Magnet assembly for linear motor having cover member covering magnet plate

A magnet assembly for a linear motor includes a cover member having weak magnetic properties, which covers one or more magnet plates, and a fixing mechanism for positioning the end parts 14c of the cover member directly above permanent magnets and detachably fixing the cover member to the magnet plate. The cover member has a first surface part covering a surface of the magnet plate which faces an armature and second surface parts continuous from the first surface part and covering side parts of the magnet plate. Furthermore, the fixing mechanism is provided on the second surface parts. Through the use of this magnet assembly for a linear motor, it is possible to minimize a rise of the cover member from the magnet plate without deteriorating workability at the time of installation or replacement of the cover member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a magnet assembly for a linear motor comprising a magnet plate as a component of the linear motor and a cover member covering the magnet plate.

2. Description of the Related Art

Conventional linear motors comprise a magnet plate formed by sequentially arranging a plurality of permanent magnets in a single direction on an iron plate, and an armature as a movable body that is arranged opposite the upper surface of the magnet plate and which can move in the aforementioned single direction. Conventionally, in such a magnet plate for a linear motor, in order to protect the surface part of the magnet plate from foreign matter, such as swarf, etc., the magnet plate is covered with a protective cover made from a thin metal plate. In such a case, unless the protective cover is fully fixed in close contact with the magnet plate, foreign matter can intrude between the protective cover and the magnet plate. As a result, the protective cover rises and can come into contact with the armature opposing the magnet plate, and at least one of the armature, the protective cover, and the magnet plate may be damaged.

As a method of securing a protective cover in close contact with a magnet plate, there is a method for affixing the protective cover to the surface part of the magnet plate using an adhesive or the like. However, in this method, it is difficult to replace the protective cover after the protective cover is adhesively fixed.

Further, there is a method for affixing a protective cover to a magnet plate using screws. In order to prevent the protective cover from rising from the magnet plate, it is preferable to affix the area as close as possible to the central part of the protective cover with screws. However, it is impossible to provide threaded holes in the portion of the magnet plate corresponding to the area close to the central part of the protective cover, due to the presence of the permanent magnets. Further, in a linear motor, it is difficult to provide sufficient space for attaching screws between the opposing faces of the magnet plate and the armature.

As a method of overcoming such problems, a method of applying a magnetizable material to a protective cover of a magnet plate for a linear motor is proposed in Japanese Patent No. 4667602 (hereinafter referred to as “Patent Document 1”). In this method, the protective cover is attracted to the magnet plate only by the magnetic attraction force of the permanent magnets without the use of an adhesive, screws, or the like, and the aforementioned rising of the protective cover is suppressed.

In the method described in Patent Document 1, since the protective cover is fixed to the magnet plate only through the magnetic attraction force of the permanent magnets, it is necessary to strengthen the magnetism of the member used for the protective cover in order to more reliably prevent the protective cover from rising.

However, the stronger the magnetism of the member used for the protective cover, the worse the workability during installation and replacement of the protective cover.

Moreover, when producing a linear motor, a plurality of magnet plates are arranged to face the armature, as the moving body of the linear motor, and are arranged in a line with the permanent magnet arrangement direction of all the magnet plates being the same. In the aforementioned Patent Document 1, it is suggested that one protective cover covers a magnet assembly for a linear motor comprising a plurality of magnet plates arranged in a line. However, Patent Document 1 does not disclose a protective cover which covers from the face of the magnet plate opposite the armature to the side part. Thus, in the case of the magnet assembly for a linear motor disclosed in Patent Document 1, both edge portions of the joint between two adjacent magnet plates are exposed. Thus, foreign matter can accumulate in this portion, and the accumulated foreign matter may damage the armature, as the moving body.

Furthermore, in the case of manufacturing a magnet assembly for a linear motor having a length exceeding, for example, 10 meters, it is difficult to cover the entire magnet assembly with one protective cover. Thus, the protective cover used must be divided into multiple cover members. In this case, there is a joint between the ends of adjacent cover members. At such a time, if the cover members are not closely fixed to the magnet plate at the ends of the cover where the joint exists, there is a possibility that foreign matter may enter from that joint between the cover member and the magnet plate. As a result, there is the problem that the cover member may rise and come into contact with the armature, which may cause damage to the armature, protective cover, magnet plate, etc.

SUMMARY OF THE INVENTION

The invention provides a magnet assembly for a linear motor which can prevent foreign matter from entering between the cover member and the magnet plate while minimizing a rise of the cover member, without a reduction in workability during installation or replacement of the cover member.

According to a first embodiment of the present disclosure, a magnet assembly for a linear motor comprises a plurality of magnet plates formed by sequentially arranging a plurality of permanent magnets on a substrate in a direction, the magnet plates being disposed opposite to an armature as a moving body of the linear motor so as to align in the direction; a cover member of weak magnetic configured to cover one or more of the magnet plates; and a fixing mechanism configured to position an end part of the cover member just above the permanent magnets, and detachably fix the cover member to the magnet plates. The cover member includes a first surface part configured to cover surfaces of the magnet plates facing the moving body, and a second surface part extending from the first surface part, and configured to cover side parts of the magnet plates. The fixing mechanism is provided on the second surface part.

The present disclosure can also provide alternative embodiments, as listed below.

A second embodiment of the present disclosure provides the magnet assembly for a linear motor of the aforementioned first embodiment, wherein the cover member may be fixed to the magnet plate by the fixing mechanism so that the edge of the cover member in the direction is positioned at a center position of the permanent magnet.

A third embodiment of the present disclosure provides the magnet assembly for a linear motor of the aforementioned first embodiment or second embodiment, wherein the permanent magnets are sequentially arranged on the substrate of each of the magnet plates in the direction at a predetermined pitch, wherein the magnet plates are arranged in the direction so that the predetermined pitch of the permanent magnets is constant across the plurality of magnet plates, and wherein the first surface part of the cover member has a length that is an integral multiple of the predetermined pitch with respect to the direction of arrangement of the magnet plates.

A fourth embodiment of the present disclosure provides the magnet assembly for a linear motor of any one of the first embodiment to the third embodiment, wherein the cover member is disposed across two adjacent magnet plates so as to cover a joint between the two magnet plates.

A fifth embodiment of the present disclosure provides the magnet assembly for a linear motor of any one of the first embodiment to the fourth embodiment, wherein the cover member includes a plurality of the cover members.

A sixth embodiment of the present disclosure provides the magnet assembly for a linear motor of any one of the first embodiment to the fifth embodiment, wherein the cover member, which covers an endmost magnet plate of the magnet assembly, includes a third surface part extending from the first surface part, and configured to cover an exposed end face part of the endmost magnet plate.

A seventh embodiment of the present disclosure provides the magnet assembly for a linear motor of any one of the first embodiment to the sixth embodiment, wherein the fixing mechanism includes a screw, a threaded hole formed at the side part of the magnet plate, and a hole formed at the second surface part, and into which the screw is inserted.

DETAILED DESCRIPTION

The embodiments of the present disclosure will now be described with reference to the drawings. In the referenced drawings, the same members or the same functional components are given the same reference numerals. For ease of understanding, the drawings are modified in scale as appropriate. Furthermore, the embodiments illustrated in the drawings are merely examples of implementation of the invention, and the invention is not limited to the illustrated embodiments.

FIG. 1is a perspective view of a magnet assembly10for a linear motor according to an embodiment, wherein a portion of cover members14of the magnet assembly10are not mounted.

As illustrated inFIG. 1, the magnet assembly10for a linear motor (hereinafter referred to as a magnet assembly) includes a plurality of magnet plates13formed by sequentially arranging a plurality of permanent magnets11on a substrate12in a direction. Further, a surface (the upper surface inFIG. 1) of the magnet plate13opposite the substrate12is made flat with using a resin or the like.

The magnet assembly10is constructed by arranging a plurality of magnet plates13so as to be opposite to an armature (not shown) as a moving body of a linear motor and align in the above-mentioned direction. Note that, although only two magnet plates13are shown inFIG. 1, the number of magnet plates13is not limited thereto. The number of magnet plates13can be freely determined depending on the distance by which the armature is moved.

Furthermore, as shown inFIG. 1, the magnet assembly10includes a plurality of cover members14of weak magnetic configured to cover one or more magnet plates13, and fixing mechanisms15configured to detachably fix the cover members14to the one or more magnet plates13.

The cover member14includes a first surface part14awhich covers the surface of the magnet plate13facing the armature (not shown), and second surface parts14bextending from the first surface part14a, and cover the side parts13aof the magnet plate13, respectively.

The fixing mechanism15is provided so that end parts14c14cof the cover member14are positioned just above the permanent magnets11.

An example of the fixing mechanism15includes a screw15a, a threaded hole15bformed at the side part13aof the magnet plate13, and a hole15cformed at the second surface part14bof the cover member14and into which the screw15ais inserted. The hole15cis not limited to a round hole, but may be a notch.

Of course, the fixing mechanism15is not limited to a fixing mechanism using screws, if the cover member14can be easily and accurately positioned.

Due to the aforementioned configuration, the end parts14cand the first surface part14aof the cover member14of weak magnetic are brought into close contact with the surface of the magnet plate13on the side facing the moving body, by the magnetic attraction force of the permanent magnets11and by the positioning of the cover member14by the fixing mechanism15. In this regard, the “end part of the cover member” mentioned here means not only the just edge in the longitudinal direction of the cover member14, but also an area of certain width from the edge.

In order to facilitate the replacement and positional adjustment of the cover member14, the cover member14is made from a member of weak magnetic so that the cover member14can be easily detached from the magnet plate13against the magnetic attractive force of the permanent magnets13. It is preferable that the magnetic material, of which the cover member14is made, has a layer thickness of 0.1 mm or more and 1.0 mm or less, and a saturation magnetic induction of e.g. 0.3 tesla or more and 1.5 tesla or less. Stainless steel may be one example of such material of weak magnetic. Of course, the material of the cover member of the invention may be any member of weak magnetic, and is not limited to stainless steel.

In the present embodiment described above, the surface of the magnet plate13facing the armature can be covered by the first surface part14aof the cover member14, and the side parts13aof the magnet plate13can be covered by the second surface parts14bof the cover member14. As a result, the surface of the magnet plate13facing the armature is not exposed to the outside. Thus, it is possible to prevent the accumulation of dust or dirt on the surface of the magnet plate13facing the armature.

Furthermore, by forming such cover member14from a member of weak magnetic, it is possible to facilitate the replacement and positional adjustment of the cover member14. However, if the magnetic properties of the cover member14of weak magnetic are too weak, the cover member and the magnet plate14may not reliably come into close contact with each other, thereby, a gap may be formed between the cover member14and the magnet plate13. Accordingly, it is desirable to not only fix the cover member14to the magnet plate13by the magnetic attraction force of the permanent magnets11, but also to reliably bring the cover member14into close contact with the magnet plate13, by additionally using the fastening of screws or the like. In this respect, the second surface parts14bof the cover member14are fixed to the side parts13aof the magnet plate13by the fixing mechanism15. Due to this, even when there is no sufficient space between the magnet plate13and the armature facing the magnet plate13, the cover member14can be fixed in close contact with the magnet plate13by the fixing mechanism15.

By making use of the magnetic attraction force of the permanent magnets11and the mechanical fixing force of the fixing mechanism15in order to tightly contact the cover member14with the magnet plate13, it is possible to bring the cover member14into close contact with the magnet plate13without setting the magnetism of the cover member14to be excessively strong. Therefore, it is possible to prevent the work efficiency for the attachment or replacement of the cover member14from being reduced.

In particular, if the end parts14cof the cover member14are not in sufficiently close contact with the magnet plate13, foreign matter such as dust or dirt can enter the gap between the cover member14and the magnet plate13from the end parts14c, as a result of which the cover member14may be spaced away therefrom. In order to address this, in the present embodiment, the fixing mechanism15is provided so that the end parts14cof the cover member14having weak magnetic properties are positioned just above the permanent magnets11, thereby the effect that the end parts14cof the cover member14is spaced away from the magnet plate13can be minimized.

The magnet assembly10of the present embodiment will be described in greater detail.

FIG. 2is a top view showing the surface of the magnet assembly10on the side facing the moving body (not shown), wherein a part of the cover members14is omitted from the magnet assembly10. Further,FIG. 3is a side view of the magnet plate13shown inFIG. 2, which shows the fixation points of the cover member14with respect to the magnet plate13.

In the present embodiment, it is preferable that the cover member14is fixed to the magnet plate13by the fixing mechanism so that the edge14dof the cover member14in the longitudinal direction (i.e., the arrangement direction of the permanent magnets11) is positioned at the center position of the permanent magnet11, as shown inFIG. 2andFIG. 3.

More specifically, a plurality of permanent magnets11are sequentially arranged on the substrate12of each magnet plate13at a predetermined pitch P. When manufacturing the magnet assembly10, two or more magnet plates13are arranged in a row, along with the permanent magnets11being arranged in the same direction in all of the magnet plates13. At this time, each magnet plate13is arranged so that the predetermined pitch P of the permanent magnets remains constant across the arranged two or more magnet plates13. Further, in order to install each magnet plate13, countersink holes17, into which screws are inserted, are provided at the upper surface of the magnet plate13.

In this configuration, there is no permanent magnet11in the vicinity of the joint16between adjacent magnet plates13(i.e., the region indicated by the dotted line indicated by arrow A inFIG. 2). Due to this, the magnetic attraction force is weak in the vicinity of the joint16. Further, the magnetic attraction force in the region between the adjacent permanent magnets11in each magnet plate13is weaker than in the regions just above the permanent magnets11.

Furthermore, in order to reduce the cogging force generated when the armature of the linear motor is moved, regarding the shape of each of the permanent magnets11, the thickness T of each permanent magnet11may be gradually reduced from the central portion (center position) of the permanent magnet11towards both sides of the permanent magnet, as shown inFIG. 3. In this case, since the distance between the permanent magnet11and the first surface part14aof the cover member14is largest in the vicinity of the joint16and in the region between adjacent permanent magnets11, the magnetic attraction force applied to the cover member14is smaller in these regions.

From the reason described above, if the edge14dof the cover member14in the longitudinal direction is disposed to be opposite to the vicinity of the joint16or the region between adjacent permanent magnets11, the edge14dof the cover member14is easily spaced away therefrom.

As already explained, if the cover member14is not in close contact with the magnet plate13at their edges14d, foreign matter such as dust or dirt may enter between the cover member14and the magnet plate13, which causes a problem that the cover member is spaced away from the magnet plate13.FIG. 4is a diagram schematically showing a situation in which such a problem occurs.

As shown inFIG. 4, the cover member14is separated from the magnet plate13due to foreign matter19entering a space between the cover member14and the magnet plate13from the edge14dof the cover member14, thereby the cover member14may contact the armature18moving along the upper surface of the magnet plate13. As a result, the armature18, the cover member14, and the magnet plate13, etc., may be damaged.

However, in the present embodiment, the edge14dof the cover member14is positioned at the center position of the permanent magnet11when the cover member14is fixed to the magnet plate13by the fixing mechanism15, as shown inFIG. 2andFIG. 3. The center position of the permanent magnet11is a location where the amount of the magnet is largest, and the distance between the cover member14and the magnet is smallest. That is, the center position of the permanent magnet11is a location where the magnetic attraction force with respect to the cover member14is strongest. As a result, it is possible to minimize the effect that the edge14dof the cover member14is spaced away from the magnet plate13, thereby, the damage to the armature18and the cover member14as described above can be prevented.

Moreover, in the state where one cover member14is fixed to the magnet plate13so that the edge14dthereof is positioned at the center of the given permanent magnet11on the magnet plate13as shown inFIG. 2, another cover member14(not shown inFIG. 2) is further fixed to the given magnet plate13. In this case, the other cover member14is fixed to the magnet plate13so that the edge14dthereof is positioned at the center of the given permanent magnet11as well. At this time, the edges14dof the two cover members14are in contact with each other at the center position of the aforementioned given permanent magnet11, and do not exist in the position of the joint16between adjacent magnet plates13.

In other words, the other cover member14is disposed across two adjacent magnet plates13so as to cover the joint16. Thus, in the present embodiment, there is no possibility that foreign matter19are deposited in the joint16between the magnet plates13, unlike in the prior art.

Further, in the present embodiment, it is preferable that not only one edge14din the longitudinal direction of the cover member14, but also the other edge14dis positioned at the center of the permanent magnet11on the magnet plate13, in order to minimize the rise thereof from the magnet plate13. To this end, it is more preferable that the first surface part14aof the cover member14has a length which is an integral multiple of the predetermined pitch P (the integer does not include zero) in the direction of the arrangement of the magnet plates13.

In this regard, if the edge14dof the cover member14is merely aligned with the center position of the permanent magnet11, a part of the upper surface of the endmost magnet plate13among the plurality of magnet plates13aligned in a row may be not covered by the cover member14.FIG. 5is a side view of a cover member14′ having a configuration which takes this problem into account, wherein the cover member14′ is attached to the endmost magnet plate13of the magnet assembly10.

As shown inFIG. 5, the cover member14′ includes a third surface part14ewhich extends from the first surface part14aand which covers the exposed end face part13bof the endmost magnet plate13of the magnet assembly10. By using the cover member14′ having such third surface part14efor the endmost magnet plate13of the magnet assembly10, it is possible to more-effectively reduce the possibility that the cover member14′ is spaced away from the magnet plate13due to the foreign matter19entering between the cover member14′ and the magnet plate13.

Next, another embodiment will be described.

FIG. 6is a longitudinal cross-sectional view showing another embodiment of the magnet plate13and the cover member14constituting the magnet assembly10for a linear motor shown inFIG. 1andFIG. 2, etc.

The side parts13aof the magnet plate13shown inFIG. 1andFIG. 2are formed to be planar portions which are substantially perpendicular to the surface of the magnet plate13facing the armature18, wherein the second surface parts14bof the cover member14covering these planar portions are integrally formed with the first surface parts14a. However, in the present disclosure, the embodiment of the side parts13aof the magnet plate13are not limited to such planar portions, buy any shape may be employed. Accordingly, the side parts13aof the magnet plate13may have structures changing in a stepwise manner, as shown inFIG. 6. In this case, as shown inFIG. 6, the second surface parts14bof the cover member14are preferably bent along the side parts13achanging stepwisely, and fixed to the side parts13aby the fixing mechanisms15such as screws.

Although the invention has been described above using representative embodiments, those skilled in the art will understand that modifications and various other alterations, omissions, and additions can be made to the components of the aforementioned embodiments without departing from the scope of the present disclosure.

Furthermore, appropriate combinations of some of the constituent elements described in the above embodiments are within the scope of the present disclosure.

Effect of the Present Disclosure

According to the above-described first embodiment, fifth embodiment and seventh embodiment of the present disclosure, a cover member can cover from the surface of the magnet place facing the armature to the side parts of the magnet plate, making it possible to prevent the accumulation of dust or dirt on the surface of the magnet plate facing the armature. By forming the cover member from a member of weak magnetic, it is easy to replace or adjust the position of the cover member. Since the fixing mechanism is provided on the second surfaces of the cover member covering the side parts of the magnet plate, even if there is not sufficient space between the magnet plate and the opposing armature, the cover member can be fixed in close contact with the magnet plate through the use of the fixing mechanism. In order to bring the cover member into close contact with the magnet plate, by combining the magnetic attraction force of the permanent magnets with the mechanical fixing force of the fixing mechanism, it is possible to bring the cover member into close contact with the magnet plate without excessively strengthening the magnetism of the cover member, thus preventing a deterioration in workability when installing or replacing the cover member.

In particular, the aforementioned fixing mechanism is provided such that the end part of the cover member having weak magnetic properties is positioned just above the permanent magnet. Thus, it is possible to prevent foreign matter from entering between the cover member and the magnet plate, minimizing a rise in the end part of the cover member.

According to the above-described second embodiment and third embodiment of the present disclosure, positioning the edge of the cover member at the center position of the permanent magnet, which is the position where the magnetic attractive force is strongest, can enhance the effect of suppressing the rise of the cover member.

According to the above-described fourth embodiment of the present disclosure, it is possible to prevent the accumulation of dust, dirt, etc., in the joint between adjacent magnet plates.

According to the above-described sixth embodiment of the present disclosure, regarding the endmost magnet plate of the magnet assembly, by covering the exposed end face part of the magnet plate with one part of the cover member, it is possible to prevent foreign matter from entering between the cover member and the magnet plate from the end face part of the endmost magnet plate. As a result, the effect of suppressing a rise of the cover member can be further enhanced.