Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2000-03-08
2001-12-11
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06329728
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a cylinder-type linear synchronous motor, and more particularly to a cylinder-type linear synchronous motor wherein a movable element carries out linear motion.
Currently, a cylinder-type linear stepping motor or linear pulse motor is commercially available as a cylinder-type linear motor. The cylinder-type linear stepping motor commercially available includes a stator constituted of a plurality of stator cores formed on an inner peripheral surface thereof with a plurality of small teeth so as to be arranged in an axial direction of a direct-acting shaft and having exciting windings wound thereon and a movable element including a movable section fixed on the direct-acting shaft, provided therein with permanent magnets and formed on an outer peripheral surface thereof with a plurality of small teeth in a manner to be arranged in the axial direction of the direct-acting shaft. In the linear stepping motor thus constructed, the exciting windings on the stator cores are excited in turn, to thereby permit thrust to be generated between the small teeth of the stator and those of the movable element, leading to linear motion of the direct-acting shaft. Unfortunately, the linear stepping motor fails to provide thrust at an increased magnitude, although it exhibits increased position control performance.
In view of the foregoing, the assignee proposed a cylinder-type linear synchronous motor which provides thrust at an increased magnitude although it is somewhat deteriorated in position control performance, as disclosed in Japanese Patent Application No. 130051/1998.
More particularly, the cylinder-type linear synchronous motor proposed is constructed into a structure that a plurality of annular windings are fitted in a plurality of slots of a stator core corresponding thereto, respectively. However, the structure causes the stator core to be designed for every motor varied in length in an axial direction thereof. Also, it renders assembling of the stator troublesome. Further, it fails to reduce a width of an opening of each of the slots positioned opposite to a movable element, to thereby enhance performance of the motor.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a cylinder-type linear synchronous motor including a stator which permits a length thereof in an axial direction of the motor to be set as desired.
It is another object of the present invention to provide a cylinder-type linear synchronous motor including a stator which is constructed so as to facilitate assembling thereof.
It is a further object of the present invention to provide a cylinder-type linear synchronous motor which includes annular windings and permits a reduction in width of an opening of each of slots of a stator facing a movable element.
In accordance with the present invention, a cylinder-type linear synchronous motor is provided. The cylinder-type linear synchronous motor generally includes a movable element and a stator. The movable element includes a direct-acting shaft arranged so as to be reciprocated in an axial direction thereof, a magnet mount fixed on the direct-acting shaft and at least one permanent magnet train constituted by a plurality of permanent magnets fixed on the magnet mount and arranged in the axial direction. The permanent magnet train may be constituted by either a plurality of permanent magnets physically combined with each other or a plurality of permanent magnets formed by physically magnetizing a single magnetic body so that N and S poles alternately appear on the magnetic body in a longitudinal direction thereof. When plural such permanent magnet trains are arranged, the permanent magnet trains are preferably spaced from each other at equal intervals in a peripheral direction of the direct-acting shaft. In this connection, annular permanent magnets magnetized so that N and S poles appear on an outer surface thereof each may be provided so as to constitute each of the permanent magnet trains. More specifically, the annular permanent magnets are securely fitted on an outer periphery of the magnet mount of the movable element so that N and S poles are alternately arranged so as to be spaced from each other at predetermined intervals in the axial direction. Such arrangement of the annular permanent magnets causes portions of the annular permanent magnets opposite to magnetic pole sections of a stator core to act as permanent magnets constituting each of the permanent magnet trains. In corporation of the annular permanent magnets into the motor permits the movable element to be simplified in structure and facilitates mounting of the permanent magnets on the magnet mount.
The stator includes at least one stator core unit and a plurality of annular windings arranged so as to be spaced from each other at predetermined intervals in the axial direction and in a manner to surround the movable element. The stator core unit includes a plurality of magnetic pole sections arranged so as to be opposite to the permanent magnet train of the movable element with a redetermined interval defined therebetween and a yoke for magnetically connecting the magnetic pole sections to each other. The magnetic pole sections are spaced from each other at intervals in the axial direction so that a slot in which each of the annular windings is fitted at a part thereof is defined between each adjacent two of the magnetic pole sections. The slots each include an opening open to the movable element and a winding receiving section in which at least a part of each of the annular windings is received. The opening has a width in the axial direction formed so as to be smaller than a width of the winding receiving section in the axial direction.
In the cylinder-type linear synchronous motor, a direction of an exciting current flowing each of the annular windings or exciting windings of the stator is shifted to change a polarity of a magnetic pole appearing on a magnetic face of each of the magnetic pole sections, to thereby generate a shifting magnetic field, resulting in generating thrust between the permanent magnet train and the plural magnetic pole sections which acts to shift the direct-acting shaft in the axial direction. An AC current may be used as the exciting current. This permits a polarity appearing on the magnetic pole face of each of the magnetic pole sections to be varied depending on a frequency of the current. Multi-phase exciting currents may be flowed through the exciting windings. This results in the motor being a multi-phase synchronous motor, to thereby provide thrust at an increased magnitude. When a polarity of the exciting current and a magnitude thereof are fixed, a position of the movable element is fixed because only suction force acts between the stator and the movable element.
In the case of a rotary motor, excitation of each magnetic pole section of a stator core unit requires winding a conductive wire on an outer periphery of the magnetic pole section. Application of such a technique of the rotary motor into a linear synchronous motor causes a length of the motor in an axial direction thereof to be increased and operation of forming windings to be highly troublesome. In view of the problem, in the present invention, the exciting windings of the stator each constituted of the annular winding formed by annularly winding a conductive wire so as to surround a circumference of the movable element. Also, the present invention, as described above, is so constructed that the slot in which each of the annular windings is fitted at a part thereof is defined between each adjacent two of the magnetic pole sections. Such construction permits a magnetic flux generated from the exciting winding fitted in each of the slots to circulatedly flow through two magnetic pole sections adjacent to the exciting winding, so that magnetic poles different from each other may appear on the magnetic pole faces of the adjacent two
Kitazawa Kazuyuki
Suzuki Nobuji
Takizawa Kazuhiko
Jones Judson H.
Ramirez Nestor
Rankin, Hill Porter & Clark LLP
Sanyo Denki Co. Ltd.
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