This application claims one or more inventions which were disclosed in Provisional Application No. 62/855,239, filed May 31, 2019, entitled “UNLOCKING MECHANISM FOR A VARIABLE CAMSHAFT PHASER”. The benefit under 35 U.S.C. § 119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference.
The invention pertains to the field of variable cam timing. More particularly, the invention pertains to an unlock mechanism for a variable camshaft timing phaser.
Internal combustion engines have employed various mechanisms to vary the relative timing between the camshaft and the crankshaft for improved engine performance or reduced emissions. The majority of these variable camshaft timing (VCT) mechanisms use one or more “vane phasers” on the engine camshaft (or camshafts, in a multiple-camshaft engine). Vane phasers have a rotor assembly with one or more vanes, mounted to the end of the camshaft, surrounded by a housing assembly with the vane chambers into which the vanes fit. It is possible to have the vanes mounted to the housing assembly, and the chambers in the rotor assembly, as well. The housing's outer circumference forms the sprocket, pulley or gear accepting drive force through a chain, belt, or gears, usually from the crankshaft, or possible from another camshaft in a multiple-cam engine.
Apart from the camshaft torque actuated (CTA) variable camshaft timing (VCT) systems, the majority of hydraulic VCT systems operate under two principles, oil pressure actuation (OPA) or torsional assist (TA). In the oil pressure actuated VCT systems, an oil control valve (OCV) directs engine oil pressure to one working chamber in the vane phaser while simultaneously venting the opposing working chamber defined by the housing assembly, the rotor assembly, and the one or more vanes. This creates a pressure differential across one or more of the vanes to hydraulically push the vane phaser in one direction or the other. Neutralizing or moving the oil control valve to a null position puts equal pressure on opposite sides of the one or more vanes and holds the vane phaser in any intermediate position. If the vane phaser is moving in a direction such that valves of the engine will open or close sooner, the vane phaser is said to be advancing and if the vane phaser is moving in a direction such that valves will open or close later, the vane phaser is said to be retarding.
The torsional assist (TA) systems operates under a similar principle with the exception that it has one or more check valves to prevent the vane phaser from moving in a direction opposite than being commanded, should it incur an opposing force such as torque.
The problem with OPA or TA systems is that the oil control valve defaults to a position that exhausts all the oil from either the advance or retard working chambers and fills the opposing chamber. In this mode, the vane phaser defaults to moving in one direction to an extreme stop where a lock pin engages, locking the movement of the rotor assembly relative to the housing assembly. The OPA or TA systems are unable to direct the vane phaser to any other position during the engine start cycle when the engine is not developing any oil pressure. This limits the vane phaser to being able to move in one direction only in the engine shut down. In the past this was acceptable because at engine shut down and during engine start the vane phaser would be commanded to lock at one of the extreme travel limits (either full advance or full retard).
Most engines with an intake phaser place the phaser in the retard position in engine shutdown using a lock pin or a series of lock pins, in preparation for the next start of a “stop-start mode” which automatically stops and automatically restarts the internal combustion engine to reduce the amount of time the engine spends idling when the vehicle is stopped, for example at a stop light or in traffic. This stopping of the engine is different than a “key-off” position or manual stop via deactivation of the ignition switch in which the user of the vehicle shuts the engine down or puts the car in park and shuts the vehicle off. In “stop-start mode”, the engine stops as the vehicle is stopped, then automatically restarts in a manner that is nearly undetectable to the user of the vehicle. In the past, vehicles have been designed primarily with cold starts in mind, since that is the most common situation. In a stop-start system, because the engine had been running until the automatic shutdown, the automatic restart occurs when the engine is in a hot state. It has long been known that “hot starts” are sometimes a problem because the engine settings necessary for the usual cold start—for example, a particular valve timing position—are inappropriate to a warm engine.
Unlocking the lock pin is dependent upon engine oil pressure available at start up.
A vane phaser with an unlocking and relocking mechanism coupled to the lock pin, which through the use of at least one solenoid can lock and unlock the vane phaser. The at least one solenoid associated with the lock pin is distinct from the solenoid used for the phaser control valve. When the at least one solenoid is energized and during rotation of the camshaft, the at least one solenoid pin makes contact with a lever attached to the lock pin, causing the lock pin to rotate. A helical feature on the lock pin itself or on the lever causes the lock pin to move axially, unlocking the phaser.
Since the mechanism is mechanical and is not dependent upon oil engine pressure, the vane phaser can be unlocked at any time the camshaft is rotating. The advantage of being independent of engine oil pressure is that the vane phaser can be unlocked prior to oil pressure build up, which can be an issue in vane phasers. Furthermore, by unlocking the vane phaser to allow early phasing, engine emissions and engine vibration can be reduced during engine startup.
A lock pin assembly received within a rotor assembly or housing assembly of a vane phaser. The lock pin comprising: a body having a first closed head end, a second end and a recessed portion between the first closed head end and the second end, a shaft having a first end and a second end, the first end attached to the second surface of the second end of the body and a second end connected to a gear having at least one tooth; a spring surrounding the shaft and adjacent the second surface of the second end of the body for biasing the first closed head end towards the recess of the housing assembly; and a pin having a first end spring biased towards the at least two axially extending grooves in the recessed portion, the pin being perpendicular to the body of the lock pin. The first closed head end having a first surface for mating with the recess of the housing assembly, and a second surface adjacent the recessed portion; the second end of the body has a first surface adjacent the recessed portion and a second surface, the first surface of the second end of the body comprising at least two repeats of a sequence of a first radiused edge, a flat, and a second radiused edge. The recessed portion is defined between the second surface of the first closed and the first surface of the second end of the body and has at least a first axially extending groove and a second axially extending groove, the first and second axially extending grooves each aligned with the flats of the first surface of the second end of the body.
In an embodiment of the present invention, rotation of the camshaft and a linear solenoid is used to mechanically lock and unlock a lock pin by changing rotational energy to linear energy, therefore circumventing hydraulic issues at startup of the engine and addressing immediate phasing needs of a vane phaser at startup without relying on hydraulic fluid to unlock the lock pin.
Referring to
The rotor assembly 105 is connected to the camshaft (not shown) and is coaxially located within the housing assembly 100. The rotor assembly 105 has a vane 104 separating a chamber 171 formed between the housing assembly 100 and the rotor assembly 105 into an advance chamber and a retard chamber. The vane 104 is capable of rotation to shift the relative angular position of the housing assembly 100 and the rotor assembly 105.
An oil control valve 170 can be located remotely from the phaser, within a bore 172 in the rotor assembly 105 which pilots in the camshaft, or in a center bolt of the phaser and controls the movement of the vane 104 to control the timing of the engine.
Within at least one vane 104 of the rotor assembly 105 is a lock pin 125. The lock pin 125 is slidably housed in a bore 108 of at least one vane 104 of the rotor assembly 105. The lock pin 125 is moveable from a first locked position in which the lock pin 125 engages a recess 127 in a first end plate 100a of the housing assembly 100, preventing movement of the rotor assembly 105 relative to the housing assembly 100 and an unlocked position in which the lock pin 125 does not engage the recess 127 in the first end plate 100a of the housing assembly 100 and the rotor assembly 105 can rotate relative to the housing assembly 100.
The lock pin 125 has a body 126 with a first closed head end 126a, a second end 126b and a recessed portion 126c between the first closed head end 126a and the second end 126b. The first closed head end 126a has a first surface 128a which can mate with the recess 127 and a second surface 128b which is adjacent the recessed portion 126c. The second end 126b of the body 126 of the lock pin 125 has a first surface 129a adjacent the recessed portion 126c and a second surface 129b which receives a shaft 130. The first surface 129a of the second end 126b has a first radiused edge 131 and a second radiused edge 132 with flats 137a-137n. Travel distance of the lock pin 125 is defined between a first set of flats 137a to the second set of flats 137b with the first and second radiused edges 131, 132 between the first and second set of flats 137a-137b. The recessed portion 126c is therefore defined between the second surface 128b of the closed head end 126a and the first surface 129a of the second end 126b. The recessed portion 126c additionally contains two or more detent grooves 133a-133n which run axially relative to a centerline C-C as shown in
A pin 140 having a first end 141 is spring 143 biased into contact with at least one of the detent grooves 133a-133n of the recessed portion 126c so that the pin 140 is perpendicular to the centerline C-C. The pin 140 is received within a recess 173 in the vane 104 and is perpendicular to the lock pin body 126. A plug 142 maintains the spring biased pin 140 in the recess 173. The force of spring 143 is tuned such that the pin 140 can be moved between the detent grooves 133a-133n and control overshoot of the lock pin rotation about the centerline C-C. The placement of the detent grooves 133a-133n additionally ensures that the lock pin 125 does not rotate once it is moved to the new position (locked or unlocked).
The shaft 130 has a first end 130a connected to the second surface 129b of the second end 126b of the lock pin body 126 and a second end 130b connected to a gear 136. The shaft 130 is received by and protrudes from a slot 147 of the second end plate 100b.
The gear or lever 136 has a plurality of radially extending teeth 136a-136n. The teeth 136a-136n are spaced apart relative to each other to allow a solenoid pin 150 to seat between the teeth 136a-136n. The number of teeth 136a-13n of the gear 136 corresponds to the number of detent grooves 133a-133n. A detent groove 133a-133n is present for each position and the number of positions is dictated by the number of teeth 136a-136n on the gear 136. The solenoid pin 150 position is stationary relative to the rotation of the phaser in the clockwise direction indicated by the arrow in
Adjacent the second surface 129b of the second end 126b of the lock pin body 126 is a lock pin spring 145 for biasing the first closed head end 126a of the lock pin 125 towards the recess 127 in the first end plate 100a of the housing assembly 100 as shown in
In an alternate embodiment, a ramp could be used to return the solenoid pin 150 to the retracted position if a latching solenoid were used. The ramp ensures that the solenoid pin 150 is retracted within a single phaser rotation. If ramp is not present, the lock pin 125 is rotated again and returned to the previous lock/unlock position.
Referring to
The housing assembly 100 of the phaser rotates in a clockwise direction as shown by the arrow as it is driven by the chain or belt. It should be noted that in the Figures, all elements except for the solenoid pin 150 of the solenoid 175 rotate with the phaser.
During the full rotation of the phaser 360°, the solenoid pin 150 of the linear solenoid 175 interfaces with gear tooth 136a of the gear 136, causing the gear 136 to turn counterclockwise. It should be noted that the solenoid pin 150 interacts with the gear 136 only once during 360° or full rotation of the phaser.
Referring to
It should be noted that while the detent grooves 133a-133n are described as being 90° apart within the recessed portion 126c of the lock pin body 126, the spacing between the detent grooves 133a-133n can be altered.
The spring biased pin 140 is seated in a detent groove 133a-133n of the recessed portion 126c of the lock pin body 126 of the lock pin 125. The pin 140 is adjacent the second surface 128b of the closed head end 126a of the lock pin body 126 of the lock pin 125 and not the first surface 129a of the second end 126b of the lock pin body 126.
Referring to
Therefore, in a locked position of the lock pin 125, spring bias pin 140 is in detent groove 133a and interfaces with flat 137a of the first surface 129a. In an unlocked position of the lock pin 125, spring bias pin 140 is in detent groove 133n and interfaces with flat 137n of the first surface 129a.
Between the locked and unlocked positions of the lock pin 125, spring bias pin 140 moves between detent grooves 133n and 133a along the first surface 129a.
Upon the next commanded lock pin change, the following detent grooves 133b, 133c would be used and 133a, 133b, 133c, 133n are used sequentially as locked or unlocked commands are received and the lock pin 125 will continue to rotate such that the detent grooves 133n and 133a are used for the next commanded lock pin change.
Within at least one vane 104 of the rotor assembly 105 is a lock pin 225. The lock pin 225 is slidably housed in a bore 108 of the vane 104 of the rotor assembly 105. The lock pin 225 is moveable from a first locked position in which the lock pin 225 engages a recess 127 in a first end plate 100a of the housing assembly, preventing movement of the rotor assembly 105 relative to the housing assembly 100 and an unlocked position in which the lock pin 225 does not engage the recess 127 in the first end plate 100a of the housing assembly 100, and the rotor assembly 105 can rotate relative to the housing assembly 100.
The lock pin 225 has a body 226 with a first closed head end 226a, a second end 226b and a recessed portion 226c between the first closed head end 226a and the second end 226b. The first closed head end 226a has a first surface 228a which can mate with the recess 127 and a second surface 228b which is adjacent the recessed portion 226c. The second end 226b of the body 226 of the lock pin 225 has a first surface 229a adjacent the recessed portion 226c and a second surface 229b which receives a shaft 230.
The first surface 229a of the second end 226b has at least two sequences of a first radiused edge 231, a second radiused edge 232 and a flat 237 that define travel distance of the lock pin 225. The recessed portion 226c is therefore defined between the second surface 228b of the closed head end 226a and the first surface 229a of the second end 226b. The recessed portion 226c additionally contains two detent grooves 233a, 233b which run axially relative to a centerline C-C as shown in
A pin 140 having a first end 141 and a spring 143 are received within a bore 173 of the vane 104 of the rotor assembly 105. The pin 140 is spring biased into contact with the recessed portion 226c of the lock pin 225 so that the pin 140 is perpendicular to the centerline C-C. A plug 142 maintains the spring biased pin 140 in the recess 173. The force of spring 143 is tuned such that the pin 140 can be moved between the detent grooves 233a, 233b and control overshoot of the lock pin 225 rotation about the centerline C-C. The placement of the detent grooves 233a-233b additionally ensures that the lock pin 225 does not rotate once it is moved to the new position (locked or unlocked). Adjacent the second surface 229b of the second end 226b of the lock pin body 226 is a lock pin spring 245 for biasing the first closed head end 228a of the lock pin 225 towards the recess 127 in the first end plate 100a of the housing assembly 100.
A shaft 230 has a first end 230a connected to the second surface 229b of the second end 226b of the lock pin body 226 and a second end 230b connected to a gear 236. The shaft 230 is received by and protrudes from a slot 147 of the second end plate 100b.
The gear or lever 236 has at least two radially extending teeth 236a, 236b. The teeth 236a, 236b are spaced apart relative to each other to allow first and second solenoid pins 150, 152 to interact with the teeth 236a, 236b. The position of the first and second solenoid pins 150, 152 is stationary relative to the rotation of the vane phaser in the clockwise direction indicated by the arrow in
The spacing of the first and second solenoid pins 150, 152 relative to each other can be set based on the application and is irrelevant as long as both solenoid pins 150, 152 do not interact with both teeth 236a, 236b of the gear 236 at the same time.
In an alternate embodiment, a ramp could be used to return at least one of the solenoid pins 150, 152 to the retracted position if a latching solenoid were used. The ramp ensures that at least one of the solenoid pins 150, 152 is retracted from interaction with the gear teeth 236a, 236b of the gear 236 in preparation for the second solenoid pin 152 to be extended. If the ramp is not present and the first solenoid pin 150 is still extended when the second solenoid pin 152 extends, the lock pin 225 is rotated again and returned to the previous lock/unlock position.
Referring to
Referring to
If the lock pin is rotated to the locked position before the rotor assembly 105 has moved to align the lock pin 225 with the recess 127 and no axial motion of the lock pin 225 is possible, the rotation of the lock pin body 226 causes the spring biased pin 140 to travel from the second detent groove 233b along the flat face 275 of the second surface 228b of the first end 226a of the body until the spring biased pin 140 seats in the first detent groove 233a, limiting the rotation of the lock pin 225.
It should be noted that while the first and second detent grooves 233a, 233b are described as being 90° apart within the recessed portion 226c of the lock pin body 226, the spacing between the detent grooves 233a, 233b can be altered.
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 is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
Number | Date | Country | |
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62855239 | May 2019 | US |