JP3357541B2 - Moving magnet type linear motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a stator having a plurality of coils arranged in a longitudinal direction and a mover having a plurality of permanent magnets arranged in a longitudinal direction of the stator. The present invention relates to a movable magnet type linear motor in which a coil is configured to exist in a magnetic gap formed on a surface of a permanent magnet, and a mover is formed to linearly move in a longitudinal direction of a stator. The present invention relates to a movable magnet linear motor having improved thrust linearity at both ends in the moving direction of a mover.

[0002]

2. Description of the Related Art Conventionally, in order to move or position an object within a long stroke range of 10 cm to 1 m, for example, a plurality of permanent magnets are provided so that different poles alternately appear in the moving direction. A plurality of coils are provided at positions facing the permanent magnets, and one of the permanent magnets and coils is used as a stator, and the other is used as a linear motor.

In such a linear motor, a magnetic circuit portion including a permanent magnet does not have a center yoke, and a magnetic flux forms a plurality of closed loops in a magnetic gap opposed to a coil. Since it is not concentrated, a uniform magnetic flux density can be secured over the entire area of a long stroke.

FIG. 6 is a front view of an essential part showing an example of a conventional movable magnet type linear motor, and FIG. 7 is a sectional view taken along the line BB in FIG. 6 and 7, the stator 1 and the mover 2 are formed so that the mover 2 can reciprocate along the longitudinal direction of the stator 1.

[0005] First, a stator 1 comprises a flat support member 4 made of a non-magnetic material, for example, a flat multi-phase coil 3.
Are arranged on both sides of the multi-phase coil 3 via an insulating plate (not shown) so as to be shifted by a predetermined amount in the longitudinal direction.
Are formed so that a direct current controlled by a magnetoelectric conversion element (not shown) such as a Hall element for position detection or a Hall IC can be supplied. Reference numeral 5 denotes an edge plate provided on the edge of the support member 4.

Next, the movable element 2 is provided on the inner surface of a yoke 6 formed of a ferromagnetic material such as mild steel in the shape of a hollow rectangular tube so that the magnetic poles adjacent to each other in the longitudinal direction of the stator 1 have different polarities. Are formed by fixing a plurality of permanent magnets 7 so that different poles face each other via a gap.

With the above configuration, when a current flows through the multi-phase coil 3, the winding direction of the multi-phase coil 3 is orthogonal to the magnetic flux generated by the permanent magnet 7, so that the permanent magnet 7 is driven by Fleming's left-hand rule. The movable element 2 to which the permanent magnet 7 is fixed moves in the longitudinal direction of the stator 1 because the movable element 2 receives the driving force in the longitudinal direction of the stator 1.

Next, when a current in the opposite direction is applied to the multiphase coil 3, a driving force in the opposite direction acts on the permanent magnet 7, so that the mover 2 moves in the opposite direction. Therefore, by controlling the energization of the polyphase coil 3 and the direction of the current, the mover 2 can be reciprocated or moved and positioned at a predetermined position.

[0009]

FIGS. 8 to 10 are cross-sectional views of the mover 2 shown in FIG. 7 taken along the line C--C, respectively, showing examples of permanent magnets 7 having different shapes and arrangements. Is omitted. FIG. 5 is a diagram showing the relationship between the moving direction position of the mover 2 and the air gap magnetic flux density.

In the above-described conventional linear motor, as shown in FIG. 6, the permanent magnet 7 is formed in a rectangular parallelepiped shape, and the cross-sectional area orthogonal to the moving direction of the mover 2 is the same, that is, the thickness dimension and the width. The dimensions are the same. In addition, the gap magnetic flux density between the plurality of permanent magnets 7 is smaller than that in the middle portion of the permanent magnet 7 due to a gap, a short circuit of magnetic flux, and the like. The air gap magnetic flux density distribution of the permanent magnet 7 in the moving direction of the mover 2 has a substantially arc shape as shown by a broken line a in FIG. 5, and is significantly different from the sinusoidal curve s. In FIG. 5, λ is a pitch in the moving direction of the mover 2 between the permanent magnets 7, 7 (a pitch between magnetic poles of the same polarity).

In general, in a motor having a permanent magnet field on the rotor side and a fixed armature on the outside, in order to always maintain the vertical relationship between the magnetic flux of the rotor and the armature magnetomotive force,
It is stated that it is necessary to establish a sinusoidal armature current and form a sinusoidal gap magnetic flux distribution by a suitable control circuit. With this configuration, the torque generated by the motor depends only on the product of the maximum value of the armature current and the maximum value of the magnetic flux density, and a torque irrelevant to the displacement angle of the rotor from the reference axis is generated. That is, the occurrence of torque ripple due to the displacement angle can be prevented.

On the other hand, a linear motor is one in which the diameters of the rotor and the armature are formed to be infinite, and the above theory is naturally applied. Therefore, if the air gap magnetic flux density distribution in the moving direction of the mover 2 in the permanent magnet 7 shown in FIG. 8 is formed in a sine wave shape, torque ripple due to the moving position of the mover 2 is eliminated, and a linear motor with excellent linearity is obtained. You can do it.

However, in the conventional linear motor, since the permanent magnet 7 is formed as shown in FIG. 8, the air gap magnetic flux density distribution in the moving direction of the mover 2 becomes a non-sinusoidal wave, and torque ripple occurs. There is a problem that linearity is impaired and positioning accuracy is adversely affected.

Next, the structure shown in FIG.
5 are provided with auxiliary permanent magnets 8 at both ends.
In this case, the air gap magnetic flux density distribution greatly deviates from the sinusoidal curve s as indicated by the chain line b, and is particularly severe at both ends of the mover 2 in the moving direction.

FIG. 10 shows a permanent magnet 7 in which the cross-sectional shape of the permanent magnet 7 is formed in a substantially semi-cylindrical shape. In FIG. 5, the air gap magnetic flux approximates to a sinusoidal curve s as shown by a curve c in FIG. A density distribution is obtained. However, as is apparent from FIG. 5, in the vicinity of the right end in the longitudinal direction, that is, in a region of ± λ / 4 from the longitudinal position where the sinusoidal curve s intersects the axis of the air gap magnetic flux density 0, the curve c has a sinusoidal shape. It is recognized that the wave curve s deviates greatly. Therefore, there is a problem that torque ripple always occurs in the mover 2 and the linearity of thrust is greatly reduced.

An object of the present invention is to provide a movable magnet type linear motor which solves the above-mentioned problems in the prior art and improves the linearity of thrust at both ends in the moving direction of the mover.

[0017]

According to a first aspect of the present invention, a flat multi-phase coil is provided with insulating plates on both sides of a flat support member made of a non-magnetic material. And a plurality of permanent magnets are arranged so that the polarity of magnetic poles adjacent to each other in the longitudinal direction of the stator is different from each other and is arranged via a magnetic gap. And a movable element formed so that opposite poles are opposed to each other, and the movable element is interposed in the stator such that the polyphase coil exists in the magnetic gap and is movable in the longitudinal direction of the stator. In addition, in a movable magnet type linear motor including a drive circuit for supplying a sine wave drive current to the polyphase coil, the thickness of the permanent magnet is set to t ₁ > t.
_e together form a (where, t _1:: thickness at the center, t _e the thickness dimension in the moving direction end portion), the permanent magnet and the polarity by adjacent permanent magnets in the moving direction end portions of the movable element The auxiliary permanent magnet formed so that the magnetic poles having different magnetic poles face the magnetic air gap is provided with a pitch λ / 4 between the permanent magnet and the magnetic pole.
(Λ is the pitch between the same poles of the permanent magnet).
The width dimension w ₂ of the auxiliary permanent magnet in the mover moving direction is defined as w ₂ <w
_1/4 (w ₁ is the width of the movable element moving direction of the permanent magnets) in
You form, was adopted the technical means that.

According to the second aspect of the present invention, there is provided a stator in which a flattened polyphase coil is disposed on one surface of a flat support member made of a nonmagnetic material so as to be shifted by a predetermined amount in the longitudinal direction. And a mover in which a plurality of permanent magnets are arranged so that the magnetic poles adjacent to each other in the longitudinal direction of the stator have different polarities, and the mover faces the polyphase coil via a magnetic gap. A movable magnet type linear motor including a drive circuit for supplying a sine wave drive current to the multi-phase coil while interposing the stator so as to be movable in the longitudinal direction of the stator as described above. The thickness dimension is t ₁ > _te
(Where t ₁ is the thickness at the center, and t _e is the thickness at the end in the movement direction), and at the both ends in the movement direction of the mover, adjacent to the permanent magnet, the polarity of the permanent magnet is set. An auxiliary permanent magnet formed such that different magnetic poles face the magnetic air gap is provided with a pitch λ / 4 (λ
Is located at the same pole pitch of the permanent magnet)
The width dimension w ₂ of the magnet in the moving direction of the mover is defined as w ₂ <w ₁ /
4 (w ₁ is the width of the movable element moving direction of the permanent magnet) formed
To that adopted the technical means that.

[0019]

[0020] In the above invention, it is possible to the permanent magnets and the auxiliary permanent magnet is formed of the same magnetic material, and the thickness t ₂ of the auxiliary permanent magnet and t ₂ <t _e. Further in the above invention, it is possible to the permanent magnets and the auxiliary permanent magnet is formed by magnetic material of different kinds, the magnetic flux density B _r2 in the auxiliary permanent magnet and the magnetic flux density B _r1 of the permanent magnet and B _r1> B _r2.

With the above configuration, the air gap magnetic flux density distribution near both ends in the moving direction of the mover can be approximated to a sinusoidal curve, and the linearity of thrust can be improved.

[0022]

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention, FIG. 3 is a sectional view taken along line AA in FIG. 1, and FIG.
FIG. 4 is an enlarged explanatory view showing the vicinity of the end of the mover in the moving direction in FIG. 3, and the same parts are denoted by the same reference numerals as in FIGS. 6 to 10. In these figures, the permanent magnet 7 has a substantially semi-cylindrical cross section as shown in FIG. 10 and a yoke 6 with a magnetic pole pitch λ / 2 therebetween.
Adheres to the inner surface of An auxiliary permanent magnet 8 is provided at both ends of the mover 2 so as to be adjacent to the permanent magnet 7 so that magnetic poles having a polarity different from that of the permanent magnet 7 face the magnetic gap.

[0023] Next in Figure 4, t _1, t _e are each thickness in the moving direction end portion of the thickness dimension and the mover 2 in the central portion of the permanent magnet 7, almost semicylindrical of t _1> t _e Form into a mold or pseudo-trapezoid. Further, it is preferable that the width dimension w ₁ of the permanent magnet 7 in the moving direction of the mover is set to be w ₁ <λ / 2. The thickness t ₂ of the auxiliary permanent magnet 8 and the width w ₂ of the mover 2 in the moving direction are t ₂ <t.
formed on _e and w ₂ <w _1/4.

It should be noted relationship t ₂ <t _e thickness dimension of the permanent magnets 7 and the auxiliary permanent magnet 8 is a case where both the permanent magnets 7 and 8 are formed of the same magnetic material, both the dissimilar magnetic material , The relationship between the magnetic flux density _Br1 of the permanent magnet 7 and the magnetic flux density _Br2 of the auxiliary permanent magnet 8 is represented by B
_{It is} assumed that _r1 > _Br2 .

It is recognized that the air gap magnetic flux density distribution in the moving direction of the mover 2 according to the above configuration approximates a sinusoidal curve s as shown by a curve d in FIG. In particular, in the region inside λ / 8 from the end of the mover 2, it is clear that the degree of approximation is extremely good as compared with the curves a to c of the conventional one.

In this case, the shapes and dimensions of the permanent magnets corresponding to the curves a to c are as shown in FIGS. 8 to 10, respectively. In these figures, the figures in parentheses are the dimensions (mm).
Is represented. Incidentally permanent magnets corresponding to the curve d is as shown in FIG. 4, the permanent magnet 7 in FIG 4 is the same size as the permanent magnets 7 shown in FIG. 10, the auxiliary permanent magnet 8 in Fig. 4, t ₂ = 3 mm, It was formed to w ₂ = 5 mm. The permanent magnet 7 and the auxiliary permanent magnet 8 were formed of an R-Fe-B-based rare earth magnet (HS-42AH manufactured by Hitachi Metals).

Next, FIG. 2 is a sectional view of a main part showing another embodiment of the present invention, and the same parts are denoted by the same reference numerals as in FIG. FIG. 2 shows an example in which a movable element 2 having a permanent magnet 7 and an auxiliary permanent magnet 8 is provided on one side of a stator 1, and the permanent magnet 7 and the auxiliary permanent magnet along the moving direction of the movable element 2 are provided. 8 is the same as that shown in FIG.
And FIG. Therefore, the same effect can be expected.

In the above description, the case where the cross-sectional profile between the central portion and the end portion of the permanent magnet 7 is formed in a straight line has been described, but this cross-sectional profile is formed as a concave curve or a convex curve. The effect is the same in the case of the above.

[0029]

According to the present invention having the above-described structure and operation, the air-gap magnetic flux density distribution near both ends in the moving direction of the mover having the permanent magnet can be approximated to a sinusoidal curve. The effect that torque ripple can be prevented and the linearity of thrust can be greatly improved can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part showing another embodiment of the present invention.

FIG. 3 is a sectional view taken along line AA in FIG.

FIG. 4 is an enlarged explanatory view showing the vicinity of an end in the moving direction of the mover in FIG. 3;

FIG. 5 is a diagram showing a relationship between a moving direction position of a mover and an air gap magnetic flux density.

FIG. 6 is a main part front view showing an example of a conventional movable magnet type linear motor.

FIG. 7 is a sectional view taken along the line BB in FIG. 6;

FIG. 8 is an explanatory cross-sectional view of the mover 2 taken along the line CC in FIG. 7;

9 is an explanatory cross-sectional view of the mover 2 in FIG. 7 taken along the line CC.

10 is an explanatory cross-sectional view of the mover 2 in FIG. 7 taken along the line CC.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator 2 Mover 3 Polyphase coil 7 Permanent magnet 8 Auxiliary permanent magnet

Continuation of the front page (56) References JP-A-4-165953 (JP, A) JP-A-6-38502 (JP, A) JP-A 63-93783 (JP, U) JP-A 1-159582 (JP , U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H02K 41/02-41/035

Claims (4)

(57) [Claims] 1. A stator comprising a flat multi-phase coil arranged on both sides of a flat support member made of a non-magnetic material, and a predetermined amount of the stator interposed via an insulating plate in a longitudinal direction. A plurality of permanent magnets are arranged so that the polarities of magnetic poles adjacent to each other in the longitudinal direction of the stator are different, and a mover formed so that different poles face each other via a magnetic gap. A drive circuit for supplying a sine-wave drive current to the multi-phase coil while interposing the multi-phase coil in the stator so that the multi-phase coil exists in the magnetic gap and movably in the longitudinal direction of the stator. the movable magnet type linear motor comprising Te, the thickness of the permanent magnet t _1> t _e together form a (where, t _1:: thickness at the center, t _e the thickness dimension in the moving direction end portion) , Adjacent to permanent magnets at both ends in the moving direction of the mover The auxiliary permanent magnet permanent magnet and the magnetic pole having different polarities are formed to face the magnetic gap, said permanent
Pitch between permanent magnet and magnetic pole λ / 4 (λ is the pitch between permanent magnets of the same pole)
Switch) and move the mover of the auxiliary permanent magnet.
The width w ₂ of the _{direction, w 2 <w 1/4} (w 1 is a permanent magnet
A movable magnet linear motor formed in a width dimension in the moving direction of the mover) . 2. A stator in which a flat multi-phase coil is disposed on one surface of a flat support member made of a non-magnetic material so as to be shifted by a predetermined amount in the longitudinal direction, and A movable element having a plurality of permanent magnets disposed so that the magnetic poles adjacent to each other in the longitudinal direction have different polarities. The movable element faces the polyphase coil via a magnetic gap and the stator. In the movable magnet type linear motor, which is provided with a driving circuit for supplying a sine-wave driving current to the polyphase coil while being interposed in the stator so as to be movable in the longitudinal direction, the thickness of the permanent magnet is set to t ₁ > T _e (where t ₁ is the thickness at the center, t _e is the thickness at the end in the movement direction), and the permanent magnet is arranged adjacent to the permanent magnet at both ends in the movement direction of the mover. So that the magnetic poles with different polarities face the magnetic gap An auxiliary permanent magnets form the permanent
Pitch between permanent magnet and magnetic pole λ / 4 (λ is the pitch between permanent magnets of the same pole)
Switch) and move the mover of the auxiliary permanent magnet.
The width w ₂ of the _{direction, w 2 <w 1/4} (w 1 is a permanent magnet
Moving magnet type linear motor, characterized in that formed in the movable element width in the moving direction). 3. The permanent magnet and the auxiliary permanent magnet are made of the same magnetic material.
And the thickness t ₂ of the auxiliary permanent magnet
<br /> movable magnet type linear motor according to claim 1 or 2, characterized in that a t ₂ <t _e. 4. The permanent magnet and the auxiliary permanent magnet is formed by the magnet different materials, permanent auxiliary magnetic flux density B _r1 in the permanent magnet
3. The movable magnet type linear motor according to claim 1 , wherein the magnetic flux density _Br2 of the _negative magnet is set to _Br1 > _Br2 .