Proportional valve

1. A proportional valve ( 1 ) with a pilot valve ( 2 ) that can be activated by a control signal and a booster valve ( 3 ) that can be actuated by means of the pilot valve ( 2 ), wherein the proportional valve ( 1 ) has a compressed-air port ( 6 ) for connection of a compressed-air supply, a working port ( 5 ) and a vent port ( 4 ),

wherein the booster valve ( 3 ) has three valve elements ( 8 , 9 , 10 ) connected in series and respectively movable in an axial direction against a spring force, namely

a first valve element ( 8 ) actuated by the pilot valve ( 2 ),

a second valve element ( 9 ), which is actuated by the first valve element ( 2 ), and

a third valve element ( 10 ), which is actuated by the second valve element ( 9 ),

wherein, in a basic position of the proportional valve ( 1 ), the first, the second and the third valve elements ( 8 , 9 , 10 ) are spaced apart from one another in pairs and, within the booster valve ( 3 ), a first sealing seat ( 26 ) acting between the first valve element ( 8 ) and the second valve element ( 9 ) and a second sealing seat ( 27 ) acting between the third valve element ( 10 ) and the housing ( 16 ) are formed and disposed in such a way that during variation of the control signal that activates the pilot valve ( 2 ) and of the resulting cascade-like positioning of the axial positions of the first, second and third valve elements ( 8 , 9 , 10 ), various switched states can be set for venting of and air admission to the working port ( 5 ) and for holding a pressure present at the working port ( 5 ),

wherein further a position sensor ( 31 ) is provided to detect the axial position of the first valve element ( 8 ) and a control unit ( 36 ) of the proportional valve ( 1 ) is set up in such a way that the measured signal of the position sensor ( 31 ) is evaluated for calculation of the control signal for the pilot valve ( 2 ), needed in order to achieve a desired switched state of the booster valve ( 3 ).

2. The proportional valve of claim 1 , wherein the position sensor ( 31 ) is set up for contactless measurement of the axial position of the first valve element.

3. The proportional valve of claim 2 , wherein the position sensor ( 31 ) is based on an optical, capacitive or magnetic measurement principle.

4. The proportional valve of claim 3 , wherein the position sensor ( 31 ) is a magnetic-field angle sensor.

5. The proportional valve of claim 4 , wherein the position sensor ( 31 ) is an AMR, TMR or GMR sensor.

6. The proportional valve of claim 1 , wherein the control unit ( 36 ) of the proportional valve ( 1 ) is set up in such a way that the control signal for the pilot valve ( 2 ), needed in order to achieve a desired switched state of the booster valve ( 3 ), is calculated by utilizing exclusively the measured signal of the position sensor ( 31 ).

7. The proportional valve of claim 1 , wherein the first valve element ( 8 ) is formed by a diaphragm disk ( 11 ) with a diaphragm-disk shank ( 12 ) that extends in axial direction and is provided with an axial bore ( 13 ),

wherein the second valve element ( 9 ) is formed by a valve tappet ( 18 ), which is spring-preloaded in a direction pointed toward the diaphragm disk ( 11 ) and is provided on an end face pointing toward the diaphragm-disk shank ( 12 ) with a first sealing seat for the free end of the diaphragm-disk shaft ( 12 ), which can be brought into contact therewith, and

wherein the third valve element ( 10 ) is formed by a base element ( 19 ), which is spring-preloaded against a second sealing seat in a direction pointing toward the valve tappet ( 18 ) and can be lifted from the second sealing seat by axial displacement of the valve tappet ( 18 ) that has been brought into contact on the base element ( 19 ).

8. The proportional valve of claim 7 , wherein the position sensor ( 31 ) interacts with a magnetic element ( 30 ) integrated in the diaphragm disk ( 11 ).

9. The proportional valve of claim 1 , wherein a surface ( 25 , 28 ) forming the first and/or second sealing seat and/or interacting therewith for fine regulation of the fluid flow is made of a polymer material.

10. The proportional valve of claim 1 , wherein the pilot valve is a 3/2-way valve.

11. The proportional valve of claim 1 , wherein the booster valve is a 3/3-way valve.