JP2006034015A - Linear motor for machine tools - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear motor capable of improving the processing speed of a laser processing machine, and capable of realizing a high-speed and high-precision processing by greatly reducing the cogging force.
SOLUTION: A plurality of identically shaped permanent magnets are wound around an armature coil and a stator attached to both surfaces of a plate-like yoke at equal intervals so as to have different polarities alternately perpendicular to the moving direction of the mover. A linear motor used in a machine tool comprising a pair of movers arranged so that the armature core faces the arrangement of permanent magnets on both sides of the stator,
Nine armature cores, each armature having a length that is eight times the magnet pitch τ, which is the sum of the width of the permanent magnet and the distance between the permanent magnets, and three armature coils of each phase wound around A linear motor for machine tools and the like characterized by comprising three mover blocks each having a length of 1/3 of the magnet pitch τ is provided.
[Selection figure] None

Description

  The present invention relates to a permanent magnet linear motor widely used for the purpose of driving a movable part of a machine tool.

  FIG. 3 is a perspective view showing an example of a laser processing machine. A table 122 is provided on the frame 121 shown in FIG. 3, and a work (not shown) to be processed is placed thereon. A driving device 123 that can move in the X-axis direction is attached above the frame 121, and a driving device 124 that can move in the Y-axis direction is attached to the X-axis direction driving device 123 via an attachment component. A driving device 125 that can move in the Z-axis direction is attached to the Y-axis direction driving device 124, and a torch 126 that emits laser light is attached to the Z-axis direction driving device 125. In FIG. 3, the wiring of the driving device, the control device, and the components that transmit the laser light are omitted. In the laser processing machine, the drive device in the X-axis and Y-axis directions is controlled by the control device, and the laser beam from the torch attached to the tip is applied to the workpiece and cut into a desired shape. Further, the distance between the torch and the workpiece is controlled by a driving device in the Z-axis direction in order to focus the laser beam. In a conventional laser processing machine, a drive device composed of a rotary servo motor and a ball screw has been used. However, there is a limit to machining at high speed, and the fast feed speed is limited to about 20 m / min. Furthermore, when the workpiece is longer than 3 m, there is a problem that the machining accuracy is lowered due to the deflection of the ball screw. Therefore, studies have been made to replace the drive unit with a linear motor.

  Since a machine tool requires a large thrust, a plurality of permanent magnets are mounted on a plate-shaped yoke with the same pitch but with different polarities alternately in the moving direction of the mover, so that they face the stator magnet row. A linear motor is used in which a mover comprising a magnetic core and an armature coil is disposed.

A conventional linear motor related to the present invention will be described with reference to FIGS.
FIG. 4 is a side view of a conventional linear motor 130 of a type in which a coil moves on a permanent magnet array composed of a plurality of permanent magnets, and FIG. 5 is a cross-sectional view taken along the line AA of FIG. As shown in FIG. 4, the conventional linear motor 130 includes a stator 133 in which a plurality of permanent magnets 132 are mounted on an iron plate 131 at equal pitches and polarities that are alternately different in the moving direction of the mover. The armature core 134 is composed of a mover 136 having an armature coil 135 wound around an armature core 134 made of a magnetic material so as to face the permanent magnet array. The armature coil 135 is concentratedly wound around the armature core 134 and has a three-phase balanced connection as a U phase, a V phase, and a W phase.
The linear motor 130 shown in FIG. 4 has eight permanent magnets opposed to nine armature cores 134, and a three-phase current is caused to flow through the armature coil 135 to create an eight-pole magnetic field as shown in the figure. The coils of each phase are arranged at various positions. When the phase of the current is controlled with respect to the magnetic field generated by the permanent magnet 132 to generate a magnetic field in the armature coil 135, the mover 136 supported by a holding mechanism (not shown) moves on the stator 133. . The arrows marked on each of the permanent magnets 132 in FIG. 4 indicate the direction of magnetization, and the arrows marked on each of the armature coils 135 in FIG. 4 indicate the winding direction.

  FIG. 6 is a cross-sectional view of the above-described conventional linear motor 130 viewed from the moving direction in a state where it is supported by the holding mechanism. As shown in FIG. 6, the mover 136 (the armature core 134 around which the armature coil 135 is wound) is fixed to the lower part of the table 140, and is attached to the tip of the vertical frame 144 that extends vertically from both lower ends of the table 140. An LM (Liner Motion) block 141 for guiding the mover 136 is fixed. The stator 133 is fixed on a base plate 143 of the linear motor, and other LM rails 142 that are paired with the LM block 141 are provided on both upper ends of the base plate 143.

  When the linear motor of FIG. 4 is incorporated, a very large magnetic attractive force acts between the permanent magnet 132 and the armature core 134, and the magnitude thereof is about several times the rated thrust. Therefore, a large force is also applied between the LM block 141 and the LM rail 142, and the frictional force becomes very large, which causes a problem that the life of the guide is reduced.

  In order to solve this, in Patent Document 1, as shown in FIG. 7, two stators 153 (including an iron plate 151 and a permanent magnet 152) are opposed to each other, and a mover 156 (an armature core 154 and an armature are interposed therebetween). Disclosed is a linear motor 150 that includes a coil 155. By doing so, the attractive force between the mover and the magnet array cancels out, and the load on the mover guide can be reduced. However, in the configuration of FIG. 7, in order to stand the stator iron plate 151 vertically with high accuracy, a certain amount of thickness is required, which is thicker than the iron plate of FIG. Further, the base plate 163 is large, which makes the entire driving device heavy. As described with reference to the laser beam machine in FIG. 3, the Y-axis direction driving device and the Z-axis direction driving device are mounted on the X-axis direction driving device. Thrust is increased and the drive device is increased in size. For this reason, weight reduction is desired for a drive device (linear motor). In order to reduce the weight of the linear motor, it is effective to reduce the weight of the stator and the base plate of the driving device that are arranged in the entire driving region. 7 also shows a table 160, an LM block 161, an LM rail 162, a base plate 163, and a vertical plate 164.

  Therefore, as in the linear motor 170 shown in FIG. 8 disclosed in Patent Document 2, a plurality of permanent magnets 172 are arranged on a single iron plate 171 at the same pitch and with different polarities alternately in the moving direction of the mover. The stator 173 is attached, and a mover 176 is formed by winding an armature coil 175 around an armature core (magnetic core) 174 made of a magnetic material so as to face the permanent magnet row. The winding method to the armature coil 175 is the same as that of the conventional linear motor 130. FIG. 9 is a cross-sectional view seen from the moving direction of the linear motor 170 described above supported by the holding mechanism. FIG. 9 also shows a table 180, an LM block 181, an LM rail 182, a base plate 183 and a vertical plate 184. The thickness of the iron plate of the linear motor 170 in FIG. 9 is about the same as that of the linear motor 150 in FIG.

High thrust can be obtained with the conventional linear motor 170 designed in this way, but an attractive force acts in the moving direction between the permanent magnet and the magnetic core even when no current is passed through the coil. This is called cogging. If the cogging is large, the position control of the linear motor will not be successful, and there is a problem that the processing accuracy of the laser processing machine is deteriorated.
JP-A-10-257750 JP 2002-34231 A

  An object of the present invention is to provide a linear motor that improves the processing speed of a laser processing machine, and to provide a linear motor that can significantly reduce cogging force and realize high-speed and high-precision processing.

In the present invention, a plurality of identically shaped permanent magnets are wound with a stator and armature coils attached at equal intervals on both surfaces of a plate-like yoke so as to have different polarities perpendicular to the moving direction of the mover. A linear motor used in a machine tool comprising a pair of movers arranged so that the armature core faces the arrangement of permanent magnets on both sides of the stator,
Each armature has a length that is eight times the magnet pitch τ, which is the sum of the width of the permanent magnet and the distance between the permanent magnets, and three armature coils for each of the U, V, and W phases. A linear motor for machine tools, comprising three mover blocks each having nine armature cores wound, wherein the distance between the blocks is set to one third of the magnet pitch τ. provide.
The present invention also provides a laser processing machine using the permanent magnet type linear motor as a three-dimensional moving mechanism.

  According to the present invention, the length of the stator magnet pitch is eight times, the number of teeth (the number of armature cores) is nine, and the mover block in which the armature coils of each phase are wound three by three. The cogging force can be greatly reduced and high-accuracy machining can be achieved by arranging three of the blocks and reducing the pitch between the blocks to 1/3 of the stator magnet pitch.

Examples of the permanent magnet used in the present invention include Nd and Sm, but are not particularly limited. The orientation of the magnet is perpendicular to the yoke.
The armature core (also referred to as a magnetic core) used in the present invention is not particularly limited as long as it is a magnetic body, but preferably has an integrated shape.

Hereinafter, an embodiment according to the present invention will be described with reference to FIG.
FIG. 1 is a diagram illustrating an embodiment of the present invention, and is a vertical sectional view of a central portion of a linear motor. As shown in FIG. 1, a linear motor 10 of the present invention has a plurality of permanent magnets 12 on a single yoke (for example, an iron plate) 11 and has different polarities alternately at the same pitch and perpendicular to the moving direction of the mover. And a pair of movers 16 (mover blocks 16a to 16a) in which an armature coil 15 is wound around an armature core (magnetic body core) 14 made of a magnetic material so as to face the arrangement of the permanent magnets. b).

The length of each mover block is eight times the stator magnet pitch, and the number of mover teeth (armature cores) is nine. The three mover blocks are arranged in series in the traveling direction, and a spacer 17 having a size of 1/3 of the stator magnet pitch is preferably inserted between the blocks (between the armature cores). . However, the space which makes the space | interval of each block the length of 1/3 of a magnet pitch may be sufficient.
The material of the spacer 17 is preferably a non-magnetic material such as non-magnetic stainless steel or aluminum in order to eliminate magnetic interference between the three mover blocks. The shape of the spacer is not particularly limited, but a rectangular parallelepiped block shape is preferable. Examples of the connection with each mover block include a method of fixing with an adhesive, a method of providing a frame separately with the mover and mechanically fixing, and the like.
The winding method for the armature coil 15 may be arranged such that there are a total of three U-phase, V-phase, and W-phase coils, and the arrangement of the U-phase, V-phase, and W-phase may be appropriately selected. For example, when the U-phase, V-phase, and W-phase coils of the first block are wound three times from the left tooth in the figure, the second block is the W-phase three by three from the left tooth. The U-phase and V-phase coils and the second block are wound with three V-phase, W-phase, and U-phase coils from the left tooth.

FIG. 2 illustrates the cogging force of the linear motor 10 of FIG. 1 having a pair of movers each having three mover blocks and the interval of which is 1/3 of the magnet pitch.
2 shows the cogging force of a conventional linear motor 170 in which each mover is constituted by one block in the traveling direction of FIG. The cogging force is a force that periodically acts in the traveling direction or the opposite direction when the mover moves, and the cycle is the pitch of the magnet. In this case, the maximum and minimum difference is 144N. If two movers whose phase of the cogging force waveform differs by 120 ° are attached to the linear motor 170 of the conventional example, the cogging force cancels out from the synthesis of the waveform. Therefore, according to the present invention in which the space between the blocks is 1/3 of the stator magnet pitch, it is considered that the cogging force can be greatly reduced.

  According to the present invention, the linear motor provided with the auxiliary core as described above can be applied to a laser processing machine using a three-dimensional moving mechanism of X, Y, and Z axes. When the laser processing machine of the present invention is used, thrust unevenness due to reduced gogging force is eliminated, position control accuracy is increased, and high-speed and accurate processing can be performed.

Example As shown in FIG. 1, the second and third mover blocks were arranged with an interval of 1/3 of the magnet pitch corresponding to 120 ° of the waveform of the cogging force. An Nd—Fe—B permanent magnet was used, and an iron yoke was used as the core material. Here, the cross-sectional dimensions in FIG. 1 were magnet width 18 mm, magnetization direction thickness 5 mm, magnet pitch = 25 mm, armature core tooth width 10 mm, tooth length 34 mm, and stator yoke thickness 19 mm. The gap between the mover and the stator magnet is 1 mm. Each width of the spacer (nonmagnetic stainless steel SUS304) of the first block, the second block, and the third block was 8.33 mm. The thickness of the mover and the stator in the cross-sectional direction was 33 mm. In order to obtain the same thrust as that of the present invention, the dimensions of the conventional example in FIG. 8 are 100 mm in thickness in the cross-sectional direction of the mover and the stator, and other dimensions are the same.
As shown by the solid line in FIG. 2, the cogging force of the present invention was reduced, and the maximum and minimum difference was 11N. As described above, the cogging force can be reduced by arranging the three-block mover core with a gap of 1/3 of the magnet pitch.
Thus, the linear motor provided with the auxiliary core could be applied to the laser processing machine used for the three-dimensional moving mechanism of the X, Y, and Z axes.

It is a figure explaining the linear motor which concerns on embodiment of this invention. It is a figure explaining the waveform of the cogging force of this invention and a prior art example. It is sectional drawing explaining a laser processing machine. It is sectional drawing explaining the relationship between the needle | mover of a conventional linear motor, and a stator. FIG. 5 is a cross-sectional view taken along line AB in FIG. 4. It is a figure explaining the holding mechanism of the linear motor of FIG. It is a figure explaining the conventional linear motor which cancels out a magnetic attraction force. It is a figure explaining the relationship between the needle | mover and stator of the conventional linear motor which cancels out magnetic attraction force. It is a figure explaining the holding mechanism of the linear motor of FIG.

Explanation of symbols

10, 130, 150, 170 Linear motor 11, 131, 151, 171 Plate-shaped yoke 12, 132, 152, 172 Permanent magnet 13, 133, 153, 173 Stator 14, 134, 154, 174 Armature core 15, 135 , 155, 175 Armature coil 16, 136, 156, 176 Movers 20, 140, 160, 180 Table 21, 141, 161, 181 LM block 22, 142, 162, 182 LM rail 23, 143, 163, 183 Base plate 24, 144, 164, 184 Vertical frame 121 Frame 122 Table 123 X-axis direction driving device 124 Y-axis direction driving device 125 Z-axis direction driving device 126 Torch

Claims (3)

A stator in which a plurality of permanent magnets having the same shape are perpendicular to the moving direction of the mover and have different polarities alternately on both surfaces of the plate-like yoke, and an armature core wound with an armature coil A linear motor used for a machine tool comprising a pair of movers arranged so as to face the arrangement of permanent magnets on both sides of the stator,
Each armature has a length that is eight times the magnet pitch τ, which is the sum of the width of the permanent magnet and the distance between the permanent magnets, and three armature coils for each of the U, V, and W phases. A linear motor for machine tools, comprising three mover blocks each having nine wound armature cores, wherein the distance between the blocks is １ ／ of the magnet pitch τ.   The linear motor for machine tools according to claim 1, further comprising a non-magnetic spacer between the blocks in order to make the distance between the blocks 1/3 of the magnet pitch τ. A laser processing machine using the permanent magnet linear motor according to claim 1 as a three-dimensional moving mechanism.

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