Patent Grant
10662825
The present teachings relate to valvetrains, particularly valvetrains providing variable valve lift (VVL) or cylinder deactivation (CDA).
Hydraulically actuated latches are used on some rocker arm assemblies to implement variable valve lift (VVL) or cylinder deactivation (CDA). For example, some switching roller finger followers (SRFF) use hydraulically actuated latches. In these systems, pressurized oil from an oil pump may be used for latch actuation. The flow of pressurized oil may be regulated by an oil control valve (OCV) under the supervision of an Engine Control Unit (ECU). A separate feed from the same source provides oil for hydraulic lash adjustment. This means that each rocker arm has two hydraulic feeds, which entails a degree of complexity and equipment cost. The oil demands of these hydraulic feeds may approach the limits of existing supply systems. In addition, there is a need to provide on board diagnostic information for cylinder deactivating and switching rocker arm assemblies.
The present teachings relate to a valvetrain suitable for an internal combustion engine that includes a combustion chamber, a moveable valve having a seat formed within the combustion chamber, and a camshaft. The valvetrain includes a rocker arm assembly that has a rocker arm and a cam follower configured to engage a cam on the camshaft as the camshaft rotates. In the present teachings, the valvetrain further includes a latch assembly. In some of these teachings, the latch assembly includes a latch pin mounted on the rocker arm and an actuator that includes an electromagnet. The actuator parts are mounted on components distinct from the rocker arm, whereby the rocker arm and the latch pin have freedom of movement independent from the electromagnet. The actuator is operative on the latch pin through magnetic force and does not require a mechanical interface with the latch pin.
The latch pin is moveable between first and second positions. The electromagnet is operable to cause the latch pin to translate between the first and second positions. One of the first and second latch pin positions may provide a configuration in which the rocker arm assembly is operative to actuate the moveable valve in response to rotation of the camshaft to produce a first valve lift profile. The other latch pin position may provide a configuration in which the rocker arm assembly is operative to actuate the moveable valve in response to rotation of the camshaft to produce a second valve lift profile, which is distinct from the first valve lift profile, or the moveable valve may be deactivated.
Using electromechanical latch assemblies instead of hydraulically-actuated latches can reduce complexity and demands for oil in some valvetrain systems. Mounting the electromagnet on a part that is distinct from the rocker arm avoids running wires to the rocker arm. Rocker arms reciprocate rapidly over a prolonged period and in proximity to other moving parts. Wires attaching to a rocker arm could be caught, clipped, or fatigued and consequently short out.
According to some aspects of the present teachings, the electromagnet is operative to cause the latch pin to translate between the first and second positions through magnetic flux following a magnetic circuit that includes a structural component of the valvetrain. The structural component may be a load-bearing member of the valvetrain. In some of these teachings, the structural component is the rocker arm on which the latch pin is mounted. In some of these teachings, the structural component is a pivot that provides a fulcrum for the rocker arm. In some of these teachings, both the rocker arm and a pivot that provides a fulcrum for the rocker arm are part of the magnetic circuit. The structural components may complete the magnetic circuit in the sense that if those components were replaced by ones made entirely from aluminum, the electromagnet would no longer be operative to cause the latch pin to translate between the first and second positions. Using these structural components to complete the magnetic circuit enables the latch assembly to have a compact design suitable for packaging within the limited space available under a valve cover.
In some of these teachings, the magnetic circuit also includes the latch pin. In an alternative teaching, rather than passing through the latch pin, the magnetic circuit is completed by another part that is mounted on the rocker arm and is positioned to act against the latch pin. The magnetic flux may be generated by the electromagnet and/or one or more permanent magnets. In some of these teachings, the electromagnet is operative to actuate the latch pin by generating, or ceasing to generate, the flux. In some of these teachings, the electromagnet is operative to actuate the latch pin by diverting the flux.
According to some aspects of the present teachings, the electromagnet is mounted in a position offset from the latch pin. More specifically, in some of these teachings the electromagnet is mounted in a position such that a line oriented in the direction along which the latch pin translates between its first and second positions while the cam is on base circle and passing through the latch pin while the cam is on base circle will not intersect the electromagnet or the space the electromagnet encloses. The present teachings enable mounting the electromagnet in an offset position, which facilitates packaging.
In some of these teachings, the electromagnet, a permanent magnet, or a combination of one or more electromagnets and permanent magnets are positioned and functional to provide a magnetic field effective to hold the latch pin in at least one of the first and second positions through magnetic flux that follows the magnetic circuit. In some of these teachings, the electromagnet is operable to alter the magnetic flux in the circuit and thereby cause the latch pin to translate between the first and second positions.
In some of these teachings, the actuator is operative to change a magnetic force on the latch pin or an abutting part mounted on the rocker arm. In some of these teachings, the actuator is operative to change a magnetic force on the latch pin. The part on which the magnetic force acts is magnetized. The change in magnetic force may include the application of the magnetic force or the removal of the magnetic force. In some of these teachings, the change in magnetic force includes a reversal of a direction in which magnetic force acts on the part.
In some of these teaching, all or a portion of the part included in the magnetic circuit is formed of a magnetically susceptible material that if replaced with aluminum would render the electromagnet inoperative to cause the latch pin to translate between the first and second positions. In some of these teachings, the magnetically susceptible material is a low coercivity ferromagnetic material.
In some of these teachings, magnetic flux following the magnetic circuit in one of a forward and a reverse direction enters the latch pin crossing directly or across an air gap from the rocker arm and leaves the latch pin crossing directly or across an air gap to a pole piece that is mounted to a component distinct from the rocker arm, whereby the rocker arm is operative to move independently from the pole piece. The pole piece may be in a fixed position relative to the electromagnet. The structure determining this flux paths relates to a compact design.
In some of these teaching, magnetic flux following the magnetic circuit passes between the latch pin and a pole piece mounted to a component distinct from the rocker arm across a variable width air gap. The width of the air gap varies as the latch pin translates between the first and second positions. In some of these teachings, the width of the air gap also varies as the rocker arm pivots during operation of the rocker arm assembly. The term pole piece as used herein may encompass any structure that completes a magnetic circuit regardless of the position of the pole piece within the magnetic circuit. In some of these teachings, the electromagnet includes a coil around a solid immovable core. That core may be considered a pole piece.
In some of these teachings, the valvetrain is installed in an engine having a cylinder head and one or more parts including a valve cover that define the limits of an enclosed space underneath the valve cover. In some of these teachings, the parts of the engine along the shortest path between the latch pin and the nearest outer edge of that enclosed space consist essentially of one or more pole pieces that complete the magnetic circuit. The outer edge may be defined by the cylinder head. The latch pin may extend outward from the back of the rocker arm assembly and there may be only a relatively narrow gap between the rocker arm assembly and the cylinder head. The electromagnet may be too large to fit within that gap; however, the gap may accommodate a pole piece that completes a magnetic circuit that includes the latch pin and the electromagnet.
In some aspects of the present teachings, the magnetic flux passes through a pivot for the rocker arm assembly. The pivot may provide a fulcrum for the rocker arm. Passing the flux through the pivot may provide a pathway through which the flux may be brought close to the latch pin or a co-acting part at a location within the rocker arm. In some of these teachings, the magnetic flux passes through the structure of the pivot. In some of these teachings, the pivot structure forms part of a magnetic circuit through which the actuator operates such that replacing that structure with aluminum would render the electromagnet inoperative to cause the latch pin to translate between the first and second positions. In some of these teachings, the pivot is made primarily of low coercivity ferromagnetic material. In some of these teachings, the pivot is a lash adjuster. In some of these teachings, the pivot is a hydraulic lash adjuster. The pivot may be relatively stationary compared to the rocker arm and flux from the electromagnet may be transferred to the pivot relatively easily.
In some of these teachings, the electromagnet is mounted to a structure that abuts a pivot providing a fulcrum for the rocker arm on which the latch pin is mounted. In some of these teachings, the electromagnet is mounted to the pivot. In some of these teachings, the electromagnet is mounted on a bracket that abuts two pivots, one associated with each of two rocker arm assemblies. In some of these teachings, the electromagnet is mounted on a bracket that abuts four pivots, each associated with a different rocker arm assembly. In some of these teachings, the electromagnet is mounted on a bracket that abuts a spark plug tower. In some of these teachings, the electromagnet is mounted on a bracket that encircles a spark plug tower. These structures may facilitate correctly positioning the electromagnet. The mounting bracket may be secured to a cylinder head. In some of these teachings, a structure through which the electromagnet is mounted also provides a component of the magnetic circuit.
In some aspects of the present teachings, there are two of the rocker arm assemblies and two of the latch pins and the electromagnet is operable to simultaneously cause both latch pins to translate between first and second positions. In some of these teachings, the two latch pins form parts of a single magnetic circuit for the electromagnet. In some of these teachings, the two rocker arm assemblies are side-by-side. In some of these teachings, the electromagnet is located between the two rocker arm assemblies. In some of these teachings, the magnetic circuit further includes two pivots, each associated with a different one of the two rocker arm assemblies.
In some of the present teachings, the valvetrain is installed within an engine having a combustion chamber and the electromagnet of the actuator is mounted in a position that is fixed with respect to the combustion chamber. In some of these teachings, the electromagnet is mounted to a cylinder head, a cam carrier, a camshaft journal, or a valve cover of the engine.
In some of these teachings, the electromagnet is mounted to a pivot. Mounting the electromagnet to a part that is distinct from the rocker arm and that is not constrained to move with the rocker arm allows wires powering the electromagnet to be maintained in relatively static positions.
In some of the present teachings, the latch pin is mounted on a rocker arm of the rocker arm assembly and, along with the rocker arm, has a range of motion relative to the actuator. An air gap in a magnetic circuit through which the actuator operates on the latch pin may vary in width in conjunction with this relative motion. The rocker arm position and thus the air gap width may be affected by rotation of the camshaft. In some of these teachings, the rocker arm assembly and the latch assembly are configured such that the actuator does not need to be operative on the latch pin except within a limited portion of rocker arm's range of motion. Actuation of the latch pin may occur only when the cam is on base circle.
In some of these teachings, the rocker arm assembly is configured whereby the rocker arm to which the latch pin is mounted remains substantially stationary when the latch pin is in a non-engaging configuration. The engaging configuration may be maintained independently from the actuator. In some of these teachings, the engaging configuration is maintained by a spring. In some of these teachings, in the engaging configuration, with each cycle of the cam the rocker arm reaches a position in which the actuator is operative to induce a magnetic force on the latch pin sufficient to overcome the spring force and hold the latch pin in the non-engaging configuration. The actuator need not be so operative throughout the cam cycle.
Some aspects of the present teachings provide a module for installation in an engine. The module includes a rocker arm assembly, a pivot, and an actuator according to the present teachings. In some of these teachings, the pivot is secured to the rocker arm assembly. In some of these teachings, the pivot is a hydraulic lash adjuster. The module may be convenient for installation in an engine and may facilitate correct positioning of the actuator relative to the rocker arm. A connecting piece that secures the pivot to the rocker arm assembly prior to installation may be removed after installation.
Some aspects of the present teachings relate to using a valvetrain within a method of operating an internal combustion engine that includes the valvetrain. In some of these teachings, the valvetrain include a rocker arm assembly that has a latch pin providing the rocker arm assembly with engaging and non-engaging configurations. In some of these teachings, the method includes operating the engine with the latch pin in one of the engaging and non-engaging configurations. An electromagnet of an actuator that is mounted within the engine but on a component distinct from a rocker arm on which the latch pin is mounted is energized to cause the latch pin to translate and thereby change the rocker arm assembly configuration. The engine is then further operated with the rocker arm assembly in the other of the engaging and non-engaging configurations. In some of these teaching, the latch pin is actuated by magnetic flux that passes through the rocker arm. In some of these teaching, the latch pin is actuated through a magnetic circuit that includes a structural component of the rocker arm assembly.
Some aspects of the present teachings relate to a method of operating an internal combustion engine in which an electrical circuit that includes an electromagnet operative to actuate a rocker arm-mounted latch pin is used to provide rocker arm position information. The method is applicable to an internal combustion engine of a type that includes a combustion chamber, a moveable valve having a seat formed in the combustion chamber, a camshaft on which a cam is mounted, a rocker arm assembly including a rocker arm and a cam follower configured to engage the cam as the camshaft rotates, and a latch assembly including a latch pin mounted on the rocker arm and an actuator that includes an electromagnet mounted to a component distinct from the rocker arm. The electromagnet is operative to cause the latch pin to translate between the first and the second position through magnetic flux that follows a magnetic circuit that passes through the latch pin and includes an air gap that varies in width in relation to a motion of the rocker arm that actuates the moveable valve. As the air gap varies in width, the magnetic reluctance of the magnetic circuit and the inductance of the electromagnet will also vary. The inductance affects current and voltage in an electrical circuit that includes the electromagnet. In some of these teachings, that effect is used to determine the rocker arm position. In some of these teachings, the method includes analyzing data relating to a current or voltage in an electrical circuit comprising the electromagnet to obtain rocker arm position information. The data may be gathered over a span of time and analyzed to determine the valve lift profile. The data is obtained while the engine is operating and the camshaft is rotating. These methods allow the same electromagnet that is used to actuate the latch pin to also be used to provide on-board diagnostic (OBD) information or for engine management.
In some of these teachings, a circuit including the electromagnet is powered to facilitate gathering the data. In some of these teachings, the electrical circuit is given a pulse insufficient to actuate the latch pin and the data relates to a current or voltage induced by the pulse. In some of these teachings, gathering the data comprises gathering the data over a cam cycle through which the electrical circuit is continuously powered with a current that does not maintain or affect the latch pin position. In some of these teachings, the electromagnet is powered with a DC current to actuate the latch pin and is powered with an AC current while gathering the data. The AC current need not affect the latch pin position. The AC signal may be driven on top of the DC current.
In some of these teachings, the rocker arm position information is used to perform a diagnostic. In some of these teachings, the method includes reporting a diagnostic result. In some of these teachings, the diagnostic determination is whether the rocker arm assembly is in the engaging configuration. In some of these teachings, the diagnostic determination is whether the latch assembly is operating correctly.
Rocker arm position information may be used to make a variety of diagnostic determinations. In some of these teachings, rocker arm position information is used to detect wear in one or more valve lift components. In some of these teachings, rocker arm position information is used to detect a collapsed lifter. In some of these teachings, rocker arm position information is used to detect valve float. In some of these teachings, rocker arm position information is used to detect a broken valve spring.
In some of these teachings, the circuit comprising the electromagnet is monitored to determine whether an event referred to as a “critical shift” has occurred. A critical shift is an event in which a latch pin slips out of engagement while the cam is lifting a rocker arm. When this happens, the rocker arm to which the latch pin is mounted rapidly returns to the position normally associated with base circle. If there is magnetic flux going through the magnetic circuit at the time of the critical shift, the current in the circuit comprising the electromagnetic will be affected and the effect may be used to detect the critical shift. In some of these teachings, the latch assembly includes a permanent magnet configured to maintain flux in the magnetic circuit while the electromagnet is off.
Some aspects of the present teachings relate to a method of using a valvetrain that provides rocker arm position information to control an engine. According to these teachings, the rocker arm position information is used to determine camshaft position, which is used in an engine management operation. In some of these teachings, the engine management operation includes regulating an ignition timing. In some of these teachings, the engine management operation includes regulating the timing of a fueling event. The rocker arm moves in relation to camshaft rotation. In some of these teachings, obtaining camshaft position information comprises determining a time at which the rocker arm reached maximum lift.
In some of these teachings, rocker arm position data is collected from two or more rocker arm assemblies. Where both rocker arm assemblies are actuated through one camshaft, obtaining data from two or more distinct rocker arms allows for a more accurate determination of camshaft position. Where the two rocker arm assemblies are actuated by different camshafts, the information may be used to determine the phase relationship between the camshafts.
In some of these teachings, rocker arm position detection is used to provide camshaft position sensing. In some of these teachings, the engine management operation is performed by a controller that is not receiving data regarding the position of the camshaft from a conventional camshaft position sensor. The engine may include a camshaft position sensor of a conventional type that is not currently functioning. In some of these teachings, using the camshaft position information in an engine management operation comprises using the camshaft position information in conjunction with data from a crank angle sensor to determine the phase relationship between a camshaft and a crankshaft. In some of these teachings the engine management operation comprises controlling a cam phaser.
In some of these teachings, the cam includes two lift lobes and the rocker arm assembly includes a latch enabling cylinder deactivation. The rocker arm position information may enable an accurate determination of where the cam is in the dual lift cycle. In a method according to these teachings, the latch is actuated twice per cam cycle, whereby through two or more cam cycles the latch is engaged whenever the cam follower is on one of the two lift lobes and disengaged whenever the cam follower is on the other of the two lift lobes. Accurate determination of the cam shaft position is an enabler for this method.
In some of the present teachings, the rocker arm to which the latch pin is mounted is of a design that was put into production for use with a hydraulically actuated latch. In some of these teachings, the rocker arm to which the latch pin is mounted includes a hydraulic chamber adapted to receive a hydraulically actuated latch pin. In some of these teachings, a magnetically actuated latch pin is installed in that hydraulic chamber. Rocker arms for commercial applications are typically manufactured using customized casting and stamping equipment requiring a large capital investment. The present disclosure provides designs that allow these same rocker arms to be used with a magnetically actuated latch pin.
Some aspects of the present teachings relate to a method of retrofitting for electromagnetic latching a rocker arm manufactured for hydraulic latching. The method includes installing a latch pin within a hydraulic chamber of the rocker arm with a portion of the latch pin protruding from the chamber. The rocker arm is installed within an engine in a magnetic circuit in which flux from an electromagnet will enter the latch pin through the rocker arm and leave the rocker arm across an air gap between the protruding portion of the latch pin and a pole piece of the latch assembly.
The primary purpose of this summary has been to present certain of the inventors' concepts in a simplified form to facilitate understanding of the more detailed description that follows. This summary is not a comprehensive description of every one of the inventors' concepts or every combination of the inventors' concepts that can be considered “invention”. Other concepts of the inventors will be conveyed to one of ordinary skill in the art by the following detailed description together with the drawings. The specifics disclosed herein may be generalized, narrowed, and combined in various ways with the ultimate statement of what the inventors claim as their invention being reserved for the claims that follow.
In the drawings, some reference characters consist of a number followed by a letter. In this description and the claims that follow, a reference character consisting of that same number without a letter is equivalent to a listing of all reference characters used in the drawings and consisting of that same number followed by a letter. For example, “valvetrain 101” is the same as “valvetrain 101A, 101B”.
Shaft 147 protrudes outward through openings 182 in the sides of outer arm 103A to engage torsion springs 145 (see
Latch assembly 105A includes an actuator 127A mounted to HLA 181 and a latch pin 114A mounted on rocker arm 103A. In this specification, the terms “latch pin” and “rocker arm” encompass the most basic structures that would be commonly understood as constituting a “latch pin” or a “rocker arm” and may further encompass parts that are rigid and rigidly held to that most basic structure. A rocker arm assembly is operative to form one or more force transmission pathways between a cam and a moveable valve. A rocker arm is a lever operative to transmits force from the cam along one or more of those pathways. The most basic structure of the rocker arm, which is its core structure, is capable of bearing the load and carrying out that function.
Latch pin 114A is translatable between a first position and a second position. The first position may be an engaging position, which is illustrated in
Actuator 127A may include an electromagnet 119 and pole pieces 131A and 131B. As the term is used in this disclosure, a pole piece may be any part formed of low coercivity ferromagnetic material and located in a position where it is operative to complete a magnetic circuit. Actuator 127A is mounted to HLA 181 through pole piece 131A, which also provides a core for electromagnet 119. HLA 181 includes an inner sleeve 175 and an outer sleeve 173. Outer sleeve 173 is installed within a bore 174 formed in cylinder head 130. Outer sleeve 173 may rotate within bore 174, but is otherwise substantially stationary with respect to cylinder head 130. Inner sleeve 175 is telescopically engaged within outer sleeve 173 and provides a fulcrum on which outer arm 103A pivots. That fulcrum may be hydraulically raised or lowered to adjust lash.
Latch pin 114A, outer arm 103A, inner sleeve 175, and outer sleeve 173 may be made entirely of low coercivity ferromagnetic material. Together with pole pieces 131A and 131B, they may form a magnetic circuit 220E, which is shown in
Magnetic circuit 220E passes through rocker arm 103A. In this disclosure, “passing through” a part means passing through the smallest convex volume that can enclose the part. When asserting that a magnetic flux that is operative “passes through” a part, the meaning is that the entirety of a portion of the magnetic flux that is sufficient to be operative passes through that part. In other words, the operability is achieved independently from any flux that follows a circuit that does not pass through the part.
Magnetic circuit 220E passes through the structure of rocker arm 103A. “Passing through the structure” of a part means passing through the material that makes up that part. If the part forms a low reluctance pathway for the magnetic flux, it may help define the magnetic circuit. Low coercivity ferromagnetic materials in particular are useful in establishing magnetic circuits. In some cases, the magnetic properties of a part are essential to the formation of a magnetic circuit through which actuator 127 is operative. A touchstone for these cases is that if that part were replaced by an aluminum part, an operability dependent on that circuit would be lost. Aluminum is an example of a paramagnetic material. For the purposes of this disclosure, a paramagnetic material is one that does not interact strongly with magnetic fields.
HLA 181 and latch pin 114A form essential parts of magnetic circuit 220E. In other words, if either of these parts were replaced by ones made entirely of aluminum, actuator 127 would cease to be operative to actuate latch pin 114A. Depending on the strength of electromagnet 109, the core structure of rocker arm 103A may also form an essential part of magnetic circuit 220E. Rocker arm 103A may be formed of low coercivity ferromagnetic material that provides a low reluctance pathway for magnetic flux crossing from HLA 181 to latch pin 114A. On the other hand, HLA 181 brings magnetic flux sufficiently close to latch pin 114A that magnetic flux may cross between HLA 181 and latch pin 114A following magnetic circuit 220E regardless of the material in between. In some of these teachings, pole pieces 192L are positioned to the sides of rocker arm 103A as illustrated in
Latch pin 114A, by virtue of being mounted to outer arm 103A, has a range of motion relative to combustion chamber 137 and actuator 127A. This range of motion may be primarily the result of outer arm 103A pivoting on HLA 181 when rocker arm assembly 115A is in the engaging configuration. On the other hand, the position of latch 117A relative to actuator 127A may be substantially fixed while latch 117A is in the non-engaging configuration. Extension and retraction of HLA 181 may introduce some relative motion, but excluding a brief period during start-up, the range of motion introduced by HLA 181 may be negligible. As long as latch pin 114A is in the non-engaging configuration, magnetic circuit 220E may remain operative whereby electromagnet 119 may act through that circuit to maintain latch pin 114A in the non-engaging configuration.
As shown in
Wires 128 may all connect to a common plug 126. In some of these teachings, two of the electromagnets 119 are connected in series or in parallel. In some of these teachings, all four of the electromagnets 119 are connected in series or in parallel. These options reduce the number of wires in plug 126 and allowing a tradeoff between circuit costs and flexibility. For example, the intake and exhaust valves in a multi-valve engine may only be subject to deactivation in pairs. In some of these teachings, a plurality of electromagnets 119 share a common ground connection. In some of these teachings, one or more electromagnets 119 are grounded through cylinder head 130.
In accordance with some of the present teachings, mounting frame 123 is supported to two or more HLAs 181 that are angled with respect to one another when installed in their bores 174. This angling may restrict vertical movement of mounting frame 123. Mounting frame 123 may not fit over HLAs 181. In an installation method, two or more HLAs 181 may be slid through openings in mounting frame 123 into their bores 174. Electromagnets 119 and wiring harness 124 may be installed on mounting frame 123 either before or after this operation. Upper frame 125 may be connected to mounting frame 123 any time after the installation of electromagnets 119. Mounting frame 123 may be further secured with connectors attaching frame 123 to cylinder head 130.
Rather than being supported on HLAs 181, mounting frame 123 may be supported by cylinder head 130. Mounting frame 123 may still abut HLAs 181, whereby HLAs 181 facilitate proper position of the pole pieces 131 on mounting frame 123. In addition, mounting frame 123 may include a circular opening 132 that is shaped to fit around a spark plug tower (not shown). The spark plug tower may then also be used to achieve correct and stable positioning of pole pieces 131.
Mounting frame 123 may be part of a valve actuation module. In the present disclosure, a valve actuation module is a structure that includes a rocker arm assembly 115 and an actuator 127 according to the present disclosure. The actuator 127 may be mounted to a pivot for the rocker arm assembly 115. For example, the actuator 127 may be mounted to an HLA 181. In some of these teachings, the HLA 181 and the rocker arm assembly 115 are held together by a removable clip (not shown). The clip may hold HLA 181 and rocker arm assembly 115 together during shipping and through installation of valve actuation module within an engine 100.
Actuator 127B places electromagnet 119 between two adjacent rocker arm assemblies 115A. When electromagnet 119 is energized, it actuates the two latch pins 114B to their non-engaging position through magnetic flux that follows the magnetic circuit 220F illustrated in
Referring to
In accordance with some of the present teachings, latch pin 114B has an expanded end 111 that does not fit within the opening in rocker arm 103A out of which latch pin 114B extends. Expanded end 111 has a larger cross-sectional area than the core 113B of latch pin 114B that travels within hydraulic chamber 177. The large cross-sectional area of end 111 facilitates its interaction with pole piece 131D. In accordance with some of these teachings, pole piece 131D is mounted to be facing end 111 when cam 167 is on base circle. The facing surfaces may be parallel or nearly parallel. In some of these teachings, the facing surfaces are generally flat. In some of these teachings, latch pin 114 contacts an actuator pole piece 131 when latch pin 114 is in the non-engaging position. In some of these teachings, one or both of the contacting surfaces has one or more dimples. Dimples may be operative to prevent end 111 and pole piece 131D from contacting over a large surface area and potentially sticking together. In some of these teachings the facing surfaces are parallel or nearly parallel to a direction of lash adjustment provided by lash adjuster 181. This geometry may facilitate maintaining operability of actuator 127B over a range of lash adjustment.
The rocker arms 103 of the examples herein are all rocker arms that have been put into production for use with a hydraulically actuated latch. For example, with reference to
In some aspects of the present teachings, act 307 generates magnetic flux that enters rocker arm 103A and actuates a latch pin 114 mounted on that rocker arm. Magnetic flux follows closed loops, so the flux that enters rocker arm 103A also leaves rocker arm 103A before returning to its source. In some of the present teachings, the flux that enters and leaves rocker arm 103A is sufficient to result in latch pin 114 actuating. The source of magnetic flux may be relatively stationary with respect to combustion chamber 137. Rocker arm 103A, on the other hand, is mobile with respect to combustion chamber 137. In some of these teachings, act 307 places a magnetic force directly on the latch pin 114. This force may initially actuate the latch pin 114 and subsequently maintain the position of latch pin 114 while engine 100 continues to operate through act 301.
Act 307 may power electromagnet 119 with either an alternating current (AC) or a direct current (DC). In some of these teachings, act 307 powers electromagnet 119 with a DC current. In some of these teachings deactivating electromagnet 119 cuts power to electromagnet 119 entirely. But in some of these teachings, deactivating electromagnet 119 simply reduces the current or changes it in such a way that latch pin 114 ceases to be held in the non-engaging position.
Act 311 is driving a circuit that includes electromagnet 119 to facilitate data collection. Driving the circuit may include pulsing the circuit. In some examples, a DC current pulse may be used. The default position for latch pin 114 could be either the engaging or the non-engaging configuration. A DC pulse could be applied on top of a DC current that is used to hold latch pin 114 in position. But in some of these teachings, the DC pulse is applied only when electromagnet 119 is not energized. In some examples, an AC current is applied to facilitate data collection while a DC current is used to actuate latch pin 114.
In some of these teachings, a circuit including electromagnet 119 is driven continuously over extended periods in a way that enables the data collection of act 313 but does not affect the position of latch pin 114. The current provided for data collection may be AC or DC. The periods may be in excess of the time taken for camshaft 169 to complete a rotation. In some examples, the current applied to facilitate data collection is insufficient in magnitude or duration to actuate latch pin 114. In some examples, the current applied to facilitate data increases the amount of force holding latch pin 114 in its current position.
Act 313 is data collection, which may take place while the circuit is being driven according to act 311. Data collection may include measuring a current or voltage in an electrical circuit comprising electromagnet 119. A time variation in that current or voltage may be measured. The data may be obtained using any suitable measuring device. Examples of measuring devices that may be suitable include, without limitation, a shunt resistor and a Hall effect sensor.
In an alternative provided by the present disclosure, the electrical circuit including electromagnet 119 is monitored passively, making action 311 optional. If there is magnetic flux in a circuit comprising electromagnet 119, any expansion or contraction of air gap 134 will produce a change in that flux and induce a current in electromagnet 119. That induced current may be detected and analyzed to determine the change in air gap 134. In some of these teaching, a permanent magnet is configured to continuously maintain a magnetic flux in a magnetic circuit comprising electromagnet 119. That flux may be insufficient to hold latch pin 114 in any particular position.
Act 315 is using the collected data to obtain position information for rocker arm 103A. An instantaneous rocker arm position may be determined. Alternatively, a set representing data collected over a span of time may be analyzed to determine, for example, a valve lift profile. The data will depend on the inductance of the circuit, which will depend on the inductance of electromagnet 119, which will depend on the magnetic reluctance of magnetic circuit 220, which will depend on the size of air gap 134, which will depend on the pivot angle of rocker arm 103A on the fulcrum provided by HLA 181, which determines the amount by which valve 185 has been lifted of its seat 186. Analyzing the data may include one or more of comparing the data to results obtained during calibration, comparing the data to model predictions, comparing the data to data obtained during a previous cam cycle, comparing the data to data obtained at other cam phases, and comparing similar data obtained from other rocker arms.
The size of air gap 134 is also affected by the position of latch pin 114. Therefore, method 310 may be modified or extended to provide a determination of whether latch pin 114 is in the extended or retracted position. In some of these teachings, information obtained from the circuit comprising electromagnet 119 is used to distinguish among three states. In the first state, latch pin 114 is in the non-engaging configuration. In the second state, latch pin 114 is in the engaging configuration and cam 167 is on base circle. In the third state, latch pin 114 is in the engaging configuration and cam 167 is off base circle. The determination of the third state may further include a determination of rocker arm position.
Act 317 is performing an operation using the rocker arm position information derived in act 315. In some of these teachings, the operation of act 317 is a diagnostic. A diagnostic operation may include a reporting step. The report may be made selectively. The report may be sending a signal, such as illuminating a warning light. In some of these teachings, the diagnostic operation includes recording a diagnostic code in a data storage device. The diagnostic code may later be read by a technician.
Some of the diagnostic determinations that may be made using the rocker arm position data include determining whether there is wear in one or more valve lift components, determining whether there is a collapsed lifter, determining whether valve float is occurring, and determining whether there is a broken valve spring. Some of these diagnostics may involve making several rocker arm position determinations to obtain sufficient information relating to a current valve lift profile. Some of these diagnostics may involve observing a variation in valve lift profile over time.
In some of these teachings, method 310 or one of the variations thereof described above is used to detect a critical shift in rocker arm assembly 115A. A critical shift is the case where latch pin 114 comes out of the engaging position while cam 167 is lifting rocker arm 103B. If this happens, rocker arm 103A will be driven by valve spring 183 to rapidly pivot from a lifted position like the one shown in
In some of these teachings, the operation of act 317 is an engine management operation. An engine management operation is one that affects a running state of engine 100. For example, the rocker arm position information may be use in a control algorithm. In some of these teachings, the rocker arm position information is used to provide camshaft position information and the camshaft position information is used in the control algorithm. The present teaching of using rocker arm position information to obtain camshaft position information and using that camshaft position information to control an engine is independent of the method by which the rocker arm position is determined or the structure used to determine the rocker arm position. The rocker arm position may be determined using any suitable device and method.
The camshaft position may be determined with greater accuracy or reliability by combining the rocker arm position information with position data from another rocker arm. The camshaft position information may be used in the same way as information from a conventional camshaft position sensor. The information may be used, for example, to determine the timing of an ignition or a fueling event. Crankshaft position information may be used in conjunction with the camshaft position information within the engine management operation. The rocker arm position information may be used to augment or substitute for the information provided by a camshaft position sensor. Here, the term camshaft position sensor is used in the sense of a device known in the industry as a camshaft position sensor.
A camshaft position sensor of a conventional type provides coarse data regarding camshaft position. Rocker arm position information can provide more precise camshaft position data. That higher precision data may be enabling for certain applications. One such application is a method of operating a cylinder deactivating rocker arm assembly actuated by a two-lobe cam. The latch can be engaged and disengaged with each cam cycle whereby the valve is lifted by one of the lobes but deactivated with respect to the other lobe.
The approximate shape of the valve lift profile may be known. Accordingly, as few as two data points may be sufficient to determine the rate of camshaft rotation and the current position (phase angle) of the camshaft. Greater numbers of data points may be used to perform statistical analysis to improve the accuracy of these determinations and/or refine a representation of the shape of the valve lift profile.
The analysis of rocker arm position information may be used to identify one or more critical points in the cam cycle. Critical points in the cam cycle include the point at which the rocker arm begins to lift and the point at which the rocker arm completes its decent. These events are closely related to valve opening and valve closing. The point at which the rocker arm reaches maximum lift is also of interest. It may be desirable to collect rocker arm position data while the rocker arm is near the point of maximum lift to obtain measurements with a high signal to noise ratio. In some of these teachings, a determination of camshaft position is used in setting the timing for a subsequent measurement of rocker arm position.
The components and features of the present disclosure have been shown and/or described in terms of certain aspects and examples. While a particular component or feature, or a broad or narrow formulation of that component or feature, may have been described in relation to only one embodiment or one example, all components and features in either their broad or narrow formulations may be combined with other components or features to the extent such combinations would be recognized as logical by one of ordinary skill in the art.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2017/056468 | 10/13/2017 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2018/075343 | 4/26/2018 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20190234247 A1 | Aug 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62409263 | Oct 2016 | US | |
| 62500022 | Feb 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15432026 | Feb 2017 | US |
| Child | 16342376 | US |
