Piezoelectric valve actuation

Abstract

A piezoelectric valve actuation system for an internal combustion engine includes a piezoelectric driver in the form of a pre-stressed wafer or strip including a layer of piezoceramic material such as lead zirconate titanate (PZT). The driver has a central portion which includes an aperture for direct engagement with a valve stem so that the valve is moved between open and closed positions directly by the piezoelectric driver. The piezoelectric driver can have end portions which attach to the engine cylinder head proximate the valve location. The piezoelectric actuator is driven by an electronic control module (ECM) providing electrical signals to control valve operation based various engine parameters along with user input.

What is claimed is:  
     
         1 . A piezoelectric actuated valve mechanism for an internal combustion engine having at least one valve with a valve stem, the valve mechanism comprising: 
 a curved, pre-stressed piezoelectric drive member having a central portion operatively coupled to the valve of the engine and a peripheral portion captively engaged by a portion of the engine proximate the valve; and    a controller input for exciting said drive member;    whereby the valve moves between an open position and a closed position based on a predetermined set of engine operating parameters and user input.    
     
     
         2 . The mechanism of  claim 1  wherein said central portion of said drive member defines an aperture in engagement with the valve stem.  
     
     
         3 . The mechanism of  claim 2  wherein said aperture is keyhole shaped and includes a first portion that receives the valve stem therethrough, and a second portion, smaller than said first portion, configured to receive a reduced diameter of a retaining groove in the valve stem.  
     
     
         4 . The mechanism of  claim 1  wherein said peripheral portion of said drive member includes first and second opposite ends.  
     
     
         5 . The mechanism of  claim 4  wherein said ends are planar in shape, the engaging portion of the engine further including at least one retaining groove captively engaging said ends.  
     
     
         6 . The mechanism of  claim 4  wherein said ends are rolled, the engaging portion of the engine further including a pair of mounting pins receivable in a respective one of said rolled ends.  
     
     
         7 . The mechanism of  claim 1  wherein said peripheral portion of said drive member is circular in shape, the engaging portion of the engine further including at least one retaining groove captively engaging said circular peripheral portion.  
     
     
         8 . The mechanism of  claim 1  wherein said drive member includes at least one layer of a piezoceramic material.  
     
     
         9 . The mechanism of  claim 8  wherein said piezoceramic material is lead zirconate titanate (PZT).  
     
     
         10 . An actuator for a valve having a valve stem, the actuator comprising: 
 a drive member including a curved, pre-stressed wafer having at least one layer of piezoceramic material, said wafer having an aperture in a central portion thereof configured for direct attachment to the valve stem whereby the valve is moved between an open position and a closed position by said drive member.    
     
     
         11 . The actuator of  claim 10  wherein said piezoceramic material comprises lead zirconate titanate (PZT).  
     
     
         12 . The actuator of  claim 10  wherein said aperture is keyhole shaped and includes a first portion configured to receive the valve stem therethrough, and a second portion, smaller than said first portion, configured to receive a reduced diameter of a retaining groove in the valve stem.  
     
     
         13 . An internal combustion engine comprising: 
 a block portion defining at least one cylinder;    at least one cylinder head attached to said block portion and defining at least one combustion chamber in said at least one cylinder, said cylinder head supporting at least two valves for said at least one cylinder;    an actuation mechanism for operating said valves between an open position and a closed position, said actuation mechanism including a curved, pre-stressed piezoelectric drive member for each said valve, each said piezoelectric drive member having a central portion thereof operatively coupled to a respective one of said valves; and    a controller input for exciting said actuation mechanism;    whereby said valve moves between said open position and said closed position based on a predetermined set of engine operating parameters and user input.    
     
     
         14 . The engine of  claim 13  wherein said actuation mechanism includes a pre-stressed wafer having at least one layer of piezoceramic material.  
     
     
         15 . The engine of  claim 14  wherein said piezoceramic material comprises lead zirconate titanate (PZT).  
     
     
         16 . The engine of  claim 13  wherein said valve includes a valve stem and said central portion of said drive member includes a keyhole shaped aperture having a first portion configured to receive said valve stem therethrough, and a second portion, smaller than said first portion, configured to receive a reduced diameter of a retaining groove in said valve stem.