JP3944808B2 - Linear motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a linear motor for, for example, a semiconductor manufacturing apparatus or an FA device that does not like cogging force, thrust ripple, or heat generation and requires high speed, high acceleration / deceleration, or high precision positioning.
[0002]
[Prior art]
A conventional linear motor is disclosed in US Pat. No. 4,633,108. This linear motor is composed of a mover in which a field permanent magnet is attached to a flat back yoke, and a stator in which concentrated winding coils are wound around teeth and arranged in a moving direction. .
Furthermore, when the pole pitch, which is the distance between adjacent permanent magnets, is λ, and the slot pitch, which is the distance between adjacent teeth, is τ, τ: λ is in a 2: 3 relationship.
[0003]
[Problems to be solved by the invention]
However, the conventional techniques have the following problems. That is, in the linear motor described in US Pat. No. 4,633,108, cogging force with a period of the slot pitch τ is generated when the mover moves due to the influence of the permanent magnets arranged at both ends of the mover. As a result, speed ripple occurs, causing various problems during transport and processing.
Further, according to the conventional configuration, when the pole pitch is λ and the slot pitch is τ, τ: λ is in the relationship of 2: 3, but this configuration can increase the winding coefficient and the number of slots per phase per pole. When applied to the arrangement method of the permanent magnets at both ends of the mover in 3/8, the cogging force increased on the contrary, and it was difficult to apply.
Therefore, the problem to be solved by the present invention is to provide a linear motor having a small speed ripple even when the weight of the mover is reduced by greatly reducing the cogging force due to the influence of the permanent magnets at both ends of the mover.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the linear motor of the present invention is provided with a three-phase armature winding on the armature, and 8N-1 (N is a natural number) first permanent magnets arranged in a line in a row, In a linear motor having 3/8 slots for each pole and each phase in which two second permanent magnets having different sizes from the first permanent magnet are arranged at both ends, the width of the first permanent magnet is W. The width W ′ of the second permanent magnet is 0.5 W <W ′ <0.6 W.
When the slot pitch is τ, the center-to-center distance λ ′ between the second permanent magnet and the first permanent magnet inside thereof is 0.9τ <λ ′ <1.0τ.
To. The configuration of the following, it is possible to reduce the cogging force generated by the influence of the permanent magnet of the mover at both ends.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 1 is a cross-sectional view as viewed from the front in claims 1 and 2, FIG. 2 is a cross-sectional view taken along the line AA 'in FIG. 1, and FIG. 3 is a diagram showing the shapes of a permanent magnet and an armature. In these drawings, 1 is a mover, 2 is a first permanent magnet unit, 3 is a second permanent magnet unit, 4 is a linear guide, 5 is a stator, 6 is a stator frame, 7 is a chevron-shaped fixing member, 8 Is a first armature unit, 9 is a second armature unit, 10 is a third armature unit, 11 is a fourth armature unit, 12 is a first permanent magnet, 13 is a second permanent magnet, 14 is a split core, Reference numeral 15 denotes an armature winding.
First, the mover 1 will be described. The mover 1 includes a linear guide 4 for supporting the mover on both sides and two field permanent magnet units 2 and 3 arranged perpendicular to the table surface. In one magnet unit, nine types of permanent magnets 12 and permanent magnets 13 are arranged in a row in total. First, the 1st permanent magnet 12 exists inside the needle | mover 1, and is arrange | positioned for every pole pitch (lambda) so that a polarity may become alternate.
The 2nd permanent magnet 13 exists in the both ends of the needle | mover 1, and is arrange | positioned so that it may become a polarity opposite to the polarity of the 1st permanent magnet 12 adjacent to it. Here, the relationship between the width W of the first permanent magnet 12 and the width W ′ of the second permanent magnet 13 is W: W ′ = 1: 0.54.
It has become.
[0006]
Next, the stator 5 will be described. The stator 5 includes four armature units 8 to 11 sandwiching two magnet units 2 and 3, a mountain-shaped fixing member 7 to which the armature units 8 to 11 are attached, a linear guide 4 and a mountain shape. It is comprised from the stator frame 6 which has received this fixing member 7. One armature unit is composed of 18 divided cores 14 and armature windings 15 concentrated on the cores in advance. Further, the surface of the armature winding 15 is stycast with a resin having good thermal conductivity.
In such a configuration, the relationship between the slot pitch τ and the pole pitch λ is τ: λ = 8: 9
Further, the relationship with the distance λ ′ from the center of the second permanent magnet 13 to the center of the adjacent first permanent magnet 12 is
τ: λ ′ = 1: 0.94
It has become.
The distance L from the left end surface of the second permanent magnet 13 to the left end surface of the adjacent first permanent magnet 12 is L = λ ′ + (W−W ′) / 2 = 0.94 × τ + 0.23 × W.
It is expressed. W is W = 0.9 × τ
If so, the relationship between the slot pitch τ and the distance L from the left end surface of the first permanent magnet 12 to the left end surface of the second permanent magnet 13 is:
L = 0.94 × τ + 0.23 × 0.9 × τ = 1.15 × τ
τ: L = 1: 1.15
It becomes.
[0007]
With the above configuration, the cogging force generated by the influence of the permanent magnets 12 and 13 at both ends of the mover 1 can be almost eliminated. Therefore, this effect will be described in comparison with a conventional example.
According to the prior art, the relationship between the slot pitch τ and the distance L is τ: L = 2: 3 = 1: 1.5.
It has become. Further, when the magnet widths W and W ′ and the slot pitch τ are the same as in the present embodiment, when the relationship between the slot pitch τ and the distance λ ′ described above is derived,
τ: λ ′ = 1: 1.29
It becomes. That is, L and λ ′ are longer in the prior art than in the embodiment of the present invention. FIG. 4 shows a result of comparison of cogging force due to such a structure difference.
As can be seen from FIG. 4, the cogging force is generated with an amplitude approximately eight times that of the present proposal if the conventional magnet arrangement is used.
Further, the cogging force varies depending on the magnitude of λ ′ / τ, and becomes minimum when λ ′ / τ = 0.94 shown in the embodiment.
FIG. 5 shows the relationship between λ ′ / τ and the cogging force.
The shape that minimizes the cogging force slightly depends on the ratio of the width W of the first permanent magnet 12 to the width W ′ of the second permanent magnet 13, but the condition is 0.9τ <λ ′ <1.0τ · ... (1) and
0.5W <W ′ <0.6W (Equation 2), the cogging force can be made relatively small.
That is, if only the expression (2) is adopted as compared with the case where W = W ′, the cogging force can be reduced to about 1/3, and further, the condition of the expression (1) is satisfied. Compared with the prior art, the cogging force can be reduced to about 1/8.
[0008]
【The invention's effect】
As described above, the cogging force due to the influence of the permanent magnets at both ends of the mover can be greatly reduced by the configuration of the present invention. Further, not only the amplitude of the cogging force but also the order of generation thereof is increased, and a linear motor with a small speed ripple can be realized even if the weight of the mover is reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view seen from the front showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view seen from the top showing an embodiment of the present invention.
FIG. 3 is a diagram showing the shape of an embodiment of the present invention.
FIG. 4 is a diagram showing cogging force waveforms according to the present invention and the prior art.
FIG. 5 is a diagram showing the relationship between the permanent magnet shape and the cogging force amplitude value of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mover, 2 1st permanent magnet unit, 3 2nd permanent magnet unit, 4 Linear guide, 5 Stator, 6 Stator frame, 7 Angle-shaped fixing member, 8 1st armature unit, 9 2nd armature unit 10 Third armature unit, 11 Fourth armature unit, 12 First permanent magnet, 13 Second permanent magnet, 14 Split core, 15 Armature winding

Claims (1)

A three-phase armature winding is applied to the armature, and 8N-1 (N is a natural number) first permanent magnets are arranged in a row in the field, and the sizes of the first permanent magnets are different at both ends. In a linear motor having 3/8 slots per pole and phase each having two second permanent magnets,
When the width of the first permanent magnet is W, the width W ′ of the second permanent magnet is
0.5W <W '<0.6W
And,
When the slot pitch is τ, the distance λ ′ between the centers of the second permanent magnet and the first permanent magnet inside thereof is
0.9τ <λ ′ <1.0τ
A linear motor characterized by that .

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