On-off valve for a gas injection system, particularly of methane, for internal combustion engines

Abstract

On-off valve intended to be arranged at the outlet of the gas accumulation reservoir in an electronic gas injection system for an internal combustion engine, presenting a valve member made of metallic material, co-operating with a valve seat made in a body, which is also made of metallic material, to ensure the good quality of tightness in all operative temperature and pressure conditions, with prolonged reliability in time.

1. Gas injection system, particularly of methane, for internal combustion engine, comprising:
 a plurality of electromagnetically controlled injectors, associated to the various cylinders in the engine,  
 a distributing manifold or rail communicating with said injectors,  
 a feeding reservoir of the distributing manifold where pressurised gas is accumulated,  
 a pressure regulating valve interposed in the connection between the reservoir and said distribution manifold,  
 an electronic control unit set up to control the injectors and to control the opening time to meter the amount of gas injected in each cylinder according to the operating conditions of the engine and,  
 an on-off valve arranged on the output of the reservoir, comprising: 
 a valve member, co-operating with a valve seat,  
 spring means tending to push said valve member in the same direction as the flow of gas from said reservoir, towards a closed condition in contact with said valve seat, and  
 a solenoid which can be energized to recall the valve member to an open condition spaced apart from said valve seat, against the action of elastic  said spring means,  
 wherein said valve member ( 18 )  is made of metallic material and in that said valve seat is made in a metallic material body, and  
 
 wherein said solenoid is suited to apply a first higher force of attraction on the valve member which is higher  in a first phase of predetermined duration, in order to cause the detachment of the valve member from its seat, and a second force of attraction on the valve member, which is lower than said first force of attraction, in a second subsequent phase to keep the valve member open, so that in the case of excessive flow of gas due to leakage in the tubes downstream with respect to the on-off valve, the valve member will close and also act as a flow limiting valve.  
 
     
     
       2. System according to  claim 1 , wherein said valve member presents a spherical conformation and the valve seat co-operating therewith consists of an impression defining an annular portion of spherical surface. 
     
     
       3. System according to  claim 1 , wherein said valve member is recalled to the closed condition by a spring tending to push it in the same direction as the flow of gas from reservoir. 
     
     
       4. An on-off valve arranged at the outlet of a gas accumulation reservoir, comprising:
   a valve member cooperating with a valve seat,        spring means tending to push said valve member in the same direction as the flow of gas from said reservoir towards, a closed condition in contact with said valve seat, and        a solenoid which can be energized for recalling said valve member to an opened condition spaced apart from said valve seat, against the action of said spring means,        wherein said valve member is made of metallic material and said valve seat is made in a body which is made of metallic material,        wherein said solenoid is suited to apply a first higher force of attraction on the valve member in a first phase of predetermined duration, in order to cause the detachment of the valve member from its seat, and a second force of attraction on the valve member, which is lower than said first force of attraction, in a second subsequent phase, to keep the valve member open, so that in the case of excessive flow of gas due to leakage in the tubes downstream with respect to the on-off valve, the valve member will close and also act as a flow limiting valve.     
     
     
       5. The on-off valve according to  claim 4 , wherein said valve member presents a spherical conformation and the valve seat co-operating therewith consists of an impression defining an annular portion of spherical surface, formed in a tapered portion of the gas outflow conduit.