EP1586752A1

EP1586752A1 - Method for controlling the lubricating oil dilution of an internal combustion engine and device for monitoring and reducing this oil dilution

Info

Publication number: EP1586752A1
Application number: EP04101510A
Authority: EP
Inventors: Yasser Mohammed Sayed Yacoub
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2004-04-14
Filing date: 2004-04-14
Publication date: 2005-10-19
Anticipated expiration: 2024-04-14
Also published as: DE602004015068D1; EP1586752B1

Abstract

The present invention relates to a method for controlling the lubricating oil dilution - in volume percent - of an internal combustion engine. Furthermore the invention relates to a device for monitoring and reducing this oil dilution.

It is an object of the present invention to provide a method, which enables technologies aiming at reduction of soot and NO_x emissions, namely control strategies making use of in-cylinder post injection(s) required for vehicels equipped with particulates filter or lean NO_x trap.

Another object of the present invention is to provide a device for monitoring and reducing the oil dilution.

According to the present invention and with respect to the first object a method is provided comprising the following steps

(a) monitoring the oil dilution ratio by calculating and/or estimating the so-called oil dilution state from measured operating parameters, and

(b) reducing the oil dilution ratio by

promoting the evaporation of the liquid contaminates - such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil - by elevating the temperature of the diluted lubricating oil, and/or
promoting the partial combustion of the diluted lubricating oil by increasing blow-by gas flow from crankcase to engine cylinder during fuel cut off in deceleration.

Description

The present invention relates to a method for controlling the lubricating oil dilution - in volume percent - of an internal combustion engine.
Furthermore the invention relates to a device for monitoring and reducing this oil dilution.
Internal combustion engines are provided with a lubricating oil circuit and corresponding devices to filter the lubricating oil in order to separate the disturbing particulates and other liquid contaminates, such as water, glycol or in particular fuel therefrom. The liquid contaminates result in a lubricating oil dilution, which is the subject matter of the present invention. In particular a fraction of the injected fuel is mixed with the oil film on the cylinder wall and scraped with the oil film and blow-by gas into the crankcase resulting in a fuel dilution of the oil.
In prior art oil filters, recyclers, refiners or the like are used in internal combustion engines to filter or treat otherwise the engine's lubricating oil which undergoes constant recycling through the engine.
A representative oil recycler is disclosed in PCT Application WO96/25996. This oil recycler serves the twofold purpose of filtering the lubricating oil as it recycles through the engine so as to remove particles therefrom and heating a portion of the lubricating oil being recycled in a heating chamber so as to evaporate liquid contaminates from the oil which passes through the chamber.
Therefore the oil recycler comprises a heated chamber adjacent a filter element. In the heated chamber a stack of spaced apart discs is arranged. The oil is filtered through the filter element and then cascades over the discs in the heated chamber, so that any contaminantes contained therein are evaporated.
The US 6,053,143 discloses a method of improving the operating efficiency and reducing certain exhaust emissions in an internal combustion engine. By continuously subjecting a potion of recycling engine lubricating oil to heat treatment in the range from 170° C to 260° C and preferably in the the range from 180° C to 240°C in a volatilization chamber or the like, an improvement in the fuel consumption as well as a reduction in the total hydrocarbons, carbon dioxide and particulates can be achieved.
It was found through exhaust emission measurements, that by operating the heating or volatilization chamber at significantly elevated temperatures in excess of that usually - i.e. operation at an upper temperatur limit of 135° C - employed to evaporate liquid contaminates to thereby additionally remove certain portions of the light fractions of the recycling engine oil, the engine efficiency is improved and percentage of total hydrocarbons, carbon monoxide and particulates can be reduced.
Internal combustion engines making use of in-cylinder post injection(s) are inherently susceptible to high oil dilution potential. Within the present invention in-cylinder post injection means an injection of additional fuel into all or some cylinders after the respective main injection but still during the power stroke.
In-cylinder post injection is an efficient method for increasing exhaust gas temperatures and/or achieving rich engine operation and at the same time maintaining neutral torque for the same operating point in normal mode. Such an operation mode with increased exhaust gas temperatures is required for example in the periodic combustion of the soot build up in a diesel particulate filter at high exhaust gas temperatures. The rich operation mode is required to regenerate the NO_x trapped during lean operation modes for the case the engine is provided with a lean NO_x trap.
Depending on the quantity and start of the post injection(s) in the expansion stroke, a fraction of the injected fuel will mix with the oil film on the cylinder wall and scraped with the oil film and blow-by gas into the engine sump causing fuel dilution of the oil. The fuel dilution caused by each injection is higher for retarded injection timing and higher quantity. Moreover, higher dilution occurs for lower oil temperatures and fuels with heavier hydrocarbons. The last mentioned problem is worse in case of diesel fuel as opposed to gasoline.
Furthermore, vehicle usage patterns significantly affect the severity of the oil dilution problem as it has an influence on the blow-by flow rate and the oil temperature. Frequent cold starts and short journeys may result in oil dilution ratios up to five times higher than fully warmed operating patterns.
The dilution of lubricating oil by fuel has adverse effects on engine wear by changing the lubricity of oil and may result in severe durability problems. This results in limiting the oil change interval i.e. for example limiting the interval to 15.000 kilometers or changing the oil annually to account for worst-case scenario at the cost of higher operational costs and less ideal use of resources.
As mentioned and as described in detail above on the one hand control strategies making use of post in-cylinder injection(s) during the power stroke are very susceptible to result in high fuel dilution of engine oil. On the other hand modern engines provided with particulates filter and/or NO_x trap are required these strategies. The fuel dilution of lubricating engine oil has an adverse effect on engine wear and may result in severe engine damage especially for in-city drive patterns, the operation mode of which is characterized in that the engine operates with low speed and low load. The in-city patterns are followed by a highway operation with full load as another worse drive pattern with respect to fuel dilution of oil.
This problem is - as described within the introduction - further magnified for diesel engine equipped with particulate filters which require periodic regeneration at high temperatures as well as internal combustion engines systems equipped with lean NO_x traps which requires frequent purging in rich mode operation.
The dilution of the oil has two aspects. One is the adverse effect on the physical properties of the lubricating oil - e.g. viscosity - which may result in higher engine wear. The other aspect is the increased level of the engine oil in the crankcase. At high dilution rates up to 25% by weight the diluted lubrication oil mixture carried over by the blow-by gases into the cylinder and during decelerations can result in an uncontrolled combustion and may result in severe engine damage.
With respect to this it is an object of the present invention to provide a method for controlling the lubricating oil dilution of an internal combustion engine, which allows a person skilled in the art to overcome the above described problems, in particular a method which enables technologies aiming at reduction of soot and NO_x emissions, namely control strategies making use of in-cylinder post injection(s) required for vehicels equipped with particulate filter or lean NO_x trap.
Another object of the present invention is to provide a device for monitoring and reducing the oil dilution i.e. a device to realize the method for controlling the lubricating oil dilution of an internal combustion engine.
According to the present invention and with respect to the first object a method is provided for controlling the lubricating oil dilution - in volume percent - of an internal combustion engine, which comprises the following steps
(a) monitoring the oil dilution ratio by calculating and/or estimating the so-called oil dilution state from measured operating parameters, and
(b) reducing the oil dilution ratio by
- promoting the evaporation of the liquid contaminates - such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil - by elevating the temperature of the diluted lubricating oil, and/or
- promoting the partial combustion of the diluted lubricating oil by increasing blow-by gas flow from crankcase to engine cylinder during fuel cut off in deceleration.
A preferred embodiment of the method is characterized in that the dilution ratio is reduced by
▪ promoting the evaporation of the liquid contaminates - such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil - by periodically elevating the temperature of the diluted lubricating oil, and
▪ promoting the partial combustion of the diluted lubricating oil by increasing blow-by gas flow from crankcase to engine cylinder during fuel cut off in deceleration.
The inventive method comprises a monitoring step which is used to determine the current oil dilution ratio by estimating and/or calculating. Within this monitoring process several operating parameters are measured, namely parameteres which are appropriate to describe the oil state, the engine state and/or the vehicle state and furthermore which are appropriate to be correlated to the most important lubrication properties of the oil in order to receive information about the current oil dilution state.
In contrast to the prior art which provides only continously operating methods and devices like the oil recycler disclosed in the WO96/25996, the inventive method enables a controlled treatment - e.g. evaporation and/or partial combustion - of the diluted fuel-oil mixture in dependency on the current oil dilution state determined within the monitoring step.
Consequently it is possible to create an open or closed control loop and to deal with the oil dilution demand oriented. The oil change interval may be adapted to different vehicle usage patterns resulting in an ideal use of resources and a reduction of vehicle operational costs. Simultaneously uncontrolled combustion and thereby caused severe engine damage could be avoided.
A preferred embodiment of the method is characterized in that the oil dilution state is calculated and/or estimated from the measured oil state and/or the engine state and/or the vehicle state, whereat the oil dilution state is preferably calculated.
In this case a preferred embodiment of the method is characterized in that the oil dilution state is calculated from the measured oil state, which provides information on the level and/or the temperature and/or the quality of the diluted lubricating oil and/or the like. For the calculation or estimation engine operating maps and/or specific vehicle maps could be used. These maps could be saved in the controller unit or in the motor control unit and are generated within experiments on an engine test bench or a chassis dynamometer.
It is the most precise possibilty to calculate the oil state using parameters which describe the oil properties directly. In other words, it is easier to draw conclusions from oil temperature, viscosity and the like relating to the oil dilution than from engine or vehicle state parameters.
Within the present invention the oil state, the engine state and the vehicle state is described by the following parameters:

Oil state:: temperature, level in the crankcase, quality, viscosity, conductivity or the like.
Engine state:: speed, driver demand, combustion mode, load, injection timing, ignition timing or the like.
Vehicle state:: speed, brake, clutch or the like.

In a first process step the measured parameters are used to determine the dilution state by means of a monitor. In a second process step this identified dilution state together with the same and/or other measured parameters are used to generate command signals by a controller for controlling the reducing of the oil dilution ratio.
In general the reduction of oil dilution could be achieved by promoting the evaporation of the liquid contaminates and/or promoting the partial combustion of the diluted lubricating oil.
A preferred embodiment of the method is characterized in that the oil dilution state is estimated, preferably the oil dilution state is estimated from the measured engine state, the oil temperature and the combustion mode, whereby the engine state provides information on the speed and/or the driver demand and/or the like.
This embodiment does not require costly measurement devices. The known parameters - i.e speed (rpm), oil temperature or the like - which are detected within the normal operation mode of an engine and the vehicle respectively are used to estimate the dilution state. Alternatively an estimation process does not need absolutely specific engine operating maps and/or specific vehicle maps. This could result in a cost advantage in contrast to the more complex calculating process.
A preferred embodiment of the method is characterized in that a command signal for an oil heating device is calculated from the engine state, the oil temperature and the dilution state, whether to promote the evaporation by elevating the temperature of the diluted lubricating oil or to impede evaporation by lowering the temperature.
The heating device of this embodiment has not a constant temperature during the operation of the engine. Following this preferred embodiment the temperature is controlled demand oriented i.e. temperature control as necessary.
A preferred embodiment of the method is characterized in that the temperature of the diluted lubricating oil is regulated by means of a bypass valve, which is used

to bypass an installed oil cooler or
to bypass an installed oil heating device or
to divide up the oil flow in two partial flows, whereby one partial flow passes a cooler and the other partial flow passes a heating device, so that the temperature of the diluted lubricating oil is regulated by the ratio and mixture of these partial flows.

The three different embodiments using a bypass valve influence the oil temperature directly. If the engine, namely the lubricating circuit, is equipped originally with an cooler, it is recommended to provide the circuit with a valve which is able to bypass said cooler, so that the oil flow does not pass the cooler and consequently the oil temperature is not lowered by the cooler.
Preferably the lubricating circuit is additionally equipped with a heating which is able to elevate the oil temperature and so to promote evaporation of the liquid contaminates, such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil.
A preferred embodiment of the method is characterized in that the bypass valve is actuated in response to the error between a desired and a measured oil temperature. This results in a closed loop controller. The desired oil temperature operates as the so-called temperature setpoint.
In this case a preferred embodiment of the method is characterized in that the desired oil temperature i.e. the temperature setpoint is calculated from the engine state and the dilution state.
A further preferred embodiment of the method is characterized in that the bypass control is activated as a function of the delayed command signal for the oil heating device. In this way both devices appropriate to affect the oil temperature work together. The bypass valve which follows the command signal without a delay and leads to a noticeable temperature change could support the heating directly i.e. the elevation of the temperature could be promoted by bypassing the cooler.
A preferred embodiment of the method is characterized in that a command signal for a blow-by-actuator is calculated from the engine state, the oil temperature and the dilution state, whether to promote or to impede the blow-by flow. In this case an embodiment of the method is preferred which is characterized in that an intake throttle is used as blow-by-actuator to lower the manifold pressure and consequently to lower the in-cylinder pressure in order to increase blow-by flow from crankcase to engine cylinder.
As mentioned above it is recommended to promote the partial combustion of the diluted lubricating oil by increasing blow-by gas flow from crankcase to engine cylinder during fuel cut off in deceleration. This is a measure to reduce the dilution ratio alternatively or additionally to the bypass valve and/or the heating device.
According to the present invention and with respect to the second object a device is provided which comprises
(a) an oil dilution state monitor for monitoring the oil dilution ratio by calculating and/or estimating the so-called oil dilution state from measured operating parameters, and
(b) an oil dilution controller for generating command signals for at least one device for controlling the oil dilution ratio by
- promoting the evaporation of the liquid contaminates - such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil - by elevating the temperature of the diluted lubricating oil, and/or
- promoting the partial combustion of the diluted lubricating oil by increasing blow-by gas flow from crankcase to engine cylinder during fuel cut off in deceleration.
A preferred embodiment of the device is characterized in that said device is provided with a bypass valve for regulating the oil temperature, which is used

to bypass an installed oil cooler or
to bypass an installed oil heating device or
to divide up the oil flow in two partial flows, whereby one partial flow passes a cooler and the other partial flow passes a heating device, so that the temperature of the diluted lubricating oil is regulated by the ratio and mixture of these partial flows,

A preferred embodiment of the device is characterized in that said device is provided with an intake throttle as blow-by-actuator to lower the manifold pressure and consequently to lower the in-cylinder pressure in order to increase blow-by flow from crankcase to engine cylinder, whereat the throttle is actuated by a blow-by command signal generated by the oil dilution controller.
A preferred embodiment of the device is characterized in that said device is provided with a heating device, whereat said heating device is actuated by a heater command signal generated by the oil dilution controller.
Embodiments of the present invention will be described below with reference to the drawings:

Figure 1: shows a scheme of an oil loop relating to a first embodiment of the control device,
Figure 2: shows schematically a first embodiment of the oil dilution control Method or rather of the device,
Figure 3: shows schematically the strategy of a first embodiment of the oil dilution state monitor or rather of the method,
Figure 4: shows schematically the strategy of a second embodiment of the oil dilution state monitor or rather of the method, and
Figure 5: shows schematically a first embodiment of the oil dilution controller method or rather of the method.

Figure 1 shows a scheme of an oil loop relating to a first embodiment of the control device.
The oil loop 8 is equipped with a cooler 1, a heating device 2 and a bypass valve 3, which is used to regulate the temperature of the diluted lubricating oil.
The illustrated embodiment of an oil loop 8 enables three different control strategies. On the one hand the bypass valve 3 could be used to bypass the installed oil cooler 1 or to bypass the installed oil heating device 2. The first circuitry results in a temperature increase, while the second leads to lower temperatures.
On the other hand the bypass valve 3 could be used to divide up the oil flow entering the loop 8 through the inlet pipe 4 in two partial flows, whereby one partial flow passes the cooler 1 via pipe 6 and the other partial flow passes the heating device 2 via pipe 7, so that the temperature of the diluted lubricating oil is regulated by the ratio and mixture of these partial flows which are brought together in the outlet pipe 5.
The oil loop 8 is equipped with a heating 2 aiming to elevate the oil temperature and to promote evaporation of the liquid contaminates, such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil this way.
Preferably the bypass valve 3 is actuated demand oriented i.e. in response to an error between a temperature setpoint and a measured oil temperature, whereat this strategy results in a closed control loop relating to the oil temperature.
Figure 2 shows schematically a first embodiment of the oil dilution control method.
First the current oil dilution ratio is determined by estimating and/or calculating within a monitoring step. Therefore an oil dilution monitor 9 is provided with several input signals. These input signals are measured operating parameters, namely parameteres which are appropriate to describe the oil state, the engine state and/or the vehicle state and furthermore which are appropriate for drawing conclusions relating to the oil dilution state.
For this the measured parameters are correlated to the most important lubrication properties of the oil within experiments on a test bench in order to generate specific maps which could be used during engine operation to receive information about the current oil dilution state.The proposed method enables a controlled treatment on demand e.g. evaporation and/or partial combustion of the diluted fuel-oil mixture taking into account the current oil dilution state.
As can be seen in Figure 2 the oil state is described by temperature, level in the crankcase, quality, viscosity, conductivity or the like. The engine state is described by speed, driver demand, combustion mode, load, injection timing, ignition timing or the like and the vehicle state is described by speed, brake, clutch or the like.
According to the illustrated control method the measured parameters are used to determine the current dilution state by means of the monitor 9 within a first process step. In a second following process step this identified dilution state together with the same and/or other measured parameters are used to generate command signals by an oil dilution controller 10 for controlling the reducing of the oil dilution ratio i.e. of the oil dilution state.
If the control device is equipped with a bypass valve and a heating device as shown in Figure 1 and additionally provided with a blow-by actuator - for example the intake throttle - the oil dilution controller 10 generates three output signals - the so-called command signals - which are used to control the above mentioned devices, namely the bypass valve, the heating device and the blow-by actuator.
In general the reduction of the oil dilution could be achieved by promoting the evaporation of the liquid contaminates and/or by promoting the partial combustion of the diluted lubricating oil.
With respect to the evaporation it is referred to figure 1 and the corresponding description. By means of a blow-by-actuator it is possible to promote or to impede the blow-by flow from crankcase to engine cylinder. Preferably an intake throttle is used as blow-by-actuator to lower the manifold pressure and therefore to lower the in-cylinder pressure in order to increase blow-by. The blow-by actuator is activated preferably within the decelaration phase during fuel cut off. This is a measure to reduce the dilution ratio alternatively or additionally to the bypass valve and/or the heating device.
Because the monitor 9 provides information about the current oil dilution state a control method could be realized which enables a treatment of the diluted oil mixture on demand. The oil change interval may be adapted to different vehicle usage patterns resulting in an ideal use of resources and a reduction of vehicle operational costs. Simultaneously uncontrolled combustion and thereby caused severe engine damage could be avoided.
Figure 3 shows schematically the strategy of a first embodiment of the oil dilution state monitor 9.
In general the oil dilution state could be achieved by calculation or estimation, whereat the illustrated monitor 9 combines both alternatives.
In the case that the oil dilution state is calculated from the measured parameters it is preferred that the oil dilution state is calculated from the oil state, which provides information on the level and/or the temperature and/or the quality of the diluted lubricating oil and/or the like. It is the most precise possibilty to calculate the oil dilution state using parameters which describe the oil properties directly. In other words, it is easier to draw conclusions from oil temperature, viscosity and the like relating to the oil dilution state than from engine or vehicle state parameters.
If the oil dilution state is estimated, the oil dilution state is preferably estimated from the measured engine state and the oil temperature, whereby the engine state provides information on the speed and/or the driver demand and/or the like.
The estimation does not require costly measurement devices because known parameters, such as speed (rpm), oil temperature or the like, which are detected within the normal engine operation are used to estimate the dilution state. This could result in a cost advantage in contrast to the more complex calculating process.
For the calculation or estimation engine operating maps and/or specific vehicle maps could be used. These maps could be saved in the controller unit or in the monitor 9 and are generated within experiments on an engine test bench or a chassis dynamometer.
If the oil dilution state is calculated and estimated two values for the dilution state are available, so that if there is appearing a fault in the calculation or in the estimation the other value could be used.
Figure 4 shows schematically the strategy of a second embodiment of the method or rather the corresponding oil dilution state monitor 9. By means of the shown oil dilution state monitor 9 the oil dilution state is estimated.
The oil dilution state is estimated from the measured engine state and the oil temperature, whereby the engine state provides information on the speed and/or the driver demand and/or the like.
The oil temperature and the engine state are used to calculate the time-based rate of dilution (in % per second) as a function of the current engine operation mode (e.g. lean, rich or heating mode) via a selector module 11. The dilution rate is integrated and discretized to provide the dilution level state (e.g. low, mid, high, too high). The integrator 12 will be reset at oil change.
Figure 5 shows schematically a first embodiment of the oil dilution controller method or rather the corresponding controller 10. A heater control 13 determines the activation/deactivation of the oil heater 2 as a function of oil temperature, engine state and oil dilution state.
A setpoint for the desired oil temperature is calculated as a function of the dilution state, engine state, and oil temperature. A bypass controller 14 - can be implemented as a classical PID controller - is implemented to achieve the desired temperature by controlling the flow rate of oil flow either through the cooler or the heater path. In order to aid accurate temperature control a feed forward term can be implemented as a function of the engine state, which would implicitly correct for the temperature and pressure fluctuation in the oil circuit as a function of engine operating condition.

Reference signs

1: cooler
2: heating device, oil heater
3: bypass valve
4: inlet pipe
5: outlet pipe
6: pipe
7: pipe
8: oil loop
9: oil dilution monitor
10: oil dilution controller
11: selector, selector module
12: integrator
13: heater control
14: bypass controller

Claims

A method for controlling the lubricating oil dilution - in volume percent - of an internal combustion engine, which comprises the following steps

(a) monitoring the oil dilution ratio by calculating and/or estimating the so-called oil dilution state from measured operating parameters, and

(b) reducing the oil dilution ratio by

promoting the evaporation of the liquid contaminates - such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil - by elevating the temperature of the diluted lubricating oil, and/or

promoting the partial combustion of the diluted lubricating oil by increasing blow-by gas flow from crankcase to engine cylinder during fuel cut off in deceleration.
A method according to claim 1, characterized in that the dilution ratio is reduced by

promoting the evaporation of the liquid contaminates - such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil - by periodically elevating the temperature of the diluted lubricating oil, and

promoting the partial combustion of the diluted lubricating oil by increasing blow-by gas flow from crankcase to engine cylinder during fuel cut off in deceleration.
A method according to any of the preceding claims, characterized in that the oil dilution state is calculated and/or estimated from the measured oil state and/or the engine state and/or the vehicle state.
A method according to any of the preceding claims, characterized in that the oil dilution state is calculated.
A method according to claim 4, characterized in that the oil dilution state is calculated from the measured oil state, which provides information on the level and/or the temperature and/or the quality of the diluted lubricating oil.
A method according to one of the claims 1 to 3, characterized in that the oil dilution state is estimated.
A method according to claim 6, characterized in that the oil dilution state is estimated from the measured engine state, the oil temperature and the combustion mode, whereby the engine state provides information on the speed and/or the driver demand and/or the like.
A method according to any of the preceding claims, characterized in that a command signal for a oil heating device (2) is calculated from the engine state, the oil temperature and the dilution state, whether to promote the evaporation by elevating the temperature of the diluted lubricating oil or to impede evaporation by lowering the temperature.
A method according to any of the preceding claims, characterized in that the temperature of the diluted lubricating oil is regulated by means of a bypass valve (3), which is used

to bypass an installed oil cooler (1) or

to bypass an installed oil heating device (2) or

to divide up the oil flow in two partial flows, whereby one partial flow passes a cooler (1) and the other partial flow passes the heating device (2), so that the temperature of the diluted lubricating oil is regulated by the ratio and mixture of these partial flows.
A method according to claim 9, characterized in that the bypass valve (3) is actuated in response to the error between a desired and a measured oil temperature.
A method according to claim 10, characterized in that the desired oil temperature i.e. the temperature setpoint is calculated from the engine state and the dilution state.
A method according to one of the claims 9 to 11 depending on claim 8, characterized in that the bypass control is activated as a function of the delayed command signal for the oil heating device (2).
A method according to any of the preceding claims, characterized in that a command signal for a blow-by-actuator is calculated from the engine state, the oil temperature and the dilution state, whether to promote or to impede the blow-by flow.
A method according to claim 13, characterized in that an intake throttle is used as blow-by-actuator to lower the manifold pressure and consequently to lower the in-cylinder pressure in order to increase blow-by flow from crankcase to engine cylinder.
A device for monitoring and reducing the lubricating oil dilution - in volume percent - of an internal combustion engine comprising

(a) an oil dilution state monitor (9) for monitoring the oil dilution ratio by calculating and/or estimating the so-called oil dilution state from measured operating parameters, and

(b) an oil dilution state controller (10) for generating command signals for at least one device for controlling the oil dilution ratio by

promoting the evaporation of the liquid contaminates - such as water, glycol and in particular the light hydrocarbon fuel components mixed with the lubricating oil - by elevating the temperature of the diluted lubricating oil, and/or

promoting the partial combustion of the diluted lubricating oil by increasing blow-by gas flow from crankcase to engine cylinder during fuel cut off in deceleration.
A device according to claim 15, characterized in that said device is provided with a bypass valve (3) for regulating the oil temperature, which is used

to bypass an installed oil cooler (1) or

to bypass an installed oil heating device (2) or

to divide up the oil flow in two partial flows, whereby one partial flow passes a cooler (1) and the other partial flow passes the heating device (2), so that the temperature of the diluted lubricating oil is regulated by the ratio and mixture of these partial flows.

whereat the bypass valve (3) is actuated in response to an error between a desired and a measured oil temperature by a bypass command signal generated by the oil dilution state controller (10).
A device according to claim 15 or 16, characterized in that said device is provided with an intake throttle as blow-by-actuator to lower the manifold pressure and consequently to lower the in-cylinder pressure in order to increase blow-by flow from crankcase to engine cylinder, whereat the throttle is actuated by a blow-by command signal generated by the oil dilution state controller (10).
A device according to one of the claims 15 to 17, characterized in that said device is provided with a heating device (2), whereat said heating device (2) is actuated by a heater command signal generated by the oil dilution state controller (10).