Electromagnetic actuator

Abstract

This invention provides an electromagnetic actuator that reduces the detachment of magnets due to deformation that occurs during operation. [Solution] An electromagnetic actuator comprising a stator extending in a first direction and a movable element movable along the first direction, wherein the movable element comprises a yoke, a housing, bolts, and a principal pole magnet whose magnetic pole orientation is perpendicular to the yoke and a co-pole magnet whose magnetic pole orientation is not perpendicular to the yoke, wherein the principal pole magnet and the co-pole magnet are fixed to the yoke with adhesive, the yoke and the housing are fastened together with bolts, and the number of bolts on the projection surface of the principal pole magnet is less than the number of bolts on the projection surface of the co-pole magnet.

Description

Technical Field

[0001] The present invention relates to an electromagnetic actuator composed of a stator and a mover. Background Art

[0002] Conventionally, electromagnetic actuators that perform linear motion have been used in driving devices requiring precise positioning, such as exposure apparatuses used in the manufacture of semiconductor devices, machine tools, and railways. For example, the electromagnetic actuator disclosed in Patent Document 1 includes a stator having a fixed coil and a mover having a movable magnet. By passing a current through the coil, magnetic flux is generated, and by interacting with the magnetic field of the magnet, a driving force is generated in the movable magnet, thereby enabling the mover to move. Prior Art Literature Patent Documents

[0003] Patent Document 1 Japanese Patent Laid-Open No. 2003-116260 Summary of the Invention Problem to be Solved by the Invention

[0004] In recent years, in order to improve the productivity of apparatuses, higher driving speed has been required. In order to achieve high-speed driving, the electromagnetic actuator used needs to generate higher thrust, and the structure of the mover that generates high thrust receives a high load accompanying the generated thrust.

[0005] As a result, the load applied to the mover causes stress concentration in the peripheral portion of the bolts disposed between components, which propagates to the adhesive fixing the magnet, and there is a possibility that the adhesive portion may peel off.

[0006] The present invention has been made in view of the above problem, and an object of the present invention is to provide an electromagnetic actuator that reduces falling-off of the magnet caused by deformation generated during driving. [Means for solving the problem]

[0007] In an electromagnetic actuator, The device comprises a stator extending in a first direction and a movable element movable along the first direction, the movable element comprising a yoke, a housing, bolts, and a principal pole magnet whose magnetic pole orientation is perpendicular to the yoke and a secondary pole magnet whose magnetic pole orientation is not perpendicular to the yoke. The main pole magnet and the co-pole magnet are fixed to the yoke with adhesive, the yoke and the housing are fastened together with bolts, and the number of bolts on the projection surface of the main pole magnet is less than the number of bolts on the projection surface of the co-pole magnet. [Effects of the Invention]

[0008] According to the present invention, an electromagnetic actuator can be realized that reduces the detachment of magnets due to deformation that occurs during operation. [Brief explanation of the drawing]

[0009] [Figure 1] (A) and (B) are diagrams showing an example configuration of an electromagnetic actuator according to Embodiment 1 of the present invention. [Figure 2] This figure shows an example of a part of the configuration of the movable element of Embodiment 1. [Figure 3] This figure shows an example configuration of the electromagnetic actuator of Embodiment 2. [Figure 4] This figure shows an example configuration of the electromagnetic actuator according to Embodiment 3. [Figure 5] (A) and (B) are diagrams showing other configuration examples of the electromagnetic actuator of Embodiment 4. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following embodiments. In each drawing, the same reference numeral is used for the same member or element, and redundant explanations are omitted or simplified.

[0011] <Embodiment 1> Figures 1(A) and 1(B) show an example configuration of an electromagnetic actuator according to Embodiment 1 of the present invention, where Figure 1(A) is a cross-sectional view in a plane including the axis 13, and Figure 1(B) is a cross-sectional view in a plane perpendicular to the axis 13.

[0012] As shown in Figures 1(A) and (B), the electromagnetic actuator of this embodiment has a stator 1 and a movable element 2. The stator 1 is a columnar shape extending in a first direction 3 and consists of a support member 10 at its axial center and a plurality of coils 4 arranged on the outer surface of the support member 10. The movable element 2 is movable along the first direction.

[0013] An insulating member, a yoke, or both may be placed between the support member 10 and the coil 4. The support member 10 functions as a base for supporting the coil 4. In addition, the support member 10 may have a coil cooling channel inside to prevent the coil temperature from rising.

[0014] Furthermore, a cooling channel may be provided in the movable part, for example, inside or on the surface of the housing 5, for circulating a cooling medium. That is, the temperature information of the electromagnetic actuator may be suppressed by having a cooling channel in at least one of the stator or the movable part.

[0015] The movable element 2 has a hollow shape that penetrates the first direction 3 and non-contactly surrounds the outer periphery of the stator 1 in a plane perpendicular to the first direction 3. As shown in Figure 1(B), two pairs of opposing magnets 6 are arranged on the inner surface of the movable element 2.

[0016] The plurality of magnets 6 include, as indicated by magnetic pole orientations 9, auxiliary pole magnets 6b magnetized along the direction of a shaft 13, and main pole magnets 6a magnetized in a direction orthogonal to the shaft 13, and are arranged so as to generate an alternating magnetic field on the inner surface of a mover.

[0017] Further, in the present embodiment, the plurality of magnets 6 are arranged in a Halbach array that generates a substantially sinusoidal magnetic field for one cycle. Note that, as shown in FIG. 1(B), in the present embodiment, the stator 1 and the mover 2 have a substantially rectangular cross-section, but may also be circular or elliptical, and the cross-sectional shape is not limited to the shape shown in FIG. 1(B).

[0018] The magnets 6 are held with part or all of their surfaces against a yoke 8 via an adhesive layer 7, and the yoke 8 is held by a housing 5 and bolts 11. That is, the main pole magnets 6a and the auxiliary pole magnets 6b are fixed to the yoke 8 with an adhesive, and the yoke 8 and the housing 5 are fastened together with the bolts 11.

[0019] As described above, the mover of the present embodiment includes the yoke 8, the housing 5, the bolts 11, the main pole magnets 6a whose magnetic pole orientations are arranged in a direction perpendicular to the yoke 8, and the auxiliary pole magnets 6b whose magnetic pole orientations are arranged in a non-perpendicular direction to the yoke 8. Note that, in a case where a cooling flow path for flowing a cooling medium is provided inside or on a surface of the housing 5, the bolts 11 are arranged at positions avoiding the cooling flow path.

[0020] The plurality of coils 4 have a plurality of phases (two phases A and B in this example). Further, in the driving method for the linear motor of the present embodiment, sine waves are supplied to the plurality of coils 4, and control is performed such that current and magnetic flux are orthogonal to each other. Furthermore, by switching coils so that sine waves are supplied only to coils among the plurality of coils 4 that face the plurality of magnets 6, heat generation is reduced.

[0021] Note that, in the electromagnetic actuator of the present embodiment, in order to efficiently use the magnetic field generated by the coil 4 as a driving force, it is desirable that the gap between the coil 4 and the magnet 6 be as small as possible.

[0022] Figure 2 shows an example of a part of the configuration of the movable element of Embodiment 1. As mentioned above, the magnet 6 is composed of a Halbach array that generates a substantially sinusoidal magnetic field, with a co-pole magnet 6b magnetized along the direction of the axis 13 and a main pole magnet 6a magnetized in a direction perpendicular to the axis 13.

[0023] At this time, the direction 12 of the force 12 acting on the magnet 6 due to the magnetic force of coil 4 is such that, for the main pole magnet 6a, it is away from the yoke 8, generating a peeling force against the adhesive layer 7. On the other hand, for the co-pole magnet 6b, it is attracted to the yoke 8, generating a compressive force against the adhesive layer 7. In other words, if damage occurs to the adhesive layer 7, the main pole magnet 6a is more likely to detach and the magnet to fall off than the co-pole magnet 6b.

[0024] On the other hand, when thrust is generated by energizing coil 4, the housing 5 deforms and stress is generated due to the inertial force generated between it and the drive object (not shown) connected to it. At that time, the deformation of the end of the movable element 2 in the direction of axis 13 is large due to the inertial force.

[0025] The generated stress propagates to the bolt 11 via the housing 5, and the stress concentrates around the bolt 11 on the yoke 8. As a result, the adhesive layer 7 may break in the part of the adhesive layer 7 closest to the bolt 11, potentially causing the adhesive to peel off.

[0026] Therefore, in this embodiment, the bolts 11 for fastening the housing 5 and the yoke 8 are placed on the projection area surface of the interpole magnet 6b, and not on the projection area surface of the main pole magnet 6a provided at the end of the movable element 2 in the axial direction 13.

[0027] In other words, when the movable element 2 deforms due to inertial force and stress is generated in the movable element, bolts are placed in areas where the deformation of the movable element is small, and bolts are not placed in areas where the deformation is large.

[0028] Therefore, even if a force acts on the magnet in the direction of adhesive peeling, concentrated stress does not occur around the bolt 11 near the main pole magnet 6a, where there is a high possibility of the magnet falling off, thus suppressing the magnet from falling off.

[0029] <Embodiment 2> Next, Figure 3 shows an example of the configuration of the electromagnetic actuator of Embodiment 2, and the electromagnetic actuator of Embodiment 2 will be described based on Figure 3. In the movable element 2 of Embodiment 2, the bolts 11 for fastening the yoke 8 and the housing 5 are arranged not only on the projection area surface of the interpole magnet 6b but also on the projection area surface of the main pole magnet 6a.

[0030] However, the number of bolts 11 arranged on the projection surface of the main pole magnet 6a is less than the number of bolts 11 arranged on the projection surface of the co-pole magnet 6b. That is, the number of bolts 11 on the projection surface of the main pole magnet 6a is less than the number of bolts 11 on the projection surface of the co-pole magnet 6b.

[0031] In particular, the number of bolts 11 on the projection surface of the main pole magnet 6a, which is located at the end of the movable element 2, is set to be less than the number of bolts 11 on the projection surface of the auxiliary pole magnet 6b, which is located elsewhere than the end of the movable element 2. In Embodiment 2, a small number of bolts 11 on the projection surface of the main pole magnet includes the case where there are no bolts on the projection surface of the main pole magnet, as in Embodiment 1.

[0032] Furthermore, the number of bolts 11 used to fasten the yoke 8 and housing 5 must be such that the fastening force necessary to hold the magnet 6 and yoke 8 is secured. Therefore, this embodiment is effective when, due to space limitations, it is not possible to place all of the bolts 11 on the projection surface of the complementary pole magnet 6b.

[0033] Thus, in this embodiment, the number of bolts 11 arranged on the projection surface of the main pole magnet 6a is fewer than the number of bolts 11 arranged on the projection surface of the co-pole magnet 6b. Therefore, when a force acting on the magnet in the direction of adhesive peeling is applied, the concentrated stress generated around the bolts near the main pole magnet 6a, where there is a high possibility of the magnet falling off, can be reduced, thereby preventing the magnet from falling off.

[0034] Furthermore, the spacing between the bolts on the projection surface of the main pole magnet 6a may be wider than the spacing between the bolts on the projection surface of the co-pole magnet 6b. Also, for example, if there are three or more bolts 11 on the projection surface of the main pole magnet 6a arranged in the direction of the axis 13 in Figure 3, the spacing between those three or more bolts 11 may be different.

[0035] For example, the distance between the two bolts 11 at the end of the movable element 2 may be wider than the distance between the other bolts 11. That is, the distance between the bolts 11 at the end of the movable element 2 on the projection area surface of the main pole magnet 6a may be wider than the distance between the other bolts 11. This makes it possible to relatively reduce the concentrated stress generated around the bolts at the end.

[0036] In this embodiment, bolts 11 are not placed on the projection area surface of the main pole magnet 6a other than the axial end of the movable element 2. This is to reduce concentrated stress on the main pole magnet 6a other than the axial end of the movable element 2 and prevent the main pole magnet 6a from falling off.

[0037] However, in order to further increase the fastening force required to hold the magnet 6 and the yoke 8, fewer bolts than the bolts 11 placed on the projected area surface of the complementary magnet 6b may be placed on the projection area surface of the main pole magnet 6a, other than the axial end of the movable element 2.

[0038] Furthermore, although Figure 3 shows bolts 11 arranged along the axis 13 on the surface of the housing 5, bolts 11 may also be provided arranged along a direction perpendicular to the axis 13 on the surface of the housing 5. Even in that case, it is desirable to have fewer bolts 11 arranged on the projection area surface of the main pole magnet 6a than fewer bolts 11 arranged on the projection area surface of the co-pole magnet 6b.

[0039] Furthermore, the arrangement pattern of the multiple bolts 11 positioned on the projection area surface of the main pole magnet 6a on the surface of the housing 5 may be different from the arrangement pattern of the multiple bolts 11 positioned on the projection area surface of the co-pole magnet 6b. Note that the above arrangement pattern includes, for example, a two-dimensional arrangement pattern such as the spacing between the multiple bolts 11 or the distance from the axis 13.

[0040] In this case, stress concentration may be prevented by ensuring that the arrangement density of the multiple bolts 11 placed on the projection area surface of the main pole magnet 6a is lower than the arrangement density of the multiple bolts 11 placed on the projection area surface of the co-pole magnet 6b.

[0041] Furthermore, if a cooling channel for circulating a cooling medium is provided inside or on the surface of the housing 5, the multiple bolts 11 arranged on the projection area surface of the main pole magnet 6a are positioned to avoid the cooling channel.

[0042] As described above, in Embodiment 2, when the housing 5 deforms due to inertial force and stress is generated in the movable element, multiple bolts are placed in areas where the deformation of the movable element is small, and fewer bolts are placed in areas where the deformation is large. Therefore, concentrated stress generated around the bolts near the main pole magnet 6a, where there is a high possibility of magnet detachment, can be reduced, and magnet detachment can be prevented.

[0043] <Embodiment 3> Next, Figure 4 shows an example of the configuration of the electromagnetic actuator of Embodiment 3, and the electromagnetic actuator of Embodiment 3 will be described based on Figure 4. The movable element 2 of Embodiment 3 is composed of a main pole magnet 6a magnetized in a direction perpendicular to the axis, and a secondary pole magnet (oblique pole) 6c whose magnetization direction is tilted axially with respect to the main pole magnet 6a.

[0044] In this embodiment, the co-pole magnets (oblique poles) 6c form a Halbach array arranged between the main pole magnets 6a, and two co-pole magnets (oblique poles) 6c are arranged between the main pole magnets 6a, with their magnetic pole directions reversed axially relative to each other.

[0045] This makes it possible to realize an electromagnetic actuator capable of generating higher thrust. Furthermore, with a Halbach array, it is possible to increase the number of co-pole magnets with even more precisely specified magnetic pole directions.

[0046] Here, the bolts 11 used to fasten the housing 5 and the yoke 8 are arranged in the same way as in Embodiment 1, on the projection plane of the co-pole magnet (oblique pole) 6c, and not on the projection plane of the main pole magnet 6a, where there is a high possibility of the magnet falling off. It is.

[0047] However, as in Embodiment 2, the number of bolts 11 arranged on the projection surface of the main pole magnet 6a may be less than the number of bolts 11 arranged on the projection surface of the co-pole magnet 6c.

[0048] <Embodiment 4> Next, Figures 5(A) and 5(B) show other configuration examples of the electromagnetic actuator of Embodiment 4. Figure 5(A) is a cross-sectional view showing a configuration example in a plane including the axis 13, and Figure 5(B) shows a configuration example viewed from below the stator towards the housing 5.

[0049] In Embodiment 4, the stator 1 has a support member 10 and a plurality of coils 4. As shown in Figures 5(A) and 5(B), for example, the coils 4 are arranged so that a portion of their winding direction is aligned with the first direction 3, and the direction of the magnetic poles generated by the coils 4 is perpendicular to the first direction 3. The movable element 2 has magnets 6 arranged on its inner surface.

[0050] Here, the arrangement of the main pole magnet 6a and the co-pole magnet 6b is a Halbach arrangement, similar to Embodiments 1 to 3. The arrangement of the bolts 11 for fastening the housing 5 and the yoke 8 is also similar to Embodiments 1 to 3, with the bolts positioned on the projection surface of the co-pole magnet 6b. Furthermore, the bolts are not positioned on the projection surface of the main pole magnet 6a, where there is a high possibility of magnet detachment.

[0051] However, as in Embodiment 2, the number of bolts 11 arranged on the projection surface of the main pole magnet 6a may be less than the number of bolts 11 arranged on the projection surface of the co-pole magnet 6b.

[0052] A key feature of Embodiment 4 is its simpler structure compared to Embodiment 1. This allows for a smaller footprint, easier manufacturing, and reduced costs.

[0053] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist. For example, an electromagnetic actuator may be used in which a fixed magnet with a rectangular cross-sectional shape is used as the stator, and a movable coil surrounding the fixed magnet is used as the movable element.

[0054] Furthermore, as mentioned above, the electromagnetic actuator may also use a fixed coil or movable magnet with a circular or elliptical cross-sectional shape, and the cross-sectional shape and configuration of the stator 1 and movable element 2 may be changed as appropriate. The present invention includes the following configuration.

[0055] (Configuration 1) An electromagnetic actuator comprising a stator extending in a first direction and a movable element movable along the first direction, wherein the movable element comprises a yoke, a housing, bolts, and a main pole magnet whose magnetic pole orientation is perpendicular to the yoke and a co-pole magnet whose magnetic pole orientation is not perpendicular to the yoke, the main pole magnet and the co-pole magnet being fixed to the yoke with adhesive, the yoke and the housing being fastened together with bolts, and the number of bolts on the projection surface of the main pole magnet being less than the number of bolts on the projection surface of the co-pole magnet.

[0056] (Configuration 2) The electromagnetic actuator according to Configuration 1, characterized in that at least one of the stator or the movable part has a cooling channel.

[0057] (Configuration 3) The electromagnetic actuator according to Configuration 1 or 2, characterized in that the stator has a coil, a support member, and a yoke disposed between the coil and the support member.

[0058] (Configuration 4) The electromagnetic actuator according to any one of Configurations 1 to 3, characterized in that the movable element has a hollow shape that penetrates in the first direction and surrounds the outer circumference of the stator in a plane perpendicular to the first direction, and two pairs of opposing magnets are arranged on the inner surface of the movable element.

[0059] (Configuration 5) An electromagnetic actuator according to any one of Configurations 1 to 4, characterized in that the bolt is not arranged on the projection area surface of the main pole magnet.

[0060] (Configuration 6) An electromagnetic actuator according to any one of Configurations 1 to 5, characterized in that the spacing between the multiple bolts on the projection area surface of the main pole magnet is wider than the spacing between the multiple bolts on the projection area surface of the co-pole magnet.

[0061] (Configuration 7) An electromagnetic actuator according to any one of Configurations 1 to 6, characterized in that the spacing of the bolts on the end side of the movable element on the projection area surface of the main pole magnet is wider than the spacing of the other bolts.

[0062] (Configuration 8) An electromagnetic actuator according to any one of Configurations 1 to 7, characterized in that the number of bolts on the projection surface of the main pole magnet arranged at the end of the movable element is less than the number of bolts on the projection surface of the co-pole magnet arranged anywhere other than the end of the movable element. [Explanation of Symbols]

[0063] 1: Stator 2: Mover 3: 1st direction 4: Coil 5: Housing 6: Magnets 6a: Main pole magnet 6b: Composite pole magnets 6c: Composite pole magnet (oblique pole) 7: Adhesive layer 8: York 9: Direction of magnetic poles 10: Support member 11: Bolt 12: Direction of the force acting on a magnet

Claims

1. The device comprises a stator extending in a first direction and a movable element movable along the first direction, wherein the movable element includes a yoke, a housing, bolts, and a principal pole magnet whose magnetic pole orientation is perpendicular to the yoke and a secondary pole magnet whose magnetic pole orientation is not perpendicular to the yoke. An electromagnetic actuator characterized in that the main pole magnet and the co-pole magnet are fixed to the yoke with adhesive, the yoke and the housing are fastened together with bolts, and the number of bolts on the projection surface of the main pole magnet is less than the number of bolts on the projection surface of the co-pole magnet.

2. The electromagnetic actuator according to claim 1, characterized in that at least one of the stator or the movable part has a cooling channel.

3. The electromagnetic actuator according to claim 1, characterized in that the stator has a coil, a support member, and a yoke disposed between the coil and the support member.

4. The electromagnetic actuator according to claim 1, characterized in that the movable element has a hollow shape that penetrates in the first direction and surrounds the outer periphery of the stator in a plane perpendicular to the first direction, and two pairs of opposing magnets are arranged on the inner surface of the movable element.

5. The electromagnetic actuator according to claim 1, characterized in that the bolt is not arranged on the projection area surface of the main pole magnet.

6. The electromagnetic actuator according to claim 1, characterized in that the spacing between the plurality of bolts on the projection area surface of the main pole magnet is wider than the spacing between the plurality of bolts on the projection area surface of the co-pole magnet.

7. The electromagnetic actuator according to claim 1, characterized in that the spacing of the bolts on the end side of the movable element on the projection area surface of the main pole magnet is wider than the spacing of the other bolts.

8. The electromagnetic actuator according to claim 1, characterized in that the number of bolts on the projection surface of the main pole magnet, which is located at the end of the movable element, is less than the number of bolts on the projection surface of the co-pole magnet, which is located elsewhere than the end of the movable element.

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