Pump for metering a liquid additive for a selective catalytic reduction device

1. A device ( 1 ) providing a dosed supply of a liquid, the device ( 1 ) comprising:

at least one pump ( 2 ) configured to deliver the liquid, the at least one pump ( 2 ) having a pump housing ( 3 ) with at least one inlet ( 4 ) and at least one outlet ( 5 );

an eccentric ( 6 ) arranged on the pump housing ( 3 );

a deformable diaphragm ( 7 ) arranged between the pump housing ( 3 ) and the eccentric ( 6 ), the deformable diaphragm ( 7 ) and the pump housing ( 3 ) delimiting at least one delivery path ( 8 ) from the at least one inlet ( 4 ) to the at least one outlet ( 5 ) and forming at least one seal ( 9 ) of the delivery path ( 8 ); and

a barb structure ( 35 ), the barb structure being arranged on at least one selected from the group: (a) the pump housing ( 3 ), (b) the eccentric ( 6 ), and (c) the deformable diaphragm ( 7 ),

wherein the at least one seal ( 9 ) is displaceable along the delivery path ( 8 ), by a movement of the eccentric ( 6 ), in a delivery direction ( 27 ) from the at least one inlet ( 4 ) to the at least one outlet ( 5 ) to deliver the liquid,

wherein the at least one pump ( 2 ) is configured such that within the at least one pump ( 2 ) a friction torque ( 13 ) that must be overcome for the eccentric ( 6 ) to move is greater than a maximum pressure torque ( 14 ) that can be generated by pressurized liquid in the at least one delivery path ( 8 ), so as to prevent movement of the eccentric ( 6 ) counter to the delivery direction ( 27 ), and

wherein the barb structure ( 35 ) is configured to contribute to the friction torque ( 13 ).

2. The device ( 1 ) as claimed in claim 1 , wherein the deformable diaphragm ( 7 ) bears at least against the pump housing ( 3 ) or against the eccentric ( 6 ) with a friction coefficient and a normal force ( 10 ), the friction coefficient and the normal force ( 10 ) resulting in the friction torque ( 13 ) within the at least one pump ( 2 ).

3. The device ( 1 ) as claimed claim 1 , wherein:

the eccentric ( 6 ) has an inner eccentric region ( 22 ), an outer bearing ring ( 21 ), and a bearing ( 20 ) arranged between the inner eccentric region ( 22 ) and the outer bearing ring ( 21 ), and

the friction torque ( 13 ) is a result of internal friction in the bearing ( 20 ).

4. The device ( 1 ) as claimed in claim 1 , wherein the at least one pump ( 2 ) has a drive unit ( 26 ), and the friction torque ( 13 ) is formed by internal friction in the drive unit ( 26 ).

5. The device ( 1 ) as claimed in claim 1 , wherein the maximum pressure torque ( 14 ) is formed on the basis of a maximum working pressure of the at least one pump ( 2 ) and a maximum encountered cross section ( 25 ) of the delivery path ( 8 ) of the at least one pump ( 2 ).

6. The device ( 1 ) as claimed in claim 5 , wherein the maximum cross section ( 25 ) of the delivery path ( 8 ) is smaller than 20 mm 2 [square millimeters].

7. The device ( 1 ) as claimed in claim 6 , wherein the maximum working pressure of the at least one pump ( 2 ) is between 6 bar and 10 bar.

8. The device ( 1 ) as claimed in claim 1 , wherein at least one selected from the group of the following parameters of the at least one pump ( 2 ) is configured such that the friction torque ( 13 ) is greater during movement of the eccentric ( 6 ) counter to the delivery direction ( 27 ) than during a movement of the eccentric ( 6 ) in the delivery direction ( 27 ):

a friction coefficient between a housing surface ( 15 ) of the pump housing that is directed toward the delivery path ( 8 ) and a diaphragm surface ( 34 ) of the deformable diaphragm ( 7 ) that is directed toward the delivery path ( 8 );

a friction coefficient between the deformable diaphragm ( 7 ) and the eccentric ( 6 );

a friction torque in a bearing ( 20 ) of the eccentric ( 6 ) of the at least one pump ( 2 ); and

a friction torque in a drive unit ( 26 ) of the at least one pump ( 2 ).

9. A motor vehicle ( 17 ) having an internal combustion engine ( 18 ), an exhaust-gas treatment device ( 16 ) configured to purify exhaust gases of the internal combustion engine ( 18 ), and a device ( 1 ), configured to deliver a liquid consisting of urea-water solution to the exhaust-gas treatment device ( 16 ), as claimed in claim 1 .

10. A device ( 1 ) providing a dosed supply of a liquid, the device ( 1 ) comprising:

at least one pump ( 2 ) configured to deliver the liquid, the at least one pump ( 2 ) having a pump housing ( 3 ) with at least one inlet ( 4 ) and at least one outlet ( 5 );

an eccentric ( 6 ) arranged on the pump housing ( 3 ); and

a deformable diaphragm ( 7 ) arranged between the pump housing ( 3 ) and the eccentric ( 6 ), the deformable diaphragm ( 7 ) and the pump housing ( 3 ) delimiting at least one delivery path ( 8 ) from the at least one inlet ( 4 ) to the at least one outlet ( 5 ) and forming at least one seal ( 9 ) of the delivery path ( 8 ),

wherein the at least one seal ( 9 ) is displaceable along the delivery path ( 8 ), by a movement of the eccentric ( 6 ), in a delivery direction ( 27 ) from the at least one inlet ( 4 ) to the at least one outlet ( 5 ) to deliver the liquid,

wherein the at least one pump ( 2 ) is configured such that within the at least one pump ( 2 ) a friction torque ( 13 ) that must be overcome for the eccentric ( 6 ) to move is greater than a maximum pressure torque ( 14 ) that can be generated by pressurized liquid in the at least one delivery path ( 8 ), so as to prevent movement of the eccentric ( 6 ) counter to the delivery direction ( 27 ), and

wherein, a barb structure ( 35 ) is provided at at least one position selected from the group of the following positions within the at least one pump ( 2 ), so as to have the effect that the friction torque ( 13 ) is greater counter to the delivery direction ( 27 ) than in the delivery direction ( 27 ):

on a housing surface ( 15 ), directed toward the delivery path ( 8 ), of the pump housing ( 3 );

on a diaphragm surface ( 34 ), directed toward the delivery path ( 8 ), of the deformable diaphragm ( 7 );

on a diaphragm surface, directed toward the eccentric ( 6 ), of the deformable diaphragm ( 7 );

on a surface, directed toward the deformable diaphragm ( 7 ), of the eccentric ( 6 );

in a bearing ( 20 ) of the eccentric ( 6 ) of the at least one pump ( 2 ); and

in a drive unit ( 26 ) of the at least one pump ( 2 ).