Linear motor

Abstract

A linear motor includes a stator (12) and a mover (11), the stator (12) including a plurality of salient poles arranged at fixed intervals along the Y-axis; the mover (11) being movable in the Y-axis direction and facing the stator (12) in the X-axis direction, wherein the mover (11) includes: a plurality of teeth (13, 14, 15) arranged along the Y-axis direction; three-phase AC windings (16, 17, 18) wound around the teeth (13, 14, 15); a mover yoke (20) connecting the plurality of teeth (13, 14, 15); permanent magnets (19), each permanent magnet (19) disposed in the gap between the teeth (13, 14, 15) of the same phase; and flux blocking elements (22), each flux blocking element (22) being embedded near the base of each tooth in the plurality of teeth (13, 14, 15), being disposed entirely within the width of each tooth in the X-axis direction, and being spaced apart from the permanent magnets in the X-axis direction.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Japanese Patent Application No. 2021-016003, filed on February 3, 2021, the entire contents of which (including the specification, claims, drawings and abstract) are incorporated herein by reference. Technical Field

[0003] This specification discloses linear motors used in industrial machinery such as machine tools. Background Technology

[0004] Linear motors are used in industrial machinery such as machine tools to achieve high speed and high precision. Among such linear motors, some achieve low cost by reducing the number of permanent magnets used by incorporating expensive permanent magnets on the mover side, and are particularly used in long-stroke machines.

[0005] Figure 6 An example of a traditional linear motor is illustrated. Figure 6 In this design, the stator 12 is, for example, laminated from magnetic steel sheets. On the surface of the stator 12, salient poles 10 are arranged at a spacing P to protrude from the stator's yoke 21. Similar to the stator 12, the mover 11 is also laminated from magnetic steel sheets and includes teeth 13 for the U phase, teeth 14 for the V phase, and teeth 15 for the W phase. Teeth 13, 14, and 15 are arranged such that they are electrically offset from each other by 120 degrees; that is, offset in the X-axis direction by one-third of the spacing P of the salient poles 10. Three-phase AC windings are wound around each of teeth 13, 14, and 15. Specifically, a three-phase AC winding 16 for the U phase is wound around tooth 13, a three-phase AC winding 17 for the V phase is wound around tooth 14, and a three-phase AC winding 18 for the W phase is wound around tooth 15. Multiple teeth in teeth 13, 14, and 15 are arranged at a distance P equal to half the distance between them, and permanent magnets 19 are disposed in the gaps between the teeth. The permanent magnets 19 are arranged such that the magnetization direction of each permanent magnet 19 is opposite to the magnetization direction of the adjacent permanent magnet 19. Figure 6 The arrow in the image indicates the magnetization direction of permanent magnet 19.

[0006] In such a linear motor, a long stroke range can be easily achieved by repeatedly arranging stator blocks of a simple structure made of inexpensive laminated electromagnetic steel sheets. Furthermore, by arranging the expensive permanent magnets 19 on the mover side to reduce the number of permanent magnets used, the production cost of the linear motor can be minimized.

[0007] To improve the responsiveness and increase thrust in the high-speed range of the aforementioned linear motor, known linear motors include a flux blocking element 22 made of a non-magnetic material in the mover 11 to reduce the inductance of the windings. Such linear motors... Figure 7 , Figure 8 and Figure 9 The diagram shows only a portion of the mover 11 corresponding to one electrical phase, while the stator 12 is omitted.

[0008] exist Figure 7 In the middle, the magnetic flux blocking member 22 is disposed between the moving magnetic yoke 20 and the teeth 13, 14 and 15, and the moving magnetic yoke 20 is separated from the teeth 13, 14 and 15.

[0009] exist Figure 8 In the middle, the magnetic flux blocking member 22 is disposed between the moving magnetic yoke 20 and the teeth 13, 14 and 15, and the moving magnetic yoke 20 is connected to the teeth 13, 14 and 15 at two positions on both ends of the magnetic flux blocking member 22 in the X-axis direction.

[0010] exist Figure 9 In the middle, the flux blocking member 22 is configured to be connected to the magnet insertion slot in which the permanent magnet 19 is inserted.

[0011] The aforementioned traditional linear motors have the following disadvantages.

[0012] exist Figure 7 In the linear motor shown, the mover yoke 20 is separated from teeth 13, 14 and 15 and is set as a separate component, which leads to an increase in the manufacturing cost of the linear motor and further leads to an increase in thrust fluctuation due to the deterioration of assembly accuracy.

[0013] exist Figure 7 and Figure 8 In the linear motor illustrated, the Y-axis dimension of the mover 11 is increased because the flux blocking element 22 is positioned between the mover yoke 20 and the teeth 13, 14, and 15. To prevent this, the Y-axis dimension of the permanent magnet 19 needs to be reduced, as does the Y-axis dimension of the flux blocking element 22, but this would result in a decrease in the thrust per unit volume of the linear motor.

[0014] exist Figure 9 In the linear motor illustrated, the flux blocking element 22 blocks the effective magnetic flux in and out of the permanent magnet 19 at the point where the permanent magnet 19 contacts the flux blocking element 22. Accordingly, the magnetic flux of the permanent magnet 19 cannot be effectively utilized, and the thrust per unit volume of the linear motor is reduced.

[0015] List of cited references: Patent document 1: JP2006-109639A. Summary of the Invention

[0016] This document discloses a linear motor comprising: a stator including a plurality of salient poles arranged at fixed intervals along a predetermined travel direction; and a mover movable in the travel direction and facing the stator in a facing direction orthogonal to the travel direction. The mover includes: a plurality of teeth arranged along the travel direction; a three-phase AC winding wound around the teeth; a mover yoke connected to the plurality of teeth; permanent magnets, each of which is disposed in a gap between teeth of the same phase; and flux blocking elements embedded near the base of each tooth in the plurality of teeth, fully disposed within the width of each tooth in the travel direction, and spaced apart from the permanent magnets in the travel direction.

[0017] In this case, the flux blocking element can be configured to span across the mover yoke and the tooth.

[0018] The dimension of the magnetic flux blocking member in the facing direction may be larger than the dimension of the magnetic flux blocking member in the traveling direction of the mover.

[0019] Each flux blocking element can be positioned at the center of each tooth in the direction of travel of the mover.

[0020] According to the linear motor disclosed in this article, it is possible to increase the thrust per unit volume of the linear motor. Attached Figure Description

[0021] Embodiments of this disclosure will be described based on the following figures, wherein:

[0022] Figure 1 A schematic structure of a linear motor is shown;

[0023] Figure 2 The magnetic flux of a linear motor is shown;

[0024] Figure 3 A schematic structure of another linear motor is shown;

[0025] Figure 4 A schematic structure of another linear motor is shown;

[0026] Figure 5 A schematic structure of another linear motor is shown;

[0027] Figure 6 A schematic structure of a conventional linear motor is shown;

[0028] Figure 7 The structure of the mover of another conventional linear motor corresponding to one electrical phase is shown;

[0029] Figure 8The structure of the mover of another conventional linear motor corresponding to one electrical phase is shown; and

[0030] Figure 9 The structure of the mover of another conventional linear motor corresponding to one electrical phase is shown.

[0031] List of reference numerals

[0032] 11 Movers

[0033] 12 stators

[0034] Teeth 13, 14, and 15

[0035] 16, 17, 18 Three-phase AC windings

[0036] 19 permanent magnet

[0037] 20. Motor magnetic yoke

[0038] 21. Stator yoke

[0039] 22 Flux Blocking Components

[0040] Magnetic flux 51, 52 Detailed Implementation

[0041] Figure 1 A schematic structure of a linear motor is shown. In the figure, the X-axis indicates the direction of travel of the mover 11, and the Y-axis indicates a direction orthogonal to the direction of travel. The stator 12 is, for example, laminated from electromagnetic steel sheets. The stator 12 includes a stator yoke 21 that is longer in the X-axis direction, and also includes a plurality of salient poles 10 that protrude from the end face of the stator yoke 21 in the Y-axis direction. The plurality of salient poles 10 are arranged at intervals of a distance P in the X-direction.

[0042] The mover 11 is, for example, laminated from magnetic steel sheets and faces the stator 12 in the Y-axis direction. The mover 11 includes a mover yoke 20, teeth 13 for the U-phase, teeth 14 for the V-phase, and teeth 15 for the W-phase. The teeth 13, 14, and 15 for these three phases are arranged such that they are offset relative to each other by an electrical angle of 120 degrees; that is, offset relative to each other in the X-axis direction by one-third of the distance P between the salient poles 10. Three-phase AC windings 16, 17, and 18 for the U-phase, V-phase, and W-phase, respectively, are wound around teeth 13, 14, and 15. Teeth of the same phase are arranged at half the distance P, and permanent magnets 19 are disposed in the gaps between the teeth (which act as magnet insertion slots). The permanent magnets 19 of the same phase are arranged such that the magnetization direction of each permanent magnet 19 is opposite to the magnetization direction of the adjacent permanent magnet 19. Figure 1 The arrow in the image indicates the magnetization direction of permanent magnet 19.

[0043] At the base of each of the plurality of teeth 13, 14, and 15, a flux blocking element 22 made of a non-magnetic material is provided to reduce the inductance of the winding. The flux blocking element 22 is disposed entirely within the width of each of the teeth 13, 14, and 15 in the X-axis direction, and is positioned near the center of each of the teeth 13, 14, and 15 in the X-axis direction. (See from...) Figure 1 It can be clearly seen that the flux blocking element 22 is separated from the adjacent permanent magnet 19 in the X-axis direction, thereby forming a small gap between the flux blocking element 22 and the adjacent permanent magnet 19.

[0044] Here, refer to Figure 2 Explain the function of the magnetic flux blocking element 22. Figure 2 The structure of the mover 11 corresponding to only one phase is shown by omitting the stator 12 and showing only one phase of the mover 11. The magnetic flux generated in the mover 11 is illustrated in the diagram. Figure 2 In this circuit, flux 51 is the magnetic flux generated when current is applied to the three-phase AC windings 16, 17, and 18. Flux 52 is the magnetic flux short-circuited from the N pole to the S pole at the end of the permanent magnet 19. Flux blocking member 22 is configured to block the passage of fluxes 51 and 52. When the passage of flux 51 is blocked and the flux quantity decreases, the inductance of the windings decreases. This enhances the responsiveness of the linear motor and increases thrust in the high-speed range. Furthermore, since flux 52 is a useless flux and does not affect thrust generation, the reduction in the amount of flux 52 increases the amount of flux effectively acting to generate thrust, thereby increasing the thrust per unit volume of the linear motor.

[0045] In this embodiment, the mover yoke 20 is not separated from teeth 13, 14, and 15 by the flux blocking element 22. This prevents increased costs in manufacturing the linear motor and also prevents increased thrust fluctuations due to deterioration in assembly precision.

[0046] Furthermore, in this embodiment, since the flux blocking member 22 is completely positioned within the width of each tooth of teeth 13, 14, and 15 in the X-axis direction, the flux blocking member 22 does not affect the Y-axis dimension of the permanent magnet 19. Therefore, the dimension of the permanent magnet 19 is not affected by the flux blocking member 22, thereby increasing the thrust per unit volume of the linear motor.

[0047] Furthermore, since there is a gap between each permanent magnet 19 and the flux blocking member 22, and they do not come into contact with the flux blocking member 22, effective magnetic flux can flow into and out of the permanent magnets without being blocked, even when the flux blocking member is present. As a result, the magnetic flux of the permanent magnet 19 can be used effectively to generate thrust, thereby increasing the thrust per unit volume of the linear motor.

[0048] When the flux blocking element 22 is configured to span the mover yoke 20 and teeth 13, 14 and 15, as follows: Figure 1 As shown, compared to the case where the flux blocking element is only provided in the mover yoke 20, the area occupied by the flux blocking element 22 in the mover yoke 20 can be reduced. If a large area of ​​the mover yoke 20 is occupied by the flux blocking element 22, magnetic saturation is likely to occur in the mover yoke 20 during the generation of thrust of the linear motor, resulting in a decrease in the generated thrust. By setting the flux blocking element 22 to span across the mover yoke 20 and teeth 13, 14, and 15, the thrust per unit volume of the linear motor can be increased.

[0049] The dimension of the flux blocking member 22 in the direction orthogonal to the travel direction of the mover 11 can be larger than its dimension in the travel direction of the mover 11. The larger the dimension of the flux blocking member 22 in the direction orthogonal to the travel direction of the mover 11, the greater the magnetic reluctance of the flux blocking member 22 to the fluxes 51 and 52. Therefore, it is possible to further block the passage of fluxes 51 and 52. This improves the responsiveness of the linear motor, increases the thrust in the high-speed range, and increases the thrust per unit volume of the linear motor.

[0050] The above structure has been given as an example, and various modifications can be made to the structure provided that each flux blocking element 22 is completely disposed within the width of each tooth of teeth 13, 14, and 15 in the X-axis direction, is disposed near the base of each tooth of teeth 13, 14, and 15 in the X-axis direction, and is spaced apart from each permanent magnet 19 in the X-axis direction. For example, as Figure 3 As shown, some flux blocking elements 22a, when spaced apart from the permanent magnet 19 in the X-axis direction, can be offset from the center of each of teeth 13, 14, and 15 in the X-axis direction. Alternatively, when the flux blocking elements 22 are disposed near the base of teeth 13, 14, and 15, the flux blocking elements 22 may not span the mover yoke 20 and teeth 13, 14, and 15. Accordingly, the flux blocking elements 22 can be configured such that their Y-axis range is completely included within the Y-axis range of teeth 13, 14, and 15, as shown. Figure 4 As shown. Alternatively, the flux blocking element 22 can be positioned entirely outside the Y-axis range of teeth 13, 14, and 15, thus eliminating the flux blocking element 22 in teeth 13, 14, and 15, as shown. Figure 5 As shown in the image.

Claims

1. A linear motor, comprising: A stator, the stator comprising a plurality of salient poles arranged at fixed intervals along a predetermined direction of travel; and A mover, which is movable along the direction of travel and faces the stator in a facing direction orthogonal to the direction of travel, wherein... The mover includes: Multiple teeth, the multiple teeth being arranged along the direction of travel. A three-phase AC winding, wherein the three-phase AC winding is wound around the teeth. A moving yoke, wherein the moving yoke connects the plurality of teeth extending from the edge of the moving yoke along the facing direction. Permanent magnets, each of which extends from the edge of the mover yoke along the facing direction and is disposed in the gap between the teeth of the same phase, and A flux blocking element, each of which is embedded near the base of each of the plurality of teeth, is positioned entirely within the width of each tooth in the direction of travel, and is spaced apart from the permanent magnet in the direction of travel. Wherein, the flux blocking member is configured to span the mover yoke and the tooth, such that a portion of the flux blocking member overlaps with the mover yoke and the remaining portion of the flux blocking member overlaps with the tooth; and Wherein, the dimension of the magnetic flux blocking member in the direction of travel is smaller than the dimension of the tooth in the direction of travel.

2. The linear motor according to claim 1, characterized in that: The dimension of the magnetic flux blocking member in the facing direction is larger than the dimension of the magnetic flux blocking member in the traveling direction of the mover.

3. The linear motor according to claim 1 or 2, characterized in that: Each of the aforementioned flux blocking elements is disposed at the center of each tooth in the direction of travel.

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