LOCKING DIFFERENTIAL

Abstract: A differential locking system in which the differential includes a differential carrier (1) which rotatably supports a pair of bevel gears (2, 3) as well as a pinion gear (4) which meshes with the bevel gears (2, 3) and is mounted for rotation on a shaft (5) supported by the differential carrier (1), said locking system including an annulus (6) splined to the carrier (1) and slideable axially of the carrier to cause engagement between splined teeth (9) on said annulus (6) and cooperating spline teeth (10) formed on one of said bevel gears (3) to lock said differential. The necessary axial movement of the annulus (6) is achieved by means of an annular piston (11) arranged in an annular cylinder (12) formed in the carrier (1) around the opposite bevel gear (2), and an actuating sleeve (13) which extends from the piston (11) to the annulus (6) to which it is rigidly attached, so that actuation of piston (11) causes said axial movement.

Description: This invention relates to locking differentials for motor vehicles and other machines. Various types of locking differential have been proposed, such as for example, in Patent Publications AU-B-511,665, AU-B-511,700, AU-A-41,416/78 and GB-A-2, 019,511.In each of the above examples, the locking mechanism is either complex, difficult or inconvenient to actuate and/or requires substantial modification to the rear axle housing and/or differential carrier to accomodate the mechanism. There is a need for a locking differential which is simple to manufacture or to convert an existing differential and which nevertheless does not require substantial modification to the differential axle housing. The invention therefore provides a differential locking system in which the differential includes a differential carrier supporting a pair of bevel gears adapted to be splined to axle shafts and at least one pinion gear which meshes with said pair of bevel gears, said locking system including locking means keyed or splined to said carrier so as to be capable of axial movement relative to said carrier, said locking means including locking tooth or spline means adapted to engage similar tooth or spline means associated with one of said bevel gears to prevent rotation of that bevel gear relative to said carrier. In one form of the invention, the locking system includes an annulus splined to the carrier and slidable axially to cause engagement between spline teeth on said annulus and said locking tooth or spline means associated with said one of said bevel gears. In a particularly preferred form of the invention, the locking system further comprises an annular chamber formed in said differential carrier and an annular piston positioned to axially move said locking means when said annular chamber is charged with compressed air or some other suitable fluid under pressure. A return spring is preferably provided to return the piston to its disengaged position on de-activation of the source of compressed air. One particularly preferred form of the invention will now be described with reference to the accompanying drawing which is a somewhat schematic sectional elevation of a differential carrier incorporating a locking system embodying the present invention. It will be appreciated that part only of the differential gear adapted to be locked by the locking system embodying the invention is shown for purposes of clarity. As is usual, the differential includes a differential carrier 1 which rotatably supports a pair of bevel gears 2,3 in the usual manner as well as a pinion gear 4 which meshes with the bevel gears 2,3 and is mounted for rotation on a shaft 5 supported by the casing 1. Half axles A1 and A2 have their splined ends engaging splined openings in the bevel gears 2,3 and passing through the casing 1 in the manner shown. The locking system embodying the present invention comprises an annulus 6 formed with outwardly directed spline teeth 7 which engage mating spline teeth 8 formed in the differential casing 1 surrounding the bevel gear 3 so that the annulus 6 is axially slidable in the splines 8 relative to the carrier 1. The annulus 6 is similarly formed with inwardly directed spline teeth 9 which are adapted to co-operate with spline teeth 10 formed around the lower periphery of the bevel gear 3. Axial movement of the annulus 8 is achieved by means of an annular piston 11 arranged in an annular cylinder 12 formed in the casing 1 around the other bevel gear 2, and to which is attached an actuating sleeve 13 which extends from the piston 11 to the annulus 6, to which it is rigidly attached. The sleeve 13 is formed with a cut-out portion 14 around the pinion 4 which enables axial movement of the sleeve 13 by means of the piston 11 to cause engagement between the spline teeth 9 on the annulus 6 and the corresponding spline teeth 10 on the bevel gear 3. The piston 11 is actuated by means of compressed air, or some other suitable fluid under pressure, which is communicated tothe cylinder 12 by means of a passage 14 formed in the casing 1, and around the inlet opening to which an annular collar 15 is sealingly arranged. Compressed air is delivered by means of a pipe 16 which is connected to a fitting (not shown) on the axle casing (not shown). A piston return spring 17 is housed in a pocket in the casing 1 and bears against the piston 11 as shown to bias the piston towards it de-activated position. It will be appreciated that compressed air may be delivered to the cylinder 12 via the pipe 16 and passage 14 by actuation of a valve suitably located in the driver's cabin of the vehicle to which the differential is fitted. The compressed air drives the piston 11 axially in the cylinder 12 and causes the sleeve 13 to axially move the annulus 6 to cause engagement between the spline theeth 9 and 10 to thereby lock the bevel gear 3 against rotation. When differential action is again required, the valve in the driver's cabin is returned to the deactivated position and the spring 17 returns the piston 11 to the position shown in the drawing whereby the spline teeth 9 on the annulus 6 are disengaged from the spline teeth 10 on the bevel gear 3. While the above described embodiment of the invention is presently preferred, it should be appreciated that the specific form described is not essential to the invention. For example, the annulus 6 may be replaced by a segment formed with spline teeth similar to 9 adapted to engage the spline teeth 10 on the bevel gear 3, in which case the sleeve 13 would be replaced by a suitable connecting rod or element. Similarly, the piston t1 may be replaced by some form of mechanically or electrically operated actuator. For example, the annulus or segment may form part of an electro-magnetic actuator to cause suitable locking of the bevel gear. In the above described embodiment, the differential casing 1 is adapted to be substituted for an existing differential casing in a non-locking differential to thereby convert the differential into a locking differential. Of course, the differential casing may be substituted at the time of initial manufacture where a locking differential is required. Although substitution of the described differential casing is presently preferred, it may be possible where the structure of the differential casing is such as to facilitate conversion, to convert an existing non-locking differential casing to a locking differential casing by the addition of the locking system components described above. The entire contents of the provisional specification lodged with Australian Patent Application No. PG 2642 are hereby imported into this specification and form part of the disclosure of this specification. The claims form part of the disclosure of this specification.

Claims: Claims: 1. A differential locking system, in which the differential includes a differential carrier supporting a pair of bevel gears adapted to be splined to axle shafts and at least one pinion gear which meshes with said pair of bevel gears, said locking system including locking means keyed or splined to said carrier so as to be capable of axial movement relative to said carrier, said locking means including locking theeth or spline means adapted to engage similar tooth or spline means associated with one of the said bevel gears to prevent rotation of that bevel gear relative to said carrier. 2. The locking system of Claim 1, wherein said locking means includes an annulus splined to said carrier and slidable axially to cause engagement between spline teeth on said annulus and said locking tooth or spline means associated with said one of said bevel gears. 3. The locking system of Claim 1 or 2, wherein said differential carrier is formed with a cylinder housing a piston connected directly or indirectly to said locking means to cause said axial movement of said locking means relative to said carrier. 4. The locking system of Claim 3, wherein said piston and cylinder are annular and are arranged to surround the axle of the other of said bevel gears, said piston being connected to said locking means by means of an annular sleeve surrounding said bevel gears and including aperture means through which the or each pinion gear is located. 5. The locking system according to Claim 3,4 or 5 wherein passage means are provided for charging said cylinder with compressed air under the control of valve means. 6. A locking differential comprising a differential carrier supporting a pair of bevel gears adapted to be splined to axle shafts and at least one pinion gear which meshes with said pair of bevel gears, and a locking system including locking means keyed or splined to said carrier so as to be capable of axial movement relative to said carrier, said locking means including locking tooth or spline means adapted to engage similar tooth or spline means associated with one of said bevel gears to prevent rotation of that bevel gear relative to said carrier, and means carried by said differential carrier for causing said axial movement of said locking means relative to said carrier. 7. A kit for converting a differential to a locking differential, said kit including locking means adapted to be keyed or splined to a differential carrier so as to be capable of axial movement relative to said carrier, said locking means including locking tooth or spline means, and a replacement bevel gear formed with tooth or splined means which are adapted to co-operate with said tooth or spline means associated with said locking means to prevent rotation of that bevel gear relative to said carrier, and means adapted to be associated with said carrier for causing axial movement of said locking means relative to said carrier to use

Inventors: ROBERTS, ANTHONY DAVID
Applicants: ARB CORPORATION LIMITED
Application year: 1985
Main classification: F16H1
IPC codes: F16H48