Parking positions for variable camshaft phaser systems and methods

Abstract

Engine control procedures for a vehicle, comprising the following: Generation of a shutdown command (468) for the vehicle's engine (102) when at least one of the following conditions is met: The driver requests that the engine (102) be switched off via an ignition system; and when one or more predefined conditions for switching off the engine (102) are met, without the driver requesting the engine (102) to be switched off via the ignition system; and when the shutdown command (468) for the engine (102) is generated, an exhaust camshaft phaser (129) is advanced from a predetermined exhaust park position, which is selected at a target exhaust gas residual; wherein, when the exhaust camshaft phaser (129) is in the specified exhaust park position, an exhaust valve (120) of a cylinder (114) is fully closed during an exhaust stroke of the cylinder (114) before a piston of the cylinder (114) reaches top dead center for the next intake stroke of the cylinder (114), so that residual exhaust gas is retained for a subsequent intake stroke.

Description

TECHNICAL AREA

[0001] The present disclosure relates to internal combustion engines of vehicles, and in particular to camshaft parking positions and camshaft phaser control systems and methods. BACKGROUND

[0002] The background description provided here serves the purpose of generally outlining the context of the disclosure. The work of the inventors mentioned herein, insofar as it is described in this background section, as well as aspects of the description that could not otherwise be considered prior art at the time of filing, are neither expressly nor implicitly recognized as prior art against the present disclosure.

[0003] Vehicles contain an internal combustion engine that generates drive torque. Specifically, an intake valve opens selectively to draw air into the engine's cylinder. The air mixes with the fuel to form a fuel / air mixture, which is then burned in the cylinder. The fuel / air mixture is compressed and combusted to drive a piston within the cylinder. An exhaust valve opens selectively to release the exhaust gases produced during combustion from the cylinder.

[0004] A rotating camshaft controls the opening and closing of the intake and exhaust valves. The camshaft contains cam lobes that are attached to it and rotate with it. The geometric profile of a cam lobe generally determines the duration the valve is open and the valve opening width or degree (valve lift). An intake camshaft phaser controls the phase of the camshaft relative to the crankshaft.

[0005] Variable valve actuation (VVA), also known as variable valve lift (VVL), improves fuel efficiency, engine efficiency, and / or power output by changing the valve lift height and duration. Two-stage VVA systems incorporate VVL mechanisms such as switchable roller rocker arms (SRFF). An SRFF connected to a valve (e.g., an intake or exhaust valve) allows the valve to be lifted in two different modes: a low-lift mode and a high-lift mode.

[0006] An engine control module (ECM) controls the engine's torque output. For example, the ECM controls the engine's torque output based on driver inputs and / or other inputs. Driver inputs can include, for example, accelerator pedal position, brake pedal position, inputs to a speed control system, and / or other driver inputs. Other inputs can come from various vehicle systems, such as a transmission control system.

[0007] A vehicle may include an automatic start-stop system, which improves the vehicle's fuel efficiency. The automatic start-stop system increases fuel efficiency by selectively switching off the engine when the vehicle is not moving. When the engine is off, the automatic start-stop system selectively restarts the engine if one or more engine start conditions are met.

[0008] Known engine control systems for vehicles are known, for example, from US 2010 / 0 222 986 A1, US 2005 / 0 229 880 A1, US 2010 / 0 313 837 A1, DE 103 60 033 A1 and DE 10 2015 107 539 A1. SUMMARY

[0009] In an embodiment not covered by the invention, an engine control system for a vehicle is disclosed. A shutdown control module generates a command to shut down a vehicle's engine when at least: a driver requests engine shutdown via an ignition system, and when one or more predetermined conditions for engine shutdown are met without the driver having requested engine shutdown via the ignition system. When the engine shutdown control command is generated, a valve control module advances an exhaust camshaft phaser, starting from a predetermined exhaust park position. When the exhaust camshaft phaser is in the predetermined exhaust park position, an exhaust valve of a cylinder is fully closed during an exhaust stroke of the cylinder before a piston of the cylinder reaches its top position to begin the next intake stroke of the cylinder.

[0010] In further embodiments, a parking pin is inserted into a recess of the camshaft phaser when the exhaust camshaft phaser is in the predetermined exhaust park position. When the parking pin is in the recess, further adjustment of the exhaust camshaft phaser is prevented.

[0011] In further embodiments, the valve control module adjusts an intake camshaft phaser to a predetermined intake park position when the control command to shut down the engine is generated. When the intake camshaft phaser is in the predetermined intake park position, an intake valve of the cylinder opens when the cylinder's piston reaches its highest position for the next intake stroke of that cylinder.

[0012] In further embodiments: a first parking pin is inserted into a recess in the exhaust camshaft phaser when the exhaust camshaft phaser is in the predetermined exhaust parking position, and its position in the first recess prevents the exhaust camshaft phaser from being advanced or re-adjusted, and a second parking pin is inserted into a second recess in the intake camshaft phaser when the intake camshaft phaser is in the predetermined intake parking position, and its position in the second recess prevents the intake camshaft phaser from being advanced or re-adjusted.

[0013] In further embodiments, the exhaust valve is completely closed for at least 2 degrees of the camshaft angle when the exhaust camshaft phaser is in the predetermined exhaust park position before the piston reaches the uppermost position for the next intake stroke during the exhaust stroke of the cylinder.

[0014] In further embodiments, the exhaust valve is completely closed for at least 5 degrees of the camshaft angle when the exhaust camshaft phaser is in the predetermined exhaust park position before the piston reaches the top position for the next intake stroke during the exhaust stroke of the cylinder.

[0015] In further embodiments, the intake valve is closed for at least 40 degrees of the camshaft angle when the intake camshaft phaser is in the predetermined intake park position after the piston has reached its lowest position.

[0016] In further embodiments, the intake valve is closed for at least 90 degrees of the camshaft angle when the intake camshaft phaser is in the predetermined intake park position after the piston has reached its lowest position.

[0017] In other embodiments, a fuel control module prevents the fuel supply to the engine when the control command to switch off the engine is generated.

[0018] In further embodiments, the valve control module controls the stroke of the inlet valve to a low-stroke mode and a high-stroke mode.

[0019] According to the invention, an engine control method is disclosed. The engine control method includes generating a control command to shut down the engine of a vehicle when at least: a driver requests the engine to shut down via an ignition system, and when one or more predetermined conditions for shutting down the engine are met without the driver having requested the engine to shut down via the ignition system. The engine control method further stipulates that when the control command to shut down the engine is generated, a valve control module advances an exhaust camshaft phaser, starting from a predetermined exhaust park position. When the exhaust camshaft phaser is in the predetermined exhaust park position, an exhaust valve of a cylinder is fully closed during an exhaust stroke of the cylinder before a piston of the cylinder reaches its top position for the next intake stroke of the cylinder.

[0020] In further embodiments, a parking pin is inserted into a recess of the camshaft phaser when the exhaust camshaft phaser is in the predetermined exhaust park position. When the parking pin is in the recess, further adjustment of the exhaust camshaft phaser is prevented.

[0021] In further embodiments, the engine control method further stipulates that when the control command to shut down the engine is generated, the exhaust camshaft phaser is adjusted to a predetermined exhaust park position. When the intake camshaft phaser is in the predetermined intake park position, an intake valve of the cylinder opens when the cylinder's piston reaches its highest position for the next intake stroke of the cylinder.

[0022] In further embodiments: a first parking pin is inserted into a recess in the exhaust camshaft phaser when the exhaust camshaft phaser is in the predetermined exhaust parking position, and its position in the first recess prevents the exhaust camshaft phaser from being advanced or re-adjusted, and a second parking pin is inserted into a second recess in the intake camshaft phaser when the intake camshaft phaser is in the predetermined intake parking position, and its position in the second recess prevents the intake camshaft phaser from being advanced or re-adjusted.

[0023] In further embodiments, the exhaust valve is completely closed for at least 2 degrees of the camshaft angle when the exhaust camshaft phaser is in the predetermined exhaust park position before the piston reaches the uppermost position for the next intake stroke during the exhaust stroke of the cylinder.

[0024] In further embodiments, the exhaust valve is completely closed for at least 5 degrees of the camshaft angle when the exhaust camshaft phaser is in the predetermined exhaust park position before the piston reaches the uppermost position for the next intake stroke during the exhaust stroke of the cylinder.

[0025] In further embodiments, the intake valve is closed for at least 40 degrees of the camshaft angle when the intake camshaft phaser is in the predetermined intake park position after the piston has reached its lowest position.

[0026] In further embodiments, the intake valve is closed for at least 90 degrees of the camshaft angle when the intake camshaft phaser is in the predetermined intake park position after the piston has reached its lowest position.

[0027] In further embodiments, the engine control method continues to prevent the fuel supply to the engine when the control command to switch off the engine is generated.

[0028] In further embodiments, the engine control method controls the stroke of the inlet valve to a low-stroke mode and a high-stroke mode.

[0029] Further areas of application of the present invention will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples are intended only for illustrative purposes and are not meant to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be more easily understood with the aid of the detailed description and the accompanying drawings, wherein: Fig. 1 is a functional block diagram of an exemplary control system; Fig. 2 is a representation of a variable valve lift system (VVL); Fig. 3 is an exemplary front view of a cam phaser system; Fig. 4 is an exemplary exploded view of the cam phaser system; Fig. 5 is an exemplary graph of the residual exhaust gas as a function of the maximum opening position of the inlet valve and the maximum opening position of the exhaust valve; Fig. 6 is a functional block diagram of an exemplary control unit; and Fig. Figure 7 is a flowchart illustrating an exemplary procedure for locking intake and exhaust camshaft phasers in their respective park positions.

[0031] The same reference numbers are used in the drawings for similar and / or identical elements. DETAILED DESCRIPTION

[0032] An engine control module (ECU) controls engine actuators based on a requested torque. Engine actuators can include, for example, a throttle valve, a fuel system, an ignition system, intake and exhaust camshaft phasers, a variable valve lift (VVL) system, and other types of engine actuators.

[0033] When the engine shutdown command is issued, the engine control module actuates the intake and exhaust camshaft phasers from their respective predefined park positions. The engine shutdown can be activated by the driver via the ignition system or by the engine control module for an automatic start / stop process. The locking pins are engaged and prevent further adjustment of the intake and exhaust camshafts when the phasers are in their predefined park positions.

[0034] In accordance with the present disclosure, the specified inlet and outlet parking positions are chosen based on a target exhaust gas residue to achieve the following: (i) Target exhaust emissions during cold engine starts and (ii) Target noise emissions, vibrations, and / or roughness for automatic start procedures. The specified exhaust park position causes the exhaust valve to close before the piston reaches top dead center between the exhaust stroke of one combustion cycle and the intake stroke of the next combustion cycle in the cylinder. The specified intake park position causes the intake valve to open after the piston has reached top dead center.

[0035] In Fig. Figure 1 shows a functional block diagram of an exemplary vehicle control system. An engine 102 generates drive torque for a vehicle. Air is drawn into the engine 102 via an intake manifold 104. The airflow into the intake manifold 104 can be regulated by a throttle valve 106. A throttle valve actuator module 108 (e.g., an electronic throttle control unit) regulates the opening of the throttle valve 106. One or more fuel injectors 110 mix fuel with air to form a combustible fuel / air mixture. A fuel actuator module 112 controls the fuel injector(s).

[0036] A cylinder 114 contains a piston (not shown) coupled to a crankshaft 116. Although the engine 102 is shown with only one cylinder 114, the engine 102 can contain more than one cylinder. A combustion cycle in the cylinder 114 can consist of four strokes: an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. An engine cycle includes one combustion cycle in each cylinder. A four-stroke combustion is given as an example; other operating cycles can also be used.

[0037] Fig. Figure 2 is a diagram showing an exemplary variable valve lift (VVL) system. Referring to Fig. 1 and Fig. 2. During the intake stroke, the piston is lowered to its lowest position, and cylinder 114 is supplied with fuel and air. This lowest position can be referred to as bottom dead center (BDC). Air flows into cylinder 114 through one or more intake valves, such as intake valve 118. One or more exhaust valves, such as exhaust valve 120, are also connected to cylinder 114. For the sake of simplicity, only intake valve 118 and exhaust valve 120 will be discussed.

[0038] During the compression stroke, the crankshaft 116 pushes the piston to its highest position. The intake valve 118 and the exhaust valve 120 can both be closed during the compression stroke, and the piston compresses the fuel / air mixture in the cylinder 114. This highest position can also be referred to as top dead center (TDC). The piston reaches TDC between the compression and combustion / expansion strokes. Specifically, the piston reaches TDC between the exhaust stroke of one combustion cycle and the intake stroke of the next. A spark plug 122 can ignite the fuel / air mixture in various engine types. An ignition actuator module 124 controls the spark plug 122.

[0039] The combustion of the fuel / air mixture pushes the piston back towards the cylinder head during the expansion stroke, thereby setting the crankshaft 116 in rotation. This rotational force can be a source of compression force for one compression stroke of a combustion cycle in the next cylinder within a predetermined firing order. Exhaust gas from the combustion of the fuel / air mixture is expelled from cylinder 114 during the exhaust stroke. The exhaust gas is expelled from cylinder 114 via the exhaust valve 120.

[0040] The opening and closing times of the intake valve 118 are controlled by an intake camshaft 126. An intake camshaft, such as the intake camshaft 126, can be mounted on each cylinder bank of the engine 102. The opening and closing times of the exhaust valve 120 are controlled by an exhaust camshaft (not shown). An exhaust camshaft can also be mounted on each cylinder bank of the engine 102. The rotation of the intake camshaft(s) and the exhaust camshaft(s) is generally driven by the rotation of the crankshaft 116, via a belt or chain drive, as discussed below.

[0041] A cam phaser controls the rotation of a corresponding camshaft. For example, the intake cam phaser 128 can control the rotation of the intake camshaft 126. The intake cam phaser 128 can adjust the rotation of the intake camshaft 126, for example, relative to the rotation of the crankshaft 116. For example, the intake cam phaser 128 can slow down or speed up the rotation of the intake camshaft 126, thereby changing the opening and closing times of the intake valve 118. An exhaust cam phaser 129 controls the rotation of the exhaust camshaft. Adjusting the rotation of a camshaft relative to the rotation of the crankshaft 116 can be referred to as camshaft phase adjustment.

[0042] A valve actuator module 130 controls the intake cam phaser 128. The valve actuator module 130, or another valve actuator module, can control the exhaust cam phaser 129. The intake and exhaust cam phasers 128 and 129 can be actuated, for example, electrically or hydraulically. A hydraulically actuated cam phaser is actuated by the pressure of a hydraulic fluid (e.g., oil) supplied to the cam phaser, as discussed below.

[0043] A variable valve lift mechanism (VVL) 136 ( Fig. 2) controls the actuation of the inlet valve 118. For example only, the VVL mechanism 136 may include a switchable roller rocker arm mechanism (SRFF). The VVL mechanism 136 is shown and discussed here as an SRFF; however, the VVL mechanism 136 may also include other types of valve lift mechanisms capable of lifting a corresponding valve to two or more different lift positions. Furthermore, the VVL mechanism 136 is shown and discussed here as connected to the inlet valve 118; however, the VVL mechanism 136, or any other VVL mechanism, may also be used similarly with the exhaust valve 120. For example only, each inlet valve and each exhaust valve of a cylinder may each be equipped with a VVL mechanism. VVL may also denote variable valve actuation (VVA).

[0044] The VVL mechanism 136 includes a lift adjuster 138 and a cam follower 140. The cam follower 140 is in mechanical contact with the valve stem 142 of the intake valve 118. A clamping element 143 presses the valve stem 142 against the cam follower 140. The cam follower 140 is also in mechanical contact with the intake camshaft 126 and the lift adjuster 138.

[0045] The intake camshaft 126 rotates about a camshaft axis 144. The intake camshaft 126 incorporates a variety of cam protrusions, including low-lift cam protrusions, such as the low-lift cam protrusion 146, and high-lift cam protrusions, such as the high-lift cam protrusion 148. For example, the intake camshaft 126 may incorporate one low-lift cam protrusion and one high-lift cam protrusion for each intake valve of a cylinder. The intake camshaft 126 may also incorporate an additional cam protrusion (not shown) for each intake valve of a cylinder for operation in a cylinder deactivation mode. The intake and exhaust valves of one or more cylinders, such as half of the cylinders of engine 102, are deactivated during operation in cylinder deactivation mode.

[0046] The low- and high-lift cam projections 146 and 148 rotate with the intake camshaft 126. Air can flow through an intake port 150 into cylinder 114 when the intake valve 118 is open. The airflow into cylinder 114 can be blocked when the intake valve 118 is closed. The intake valve 118 is selectively lifted (i.e., opened) and lowered (i.e., closed) by the intake camshaft 126.

[0047] In particular, the inlet valve 118 is opened and closed by the low-lift cam projection 146 or the high-lift cam projection 148.

[0048] A cam projection in contact with the cam follower 140 exerts a force on the cam follower 140 towards the valve stem 142 and then on the lift adjuster 138. The lift adjuster 138 is foldable and allows the intake valve 118 to open in two different positions: a low-lift position and a high-lift position. The valve actuator module 130 can control a lift actuator module 152 and thus the actuation of the intake camshaft 126 (e.g., linear actuation along the axis 144), thereby determining whether the low-lift or high-lift cam projection 146 or 148, respectively, contacts the cam follower 140.

[0049] In summary, during operation in low-lift mode, the low-lift cam projection 146 generates a pivoting movement of the VVL mechanism 136 according to the geometry of the low-lift cam projection 146. The pivoting movement of the VVL mechanism 136 caused by the low-lift cam projection 146 opens the inlet valve 118 by a first predetermined stroke. During operation in high-lift mode, the high-lift cam projection 148 generates a pivoting movement of the VVL mechanism 136 according to the geometry of the high-lift cam projection 148. The pivoting movement of the VVL mechanism 136 caused by the high-lift cam projection 148 opens the inlet valve 118 by a second predetermined stroke. The second predetermined stroke is greater than the first predetermined stroke.

[0050] When the high-lift cam projection 148 is applied, the opening period (duration) of the inlet valve 118 can be longer than the opening period of the inlet valve 118 when the low-lift cam projection 146 is applied. In particular, the low-lift cam projection 146 can delay the opening of the inlet valve and accelerate the closing of the inlet valve compared to the high-lift cam projection 148. The present disclosure describes an exemplary hydraulic VVL system; however, the present disclosure also applies to other types of VVL systems, including electromechanical VVL mechanisms and other types of VVL mechanisms.

[0051] Fig. Figure 3 shows an exemplary front view of a hydraulic cam phaser system. A first gear 204 can be coupled to the crankshaft 116, and a second gear 208 can be coupled to a camshaft, such as the intake camshaft 126. A chain 212 can be placed around the first and second gears 204 and 208, such that the rotation of the first gear 204 causes the second gear 208 to rotate. In this way, the rotation of the crankshaft 116 drives the rotation of the intake camshaft 126.

[0052] A fluid control valve 216 controls the flow of hydraulic fluid (e.g., engine oil) to the feed chambers 220 and the retarder chambers 224. The fluid control valve 216 can also be referred to as an oil control valve (OCV). The valve actuator module 130 controls the actuation of the fluid control valve 216 to regulate the pressure of the hydraulic fluid in the feed chambers 220 and the retarder chambers 224. The pressure of the hydraulic fluid in the feed and retarder chambers 220 controls the phase setting of the intake camshaft 126.

[0053] For example, if the pressure in the feed chambers 220 is higher than the pressure in the retardation chambers 224, the intake camshaft 126 rotates earlier than the crankshaft 116. Conversely, if the pressure in the feed chambers 220 is lower than the pressure in the retardation chambers 224, the intake camshaft 126 rotates later than the crankshaft 116.

[0054] The second gear 208 is connected to the camshaft assembly. Fig. Figure 4 shows an exemplary exploded view of the camshaft assembly. One or more recesses are provided in the camshaft phase adjuster assembly, such as the recesses 228. One or more locking pins, such as the locking pins 232, are actuated and inserted into the recesses 228 when the intake camshaft 126 approaches a predetermined intake park position. The locking pin(s) come into mechanical contact with one or more inner surfaces of the recess(s) when the intake camshaft 126 approaches the predetermined intake park position, thus locking the rotation of the intake camshaft 126 relative to the rotation of the crankshaft 116 and preventing changes to the intake camshaft 126 setting.

[0055] The locking pin(s) remain in the recess(s) while the engine 102 is switched off and also remain in the recess(s) when the engine 102 is restarted. The locking pin(s) can be pulled out of the recess(s), thus enabling phase adjustment of the intake camshaft 126 when the engine 102 is started or running. By way of example only, the locking pin(s) can be pulled out by pressure of the hydraulic fluid in the feed chambers 220 or the retardation chambers 224. The example of a hydraulic camshaft phase adjuster is presented here, but this disclosure applies equally to electric camshaft phase adjusters. Electric camshaft phase adjusters also include recesses for locking pins to lock the electric camshaft phase adjusters in predetermined park positions.

[0056] The example in the Fig. 3 and Fig. As regards the intake camshaft 126, the exhaust cam phaser 129 adjusts the exhaust camshaft in the same way. In particular, a third gear can be coupled to the crankshaft 116, and a fourth gear can be coupled to the exhaust camshaft. A chain can be placed around the second and third gears, so that the rotation of the second gear sets the third gear in motion. In this way, the rotation of the crankshaft 116 drives the rotation of the exhaust camshaft.

[0057] The pressure of the hydraulic fluid in the feed and retardation chambers of the exhaust cam phaser 129 controls the exhaust camshaft relative to the crankshaft 116. The valve actuator module 130 can control a second fluid control valve or the fluid control valve 216 to regulate the pressure of the hydraulic fluid in the feed and retardation chambers.

[0058] The fourth gear is coupled to the exhaust cam phaser assembly. One or more locking pins are actuated and inserted into one or more recesses in the exhaust cam phaser assembly when the exhaust camshaft approaches a predetermined intake park position. The locking pin(s) come into mechanical contact with one or more inner surfaces of the recess(s) when the exhaust camshaft approaches the predetermined exhaust park position, thus locking the rotation of the exhaust camshaft relative to the rotation of the crankshaft 116 and preventing changes to the exhaust camshaft setting.

[0059] The locking pin(s) remain in the recess(s) while engine 102 is switched off and also remain in the recess(s) when engine 102 is restarted. The locking pin(s) can be pulled out of the recess(s), thus enabling phase adjustment of the exhaust camshaft when engine 102 is running. For example, the locking pin(s) can be pulled out by pressure from the hydraulic fluid.

[0060] Vehicle manufacturers define target values ​​for specific engine start parameters. The specified intake and exhaust park positions can be selected based on one or more of these target values. For example, the specified intake and exhaust park positions can be selected based on a target residual exhaust gas volume in the cylinders. This target residual exhaust gas volume can be determined based on the achievement of one or more exhaust emission target parameters during cold engine starts. In one example, the target residual exhaust gas volume corresponds to 8.5 percent of the exhaust gas for each combustion cycle.

[0061] During engine assembly, the camshaft phasers, including the recesses for locking pins, are installed (e.g., attached to the camshafts) so that the locking pins are inserted into the recesses when the camshafts are approximately in their predetermined intake and exhaust parking positions. The arrangement of the locking pins and / or the recesses can be determined based on the predetermined intake and exhaust positions.

[0062] To achieve the target exhaust gas residual quantity, the predetermined intake and exhaust parking positions can be selected so that the exhaust valve closes after the intake valve opens. The intake valve normally opens during the intake stroke. If the exhaust valve closes after the intake valve opens, the intake and exhaust valves of a cylinder are open simultaneously for a certain period. This situation can be described as valve overlap.

[0063] Fig. Figure 5 shows an exemplary graph of the target exhaust gas residual quantity as a function of the maximum intake valve opening position (IMOP) 304 and the maximum exhaust valve opening position (EMOP) 308. IMOP 304 is given in degrees of crankshaft angle (CAD) after the TDC (between the intake and exhaust strokes), and EMOP 308 in CAD before the TDC (between the intake and exhaust strokes). The valve opening and closing positions depend on the time the cam projections take to lift the corresponding valves. Maximum opening positions correspond to crankshaft angles at which the corresponding valves are maximally open.

[0064] Example curve 312 plots combinations of IMOP and EMOP to achieve a target exhaust gas residual volume of 8.5 percent. An exhaust gas residual volume of 8.5 percent means that 8.5 percent of the total mass in the cylinder for a combustion process is exhaust gas from the last combustion cycle of the cylinder. The remainder of the total mass consists of air and fuel. The example of 8.5 percent is shown and specified here, but other target exhaust gas residual volumes can also be used. Point 316 represents a first combination of IMOP and EMOP to achieve a target exhaust gas residual volume of 8.5 percent.

[0065] Starting from the EMOP 308 for point 316, the exhaust valve closes after the intake valve opens, and both the intake and exhaust valves are open for a certain overlap period during engine start. Without other actions, such as adjusting the intake and / or exhaust camshaft, the intake and exhaust park positions resulting from the EMOP and IMOP of point 316 may not be close enough to the desired noise, vibration, and / or harshness (NVH) target values ​​for automatic start procedures.

[0066] Item 320 corresponds to a second combination of IMOP and EMOP for predefined intake and exhaust parking positions to achieve the target exhaust gas residual volume. Starting from EMOP 308 for Item 320, the exhaust valve closes upstream of the TDC between the exhaust and intake strokes. In other words, the predefined exhaust parking position causes the exhaust valve to close upstream of the TDC between the intake and exhaust strokes. The predefined exhaust parking position can correspond to the exhaust valve closing at least 1 CAD upstream of the TDC, at least 2 CAD upstream of the TDC, at least 3 CAD upstream of the TDC, at least 5 CAD upstream of the TDC, at least 7 CAD upstream of the TDC, at least 10 CAD upstream of the TDC, or at least 15 CAD upstream of the TDC in various applications.

[0067] The specified intake park position for point 320 causes the intake valve to open after the exhaust valve closes and after the TDC (Total Discharge Cycle) between the exhaust and intake strokes. For a 4-stroke engine, in which the 4 strokes occur during 2 revolutions of the crankshaft 116, the specified intake park position can correspond to the maximum intake valve opening of at least 90 CAD after the TDC, at least 100 CAD after the TDC, at least 110 CAD after the TDC, at least 120 CAD after the TDC, at least 130 CAD after the TDC, at least 140 CAD after the TDC, or at least 150 CAD after the TDC in various applications. The opening examples given here are not the only ones; other maximum openings are possible.

[0068] The specified intake park position for point 320 causes the intake valve (IVC) to close after the BDC. The further the IVC is located from the BDC (e.g., after it), the lower the effective compression ratio. A lower effective compression ratio can provide better NVH parameters for auto-starts. The specified intake park position can correspond to the intake valve closing point being between approximately 40 CAD and approximately 130 CAD after the BDC. An example is approximately 110 CAD after the BDC.

[0069] When the exhaust valve closes before the TDC (Torque Discharge Control) between the exhaust and intake strokes, residual exhaust gas is retained in the cylinder for the next combustion cycle. The combination of the specified intake and exhaust parking positions from point 320 further approximates the achieved values ​​for cold starts and automatic starts closer to the target exhaust emission parameters and NVH (noise, vibration, and harshness) without requiring camshaft adjustment during engine start. Since curve 312 for generating the target residual exhaust gas quantity is relatively flat over a wide IMOP (Initial Operating Mode) range, the emission targets can be achieved with relatively advanced exhaust parking positions in both high-stroke and low-stroke operation.

[0070] Under certain circumstances, such as engine starts at high altitudes, the valve lift can be bypassed or parked in low-lift mode during the starting process. Low-lift operation brings forward the closing of the intake valve and increases the effective compression ratio, making the engine easier to start during cold starts and / or at high altitudes. Specifically, the temperature of the air, fuel, and residual exhaust gas in the cylinder is higher during low-lift operation, facilitating fuel vaporization and mixing and improving starting performance. However, the ability to perform automatic starts and stops may be affected under certain ambient temperature and altitude conditions.

[0071] With reference to Fig. 1-3 An engine control module (ECM) 160 regulates the operation of the engine 102 to achieve a requested torque when the engine 102 is running. For example, based on the requested torque, the ECM 160 can control the opening of the throttle valve 106, the amount and timing of fuel injection, the ignition timing, the camshaft phase setting, the lift mode, and other engine operating parameters.

[0072] The ECM 160 can regulate the torque output of the 102 engine, based on, for example, driver inputs and inputs from various vehicle systems. These vehicle systems can include, for example, a transmission system, a hybrid control system, a stability control system, a chassis control system, or other suitable vehicle systems.

[0073] A driver input module 170 forwards the driver inputs to the ECM 160. These inputs can include, for example, an accelerator pedal position (APP), a brake pedal position (BPP), inputs to a speed control system, and vehicle operating inputs. An APP sensor 174 measures the position of an accelerator pedal (not shown) and generates the APP based on the actual position. A BPP sensor 178 monitors the actuation of a brake pedal (not shown) and generates the BPP accordingly. A speed control system 182 provides the speed control inputs, such as a desired vehicle speed, based on inputs to the speed control system 182.

[0074] Vehicle control commands can include, for example, vehicle start commands and vehicle stop commands. These commands can be input, for example, by operating an ignition key, one or more buttons / switches, and one or more suitable ignition input devices, such as an ignition input device 186.

[0075] In vehicles with manual transmissions, the driver inputs to the ECM 160 can also include a clutch pedal position (CPP). A CPP sensor 190 monitors the actuation of a clutch pedal (not shown) and generates the CPP accordingly. The clutch pedal can be actuated to engage a transmission with the engine 102 and to disengage the transmission from the engine 102. The APP sensor 174, the BPP sensor 178, and the CPP sensor 190 are shown and described here; one or more additional APP, BPP, and / or CPP sensors may be present.

[0076] The ECM 160 selectively shuts down engine 102 when an engine shutdown command is received. For example, the ECM 160 can lock the fuel injection and ignition, set the intake and exhaust camshafts to their predetermined intake and exhaust park positions, and perform other engine shutdown operations to shut down engine 102 when a vehicle shutdown command is received. Upon receiving a vehicle shutdown command, the ECM 160 can engage the ignition and fuel supply to engine 102, engage a starter motor (not shown) to engine 102, and energize the starter motor to start engine 102.

[0077] The ECM 160 can also selectively perform auto-stop and auto-start operations for the engine 102. An auto-stop operation involves shutting down the engine 102 when one or more predefined shutdown criteria are met, even if the vehicle has not been ordered to shut down (e.g., while the ignition system is in the ON state). The ECM 160 disables fuel injection and ignition, sets the intake and exhaust camshafts to their predefined intake and exhaust park positions, and performs other engine shutdown actions to shut down the engine 102 for an auto-stop operation.

[0078] While engine 102 is shut down for an auto-stop operation, the ECM 160 can selectively perform an auto-start operation. An auto-start operation may include, for example, activating the fuel supply and ignition, engaging the starter motor with engine 102, and supplying power to the starter motor to start engine 102.

[0079] The ECM 160 sets the intake and exhaust camshafts to their respective park positions, as specified for engine shutdown. As described above, engine shutdowns are performed in response to a vehicle shutdown command and for auto-stop procedures. In the specified park positions, the locking pins engage the gears coupled to the intake and exhaust camshafts, preventing any further movement of the camshafts.

[0080] The exhaust valve closes in the predetermined exhaust park position before the TDC (Torque Discharge Control) between the intake and exhaust strokes. The intake valve opens after the TDC between the intake and exhaust strokes, and the intake valve closes after the BDC (Battery Discharge Control). Therefore, residual exhaust gas remains in each cylinder from one combustion cycle to the next.

[0081] The ECM 160 can control the stroke mode based on ambient temperature and / or pressure when an engine shutdown occurs, such as during a vehicle shutdown or auto-stop procedure. The ECM 160 operates the VVL system in low-stroke mode, producing a higher effective compression ratio, when the ambient temperature is below a preset temperature. However, auto-stops can be disabled for operation in low-stroke mode. The higher effective compression ratio can enhance fuel vaporization during engine start-up. If the ambient temperature exceeds the preset temperature, the ECM 160 can switch the VVL system to high-stroke mode, reducing the effective compression ratio.

[0082] In Fig. Figure 6 shows a functional block diagram of an exemplary implementation of the ECM 160. A speed request module 404 can determine a speed request 408 based on one or more driver inputs 412, such as an accelerator pedal position, a brake pedal position, a speed controller input, and / or one or more suitable driver inputs. The speed request module 404 can additionally or alternatively determine the speed request 408 based on one or more further speed requests, such as speed requests generated by the ECM 160 and / or speed requests received from other vehicle modules, such as a transmission control module, a hybrid control module, a chassis control module, etc.

[0083] One or more motor actuators can be controlled based on the speed request 408 and / or one or more other parameters. For example, a throttle control module 416 determines a target throttle opening 420 based on the speed request 408. The throttle actuator module 108 controls the opening of the throttle valve 106 based on the target throttle opening 420.

[0084] An ignition control module 424 determines an ignition timing 428 based on the speed request 408. The ignition actuator module 124 generates the ignition spark based on the target ignition timing 428. A fuel control module 432 determines one or more target fuel supply parameters 436 based on the speed request 408. For example, the target fuel supply parameters 436 can determine the fuel injection quantity, the number of fuel injections required for this quantity, and the respective injection timing. The fuel actuator module 112 injects fuel based on the target fuel supply parameters 436.

[0085] A valve control module 440 can determine the intake and exhaust cam phaser setpoints 444 and 448 based on the speed request 408. The valve actuator module 130 controls the intake cam phaser 128 and the exhaust cam phaser, respectively, based on the intake and exhaust cam phaser setpoints 444 and 448. One or more engine actuators can be controlled based on the speed request 408.

[0086] The valve control module 440 also defines a target lift mode 452. Based on the target lift mode 452, the valve actuator module 130 controls the VVL system to actuate the intake valve in target lift mode 452. For example, the valve actuator module 130 controls the VVL system to actuate the intake valve in low lift mode when the target lift mode 452 indicates low lift mode. The valve actuator module 130 controls the VVL system to actuate the intake valve in high lift mode when the target lift mode 452 indicates high lift mode. The valve actuator module 130 controls the VVL system to deactivate the intake and exhaust valves when the target lift mode 452 is the cylinder deactivation mode.

[0087] A start-stop control module 460 controls the starting and stopping of the engine 102. The start-stop control module 460 generates an engine start command 464 when the driver issues a vehicle start command via an ignition input device 186, such as an ignition button, an ignition key, etc. A starter control module 470 moves the starter and applies voltage to start the engine 102 when the engine start command 464 is generated. After the engine start command 464 has been generated, the fuel control module 432 and the ignition control module 424 begin supplying the engine 102 with fuel and spark.

[0088] The start-stop control module 460 generates an engine shutdown command 468 when the driver enters a vehicle stop command via the driver ignition input device 186. The fuel control module 432 cuts off the fuel supply to engine 102 to shut down engine 102 when the engine shutdown command 468 is generated. The ignition control module 424 can interrupt the generation of ignition sparks when the engine shutdown command 468 is generated. The vehicle start and vehicle stop commands can be indicated via a vehicle operating signal 472. For example, the vehicle operating signal 472 can be set to a first state for a vehicle start command and a second state for a vehicle shutdown command.

[0089] The start-stop control module 460 also generates the engine shutdown command 464 to execute an auto-stop operation. For example, the start-stop control module 460 executes an auto-stop operation when the vehicle speed 476 is below a predetermined speed (or is zero) and the driver applies the brake pedal. Application of the brake pedal can be indicated by a brake pedal position (BPP) 480, measured, for example, by a BPP sensor. The vehicle speed 476 can be measured by a sensor or determined from one or more other parameters, such as the rotational speed of one or more wheels measured by wheel speed sensors.

[0090] Auto-stop and auto-start operations are performed while the vehicle's ignition system is ON, without the driver requesting that the engine (102) or the vehicle be stopped. Specifically, auto-stop and auto-start operations are performed between the driver's input of a vehicle start command and the next vehicle stop command.

[0091] The start-stop control module 460 also generates the engine start command 464 to execute an auto-start operation when the engine 102 is off for an auto-stop operation. For example, the start-stop control module 460 can execute an auto-start operation when the driver releases the brake pedal while the engine 102 is off for an auto-stop operation. The release of the brake pedal can be indicated by the BPP 480. The start-stop control module 460 can also execute an auto-start operation if one or more conditions for executing an auto-start operation are met while the engine 102 is off for an auto-stop operation.

[0092] The valve control module 440 sets the intake and exhaust cam phaser target positions 444 and 448 to the predefined intake and exhaust parking positions when the engine shutdown command 468 is generated. The valve actuator module 130 controls the intake and exhaust cam phasers to adjust the intake and exhaust camshafts to their respective predefined intake and exhaust parking positions.

[0093] The locking pins lock the camshaft phasers coupled to the intake and exhaust camshafts when the intake and exhaust camshafts are approximately in their predetermined intake and exhaust parking positions, thus preventing any adjustment of the intake and exhaust camshafts. During engine assembly, the camshaft phasers are coupled to the intake and exhaust camshafts so that the locking pins are inserted into the recesses and lock them when the intake and exhaust camshafts are approximately set to their predetermined intake and exhaust parking positions.

[0094] As discussed above, the preset exhaust park position causes the exhaust valve to close before the TDC (Torque Discharge Control), between the exhaust and intake strokes during operation in high- and low-stroke modes. The preset intake park position causes the intake valve to open after the TDC, between the exhaust and intake strokes, and to close after the BDC (Battery Discharge Control). Closing the exhaust valve before the TDC allows residual exhaust gas to remain in the cylinders. Closing the intake valve after the BDC reduces the effective compression ratio and therefore provides improved NVH (Noise, Vibration, and Harshness) performance.

[0095] If the engine temperature 484 and / or the air density are low (e.g., at high altitudes) and a vehicle start command is received, the injected fuel may not vaporize sufficiently. At a higher effective compression ratio, the injected fuel can vaporize more effectively. Therefore, at low engine temperatures 484, the valve control module 440 can switch the target lift mode 452 to low lift mode, or maintain the target lift mode 452 in low lift mode when the engine is started.

[0096] Fig.Figure 7 is a flowchart illustrating an exemplary procedure for locking the intake and exhaust cam phasers in their respective park positions. At 504, the valve control module 440 determines whether the engine 102 should be shut down if it is running. The engine 102 can be shut down, for example, in response to a vehicle shutdown command from the driver or for an auto-stop operation. For example, the valve control module 440 can determine that the engine 102 should be shut down when the engine shutdown command 464 is generated. The control continues with 508 if 504 is true. If 504 is false, the control remains at 504.

[0097] At 508, the valve control module 440 sets the intake cam phaser setpoint position 444 to the preset intake park position and the exhaust cam phaser setpoint position 448 to the preset exhaust park position. The preset exhaust park position causes the exhaust valve to close before the TDC (Torque Discharge Control) between the exhaust and intake strokes during operation in high- and low-lift modes. The preset intake park position causes the intake valve to close during the compression stroke, specifically after the BDC (Battery Discharge Control), which defines the intake and compression strokes. Closing the exhaust valve before the TDC allows residual exhaust gas to remain in the cylinders to meet emission parameter setpoints during a cold start. Closing the intake valve after the BDC reduces the effective compression ratio and lowers NVH (noise, vibration, and harshness) values ​​for automatic starts.

[0098] At 512, the valve control module 440 controls the intake cam phaser 128 and the exhaust cam phaser, respectively, starting from the intake and exhaust cam phaser target positions 444 and 448. Likewise, the valve actuator module 130 sets the intake and exhaust camshafts to the predetermined intake and exhaust parking positions at 512. For example, the valve actuator module 130 can control one or more hydraulic fluid control valves to regulate the pressure of the hydraulic fluid in the feed and retardation chambers of the intake and exhaust cam phasers, starting from the predetermined intake and exhaust parking positions. The locking pins hold the gears coupled to the intake and exhaust camshafts in place when the intake and exhaust camshafts are approximately in their respective predetermined intake and exhaust parking positions, and prevent the intake and exhaust camshafts from being adjusted.The term "approximately" is used because the recesses may be slightly larger than the locking pins.

[0099] The above description of the embodiments is for illustrative purposes only and is in no way intended to limit the scope of the invention, its applications, or uses. The broad range of applications of the disclosure can be implemented in a variety of forms. Even though this disclosure contains specific examples, the actual scope of the disclosure should not be limited thereby, since other modifications will become apparent upon study of the drawings, the description, and the following claims. It should be noted that one or more steps in a process can be carried out in a different order (or simultaneously) without altering the principles of the present disclosure.Furthermore, although each of the embodiments described above is characterized by certain features, one or more of these features described in relation to each embodiment of the disclosure may be implemented and / or combined in any of the other embodiments, even if this combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments against each other remain within the scope of this disclosure.

[0100] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "intervening," "coupled," "adjacent," "next to," "on top of," "above," "below," and "arranged." Unless expressly described as "direct," a relationship can be direct if a relationship between a first and second element is described in the above disclosure when no other intervening elements exist between the first and second element; however, it can also be indirect if one or more intervening elements (either spatial or functional) exist between the first and second element.As used herein, the phrase "at least one of A, B and C" should be understood to mean a logic (A OR B OR C) using a non-exclusive logical OR, and should not be understood to mean "at least one of A, at least one of B and at least one of C".

[0101] In this application, including the following definitions, the term "module" or "controller" may be replaced by the term "circuit." The term "module" may refer to, be part of, or include: an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field-programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; a memory (shared, dedicated, or group) that stores code executed by a processor; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a Systemon chip.

[0102] The module can contain one or more interface circuits. In some examples, the interface circuits can include wired or wireless interfaces connected to a local area network (LAN), the internet, a wide area network (WAN), or combinations thereof. The functionality of any given module in the current disclosure can be distributed across multiple modules connected via interface circuits. For example, many modules allow load balancing. In another example, a server module (also known as a remote or cloud server) can perform some functions on behalf of a client module.

[0103] The term "code," as used above, can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, and / or objects. The term "shared processor" includes a single processor that executes all or part of the code from multiple modules. The term "group processor" includes a processor that, in combination with additional processors, executes some or all of the code from one or more modules. References to multiple processor circuits include multiple processor circuits on separate matrices, multiple processor circuits on single matrices, multiple cores of a single-processor circuit, multiple threads of a single-processor circuit, or a combination of the above. The term "shared memory" includes a single memory that stores all or part of the code from multiple modules.The term "group memory" encompasses a memory circuit that, in combination with additional memory, stores all or part of the code from one or more modules.

[0104] The term "memory" can be a subset of the term "computer-readable medium." The term "computer-readable medium," as used herein, encompasses non-transient electrical and electromagnetic signals that propagate through a medium (as on a carrier wave) and can thus be considered concrete and non-transient. Non-restrictive examples of a non-transient, concrete computer-readable medium include non-volatile memory circuits (e.g., a flash memory circuit, a erasable programmable read memory circuit, or a mask read memory circuit), volatile memory circuits (e.g., a static RAM circuit or a dynamic RAM circuit), magnetic storage media (e.g., an analog or digital magnetic tape or a hard disk), and optical storage media (e.g., a CD, DVD, or Blu-ray Disc).

[0105] The devices and methods described in this application can be implemented, in whole or in part, by a dedicated computer, by configuring a general-purpose computer to execute one or more specific functions from computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into computer programs through the routine work of a qualified technician or programmer.

[0106] Computer programs contain processor-executable instructions stored on at least one non-transient, concrete, machine-readable medium. Computer programs may also contain and / or be based on stored data. Computer programs may include an input / output system (BIOS) that interacts with the hardware of the specialized computer, device drivers that interact with specific devices of the computer, or one or more operating systems, user applications, background services, background applications, etc.

[0107] Computer programs can include: (i) descriptive text that is parsed, such as HTML (hypertext markup language) or XML (extensible markup language), (ii) assembly code, (iii) object code created from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. For example only, source code can be written using the syntax of languages ​​such as C, C++, C#, Objective-C, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, JavaScript®, HTML5, Ada, ASP (active server pages), PHP, Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic (1), Lua, and Python®.

Claims

[1] Engine control method for a vehicle, comprising: Generating a shutdown command (468) for the engine (102) of the vehicle if at least one of the following conditions is met: the driver requests the engine (102) to be switched off via an ignition system; and when one or more predetermined conditions for switching off the engine (102) are met without the driver requesting the engine (102) to be switched off via the ignition system; and when the shutdown command (468) for the engine (102) is generated, advancing an exhaust camshaft phaser (129) from a predetermined exhaust parking position selected on a target exhaust residue; wherein, when the exhaust camshaft phaser (129) is in the predetermined exhaust parking position, an exhaust valve (120) of a cylinder (114) is fully closed during an exhaust stroke of the cylinder (114) before a piston of the cylinder (114) reaches top dead center for the next intake stroke of the cylinder (114), so that residual exhaust gas is retained for a following intake stroke. [2] The engine control method of claim 1, wherein a locking pin (232) is inserted into a recess (228) in the camshaft phaser (129) when the exhaust camshaft phaser (129) is in the predetermined exhaust parking position, the locking pin (232) in the recess (228) preventing the exhaust camshaft phaser (129) from being advanced or retarded. [3] The engine control method of claim 1, further comprising resetting an intake camshaft phaser (128) to a predetermined intake park position when the engine shutdown command (468) is generated, wherein an intake valve (118) of the cylinder (114) opens when the intake camshaft phaser (128) is in the predetermined intake park position after the piston of the cylinder (114) has reached top dead center for the next intake stroke of the cylinder (114). [4] An engine control method according to claim 3, wherein: a first locking pin (232) is inserted into a first recess (228) in the exhaust camshaft phaser (129) when the exhaust camshaft phaser (129) is in the predetermined exhaust parking position, and when the locking pin (232) is inserted in the first recess (228), prevents the exhaust camshaft phaser (129) from being advanced or retracted; and a second locking pin (232) is inserted into a second recess (228) in the intake camshaft phaser (128) when the intake camshaft phaser (128) is in the predetermined intake parking position, and when the locking pin (232) is inserted in the second recess (228), the advancing or retracting of the intake camshaft phaser (128) is prevented. [5] The engine control method of claim 3, wherein when the exhaust camshaft phaser (129) is in the predetermined exhaust parking position, the exhaust valve (120) is fully closed at at least 2 degrees of crankshaft angle during the exhaust stroke of the cylinder (114) before the piston reaches top dead center for the next intake stroke. [6] The engine control method of claim 3, wherein when the exhaust camshaft phaser (129) is in the predetermined exhaust parking position, the exhaust valve (120) is fully closed at at least 5 degrees of crankshaft angle during the exhaust stroke of the cylinder (114) before the piston reaches top dead center for the next intake stroke. [7] The engine control method of claim 3, wherein when the intake camshaft phaser (128) is in the predetermined intake parking position, the intake valve (118) of the cylinder (114) closes at least 40 degrees of crankshaft angle after the piston reaches the next bottom dead center. [8] The engine control method of claim 3, wherein when the intake camshaft phaser (128) is in the predetermined intake parking position, the intake valve (118) of the cylinder (114) closes at least 90 degrees of crankshaft angle after the piston reaches the next bottom dead center. [9] The engine control method of claim 1, further comprising deactivating the fuel supply to the engine (102) when the engine shutdown command (468) is generated. [10] The engine control method of claim 1 further comprising controlling the opening of the intake valve (120) in a low lift or a high lift mode.

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