1. Field of the Invention
The present invention relates to a linear motor drive unit which is connected to a movable body supported movably on a stationary portion such as a head, like a work table and the like of a machine tool for instance, and which drives such a movable body in reciprocation while giving a predetermined movement amount to it.
2. Description of the Related Art
In various tables of the machine tool, a travelling portion of an industrial robot, various carrier apparatuses and the like, it is required to linearly guide the movable body on the stationary portion such as head and column, and position it to a predetermined position. Hitherto, as such a guide structure of the movable body, one shown in FIG. 6 is generally well known. Concretely, it is constituted such that a movable body 102 is supported by arranging one pair of linear guide units 101, 101 on a stationary portion 100, a ball screw 103 is disposed below the movable body 102, and the ball screw 103 is driven by a rotary motor 104. The linear guide unit 101 is composed of a track rail 105 incorporated through balls, and slide blocks 106. Accordingly, by fixing the track rails 105 to the stationary portion 100 and the slide blocks 106 to the movable body 102, it becomes possible to freely guide the movable body 102 on the stationary portion 100 along the track rails 105. Further, the ball screw 103 is one in which a screw shaft 107 meshes with a nut member (not shown in the drawing) through balls and the nut member is fixed to the movable body 102, while the screw shaft 107 is provided rotatively and parallel to the track rails 105 of the linear guide units 101. Therefore, it is adapted such that if the screw shaft 107 is rotated by the rotary motor 104, the nut member is moved on the screw shaft 107 in compliance with rotations of the rotary motor 104 to thereby give a thrust in a direction along the track rails 105 to the movable body 102 and, further, the movable body 102 can be stopped at a predetermined position.
In order to accurately position the movable body on the stationary portion by using the ball screw in this manner, it is required to suitably control a rotational speed and a rotational amount of the rotary motor. However, a precision rotary motor unitized with an encoder being stored and a feedback control function being provided is supplied in a market in various kinds. Accordingly, a person who intends to construct the aforesaid guide structure can very easily construct it merely by purchasing that precision rotary motor, installing it to the stationary portion, and connecting it to the screw shaft through a coupling.
On the other hand, in recent years, also a guide structure in which the movable body is directly driven by using a linear motor without using the ball screw becomes increased. However, different from the rotary motor in which a stator and a rotor are integrated within a casing, magnet plates and coils are under a separated state in the linear motor, so that there arises a necessity to individually fix the magnet plates to the stationary portion and the coils to the movable body. That is, the linear motor is not traded under a state that the magnet plates and the coils are integrated, so that a handling after the purchase is very troublesome. Especially, since it is required that the magnet plate and the coil are faced each other with a very small predetermined gap, in case where these magnet plate and coil are individually handled, a work for attaching them requires much labor, and such a trouble that the magnet plate is brought into contact with the coil to thereby damage them and such an accident that a hand is nipped between the magnet plate and the coil are liable to occur.
Further, also a linear encoder for detecting a movement amount of the coil with respect to the magnet plate is completely separately traded and, in order to realize the feedback control function, it is necessary to purchase the linear encoder separately from the linear motor and incorporate it to the stationary portion and the movable body. And, when completely individually incorporating the magnet plate, the coil and the linear encoder in this manner, a constant accuracy is required for every attaching work, so that the work becomes very troublesome.
Also a linear motor in which these magnet plate, coil and linear encoder are completely unitized exists in the market, but such a linear motor is directed to a specified use, so that a room for improving it in compliance with required conditions scarcely exists.
The invention has been made in view of such problems, and its object is to provide a linear motor drive unit capable of being easily and safely attached as a drive source of various guide structures, and capable of being flexibly applied to required uses.
In order to achieve the above object, the invention provides a linear motor drive unit attached to a movable body linearly movable with respect to a stationary portion and used for the purpose of giving a thrust to the movable body, comprising: a long base plate; a magnet plate which is provided on the base plate, and in which plural magnetic poles are arranged at a predetermined pitch along a longitudinal direction of the base plate; a top plate having a face for attaching the movable body; a movable element fixed to the top plate and facing the magnet plate; one pair of track rails provided on the base plate along both sides of the magnet plate; and slide members fixed to the top plate along both sides of the movable element and moving on the track rails while keeping an un-contact state between the movable element and the magnet plate; characterized in that the track rails and the slide members are constituted so as to be able to freely divide in a direction along which the movable element is separated from the magnet plate.
According to such a technical means, since the magnet plate is fixed to the base plate, while the movable element is fixed to the top plate and, moreover, since the top plate is incorporated to the base plate through the slide members and the track rails, it becomes possible to handle the magnet plate and the movable element as an integrated one in which they are unitized. Therefore, a work for attaching the magnet plate and the movable element to the stationary portion and the movable body can be easily performed, so that it become possible to avoid such troubles that, during such a work, the magnet plate is damaged and a hand is nipped between the magnet plate and the movable element. That is, since the track rails and the slide members are constituted so as to be able to divide in a direction along which the movable element is separated from the magnet plate, by inserting the linear motor drive unit of the invention to a lower side of the movable body supported movably by linear guide units, and fixing respectively the base plate to the stationary portion and the top plate to the movable body, the magnet plate and the movable element can be easily faced with a predetermined gap.
Further, it is also possible to incorporate a linear encoder between the base plate and the top plate and, in case of being constituted in such a manner, since the linear motor and the linear encoder can be handled as an integrated one in which they are unitized, it becomes also possible to construct easily and within a short time a guide structure having a feedback control function.
Accordingly, the linear motor drive unit of the invention can be easily applied to a wide use, and it becomes possible to intend to reduce a cost by mass production.
Further, in regard to a limited use, it is also possible to use the top plate as a table as it is. In this case, since it results in the fact that a magnetic force applied between the magnet plate and the movable element gives a pre-load between the track rail and the slide member, it becomes possible, in a range not impairing such a pre-load, to use the top plate as the table.