Oil pressure modification for variable camshaft control

Abstract

Engine process, which includes the following: in response to an engine operating condition, adjusting a valve coupled to a hydraulic variable camshaft control actuator to initiate camshaft adjustment and adjusting an oil pressure supplied to the valve based on a camshaft adjuster position and Reducing the oil pressure supplied to the valve for a predetermined time interval to a threshold level to unlock a camshaft adjuster locking pin, but not moving a camshaft adjuster if the camshaft adjuster locking pin is in a home position, and then increasing the oil pressure supplied to the valve to move the camshaft adjuster.

Description

[0001] The present application relates to methods for operating an engine with variable cam timing (VCT). General state of the art and brief description of the invention

[0002] Internal combustion engines can use variable cam timing (VCT) to improve a vehicle's fuel economy and emissions performance. One variable cam timing method uses an oil pressure actuated (OPA) device, such as a multi-plate camshaft adjuster. The adjuster can be controlled by an electromechanically actuated spool valve that directs the oil flow to one side or the other of the plate. The performance of this device thus depends on the oil pressure, which may be set lower under nominal conditions for fuel economy or to reduce parasitic loads.

[0003] The inventors of the present invention recognized that VCT adjusters may not reach a target position under certain conditions, for example, if the camshaft adjuster temperatures are higher than the oil sump temperature or if the VCT adjusters are worn. This condition can be further exacerbated if the oil pressure is set lower for fuel economy or to reduce parasitic loads. Reduced oil pressure can also reduce the adjustment speed of the VCT adjusters, which, for example, affects engine response, boost pressure build-up time, and the ability to achieve optimal brake-specific fuel consumption due to engine breathing.

[0004] In some examples, VCT adjusters are equipped with a locking pin in their initial position to prevent rattling. These pins can be pushed out by the same oil that moves the cams. However, there is a race condition when the cam is commanded to move first, so if the cam moves first, it can block the pin in the locked position, thus preventing further cam movement.

[0005] From DE 11 2006 001 043 T5 and DE 10 2008 047 117 A1 it is known, in response to an engine operating condition, to adjust a valve coupled to a hydraulic variable camshaft control actuator to initiate a camshaft adjustment and to adjust an oil pressure supplied to the valve on the basis of a camshaft adjuster position.

[0006] DE 10 2005 022 764 A1 discloses a control of oil pressure for a variable valve timing control device.

[0007] The problems listed above are at least partially solved by the features of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0008] Accordingly, one of the methods comprises the following: in response to an operating condition, adjusting a valve coupled to a hydraulic variable camshaft control actuator to initiate camshaft adjustment and adjusting the oil pressure supplied to the valve based on a camshaft adjuster position. In some examples, if a camshaft adjuster locking pin is in a home position, the method may further comprise: reducing the oil pressure supplied to the valve for a predetermined time interval to a threshold level sufficient to unlock the locking pin but not move the camshaft adjuster, and then increasing the oil pressure supplied to the valve to move the camshaft adjuster.

[0009] In this way, oil pressure can be increased if the adjustment position is not reached, thus increasing the pump output (e.g., a variable oil pump (VOP)) to assist in pushing the cams into a target position. Furthermore, the degree of oil pressure compensation can be proactive and reactive. For example, the error can be stored in a weighted additive manner for future use and can be used to estimate the age of the VCT adjuster. Additionally, the VCT pin release can be made more controllable by reducing the oil pressure to a level at which the pin preferentially responds and the cam adjuster does not. Since the oil pressure can still be set lower while achieving VCT control, and increased when required by the VCT system under selected conditions, fuel economy can be improved.

[0010] It is understood that the above brief outline is presented to introduce, in simplified form, a selection of concepts that are described in more detail in the full description. It is not intended to identify any important 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 address any disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows a partial view of an engine and related systems. Fig. Figure 2 shows a block diagram of an engine oil lubrication system. Fig. Figure 3 shows an exemplary VCT adjuster and hydraulic system. Fig. Figure 4 shows an exemplary method for modifying the oil pressure supplied to a variable valve control system according to the disclosure. Fig. Figure 5 shows an exemplary method for determining the extent of pressure compensation for a variable valve control system according to the disclosure. Detailed description

[0011] The following description concerns systems and methods for controlling a vehicle engine, where the engine has a variable cylinder valve system, such as variable cam timing (VCT). The engine (such as the one in Fig. 1 shown) may, for example, include a VCT adjuster to adjust the cam timing (such as the degree of cam retardation or cam advance), with the adjuster operating in a hydraulic system (as in Fig. 2) is included. Furthermore, the motor may include a corresponding hydraulic control system with a slide valve, as described in Fig. 3 shown. The amount of oil supplied to the VCT adjusters can be controlled using a control algorithm, as shown in Fig. As shown in Figure 4, adjustments can be made to push an adjuster into a target position and / or to increase the adjustment rate of an adjuster during an adjustment event. In some examples, the degree of oil pressure compensation can be based on a target, actual, and modeled adjustment rate, as in the exemplary procedure in Figure 4. Fig. 5 shown.

[0012] Fig. Figure 1 shows an embodiment of a combustion chamber or cylinder of the internal combustion engine 10. Fig. Figure 1 shows that the motor 10 can receive control parameters from a control system including a controller 12, as well as input from a vehicle operator 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 (here also referred to as "combustion chamber") 30 of the engine 10 can contain combustion chamber walls 32 with a piston 36 positioned therein. The piston 36 can be coupled to a crankshaft 40, so that a pendulum motion of the piston is translated into a rotary motion 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 starting the engine 10. The crankshaft 40 is coupled to an oil pump 208 to pressurize the engine oil lubrication system 200 (the coupling of the crankshaft 40 to the oil pump 208 is not shown). A housing 136 is hydraulically coupled to the crankshaft 40 via a timing chain or a timing belt (not shown). The 208 oil pump can be adjusted to increase or decrease the oil pressure.

[0014] Cylinder 30 can receive intake air via an intake manifold or intake air passages 44. The intake air passage 44 can communicate with other cylinders of the engine 10 in addition to cylinder 30. In some embodiments, one or more of the intake passages can include a charging device such as a turbocharger or a supercharger. A throttling system with a throttle plate 62 can be provided along an intake passage of the engine to vary the flow rate and / or pressure of the intake air supplied to the engine cylinders. In this particular example, the throttle plate 62 is coupled to an electric motor 94, so that the position of the elliptical throttle plate 62 is controlled by the controller 12 via the electric motor 94. This configuration can be referred to as electronic throttle control (ETC), which can also be used during idle speed control.

[0015] The combustion chamber 30 is shown communicating with the intake manifold 54 and the exhaust manifold 48 via the respective intake valves 52a and 52b (not shown) and exhaust valves 54a and 54b (not shown). While four valves per cylinder can be used, 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 coupled to the exhaust manifold 48 upstream of a catalyst 70 (where the sensor 76 can correspond to various different sensors). For example, the sensor 76 can be any of the many known sensors for providing an indication of the air-fuel ratio in the exhaust gas, such as a linear oxygen sensor, a wideband oxygen sensor (UEGO), a dual-state oxygen sensor, an EGO, a HEGO, or an HC or CO sensor. An exhaust gas purification device 72 is shown positioned downstream of the catalyst 70. The exhaust gas purification device 72 can be a three-way catalyst, a NOx trap, various other exhaust gas purification devices, or combinations thereof.

[0017] In some embodiments, each cylinder of the engine 10 may contain a spark plug 92 for initiating combustion. Under selected operating modes, the ignition system 88 can deliver a spark to the combustion chamber 30 via the spark plug 92 in response to an ignition advance signal SA from the controller 12. However, in some embodiments, the spark plug 92 may be omitted, for example, if the engine 10 can initiate combustion via auto-ignition or by fuel injection, as may be the case with some diesel engines.

[0018] In some embodiments, each cylinder of the engine 10 can be configured with one or more fuel injectors to supply fuel to it. As a non-limiting example, a fuel injector 66A is shown directly coupled to cylinder 30 to inject fuel there proportionally to the pulse width of a signal dfpw received by the controller 12 via an electronic driver 68. In this way, the fuel injector 66A delivers what is known as direct injection (hereinafter also referred to as “DI”) of fuel into cylinder 30.

[0019] The engine 10 may further include a compression device such as a turbocharger or supercharger, which contains at least one compressor 162 arranged along a compressor passage 44 and which may include a boost sensor for measuring air pressure. For a turbocharger, the compressor 162 may be driven at least partially by a turbine 164 (e.g., via a shaft) arranged along the outlet passage 48. For a supercharger, the compressor 162 may be driven at least partially by the engine and / or an electric machine and may not contain a turbine. Thus, the degree of compression supplied to the one or more cylinders of the engine via a turbocharger or supercharger can be varied by the controller 12.

[0020] The controller 12 is shown as a microcomputer, with a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory chip 106, a random access memory 108, a working memory 110 and a conventional data bus.The controller 12 is shown to receive, in addition to the signals already discussed, various signals from sensors coupled to the engine 10, including measurement of the intake air mass flow (MAF - Mass Air Flow) from an air mass flow sensor 100 coupled to the throttle 62; the engine coolant temperature (ECT - Engine Coolant Temperature) from a temperature sensor 112 coupled to a cooling sleeve 114; an ignition profile pickup signal (PIP - Profile Ignition Pickup) from a Hall effect sensor 118 coupled to the crankshaft 40; a throttle position TP from a throttle position sensor 20; an absolute manifold pressure signal MAP from a sensor 122; a knock indication from a knock sensor 182; and an indication of the absolute or relative ambient humidity from a sensor 180.An engine speed signal (RPM) is generated by controller 12 in the conventional manner from the PIP signal, and the manifold pressure signal (MAP) from a manifold pressure sensor provides an indication of vacuum or pressure in the intake manifold. During stoichiometric operation, this sensor can provide an indication of the engine load. Additionally, this sensor, together with the engine speed, can provide an estimate of the charge (including air) drawn 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 crankshaft revolution.

[0021] In this particular example, a temperature T is used. cat1 of the catalyst 70 by a temperature sensor 124 and a temperature T cat2The exhaust gas purification device 72 is supplied by a temperature sensor 126. In an alternative embodiment, the temperature Tcat1 and the temperature Tcat2 can be inferred from the engine operation.

[0022] Continued with Fig. Figure 1 shows a system 19 for variable camshaft timing (VCT). In this example, an overhead cam system is shown, although other approaches can be used. In particular, the camshaft 130 of engine 10 is shown communicating with rocker arms 132 and 134 to actuate the intake valves 52a, 52b and exhaust valves 54a, 54b. The VCT system 19 can be oil-pressure actuated (OPA), cam-torque actuated (CTA), or a combination thereof. By adjusting several hydraulic valves to direct a hydraulic fluid, such as 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 explained here, the operation of the hydraulic control valves can be controlled by respective control solenoids. In particular, an engine controller can send a signal to the solenoids to move a control spool that regulates the flow of oil through the adjuster cavity. As used herein, the terms cam advance and retard refer to relative cam timing because a fully advanced position can still produce an intake valve opening retarded with respect to top dead center, just as an example.

[0023] The camshaft 130 is hydraulically coupled to the housing 136. The housing 136 forms a gear with several teeth 138. In this embodiment, the housing 136 is mechanically coupled to the crankshaft 40 via a timing chain or timing belt (not shown). Therefore, the housing 136 and the camshaft 130 rotate at essentially equivalent speeds and synchronously with the crankshaft. In an alternative embodiment, such as in a four-stroke engine, the housing 136 and the crankshaft 40 can be mechanically coupled to the camshaft 130, so that the housing 136 and the crankshaft 40 can rotate synchronously at a different speed than the camshaft 130 (e.g., a ratio of 2:1, where the crankshaft rotates at twice the speed of the camshaft). In the alternative embodiment, the teeth 138 can be mechanically coupled to the camshaft 130.By manipulating the hydraulic coupling as described herein, the relative position of the camshaft 130 to the crankshaft 40 can be changed by hydraulic pressures in the late adjustment chamber 142 and the early adjustment chamber 144 (not in . Fig. 3 shown, but in Fig. (1 shown) can be varied. By allowing high-pressure hydraulic fluid to enter the retardation chamber 142, the relative relationship between camshaft 130 and crankshaft 140 is retarded. Thus, the intake valves 52a, 52b and the exhaust valves 54a, 54b open and close at a time earlier than normal relative to the crankshaft 40. By allowing high-pressure hydraulic fluid to enter the advancement chamber 144, the relative relationship between camshaft 130 and crankshaft 40 is similarly advanced. Thus, the intake valves 52a, 52b and the exhaust valves 54a, 54b open and close at a time later than normal relative to the crankshaft 40.

[0024] Although this example shows a system where the intake and exhaust valve timing is controlled simultaneously, variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, dual identical variable cam timing, or other variable cam timing configurations can be used. Variable valve lift can also be employed. Furthermore, cam profile switching can be used to provide different cam profiles under varying operating conditions. The valve train can also be a roller rocker arm, a direct-acting mechanical bucket, an electro-hydraulic system, or other alternatives to rocker arms.

[0025] Continuing with the variable cam timing system, teeth 138, which rotate synchronously with the camshaft 130, allow a measurement of the relative cam position via a cam timing sensor 150, which supplies a VCT signal to the controller 12. Teeth 1, 2, 3, and 4 can be used to measure cam timing and are evenly spaced (for example, in a twin-bank V8 engine, 90 degrees apart), while tooth 5 can be used for cylinder identification. Additionally, the controller 12 sends control signals (LACT, RACT) to conventional solenoid valves (not shown) to control the flow of hydraulic fluid either into the late-adjustment chamber 142, the early-adjustment chamber 144, or to no flow at all.

[0026] Relative cam timing can be measured in a variety of ways. Generally speaking, the time or angle of rotation between the rising edge of the PIP signal and the reception of a signal from one of the several teeth 138 on the housing 136 provides a measure of relative cam timing. For the specific example of a two-bank V-8 engine with a five-tooth gear, a measure of cam timing for a given bank is received four times per revolution, using the extra signal for cylinder identification.

[0027] As described above, shows 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.

[0028] Fig. Figure 2 shows an embodiment of an engine oil lubrication system 200 with an oil pump 208 coupled to the crankshaft 40 (not shown) and with various oil subsystems 216, 218, 220. The oil subsystem can utilize the oil flow to perform a certain function, such as lubrication, actuation of an actuator, etc. For example, one or more of the oil subsystems 216, 218, 220 can be hydraulic systems with hydraulic actuators and hydraulic control valves. Furthermore, the oil subsystems 216, 218, 220 can be lubrication systems such as passages for supplying oil to moving components such as camshafts, cylinder valves, etc. Further, non-limiting examples of oil subsystems include camshaft adjusters, cylinder walls, various bearings, etc.

[0029] Oil is supplied to the oil subsystem via a supply channel, and oil is returned via a return channel. Some embodiments may have fewer or more oil subsystems.

[0030] Continued with Fig. 2. In conjunction with the rotation of the crankshaft 40 (not shown), the oil pump 208 draws oil from an oil reservoir 204, which is mounted in an oil pan 202, through the supply channel 206. The oil is supplied under pressure by the oil pump 208 through the supply channel 210 and the oil filter of the main oil gallery 214. The pressure in the main oil gallery 214 is a function of the force generated by the oil pump 208 and / or the oil flow entering each oil subsystem 216, 218, 220 through supply channels 214a, 214b, 214c. Oil flows back to the oil reservoir 204 at atmospheric pressure through the return channel 222. An oil pressure sensor 224 measures the main oil gallery pressure and sends the pressure data to the controller 12 (not shown). The pressure in the main gallery can be increased or decreased, for example, by increasing or decreasing the force generated by the oil pump 208 in response to signals received by the controller 12.

[0031] The level of the main gallery oil pressure can affect the performance of one or more of the oil subsystems 216, 218, 220. For example, the force generated by a hydraulic actuator is directly proportional to the oil pressure in the main gallery. High oil pressure allows the actuator to respond more strongly, while low oil pressure reduces its response. Low oil pressure can also limit the effectiveness of the engine oil in lubricating moving components. For instance, if the main gallery oil pressure falls below a threshold pressure, a reduced flow of lubricating oil may be supplied, potentially leading to component degradation.

[0032] Fig. Figure 3 shows an exemplary oil subsystem 220. The oil subsystem 220 (here also referred to as the "adjuster") consists of a variable cam control actuator (here also referred to as the "actuator") 360, a variable force solenoid (here also referred to as the "solenoid") 310, an oil control spool valve (here also referred to as the "spool valve") 300, a cam pin 370, and hydraulic channels (here also referred to as "channels") 316, 317, 318, 320, 322. Channel 316 connects the main gallery 214 to the spool valve 300; channels 317 and 318 connect the spool valve 300 to the return channel 222. Channel 320 connects the slide valve 300 to the retardation chamber 142 in the actuator 360 via a cam pin passage 342, while channel 322 connects the slide valve 300 to the advancement chamber 144 in the actuator 360 via the cam pin passage 344. The cam pin 370 contains the camshaft 130, cam pin passages 342 and 344, a cam pin cap 380, and a cylinder head cam bore 381.The cam pin cap 380, which is mechanically coupled to the cylinder head (not shown), forms a cylindrical bearing in which the camshaft 130 can rotate. Fig. Figure 3 shows a cutaway view of the cam pin cap 380 with the cap top 380a, the cylinder head cam bore 381, and a cap sealing shoulder 380c. Oil passages can be integrated into the cam pin cap 380, as shown on both sides of the cap sealing shoulder 380c. The cam pin passage 342 provides a hydraulic channel for oil between the channel 320 and the retard chamber 142. The cam pin passage 344 provides a hydraulic channel between the channel 322 and the advance chamber 144. The cap sealing shoulder 380c provides separation between the cam pin passages 342 and 344. Thus, in a given example, a cam-fed, oil-pressure-operated system can be used.

[0033] The actuator 360 consists of a rotor 330, the housing 136, the retardation chamber 142, the advance chamber 144 (not shown), a locking pin 332, and an optional return spring 334. The rotor 330 is mounted on the camshaft 130 so that it rotates at the same speed as the camshaft 130. The rotor 330 is hydraulically coupled to the housing 136. Adjustment vanes 330a, 330b, 330c, and 330d move within the recesses formed by the retardation chamber 142 and the advance chamber 144. The slide valve 300 allows the rotor 330 to move by permitting an oil flow into the late adjustment chamber 142 and out of the early adjustment chamber 144 or vice versa, depending on the desired direction of movement (i.e., whether cam early adjustment or cam late adjustment is desired).During cam retardation, oil flows from the supply channel 316 through the slide valve 300 and the channel 320 and the cam pin passage 342 into the retardation chamber 142, while oil from the advancement chamber 144 is forced into the cam pin passage 344 and the channel 322 through the slide valve 300 and out of the channel 318. During cam advance, oil flows from the supply channel 316 through the slide valve 300 and the channel 322 and the cam pin passage 344 into the advancement chamber 144, while oil from the retardation chamber 142 is forced into the cam pin passage 342 and the channel 320 through the slide valve 300 and out of the channel 317. The housing 136 forms a mechanical stop for the rotor 330.When the retard chamber 142 is fully open and the rotor 330 rests against the housing 136, the actuator 360 is in the retard end position (also referred to here as the "base position"), and the cam timing is maximally retarded. When the advance chamber 144 is fully open and the rotor 330 rests against the housing 136, the actuator 360 is in the advance end position, and the cam timing is maximally advanced. An optional return spring 334 and the locking pin 332 can hold the rotor 330 in the base position when the oil pressure is low, such as during a cold start. As the oil pressure increases, the locking pin 332 can be retracted, allowing the rotor 330 to move freely as described above. When the return spring 334 is present, the return spring 334 generates a force that biases the rotor 330 to the base position regardless of the oil pressure.

[0034] The slide valve 300 consists of a sleeve 308 for receiving a slide 314 with slide shoulders 314a, 314b, 314c and a preload spring 312. A solenoid 310, controlled by the electronic control unit (ECU) 302 (which may be the controller 12), moves the slide 314 within the sleeve 308. The position of the slide 314 is determined by balancing the force of the preload spring 312 against the force generated by the solenoid 310. Slide shoulders 314a, 314b, 314c are used to restrict or block the oil flow through the hydraulic channels.The slide 314 can be adjusted so that the slide valve 300 operates in several ranges, including a first range that generates a hydraulic force in a first direction on the actuator to a first end position, a second range that generates a hydraulic force in a second, opposite direction on the actuator to a second, opposite end position, and a neutral range between the first and second ranges. For example, the first range is a retard range and the second range is an advance range.

[0035] In the retarded timing range, oil flows from the slide valve 300 into the retarded timing chamber 142, forcing the actuator 360 to retard the camshaft timing to its maximum retarded position. Slide section 314a blocks channel 317, a channel is open from channel 316 to channel 320 between slide sections 314a and 314b, and a channel is open from channel 322 to channel 318 between slide sections 314b and 314c. The retarded timing range is in effect when the solenoid 310 is not energized (e.g., no current is applied to it) and the actuator 360 is in its base position. In the area where the camshaft is advanced, oil flows from the slide valve 300 into the advance chamber 144, forcing the actuator 360 to overcome the return spring 334 and advance the camshaft control to the maximum advanced position.The coil section 314c blocks channel 318. One channel is open from channel 316 to channel 322 between slide sections 314b and 314c, and one channel is open from channel 320 to channel 317 between slide sections 314a and 314b in the advancing range. In the neutral range, hydraulic forces on the actuator are essentially balanced, so that the actuator 360 neither advances nor retards the cam timing. Torque from the return spring 334 is counteracted by a positive pressure differential from the advancing chamber 144 to the retarding chamber 142. In the neutral area, the slide stop 314c blocks the channel 318, a weak channel is open from the channel 316 to the channel 322 between the slide stops 314b, 314c, and a weak channel is open from the channel 320 to the channel 317 between the slide stops 314a, 314b.

[0036] Fig. Figure 4 shows an exemplary method 400 for modifying the oil pressure in an engine oil lubrication system, e.g. the lubrication system 200, which supplies oil to a camshaft adjuster, e.g. the adjuster 220.

[0037] In procedure 400 of the 402 procedure, this involves determining whether the entry conditions for initiating a camshaft timing adjustment are met. For example, the controller 12 may initiate a camshaft timing adjustment depending on factors such as engine load or engine speed. Thus, the entry conditions may include engine speed or engine load at a threshold value. Other examples of entry conditions may be based on barometric pressure, driver-requested torque (e.g., from a pedal position sensor), manifold pressure (MAP), manifold air flow (MAF), an approximate amount of residue left in the cylinder(s) from the previous combustion cycle, engine temperature, ambient air temperature, knock limits, etc.

[0038] If the entry conditions at 402 are met, procedure 400 proceeds to 404. At 404, procedure 400 involves adjusting a valve coupled to a hydraulic actuator of the variable camshaft timing system to initiate camshaft adjustment. For example, the adjusted valve may be a hydraulic spool valve, such as spool valve 300, and adjusting the valve may involve sending a control signal to a solenoid coupled to the hydraulic spool valve. As described above, adjusting the spool valve in the adjuster causes oil from the engine oil lubrication system 200 to initiate movement of the adjuster to adjust the camshaft timing.

[0039] If, as noted above, a VCT adjuster is in a home position with a locking pin in place, the same oil that pushes the cam can be used to unlock the locking pin. In some examples, under certain conditions, the oil pressure supplied to the adjuster may cause the cam to move before the locking pin is unlocked, causing the locking pin to seize in place and preventing further movement of the cam adjuster. Thus, in 406, method 400 involves determining whether a locking pin is in a home position so that the oil pressure can be reduced to unlock the locking pin before the cam is caused to move.

[0040] If the locking pin is in a home position at 406, procedure 400 proceeds to 408. At 408, procedure 400 involves reducing the oil pressure supplied to the valve to a threshold level for a predetermined time interval to unlock the locking pin without moving the camshaft adjuster. In this way, a temporary reduction in oil pressure can unlock the locking pin without causing the adjuster to move, thus preventing the locking pin from becoming stuck in place. The threshold level and the time interval for reduced pressure can be based on a variety of factors, including the area of ​​the locking pin, the locking pin spring rate, the area of ​​a camshaft adjuster, the camshaft adjuster spring rate, and the coefficient of camshaft friction.

[0041] The extent to which the oil pressure is reduced can depend on a current pressure reading in the engine oil lubrication system 200. For example, the oil pressure in the engine lubrication system may be lower under certain conditions due to oil consumption by other oil subsystems.

[0042] If the locking pin at 406 is not in a home position, or if the locking pin at 408 is unlocked, procedure 400 proceeds to 410. At 410, procedure 400 involves adjusting the oil pressure in the engine oil lubrication system to adjust the amount of oil pressure supplied to the slide valve. For example, as noted above, VCT adjusters may not reach a target position under certain conditions, such as when camshaft adjuster temperatures exceed the oil sump temperature or when the VCT adjusters are worn. Furthermore, this condition may be made more difficult if the oil pressure is set lower for fuel economy or to reduce parasitic loads.Reduced oil pressure can also reduce the adjustment speed of the VCT adjusters, affecting engine response, boost pressure build-up time, and the ability to achieve optimal brake-specific fuel consumption due to engine breathing, for example. Therefore, the oil pressure supplied by the engine oil lubrication system 200 can be increased after the slide valve has been adjusted to a threshold level to provide additional oil pressure to the adjuster.

[0043] For example, as below regarding Fig. 5 described, the extent of the oil pressure adjustment is based on a position of the camshaft adjuster, modeled, actual and desired camshaft adjustment rates, adjuster temperature, oil sump temperature, adjuster age, etc.

[0044] In procedure 400 of 414, this involves determining whether a target adjustment position has been reached after a predetermined time interval. For example, a VCT target position can be determined based on estimated motor operating conditions and / or various sensor readings.

[0045] If a target adjustment position has been reached at 414, procedure 400 continues to 422 to increase the oil pressure. For example, the oil pressure in the engine oil lubrication system can be reduced to a baseline level for fuel economy and to reduce parasitic losses associated with maintaining higher oil pressures in the system.

[0046] However, if the target adjustment position has not been reached at 414, procedure 400 continues to 416. At 416, procedure 400 involves determining whether a pressure increase threshold has been reached. For example, the oil pump 208 may have a pressure threshold that it can deliver to the oil in the engine oil lubrication system 200, such that no further pressure increases are possible.

[0047] If a pressure threshold has not been reached at 416, procedure 400 proceeds to 418. At 418, procedure 400 involves increasing the oil pressure supplied to the valve. As noted above, increasing the oil pressure supplied to the valve may involve adjusting the oil pressure in the engine oil lubrication system to alter the oil pressure level supplied to the spool valve. In this example, the oil pressure supplied by the engine oil lubrication system 200 may be increased, after the spool valve has been adjusted to a threshold level, to provide additional oil pressure to the adjuster to assist it in reaching a target position. As another example, the oil pressure supplied by the engine oil lubrication system 200, along with spool valve adjustments, may be increased to provide additional oil pressure to the adjuster to assist it in reaching a target position. As below regarding Fig. As described in section 5, the extent of the oil pressure adjustment can be based on the position of the camshaft adjuster, the modeled, actual and desired camshaft adjustment rates, the adjuster temperature, the oil sump temperature, the adjuster age, etc.

[0048] In some examples, procedure 400 may involve further monitoring of the adjuster position and further increasing the oil pressure supplied to the valve until a target position is reached or until a pressure threshold is reached.

[0049] If no target position has been reached at step 416 and no oil pressure threshold has been reached, procedure 400 then proceeds to step 420 to indicate a deterioration in the quality of the camshaft adjuster. For example, a deterioration indication can be sent to an on-board diagnostic system to indicate a deterioration in the quality of the VCT system. The oil pressure can then be reduced to a baseline value at step 422 as described above.

[0050] When implementing the procedure of Fig. 4. A reduced oil pressure can be maintained while still achieving VCT control. Under selected conditions, the oil pressure can be increased to assist operation and then reduced back to a baseline oil pressure. For example, the adjuster spool valve can be used for VCT control with reduced oil pressure under nominal conditions. In situations where the quality of a camshaft adjuster has deteriorated or the oil sump temperature has increased, the oil pressure in the engine oil lubrication system can be temporarily increased to assist the adjuster in reaching a target position within a specified timeframe.

[0051] Fig. Figure 5 shows an exemplary method 500 for determining a degree of pressure compensation for a variable valve control system and for adjusting the oil pressure supplied to the spool valve accordingly.

[0052] In procedure 502, method 500 involves determining whether entry conditions for adjusting the oil pressure in an engine oil lubrication system are met. Entry conditions may include the slide valve 300 being adjusted to a threshold value, the camshaft adjuster temperature being above an oil supply temperature, the age of a camshaft adjuster exceeding a threshold, a camshaft adjuster not reaching its target position after a time interval, etc.

[0053] In procedure 504, method 500 involves calculating the difference between a modeled adjustment rate and an actual adjustment rate. For example, the actual adjustment rate could be the camshaft adjustment rate during a previous adjustment event, stored in a memory component of controller 12. The modeled adjustment rate can be calculated based on various engine operating parameters such as engine load, engine speed, etc. This difference yields an expected adjustment rate error, which can be used to adjust the oil pressure supplied to the valve to compensate for the error.

[0054] In procedure 506, procedure 500 involves calculating the difference between a modeled adjustment rate and a desired adjustment rate to obtain a predicted adjustment rate error. The desired adjustment rate can be a predetermined value based on engine operating conditions and a VCT system configuration, e.g., determined by a rate of change of actuator position / cam timing based on a conversion such as a calibratable table. This difference yields a predicted adjustment rate error, which can also be used to adjust the oil pressure supplied to the valve to compensate for the error.

[0055] In procedure 500, part 508 involves taking a maximum value for the difference between the modeled adjustment rate and the actual adjustment rate, and for the difference between the modeled adjustment rate and the desired adjustment rate, in order to account for the two errors determined in steps 504 and 506 described above. The adjustment of the oil pressure supplied to the valve can then be based on this maximum value.

[0056] In procedure 500, method 510 involves storing the difference between the modeled adjustment rate and the actual adjustment rate for use when adjusting the oil pressure supplied to the valve during a subsequent camshaft adjustment event. In some examples, this error can be saved for future use in a weighted additive manner.

[0057] In procedure 500 of 512, the procedure involves estimating the age of a camshaft adjuster based on the difference between the modeled adjustment rate and an actual adjustment rate. For example, a lookup table can be used to estimate the age of the camshaft adjusters based on one or more of the faults identified above. The estimated age of the camshaft adjuster can be used during subsequent adjustment events to predict the amount of additional oil pressure supplied to the adjuster and adjust it accordingly. Furthermore, the estimated camshaft age can be used for diagnostic purposes when a deterioration condition of the adjusters is indicated.

[0058] In procedure 500, procedure 514 involves adjusting the oil pressure supplied to the valve by an amount based on a pressure measurement in an engine lubrication system, in addition to the fault terms determined in the actions described above. For example, this adjustment may depend on the level of oil consumption by other oil subsystems coupled to the engine oil lubrication system, together with one or a combination of the fault terms determined above.

[0059] For example, the oil pressure can be adjusted based on the maximum value of a difference between the modeled adjustment rate and the actual adjustment rate, and a difference between the modeled adjustment rate and the desired adjustment rate, to account for the two errors determined in steps 504 and 506 described above. In this way, the oil pressure adjustment can be increased to account for both error values ​​obtained from previous adjustment events and predicted error values ​​based on current operating conditions such as engine load and engine speed.

[0060] Note that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. 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. As such, various actions, operations, or functions shown may be performed in the sequence shown, in parallel, or in some cases, omitted. Likewise, the processing sequence is not necessarily required to achieve the features and benefits of the exemplary implementations described herein, but is presented for the convenience of illustration and description. One or more of the actions or functions shown may be performed repeatedly, depending on the specific strategy used.Furthermore, the described actions can graphically represent a code that is encoded as microprocessor instructions and stored in the computer-readable storage medium in the engine control system.

[0061] It is understood that the configurations and routines disclosed herein are exemplary and that these specific embodiments are not to be considered limiting, as numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, four-stroke boxer, gasoline, diesel, and other engine types and fuel types. The subject matter of this disclosure includes all novel and non-obvious combinations and partial combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0062] The following claims highlight certain combinations and partial combinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims should be understood to include the integration of one or more such elements, with two or more such elements neither required nor excluded. Other combinations and partial combinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the claims presented or by filing new claims in this or a related application.

[0063] Such claims, whether broader, narrower, the same or different from the original claims with regard to the scope of protection, are also to be regarded as included in the subject matter of the present disclosure.

Claims

[1] Engine process comprising the following: in response to an engine operating condition, adjusting a valve coupled to a hydraulic variable camshaft control actuator to initiate camshaft adjustment and adjusting an oil pressure supplied to the valve based on a camshaft adjuster position and Reducing the oil pressure supplied to the valve for a predetermined time interval to a threshold level to unlock a camshaft adjuster locking pin, but not moving a camshaft adjuster if the camshaft adjuster locking pin is in a home position, and then increasing the oil pressure supplied to the valve to move the camshaft adjuster. [2] Engine method according to claim 1, wherein the oil pressure supplied to the valve is adjusted by an amount based on a modeled, actual and desired camshaft adjustment rate. [3] Motor method according to claim 2, wherein the actual adjustment rate is an adjustment rate of the camshaft during a previous adjustment event. [4] Motor method according to claim 2, wherein the extent is determined by taking a maximum value of a difference between the modeled adjustment rate and an actual adjustment rate and a difference between the modeled adjustment rate and the desired adjustment rate. [5] Engine method according to claim 4, wherein the difference between the modeled adjustment rate and the actual adjustment rate during a subsequent camshaft adjustment event is used to adjust the oil pressure supplied to the valve. [6] Engine method according to claim 4, further comprising estimating the age of a camshaft adjuster based on the difference between the modeled adjustment rate and the actual adjustment rate and increasing the oil pressure supplied to the valve based on an increase in age. [7] Engine method according to claim 1, wherein adjusting the oil pressure supplied to the valve on the basis of the camshaft adjuster position includes increasing the oil pressure supplied to the valve if no camshaft adjuster target position is reached after a predetermined time interval. [8] Engine method according to claim 1, further comprising indicating a deterioration in the quality of the camshaft adjuster if, after a predetermined time interval following adjustment of the oil pressure supplied to the valve, the camshaft adjuster target position has not been reached. [9] Engine method according to claim 1, wherein the oil pressure supplied to the valve is adjusted in response to the valve adjustment reaching a threshold value. [10] Engine method according to claim 1, further comprising increasing the oil pressure supplied to the valve when a camshaft adjuster temperature is above an oil supply temperature. [11] Engine method according to claim 1, wherein the oil pressure supplied to the valve is adjusted by an amount based on a pressure measurement in an engine lubrication system. [12] Motor method according to claim 1, wherein the valve is a hydraulic spool valve and adjusting the valve includes sending a control signal to a solenoid coupled to the hydraulic spool valve. [13] Engine method according to claim 1, wherein the threshold dimension is based on an area of ​​the camshaft adjuster locking pin, a locking pin spring rate, an area of ​​the camshaft adjuster, a camshaft adjuster spring rate and a coefficient of camshaft friction. [14] Engine method according to claim 1, wherein the oil pressure supplied to the valve is reduced to a predetermined level in response to the camshaft adjuster reaching a camshaft adjuster target position. [15] Engine method comprising the following: in response to an engine operating condition: Adjusting a valve coupled to a hydraulic variable camshaft control actuator to initiate camshaft adjustment; If a camshaft adjuster locking pin is in a home position, reduce the oil pressure supplied to the valve to a threshold level for a predetermined time interval to unlock the camshaft adjuster locking pin, but not to move a camshaft adjuster; Increasing the oil pressure supplied to the valve to move the camshaft adjuster. [16] Engine method according to claim 15, wherein the oil pressure supplied to the valve is increased by an extent which is determined by taking a maximum value of a difference between a modeled adjustment rate and an actual adjustment rate and a difference between the modeled adjustment rate and a desired adjustment rate. [17] Engine method according to claim 15, further comprising increasing the oil pressure supplied to the valve by an additional amount if, after the predetermined time interval, no camshaft adjuster target position is reached and the valve adjustment reaches a threshold value. [18] Engine method comprising the following: in response to an engine operating condition, adjusting a valve coupled to a hydraulic variable camshaft control actuator to initiate camshaft adjustment and reducing an oil pressure supplied to the valve to a threshold level for a predetermined time interval in order to unlock a camshaft adjuster locking pin, but not to move a camshaft adjuster. [19] Engine method according to claim 18, wherein the threshold dimension is based on an area of ​​the camshaft adjuster locking pin, a locking pin spring rate, an area of ​​the camshaft adjuster, a camshaft adjuster spring rate and a coefficient of camshaft friction.

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