Motor Reducer With Braking Means

1. Field of the Invention

This invention relates to motor speed reducers incorporating brakes and especially to such speed reducers in which the brakes are adapted to dissipate kinetic energy of the vehicle adiabatically.

2. Discussion of Related Art

Numerous motor reducers with braking means exist. Some are equipped with brakes acting on the mechanical elements of the reducer rotating at a low velocity, while others have brakes acting directly on the electric motor or on the mechanical elements rotating at a high velocity. However, in order to absorb the kinetic energy acquired by a vehicle in motion in an adiabatic manner, it is necessary for the braking means to consist of a certain mass. If this mass is distributed over one or more mechanical elements rotating at a high velocity, the manufacture and use of such mechanical elements poses certain important problems of equilibrium. Furthermore, the braking of elements rotating at high velocities generates thermal phenomena that are difficult to control. Conversely, if braking is effected on elements rotating at a low velocity, it is necessary, in order to apply sufficient braking power, to develop a very high braking force couple. In this case, the dimensions and the weight of the pieces constituting these mechanisms are large and thus generate space and weight problems which are incompatible with advanced vehicle concepts. In a general manner, all brakes are located within the mechanical unit constituting the motor-reducer-brake assembly and during braking they generate heat, which strongly heats the oil bath, thereby shortening the life of the lubricant.

The present invention remedies these disadvantages by effecting braking on mechanical elements placed outside the housing of the motor-reducer-brake assembly and rotating at an intermediate speed. In this fashion, the brake elements, located outside, are well cooled and readily accessible for control, inspection and repair. The rotating parts of the braking means have sufficient mass to absorb the kinetic energy of the vehicle adiabatically and pose no balancing problems, as they are rotating at a moderate velocity. The stationary parts of the braking means are able to develop high braking power by applying a moderate force couple and they are of reduced weight and volume.

The invention will become more apparent with the aid of the single figure representing a cross-section through the motor-reducer-brake.

A frame 1 supports a stator 2 of an electric motor, having a rotor 3 rotating at a high velocity. The rotor 3 is equipped with an elastic shaft 4 carrying at one end a pinion 5 meshing with a first gear train of the reducer. The elastic shaft 4 rests on two bearings, of which a single bearing 6 is shown in the FIGURE. The bearing 6 is part of a intermediate mechanical element 7, which also performs other functions. In effect, the mechanical element 7 is equipped with a collar, serving as the locking flange 8 for the entire mechanical unit. Furthermore, the center body of the intermediate mechanical element 7 possesses a symmetry of revolution and is provided inside with a toothed ring 9 upon which the satellite pinions 10 of a shaft 11 rotate at a moderate velocity. Shaft 11 has an external ferrule 12. The center body of the intermediate mechanical element 7 also performs the function of a journal 13 by receiving the wheel hub 15. Finally, the intermediate mechanical element 7 serves as the support for the satellite holder 16 of the second gear train of the reducer. On the satellite holder 16, the satellites 17 are mounted; they mesh on the one hand with a pinion 18 that is integral with the shaft 11 rotating at a moderate speed, and on the other, with an inner ring 19 that belongs to the wheel hub 15. The wheel hub 15 also performs a number of functions. In addition to the abovementioned function of serving as the inner toothed ring 19 of the second gear train of the reducer, it supports a bearing 20 of the shaft 11 rotating at a moderate velocity and serves as the housing 21 of the reducer assembly, insuring the tightness of the assembly by means of the double gaskets 22 and 23.

This mechanical unit thus has a ferrule 12 rotating at a moderate velocity and carrying, in a preferred embodiment, a brake disc 24, secured thereto by appropriate means. The brake disk 24 rotates at a moderate velocity and has sufficient mass to be able to effect substantial adiabatic braking without generating balancing problems. Furthermore, the stationary parts of the braking system, not shown, collaborate with the brake disk 24 in developing high braking power by the application of a moderate braking force couple. The said stationary parts of the braking system thus may consist of mechanical elements of reduced weight and volume. On the other hand, the outside location of all of the elements of the brake insures excellent cooling of all of the active parts, simplifies the entire cooling system of the brake and provides the great advantage of ready accessability for inspection and repair.