The present disclosure relates to engine oil pressure prediction, and more specifically to engine oil supply pressure prediction based on a downstream oil pressure measurement.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Engines typically include an oil supply pressure sensor to monitor oil pressure supplied to a lubricated portion of the engine, such as the main bearings. With additional hydraulically actuated components such as cam phasers and multi-step lifters being incorporated into engines, additional oil pressure sensors may be needed at locations downstream of an oil supply pressure sensor. Additional oil pressure sensors may add additional cost and complexity to engines.
A method may include opening an oil control valve (OCV) in an engine to provide an oil flow that actuates a cam phaser, measuring a first engine oil pressure at a location between the OCV and the cam phaser when the OCV is open, and determining a second engine oil pressure at a location between the OCV and an oil pump outlet location based on said first engine oil pressure.
A control module may include a cam phaser control module, a cam phaser oil pressure determination module, and a system oil pressure prediction module. The cam phaser control module may control an oil control valve (OCV) to control an oil flow to a cam phaser. The cam phaser oil pressure determination module may be in communication with the cam phaser control module and may determine a first engine oil pressure at a location between the OCV and the cam phaser when the OCV is in an open position. The system oil pressure prediction module may determine a second engine oil pressure at a location between the OCV and an oil pump outlet based on the first engine oil pressure.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality.
Referring now to
Intake system 14 may include an intake manifold 40 and a throttle 42 in communication with an electronic throttle control (ETC) 44. Throttle 42 and intake valves 24 may control an air flow into engine 12. Fuel injector 20 may control a fuel flow into engine 12 and spark plug 22 may ignite the air/fuel mixture provided to engine 12 by intake system 14 and fuel injector 20. Intake and/or exhaust valve lifters 28, 30 may include multi-step lifters, such as two-step lifters.
With additional reference to
Control module 15 may be in communication with engine 12 and may receive a signal from engine 12 indicative of a current engine speed. Control module 15 may additionally be in communication with intake and exhaust cam phaser systems 36, 38 and ETC 40. More specifically, in the present example control module 15 may be in communication with OCV 56 and intake phaser 58 to control opening of OCV 56 and to determine phasing rate and location of cam phaser 58. With reference to
Cam phaser control module 66 may control the opening of OCV 56 and therefore the phasing rate and displacement of cam phaser 58. Cam phaser oil pressure determination module 68 may be in communication with and receive a signal from cam phaser control module 66 that indicates a position of OCV 56 and a phasing rate of cam phaser 58. Cam phaser oil pressure determination module 68 may determine the oil pressure at a location between OCV 56 and cam phaser 58. The determined oil pressure may be used for evaluation of the intake and/or exhaust valve lifters 28, 30 when multi-step lifters are incorporated into engine 12. The determined oil pressure may additionally be used to estimate or predict an oil supply pressure. The oil supply pressure may include an oil pressure at a location in oil system 46 between oil pump 48 and OCV 56, and more specifically an oil pressure at main bearing gallery 52.
System oil pressure prediction module 70 may be in communication with cam phaser oil pressure determination module 68 and may receive the determined oil pressure. System oil pressure prediction module 70 may estimate a system oil flow rate and predict the oil supply pressure.
With reference to
Prediction of the oil supply pressure (Ps) using the determined oil pressure (Pd) may include a calculation of the oil supply pressure based on the following equations:
where Ps is the oil supply pressure, Pd is the determined oil pressure (a downstream oil pressure between OCV 56 and cam phaser 58 in the present example), {dot over (V)} is an estimated system volumetric oil flow rate, ρ is oil density, ν is oil viscosity, Cd is a discharge coefficient, As is a supply side reference area, Ad is a downstream side reference area, g is the gravitational constant (9.81 m/s2), and h is the height of the location of Pd relative to Ps.
A matrix of discharge coefficients (Cd) may be determined for a variety of engine operating conditions. The discharge coefficients (Cd) may be determined from component level testing and may be a function of volumetric oil flow rate ({dot over (V)}), oil density (ρ), and oil viscosity (ν), as shown in equation (2) above. More specifically, the discharge coefficients (Cd) may be calculated based on the component level testing.
For example, a known volumetric oil flow rate ({dot over (V)}) may be supplied to the engine 12 at a location corresponding to an oil pump outlet. A range of volumetric oil flow rates ({dot over (V)}1, {dot over (V)}2, . . . , {dot over (V)}n) may be supplied for a variety of engine conditions including oil temperatures (which accounts for oil density (ρ) and oil viscosity (ν)) as well operating conditions of cam phasers 58, 64. A first oil pressure measurement (P1) that generally corresponds to determined oil pressure (Pd) may be taken at pressure sensor 60 and a second oil pressure measurement (P2) that generally corresponds to oil supply pressure (Ps) may be taken upstream of first oil pressure measurement (P1). For example, second oil pressure measurement (P2) may be taken at main bearing gallery 52. A range of first oil pressures (P11, P12, . . . , P1n) and second oil pressures (P21, P22, . . . , P2n) may be collected that correspond to the range of volumetric oil flow rates ({dot over (V)}1, {dot over (V)}2, . . . , {dot over (V)}n).
Equation (1) may be manipulated to solve for discharge coefficient (Cd) using the first and second oil pressure measurements (P1, P2) as seen below in equation (3):
A range of discharge coefficients (Cd1, Cd2, . . . , Cdn) may be calculated that correspond to the range of volumetric oil flow rates ({dot over (V)}1, {dot over (V)}2, . . . , {dot over (V)}n) first oil pressures (P11, P12, . . . , P1n) and second oil pressures (P21, P22, . . . , P2n). Supply and discharge side reference areas (As, Ad) may be selected, where As is not equal to Ad. Supply and discharge side reference areas (As, Ad) may be selected in a relatively arbitrary manner, as long as the same supply and discharge side reference areas (As, Ad) are used for the calculation of each of discharge coefficients (Cd1, Cd2, . . . , Cdn) and for the calculation of the supply pressure (Ps).
The range of discharge coefficients (Cd1, Cd2, . . . , Cdn) may form a matrix of discharge coefficients for use in the calculation of the supply pressure (Ps). The values for the range of discharge coefficients may form a regression-based function or may be incorporated into a look-up table. Therefore, based on estimated system oil flow rate ({dot over (V)}), the supply pressure (Ps) may be predicted based on the determined oil pressure (Pd) from pressure sensor 60.
Alternatively, oil supply pressure (Ps) may be determined from a purely empirical regression equation shown in equation (4) below:
P
s
=f(Pd,RPM,T,{dot over (φ)}I,{dot over (φ)}E); (4)
where Pd is the determined oil pressure, as discussed above, RPM is engine speed (revolutions/minute), T is oil temperature, {dot over (φ)}I is intake phaser phasing rate, and {dot over (φ)}E is exhaust phaser phasing rate. Equation (4) may be derived experimentally from engine testing. Engine speed (RPM) may be used where oil pump 48 is driven by a mechanical component of engine 12 such as the crankshaft. Engine speed (RPM) may be disregarded where oil pump 48 is driven independently from engine 12, such as by an electric motor.
In either oil supply pressure (Ps) determination method, pressure sensor 60 may generally provide for the estimation of a system supply pressure, eliminating the need for an additional oil pressure sensor.
This application claims the benefit of U.S. Provisional Application No. 61/015,358, filed on Dec. 20, 2007. The disclosure of the above application is incorporated herein by reference.
Number | Date | Country | |
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61015358 | Dec 2007 | US |