Linear motor

Abstract

To provide a linear motor which can maintain large thrust even at high speed in a work area.SOLUTION: A linear motor 1 is constituted by oppositely arranging a needle 2 arranged with a plurality of permanent magnets 21 and a stator 3 formed by winding a coil 33 around each of a plurality of magnetic pole teeth 32. A movable area of the needle 2 has: a work area in which processing to a processing object is performed; and a conveyance area for conveying the processing object to the work area, and the number of windings of the coil 33 corresponding to the conveyance area is less than the number of windings of the coil 33 corresponding to the work area.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a linear motor that combines a mover and a stator to extract linear motion output.

Background Art

[0002] In semiconductor manufacturing equipment, liquid crystal display substrate manufacturing facilities, etc., a mechanism is required to accurately convey a workpiece with low vibration within a plane perpendicular to the gravitational direction. An actuator that can move independently on linearly arranged guides moves a table on which the workpiece is placed. Since high accuracy and no vibration are required for the movement of this table, a method of converting the force of a rotary machine used in a general processing apparatus into linear movement by a ball screw is not used, and a linear motor capable of directly performing linear movement is used as a drive source.

[0003] As such a linear motor, a movable magnet type linear motor having a configuration in which a mover in which a plurality of permanent magnets are arranged so that magnetism alternates and a stator in which coils having the same number of turns are wound around a plurality of magnetic pole teeth are arranged corresponding to each other with a predetermined distance therebetween is known. By flowing an alternating current whose polarity and magnitude are synchronized with the moving distance with respect to the field magnet period of the mover through the coils of the stator, a thrust is generated in the moving direction by the attractive and repulsive forces with the permanent magnets, and the mover is linearly moved with respect to the stator. As linear motors having such a configuration, various ones have been proposed (Patent Documents 1, 2, etc.).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a moving magnet type linear motor, the effective stroke (length of the movable range) of the mover is equal to or less than the value obtained by subtracting the total length of the mover from the total length of the stator. Therefore, in order to increase the effective stroke, it is necessary to reduce the length of the mover or increase the length of the stator. In the former case, since the resulting thrust decreases, a desired large thrust cannot be provided, which is not practical.

[0006] On the other hand, in the latter case, the number of coils provided increases as the length of the stator increases. As a result, since the inductance of the stator increases, there is a problem that the thrust decreases when the speed of the mover increases as the stroke becomes longer.

[0007] By the way, for example, when applying a linear motor to a processing apparatus that performs wire bonding processing, flip chip bonding processing, etc., a uniformly large thrust is not necessarily required over the entire stroke of the linear motor. A large thrust is required in the working area where the bonding process is performed on the object to be processed, but a relatively small thrust is sufficient in the transfer area where the object to be processed is transferred to the working area.

[0008] The present invention has been made in view of such circumstances, and an object thereof is to provide a linear motor that can maintain a large thrust even at a high speed in the working area.

Means for Solving the Problems

[0009] The linear motor according to the present invention includes a mover in which a plurality of permanent magnets are arranged, and a stator in which coils are wound around a plurality of magnetic pole teeth, respectively. In the linear motor in which the movable region of the mover has a first region and a second region to which the mover moves up to the first region, the number of turns of the coil corresponding to the second region is made less than the number of turns of the coil corresponding to the first region.

[0010] The linear motor according to the present invention is a linear motor used for the movement of an object to be processed, wherein the first region is a working region for performing processing on the object to be processed, and the second region is a conveying region for conveying the object to be processed to the working region.

[0011] The linear motor according to the present invention is characterized in that the number of turns of the coil corresponding to the second region is 1 / 5 to 1 / 3 of the number of turns of the coil corresponding to the first region.

[0012] The linear motor according to the present invention is characterized in that a 7-pole 6-slot configuration having seven permanent magnets, six magnetic pole teeth and coils is used as a basic unit.

[0013] In the linear motor of the present invention, the movable region of the mover has a first region (a working region where processing is performed on the object to be processed) and a second region (a conveying region for conveying the object to be processed to the working region) to which the mover moves to the first region, and the number of turns of the coil of the stator corresponding to the second region (conveying region) is made smaller than the number of turns of the coil of the stator corresponding to the first region (working region). In other words, in the effective stroke, the number of turns of the coil corresponding to the conveying region that does not require a particularly large thrust is made smaller than the number of turns of the coil corresponding to the working region that requires a large thrust. When the length of the effective stroke is the same (the number of coils is the same), in the linear motor of the present invention, the inductance of the stator is smaller than that of the conventional linear motor in which the number of turns of the coil is uniform over the entire region, so that a large thrust can be maintained even at a high speed. Although there is concern about a decrease in thrust by reducing the number of turns of the coil, the portion where the number of turns is reduced corresponds to the conveying region where a small thrust is sufficient, so that a desired large thrust can be provided in the working region without being affected by the decrease in the number of turns of the coil.

[0014] In the linear motor of the present invention, the number of turns of the coil corresponding to the second region (conveying region) is set to 1 / 5 to 1 / 3 of the number of turns of the coil corresponding to the first region (working region). Therefore, while providing the desired thrust required in each of the first region (working region) and the second region (conveying region), a large thrust can be maintained even at a high speed in the first region (working region).

[0015] In the linear motor of the present invention, a 7-pole 6-slot configuration having 7 permanent magnets and 6 coils is used as the basic unit. Therefore, a high thrust can be obtained with a lightweight mover, and a high-speed response can be realized.

Advantages of the Invention

[0016] According to the linear motor of the present invention, the number of turns of the coil corresponding to the region that does not require a very large thrust is made smaller than the number of turns of the coil corresponding to the region that requires a large thrust. Therefore, while providing the desired thrust in both regions, it is possible to maintain a large thrust even at a high speed with respect to the region that requires a large thrust.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described in detail based on the drawings showing its embodiments.

[0019] FIG. 1 and FIG. 2 are a perspective view and a side view showing the configuration of the linear motor 1 of the present invention, and FIG. 3 is a side view showing the configuration of a basic unit in the linear motor 1. The linear motor 1 of the present invention has a mover 2 and a stator 3 opposed to each other with a predetermined distance therebetween.

[0020] First, referring to FIG. 3, the configuration of the basic unit of the linear motor 1 will be described. The basic unit of the mover 2 is configured by supporting and fixing seven rectangular permanent magnets 21 at equal pitches to a thin plate-shaped back yoke 22 and juxtaposing them in the moving direction (the left-right direction in FIG. 3). Each permanent magnet 21 is magnetized in the thickness direction (the up-down direction in FIG. 3), and the magnetization directions of adjacent permanent magnets 21, 21 are opposite to each other. That is, the permanent magnet 21 magnetized in the direction from the mover 2 side to the stator 3 side (the direction from top to bottom in FIG. 3) and the permanent magnet 21 magnetized in the direction from the stator 3 side to the mover 2 side (the direction from bottom to top in FIG. 3) are alternately arranged. Note that the plurality of permanent magnets 21 may be arranged in a skewed manner inclined by about 3 degrees with respect to the moving direction. For example, the permanent magnet 21 is made of a neodymium magnet, a ferrite magnet, a samarium cobalt magnet, etc., and the back yoke 22 is formed of a soft magnetic metal such as a silicon steel material.

[0021] On one hand, the basic unit of the stator 3 is configured by integrally providing six rectangular magnetic pole teeth 32 at equal pitches in the moving direction on a thin plate-shaped core 31, and winding coils 33 around each magnetic pole tooth 32. For example, the core 31 and the magnetic pole teeth 32 are integrally formed by laminating silicon steel sheets, and the coil 33 is an enamel-coated wire. U, V, and W in FIG. 3 respectively indicate the U-phase, V-phase, and W-phase of a three-phase AC power supply. In order to perform three-phase parallel energization, six slots with three pairs of forward and reverse slots as one set are used as the basic unit.

[0022] As described above, the linear motor 1 of the present invention has a seven-pole six-slot configuration having seven permanent magnets 21, six magnetic pole teeth 32, and coils 33 as the basic unit (basic unit). Then, a plurality of basic units of the seven-pole six-slot having such a configuration are connected together to form the linear motor 1. Since the seven-pole six-slot is the basic configuration, a lightweight mover can obtain a high thrust and achieve a high-speed response.

[0023] In the embodiment shown in FIG. 2, the linear motor 1 is configured by combining two basic units of the mover 2 and five basic units of the stator 3. Therefore, in this embodiment, the mover 2 has 14 permanent magnets 21, and the stator 3 has 30 magnetic pole teeth 32 and coils 33. And since the effective stroke (length of the movable range) of the mover 2 in the linear motor 1 is the length obtained by subtracting the total length of the mover 2 from the total length of the stator 3, the effective stroke of the linear motor 1 shown in FIG. 2 is three basic units.

[0024] The linear motor 1 of the present invention can be applied to a wire bonder that performs wire bonding processing on an object to be processed. By driving the linear motor 1, the object to be processed is transported to the working area, and then wire bonding processing is performed on the object to be processed while driving the linear motor 1 in the working area. Therefore, the linear motor 1 has a transport area for transporting the object to be processed to the working area and a working area for actually performing wire bonding processing on the object to be processed. Specifically, as shown in FIG. 2, there are a transport area of two basic units and a working area of three basic units.

[0025] When a three-phase alternating current is passed through the coil 33 of the stator 3 to generate a magnetic field in the magnetic pole teeth 32, the permanent magnet 21 of the mover 2 is sequentially magnetically attracted and repelled by this magnetic field, generating a thrust force on the mover 2, and the mover 2 performs a linear motion with respect to the stator 3. Utilizing this linear motion caused by the thrust force, the conveyance of the workpiece to the working area and the movement of the workpiece in the wire bonding process in the working area are carried out.

[0026] In the stator 3 of the linear motor 1 of the present invention, the number of turns of the coil 33 wound around each magnetic pole tooth 32 is not made equal throughout the entire area, but the number of turns of the coil 33 corresponding to the conveyance area is made less than the number of turns of the coil 33 corresponding to the working area. Specifically, in the conveyance area (the fourth unit and the fifth unit on the right side in FIG. 2), the number of turns of each coil 33 is 7 turns, and in the working area (the first unit, the second unit, and the third unit on the left side in FIG. 2), the number of turns of each coil 33 is 28 turns.

[0027] FIG. 4 is a side view showing the configuration of a linear motor 10 as a comparative example. In FIG. 4, the same reference numerals are given to the same or corresponding parts as in FIG. 2. The linear motor 10 in FIG. 4 is a combination of two basic units of the mover 2 and five basic units of the stator 3, similar to the embodiment shown in FIG. 2. Also, the configuration of the mover 2 in the linear motor 10 is the same as the configuration of the mover 2 in the linear motor 1.

[0028] However, the configuration of the stator 3 is different between the linear motor 10 and the linear motor 1. In the linear motor 1, the number of turns of the corresponding coil 33 is different between the working area and the conveyance area (28 turns and 7 turns), whereas in the linear motor 10, the number of turns of the coil 33 is uniformly 28 turns throughout the entire area.

[0029] When the linear motor 1 is applied to a wire bonder, a large thrust is not required in the transfer area for transporting the object to be processed to the working area, but a large desired thrust is required in the working area for performing the bonding process on the object to be processed. Therefore, in the present invention, the number of turns of the coil 33 corresponding to the transfer area where even a relatively small thrust causes no problem is made smaller than the number of turns of the coil 33 corresponding to the working area where a large thrust is required.

[0030] With such a configuration, compared with the linear motor 10 of the comparative example in which the number of turns of the coil 33 is uniform as shown in FIG. 4, the inductance of the stator 3 becomes smaller. As a result, in the linear motor 1 of the present invention, in the working area, it is possible to maintain a large thrust even at a higher speed. This is because, since the inductance of the stator 3 becomes smaller, the current can be increased until magnetic saturation is reached.

[0031] By the way, in the linear motor 1 of the present invention, since the number of turns of the coil 33 is made smaller, a decrease in thrust is a concern. However, since the portion where the number of turns is made smaller corresponds only to the transfer area where even a small thrust is sufficient, it is possible to provide a large desired thrust in the working area without being affected by the decrease in the number of turns of the coil 33.

[0032] The characteristics comparison between the linear motor 1 having the configuration shown in FIG. 2 (hereinafter, also simply referred to as the present invention example) and the linear motor 10 having the configuration shown in FIG. 4 (hereinafter, also simply referred to as the comparative example) will be described.

[0033] FIG. 5 is a graph showing the characteristics of the present invention example and the comparative example. In FIG. 5, the horizontal axis represents the speed (m / s), the vertical axis represents the maximum thrust (N), and a and b represent the characteristics of the present invention example and the comparative example, respectively. Both the present invention example and the comparative example can provide a maximum thrust of 1000 N. However, in the comparative example, the maximum thrust of 1000 N can be maintained only up to the maximum speed of 1.4 m / s, whereas in the present invention example, the maximum thrust of 1000 N can be maintained even up to the maximum speed of 1.8 m / s.

[0034] In the linear motor 1 of the present invention, since the number of turns of the coil 33 corresponding to the conveyance region is set to 1 / 4 of the number of turns of the coil 33 corresponding to the work region, the thrust constant in the conveyance region decreases to 1 / 4 of that in the work region due to the characteristics of the linear motor. Therefore, if the control constant (gain) of the drive circuit of the linear motor 1 is kept constant over the entire region, unstable operation will occur. Thus, in the present embodiment, a linear encoder for detecting the current position of the mover 2 is provided, and based on the position information of the mover 2 obtained from this linear encoder, the control constant of the drive circuit is changed from the upper controller to ensure stable operation. For example, when the mover 2 is located in the conveyance region, a large control constant is set; when the mover 2 is located in the work region, a small control constant is set; and when the mover 2 is located across the conveyance region and the work region, an intermediate control constant is set to achieve stable constant-speed motion.

[0035] Hereinafter, other embodiments of the present invention will be described. FIG. 6 is a side view showing the configuration of the linear motor 1 according to another embodiment of the present invention. In FIG. 6, the same or corresponding parts as those in FIG. 2 are denoted by the same reference numerals.

[0036] In the embodiment shown in FIG. 6, the linear motor 1 is configured by combining two basic units of the mover 2 and six basic units of the stator 3. Therefore, in this embodiment, the mover 2 has 14 permanent magnets 21, and the stator 3 has 36 magnetic pole teeth 32 and coils 33. The effective stroke of the linear motor 1 shown in FIG. 6 is equivalent to four basic units, and as shown in FIG. 6, there are a conveyance region equivalent to three basic units and a work region equivalent to three basic units. The number of turns of each coil 33 corresponding to the work region (the first unit, the second unit, and the third unit on the left side) is set to 28 turns, while the number of turns of each coil 33 corresponding to the conveyance region (the fourth unit, the fifth unit, and the sixth unit on the right side) is reduced to 7 turns. Also in this linear motor 1, similar to the example of the present invention described above, the maximum thrust is 1000 N, and this maximum thrust can be maintained up to a maximum speed of 1.8 m / s.

[0037] FIG. 7 is a side view showing the configuration of the linear motor 1 according to still another embodiment of the present invention. In FIG. 7, the same or corresponding parts as those in FIG. 2 are denoted by the same reference numerals.

[0038] In the embodiment shown in FIG. 7, the linear motor 1 is configured by combining two basic units of the mover 2 and four basic units of the stator 3. Therefore, in this embodiment, the mover 2 has 14 permanent magnets 21, and the stator 3 has 24 magnetic pole teeth 32 and coils 33. The effective stroke of the linear motor 1 shown in FIG. 7 is equivalent to two basic units. As shown in FIG. 7, there are a conveyance area equivalent to one basic unit and a working area equivalent to three basic units. The number of turns of each coil 33 corresponding to the working area (the first unit, the second unit, and the third unit on the left side) is set to 28 turns, while the number of turns of each coil 33 corresponding to the conveyance area (the fourth unit on the right side) is reduced to 7 turns. In a linear motor having a similar configuration with a uniform number of turns of the coil over the entire area, the maximum thrust of 1000 N can be maintained only up to a maximum speed of 2.2 m / s, whereas in the linear motor 1 shown in FIG. 7, this maximum thrust of 1000 N can be maintained up to a maximum speed of 2.7 m / s.

[0039] FIG. 8 is a side view showing the configuration of the linear motor 1 according to still another embodiment of the present invention. In FIG. 8, the same or corresponding parts as those in FIG. 2 are denoted by the same reference numerals.

[0040] In the embodiment shown in FIG. 8, a linear motor 1 is constituted by combining one basic unit of the mover 2 and four basic units of the stator 3. Therefore, in this embodiment, the mover 2 has seven permanent magnets 21, and the stator 3 has twenty-four magnetic pole teeth 32 and coils 33. The effective stroke of the linear motor 1 shown in FIG. 8 is equivalent to three basic units, and as shown in FIG. 8, there are a conveyance area equivalent to two basic units and a working area equivalent to two basic units. The number of turns of each coil 33 corresponding to the working area (the first unit and the second unit on the left side) is set to 28 turns, while the number of turns of each coil 33 corresponding to the conveyance area (the third unit and the fourth unit on the right side) is reduced to 7 turns. In the linear motor 1 shown in FIG. 8, since the mover 2 is constituted by one basic unit, the maximum thrust is 500 N. In a similar configuration with a uniform number of turns of the coil over the entire area, this maximum thrust of 500 N can only be maintained up to a maximum speed of 2.9 m / s, whereas in the linear motor 1 of the present invention, this maximum thrust of 500 N can be maintained up to a maximum speed of 3.2 m / s.

[0041] Although some embodiments have been described, the linear motor 1 can adopt an arbitrary 7m-pole 6n-slot configuration (m and n are natural numbers, m < n), and the number of basic units constituting each of the working area and the conveyance area may be determined according to the size of the workpiece (such as a semiconductor wafer) to be applied.

[0042] In the above-described embodiment, the number of turns of the coil 33 corresponding to the working area is set to 28 turns, and the number of turns of the coil 33 corresponding to the conveyance area is set to 7 turns, and the ratio of the latter to the former is 1 / 4. However, this is merely an example, and the number of turns of the coil 33 corresponding to each area is not limited to these. The number of turns of the coil 33 corresponding to the conveyance area is preferably 1 / 5 to 1 / 3 of the number of turns of the coil 33 corresponding to the working area. By setting the ratio of the number of turns of the coil 33 within such a numerical range, it is possible to maintain a large thrust even at a high speed in the working area while providing the desired thrust required in each of the working area and the conveyance area.

[0043] In the above-described embodiment, the case of applying to a wire bonder has been described. However, similar to the wire bonder, the linear motor of the present invention can also be applied to other processing apparatuses such as a flip chip bonder that successively performs a conveyance process of a workpiece that does not require a very large thrust and a working process on a workpiece that requires a large thrust.

[0044] In the above-described embodiment, an example in which the basic configuration is 7 poles and 6 slots has been described. However, the present invention is not limited to this, and the present invention can also be applied to a linear motor having other basic configurations such as an 8-pole 9-slot configuration in which the basic unit has 8 permanent magnets, 9 magnetic pole teeth, and coils, and a 10-pole 9-slot configuration in which the basic unit has 10 permanent magnets, 9 magnetic pole teeth, and coils.

[0045] The disclosed embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Explanation of Reference Numerals

[0046] 1 Linear motor 2 Mover 3 Stator 21 Permanent magnet 22 Back yoke 31 Core 32 Magnetic pole tooth 33 Coil

Claims

1. A linear motor comprising a mover in which a plurality of permanent magnets are arranged, a stator in which coils are wound around a plurality of magnetic pole teeth respectively, a linear encoder for detecting the position of the mover, a drive circuit for passing a current through the coils, and a controller for setting a control gain of the drive circuit and controlling the drive circuit, wherein a movable region of the mover has a first region and a second region to which the mover moves up to the first region, the number of turns of the coil corresponding to the second region is made less than the number of turns of the coil corresponding to the first region, and the control gain when the mover is located in the second region is set to be larger than the control gain when the mover is located in the first region according to the position of the mover. A linear motor characterized by that.

2. A linear motor used for moving an object to be processed, wherein the first region is a working region for performing processing on the object to be processed, and the second region is a transport region for transporting the object to be processed to the working region. The linear motor according to claim 1, characterized by that.

3. The linear motor according to claim 1 or 2, characterized in that the number of turns of the coil corresponding to the second region is 1 / 5 to 1 / 3 of the number of turns of the coil corresponding to the first region.

4. The linear motor according to any one of claims 1 to 3, characterized in that a 7-pole 6-slot configuration having the seven permanent magnets, the six magnetic pole teeth and coils is used as a basic unit.

Images