Patent Application
20050045128
The invention pertains to the field of cam shaft disposition within an internal combustion engine. More particularly, the invention pertains to camshaft incorporating variable camshaft timing (VCT) phaser rotor.
The performance of an internal combustion engine can be improved by the use of dual camshafts, one to operate the intake valves of the various cylinders of the engine and the other to operate the exhaust valves. Typically, one of such camshafts is driven by the crankshaft of the engine, through a sprocket and chain drive or a belt drive, and the other of such camshafts is driven by the first, through a second sprocket and chain drive or a second belt drive. Alternatively, both of the camshafts can be driven by a single crankshaft powered chain drive or belt drive. Engine performance in an engine with dual camshafts can be further improved, in terms of idle quality, fuel economy, reduced emissions or increased torque, by changing the positional relationship of one of the camshafts, usually the camshaft which operates the intake valves of the engine, relative to the other camshaft and relative to the crankshaft, to thereby vary the timing of the engine in terms of the operation of intake valves relative to its exhaust valves or in terms of the operation of its valves relative to the position of the crankshaft.
Consideration of information disclosed by the following U.S. patents, which are all hereby incorporated by reference, is useful when exploring the background of the present invention.
U.S. Pat. No. 5,002,023 describes a VCT system within the field of the invention in which the system hydraulics includes a pair of oppositely acting hydraulic cylinders with appropriate hydraulic flow elements to selectively transfer hydraulic fluid from one of the cylinders to the other, or vice versa, to thereby advance or retard the circumferential position on of a camshaft relative to a crankshaft. The control system utilizes a control valve in which the exhaustion of hydraulic fluid from one or another of the oppositely acting cylinders is permitted by moving a spool within the valve one way or another from its centered or null position. The movement of the spool occurs in response to an increase or decrease in control hydraulic pressure, PC, on one end of the spool and the relationship between the hydraulic force on such end and an oppositely direct mechanical force on the other end which results from a compression spring that acts thereon.
U.S. Pat. No. 5,107,804 describes an alternate type of VCT system within the field of the invention in which the system hydraulics include a vane having lobes within an enclosed housing which replace the oppositely acting cylinders disclosed by the aforementioned U.S. Pat. No. 5,002,023. The vane is oscillatable with respect to the housing, with appropriate hydraulic flow elements to transfer hydraulic fluid within the housing from one side of a lobe to the other, or vice versa, to thereby oscillate the vane with respect to the housing in one direction or the other, an action which is effective to advance or retard the position of the camshaft relative to the crankshaft. The control system of this VCT system is identical to that divulged in U.S. Pat. No. 5,002,023, using the same type of spool valve responding to the same type of forces acting thereon.
U.S. Pat. Nos. 5,172,659 and 5,184,578 both address the problems of the aforementioned types of VCT systems created by the attempt to balance the hydraulic force exerted against one end of the spool and the mechanical force exerted against the other end. The improved control system disclosed in both U.S. Pat. Nos. 5,172,659 and 5,184,578 utilizes hydraulic force on both ends of the spool. The hydraulic force on one end results from the directly applied hydraulic fluid from the engine oil gallery at full hydraulic pressure, PS. The hydraulic force on the other end of the spool results from a hydraulic cylinder or other force multiplier which acts thereon in response to system hydraulic fluid at reduced pressure, PC, from a PWM solenoid. Because the force at each of the opposed ends of the spool is hydraulic in origin, based on the same hydraulic fluid, changes in pressure or viscosity of the hydraulic fluid will be self-negating, and will not affect the centered or null position of the spool.
U.S. Pat. No. 5,289,805 provides an improved VCT method which utilizes a hydraulic PWM spool position control and an advanced control method suitable for computer implementation that yields a prescribed set point tracking behavior with a high degree of robustness.
In U.S. Pat. No. 5,361,735, a camshaft has a vane secured to an end for non-oscillating rotation. The camshaft also carries a timing belt driven pulley which can rotate with the camshaft but which is oscillatable with respect to the camshaft. The vane has opposed lobes which are received in opposed recesses, respectively, of the pulley. The camshaft tends to change in reaction to torque pulses which it experiences during its normal operation and it is permitted to advance or retard by selectively blocking or permitting the flow of engine oil from the recesses by controlling the position of a spool within a valve body of a control valve in response to a signal from an engine control unit. The spool is urged in a given direction by rotary linear motion translating means which is rotated by an electric motor, preferably of the stepper motor type.
U.S. Pat. No. 5,497,738 shows a control system which eliminates the hydraulic force on one end of a spool resulting from directly applied hydraulic fluid from the engine oil gallery at full hydraulic pressure, Ps, utilized by previous embodiments of the VCT system. The force on the other end of the vented spool results from an electromechanical actuator, preferably of the variable force solenoid type, which acts directly upon the vented spool in response to an electronic signal issued from an engine control unit (“ECU”) which monitors various engine parameters. The ECU receives signals from sensors corresponding to camshaft and crankshaft positions and utilizes this information to calculate a relative phase angle. A closed-loop feedback system which corrects for any phase angle error is preferably employed. The use of a variable force solenoid solves the problem of sluggish dynamic response. Such a device can be designed to be as fast as the mechanical response of the spool valve, and certainly much faster than the conventional (fully hydraulic) differential pressure control system. The faster response allows the use of increased closed-loop gain, making the system less sensitive to component tolerances and operating environment.
U.S. Pat. No. 5,657,725 shows a control system which utilizes engine oil pressure for actuation. The system includes A camshaft has a vane secured to an end thereof for non-oscillating rotation therewith. The camshaft also carries a housing which can rotate with the camshaft but which is oscillatable with the camshaft. The vane has opposed lobes which are received in opposed recesses, respectively, of the housing. The recesses have greater circumferential extent than the lobes to permit the vane and housing to oscillate with respect to one another, and thereby permit the camshaft to change in phase relative to a crankshaft. The camshaft tends to change direction in reaction to engine oil pressure and/or camshaft torque pulses which it experiences during its normal operation, and it is permitted to either advance or retard by selectively blocking or permitting the flow of engine oil through the return lines from the recesses by controlling the position of a spool within a spool valve body in response to a signal indicative of an engine operating condition from an engine control unit. The spool is selectively positioned by controlling hydraulic loads on its opposed end in response to a signal from an engine control unit. The vane can be biased to an extreme position to provide a counteractive force to a unidirectionally acting frictional torque experienced by the camshaft during rotation.
U.S. Pat. No. 6,247,434 shows a multi-position variable camshaft timing system actuated by engine oil. Within the system, a hub is secured to a camshaft for rotation synchronous with the camshaft, and a housing circumscribes the hub and is rotatable with the hub and the camshaft and is further oscillatable with respect to the hub and the camshaft within a predetermined angle of rotation. Driving vanes are radially disposed within the housing and cooperate with an external surface on the hub, while driven vanes are radially disposed in the hub and cooperate with an internal surface of the housing. A locking device, reactive to oil pressure, prevents relative motion between the housing and the hub. A controlling device controls the oscillation of the housing relative to the hub.
U.S. Pat. No. 6,250,265 shows a variable valve timing system with actuator locking for internal combustion engine. The system comprising a variable camshaft timing system comprising a camshaft with a vane secured to the camshaft for rotation with the camshaft but not for oscillation with respect to the camshaft. The vane has a circumferentially extending plurality of lobes projecting radially outwardly therefrom and is surrounded by an annular housing that has a corresponding plurality of recesses each of which receives one of the lobes and has a circumferential extent greater than the circumferential extent of the lobe received therein to permit oscillation of the housing relative to the vane and the camshaft while the housing rotates with the camshaft and the vane. Oscillation of the housing relative to the vane and the camshaft is actuated by pressurized engine oil in each of the recesses on opposed sides of the lobe therein, the oil pressure in such recess being preferably derived in part from a torque pulse in the camshaft as it rotates during its operation. An annular locking plate is positioned coaxially with the camshaft and the annular housing and is moveable relative to the annular housing along a longitudinal central axis of the camshaft between a first position, where the locking plate engages the annular housing to prevent its circumferential movement relative to the vane and a second position where circumferential movement of the annular housing relative to the vane is permitted. The locking plate is biased by a spring toward its first position and is urged away from its first position toward its second position by engine oil pressure, to which it is exposed by a passage leading through the camshaft, when engine oil pressure is sufficiently high to overcome the spring biasing force, which is the only time when it is desired to change the relative positions of the annular housing and the vane. The movement of the locking plate is controlled by an engine electronic control unit either through a closed loop control system or an open loop control system.
U.S. Pat. No. 6,263,846 shows a control valve strategy for vane-type variable camshaft timing system. The strategy involves an internal combustion engine that includes a camshaft and hub secured to the camshaft for rotation therewith, where a housing circumscribes the hub and is rotatable with the hub and the camshaft, and is further oscillatable with respect to the hub and camshaft. Driving vanes are radially inwardly disposed in the housing and cooperate with the hub, while driven vanes are radially outwardly disposed in the hub to cooperate with the housing and also circumferentially alternate with the driving vanes to define, circumferentially alternating advance and retard chambers. A configuration for controlling the oscillation of the housing relative to the hub includes an electronic engine control unit, and an advancing control valve that is responsive to the electronic engine control unit and that regulates engine oil pressure to and from the advance chambers. A retarding control valve responsive to the electronic engine control unit regulates engine oil pressure to and from the retard chambers. An advancing passage communicates engine oil pressure between the advancing control valve and the advance chambers, while a retarding passage communicates engine oil pressure between the retarding control valve and the retard chambers.
U.S. Pat. No. 6,311,655 shows multi-position variable cam timing system having a vane-mounted locking-piston device. An internal combustion engine having a camshaft and variable camshaft timing system, wherein a rotor is secured to the camshaft and is rotatable but non-oscillatable with respect to the camshaft is described. A housing circumscribes the rotor, is rotatable with both the rotor and the camshaft, and is further oscillatable with respect to both the rotor and the camshaft between a fully retarded position and a fully advanced position. A locking configuration prevents relative motion between the rotor and the housing, and is mounted within either the rotor or the housing, and is respectively and releasably engageable with the other of either the rotor and the housing in the fully retarded position, the fully advanced position, and in positions therebetween. The locking device includes a locking piston having keys terminating one end thereof, and serrations mounted opposite the keys on the locking piston for interlocking the rotor to the housing. A controlling configuration controls oscillation of the rotor relative to the housing.
U.S. Pat. No. 6,374,787 shows a multi-position variable camshaft timing system actuated by engine oil pressure. A hub is secured to a camshaft for rotation synchronous with the camshaft, and a housing circumscribes the hub and is rotatable with the hub and the camshaft and is further oscillatable with respect to the hub and the camshaft within a predetermined angle of rotation. Driving vanes are radially disposed within the housing and cooperate with an external surface on the hub, while driven vanes are radially disposed in the hub and cooperate with an internal surface of the housing. A locking device, reactive to oil pressure, prevents relative motion between the housing and the hub. A controlling device controls the oscillation of the housing relative to the hub.
U.S. Pat. No. 6,477,999 shows a camshaft that has a vane secured to an end thereof for non-oscillating rotation therewith. The camshaft also carries a sprocket that can rotate with the camshaft but is oscillatable with respect to the camshaft. The vane has opposed lobes that are received in opposed recesses, respectively, of the sprocket. The recesses have greater circumferential extent than the lobes to permit the vane and sprocket to oscillate with respect to one another. The camshaft phase tends to change in reaction to pulses that it experiences during its normal operation, and it is permitted to change only in a given direction, either to advance or retard, by selectively blocking or permitting the flow of pressurized hydraulic fluid, preferably engine oil, from the recesses by controlling the position of a spool within a valve body of a control valve. The sprocket has a passage extending therethrough the passage extending parallel to and being spaced from a longitudinal axis of rotation of the camshaft. A pin is slidable within the passage and is resiliently urged by a spring to a position where a free end of the pin projects beyond the passage. The vane carries a plate with a pocket, which is aligned with the passage in a predetermined sprocket to camshaft orientation. The pocket receives hydraulic fluid, and when the fluid pressure is at its normal operating level, there will be sufficient pressure within the pocket to keep the free end of the pin from entering the pocket. At low levels of hydraulic pressure, however, the free end of the pin will enter the pocket and latch the camshaft and the sprocket together in a predetermined orientation.
In some VCT systems, a phaser having a rotor needs to be rigidly affixed to a cam shaft and angularly adjustable in relation to other parts of the phaser.
Referring to
Japanese Patent publication number 04209912 (A), entitled: VALVE SYSTEM OF ENGINE teaches an improved apparatus having a simplified structure with improved supporting rigidity by holding the hub of a variable valve timing mechanism on a cam shaft end part by a means of a cylindrical shaft member to fasten the hub by means of a fastening member, and bearing-supporting the shaft member on a cylinder head.
The use of a hub on a variable valve timing mechanism to fasten the same onto a cam shaft is known. Japanese Patent 04209912 (A) teaches a simplified structure having improved supporting rigidity by holding the hub of a variable valve timing mechanism on a cam shaft end part by a means of a cylindrical shaft member to fasten the hub by means of a fastening member, and bearing-supporting the shaft member on a cylinder head. The structure of the device is as follows. In a V typed engine 1 provided with a DOHC valve system, gears 7, 8 provided between cams are arranged on respective one end parts of an intake side cam shaft 2 and an exhaust side cam shaft 3 so as to engage each other as a driving wheel provided between the cams. A variable valve timing mechanism 20 is arranged inside the boss part 7a of the gear 7 provided between the cams of the intake side. A cylindrical shaft member 17a for holding the hub 21 of the variable valve timing mechanism 20 is provided on the center part of the gear 7 provided between the cams of the intake side, and the shaft member 17 is installed by a jointing member 18 jointed on the cam shaft 2. The journal part 17a of the shaft member 17 is bearing-supported on a front end bearing part 5a mounted in the forward of the gear chamber 9 of a cylinder head 4. However, this seems not like your invention in that a fastening member is still required.
The use of brazing in forming a cam shaft is known. Japanese Patent 60021195 (A) teaches a device that has a joined cam shaft consisting of joint members and a shaft member joined to the strength equivalent to the strength of the base metal by subjecting the shaft part of the cam shaft consisting of a steel material and fitting members such as cam members, journal members, etc. formed of a cast iron to join by copper brazing in a furnace. The device includes a shaft part 2 consisting of a hollow or solid steel material and separately manufactured fitting members made of a cast iron such as cam members 4, journal members 5, etc. are disposed in prescribed positions and are joined under the following conditions: The shaft part 2 and the above-described fitting members are joined by brazing in a furnace for ≧15 min in a temp. range of 1,090W1,150° C. non-oxidizing atmosphere. It is necessary in this case to maintain the hardness of the cast iron fitting members within a 130W320Hv range. The joint strength between the fitting members and the shaft member is thus made equivalent to or higher than the strength of the base metal. However, no rotor of a VCT phaser is involved herein.
The forming of cam lobes by means of swaging is known. European patent EP0313985B1 teaches a method of making a camshaft from a blank (9) having a cam shape, the configuration of the camshaft with the cams (16) and the bearings (13) being moulded into the blank (9) by swaging and circular kneading by means of tool segments which at least partially surround the blank (9) and exert radial compressive forces thereon and thus alter the shape and the cross section of the blank (9), characterised in that, in a first step, the cam-shaped blank (9) is given an at least approximately circular shape by preforming by means of forging or hammering in the region of the bearings (13) of the camshaft, and that subsequently, in a second step, the configuration of the camshaft with the cams (16) and the bearings (13) is moulded by swaging and circular kneading by means of tool elements which at least partially surround the blank and exert radial compressive forces thereon and thus alter its shape and cross section both in the region of the bearings (13) and in the remaining regions of the camshaft. However, no rotor of a VCT phaser is involved herein.
However, in virtually all VCT technology applications, the VCT units such as a phaser need to be downsized in order to reduce packaging requirements. Form factor that limits the axial and radial package of a VCT needs to be suitably reduced. Further, the use of a more permanent means of affixing the rotor of a phaser to the camshaft will allow for reduction in the radial packaging requirements.
In a VCT device, permanent means of affixing part of the VCT device onto a shaft is provided.
In a VCT device, a set of non-reversible means of affixing part of the VCT device onto a shaft is provided.
In VCT systems, the rotor of a phaser is permanently, non-reversibly affixed onto a cam shaft.
A VCT device having reduced form factors are provided. The reduced form factors include axial reduction and radial reduction.
A VCT device free from area on its frontal face for receiving connecting members such as bolt or screws is provided.
Accordingly, in a VCT system having a phaser coupled to a shaft, which can be a driving or driven shaft, an apparatus is provided. The apparatus includes: the phaser having a rotor irreversibly connected to one end of the shaft free of any region (18) having openings for accommodating independent fastening members, thereby the axial and radial dimension of the apparatus is reduced.
Accordingly, in a VCT system having a phaser coupled to a shaft, which can be a driving or driven shaft, an apparatus is provided. The apparatus includes: a means for irreversibly connecting a rotor of the phaser to one end of the shaft free of any region (18) having openings for accommodating independent fastening members, thereby the axial and radial dimension of the apparatus is reduced.
Accordingly, a method for coupling part of a VCT device to a shaft is provided. The method includes the steps of: providing a phaser having a rotor rotating in relation to an opposite part of the phaser, wherein the phaser is axially reduced by eliminating at least one part of the phaser; and irreversibly connecting the rotor to the shaft
It is desirable to suitably shorten the axial length of a VCT device such as a phaser by eliminating mounting flange 8 onto a shaft such as the cam shaft 9. As can be seen, by eliminating flange 8, the axial length of the VCT device is shortened in that some axial dimensional contribution in length of flange 8 is reduced. Flange 8 has openings or wholes for accommodating or receiving connecting members such as screws 14 for connecting portions of the phaser such as the rotor 1 onto cam shaft 9. New means for connecting portions of the phaser such as the rotor 1 onto cam shaft 9 is disclosed infra. Further, it is desirable to suitably reduce dimensionally the radial size of the VCT device by eliminating fasteners such as screws 14. Thereby region 18 can be eliminated. By eliminating region 18, the radial dimension of the VCT device can be reduced.
Referring to
Referring to
Vanes 16 are provided that may have similar or different size as that of
Referring to
Referring to
By way of an example, the present invention teaches method and apparatus to apply VCT technology to desired applications such as connecting parts of a phaser on a first end of a cam shaft. The relevant size of units such as rotor 1a size must be downsized in order to reduce packaging requirements. One factor that limits the axial and radial package of prior art product is the bolt circle diameter that affixes the phaser rotor to the end of the camshaft. In other words, region 18 of
The rotor and bearing surface could be affixed onto the end of the cam shaft in a number of ways. The means of affixing the rotor to the end of the camshaft would include but not be limited to the following 5 scenarios.
1 Pressing the Rotor onto a Straight Hub
By pressing the rotor onto a straight hub at one end of cam shaft, rotor such as rotor 1a or rotor 1b may be permanently affixed onto cam shaft 9. As can be seen, no extra connecting members such as screw 14 or flange 8 is needed herein. By way of an example, cam shaft 9 may have one end 30 disposed to be fitted into opening 19 of rotor 1a as shown in
Hub is referred to as a cylindrical projection on the end of the camshaft onto which the inner diameter of the phaser is pressed. As shown in
2. Pressing the Rotor onto a Hub Using a Straight Spline on One Component and a Helical Spline on the Second Component
This second means of irreversible connection is similar to the first means in that the rotor is pressed upon a hub of a cam shaft. The difference is that one component such as the rotor may have an opening 19, wherein an inside surface of opening 19 of the rotor 1a may be lined with straight spline. Whereas another component such as the cam shaft 9 may have one end 30a may have a non-straight spline such as a helical spline. By way of an example, as shown in
3. Brazing the Rotor onto the Camshaft
Brazing the rotor onto the camshaft is another means to irreversibly affix the rotor such as rotor 1a onto a cam shaft 9. Any known means of brazing is contemplated by the present invention.
4. Swaging the Rotor onto the Camshaft
Rotor can also be swaging onto the cam shaft. For example, referring to
As can be appreciated, swaging is a process that is used to reduce or increase the diameter of tubes or rods such as a cam shaft. Swaging may be done by placing cam shaft 9 inside a die that applies compressive force by hammering radially. In addition, swaging can be achieved by placing a mandrel inside the internal opening 19a and applying radial compressive forces on the outer diameter. As can be appreciated, the inner diameter can be a different shape, for example the internal opening 19a may be a hexagon, and the resultant outer diameter after swaging can still be substantially circular.
To apply swaging, the existence of internal opening 19a is helpful, but not necessary. The net result is to permanently or irreversibly affix the rotor and the cam shaft.
5. Ballizing the Rotor onto the Camshaft where the Camshaft is a Hollow Component
If the cam shaft is formed such that opening 19a transcend or is formed throughout the cam shaft structure, ballizing may be a means of permanently or irreversibly affixing rotor 1a onto cam shaft 9. Initially, shaft 9 is place within rotor 1a such that a first end 30c of cam shaft 9 is within opening 19 of the rotor 1a. A ball 32 made of materials such as a tungsten carbide speeds through opening 19a of cam shaft 9 at a desired speed along a direct such as direction 34. Noted that the direction of travel for ball 32 may be the reverse of direction 34, in other words, the direction of travel may be 180 degrees of direction 34. Therefore, by balling the rotor onto the camshaft where the camshaft is a hollow component, the net result is achieved in that the rotor and the cam shaft is permanently or irreversibly affixed together.
Alternatively, the rotor and bearing surface may also be machined as part of the camshaft itself.
It is noted that in the preferred embodiment, the rotor is connected to a cam shaft. However, the present invention contemplates the coupling or connecting of the rotor of a phaser onto any driving or driven shaft. For example, the rotor may be coupled to a crank shaft, or to any cam shaft whether the cam shaft is a driving or driven shaft.
The following are terms and concepts relating to the present invention.
It is noted the hydraulic fluid or fluid referred to supra are actuating fluids. Actuating fluid is the fluid which moves the vanes in a vane phaser. Typically the actuating fluid includes engine oil, but could be separate hydraulic fluid. The VCT system of the present invention may be a Cam Torque Actuated (CTA)VCT system in which a VCT system that uses torque reversals in camshaft caused by the forces of opening and closing engine valves to move the vane. The control valve in a CTA system allows fluid flow from advance chamber to retard chamber, allowing vane to move, or stops flow, locking vane in position. The CTA phaser may also have oil input to make up for losses due to leakage, but does not use engine oil pressure to move phaser. Vane is a radial element actuating fluid acts upon, housed in chamber. A vane phaser is a phaser which is actuated by vanes moving in chambers.
There may be one or more camshaft per engine. The camshaft may be driven by a belt or chain or gears or another camshaft. Lobes may exist on camshaft to push on valves. In a multiple camshaft engine, most often has one shaft for exhaust valves, one shaft for intake valves. A “V” type engine usually has two camshafts (one for each bank) or four (intake and exhaust for each bank).
Chamber is defined as a space within which vane rotates. Chamber may be divided into advance chamber (makes valves open sooner relative to crankshaft) and retard chamber (makes valves open later relative to crankshaft). Check valve is defined as a valve which permits fluid flow in only one direction. A closed loop is defined as a control system which changes one characteristic in response to another, then checks to see if the change was made correctly and adjusts the action to achieve the desired result (e.g. moves a valve to change phaser position in response to a command from the ECU, then checks the actual phaser position and moves valve again to correct position). Control valve is a valve which controls flow of fluid to phaser. The control valve may exist within the phaser in CTA system. Control valve may be actuated by oil pressure or solenoid. Crankshaft takes power from pistons and drives transmission and camshaft. Spool valve is defined as the control valve of spool type. Typically the spool rides in bore, connects one passage to another. Most often the spool is located on center axis of rotor of a phaser.
Differential Pressure Control System (DPCS) is a system for moving a spool valve, which uses actuating fluid pressure on each end of the spool. One end of the spool is larger than the other, and fluid on that end is controlled (usually by a Pulse Width Modulated (PWM) valve on the oil pressure), full supply pressure is supplied to the other end of the spool (hence differential pressure). Valve Control Unit (VCU) is a control circuitry for controlling the VCT system. Typically the VCU acts in response to commands from ECU.
Driven shaft is any shaft which receives power (in VCT, most often camshaft). Driving shaft is any shaft which supplies power (in VCT, most often crankshaft, but could drive one camshaft from another camshaft). ECU is Engine Control Unit that is the car's computer. Engine Oil is the oil used to lubricate engine, pressure can be tapped to actuate phaser through control valve.
Housing is defined as the outer part of phaser with chambers. The outside of housing can be pulley (for timing belt), sprocket (for timing chain) or gear (for timing gear). Hydraulic fluid is any special kind of oil used in hydraulic cylinders, similar to brake fluid or power steering fluid. Hydraulic fluid is not necessarily the same as engine oil. Typically the present invention uses “actuating fluid”. Lock pin is disposed to lock a phaser in position. Usually lock pin is used when oil pressure is too low to hold phaser, as during engine start or shutdown.
Oil Pressure Actuated (OPA) VCT system uses a conventional phaser, where engine oil pressure is applied to one side of the vane or the other to move the vane.
Open loop is used in a control system which changes one characteristic in response to another (say, moves a valve in response to a command from the ECU) without feedback to confirm the action.
Phase is defined as the relative angular position of camshaft and crankshaft (or camshaft and another camshaft, if phaser is driven by another cam). A phaser is defined as the entire part which mounts to cam. The phaser is typically made up of rotor and housing and possibly spool valve and check valves. A piston phaser is a phaser actuated by pistons in cylinders of an internal combustion engine. Rotor is the inner part of the phaser, which is attached to a cam shaft.
Pulse-width Modulation (PWM) provides a varying force or pressure by changing the timing of on/off pulses of current or fluid pressure. Solenoid is an electrical actuator which uses electrical current flowing in coil to move a mechanical arm. Variable force solenoid (VFS) is a solenoid whose actuating force can be varied, usually by PWM of supply current. VFS is opposed to an on/off (all or nothing) solenoid.
Sprocket is a member used with chains such as engine timing chains. Timing is defined as the relationship between the time a piston reaches a defined position (usually top dead center (TDC)) and the time something else happens. For example, in VCT or VVT systems, timing usually relates to when a valve opens or closes. Ignition timing relates to when the spark plug fires.
Torsion Assist (TA) or Torque Assisted phaser is a variation on the OPA phaser, which adds a check valve in the oil supply line (i.e. a single check valve embodiment) or a check valve in the supply line to each chamber (i.e. two check valve embodiment). The check valve blocks oil pressure pulses due to torque reversals from propagating back into the oil system, and stop the vane from moving backward due to torque reversals. In the TA system, motion of the vane due to forward torque effects is permitted; hence the expression “torsion assist” is used. Graph of vane movement is step function.
VCT system includes a phaser, control valve(s), control valve actuator(s) and control circuitry. Variable Cam Timing (VCT) is a process, not a thing, that refers to controlling and/or varying the angular relationship (phase) between one or more camshafts, which drive the engine's intake and/or exhaust valves. The angular relationship also includes phase relationship between cam and the crankshafts, in which the crank shaft is connected to the pistons.
Variable Valve Timing (VVT) is any process which changes the valve timing. VVT could be associated with VCT, or could be achieved by varying the shape of the cam or the relationship of cam lobes to cam or valve actuators to cam or valves, or by individually controlling the valves themselves using electrical or hydraulic actuators. In other words, all VCT is VVT, but not all VVT is VCT.
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments are not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
