SYSTEMS AND METHODS FOR ESTIMATING COMBUSTION ENGINE OIL TEMPERATURE

Abstract

Internal combustion engine processes, including: Setting an internal combustion engine torque actuator based on the internal combustion engine oil temperature (EOT), estimated by applying an excitation signal, comprising a pulse-width modulated duty cycle, a voltage and an electric current, applied to a solenoid valve (OCV) of a variable cam control (VCT) device, and using an associated relationship stored in non-volatile memory (110) that controls the camshaft solenoid duty cycle and relates the camshaft angular velocity of the device to the combustion engine oil temperature (EOT), wherein the adjustment is made in response to degradation of a sensor used to measure the combustion engine oil temperature (EOT) directly or indirectly, and damage to the non-volatile memory (110), wherein the non-volatile memory (110) includes a keep-alive memory (KAM) of a combustion engine control unit (12), wherein the sensor includes one or more of an combustion engine oil temperature sensor (EOT) coupled to an oil pan, a combustion engine coolant temperature sensor (ECT), an air charge temperature sensor (ACT), and a mass airflow sensor (MAF).

Description

Area

[0001] The present description generally relates to methods and systems for estimating an internal combustion engine oil temperature in an internal combustion engine system configured with an oil pressure-actuated VCT mechanism. General state of the art / Summary

[0002] An internal combustion engine control system uses several variables to adjust various internal combustion engine operations. For example, an estimated value of the engine oil temperature (EOT) can be used to calculate total friction and pumping losses in an internal combustion engine, which in turn is used for torque control. As another example, EOT is used for powertrain limiting, restricting the engine idle speed, as well as maximum and minimum permissible engine speeds, to protect the engine from extreme temperature conditions (such as those that can occur when the EOT is too high or too low). EOT values ​​can also be used to adjust variable camshaft timing, control positive crankcase ventilation, and monitor engine oil life.

[0003] Several approaches to EOT estimation have been developed. Some approaches rely on direct EOT estimation via a temperature sensor coupled to an internal combustion engine oil pan. Other approaches use an (indirect) EOT derivation logic, combining signals from various internal combustion engine sensors, such as an ECT sensor, a mass airflow (MAF) sensor, an ACT sensor, etc., with a final derived EOT value stored in an internal combustion engine control unit (e.g., a keep-alive memory or KAM) to generate derived values ​​during engine operation.

[0004] Furthermore, DE 11 2015 001 040 T5 describes a mechanism for variable valve timing control in which a control unit adjusts the opening degree of a hydraulic control valve when hydraulic pressure increases, in order to reduce the oil pressure supplied to the leading angle chamber or the lagging angle chamber, which is used to change the phase angle of the camshafts relative to the crankshaft. An oil temperature sensor detects the oil temperature in the hydraulic circuit, and the control unit takes the detected oil temperature into account when adjusting the opening degree.

[0005] The inventors included herein have, however, recognized potential problems with such approaches. For example, in the direct estimation approach, degradation of the temperature sensor can lead to inaccurate EOT measurements. Similarly, in the indirect estimation approach, degradation of any of the KAM, ECT, MAF, and ACT sensors (or any other sensor used in the EOT derivation logic) can render the derived EOT value unreliable. Even if the sensors are functioning, conditions may exist where the input from one or more sensors is unreliable for EOT estimation. For example, during warm engine starts, the engine coolant may be significantly warmer than the engine oil.The internal combustion engine control unit (ICU) can use a cooldown time (i.e., the total amount of time elapsed since the engine was switched off), the internal combustion engine coolant temperature estimated by the ECT sensor, and a last estimated EOT value before the engine was switched off to calculate an initial EOT estimate for the EOT derivation logic during the subsequent engine start. If either the cooldown time or the last estimated EOT value is corrupted due to a KAM (Combined Engine Control Module) fault, then the initial EOT estimate may be inaccurate, at least for the first few minutes of vehicle operation. This inaccuracy in the EOT estimation can lead to suboptimal engine performance. Additionally, overheating of the engine oil can lead to deterioration of engine components and a reduction in engine lifespan.

[0006] To mitigate the problems described, the present invention proposes an internal combustion engine method according to claim 1 and an internal combustion engine system according to claim 9. Preferred embodiments of the invention are the subject of the dependent claims.

[0007] The inventors herein have recognized that the temperature dependence of an oil control valve (OCV) on a variable camshaft timing (VCT) mechanism can be advantageously exploited for reliable EOT estimation. For example, the relationship can be used to derive EOT when a sensor used in the EOT estimation is impaired and / or when internal combustion engine conditions make the sensor output less reliable. In one example, internal combustion engine oil temperature can be estimated by a method for an internal combustion engine comprising: adjusting an internal combustion engine torque actuator in response to the internal combustion engine oil temperature, wherein the internal combustion engine oil temperature is derived from an associated relationship, stored in memory, between the camshaft solenoid duty cycle and the camshaft angular velocity of a variable camshaft timing device.

[0008] As an example, an internal combustion engine can be configured with an oil pressure-operated VCT device actuated by a solenoid-operated oil control valve (OCV). The VCT device may include an intake cam and an exhaust cam. Given that the EOT estimation conditions are met and one or more EOT faults are present, EOT estimation can be applied via an associated relationship between the camshaft solenoid duty cycle and the camshaft angular velocity. The one or more EOT faults may involve degradation of a sensor used to measure EOT (such as an EOT sensor, an ECT sensor, an ACT sensor, etc.). Alternatively, the one or more EOT faults may involve conditions where the sensor output is unreliable, such as when the KAM is corrupted or during a hot start of an internal combustion engine.During these conditions, the control unit can apply an excitation pulse to one of the intake and one of the exhaust cams. For example, the control unit can pass a current with a defined duty cycle pulse width through a solenoid coil of the overhead camshaft circulator (OCV), which controls the cams. The duty cycle can be selected such that the piston valve moves to a position that directs combustion engine oil to the camshaft pressure chambers, thereby rotating the camshaft (in an advanced or retarded direction, as required based on the selected control unit) relative to the camshaft. The control unit can measure a change in camshaft speed or velocity (for example, via a camshaft position sensor) according to the applied duty cycle and estimate a zero duty cycle of the OCV accordingly.Based on the estimated zero duty cycle and, furthermore, on an associated and calibrated relationship between camshaft angular velocity and solenoid duty cycle (e.g., associated via an inverse model), the control unit can derive an EOT (Electro-Off Temperature). The estimated EOT can be used to reliably calculate internal combustion engine torque and to actuate one or more torque actuators.

[0009] In this way, a reliable EOT estimate can be provided during conditions where sensors regularly used to measure or estimate EOT are impaired, or when the output of these sensors is unreliable. The engineering benefit of relying on an associated relationship between the applied duty cycle of an oil control valve (OCV) of an oil-pressure-actuated VCT and the angular velocity of the cam actuated by the OLV is that a more robust method of EOT estimation can be provided. By exploiting the temperature dependence of an OCV resistance when estimating EOT, the need for dedicated sensors is reduced, enabling a reduction in components and improving the robustness of the approach with respect to various EOT errors.More reliable estimation of EOT improves the accuracy of torque estimation and the limitation of internal combustion engine torque for temperature protection.

[0010] It is understood that the foregoing summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the detailed description. It is not intended to identify important or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that overcome the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows an exemplary internal combustion engine system that incorporates a variable camshaft control (VCT) device. Fig. Figure 2 represents an example of an oil control valve (OCV) of the VCT. Fig. Figure 3 represents an exemplary VCT adjustment system. Fig. Figure 4 shows a high-level flowchart for estimating an internal combustion engine oil temperature. Fig. Figure 5 represents an exemplary zero duty cycle determination for the OCV. Fig. Figure 6 represents an exemplary assignment of a relationship between the zero work cycle and the EOT. The Fig. Figures 7-10 represent exemplary EOT estimation results. Detailed description

[0011] The following description relates to systems and methods for controlling an internal combustion engine of a vehicle, wherein the internal combustion engine has a variable camshaft timing (VCT) device which is actuated using oil pressure via an oil control valve, as described in the Fig. shown in Figures 1-2. An internal combustion engine control unit may be designed to execute a control routine, such as the exemplary routine from Figure 1-2. Fig. 4. To estimate the combustion engine oil temperature (EOT) during conditions where standard EOT estimation methods are unreliable, such as due to sensor degradation or unreliable sensor output. The controller can apply a pulse width signal to induce a zero duty cycle of the oil control valve ( Fig. 5) to learn and then determine the EOT based on an associated relationship between VCT work cycle and EOT ( Fig. 6) to derive. Exemplary EOT estimates are provided in relation to the examples from the Fig. Shown 7-10.

[0012] Fig. Figure 1 shows an exemplary embodiment of a combustion chamber or cylinder of an internal combustion engine 10. Fig. Figure 1 shows that the internal combustion engine can receive 10 control parameters from a control system, which includes the controller 12, as well as an input from a driver 190 via an input device 192. In this example, the input device 192 includes an accelerator pedal and a pedal position sensor 194 for generating a proportional pedal position signal PP.

[0013] The cylinder (hereinafter also referred to as "combustion chamber") 30 of the internal combustion engine 10 can have combustion chamber walls 32 in which a piston 36 is positioned. The piston 36 can be coupled to the crankshaft 40, so that a reciprocating movement of the piston is translated into a rotary movement of the crankshaft. The crankshaft 40 can be coupled to at least one drive wheel of the passenger car via a transmission system. Furthermore, a starter motor can be coupled to the crankshaft 40 via a flywheel to enable the starting of the internal combustion engine 10. The housing 136 is hydraulically coupled to the crankshaft 40 via a timing chain or a timing belt (not shown).

[0014] Cylinder 30 can receive intake air via an intake manifold or air ducts 44. In addition to cylinder 30, the intake air duct 44 can also communicate with other cylinders of the internal combustion engine 10. In some embodiments, one or more of the intake ducts can include a charging device, such as a turbocharger or a supercharger. A throttle system, comprising a throttle plate 62, can be provided along an intake duct of the engine to vary the flow rate and / or pressure of the intake air supplied to the engine's cylinders. In this specific example, the throttle plate 62 is coupled to an electric actuator 94, such that the position of the elliptical throttle plate 62 is controlled by the controller 12 via the electric actuator 94. This design can be referred to as electronic throttle control (ETC), which can also be used for idle speed control.

[0015] In the diagram, the combustion chamber 30 communicates with the intake manifold 44 and exhaust manifold 48 via the respective intake valves 52a and 52b (not shown) and exhaust valves 54a and 54b (not shown). Therefore, while four valves can be used per cylinder, in another example a single intake and a single exhaust valve per cylinder can be used. In yet another example, two intake valves and one exhaust valve per cylinder can be used.

[0016] The exhaust manifold 48 can receive exhaust gases from other cylinders of the engine 10 in addition to those from cylinder 30. An exhaust gas sensor 76 is shown to be coupled to the exhaust manifold 48 upstream of the catalytic converter 70 (where the sensor 76 can correspond to various sensors). For example, the sensor 76 could be any of the many known sensors for providing information about the air-fuel ratio in the exhaust gas, such as a linear lambda sensor, a UEGO, a dual-state lambda sensor, an EGO, a HEGO, or an HC or CO sensor. The emission control device 72 is shown to be positioned downstream of the catalytic converter 70. The emission control device 72 could be a three-way catalytic converter, a NOx trap, various other emission control devices, or combinations thereof.

[0017] In some embodiments, each cylinder of the internal combustion engine 10 may have a spark plug 92 to initiate combustion. The ignition system 88 can provide a spark to the combustion chamber 30 via the spark plug 92 in response to a pre-ignition signal SA from the control unit 12 under selected operating modes. However, in some embodiments, the spark plug 92 may be omitted, for example, if the engine 10 can initiate combustion by auto-ignition or by fuel injection, as may be the case with some diesel engines.

[0018] In some embodiments, each cylinder of the internal combustion engine 10 can be equipped with one or more fuel injection devices to supply it with fuel. As a non-limiting example, the fuel injection device 66A shown is directly coupled to cylinder 30 to inject fuel directly into it in proportion to the pulse width of the signal dfpw received by the control unit 12 via an electronic driver 68. In this way, the fuel injection device 66A provides so-called direct injection (hereinafter also referred to as "DI") of fuel into cylinder 30. The fuel injection device can be mounted, for example, in the side of the combustion chamber (as shown) or in the top of the combustion chamber (near the spark plug).Fuel can be supplied to the fuel injection device 66A by a fuel system comprising a fuel tank, a fuel pump, and a fuel distributor. In some embodiments, the combustion chamber 30 may alternatively or additionally include a fuel injection device arranged in the intake manifold 44 in a configuration that provides so-called port fuel injection into the intake manifold upstream of the combustion chamber 30.

[0019] The controller 12 is shown as a microcomputer comprising a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this specific example as a read-only memory chip 106, direct access memory 108, maintenance memory 110 and a conventional data bus.For the control unit 12, it is shown that, in addition to the signals discussed previously, it can receive various signals from sensors coupled to the motor 10, including the measurement of the mass airflow (MAF) from a mass airflow sensor 100 coupled to the throttle 20; the engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; a profile ignition pulse (PIP) signal from a Hall effect sensor 118 coupled to the crankshaft 40; the throttle position TP from the throttle position sensor 20; an absolute manifold pressure signal MAP from the sensor 122; a knock indication from the knock sensor 182; and an indication of absolute or relative ambient humidity from the sensor 180.An internal combustion engine speed signal (RPM) is generated by control unit 12 using the PIP signal in the conventional manner, and the manifold pressure signal (MAP) from a manifold pressure sensor provides an indication of the vacuum or pressure in the intake manifold. During stoichiometric operation, this sensor can provide an indication of the engine load. Furthermore, this sensor, together with the engine speed, can provide an estimate of the charge (including air) being introduced into the cylinder. In one example, sensor 118, which is also used as an engine speed sensor, generates a predetermined number of evenly spaced pulses per revolution of the crankshaft.

[0020] In this particular example, the temperature Tcat1 of the catalyst 70 is provided by the temperature sensor 124, and the temperature Tcat2 of the emission control device 72 is provided by the temperature sensor 126. In an alternative embodiment, the temperature Tcat1 and the temperature Tcat2 can be derived from the operation of the internal combustion engine.

[0021] With further reference to Fig. Figure 1 shows a variable camshaft timing (VCT) system 19. This example depicts a system with overhead cams, although other approaches are also possible. Specifically, the camshaft 130 of the internal combustion engine 10 communicates with rocker arms 132 and 134 to actuate the intake valves 52a, 52b and exhaust valves 54a, 54b. In the illustrated example, the VCT system 19 is oil pressure actuated (OPA), whereby the actuation of a camshaft adjuster of the VCT system is enabled by oil pressure from the oil flow through a piston valve. In alternative examples, the VCT system 19 can be cam torque actuated (CTA), whereby the actuation of the camshaft adjuster is enabled by cam torque pulses.By adjusting a multitude of hydraulic valves to direct a hydraulic fluid, specifically combustion engine oil, into the cavity (such as an advance chamber or a retard chamber) of a camshaft adjuster, the valve timing can be changed, i.e., advanced or retarded. As further elaborated here, the operation of the hydraulic control valves can be controlled by individual magnetic switches. In particular, an engine control unit can transmit a signal to the magnetic switches to move a piston valve (also referred to herein as an oil control valve, OCV), which directs the oil flow through the cavity of the camshaft adjuster.In the sense used here, the advanced and trailing cam control refer to relative cam control insofar as a fully advanced position with respect to top dead center can still provide a delayed intake valve opening, to give just one example. An example of the operation of the OCV of the VCT system 19 is in relation to the . Fig. 2-3 shown.

[0022] The camshaft 130 is hydraulically coupled to the housing 136. The housing 136 forms a gear having a plurality of teeth 138. In the exemplary embodiment, the housing 136 is mechanically coupled to the crankshaft 40 via a timing chain or timing belt (not shown). As a result, the housing 136 and the camshaft 130 rotate at a speed that is essentially equivalent to each other and synchronous with respect to the crankshaft. In an alternative embodiment, such as in a four-stroke engine, the housing 136 and the crankshaft 40 can, for example, be mechanically coupled to the camshaft 130 so that the housing 136 and the crankshaft 40 can rotate synchronously at a speed that differs from that of the camshaft 130 (e.g., by a ratio of 2:1, with the crankshaft rotating twice as fast as the camshaft).In the alternative embodiment, the teeth 138 can be mechanically coupled to the camshaft 130. By manipulating the hydraulic coupling, as described here, the relative position of the camshaft 130 to the crankshaft 40 can be varied by hydraulic pressures in the retardation chamber 142 and advancement chamber 144. By allowing high-pressure hydraulic fluid to enter the retardation chamber 142, the relative relationship between the camshaft 130 and the crankshaft 40 is retarded. Thus, the intake valves 52a, 52b and exhaust valves 54a, 54b open and close later than is normally the case relative to the crankshaft 40. By allowing high-pressure hydraulic fluid to enter the advancement chamber 144, the relative relationship between the camshaft 130 and the crankshaft 40 is analogously advanced.Thus, the intake valves 52a, 52b and exhaust valves 54a, 54b open and close earlier than is normally the case in relation to the crankshaft 40.

[0023] While this example demonstrates a system where intake and exhaust valve timing are controlled simultaneously, variable intake camshaft timing, variable exhaust camshaft timing, dual independent variable camshaft timing, dual identical variable camshaft timing, or other types of variable camshaft timing can also be used. Furthermore, variable valve lift can be employed. Additionally, camshaft profile switching can be used to provide different cam profiles under varying operating conditions. Moreover, the valve train can consist of a roller rocker arm, a direct-acting mechanical tappet, electro-hydraulic components, or other alternatives to rocker arms.

[0024] Continuing with the variable cam timing system, teeth 138, which rotate synchronously with the camshaft 130, enable the relative cam position to be measured by the cam control sensor 150, which provides a VCT signal to the control unit 12. Teeth 1, 2, 3, and 4 can be used to measure the cam timing and are evenly spaced (for example, in a two-bank V8 internal combustion engine, spaced 90 degrees apart), while tooth 5 can be used for cylinder detection. Additionally, the control unit 12 sends control signals (LACT, RACT) to conventional solenoid valves (not shown) to control the flow of hydraulic fluid into either the late-adjustment chamber 142, the early-adjustment chamber 144, or neither.

[0025] There are numerous ways to measure relative cam timing. Generally speaking, the timing, or rotational angle, between the rising edge of the PIP signal and the reception of a signal from one of the multitude of teeth 138 on the housing 136 provides a measure of relative cam timing. In the specific example of a V-8 internal combustion engine, which has two cylinder banks and a five-tooth gear, a measure of cam timing for each bank is received four times per revolution, with the additional signal being used for cylinder identification.

[0026] As previously described, Fig. 1 merely one cylinder of a multi-cylinder engine and that each cylinder has its own set of inlet / outlet valves, fuel injectors, spark plugs, etc.

[0027] Fig. Figure 2 shows an example of an oil control valve (OCV) 200 of the VCT system 19. Fig. 1. The OCV 200 is configured as a piston valve (and may herein be referred to as a piston valve) having a piston 212 positioned within the housing 210. As shown, the piston 212 is spring-loaded within the housing 210 by a spring 216. A position of the piston valve is set by an internal combustion engine control unit by sending a PWM duty cycle command 202 to a driver circuit 219, which is placed between the battery 218, which provides the supply voltage, and the solenoid 214. The driver circuit applies PWM voltage to the solenoid 214, which drives a current through the solenoid 214, and the solenoid exerts an external force on the piston valve, the magnitude of the force being proportional to the magnitude of the current flowing through the solenoid 214.Therefore, the magnitude of the current, and consequently the force exerted on the piston valve, depends on the resistance of the solenoid coil, the supply voltage, and the selected PWM duty cycle. The position of the piston valve is thus controlled by adjusting the PWM duty cycle, since the resistance of the solenoid coil and the supply voltage are fixed parameters.

[0028] By varying the position of the piston valve, oil is directed into or out of the pressure chambers that drive the camshaft to rotate in the advance or retard direction. This makes the rotational speed of the camshaft proportional to the oil pressure in the chamber. For example, by adjusting the position of the piston valve, oil can be supplied to the advance chamber 220 via the oil supply 204 or the oil channel 232, or drained from the retard chamber 222, to advance the valve timing. Alternatively, by adjusting the position of the piston valve, oil can be supplied from the oil supply 204 to the advance chamber 222 and drained from the retard chamber 220 via an oil channel 230 to retard the valve timing.Finally, by adjusting the position of the piston valve, the oil channels 230 and 232 to the advance and retard chambers can be blocked, thus keeping the valve train stationary. The duty cycle required to hold the piston valve in this position is called the zero duty cycle.

[0029] Fig. Figure 3 shows a VCT adjuster 300 in an advanced position. In one example, the VCT adjuster 300 can override the VCT adjuster 19. Fig. 1 include. Fig. Figure 3 further represents a solenoid-operated piston valve 309 coupled to the VCT adjuster 300. The piston valve 309 is shown in an early adjustment region of the piston as a non-limiting example. It is understood that the piston valve can have an infinite number of intermediate positions, such as positions in the early adjustment region, the zero region, and the locking region of the piston (as elaborated below). The position of the piston valve can not only control a direction of movement of the VCT adjuster but can also control the rate of movement of the VCT adjuster depending on the individual piston position.

[0030] Internal combustion engines employ various mechanisms to vary the angle between the camshaft and the crankshaft for improved combustion engine performance or reduced emissions. Most of these variable camshaft timing (VCT) mechanisms utilize one or more vane adjusters on the internal combustion engine camshaft (or camshafts in a multi-camshaft internal combustion engine), such as the VCT adjuster 300. The VCT adjuster 300 may have a rotor 305 with one or more vanes 304, attached to the end of a camshaft 326, surrounded by a housing assembly 340 with vane chambers into which the vanes fit. In an alternative example, the vanes 304 may be attached to the housing assembly 340, and the chambers may be attached within the rotor assembly 305.The outer circumference 301 of the housing forms the sprocket, pulley or gear that receives driving force via a chain, belt or gears, normally from the crankshaft or from another camshaft in an internal combustion engine with multiple cams.

[0031] The VCT adjuster 300 is depicted as an oil pressure-operated adjuster. Oil pressure is applied to the camshaft via pressure chambers 302 and 303 to move the vane 304. The advance and retard chambers 302 and 303 are arranged to withstand pressure pulses on the camshaft 326 and are alternately pressurized by the oil pressure pulses. The piston valve 309 allows the vane 304 to move within the adjuster by permitting fluid flow from the advance chamber 302 to the retard chamber 303, or vice versa, depending on the desired direction of movement. For example, if the desired direction of movement is retardation, the piston valve 309 allows the vane to move by permitting fluid flow from the retard chamber to the advance chamber.In contrast, if the desired direction of movement is in the early adjustment direction, the piston valve 309 allows the vane to move by enabling fluid flow from the early adjustment chamber to the late adjustment chamber.

[0032] The housing assembly 340 of the VCT adjuster 300 has an outer circumference 301 for receiving drive force. The rotor assembly 305 is connected to the camshaft 326 and is located coaxially within the housing assembly 340. The rotor assembly 305 has a vane 304 that divides a chamber formed between the housing assembly 340 and the rotor assembly 305 into an advance chamber 302 and a retard chamber 303. The vane 304 is rotatable to shift the relative angular position of the housing assembly 340 and the rotor assembly 305. Additionally, a hydraulic locking circuit 333 and a locking pin circuit 323 are also provided. The hydraulic locking circuit 333 and the locking pin circuit 323 are fluid-coupled, so that they are essentially one circuit, as discussed above, but are discussed separately for the sake of simplicity and to better distinguish their respective functions.The hydraulic locking circuit 333 comprises a pilot-operated valve 330 pre-tensioned by a spring 331, an early-adjustment locking line 328 connecting the early-adjustment chamber 302 to the pilot-operated valve 330 and a common line 314, and a late-adjustment locking line 334 connecting the late-adjustment chamber 303 to the pilot-operated valve 330 and the common line 314. The early-adjustment locking line 328 and the late-adjustment locking line 334 are located at a predetermined distance or length from the vane 304. The pilot-operated valve 330 is located in the rotor assembly 305 and is fluidically connected via a connecting line 332 to the locking pin circuit 323 and the supply line 319.The locking pin circuit 323 includes a locking pin 325, the connecting line 332, the pilot-operated valve 330, a supply line 319a and an outlet line 322.

[0033] The pilot-operated valve can be actuated between two positions, where the first position can correspond to a closed or off position and the second position to an open or on position. The pilot-operated valve can be commanded to these positions by the piston valve. In the first position, the pilot-operated valve is pressurized by internal combustion engine-generated oil pressure in line 332, which positions the pilot-operated valve so that fluid is prevented from flowing between the advance and retard chambers through the pilot-operated valve and the locking circuit 333. In the second position, there is no internal combustion engine-generated oil pressure in line 332.The absence of pressure in line 332 allows the spring 331 to position the pilot-operated valve so that fluid between the locking line from the early adjustment chamber and the locking line from the late adjustment chamber can flow through the pilot-operated valve and a common line, thus moving and holding the rotor assembly in the locking position.

[0034] The locking pin 325 is slidably arranged in a bore in the rotor assembly 305 and has an end section that is biased by a spring 324 towards a recess 327 in the housing assembly 340 and fits into it. Alternatively, the locking pin 325 can be arranged in the housing assembly 340 and can be biased by the 324 towards a recess 327 in the rotor assembly 305. The opening and closing of the hydraulic locking circuit 333 and the pressurization of the locking pin circuit 323 are both controlled by switching / moving the piston valve 309.

[0035] The piston valve 309 comprises a piston 311 with cylindrical webs 311a, 311b, and 311c, which are slidably mounted in a sleeve 316 within a bore in the rotor 305, and provides control in the camshaft 326. One end of the piston contacts a spring 315, and the opposite end of the piston contacts a pulse-width modulated variable force (VFS) solenoid 307. The solenoid 307 can also be linearly controlled by varying the duty cycle, current, voltage, or other methods, as applicable. Additionally, the opposite end of the piston 311 can contact or be influenced by an electric motor or other actuators.

[0036] The position of piston 311 is influenced by spring 315 and solenoid 307, which is controlled by control 12. Further details regarding the control of the adjuster are discussed below. The position of piston 311 controls the movement of the adjuster, including its direction and rate of movement. For example, the piston position determines whether the adjuster is to move toward the advance position, a hold position, or the retard position. Additionally, the piston position determines whether the locking pin circuit 323 and the hydraulic locking circuit 333 are open (on) or closed (off). In other words, the position of piston 311 actively controls the pilot-operated valve 330. The piston valve 309 has an advance mode, a retard mode, a zero mode, and a hold mode.These control modes can be directly associated with positioning regions. Thus, specific regions of the piston valve stroke can enable the piston valve to operate in the advance, retard, zero, and hold modes. In the advance mode, the piston 311 is moved to a position in the advance region of the piston valve, allowing fluid to flow from the retard chamber 303 through the piston 311 to the advance chamber 302, while preventing fluid from leaving the advance chamber 302. Additionally, the hold circuit 333 is held off or closed.In the retard mode, piston 311 is moved to a position in the retard region of the piston valve, allowing fluid to flow from the advance chamber 302 through piston 311 to the retard chamber 303, while preventing fluid from exiting the retard chamber 303. Additionally, the locking circuit 333 is held off or closed. In the zero mode, piston 311 is moved to a position in the zero region of the piston valve, blocking the outlet of fluid from both the advance and retard chambers 302 and 303, while the locking circuit 333 remains off or closed. In the locking mode, the piston is moved to a position in the locking region. Three functions occur simultaneously in the locking mode.The first function in the locking mode is that the piston 311 moves to a position where the piston collar 311b prevents the flow of fluid from line 312 between the piston collars 311a and 311b from entering any of the other lines and line 313, thus effectively removing the control of the adjuster from the piston valve 309. The second function in the locking mode is to open or engage the locking circuit 333. This gives the locking circuit 333 complete control over the movement of the adjuster to advance or retard positions until the vane 304 reaches an intermediate phase angle position. The third function in the locking mode is to release the locking pin circuit 323, allowing the locking pin 325 to engage in the recess 327.The intermediate phase angle position, also referred to herein as the intermediate locking position and the locking position, is defined as a position in which the vane 304 is located between an early timing wall 302a and a late timing wall 303a, the walls defining the chamber between the housing assembly 340 and the rotor assembly 305. The locking position can be any position between the early timing wall 302a and the late timing wall 303a and is determined by the position of locking channels 328 and 334 with respect to the vane 304.Specifically, the position of the locking channels 328 and 334 relative to the vane 304 defines a position in which no channel can be exposed to the advance and retard chambers 302 and 303, thus completely disabling communication between the two chambers when the pilot-operated valve is in the second position and the adjustment circuit is off. Commanding the piston valve to the locking region can also be referred to as a "locking" or "permanent locking" of the cam adjuster, in relation to the hardware component (locking pin) involved in locking the cam adjuster in the center locking position.

[0037] Based on the duty cycle of the pulse-width modulated variable-force solenoid 307, the piston 311 moves to a corresponding position along its stroke. For example, if the duty cycle of the variable-force solenoid 307 is approximately 30%, 50%, or 100%, the piston 311 moves to positions corresponding to the retard mode, the zero mode, or the advance mode, respectively. The pilot-operated valve 330 is pressurized and moves from the second position to the first position, while the hydraulic locking circuit 333 is closed, and the locking pin 325 is pressurized and released.As another example, when the duty cycle of the variable-force solenoid 307 is set to 0%, the piston 311 is moved into the locking mode, causing the pilot-operated valve 330 to vent and move to its second position, the hydraulic locking circuit 333 to open, and the locking pin 325 to vent and engage in the recess 327. By selecting a duty cycle of 0% as the outermost position along the piston stroke to open the hydraulic locking circuit 333, open the pilot-operated valve 330, and vent the locking pin 325 and engage in the recess 327 when power or control is disconnected, the adjuster can move to a locked position by default, thus improving the positional security of the cam adjuster.It should be noted that the duty cycle percentages listed above are provided as non-limiting examples and that alternative duty cycles may be used to move the piston of the piston valve between the different piston regions in alternative embodiments. For example, at a 100% duty cycle, the hydraulic locking circuit 333 may alternatively be open, the pilot-operated valve 330 may be vented, and the locking pin 325 may be vented and engaged in the recess 327. In this example, the locking region of the piston valve may be adjacent to the advance region instead of the retard region. In another example, the locking mode may be at a duty cycle of 0%, and duty cycles of approximately 30%, 50%, and 100% may move the piston 311 to positions corresponding to the advance mode, the zero mode, and the retard mode, respectively.Similarly, in this example, the early adjustment region of the piston valve is located next to the locking region.

[0038] Under selected conditions, a controller can assign one or more regions of the piston by varying the duty cycle commanded to the piston and correlating this with corresponding changes in the adjuster position. For example, a transit region between the locking region and the retard region of the piston, also referred to herein as the "no-fly zone," can be assigned by correlating movement of the piston valve from the locking region into the retard region with movement of the adjuster from the center locking position toward a retarded position.

[0039] Fig. Figure 3 shows the adjuster 300 moving towards the advance position. To move the adjuster towards the advance position, the duty cycle of the piston valve is increased to over 50% and, if necessary, up to 100%. As a result, the force of the solenoid 307 on the piston 311 is increased, and the piston 311 is moved to the right towards an advance region and actuated in an advance mode until the force of the spring 315 balances the force of the solenoid 307. In the advance mode shown, the piston skirt 311a blocks line 312, while lines 313 and 314 are open. In this scenario, oil pressure pulses pressurize the retardation chamber 303, causing fluid to move from the retardation chamber 303 into the advance chamber 302, thereby moving the wing 304 in the direction shown by arrow 345.Hydraulic fluid exits the retardation chamber 303 between the piston skirts 311a and 311b through line 313 to the piston valve 309 and circulates back to the central line 314 and line 312, which leads to the advancement chamber 302. The pilot-operated valve is held in the first position and is blocked by the locking lines 328 and 334.

[0040] In an alternative example, the duty cycle of the piston valve is reduced to below 50% and, if necessary, to as low as 30% to move the adjuster toward the retarded position. As a result, the force of the solenoid 307 on the piston 311 is reduced, and the piston 311 is moved to the left toward a retarded region and actuated in a retarded mode until the force of the spring 315 balances the force of the solenoid 307. In the retarded mode, the piston skirt 311b blocks line 313, while lines 312 and 314 are open. In this scenario, oil pressure pulses pressurize the advance chamber 302, causing fluid to move from the advance chamber 302 into the retard chamber 303, thereby moving the vane 304 in a direction opposite to that indicated by arrow 345.Hydraulic fluid exits the early adjustment chamber 302 between the piston skirts 311a and 311b through line 312 to the piston valve 309 and circulates back to the central line 314 and line 313, which leads to the late adjustment chamber 303. The pilot-operated valve is held in the first position and is blocked by the locking lines 328 and 334.

[0041] In this way, the components from Fig. 1-3 an internal combustion engine system comprising a variable cam control device, including a cam, an oil pressure actuated adjuster, a camshaft, a piston valve and a solenoid; a cam position sensor coupled to the cam; a battery; an internal combustion engine coolant temperature sensor; an intake air charge temperature sensor; an air mass flow sensor, and a control unit.The control system may include computer-readable instructions stored in non-volatile memory for the following: in response to at least one diagnostic flag being set with respect to estimating internal combustion engine oil temperature, applying an excitation pulse to the solenoid to move the piston valve, with one duty cycle of the excitation pulse being set to move the cam outside a stop region; measuring an angular velocity of the camshaft after application via the cam position sensor; estimating a zero duty cycle of the solenoid valve based on the applied duty cycle; and estimating an internal combustion engine oil temperature based on an associated relationship between the estimated zero duty cycle and the measured angular velocity.The control system can further include instructions to limit each of an upper and a lower internal combustion engine speed threshold based on the estimated internal combustion engine oil temperature, whereby the upper internal combustion engine speed threshold is decreased and the lower internal combustion engine speed threshold is increased when the estimated internal combustion engine oil temperature exceeds a temperature threshold. At least one diagnostic flag related to the estimated internal combustion engine oil temperature can be set in response to one of the following conditions: degradation of the internal combustion engine coolant temperature sensor, degradation of the intake air temperature sensor, degradation of the mass airflow sensor, memory damage, and an internal combustion engine warm start condition.In one example, the associated relationship is stored in memory and uses a last estimated internal combustion engine oil temperature, the estimated zero duty cycle, and the measured angular velocity as inputs. Furthermore, the cam can be either an intake cam or an exhaust cam, with the controller further including instructions to select the intake cam when the internal combustion engine controller provides an intake cam shift command, and to select an exhaust cam when the controller provides an exhaust cam shift command. The zero duty cycle can include a duty cycle quantity that results in zero angular velocity for the VCT device outside of a stop or pin-lock position.Furthermore, the control unit may include additional instructions for the following: in response to the fact that no diagnostic flag related to estimating the internal combustion engine oil temperature is set, estimating the internal combustion engine oil temperature based on an output from one or more of the internal combustion engine coolant temperature sensor, the intake air charge temperature sensor, and the mass airflow sensor.

[0042] With reference to Fig. Figure 4 describes an exemplary routine 400 for estimating EOT via an associated relationship between commanded solenoid duty cycle and internal combustion engine oil temperature. Routine 400 can be executed by an internal combustion engine control unit, such as the control unit 12 from the Fig. 1-3 can be performed under input conditions for EOT estimation if EOT quantities measured or derived via existing internal combustion engine sensors cannot be reliable.

[0043] For error code 402, the routine involves estimating and / or measuring engine operating conditions. These can include, for example, determining whether the internal combustion engine is off or running, and measuring parameters such as engine speed, engine temperature, ambient conditions (ambient temperature, pressure, humidity, etc.), torque demand, manifold pressure, manifold airflow, catalytic converter conditions, oil temperature, oil pressure, cooldown time (time elapsed since the internal combustion engine was last shut down), etc.

[0044] At 404, it can be determined whether the conditions for EOT estimation have been met. In one example, EOT estimation might be triggered in response to an internal combustion engine start. In another example, EOT estimation might be performed while the engine is running, such as when a threshold for the time (or duration) of vehicle travel since the last EOT estimation has elapsed. Thus, EOT estimation may be required when an internal combustion engine is running or immediately before (or at) an engine start for estimating (actual) torque, boost control, determining variable camshaft (or valve) timing, scheduling and estimating positive crankcase ventilation, monitoring oil life, powertrain limitation, and powertrain protection.For example, EOT estimation can be triggered in response to an internal combustion engine control unit needing to calculate the total friction and pumping torque losses of the internal combustion engine, which is then used to calculate the total crankshaft torque loss and subsequently the internal combustion engine torque output. As another example, EOT estimation can be triggered after a threshold for the duration of internal combustion engine operation has been reached for powertrain limitation and protection, thus reducing powertrain overheating or underheating.

[0045] If the conditions for EOT estimation at 406 are not met, the internal combustion engine control unit (ICU) will not measure or derive the EOT. For example, if the internal combustion engine has been shut off, it will remain off. Similarly, if the internal combustion engine is running, it will continue to run without updating the last EOT estimate stored in the ICU's memory. Furthermore, the ICU will continue to adjust internal combustion engine actuators based on the last estimated EOT stored in the control unit's memory. For example, torque output and powertrain limiting can be performed based on the last estimated EOT.

[0046] If the conditions for EOT estimation at 408 are met, the control unit checks for various fault flags generated by relevant characteristics of the internal combustion engine system. These fault flags indicate whether the (last) measured / guided EOT value is reliable. For example, the control unit can retrieve all diagnostic codes and flags that have been set and determine if any of them are related to EOT estimation. Thus, EOT can be measured directly via an EOT sensor coupled to an internal combustion engine oil pan. However, such EOT sensors can be expensive and prone to wear. Therefore, in some internal combustion engine systems, EOT can be derived indirectly via one or more other internal combustion engine sensors, such as an intake air temperature (ACT) sensor, an exhaust gas temperature (ECT) sensor, and / or an intake air mass flow (MAF) sensor.The EOT can be derived based on the output of one or more of the ACT sensor, the ECT sensor and the MAF sensor, and a final EOT estimate stored in the control unit's memory, such as the KAM.

[0047] Estimating EOT based on one or more of the ACT sensor, the ECT sensor, and the MAF sensor is included.

[0048] As an example, the retrieved error flags might include a KAM fault flag, indicating that the controller's non-volatile memory (e.g., the KAM) is corrupted and therefore any variable stored in the KAM is unreliable. In other examples, the error flag might indicate a faulty condition in the internal combustion engine's electronic control module that is not limited to the keep-alive memory.

[0049] As another example, the fault flag may indicate the degradation of a sensor used to measure the internal combustion engine oil temperature, either directly or indirectly. For instance, a fault flag from an ACT sensor may indicate either that an intake air temperature (ACT) sensor coupled to the internal combustion engine intake manifold is malfunctioning, that the ACT sensor output is damaged, or that the internal combustion engine operating conditions are such that an EOT estimated based on an ACT sensor output is unreliable. ACT can be used as an input to a thermal model used to derive the EOT, with ACT acting as a substitute for the ambient temperature. The ACT value may be unreliable if the ACT sensor is malfunctioning or has failed, or if the data transmission between the ACT sensor and the PCM is damaged (such as due to KAM damage).In one example, the combustion engine operating conditions may be such that the output of the ACT sensor is reliable for ACT estimation, but not for EOT estimation.

[0050] As another example, the fault flag may include a fault flag from an ECT sensor, indicating either that an internal combustion engine coolant temperature (ECT) sensor coupled to the internal combustion engine coolant system is malfunctioning, that the ECT sensor output is damaged, or that the internal combustion engine operating conditions are such that an EOT estimate based on the ECT sensor output is unreliable. For example, the internal combustion engine operating conditions may be such that the ECT sensor output is reliable for ECT estimation (such as estimating an internal combustion engine temperature) but not for EOT estimation. For instance, the ECT sensor output may be unreliable during an internal combustion engine hot start condition but reliable during an internal combustion engine cold start condition.For example, the estimated ECT value during vehicle startup may not be transmitted to the control unit quickly enough, resulting in the EOT derivation logic being initialized with a default ECT value (such as 60 degrees Celsius). While this does not affect cold starts of combustion engines, during warm starts, where the actual ECT value is significantly higher than the default (e.g., at or above 190 degrees Celsius), the estimated EOT may deviate from its true value by approximately 50% because the initial / default ECT value is used to initialize the derived thermal EOT model (instead of the actual ECT value).

[0051] As another example, the fault flag could include a fault flag from a MAF sensor, indicating either that a mass airflow (MAF) sensor coupled to the internal combustion engine intake is malfunctioning, that the MAF sensor output is damaged, or that the internal combustion engine operating conditions are such that an EOT estimate based on the MAF sensor output is unreliable. For example, the internal combustion engine operating conditions might be such that the MAF sensor output is reliable for MAF estimation (such as estimating intake charge volume or intake charge flow), but not for EOT estimation.

[0052] In yet another example, where the vehicle is equipped with an EOT sensor, the fault flag may include an EOT sensor fault flag indicating either that the EOT sensor coupled to the internal combustion engine oil pan is faulty or that the output of the EOT sensor is damaged.

[0053] In one example, during internal combustion engine starts, an internal combustion engine control unit (ICU) can use a combination of the cool-down time, the measured internal combustion engine coolant temperature, and the last sample of the EOT (Electro-Off Temperature) before the engine shuts down, stored in the KAM (Combined Engine Control Module), to calculate an initial estimate for the EOT derivation logic. If either the last EOT value or the cool-down time is corrupted due to a KAM fault, if the ECT (Exhaust Gas Temperature) sensor is faulty, or if the internal combustion engine coolant is significantly warmer than the internal combustion engine oil (as can occur during warm starts), then the initial EOT estimate may be inaccurate. This can result in an inaccurate derived EOT value during the first few minutes of vehicle operation. A KAM fault would produce the same effect.For example, if the battery is disconnected from the PCM, thus resetting the KAM, the cool-down timer is reset and the initialization of the derived EOT, which depends on the cool-down time, is inaccurate. In other examples, 410 can be used to determine whether a warm-start condition for the combustion engine is present.

[0054] If no EOT fault is detected, as can occur if no fault flags related to EOT estimation are retrieved (or if an internal combustion engine warm start condition is not confirmed), then the routine at 412 involves estimating or measuring EOT using any one or more of the standard EOT estimation methods. For example, EOT can be measured directly based on the output of the EOT sensor. As another example, EOT can be derived from measured ACT, measured ECT, or measured MAF. The thermal model for the EOT derivation logic can be summarized according to the following equation: EOT=EOT_ss+k_ect*(ect−200)+k_amb*(act−100) where EOT_ss is a set end value of EOT, calculated (via a 2D lookup table) based on engine speed and engine load. EOT is then low-pass filtered to obtain the final value EOT_filt, which is used by the powertrain features. The time constant of this low-pass filter also depends on the engine speed. Thus, the EOT derivation calculation, in addition to ECT and ACT, is dependent on the engine speed in several ways during normal operation.

[0055] Then, at 414, the controller can adjust one or more internal combustion engine torque actuators based on the estimated EOT. For example, the controller can compare the estimated EOT to upper and lower threshold values, and based on this comparison, it can select an internal combustion engine torque actuator, as well as the quantity and direction for adjusting the selected torque actuator. As an example, in response to the estimated EOT being higher than an upper threshold, an internal combustion engine output may be limited, boost pressure may be limited, and / or internal combustion engine torque delivered in response to an operator torque request may be limited. As another example, an internal combustion engine idle speed may be limited to reduce internal combustion engine overheating and for protection against low internal combustion engine oil temperature.As another example, upper and lower limits of internal combustion engine speed within a permissible internal combustion engine speed range may be restricted (e.g., by reducing the upper threshold of the internal combustion engine speed and / or raising the lower threshold of the internal combustion engine speed) if the EOT is too low (e.g., below a lower threshold) or too high (e.g., above an upper threshold) in order to protect the internal combustion engine from extreme temperature conditions.

[0056] Returning to 410, if an EOT fault is detected, such as when a flag or diagnostic code corresponding to the EOT estimate is set (or when warm start conditions are confirmed), it can be inferred that the memory and / or sensor signals relevant to the EOT calculation are damaged and unreliable. During these conditions, an alternative approach can be used to derive the EOT, thus enabling control of internal combustion engine torque and powertrain temperature. As detailed below, the inventors have recognized that during these conditions, the temperature dependence of the oil control valve (OCV) of the variable camshaft timing (VCT) system, configured as a solenoid valve, can be exploited to use the OCV as an EOT sensor.

[0057] It is understood that, while the presented routine demonstrates EOT estimation using an OCV of a VCT system, in other examples the EOT estimation method can be used as a primary tool to estimate the internal combustion engine oil temperature. Alternatively, the method can be used in conjunction with existing tools as an auxiliary method to serve as an additional EOT source, which can be used in situations where the EOT quantities provided by the sensors are unreliable or cannot be reliably provided by existing tools.

[0058] If any EOT fault is detected, the procedure at 416 involves applying an excitation profile (such as an excitation signal or pulse in the form of a cam position command, voltage, electric current, or pulse-width modulated duty cycle) to an intake or exhaust cam of the VCT device. Specifically, the excitation signal is applied to the variable camshaft control solenoid valve coupled to the intake or exhaust cam. The excitation profile or pulse applied may include an amplitude, frequency, and duration of application.The control unit can use a battery coupled to the internal combustion engine or power transmission (such as a battery coupled to the internal combustion engine's alternator, or an electric motor's battery coupled to the internal combustion engine) as a power source to apply a pulse-width modulation (PWM) duty cycle to the solenoid coil of the oil control (piston) valve (the VCT device). The PWM duty cycle drives a current through the solenoid coil to vary the position of the piston valve. The PWM duty cycle can be selected to determine a zero duty cycle of the OCV. Specifically, the applied duty cycle moves one of the intake and exhaust cams outside of a stop position (or pin-lock position).As used herein, the zero duty cycle refers to a duty cycle that results in zero angular velocity for the VCT device outside of the stop or pin-lock position. For example, a cam position reference command may be provided to a closed-loop VCT controller, such that the cam position is maintained at a predetermined setpoint. The zero duty cycle can then be determined based on the PWM duty cycle applied by the VCT controller to the solenoid to maintain the cam position at the setpoint. In this way, applying the excitation signal may involve applying, via a closed-loop controller, a reference angular position command to vary the angular velocity of the VCT device's camshaft.The controller can then measure the camshaft angular velocity and the duty cycle (or the voltage or electrical current of the excitation signal) applied to the solenoid by the closed-loop controller. In another example, the PWM duty cycle can be set directly without using a closed-loop controller to determine the zero duty cycle. Duty cycle pulses with incrementally increasing amplitudes can be applied to the oil control solenoid for fixed periods, and the measured cam position signal can be monitored to determine the zero duty cycle. Furthermore, applying the excitation signal can involve applying an incrementally increasing duty cycle, voltage, or electrical current to the solenoid of the piston valve and measuring the camshaft angular velocity after each increment.

[0059] In one example, the applied excitation profile (which can be a duty cycle, voltage, or electric current) can depend on the specific approach or parameter to be used to derive the EOT. For example, for a zero-duty-cycle approach, the excitation profile can be a step reference instruction, as shown in the example from Fig. 5 (at 504) elaborated. The excitation profile can be a ramp command with a specific commanded cam speed. Within this, the zero duty cycle approach can be a limiting or special case thereof, where a specific ramp command has a commanded cam speed of 0 degrees per second.

[0060] In one example, the control unit can select between the intake cam and the exhaust cam to apply the excitation profile based on its ability to apply the excitation profile in a non-contact manner. That is, without the ability to apply an excitation pulse (which is superimposed on the VCT system for a short period), but instead using the VCT command profiles inherent in the normal operation of the internal combustion engine. In this case, the control unit can select the intake cam when the internal combustion engine requests intake cam movement and select the exhaust cam when the engine control unit requests exhaust cam movement.

[0061] The inventors hereby recognize that a relationship or defined mapping exists between the PWM duty cycle (DC) applied to the solenoid coil of the piston valve and the angular velocity of the camshaft. Furthermore, this mapping can be characterized by applying a known PWM duty cycle signal and measuring the resulting camshaft angular velocity, assuming a constant solenoid coil resistance and a known battery voltage. Specifically, the PWM duty cycle changes the position of the piston valve, which in turn adjusts the oil pressure within the pressure chambers of the overpressure valve (OCV), which in turn drives the angular velocity of the camshaft relative to the camshaft. The angular velocity of the camshaft can then be measured using the camshaft position sensor.Since the solenoid resistance varies with the solenoid temperature, it is not a constant term but instead varies with the temperature. Furthermore, the solenoid resistance is largely determined by the combustion engine oil temperature near the OCV (over-cycle valve) due to the proximity of the combustion engine oil to the solenoid. Thus, by mapping this relationship, the EOT (end of top dead center) can be reliably derived without requiring any of the standard sensors such as an EOT sensor, an ECT (end of top dead center) sensor, or an ACT (end of top dead center) sensor. In particular, after applying an excitation signal to the solenoid of a VCT (variable camshaft timing) device, the EOT can be estimated from a mapped relationship stored in non-volatile memory, where the mapping relates the camshaft solenoid duty cycle and camshaft angular velocity of the VCT device to the combustion engine oil temperature.The assignment of the relationship also involves assigning a relationship between the EOT and the zero work cycle of the OCV.

[0062] In document 417, the procedure involves determining a cam position and / or cam speed when the PWM duty cycle is applied. For example, the control may refer to an output of a cam position sensor coupled to the excited intake or exhaust cam to determine a change in the cam's position from an initial position before the PWM duty cycle was applied to a final position after the excitation pulse is applied. In another example, the cam position sensor output may be used to determine a direction of cam movement and a rate of change of cam position (such as a rate of change of cam position in either a retarded or an advanced position). Further still, the cam position sensor may be used to measure the angular velocity of the camshaft.

[0063] In section 418, the procedure involves determining a zero duty cycle according to the OCV based on the PWM duty cycle applied to the solenoid. The zero duty cycle refers to the duty cycle that must be applied to the solenoid to maintain the cam position at a constant position (excluding pin-lock positions such as 0 degrees or the center-lock position, where the locking mechanism maintains the cam position without requiring a duty cycle input). The zero duty cycle determination can be performed using one of several methods. For example, in section 420, the zero duty cycle is determined by low-pass filtering of the applied PWM duty cycle. As another example, in section 422, the zero duty cycle is determined by Kalman filtering of the PWM duty cycle (also referred to herein as a recursive least-squares method).Overall, the control system calculates the zero duty cycle or the duty cycle required to achieve a commanded rate of change of cam position.

[0064] Determining the zero duty cycle by low-pass filtering the PWM duty cycle at 420 involves applying a step cam position reference command to the cam gear, so that the cam gear is commanded to a position different from the stop position or the center lock position (such as the 10-30 degree advance position). The cam position and / or cam speed can be monitored during movement, for example, via a cam position sensor coupled to the cam. When the cam position and / or cam speed reaches a threshold, the low-pass filter acting on the PWM duty cycle can be activated. Alternatively, a timer can be used to activate the low-pass filter.However, if a timer is started, a conservative threshold can be chosen to ensure that the cam wheel is in a steady position when the filter is switched on. The low-pass filter can be, as a non-limiting example, an averaging filter, a moving average (FIR) filter, or an IIR filter. The low-pass filter can filter out the high-frequency components of the signal and can have a DC gain of one. Other types of filters can also be used. After a predetermined amount of filtering time, which may depend on the type and time constant of the chosen filter (e.g.,(The filtering time could be as low as 100 ms if an IIR filter is used, or could be 1 s or more if an FIR filter is used.) Once the filtering time has elapsed, the output of the low-pass filter can be retrieved and used as an input to determine a zero duty cycle value (DC_null value) which is fed into a model, lookup table, or algorithm to guide an estimated EOT (EOT_est), as discussed below.

[0065] Determining the zero duty cycle via Kalman filtering at 422 involves applying recursive least squares estimation (RLS) to fit the PWM duty cycle and cam speed measurements to an operator in a lookup table and then estimating the DC_null value from the lookup table. An RLS estimator can be used to obtain a 1-dimensional lookup table that maps cam speed to the PWM duty cycle. The lookup table can have at least two input breakpoints, and the input domain can cover a cam speed of zero. As a non-restrictive example, the input breakpoints can be selected as [-23 0 10.5] in [° / s], so the input domain covers a cam speed of zero.In this case, the entries of the lookup table can be estimated by the RLS estimator with a similar step cam position instruction as in the low-pass filtering method (from 420), and the entry corresponding to the cam speed of zero can provide an accurate estimate of the DC_null value, which can be used to derive EOT_est.

[0066] In the 424 procedure, this involves estimating the EOT using a mapping between the determined zero-duty cycle and the EOT. The calculated zero-duty cycle is passed through a mapping function, which may be a lookup table-based mapping or another functional relationship, to estimate the EOT. The zero-duty cycle-EOT mapping may be pre-calibrated, as described below. The mapping may be a pre-calibrated mapping that takes the estimated zero-duty cycle as an input and produces the estimated internal combustion engine oil temperature as an output.In one example, the associated relationship between the camshaft duty cycle, camshaft angular velocity, and internal combustion engine oil temperature in the full operating range of the internal combustion engine is available in the form of a lookup table or other mathematical relationship from a pre-calibration procedure performed in a test vehicle or test bench environment, with accurate internal combustion engine oil temperature measurements available.

[0067] As discussed above, the PWM voltage applied to the solenoid of the piston valve (the OCV) and the solenoid resistance are the two independent variables that control the angular velocity of the camshaft. However, since the battery voltage is known and the solenoid resistance is largely determined by the EOT, we can treat the duty cycle of PWM (DC) and EOT as the independent variables and form a mapping relationship to characterize the actuator according to equation (1) as follows: CAM SPEED = F(EOT,DC).

[0068] An inverse model with respect to EOT is characterized next, since the angular velocity of the cam gear is measurable via a cam position sensor and the PWM DC applied to the solenoid is known. The inverse model can be used to calculate the EOT using the applied PWM DC and the measured angular cam speed according to the following equation (2): EOTest=F−1(CAM SPEED,DC) where EOT est the estimated EOT is and F -1 the reverse model is applied in relation to the EOT.

[0069] As an example, the EOT estimation can be performed at a predefined cam speed to simplify the calculation and make it more practical for implementation. For example, if the cam speed is zero, the estimation can be reduced to equation (3) as follows: EOTest=Fnull−1(DCnull), where Fnull−1(X)=F−1(0,X), and DC null This is the zero-duty cycle (that is, the duty cycle produces zero angular velocity of the cam gear). It is understood that, although the procedure is based on Fig. 4. EOT is assigned based on an associated relationship to a zero duty cycle and a zero cam speed. In alternative examples, the assignment can be adapted (by adjusting the corresponding equations (1) - (3)) for any cam speed value within the bandwidth of the cam position sensor. In other words, equation (3) can be generalized so that it includes cam speeds other than zero within the bandwidth of the cam position sensor.

[0070] Fig. Figure 5 shows a zero cycle determination for assignment 500. In particular, the curves 502-508 from assignment 500 represent a zero cycle determination using both low-pass filtering and the Kalman method, as discussed in [reference]. Fig. 4 (at 422 and 424) represents a DC_null value for a 2014 Ford KA as a test vehicle with a 1.5-1-PFI-Sigma internal combustion engine with an internal combustion engine speed of 1500 min -1 to obtain. A duty cycle applied to an intake cam during an excitation pulse is shown in graph 502. A corresponding change in the cam angle is shown in graph 504. The zero duty cycle estimate based on the applied duty cycle and the measured change in the cam angle are shown in graph 506. An EOT derived from the estimated zero duty cycle via a defined mapping is shown in graph 508.

[0071] In the example from assignment 500, referring to traces 502-508, a step reference command of -10 degrees is applied to the intake cam gear at approximately t = 17 s, and both low-pass filtering and RLS algorithms are enabled near t = 25 s. A simple averaging filter is used for the low-pass filtering algorithm. For the RLS algorithm, a forgetting factor of 0.995 is used with an initial covariance matrix of 10*I, where I is the 3x3 identity matrix. Five seconds after the step reference command is applied, both algorithms are enabled, and estimates for the DC_null value are retrieved from each algorithm. In the example shown, the DC_null value, estimated via both low-pass and Kalman filtering, approaches 0.363. The associated EOT estimate is approximately 91 °F.

[0072] Focusing on the zero-work cycle approach, without limiting its general applicability, it is concluded from equation (3) that using the inverse model (Fnull−1) and with real-time knowledge of the DC zero duty cycle null the EOT control est can be calculated at any time during combustion engine operation.

[0073] The controller can perform the assigned inverse function. (Fnull−1) Modeling can be done using various approaches. Regardless of the approach used, it is possible to... Fnull−1 For simple implementation in embedded hardware, it can be modeled as a lookup table stored in the memory of the controller (such as in the KAM).

[0074] The various methods used to map the inverse function include a first method that builds upon existing calibration mappings in the controller's memory. For example, a first mapping relationship, "fnvct_rate2dc_base," might be an existing calibration mapping in the controller's memory that maps the EOT (end of rotation) and the cam angular velocity (or "rate") in a PWM duty cycle, where the cam rate is the same as the cam speed. This mapping may have been used to determine a cam response time and, during a diagnostic routine, to deduce whether a cam is functioning or faulty. Additionally, the mapping might also be used as a labeling table for the forward-coupled VCT controller to use in calculating a forward-coupled duty cycle.This table uses the VCT control function to calculate a forward-feed VCT duty cycle in response to a reference cam position command. The input to this table is the requested VCT change rate (or cam speed), calculated based on the difference between the actual cam position and the reference cam position, and the EOT (end of top dead center); the output is the forward-feed duty cycle to be applied to the solenoid.

[0075] This assignment can also be used to obtain Fnull−1 can be used. Assuming that fnvct_rate2dc_base is accurately calibrated and represents the actual response of the actuator, the entries of this mapping can be used to create a model. Fnull−1 to generate that exactly represents the EOT relationship set out in equation (3).

[0076] With brief reference to Fig. 6 is a non-restrictive example of creating a model of Fnull−1 shown using an existing mapping. It is a lookup table 600 “fnvct_rate2dc_base” to a lesser extent, which is in Fig. Figure 6 should be taken into account, assuming that it is calibrated to optimize the VCT control characteristic. The DC entries in the column associated with 0 cam rate (highlighted by the dashed block 602) can be used to determine a Fnull−1 to generate a lookup table, as shown in Table 620, which can be used for EOT estimation within the range [120, 180] °F. As an example, during vehicle operation, when DC nullThe estimated EOT of 126 °F is derived from Table 620 by underpolishing between adjacent table entries, as prescribed by well-known algebra in the field of lookup tables.

[0077] One advantage of using an existing mapping to model the inverse function is that it can be less computationally intensive and therefore easier to implement. Since this approach utilizes the calibration efforts already made to create the reference mapping (here, "fnvct_rate2dc_base"), it requires almost no calibration effort. However, it relies on the assumption that the calibration of fnvct_rate2dc_base accurately represents the OCV and, furthermore, on the even more restrictive assumption that fnvct_rate2dc_base exists primarily in the powertrain strategy. Conditions or situations may exist where the reference mapping is unavailable, inaccessible, or unreliable.

[0078] Now, an alternative data-driven approach to creating a lookup table model of Fnull−1 without using fnvct_rate2dc_base from the VCT feature. The data-driven approach can be applied during a vehicle's calibration phase (when other vehicle software is being calibrated). Additionally or optionally, the alternative approach can be extended to adaptively (e.g., in real time) build the lookup table during vehicle operation to correct initial calibration errors and switching time variations. The only required assumption for the data-driven approach is that the EOT during the acquisition of the data used to create the Fnull−1 used, accurately measured, or derived. That is, it can only be confirmed that none of the error modes (such as the EOT errors detected at 410) that affect the EOT measurements occur during the calibration of Fnull−1 applicable. For example, it may be confirmed that none of the following can affect EOT measurements during calibration: an ECT sensor fault, an ACT sensor fault, or a KAM control fault. If this assumption holds true, the creation Fnull−1 by selecting one or more DCs null -breakpoints for the lookup table are used. One or more DCs null Breakpoints, as well as the entries of the lookup table corresponding to these breakpoints, can be selected based on an optimization routine that provides the best fit of the lookup table for the collected data points, where the data points are measured EOT quantities provided by the aforementioned EOT measurement / derivation methods, and DC null -Values ​​that can be determined by using the low-pass filtering method or the RLS method, as described above.

[0079] An example of selecting one or more breakpoints is given with reference to assignment 1000. Fig. 10 shown.

[0080] For example, if 0.363 is considered a DC null -Stopping point for Fnull−1 chosen, which in Fig. The 5 profiles shown can be used to select the entry from the lookup table. Fnull−1 to fill in accordingly 0.363, which would result in this entry being selected as 91 degrees Celsius, as suggested by both low-pass filtering and RLS methods. Similar profiles can be applied at different EOTs to achieve a Fnull−1 -to fill out a lookup table that covers a large range of EOT, which can later be used in equation (3) for EOT estimation. It is understood that the input to the table is a zero duty cycle (such as the zero duty cycle breakpoints) and the output is an estimated EOT.

[0081] In relation to Fig. 6 is a model of a lookup table for Fnull−1, obtained by applying EOT holding points, shown in Table 630. The holding points were chosen as [100, 120, 140, 160, 175, 185, 190, 195] °F. The vehicle was run at a crankshaft speed of 1500 rpm for approximately 30 minutes. -1 left idling and the step-by-step excitation profile similar to that found in Fig. The method shown in Figure 5 was applied near the breakpoint temperatures to obtain the corresponding DC_null entries.

[0082] With renewed reference to Fig. 4. The controller can adjust one or more internal combustion engine torque actuators based on the estimated EOT (Electro-Off Time). For example, the controller can compare the estimated EOT with upper and lower threshold values ​​and, based on this comparison, select an internal combustion engine torque actuator, as well as the quantity and direction for adjusting the selected torque actuator. As an example, in response to the estimated EOT being higher than an upper threshold, an internal combustion engine output may be limited, boost pressure may be limited, and / or internal combustion engine torque delivered in response to an operator torque request may be limited. As another example, an internal combustion engine idle speed may be limited to reduce internal combustion engine overheating.As another example, upper and lower limits of internal combustion engine speed within a permissible internal combustion engine speed range may be restricted (e.g., by reducing the upper threshold of the internal combustion engine speed and / or raising the lower threshold of the internal combustion engine speed) if the EOT is too low or too high in order to protect the internal combustion engine from extreme temperature conditions.

[0083] Next, at point 428, it can be determined whether a one-time EOT estimate is required or whether continuous EOT monitoring is necessary. This can be based on the EOT fault that triggered the alternative EOT estimation, as well as on the combustion engine parameter that is controlled based on the EOT estimate. As an example, a one-time EOT estimate may be required to provide robustness against potential signal loss due to a KAM fault (e.g., KAM damage) or low reliability of a functional ECT sensor during warm start conditions. In this case, the controller can select the procedure from point 428. Fig. 4. Execute only once, precisely after a warm start of the combustion engine, where a significant temperature difference may exist between the ECT temperature and the EOT temperature. As another example, continuous EOT estimation may be required to provide robustness against a potential loss of sensor signal during vehicle operation due to a permanent sensor fault, such as ACT sensor or KAM sensor interference. In this case, the control unit can execute the procedure continuously or repeatedly as long as the corresponding sensor fault (or the EOT fault flag) is set.

[0084] If a one-time estimate is required, the controller can update the EOT estimate at 430, and the routine will end. Another derivation of the routine can only be triggered if an EOT estimate is required and EOT errors have been determined, as discussed above in 404 and 410.

[0085] If continuous estimation is required, the controller can execute the routine continuously and keep the EOT estimate up-to-date after each derivation of the routine.

[0086] Since the excitation profile applied to the intake or exhaust cam can overlap with VCT operation itself, even briefly at 432 in continuous mode, the controller can pause the routine and start a timer. Starting the timer allows the routine to be paused only for a predetermined period. The length of this pause can be defined by a predetermined time threshold. At 434, it can be determined whether the predetermined time threshold has been reached since the timer was started. If not, the controller can wait for the predetermined time threshold to expire. Otherwise, if the predetermined time threshold for the timer has expired, the routine returns to 408 and starts monitoring the relevant fault flags that indicate EOT errors. The routine then repeats.

[0087] This allows for a more reliable EOT estimate, particularly when selected fault codes are set. Specifically, because the determined EOT estimate, based on the associated relationship between solenoid duty cycle and cam movement, does not rely on sensors such as the ECT sensor, the MAF sensor, the ACT sensor, or any variables stored in the KAM, the method can be more robust with respect to sensor failures, KAM damage, and unreliability during warm-start conditions of the internal combustion engine.

[0088] It goes without saying that, although the procedure is made up of Fig. The fact that Figure 4 shows that the EOT is estimated via the associated relationship between VCT solenoid duty cycle, VCT angular velocity, and internal combustion engine oil temperature in response to a fault flag (indicating a fault in an EOT sensor, MAF sensor, ECT sensor, ACT sensor, and / or KAM) is not to be interpreted as restrictive. In other examples, the EOT may be estimated via the associated relationship in response to a fault in any internal combustion engine component generally used in EOT estimation. Furthermore, EOT estimation via the associated relationship may be used as a primary or standard procedure for EOT estimation, reducing sensor dependency (e.g., reducing the need for an EOT sensor).In other examples, the EOT estimation via the mapping relationship can be used to confirm the sensor-based EOT estimation, or vice versa, where the mapping relationship is the standard procedure for EOT estimation and the sensor-based EOT estimation can be used to confirm the mapping-based approach. In still other examples, both the sensor-based EOT estimation and the mapping-based estimation can be used, with the weighting of each approach varying based on the internal combustion engine operating conditions. For example, the weighting of the sensor-based approach might be increased during a cold start of the internal combustion engine, while the weighting of the mapping-based approach might be increased during a warm start of the internal combustion engine.

[0089] Fig. Figure 7 shows an EOT estimate during a cold start of the internal combustion engine at mapping 700. In particular, curves 702-708 from mapping 700 represent a zero-cycle determination via Kalman filtering to obtain DC_null values ​​on a test vehicle with a 1.5-1 PFI internal combustion engine. A duty cycle applied to an intake cam during an excitation pulse is shown in curve 702 (actual duty cycle applied, represented by line 710, versus reference command, represented by line 712). A corresponding change in cam angle is shown in curve 704. The zero-work cycle estimate based on the applied duty cycle and the measured change in cam angle are shown in curve 706. An EOT derived from the derived zero-work cycle via a defined mapping is shown in curve 708.

[0090] In the example from assignment 700, a vehicle is cold-started and runs at idle speed for approximately 10 minutes until the EOT reaches approximately 125°F. Data is then recorded while a step reference command of -10 degrees is applied to the intake cam gear, as shown with reference to graph 702. Approximately 10 seconds after the step reference command, the RLS zero-duty-cycle estimation algorithm is activated, and EOT estimates are subsequently determined by applying equation (3). The RLS algorithm uses a forgetting factor of 0.995 with an initial covariance matrix of 10*I, where I is the 3x3 identity matrix. 5 seconds after applying the algorithms, estimates for the DC_null value are retrieved. Fnull−1 -Lookup table, previously at 630 Fig. The EOT described in section 6 is also generated. Referring to graph 708, the estimated EOT at standby start (solid line / red line), as determined via the sensorless filtering and data-driven approach discussed above, converges to the derived EOT (dashed line / blue line), determined via the EOT derivation logic that uses the KAM variables for initialization and the onboard ACT and ECT sensors after initialization.

[0091] Fig. Figure 8 shows an EOT estimate during a warm start of the internal combustion engine at mapping 800. In particular, curves 802-808 from mapping 800 represent a zero-cycle determination via Kalman filtering to obtain a DC_null value for a test vehicle with a 1.5-1 PFI internal combustion engine. A duty cycle applied to an intake cam during an excitation pulse is shown in curve 802. A corresponding change in the cam angle is shown in curve 804. The zero-work cycle estimate based on the applied duty cycle and the measured change in the cam angle are shown in curve 806. An EOT derived from the estimated zero-work cycle via a defined mapping is shown in curve 808.

[0092] According to the allocation that is in Fig. As shown in Figure 7, the internal combustion engine was off for approximately 5 minutes before the restart. During the restart, a KAM fault is determined to have occurred, triggering an EOT fault code. This causes the derived EOT calculation logic to start with an incorrect initial condition. As a result, the derived EOT value is approximately 77°F at the time of the vehicle restart. This value is inaccurate because the internal combustion engine oil temperature cannot have cooled by more than 50°F within 5 minutes (the outside temperature was approximately 65°F). Furthermore, since the internal combustion engine coolant temperature was measured at 196°F when the engine was off and at 188°F when the engine was restarted, the EOT is expected to actually increase during the initial minutes of the engine being off.Referring to traces 802-808, a 10-degree step reference command is applied to the VCT intake cam gear approximately 10 seconds after the vehicle restarts, and the EOT estimation algorithm is activated shortly thereafter. The estimated EOT converges to approximately 143 degrees in about 5 seconds, which is a plausible value given an expected oil temperature increase of about 10 degrees over 5 minutes in an environment where the internal combustion engine coolant temperature is approximately 190°F. This example provides validation for the described derivation-based approach and demonstrates a potential use for the algorithm to replace the initial value of the derived EOT logic with the estimate determined based on the EOT mapping during a warm start by executing a rapid estimation profile in the first few seconds of idle time after the internal combustion engine starts.Referring to curve 808, the curve shown with a solid line (blue) is the derived EOT, which is the existing EOT signal generated by the ACT and ECT sensors.

[0093] Specifically, the internal combustion engine restarts after approximately 5 minutes of cooldown period, and during the restart, a fault in the keep-alive memory (KAM) causes the controller to initiate the EOT derivation logic from an incorrect initial condition. As a result, the derived EOT value is approximately 80°F throughout the run. Since the last derived EOT before the engine shut down was 130°F, and the internal combustion engine coolant temperature is approximately 190°F, the EOT is expected to actually increase during the brief cooldown period. The current EOT estimation algorithm results in an estimated EOT of 143°F after the engine restarts, which is as expected.

[0094] In a continuation of this experiment, the algorithm according to the invention for EOT estimation and the previous / existing algorithm for EOT derivation at assignment 900 from Fig. 9. In particular, the recorded EOT data are shown in graphs 902-906. Data were collected at the time points corresponding to the square symbols. The lines between the squares are generated by linear interpolation and do not correspond to the actual data values. The internal combustion engine was allowed to idle for a few minutes until the inferred EOT reached 100 °F (corresponding to t=0). Then, EOT estimates were collected at specific time points up to approximately t = 200 seconds using the mapping-based approach discussed herein. The internal combustion engine was then switched off and allowed to cool for approximately 510 seconds before being restarted. After restarting, the collection of estimated and inferred EOT values, as well as the measured ECT values, was resumed.During the internal combustion engine restart, the same / above-described KAM error caused the previous / existing derived EOT algorithm to start with an erroneous initial value of approximately 80°F. As used herein, derived EOT refers to the existing original EOT algorithm, which represents the previous EOT algorithm running on the test vehicle. This is called derived because it uses ACT / ECT sensors (rather than an EOT sensor) to calculate an EOT value. On the other hand, estimated EOT refers to the EOT estimated via the mapping of the present disclosure. It is observed that the derived EOT and the estimated EOT are nearly identical until the internal combustion engine is turned off. After restarting, the difference between the estimated EOT and the derived EOT is large due to the KAM error.The existing algorithm for EOT derivation is flawed due to the KAM error, whereas the EOT estimates provided by the mapping of the present disclosure remain plausible based on the off-time (or cool-down time) of the internal combustion engine, the EOT value before the engine shut-off, and the ECT value before and after the engine shut-off, demonstrating the accuracy of the mapping. In particular, since the EOT estimation via the mapping does not require KAM parameters and ECT / ACT sensors, the estimate is immune to any type of error mode occurring in these components, which is relevant for a given KAM error mode. Fig. 9 is validated. Since the impact of initialization errors on the existing EOT derivation logic diminishes over time, the derived EOT algorithm becomes more accurate with increasing time, and the associated EOT estimation algorithm and the earlier EOT derivation algorithm appear to converge closely over time, as in Fig. 9 shown.

[0095] In this way, during a cold start condition, an internal combustion engine control unit can estimate the combustion engine oil temperature based on each of the measured combustion engine coolant temperature, the measured ambient temperature, and the measured charge air temperature (or measure the combustion engine oil temperature directly via a dedicated sensor). In contrast, during a warm start condition, the control unit can estimate the combustion engine oil temperature based on an associated relationship between the solenoid duty cycle of a piston valve in a variable camshaft timing device, the angular velocity of a cam actuated by the piston valve, and the combustion engine oil temperature.For example, during the warm start condition of the internal combustion engine, the engine oil temperature can be estimated based on the associated relationship for an initial duration since the first combustion event of the warm start. After this initial duration, the engine oil temperature can be estimated based on each of the measured engine coolant temperature, ambient temperature, and charge air temperature. For the initial duration, the engine oil temperature can be estimated independently of the measured engine coolant temperature, ambient temperature, and charge air temperature.Furthermore, during a warm start condition, the control unit can set the solenoid duty cycle applied to the piston valve to move the cam from its current position to a final position outside of a locked position, and measure the angular velocity via a position sensor coupled to the cam after the solenoid duty cycle has been applied. As an example, mapping during a warm start can involve estimating a zero duty cycle of the piston valve based on the set solenoid duty cycle and the measured angular velocity; and estimating the combustion engine oil temperature by routing the estimated zero duty cycle value through a mapping relationship between the zero duty cycle and the combustion engine oil temperature. In this way, the accuracy of the EOT estimation can be improved with reduced dependence on existing sensors.The technical effect of exploiting the dependence of the combustion engine oil temperature on the solenoid resistance of a VCT piston valve (or OCV) can be experienced. A defined mapping between the PWM duty cycle (DC) applied to the piston valve's solenoid and the camshaft angular velocity can be explored. By characterizing this mapping through the application of a known PWM duty cycle signal and measuring the resulting camshaft angular velocity, the EOT can be derived without requiring dedicated sensors. Building upon this mapping, EOT estimation can be performed even when standard EOT estimation sensors (such as an ECT sensor, an ACT sensor, or an EOT sensor) are compromised, and during conditions where sensor output is unreliable, such as during hot engine starts or when a control memory is damaged.Improving the EOT estimation improves the internal combustion engine torque control.

[0096] An exemplary internal combustion engine method comprises the following: adjusting an internal combustion engine torque actuator based on internal combustion engine oil temperature, estimated by applying an excitation signal, comprising a pulse-width modulated duty cycle, voltage and electric current, to a solenoid valve of a variable cam control device, and using an associated relationship, stored in non-volatile memory, that relates the camshaft solenoid duty cycle and camshaft angular velocity of the device to the internal combustion engine oil temperature.In the preceding example, the adjustment additionally or optionally occurs in response to degradation of a sensor used to directly or indirectly measure the internal combustion engine oil temperature, and damage to the non-volatile memory, wherein the non-volatile memory comprises a keep-alive memory of an internal combustion engine control unit, and wherein the sensor comprises one or more of an internal combustion engine oil temperature sensor coupled to an oil pan, an internal combustion engine coolant temperature sensor, an air charge temperature sensor, and an air mass flow sensor. In any or all of the preceding examples, the adjustment additionally or optionally occurs in response to a warm start condition of the internal combustion engine.In any or all of the preceding examples, the applied duty cycle additionally or optionally moves the intake and exhaust cams outside of a stop position. In any or all of the preceding examples, estimating internal combustion engine oil temperature further includes, additionally or optionally: estimating a zero duty cycle of the piston valve solenoid by low-pass or Kalman filtering of the applied duty cycle, wherein the zero duty cycle includes a duty cycle quantity that results in zero angular velocity for the VCT device outside of a stop or pin-lock position; and estimating the internal combustion engine oil temperature via a pre-calibrated mapping that takes the estimated zero duty cycle as input and produces the estimated internal combustion engine oil temperature as output.In any or all of the preceding examples, applying an excitation signal additionally or optionally includes: applying a stepwise increasing duty cycle, voltage, or electrical current to the solenoid and measuring the camshaft angular velocity after each stepwise increase. In any or all of the preceding examples, applying the excitation signal additionally or optionally includes: applying, via a closed-loop controller, a reference angular position command to vary the angular velocity of a camshaft of the device, and measuring the camshaft angular velocity and a result of the duty cycle, voltage, and electrical current applied to the solenoid by the closed-loop controller.In any or all of the preceding examples, adjusting the internal combustion engine torque actuator based on the estimated internal combustion engine oil temperature additionally or optionally involves limiting one or more of the internal combustion engine torque, engine speed, and boost pressure outputs in response to the derived internal combustion engine oil temperature exceeding a temperature threshold. In any or all of the preceding examples, the variable camshaft control device uses an oil control solenoid actuator.

[0097] Another exemplary method comprises the following: during a cold start condition of an internal combustion engine, estimating an internal combustion engine oil temperature based on each of the measured internal combustion engine coolant temperature, measured ambient temperature, and measured air charge temperature; and during a warm start condition of an internal combustion engine, estimating the internal combustion engine oil temperature based on an associated relationship between the solenoid coil duty cycle of a piston valve of a variable cam control device, an angular velocity of a cam actuated by the piston valve, and the internal combustion engine oil temperature.In the preceding example, additionally or optionally, during the warm start condition of the internal combustion engine, the engine oil temperature is estimated based on the associated relationship for an initial duration since the first combustion event of the warm start, and after the initial duration, the engine oil temperature is estimated based on each of the measured engine coolant temperature, ambient temperature, and charge air temperature. In one or all of the preceding examples, additionally or optionally, for the initial duration, the engine oil temperature is estimated independently of the measured engine coolant temperature, ambient temperature, and charge air temperature.In one or all of the preceding examples, additionally or optionally, the method further comprises the following during a warm start condition: setting the solenoid duty cycle applied to the piston valve to move the cam from a current position to a final position outside of a locked position; and measuring the angular velocity via a position sensor coupled to the cam after the application of the solenoid duty cycle.In any or all of the preceding examples, the mapping during warm start additionally or optionally includes: estimating a piston valve zero duty cycle based on the set solenoid duty cycle and the measured angular velocity; and estimating the internal combustion engine oil temperature by passing the estimated zero duty cycle value through a mapped relationship between the zero duty cycle and the internal combustion engine oil temperature.

[0098] An exemplary internal combustion engine system may include a variable camshaft timing (VCT) device comprising a cam, a camshaft adjuster, a camshaft, a piston valve and a solenoid; a cam position sensor coupled to the cam; a battery; an internal combustion engine coolant temperature sensor; an intake air charge temperature sensor; an air mass flow sensor; and a controller.The control system may include computer-readable instructions stored in non-volatile memory for the following: in response to at least one diagnostic flag being set with respect to estimating internal combustion engine oil temperature, applying an excitation pulse to the solenoid to move the piston valve, with one duty cycle of the excitation pulse being set to move the cam outside a stop region; measuring an angular velocity of the camshaft after application via the cam position sensor; estimating a zero duty cycle of the solenoid valve based on the applied duty cycle; and estimating an internal combustion engine oil temperature based on an associated relationship between the estimated zero duty cycle and the measured angular velocity.In the preceding example, the control may additionally or optionally include instructions to limit each of an upper and a lower internal combustion engine speed threshold based on the estimated internal combustion engine oil temperature, with the upper internal combustion engine speed threshold being decreased and the lower internal combustion engine speed threshold being increased when the estimated internal combustion engine oil temperature exceeds a temperature threshold. In any or all of the preceding examples, additionally or optionally, at least one diagnostic flag related to the estimated internal combustion engine oil temperature is set in response to one of the following conditions: degradation of the internal combustion engine coolant temperature sensor, degradation of the intake air temperature sensor, degradation of the mass airflow sensor, memory damage, and an internal combustion engine warm start condition.In any or all of the preceding examples, additionally or optionally, the associated relationship is stored in the memory and uses a last estimated internal combustion engine oil temperature, the estimated zero duty cycle, and the measured angular velocity as inputs. In any or all of the preceding examples, additionally or optionally, the cam is one of an intake cam and one exhaust cam, the memory is a keep-alive memory, and the zero duty cycle includes a duty cycle quantity that results in zero angular velocity for the VCT device outside of a stop or pin-lock position.In any or all of the preceding examples, additionally or optionally, the controller includes further instructions in response to the fact that no diagnostic flag related to estimating the internal combustion engine oil temperature is set, estimating the internal combustion engine oil temperature based on an output from one or more of the internal combustion engine coolant temperature sensor, the intake air charge temperature sensor, and the mass airflow sensor.

[0099] In another embodiment, a method for an internal combustion engine comprises: applying an excitation signal to a solenoid valve of a variable camshaft timing (VCT) device; estimating an internal combustion engine oil temperature from an associated relationship stored in non-volatile memory that relates the camshaft solenoid duty cycle and camshaft angular velocity of the VCT device to the internal combustion engine oil temperature; and adjusting an internal combustion engine torque actuator based on the estimated internal combustion engine oil temperature. In the preceding example, additionally or optionally, the VCT device is oil pressure actuated. In yet another embodiment, the internal combustion engine is coupled in a hybrid electric vehicle system.

[0100] It should be noted that the exemplary control and estimation routines contained herein can be used with various internal combustion engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-volatile memory and can be executed by the control system, which includes the control unit in combination with the various sensors, actuators, and other internal combustion engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Similarly, the processing sequence is not strictly necessary to achieve the features and advantages of the embodiments described here, but is provided for easier illustration and description. One or more of the illustrated actions, operations, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, operations, and / or functions can graphically represent code to be programmed in the non-volatile memory of the computer-readable storage medium within the internal combustion engine control system. The described actions are performed by executing the instructions in a system that includes the various internal combustion engine hardware components in combination with the electronic control unit.

[0101] It is understood that the configurations and routines disclosed herein are exemplary and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the foregoing technology can be applied to V-6, I-4, I-6, V-12, 4-cylinder boxer, and other types of internal combustion engines. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0102] The following claims highlight certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more such elements, without requiring or excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application.Such patent claims, regardless of whether they have a broader, narrower, the same or a different scope of protection compared to the original patent claims, are also considered to be included in the subject matter of the present disclosure.

[0103] According to the present invention, an internal combustion engine method is provided; adjusting an internal combustion engine torque actuator based on the internal combustion engine oil temperature, estimated by applying an excitation signal, comprising a pulse-width modulated duty cycle, a voltage and an electric current, to a solenoid valve of a variable cam control device, and using an associated relationship, stored in non-volatile memory, which relates the camshaft solenoid coil duty cycle and camshaft angular velocity of the device to the internal combustion engine oil temperature.

[0104] According to one embodiment, the adjustment occurs in response to degradation of a sensor used to measure the internal combustion engine oil temperature directly or indirectly, and damage to the non-volatile memory, wherein the non-volatile memory includes a keep-alive memory of an internal combustion engine control unit, and wherein the sensor includes one or more of an internal combustion engine oil temperature sensor coupled to an oil pan, an internal combustion engine coolant temperature sensor, an air charge temperature sensor, and an air mass flow sensor.

[0105] According to one embodiment, the adjustment occurs in response to a warm start condition of an internal combustion engine.

[0106] According to one embodiment, the applied working cycle moves one of the inlet and outlet cams outside a stop position.

[0107] According to one embodiment, estimating the internal combustion engine oil temperature further includes: estimating a zero duty cycle of the piston valve solenoid coil by low-pass or Kalman filtering of the applied duty cycle, wherein the zero duty cycle includes a duty cycle quantity that results in zero angular velocity for the VCT device outside of a stop or pin-lock position; and estimating the internal combustion engine oil temperature via a pre-calibrated mapping that takes the estimated zero duty cycle as input and produces the estimated internal combustion engine oil temperature as output.

[0108] According to one embodiment, applying an excitation signal involves: applying a stepwise increasing duty cycle, voltage or electric current to the magnetic coil and measuring the camshaft angular velocity after each stepwise increase.

[0109] According to one embodiment, applying the excitation signal includes the following: applying, via a closed-circuit controller, a reference angle position command to vary the angular velocity of the camshaft, and measuring the camshaft angular velocity and a duty cycle, voltage, and electrical current applied to the solenoid by the closed-circuit controller.

[0110] According to one embodiment, adjusting the internal combustion engine torque actuator based on the estimated internal combustion engine oil temperature involves limiting one or more of the internal combustion engine torque, internal combustion engine speed, and boost pressure outputs in response to the derived internal combustion engine oil temperature being higher than a temperature threshold.

[0111] According to one embodiment, the device for variable camshaft control uses a magnetic oil control actuator.

[0112] According to the present invention, a method is provided for estimating the combustion engine oil temperature during a cold start condition of an internal combustion engine based on each of the measured combustion engine coolant temperature, measured ambient temperature, and measured air charge temperature; and for estimating the combustion engine oil temperature during a warm start condition of an internal combustion engine based on an associated relationship between the solenoid coil duty cycle of a piston valve of a variable cam control device, an angular velocity of a cam actuated by the piston valve, and the combustion engine oil temperature.

[0113] According to one embodiment, during the warm start condition of the internal combustion engine, the internal combustion engine oil temperature is estimated based on the associated relationship for a first duration since a first combustion event since the internal combustion engine warm start, and after the first duration, the internal combustion engine oil temperature is estimated based on a combination of measured internal combustion engine coolant temperature, measured ambient temperature and / or measured air charge temperature.

[0114] According to one embodiment, for the first duration the combustion engine oil temperature is estimated independently of the measured combustion engine coolant temperature, the measured ambient temperature and the measured air charging temperature.

[0115] According to one embodiment, the invention is further characterized by the following: during a warm start condition, setting the solenoid coil duty cycle applied to the piston valve to move the cam from a current position to a final position outside a fixed locking position; and measuring the angular velocity via a position sensor coupled to the cam after the application of the solenoid coil duty cycle.

[0116] According to one embodiment, the mapping during warm start includes: estimating a zero-duty cycle of the piston valve based on the set solenoid coil duty cycle and the measured angular velocity; and estimating the internal combustion engine oil temperature by passing the estimated zero-duty cycle value through a mapped relationship between the zero-duty cycle and the internal combustion engine oil temperature.

[0117] According to the present invention, an internal combustion engine system is provided comprising: a variable cam control (VCT) device comprising a cam, a camshaft adjuster, a camshaft, a piston valve, and a solenoid; a cam position sensor coupled to the cam; a battery; an internal combustion engine coolant temperature sensor; an intake air charge temperature sensor; an air mass flow sensor; and a controller comprising computer-readable instructions stored on non-volatile memory for: in response to at least one diagnostic flag being set with respect to estimating internal combustion engine oil temperature, applying an excitation pulse to the solenoid to move the piston valve, wherein one duty cycle of the excitation pulse is set to move the cam outside a stop region;Measuring the angular velocity of the camshaft after application via the cam position sensor; estimating the zero duty cycle of the coil valve based on the applied duty cycle; and estimating the combustion engine oil temperature based on an associated relationship between the estimated zero duty cycle and the measured angular velocity.

[0118] According to one embodiment, the control further includes instructions for the following: limiting each of an upper and a lower internal combustion engine speed threshold based on the estimated internal combustion engine oil temperature, wherein the upper internal combustion engine speed threshold is decreased and the lower internal combustion engine speed threshold is increased when the estimated internal combustion engine oil temperature exceeds a temperature threshold.

[0119] According to one embodiment, at least one diagnostic flag is set in response to degradation of the combustion engine coolant temperature sensor, degradation of the intake air charge temperature sensor, degradation of the mass airflow sensor, damage to the memory, and a combustion engine warm start condition.

[0120] According to one embodiment, the associated relationship is stored in the memory and uses a last estimated combustion engine oil temperature, the estimated zero duty cycle, and the measured angular velocity as inputs.

[0121] According to one embodiment, the cam is a combination of an inlet cam and an outlet cam, the memory is a keep-alive memory, and the zero duty cycle includes a duty cycle quantity that results in zero angular velocity for the VCT device outside of a stop or pin-lock position.

[0122] According to one embodiment, the control includes further instructions for the following: in response to the fact that no diagnostic flag related to estimating the internal combustion engine oil temperature is set, estimating the internal combustion engine oil temperature based on an output from one or more of the internal combustion engine coolant temperature sensor, the intake air charge temperature sensor, and the mass airflow sensor.

Claims

[1] Internal combustion engine processes, comprising: Setting an internal combustion engine torque actuator based on the internal combustion engine oil temperature (EOT), estimated by applying an excitation signal, comprising a pulse-width modulated duty cycle, a voltage and an electric current, applied to a solenoid valve (OCV) of a variable cam control (VCT) device, and using an associated relationship stored in non-volatile memory (110) that controls the camshaft solenoid duty cycle and relates the camshaft angular velocity of the device to the combustion engine oil temperature (EOT), wherein the adjustment is made in response to degradation of a sensor used to measure the combustion engine oil temperature (EOT) directly or indirectly, and damage to the non-volatile memory (110), wherein the non-volatile memory (110) includes a keep-alive memory (KAM) of a combustion engine control unit (12), wherein the sensor includes one or more of an combustion engine oil temperature sensor (EOT) coupled to an oil pan, a combustion engine coolant temperature sensor (ECT), an air charge temperature sensor (ACT), and a mass airflow sensor (MAF). [2] Method according to claim 1, wherein the adjustment is performed in response to an internal combustion engine warm start condition. [3] Method according to claim 1, wherein the applied working cycle moves one of the inlet and outlet cams outside a stop position. [4] The method of claim 1, wherein estimating the internal combustion engine oil temperature (EOT) further comprises: Estimating a zero duty cycle of the piston valve (309) by low-pass or Kalman filtering of the applied duty cycle, wherein the zero duty cycle includes a duty cycle quantity that results in zero angular velocity for the VCT device (VCT) outside of a stop or pin-lock position; and Estimating the internal combustion engine oil temperature (EOT) via a pre-calibrated mapping that uses the estimated zero duty cycle as input and produces the estimated internal combustion engine oil temperature (EOT) as output. [5] Method according to claim 1, wherein applying an excitation signal includes: Applying a stepwise increasing duty cycle, voltage or electric current to the magnetic coil (307) and measuring the camshaft angular velocity after each stepwise increase. [6] Method according to claim 1, wherein applying the excitation signal includes: Applying, via a closed-circuit control, a reference angle position command to vary the angular velocity of the camshaft, and measuring the camshaft angular velocity and one of the duty cycle, voltage and electrical current applied to the solenoid coil (307) by the closed-circuit control. [7] Method according to claim 1, wherein adjusting the internal combustion engine torque actuator based on the estimated internal combustion engine oil temperature (EOT) includes limiting one or more of an internal combustion engine torque, an internal combustion engine speed (RTM) and a boost pressure output of the internal combustion engine in response to the derived internal combustion engine oil temperature (EOT) being higher than a temperature threshold. [8] Method according to claim 1, wherein the device for variable camshaft control uses a magnetic oil control actuator. [9] Internal combustion engine system, comprising: a variable cam control (VCT) device comprising a cam, a camshaft adjuster, a camshaft, a piston valve (309) and a solenoid coil (307); a cam position sensor that is coupled to the cam; a battery (218); an internal combustion engine coolant temperature sensor (ECT); an intake air temperature sensor; an air mass flow sensor (MAF); and a control, including computer-readable instructions stored on non-volatile memory (110) for the following: in response to the fact that at least one diagnostic flag relating to estimation of internal combustion engine oil temperature (EOT) is set, Applying an excitation pulse to the solenoid coil (307) to move the piston valve (309), wherein one working cycle of the excitation pulse is set to move the cam outside a stop region; Measuring the angular velocity of the camshaft after application via the cam position sensor; Estimating a zero duty cycle of the coil valve based on the applied duty cycle; and Estimating an internal combustion engine oil temperature (EOT) based on an associated relationship between the estimated zero-duty cycle and the measured angular velocity. [10] System according to claim 9, wherein the control further includes instructions for the following: Limiting each of an upper and a lower internal combustion engine speed threshold based on the estimated internal combustion engine oil temperature (EOT), wherein the upper internal combustion engine speed threshold is decreased and the lower internal combustion engine speed threshold is increased when the estimated internal combustion engine oil temperature (EOT) exceeds a temperature threshold. [11] System according to claim 9, wherein the at least one diagnostic flag related to the estimation of the internal combustion engine oil temperature (EOT) is set in response to one of the following: degradation of the internal combustion engine coolant temperature sensor (ECT), degradation of the intake air charge temperature sensor, degradation of the mass airflow sensor (MAF), damage to the memory and an internal combustion engine warm start condition. [12] System according to claim 9, wherein the associated relationship is stored in the memory and uses a last estimated combustion engine oil temperature (EOT), the estimated zero duty cycle and the measured angular velocity as inputs. [13] System according to claim 9, wherein the cam is one of an inlet cam and an outlet cam, the memory is a keep-alive memory (KAM) and the zero duty cycle includes a duty cycle quantity that results in zero angular velocity for the VCT device (VCT) outside of a stop or pin locking position. [14] System according to claim 9, wherein the control further includes instructions for the following: In response to the fact that no diagnostic flag related to estimating the engine oil temperature (EOT) is set, estimating the engine oil temperature (EOT) is based on an output from one or more of the engine coolant temperature (ECT) sensor, the intake air charge temperature sensor, and the mass airflow (MAF) sensor.

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