Lubrication system for reduction unit, in particular epicycloidal speed reducer

0001The invention relates to the lubrication of epicycloidal reduction units, in particular small-sized ones associated to electric motors, of the "brushless" or of the "step" type, or direct current type, etc.

0002As known, such ratiomotor units are frequently applied in the construction of automatic machines, and in general, where it is necessary to actuate mechanisms with highly accurate movements.

0003It is therefore necessary that the reduction unit be provided with features suitable for those of the motors they are associated to, and therefore they must be constructed with accurate processes and very strict tolerances, so as to obtain accurate and almost clearance-free couplings.

0004The lubrication of the above motors is obtained by pouring a certain amount of lubricating oil (about 30% of the free volume) into the casing that contains the gearings; the motion of the latter causes the oil shaking, which is projected into all directions, thus reaching the means to be lubricated.

0005Due to the very limited sizes of the reduction units, the thermal exchange surface with the exterior is necessarily restricted; moreover, both the free volume inside the reduction and consequently the lubricant that can be poured therein are limited as well.

0006As a consequence, when the reduction units are subject to a very intensive use, overheating occurs that produces a series of disadvantages, such as increase of the inside temperature, abnormal power consumption, loss of the lubricant viscosity characteristics and therefore early wear of the gears, as well as their seizure, sometimes.

0007Object of the present invention is that of proposing a lubrication system for epicycloidal reduction units which should allow maintaining the operating temperature of the latter within fixed values, irrespective of the use conditions.

0008Another object of the invention is that of proposing a lubrication system which should be easily applicable to normal-production reduction units without requiring changes to the moving parts and without altering any functional feature.

0009The proposed system will appear more clearly from the following description, according with what reported in the claims and with reference to the attached drawing table, which shows a longitudinal section of an epicycloidal reduction unit provided with the lubrication system under discussion.

0010With reference to said figure, reference R globally denotes an epicycloidal reduction unit, provided with the lubrication system object of the present invention.

0011The reduction unit R is of the known type, for example a two-stage one, and it is provided for being coupled with electric motors, for example of the "brushless" or "step" type, or of direct current operated type, not shown.

0012The gearings 2 of the reduction unit R are housed into a sealed casing 1, also adapted for containing lubricating oil L for lubricating the same gearings 2, as detailed hereinafter.

0013The lubrication system under discussion comprises a tank 3, arranged outside the casing 1, in a position overhanging the latter with the reduction unit R set up for work.

0014The tank 3 is provided with a removable cover 3b, wherein there is made at least one calibrated hole 30, adapted for making the same tank 3 communicating with the exterior, which also communicates with the interior of the casing 1 by a duct 4 extending between the relevant bottom 3a and the top wall 1a of the casing 1.

0015The introduction of lubricating oil L into the reduction unit R is done through the tank 3, after the removal of the related cover 3b; the quantity of oil introduced is such as to fill the casing 1 fully and the same tank 3 partly.

0016The operation of the proposed lubrication system is very simple and totally spontaneous; the lubricating oil L is moved by the gearings 2 and made to circulate between the casing 1 and the tank 3, and vice versa, through the duct 4, with the speed function of the speed of rotation of the same gearings 2.

0017During said circulation, the oil yields part of its heat to the walls of the tank 3, which, being outside the casing 1, remains cooler than the latter.

0018The larger quantity of oil L in circulation compared to the reduction units of the known type, along with the extended thermal exchange surface, given by the walls of the same tank 3, ensures a good oil cooling, sufficient to keep the operating temperatures of the oil and of the reduction unit means within values that are largely lower than the overheating ones, also in case of especially heavy duty.

0019Any overpressures generated into the casing 1 are vented outside through the calibrated venting hole 30.

0020According to a first construction variant, not shown, two ducts 4 are provided, suitably arranged so that one is for delivery, from the casing 1 to the tank 3, and the other is for return, when the gearings 2 are actuated in one direction.

0021By rotating the gearings 2 in the opposed direction, there occurs an exchange of function between the two ducts 4, so that the delivery one becomes for return and vice versa.

0022By said first variant it is possible to increase the circulation speed of the lubricating oil L from the casing 1 to the tank 3 and vice versa, thus increasing the extent of the cooling.

0023A second variant, also not shown, provides for the tank 3 to be finned, for a further extension of the thermal exchange surface.

0024The proposed solution is as simple as effective, as the tests performed have unequivocally confirmed.

0025The system can be applied to the reduction units already normally produced without any other change than a hole into the casing, thus with the certainty of changing no functional feature at all.

0026If deemed advantageous, it is also possible to modify already produced reduction units to provide them with the lubrication system described.

0027The additional cost of the system for the production of the reduction units is minimal, and if compared to the advantages obtained, almost insignificant.