Patent Publication Number: US-10329969-B2

Title: System and method of adjusting actuation timing of valves in a piston engine

Description:
This application claims the benefit of U.S. Provisional Ser. No. 62/077,686 filed on Nov. 10, 2014, the entire contents of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to variable valve actuation assemblies for piston engines, and more particularly relates to making adjustments to the actuation timing of valves in piston engines. 
     BACKGROUND 
     Variable valve actuation (VVA) assemblies are commonly equipped in piston engines such as automotive internal combustion engines, and are used for controlling actuation timing of valves in the engines. The actuation timing involves opening and closing intake and exhaust valves. Intake valves admit air or air-fuel mixture into engine cylinders, and exhaust valves let exhaust gasses out of the cylinders. In general, the VVA assemblies can help improve fuel economy, reduce exhaust emissions, and enhance engine performance in the associated automobiles. An engine typically includes more than one VVA assembly—for instance, a single VVA assembly at each cylinder of the engine. And each VVA assembly typically includes any number of mechanical components, electrical components, hydraulic components, or pneumatic components. 
     In one embodiment, a system that provides adjustable actuation timing of one or more valve(s) in a piston engine includes a position sensor and a variable valve actuation assembly. The position sensor takes position readings of the valve as the valve actuates in the piston engine. The variable valve actuation assembly is equipped at the valve and controls actuation timing of the valve. Actuation timing of the valve can be adjusted based, in part or more, upon one or more position reading(s) of the valve taken by the position sensor. 
     SUMMARY 
     In one embodiment, a system that provides adjustable actuation timing of one or more valve(s) in a piston engine includes a position sensor and a variable valve actuation assembly. The position sensor takes position readings of the valve as the valve actuates in the piston engine. The variable valve actuation assembly is equipped to the valve and controls actuation timing of the valve. Actuation timing of the valve can be adjusted based, in part or more, upon one or more position reading(s) of the valve taken by the position sensor. 
     In another embodiment, a method of adjusting actuation timing of one or more valve(s) in a piston engine by way of one or more variable valve actuation assembly(ies) includes several steps. One step involves taking a first position reading of the valve in the piston engine when the valve is at a closed position. Another step involves taking a second position reading of the valve when the valve is at a fully open position. Another step involves using the first and second position readings to calibrate subsequent position readings of the valve. Yet another step involves taking a third position reading of the valve before slowdown occurs adjacent the closed position. Yet another step involves referencing the third position reading to a predefined position of the valve. And yet another step involves making adjustments to the actuation timing of the valve, if called for, based in part or more upon the third position reading being referenced to the predefined position. 
     In yet another embodiment, a system that provides adjustable actuation timing of valves in a piston engine includes a first position sensor, a first lost motion assembly, a second position sensor, a second lost motion assembly, and an electronic control unit. The first position sensor is located near a first valve of a first cylinder of the piston engine. The first lost motion assembly actuates the first valve, and includes a first master piston, a first slave piston, and a first solenoid valve. The second position sensor is located near a second valve of a second cylinder of the piston engine. The second lost motion assembly actuates the second valve, and includes a second master piston, a second slave piston, and a second solenoid valve. The electronic control unit receives a first position reading from the first position sensor of the first valve before slowdown occurs adjacent a closed position. The first position reading is referenced to a first predefined position. Actuation timing of the first valve via activation and deactivation of the first solenoid valve can be adjusted based, in part or more, upon the first position reading being referenced to the first predefined position. The electronic control unit receives a second position reading from the second position sensor of the second valve before slowdown occurs adjacent a closed position. The second position reading is referenced to a second predefined position. Actuation timing of the second valve via activation and deactivation of the second solenoid valve can be adjusted based, in part or more, upon the second position reading being referenced to the second predefined position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of an embodiment of a variable valve actuation assembly with an embodiment of a position sensor; 
         FIG. 2  is another schematic of the variable valve actuation assembly and position sensor of  FIG. 1 ; 
         FIG. 3  is a flow chart presenting an embodiment of a method of adjusting actuation timing of valves in a piston engine via variable valve actuation assemblies; and 
         FIG. 4  is a graph plotting valve lift on the y-axis and crank angle on the x-axis. 
     
    
    
     DETAILED DESCRIPTION 
     The figures illustrate an embodiment of a system and method that provide adjustable actuation timing of valves in a piston engine. The actuation timing can involve opening and closing intake and exhaust valves in an internal combustion engine of an automobile. While described in greater detail below, in general, the system and method make needed adjustments to actuation timing in order to account for performance variations among variable valve actuation assemblies in the piston engine, and to account for performance variations among variable valve actuation assemblies between piston engines of the same kind. A position sensor is employed, and its position readings are used as a basis for any adjustments. The system and method bring greater precision and better reliability and consistency to valve actuation timing in piston engines and help ensure improved fuel economy, reduced exhaust emissions, and overall enhanced engine performance in the associated automobiles. Further, the system and method can be used for monitoring the functionality of variable valve actuation assemblies and observe any malfunctions. 
     The system can have different designs, constructions, and components depending on—among other potential determinants—the architecture of the associated piston engine and the architecture of the associated valvetrain. In the embodiment presented by  FIGS. 1 and 2 , the system includes a variable valve actuation (VVA) assembly  10 , a position sensor  12 , and an electronic control unit (ECU)  14 . In general, VVA assemblies control actuation timing and advance or retard opening and closing movements of intake and exhaust valves. The exact actuation timing is ordinarily controlled according to an engine performance strategy set by the automobile manufacturer. A piston engine can sometimes be equipped with one or more VVA assemblies at each of its cylinders for independent control of the valves at the cylinders. And like the larger system, VVA assemblies can have different designs, constructions, and components depending upon engine and valvetrain architecture. Variable valve actuation assemblies can include any number of mechanical components, electrical components, hydraulic components, or pneumatic components. In  FIGS. 1 and 2 , the VVA assembly  10  is a lost motion assembly. Types of VVA assemblies include electro-mechanical actuation assemblies, electro-magnetic actuation assemblies, electro-hydraulic actuation assemblies, and pneumatic actuation assemblies. 
     The lost motion assembly  10  actuates the opening and closing movements of valves  16  in a cylinder of the associated piston engine. The valves  16  can be intake or exhaust valves. In the example of  FIGS. 1 and 2 , the lost motion assembly  10  includes a master piston  18 , a solenoid valve  20 , an accumulator  22 , a check valve  24 , a slave piston  26 , and a fluid-flow circuit  28 . The master piston  18  has a spring  30  and a push rod  32  that reciprocates in response to engagement by a cam  34  of an engine camshaft. The cam  34  directly impinges a rocker arm  36 , which in turn impinges the master piston  18 . The cam  34  has a base  38  and a lobe  40 . The solenoid valve  20  is commanded to activate and deactivate in order to regulate fluid-flow in the fluid-flow circuit  28 . When activated, the solenoid valve  20  is brought to an open state and permits fluid-flow; and when deactivated, the solenoid valve  20  is brought to a closed state and prevents fluid-flow. The solenoid valve  20  could be normally-opened or normally-closed. The accumulator  22  stores pressurized fluid in a reservoir via a spring  42 . The check valve  24  opens to permit fluid-flow from a supply  44 , which can be fed fluid from a pump. Other components of the lost motion assembly  10  prompt the slave piston  26  to reciprocate a bridge  46  outward and inward to open and close the valves  16 . A valve catch in the slave piston  26  slows-down the closing movement of the valves  16  as the valves  16  are about to be seated in their fully closed position. Lastly, the fluid-flow circuit  28  fluidly communicates the components of the lost motion assembly  10  via a hydraulic fluid. Still, the lost motion assembly  10  can have more, less, and/or different components than those depicted in the figures and described here. 
     The position sensor  12  senses the position and movement of the valves  16  as the valves  16  open and close, and sends the corresponding position readings as input to the ECU  14 . In the associated piston engine there can be multiple position sensors, the exact number of which may depend on the number of valves and on the number of cylinders in the engine. However many there are, an individual position sensor  12  can be located at the valves  16 , at the slave piston  26 , at the bridge  46 , or at another location where the position sensor  12  can properly sense the position and movement of the valves  16 . Its exact location may be dictated by the type of position sensor and the valvetrain architecture. Referring again to the example of  FIGS. 1 and 2 , the position sensor  12  is mounted on a rod of the slave piston  26  near the bridge  46 . The position sensor  12  may be of different types, and one type is a variable inductance position sensor. In general, variable inductance position sensors are made up of a coil  48  and a metal target  50 . As the metal target  50  moves relative to the coil  48 , the frequency of the related circuit changes in proportion to the movement. The change in frequency can be converted into an appropriate signal for the ECU  14 , and can be related to corresponding valve positions. These types of valves and their operations and the attendant computations will be known to skilled artisans. Still, another type of position sensor is a variable reluctance position sensor. 
     The ECU  14  electrically communicates with the position sensor  12  and receives input from the position sensor  12  in the form of position readings. The ECU  14  may manage the functionality of the lost motion assembly  10 , and hence may command the activation and deactivation of the solenoid valve  20 . There could be a single ECU  14  that electrically communicates with all of the VVA assemblies  10  in the associated piston engine, or there may be multiple ECUs  14  electrically communicating with individual VVA assemblies  10 . Further, the ECU  14  could be part of another ECU in the associated automobile or could itself constitute another automobile ECU. Or the ECU  14  could electrically communicate with another automobile ECU such as an engine ECU. Whatever the arrangement, the ECU  14  can perform one or more of the method steps described below with reference to  FIG. 3 . The method steps can be implemented in a computer program product, like the ECU  14 , with instructions carried on a computer readable medium. The ECU  14  may include software programs with instructions in source code, object code, executable code, or some other format; may include firmware programs; may include hardware description language (HDL) files; and may include any program related data. The data may involve data structures, look-up tables, or data in any other suitable format. And the instructions may involve modules, routines, objects, components, and/or the like. 
     The system and method detailed in this description make needed adjustments to the actuation timing of the valves  16  in order to reconcile performance variations of individual VVA assemblies  10  in the associated piston engine, and to reconcile performance variations among multiple VVA assemblies  10  in multiple piston engines. It has been observed that differences among components in the VVA assemblies  10  can result in appreciable performance variations—for instance, actuation timing in an individual VVA assembly  10  can be off by as much eight crank angle degrees (8°) from its expected and predefined timing, and can be off by as much as sixteen crank angle degrees (16°) between a pair of VVA assemblies  10  in a piston engine. Other variation magnitudes are of course possible. The differences are found in components of the VVA assemblies  10 , such as mechanical, electrical, hydraulic, or pneumatic components, depending on the particular type of VVA assembly. The differences can involve imprecisely manufactured and imprecisely installed components, manufacturing tolerances, wear on components over the lifetime of their use, slower response rates for electrical components, and fluid leakages in hydraulic and pneumatic components. In the example of the lost motion assembly  10  of the figures, these differences can present themselves via slower activation and deactivation response rates of the solenoid valve  20 , leakage somewhere in the fluid-flow circuit  28 , and even viscosity fluctuations of the hydraulic fluid in the fluid-flow circuit  28  as temperatures increase and decrease. Still, differences can arise in other ways. 
     Once the performance variations are reconciled, the system and method bring greater precision and better consistency to the actuation timing of the valves  16 , and hence improve fuel economy, reduce exhaust emissions, and enhance overall engine performance in the associated automobiles. And because greater precision is effectuated with the system and method, other components of the VVA assemblies  10  may themselves have less precision and may therefore be less costly to produce. For instance, in the example of the lost motion assembly  10 , the solenoid valve  20  may not necessarily activate and deactivate with higher levels of exactitude. 
     An embodiment of the method is presented in the flow chart of  FIG. 3 . Other embodiments can employ more, less, and/or different steps than those set forth in the figure, and the steps need not necessarily be performed in the order described here. A step  110  involves taking a first position reading of the valves  16  when the valves  16  are at a fully closed position. The first position reading is taken by the position sensor  12  and sent to the ECU  14 .  FIG. 1  depicts the fully closed position where the valves  16  are fully seated and block-off associated intake and/or exhaust passages. In the example lost motion assembly  10 , the cam  34  engages the rocker arm  36  with its base  38  at step  110 , and the solenoid valve  20  is deactivated. Referring now to  FIG. 4 , the first position reading is taken at a zero lift point A on the graph. The zero lift point A represents the fully closed position. The graph of  FIG. 4  plots valve actuation with valve lift displacement on the y-axis and crank angle degrees on the x-axis. The solid line B denotes actuation of the valves  16  without advancing or retarding the opening and closing movements, while the broken line C denotes an early closing valve actuation. The left side of the solid line B up to its peak marks the opening movement of the valves  16  from initial opening to full opening, and the right side of the solid line B marks the closing movement of the valves  16  from full opening to full closing. Other valve actuations not depicted in  FIG. 4  include a late opening valve actuation. 
     Referring back to  FIG. 3 , a step  120  involves taking a second position reading of the valves  16 , this time when the valves  16  are at a fully open position. Like the first position reading, the second position reading is taken by the position sensor  12  and sent to the ECU  14 .  FIG. 2  depicts the fully open position where the valves  16  permit flow through the associated intake and/or exhaust passages. In the example lost motion assembly  10 , the cam  34  engages the rocker arm  36  at a peak of its lobe  40  at step  120 , and the solenoid valve  20  is activated and the slave piston  26  drives the bridge  46  outward to its greatest extent. Referring again to  FIG. 4 , the second position reading is taken at a maximum lift point D, which represents the fully open position. 
     The method further includes a step  130  that involves using the first and second position readings of steps  110 ,  120  to calibrate subsequent position readings taken by the position sensor  12 . In this sense, the first and second position readings could be considered calibration position readings. The calibration relates and references position sensor readings to physical positions of the valves  16 . In the example of the variable inductance position sensor  12 , a given hertz value of the sensor  12  is corresponded to a given displacement value of the valves  16  measured relative to the fully closed position of the valves  16 . The calibration can occur at any time and any number of times amid the operation of the associated piston engine, and the occurrence may be dictated by the engine performance strategy set by the automobile manufacturer. For instance, initial calibration can be executed at engine start-up, and ensuing re-calibrations can be executed when the engine is warmer and at a pre-established temperature, or when the engine is at a wide-open throttle operating condition. Still, the calibration could involve other and different steps, and whether the steps  110 ,  120 ,  130  are performed at all may depend on the type of position sensor  12  put to use in the system. Since the calibration takes place after the VVA assembly  10  is installed in the associated piston engine, imprecisely manufactured and imprecisely installed components and other differences set out above are accounted for. 
     After calibration, if indeed executed, a step  140  involves taking a third position reading of the valves  16  via the position sensor  12 . Like other position readings, the third position reading is sent to the ECU  14 . The third position reading can be taken with each opening and closing phase of the valves  16  as the valves  16  continuously actuate during engine operation, or can be taken at more infrequent intervals. Further, the position sensor  12  can take the third position reading at varied points throughout a single actuation of the valves  16 . The third position reading in  FIG. 4 , for instance, is taken at a point E amid the closing movement of the valves  16 . In this example, the point E is just before a slowdown occurs to the valves  16  as the valves  16  are approaching the fully closed position. The slowdown is effected by the valve catch of the slave piston  26 , and is denoted in the graph by the bracket F. In a specific example, the point E can be situated at approximately 1 millimeter (mm) to 2 mm before the fully closed position as illustrated in the enlargement of  FIG. 4 . Still, the third position reading could be taken at approximately 1 mm to 2 mm after the initial opening movement of the valves  16 , or at another point and another displacement along the plot of  FIG. 4  such as when the valves  16  are seated in their fully closed position. 
     Referring again to  FIG. 3 , a step  150  involves referencing the third position reading of step  140  to a predefined position of the valves  16 . The predefined position is typically according to the engine performance strategy set by the automobile manufacturer, and serves as the expected position of the valves  16  if the valves  16  strictly conformed to the engine performance strategy. And referencing the third position reading to the predefined position may mean comparing values and examining any discrepancies between the third position reading and the predefined position. If discrepancies exist, then a step  160  is performed. The step  160  involves making adjustments to the actuation timing of the valves  16  based on the step  150 . For example, if the predefined position has a value of X and the third position reading has a value of X+4°, then adjustments would be made to narrow or altogether eliminate the margin of the four degree discrepancy. The adjustments can be effected in various ways, depending on the particular type of VVA assembly in the system. In the example of the lost motion assembly  10 , the scheduled activation and deactivation can be altered per the existing discrepancy. The activation can be accelerated or decelerated, the deactivation can likewise be accelerated or decelerated, or a combination of these actions can be effected. And after the adjustments are made—whatever they may be—the steps  140 ,  150 , and  160  can be repeated. In this way, the method provides a closed-loop feedback process that more precisely controls actuation timing of the valves  16 . 
     Furthermore, the system and method detailed in this description could be used as part of an engine diagnostic procedure in which the functionality of the VVA assemblies  10  is monitored. The system and method may detect malfunctions that occur. In the example of the lost motion assembly  10 , for instance, a jammed solenoid valve  20  or a loss of pressure in the fluid-flow circuit  28  might be evidenced by an unusually large discrepancy. 
     The foregoing description is considered illustrative only. The terminology that is used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations will readily occur to those skilled in the art in view of the description. Thus, the foregoing description is not intended to limit the invention to the embodiments described above. Accordingly the scope of the invention as defined by the appended claims.