Proportional throttle valve

1. A proportional throttle valve, comprising

a valve housing having a fluid inlet and a fluid outlet;

a valve piston movably guided in a longitudinal direction in said valve housing;

a compression spring pretensioning said valve piston against a stroke stop defining a closed position;

a pressure limiting valve integrated in said valve housing and in said valve piston and exposed to fluid pressure on a back side of said valve piston to move away from said stroke stop in opposition to pretensioning of said compression spring when a definable pressure is exceeded at said fluid inlet, fluid pressure at said fluid inlet acting on a valve seat of said pressure limiting valve and being routed via a radially offset axial bore in said valve piston to said back side of said valve piston via an orifice, a piston bore extending axially in said valve piston and a radial bore in said valve piston to a pilot chamber for pressure balancing of said valve piston; and

an actuating magnet directly coupled to said valve piston.

2. A proportional throttle valve according to claim 1 wherein

the fluid pressure at said fluid inlet prevails on said valve seat of said pressure limiting valve and opens said pressure limiting valve when the definable pressure is reached to produce a pressure drop at said orifice and to cause a resulting force on said valve piston displacing said valve piston to connect said fluid inlet to said fluid outlet.

3. A proportional throttle valve according to claim 1 wherein

said pressure limiting valve maintains functioning relative to said valve piston in a deenergized state of an actuating magnet system coupled to said valve piston.

4. A proportional throttle valve according to claim 1 wherein

said actuating magnet comprises a magnetic coil and an actuating element movably mounted therein, said actuating element being coupled to said valve piston to move said valve piston in said valve housing upon energizing said magnetic coil in opposition to said pretensioning of said compression spring from the closed position to an open position.

5. A proportional throttle valve according to claim 4 wherein

said actuating magnet comprises a magnetic housing with a cylindrical guide projecting into said valve housing and sealed thereto, said actuating element projecting into said cylindrical guide.

6. A proportional throttle valve according to claim 5 wherein

said valve piston comprises a prolongation connected to said actuating element.

7. A proportional throttle valve according to claim 6 wherein

said compression spring surrounds said prolongation a space in said valve housing, said space having a bottom defining said stroke stop, said stroke stop separating said back side of said valve piston from a main control section of said valve piston controlling fluid flow through said fluid inlet and said fluid outlet.

8. A proportional throttle valve according to claim 7 wherein

said pressure limiting valve comprises a limiting valve housing fixedly connected in said valve piston and extending concentrically along a longitudinal axis of said valve piston, a valve member movably mounted in said limiting valve housing along said longitudinal axis to engage with and to disengage from said valve seat and a limiting compression spring biasing said valve member against said valve seat.

9. A proportional throttle valve according to claim 8 wherein

said valve seat is adjacent an end of said piston bore and has an opening therein providing fluid communication between said piston bore and said fluid outlet via passages in said housing when said valve member is disengaged from said valve seat.

10. A proportional throttle valve according to claim 1 wherein

said pressure limiting valve comprises a limiting valve housing fixedly connected in said valve piston and extending concentrically along a longitudinal axis of said valve piston, a valve member movably mounted in said limiting valve housing along said longitudinal axis to engage with and to disengage from said valve seat and a limiting compression spring biasing said valve member against said valve seat.

11. A proportional throttle valve according to claim 10 wherein

said valve seat is adjacent an end of said piston bore and has an opening therein providing fluid communication between said piston bore and said fluid outlet via passages in said housings when said valve member is disengaged from said valve seat.