WO2008041243A2

WO2008041243A2 - Method and system for sensing oil level

Info

Publication number: WO2008041243A2
Application number: PCT/IN2007/000447
Authority: WO
Inventors: Joseph Abraham; Sivakumar Ganesan; Krishnamoorthy Nellikunja Ravindra
Original assignee: Bajaj Auto Limited
Priority date: 2006-10-06
Filing date: 2007-09-27
Publication date: 2008-04-10
Also published as: WO2008041243A3; TW200823357A

Abstract

A method and system for providing an indication of quantum of oil in a lubricating system of an engine comprising, sensing a combination of engine operating parameters, control means for qualitatively assessing the quantum of oil based on sensed engine operating parameters and controlling the operation of the engine on the basis of the output of control means.

Description

METHOD AND SYSTEM FOR SENSING OIL LEVEL

This invention relates to a method and system for sensing oil level, for example in an internal combustion engine.

BACKGROUND OF INVENTION

An internal combustion engine employs different types of oils for achieving desired performance of the vehicle. Oils such as lubricating oil, brake oil and so on are commonly used.

Lubricating oil is important for any internal combustion engine. It performs the function of lubricating the moving parts / components of the engine by forming a thin film of oil between the moving parts, which reduces friction. To ensure optimum performance of the engine, it is desirable that a continuous supply of oil is available to the moving parts.

The lubricating oil is stored in the engine in a reservoir or sump and is delivered to the moving parts of the engine in many different ways. A desired quantum of oil is required to be available in the reservoir or sump to adequately lubricate the moving parts.

The quantum of oil available in the reservoir is required to be periodically checked. This is accomplished in many different ways in conventional internal combustion engines. For example, a calibrated oil dipstick may be inserted into the oil sump through a suitably provided slot to check the level of oil. A transparent window, called an oil window, may be provided to allow visual inspection of oil level. The oil level may be inspected when the engine is hot or cold depending on the design aspects. Generally, the oil window method or the dipstick method is employed when the vehicle is not running for at least six hours allowing adequate time for the oil in circulation to settle. Thus, these conventional methods cannot be used when the engine is running, unless a specific and accurate calibration is employed other wise. One of the disadvantages of this system of oil level inspection is that it requires manual actions. In many instances, the rider may simply forget to inspect the oil level on a regular basis.

It is a characteristic property of the oil that its pressure varies with operating temperatures in the engine. For example, the oil pressure increases progressively as the engine commences running. Owing to turbulence caused by the moving parts and transfer of combustion heat through parts of the engine the oil temperature increases with time. Above a certain operating temperature, the oil pressure may begin to reduce due to a reduction in oil viscosity. Thus, measurement of oil pressure alone will not give a correct indication on the availability of required quantum of oil. A more accurate system is required to indicate the incidence of low oil level in the engine to thwart potential damage to engine parts.

SUMMARY OF INVENTION

It is an object of the present invention to provide a method and system for providing an indication of oil level that addresses one or more of the above noted disadvantages.

It is a further object of the invention to protect the engine and its parts from potential damage caused due to insufficient availability of lubricating oil.

With these objects in view, in a first aspect the present invention provides a method for providing an indication of oil level in a lubricating system of an engine, the method comprising:

(a) Sensing a plurality of engine operating parameters; and

(b) combining the parameters to provide an indication of oil level.

In a second aspect the present invention provides a control means for controlling an engine, the control means arranged to receive information relating to a plurality of sensed engine parameters and to combine the parameters to provide an indication of oil level, wherein the control means relates the combination of sensed engine operating parameters to a qualitatively assessed amount of oil present in the lubricating system and initiates a control action based on the qualitatively assessed amount of oil.

By "indication of oil level" is intended the evaluation or quantification (which need not be precise) of an amount of oil available for lubrication of the engine. Thus the invention provides an indirect method of assessing an oil amount. A precise level determination, as such, is not required.

The control means evaluates the relationship between the sensed engine operating parameters to assess oil amount. That is, a low oil level indication may correspond with a particular combination of engine operating parameters. Three suitable and preferred engine operating parameters to be used in the method are oil temperature, oil pressure and engine speed. These engine operating parameters are sensed or otherwise determined. If the control means determines that oil temperature is less than a predetermined value, engine speed is more than a specified value and oil pressure is less than a predetermined value, then oil level may be qualitatively assessed as LOW. Trends in the sensed values may also be evaluated. The time for which the sensed values exceed or fall below the threshold may also be a relevant control parameter. Other engine operating conditions may be used by the control means to evaluate available oil level.

Because the suite of preferred sensors (that is oil temperature, oil pressure and engine speed) on an individual basis provide valuable engine operating information, their use in an innovative way to provide indicative oil level information provides additional justification for their inclusion in an engine package. This additional synergy is particularly important to the 2 and 3 wheeler markets where costs are heavily scrutinized.

The preferred parameters of oil pressure, oil temperature and engine speed have certain typical relationships which assist in implementing the method. Oil pressure decreases with increase in temperature and decrease in oil level below a particular value. Oil pressure increases with increase in engine speed. Engine and oil temperatures increase after start-up and further running.

The predetermined engine operating parameter values to be employed by the control means to assess oil amount may be selected in accordance with oil or lubricant specification for a particular lubricant.

In the event that the oil level is assessed LOW, the control means may initiate a number of control actions. First, a warning indication may be provided to the vehicle operator. Such warning indication may be visual, audible or both. Second, engine operation could be modified or stopped altogether. Alternatively, or additionally, advice may be provided to the vehicle operator that oil level is judged unacceptable. Time to next oil service could also be assessed and the vehicle operator notified.

The method is especially suitable for qualitatively assessing a level of lubricating oil available for lubrication of an internal combustion engine, particularly a four stroke engine. The engine may be used in a two, three or four wheel vehicle. The application to 2 and 3 wheeled vehicles is especially advantageous.

In another aspect of the invention, there is provided an oil level sensing system comprising:

(a) a combination of sensors for sensing engine operating parameters; and

(b) control means for controlling the engine with a control means on the basis of the sensed engine operating parameters;

wherein the control means is programmed to relate the combination of sensed engine operating parameters to a qualitatively assessed amount of oil present in the lubricating system and initiate a control action based on the qualitatively assessed level or amount of oil. An indication means and/or an engine management system may implement the desired control action, whether it be a warning signal that oil level is low or a modification of engine operating conditions to compensate for the low oil level. The control means may initiate stopping of the engine.

Control systems and vehicles adopting the oil level sensing methodology of the invention form further aspects of the invention.

Advantageously, the invention allows oil level to be sensed without need for manual intervention. The control means, electronic or otherwise, may also implement other engine management strategies to prevent engine damage due to lack of requisite amount of oil for lubrication.

DESCRIPTION OF PREFERRED EMBODIMENTS:

The invention may be better understood from the following detailed description of preferred embodiments thereof made with reference to the accompanying drawings, in which:

Figure 1 illustrates a pictorial representation of an oil level indication system according to one embodiment of the present invention.

Figure 2 illustrates the logic diagram of the oil level indication system of Figure 1.

Figure 1 illustrates an engine 1 having a crankcase assembly 2, an oil cooler 4 and a microcontroller 8 for controlling engine operation in accordance with sensed engine operating parameters. Microcontroller 8 is programmed with logic for analyzing the input from a number of engine operating condition sensors to qualitatively assess an available amount of engine oil.

Crankcase assembly 2 is provided with an opening 11 into which oil temperature sensor 6 is fitted. Temperature sensor 6 is a negative temperature coefficient thermistor, which continuously measures oil temperature and provides temperature signals to the microcontroller 8.

Oil cooler 4 is provided with an adapter 12 to which an oil pressure sensor 5 is fitted. A conventional speed sensor 7 for measuring engine speed is connected to pick up coil 3 of engine. The combination of sensors 5, 6, and 7 all provide signals to microcontroller 8. Microcontroller 8 assesses the relative values of each of the sensed oil pressure, oil temperature and engine speed signals and, in the event of judging a sensed LOW oil level, initiates a control action in the form of illumination of warning lamp 10 provided in the instrument console 9 of the vehicle (not shown).

Figure 2 illustrates the operating logic diagram of the oil level indication system of the invention demonstrating how the microcontroller 8 judges oil level or available oil amount. The microcontroller 8 senses the input from oil temperature sensing means 6 and if oil temperature is below a predetermined value, the micro-controller 8 checks the engine speed. If sensed engine speed is above a predetermined value for a predetermined period, the microcontroller 8 checks the input signal from oil pressure sensor 5. If sensed oil pressure is below a predetermined value, microcontroller 8 sends a signal to a signal generating means, which in turn triggers the warning lamp 10 to indicate that the available quantum of lubricating oil is low. The microcontroller 8 can also initiate other control actions such as modification or stopping of the engine.

The method and system involves algorithms, which may take the form of maps for likely oil level for varying combinations of oil temperature, oil pressure and engine speed conditions to judge probable instances of lower than desired oil level in the engine 1. A steady state of engine operation is signified by a second engine operating parameter - engine speed - being above a predetermined value and the oil temperature (the first parameter) being at an operating level, below the predetermined value. Two of the three selected engine operating parameters have values indicating a situation, where the oil pressure must be at a certain level for safe and efficient running of the engine; else it would cause serious problems to the engine 1.

At this point, measurement of oil pressure provides a more accurate evaluation of the quantum of oil available for lubrication. This is accentuated by a property of the oil that its pressure commences to reduce after reaching this temperature threshold. Then, in the event of oil pressure being lower than the predetermined value, when the engine is running above a certain speed, and the oil temperature is higher than the predetermined value, a clear indication of lower than desired quantum of oil is provided.

It will be understood that the predetermined value for oil pressure represents a pressure which correlates to a LOW oil level, given the other measured parameters. The oil pressure level of itself may be acceptable for engine operation. The present invention achieves its effect by consideration of the combination of parameters, not the observation of any one parameter in isolation.

It can be observed from Figure 2 that, in the event of any of the selected engine operating parameters not meeting the predetermined values, that is:

(a) if the oil temperature is more than the predetermined value ;or

(b) if the engine speed is below a predetermined value; or

(c) if the oil pressure sensed is above the predetermined value no trigger signal is communicated to warning lamp 10 indicating to the vehicle operator that oil level for engine 1 is within acceptable limits.

Example

A motorcycle was fitted with an oil quantity indication system as above described. A control unit for the motorcycle was programmed with predetermined values for the selected engine operating parameters following laboratory testing. The predetermined value for oil temperature is set at 60⁰C; the predetermined value for engine speed is set at 3,500 rpm and the predetermined value for oil pressure is set at 0.2 bar. These values were established for a specified type of lubricating oil. However, values for different specifications of lubricating oils may vary.

With reference to Figures 1 and 2 and above description, it can be observed that a low oil level warning is given to the rider by a warning lamp 10 prominently located on the instrument console 9 which is thereby prompting the rider to take necessary steps to add oil and prevent engine damage.

Modifications and variations to the method and system of the invention may be apparent to skilled readers of this disclosure. For example, another combination of engine operating condition sensors may be selected to indicate low oil level. Further, the visual or audible indication/warning to the vehicle operator may be in different forms. All such modifications and variations are deemed within the scope of the invention.

Claims

CLAIMS:

1^*. A method for providing an indication of oil level in a lubricating system of an engine, the method comprising: a. sensing a plurality of engine operating parameters; and b. combining the parameters to provide an indication of oil level.

2. The method as claimed in Claim 1 where the engine is in a running condition.

3. The method as claimed in Claim 1 or 2 where one of the engine operating parameters is lubricating oil temperature.

4. The method as claimed in any one of Claims 1 to 3 where one of the engine operating parameters is lubricating oil pressure.

5. The method as claimed in any one of Claims 1 to 4 where one of the engine operating parameters is engine speed.

6. A method of controlling the operation of an engine, comprising the steps of providing an indication of oil level as claimed in any preceding claim using a control means, and controlling the operation of the engine on the basis of the output of the control means.

7. The method as claimed in Claim 6 where control means activates visual or audio alert to the vehicle operator if the assessed quantum of lubricating oil is lower than a predetermined value.

8. The method as claimed in Claim 6 where control means activates engine shut off system if the assessed quantum of lubricating oil is lower than desired.

9. The method as claimed in Claim 7 or 8, where the quantum of lubricating oil is assessed as LOW when oil pressure is below a predetermined value and other engine parameters meet predefined conditions, the predetermined value representing an oil pressure which of itself is acceptable for engine operation.

10. A control means for controlling an engine, the control means arranged to receive information relating to a plurality of sensed engine parameters and to combine the parameters to provide an indication of oil level, wherein the control means relates the combination of sensed engine operating parameters to a qualitatively assessed amount of oil present in the lubricating system and initiates a control action based on the qualitatively assessed amount of oil.

11. The control means as claimed in Claim 10 where one of the sensed parameters is lubricating oil temperature.

12. The control means as claimed in Claim 10 or 11 where one of the sensed parameters is lubricating oil pressure.

13. The control means as claimed in claim 12 where the control action is initiated when oil pressure is below a predetermined value and other engine parameters meet predefined conditions, the predetermined value representing an oil pressure which of itself is acceptable for engine operation.

14. The control means as claimed in any one of Claims 10 to 13 where one of the sensed parameters is engine speed.

15. The control means as claimed in Claim 10 where the control means is a micro controller.

16. The control means as claimed in any one of Claims 10 to 15 where the control means initiates the control action if the assessed quantum of lubricating oil is lower than a predetermined value.

17. The control means as claimed in any one of Claims 10 to 16 where the control action is the sounding of an audio alert device.

18. The control means as claimed in any one of Claims 10 to 16 where the control action is the display of a visual alert device.

19. The control means as claimed in any one of Claims 10 to 16 where the control action is the activation of an engine stop switch.

20. The method or control means as substantially claimed above and applied to an automotive vehicle.

21. The method or control means as substantially claimed above and applied to a two wheel vehicle.

22. The method or control means as substantially claimed above and applied to a three wheel vehicle.