Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1990-10-31
1992-07-14
Stephan, Steven L.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 52, 310 80, 310 61, H02K 908, H02K 706, H02K 710, H02K 132
Patent
active
051305852
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hollow shaft motor through which is passed a ball screw shaft attached to a driven body and which drives that boll screw shaft, more particularly relates to a hollow shaft motor which enables cooling by a gas.
BACKGROUND ART
In the past, when driving machine tool tables and other driven bodies by a ball screw shaft and ball nut mechanism, the ball nut is attached to the driven body and the ball screw shaft is connected through a coupling etc. to the output shaft of the motor positioned at one end of the ball screw shaft. With this structure, however, it is not possible to make the apparatus compact as a whole and further it is difficult to make the force act on the center of gravity of the driven body. Therefore, a so-called hollow shaft motor has been proposed in which a ball nut is attached to the motor and a ball screw shaft is passed through the motor.
The ball screw shaft and ball nut, however, are susceptible to heat conducted from the motor, which is a heat generating body, and suffer from heat expansion, which has a detrimental effect on the ball screw shaft and ball nut mechanism, for which high precision operation is required. Further, a ball nut is attached to one end of a cylindrical shaft through which the ball screw shaft is passed. Consequently, the ball screw shaft and the cylindrical shaft form between them a bag with one end closed, so there is the problem that it is difficult to radiate away the heat.
DISCLOSURE OF THE INVENTION
Therefore, the present invention has as its object the resolution of the above problem by providing a hollow shaft motor having a cooling mechanism for the ball screw shaft and ball nut mechanism.
In view of the above object, the present invention provides a hollow shaft motor having a cylindrical shaft which has a ball screw shaft passed therethrough and which fixes a rotor at an outer circumference of a predetermined position in the longitudinal direction, one end of said shaft having a ball nut attached thereto, the ball nut being threaded together with the ball screw shaft, the hollow shaft motor characterized in that provision is made of a hole for introducing cooling gas into a motor housing at the side of a stator attached to the motor housing near to the ball nut and in that provision is made of other holes for introducing cooling gas in the cylindrical shaft in substantially the radial direction at the same side of the rotor opposing the stator, these being communicated with the bore of the cylindrical shaft.
The cooling medium is introduced from an introducing hole provided in the housing to the inside of the motor so as to cool the stator and rotor. Further, the cooling air is led from the other introducing holes provided in the cylindrical shaft to the inside of the cylindrical shaft to cool the ball screw shaft. On the other hand, the above-mentioned introducing holes are provided at the side of the stator and rotor near to the ball nut, so heat generated by the stator and rotor are blocked from being conducted to the ball nut.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view of a hollow shaft motor according to the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Below, the present invention will be explained in further detail based on the embodiment shown in the attached drawing. In the front and back of a stator having a winding 26 are provided a front housing 12 and a rear housing 14. These housings 12 and 14 support in a rotatable fashion a cylindrical shaft 20 provided with a bore 32 through a front bearing 16 and a rear bearing 42. At the front end of the cylindrical shaft 20 is fixed a ball nut 22. A ball screw shaft 24 screwed together with the nut 22 passes through the bore 32 of the cylindrical shaft 20. Further, a rotor 18 is fixed to the outer circumference of the cylindrical shaft 20 at a position opposing the stator 10.
The front housing 12 is provided with an introducing hole 28 for introducing compressed air, as a cooling gas, at a pos
REFERENCES:
patent: 3278774 (1966-10-01), Roller et al.
patent: 3402308 (1968-09-01), Henschke
patent: 3829726 (1974-08-01), Nilsson
patent: 4586394 (1986-05-01), Perkins
Endo Yuichi
Iwamatsu Noboru
Fanuc Ltd.
LaBalle C.
Stephan Steven L.
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