JP3835946B2 - Moving coil linear motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a linear motor in which a mover coil linearly moves in a magnetic space formed between opposing yokes, and the maximum current value of the mover coil is maintained and thermal demagnetization of a permanent magnet is suppressed to a maximum. The present invention relates to a moving coil linear motor that can improve thrust.
[0002]
[Prior art]
Conventionally, as a driving device for positioning an object within a relatively long stroke range of several tens to 100 cm, for example, a movable device disclosed in Japanese Patent Publication No. 58-49100 and Japanese Utility Model Publication No. 63-93783 is disclosed. A coiled linear motor is used. This moving coil linear motor will be described with reference to FIG. First, reference numeral 1 denotes a yoke which is formed into a gate shape by assembling, for example, a U-shape or a flat plate by a ferromagnetic material such as an iron plate. Reference numeral 2 denotes a permanent magnet which is magnetized in the thickness direction and is arranged and fixed in the longitudinal direction of the yoke 1 so that NS magnetic poles alternately appear on the surface. It arrange | positions so that the different poles of the permanent magnet 2 may oppose. Reference numeral 4 denotes a support plate made of a ferromagnetic material similar to that of the yoke 1 and fixed to both ends in the longitudinal direction of the yoke 1 in order to secure the magnetic space 3.
[0003]
In the following, 5 are formed by flat polyphase coil as the magnetic flux and the winding direction of the magnetic space 3 on the movable element with integrated coils and the holder or the like are orthogonal. This is because, for example, the three-phase coils are arranged slightly shifted in the arrangement direction of the permanent magnet 2 and the direction of the magnetic pole is detected via means such as a magnetic field detection element (MR sensor). A sine wave current is applied to switch between driving and its direction. Note that a table 6 or the like indicated by a dotted line in the figure is attached to the mover, and this linear movement is used.
[0004]
With the above configuration, when a current is passed through the coil 5, the winding direction of the coil 5 is orthogonal to the magnetic flux generated by the permanent magnet 2, so that the coil 5 generates a driving force in the longitudinal direction of the yoke 1 according to Fleming's left-hand rule. The mover that integrally supports the coil 5 moves in the longitudinal direction of the yoke 1. Next, when a current in the opposite direction to the coil 5 is passed, a driving force in the opposite direction to the coil 5 acts on the coil 5, and the mover moves in the opposite direction. Accordingly, by selecting the energization and the direction of the coil 5 and detecting the position by the MR sensor, the mover can be controlled to move to a predetermined position.
[0005]
According to this moving coil type linear motor, there is no center yoke in the magnetic circuit section, and the magnetic flux forms a plurality of closed loops in the magnetic space so that the magnetic flux is not concentrated on a part of the magnetic path. A uniform magnetic flux density can be generated over the entire long stroke. Further, since the mass of the mover is small and the cogging torque is small, there is an advantage that the linear motor has a good speed response.
[0006]
However, on the other hand, since many coils are arranged in a narrow magnetic space, the efficiency of heat exchange and heat diffusion by natural convection is poor, and the coil 5 that is a heat source is present on the mover side, so that it is difficult to adopt cooling means. There is a structural problem. Furthermore, since the electrical resistance value of the coil itself increases due to the heat generation of the coil 5 and Joule heat loss increases, the effective power decreases. For this reason, the power supplied to the coil 5 is limited to a value that does not cause the coil heat generation to be a practical problem. On the other hand, the heat from the coil 5 is also transmitted to the opposing permanent magnet 2, the temperature of the permanent magnet 2 rises, and the generated magnetic flux decreases due to thermal demagnetization. From the above, there is a problem in performance that the generated thrust is reduced.
[0007]
Therefore, it is desired to cool the coils, it has been proposed to cool the coil plurality of axial flow fan provided on the side portions of the fixed yoke according, for example, in real-Open No. 4-34878.
[0008]
[Problems to be solved by the invention]
However, the cooling means disclosed in Japanese Utility Model Laid-Open No. 4-34878 results in an increase in the size and complexity of the linear motor by providing an axial fan. Normally, in the case of a movable magnet type linear motor, the coil side does not move, so the means for cooling this can be carried out relatively efficiently by either water cooling or air cooling. It was difficult to take an efficient cooling structure because it moved. Therefore, the actual condition is that the moving coil linear motor is not provided with a cooling means.
[0009]
Therefore, the present invention relates to the latter prior art described above and solves the problems, and includes an air cooling means that makes the coil cooling structure inexpensive and simple and provides an efficient cooling effect. Another object of the present invention is to provide a moving coil linear motor.
[ 0010 ]
[Means for Solving the Problems]
In the present invention, a plurality of permanent magnets are alternately arranged in the longitudinal direction of the yoke so that the magnetic poles are different from each other, and a mover having a coil in a magnetic space formed along the surface of the permanent magnet is provided as the permanent magnet. In the movable coil linear motor that is movably provided in the magnet arranging direction, a concave groove that is continuous in the longitudinal direction is formed on the magnet arranging surface of the yoke, and the permanent magnet covers the concave groove. It is a movable coil type linear motor which is arranged at a predetermined interval and blows air into the magnetic space from the gap of the permanent magnet by supplying air into the concave groove to cool the coil.
[ 0011 ]
In the present invention, by providing a predetermined gap between adjacent permanent magnets, air can be blown into the magnetic space from the gap to efficiently cool the coil. Then, Runode to form the air supply passage into the groove, working even yoke long is not restricted to very easily yoke length. Therefore, it is particularly suitable for a long linear motor such as a linear motor having a yoke with a driving distance of 10 cm or more. By the above, even a movable coil type linear motor can be provided with a simple and inexpensive cooling means, and both the heat loss on the coil side and the thermal demagnetization on the magnet side are reduced to achieve high thrust of the linear motor, This can be maintained .
[ 0012 ]
In addition, having a gap between the permanent magnets acts to make the magnetic flux distribution sinusoidal and contributes to improvement in controllability. Normally, a predetermined gap Lg between adjacent permanent magnets, an alternating magnetic field period When Lm in order to effectively generate a magnetic flux amount between the opposing permanent magnets, to fall within the Lm / 3~Lm / 8 Ru is set to. For example, when the period of the alternating magnetic field is 16 to 100 mm , the gap between the permanent magnets is set to a range of about 4 to 25 mm. However, in the present invention, since a structure in which blown air from the groove formed in the magnet installation surface, in order to provide a nozzle function efficiency balloon consider port of the cooling, Lg is 0.05 it preferably is in the range of about 5mm. Further, the groove may be a yoke and magnets provided a plurality of if those large is efficient.
[ 0013 ]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, details of the present invention will be described with reference to the drawings. FIG. 1 is a partial top view of a linear motor showing an embodiment of the present invention , and FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a partial top view of a linear motor showing a reference example, and FIG. 4 is a sectional view taken along line BB in FIG. FIG. 5 is a cross-sectional view of an essential part showing a modification of FIG. FIG. 6 is a partial top view of a linear motor showing another embodiment of the present invention . FIG. 7 is a partial top view of a linear motor showing another reference example. Incidentally, these figures are a diagram schematically showing a structure schematically, it does not exactly match the actual linear motor. Moreover, about the structure similar to the prior art shown in FIG. 8 , the same code | symbol is attached | subjected and the description is abbreviate | omitted.
[ 0014 ]
As shown in FIGS. 1 and 2, the yoke 7 is arranged opposite to the left and right, and a flat plate made of a ferromagnetic material such as mild steel, is composed of a same plate-shaped lower yoke 73, opposite the yoke A magnetic space 3 is formed along the magnet surface. The lower yoke may be of opposite flat and also separate those integrated. And in the longitudinal direction of the magnet arrangement surface 71 of the yoke 7, permanent magnets, for example Nd-Fe-B based anisotropic sintered magnet 2 so that the different polarities alternately, and the polarity between the opposing permanent magnets Are arranged and fixed differently. Mover 5 consisting of a multi-phase coil similarly to the prior art described above in the magnetic space 3 are placed, in the multi-phase coil by supplying a sinusoidal drive current from the drive circuit (not shown) that it is configured to make linear movement (up and down direction). In addition, the space | interval of the permanent magnet 2 and the needle | mover 5 is set to about 0.05-2 mm , for example . The structure of the material and the mover permanent magnets are not shall be limited to the embodiments described above.
[ 0015 ]
In this embodiment, grooves 70 are continuous in a longitudinal direction to the magnet arrangement surface 71 of the yoke 7 and is formed, the groove 70 can be easily and inexpensively formed by milling. Furthermore, the permanent magnet 2 is directly fixed to the magnet arrangement surface 71 with an adhesive so as to cover the concave groove 70 at a predetermined interval. Although it is preferable that the chosen way intervals alternating field permanent magnet 2 at this time is closer to the perfect sine wave, in order to blow cooling air efficiently, several mm / 10 ~ several mm of It is preferable to make it into the size of a nozzle. That it is, in the present invention may be Re to select the spacing of the permanent magnet in consideration of the blowing efficiency of the shape and the cooling air of the alternating magnetic field. Since one end of the groove 70, not shown air supply port is provided, the groove 70 is ing a supply passage for the cooling air. Therefore, when supplying the cooling air by the air pressure driving source and a compressor and the like from the air supply port provided at one end of the yoke 7, to cool the permanent magnet 2 from the rear during the over-passing the groove 70, air is The blower movable element 5 can be directly cooled into the magnetic space 3 from the gap ( opening 72 ) between the permanent magnets. According to the above embodiment, it is possible to easily form the cooling air supply passage as compared with the following reference example.
[ 0016 ]
The cooling air supply passage can be configured as shown in FIGS. 3 and 4 , but the structure is somewhat complicated. That the groove 80 provided on the back 86 side of the yoke 8, the groove 80 of this, to form the air supply passage through the seal member was sealed with a lid member 85, a yoke 8, communicating with the groove 80 the communication hole 84 provided state, and are not open 82 of the communication hole 84 so as to be positioned between the permanent magnet 2 and to supply cooling air from one end of the yoke 8, the sealed grooves 80 Although cooling air can be blown directly from the opening 82 into the magnetic gap 3 through the communicating hole 84, the coil of the mover 5 can be directly cooled, but the number of parts is increased as compared with the above embodiment. Further, as shown in FIG. 5, when the box-shaped member 88 is fixed to the yoke 8 by welding or the like with a concave cross section, the size is increased as compared with the above embodiment.
[ 0017 ]
Figure 6 shows another embodiment of the present invention, a structure in which a supply passage for the cooling air to the moving coil type linear motor having a center yoke. That is, the groove 70 constituting a supply passage for the cooling air, also provided on the center yoke side of the yoke 9, yet are those provided two grooves 70 in parallel, the yoke and the permanent magnet becomes large in size and coil There the case of an increase, it is preferable that'll improve the cooling capacity in this way.
[ 0018 ]
In the reference example of FIG. 7, a permanent magnet is provided only on one yoke 9L of the pair of yokes 9R and 9L , and a concave groove 90 is provided on the back side of the yokes 9R and 9L on both sides. Although the communication hole 94 is provided and cooling air can be blown onto the coil, this linear motor has a more complicated yoke structure than the above embodiment .
[ 0019 ]
【The invention's effect】
As described above, according to the present invention, in the moving coil type linear motor, the concave groove continuous in the longitudinal direction is formed on the magnet mounting surface of the yoke, and the permanent magnet is arranged at a predetermined interval so as to cover the concave groove. Since air is blown into the magnetic space from the gap between adjacent permanent magnets by supplying air to the groove, the coil is cooled, so the movable coil and permanent magnet can be cooled with a simple structure. Can do. Therefore , it is not necessary to limit the current supplied to the linear motor by reducing both the heat loss of the coil and the thermal demagnetization of the magnet , and high thrust can be obtained .
[Brief description of the drawings]
FIG. 1 is a partial top view of a linear motor showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a partial top view of a linear motor showing a reference example.
4 is a cross-sectional view taken along line BB in FIG.
FIG. 5 is a cross-sectional view of a main part showing a modification of FIG . 4 ;
FIG. 6 is a cross-sectional view of a linear motor showing another embodiment of the present invention.
FIG. 7 is a partial top view of a linear motor showing another reference example.
FIG. 8 is a top view showing an example of a conventional moving coil linear motor.
[Explanation of symbols]
1: yoke 2: permanent magnet 3: magnetic space 4: support plate 5: mover 6: table 7, 8, 9: yoke 70, 80, 90: concave groove 71, 81: magnet arrangement surface 72, 82: gap Opening 73, 83: Lower base 84, 94: Communication hole 85: Lid member 85: Recessed box member

Claims (2)

A plurality of permanent magnets arranged so as poles different alternately in the longitudinal direction of the yoke, disposed of the permanent magnet mover having a coil on the permanent magnet in a magnetic space formed along the surface In the movable coil type linear motor that is provided so as to be movable in the direction, a concave groove that is continuous in the longitudinal direction is formed on the magnet mounting surface of the yoke, and the permanent magnet has a predetermined interval so as to cover the concave groove. The movable coil linear motor is characterized in that air is blown into the magnetic space through the gap between the permanent magnets by supplying air to the concave groove, thereby cooling the coil. 2. The moving coil linear motor according to claim 1 , wherein the predetermined gap between adjacent permanent magnets is in the range of 0.05 to 5 mm .

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