit. - 3

The predetermined soot in oil limit may be below the maximum permitted soot in oil limit.

The controller may be further operable to estimate the total soot extracted from the oil by the filter and indicate to an operator of the engine when the total soot collected by the filter is greater than a predetermined limit.

The predetermined limit may be substantially equal to the maximum amount of soot that can be stored in the filter.

According to a second aspect of the invention there is provided a method for monitoring the operation of an internal combustion engine having at least one filter to remove soot from oil used to lubricate the engine, the method comprising estimating the soot accumulated in the oil during operation of the engine, estimating the soot removed from the oil by the filter during operation of the engine and using the estimates of soot accumulated and soot removed to estimate the concentration of soot in the oil.

The method may further comprise comparing the estimate of soot in oil concentration with a maximum soot in oil concentration and alerting an operator of the engine if the estimated soot in oil concentration exceeds the maximum soot in oil concentration.

The filter may be a bypass filter and the method may further comprise circulating oil through the filter only when the soot in oil concentration exceeds a predetermined limit.

The method may further comprise estimating the total amount of soot removed by the filter and indicating to an operator of the engine when the total amount of soot stored is greater than a predetermined limit. - 4

The method may further comprise using data relating to the history of the oil to refine the estimate of soot in oil concentration.

The method may further comprise refining the estimate of soot in oil concentration based upon the level signal received from the oil temperature and level sensor.

The invention will now be described by way of example with reference to the accompanying drawing of which: Fig 1 is a block diagram of a system according to a first aspect of the invention; Fig 2 is a flow chart showing one embodiment of a method according to a second aspect of the invention; Fig.3 is a flow chart showing a further function performed according to the method; and Fig.4 is a schematic view of an engine having a system according to the invention With reference to Figs 1 and 4 there is shown an internal combustion engine in the form of a diesel engine 5 having an electronic control unit or controller 10 connected thereto to control operation of the engine 5 and to perform various data processing functions The controller 10 is operatively connected to and controls the output from a variable displacement oil pump 15 which is arranged to pump oil from an oil storage reservoir or sump 6 through an oil cooler 7 and a main or full flow filter 8 to the engine 5.

The oil is circulated through the engine 5 in the normal manner and is then returned to the sump 6.

The full flow filter 8 is designed to capture major debris in the oil without producing excessive back pressure or pressure loss and so has a relatively coarse filter medium so that it can only capture debris having a particles size of more than approximately 15 microns. The full flow filter 8 is therefore, under normal operating conditions when the soot is dispersed in the oil in the form of fine particles, too coarse to capture soot particles In the oil which require a filter able to capture 2 micron particles.

In order to remove soot particles from the oil a bypass filter 16 Is connected to the main oil circuit via a control valve 17. The control valve 17 is controlled by the controller 10 to allow oil to flow through the bypass filter 16 when required to remove soot from the oil.

In this case the bypass filter is a centrifugal filter but it will be appreciated that other types of filter could be used.

The controller 10 is arranged to receive inputs from a number of sensors including an engine operating condition sensor 11, an oil temperature and level sensor 12, a service history sensor 13 and a filter sensor 14.

The engine operating condition sensor 11 is not a single sensor but is two separate sensors, therebeing an engine speed sensor (not shown) and an engine load sensor (not shown) which respectively provide signals to the controller 10 which indicate the speed and load on the engine 5. These signals are used by the controller 10 to drive the soot map to estimate the soot being deposited into the oil. That is to say the soot map contains a relationship between engine speed and load and likely soot deposition. A technique for estimating the soot content of oil is described in more detail in US Patent Application 2003/0051696.

The temperature and level sensor 12 provides data relating to the temperature of the oil and the level of the oil in the sump 6. This information is used by the controller 10 to determine the temperature of the oil and whether any oil has been added to the sump 6 and, if oil has been added, the quantity of oil added - 6 The service history sensor 13 provides information regarding when the oil is changed and when the full flow and bypass filters 8 and 16 are changed This information is downloaded to the controller 10 from a computer based diagnostic tool used by a garage to service the engine 5 however it will be appreciated that it could be provided in some other manner.

The filter sensor 14 monitors the rotational speed of the centrifugal bypass filter 16 from which an estimate of the soot removed from the oil can be obtained by converting the rate of soot removed per second derived from the sensor 14 Into an actual mass of soot. A technique that could be applied to estimate the soot removed by the centrifugal filter 16 is disclosed in US Patent application 2003/0078152 If an alternative type of filter is used for the bypass filter then a different technique would be used to estimate the mass of soot removed.

The operation of the system Will be described In greater detail with reference to the method embodied in the controller hereinafter but in simplified terms the system operates as follows.

The estimated soot produced by the engine 5 deposited in the oil is calculated using a -soot map stored In a memory of the controller 10 and the inputs received from the engine operating condition sensor 11. The soot removed from the oil by the centrifugal bypass filter 16 is calculated in a filter soot calculator using the input from the filter sensor 14.

These two figures are then used to estimate the soot remaining in the oil. This estimate is then refined using the data from the service history sensor 13 and the temperature and level sensor 12 to account for oil added to the engine or for oil changes. This provides an estimate of the current soot in oil concentration. - 7

The controller 10 is further operable to perform several other functions depending upon this determination of soot in oil concentration.

If the concentration is above a first predetermined limit, the controller 10 is operable to open the valve 17 so as to allow oil to flow through the centrifugal filter 16 but, if the soot in oil concentration Is below this limit, the valve 17 Is kept closed and so no oil flows through the centrifugal filter 16. This is advantageous because it permits the use of the bypass filter only when it is actually required to remove soot from the oil. This first predetermined limit is set to be at a level below which no damage will occur to the engine 5 due to the soot in the oil. The advantage of this selective use of the bypass filter is lower energy usage because, irrespective of the type of filter used to remove the soot from the oil, energy will be used in passing the oil through a filter capable of removing the small particles of soot from the oil.

A further advantage of the system shown in Figs. 1 and 4 is that a variable output pump 15 is used which is controlled by the controller 10 and so the output from the pump is not directly related to the speed of the engine 5. This allows the pump 15 to be activated whenever required to provide a desired oil flow rate. It is therefore possible to arrange for the pump 15 to provide a relatively high pressure of say 5 bar (500 kPa) even if the engine Is Idling thereby allowing efficient soot removal by the centrifugal filter 16 irrespective of the operating speed of the engine 5.

If the soot in oil concentration exceeds a maximum permitted limit then the controller is operable to warn an operator of the engine 5 that the oil needs to be changed. In this case this is achieved by illuminating an oil change Indicator lamp 21 but it could be achieved in other ways both visual and audible. A typical maximum concentration would be 3% by mass of soot In the oil. It will be appreciated that this could also be expressed as a mass of soot In grams per lithe of oil. - 8

The controller 10 is also operable to calculate the total amount of soot that has been removed from the oil by the centrifugal filter 16. This is done by a soot storage calculator which keeps a continuous track of the soot removed which Is equal to the soot being stored in the centrifugal filter 16. When the amount of soot stored in the centrifugal filter 16 exceeds a predetermined limit equivalent to the maximum safe amount of soot that can be stored in the centrifugal filter 16. When this limit is exceeded the controller is operable to warn the operator of the engine 5. In this case this is achieved by illuminating a filter change lamp 22 but it could be achieved In other ways both visual and audible.

With reference to Figs 2 and 3 there Is shown a method which Is stored in the controller 10 for performing the functions previously described.

With particular reference to Fig.2 the method starts at step 100 which could correspond to an engine run Input such as 'key on'.

At step 110 the amount of soot produced by the engine 5 and transferred to the oil (SPRODUCED) jS calculated using the soot map and the values of engine speed and load received from the engine operating conditions sensor 11.

At step 120 the amount of soot removed from the oil by the centrifugal filter 16 (SREMOVED) IS calculated based upon the rotational speed of the centrifugal filter 16 as sensed by the sensor 14.

In step 130 an estimate of the soot in the oil concentration is made based upon the calculated introduction and removal values using the equation: SC = (SPRODUCED - SREMOVED) / OV grams per litre where Sc is the soot content of the oil and Ov is the volume of oil in the engine 5. - 9 -

This estimate is refined at step 140 in one of two ways, if the service history sensor 13 indicates that the oil has been changed then the calculation will be performed based upon the new value for oil content received from the service history sensor 13 and the knowledge that the new oil will have a zero soot concentration. In other words refilling with oil will reset the system so far as the soot in oil concentration calculation is concerned.

If the service history sensor 13 indicates that oil has been added to the engine 5 the controller 10 will update the volume of oil value based upon the newly added oil and will also correct the calculation for the newly added oil. This is because the newly added oil will have no soot content and so the new soot in oil concentration will be a combination of the soot in oil concentration for the old oil and zero for the new oil.

For example suppose the old oil has a soot concentration of X g/litre and there is 4 litres of old oil in the engine and 1 litre of new oil has been added the refined Sc will be: Sc = (4 * X + 1*0)/ (4+1) = 0.8X g/litre The value of 4 litres will be obtained from the temperature and level sensor 12 which is also used to determine when a user of the engine 5 adds oil to the engine 5 and when oil is used. The temperature and level sensor 12 is also used to provide information about changes to the amount of oil in the engine 5 which can be deduced from the oil level in the sump 6 This Information Is used to refine the calculation of soot in oil calculation but in this case the refinement takes place in the initial calculation of soot in oil calculation at step 130 by correcting the volume of oil value ( Ov) based upon the measured oil level if the level of oil Is falling or at step 140, if the level In oil has increased which indicates the addition of oil and is treated as described above. In this way the soot in oil concentration is always calculated based upon the best estimate of the actual oil content of the engine 5 and not upon a theoretical value. - 1 0

The next step is to determine whether soot needs to be removed from the oil to prevent damage to the engine 5. This is achieved by comparing the calculated soot content Sc with a predetermined limit So,, for soot in oil concentration that is known will cause little or no damage to the engine 5 If the soot in oil concentration is less than the limit there is no need to remove soot from the oil and the method returns back to step 110.

It will be appreciated that because the temperature and volume of oil can be obtained from the temperature and level sensor 12 it would also be possible to calculate a % mass of soot In the oil.

If however, the soot in oil concentration is greater than the predetermined limit then it is necessary to remove soot from the oil and the method proceeds to step 160 where the bypass filter 16 is activated and the pump 15 is operated to pass oil at the correct pressure through the bypass filter 16 to remove soot therefrom. This process of filtering continues for a predetermined period of time estimated to be sufficient to remove sufficient soot from the oil that it Will not adversely affect the durability of the engine 5. It will be appreciated that various techniques could be used to determine how long the bypass filter 16 needs to operate.

After filtering is complete the soot in oil concentration is rechecked against a second higher level Sc MAX SC MAX iS a level of soot in oil that will cause damage to the engine 5 and is a higher concentration than the predetermined limit used in step 150. If the soot in oil concentration Sc exceeds Sc MAX then the method advances to step 180 where an oil change lamp 21 is activated whereas if the soot in oil concentration is below Sc MAX the method returns to step 110. In practice the oil change lamp 21 will only be illuminated due to soot If the bypass filter 16 is full or stops working for some reason for otherwise the bypass filter 16 will make sure that the soot in oil concentration remains below this maximum limit. - 11

Ths process will continue while the engine 5 is operating and the data at engine switch off will be stored by the controller 10 to act as initiation data when the engine 5 is restarted and the method is reactivated This ensures that an accurate calculation of soot in oil concentration is maintained at all times. It will be appreciated that this method can operate continuously while the engine 5 is operating or can operate only once when the engine 5 is started or could be arranged to operate at specific elapsed hours of engine running or any other desired frequency.

It will be appreciated that the method could also compare the rate of soot deposition in the bypass filter 16 with expected rates of deposition based upon the engine load and speed and determine whether the rate of deposition Is exceptionally high or higher than would be expected. This could indicate that the engine 5 Is not operating correctly or that the system for calculating the rate of soot deposition is faulty in either case it is a useful diagnostic tool which could also be used to indicate to a user that a system check is advisable.

Referring now to Fig. 3 a routine for calculating the soot stored in the bypass filter 16 is shown. Step 100 corresponds to step 100 on Fig.2 and in practice this routine will be interlinked with those shown on Figs 2 and 3. In step 310 an estimate of the soot stored in the filter (Ss) is made. This is done by using the value of soot removed provided from the filter sensor 14 which is then integrated or summed to provide a figure for the total amount of soot stored in the bypass filter 16 It will be appreciated that this figure is only an estimate because the signal from the sensor 14 only provides a value of filter rotational speed and the relationship between this and the actual soot removed is not an exact one but an estimate. In addition, some soot may escape from the bypass filter 16 back into the oil during transient operating conditions such as when the centrifugal filter 16 first starts to rotate. However, the estimate Is sufficiently accurate to provide a guide as to when the filter 16 is becoming full and needs replacement or emptying. - 12

At step 320 the estimated amount of soot stored (Ss) is compared with a maximum permissible amount of stored soot (Ss MAX) and If the estimated amount of stored soot (Ss) exceeds the maximum level (Ss MAX) the method proceeds to step 330 where a filter change lamp 22 is illuminated otherwise the method reverts to step 310 where a new updated estimate is made. The calculation Is nitialised or reset to zero whenever a new bypass filter 16 is fitted based upon Information received from the service history sensor 13.

Therefore in summary, the invention maximizes the service life of the oil to permit the largest possible interval between services. It reduces the possibility of engine damage through degraded oil. It reduces operating costs for the customer by reducing number of services required and hence reduces the cost of servicing.

A secondary benefit is improved fuel consumption as the variable flow oil pump only supplies the extra flow of oil to drive the centrifugal filter when necessary to clean the oil A tertiary benefit is that soot accumulation in the oil can be compared to predicted levels and excessive generation of soot detected and a service check requested.

It will be appreciated by a man skilled in the art that the invention has been described by way of example with reference to specific embodiments of the Invention but it will be appreciated that the invention is not so limited and that venous alternatives or modifications to the described embodiments could be produced without departing from the scope of the invention. For example although the invention has been described with reference to a diesel engine it Is not so limited and can be used with any engine in which soot is transferred to the oil and for which it is desirable to extend between service intervals.

Similarly although the invention has been described with reference to the use of a single controller it will be appreciated that there could be several interlinked computational devices. - 13

lt will further be appreciated that instead of using an intelligent centrifugal filter having a speed sensor to estimate the soot removed from the oil or the soot stored in the filter it would be possible to use a conventional centrifugal filter and through prior test work establish a look up table from which the soot removed and the soot stored could be obtained using information relating to the period of time filtration has been in operation and other factors such as engine speed and load and oil pressure and temperature.

Claims

CLAI MS

1. A system for monitoring the operation of an oil lubricated internal combustion engine, the system comprising at least one filter to remove soot from the lubricating oil, a controller operatively connected to one or more sensors used to supply signals indicative of soot production and soot removal to the controller, wherein the controller is operable to calculate an estimate of soot produced by the engine and deposited In the oil from the soot production sensor or sensors, estimate the soot removed from the oil by the or each filter from the soot removal sensor or sensors and estimate a soot in oil concentration based upon the estimates of soot deposited and soot removed from the oil.

2. A system as claimed in claim 1 wherein, if the concentration of soot in the oil is above a maximum permitted soot in oil concentration limit, the controller is further operable to activate an operator warning device to indicate that the oil needs to be changed.

3 A system as claimed in claim 1 or in claim 2 wherein the controller is further operable to receive at least one signal Indicative of engine service history.

4 A system as claimed in claim 3 wherein the engine service history includes data relating to the oil change history and the controller Is operable to refine the estimate of soot in oil concentration based upon the oil change history.

5. A system as claimed in claim 3 wherein the engine service history Includes data regarding when the soot removal filter was fitted.

6. A system as claimed in any of claims 1 to 5 wherein the controller Is operable to receive one or more signals from an oil temperature and level sensor. - 15

7. A system as claimed in claim 6 wherein the controller is operable to refine the soot in oil concentration based upon the oil level signal received from the oil temperature and level sensor.

8. A system as claimed in any of claims 1 to 7 wherein the filter used to remove soot from the oil is a bypass filter and the controller is further operable to control usage of the bypass filter such that oil is only passed through the bypass filter when the soot in oil concentration exceeds a predetermined soot in oil limit.

9. A system as claimed in claim 8 wherein the predetermined soot in oil limit is below the maximum permitted soot in oil limit.

10. A system as claimed in any of claims 1 to 9 wherein the controller is further operable to estimate the total soot extracted from the oil by the filter and indicate to an operator of the engine when the total soot collected by the filter is greater than a predetermined limit.

11. A system as claimed in claim 10 wherein the predetermined limit is substantially equal to the maximum amount of soot that can be stored in the filter.

12. A method for monitoring the operation of an internal combustion engine having at least one filter to remove soot from oil used to lubricate the engine, the method comprising estimating the soot accumulated in the oil during operation of the engine, estimating the soot removed from the oil by the filter during operation of the engine and using the estimates of soot accumulated and soot removed to estimate the concentration of soot in the oil.

13. A method as claimed in claim 12 wherein the method further comprises comparing the estimate of soot in oil concentration with a maximum soot in oil concentration and - 16 alerting an operator of the engine if the estimated soot in oil concentration exceeds the maximum soot in oil concentration.

14. A method as claimed in claim 12 or In claim 13 wherein the filter Is a bypass filter and the method further comprises circulating oil through the filter only when the soot in oil concentration exceeds a predetermined limit.

15. A method as claimed in any of claims 12 to 14 wherein the method further comprises estimating the total amount of soot removed by the filter and indicating to an operator of the engine when the total amount of soot stored Is greater than a predetermined limit 16. A method as claimed In any of claims 12 to 15 wherein the method further comprises using data relating to the history of the oil to refine the estimate of soot in oil concentration 17. A method as claimed in claim 16 wherein the method further comprises refining the estimate of soot in oil concentration based upon the level signal received from the oil temperature and level sensor.

19. A system substantially as described herein with reference to the accompanying drawing.

20. A method substantially as described herein with reference to the accompanying drawing.