SYSTEM FOR DETECTING A FAILURE IN A COMBUSTION ENGINE LUBRICATING OIL SYSTEM PROVIDED WITH AN ADJUSTABLE OIL SOURCE

Abstract

 Method for detecting a failure in a combustion engine lubricating oil system provided with an adjustable oil source. The method is based on the comparison of the actual pressure and an expected one for a given control signal of said adjustable oil source or on the comparison of the actual signal control with an expected one for a given oil pressure, and in case a mismatch is detected an action is carried out.

Description

Field of the invention

[0001] The present invention relates to a system for detecting a failure in a lubricating oil circuit provided with an adjustable oil source, in the field of the internal combustion engines.

Description of the prior art

[0002] US5339775 shows a lubricating system comprising a bypass valve connected to the outlet of an oil pump in order to adjust the oil pressure according to certain parameters. Other systems exploit the implementation of a variable pump.

[0003] An oil source refers herein both to the fixed pump with controllable bypass valve or to a variable pump or another similar equivalent system.

[0004] The parameters usually acquired are the oil temperature, the oil pressure.

[0005] Such systems usually adapt the oil source in order to achieve a predefined pressure in the main gallery of the lubricating oil circuit.

[0006] Suitable maps can be stored in a non volatile memory of the engine control unit in order to adapt the oil pressure in the main gallery according to the combustion engine operating conditions.

[0007] The control system could be exploited also for other different aims.

Summary of the invention

[0008] The main object of the present invention is to provide a system for detecting a failure in the combustion engine lubricating oil system provided with an adjustable oil source.

[0009] The main principle of the invention is based on the comparison of the actual pressure and an expected one for a given control signal of said adjustable oil source or on the comparison of the actual signal control with an expected one for a given oil pressure, and in case a mismatch is detected an action is carried out.

[0010] According to a first implementation of the invention in a memory of a control unit a function is stored, or arrays or maps, to calculate or contain control signal values, for controlling the adjustable oil source, and two or more corresponding pressure values for at least a predetermined point of the lubricating oil circuit in normal operating condition of the combustion engine. These pressure values are referred as "expected pressure values" and these control signal values are referred as "expected control signal values".

[0011] When the control unit experiences a mismatch between one expected pressure value and an effectively measured pressure value, corresponding to the same expected control signal value, a failure is detected in the lubricating oil system and, according to the magnitude of such a mismatch, a suitable action is carried out.

[0012] In the same manner, when the control unit experiences a mismatch between one expected control signal and an actual one in order to force the measured oil pressure to an expected oil pressure value, a failure is detected in the lubricating oil system and, according to the magnitude of such a mismatch, a suitable action is carried out.

[0013] This second embodiment is particularly indicated for those oil source controlled through a feedback control scheme.

[0014] For example, when a bearing fails, the oil path, through said bearing, could be interrupted or enlarged by determining, respectively, an oil pressure increase or drop with respect to an expected pressure value.

[0015] Nozzles are implemented in order to cool the engine pistons though the same combustion engine lubricating oil. When, due to impurities, the nozzle is obstructed, an oil pressure increase with respect to an expected pressure value.

[0016] Similarly, when an oil pump or its variable actuator or its bypass valve fails, an oil pressure variation with respect to an expected one is experienced.

[0017] When the adjustable oil source is controlled according a feedback control scheme such pressure variation is reflected on the control signals controlling the adjustable oil source

[0018] Thanks to the present invention, such pressure/control signal variation with respect to a predetermined one is detected and exploited to detect a failure in the combustion engine lubricating oil system.

[0019] Such failures could lead to severe damage or even the destruction of the combustion engine, therefore, the present invention permits to avoid such relevant problems.

[0020] These and further objects are achieved by means of the attached claims, which describe preferred embodiment of the invention, forming an integral part of the present description.

Brief description of the drawings

[0021] The invention will become fully clear from the following detailed description, given by way of a mere exemplifying and non limiting example, to be read with reference to the attached drawing figures, wherein:

• Fig. 1 shows a flow chart disclosing a preferred embodiment of a failure detection method according to the present invention,
• Fig. 2 shows another flow chart disclosing another preferred embodiment of a failure detection method according to the present invention
• Fig. 3 shows schematically a combustion engine comprising an engine control unit implementing the method object of the present invention.

[0022] The same reference numerals and letters in the figures designate the same or functionally equivalent parts.

[0023] According to the present invention, the term "second element" does not imply the presence of a "first element", first, second, etc.. are used only for improving the clarity of the description and they should not be interpreted in a limiting way.

Detailed description of the preferred embodiments

[0024] The present invention refers to a internal combustion engine 10, see figure 3, provided with a lubricating oil system having at least

• a adjustable oil source AS, namely a variable oil pump or a fixed pump P with a controllable bypass valve 34,38 or an equivalent system,
• an oil circuit 30, per se known,
• at least one oil pressure sensor 47 arranged in predetermined point of the oil circuit and
• preferably an oil temperature sensor 44.

[0025] A control unit 40 controls the actuation of the oil source AS, for example, through the controllable valve 34,38, in order to lubricate and/or cool engine components, such as valve actuation 26, bearing 24 and oil nozzle (not shown). According to an embodiment of the present invention, a first phase is carried out on one ore more test engines, preferably at bench test: two or more control signal values of the adjustable oil source for corresponding two or more engine operation points are stored in a first location of a non-volatile memory of a control unit 40, while two or more corresponding pressure values, measured by said at least one oil pressure sensor 42, are measured and stored in a second location of said non-volatile memory.

[0026] According to a first embodiment of the invention, the method is executed when the oil temperature exceeds a predefined temperature threshold, due to the fact that the oil viscosity, and thus, the oil pressure are influenced by the oil temperature.

[0027] According to a second embodiment of the invention, the pressure values are mapped in a multidimensional array on temperature discrete values, in order to account for the viscosity variation, that, as known varies with the temperature.

[0028] During the life of the same combustion engines or others of the same type of said test engines, the oil pressure is continuously acquired and, according to a given engine operation point an actual control signal value for controlling the adjustable oil source is determined or acquired. An expected oil pressure is acquired from said non-volatile memory and compared with a measured one.

[0029] When, for one control signal value, the detected actual pressure does not match with the corresponding expected pressure value stored (or run time calculated), an action is carried out.

[0030] According to a preferred implementation of the present invention, a mismatch lower than a first threshold Th1 is neglected, while a mismatch exceeding said first threshold Th1 determines, for example, the activation of a lamp in the dashboard (Action 1), while a mismatch exceeding a second threshold Th2 determines the activation of a recovery mode (Action 2), wherein the combustion engine is controlled in order to limit its speed and torque.

[0031] Th1 is lower than Th2.

[0032] Preferably, also an engine speed sensor 46 and a engine load sensor/estimator 48 are connected to the control unit in order to determined the engine operation point. Preferably, such control unit coincides with the Engine Control Unit.

[0033] The method can be favourable executed when the oil temperature exceeds a predetermined threshold, namely when the oil viscosity is stabilized and the result of the method is meaningful.

[0034] According to another preferred embodiment of the present invention, the control signal values are interrelated with the oil pressures values and the oil temperature values, in order to account also for the viscosity variations of the oil.

[0035] In DE10141786 neural networks are implemented to run time calculate the expected oil pressure according to several engine parameters. The predetermined strategies to control the oil source can be any, and in any case, not relevant for the present invention.

[0036] Therefore, instead of storing arrays or maps in the control unit memory, a function/algorithm is stored and executed by the control unit 40 in order to run time calculate an expected oil pressure (or control signal) and to compare such expected oil pressure (or control signal), on the basis of the corresponding control signal of the controllable oil pump (or pressure) with the actual measured one.

[0037] Thus, according to the specific implementation, such expected oil pressure values can be pre-stored or run time calculated.

[0038] Figure 1 shoes an example of implementation of the present invention comprising the following steps:

• step 1: Start
• step 2: Acquisition or calculation of control signal value V for controlling an adjustable oil source AS,
• Step 3: Acquisition or calculation of an expected pressure value EP corresponding to said control signal value V,
• Step 3bis: Measurement of an actual oil pressure value AP,
• Step 4: comparing said expected pressure value EP with said actual pressure value, in case a difference is under a first threshold Th1, return to step 1, otherwise
• Step 5: comparing said expected pressure value EP with said actual pressure value, in case a difference is under a second threshold Th2 then
• Step 6: perform Action 1, otherwise
• Step 7: perform Action 2.

[0039] After Actions 1 and 2, the method can be stopped or executed continuously restarting form step 1.

[0040] According with the specific implementation of the present invention, at START step, engine parameters are acquired, including the engine operating point and the engine oil temperature.

[0041] Therefore, in case the oil pressure values are not considered as interrelated with oil temperature values, then the method is not executed until the oil temperature is under said predetermined threshold. Vice versa, in case the method is capable to account for the oil viscosity variation for example through a temperature sensor or a viscosity sensor, for example at step 3, the method is always executed without restrictions.

[0042] Therefore, it should be understood, that if also the oil temperature is accounted, and/or its viscosity, the 2D map shown on figure 1 becomes a 3D map or a multidimensional map according to the number of parameters accounted, influencing the pressure in the oil circuit with the same control signal applied to the oil source.

[0043] Figure 2 shows another embodiment of the present invention comprising the following steps:

• step 11: acquisition or calculation of an expected oil pressure value (EP) in at least one predetermined point of an oil circuit of said lubricating oil system,
• Step 12: acquisition or calculation of an expected control signal for said adjustable oil source corresponding to said expected oil pressure value (EP),
• Step 13: measurement of an oil pressure value (AP) in said at least one predetermined point of said oil circuit,
• Step 14: calculating an actual control signal in order to force said actual oil pressure (AP) to match with said expected one (EP),
• Step 15: comparing said expected control signal value with said actual control signal value, in case a difference is under a threshold (Th1, Th2), repetition of the above steps, otherwise
• Step 16, Step 17: performing a predetermine action as disclosed above.

[0044] As for the previous embodiment of figure 1, also in this embodiment the method can be executed when the oil temperature is stabilized over a predetermined threshold or, as alternative, the oil viscosity, function of the oil temperature, is accounted at the step 12, when the control signal of the oil source is run time calculated or acquired by a map stored in the control unit memory.

[0045] According to a preferred embodiment of the invention, the oil source AS, is controlled through a feedback control scheme based on the same pressure sensor. It is however possible to compare the value of the pulse-width modulation (PWM) control signal at any engine condition point to pre-defined values, and if the difference ECS-ACS exceeds a pre-defined threshold, which accounts for expected engine-to-engine differences, a diagnostic for an oil system check is flagged.

[0046] It should be understood that PWM is only one over several implementable control techniques.

[0047] In other word, the present invention can be also implemented comparing an expected control signal with an actual one for a measured pressure. This signals comparison is equivalent to the pressures comparison, but more suitable in those cases where a feedback control is implemented.

[0048] This invention can be implemented advantageously in a computer program comprising program code means for performing one or more steps of such method, when such program is run on a computer. For this reason, the patent shall also cover such computer program and the computer-readable medium that comprises a recorded message, such computer-readable medium comprising the program code means for performing one or more steps of such method, when such program is run on a computer.

[0049] Many changes, modifications, variations and other uses and applications of the subject invention will become apparent to those skilled in the art after considering the specification and the accompanying drawings which disclose preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the scope of the invention are deemed to be covered by this invention.

[0050] It should be understood that all the single features and/or embodiments can be combined between each other. In addition, the features disclosed in the prior art background are introduced only in order to better understand the invention and not as a declaration about the existence of known prior art. Therefore, also the features described in the prior art background can be considered in combination with those mentioned in each embodiment of the detailed description.

[0051] Further implementation details will not be described, as the man skilled in the art is able to carry out the invention starting from the teaching of the above description.

Claims

1. Method for detecting a failure in a combustion engine lubricating oil system provided with an adjustable oil source, controlled through a control signal, the method being based on the comparison of an actual measured pressure and an expected one for a given control signal of said adjustable oil source or on a comparison of an actual signal control with an expected one for a given oil pressure, and in case of a mismatch is detected between said pressures or between said control signals an action is carried out.

2. Method according to claim 1, comprising the following steps:

- (step 2) acquisition or calculation of a control signal value (V) for controlling said adjustable oil source (AS),

- (Step 3) Acquisition or calculation of an expected pressure value (EP) corresponding to said control signal value (V) in a predetermined point of an oil circuit of said lubricating oil system,

- (Step 3bis) Measurement of an actual oil pressure value (AP) in said predetermined point of an oil circuit,

- (Step 4) comparing said expected pressure value (EP) with said actual pressure value (AP), in case a difference is under a threshold (Th1, Th2), repetition of the above steps, otherwise

- (Step 6, Step 7) performing a predetermined action.

3. Method according to claim 2, wherein two or more expected pressure values (EP) are stored in a first location of a non volatile memory of a first control unit.

4. Method according to claim 2, wherein said expected pressure value (EP) is run time calculated on the basis of combustion engine parameters.

5. Method according to any one of previous claim 4, wherein said combustion engine parameters include at least one of

- oil temperature,

- environment temperature,

- engine torque delivered,

- engine speed

- a viscosity sensor.

6. Method according to claim 1, comprising the following steps:

- (step 11) acquisition or calculation, according to combustion engine parameters, of an expected oil pressure value (EP) in one predetermined point of an oil circuit of said lubricating oil system,

- (Step 12) acquisition or calculation of an expected control (ECS) signal for said adjustable oil source corresponding to said expected oil pressure value (EP),

- (Step 13) measurement of an oil pressure value (AP) in said one predetermined point of said oil circuit,

- (Step 14) calculating an actual control signal in order to force said actual oil pressure to match with said expected one (EP),

- (Step 15) comparing said expected control signal value (ECS) with said actual control signal value (ACS), in case a difference is under a threshold (Th1, Th2), repetition of the above steps, otherwise

- (Step 17, Step 18) performing a predetermine action.

7. Method according to claim 6, wherein two or more expected control signals values (ECS) are stored in a first location of a non volatile memory of a first control unit.

8. Method according to claim 6, wherein said expected control signal values are run time calculated according to the oil circuit characteristics and combustion engine parameters.

9. Method according to any of the previous claims from 1 to 8, wherein said action comprises at least one of the following:

- signaling a malfunction on the lubricating oil system,

- forcing a recovery mode in the combustion engine performances.

10. Method according to any of the previous claims, wherein the method is executed when an oil temperature exceed a predetermined threshold or wherein said expected oil pressure or said expected control signal accounts for an oil viscosity variation as function of an oil temperature.

11. System for detecting a failure in a combustion engine lubricating oil system provided with an adjustable oil source and control means (40) controlling said adjustable oil source (AS) by means of a relating control signal according to a predetermined control strategy, at least a pressure sensor (47) arranged in a predetermined point of an oil circuit of said lubricating oil system, wherein said control means are adapted to perform all the steps of any of the previous claim from 1 to 10.

12. Internal combustion engine comprising a lubricating oil system provided with an adjustable oil source and control means (40) controlling said adjustable oil source (AS) by means a relating control signal according to a predetermined control strategy and characterized in comprising a system for detecting a failure in said combustion engine lubricating oil system according to claim 11.

13. Terrestrial vehicle or fixed installation characterized in comprising the combustion engine according to claim 12.

14. Computer program comprising computer program code means adapted to perform all the steps of any of the claims from 1 to 10, when said program is run on a computer.

15. A computer readable medium having a program recorded thereon, said computer readable medium comprising computer program code means adapted to perform all the steps of any of the claims from 1 to 10, when said program is run on a computer.

Drawing