SEALING DEVICE BETWEEN A HYDRAULIC PUMP BODY AND A TRANSMISSION ELEMENT

The present invention relates to the field of hydraulic motor vehicle powered by a hydraulic unit including a hydraulic drive of an axle, which has a closed hydraulic pump driven by the vehicle's prime mover driving a first axle of the vehicle, and a hydraulic motor receiving hydraulic pressure created by the pump, for driving a second axle.

More specifically, it relates to a sealing device between the interior of a hydraulic pump body, comprising a first hydraulic fluid, and a first rotating shaft within a second hollow shaft extending through the pump body Y being lubricated by a second hydraulic fluid distinct from the first.

The invention also concerns a vehicle powertrain having a prime mover for driving the two wheels of a vehicle axle trees relays connected to a differential transmission, and a hydraulic pump driven from the same transmission differential of a hollow shaft 1' wherein rotates relay shaft of the transmission.

The invention also relates to a vehicle comprising such a power train.

When a hydraulic pump draws the differential motion transmission of an engine main body, which distributes the motion of the motor between the two wheels of a first axle, it is generally added to it, and most often fixed to the differential casing.

In an arrangement used in some transmissions purely mechanical four-wheel drive, the movement may be taken by a hollow shaft on the differential housing. This hollow shaft is transverse to the main axis of the vehicle, and contains relay shaft toward a front wheel, which rotates inside thereof with a velocity differential of up to + or - 300 revolutions per minute, according to slip between the wheels of the same axle. In the case of a four wheel drive system purely mechanical, the motion is transferred by a bell crank at 90° towards the rear axle of the vehicle. In the case of a hydraulically driven vehicle, the hollow shaft may be the motion input shaft of a hydraulic pump, which creates a hydraulic pressure drive to the rear axle, from mechanical energy taken from the differential.

An arrangement of this type is shown in Figure 1, where it is recognized the engine block 1 of a vehicle, its differential 2, and a pump body 3 secured by screws 4 thereon. Relay shaft 6, driven by the differential gearing mechanism (not shown), passes right through the pump 3, and exits through a cover 6b belonging to the shaft relay assembled, attached by screws 6a on the pump body. The pump 3 contains a functional fluid circulated through a pressure circuit 3a, 3b, to a hydraulic motor (not shown), driving another axle of the vehicle.

The motion of the shaft 6 relay is transmitted to a drive shaft 7 by a splined connection, and directs it to a wheel (not shown). Inside the body of the pump 3, the shaft relay 6, rotates, in a hollow shaft 9 (fig. 2), which receives as its movement from the differential. The transmission oil, lubricating the differential, is projected between the relay shaft and the hollow shaft, and extends up to the end of the latter. The pump includes its own functional fluid, separate from the transmission oil, and which must not be mixed thereto at the end of the hollow shaft, due to their different nature.

As shown in Figure 2, at this point there is an end of the hollow shaft 9, through which the shaft 6 relay, which extends outside of the pump. A fundamental problem at proper operation of the pump and the transmission, is to provide a seal therebetween, prior to exiting the shaft relay. The layout constraints are, on the one hand that there is a speed differential between the shaft and the hollow shaft relay, itself rotatably with respect to the pump housing, and that the functional fluid within the pump, should not mingle with the transmission lubricating oil, flowing between the shaft and the hollow shaft relay.

Finally, the difference in diameters between the shaft and the hollow shaft relay, is too narrow in order to superpose two seals radially on either side of 1' hollow shaft.

The present invention aims to provide a seal between the pump and the shaft relay at the end of the hollow shaft passing therethrough, into a particularly stressed.

For this purpose, it proposes a sealing device consisting of a rigid ring attached on the hollow shaft and two dynamic seals positioned on two opposite faces thereof, bearing on the ring and the housing of the pump body on the one hand, and on the ring and the shaft relay on the other hand.

The tightness of the hydraulic pump and the transmission to the output shaft relay, is ensured by the same support.

The invention will be better understood upon reading of the following description of a non-limiting embodiment thereof, by referring to the accompanying drawings, on which:

figure 1 is an exterior view of a power unit provided with a hydraulic pump attached to the differential, and

figure 2, illustrates the sealing arrangement proposed.

Figure 2, is shown in partial cut the pump body 3 (without its internal mechanism), indicating however by an arrow fl., the arrival of the oil to its inner race 3d. The shaft relay 6 and the hollow shaft 9 are also represented. The shaft relay 6 is supported by its cover 6b, 6d in bearings retained by " snap ring " 6c. The arrival of the transmission oil towards the end of the hollow shaft 9, is indicated by an arrow f2. The sealing device 12 proposed, is arranged inside the cover of the shaft relay 6b, attached to the body of the pump 3. the pump comprises a first hydraulic fluid. The shaft relay 6 rotates within the hollow shaft 9 which extends through the pump body. There is lubricated by the oil of the transmission, which constitutes a second hydraulic fluid distinct from the first. The shaft relay 6 exits the pump through its cover 6b, wherein it is supported by a bearing 6d, external to the pump body. The bearing 6d is an atmospheric, and is not lubricated.

The sealing device proposed is composed of a rigid ring 11, fixed on the hollow shaft 9, and two dynamic seals 12a and 12b positioned on two opposite faces thereof, bearing on the ring 11 and the housing of the pump body 3c on one side and with the ring 11 and the shaft relay 6 on the other hand. By dynamic seal, as used herein that each joint 12 has a lip in sliding contact on a surface of rotating contact, e.g. the banded for the upper seal ring and the shaft 6 relay for the bottom seal. The two seals 12 are therefore advantageously of lip seals. The ring 11 is preferably shrunk on a cylindrical outer 9a of the hollow shaft 9.

As discussed above, the invention extends to an aircraft engine (cGMP) vehicle, comprising a main motor for driving the two wheels of a vehicle axle trees relays connected to a differential transmission, a hydraulic pump driven from the same transmission differential by a hollow shaft within which rotates a relay transmission shafts, and the sealing device proposed. In the GMP, the banded ring 11 provides a double seal, by supporting on its upper part the seal 12b of the hydraulic motor, and on its lower the sealing gasket 12a for the output of the transmission. Another vehicle axle can be driven by means of hydraulic pressure supplied by the pump, without sealing problem, or oils, at the outlet of the shaft extends through the pump.

mixing relay