Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2000-04-21
2002-02-19
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
C310S013000
Reexamination Certificate
active
06348746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a slider unit with a built-in moving-coil linear motor, which has been extensively used in semiconductor and liquid crystal display industries, measuring instruments, assembling machines, machine tools, industrial robots, conveyors and others.
2. Description of the Prior Art
In recent years, multi-axis stages and moving mechanisms such as X-Y plotters employed in the diverse technical fields as described above have required more and more a slider unit, which is compact or slim in construction and light in weight, and moreover able to operate with high propulsion, high speed and high response to provide high speed travel and accurate position control for works, tools, articles and instruments. Linear motors commonly used in the slider units involve two broad types. The first, called moving-magnet linear motor, has a stator of an armature coil arranged lengthwise over the entire length of a bed of stationary part, and a moving-field magnet of permanent magnet arranged on a table movable in a sliding manner along the length of the bed. The second, called moving-coil linear motor, has a stator of field magnet mounted on the bed, and moving-armature coils distributed in space one after another on the table such that they lie a preselected electrical angle out of phase.
A moving-coil linear motor is disclosed in Japanese Patent Laid-Open No. 68365/1993, in which field magnets on a stator are arranged with unlike poles opposing to each other and alternating lengthwise. A slider is mounted to the stator for sliding movement through linear motion guide units. The slider is provided with a moving element having armature coils, which are distributed in space so that their magnetic axes lie 120° apart. The armature coils are applied with the currents of U-, V- and W-phases that are 120° in the electrical angle out of phase, and therefore a driving force of a desired direction may occur in the moving element by the control of the conducting direction.
Japanese Patent Laid-Open No. 311723/1994 discloses a dc linear motor and a driving unit provided with the same. In the linear motor, the armature coils are joined to the coil boards with machine screws through the intermediate assembling parts, together with the coil yokes that are provided separately to fasten the armature coils and coil boards. Thus, the linear motor is constructed with a series of motor units connected, each of which is composed of at least two armature coils, a combined coil board and circuit board allotted to the set of armature coils. The driving unit may ensure the stroke most suitable for the operating stroke by either increasing or reducing any number of the motor units connected, depending on the apparatus employing the linear motor.
Japanese Patent Laid-Open No. 38503/1994 discloses a moving-coil linear motor, in which permanent magnets are arranged such that the poles on the magnets alternate lengthwise in polarity, and a moving element is arranged for lengthwise movement. The moving element is provided with polyphase coils exposed in a magnetic gap formed on surfaces of the permanent magnets, and field detecting means to control the conducting direction to the polyphase coils. In the prior linear motor, the permanent magnets are arranged spaced apart and another permanent magnets magnetized lengthwise are alternately arranged and fixed between any adjoining first permanent magnets such that any like polarity comes near on their surfaces, thereby proving a continuous row of permanent magnets.
In addition, a moving-coil linear motor is disclosed in Japanese Patent Laid-Open No. 127037/1998, which comprises a stator of integral permanent magnet magnetized such that poles on the magnet alternate lengthwise in polarity, and a polyphase coil arranged for lengthwise movement along the permanent magnet in a magnetic gap shaped by the permanent magnets.
Japanese Patent Laid-Open No. 64487/1993 discloses a positioning table composed of a moving-magnet of permanent magnet attached to a worktable, means for detecting a position of the table, a coil for a stator made conductive depending on the position of the table, and a polyphase motor changing selectively over a conducting direction of electric current.
Moreover, Japanese Patent Laid-Open No. 300721/1993 discloses a linear motor for sliding means, in which a yoke magnet is composed of a upper plate, lower plate and connecting plate, which are prepared separately and then assembled integrally with fixing means such as machine screws. According to this prior linear motor, the parts for the yoke magnet, or the upper plate, lower plate and connecting plate, must be made great in thickness to render less the flexure that might be caused by the attractive force exerted from the opposing magnets. As a result, the sliding means becomes large in height in cross section thereof, thus failing in compactness of the entire apparatus.
For the slider unit having the moving-coil linear motor that is linearly moved together with a worktable by virtue of interaction between magnetic flux generated in a pair of field magnets arranged on confronting inside surfaces of the magnet yoke, each to each surface, and an electric current flowing through an armature coil arranged in a gap provided between the field magnets, thus, an improved linear motor has been desirable, which has the stiffness enough to withstand the attractive force due to the magnet even when the magnet yoke is made less in thickness, so that the slider unit may be made entirely slim or compact in construction and the worktable may operate with highly accurate speed and position control.
SUMMARY OF THE INVENTION
The present invention, therefore, has as its primary object to overcome the subject as described just above and more particular to provide a slider unit with a built-in moving-coil linear motor, in which driving means actuated by the moving-coil linear motor is incorporated, and a magnet yoke, despite made less in thickness, is enhanced in stiffness, thereby relieved from possible strain due to the magnetic force so that the slider unit may be reduced overall height to be made slim in construction and also makes it possible to provide accurate speed and position control.
The present invention is concerned with a slider unit with a built-in moving-coil linear motor, comprising a bed supporting thereon a magnet yoke, a table movable through linear motion guide units in a sliding manner with respect to the bed, end plates mounted to lengthwise opposing ends of the bed, each to each end, a pair of field magnets arranged on inwardly confronting surfaces of the magnet yoke in such a manner that poles on the field magnets alternate in polarity along a moving direction of the table and also unlike poles confront each other across an air gap between the field magnets, and a moving-coil assembly mounted to the table and provided with armature coils arranged in the air gap, wherein the moving-coil assembly moves together with the table by virtue of electromagnetic interaction of magnetic flux of the field magnets with current flowing in the armature coils, the magnet yoke is composed of a pair of confronting sections having thereon the field magnets, each to each section, and a connecting section to join the confronting sections to each other at their lengthwise edges extending along the moving direction of the table, and the moving-coil assembly extends into the air gap, with passing through a sidewise opening formed at another edges of the confronting sections extending along the moving direction of the table.
In accordance with an aspect of the present invention, the connecting section is formed integrally with the confronting sections. Moreover, it is preferable that both the table and the bed are made of aluminum alloys.
In accordance with another aspect of the present invention, the bed is composed of a bottom and a pair of upright walls rising at sidewise opposing sides of the bottom and extending along the moving direction of the table
Fujisawa Shoji
Ida Eiji
Browdy and Niemark
Nguyen Tran
Nippon Thompson Co. Ltd.
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