JP2000245132A - Moving-coil linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moving-coil linear motor capable of having a simple air-cooling structure and attaining high efficiency. SOLUTION: This moving-coil linear motor is provided with a plurality of permanent magnets 2, so that poles are alternately different from each other in the longitudinal direction of on yoke 8L of yokes which face the permanent magnets, and the heteropoles face each other via a magnetic space 3, a mover 5 which has a polyphase coil and is movably disposed in the magnetic space 3 in the arrangement direction of the permanent magnet 2, and a drive circuit for supplying drive current to the polyphase coil. A passage is formed which consists of a recessed groove 80, which continues in a longitudinal direction on the back face of the other yoke 8R and is closed, and communicating hole 84 is formed which communicates the magnetic space 3 and the recessed groove 80, so that air is supplied to the passage of the recessed groove 80 to blow air against the magnetic space 3 via the communicating hole 84, thus it is possible cool the polyphase coil and reduce the temperature rise in the permanent magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor in which a mover coil moves linearly in a magnetic space formed between opposing yokes, and maintains a maximum current value of the mover coil and heats a permanent magnet. The present invention relates to a moving coil linear motor capable of improving the maximum thrust by suppressing demagnetization.

[0002]

2. Description of the Related Art Conventionally, as a driving device for positioning an object within a relatively long stroke range of several tens to 100 cm, for example, Japanese Patent Publication No. 58-49100
And a moving coil type linear motor as disclosed in JP-A-63-93783. This moving coil type linear motor will be described with reference to FIG. First, reference numeral 1 denotes a yoke which is formed in a gate shape by assembling a U-shaped or flat plate using a ferromagnetic material such as an iron plate. 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 appear alternately on the surface. The different poles of the permanent magnet 2 are arranged so as to face each other. 4 is a support plate for the yoke 1
The yoke 1 is made of the same ferromagnetic material and is fixed to both ends in the longitudinal direction of the yoke 1 in order to secure the magnetic space 3.

[0005] Next, reference numeral 5 denotes a mover integrally provided with a coil, a holder, and the like, which is formed of a flat multiphase coil whose winding direction is orthogonal to the magnetic flux in the magnetic space 3. This means, for example, that three-phase coils are arranged with a slight shift in the direction in which the permanent magnets 2 are arranged, and the direction of the magnetic poles is changed to a magnetic field detecting element (MR).
The driving and the direction are switched by applying a single-phase or three-phase sine wave current to the detection. A table 6 and the like indicated by a dotted line in the figure are attached to the mover, and a linear movement of the table 6 is used.

With the above configuration, when a current is applied to the coil 5, the winding direction of the coil 5 is orthogonal to the magnetic flux generated by the permanent magnet 2. Therefore, the coil 5 is moved in the longitudinal direction of the yoke 1 according to Fleming's left-hand rule. A driving force is obtained, and the mover integrally supporting the coil 5 moves in the longitudinal direction of the yoke 1. Next, when a current in the opposite direction is applied to the coil 5, a driving force in the opposite direction acts on the coil 5, so that the mover moves in the opposite direction. Therefore, the coil 5
The movable element can be controlled to move to a predetermined position by selecting the power supply and its direction and detecting the position with an MR sensor.

According to this moving coil type linear motor,
There is no center yoke in the magnetic circuit part, and the magnetic flux forms a plurality of closed loops in the magnetic space, so that the magnetic flux does not concentrate on a part of the magnetic path, so it is uniform throughout the long stroke High magnetic flux density can be generated. Further, the mass of the mover is small and the cogging torque is also small, so that the linear motor has a feature of good responsiveness.

However, since the coil 5 is arranged in the narrow magnetic space 3, the efficiency of heat exchange and heat dissipation by natural convection is low, and the coil 5, which is a heat source, is located on the mover side, so that cooling is not performed. There is a structural problem that it is difficult to take measures. Furthermore, the electric power of the coil itself increases due to the heat generated by the coil 5 and the Joule heat loss increases, so that the effective power decreases. For this reason, the power supplied to the coil 5 is limited to a value at which the heat generation of the coil does not cause 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 performance problem that the generated thrust is reduced.

Therefore, it is desired to cool the coil. For example, Japanese Utility Model Laid-Open No. 4-34878 proposes providing a plurality of axial fans on a side surface of a fixed yoke to cool the coil.

[0008]

However, in the cooling means disclosed in Japanese Utility Model Laid-Open No. 4-34878, the provision of an axial fan results in an increase in the size and the structure of the linear motor. Usually, in the case of a moving magnet type linear motor, the coil side does not move, so the means for cooling this can be implemented relatively efficiently with water cooling or air cooling, but in the case of a moving coil type linear motor, the coil side moves, It was difficult to take an efficient cooling structure. Therefore, the actual situation is that the moving coil linear motor does not include the cooling means.

Accordingly, the present invention is concerned with the latter conventional technique described above and solves the problem. An air cooling means which makes the air cooling structure of the coil inexpensive and simple and which can obtain an efficient effect. It is an object of the present invention to provide a moving coil type linear motor provided with:

[0010]

According to the present invention, a plurality of permanent magnets are alternately arranged in the longitudinal direction of a yoke so that magnetic poles are different from each other, and a coil is placed in a magnetic space formed along the surface of the magnet. In the moving coil linear motor in which the provided mover is provided so as to be movable in the direction in which the permanent magnet is provided, the permanent magnet is provided only in one yoke, and the other yoke is continuous in the longitudinal direction. To provide a closed passage,
Forming a communication hole connecting the magnetic space and the passage,
A moving coil linear motor configured to cool the coil by supplying air to the passage to blow air into the magnetic space through the communication hole.

Here, the passage is formed by forming a continuous groove in the longitudinal direction and sealingly closing the groove, or is fixed by sealing the concave member continuous in the longitudinal direction. Alternatively, it can be provided by a pipe-like material. A plurality of air passages serving as cooling air passages can be provided up and down as appropriate. In the above description, air cools the coil,
This means that at least the coil is cooled, and it does not prevent indirectly cooling the permanent magnet and the like.

As described above, the coil can be efficiently cooled by blowing air into the magnetic space from the yoke on which the permanent magnet is not disposed among the opposing yokes. And
Since the air supply passage is formed as a closed concave groove, even a long yoke can be processed extremely easily, and the length of the yoke is not restricted. Therefore, the driving distance is 10c
It is particularly suitable for a long linear motor such as a linear motor having a yoke of m or more. In this way, even a moving coil type linear motor can be provided with a simple and inexpensive cooling means, reducing both the heat loss on the coil side and the heat demagnetization on the magnet side to achieve a high thrust of the linear motor. , Which can be kept.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partial top view of a linear motor showing a first embodiment, and FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a cross-sectional view of a linear motor showing another embodiment. These drawings are simplified diagrams showing the outline of the structure, and do not show the actual structure. The same reference numerals are given to the same components as those in the related art, and the description thereof will be omitted.

In FIGS. 1 and 2, a yoke 8 has flat plates 8R and 8L made of a ferromagnetic material such as mild steel opposed to each other on the left and right sides.
It is also composed of a flat bottom yoke 83,
The magnetic space 3 is formed along the surface of the magnet between the opposing yokes. It should be noted that the bottom yoke 83 may be integrated or assembled separately. A permanent magnet, for example, Nd-
The Fe—B based anisotropic sintered magnets 2 are arranged and fixed adjacent to each other so that their polarities are alternately different. A mover 5 composed of a multi-phase coil is provided in the magnetic space 3 in the same manner as in the related art described above, and a drive circuit (not shown) is provided in the multi-phase coil.
This is a moving coil type linear motor that is supplied with a sine wave drive current from the controller and is moved linearly (vertically in the drawing). The distance between the permanent magnet 2 and the mover 5 is actually 0.0
It is provided with a gap of about 2 to 2 mm. Also,
Embodiments of the permanent magnet and the mover are not limited to the above.

Next, a groove 8 is formed on the back surface 86 side of the right yoke 8R.
0, and the lid member 85 is hermetically closed via a seal member to form an air supply passage. A communication hole 84 communicates between the closed groove-shaped passage 80 and the magnetic space 3. Note that the communication hole 84 may be configured so that the concave groove is provided so as to penetrate the yoke, and is also used. Further, as another embodiment of the passage, for example, the one shown in FIG. 3 may be used. In this example, a box-shaped member 88 having a concave cross section and a length is hermetically fixed to the yoke 8R by means such as welding. In addition, a structure in which a pipe-shaped pipe is additionally provided is also conceivable. The permanent magnet 2 is directly fixed to the magnet mounting surface 81 of the yoke 8L so that the alternating magnetic field of the permanent magnet 2 approaches a more complete sine wave. The shape and the magnetic force and shape of the permanent magnet are set in consideration of the optimum.

As described above, when cooling air is supplied from one end of the air supply passage 80 of the yoke 8R by a pneumatic drive source or an air compressor of the device, the air passes through the air passage of the sealed groove 80 and the communication hole 84. Cooling air is blown into the magnetic space 3 to directly cool the coil of the mover 5. At this time, since the cooling air is blown to the mover from right beside the through-hole, the cooling efficiency is further improved as compared with the air flow along the longitudinal direction and the fan.

Further, although the cooling efficiency is reduced, as another embodiment, a concave groove is provided in the bottom surface 87 of the bottom base 83, and the concave groove is similarly closed by a lid member and the like, and the communication is established with the magnetic space. A hole may be formed in the longitudinal direction, and cooling air may be blown out from below to cool the mover coil. According to each of the above embodiments, both heat generation of the coil and temperature rise of the permanent magnet can be suppressed.
A large current can be passed, and the thrust of the linear motor can be increased.

[0018]

According to the present invention, a groove is formed on the back surface of the yoke and the like, and the groove is closed to form a passage. Further, since a communication hole is formed, cooling air is supplied into the magnetic space so that the movable coil is formed. And the temperature rise of the permanent magnet can be suppressed. At this time, the processing of the air supply passage can be made extremely easy and inexpensive even with a long yoke, which is effective. As described above, both the heat loss on the coil side and the heat demagnetization on the magnet side are reduced, and a high thrust can be obtained without limiting the current supplied to the linear motor. Further, the application range of the linear motor can be expanded.

[Brief description of the drawings]

FIG. 1 is a partial top view of a linear motor showing one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view of a linear motor showing another embodiment of the air passage of the present invention.

FIG. 4 is a top view showing an example of a conventional moving coil type linear motor.

[Explanation of symbols]

1: yoke 2: permanent magnet 3: magnetic space 4: support plate 5: mover 6: table etc. 8 (8R, 8L): yoke 80: concave groove 81: yoke magnet arrangement surface 83: bottom yoke 84: communication Hole 85: Lid member 86: Yoke back surface 87: Yoke bottom surface 88: Recessed box member

Continued on the front page F-term (reference)

Claims (2)

[Claims] 1. A movable element having a coil provided in a magnetic space formed along a surface of a magnet, wherein a plurality of permanent magnets are alternately arranged in a longitudinal direction of a yoke so that magnetic poles are different from each other. In the moving coil type linear motor that is provided so as to be movable in the disposing direction, the permanent magnet is disposed only in one yoke, and the other yoke is provided with a continuously closed passage in the longitudinal direction, A communication hole that connects the magnetic space and the passage is formed, and air is blown into the magnetic space through the communication hole by supplying air to the passage to cool the coil. Moving coil linear motor. 2. The moving coil linear motor according to claim 1, wherein the passage is formed by forming a groove continuous in the longitudinal direction on the back surface of the yoke and sealingly closing the groove.