Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-08-10
2001-12-11
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S058000, C310S061000, C310S07500D, C310S06700R, C417S366000, C417S410300
Reexamination Certificate
active
06329731
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a driving unit including an electric motor and a planetary gear provided with an input shaft driven by said motor and an output shaft, said unit being provided with a cooling circuit for said motor including a positive displacement pump assuring the flow of a liquid in said circuit, the planetary gear including three main elements, namely: a sun wheel, a planet wheel carrier provided with several planet wheels, and a ring gear having an inner toothing meshed with said planet wheels, one of said three main elements being connected to the input shaft, another element being connected to the output shaft and the third acting as a reaction element.
DESCRIPTION OF THE RELATED ART
The heat generated by the electric motor has to be evacuated to avoid any risk of it overheating. In the prior art, this cooling may be assured by a cooling circuit which passes through the electric motor and wherein a coolant flows as a result of a pump located outside said electric motor. However, a unit of this type is bulky because it requires a mechanical transmission between the motor and the pump, as well as conduits for the liquid between these two elements and a radiator where the liquid is cooled.
For example, U.S. Pat. No. 5,127,485 discloses a driving unit of the type specified in the preamble, in the form of a compact unit driving a single wheel of a vehicle such as a golf cart. The bottom part of the casing which is common to the electric motor and the planetary gear contains oil which is pumped via an oil pump driven by a distinct electric motor, controlled as a function of the temperature of the main motor or the current passing through it, in order to cool the motor by flowing over the coils of its stator and over its rotor after having passed through a cooling radiator incorporated in the casing. Since this cooling system requires an additional motor to drive the pump and a special control unit to control the motor, it can be liable to breakdown and thus does not,guarantee sufficient cooling in all circumstances.
SUMMARY OF THE INVENTION
The object of the invention is thus to overcome the drawbacks of the prior art and to cool the electric motor using a particularly simple and compact device.
This object is achieved using a driving unit of the type indicated above, characterised in that the pump is driven by the planetary gear reaction element.
Thus, a mechanical member which is already present in the driving unit is used to drive the pump, which simplifies the construction in all circumstances. Moreover, the pump may advantageously be placed in the same casing as the planetary gear, which avoids using connecting conduits.
Preferably, the reaction element is the ring gear of the planetary gear and this ring gear forms at least part of the rotor of said pump.
Preferably the cooling circuit is provided with at least one adjustable valve, for example a flow limiter valve, controlled by an electronic control unit. It is thus possible to adjust the cooling of the motor automatically, as required by regulating the flow rate of coolant supplied by the pump.
Moreover, it is possible to cool the motor even when the output shaft is at rest. Indeed, in this case, the motor can be rotated by letting the reaction element rotate, which causes the coolant to flow.
Finally, according to a variant of the invention, the pump, the adjustable valve and the electronic control unit form a regulating means acting on the reaction element to regulate the speed and/or torque of the output shaft.
REFERENCES:
patent: 4578609 (1986-03-01), McCarty
patent: 5127485 (1992-07-01), Wakuta et al.
patent: 5718302 (1998-02-01), Hasebe et al.
patent: 6087744 (2000-07-01), Glauning
patent: 197 32 637 (1999-02-01), None
patent: 0 660 492 (1995-06-01), None
patent: 0 785 612 (1997-07-01), None
Arbanas Viktor
Zysset Ernst
Griffin & Szipl, P.C.
Mullins Burton S.
The Swatch Group Management Services AG
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