Oil pressure control of variable camshaft timing system

Abstract

The present application relates to oil pressure control of a variable camshaft timing system, and provides methods and systems for regulating the oil pressure supplied to an engine and a VCT system in response to conditions of the variable cam timing (VCT) system. In one example, a method includes regulating the oil pressure based on engine speed, engine load, and engine oil temperature, and increasing the oil pressure to an upper threshold oil pressure for a duration of the transition in response to a request to transition the VCT system during a particular engine operating condition.

Description

Technical Field

[0001] The present invention generally relates to methods and systems for controlling a vehicle engine to regulate oil pressure supplied to the engine and a variable camshaft timing system in response to operating conditions of the variable camshaft timing system. Background Art

[0002] Internal combustion engines may employ variable cam timing (VCT) to improve vehicle fuel economy and emissions performance. Many variable camshaft timing systems employ vane-type cam phasers that can be controlled by an electromechanically actuated spool valve that directs oil flow to one side or the other of the vanes to actuate the phaser and thereby adjust the camshaft timing relative to the engine crankshaft timing. Actuation of these variable timing systems, and thus the timing of the engine cylinder valves, is highly dependent on oil flow and oil pressure in the VCT system. Modern oil control systems may include an oil pump, referred to as a variable displacement oil pump (VDOP), that can be calibrated to adjust pump operation in response to parameters such as engine temperature, engine load, and engine speed. These oil control systems typically provide competing and overlapping demands for multiple engine subsystems, including bearings, hydraulic valve mechanisms, VCT systems, and piston cooling nozzles. Additionally, to minimize parasitic losses and improve fuel economy, the variable displacement oil pump is typically calibrated to provide the lowest oil pressure necessary to lubricate engine components, provide adequate cooling, and actuate engine components.

[0003] The inventors have recognized that by controlling the oil pressure of the VCT system based on conventional engine operating parameters, under certain operating conditions, namely those conditions that require a sudden or significant transition of the VCT phaser, the VCT phaser may not be supplied with sufficient oil pressure to facilitate the desired phaser response. Operating a VCT system with reduced operating oil pressure causes a decrease in the phasing speed of the VCT phaser, which in turn results in degradation of the performance of the VCT system. Degraded performance of the VCT system can include delayed engine response, turbo spool up time lag, and noise, harshness, and vibration (NVH) issues.

[0004] Other attempts to provide sufficient oil pressure to a VCT system include incorporating an auxiliary system to allow for the short duration, high flow rate pulses required to switch VCT phasers. An example method is shown by Aimone in U.S. Patent 6,871,620. Therein, Aimone discloses an engine system having, in addition to a conventional oil pump, a demand auxiliary oil pump used in conjunction with an accumulator to provide sufficient oil pressure to the VCT system at very low engine speeds or when the VCT unit returns to the locked starting position. Other attempts to provide sufficient oil pressure to the VCT system include increasing the size of a fixed rate oil pump to meet the oil pressure requirements of the VCT system. Another attempt to provide sufficient oil pressure to the VCT system includes regulating the oil pressure delivered to the VCT system based on a comparison of a modeled phasing rate and an actual phasing rate of the VCT, and correlating this data to the pressure within the engine oil system.

[0005] However, the present inventors have recognized potential problems with such systems. As an example, adding an auxiliary oil system to supply the VCT system increases cost and vehicle complexity. Operating the auxiliary pump can add additional load to the engine, thereby reducing performance, and adding a pump and accumulator to an already compact engine bay may not be feasible. It is well known that increasing the size of a fixed rate engine oil pump to meet the periodic high demands of the VCT system increases parasitic losses and degrades fuel economy. As another example, regulating the oil pressure of the VCT system based on a computationally intensive model may not accurately represent actual, instantaneous engine operating conditions. Additionally, such a system may not be able to perform the calculations quickly enough to regulate the VCT on demand. SUMMARY OF THE INVENTION

[0006] In one example, the above problem can be solved by a method for regulating the oil pressure supplied to an engine and a variable cam timing (VCT) system to a first level based on engine speed, engine load, and engine oil temperature; and increasing the oil pressure to a second level higher than the first level for a duration in response to a condition of the VCT system. In this way, during operating conditions including a sudden or significant switch of the VCT system, the VCT system can be supplied with sufficient oil pressure.

[0007] As an example, the method may include: during a first condition, regulating the output of an oil pump supplying oil to the engine and a variable cam timing (VCT) system to a first level based on engine speed, engine load, and engine oil temperature. During a second condition, the method may include regulating the output of the oil pump to a second level based on a commanded position of the VCT system rather than based on engine speed, engine load, and engine oil temperature, wherein the second level is higher than the first level.

[0008] In this way, the variable displacement oil pump can be selectively controlled to supply the VCT system with an increased oil pressure level under certain operating conditions of the VCT system, thereby creating an efficient oil delivery system that can minimize additional losses and improve fuel economy while always meeting the intermittent high demands of the VCT system. Since the existing engine oil pump is used to supply the VCT system instead of adding an auxiliary oil system, the system cost can be reduced. By quickly providing the necessary oil pressure for rapid conversion to the VCT system, turbo lag and NVH problems can be reduced, while the engine response ability and performance can be improved.

[0009] It should be understood that the above summary of the invention introduces a series of concepts in a simplified manner that are further described in the detailed description. This does not mean establishing the key or essential features of the claimed subject matter, the scope of which is uniquely defined by the appended claims. Additionally, the claimed subject matter is not limited to embodiments that solve any disadvantages described above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic diagram of an engine including a variable cam timing (VCT system) is shown.

[0011] Figure 2 Another schematic diagram of a variable cam timing (VCT) system for an engine is shown.

[0012] Figure 3 A calibration chart showing the oil pressure and engine load for changing engine speed is shown.

[0013] Figure 4 A calibration chart showing the oil pressure and engine oil temperature for changing engine speed is shown.

[0014] Figure 5 A flowchart of an exemplary routine for regulating the oil pressure supplied to the engine and the variable cam timing (VCT) system based on engine operating conditions and the conditions of the VCT system is shown.

[0015] Figure 6 An exemplary operation of the engine and the oil pump in response to the conditions of the VCT system is shown. DETAILED DESCRIPTION

[0016] The following description relates to systems and methods for controlling the oil pressure of a vehicle engine having variable cam timing, such as the engine shown, to regulate the oil pressure generated by an oil pump (e.g., a variable displacement oil pump) in response to engine operating conditions and the operating conditions of the variable cam timing system. The engine may include one camshaft per row of engine cylinders to control the intake valves and exhaust valves, as shown Figure 1 in the example. Figure 1As shown, or the engine may include more than one camshaft per row of engine cylinders to independently control the intake valves and intake valves, as Figure 2 shown. Generally, the controller may calibrate the oil pressure of the variable displacement oil pump to adjust the oil pressure in response to operating parameters such as engine load, engine speed, and engine temperature. Figure 3 And Figure 4 show two exemplary calibration charts for adjusting the oil pressure based on these engine operating parameters. Additionally, the engine controller may be configured to execute control routines, such as Figure 5 the exemplary routine of Figure 6 to adjust the output of the engine oil pump in response to engine conditions such as engine load, engine speed, and engine oil temperature, and when the selection condition of the VCT system is met, the controller may increase the output of the engine oil pump to a level higher than the above based on engine speed, engine load, and engine oil temperature. Thus, sufficient oil pressure can be supplied to the VCT system during the selection condition.

[0017] Now turning to Figure 1 , Figure 1 shows a schematic diagram of an engine 10 including a variable cam timing (VCT system). The engine 10 is included in a vehicle system 5. It should be understood that the engine 10 can be any engine configuration. In one embodiment, the engine 10 can be a V-8 engine with two rows of cylinders and four cylinders per row. However, in alternative embodiments, the engine 10 can have alternative configurations, such as an alternative number of cylinders (e.g., V-4, V-6, etc.), or a coaxial arrangement of cylinders (e.g., I-3, I-4, etc.). As a non-limiting example, the engine 10 can be included as part of a passenger vehicle propulsion system. The engine 10 can be controlled at least in part by a control system including a controller 12 and by input from a vehicle operator 32 via an input device 34. In this embodiment, the input device 34 includes an accelerator pedal and a pedal position sensor 36 for generating a proportional pedal position signal PP.

[0018] Engine 10 shows an exemplary cylinder 102 (also referred to as combustion chamber 102) that is part of an engine block region 100 that includes a cylinder head and an engine block. The cylinder head may include, for example, one or more valves that are selectively in communication with an intake system and an exhaust system, while the engine block may include a plurality of cylinders, a crankshaft, etc. It should be understood that the engine block region 100 may include additional components and / or Figure 1 replacement components for the components shown other than Figure 1 the components shown without departing from the scope of the present disclosure.

[0019] Cylinder 102 of engine 10 includes a cylinder wall 104 having a piston 106 disposed therein. Piston 106 is shown coupled to crankshaft 108 such that the reciprocating motion of the piston is converted into rotational motion of the crankshaft. In some examples, vehicle 5 may be a hybrid vehicle having multiple torque sources available for one or more wheels 55. In the example shown, vehicle 5 includes engine 10 and electric machine 52. Electric machine 52 may be a motor or a motor / generator (M / G). When one or more clutches 56 are engaged, crankshaft 108 of engine 10 and electric machine 52 are connected to wheels 55 through transmission 54. In the illustrated embodiment, a first clutch 56 is provided between crankshaft 108 and electric machine 52, and a second clutch 56 is provided between electric machine 52 and transmission 54. Controller 12 may send signals to the actuators of each clutch 56 to engage or disengage the clutch so as to connect or disconnect crankshaft 108 from electric machine 52 and the components connected thereto, and / or to connect or disconnect electric machine 52 from transmission 54 and the components connected thereto. Transmission 54 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0020] Electric machine 52 receives electrical power from traction battery 58 to provide torque to wheels 55. Electric machine 52 may also operate as a generator to provide electrical power to charging battery 58, such as during a braking operation.

[0021] In other examples, vehicle 5 is a conventional vehicle having only an engine, or an electric vehicle having only (one or more) electric machines. In the conventional vehicle example, crankshaft 108 may be coupled to at least one drive wheel of the vehicle through an intermediate transmission system without an intermediate electric machine. Additionally, a conventional starter motor may be coupled to crankshaft 108 through a flywheel (not shown) to effect the starting operation of engine 10.

[0022] The cylinder 102 receives intake air from the intake manifold 110 via the intake passage 112 and discharges combustion gases via the exhaust passage 114. The intake manifold 110 and the exhaust passage 114 may be selectively in communication with the cylinder 102 via corresponding intake valves 116 and exhaust valves 118. In some examples, the cylinder 102 may include two or more intake valves and / or two or more exhaust valves. In some examples, the engine 10 may be a variable displacement engine (VDE) having one or more cylinders 102 with selectively deactivatable intake valves 116 and selectively deactivatable exhaust valves 118.

[0023] In some embodiments, one or more of the intake passages may include a boosting device such as a turbocharger or a supercharger. For example, Figure 1 An engine 10 configured with a turbocharger 150 is shown, the turbocharger 150 including a compressor 152 disposed between the intake manifold 110 and the intake passage 112 and an exhaust turbine 154 disposed along the exhaust passage 114. The compressor 152 may be at least partially powered by the exhaust turbine 154 via a shaft 156, where the boosting device is configured as a turbocharger. However, in other examples, such as where the engine 10 has a supercharger, the exhaust turbine 154 may be optionally omitted, where the compressor 152 may be powered by a mechanical input from a motor or the engine 10.

[0024] In some embodiments, each cylinder of the engine 10 may include a spark plug 120 for initiating combustion. In a selected operating mode, the ignition system 188 may provide an ignition spark to the combustion chamber 102 via the spark plug 120 in response to a spark advance signal SA from the controller 12. However, in some embodiments, the spark plug 120 may be omitted, such as where the engine 10 may initiate combustion by auto-ignition or fuel injection, as may be the case with some diesel engines.

[0025] The fuel injector 122 is shown directly coupled to the combustion chamber 102 to directly inject fuel into the combustion chamber 102 in proportion to the pulse width of a signal FPW received from the controller 12 via an electronic driver 168. In this manner, the fuel injector 122 provides so-called direct injection of fuel into the cylinder 102. While Figure 1It is shown that the fuel injector 122 is positioned on one side of the cylinder 102, but alternatively it can be located at the top of the piston, such as near the position of the spark plug 120. Due to the low volatility of some alcohol-based fuels, such a position can be beneficial for mixing and combustion when operating the engine with alcohol-based fuels. Alternatively, the injector can be located at the top and near the intake valve to improve mixing. Fuel can be delivered to the fuel injector 122 through a fuel delivery system (not shown) including a fuel tank, a fuel pump, and a fuel rail. In some embodiments, the combustion chamber 102 can alternatively or additionally include a fuel injector disposed in the intake manifold 110, which is configured to provide so-called port injection of fuel in the intake passage upstream of the cylinder 102.

[0026] The intake manifold 44 is shown as having a throttle 124, and the throttle 124 includes a throttle plate 126 whose position controls the airflow. In this particular example, the position of the throttle plate 126 can be changed by the controller 12 by providing a signal to an electric motor or actuator including the throttle 124, and such a configuration can be referred to as electronic throttle control (ETC). In this way, the throttle 124 can be operated to change the intake air provided to the cylinder 102 and other cylinders within the engine 10. It should be understood that in alternative embodiments, the throttle 124 can be located upstream of the compressor 152, or can have a first throttle located upstream and downstream of the compressor 152. The intake passage 112 can include a mass air flow (MAF) sensor 128 and a manifold absolute pressure (MAP) sensor 130 for providing corresponding signals MAF and MAP to the controller 12.

[0027] The exhaust sensor 132 is shown as being coupled to the exhaust passage 114 upstream of the catalytic converter 170. The exhaust sensor 132 can be any suitable sensor for providing an indication of the exhaust air-fuel ratio, such as a linear oxygen sensor or a UEGO (universal or wide-range exhaust oxygen) sensor, a two-state oxygen sensor or an EGO sensor, a HEGO (heated EGO) sensor, a NOx sensor, a HC sensor, or a CO sensor. The exhaust system can include a light-off catalyst and an underfloor catalyst, as well as an exhaust manifold, upstream and / or downstream air-fuel ratio sensors. In one example, the catalytic converter 170 can include a plurality of catalyst bricks. In another example, multiple emission control devices can be used, each having a plurality of bricks. In one example, the catalytic converter 170 can be a three-way catalytic converter. The engine 10 can further include one or more exhaust gas recirculation passages (not shown) for recirculating a portion of the exhaust from the engine exhaust passage to the engine intake passage. In this way, by recirculating some exhaust, the engine dilution is affected, which can be beneficial for the performance of the engine by reducing engine knock, cylinder peak combustion temperature and pressure, throttle losses, and NOx emissions.

[0028] The engine 10 includes an oil delivery system 180 for providing oil for component cooling and lubrication and for an oil pressure actuation (OPA) system. The VCT system in the described embodiment is a non-limiting example of an OPA system. The oil delivery system 180 may include an oil pump 182 coupled to the engine and a VCT system that receives instructions from the controller 12 to regulate the oil output pressure and / or flow rate. In one example, the oil pump 182 may be a variable displacement oil pump or a variable flow oil pump, including but not limited to an axial piston pump, a bent axis pump, or a variable displacement vane pump. In other examples, the oil pump 182 may be a fixed rate oil pump having a regulator or an actuatable valve to selectively control the pump output or other suitable types of oil pumps having variable outputs. In another non-limiting example, the oil delivery system 180 may include an active pressure relief valve (not shown). Wherein, the oil pressure output may be increased or decreased due to the actuation of the active pressure relief valve. In addition, the active pressure relief valve may be controlled by a control solenoid valve actuatable by the controller 12.

[0029] An oil pressure sensor 184 in the oil delivery system 180 may be used to determine the oil pressure generated by the oil pump 182. In some examples, the control of the oil pressure may be feedback-based, where the controller 12 receives a signal from the oil pressure sensor 184 to regulate the operation of the oil pump 182 to achieve or maintain a desired oil pressure. The oil pump 182 may be coupled to the crankshaft 108 to provide rotational power for the operation of the oil pump 182. In one example, the oil pump 180 includes a plurality of internally mounted rotors (not shown) that are eccentrically mounted. At least one internal rotor may be controlled by the controller 12 to change the position of the rotor relative to one or more other rotors to regulate the output flow rate of the oil pump 182 and thereby regulate the oil pressure. For example, an electronically controlled rotor may be coupled to a rack and pinion assembly that is adjusted via the controller 12 to change the rotor position. The oil pump 182 may selectively supply oil to various regions and / or components of the engine 10 to provide cooling and lubrication, or to actuate the movement of components. The controller 12 may regulate the output flow rate or oil pressure of the oil pump 182 to adapt to different operating conditions, thereby providing different levels of cooling and / or lubrication. In addition, the oil pressure output from the oil pump 182 may be adjusted to reduce fuel consumption and / or the energy consumption of the oil pump 182.

[0030] It should be understood that any suitable oil pump configuration may be implemented to change the oil pressure and / or oil flow rate. In some embodiments, the oil pump 182 may be coupled to the camshaft instead of the crankshaft 108, or may be powered by a different power source, such as a motor, etc. The oil pump 182 may include additional components not shown Figure 1 such as a hydraulic regulator, an electro-hydraulic solenoid valve, etc. (not shown).

[0031] Based on the oil flow and pressure requirements of the components, the oil pumped by the oil pump 182 can be delivered to the components through one or more conduits 186. For example, the oil pump 182 can pump oil through a first conduit of the conduits 186 to the engine block region 100 to provide an oil flow to a first set of components. In one embodiment, the first set of components can include a variable camshaft timing (VCT) system 160. In other non-limiting embodiments, the oil pump 180 can pump oil through a second conduit of the conduits 186 to a second set of components, which can include, for example, a turbocharger 150, bearings (not shown), and piston cooling nozzles (not shown) in the engine block region 100. Based on the higher pressure and lower oil flow requirements for component cooling and lubrication, the first set of components can be grouped independently of the second set of components. It should be understood that any number of engine components that use oil can be coupled to the oil delivery system 180.

[0032] The cylinder head and the engine block region 100 house a variable valve operating system, such as the VCT system 160. In this embodiment, an overhead cam system is illustrated, but other methods can be used. Specifically, the camshaft 166 of the engine 10 is shown in communication with rocker arms 162 and 164 to actuate an intake valve 116 and an exhaust valve 118, respectively. The VCT system 160 can be oil pressure actuated (OPA). By adjusting a plurality of hydraulic valves to direct a hydraulic fluid, such as engine oil, into chambers (such as an advance chamber or a retard chamber) of a camshaft phaser, the valve timing can be changed (e.g., advanced or retarded). Figure 2 A non-limiting embodiment of a camshaft phaser is shown. The operation of the hydraulic control valves can be controlled by respective control solenoid valves. Specifically, the engine controller can transmit a signal to the solenoid valve to move a valve spool that regulates the oil flow through the phaser chambers. As used herein, the advance and retard of cam timing refer to relative cam timing, because, as an example, with respect to top dead center, a fully advanced position can still provide a retarded intake valve opening.

[0033] The camshaft 166 is hydraulically coupled to a housing 169. The housing 169 forms a gear having a plurality of teeth 171. In this exemplary embodiment, the housing 169 is mechanically coupled to the crankshaft 108 by a timing chain or a timing belt (not shown). Thus, the housing 169 and the camshaft 166 rotate at substantially the same speed as each other and are synchronized with the crankshaft 108. In an alternative embodiment, such as in a four-stroke engine, for example, the housing 169 and the crankshaft 108 can be mechanically coupled to the camshaft 166 such that the housing 169 and the crankshaft 108 can rotate synchronously at a different speed (e.g., a ratio of 2:1, where the crankshaft rotates at twice the speed of the camshaft). In this alternative embodiment, the teeth 171 can be mechanically coupled to the camshaft 166.

[0034] By manipulating a hydraulic coupler (e.g., a phaser) contained within the housing 169 described herein, the relative position of the camshaft 166 with respect to the crankshaft 108 can be changed by hydraulics in the retard chamber 172 and the advance chamber 174. For example, by allowing high-pressure hydraulic fluid to enter the retard chamber 172, the relative relationship between the camshaft 166 and the crankshaft 108 can be retarded. Thus, the intake valve 116 and the exhaust valve 118 can be opened and closed at a time later than normal with respect to the crankshaft 108. Similarly, by allowing high-pressure hydraulic oil to enter the advance chamber 174, the relative relationship between the camshaft 166 and the crankshaft 108 can be advanced. Thus, the intake valve 116 and the exhaust valve 118 can be opened and closed at a time earlier than normal with respect to the crankshaft 108.

[0035] Although this embodiment shows a system in which intake valve timing and exhaust valve timing are simultaneously controlled, variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, dual equal variable cam timing, or other variable cam timing can be used. In addition, variable valve lift can be used. In addition, camshaft profile switching can be used to provide different cam profiles under different operating conditions. In addition, the valve train can be a roller finger follower, a direct-acting mechanical piston, an electro-hydraulic component, or other rocker arm alternatives.

[0036] Continuing with the VCT system 160, the teeth 171 that rotate synchronously with the camshaft 166 allow the relative cam position to be measured by the cam timing sensor 176 that provides a signal VCT to the controller 12. While the tooth 6 can be used for cylinder identification, the teeth 1, 2, 3, and 4 can be used for cam timing measurement and are equally spaced (e.g., in a V-8 dual-row engine, spaced 90 degrees apart from each other). In addition, the controller 12 will send control signals (LACT, RACT) to a conventional solenoid valve (not shown) to control the flow of high-pressure hydraulic fluid into the retard chamber 172 and / or the advance chamber 174. In one embodiment, the high-pressure hydraulic fluid can be oil pumped by the oil pump 182.

[0037] The relative cam timing can be measured in various ways. Generally speaking, the time or rotational angle between the rising edge of the PIP signal and the signal received from one of the multiple teeth 171 on the housing 169 gives a measurement of the relative cam timing. For a specific example of a V-8 engine with two cylinder banks and five gears, by means of an additional signal for cylinder identification, the cam timing of a specific bank is measured four times per revolution.

[0038] As described above, Figure 1 One cylinder in a multi-cylinder engine is shown, and each cylinder can similarly include its own set of intake valves / exhaust valves, fuel injectors, ignition systems, etc.

[0039] The controller 12 is shown as a microcomputer in Figure 1 and includes a microprocessor unit 14, an input / output port 16, an electronic storage medium having a permanent memory for executable programs and calibration values shown as a read-only memory chip 18 in this particular embodiment, a random access memory 20, a non-volatile memory 22, and a data bus. In addition to the signals previously discussed, the controller 12 is shown as also receiving various signals and information from sensors coupled to the engine 10, including a measurement of intake mass air flow (MAF) from a mass air flow sensor 128, a measurement of manifold absolute pressure (MAP) from a MAP sensor 130, a measurement of engine coolant temperature (ECT) from a temperature sensor 134 coupled to the coolant jacket 136, a measurement of a surface ignition sensing signal (PIP) from a Hall effect sensor 138 (or other type) coupled to the crankshaft 108, and a measurement of throttle position (TP) from a throttle position sensor 140. Additionally, the controller 12 receives an input regarding engine oil temperature (EOT) from an engine oil temperature sensor 142. The engine oil temperature sensor 142 may be mounted in the engine block region 100. In some embodiments, the engine oil temperature sensor may be mounted in the engine block or in the cylinder head. This information can be used to determine the operating mode of the oil delivery system, and the output of the oil delivery system 180 will be described in more detail in conjunction with Figure 3 , Figure 4 and Figure 5 below.

[0040] The controller 12 may receive signals from various sensors in Figure 1 and use various actuators in Figure 1 to regulate engine operation based on the received signals and instructions stored in the controller's memory. For example, the controller 12 may include a memory having computer-readable instructions for actuating a variable displacement oil pump to output oil at an upper threshold level in response to a command to advance the intake cam when the engine speed is below a threshold speed and the engine oil temperature is above a threshold temperature or in response to a command to return the intake cam to a reference (e.g., original) position that is a crank angle amount away from the current position by a threshold amount. The controller 12 may otherwise actuate the oil pump to output oil at a second level below the upper threshold level, the second level being based on engine speed, engine load, and engine oil temperature.

[0041] In some embodiments, adjusting the oil pump 182 may include adjusting the actuator of the oil pump 182 to adjust the oil output of the pump. Adjusting the actuator of the oil pump may include the controller sending a signal to the actuator of the pump based on a first relationship between oil pressure, engine load, and engine speed and a second relationship between oil pressure, engine oil temperature, and engine speed so as to adjust the oil output of the pump.

[0042] The engine speed signal RPM is generated by the controller 12 in a conventional manner from the signal PIP and the manifold absolute pressure signal MAP from the manifold absolute pressure sensor 130 provides an indication of the vacuum or pressure in the intake passage 112. During stoichiometric operation, one or more of the MAF sensor and the MAP sensor may be used to provide an indication of engine load. The use of the MAF and / or MAP sensors and the engine speed may provide an estimate of the charge (including air) entering the engine cylinders, which can be used to determine the engine load. In some embodiments, the engine load may be a calculated load value (CLV) or an absolute load value (ALV). It should be understood that the engine load can be characterized in multiple ways. An example method of quantifying the engine load is by the ratio of the current air flow rate through the engine cylinders divided by the maximum possible air flow rate through the cylinders. This ratio can be 1 at wide open throttle. A supercharged engine may be able to achieve an engine load greater than 1 as compressed air (e.g., air at a pressure greater than atmospheric pressure) is forced into the engine cylinders. Similarly, it should be understood that the calibration of the oil pump 182 can also use data regarding the indication of engine load based on the MAF or MAP sensor indication in addition to the engine load. In one embodiment, the oil flow pressure from the oil pump 182 may be adjusted in response to an indication of engine torque or an indication of engine vacuum. Additionally, it should be understood that in addition to the engine oil temperature, the calibration of the oil pump 182 can also use data regarding the indication of engine temperature. In one embodiment, the oil flow from the oil pump 182 may be adjusted in response to the engine coolant temperature or another suitable temperature indication.

[0043] In one embodiment, the Hall effect sensor 138, which can also function as an engine speed sensor, generates a predetermined number of equally spaced pulses per revolution of the crankshaft. As described below, the engine speed, engine load, and engine oil temperature measurements can be used to determine the pump output.

[0044] As another example, adjusting the oil flow delivered to the VCT system 160 can include the controller 12 receiving an indication of the VCT phaser position from the cam timing sensor 176, an indication of the engine speed from the Hall effect sensor 138, and an indication of the engine oil temperature from the engine oil temperature sensor 142. In one non-limiting example, in response to these indications, including a request to move the VCT phaser from a position more than a threshold distance away from an original position to the original position, the controller 12 can command the actuator of the oil pump 182 to increase the output of the oil pump 182 to an upper threshold oil pressure in order to provide an increased oil flow to the VCT system 160. In one example, the upper threshold oil pressure can be the maximum oil pressure that the oil pump 182 is capable of generating.

[0045] In this way, during some operating conditions of the VCT system, the movement speed of the VCT system (e.g., the VCT phaser) can be increased by providing an increased oil pressure to the VCT system. An exemplary operating condition of the VCT system can include a request to advance the intake cam of the VCT system when the engine oil temperature is higher than a threshold oil temperature and the engine speed is lower than a threshold engine speed. Another exemplary operating condition of the VCT system can include a request to return the VCT system from a position at a crank angle degree that is a threshold amount away from a reference position to the reference position. In one example, the request to return the VCT system to the reference position can be in response to an engine stall condition.

[0046] Figure 1 The VCT system 160 is shown as having a single camshaft 166 that can adjust the intake valve 116 and the exhaust valve 118. Alternatively, Figure 2 Another schematic illustration of a variable cam timing (VCT) system 250 for an engine 200 is shown. It should be understood that the engine 200 can be the same as the engine 10 ( Figure 1 shown), but the engine 200 can include a VCT system that is configured to adjust the timing of the intake valve using a first camshaft while adjusting the timing of the exhaust valve using a second camshaft. It should be understood that in other examples, the VCT system can be configured to adjust the timing of the intake cam or the timing of the exhaust cam. The engine components of the engine 200 not shown in Figure 2 can be the same as those of the engine 10 shown in Figure 1 shown.

[0047] As shown, the engine 200 includes a first cylinder 202 and a second cylinder 222. However, it should be understood that in other examples, the number of cylinders in the engine can be different. For example, in one example, the engine 200 can include four cylinders.

[0048] The cylinders are arranged in an in-line configuration. That is, a plane extends through the centerlines of each cylinder. However, other cylinder positions are predictable. The intake valve 204 and exhaust valve 206 of the first cylinder 202 are shown. It should be understood that the valves can be disposed in the intake passage and exhaust passage, respectively. Similarly, the intake valve 224 and exhaust valve 226 are coupled to the second cylinder 222. The intake valve 224 and exhaust valve 226 are configured to open during the combustion operation. Specifically, as Figure 1 shown, the intake valve 224 can effect fluid communication between the second cylinder 222 and the intake manifold 110 in the open configuration, and as Figure 1 shown, prohibit fluid communication between the second cylinder 222 and the intake manifold 110 in the closed configuration. Further, as Figure 1 shown, the exhaust valve 226 can effect fluid communication between the second cylinder 222 and the exhaust passage 114 in the open configuration, and as Figure 1 shown, prohibit fluid communication between the second cylinder 222 and the exhaust passage 114 in the closed configuration.

[0049] The VCT system 250 can include an intake camshaft 208 and / or an exhaust camshaft 228. The intake camshaft 208 can include intake cams 210 and 230 coupled to the intake camshaft. The intake cams 210 and 230 are configured to periodically actuate the intake valves during the combustion operation. Similarly, the exhaust camshaft 228 can include exhaust cams 212 and 232 coupled to the exhaust camshaft. The exhaust cams 212 and 232 are configured to periodically actuate the exhaust valves during the combustion operation. It should be understood that the circumferential positions of the intake cams and / or exhaust cams can be changed to effect actuation of the intake valves and exhaust valves at different time intervals.

[0050] The VCT system 250 further includes a first phaser 214 (e.g., intake phaser) and a second phaser 234 (e.g., exhaust phaser). As shown, the first phaser 214 is coupled to the intake camshaft 208. Further, the second phaser 234 is coupled to the exhaust camshaft 228. The first phaser and the second phaser can be configured to adjust Figure 1 shown, the phase between the crankshaft 108 and the corresponding camshaft. The first phaser 214 can be the same as the second phaser 234. However, in other examples, the phasers (214 and 234) can have different configurations. The VCT system 250 can further include a mechanical linkage 260 that couples the crankshaft 108, as Figure 1 shown, to the camshafts (208 and 228).

[0051] The first intake phaser 214 may include a locking mechanism 218 represented generally via a block. Similarly, the second exhaust phaser 234 may also include a locking mechanism 238. In one example, the locking mechanisms (218 and 238) may be the same or may have different configurations. In some examples, the locking mechanism may include an actuatable pin that engages a locking groove to lock the phaser in an original position.

[0052] The controller 12 (as Figure 1 shown) may be configured to control the VCT system 250 to advance or retard intake valve timing and / or exhaust valve timing. Specifically, the controller 12 may be electrically (e.g., wired and / or wirelessly) coupled to control valves 220 and 240 (such as solenoid valves) in the VCT system 250. The control valves 220 and 240 may be coupled to or integrated into their respective phasers. The control valves 220 and 240 may be configured to adjust the phase between the crankshaft 108 and the corresponding camshaft as Figure 1 shown. Specifically, the control valves 220 and 240 may be oil control valves configured to hydraulically adjust the phase angle between the crankshaft 108 and the camshaft 208 or between the crankshaft 108 and the camshaft 228 as Figure 1 shown. Thus, the control valves 220 and 240 may receive oil from conduits in the engine. However, other suitable types of control valves may be contemplated.

[0053] The camshaft bearings 270 are coupled to the intake camshaft 208 and the exhaust camshaft 228. The camshaft bearings 270 are configured to support the camshafts to which they are coupled and enable rotation of the camshafts. The spark plug 221 is also shown coupled to the first cylinder 202. A second spark plug 241 or other suitable ignition device may be coupled to the second cylinder 222.

[0054] As previously described, the output of the oil pump, which in one example is the output of a variable displacement oil pump, may be actively controlled by the vehicle controller to meet the engine cooling, lubrication, and engine actuation requirements for a given operating condition. Specifically, a controller, such as Figure 1 the controller 12 in

[0055] may refer to calibration data stored in its memory to adjust the output of the oil pump, such as the oil pump 182 coupled to the engine. In one non-limiting example, the adjustment of the oil pump output may be in response to engine parameters such as engine oil temperature, engine load, and engine speed.

[0055] Now turning to Figure 3 FIG. 300 shows an exemplary calibration chart for oil pressure and engine load for varying engine speeds to determine the target oil pressure output from the engine oil pump, such as Figure 1The engine oil pump 182. It should be understood that in some examples, the engine oil pump can be a variable displacement or variable flow type pump. The calibration chart 300 shows the relationship between the target oil pressure from a variable displacement oil pump and the engine load at various engine speeds. In a non-limiting example, the output of the MAF and / or MAP sensors (e.g., Figure 1 the MAF sensor 128 and the MAP sensor 130) can be used to determine the engine load. In a non-limiting example, the output of a Hall effect sensor (e.g., Figure 1 the Hall effect sensor 138) can be used to determine the engine speed. As shown in the calibration chart 300, illustration 302 shows that at a reduced engine speed (e.g., 1000 rpm, in one example), the target oil pressure remains reduced and stable, while the engine load has little effect on the target oil pressure. Illustration 304 shows that at an increased engine speed (e.g., 4000 rpm, in one example), the target oil pressure remains increased and stable, and again the engine load has little effect on the target oil pressure. Illustration 306 shows that at a medium engine speed (e.g., 2500 rpm, in one example), the target oil pressure increases as the engine load increases. It should be understood that Figure 3 the correlation between the engine load and the target oil pressure shown is presented as an illustrative example, and any suitable correlation can also be employed. Additionally, in an alternative embodiment, when the calibration chart 300 includes three engine speed curves, the calibration chart can include additional or different engine speed curves. In some examples, tables or mapping data can be used to determine the target oil pressure. In other examples, instead of calibrating the target oil pressure using the engine load, operating parameters such as engine torque and / or vacuum can be used.

[0056] Now turning to Figure 4 , another exemplary calibration chart 400 for engine oil temperature and oil pressure for varying engine speeds 400 is shown to determine the target oil pressure output from a variable displacement oil pump such as Figure 1 the oil pump 182 in. Again, it should be understood that in some examples, the engine oil pump can be a variable displacement or variable flow type pump. The calibration chart 400 shows the target oil pressure relative to the engine temperature for various engine speeds (as shown by curves 402, 404, 406, and 408 in Figure 4 ). In a non-limiting example, the engine temperature can be the engine oil temperature measured by an engine oil temperature sensor (e.g., Figure 1 the engine oil temperature sensor 142 in). In a non-limiting example, the output of a Hall effect sensor (e.g., Figure 1The output of the Hall effect sensor 138) in is used to determine the engine speed. At relatively low engine temperatures, the target oil pressure can be at the upper threshold regardless of the engine speed. As the engine oil temperature increases, as Figure 4 shown, the target oil pressure can decrease. In one example, when the engine speed increases with the engine temperature, the target oil pressure also increases. The exemplary upper threshold target oil pressure is shown by the dashed line 410 in Figure 4 . In some examples, the upper threshold target oil pressure can be the maximum oil pressure that can be generated by the oil pump. In other examples, the upper threshold target oil pressure can be the oil pressure and / or oil flow rate that enables the VCT system to switch more quickly under a given operating condition. It should be understood that the controller can refer to more than one upper threshold target oil pressure. For example, depending on the engine operating conditions (engine oil temperature and engine load), a unique upper threshold target oil pressure can be indicated for each of these operating conditions that enables the VCT system to switch most quickly. The shaded area 412 including the data point 414 can be regarded as a warm-up idle condition. Specifically, the engine speed can be lower than the idle threshold 402 (e.g., 1000 rpm in one non-limiting example) and the engine temperature (e.g., engine oil temperature) can be higher than the value shown by the dashed line 416 that can be regarded as the "warm-up" threshold. Further discussion regarding the data points 414 and 418 will be provided below with reference to Figure 5 .

[0057] It should be understood that multiple suitable methods can be employed to characterize the target oil pressure. In some examples, one or more tables or charts can be stored in the memory of the controller (e.g., the controller 12 shown in Figure 1 ) and used by the controller to determine the target oil pressure for the current engine speed, engine load, and engine oil temperature. In other examples, similar to the charts shown in Figure 3 and Figure 4 , an algorithm, formula, or computational model of one or more relationships between the target oil pressure and the engine speed, engine load, and engine oil temperature can be stored in the controller memory and used to determine the target oil pressure. Additionally, several calibration correlations can be referenced (e.g., looked up in the controller's memory), and the highest oil pressure or the lowest oil pressure referenced can be represented as the target oil pressure for a given operating condition. For example, if the target oil pressure at a given engine speed and engine load shown in Figure 3 is greater than the target oil pressure under the same conditions (e.g., the same engine speed and corresponding engine load) shown in Figure 4 , the vehicle controller can actuate the oil pump (e.g., the oil pump 182 in Figure 1 ) to output a higher target oil pressure (e.g., the target oil pressure in Figure 3 ).

[0058] Now turning to Figure 5, a flowchart of an exemplary routine 500 for regulating the oil pressure supplied to an engine and a variable cam timing (VCT) system based on engine operating conditions and the status of the VCT system is shown. The instructions for implementing method 500 and the remaining methods included herein may be executed by a controller (e.g., Figure 1 's controller 12) based on instructions stored in the controller's memory and in conjunction with signals received from sensors of the engine system such as those referenced above Figure 1 . According to the methods described below, the controller may employ engine actuators of the engine system to regulate engine operation. In one example, the controller may control a target engine oil pressure based on sensor inputs indicative of engine oil temperature, engine speed, and engine load. Specifically, the controller may receive an indication of engine oil temperature from a temperature sensor (e.g., Figure 1 's temperature sensor 142), an indication of engine speed from a sensor (e.g., Figure 1 's Hall effect sensor 138), and an indication of engine load from a mass air flow sensor (e.g., Figure 1 's MAF sensor 128). In one non-limiting example, in response to an indication of increased engine oil temperature at a constant engine speed and engine load, the controller may send a signal to an actuator (e.g., a regulator) of the oil pump to selectively reduce the target engine oil pressure in order to provide an appropriate amount of oil flow and pressure, and thereby provide a desired amount of cooling, lubrication, and / or actuation for oil pressure-actuated devices. An example of an oil pressure-actuated device is a hydraulic valve lifter coupled to an engine cylinder, where oil flow and / or oil pressure are used to regulate valve clearance. In another non-limiting example, in response to a command to adjust the timing (e.g., intake cam timing) of a VCT system (e.g., Figure 1 's VCT system 160 and / or Figure 2 's VCT system 250) during a selected engine operating condition, the controller may send a signal to an actuator of the oil pump to increase the target engine oil pressure to an upper threshold value. As further explained below, this upper threshold value may be greater than the level commanded based solely on engine oil temperature, engine speed, and engine load (e.g., using a chart, table, or relationship such as those shown in Figure 3-4 ).

[0059] At 502, the routine includes estimating and / or measuring an engine (such as Figure 1Engine operating conditions of the illustrated engine 10). Engine operating conditions can include, but are not limited to, engine speed (Ne), engine load, desired engine torque (Tq), manifold absolute pressure (MAP), manifold air flow (MAF), engine coolant temperature (ECT), engine oil temperature (EOT), accelerator pedal position, current timing and position of the VCT system, and environmental conditions such as humidity and barometric pressure. At 504, the routine includes adjusting engine oil pressure based on engine speed, engine load, and engine oil temperature. Adjusting the oil pressure at 504 can include adjusting the oil pressure output by an oil pump that supplies oil to the engine and the VCT system (as referenced in Figure 1-2 described). It should be understood that adjusting the oil pressure of the oil pump can include adjusting the oil flow through the oil pump. For simplicity, adjusting the output of the oil pump can be synchronized with adjusting one or more of the oil flow rate, oil pump pressure, and oil pump power of the oil pump. Adjusting the output of the oil pump can include increasing the current to the oil pump. In one example, adjusting the oil pressure includes actuating an oil pump coupled to the engine (e.g., Figure 1 the oil pump 182 in) to control one or more of the oil pressure and oil flow rate from the oil pump. In one non-limiting example, actuation can be performed through an oil pump regulator. In some examples, the oil pump can be actuated to increase the oil pressure or oil flow rate so that engine components downstream of the oil pump (including the VCT system) can receive an increased oil flow rate and / or oil pressure to facilitate increased cooling of the engine components, increased lubrication of the engine components, and / or increased actuation of the engine components. In one embodiment, the described oil pump can be a variable displacement oil pump (VDOP), but it should be understood that other types of pumps can be used in combination with methods for actively regulating the oil output from the oil pump. Other exemplary methods for actively regulating the oil output from the oil pump can include valves or regulators coupled to the oil pump.

[0060] Adjusting the oil pressure based on engine speed, engine load, and engine oil temperature can be accomplished by using one or more of a plurality of calibration tables and / or charts that can be stored in the memory of the controller and then looked up by the controller during engine operation, using mapping data, using formulas or algorithms, and / or using a computational model of the engine operating conditions. Two non-limiting examples of calibration charts that can be used to determine the target oil pressure are shown in Figure 3 and Figure 4 shown. Therein, when the engine speed, engine load, and engine oil temperature are known, the target oil pressure can be determined. For example, the controller can use a first chart (e.g., Figure 3 the chart 300 shown) or the relationship between engine oil pressure, engine load, and engine speed to look up a first target oil pressure, and then use a second chart (e.g., Figure 4Find a second target oil pressure based on the relationship between the shown graph 400), engine oil pressure, engine oil temperature, and engine speed. In some examples, the controller (e.g., Figure 1 the controller 12 in

[0061] Figure 2 Figure 2

[0062] the intake camshaft in

[0062] can then select the higher of the first and second target oil pressures and then actuate the oil pump to output the higher of the first and second target oil pressures. In this way, the oil pressure supplied to the VCT system and the engine is regulated to a level (e.g., a first level) based on each (e.g., all) of engine speed, engine load, and engine oil temperature. For example, the controller can determine the oil pressure supplied to the engine and the VCT system according to each of engine speed, engine load, and engine oil temperature. In some examples, the method at 504 can include regulating the oil pressure based on the stored relationship as described above based on engine speed, engine load, and engine oil temperature (as determined based on signals received from engine sensors) rather than based on the operation of the VCT system. In other examples, and depending on the operating conditions, the lower of the two reference values can be set as the target oil pressure. At 506, the routine includes determining whether one or more of an intake advance request for the VCT system (e.g., the intake cam of the VCT system) and an exhaust advance request for the VCT system (e.g., the exhaust cam of the VCT system) have been received. In one non - limiting example, when there is a torque request at a reduced engine speed, a request to advance the timing of the intake valve can be generated by adjusting the position of the intake camshaft. Since the intake camshaft (e.g., Figure 2 the intake camshaft in Figure 2 is advanced, the intake valve (e.g.,

[0062] the intake valve 204 in Figure 2

[0062] can open before top dead center (TDC) and close earlier than when the intake camshaft is not advanced, thereby causing combustion at a higher compression ratio. This increases the available torque at low engine speeds. An intake advance request can be generated in response to the operator depressing the accelerator pedal or increasing the drive torque demand. It should be understood that by adjusting the intake phaser, the position and timing of the intake cam can be correspondingly adjusted. Since the position and timing of the intake cam are adjusted, the position and timing of the intake valve can be correspondingly adjusted. Thus, the adjustment of the above - mentioned components of the VCT system can be collectively referred to as adjusting the VCT system or adjusting the position of the VCT system. Similarly, the reference position or original position of the intake phaser is related to moving the intake camshaft to the reference position or original position, which is also related to moving the VCT system to the reference position or original position. For engine embodiments including respective intake VCT systems and exhaust VCT systems, the above relationships also apply to the exhaust phaser, exhaust cam, exhaust valve, and exhaust VCT system.If intake advance is not requested, such as when engine load is relatively low or driver torque demand is relatively low, the routine moves to 508, where the controller determines whether an in-position request for the VCT (e.g., Figure 2 the VCT intake phaser 214 or the exhaust phaser 234 in has been received. It should be understood that the in-position request can include a request to move the VCT system (e.g., one or more of the intake phaser and the exhaust phaser) to a reference position (also referred to herein as the original position). In one non-limiting example, an in-position request for the VCT system can be generated when the VCT system is at any position from 3 crank angle degrees to 60 crank angle degrees from the original position, but other crank angle degrees are contemplated. It should be understood that the request to return the VCT system to the reference position can be in response to one or more of an engine stall condition, an engine shutdown request, or a request to perform a camshaft position learning routine. The camshaft learning routine can include intentionally locking one or more camshafts in the original position to determine the appropriate zero-degree position. In this way, the zero-degree camshaft position for a given engine operating condition can be learned and this zero-degree camshaft position is referenced by the controller for future transitions of the VCT system.

[0063] In some examples, moving the VCT system to the reference position can include moving the intake camshaft to a fully retarded position and / or moving the exhaust camshaft to a fully advanced position. In other examples, moving the VCT to the reference position can include moving the intake camshaft to a fully advanced position. Additionally, some VCT systems employ a known "mid-lock" or "intermediate lock" system, where the reference position for one or more of the intake camshaft and the exhaust camshaft is neither a fully advanced position nor a fully retarded position. In some examples, an in-position request for the VCT system can be generated when engine load decreases or when the controller receives a decrease in operator torque request. Placing the engine from an engine speed above idle to an idle condition or to an engine shutdown condition (e.g., turning off the engine) can also initiate an in-position request for the VCT system.

[0064] If an in-position request for the intake phaser is not received, the routine continues to 510, where the routine includes continuing to adjust the oil pressure based on engine speed, engine load, and engine oil temperature before the routine ends, as described above with reference to 504.

[0065] If, at 508, the controller determines that an in - position request for the VCT system or the VCT intake phaser has been received, then the routine proceeds to 512, where the routine includes determining whether the current position of the intake phaser is greater than a threshold number of crankshaft degrees of rotation from the original position. In one example, the threshold number of crankshaft degrees of rotation can be 25 crankshaft degrees of rotation. In other examples, the threshold number of crankshaft degrees of rotation can be between 20 and 30 crankshaft degrees of rotation. In some examples, an engine stall condition can generate a request to return the VCT system (e.g., the intake phaser) from a position greater than the threshold number of crankshaft degrees of rotation from the original position to a reference position. If the intake phaser is not greater than the threshold number of crankshaft degrees of rotation from the original position, then the routine proceeds to 514, where the routine includes the controller commanding the intake phaser of the intake cam to return to the original position while continuing to adjust the oil pressure according to the method described above at 504 based on engine speed, engine load, and engine oil temperature. In one example, commanding the intake phaser to return to the original position can include the controller sending a signal to actuate an electro - mechanical spool valve coupled to the VCT system to direct oil flow to one side of the intake phaser, thereby actuating the vane and causing the intake phaser to move toward the original position.

[0066] If the intake phaser is greater than the threshold number of crankshaft degrees of rotation from the original position, then the routine proceeds to 516, where the routine includes adjusting the oil pressure to an upper threshold oil pressure. As an example, the method at 516 can include the controller commanding the oil pump to adjust the oil pressure to the upper threshold oil pressure. In one example, the upper threshold oil pressure can be the maximum oil pressure that the oil pump can generate. In other examples, the upper threshold oil pressure can be determined based on the oil pressure that can achieve a faster (e.g., the fastest) transition speed of the VCT phaser. For example, the upper threshold oil pressure can be the pressure required to transition the intake camshaft from the current position, which is separated from the original position by the threshold number of crankshaft degrees of rotation, to the original position. Thus, the VCT system is provided with an appropriate oil pressure to quickly transition from the current position to the original position, which can result in improved responsiveness and performance. It should be understood that additionally or alternatively, the oil pump can monitor its output with respect to oil flow rate rather than oil pressure. Thus, the controller commands the oil pump to increase the oil pressure to the upper threshold oil pressure even when the controller will adjust the oil pressure to different levels based on engine oil temperature, engine load, and engine speed, as described above at 504. Thus, according to the relationship discussed above at 504, the upper threshold oil pressure can be greater than the oil pressure level that can be determined based on the current engine speed, engine load, and engine oil temperature.

[0067] The routine then proceeds to 518, where the routine includes determining whether a VCT system (e.g., the VCT phaser of the intake cam) is in the commanded position. In one example, with respect to a VCT home request, the commanded position can include the VCT phaser being fully in the original (e.g., reference) position and actuating a locking mechanism (e.g., Figure 2 the locking mechanism 218 in ) to lock the VCT phaser into the original position. In other examples, with respect to a VCT home request, the VCT phaser can be fully in the original position but not locked by the locking mechanism. If the VCT phaser is not in the commanded position, the routine proceeds to 520, where the routine includes continuing to deliver an upper threshold oil pressure for a duration. In one example, the duration is the time elapsed between a first event and a second event, the first event including a command to transition the VCT system, and the second event including confirmation that the VCT system (e.g., the VCT phaser) is in the commanded position. In other examples, the duration is the duration of transitioning from the current position of the VCT system prior to the condition of the VCT system to the commanded position of the VCT system. Thus, the oil pump maintains the oil pressure output at a second level (e.g., upper threshold oil pressure) higher than a first level (e.g., the pressure indicated by engine speed, engine load, and engine oil temperature) for a duration. Accordingly, the routine continuously achieves sufficient oil pressure for the VCT system throughout the duration of the VCT transition. The VCT phaser position can be determined by the output from a cam timing sensor (e.g., Figure 1 the cam timing sensor 176 in ).

[0068] If the VCT phaser is in the commanded position (e.g., the original position), the routine proceeds to 522, where the routine includes, prior to ending the routine, returning the oil pressure to a pressure level based on engine speed, engine load, and engine oil temperature according to the method described at 504. In one example, returning the oil pressure to a pressure level based on engine speed, engine load, and engine oil temperature can include reducing the oil pressure from the upper threshold pressure and returning to controlling the oil pump output based on calibration data (e.g., the relationship between each of engine speed, engine load, and engine oil temperature and engine oil pressure, as described above with reference to 504 and Figure 3-4 described). As previously described, in some examples, one or more calibration tables or charts can be used to look up and determine the oil pressure output of the oil pump based on the current engine speed, engine load, and engine oil temperature values as determined by engine sensors. In other examples, an algorithm, formula, or computational model of engine operation can be used based on the current engine speed, engine load, and engine oil temperature values to determine the target oil pressure. Additionally, several calibration correlations can be referenced (e.g., looked up in the controller's memory), and either the highest referenced oil pressure or the lowest referenced oil pressure can represent the target oil pressure for a given operating condition.

[0069] If an intake advance request is received at 506, the routine proceeds to 524, where the routine includes determining whether the engine oil temperature is greater than a threshold engine oil temperature. In one example, when the engine oil viscosity is suitable for the desired control method, the threshold engine oil temperature can be a temperature that takes into account a warm engine condition, such as Figure 4 the warm engine condition 408 shown. If the engine oil temperature is not greater than the threshold oil temperature, then the routine proceeds to 526, where the routine includes advancing the intake camshaft while continuing to adjust the oil pressure based on engine speed, engine load, and engine oil temperature, as described above at 504. For example, the method at 526 can include advancing the intake cam when transmitting oil to the VCT system at a level below an upper threshold oil pressure and based on engine speed, engine load, and engine oil temperature.

[0070] If the engine oil temperature is greater than the threshold engine oil temperature at 524, then the routine proceeds to 528, where the routine includes determining whether the engine speed is less than an engine speed threshold. In one non-limiting example, the engine speed threshold can be an engine idle condition. The engine idle condition can include an engine operating condition that does not include an operator torque demand, such as can be indicated by the actuation of an accelerator pedal (e.g., Figure 1 the accelerator pedal 34 in ). In some examples, the engine idle condition can include an engine speed of 500 - 1250 rpm, but it can be expected that the idle condition can include different engine speed ranges. The engine speed can be determined by an engine speed sensor coupled to the engine crankshaft (e.g., Figure 1 the crankshaft 108 in ). In one example, the engine speed sensor can be a Hall effect sensor.

[0071] If the engine speed is not less than the threshold, then the routine proceeds to 526, where the routine includes advancing the intake camshaft while continuing to adjust the oil pressure based on engine speed, engine load, and engine oil temperature. If the engine speed is less than the threshold, then the routine proceeds to 516, where the routine includes adjusting the oil pressure to an upper threshold oil pressure, as described above. As an example, the routine at 516 can include the controller commanding the oil pump to adjust the oil pressure to the upper threshold oil pressure. In one example, the upper threshold oil pressure can be the maximum oil pressure that the oil pump can generate. In other examples, the upper threshold oil pressure can be determined based on the oil pressure that can achieve the fastest switching speed of the VCT phaser. Refer to Figure 4 shows an example of such a control method. Data point 414 is when the engine oil temperature is above the warm engine oil temperature threshold and the engine speed is below the idle threshold (e.g., Figure 4An example of an engine operating condition that occurs when the engine is in the "warm-up idle condition" as shown by the shaded area. If an intake advance request is received when the engine condition is in the shaded area as shown by data point 414, the method includes increasing the target oil pressure to the upper threshold oil pressure as shown by data point 418 in Figure 4 (rather than the oil pressure corresponding to data point 414). Thus, in response to an intake advance request during the warm-up idle condition, when the engine oil temperature is greater than the threshold oil temperature and the engine speed is less than the threshold speed, the controller can increase the oil pressure from the oil pump to the upper threshold, even when the oil pressure recommended for a given operating condition (e.g., engine load, engine speed, engine oil temperature) indicates a lower oil pressure is appropriate. For example, the target oil pressure determined based on the relationship between the oil pressure and oil temperature, engine load, and engine speed (e.g., as shown in Figure 3-4 ) can be less than the upper threshold oil pressure. Since the oil pressure is increased to the upper threshold during the intake advance request, the VCT system can respond more quickly to the intake advance request, thereby improving the response ability of the VCT system, which can reduce NVH problems and improve performance. It should be understood that additionally or alternatively, the oil pump can monitor the output regarding the oil flow rate instead of the output regarding the oil pressure.

[0072] As described above, at 518, the routine includes determining whether the VCT (e.g., VCT system, VCT phaser) is in the commanded position. In one example, with respect to the intake advance request, the VCT in the commanded position can include a VCT phaser that has transitioned to a more advanced position prior to the intake advance request. The VCT phaser position can be determined via a cam timing sensor (e.g., the cam timing sensor 176 in Figure 1 ).

[0073] If the VCT phaser is not in the commanded advanced position, then the routine proceeds to 520, where the routine includes continuing to deliver the upper threshold oil pressure until the VCT phaser is in the commanded advanced position. The VCT phaser position can be determined via a cam timing sensor (e.g., the cam timing sensor 176 in Figure 1 ).

[0074] If the VCT phaser is in the commanded advanced position, then the routine proceeds to 522, where the routine includes returning the oil pressure to a pressure level based on the engine speed, engine load, and engine oil temperature before the routine ends. In one example, returning the oil pressure to a pressure level based on the engine speed, engine load, and engine oil temperature can include reducing the oil pressure from the upper threshold pressure to the pressure determined by the engine oil pressure and temperature, engine speed, and engine load (e.g., based on Figure 3-4A lower level governed by the relationship between the calibration data shown above. As previously mentioned, in some examples, one or more calibration tables or charts can be used. In other examples, algorithms, formulas, or computational models of engine operation can be used to determine the target oil pressure. Additionally, several calibration correlations can be referenced, and either the highest oil pressure or the lowest oil pressure referenced can be expressed as the target oil pressure for a given operating condition.

[0075] Now turning to Figure 6 , exemplary illustration 600 shows an example operation of an engine (such as Figure 1 or Figure 2 the engine system shown above) and an oil pump in response to the conditions of the VCT system. The horizontal axis (X-axis) represents time and the vertical markers t1 - t5 represent important times of engine and oil pump operation. Referring to Figure 6 , illustration 602 shows the accelerator pedal position changing over time. Illustration 604 shows the engine speed (Ne) changing over time. Illustration 606 shows the timing of the intake cam of the VCT system coupled to the engine. Illustration 608 shows the change in engine oil temperature. Illustration 610 shows the change in engine load. Illustration 612 shows the target oil pressure (e.g., the target oil pressure output of the oil pump) for controlling the engine oil pump. As previously mentioned, it should be understood that in some examples, the engine oil pump can be a variable displacement or variable flow type pump.

[0076] Before time t1, the accelerator pedal is in a steady position indicating that the operator requests a steady and increasing speed, as shown in illustration 602. The engine speed follows a similar trajectory (illustration 604) and is higher than the idle threshold engine speed, as shown by the dashed line illustration 605. The VCT system is generally maintained at MBT timing, as shown in illustration 606. As shown by the dashed line illustration 607, MBT timing can also be referred to as minimum spark timing, which is the timing that achieves peak torque or maximum brake torque. There can be different MBT timings for different operating conditions, where for a given air-fuel ratio, engine operation at MBT timing can produce the maximum work output. It should be understood that MBT can coincide with the VCT system in its original position (e.g., reference position), in which the intake cam is neither advanced nor retarded. The engine oil temperature can increase, as shown in illustration 608. The engine load can be increased, as shown in illustration 610. As previously mentioned, it should be understood that the engine load can be characterized using multiple methods. An exemplary method of quantifying the engine load is by the ratio of the current air flow rate through the engine cylinder to the maximum possible air flow rate through that cylinder. Using this method, MAF and / or MAP sensor data can be used to determine the engine load. Alternatively, an indication of the engine load other than based on the MAF or MAP sensor indication can be used. In one example, the engine load can be indicated by engine torque or engine vacuum. The target oil pressure also increases and stabilizes, as shown in illustration 612. Based on calibration data, the vehicle controller can command the target oil pressure. As previously mentioned, the calibration data for controlling the target oil pressure can be based on engine parameters including engine oil temperature, engine load, and engine speed, as described above with reference to Figure 3-4 as described. Thus, before time t1, the target oil pressure is below the upper threshold oil pressure (as shown by the dashed line illustration 613).

[0077] At time t1, a reduction in torque demand occurs, as indicated by a decrease in the actuation of the accelerator pedal (illustration 602). The engine speed (illustration 604) follows a similar trajectory, thus reducing speed as the accelerator pedal is gradually released. The timing of the VCT system can generally remain at MBT, as shown in illustration 606. The engine oil temperature (illustration 608) can slightly decrease as the engine load decreases (illustration 610). As the engine oil temperature and engine load decrease, the target oil pressure can also decrease, as shown in illustration 612.

[0078] At time t2, the accelerator pedal is depressed, such as may occur when accelerating on an on-ramp to enter highway traffic, which is indicated by the accelerator pedal position (graphic 602). In some examples, this may be considered a wide open throttle (WOT) condition. Accordingly, the engine speed increases, as shown in graphic 604. The controller may request the VCT system to advance the intake cam, as shown in graphic 606. The engine load increases under the WOT condition, as shown in graphic 610 and the engine oil temperature (graphic 608) may gradually increase in response to the increase in engine load. Prior to depressing the accelerator pedal at time t2, an intake advance request is generated and the engine operating condition is considered a warm idle condition, as indicated by an engine oil temperature above the warm-up threshold temperature (dashed graphic 609) and an engine speed below the idle threshold (dashed graphic 605). Due to these engine operating conditions, shortly after time t2, the controller may recognize these conditions and in response to these conditions, the controller may command the target oil pressure to the upper threshold oil pressure (as shown by the dashed graphic 613) in order to provide sufficient oil pressure to the VCT system to quickly transition to the commanded position without lag or NVH issues. Accordingly, after time t2, in response to the request to advance the intake cam, when the engine speed is below the corresponding engine speed threshold and the engine oil temperature is above the corresponding oil temperature threshold, the controller stops regulating the target oil pressure based on engine speed, engine load, and engine oil temperature (e.g., according to a stored relationship, as Figure 3-4 shown) and instead increases the target oil pressure to the upper threshold oil pressure.

[0079] When the controller confirms that the VCT system has reached the commanded position, the target oil pressure is maintained at the upper threshold oil pressure until time t3. In the example shown, the controller may confirm that the VCT has reached the commanded advance position by receiving an indication of the VCT phaser position from a cam timing sensor (e.g., Figure 1 the cam timing sensor 176 in

[0080] ). At time t3, the controller may employ calibration data based on engine speed, engine load, and engine temperature to command the oil pump to return to controlling the output of the oil pump, which may include reducing the oil pressure to a level below the upper threshold oil pressure.

[0080] At time t3, the accelerator pedal again finds a steady position indicating a request for a steady and increasing vehicle speed, as shown in graphic 602. The engine speed follows a similar trajectory (graphic 604). The conditions remain relatively stable between times t3 and t4, but it should be understood that the engine oil temperature may steadily increase with extended engine operation under the current operating conditions. Between times t3 and t4, the target oil pressure may be controlled based on each of engine speed, engine load, and engine oil temperature and accordingly the target oil pressure may increase slightly, as shown in graphic 612, but remains below the upper threshold oil pressure.

[0081] At time t4, there is a sudden drop in the operator's torque demand. Thus, at t4, the operator releases the accelerator pedal (illustrated as 602) and the engine speed can rapidly decrease (illustrated as 604). In response to the sudden decrease in torque demand, when the throttle suddenly closes, the engine load can decrease (illustrated as 610). When the engine may no longer be operating under increasing engine load, the engine oil temperature can begin to drop, as illustrated in 608. In response to the operating conditions, shortly after time t4, due to the sudden decrease in torque demand, the controller can receive an indication requesting the VCT system to return to a reference (e.g., original) position. In the example shown, prior to time t4, the VCT system may already be at a position that is greater than a threshold number of crankshaft angle degrees from the reference (e.g., original) position. Thus, the controller can command the oil pump to increase the target oil pressure output to an upper threshold oil pressure (e.g., the dashed line illustrated as 613), as shown in illustration 612.

[0082] When the controller confirms that the VCT system has reached the commanded original (e.g., reference) position, the target oil pressure remains at the upper threshold oil pressure (illustrated as 612) until time t5, as shown in illustration 606. In the example shown, the controller can confirm that the VCT has reached the commanded advanced position by receiving an indication of the VCT phaser position from a camshaft timing sensor (e.g., Figure 1 the camshaft timing sensor 176 in

[0083] In this way, during certain operating conditions of the VCT system, the variable displacement oil pump can be selectively controlled to provide an increased level of oil pressure to the VCT system, thereby obtaining an effective oil delivery system that can minimize additional losses and improve fuel economy, while always meeting the intermittent high demands of the VCT system. The technical effect of canceling the default control of the existing engine oil pump in response to the operating conditions of the VCT system is that an increased oil pressure can be provided within a short duration to prompt a rapid transition of the VCT system without increasing additional losses or reducing fuel economy. Additionally, since the necessary oil pressure is rapidly provided to the VCT system for rapid transition, turbo lag and NVH issues are reduced while engine response capabilities and performance are improved.

[0084] A method for an engine includes: regulating an oil pressure supplied to the engine and a variable cam timing (VCT) system to a first level based on engine speed, engine load, and engine oil temperature; increasing the oil pressure to a second level higher than the first level for a duration in response to a condition of the VCT system. In a first example of the method, when the engine oil temperature is higher than a threshold oil temperature and the engine speed is lower than a threshold engine speed, the condition of the VCT system includes a request to advance an intake cam of the VCT system. A second example of the method optionally includes the first example and further includes where the condition of the VCT system includes a request to return the VCT system from a position of a crank angle degree a threshold amount from a reference position to the reference position. A third example of the method optionally includes one or more of the first example and the second example and further includes where the request to return the VCT system to the reference position is in response to one or more of an engine stall condition, an engine shutdown request, or a request to perform a camshaft position learning routine. A fourth example of the method optionally includes one or more of the first through third examples and further includes where regulating the oil pressure supplied to the engine and the VCT system includes actuating a variable displacement oil pump to output oil to the engine and the VCT system at the first level or the second level. A fifth example of the method optionally includes one or more of the first through fourth examples and further includes: determining the first level based on a first relationship between oil pressure, engine load, and engine speed and a second relationship between oil pressure, engine oil temperature, and engine speed. A sixth example of the method optionally includes one or more of the first through fifth examples and further includes determining the first level by selecting a maximum value determined from each of the first relationship and the second relationship. A seventh example of the method optionally includes one or more of the first through sixth examples and further includes where the duration is a duration from a current position of the VCT system before the condition of the VCT system to a commanded position of the VCT system. An eighth example of the method optionally includes one or more of the first through seventh examples and further includes: returning the oil pressure to the first level after regulating the VCT system to the commanded position.

[0085] Another method for an engine includes, during a first condition, adjusting a supply pressure of an oil pump that supplies oil to the engine and a variable cam timing (VCT) system to a first level based on an engine speed, an engine load, and a relationship between the engine speed and an engine oil temperature; and during a second condition, adjusting the supply pressure to a second level based on a commanded position of the VCT system rather than based on the relationship, wherein the second level is greater than the first level. In a first example of the method, the oil pump is a variable displacement oil pump. A second example of the method optionally includes the first example and further includes: determining a third level of the supply pressure based on the relationship between the engine speed and the engine load and determining a fourth level of the supply pressure based on the relationship between the engine speed and the engine oil temperature, and wherein the first level of the supply pressure is selected as the maximum of the third level and the fourth level. A third example of the method optionally includes one or more of the first and second examples and further includes wherein the commanded position is an advanced position of an intake cam of the VCT system. A fourth example of the method optionally includes one or more of the first to third examples and further includes wherein when the engine speed is below a speed threshold and the engine oil temperature is above a temperature threshold, adjusting the supply pressure to the second level is further based on the advanced position. A fifth example of the method optionally includes one or more of the first to fourth examples and further includes wherein the commanded position of the VCT system is a reference position, and wherein adjusting the supply pressure to the second level is responsive to a crank angle of a threshold amount of the current position of the VCT system from the reference position. A sixth example of the method optionally includes one or more of the first to fifth examples and further includes, after adjusting the VCT system to the commanded position during the second condition, returning the supply pressure to the first level.

[0086] A system for an engine includes: a variable cam timing (VCT) system that includes an intake cam; a variable displacement oil pump fluidly coupled to the engine and the VCT system; and a controller that includes a memory with computer-readable instructions for: actuating the variable displacement oil pump to output oil at an upper threshold level only in response to a command to advance the intake cam or return the intake cam to a reference position at a crank angle of a threshold amount of crank angle degrees from a current position when engine speed is less than a threshold speed and engine oil temperature is greater than a threshold temperature; and otherwise, actuating the variable displacement oil pump to output oil at a second level that is lower than the upper threshold level, the second level being based on engine speed, engine load, and engine oil temperature. In a first example of the system, the computer-readable instructions include actuating the variable displacement oil pump to reduce the oil output to the second level when the intake cam reaches the commanded position. A second example of the method optionally includes the first example and further includes where the threshold amount of crank angle degrees is in a range of 20 - 30 crank angle degrees. A third example of the method optionally includes one or more of the first and second examples and further includes where the upper threshold level is the maximum oil pressure output of the variable displacement oil pump.

[0087] In another illustration, a method includes: during a first condition, actuating a variable displacement oil pump to output oil at a first level that is lower than an upper threshold level, where the first level is based on each of engine speed, engine load, and engine oil temperature; and during a second condition that includes one of a command to advance the intake cam when engine speed is below a threshold speed and engine oil temperature is above a threshold temperature and a command to return the intake cam to a reference position at a crank angle of a threshold amount of crank angle degrees from a current position, actuating the variable displacement oil pump to output oil at the upper threshold level instead of the first level.

[0088] Note that the exemplary control and estimation routines included herein can be used with a variety of engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific routines disclosed herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threaded, and the like. As such, the various actions, operations, and / or functions shown can be executed in the order shown, in parallel, or in some cases omitted. Similarly, the order of processing is not essential to achieve the features and advantages of the exemplary embodiments described herein, but is for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeated according to the particular strategy used. Further, the actions, operations, and / or functions described can be graphically represented as code programmed into the non-transitory memory of a computer-readable storage medium of the engine control system, where the described actions are implemented by executing instructions in a system including various engine hardware components coupled to an electronic controller.

[0089] It should be understood that the configurations and routines disclosed herein are exemplary in nature and these specific embodiments should not be considered limiting in any sense, as many variations are possible. For example, the above techniques can be applied to V-6, I-4, I-6, V-12, opposed 4-cylinder, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations as well as other features, functions, and / or properties disclosed herein.

[0090] The appended claims particularly point out certain combinations and sub-combinations that are regarded as novel and non-obvious. These claims may refer to "a" element or "a first" element or the equivalent thereof. Such claims should be understood to include the combination of one or more such elements, neither requiring nor precluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or characteristics may be claimed by modifying the present claims or by filing new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope from the original claims, should be regarded as included within the subject matter disclosed herein.

Claims

1. A method for an engine, comprising: Adjusting the oil pressure supplied to the engine and a variable cam timing system, i.e., a VCT system, to a first level based on engine speed, engine load, and engine oil temperature; And In response to a request to advance the intake cam of the VCT system, increasing the oil pressure to a second level higher than the first level for a duration by adjusting the oil output of an engine oil pump, wherein the duration is the duration from the current position of the VCT system before the request to advance the intake cam of the VCT system to the commanded position of the VCT system.

2. The method according to claim 1, wherein the request to advance the intake cam of the VCT system further comprises advancing the intake cam when the engine oil temperature is higher than a threshold oil temperature and the engine speed is lower than a threshold engine speed.

3. The method according to claim 1, wherein increasing the oil pressure to the second level further responds to a request to return the VCT system from a position at a crank angle offset from a reference position by a threshold amount to the reference position.

4. The method according to claim 3, wherein the threshold amount of crank angle is in the range of 20 - 30 crank angles.

5. The method according to claim 3, wherein the request to return the VCT system to the reference position responds to one or more of the following: an engine stall condition, an engine shutdown request, and a request to execute a camshaft position learning routine.

6. The method according to claim 1, wherein adjusting the oil pressure supplied to the engine and the VCT system comprises actuating a variable displacement oil pump to output oil to the engine and the VCT system at the first level or the second level.

7. The method according to claim 1, further comprising: Determining the first level based on a first relationship between oil pressure, engine load, and engine speed and a second relationship between oil pressure, engine oil temperature, and engine speed.

8. The method according to claim 7, further comprising determining the first level by selecting the maximum value determined from each of the first relationship and the second relationship.

9. The method according to claim 1, further comprising: Returning the oil pressure to the first level after adjusting the VCT system to the commanded position.

10. A system for an engine, comprising: A variable cam timing system, i.e., a VCT system, including an intake cam; A variable displacement oil pump fluidly coupled to the engine and the VCT system; And A controller including a memory having computer-readable instructions for: Actuating the variable displacement oil pump to output oil at an upper threshold level only in response to a command to advance the intake cam when the engine speed is lower than a threshold speed and the engine oil temperature is higher than a threshold temperature or to return the intake cam to a reference position at a crank angle offset from the current position by a threshold amount; And Otherwise, actuating the variable displacement oil pump to output oil at a second level lower than the upper threshold level, the second level being based on engine speed, engine load, and engine oil temperature.

11. The system according to claim 10, wherein the computer-readable instructions comprise: When the intake cam reaches the commanded position, actuate the variable displacement oil pump to reduce the oil output to the second level.

12. The system according to claim 10, wherein the threshold amount of crank angle degrees is in the range of 20 - 30 crank angle degrees.

13. The system according to claim 10, wherein the upper threshold level is the maximum oil pressure output of the variable displacement oil pump.

14. The system according to claim 10, wherein the computer-readable instructions include determining a third output level of the variable displacement oil pump based on a relationship between engine speed and engine load, and determining a fourth output level of the variable displacement oil pump based on a relationship between engine speed and engine oil temperature, and wherein the upper threshold level is selected as the maximum of the third output level and the fourth output level from the third output level and the fourth output level.

Images