Air control device including air switching valve driven by motor

Abstract

An air control device is advantageously used as a device for supplying secondary air to a catalyzer contained in an exhaust pipe of an internal combustion engine. The air control device includes an electric motor, a speed reduction mechanism, a valve having a valve shaft and a biasing spring. These components are all contained in a housing that has a valve port formed therein. The valve is driven to open the valve port by the electric motor against a biasing force of the biasing spring. A rotational movement of a final gear in the speed reduction mechanism is converted into a linear movement of the valve shaft to thereby open the valve port. Since the biasing spring such as a torsion spring is wound around a flange connected to an axis of the final gear, a length of the valve shaft is made short, and the device as a whole is made compact.

1 . An air control device comprising: 
 a housing having a valve port formed therein;    a valve disposed in the housing for opening or closing the valve port, the valve having a valve shaft and a valve head;    a valve driving mechanism including an electric motor, a speed reduction mechanism having a plurality of gears including a final gear engaging with a rack formed on the valve shaft so that a rotational movement of the final gear is converted to a linear movement of the valve shaft for opening or closing the valve port; and    biasing means for biasing the valve in a direction to close the valve port, wherein:    the biasing means is disposed around an axis of the final gear.    
   
   
       2 . The air control device as in  claim 1 , wherein: 
 the axis of the final gear is disposed perpendicularly to the valve shaft.    
   
   
       3 . The air control device as in  claim 2 , wherein: 
 the biasing means is a torsion spring wound around the axis of the final gear.    
   
   
       4 . The air control device as in  claim 3 , wherein: 
 a torsional resilient force is accumulated in the torsion spring when the axis of the final gear is driven in a direction to open the valve port.    
   
   
       5 . The air control valve as in  claim 2 , wherein: 
 the rack is formed on the valve shaft at its end portion opposite to an end where the valve head is connected; and    the rack engages with a pinion connected to the axis of the final gear.    
   
   
       6 . The air control valve as in  claim 1 , wherein: 
 the valve driving mechanism is contained in the housing together with the valve; and    the housing is fixed to an air passage communicating with the valve port in a cantilever fashion.    
   
   
       7 . The air control valve as in  claim 1 , wherein: 
 the air control device controls airflow of secondary air supplied from an air pump to a calalyser in an exhaust pipe of an automotive vehicle.    
   
   
       8 . The air control valve as in  claim 7 , further comprising a one-way valve for preventing exhaust gas from flowing into the valve port while permitting the secondary air to flow out through the valve port.  
   
   
       9 . An air control device comprising: 
 a housing having a valve port formed therein;    a valve disposed in the housing for opening or closing the valve port, the valve having a valve shaft and a valve head;    a valve driving mechanism including an electric motor, a speed reduction mechanism having a plurality of gears including a final gear engaging with a rack formed on the valve shaft so that a rotational movement of the final gear is converted to a linear movement of the valve shaft for opening or closing the valve port; and    biasing means for biasing the valve in a direction to open the valve port, wherein:    the biasing means is disposed around an axis of the final gear.