Magnetic track base for fixed part of linear motor

Abstract

The invention relates to a magnetic track base (20) for a fixed part (10) of a linear motor, comprising a magnetic receiving portion (22) configured to fixedly receive a permanent magnet (52), a track receiving portion (26) configured to fixedly receive a track (50) along both sides of the magnet receiving portion (22), and an encoder scale support accommodating portion (30) configured to fixedly accommodate the encoder scale support (40). The encoder scale support receiving portion comprises a plurality of separate projections (31) mechanically separate from the remainder of the magnetic track base (20) and arranged to receive a bottom side of the encoder scale support (40) to prevent or at least reduce the rotation of the encoder scale support (40) when the magnetic track base (20) is subjected to an external force. Deformation of the encoder scale support receiving portion (30) may be caused by deformation of the remainder of the magnetic track base (20).

Description

Technical Field

[0001] The present invention relates to a magnetic track base for a fixed component of a linear motor. The present invention also relates to a motion positioning system, in particular a wafer positioning system, comprising at least one linear motor, the fixed component of which comprises a magnetic track base. Background Art

[0002] XY motion positioning systems require high-precision linear encoders to provide accurate positioning. Therefore, the encoder scale must remain as stable as possible while withstanding external disturbances to avoid loss of accuracy.

[0003] The encoder scale support is usually screwed to the magnetic track base together with other elements, such as the mechanical bearing track and the magnets of the magnetic track, without any special design attention to the magnetic track base. In most cases, the scale and the carrier consist of materials with different thermal expansion behaviors. Therefore, the static fixation must be designed so that the carrier does not exert a restraining force on the scale when the temperature changes.

[0004] Some encoder scale support geometries, such as that disclosed in EP3705850, can be made very insensitive to some disturbances by adding separation means such as hinges and blades thereto. However, such solutions are rather complex to implement and therefore expensive. Summary of the invention

[0005] Therefore, an object of the present invention is to provide a magnetic track base for a fixed part of a linear motor which is not subject to the above limitations.

[0006] More specifically, the object of the present invention is to provide a magnetic track base, which includes an encoder scale support accommodating portion, which portion will not deform when subjected to external forces, or at least deform less than a conventional scale support.

[0007] Another object of the present invention is to provide a magnetic rail base that is easy to produce and cost-effective.

[0008] These objects are mainly achieved by a magnetic track base for a fixed component of a linear motor, the magnetic track base comprising a magnetic receiving portion configured to fixedly receive a permanent magnet, a track receiving portion configured to fixedly receive a track along both sides of the magnet receiving portion, and an encoder scale support receiving portion configured to fixedly receive an encoder scale support. The encoder scale support receiving portion comprises a plurality of separate protrusions that are mechanically separated from the rest of the magnetic track base and arranged to receive the bottom side of the encoder scale support to prevent or at least reduce deformation of the encoder scale support receiving portion that may be caused by deformation of the rest of the magnetic track base when the magnetic track base is subjected to external forces.

[0009] In an embodiment, the plurality of separated protrusions comprises a corresponding plurality of fixed protrusions and a separation member for mechanically separating each fixed protrusion from the rest of the magnetic rail base.

[0010] In an embodiment, each separation member is a cut-out portion arranged around a corresponding fixing projection.

[0011] In an embodiment, each cut-out portion is in the form of a U-shaped through slot extending from a top side to a bottom side of the magnetic rail base.

[0012] In an embodiment, each fixing protrusion comprises a top planar surface including a fixing hole, the top planar surface being raised above the surface of the magnetic receiving portion.

[0013] In an embodiment, a plurality of fixing protrusions are arranged along a longitudinal direction between the magnetic receiving portion and one rail receiving portion.

[0014] In an embodiment, the magnetic receiving portion includes a plurality of pairs of threaded holes for fixing the permanent magnets with screws and a plurality of pairs of through holes for fixing the magnetic rail base to the magnetic rail base support.

[0015] In an embodiment, the cut-outs each surround one of the pairs of through holes for fixing the magnetic rail base to the magnetic rail base support such that the fixing projections are rigidly fixed to the support.

[0016] In an embodiment, the magnetic track base is unitary.

[0017] In an embodiment, the encoder scale support has a substantially constant L-shaped cross-section which forms a seat along the length of the support which is fixed to the encoder scale support receiving portion.

[0018] Another aspect of the present invention relates to a fixing component of a linear motor, the fixing component comprising a magnetic track base according to any one of the above embodiments, a magnet fixed to a magnetic receiving portion, a track fixed to the track receiving portion on both sides of the magnet, an encoder scale support fixed to an encoder scale support receiving portion, and an encoder scale fixed to the encoder scale support.

[0019] Another aspect of the invention relates to a linear motor comprising the above-mentioned fixed component and a moving component, the moving component including a coil assembly, a slider slidably engaged with a corresponding track of the fixed component, and an optical reader arranged to move along an encoder scale.

[0020] Other aspects of the present invention relate to a motion positioning system, in particular a wafer positioning system, which comprises at least one of the above-mentioned linear motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The invention will be better understood with the aid of the description of embodiments given by way of example and illustrated by the accompanying drawings, in which:

[0022] - Figure 1 shows a perspective view of a magnetic track base according to an embodiment;

[0023] - Figure 2 Shows Figure 1 An enlarged view of one of the plurality of fixing protrusions;

[0024] - Figure 3 A perspective view of an encoder scale support is shown, which is designed to be fixed to Figure 1 The encoder scale support member accommodating portion of the magnetic track base;

[0025] - Figure 4a shows a simulation of a magnetic track including an encoder scale support when exposed to an external force of 5000 [N], where the deformation of the component is magnified twenty thousand times;

[0026] - Figure 4b Shows Figure 4a The simulation of the encoder scale support, the deformation of the scale support is magnified 100,000 times;

[0027] - Figure 5a shows a simulation of a conventional magnetic track including an encoder scale support when exposed to an external force of 5000 [N], where the deformation of the components is magnified twenty thousand times;

[0028] - Figure 5b Shows Figure 5a The simulation of the encoder scale support, the deformation of the scale support is magnified 100,000 times;

[0029] - Figure 6 shows a perspective view of a wafer positioning system according to an embodiment, the wafer positioning system including a motion system consisting of x and y linear motors, both of which include magnetic track bases;

[0030] - Figure 7 Shows Figure 6 A perspective view of the motion system of the wafer positioning system, with some components hidden to highlight the encoder scale support, and

[0031] - Figure 8 Shows Figure 6 Side view of the movement system. DETAILED DESCRIPTION

[0032] refer to Figure 1 , the magnetic rail base 20 is specifically designed to support Figure 3The encoder scale support 40 has no deformation or minimal deformation when subjected to external force. The magnetic track base 20 is designed to be integrated in a motion positioning system, especially Figures 6 to 8 The linear motor fixing component 10 of the wafer positioning system 100 is shown.

[0033] The magnetic track base 20 is configured to support the permanent magnets 52 and the track 50, which is slidably engaged with the slider 62 of the movable part 60 including the coil assembly 61. The coil assembly includes a set of electromagnetic coils, which are wound around an iron core and are suitable for being energized sequentially to move the movable part 60 over and along the magnetic track made of the permanent magnets 52.

[0034] The above-mentioned external forces have different natures, such as the attraction between the magnet and the core of the movable part, the thermal stress caused by the different thermal expansion between the track 50 and the magnetic rail base 20, and the mechanical stress in the track caused by the incomplete alignment between the track 50 and the corresponding fixed part 10 and the slider 62 of the movable part 60.

[0035] The magnetic rail base 20 includes a magnetic receiving portion 22 configured to fixedly receive the permanent magnet 52, a track receiving portion 26 configured to fixedly receive the track 50 along both sides of the magnetic receiving portion 22, and an encoder scale support member receiving portion 30 configured to fixedly receive the encoder scale support member 40. The magnetic receiving portion 22 includes a plurality of pairs of threaded holes 25 for fixing the permanent magnet 52 with screws and a plurality of pairs of through holes 24 for fixing the magnetic rail base 20 to a support member (not shown).

[0036] The encoder scale support receiving portion 30 includes a plurality of separated protrusions 31 that are mechanically separated from the rest of the magnetic track base 20. In the illustrated embodiment, the plurality of separated protrusions 31 include fixed protrusions 32 arranged along the longitudinal direction between the magnetic receiving portion 22 and one track receiving portion 26 of the magnetic track base 20. A corresponding plurality of separation members 38 are arranged around each fixed protrusion 32 for mechanical separation between each fixed protrusion 32 and the longitudinal side of the magnetic track base 20. The separation members 38 may be, for example, cut-outs 38, each of which is arranged around a corresponding fixed protrusion 32 and surrounds the through hole 24, so that the fixed protrusion 32 is rigidly fixed to the magnetic track base support.

[0037] refer to Figure 2 Each fixing projection 32 includes a top flat surface 33 that protrudes above the surface of the magnet receiving portion 22 so that the encoder scale support 40 is away from the magnet receiving portion 22 and rises therefrom. Each cutout 38 is in the form of a U-shaped through slot extending from the top side 20a to the bottom side 20b of the magnetic track base 20. The design has rounded corners so that the groove can be easily milled in the base.

[0038] refer to Figure 3 , the encoder scale support 40 has a generally constant L-shaped cross section that forms a seat 44 fixed to the encoder scale support receiving portion 30 along the length of the support 40, and a scale receiving side 42 to which the encoder scale (not shown) is fixed. The scale receiving side 42 may include some grooves for bonding the encoder scale at its reference point. The top flat surface 33 of the fixing protrusion 32 may include a fixing hole 34 to screw the seat 44 of the encoder scale support 40 to the encoder scale support receiving portion 30.

[0039] The cutout 38 of the encoder scale support accommodating portion 30 to which the encoder scale support 40 is fixed allows the scale support 40 to be mechanically separated from the rest of the magnetic track base 20. Therefore, as described above, the deformation of the magnetic track base 20 caused by the external force does not negatively affect the shape of the encoder scale support accommodating portion 30, or at least has a negative impact to a lesser extent than the conventional scale support accommodating portion. Therefore, the deformation of the encoder scale support 40 does not occur, or occurs within an acceptable range for high-precision positioning.

[0040] The magnet rail base 20 is a monolithic piece, typically made of aluminum, and is obtained by a milling process.

[0041] refer to Figures 4a to 5b , it can be seen that compared with the traditional magnetic track base, Figure 1 The encoder scale support of the magnetic track base of the embodiment shown in the figure is much less affected by deformation of the rest of the magnetic track base. In fact, the encoder scale support deformation is reduced by more than five times compared to a conventional magnetic track without mechanical separation. The protected improvement is also effective for other mechanical bearing disturbances. For example, when recirculating ball bearings or roller bearings are used for the slider 62, the balls or rollers will move cyclically, moving from the return area to the load-bearing area. This may produce periodic force disturbances, from which the encoder scale support must be separated.

[0042] Figures 6 to 8The wafer positioning system 100 shown in FIG. 1 comprises a first linear motor and a second linear motor as described above, the second linear motor comprising a fixed part 70 mounted on a movable part 60 of the first linear motor, the movable part 60 being equipped with an optical position sensor unit 64, which is arranged to move along an encoder scale for accurate positioning along the X axis of the coordinate system of the wafer positioning system 100. The fixed part 70 of the second linear motor also comprises an encoder scale support 72, on which an encoder scale (not shown) is fixed. The wafer stage 90 is mounted on a movable part 80 of the second linear motor, the movable part 80 being equipped with an optical position sensor unit 82, which is arranged to move along the encoder scale for accurate positioning along the Y axis of the coordinate system of the wafer positioning system 100.

[0043] Reference numerals list

[0044] Fixing part 10

[0045] Magnetic rail base 20

[0046] Top side 20a

[0047] Bottom side 20b

[0048] Magnet accommodating portion 22

[0049] The first set of fixing holes 24

[0050] The second set of fixing holes 25

[0051] Rail receiving portion 26

[0052] Fixing hole 28

[0053] Encoder scale support member accommodation portion 30

[0054] Separated protrusion 31

[0055] Fixing protrusion 32

[0056] Flat surface 33

[0057] Hole 34

[0058] Separation member 38 (eg, cutaway portion)

[0059] Encoder scale support 40

[0060] Scale receiving side 42

[0061] Support 44

[0062] Track 50

[0063] Magnet 52

[0064] Movable part 60

[0065] Coil assembly 61

[0066] Slider 62

[0067] Optical position sensor unit 64

[0068] Fixing member 70

[0069] Encoder scale support 72

[0070] Movable parts 80

[0071] Optical position sensor unit 82

[0072] Wafer stage 90

[0073] Wafer positioning system 100 .

Claims

1. A magnetic track base (20) for a fixed component (10) of a linear motor, comprising a magnetic receiving portion (22) configured to fixedly receive a permanent magnet (52), a track receiving portion (26) configured to fixedly receive a track (50) along two sides of the magnetic receiving portion (22), and an encoder scale support member receiving portion (30) configured to fixedly receive an encoder scale support member (40), wherein: The encoder scale support accommodating portion (30) comprises a plurality of separate protrusions (31) which are mechanically separated from the rest of the magnetic track base (20) and are arranged to accommodate the bottom side of the encoder scale support (40) so as to prevent or at least reduce deformation of the encoder scale support accommodating portion (30) which may be caused by deformation of the rest of the magnetic track base (20) when the magnetic track base (20) is subjected to external force.

2. The magnetic rail base (20) according to claim 1, wherein: The plurality of separated protrusions (31) include a corresponding plurality of fixed protrusions (32) and a separation member (38) for mechanically separating each fixed protrusion (32) from the remaining portion of the magnetic rail base (20).

3. The magnetic rail base (20) according to claim 2, wherein: Each separation member is a cut-out portion arranged around a corresponding fixing projection (32).

4. The magnetic rail base (20) according to claim 3, wherein: The cut-out portion is in the form of a U-shaped through groove, and the U-shaped through groove extends from the top side (20a) to the bottom side (20b) of the magnetic rail base (20).

5. The magnetic track base (20) according to any one of claims 2 to 4, wherein: Each fixing protrusion (32) includes a top flat surface (33) including a fixing hole (34), the surface (33) protruding above the surface of the magnetic receiving portion (22).

6. The magnetic track base (20) according to any one of claims 2 to 5, wherein: The plurality of fixing protrusions (32) are arranged along a longitudinal direction between the magnetic receiving portion (22) and a rail receiving portion (26).

7. The magnetic track base (20) according to any one of the preceding claims, wherein: The magnetic receiving portion (22) comprises a plurality of pairs of threaded holes (25) for fixing the permanent magnets (52) with screws, and a plurality of pairs of through holes (24) for fixing the magnetic track base (20) to the magnetic track base support.

8. The magnetic rail base (20) according to claim 7, wherein: The cutouts (38) each surround one of the pairs of through holes (24) for fixing the magnetic rail base (20) to the magnetic rail base support so that the fixing protrusions (32) are rigidly fixed to the support.

9. The magnetic track base (20) according to any one of the preceding claims, wherein: The magnetic track base is integral.

10. The magnetic track base (20) according to any one of the preceding claims, wherein: The encoder scale support (40) has a substantially constant L-shaped cross-section which forms a seat (44) along the length of the support which is fixed to the encoder scale support receiving portion (30).

11. A fixed component (10) of a linear motor, comprising a magnetic rail base (20) according to any one of the preceding claims, a magnet (52) fixed to the magnetic receiving portion (22), a track (50) fixed to the track receiving portion on both sides of the magnet (52), an encoder scale support (40) fixed to the encoder scale support receiving portion (30), and an encoder scale fixed to the encoder scale support (40).

12. A linear motor comprising a fixed component (10) according to claim 11 and a moving component (70), the moving component comprising a coil assembly (60), a slider (62) slidably engaged with a corresponding track (50) of the fixed component (10), and an optical reader (64) arranged to move along the encoder scale.

13. A kinematic positioning system, in particular a wafer positioning system, comprising at least one linear motor according to claim 12.

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