Limited slip differential with integrated solenoid valve and plenum
An apparatus and method for controlling a limited slip differential uses a solenoid operated valve having an armature attached a differential case of the differential for rotation therewith, and an actuating coil operatively attached to a non-rotating differential housing, for modulating pressure in a hydraulically actuated limited slip device of the limited slip differential. The actuating coil is mounted on a non-rotating plenum, sealed to the differential case with low pressure dynamic seals.
1. A differential comprising:
a non-rotating differential housing;
a differential case rotatably mounted within the housing and adapted to be driven by an input shaft;
a differential gear assembly mounted within the differential case and adapted for attachment to a pair of output shafts for allowing differential rotational speed between the output shafts;
a hydraulically actuated limited slip device disposed within the differential case for retarding differential rotational speed between the output shafts, wherein the differential case includes an outlet passage for the hydraulically actuated limited slip device;
a solenoid operated valve for selectively modulating fluid flow through the outlet passage as a function of electrical current passed through an actuating coil, the solenoid valve comprising:
an armature attached to the differential case for rotation therewith, wherein the actuating coil is operatively attached to the non-rotating differential housing, with the armature operatively attached to the hydraulically actuated limited slip device for modulating pressure in the limited slip device;
a valve seat in the outlet passage;
a ball retained in the outlet passage adjacent the seat and configured for seated engagement with the valve seat; and
a push rod affixed to the armature for movement therewith, and extending through the outlet passage for sliding movement with respect thereto, and contacting the ball for regulating a position of the ball in relation to the valve seat.
2. The differential of claim 1 further comprising a plenum for hydraulic fluid attached and fixed against rotation in relation to the differential housing and sealed in fluid communication with the hydraulically actuated limited slip device for receiving fluid from the solenoid operated valve.
3. The differential of claim 2 wherein the actuating coil of the solenoid operated valve is fixedly attached to the plenum.
4. The differential of claim 1 wherein:
the hydraulically actuated limited slip device further includes a gerotor pump having an inner gear adapted for attachment to one of the output shafts for rotation therewith and an outer gear attached to the differential case for rotation relative to the inner gear and the differential case; and
the outlet passage is disposed adjacent an intersection of the inner and outer gears of the gerotor pump.
5. The differential of claim 1 wherein:
the hydraulically actuated limited slip device further includes a gerotor pump having an inner gear adapted for attachment to one of the output shafts for rotation therewith and an outer gear attached to the differential case for rotation relative to the inner gear and the differential case; and
the outlet passage is disposed outside of the outer gear of the gerotor pump.
6. The differential of claim 1 further comprising a retaining device attached to the differential case for retaining the push rod in the outlet passage.
7. The differential of claim 6 further including a preload spring operatively disposed between the retaining device and the push rod for urging the push rod toward a preload position in the outlet passage.
8. The differential of claim 7 wherein the preload spring urges the push rod toward the preload position whereat the push rod holds the ball in seated engagement with the valve seat, and the solenoid operated valve generates a force aiding the preload spring in urging the pushrod toward the preload position when electrical current is passing through the actuating coil.
9. A solenoid operated valve apparatus for a differential having a differential gear assembly mounted within a rotatable differential case and adapted for attachment to a pair of output shafts for allowing differential rotational speed between the output shafts, and a hydraulically actuated limited slip device disposed within the differential case for retarding differential rotational speed between the output shafts, the valve apparatus comprising:
an armature attached to the differential case for rotation therewith, and operatively attached to the hydraulically actuated limited slip device for modulating pressure in the limited slip device the differential case including an outlet passage for the hydraulically actuated limited slip device;
an actuating coil adapted for attachment to a non-rotating support for actuating the armature;
a valve seat in the outlet passage;
a ball retained in the outlet passage adjacent the seat and configured for seated engagement with the valve seat; and
a push rod affixed to the armature for movement therewith, and extending through the outlet passage for sliding movement with respect thereto, and contacting the ball for regulating a position of the ball in relation to the valve seat;
wherein the solenoid operated valve apparatus is arranged to selectively modulate fluid flow through the outlet passage as a function of electrical current passed through the actuating coil.
10. The solenoid operated valve apparatus of claim 9 , further comprising:
a retaining device attached to the differential case for retaining the push rod in the outlet passage; and
a preload spring operatively disposed between the retaining device and the push rod for urging the push rod toward a preload position in the outlet passage.
11. The solenoid operated valve apparatus of claim 10 wherein the preload spring urges the push rod toward the preload position whereat the push rod holds the ball in seated engagement with the valve seat, and the armature generates a force aiding the preload spring in urging the pushrod toward the preload position when electrical current is passing through the actuating coil.
12. The solenoid operated valve apparatus of claim 9 further comprising a plenum for hydraulic fluid fixed against rotation with respect to the actuating coil and sealed in fluid communication with the hydraulically actuated limited slip device for receiving fluid from the solenoid operated valve.
13. The solenoid operated valve apparatus of claim 12 wherein the actuating coil of the solenoid operated valve is fixedly attached to the plenum.