GEARBOX WITH A STATIONARY FEED CANNULA

Description

[0001] The present invention relates to the lubrication of a hollow shaft, and a set of gearbox pinions.

[0002] More specifically, it relates to a gearbox according to claim 1.

[0003] Gearbox lubrication is generally done by means of an oil bath. The lubricant is sprayed throughout the gearbox by the rotation of the gearbox's mechanical components, particularly the differential crown. The pinions are lubricated by direct spraying. The shafts are often hollow, with the oil circulating inside them.

[0004] The presence of an additional electric motor increases the overall height of a hybrid gearbox compared to conventional gearboxes. Under these conditions, the oil can hardly be sprayed over the entire height of the gearbox, especially at low speeds. The oil spray inside the gearbox is then no longer sufficient to meet lubrication requirements.

[0005] Publication FR 2 877 065 discloses a device for the forced lubrication of gear wheels, comprising a fixed supply cannula, housed inside a hollow shaft and pierced with lubrication holes targeted on the pinions.

[0006] Publication FR 2 888 909 describes another gearbox, in which the oil reaches the inlet of an internal lubrication device, by projection inside the gearbox.

[0007] In some hybrid architectures, the arrangement adopted to simultaneously ensure the motion input of a thermal engine and an electric traction machine, on the primary line of the gearbox, is to fit two concentric shafts, fixing them respectively to the thermal engine and to the electric machine. When the two motive sources are arranged at the two ends of the primary line, there is no longer an opening available to let oil into a lubrication cannula.

[0008] The present invention aims to ensure the internal lubrication of a hollow gearbox shaft, when the ends of this shaft are not accessible from the inside of the gearbox, to introduce oil into a forced feed cannula.

[0009] To this end, it proposes that the inlet of the cannula receives oil from an external lubrication circuit, through an opening in the casing.

[0010] In a particular embodiment of the invention, the hollow shaft contains a solid shaft concentric therewith, which carries pinions, and has an internal bore in sealed connection with an outlet of the cannula.

[0011] The gearbox proposed by the invention comprises such a lubrication device.

[0012] This solution is applicable to lubricate any hollow shaft, whose inlet is not easily accessible. However, it finds a preferred application on hybrid gearboxes, with press-fitted primary shafts, connected to the thermal engine and to an electric machine.

[0013] The present invention will be better understood upon reading the following description of a non-limiting embodiment thereof, with reference to the appended drawings, in which: THE figure 1A et 1B are two exterior overviews of the same box, in different orientations. figure 2 is a partial section of the box, and the figures 3A et 3B show the solid shaft, and the hollow shaft of the box, with the cannula.

[0014] The lubrication system illustrated by the figures 1A et 1B allows the desired quantity of oil to be brought into the primary line 2 of the gearbox 1, via two conduits: a first conduit 3a in the upper part of the gearbox, and a second conduit 3b at the level of the primary line 2. An external pump 4 circulates the oil in this circuit, outside the gearbox. It circulates the oil contained in the lower part of the gearbox. This pump is preferably electric in order to easily control it according to the rotation speed of the different shafts and the lubrication requirements.

[0015] The box thus has an oil inlet 10b in the upper part, and another oil inlet at its primary line. The external circuit comprises the pump 4, circulating the oil contained in the lower part of the box 1, and the conduits 3a, 3b: the conduit 3b connected to the inlet of the cannula, and the conduit 3a connected to an inlet point of the box 10b higher than the hollow shaft 7. In the non-limiting example which is described, the pump 4 is located outside the casing. Within the scope of the invention, it can also be located inside the box 1.

[0016] The same gearbox 1, in section on the figure 2 , comprises a solid primary shaft 6 and a concentric hollow primary shaft 7. The proposed lubrication device comprises a cannula 5, the end of which also appears on the figures 3A et 3B . The cannula 5 allows the oil to be brought from the outside of the gearbox to the inside of the shafts to be lubricated 6 and 7. The inlet 5a of the cannula receives the oil from the external lubrication circuit, through an opening 10a of the casing 10.

[0017] The two shafts 6, 7 are the concentric primary shafts of the gearbox 1, connected respectively to the heat engine and to an electric machine (not shown). The proposed device is intended to lubricate the gearbox 1, through the hollow shaft 7 internal to the casing 10 of the gearbox: this device comprises the fixed supply cannula 5 which extends inside the hollow shaft 7. The solid shaft 6 has an internal longitudinal bore 13, which follows the cannula 5. The bore 13 is in sealed connection with the cannula 5, and has targeted lubrication holes 8, located for example under the gear pinions 9. The holes 8 are visible on the figures 3A et 3B . The cannula 5 is fixed on the casing 10 of the box. It is engaged inside the hollow shaft 7.

[0018] On the figure 3A , we see the cannula 5 and the solid shaft 6, without the hollow shaft. On the figure 3B we see the hollow shaft which partially covers the cannula 5 and the solid shaft 6. The outlet end 5b of the cannula facing the longitudinal bore 13 of the solid shaft 6, is open, so that the oil penetrates into the solid shaft 6. The end 5b of the cannula carries a seal 11 and a guide bearing 12 in the hollow shaft, which ensure the connection of the cannula 5 with the latter.

[0019] As indicated above, the cannula 5 is supplied with oil by the pump through the conduit 3b. The inlet of the cannula receives the oil from the external lubrication circuit through this conduit, through the opening 10a of the casing. The pump 4 simultaneously supplies the conduit 3a to lubricate the upper part of the gearbox, and the conduit 3b to supply the cannula 5. This double supply makes it possible to optimize the overall lubrication of the entire gearbox. The routing of the oil to targeted lubrication points makes it possible to optimize the mechanical efficiency of the gearbox. By bringing the oil directly to the places where it is needed, it is possible to lower the total quantity of oil required in the gearbox. The reduction in the volume of oil reduces friction in the gearbox and improves its efficiency.

Claims

1. Gearbox (1) comprising, in a casing, a hollow primary shaft (7) concentric to a solid shaft (6), and a lubricating device comprising, on the one hand, a cannula (5) for supplying targeted lubrication points (8) of the gearbox, said cannula being fixed to the casing of the gearbox (1) and extending inside the hollow shaft (7), and, on the other hand, a lubricating circuit (3a, 3b) external to the gearbox (1),said lubricating device in which the inlet (5a) of the cannula (5) receives oil from the external circuit (3a, 3b) through an opening (10a) in the housing, characterized in that the external circuit comprises a pump (4) circulating the oil contained in the lower part of the gearbox (1), a first duct (3) connected to the inlet (5a) of the cannula, and a second circuit (3a) connected to an inlet point (10b) of the gearbox higher than the hollow shaft (7).

2. Gear according to claim 1, characterized in that the hollow shaft surrounds a solid shaft (6) which is concentric with it, carries the gears and has an internal bore (13) in sealed communication with the outlet (5b) of the cannula.

3. Gear according to claim 2, characterized in that the solid shaft (6) has lubrication holes (8) for pinions (9).

4. Gear according to claim 3, characterized in that the end (5b) of the cannula facing the solid shaft (6) carries a seal (11) and a guide bearing (12) in the hollow shaft connecting the cannula (5) to the latter.