Electro-magnetic actuator for torque coupling with variable pressure-control spool valve

1. A torque-coupling assembly comprising:

a rotatable torque-coupling case;

at least one output shaft drivingly operatively connected to said torque-coupling case;

a friction clutch assembly for selectively engaging and disengaging said torque-coupling case and said at least one output shaft;

a hydraulic pump for generating a hydraulic fluid pressure to frictionally load said clutch assembly;

a fluid control passage through which a hydraulic fluid is discharged from said torque-coupling case; and

a variable pressure-control valve assembly including a spool valve disposed in said fluid control passage and an electro-magnetic actuator for producing a variable axial electro-magnetic force acting against said spool valve so as to selectively adjust the position of said spool valve in said fluid control passage in order to selectively control the flow rate of said hydraulic fluid in said fluid control passage;

said electro-magnetic actuator including an electro-magnetic coil assembly and an armature axially movable relative thereto;

said armature is disposed radially inwardly of said electro-magnetic coil assembly.

2. The torque-coupling assembly as defined in claim 1 , wherein the position of said spool valve is selectively adjustable between an open position allowing flow of said hydraulic fluid though said fluid control passage and a closed position blocking flow of said hydraulic fluid though said fluid control passage.

3. The torque-coupling assembly as defined in claim 2 , wherein said spool valve includes a spool member disposed in a valve chamber for sliding movement therewithin; said spool valve is mounted to said armature.

4. The torque-coupling assembly as defined in claim 3 , wherein said valve chamber is formed in said torque-coupling case of said torque-coupling assembly across said fluid control passage.

5. The torque-coupling assembly as defined in claim 4 , wherein said spool member includes two substantially cylindrical land portions axially spaced by a central portion of a reduced size relative to said land portions; said land portions of said spool member slidingly engage a complementary inner peripheral surface of said valve chamber.

6. The torque-coupling assembly as defined in claim 5 , wherein in said open position said reduced diameter central portion of said spool member is axially registered with said fluid control passage so as to allow hydraulic fluid flow in said fluid control passage through said spool valve across said spool member; and wherein in said closed position one of said land portions of said spool member blocks said fluid control passage.

7. The torque-coupling assembly as defined in claim 3 , further comprising a non-rotatable plenum plate mounted to said torque-coupling case so as to form an annular hydraulic plenum chamber defined between said plenum plate and said torque-coupling case.

8. The torque-coupling assembly as defined in claim 7 , further comprising a preloaded spring operatively disposed between said plenum plate and said armature for urging said spool valve toward said open position thereof.

9. The torque-coupling assembly as defined in claim 8 , wherein said variable electro-magnetic force produced by said electro-magnetic actuator urges said spool member against a resilient force of said spring so as to selectively adjust the position of said spool valve between an open position allowing flow of said hydraulic fluid through said fluid control passage and a closed position blocking flow of said hydraulic fluid through said fluid control passage.

10. The torque-coupling assembly as defined in claim 7 , wherein said electro-magnetic actuator is non-rotatably secured to said plenum plate.

11. The torque-coupling assembly as defined in claim 7 , further comprising an annular bushing disposed within an annular bore of said armature for rotatably supporting said plenum plate to said torque-coupling case and a plenum passage formed between said armature and said bushing for providing fluid communication through said electro-magnetic actuator.

12. The torque-coupling assembly as defined in claim 11 , wherein said plenum passage is defined by a set of circumferentially distributed axial passageways formed in said bushing.

13. The torque-coupling assembly as defined in claim 1 , further including a piston assembly disposed within said torque-coupling case between said pump and said clutch assembly and defining a pressure chamber, wherein said variable pressure-control valve assembly selectively controls a hydraulic pressure attainable within said pressure chamber.

14. The torque-coupling assembly as defined in claim 13 , wherein said variable pressure-control valve assembly selectively controls said pressure attainable within said pressure chamber between a maximum pressure when said spool valve is in said closed position and a minimum pressure when said spool valve is in said open position.

15. The torque-coupling assembly as defined in claim 14 , wherein said minimum pressure attainable within said pressure chamber is at a level that prevents actuation of said friction clutch assembly.

16. The torque-coupling assembly as defined in claim 14 , wherein said maximum pressure attainable within said pressure chamber is at a level that enables complete actuation of said friction clutch assembly.

17. The torque-coupling assembly of claim 14 , wherein said hydraulic pressure attainable within said pressure chamber is adjustable between said minimum pressure and said maximum pressure so as to enable partial actuation of said friction clutch assembly.

18. The torque-coupling assembly as defined in claim 1 , wherein said selective control of said friction clutch assembly is determined in response to at least one vehicle parameter.

19. A torque-coupling assembly comprising:

a rotatable torque-coupling case;

at least one output shaft drivingly operatively connected to said torque-coupling case;

a friction clutch assembly for selectively engaging and disengaging said torque-coupling case and said at least one output shaft;

a hydraulic pump for generating a hydraulic fluid pressure to frictionally load said clutch assembly;

a fluid control passage through which a hydraulic fluid is discharged from said torque-coupling case;

a non-rotatable plenum plate mounted to said torque-coupling case so as to form an annular hydraulic plenum chamber defined between said plenum plate and said torque-coupling case; and

a variable pressure-control valve assembly including a spool valve disposed in said fluid control passage and an electro-magnetic actuator disposed in said plenum chamber for producing a variable axial electro-magnetic force acting against said spool valve so as to selectively adjust the position of said spool valve in said fluid control passage in order to selectively control the flow rate of said hydraulic fluid in said fluid control passage;

said electro-magnetic actuator including an electro-magnetic coil assembly and an armature axially movable relative thereto;

the position of said spool valve being selectively adjustable between an open position allowing flow of said hydraulic fluid through said fluid control passage and a closed position blocking flow of said hydraulic fluid through said fluid control passage;

said spool valve including a spool member disposed in a valve chamber for sliding movement therewithin and mounted to said armature.

20. The torque-coupling assembly as defined in claim 19 , further comprising a preloaded spring operatively disposed between said plenum plate and said armature for urging said spool valve toward said open position thereof.