Electronic lock for VCT phaser

Abstract

A lock mechanism for a phaser of a variable cam timing system is actuated by an electromagnetic force. Since the lock mechanism is not dependent upon engine oil pressure, it is actuatable at any time from engine startup to engine shutdown. A lock solenoid is preferably used to actuate a lock pin, which is otherwise urged toward a lock hole and a locked position by a spring force, to an unlocked position. The lock solenoid preferably acts on a pin lock plate that is coupled to the lock pin. A preferred startup method and a preferred shutdown method are also described.

1 . A variable cam timing phaser for an internal combustion engine comprising: 
 a housing with an outer circumference for accepting drive force;    a rotor for connection to a camshaft coaxially located within the housing, the housing and the rotor defining at least one vane separating a chamber into an advance chamber and a retard chamber, the rotor being capable of rotation within the housing to shift the relative angular position of the housing and the rotor; and    a lock mechanism comprising: 
 a lock solenoid;  
 a lock plate in proximity to the lock solenoid such that the lock plate moves between a first position when the lock solenoid is in an energized state and a second position when the lock solenoid is in a de-energized state;  
 a lock plate spring biasing the lock plate toward the second position; and  
 a lock pin coupled to the lock plate for movement therewith;  
 wherein when the lock plate is in the first position, the lock pin is in an unlocked state such that the lock pin does not prevent rotation of the rotor within the housing; and  
 wherein when the lock plate is in the second position, the lock pin is in a locked state such that the lock pin extends into a lock hole, thereby preventing rotation of the rotor within the housing.  
   
   
   
       2 . The variable cam timing phaser of  claim 1 , wherein the lock pin is located within the housing in the unlocked state and the lock hole is located in the rotor.  
   
   
       3 . The variable cam timing phaser of  claim 2 , wherein the lock pin is located such that the vane is in a mid position when the phaser is in the locked state.  
   
   
       4 . The variable cam timing phaser of  claim 2 , wherein the lock pin is located such that the vane is in an end position when the phaser is in the locked state.  
   
   
       5 . The variable cam timing phaser of  claim 1 , wherein the lock pin is located within the rotor in the unlocked state and the lock hole is located in the housing on a side opposite to the lock solenoid.  
   
   
       6 . The variable cam timing phaser of  claim 5 , wherein the lock pin is urged toward the lock plate by a lock pin spring opposing the lock plate spring.  
   
   
       7 . The variable cam timing phaser of  claim 5 , wherein the lock hole is located such that the vane is in a mid position when the phaser is in the locked state.  
   
   
       8 . The variable cam timing phaser of  claim 5 , wherein the lock hole is located such that the vane is in an end position when the phaser is in the locked state.  
   
   
       9 . The variable cam timing phaser of  claim 1  further comprising: 
 a variable force solenoid, wherein the lock solenoid is mounted with and around the variable force solenoid; and    a spool valve actuated by the variable force solenoid to regulate a position  5  of the phaser.    
   
   
       10 . The variable cam timing phaser of  claim 1  further comprising: 
 a linear actuator selected from the group consisting of: 
 a) a stepper motor;  
 b) a vacuum actuator;  
 c) a differential pressure controller; and  
 d) a regulated pressure controller; and  
   a spool valve actuated by the linear actuator to regulate a position of the phaser.    
   
   
       11 . The variable cam timing phaser of  claim 1 , wherein the lock pin and the lock plate are coupled to move together.  
   
   
       12 . A method of controlling a variable cam timing phaser having a housing with an outer circumference for accepting drive force, a rotor for connection to a camshaft coaxially located within the housing, a lock solenoid, a lock plate in proximity to the lock solenoid, a lock plate spring biasing the lock plate toward the second position, and a lock pin coupled to the lock plate for movement therewith, during startup of an internal combustion engine comprising the step of: 
 a) energizing the lock solenoid to move the lock plate coupled to the lock pin to a position wherein the lock pin is removed from a lock hole such that the lock pin does not prevent rotation of the rotor within the housing.    
   
   
       13 . The method of  claim 12  further comprising the steps of: 
 b) determining if conditions have been met to move the phaser; and    c) if conditions have been met, energizing a variable force solenoid to move a spool in a spool valve, thereby moving the phaser.    
   
   
       14 . A method of controlling a variable cam timing phaser having a housing with an outer circumference for accepting drive force, a rotor for connection to a camshaft coaxially located within the housing, a lock solenoid, a lock plate in proximity to the lock solenoid, a lock plate spring biasing the lock plate toward the second position, and a lock pin coupled to the lock plate for movement therewith, during shutdown of an internal combustion engine comprising the step of: 
 a) de-energizing the lock solenoid to release the lock plate coupled to the lock pin, thereby allowing the lock pin to extend into a lock hole to prevent rotation of a rotor within a housing.    
   
   
       15 . The method of  claim 14  further comprising the step of: 
 b) moving the phaser to a locked position when the engine is at idle such that the lock pin is aligned with the lock hole.    
   
   
       16 . The method of claim.  14  further comprising the steps of: 
 b) determining the position of the phaser when the engine is turned off; and    c) moving the phaser to a locked position as the engine is slowing down such that the lock pin is aligned with the lock hole.