Abstract:
A solenoid operated valve suitable for controlling flow of air for injection into the exhaust of an engine, the poppet is connected to the solenoid armature in a lost-motion connection. Upon energization, the armature achieves momentum during the lost-motion movement and imports an impulse to the poppet to ensure movement in the event of any tendency of the poppet to stick. A one-way valve prevents exhaust back pressure from opening the poppet.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to the controlling of injection of air into the exhaust stream of an internal combustion engine particularly for the purpose of reducing emissions in motor vehicle engine applications.  
           [0002]    Heretofore, it has been the practice in controlling such air injection to utilize an engine driven air pump with its outlet connected to the inlet of the diaphragm operated valve actuated in response to an engine inlet manifold vacuum signal. Failures of this type of valve to open have been experienced at high elevations with reduced atmospheric pressure and at high engine loads with reduced engine manifold vacuum,. This has resulted in insufficient air being injected into the exhaust stream in increased engine emissions when the engine is operating under heavily loaded conditions.  
           [0003]    It has been suggested to utilize an electrically operated valve in place of a pressure responsive diaphragm operated valve. However, electrically operated valves, particularly of the solenoid operated type have been found to have insufficient force, when operated on the low voltage vehicles power supply, to open the valve in the event the valve obturator or poppet sticks due to buildup on the valve seat of residue from products of combustion.  
           [0004]    It has thus been desired to find a way or means of electrically operating a valve for controlling flow of secondary air for injection into the exhaust of an internal combustion engine which is not subject to sticking when operated by a relatively low powered electric actuator and which is relatively low in manufacturing cost so as to remain competitive in high volume mass production motor vehicle applications.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    The present invention provides an electrically operated valve for controlling flow of pressurized air for injection into the exhaust system of an engine which is able to overcome the pressure forces of the engine exhaust acting on the poppet with a relatively low powered electrical actuator. The electrically operated actuator has an operating member connected to the valve obturator or poppet in a manner which permits lost motion during initial energization of the actuator such that the operating rod acquires sufficient momentum with a relatively low electrical current actuating force to actuate the poppet with an impulse sufficient to overcome the pressure forces of the exhaust back pressure acting on the obturator and any residue tending to hold the poppet closed. A one-way valve is disposed in the outlet of the valve assembly to prevent exhaust backflow to the source of pressurized air.  
           [0006]    The present invention thus provides an electrically operated valve capable of operating on a relatively low voltage low current power supply and which provides for positive opening of the valve obturator in order to prevent sticking on the valve seat and is particularly suitable for controlling flow of pressurized air to an engine exhaust system where the valve obturator and valve seat are exposed to the products combustion which can form residue and buildup on the seat and obturator in prolonged service. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a cross-section of the valve assembly taken through the center line of the valve operating rod; and,  
         [0008]    [0008]FIG. 2 is an enlarged view of a portion of FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0009]    Referring to FIG. 1, the valve assembly of the present invention is indicated generally at  10  and has a valve body  12  provided with an inlet fitting  14  which has inlet passage  16  therein. In a vehicle internal combustion engine application of the present invention, valve  10  is connected via a conduit  18  to the outlet of an air pump  20  typically connected to and driven by a vehicle engine  22 . The valve body  12  has an outlet portion  24  which has a one-way valve indicated generally at  26  communicating with an outlet passage  28  and with a flow passage  30  provided in the valve body  12 . Outlet portion  24  in the illustrated embodiment is a separate member attached to body  12 , but it will be understood that portion  24  may, alternatively, integrally formed with body  12 .  
         [0010]    Outlet passage  28  is formed in a fitting  32  which is provided on an outlet cover member  34  disposed over the one-way valve  26  and secured to the body portion  24 .  
         [0011]    In the motor vehicle engine application of the invention valve assembly  10  shown in FIG. 1, the outlet fitting  32  is connected to a conduit  36  which is connected to an inlet fitting  38  provided on the exhaust manifold  40  of the engine.  
         [0012]    Valve body  12  has a valving chamber  42  formed which communicates with inlet passage  16  through valve seat  44  and also with the flow passage  30 . A valve obturator or poppet  46  is disposed in the chamber  42  and configured to contact and seal on the valve seat  44 . An operating member or rod  48  has one end thereof connected to the obturator  46 ; and, the operating rod extends through the upper portion  50  of the valve body  12  and exteriorly thereof and is slidably supported therein by a suitable bearing  52 .  
         [0013]    A flexible seal  54  of the bellows type is disposed over the rod and prevents flow of fluid through the bearing  52 , yet permits axial movement of the rod in the bearing. A spring  56  is disposed in the chamber  42  and is operative to urge the obturator  46  in a direction for seating against valve seat  44 .  
         [0014]    An electrical operator in the form of a solenoid, indicated generally at  58 , is attached to the upper portion of the body  50  and retained thereon by a cap or cover  60  secured to the upper portion of the body  50  by any suitable expedient as for example a threaded connection as denoted by reference numeral  62 . The solenoid assembly  58  includes an annular pole piece or flux collector  64  over which is received bobbin  66  upon which is wound a coil  68  typically of“magnet” wire. An armature of magnetically permeable material is disposed slidably within the pole piece  64  and is operative for movement upon electrical energization of the coil  68 . The coil  68  is surrounded by a flux collector  70  in the form of a pole frame which completes the flux loop about the coil in conjunction with the pole piece  64 ; and, another pole piece  72  disposed at the upper end of the pole frame  70  as denoted by reference numeral  72 .  
         [0015]    Referring to FIG. 2, a portion of the armature  74  is shown with the upper end of the operating rod  48  received in sliding arrangement in a bore  76  formed in the armature. The upper end of the rod  48  has a radially outwardly extending flange  78  formed thereon, the underside of which is spaced from the bottom  80  of a counter bore formed in the armature so as to provide a limited lost motion movement of the armature with respect to the undersurface of the flange  28  by an amount denoted by the reference character“d” and the dashed line in FIG. 2.  
         [0016]    It will be understood, that upon energization of the coil, the armature  74  moves in an upward direction through the distance“d” as shown by the dashed lines in FIG. 2 and attains a velocity and momentum with respect to the undersurface of the flange  78  and contacts flange  78  with an impulse. This impulse results in providing adequate force to overcome any“sticking” and therefore ensures raising of the obturator  46  from the valve seat  44  to open the valve.  
         [0017]    The position of the obturator or poppet  46  with respect to the valve seat  44  is thereafter determined by the number of ampere turns of the coil in a manner well known in the art. It will be understood that the number of ampere turns of the coil at the available level of excitation current is sufficient to overcome the bias of the spring  56 .  
         [0018]    The present invention thus enables the valve of the present invention to open with a minimum number of ampere turns of coil excitation and yet is capable of overcoming any“sticking” of the poppet or obturator to the valve seat which may be caused by combustion residue deposited on the valve seat or the poppet.  
         [0019]    Referring again to FIG. 1, the one-way valve  26  is shown in solid outline in the open position; however, it will be understood that in the coil deenergized state of the valve, the valve member  76  will be moved to the position shown in dashed outline under the force of the back pressure of the exhaust from the engine, thereby closing the outlet of the valve from communication with the valve outlet passage  28 .  
         [0020]    Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.