JP3238045B2 - Linear motor - Google Patents

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 movable coil linearly moves in a magnetic gap formed between opposed permanent magnets, and maintains a maximum current value of the movable coil and reduces heat of the permanent magnet. The present invention relates to a linear motor capable of improving a maximum thrust by suppressing magnetic force.

[0002]

2. Description of the Related Art Conventionally, as a drive device for positioning an object within a long stroke range of 10 cm to 100 cm, for example, Japanese Patent Publication No. 58-49100 and Japanese Utility Model Application Laid-Open No. 63-93783 are disclosed. Such moving coil type linear motors are frequently used. In this linear motor, a plurality of permanent magnets magnetized in the thickness direction are arranged so as to face each other so that the magnetizing directions are different, and the linear motor moves in a direction perpendicular to the magnetic flux in the magnetic gap formed between the facing permanent magnets. Having a structure in which a movable coil assembly is provided.

In such a linear motor, there is no center yoke in the magnetic circuit portion, and the magnetic flux forms a plurality of closed loops in the magnetic gap, so that the magnetic flux does not concentrate on a part of the magnetic path. , A uniform magnetic flux density can be generated over the entire area of a long stroke.

FIG. 8 is an explanatory view of a main part of a conventional linear motor. In FIG. 8 , reference numeral 1 denotes a yoke formed of a ferromagnetic material such as an iron plate into, for example, a flat plate shape. Reference numeral 2 denotes a permanent magnet, which is magnetized in the thickness direction, and arranged and fixed in the longitudinal direction of the yoke 1 so that NS magnetic poles appear alternately on the surface. The yoke 1 formed as described above is disposed via the magnetic gap 3 so that the different poles of the permanent magnet 2 face each other. Reference numeral 4 denotes a support plate, and a yoke 1 for securing the magnetic air gap 3.
At both ends in the longitudinal direction. Note that the support plate 4 is preferably formed of the same ferromagnetic material as the yoke 1.

[0005] Next, reference numeral 5 denotes a coil, which is formed by a flat multi-phase coil whose winding direction is orthogonal to the magnetic flux in the magnetic gap 3. That is, a plurality of coils can be arranged by being slightly shifted in the direction in which the permanent magnets 2 are arranged, the direction of the magnetic pole can be detected via means such as a magnetic field detecting element, and the coil to which current flows and the direction can be switched. It is formed as follows.
The coil 5 is integrally supported by a holder (not shown) to form a mover.

[0006] 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. The movable element (not shown) integrally supporting the coil 5 is provided with the yoke 1.
Move in the longitudinal direction. 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 movable element can be moved to a predetermined position by selecting the energization of the coil 5 and the direction of the current.

[0007]

The moving coil type linear motor having the above-described structure is widely used as a linear motor having good responsiveness because the mass of the mover is small and the cogging torque is also small. However, since the coil 5 which is a heat source is located on the mover side, it is difficult to employ a forced cooling means, and since the coil 5 is arranged in the narrow magnetic gap 3, heat exchange or heat dissipation by natural convection is difficult. There is a problem.

On the other hand, the heat from the coil 5 is also transmitted to the permanent magnet 2 disposed through the movable element and the narrow magnetic gap 3 so that the temperature of the permanent magnet 2 increases, and the generated magnetic flux decreases due to thermal demagnetization. Therefore, the thrust is reduced. In addition, the electric resistance of the coil 5 itself increases due to the heat generated by the coil 5, and the Joule heat loss increases. As a result, the effective power decreases. For this reason, the power supplied to the coil 5 is limited to a certain value or less such that the heat generation of the coil does not cause a problem in practice. There is a problem that it is difficult.

The present invention solves the above-mentioned problems in the prior art, and provides a linear motor capable of preventing heat demagnetization of a permanent magnet and suppressing heat generation of a coil, thereby generating and maintaining a large output. The purpose is to:

[0010]

In order to achieve the above object, according to the present invention, a plurality of permanent magnets are separated through magnetic gaps so that magnetic poles adjacent in the longitudinal direction have different polarities. In a linear motor, which is disposed so as to face each other, and a movable element formed of a polyphase coil is provided in the magnetic gap so as to be movable in a direction in which the permanent magnet is provided, a cooling pipe for flowing a refrigerant near the permanent magnet. Between the permanent magnet and the cooling pipe
In the meantime, a nonmagnetic metal with a melting point lower than the Curie point of the permanent magnet
Others that form a filler layer made of a nonmagnetic alloy, employing the technical means of.

[0011] In the present invention, Ru can Aitonaru between the permanent magnet provided with a cooling tube, or a cooling tube directly above and / or directly below the permanent magnets.

[0012]

In the present invention, the refrigerant is not limited to water, antifreeze, inert liquid and other liquids, such as ammonia, sulfur dioxide, ethyl chloride, methyl chloride, and fluorocarbons such as freon, yukon and genetron.
It is also possible to use one or more of ethylene fluoride, ethylene glycol, diethylene glycol, etc., and a substance that releases or absorbs a large latent heat according to its volume to cool due to a phase change between liquid and gas. it can.

The permanent magnet used in the present invention can be manufactured by a known manufacturing method (for example, powder metallurgy, plastic working (upsetting, extrusion, rolling, etc.), bond magnet method, casting, ultra-quenching, etc.). It is something. A general formula representing the basic composition of the permanent magnet is R-Fe-B.
System, R-Co ₅ system, R ₂ -Co ₁₇ system, R-Fe-N system (R is one or more types of rare earth elements including Y, Co if necessary, Al, Nb, Ga,
Fe, Cu, Zr, Ti, Hf, Ni, V, Si, S
n, Cr, Mo, Zn, Pt, Bi, Ta, W, Sb,
One or two or more elements selected from Ge, Mn, and the like that are effective for magnetic properties can be contained. In addition, O, C,
One or more inevitable impurity elements selected from N, H, P, S and the like can be contained. ), A ferrite magnet, an alnico magnet, Fe-Cr
One or more known permanent magnet materials such as a -Co magnet and a Mn-Al-C magnet can be used.

Further, one or two of the above-mentioned permanent magnet materials may be used.
And a known thermoplastic resin or thermosetting resin or rubber material or one of them.
The permanent magnet of the present invention may be constituted by a known bonded magnet material (preferably an anisotropic magnet) mainly composed of a kind or two or more kinds. Note that among the above, R-Fe
It is preferable to form an oxidation-resistant coating layer on the surface of the -B permanent magnet to prevent oxidation.

As such a coating layer, for example, Ni,
Cu, Al, Zn, Cr, Ni-P, Ti, Sn, P
A plating layer made of one or more of b, Pt, Ag, Au and the like and formed by a known electroless or electroplating means can be employed. Other than this, for example, vacuum deposition (for example, there is a method of uniformly coating the front surface with a known metal or resin having high oxidation resistance), ion sputtering,
One or more of known coating layer forming means such as ion plating, IVD, and BVD can be employed. Also, an epoxy resin or the like may be electrodeposited.

When more excellent oxidation resistance is imparted, the above-mentioned coating layer forming means may be combined with, for example, C
Ni plating (layer thickness of several μm to several tens of μm) is coated on u plating (layer thickness of several μm to several tens of μm), and further, an epoxy resin is electrodeposited thereon (several μm to several tens of μm) Layer thickness)
It is preferable to adopt such a configuration. Of the above, Nd-Fe-B-based anisotropic sintered magnets and / or bonded magnets (preferably anisotropic magnets) are particularly preferred from the viewpoint of increasing the magnetic flux of permanent magnets for linear motors.

The low-melting non-magnetic metal or non-magnetic alloy usable in the present invention includes, for example, Sn,
Nonmagnetic metals having a melting point lower than the Curie point of permanent magnets such as Bi, Pb, Cd and In, or binary systems of these metals (for example, so-called solder alloys of Pb-Sn system) or ternary systems. (For example, Bi-Pb-Sb type or the like.) The above multi-component non-magnetic alloy is preferable, and the molten metal or alloy for forming a filler layer having good thermal conductivity in a gap around a cooling pipe is preferred. Loss of magnetic force of the permanent magnet due to heating during injection can be prevented.

Among the low melting point nonmagnetic metals or nonmagnetic alloys, those having a melting point of 120 ° C. or less (for example, Bi50% -Cd12.5% -Pb25% -Sn1
Wood's Metal of 2.5% composition (melting point 68 ° C); B
i49.5% -Cd10.1% -Pb27.3% -Sn13.1
% Quaternary eutectic alloy (melting point 70 ° C.);
Rose's composed of 50% -Pb28% -Sn22%
Alloy (melting point 100 ° C) and the like. In addition,% is weight%. Is particularly preferred. That is, when the molten metal or alloy is injected into the gap, the heating temperature of the permanent magnet is 12
If the temperature is 0 ° C. or lower, the thermal demagnetization of the permanent magnet can be suppressed within a range that can be practically used.

In the linear motor, in recent years, the above-mentioned R-Fe-B permanent magnet (high Br type is particularly preferably used) suitable for increasing the amount of magnetic flux (that is, increasing the thrust) is frequently used. When the temperature exceeds 100 ° C., the thrust of the linear motor is significantly reduced due to rapid thermal demagnetization. Further, when the oxidation-resistant coating formed on the surface of the R-Fe-B-based permanent magnet exceeds 120 ° C, there is a problem that the permanent magnet characteristics are significantly deteriorated due to rapid deterioration and damage. Therefore, the above melting point is particularly preferably 120 ° C. or lower.

[0021]

According to the above construction, it is possible to prevent the temperature of the permanent magnet from rising, prevent the magnetic flux generated by thermal demagnetization from decreasing, and improve the thrust. On the other hand, since the magnetic gap in which the multi-phase coil is disposed is also cooled, heat dissipation of the multi-phase coil is promoted, and the temperature rise of the multi-phase coil is also suppressed, so that a decrease in effective power can be suppressed, It contributes to the improvement of thrust.

[0022]

FIG. 1 is a sectional view showing a main part of a first embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a base, which is formed in a flat plate shape from a ferromagnetic material such as mild steel. Reference numeral 12 denotes a center yoke, and 13 denotes a side yoke.
It is formed in the shape of a flat plate using the same material as that of No. 1 and is fixed on the base 11 with an interval. Next, reference numeral 14 denotes a permanent magnet, for example, a rare earth permanent magnet (Nd-F manufactured by Hitachi Metals, Ltd.).
An e-B based anisotropic sintered magnet (HS-32BV) having a multilayer film of Cu plating and Ni plating formed on its surface as an oxidation-resistant coating) to form a shape and dimensions as described below, Yoke 12 and side yoke 13
A plurality of magnetic poles are arranged on the respective opposing surfaces such that adjacent magnetic poles have different polarities via magnetic gaps 15 so as to have different polarities. In FIG. 1, the direction in which the permanent magnets 14 are arranged is a direction orthogonal to the paper surface.

Next, reference numeral 16 denotes a mover, and a carriage 17
The coil frame 18 is fixed to the bottom of the magnetic space 15 so as to be movable within the magnetic gap 15 in a direction perpendicular to the plane of the drawing. The coil frame 18 is formed of a non-magnetic material in order to prevent thrust ripple from occurring. That is, for example, a frame made of an aluminum alloy (the surface is anodized to impart insulation).
A substrate made of a resin (for example, epoxy resin containing glass) is mounted on the surface of the substrate, and a coil 19 described later is fixed on the substrate.

If the coil frame 18 is formed of a magnetic material, or if the back yoke exists on the side of the mover 16, imbalance due to the attractive force of the permanent magnet 14 occurs, which is one of the causes of thrust ripple. . 1
Reference numeral 9 denotes a coil, which is formed in a flat shape and provided on both surfaces of the coil frame 18.

Next, a cooling pipe 21 is provided with a space between adjacent permanent magnets as described later, and a continuous S is provided in the space.
It is arranged in a letter shape and the refrigerant is circulated. The cooling pipe 21 is made of a known non-magnetic metal material having good heat conduction, for example, aluminum,
It is preferable to form from copper or an alloy thereof from the viewpoint of the cooling effect. Also, as described above, the cooling pipe 21
In the linear motor, the magnetic flux density distribution in the moving direction of the polyphase coil in the magnetic gap can be made sinusoidal in the linear motor, greatly reducing the torque ripple and securing excellent linearity. preferable.

In the present embodiment, the cooling pipe 21 is formed of an aluminum alloy, and is fixed close to the permanent magnet 14 with an adhesive or other filler. In particular, according to the study of the present inventor, when a filler layer made of the above-mentioned low-melting non-magnetic metal or non-magnetic alloy is formed in the gap around the cooling pipe 21 as described later, the cooling pipe 21 and the permanent magnet 14 It has been found that the thermal conductivity between the two increases and the cooling capacity increases significantly.

That is, when the filler layer does not exist, the gap is covered with an adhesive (for example, an epoxy resin or an araldite) and an air layer. In addition, heat conduction between the cooling pipe 21 and the permanent magnet 14 is significantly impaired, and the cooling effect on the permanent magnet 14 and the coil 19 is reduced.

Instead of the filler layer made of a non-magnetic metal or a non-magnetic alloy having a low melting point, a non-magnetic and thermally conductive filler (for example, epoxy resin) may be used. For example, even if a filler containing carbon fibers, SiC powder, graphite powder, Al powder, Cu powder, etc.) is used, and the cooling tube 21 is adhered and fixed, a good cooling effect can be obtained.

As the refrigerant to be circulated in the cooling pipe 21, it is most convenient to use water. However, a cooling medium for an automobile radiator such as an antifreeze or an inert liquid may be used.

FIG. 2 is a perspective view of a main part showing the coil frame 18 in FIG. 1, and the same parts are denoted by the same reference numerals as in FIG. The coil 19 is, for example, a three-phase coil (JP-A-62
193543), and all the phases are connected in series, and the respective phases are connected in a Y-shape.

The linear motor of the present invention uses a polyphase coil as described above to supply a sine-wave driving current to the polyphase coil. The power factor decreases as the number of phases increases. Therefore, it is necessary to increase the input current. Therefore, it is desirable to adopt a two-phase or three-phase conduction method. That is, it is desirable that the linear motor of the present invention has a configuration in which a magnetic circuit having a permanent magnet of a specific shape as described later is combined with a two-phase or three-phase sine wave current output type drive circuit.

FIG. 3 shows the coil 19 shown in FIGS.
It is a main part side view showing a positional relationship between the position detection element,
The same parts are denoted by the same reference numerals as in FIGS. 1 and 2. In FIG. 3, the mover 16 has three flat coils Lu ₁ , Lw ₁ , Lv ₁ wound in a plane parallel to the paper with a width of １ ／ of the magnetic pole pitch lm of the permanent magnet 14. A coil 19a which is displaced only (the central portions of the mutually flat coils located in the magnetic gap 15 do not overlap and form the same plane), and coils 19b and 19c which are configured similarly to the coil 19a. ing. The mover 16 is provided with three position detecting elements 20 at an interval lh which is 1/6 of the coil pitch Ic (equal to the magnetic pole pitch Im). These position detecting elements 20 are offset from the flat coils Lu ₁ , Lw ₁ , Lv ₁ to the interval l ′, respectively, but since this offset state can be processed electrically, there is no practical problem at all. .

Then, the driving circuit (not shown) generates 12
By generating a three-phase current waveform shifted by 0 ° and supplying the three-phase current waveform to the flat coils Lu ₁ , Lw ₁ , and Lv ₁ (arrows in FIG. 3 indicate the direction of the current), the mover 16 is continuously connected. Move. In the case of three phases, the interval lh between the position detecting elements 20 is theoretically the coil pitch lc (the magnetic pole pitch lm).
3), but in the example shown in FIG. 3, it is set as described above for mounting reasons. That is, the flat coils Lu ₁ , Lw ₁ , Lv _1, etc.
This is because, by reversing the energization direction, it can be arranged at any position every n times (n is a positive integer) times 180 °.

In this embodiment, the position detecting element 2
The direction of the flat coil to be energized and the current is switched or selected by 0 and a control circuit (not shown).
As the position detection element 20, a known element such as a Hall element can be used. The control circuit also uses a normal permanent magnet as a field. For example, the configuration may be the same as that of the synchronous AC servomotor.

Further, in the present invention, a three-phase coil (19
Even when a to 19b) are of a six-row type, position detection can be performed using three position detection elements 20. Accordingly, a single-phase or three-phase sine wave current is used as the supplied current, and only the timing of inverting the Hall element from positive (negative) to negative (positive) (zero cross) is used as a synchronization means. . When the two-phase energization method is adopted,
The position detecting elements 20 may be provided on the mover 16 at intervals of 1/4 of the magnetic pole pitch lm, and a two-phase current waveform shifted by 90 degrees may be generated by a driving circuit and supplied to the coil.

FIG. 4 is an enlarged side view of a main part showing the permanent magnet 14 and the cooling pipe 21 in FIG.
Are indicated by the same reference numerals. In FIG. 4, the permanent magnet 14
Is described in, for example, Japanese Patent Application Laid-Open No.
As described in No. 300484), the contours of the upper and lower edges are formed in a sine wave shape, and are magnetized in the thickness direction. By forming the contour of the permanent magnet 14 in this manner, the permanent magnet 1
4, the magnetic flux density distribution in the arrangement direction becomes sinusoidal,
It has been confirmed that the torque ripple is greatly reduced and excellent linearity is exhibited.

The cooling pipe 21 is provided between the adjacent permanent magnets 14, 14.
A gap is provided between the cooling pipes 21. The gap is connected to a coolant supply source (not shown) in order to allow the coolant to flow through the cooling pipe 21. The cooling pipe 21 is provided in advance by being fixed with an adhesive (for example, an epoxy-based adhesive) so as to be in contact with the permanent magnet 14, the center yoke 12, and the side yoke 13, and a gap 22 between these members is provided.
In this case, Wood's Metal (melting point 68 ° C.) having good thermal conductivity is heated and melted with an electric iron and poured, and cooled and solidified to form a low melting point and nonmagnetic filler layer 22 a around the cooling pipe 21. .

With the above configuration, the permanent magnet 14 is cooled with a very good heat conduction by the coolant such as water flowing through the cooling pipe 21, so that the heat from the coil 19 moving in the magnetic gap 15 in FIG. The resulting temperature increase of the permanent magnet 14 is also suppressed. Therefore, a decrease in the amount of magnetic flux generated from the permanent magnet 14 due to thermal demagnetization is prevented, and at the same time, an increase in coil conduction resistance due to a rise in temperature of the coil 19 is suppressed, so that a thrust on the mover 16 can be improved.

Since the cooling pipe 21 is disposed so as to face the magnetic gap 15 as shown in FIG. 1, it also contributes to cooling of the atmosphere in the magnetic gap 15 and indirectly moves the movable element 16.
Of the multi-phase coil 19 is promoted. Therefore, an increase in electric resistance due to heat generation of the polyphase coil 19 is suppressed, and a decrease in effective power is suppressed. As a result, the thrust on the mover 16 is reduced by 40 as compared with a case where the cooling pipe 21 is not arranged.
%, Which is a significant improvement.

FIG. 5 is an enlarged side view of a main part showing a permanent magnet 14 and a cooling pipe 21 according to a second embodiment of the present invention. FIG. 6 is a partial cross-sectional view of FIG. 3 are denoted by the same reference numerals. 5 and 6, the permanent magnet 14 has a substantially trapezoidal cross-sectional shape, and is disposed adjacent to the slope 23 so as to face the magnetic gap 15. The cooling pipe 21 is arranged in a continuous S-shape in a recess formed by the slopes 23 between the adjacent permanent magnets 14 and connected to a coolant supply source (not shown). The gap 22 between the cooling pipe 21 and the slopes 23, 23 is filled with Rose's Alloy (melting point 100 ° C.) having good heat conduction, and a low melting point and non-magnetic filler layer 22a is provided around the cooling pipe 21. Form. The operation of the above configuration is the same as that of the embodiment shown in FIG.

FIG. 7 is a sectional view of a main part showing a magnetic circuit according to a third embodiment of the present invention, and the same parts are denoted by the same reference numerals as in FIG. In FIG. 7, the permanent magnet 14 is formed in, for example, a rectangular shape and at least upper and lower edges are parallel. The cooling pipe 21 is made of, for example, a pipe made of a square aluminum alloy, and
It is arranged immediately above and immediately below. Cooling pipe 2
1 and the permanent magnet 14 and the gaps 22 existing between the center yoke 12 and the side yokes 13, Bi49.5% -Cd10.1% -Pb27.3% -Sn by weight.
Filler layer 22a is formed by filling 13.1% quaternary eutectic alloy (melting point: 70 ° C.). The operation of the above configuration is the same as that of the embodiment shown in FIGS.

[0042]

[0043]

[0044]

Table 1 is a table showing the improvement rate of thrust in each of the above embodiments. In this case, the thrust is measured at the time when the temperature rise due to the heat generation of the multi-phase coil constituting the mover is saturated, that is, when the linear motor starts to operate.
Performed after 0 minutes.

[0046]

[Table 1]

As apparent from Table 1, in each of the first to third embodiments, a thrust improvement of 40% is achieved as compared with the case where no cooling pipe or flow path is provided. Further, in each of the first to third embodiments, the improvement rate of the thrust when only the cooling pipe was arranged without using the filler layer shown in Table 1 was higher than the case where the cooling pipe was not arranged. Also 2
0% has been achieved.

[0048]

Since the present invention has the configuration and operation as described above, the following effects can be obtained. (1) Since the permanent magnet is cooled by the refrigerant flowing through the cooling pipe or the flow path, the temperature of the permanent magnet is prevented from rising due to heat radiation from the polyphase coil constituting the mover, and the heat of the permanent magnet is prevented. As a result of preventing the generated magnetic flux from being reduced by the demagnetization, the thrust on the mover is improved. (2) Since the atmosphere in the magnetic gap in which the multi-phase coil is disposed and moves is also cooled by the refrigerant flowing through the cooling pipe or the flow path, the heat dissipation of the multi-phase coil is promoted, and the multi-phase coil is cooled. It suppresses a temperature rise, suppresses a decrease in effective power, and contributes to an improvement in thrust for the mover. (3) In connection with the above (1) and (2), the present invention can be applied to a motor with a larger thrust, and the applicable range of the moving coil type linear motor can be expanded.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part showing a coil frame 18 in FIG.

FIG. 3 is a side view of a main part showing a positional relationship between a coil 19 and a position detecting element in FIGS. 1 and 2;

FIG. 4 is an enlarged side view of a main part showing a permanent magnet 14 and a cooling pipe 21 in FIG. 1;

FIG. 5 is an enlarged side view of a main part showing a permanent magnet 14 and a cooling pipe 21 according to a second embodiment of the present invention.

6 is a partial cross-sectional view in the direction of arrow A in FIG. 5;

FIG. 7 is a sectional view showing a main part of a magnetic circuit according to a third embodiment of the present invention.

FIG. 8 is an explanatory view of a main part showing a conventional linear motor.

[Explanation of symbols]

 14 permanent magnet 16 mover 21 cooling pipe 22a filler layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-110932 (JP, A) JP-A-1-27063 (JP, A) JP-A-49-70102 (JP, A) JP-A-4- 185250 (JP, A) Japanese Utility Model 3-104087 (JP, U) (58) Fields studied (Int. Cl. ⁷ , DB name) H02K 41/02-41/035 H02K 9/00-9/28

Claims (3)

(57) [Claims] 1. A plurality of permanent magnets are arranged so that magnetic poles adjacent to each other in the longitudinal direction have different polarities so that different poles face each other via a magnetic gap. In the linear motor, the movable element is provided so as to be movable in the direction in which the permanent magnet is provided . A cooling pipe for circulating the refrigerant is provided in proximity to the permanent magnet, and a permanent magnet is provided between the permanent magnet and the cooling pipe.
Non-magnetic metal or non-magnetic with a lower melting point than the Curie point
A linear motor comprising a filler layer made of a conductive alloy . 2. The linear motor according to claim 1, wherein a cooling pipe is provided between adjacent permanent magnets. 3. The linear motor according to claim 1, wherein a cooling pipe is provided immediately above and / or immediately below the permanent magnet.