Method and system for adjusting camshafts

Abstract

Engine operating procedures, comprising: Rotating a first engine via an electric motor and finding a camshaft angle of the first engine, wherein an intake manifold pressure is a minimum value, while no fuel is supplied to the first engine; adjusting a first camshaft position of the first engine by means of a controller in response to an error between a predetermined camshaft position of a second engine and the camshaft angle of the first engine at which the intake manifold pressure is the minimum value; and Moving a camshaft of the first engine to the set first camshaft position by means of the controller.

Description

Area

[0001] The present description relates to methods and a system for operating a powertrain including an engine with variable valve timing. The methods and systems may be particularly useful for hybrid vehicles including an engine and a belt-integrated starter / generator and / or a motor / generator. Background and brief description

[0002] An internal combustion engine may incorporate adjustable intake camshafts and / or adjustable exhaust camshafts. The adjustability of the intake camshafts and exhaust camshafts offers opportunities to improve engine performance, emissions, and fuel efficiency. However, if the camshafts are not positioned correctly, the benefits of variable valve timing cannot be fully realized. Variations in the manufacturing of camshafts and camshaft actuators can lead to camshaft positioning errors. Furthermore, the installation of camshafts and camshaft actuators in an engine can lead to camshaft positioning errors.If an engine control system is programmed with desired camshaft positions based on the operation of a development engine, and if the camshafts and camshaft actuators of a production engine are positioned differently than the camshafts and camshaft actuators of the development engine when aligned to the same position, then the performance, emissions, and fuel efficiency of the production engine may deteriorate. Thus, it would be desirable to provide a way to correct intake and exhaust camshaft positioning errors.

[0003] The document DE 10 2016 216 652 A1 discloses a method, a control device and a system for detecting a deviation of an actual actuation time of a gas exchange valve of an internal combustion engine from a predetermined actuation time.

[0004] The document DE 10 2015 209 665 B4 discloses a method for identifying valve timing of an internal combustion engine.

[0005] The inventors of this application have recognized the above-mentioned disadvantages and developed an engine operating method comprising: adjusting a first camshaft position of a first engine by means of a controller in response to an error between a predetermined camshaft position of a second engine and a second camshaft position of the first engine; and moving a camshaft of the first engine to the adjusted first camshaft position by means of the controller.

[0006] By adjusting a first camshaft position of a first engine in response to an error between a predetermined camshaft position of a second engine and a second camshaft position of the first engine, it may be possible to provide the technical result of adjusting the camshaft timing of the first engine to match the camshaft timing of the second engine, so that the performance, emissions, and fuel efficiency of the first engine more closely match the performance, emissions, and fuel efficiency of the second engine. For example, camshaft timings that provide desired performance, emissions, and fuel efficiency for the second engine may be stored in a memory of a controller of the first engine.The camshaft timings stored in memory can be adjusted based on a camshaft angle at which the intake manifold pressure of the first engine is at a minimum. The crankshaft angle at which the intake manifold pressure for the first engine is at a minimum is compared to the crankshaft angle at which the intake manifold pressure for the second engine is at a minimum. The camshaft timings stored in memory are adjusted based on the comparison. In this way, the camshaft timing of one engine can be matched to the camshaft timing of another engine, even if some manufacturing variance exists in the engine system.

[0007] The present description can offer several advantages. For example, the approach can improve vehicle performance, fuel efficiency, and emissions. Furthermore, the approach can reduce variations in performance, fuel efficiency, and emissions within a vehicle group. Furthermore, the approach can be implemented in a vehicle on the road or in a manufacturing or testing facility.

[0008] The above advantages and other advantages and features of the present description will be readily apparent from the following Detailed Description taken alone or in conjunction with the accompanying drawings.

[0009] It should be understood that the foregoing summary is provided to introduce, in a simplified manner, a selection of concepts that are further described in the detailed description. It is not intended to identify central or essential features of the claimed subject matter, the scope of which is defined solely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Brief description of the drawings

[0010] The advantages described herein will be more fully appreciated by reading an example of an embodiment, referred to herein as the detailed description, when considered alone or with reference to the drawings, in which: Fig. 1 is a schematic diagram of an engine; Fig. 2 a schematic representation of a power transmission of a hybrid vehicle; Fig. 3A and Fig. 3B show example graphs of engine intake manifold pressure versus exhaust camshaft position; Fig. 4 shows a block diagram of a camshaft positioning system; and Fig. 5 describes a method for adjusting the camshaft timing. Detailed description

[0011] This description relates to adjusting the camshaft timing of an engine of a vehicle. The engine may include intake camshafts and exhaust camshafts, as described in Fig. 1. The engine may be included in a drive train of a hybrid vehicle, as shown in Fig. 2. The intake manifold pressure of the engine over a range of camshaft positions can be expressed as a curve as shown in Fig. 3A and Fig. 3B. The camshafts can be operated by means of a control system as shown in Fig. 4. The system of Fig. 1 and Fig. 2 may be amended in accordance with the procedure of Fig. 5 to align the camshaft timing between two different engines.

[0012] Referring to Fig. 1, an internal combustion engine 10 comprising a plurality of cylinders, one of which cylinders is Fig. 1, is controlled by an electronic engine controller 12. The engine 10 includes a cylinder head 35 and a block 33, which include a combustion chamber 30 and cylinder walls 32. A piston 36 is positioned therein and reciprocates via a connection to a crankshaft 40. A flywheel 97 and a ring gear 99 are coupled to the crankshaft 40. An optional starter 96 (e.g., a low-voltage electric machine (operated at less than 30 volts)) includes a pinion shaft 98 and a pinion gear 95. The pinion shaft 98 can selectively drive the pinion gear 95 forward to engage the ring gear 99. The starter 96 can be mounted directly to the front of the engine or the rear of the engine. In some examples, the starter 96 can selectively supply torque to the crankshaft 40 via a belt or chain. In one example, the starter 96 is in a ground state when it is not engaging the engine crankshaft.

[0013] The combustion chamber 30 is shown via a respective intake valve 52 and exhaust valve 54 in communication with an intake manifold 44 and an exhaust manifold 48. Each intake and exhaust valve may be operated by an intake camshaft 51 and an exhaust camshaft 53. The position of the intake camshaft 51 may be determined by an intake cam sensor 55. The position of the exhaust camshaft 53 may be determined by an exhaust cam sensor 57. A position of the intake camshaft 51 may be moved relative to a position of the crankshaft 40 via an intake camshaft synchronizer 59. A position of the exhaust camshaft 53 may be moved relative to a position of the crankshaft via an exhaust camshaft synchronizer 58. The intake and exhaust camshaft synchronizing devices 58 and 59 may be electrically controlled, hydraulically operated devices.

[0014] A fuel injector 66 is shown arranged to inject fuel directly into the cylinder 30, known to those skilled in the art as direct fuel injection. The fuel injector 66 delivers liquid fuel proportional to the pulse width from a controller 12. The fuel may be delivered to the fuel injector 66 via a fuel system (not shown) that includes a fuel tank, a fuel pump, and a fuel rail (not shown). In one example, a two-stage high-pressure fuel system may be used to generate higher fuel pressures.

[0015] Additionally, the intake manifold 44 is shown communicating with a turbocharger compressor 162 and an engine air intake 42. In other examples, the compressor 162 may be a supercharger compressor. A shaft 161 couples a turbocharger turbine 164 to the turbocharger compressor 162. An optional electronic throttle 62 adjusts a position of a throttle plate 64 to control airflow from the compressor 162 to the intake manifold 44. The pressure in a boost chamber 45 may be referred to as a throttle inlet pressure because the inlet of the throttle 62 is located in the boost chamber 45. The throttle outlet is located in the intake manifold 44. In some examples, the throttle 62 and the throttle plate 64 may be positioned between the intake valve 52 and the intake manifold 44 such that the throttle 62 is a port throttle.A wastegate 163 can be adjusted via the controller 12 to allow exhaust gases to selectively bypass the turbine 164 to control the speed of the compressor 162. An air filter 43 cleans air entering the engine air intake 42.

[0016] An aspirator or venturi 65 receives pressurized air from the boost chamber 45, causing a low-pressure zone to develop in the aspirator 85. The low-pressure region causes air from a vacuum reservoir 89 (connecting line not shown), along with the pressurized air, to flow to the aspirator 85 and into the intake manifold 44. A valve 47 controls the flow of pressurized air through the aspirator 65 so that the aspirator 65 is shut off when the valve 47 is closed, and the aspirator 65 can provide vacuum when the valve 47 is open and positive pressure is present in the boost chamber 45. Air can also be drawn from the vacuum reservoir 89 into the intake manifold 44 when the pressure in the intake manifold 44 is lower than the pressure in the vacuum reservoir 89. The vacuum container 89 provides vacuum to the vacuum consumers 87.The vacuum consumers may include, among others, brake boosters, wastegate actuators, and the vehicle's air conditioning control systems. Valve 91 may be closed to stop airflow from vacuum reservoir 89 into intake manifold 44. Intake manifold 44 may also provide a vacuum to a carbon-filled canister 81 used to store fuel vapors from a fuel tank (not shown). Valve 93 may be closed to stop airflow from carbon-filled canister 81 into intake manifold 44.

[0017] Exhaust gas may be recirculated from the exhaust manifold 48 to the intake manifold 44 via a conduit 95 and an exhaust gas recirculation (EGR) valve 77. The intake manifold may also receive gases from the crankcase via a crankcase vent valve 78 and a crankcase vent line 73.

[0018] A distributorless ignition system 88 provides an ignition spark to the combustion chamber 30 via a spark plug 92 in response to the controller 12. A wideband oxygen sensor (UEGO sensor) 126 is shown coupled to the exhaust manifold 48 upstream of a catalytic converter 70. Alternatively, a binary oxygen sensor may replace the UEGO sensor 126.

[0019] In one example, the catalyst 70 may include multiple catalyst bricks. In another example, multiple emission control devices, each with multiple bricks, may be used. In one example, the catalyst 70 may be a three-way catalyst.

[0020] The control 12 is in Fig. 1 as a conventional microcomputer comprising: a microprocessor unit 102, input / output ports 104, a read-only memory 106 (e.g., non-volatile memory), a random access memory 108, a keep-alive memory 110, and a conventional data bus.The controller 12 is shown receiving various signals from sensors connected to the engine 10, in addition to the signals previously discussed, including: engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 to detect the force applied by a human driver 132; a position sensor 154 coupled to a brake pedal 150 to detect a force applied by a human driver 132; a measurement of engine manifold pressure (MAP) from a pressure sensor 122 coupled to the intake manifold 44; an engine position sensor from a Hall effect sensor 118 that detects the position of the crankshaft 40; a measurement of air masses entering the engine from a sensor 120; and a measurement of throttle position from a sensor 68.Barometric pressure may also be sensed for processing by controller 12 (sensor not shown). In a preferred aspect of the present description, engine position sensor 118 generates a predetermined number of evenly spaced pulses with each revolution of the crankshaft, from which engine speed (RPM) can be determined.

[0021] During operation, each cylinder within the engine 10 typically undergoes a four-stroke cycle: the cycle includes the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. During the intake stroke, the exhaust valve 54 closes and the intake valve 52 generally opens. Air is directed into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves toward the bottom of the cylinder to increase the volume within the combustion chamber 30. The position where the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 has reached its largest volume) is commonly referred to by those skilled in the art as bottom dead center (BDC).

[0022] During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air within the combustion chamber 30. The point at which the piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 has reached its smallest volume) is commonly referred to by those skilled in the art as top dead center (TDC). In a process referred to herein as injection, fuel is introduced into the combustion chamber. In a process referred to herein as ignition, the injected fuel is ignited by known ignition devices, such as a spark plug 92, resulting in combustion.

[0023] During the power stroke, the expanding gas pushes the piston 36 back to BDC. The crankshaft 40 converts the piston motion into rotating shaft torque. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture to the exhaust manifold 48, and the piston returns to TDC. It should be noted that the above is shown only as an example, and that intake and exhaust valve opening and / or closing timing may vary to provide positive or negative valve overlap, late intake valve closure, and various other examples.

[0024] Fig. 2 is a block diagram of a vehicle 225 including a drivetrain or transmission 200. The drivetrain of the Fig. 2 includes the Fig. 1. The powertrain 200 is shown including a vehicle system controller 255, the engine controller 12, an electric machine controller 252, a transmission controller 254, an energy storage device controller 253, and a brake controller 250. The controllers may communicate via the controller area network (CAN) 299. Each of the controllers may provide information to other controllers, such as torque output limits (e.g., the torque output of the controlled device or component not to be exceeded), torque input limits (e.g., the torque input of the controlled device or component not to be exceeded), torque output of the controlled device, sensor and actuator data, diagnostic information (e.g.,Information about a transmission in poor condition, information about an engine in poor condition, information about an electric machine in poor condition, information about brakes in poor condition). Further, the vehicle system controller 255 may provide commands to the engine controller 12, the electric machine controller 252, the transmission controller 254, and the brake controller 250 to satisfy driver input requests and other requests based on vehicle operating conditions.

[0025] For example, in response to a driver releasing an accelerator pedal and a vehicle speed, the vehicle system controller 255 may request a desired wheel torque or wheel force level to provide a desired rate of vehicle deceleration. The desired wheel torque may be provided by the vehicle system controller 255 by requesting a first braking torque from the electric machine controller 252 and a second braking torque from the braking controller 250, wherein the first and second torques provide the desired braking torque at the vehicle wheels 216.

[0026] In other examples, the distribution of the controlling powertrain devices may be different than in Fig. 2. For example, a single controller may replace the vehicle system controller 255, the engine controller 12, the electric machine controller 252, the transmission controller 254, and the brake controller 250. Alternatively, the vehicle system controller 255 and the engine controller 12 may be a single unit, while the electric machine controller 252, the transmission controller 254, and the brake controller 250 are standalone controllers.

[0027] In this example, the powertrain 200 may be driven by the engine 10 and the electric machine 240. In other examples, the engine 10 may be omitted. The engine 10 may be connected to a Fig. 1 via a belt-driven integrated starter / generator (BISG) 219 or via a powertrain integrated starter / generator (ISG) 240, also known as a motor / generator. The powertrain ISG 240 (operated at greater than 30 volts) may also be referred to as an electric machine, a motor, and / or a generator. Furthermore, the torque of the engine 10 may also be adjusted using a torque actuator 204, such as a fuel injector, a throttle, etc.

[0028] The BISG is coupled to the engine 10 via a belt 231. The BISG may be coupled to the crankshaft 40 or a camshaft (e.g., 51 or 53). The BISG may operate as a motor when supplied with electrical power via an electrical energy storage device 275. The BISG may operate as a generator, supplying electrical power to the electrical energy storage device 275.

[0029] Engine output torque may be transmitted through a dual-mass flywheel 215 to an inlet or first side of a powertrain disconnect clutch 235. A disconnect clutch 236 may be electrically or hydraulically actuated. The downstream or second side 234 of the disconnect clutch 236 is shown mechanically coupled to the ISG input shaft 237.

[0030] The ISG 240 may be operated to provide torque to the powertrain 200 or to convert powertrain torque into electrical energy that is stored in an electrical energy storage device 275 in a regeneration mode. The ISG 240 is in electrical communication with the energy storage device 275. The ISG 240 has a higher output torque capacity than the Fig. 1 or the BISG 219. Further, the ISG 240 directly drives the driveline 200 or is directly driven by the driveline 200. There are no belts, gears, or chains to couple the ISG 240 to the driveline 200. Instead, the ISG 240 rotates at the same rate as the driveline 200. The electrical energy storage device 275 (e.g., a high-voltage battery or power source) may be a battery, a capacitor, or an inductor. The downstream side of the ISG 240 is mechanically coupled to an impeller 285 of a torque converter 206 by means of a shaft 241. The upstream side of the ISG 240 is mechanically coupled to a disconnect clutch 236. The ISG 240 may provide positive torque or negative torque to the powertrain 200 by operating as a motor or generator as commanded by the electric machine controller 252.

[0031] The torque converter 206 includes a turbine 286 for outputting torque to an input shaft 270. The input shaft 270 mechanically couples the torque converter 206 to an automatic transmission 208. The torque converter 206 also includes a torque converter bypass lock-up clutch (TCC) 212. Torque is transferred directly from the impeller 285 to the turbine 286 when the TCC is locked. The TCC is electrically actuated by the controller 254. Alternatively, the TCC may be hydraulically locked. In one example, the torque converter may be referred to as a component of the transmission.

[0032] When the torque converter clutch 212 is fully disengaged, the torque converter 206 transfers engine torque to the automatic transmission 208 via fluid communication between the torque converter turbine 286 and the torque converter impeller 285, enabling torque multiplication. Conversely, when the torque converter clutch 212 is fully engaged, the engine output torque is transferred directly to an input shaft 270 of the transmission 208 via the torque converter clutch. Alternatively, the torque converter clutch 212 may be partially engaged, allowing the amount of torque sent directly to the transmission to be adjusted.The transmission controller 254 may be configured to adjust the amount of torque transferred from the torque converter 212 by adjusting the torque converter lock-up clutch in response to various engine operating conditions or based on a driver-based engine operating request.

[0033] The torque converter 206 also includes a pump 283 that pressurizes fluid to operate the release clutch 236, a forward clutch 210, and gear clutches 211. The pump 283 is driven by an impeller 285 that rotates at the same speed as the ISG 240.

[0034] The automatic transmission 208 includes the gear clutches (e.g., gears 1-10) 211 and the forward clutch 210. The automatic transmission 208 is a fixed-ratio transmission. The gear clutches 211 and the forward clutch 210 can be selectively engaged to change a gear ratio from an actual total number of rotations of the input shaft 270 to an actual total number of rotations of the wheels 216. The gear clutches 211 can be engaged or disengaged by adjusting fluid supplied to the clutches via shift control solenoid valves 209. Torque output from the automatic transmission 208 can also be transmitted to the wheels 216 to propel the vehicle via the output shaft 260.In particular, the automatic transmission 208 may transmit input drive torque to the input shaft 270 in response to a vehicle driving condition prior to transmitting output drive torque to the wheels 216. The transmission controller 254 selectively activates or selectively engages the TCC 212, the gear clutches 211, and the forward clutch 210. The transmission controller also selectively deactivates or selectively disengages the TCC 212, the gear clutches 211, and the forward clutch 210.

[0035] Furthermore, a frictional force may be applied to the wheels 216 by engaging friction wheel brakes 218. In one example, the friction wheel brakes 218 may be engaged in response to the driver pressing their foot on a brake pedal (not shown) and / or in response to instructions in the brake controller 250. Further, the brake controller 250 may apply the brakes 218 in response to information and / or requests made by the vehicle system controller 255. In the same way, a frictional force on the wheels 216 may be reduced by releasing the wheel brakes 218 in response to the driver releasing their foot from a brake pedal, in response to brake controller instructions and / or vehicle system control instructions and / or information. For example, the vehicle brakes may apply a frictional force to the wheels 216 as part of an automated engine stop procedure via the controller 250.

[0036] In response to a request to accelerate the vehicle 225, the vehicle system controller may receive a driver-requested torque or power request from an accelerator pedal or other device. The vehicle system controller 255 then allocates a portion of the requested driver-requested torque to the engine and the remaining portion to the ISG or BISG. The vehicle system controller 255 requests the engine torque from the engine controller 12 and the ISG torque from the electric machine controller 252. If the ISG torque plus the engine torque is less than a transmission input torque limit (e.g., a threshold not to be exceeded), the torque is provided to the torque converter 206, which then transmits at least a fraction of the requested torque to the transmission input shaft 270.In response to shift schedules and TCC lock schedules, which may be based on input shaft torque and vehicle speed, the transmission controller 254 selectively locks the torque converter clutch 212 and engages gears via the gear clutches 211. Under some conditions, when it may be desired to charge the electric energy storage device 275, a charging torque (e.g., a negative ISG torque) may be requested while a non-zero driver demand torque is present. The vehicle system controller 255 may request increased engine torque to overcome the charging torque to achieve the driver demand torque.

[0037] In response to a request to decelerate the vehicle 225 and provide regenerative braking, the vehicle system controller may provide a negative desired wheel torque based on the vehicle speed and brake pedal position. The vehicle system controller 255 then allocates a fraction of the negative desired wheel torque to the ISG 240 (e.g., desired powertrain wheel torque) and the remaining fraction to the friction brakes 218 (e.g., desired friction brake wheel torque). Further, the vehicle system controller may notify the transmission controller 254 that the vehicle is in regenerative braking mode, so that the transmission controller 254 shifts the gears 211 based on a unique shift schedule to increase regeneration efficiency.The ISG 240 supplies negative torque to the transmission input shaft 270, but the negative torque provided by the ISG 240 may be limited by the transmission controller 254, which outputs a limit on the negative transmission input shaft torque (e.g., a threshold not to be exceeded). Further, the negative torque of the ISG 240 may be limited (e.g., limited to less than a negative threshold torque) based on operating conditions of the electrical energy storage device 275, by the vehicle system controller 255, or by the electric machine controller 252. Any portion of the desired negative wheel torque that cannot be provided by the ISG 240 due to transmission or ISG limitations may be allocated to the friction brakes 218, such that the desired wheel torque is provided by a combination of negative wheel torque from the friction brakes 218 and the ISG 240.

[0038] Accordingly, the torque control of the various powertrain components may be monitored by the vehicle system controller 255, with local torque control for the engine 10, the transmission 208, the electric machine 240, and the brakes 218 being provided via the engine controller 12, the electric machine controller 252, the transmission controller 254, and the brake controller 250.

[0039] As one example, engine torque output may be controlled by adjusting a combination of ignition timing, fuel pulse width, fuel pulse timing, and / or air charge by controlling throttle opening and / or valve timing, valve lift, and boost for turbocharged or supercharged engines. In the case of a diesel engine, controller 12 may control engine torque output by controlling a combination of fuel pulse width, fuel pulse timing, and air charge. In all cases, engine control may be performed on a cylinder-by-cylinder basis to control engine torque output.

[0040] The electric machine controller 252 may, as known in the art, control the torque output and electrical energy production of the ISG 240 by adjusting current flowing to and from field and / or armature windings of the ISG.

[0041] The transmission controller 254 receives the transmission input shaft position via position sensor 271. The transmission controller 254 may convert the transmission input shaft position into input shaft speed by differentiating a signal from position sensor 271 or counting a number of known angular distance pulses over a predetermined time interval. The transmission controller 254 may receive the transmission output shaft torque from torque sensor 272. Alternatively, sensor 272 may be a position sensor or a torque and position sensor. If sensor 272 is a position sensor, the controller 254 may count shaft position pulses over a predetermined time interval to determine the transmission output shaft speed. The transmission controller 254 may also differentiate the transmission output shaft speed to determine the transmission output shaft acceleration.The transmission controller 254, the engine controller 12, and the vehicle system controller 255 may also receive additional transmission information from sensors 277, which may include, but are not limited to, output line pressure sensors, transmission hydraulic pressure sensors (e.g., gear clutch fluid pressure sensors), ISG temperature sensors, BISG temperature sensors, and ambient temperature sensors.

[0042] The brake controller 250 receives wheel speed information via a wheel speed sensor 221 and braking requests from the vehicle system controller 255. The brake controller 250 may also receive brake pedal position information from the Fig. 1 directly or via CAN 299. The brake controller 250 may provide braking in response to a wheel torque command from the vehicle system controller 255. The brake controller 250 may also provide anti-skid and vehicle stability braking to enhance vehicle braking and stability. Therefore, the brake controller 250 may provide a wheel torque limit (e.g., a not-to-be-exceeded negative threshold wheel torque) to the vehicle system controller 255 so that the negative ISG torque does not cause the wheel torque limit to be exceeded. For example, if the controller 250 outputs a negative wheel torque limit of 50 Nm, the ISG torque is adjusted to provide less than 50 Nm (e.g., 49 Nm) of negative torque to the wheels, including taking into account the transmission gearing.

[0043] In other examples, the engine 10 may be coupled to an electric dynamometer that rotates the engine 10 while it is not receiving fuel. In still further examples, the engine 10 may be coupled to an electric motor of a parallel or series-connected hybrid powertrain. Thus, camshaft timing may be revised for a non-reference engine at various settings.

[0044] A reference engine 201 is shown and forms the basis for camshaft positions used in intake and exhaust camshaft plans shown in Fig. 4 (e.g., 402 and 406) stored in the memory of the controller 12. Testing of the engine performance, emissions, and fuel efficiency of the reference engine 201 may form the basis for camshaft degree values stored in the plans.

[0045] The system of Fig. 1 and Fig. 2 provides a system comprising: an engine; a transmission coupled to the engine; an electric machine; and a vehicle system controller including executable instructions stored in non-volatile memory for rotating the engine at a constant predetermined speed without supplying fuel to the engine, and adjusting a position of a camshaft of the engine based on a crankshaft angle at which an intake manifold pressure is a minimum value while the engine is rotating at the constant predetermined speed. The system further includes additional instructions for determining a line equation based on a plurality of intake manifold pressures sampled while the engine is rotating at the constant predetermined speed without supplying fuel to the engine.

[0046] In some examples, the system further includes additional instructions to flow a constant amount of air through the engine while the engine is rotating at the constant predetermined speed without supplying fuel to the engine. The system further includes an aspirator, wherein at least a portion of the constant amount of air flows through the aspirator. The system further includes an EGR valve and additional instructions to close the EGR valve while the engine is rotating at the constant predetermined speed without supplying fuel to the engine. The system further includes a canister purge valve and additional instructions to close the canister purge valve while the engine is rotating at the constant predetermined speed without supplying fuel to the engine.

[0047] Referring to Fig. 3A and Fig. 3B shows example graphs of engine intake manifold pressure versus camshaft position. The graphs illustrate options for correcting the camshaft position of a production engine that incorporates control with camshaft schedules based on the operation of a development engine.

[0048] Referring to the graphics of the Fig. 3A and Fig. 3B, the vertical axes represent the absolute pressure in the engine's intake manifold (manifold absolute pressure - MAP), and MAP increases in the direction of the vertical axis arrow. The horizontal axes represent camshaft position in degrees of camshaft advance from a base position of zero degrees. Camshaft advance increases in the direction of the horizontal axis arrow. Curve 302 shows MAP versus commanded exhaust cam position for a development or reference engine. Curve 304 shows MAP versus commanded exhaust cam position for a non-reference engine or the engine for which the camshaft position is being corrected.

[0049] Curve 302 has a minimum value at 320 and intersects the vertical axis at 321. Curve 304 has a minimum value at 330 and intersects the vertical axis at 331. Curve 304 is offset from curve 302 in a horizontal direction by approximately three degrees. Consequently, if the camshaft of the non-reference engine is commanded to ten degrees, then it is actually positioned at a location corresponding to thirteen camshaft degrees of the reference engine. Thus, the camshaft of the non-reference engine is positioned three degrees away from where it should be. Consequently, the performance, emissions, and fuel efficiency of the non-reference engine may degrade.

[0050] Curves 302 and 304 are generated by rotating the reference engine and the non-reference engine at the same predetermined speed without supplying fuel to the respective engines. The MAP for the reference engine is recorded at selected exhaust camshaft positions. The MAP for the non-reference engine is similarly recorded at selected exhaust camshaft positions. A least-squares fit curve is applied to the MAP and exhaust camshaft data for the reference engine to generate curve 302. A least-squares fit curve is applied equally to the MAP and exhaust camshaft data for the non-reference engine to generate curve 304.

[0051] The graphic in Fig. 3B shows curve 304 aligned with curve 302. Curve 304 is aligned with curve 302 by adding an offset of minus three camshaft degrees from the values of curve 304. In one example, the offset may be determined by finding the minimum of curve 302 and the minimum of curve 304. The offset value of curve 304 may be found by subtracting the number of camshaft degrees corresponding to the minimum MAP of curve 304 from the number of crankshaft degrees corresponding to the minimum MAP of curve 302. Additionally, in some examples, curve 304 may be shifted to a position where it overlaps curve 302 when the minimum MAP corresponds to more than a single camshaft position by shifting curve 304 until it intersects the vertical axis at the same point where curve 302 intersects the vertical axis. As particularly illustrated in Fig. 3B, curve 304 is shifted to the left by a camshaft offset degree amount until curve 304 intersects the vertical axis at 321. In this way, the commanded camshaft position of the non-reference engine is adjusted to match the camshaft position of a reference engine, allowing the non-reference engine to function similarly to the reference engine.

[0052] Referring to Fig. 4 is a block diagram of a portion of a camshaft control system 400. The camshaft control system 400 may be used in the systems of Fig. 1 and Fig. 2. Furthermore, the Fig. 4 shown camshaft control system 400 with the method of Fig. 5. Instructions representing the camshaft control system 400 may be stored in a memory of the Fig. 1 shown control 12.

[0053] The engine speed and desired engine torque are used to index the intake camshaft schedule 402 and the exhaust camshaft schedule 406. The intake camshaft schedule 402 and the exhaust camshaft schedule 406 include and output empirically determined crankshaft positions that enhance engine operation at the engine speed and desired engine torque used to index the respective schedules. Based on the engine speed and desired engine torque, the intake camshaft position table 402 outputs an intake camshaft position (e.g., ten degrees advanced from a base position) and the exhaust camshaft position table 406 outputs an exhaust camshaft position (e.g., five degrees advanced from a base position). The values in the intake and exhaust camshaft schedules (e.g., tables or functions) may be from a reference engine.

[0054] An intake camshaft offset 403 is added at a summing node 403a to the camshaft position output from the intake camshaft table 402. Similarly, an exhaust camshaft offset 407 is added at a summing node 407a to the camshaft position output from the exhaust camshaft table 406. The adjusted intake camshaft position is used to index an intake camshaft transfer function 404, and the transfer function 404 outputs an electrical signal with a pulse width based on the adjusted intake camshaft position. Similarly, the adjusted exhaust camshaft position is used to index an exhaust camshaft transfer function 408, and the transfer function 408 outputs an electrical signal with a pulse width based on the adjusted exhaust camshaft position.The transfer functions 404 and 408 include empirically determined pulse width values that provide the adjusted intake and exhaust camshaft positions.

[0055] Offset corrections to the intake camshaft of a non-reference engine can be used to adjust the value of the intake camshaft offset 403. For example, if the intake camshaft offset value of the non-reference engine is three camshaft degrees, an initial value of zero for the intake camshaft offset 403 can be replaced with a value of three. Offset corrections to the exhaust camshaft of a non-reference engine can be used to adjust the value of the exhaust camshaft offset 407. For example, if the exhaust camshaft offset value of the non-reference engine is five camshaft degrees, an initial value of zero for the exhaust camshaft offset 407 can be replaced with a value of five.

[0056] Alternatively, any empirically determined values stored in intake camshaft table 402 may be adjusted (e.g., increased or decreased) with an intake camshaft offset to adjust the intake camshaft operation of the non-reference engine to function like the intake camshaft operation of the reference engine. Similarly, any empirically determined values stored in exhaust camshaft table 407 may be adjusted (e.g., increased or decreased) with an exhaust camshaft offset to adjust the exhaust camshaft operation of the non-reference engine to function like the exhaust camshaft operation of the reference engine.

[0057] Referring to Fig. 5 shows an exemplary flowchart for a method for operating an engine with variable valve timing. The method of Fig. 5 can be found in the system of Fig. 1 and Fig. 2 and may interact with it. Furthermore, at least parts of the procedure of the Fig. 5 may be included as executable instructions stored in a non-volatile memory, while other parts of the method may be carried out via a controller that converts operating states of devices and actuators in the physical world.

[0058] The procedure of Fig. 5 can be performed using a controller and a non-reference motor.

[0059] At 502, method 500 assesses whether conditions exist to verify and / or correct camshaft positions of a non-reference engine. In one example, conditions exist to verify and / or correct camshaft positions of a non-reference engine when a human technician requests camshaft position adjustments. In another example, conditions exist to verify and / or correct camshaft positions of a non-reference engine when a vehicle is stopped with its transmission in park or neutral. Further, method 500 may require the engine to be at its nominal warm operating temperature. If method 500 assesses that camshaft position adjustments are requested, the answer is yes, and method 500 proceeds to 504. Otherwise, the answer is no, and method 500 proceeds to 580.

[0060] At 580, method 500 positions intake and exhaust camshafts according to engine speed, engine torque, and existing intake and exhaust camshaft offset values determined by method 500. For example, if a human driver requests 100 Nm of torque at an engine speed of 2000 rpm, the intake and exhaust camshaft positions are output from tables or functions based on 100 Nm and 2000 rpm. The values in the intake and exhaust camshaft maps may be from a reference engine. The intake and exhaust camshaft offset values are added to the value output by the tables and functions, and intake and exhaust camshaft synchronizers are commanded using an electrical pulse-width modulated signal. The intake and exhaust camshaft synchronizers adjust the intake and exhaust camshafts relative to the engine crankshaft.In other examples, the intake and exhaust camshaft offset values may differ from values specified in the intake and exhaust maps (e.g., 402 and 406 of the . Fig. 4) are stored, subtracted from, or added to. In this way, the offset adjustment can be used to correct intake and exhaust camshaft positions. Method 400 proceeds to the end after the requested intake and exhaust camshaft positions have been provided.

[0061] At 504, method 500 closes air passages entering the engine intake manifold. For example, the EGR passage may be closed by closing a valve. A crankcase ventilation passage may be closed by closing a crankcase ventilation valve. A passage for a carbon-filled evaporative emissions canister may be closed by closing a valve. A passage leading to a vacuum reservoir may also be closed. By closing the air passages leading into the engine intake manifold, MAP values determined while the engine is running without fuel may be more reproducible. Method 500 proceeds to 506.

[0062] At 506, method 500 adjusts a device to provide a constant airflow through the engine while the engine is rotating without fuel. In one example, a passage through an aspirator may be opened to provide a constant airflow through the engine. The aspirator may provide a fixed restriction to regulate airflow into the engine. Further, a central throttle of the engine may be positioned against a throttle stop to help provide the constant airflow through the engine when the engine is rotating. Method 500 proceeds to 508 after one or more devices have been adjusted to provide a constant airflow rate through the engine when the engine is rotating.

[0063] At 508, method 500 rotates the engine without providing fuel to the engine. In one example, the engine is rotated by an electric machine, such as a motor, an ISB, or a BISG. The engine is rotated at a constant predetermined speed. Method 500 proceeds to 510 after the engine begins rotating.

[0064] At 510, method 500 positions the intake camshaft of the engine at a first predetermined position and the exhaust camshaft of the engine at a first predetermined position. In one example, the first predetermined position for the exhaust camshaft is a home position where the exhaust camshaft can be held in position via a pin. Similarly, the first predetermined position for the intake camshaft is a home position where the intake camshaft can be held in position via a pin. Alternatively, the exhaust camshaft may be positioned where the non-reference engine is expected to provide a MAP value that is higher than a minimum value but less than a value when the exhaust camshaft is at its home position.By positioning the exhaust camshaft offset by a number of degrees from its base position, but less than a camshaft position at which MAP is a minimum, a total actual number of MAP values and crankshaft positions may be reduced while still providing an opportunity to determine a minimum MAP and its corresponding camshaft position. Method 500 proceeds to 512.

[0065] At 512, method 500 determines the engine MAP at the exhaust camshaft position using a pressure sensor and stores the MAP value along with the exhaust camshaft position in memory. Method 500 proceeds to 514.

[0066] At 514, method 500 judges whether MAP has increased over at least three consecutive exhaust camshaft positions. Alternatively, method 500 judges whether the exhaust camshaft position has reached a predetermined position (e.g., a position most advanced or retracted from the exhaust camshaft's base position). If so, the answer is yes, and method 500 proceeds to 516. Otherwise, the answer is no, and method 500 proceeds to 560.

[0067] At 560, method 500 increments the exhaust camshaft position and advances or resets the exhaust camshaft to the incremented position. For example, the exhaust camshaft position may be advanced from zero degrees to two degrees relative to the crankshaft. Method 500 returns to 512.

[0068] At 516, method 500 fits a curve to the MAP and exhaust camshaft position data. In one example, method 500 uses a least-squares fit curve to determine a polynomial equation that fits the MAP and exhaust camshaft position data. Method 500 proceeds to 518.

[0069] At 518, method 500 retrieves a polynomial equation fitting a MAP versus exhaust camshaft position curve for a reference engine from the memory of controller 12. Alternatively, method 500 may retrieve a camshaft position from memory based on where the polynomial is a minimum, where the polynomial is based on the MAP and exhaust camshaft position data from a reference engine. Method 500 proceeds to 520.

[0070] At 520, method 500 determines an exhaust camshaft position offset from a reference engine. In one example, a minimum value of the polynomial determined at 516 is determined by taking a derived value of the polynomial determined at 516 and setting it to zero. The non-reference engine camshaft position at which the derived value of the non-reference engine polynomial is zero corresponds to a non-reference engine camshaft position where MAP is a minimum value for the non-reference engine. Similarly, the reference engine camshaft position at which the derived value of the reference engine polynomial curve is zero corresponds to a reference engine camshaft position where MAP is a minimum value for the reference engine.The exhaust camshaft offset or error may be determined by subtracting the camshaft position of the non-reference engine at which the derived value of the non-reference engine polynomial is zero from the camshaft position of the reference engine at which the derived value of the reference engine polynomial curve is zero. Method 500 proceeds to 522.

[0071] At 522, method 500 sets an exhaust camshaft offset for the non-reference engine. In one example, a value stored in memory (e.g., 407 of Fig. 4) stored exhaust camshaft offset is set to the exhaust camshaft offset determined at 520. In another example, the exhaust camshaft offset determined at 520 is set to an exhaust camshaft schedule as shown in Fig. 4. Method 500 proceeds to 524.

[0072] At 524, method 500 repositions the exhaust camshaft to its home position or another predetermined position and positions the intake camshaft of the non-reference engine to a predetermined position, such as its home position. Method 500 proceeds to 526.

[0073] At 526, method 500 determines the engine MAP at the intake camshaft position using a pressure sensor and stores the MAP value along with the intake camshaft position in memory. Method 500 proceeds to 528.

[0074] At 528, method 500 judges whether MAP has increased over at least three consecutive intake camshaft positions. Alternatively, method 500 judges whether the intake camshaft position has reached a predetermined position (e.g., a position most advanced or retracted from the base position of the exhaust camshaft). If so, the answer is yes, and method 500 proceeds to 530. Otherwise, the answer is no, and method 500 proceeds to 550.

[0075] At 550, method 500 increments the intake camshaft position and advances or resets the intake camshaft to the incremented position. For example, the intake camshaft position may be advanced from zero degrees to two degrees relative to the crankshaft. Method 500 returns to 526.

[0076] At 530, method 500 fits a curve to the MAP and intake camshaft position data. In one example, method 500 uses a least-squares fit curve to determine a polynomial equation that fits the MAP and intake camshaft position data. Method 500 proceeds to 532.

[0077] At 532, method 500 retrieves a polynomial equation fitting a MAP versus intake camshaft position curve for a reference engine from the memory of controller 12. Alternatively, method 500 may retrieve a camshaft position from memory based on where the polynomial is a minimum, where the polynomial is based on the MAP and intake camshaft position data from a reference engine. Method 500 proceeds to 534.

[0078] At 534, method 500 determines an intake camshaft position offset from a reference engine. In one example, a minimum value of the polynomial determined at 530 is determined by taking a derived value of the polynomial determined at 530 and setting it to zero. The non-reference engine camshaft position at which the derived value of the non-reference engine polynomial is zero corresponds to a non-reference engine camshaft position at which MAP is a minimum value for the non-reference engine. For example, if the polynomial is defined as y=x 2 -10x+50, where y is the MAP and x is the intake camshaft position, then the derived value is dydx=2x−10, which, when set to zero, is 2x - 10 = 0 or x=5. The value five is the intake camshaft position at which MAP is a minimum. Similarly, the reference engine camshaft position at which the derived value of the reference engine polynomial curve is zero corresponds to a reference engine camshaft position at which MAP is a minimum value for the reference engine. This position may also be stored in the memory of the non-reference engine controller as a predetermined reference engine position. The intake camshaft offset may be determined by subtracting the non-reference engine camshaft position at which the derived value of the non-reference engine polynomial is zero from the reference engine camshaft position at which the derived value of the reference engine polynomial curve is zero.This is the offset or error between the intake camshaft position of the non-reference engine and the intake camshaft position of the reference engine. Method 500 proceeds to 536.

[0079] At 536, method 500 sets an intake camshaft offset for the non-reference engine. In one example, a value stored in memory (e.g., 407 of Fig. 4) stored intake camshaft offset is set to the intake camshaft offset determined at 520. In another example, the intake camshaft offset determined at 520 is set to an intake camshaft schedule as shown in Fig. 4, added to or subtracted from it. The method 500 proceeds to 538.

[0080] At 538, method 500 positions intake and exhaust camshafts according to engine speed, engine torque, and revised intake and exhaust camshaft offset values determined at 520 and 534. For example, if a human driver requests a torque of 200 Nm at an engine speed of 3000 rpm, the intake and exhaust camshaft positions are output from tables or functions based on 200 Nm and 3000 rpm. The values in the intake and exhaust camshaft maps may be from a reference engine. The intake and exhaust camshaft offset values are added to the value output by the tables and functions, and intake and exhaust camshaft synchronizers are commanded using an electrical pulse-width modulated signal, such as in Fig. 4. The intake and exhaust camshaft synchronizers adjust the intake and exhaust camshafts relative to the engine crankshaft. In other examples, the intake and exhaust camshaft offset values may be adjusted to values specified in the intake and exhaust schedules (e.g., 402 and 406 of Fig. 4) are stored. In this way, the offset adjustment can be used to correct intake and exhaust camshaft positions. Method 500 proceeds to the end after the requested intake and exhaust camshaft positions have been provided.

[0081] Thus, the procedure of Fig. 5 provides an engine operating method, comprising: adjusting a first camshaft position of a first engine using a controller in response to an error between a predetermined camshaft position of a second engine and a second camshaft position of the first engine; and moving a camshaft of the first engine to the adjusted first camshaft position using the controller. The method includes adjusting the first camshaft position by adding an offset to a camshaft position output of a lookup table or a function stored in the memory of the controller. The method includes adjusting the first camshaft position by adding an offset to one or more values in a lookup table or a function stored in the memory of the controller.The method includes adjusting the first camshaft position by adding an offset to a camshaft position output of a table or function stored in memory of the controller, and further comprising adjusting the first camshaft of the first engine prior to adjusting a second camshaft of the first engine based on a second predetermined camshaft position of the second engine, wherein the first camshaft is an exhaust camshaft and the second camshaft is an intake camshaft. The method includes storing the predetermined camshaft position of the second engine in memory of the controller. The method includes determining the predetermined camshaft position of the second engine based on an intake manifold pressure of the second engine.The method includes determining the second camshaft position of the first engine based on an intake manifold pressure of the first engine. The method further includes determining the second camshaft position of the first engine based on data sampled while the first engine is rotating without fuel being delivered to the first engine.

[0082] The procedure of Fig.5 also provides an engine operating method comprising: rotating a first engine via an electric motor and finding a camshaft angle of the first engine, wherein an intake manifold pressure is a minimum value, while no fuel is supplied to the first engine; adjusting a first camshaft position of a first engine via a controller in response to an error between a predetermined camshaft position of a second engine and the camshaft angle of the first engine at which the intake manifold pressure is the minimum value; and moving a camshaft of the first engine to the adjusted first camshaft position via the controller.

[0083] In some examples, the method further comprises fully closing a throttle of the first engine while the first engine is rotating and while no fuel is being supplied to the first engine. The method further comprises flowing air through an aspirator while the first engine is rotating and while no fuel is being supplied to the first engine. The method further comprises rotating the first engine without supplying fuel to the first engine and while a transmission coupled to the first engine is in park or neutral. The method includes where the electric motor is an integrated starter / generator or a belt-driven starter / generator. The method includes where finding the camshaft angle includes finding a line equation based on the intake manifold pressure, which is a minimum value, and a plurality of other intake manifold pressures.The method includes rotating the first engine at a constant speed and further includes maintaining an exhaust camshaft of the first engine at a fixed position while moving an intake camshaft of the first engine and rotating the first engine at the constant speed.

[0084] It should be noted that the example control and estimation routines contained herein may be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by the control system, including the controller in combination with various sensors, actuators, and other engine components. The particular routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, various illustrated acts, operations, and / or functions may be performed in the illustrated order, in parallel, or in some cases omitted.Likewise, the processing order is not required to achieve the features and advantages of the embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and / or functions may be performed repeatedly, depending on the particular strategy employed. Furthermore, at least a portion of the described acts, operations, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer-readable storage medium in the control system. The control acts may also transform the operating state of one or more sensors or actuators in the physical world when the described acts are performed by executing the instructions in a system that includes the various hardware components in combination with one or more controllers.

[0085] This concludes the description. Upon reading this description, those skilled in the art will be aware of various changes and modifications without departing from the spirit and scope of the description. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating on natural gas, gasoline, diesel, or alternative fuel configurations could advantageously utilize the present description.

Claims

[1] Engine operating method, comprising: Rotating a first engine via an electric motor and determining a camshaft angle of the first engine, wherein an intake manifold pressure is a minimum value, while no fuel is supplied to the first engine; adjusting a first camshaft position of the first engine by means of a controller in response to an error between a predetermined camshaft position of a second engine and the camshaft angle of the first engine at which the intake manifold pressure is the minimum value; and Moving a camshaft of the first engine to the set first camshaft position by means of the controller. [2] The method of claim 1, further comprising fully closing a throttle of the first engine while the first engine is rotating and while no fuel is being supplied to the first engine. [3] The method of claim 1, further comprising flowing air through an aspirator while the first engine is rotating and no fuel is supplied to the first engine. [4] The method of claim 1, further comprising rotating the first engine while no fuel is supplied to the first engine and a transmission coupled to the first engine is in park or neutral. [5] The method of claim 1, wherein the electric motor is an integrated starter / generator or a belt-driven integrated starter / generator; and further comprising closing an EGR valve while the first engine is rotating and while no fuel is being supplied to the first engine. [6] The method of claim 1, wherein determining the camshaft angle of the first engine comprises determining an equation of a line based on the intake manifold pressure being the minimum value and a plurality of other intake manifold pressures depending on the exhaust cam position. [7] The method of claim 1, wherein the first engine rotates at a constant speed, and further comprising maintaining an exhaust camshaft of the first engine in a fixed position while moving an intake camshaft of the first engine and rotating the first engine at the constant speed. [8] System comprising: an engine; a transmission coupled to the engine; an electrical machine; and a vehicle system controller including executable instructions stored in non-volatile memory to rotate the engine at a constant predetermined speed without supplying fuel to the engine, and adjusting a position of a camshaft of the engine based on a crankshaft angle at which an intake manifold pressure is a minimum value while the engine is rotating at the constant predetermined speed. [9] The system of claim 8, further comprising additional instructions to determine a line equation based on a plurality of intake manifold pressures sampled while the engine is rotating at the constant predetermined speed without fuel being supplied to the engine as a function of exhaust cam position. [10] The system of claim 8, further comprising additional instructions to flow a constant amount of air through the engine while the engine is rotating at the constant predetermined speed without supplying fuel to the engine. [11] The system of claim 10, further comprising an aspirator, and wherein at least a portion of the constant amount of air flows through the aspirator. [12] The system of claim 8, further comprising an EGR valve and additional instructions to close the EGR valve while the engine is rotating at the constant predetermined speed without supplying fuel to the engine. [13] The system of claim 8, further comprising a canister purge valve and additional instructions to close the canister purge valve while the engine is rotating at the constant predetermined speed without supplying fuel to the engine.

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