Variable cam timing system and method for operating the same

Abstract

The present disclosure provides a "variable cam timing system and a method for operating the system". A variable cam timing system in an engine is provided. The variable cam timing system includes a camshaft that receives a rotational input from a crankshaft. The camshaft includes: a valve cam that rotationally actuates a valve coupled to a cylinder; and a zero cam that actuates a zero follower including a zero spring that applies a return force on the zero cam during interaction between the zero cam and the zero follower, wherein the zero follower is independent of the cylinder.

Description

Technical Field

[0001] The present description generally relates to variable cam timing systems and methods for operating variable cam timing systems. Background Art

[0002] Variable cam timing (VCT) devices with camshaft torque actuation (CTA) rely on camshaft torque caused by cylinder valve lift events to adjust the engine's camshaft timing. When a torque-actuated cam phaser is used in conjunction with a valve deactivation system, such valve lift may not occur, and the resulting reduction or (in some cases) absence of camshaft torque may prevent reliable actuation of the camshaft phaser. As a result, desired camshaft timing adjustments may not be achieved during valve deactivation.

[0003] US 7,255,077 discloses a cam phaser that adjusts the cam timing of a valve. However, if the cam phaser is used in conjunction with a valve deactivation device, the phaser may become inoperable due to a reduction in cam torque. Therefore, valve timing and valve deactivation cannot be performed simultaneously in such an engine, thereby reducing engine efficiency. Summary of the invention

[0004] Recognizing the above problems and attempting to solve at least some of them, the inventors have developed a variable cam timing system in an engine. The variable cam timing system includes a camshaft that receives a rotational input from a crankshaft. The camshaft includes: a valve cam that rotationally actuates a valve coupled to a cylinder; and a zero cam, wherein the zero cam actuation includes a zero follower of a zero spring that applies a return force on the zero cam during interaction between the zero cam and the zero follower, wherein the zero follower is independent of the cylinder. In this way, a follower that is not associated with valve actuation can be used to generate camshaft torque. Therefore, a cam phaser coupled to the camshaft can operate over a wider range of engine operating conditions, thereby improving engine efficiency.

[0005] In addition, in one example, the zero follower can be selectively engaged and disengaged. For example, in response to deactivation of the valve, the zero follower can be enabled. Therefore, the efficiency of the system can be improved by providing additional camshaft torque only when needed to reduce losses caused by the interaction between the zero cam and the zero follower.

[0006] It should be understood that the above summary is provided to introduce a series of concepts further described in the detailed description in a simplified form. This is not meant to identify the key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed description. In addition, 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

[0007] Figure 1 A schematic diagram of an internal combustion engine including a variable cam timing system is shown.

[0008] Figure 2 A diagram of an exemplary torque-actuated cam phaser is shown.

[0009] Figure 3 A diagram showing an exemplary variable cam timing system.

[0010] Figure 4 A detailed view of a zero cam deactivation device included in a variable cam timing system is shown.

[0011] Figure 5 A method for operating a variable cam timing system is shown.

[0012] Figure 6 Another method for operating a variable cam timing system is shown.

[0013] Figure 7 A timing diagram showing an exemplary variable cam timing system control strategy. DETAILED DESCRIPTION

[0014] A variable cam timing system is described herein that generates supplemental camshaft torque to enable a torque-actuated cam phaser to operate over a wider range of conditions. Operating the cam phaser over an extended range of conditions enables improved engine efficiency while reducing emissions. In one example, a variable cam timing system includes a zero cam rotationally coupled to a camshaft that cyclically actuates a zero follower that is independent of valve actuation. Thus, the zero cam and the zero follower are not associated with engine valve actuation and are separated from the cylinder valves in the engine. The interaction between the zero cam and the zero follower generates a camshaft torque that can be utilized by a torque-actuated cam phaser to adjust (e.g., advance or retard) valve timing. In one example, a variable cam timing system may include a zero cam deactivation device that is designed to enable and deactivate a zero follower to change the amount of torque applied to the camshaft via the zero follower. For example, a zero follower may be enabled in response to deactivation of an engine valve to increase camshaft torque. Thus, a desired amount of camshaft torque can be selectively generated to enable operation of a torque-actuated cam phaser to adjust valve timing during valve deactivation periods. In this way, camshaft torque can be regulated to facilitate operation of a torque-actuated cam phaser to improve combustion efficiency and reduce emissions. Continuing with reference to this example, the zero follower can be deactivated in response to reactivation of an engine valve, thereby reducing losses in the system caused by the interaction between the zero cam and the zero follower. In this way, the zero cam and the zero follower can only be activated when additional camshaft torque is required to operate the cam phaser, and can be deactivated when no additional camshaft torque is required to operate the cam phaser. Thus, the efficiency of the variable cam timing system is further improved.

[0015] Figure 1 A schematic diagram showing an engine with a variable cam timing system. Figure 2 Shown may include Figure 1 An example of a torque-actuated cam phaser in an engine is shown. Figure 3 and Figure 4 Various exemplary variable cam timing systems are shown. Figure 5 and Figure 6 A method for operating a variable cam timing system is shown. Figure 7 A diagram is shown illustrating diagrams and control signals associated with a method for operating a variable cam timing system.

[0016] Go to Figure 1 , schematically illustrates an engine 10 with a variable cam timing system 12 in a vehicle 14. Figure 1 Schematic diagrams of various engines and engine systems are provided, but it should be understood that at least some components may have similar Figure 1 The components shown have different spatial positions and greater structural complexity than that shown. Figures 2 to 4 The structural details of the components are discussed in more detail.

[0017] exist Figure 1 Also depicted is an intake system 16 that provides intake air to the cylinder 18. A piston 20 is positioned in the cylinder 18. The piston 20 is coupled to a crankshaft 21 via a piston rod 22 and / or other suitable mechanical components. The cylinder 18 is formed by a cylinder block 24 coupled to a cylinder head 26. Although Figure 1 Engine 10 is depicted as having one combustion chamber. However, in other examples, engine 10 may have additional combustion chambers. For example, engine 10 may include multiple combustion chambers, which may be positioned in groups in some cases.

[0018] The intake system 16 includes an intake duct 28 and a throttle 30 coupled to the intake duct. The throttle 30 is configured to regulate the amount of air provided to the cylinder 18. In the depicted example, the intake duct 28 feeds air to an intake manifold 32. In turn, the intake manifold 32 directs the air to an intake valve 34. The intake valve 34 opens and closes to allow intake air flow into the cylinder at a desired time period. In addition, in other examples, such as in a multi-cylinder engine, additional intake runners may diverge from the intake manifold and feed intake air to other intake valves. It should be appreciated that the intake manifold 32 and the intake valve 34 are included in the intake system 16. In addition, Figure 1 The engine shown includes two intake valves and two exhaust valves. However, in other examples, cylinder 18 may include a single intake valve and / or a single exhaust valve or more than two intake valves and / or exhaust valves. In addition, the engine may include additional cylinders that may have a similar number of intake valves and / or exhaust valves or an alternative number of intake valves and / or exhaust valves.

[0019] Intake valve 34 is actuated by intake valve actuator 36. Likewise, exhaust valve 38 is actuated by exhaust valve actuator 40. The valve actuator may include springs, tappets, rocker arms, and / or other suitable components that enable valve opening and closing to occur in response to cam actuation of the actuator. Figure 3 to Figure 4 The structural details of the valve actuators are discussed in greater detail. Furthermore, it should be appreciated that the intake valve actuators and the exhaust valve actuators may include similar actuator components, or may have different components that facilitate actuation in other examples.

[0020] The intake valve actuator 36 is activated by an intake cam 42 that is rotatably coupled to an intake camshaft 44. Likewise, the exhaust valve actuator 40 is activated by an exhaust cam 46 that is rotatably coupled to an exhaust camshaft 48. The intake camshaft 44 and the exhaust camshaft 48 are each coupled to the crankshaft 21 (indicated via arrows 50). A chain, belt, and / or other mechanical components may facilitate the rotational connection between the camshaft and the crankshaft.

[0021] A torque-actuated cam phaser 52 (eg, a torque-actuated variable cam timing (VCT) phaser) is coupled to the intake camshaft 44. The torque-actuated cam phaser 52 is designed to utilize torque from the camshaft to cause phase adjustment of the camshaft to advance and retard valve timing. Figure 2 An exemplary torque-actuated phaser is shown in and discussed in greater detail herein.

[0022] The intake valve deactivation device 54 is also connected to the intake valve actuator 36. The intake valve deactivation device 54 is configured to independently enable and deactivate the intake valve. In one example, the intake valve deactivation device can be an unlockable roller finger follower (DRFF) that mechanically disconnects the valve from the camshaft when in cylinder deactivation mode. In one example, the unlockable roller finger follower can be similar to the zero cam deactivation device described herein. Therefore, both the intake valve deactivation device and the zero cam deactivation device can use an unlockable roller finger follower. In this example, a control action can be taken to cause the intake valve deactivation device to receive high oil pressure when the zero cam deactivation device receives low oil pressure, or vice versa. The oil pressure can be controlled by using an electrically actuated oil control valve, which controls whether the roller finger follower is receiving high oil pressure and is therefore locked together or whether it is receiving low oil pressure or not receiving any oil pressure and is therefore not locked. When the roller thumb followers are locked together, valve lift will occur normally. When the roller thumb followers are unlocked, the camshaft lobes cannot exert force on the valves and therefore valve lift will not occur.

[0023] exist Figure 1 In one embodiment, the intake valve has a deactivation device and a cam phaser. However, additionally or alternatively, the exhaust valve may have a corresponding deactivation device and a cam phaser. Furthermore, in other examples, the valve deactivation device may be used to activate and deactivate the intake valve and the exhaust valve. Still further, in other examples, the valve deactivation device may be coupled to additional engine cylinders.

[0024] The variable cam timing system 12 is shown to include a zero cam 56 that is rotationally coupled to the intake camshaft 44. The variable cam timing system 12 also includes a zero follower 58 that interacts with the zero cam 56 during the rotation of the camshaft to generate torque on the camshaft. The zero cam 56 and the zero follower 58 are not connected to the cylinder 18. Therefore, in the case of a multi-cylinder engine, the zero cam 56 and the zero follower 58 can be spaced apart and disconnected from any valve corresponding to the cylinder 18 or other cylinders in the engine. In this way, the zero cam 56 and the zero follower 58 can be independent of the cylinder 18. The zero cam is provided to apply torque on the camshaft to enable the torque-actuated cam phaser to operate as needed. For example, when one or more intake valves 34 are deactivated, it may not be possible to provide enough torque to the camshaft to enable the cam phaser that utilizes the camshaft torque to function.

[0025] The variable cam timing system 12 may also include a zero cam deactivation device 60 designed to activate and deactivate the zero follower. Deactivation of the zero follower includes moving the zero follower into an inactive position that inhibits interaction between the zero cam and the zero follower during crankshaft rotation to selectively generate a camshaft torque that can be used to operate the torque-actuated cam phaser. However, in other examples, the variable cam timing system 12 may not include a zero cam deactivation device. In such examples, the zero cam and the zero cam follower may continuously and cyclically interact with each other during engine operation.

[0026] It should also be understood that the variable cam timing system 12 may also include a torque-actuated cam phaser 52 and / or a valve deactivation device 54. In the example shown, the variable cam timing system 12 includes an oil control valve 90, which provides pressurized lubricant (e.g., oil) to the valve deactivation device 54 and the zero cam deactivation device 60 via an oil line 92. It should also be understood that another oil control valve can also provide pressurized lubricant to the torque-actuated cam phaser 52. Further, in other examples, a separate oil control valve can provide pressurized lubricant to the valve deactivation device 54 and the zero cam deactivation device 60. These oil control valves can be controlled via the controller 100 discussed in more detail herein. It should be understood that the oil pressure provided to the valve deactivation device and the zero cam deactivation device can trigger the activation and deactivation of the device. The oil control valve 90 is designed to regulate the amount and pressure of oil provided to the valve deactivation device 54 and the zero cam deactivation device 60, and can therefore initiate the deactivation and activation of the device. It should be appreciated that the oil control valve 90 may be operable to supply oil from a lubricant pump and a lubricant reservoir (such as those discussed in greater detail herein). Figure 2A lubricant pump 268 and a lubricant reservoir 270 are shown receiving lubricant. Additionally, in other cases, the variable cam timing system 12 may include separate oil control valves and / or other actuators corresponding to the valve deactivation device and the zero cam deactivation device.

[0027] Figure 1 Also shown is a fuel delivery system 62. The fuel delivery system 62 provides pressurized fuel to the fuel injectors 64. In the example shown, the fuel injectors 64 are direct fuel injectors coupled to the cylinders 18. Additionally or alternatively, the fuel delivery system 62 may also include a port fuel injector designed to inject fuel upstream of the cylinders 18 into the intake system 16. The fuel delivery system 62 includes a fuel tank 66 and a fuel pump 68 designed to flow the pressurized fuel to downstream components. A fuel line 70 provides fluid communication between the fuel pump 68 and the fuel injectors 64. The fuel delivery system 62 may include conventional components (such as a high pressure fuel pump, a check valve, a return line, etc.) for enabling fuel to be provided to the injectors at a desired pressure.

[0028] An exhaust system 72 configured to manage exhaust gas from cylinders 18 is also included. Figure 1 14 is depicted. Exhaust system 72 includes exhaust valve 38, which is designed to open and close to allow and inhibit exhaust gas flow from the combustion chamber to downstream components. Exhaust system 72 also includes emission control device 74, which is coupled to exhaust conduit 76 downstream of exhaust manifold 78. Emission control device 74 may include filters, catalysts, absorbers, etc. for reducing tailpipe emissions. Engine 10 also includes ignition system 80 (e.g., spark plugs), which includes energy storage device 82 designed to provide energy to ignition device 84. Additionally or alternatively, engine 10 may perform compression ignition.

[0029] During engine operation, the cylinder 18 typically undergoes a four-stroke cycle, which includes: an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During the intake stroke, typically, the exhaust valve is closed and the intake valve is open. Air is introduced into the combustion chamber via a corresponding intake duct, and the piston moves to the bottom of the combustion chamber to increase the volume within the combustion chamber. The position of the piston near the bottom of the combustion chamber and at the end of its stroke (e.g., when the combustion chamber is at its maximum volume) is typically referred to by those skilled in the art as the bottom dead center (BDC). During the compression stroke, the intake and exhaust valves are closed. The piston moves toward the cylinder head to compress the air within the combustion chamber. The point at which the piston is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber is at its minimum volume) is typically referred to by those skilled in the art as the 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 fuel injected into the combustion chamber is ignited via a spark from an ignition device, resulting in combustion. However, in other examples, compression may be used to ignite the air-fuel mixture in the combustion chamber. During the expansion stroke, the expanding gases push the piston back to BDC. The crankshaft converts this piston movement into a rotational torque of the rotating shaft. During the exhaust stroke, in a conventional design, the exhaust valve opens to release the remaining burned air-fuel mixture to the corresponding exhaust passage, and the piston returns to TDC.

[0030] The engine 10 may also include an engine lubrication system (not shown). The engine lubrication system may include lubricant lines, valves, nozzles, etc. for delivering lubricant (e.g., oil) to lubricated components such as pistons, camshafts, crankshafts, etc. It should be appreciated that the oil control valve 90 and oil line 92 may draw oil from the engine lubrication system.

[0031] Figure 1 Also shown is a controller 100 in the vehicle 14. Specifically, the controller 100 is Figure 1 1 is a conventional microcomputer, which includes: a microprocessor unit 102, an input / output port 104, a read-only memory 106, a random access memory 108, a keep-alive memory 110, and a conventional data bus. The controller 100 is configured to receive various signals from sensors coupled to the engine 10. The sensors may include: an engine coolant temperature sensor 130, an exhaust gas composition sensor 132, an exhaust gas airflow sensor 134, an intake airflow sensor 136, a manifold pressure sensor 137, an engine speed sensor 138, etc. In addition, the controller 100 is also configured to receive a throttle position (TP) from a throttle position sensor 112 coupled to a pedal 114 actuated by a driver 116.

[0032] In addition, the controller 100 may be configured to trigger one or more actuators and / or send commands to components. For example, the controller 100 may trigger adjustments to the throttle 30, the torque-actuated cam phaser 52, the valve deactivation device 54, the zero cam deactivation device 60, the fuel injector 64, etc. Specifically, the controller 100 may be configured to send a signal to the zero cam deactivation device 60 to enable and disable the zero follower. The controller 100 may also be configured to send a control signal to the valve deactivation device 54 to enable and disable the intake valve 34. In addition, the controller 100 may be configured to send a control signal to the fuel pump 68 and the fuel injector 64 to control the amount and timing of the fuel injection provided to the cylinder 18. The controller 100 may also send a control signal to the throttle 30 to change the engine speed.

[0033] Thus, the controller 100 receives signals from various sensors and, based on the received signals and instructions stored in a memory (e.g., non-transitory memory) of the controller, employs various actuators to adjust engine operation. Thus, it should be appreciated that the controller 100 may send and receive signals from the variable cam timing system 12. For example, adjusting the zero cam deactivation device 60 may include adjusting a component in the zero cam deactivation device 60 to trigger a device actuator for enabling and disabling a zero follower. In yet another example, enabling and disabling a valve deactivation device may include adjusting a deactivator actuator that triggers valve enablement or deactivation. In yet another example, the amount of adjustment for a component, device, actuator, etc. may be empirically determined and stored in a predetermined lookup table and / or function. For example, one table may correspond to a condition determined when the zero cam deactivation device 60 should enable a zero follower, and another table may correspond to a condition determined when the zero cam deactivation device 60 should deactivate a zero follower. In other examples, one table may correspond to conditions where the intake cam is advanced via the phaser, while another table may correspond to conditions where the intake cam is retarded via the phaser. The table may be linked to engine operating conditions (such as engine speed, engine load, and other engine operating conditions). In addition, the table may output the amount of fuel injected into the combustion chamber via the fuel injector at each cylinder cycle. Therefore, it should be understood that the controller 100 can be configured to implement the methods, control strategies, etc. described herein with respect to variable cam timing systems and engines.

[0034] In one example, the controller 100 may be configured to enable a zero follower via a zero cam deactivation device during a first operating condition and to disable the zero follower during a second operating condition different from the first operating condition. For example, the first operating condition may include a condition in which one or more intake valves are deactivated via a valve deactivation device 54, and the second condition may include a condition in which the intake valve is enabled via the valve deactivation device. In other examples, the zero follower may be enabled when the camshaft torque drops below a threshold and disabled when the camshaft torque rises above a threshold. A threshold value (e.g., a threshold camshaft phase rate) may be determined based on the number of valve lift events in an engine cycle. This characterization may allow a comparison between a desired phase rate and a maximum achievable rate taking into account the number of valve lift events currently available. In one example, a zero cam spring may be enabled when it is determined that the desired phase rate is greater than the maximum achievable rate. Additionally, in such an example, the zero cam spring is inactive when the remaining valve lift events are sufficient taking into account the currently desired phasing rate.

[0035] Figure 2 An exemplary torque-actuated VCT phaser 200 is shown. Specifically, in the example shown, the VCT phaser 200 is in an advanced position. Figure 2 The VCT phaser 200 shown is Figure 1 An example of a cam phaser 52 is shown. Thus, the VCT phaser 200 may include Figure 1 The variable cam timing system 12 is shown.

[0036] The spool valve 202 is coupled to the VCT phaser. In one example, the spool valve 202 can be a solenoid operated spool valve. The spool valve 202 is shown as being positioned in the advance section of the spool. However, it should be appreciated that the spool valve can also be placed in a retarded configuration and other intermediate positions. Furthermore, the spool valve can be continuously adjusted. Additionally, the configuration of the spool valve sets the direction of movement (e.g., advance direction, retarded direction) and the rate of movement of the VCT phaser 200.

[0037] The VCT phaser 200 also includes a rotor 204 mounted to the end of a camshaft 205. The rotor 204 includes one or more vanes 206. In addition, the rotor 204 is surrounded by a housing assembly 208. The housing assembly 208 includes a vane chamber 209 having the vanes 206 positioned therein. In another example, the vanes 206 may be included in the housing assembly 208 and the vane chamber 209 may be included in the rotor 204. The periphery 210 of the housing assembly 208 forms a sprocket 212, pulley or gear, which receives a driving force typically from the crankshaft or from another camshaft in a multi-cam engine through a chain, belt or gear.

[0038] The VCT phaser 200 is designed as a cam torque-actuated phaser. In this way, the torque reversal in the camshaft caused by the force of opening and closing the engine valve can help move the vane 206. The advance chamber 214 and the retard chamber 216 can be arranged to resist positive torque pulsations and negative torque pulsations in the camshaft 205, respectively. In addition, the advance chamber 214 and the retard chamber 216 can be pressurized by the cam torque, respectively, alternatively. Depending on the desired direction of movement, the slide valve 202 enables the vane 206 in the phaser to move by allowing fluid to flow from the advance chamber 214 to the retard chamber 216 or vice versa. For example, when it is desired to move the vane in the advance direction, the slide valve 202 is adjusted to allow fluid to flow from the retard chamber to the advance chamber. On the other hand, when it is desired to move the vane in the retard direction, the slide valve 202 is adjusted to allow fluid to flow from the advance chamber to the retard chamber.

[0039] The rotor 204 is connected to the camshaft 205 and is coaxially positioned within the housing assembly 208. It should be understood that the vanes 206 are designed to change the relative angular position of the housing assembly 208 and the rotor 204. In addition, Figure 2 A hydraulic brake circuit 218 is also shown, and a locking pin circuit 220 is also presented. The hydraulic brake circuit 218 and the locking pin circuit 220 are fluidly coupled. Thus, in one example, the hydraulic brake circuit and the locking pin circuit may form a single hydraulic circuit. The hydraulic brake circuit 218 includes a spring 222 and a loaded pilot valve 224. The hydraulic brake circuit 218 also includes an advance brake line 226, which fluidly connects the advance chamber 214 to the pilot valve 224. The hydraulic brake circuit also includes a common line 228 and a retard brake line 230, which hydraulically couples the retard chamber 216 to the pilot valve 224 and the common line 228. The advance brake line 226 and the retard brake line 230 are a predetermined distance from the vane 206. The pilot valve 224 is located in the rotor 204 and is fluidly connected to the locking pin circuit 220 and the supply line 232 via a connecting line 234. The locking pin circuit 220 includes a locking pin 236 , a connecting line 234 , a pilot valve 224 , a supply line 232 , and an exhaust line 238 (dashed line).

[0040] The pilot valve may have two positions between which it can be adjusted. The first position may be a closed position, and the second position may be an open position. The spool valve may trigger the pilot valve to adjust to two positions (i.e., open and closed). In the first position, the pilot valve is pressurized by the oil pressure generated by the engine in line 234, which positions the pilot valve to substantially block (e.g., prevent) fluid from flowing between the advance chamber and the retard chamber through the pilot valve and the brake circuit 218. In the second position of the pilot valve, there is no oil pressure generated by the engine in line 234. The absence of pressure in line 234 enables the spring 222 to adjust the pilot valve, thereby allowing fluid to flow between the brake line from the advance chamber and the brake line from the retard chamber through the pilot valve and the common line, so that the rotor assembly moves to and remains in the locked position.

[0041] The locking pin 236 is positioned in a hole in the rotor 204 and can slide therein. The locking pin 236 has an end portion that is biased toward and fits into a groove 240 in the housing assembly 208. A spring 242 enables the locking pin 236 to be biased toward the groove 240. In other examples, the locking pin can be positioned in the housing assembly with a spring and the rotor 204, which may include a groove. It should be understood that the opening and closing action in the hydraulic brake circuit 218 and the pressurization of the locking pin circuit 220 are controlled by spool valve regulation.

[0042] The spool valve 202 includes a spool 244 having cylindrical shoulders 246, 248, 250 positioned within a sleeve 252. In turn, the sleeve 252 is positioned within a bore of the rotor 204 and a camshaft guide. One end of the spool interacts with a spring 254. The other end of the spool interacts with a pulse width modulated variable force solenoid 256. In some cases, the solenoid 256 may also be controlled by varying a duty cycle, current, voltage, and / or other techniques. Additionally, the spool 244 may be coupled to and / or include a motor and / or other actuator.

[0043] The position of the spool is adjusted by the interaction between the spring 254, the solenoid 256 and the controller 258. The position of the spool 244 controls the movement of the phaser (e.g., the direction and rate of movement). For example, the position of the spool determines whether the phaser moves toward an advance position, toward a holding position, or toward a retarded position. Thus, the spool 244 can provide active pilot valve regulation. Therefore, the spool valve 202 has an advance mode, a retarded mode, a zero mode, and a detent mode. These control modes correspond to different spool valve positions. Specifically, a specific region of the stroke of the spool valve can allow the spool valve to operate in an advance mode, a retarded mode, a zero mode, and a detent mode.

[0044] In the advance mode, spool 244 moves to a position in the advance region of the spool valve, allowing fluid to flow from retard chamber 216 through spool 244 to advance chamber 214 while preventing fluid from leaving advance chamber 214. Additionally, brake circuit 218 remains closed.

[0045] In the retard mode, the spool 244 moves to the retard region of the spool valve, thereby enabling fluid to flow from the advance chamber 214 through the spool 244 and to the retard chamber 216, while preventing fluid from leaving the retard chamber 216. In addition, the brake circuit 218 remains closed.

[0046] In the zero mode, the spool 244 moves to a position in the zero region of the spool valve, thereby inhibiting fluid flow from the advance chamber 214 and the retard chamber 216, respectively, while continuing to maintain the brake circuit 218 in a closed configuration. In the braking mode, the spool moves to a position in the braking region. In the braking mode, three functions can be performed at overlapping time intervals. The first function in the braking mode is that the spool 244 moves to a position in which the spool shoulder 248 blocks the flow of fluid from the pipeline 260 between the spool shoulder 246 and the spool shoulder 248 into any other pipeline and the pipeline 262. In this way, the control of the phaser is stopped. The second function in the braking mode can be the configuration of the braking circuit 218. In this way, the braking circuit 218 controls the phaser moving to the advance or retard position until the vane 206 reaches the intermediate phase angle position. The third function in the braking mode is a mode that vents the locking pin circuit 220, which allows the locking pin 236 to cooperate with the groove 240. The intermediate phase angle position (e.g., intermediate locked position or locked position) may include a position where the vane 206 is located between the advance wall 264 and the retard wall 266, which define a chamber between the housing assembly 208 and the rotor 204. The locked position may be a position anywhere between the advance wall 264 and the retard wall 266. The locked position may be set by the position of the brake lines 226 and 230 relative to the vane 206. Specifically, the position of the brake lines 226 and 230 relative to the vane 206 may include a position where neither passage is exposed to the advance chamber 214 and the retard chamber 216. Thus, when the pilot valve is in the second position, communication between the two chambers and the phasing circuit is suspended (e.g., disabled). Commanding the spool valve to the braking region may also be referred to herein as commanding "locking."

[0047] Based on the duty cycle of the pulse width modulated variable force solenoid 256, the spool 244 moves to a corresponding position along its stroke. In one example, when the duty cycle of the variable force solenoid 256 is approximately 30%, 50%, or 100%, the spool 244 moves to positions corresponding to the retard mode, the zero mode, and the advance mode, respectively, and the pilot valve 224 is pressurized and moves from the second position to the first position, while the hydraulic detent circuit 218 is closed and the locking pin 236 is pressurized and released. In one example, when the duty cycle of the variable force solenoid 256 is set to 0%, the spool 244 moves to the detent mode, causing the pilot valve 224 to be vented and moved to the second position, the hydraulic detent circuit 218 is opened, and the locking pin 236 is vented and engaged with the groove 240. Selecting a duty cycle of 0% as the position along the spool valve stroke enables the hydraulic detent circuit 218 to be opened, the pilot valve 224 to be vented, and the locking pin 236 to be vented and engaged with the groove 240. In the event of a loss of power or control, the phaser may default to the locked position. It should be appreciated that the duty cycle percentages previously described are provided as non-limiting examples, and that in alternative examples, many different duty cycles may be used to move the spool of the spool valve between different spool areas. For example, at a 100% duty cycle, the hydraulic detent circuit 218 may be open and the pilot valve 224 may be vented while the locking pin 236 engages the groove 240.

[0048] Figure 2 Also shown is a lubricant pump 268 in fluid communication with the lubricant reservoir 270. The lubricant pump 268 is in fluid communication with the supply line 232. It should be appreciated that the lubricant pump 268 may also provide lubricant to other components in the engine, such as Figure 1 The piston 20, crankshaft 21, etc. shown. Therefore, the lubricant pump 268 and the lubricant reservoir 270 may be included in the lubrication system. It should be understood that a variety of torque-actuated cam phasers have been envisioned. For example, in one example, a cam torque-actuated phaser with an end lock configuration can be used, which means that the locking position is located at one end of the travel range (e.g., the maximum travel range). In another example, a cam torque-actuated phaser with intermediate locking can be used. Intermediate locking means that the locking position is located somewhere between the end positions. In yet another example, a cam torque-actuated phaser with oil pressure assistance can be used, which means that in some cases discrete chambers or all chambers are assisted by oil pressure.

[0049] Figure 3 An example of a variable cam timing system 300 is shown. It should be appreciated that Figure 3 The variable cam timing system 300 shown is Figure 1 An example of a variable cam timing system 12 is shown. In addition, Figure 3The variable cam timing system 300 shown may also include Figure 2 The VCT phaser 200 is shown.

[0050] The variable cam timing system 300 includes a camshaft 302. The camshaft 302 is designed to receive a variable cam timing signal from a crankshaft such as Figure 1 The camshaft 302 includes a rotational input of the crankshaft 21 shown. In addition, the camshaft 302 includes a valve cam 304, which cyclically actuates a valve actuator 306 during engine operation, and the valve actuator 306 cyclically actuates a valve 308. In one example, the valve 308 can be coupled to a separate cylinder. However, in other examples, the valve 308 can be coupled to a common cylinder.

[0051] Camshaft 302 also includes a zero cam 310. Zero cam 310 includes a plurality of lobes 312 having noses 313 extending away from a rotational axis 314 of the zero cam and positioned on a common radial plane 316. Thus, each nose 313 may extend radially away from the rotational axis 314. However, in other examples, zero cam 310 may include a single lobe, more than two lobes, etc.

[0052] The variable cam timing system 300 also includes a zero cam deactivation device 318. The zero cam deactivation device 318 is configured to activate and deactivate a zero follower 320. It should be appreciated that when the zero follower 320 is activated, the follower cyclically interacts with the lobe 312 of the zero cam 310. The zero follower 320 includes a spring 322, and thus when the zero follower is cyclically actuated by the lobe 312, the zero follower applies torque to the camshaft 302.

[0053] Figure 4 A detailed view of an exemplary zero cam deactivation device 400 is shown. The zero cam deactivation device 400 may include Figure 1 and Figure 3 Any of the variable cam timing systems shown. The zero cam deactivation device 400 includes a latch 402 and a latch actuator 404. The latch 402 and the latch actuator 404 are shown as being integrated into a first portion 405 of a zero follower 406. The latch 402 can extend and retract to couple and disconnect the first portion 405 of the zero follower 406 with a second portion 408 of the zero follower 406. In this manner, the zero follower 406 can be activated and deactivated. The zero follower 406 is also shown as pivoting about a follower pivot 410. The zero follower 406 also includes a spring 412 coupled to a zero shaft 414. However, other zero follower actuation kinematics have been contemplated. In one example, the zero cam deactivation device 400 can be similar to Figure 1The intake valve deactivation device 54 is shown. Thus, the zero cam deactivation device may include a DRFF. In such an example, the zero cam deactivation device 400 may include an electrically actuated oil control valve similar to the oil control valve discussed above with respect to the intake valve deactivation device 54. Thus, the oil pressure may determine whether the zero cam deactivation device is locked, thereby allowing the zero spring to exert force on the camshaft, or unlocked, thereby preventing the zero spring from exerting force on the camshaft and thereby reducing friction losses.

[0054] Figure 4 Also shown in FIG. 4 is a zero cam 416. In the example shown, the zero cam 416 also includes a plurality of lobes 418. However, in other examples, the zero cam may include a single lobe or more than three lobes. Lobe 418 includes a nose that extends radially away from the axis of rotation of the camshaft 420. In this manner, the zero cam will apply torque to the camshaft multiple times per engine cycle.

[0055] In the example shown, the angles 422 formed between the sequential lobes 418 are substantially equal. Specifically, the angles 422 formed between the sequential lobes are all 120°. However, in other examples, the angles formed between the lobes may vary and / or may not be equal. When the timing of the cylinder lift events in a group is not evenly spaced in the engine cycle, the angular spacing between the zero lobes may be unequal. In one example, the zero lobes may be designed to apply torque at the same point in the engine rotation as the deactivated cylinders. In one use case scenario, the camshaft is designed to control the valve lift of four different cylinders. In this use case scenario, two cylinders may be deactivated, which may be the first and last to be lifted in the engine cycle. Thus, in the use case system, the angular arrangement of the zero lobes may be such that the lobes will intersect at an angle of nearly 90 degrees, but then a portion of the shaft will have no lobes present, and instead it will be at the base circle, so there will be no torque applied to the camshaft. However, many suitable lobes arrangements have been envisioned.

[0056] Figures 2 to 4An exemplary configuration with relative positioning of various components is shown. If shown as directly contacting each other or directly connected, then at least in one example, these elements can be referred to as directly contacting or directly connected, respectively. Similarly, the elements shown as being adjacent or adjacent to each other can be adjacent or adjacent to each other, respectively, at least in one example. As an example, the components placed in coplanar contact with each other can be referred to as being in coplanar contact. As another example, the elements positioned to be separated from each other and having only a certain space between them without other components can be referred to as such in at least one example. As another example, the elements shown as being above / below each other, on both sides opposite to each other, or on the left / right side of each other can be referred to as such relative to each other. In addition, as shown in the figure, in at least one example, the topmost element or the vertex of the element can be referred to as the "top" of the component, and the bottommost element or the bottommost point of the element can be referred to as the "bottom" of the component. As used herein, top / bottom, upper / lower, above / below can be relative to the vertical axis of the accompanying drawings, and can be used to describe the positioning of the elements of the accompanying drawings relative to each other. In this way, in one example, the element shown as being above other elements is vertically positioned above other elements. As yet another example, the shapes of elements depicted in the drawings may be referred to as having those shapes (e.g., as being round, straight, planar, curved, rounded, chamfered, angled, etc.). Additionally, in at least one example, elements shown as intersecting each other may be referred to as intersecting elements or intersecting each other. Still further, in one example, elements shown as being within another element or shown as being outside another element may be referred to as such.

[0057] Figure 5 A method 500 for operating a variable cam timing system in an engine is shown. The method 500 and other methods described herein may be described above with respect to Figures 1 to 4 The variable cam timing system and engine described herein may be implemented, or in other examples, may be implemented by other suitable variable cam timing systems and engines. Instructions for implementing method 500 and other methods described herein may be provided by a controller based on instructions stored in a memory (e.g., non-transient) that can be executed by the controller and in combination with sensors in the engine and corresponding systems (such as those described above with reference to Figures 1 to 4 According to the method described below, the controller may use a variable cam timing system and an engine actuator of the engine to adjust engine operation.

[0058] At 502, the method includes cyclically actuating a valve coupled to a cylinder using a valve cam rotationally coupled to a camshaft. Next, at 504, the method includes determining operating conditions. The operating conditions may include engine speed, engine load, engine temperature, throttle position, manifold air pressure, exhaust composition, etc.

[0059] At 506, the method includes determining whether the valve should be deactivated based on operating conditions (e.g., engine speed and / or engine load). In one example, valve deactivation can be determined based on an engine speed and / or engine load threshold. For example, the valve can be deactivated when the engine speed is less than 3,000 RPM, 3,500 RPM, 4,000 RPM, etc. In addition, in one example, the deactivated valve can be coupled to a first cylinder and a valve coupled to a second cylinder can be enabled. In another example, the deactivated valve can be coupled to a first cylinder and a second valve coupled to the first cylinder can be enabled. If it is determined that the valve should not be deactivated (no at 506), the method moves to 508. At 508, the method includes maintaining valve activation and zero follower deactivation.

[0060] However, if it is determined that the valve should be deactivated (yes at 506), the method proceeds to 510. At 510, the method includes deactivating the first valve by operation of a valve deactivation device. For example, the valve may be deactivated via oil pressure control. The oil pressure may be controlled by using an electrically actuated oil control valve. For example, the valve may control the oil pressure to the roller finger follower so that when the roller finger follower in the valve deactivation device receives high oil pressure, the roller finger follower may be locked together, and when the latch receives low pressure or, in some cases, no pressure, the roller finger follower may not be locked. When the roller finger followers are locked together, valve lift may typically occur. When the roller finger follower is not locked, the camshaft lobe may not be able to apply force on the valve, and therefore valve lift may not occur.

[0061] At 512 , the method includes activating the zero follower. Activating the zero follower may include operating a zero cam deactivation device to enable interaction between the zero cam and the zero follower to generate camshaft torque.

[0062] At 514, the method includes adjusting the valve timing of the second valve using a torque-actuated cam phaser rotationally coupled to the camshaft during the interaction between the zero cam and the zero follower. In this way, the torque-actuated cam phaser can be operated during the valve deactivation period to improve combustion efficiency and reduce emissions. In one example, the second valve can be coupled to a different cylinder than the first valve. Further, in such an example, the first valve and the second valve can be an intake valve or an exhaust valve. However, in other examples, the first valve and the second valve can be coupled to a common cylinder.

[0063] At 516, the method includes determining whether the first valve should be activated. It should be appreciated that such a determination may take into account engine operating conditions (such as engine speed and / or engine load). For example, when the engine speed increases above a threshold (e.g., 3,000 RPM, 3,500 RPM, 4,000 RPM, etc.), it may be determined that the first valve should be activated. If it is determined that the first valve should not be activated (NO at 516), the method proceeds to 518. At 518, the method includes maintaining valve deactivation and zero follower activation.

[0064] However, if it is determined that the first valve should be activated (YES at 516), the method moves to 520. At 520, the method includes activating the first valve. Activating the first valve may include operating a valve deactivation device to enable the valve to cyclically open and close during a combustion cycle.

[0065] At 522 , the method includes deactivating the zero follower. Deactivation of the zero follower may include operating a zero cam deactivation device to prevent interaction between the zero follower and the zero cam.

[0066] Next, at 524, the method includes adjusting valve timing of the first valve and the second valve using the torque-actuated cam phaser. For example, the first valve and the second valve may be advanced or retarded, respectively. Method 500 enables activation and deactivation of a zero follower based on valve deactivation, which enables the torque-actuated cam phaser to operate during valve deactivation, thereby improving combustion efficiency and reducing emissions.

[0067] Figure 6 Another method 600 for operating a variable cam timing system and an engine is shown. The method 600 includes: At 602, the method includes determining operating conditions. The operating conditions may include engine speed, engine load, engine temperature, valve activation state, camshaft torque, etc. In one example, the camshaft torque can be calculated based on the engine load and engine speed and the valve activation state. In other examples, the camshaft torque can be detected by a torque sensor coupled to the camshaft.

[0068] At 604, the method includes determining whether the camshaft torque is less than a threshold. In one example, the threshold can be determined based on the number of valve lift events in the engine cycle. For example, the threshold camshaft phase rate can depend on the number of valve lift events in the engine cycle. This characterization allows a comparison between the desired phase rate and the maximum achievable rate taking into account the number of valve lift events currently available. In one example, when it is determined that the desired phase rate is greater than the maximum achievable rate, the zero lobe spring can be enabled, and the zero lobe spring is ensured to be inactive when the remaining valve lift events are sufficient considering the current desired phasing rate. If it is determined that the camshaft torque is not less than the threshold (no at 604), the method includes maintaining the deactivation of the zero follower at 606. On the other hand, if it is determined that the camshaft torque is less than the threshold (yes at 604), the method moves to 608, where the method includes enabling the zero follower so that the interaction between the zero follower and the zero cam can generate the camshaft torque. It should be understood that camshaft torque can be used to operate a torque-actuated cam phaser to advance or retard valve timing. It should also be understood that deactivating one or more valves coupled to one or more cylinders in an engine while activating other valves in the engine can result in a reduction in camshaft torque.

[0069] At 610, the method includes determining whether the camshaft torque is greater than a threshold. If it is detected that the camshaft torque is not greater than the threshold (no at 610), the method proceeds to 612, where the method includes maintaining the activation of the zero follower. However, if it is determined that the camshaft torque is greater than the threshold (yes at 610), the method moves to 614. At 614, the method includes deactivating the zero follower to prevent interaction between the zero cam and the zero follower. In this way, the zero cam follower can be deactivated to reduce energy loss in the variable cam timing system.

[0070] Now turn Figure 7 , graph 700 depicts exemplary variable cam timing system control signals along with camshaft torque maps, such as Figures 1 to 6 As described. Figure 7 The examples are drawn substantially to scale, even though not every point is labeled with a numerical value. Thus, relative differences in timing can be estimated by the size of the drawing. However, other relative timings may be used if desired. In addition, time is represented on the x-axis for each curve and graph. It should also be understood that Figure 7 The diagrams in are given as examples, and in other examples, the timing, thresholds, etc. of the control signals may vary.

[0071] Continue to refer Figure 7, graph 702 depicts the control signal sent to the valve deactivation device. Graph 704 indicates the control signal sent to the zero cam deactivation device. Curve 706 depicts the camshaft torque curve. The control signals sent to the zero cam deactivation device and the valve deactivation device both include two values ​​(ie, enabled and disabled).

[0072] At t1, the valve switches from an enabled configuration to a disabled configuration. In response to the valve deactivation, a zero follower is activated via a zero cam deactivation device. At t1, the camshaft torque also drops below a threshold value 708. As previously described, the camshaft torque may additionally or alternatively be used as a trigger for zero cam deactivation / activation. Furthermore, in some examples, the cam follower may be activated when multiple engine valves are deactivated.

[0073] At t2, the valve switches from the deactivated configuration to the activated configuration. In response to the valve activation, the zero follower is deactivated via the zero cam deactivation device. In this way, when no additional camshaft torque is required to assist the operation of the torque-actuated cam phaser, the losses caused by the interaction between the zero follower and the zero cam can be avoided.

[0074] The technical effect of the variable cam timing system operating method described herein is to expand the operating window of the torque-actuated cam phaser to include periods of valve deactivation. Therefore, both cam phasing and valve deactivation can be implemented in the engine, thereby improving engine efficiency and reducing emissions.

[0075] The invention will be further described in the following paragraphs. In one aspect, a variable cam timing system in an engine is provided. The variable cam timing system includes a camshaft receiving a rotational input from a crankshaft, the camshaft including: a valve cam that rotationally actuates a valve coupled to a cylinder; and a zero cam that actuates a zero follower including a zero spring that applies a return force on the zero cam during interaction between the zero cam and the zero follower, wherein the zero follower is independent of the cylinder.

[0076] In another aspect, a method for operating a variable cam timing system is provided. The method includes: cyclically actuating a valve coupled to a cylinder using a valve cam rotationally coupled to a camshaft; deactivating the valve by operation of a valve deactivation device; and in response to deactivation of the valve, activating a zero follower including a zero spring, the zero spring exerting a return force on the zero cam coupled to a crankshaft during interaction between the zero cam and the zero follower.

[0077] In another aspect, a variable cam timing system in an engine is provided. The variable cam timing system includes a camshaft receiving a rotational input from a crankshaft, the camshaft including: a valve cam lobe that rotationally actuates a valve coupled to a cylinder; a zero cam that actuates a zero follower including a zero spring that applies a return force on the zero cam during interaction between the zero cam and the zero follower, wherein the zero follower is independent of the cylinder; and a torque-actuated cam phaser that rotationally couples to the camshaft.

[0078] In any of the aspects or combinations of aspects herein, the variable cam timing system may also include: a zero cam deactivation device, which is designed to enable and deactivate the zero follower, wherein deactivating the zero follower includes moving the zero follower to an inactive position, and the inactive position inhibits interaction between the zero cam and the zero follower during rotation of the zero cam.

[0079] In any of the aspects or combinations of aspects herein, the variable cam timing system may further include: a controller including code stored in a memory executable by a processor to enable the zero follower via the zero cam deactivation device when a first operating condition occurs.

[0080] In any of the aspects or combinations of aspects herein, the first operating condition may include a condition where the valve is deactivated via a valve deactivation device coupled to the valve.

[0081] In any of the aspects or combinations of aspects herein, the controller may further include code stored in memory executable by the processor to deactivate the zero follower when a second operating condition occurs.

[0082] In any of the aspects or combinations of aspects herein, the second operating condition may include a condition where the valve is activated via the valve deactivation device.

[0083] In any of the aspects or combinations of aspects herein, the variable cam timing system may further include a torque-actuated cam phaser rotationally coupled to the camshaft.

[0084] In any of the aspects or combinations of aspects herein, the torque-actuated cam phaser may adjust cam timing during interaction between the zero cam and the zero follower.

[0085] In any of the aspects or combination of aspects herein, the zero cam may include a plurality of noses extending away from an axis of rotation of the zero cam and actuating the zero follower during rotation of the camshaft.

[0086] In any of the aspects or combinations of aspects herein, the valve may be an intake valve.

[0087] In any of the aspects or combinations of aspects herein, deactivating the valve may include operating an oil pressure control valve to deliver pressurized oil to the valve deactivation device to deactivate the valve, and activating the zero follower includes operating the oil pressure control valve to deliver the pressurized oil to activate the follower.

[0088] In any of the aspects or combinations of aspects herein, the method may further include: activating the valve through operation of the valve deactivation device; and in response to activation of the valve, deactivating the zero follower to inhibit interaction between the zero cam and the zero follower.

[0089] In any of the aspects or combination of aspects herein, the zero follower may be deactivated when the camshaft torque decreases below a threshold.

[0090] In any of the aspects or combinations of aspects herein, the method may further include adjusting valve timing during interaction between the zero cam and the zero follower using a torque-actuated cam phaser rotationally coupled to the camshaft.

[0091] In any of the aspects or combinations of aspects herein, the variable cam timing system may also include: a zero cam deactivation device, which is designed to enable and deactivate the zero follower, wherein deactivating the zero follower includes moving the zero follower to an inactive position, wherein the inactive position inhibits interaction between the zero cam and the zero follower during rotation of the zero cam; and a controller, which includes code stored in a memory and executable by a processor to enable the zero follower via the zero cam deactivation device when the valve is deactivated, wherein the deactivation is triggered by a valve deactivation device connected to the valve.

[0092] In any of the aspects or combinations of aspects herein, the controller may further include code stored in memory executable by the processor to deactivate the zero follower upon activation of the valve, the valve activation being triggered by the valve deactivation device.

[0093] In any of the aspects or combinations of aspects herein, the variable cam timing system may further include an oil control valve that delivers pressurized oil to the valve deactivation device and the zero cam deactivation device.

[0094] In any of the aspects or combination of aspects herein, the null cam may include a plurality of lobes having a nose extending away from an axis of rotation of the null cam and positioned on a common radial plane.

[0095] It should be noted that the exemplary control and estimation procedures included herein can be used with various engine and / or vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-transitory memory and can be implemented by a control system including a controller in combination with various sensors, actuators and other engine hardware. The specific procedures described herein may represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). In this way, the various actions, operations and / or functions shown may be performed in the order shown, may be performed in parallel, or in some cases, may be omitted. Similarly, the processing order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations and / or functions shown may be repeatedly performed according to the specific strategy used. In addition, the actions, operations and / or functions may graphically represent the code in the non-transitory memory of a computer-readable storage medium to be programmed into the engine control system, wherein the actions are implemented by executing the instructions in a system including various engine hardware components in combination with an electronic controller.

[0096] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be considered in a limiting sense, as many variations are possible. For example, the above technology can be applied to V-6, inline 4, inline 6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or characteristics disclosed herein.

[0097] The following claims particularly point out certain combinations and subcombinations believed to be novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include the incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or characteristics may be claimed by amendment of the present claims or by presenting new claims in this or a related application. Such claims are also deemed to be included in the subject matter of the present disclosure, whether broader, narrower, the same, or different in scope than the original claims.

[0098] According to the present invention, a variable cam timing system in an engine is provided, which has a camshaft that receives a rotational input from a crankshaft, the camshaft including: a valve cam that rotationally actuates a valve coupled to a cylinder; and a zero cam that actuates a zero follower including a zero spring that applies a return force on the zero cam during interaction between the zero cam and the zero follower, wherein the zero follower is independent of the cylinder.

[0099] According to one embodiment, the above invention is further characterized by a zero cam deactivation device, which is designed to activate and deactivate the zero follower, wherein deactivating the zero follower includes moving the zero follower to an inactive position, which inhibits the interaction between the zero cam and the zero follower during the rotation of the zero cam.

[0100] According to one embodiment, the controller includes code stored in the memory executable by the processor to enable the zero follower via the zero cam deactivation device when a first operating condition occurs.

[0101] According to one embodiment, the above invention is further characterized in that the first operating condition includes a condition in which the valve is deactivated via a valve deactivation device coupled to the valve.

[0102] According to one embodiment, the controller further includes code stored in the memory and executable by the processor to deactivate the zero follower when a second operating condition occurs.

[0103] According to one embodiment, the above invention is further characterized in that the second operating condition includes a condition in which the valve is activated via the valve deactivation device.

[0104] According to one embodiment, the above invention is further characterized by a torque-actuated cam phaser rotationally coupled to the camshaft.

[0105] According to one embodiment, the torque actuated cam phaser adjusts cam timing during interaction between the zero cam and the zero follower.

[0106] According to one embodiment, the zero cam comprises a plurality of noses extending away from the axis of rotation of the zero cam and actuating the zero follower during rotation of the camshaft.

[0107] According to one embodiment, the valve is an intake valve.

[0108] According to the present invention, a method for operating a variable cam timing system is provided, comprising: cyclically actuating a valve connected to a cylinder using a valve cam rotationally connected to a camshaft; deactivating the valve by operation of a valve deactivation device; and in response to deactivation of the valve, enabling a zero follower including a zero spring, wherein the zero spring applies a return force on the zero cam connected to the crankshaft during interaction between the zero cam and the zero follower.

[0109] According to one embodiment, deactivating the valve includes operating an oil pressure control valve to deliver pressurized oil to the valve deactivation device to deactivate the valve, and activating the zero follower includes operating the oil pressure control valve to deliver the pressurized oil to activate the follower.

[0110] According to one embodiment, the above invention is further characterized by: activating the valve by operation of the valve deactivation device; and in response to activation of the valve, deactivating the zero follower to inhibit interaction between the zero cam and the zero follower.

[0111] According to one embodiment, the zero follower is deactivated when the camshaft torque decreases below a threshold value.

[0112] According to one embodiment, the method includes adjusting valve timing during interaction between the zero cam and the zero follower using a torque-actuated cam phaser rotationally coupled to the camshaft.

[0113] According to the present invention, a variable cam timing system in an engine is provided, which has: a camshaft receiving a rotational input from a crankshaft, the camshaft including: a valve cam lobe, the valve cam lobe rotationally actuating a valve connected to a cylinder; a zero cam, the zero cam actuating a zero follower including a zero spring, the zero spring applying a return force on the zero cam during interaction between the zero cam and the zero follower, wherein the zero follower is independent of the cylinder; and a torque-actuated cam phaser, the torque-actuated cam phaser rotationally connected to the camshaft.

[0114] According to one embodiment, the above invention is further characterized by: a zero cam deactivation device, which is designed to enable and deactivate the zero follower, wherein deactivating the zero follower includes moving the zero follower to an inactive position, and the inactive position inhibits the interaction between the zero cam and the zero follower during the rotation of the zero cam; and a controller, which includes a code stored in a memory and can be executed by a processor to enable the zero follower via the zero cam deactivation device when deactivating the valve, and the deactivation is triggered by a valve deactivation device connected to the valve.

[0115] According to one embodiment, the controller further comprises code stored in the memory executable by the processor to deactivate the zero follower upon activation of the valve, the valve activation being triggered by the valve deactivation device.

[0116] According to one embodiment, the above invention is further characterized by an oil control valve that delivers pressurized oil to the valve deactivation device and the zero cam deactivation device.

[0117] According to one embodiment, the zero cam comprises a plurality of lobes having noses extending away from the axis of rotation of the zero cam and positioned on a common radial plane.

Claims

1. A variable cam timing system in an engine, comprising: A camshaft receiving a rotational input from the crankshaft, the camshaft comprising: a valve cam that rotationally actuates a valve coupled to the cylinder; and A zero cam actuates a zero follower including a zero spring, the zero spring exerting a return force on the zero cam during interaction between the zero cam and the zero follower, wherein the zero follower is independent of the cylinder, and wherein the zero follower is activated in response to deactivation of the valve.

2. The variable cam timing system of claim 1 further comprising: A zero cam deactivation device is designed to activate and deactivate the zero follower, wherein deactivating the zero follower includes moving the zero follower to an inactive position that inhibits interaction between the zero cam and the zero follower during rotation of the zero cam.

3. The variable cam timing system of claim 2 further comprising: A controller including code stored in a memory executable by a processor to enable the zero follower via the zero cam deactivation device when a first operating condition occurs.

4. The variable cam timing system of claim 3, wherein the first operating condition comprises a condition wherein the valve is deactivated via a valve deactivation device coupled to the valve.

5. The variable cam timing system of claim 3 wherein said controller further comprises code stored in memory executable by said processor to deactivate said zero follower when a second operating condition occurs.

6. The variable cam timing system of claim 5, wherein the second operating condition includes a condition wherein the valve is activated via the valve deactivation device.

7. The variable cam timing system of claim 1 further comprising a torque-actuated cam phaser rotationally coupled to the camshaft.

8. The variable cam timing system of claim 7 wherein said torque actuated cam phaser adjusts cam timing during interaction between said zero cam and said zero follower.

9. The variable cam timing system of claim 1 wherein said zero cam includes a plurality of noses extending away from an axis of rotation of said zero cam and actuating said zero follower during rotation of said camshaft.

10. The variable cam timing system of claim 1, wherein the valve is an intake valve.

11. A method for operating a variable cam timing system, comprising: cyclically actuating valves coupled to the cylinders using valve cams rotationally coupled to the camshaft; deactivating the valve by operation of the valve deactivation device; as well as In response to deactivation of the valve, a zero follower is activated that includes a zero spring that exerts a return force on the zero cam coupled to a crankshaft during interaction between the zero cam and the zero follower.

12. The method of claim 11, wherein deactivating the valve comprises operating an oil pressure control valve to deliver pressurized oil to the valve deactivation device to deactivate the valve, and activating the zero follower comprises operating the oil pressure control valve to deliver the pressurized oil to activate the zero follower.

13. The method of claim 11, further comprising: enabling the valve by operation of the valve deactivation device; as well as In response to activation of the valve, the zero follower is deactivated to inhibit interaction between the zero cam and the zero follower.

14. The method of claim 11, further comprising: Valve timing is adjusted during interaction between the zero cam and the zero follower using a torque-actuated cam phaser rotationally coupled to the camshaft.

Images