Exhaust gas treatment device and nozzle for the same

Abstract

A nozzle ( 1 ) includes a nozzle body ( 10 ), a piston ( 2 ) movably disposed inside the nozzle body ( 10 ), and a spring ( 3 ) between the nozzle body ( 10 ) and the piston ( 2 ). A reducing agent flow channel ( 12 ) extends between a nozzle inlet ( 11 ) and a nozzle orifice ( 14 ), which widens towards a nozzle opening ( 13 ). A piston head ( 21 ) closes or opens the nozzle orifice ( 14 ). The spring ( 3 ) biases the piston ( 2 ) to close the nozzle orifice ( 14 ) with the piston head ( 21 ). A largest diameter (D 13 ) of the nozzle opening ( 13 ) is larger than a largest diameter (D 21 ) of the piston head ( 21 ). An exhaust gas treatment device ( 5 ) includes a tank ( 51 ) for the liquid reducing agent, the nozzle ( 1 ), a reducing agent pump ( 53 ) and a reducing agent conduit ( 52 ). A control ( 54 ) is configured to operate the reducing agent pump ( 53 ) continuously with variable output.

What is claimed is: 
     
         1 . A nozzle for an exhaust gas treatment system, the nozzle comprising:
 a nozzle body comprising a nozzle inlet for a liquid reducing agent, a nozzle orifice, a flow channel, for the reducing agent, formed between the nozzle inlet and the nozzle orifice, the nozzle orifice widening from the flow channel towards a nozzle opening;   a piston movably disposed inside the nozzle body and having a piston head, the piston head being disposed inside the nozzle orifice and being configured to selectively close or open the nozzle orifice; and   a spring sandwiched between the nozzle body and the piston and biasing the piston in a direction in which the piston head closes the nozzle orifice, wherein a largest diameter of the nozzle opening is larger than a largest diameter of the piston head.   
     
     
         2 . The nozzle according to  claim 1 , wherein the largest diameter of the nozzle opening is larger than a largest diameter of the piston head by at least 5%. 
     
     
         3 . The nozzle according to  claim 1 , wherein the nozzle orifice extends beyond the piston head at least in an operational state where the piston head abuts against the nozzle orifice to thereby close the nozzle orifice, thus providing a guiding area for the liquid reducing agent exiting the nozzle. 
     
     
         4 . The nozzle according to  claim 3 , wherein the nozzle orifice extends beyond the piston head in all positions of the piston head. 
     
     
         5 . The nozzle according to  claim 3 , wherein the nozzle orifice extends beyond the piston head in an operational state where the piston head abuts against the nozzle orifice to thereby close the nozzle orifice by at least one of:
 8.6% or more than 8.6% of a largest diameter of the piston head;   17% or more than 17% of a largest diameter of the piston head;   64% or more than 64% the largest diameter of the piston head;   more than half of the largest diameter of the piston head.   
     
     
         6 . The nozzle according to  claim 1 , wherein the nozzle orifice ( 14 ) forms an opposite angle with the piston head, the opposite angle being larger than 1° at the point of contact of the piston in a piston closed position. 
     
     
         7 . The nozzle according to  claim 1 , wherein:
 a diameter of the nozzle orifice increases in a longitudinal direction of the flow channel or of the piston continuously along a direction facing away from the flow channel or from a piston foot of the piston with an increasing gradient; or   a diameter of the nozzle orifice increases in a longitudinal direction of the flow channel of the piston linearly along a direction facing away from the flow channel or from a piston foot of the piston.   
     
     
         8 . The nozzle according to  claim 1 , wherein:
 a diameter of the piston head increases in a longitudinal direction of the piston continuously along a direction facing away from a piston foot of the piston with an increasing gradient; or   a diameter of the piston head increases in a longitudinal direction of the piston linearly along a direction facing away from a piston foot of the piston.   
     
     
         9 . The nozzle according to  claim 1 , wherein:
 the nozzle opening and a cross section through the piston head, perpendicular to a longitudinal direction of the piston, each have a circular shape; or   the nozzle opening and a cross section through the piston head, perpendicular to the longitudinal direction of the piston, each have an oval shape; or   the nozzle opening and a cross section through the piston head, perpendicular to the longitudinal direction of the piston, each have a geometrically similar polygonal shape; or   the nozzle opening and a cross section through the piston head, perpendicular to the longitudinal direction of the piston, each have a similar geometrically asymmetric shape.   
     
     
         10 . The nozzle according to  claim 1 , wherein the transition between a piston foot of the piston and the piston head is continuous along a longitudinal direction of the piston or has a kink. 
     
     
         11 . An exhaust gas treatment device for motor vehicles, the exhaust gas treatment device comprising:
 a tank for a liquid reducing agent;   a nozzle having an integrated passive valve, the nozzle comprising:
 a nozzle body comprising a nozzle inlet for a liquid reducing agent, a nozzle orifice, a flow channel, for the reducing agent, formed between the nozzle inlet and the nozzle orifice, the nozzle orifice widening from the flow channel towards a nozzle opening; 
 a piston movably disposed inside the nozzle body and having a piston head, the piston head being disposed inside the nozzle orifice and being configured to selectively close or open the nozzle orifice; and 
 a spring sandwiched between the nozzle body and the piston and biasing the piston in a direction in which the piston head closes the nozzle orifice, wherein a largest diameter of the nozzle opening is larger than a largest diameter of the piston head; 
   a reducing agent conduit for passing the liquid reducing agent from the tank to the nozzle inlet of the nozzle;   a reducing agent pump disposed along the reducing agent conduit between the tank and the nozzle; and   a control for controlling the reducing agent pump, the control being configured to operate the reducing agent pump continuously with variable output.   
     
     
         12 . The exhaust gas treatment device according to  claim 11 , wherein the control is further configured to operate the nozzle continuously with variable output. 
     
     
         13 . The exhaust gas treatment device according to  claim 11 , wherein the reducing agent pump a gear pump comprising one of an internal gear pump or an external gear pump, or a gerotor pump or a screw pump. 
     
     
         14 . The exhaust gas treatment device according to  claim 11 , further comprising a pressure sensor located along the reducing agent conduit between the reducing agent pump and the nozzle, the pressure sensor being configured to determine a pressure of the reducing agent in the reducing agent conduit. 
     
     
         15 . The exhaust gas treatment device according to  claim 11 , further comprising a heater configured to heat at least one of the tank, the reducing agent conduit, and the nozzle. 
     
     
         16 . The exhaust gas treatment device according to  claim 11 , further comprising:
 a compressed air source configured to blow pressurized air through the reducing agent conduit and through the nozzle in order to drain the reducing agent from the reducing agent conduit and from the nozzle.   
     
     
         17 . The exhaust gas treatment device according to  claim 11 , further comprising:
 an exhaust gas line for passing exhaust gas to be treated, the nozzle orifice of the nozzle being positioned centrally in the exhaust gas line; and   a catalytic converter disposed along the exhaust gas line downstream of the nozzle and being configured for a selective catalytic reduction of the exhaust gas using the reducing agent injected by the nozzle.   
     
     
         18 . The exhaust gas treatment device according to  claim 11 , wherein neither the nozzle nor the reducing agent pump are clocked.