Linear motor and device with linearly moving frame

Abstract

Linear motor for imparting a thrust to a movable unit (3) capable of linearly moving freely in a direction of movement (A), comprising: a base plate (2) which has a flat shape extending longitudinally in the direction of movement (A) and which is magnetically conductive to perform the function of a stator; a frame (3) having a flat shape extending in the direction of movement (A), which is formed from magnetically non-conductive material, to face the base plate (2) and which is movable relative to the base plate (2) by a linear guide (4) arranged on the base plate (2), thus functioning as a movable unit (3); a number of permanent magnets (61) arranged on one side of the base plate (2) by arranging a positive and a negative pole in the direction of movement (A); and a number of flat-shaped ring-like coils (5, 5U, 5V, 5W) arranged along the arrangement direction of the permanent magnets (61) and fixed as armatures to one side of the frame (3) so as to face the permanent magnets (61) while leaving an electromagnetic gap; a number of reinforcing members (51) made of magnetically non-conductive material, arranged within the respective ring-like coils (5, 5U, 5V, 5W) and having a flat shape, wherein a surface of the frame (3) fixing the coils (5, 5U, 5V, 5W) is provided with a recess portion (3B) providing an air gap between the surface to which the coils (5, 5U, 5V, 5W) are fixed and the coils (5, 5U, 5V, 5W); wherein the coils (5, 5U, 5V, 5W) are connected at their two ends to the frame (3) through their two side portions (5A) around the recess portion (3B) via a thermally conductive fixing coating (52); wherein the area of ​​the side of the frame (3) on which the recessed portion (3B) is arranged and the coils (5, 5U, 5V, 5W) are fixed is made of magnetically non-conductive material.

Description

RELATIONSHIPS WITH RELATED APPLICATIONS

[0001] The invention includes subject matter related to Japanese patent application JP 2004-258878, filed with the Japan Patent Office on September 6, 2004, and priority is claimed from this application. BACKGROUND OF THE INVENTION 1. Field of the Invention

[0002] The invention relates to a linear motor that provides thrust for free linear movement in one direction, and to a device with a linearly moving frame that is capable of moving a frame or a carriage or table by means of the provided linear motor. 2. Description of the state of the art

[0003] A moving magnet type and a moving coil type are already known in a coreless linear motor of the relevant prior art. In the moving magnet type linear motor, coils must be provided at corresponding parts on the power supply side (primary side) over almost the entire range of a moving stroke on the magnet side (secondary side). Therefore, the moving magnet type linear motor is a costly device.

[0004] Compared to it, the linear motor of the moving coil type does not have such a disadvantage and is superior in this respect.

[0005] The patent US 5 723 917 A shows a linear motor which has an armature block into which the windings extend.

[0006] The document JP H02- 65 656 A shows a linear motor in whose edge areas guide rails are arranged on which a carriage is guided, which is driven by a linear drive.

[0007] The document DE 696 11 387 T2 shows a tubular magnet carrier for a linear electromechanical transducer, wherein a high resistance is generated by the arrangement of magnet segments in the tube, which are spaced apart by slots.

[0008] The document JP H09-19 129 A shows a linear motor comprising a plurality of permanent magnets and a driver circuit to control a polyphase winding.

[0009] Document DE 103 92 882 T5 discloses a linear motor and a guide mechanism which guides a relative movement between a main side of the linear motor, which is a powered side thereof, and a sub-side of the linear motor, which is a non-powered side thereof, and which carries a load, wherein the guide mechanism comprises a rail and a movable part which is provided to be movable relative to the rail, and the main side of the linear motor is directly or indirectly connected to the rail or the movable part of the guide mechanism, wherein a heat insulation device for blocking heat generated by the main side of the linear motor is provided between the main side and the rail or the movable part of the guide mechanism to which the main side is connected.

[0010] As linear motors of the movable coil type, there are known those which comprise a flat (approximately track-shaped) coil as an armature fitted in a movable body mounting plate between magnets arranged to face each other and to be located on both sides in the thickness direction of the movable body mounting plate (see, for example, Japanese Unexamined Patent Publication (Kokai) No. JP 2003-116262 A).

[0011] Fig. 10 is a view of an arrangement of a coreless linear motor described in the patent publication, viewed in cross section perpendicular to the longitudinal direction (moving direction). Fig. 11 is a perspective view of a reinforcement member that can be attached to the movable body attachment plate and a coil that is attached by being fitted into the reinforcement member.

[0012] The coreless linear motor 100, which is Fig. 10, has a side yoke 101 with a cross-section in the shape of a recess, and a row of permanent magnets 104 and 105 are arranged on the opposite surfaces of an upper frame (upper side yoke 102) and a lower frame (lower side yoke 103) of the yoke 101, respectively. The magnets constituting the permanent magnet rows 104 and 105 are aligned in the longitudinal direction (motor movement direction) of the side yoke 101 such that their magnetic polarities are opposite to those of the adjacent magnet, and the magnetic polarities of the opposing magnets on the upper and lower surfaces of the yoke are different from each other.Between the opposing permanent magnet rows 104 and 105, the movable body fixing plate 106, which is attachable to a movable body at its open end, is inserted, and reinforcing members 108, which are mounted together with the coils 107, are fixed on both sides in the thickness direction.

[0013] The reinforcing part 108 has an approximately flat shape, as shown in Fig. 11, and is made of a non-magnetic material, such as a synthetic resin. On one of the main surfaces (surface opposite the magnets) of the reinforcement member 108, annular grooves 108A are formed, into which the hollow coils 107 are approximately fitted. On the reinforcement member 108, for a three-phase coil motor ( Fig. 11) Three annular grooves 108A are formed along the moving direction A of the motor, and each of the hollow coils 107 is fitted into each of the annular grooves 108A. A raised portion 108B corresponding to a coil body is formed in advance at approximately the central portion of the annular groove 108A, and a hollow portion 107A of the coil fits into the raised portion 108B. Thus, each of the coils 107 after assembly is in a state where most of the surfaces, except for the surface opposite the magnet, are covered by a synthetic resin or other non-magnetic material.

[0014] The reinforcement members 108 attached to the coils 107 are fixed to both sides in the thickness direction of the movable body fixing plate 106 and inserted into the space between the opposing magnets in the side yoke 101, as shown in Fig. 10. The movable body mounting plate 106 is simultaneously supported, so that it is linearly freely movable, by the side yoke 101 or a base plate for the side yoke 101 attached thereto (not shown).

[0015] When a three-phase alternating current flows to the three coils 107 as armatures, a Lorentz force due to the magnetic induction and the electric field strength affects the assembled body, that is, the movable body fixing plate 106, the coils 107 and the reinforcing members 108 as a movable unit to be attached to a movable body, and generates a drive for a linear motor.

[0016] The coreless linear motor of the moving coil type can be used in various ways as a compact linear moving frame, which can be installed in machining centers and various manufacturing equipment, etc. In this case, the frame must be compact, have good controllability, and low power consumption.

[0017] The coreless linear motor 100 from Fig. However, the construction shown in Figure 10 has disadvantages which must be eliminated and which are explained below, for example when it is used for a device with a linearly moving frame.

[0018] In the Fig. In the linear motor structure shown in Figure 10, flat-shaped coils 107 are opposed to the rows of permanent magnets 104 and 105. The coils 107, the rows 104 or 105 of permanent magnets, the upper yoke side 102, and the lower yoke side 103 form a magnetic circuit. However, it is difficult to achieve a flat body with this structure, as can be seen from the following points (1) to (4). (1) As in Fig. 10, two coils 107 are arranged in the thickness direction, each coil 107 being opposite the row 104 or 105 of permanent magnets, leaving a magnetic gap. (2) Considering the upper side yoke 102 and the lower side yoke 103 in the thickness direction, the yoke of a magnetic circuit must be provided twice. The upper side yoke 102 and the lower side yoke 103 must have a certain thickness so as not to cause magnetic saturation. It should be noted that even if the effect of magnetic saturation is small and the yoke can be made flat to a certain extent, strong magnetic attraction forces occur between the upper side yoke 102 and the lower side yoke 103, and there is a mechanical limit in strength, so the yokes must have a certain thickness. (3) For mechanical strength, the movable body fixing plate 106 must also be made thick to a certain extent. (4) If it is desired to position a frame (not shown) higher than the upper side yoke 102, an air gap must be provided between the frame and the upper side yoke 102 because the upper side yoke 102 is fixed.

[0019] From the above points (1) to (4) it follows that the linear motor 100 itself in its Fig. 10, the structure is thick, so that when it is connected to a linearly moving frame, the disadvantage arises that the device with the linearly moving frame can hardly be made flat because of this structure.

[0020] The coil body of the coils 107 is made of plastic, for example, and a large part of the surfaces, except for the opposing magnetic surfaces, is enclosed by the reinforcing parts 108 made of plastic, as shown in Fig. 11, so that heat radiation is low and overheating is easily caused when a current flows through the coils 107. Therefore, it is not possible to pass a large amount of current through the coils 107, so the magnetic field must be intensified and the thickness of the magnets constituting the rows 104 and 105 of permanent magnets, as well as the thickness of the yokes (upper and lower side yokes 102 and 103, respectively) must be large.

[0021] The distance from the mounting portion of the coils 107 to the point where thrust is applied (i.e., the position of the stage) is large, and thrust is also transmitted to the stage through the movable body fixing plate 106, which has an L-shaped cross section, so that a force generating vibration, particularly in the shear direction, is easily generated and hinders the function of the stage. Therefore, a decrease in the control advantage is caused, and a decrease in the stability of the stage speed, a decrease in the setting time for setting up the stage, and a decrease in the holding accuracy become disadvantages. SUMMARY OF THE INVENTION

[0022] According to the invention, the number of parts such as coils and magnets can be reduced, and a limitation of mechanical strength caused by attractive forces between magnets can be eliminated, and a linear motor can be provided in which sufficient heat radiation of the coils is achieved and the need to intensify the magnetic field is eliminated.

[0023] Furthermore, according to the invention, after mounting a flat body in the same manner as the above-mentioned linear motor, the distance between the mounting portion of the coils to the point where the thrust is applied is shortened, and the generation of an occurring force is limited by directly transmitting the thrust to the stage, so that as a result, a flat linearly moving stage with high control advantage is provided.

[0024] According to the invention, there is provided a linear motor which imparts thrust to a movable unit capable of linearly moving freely in one direction with respect to a stator, and which comprises a plurality of permanent magnets arranged on the stator side by arranging a positive pole and a negative pole in one direction, respectively; wherein a plurality of flat-shaped coils are arranged along the arrangement direction of the permanent magnets and are fixed as armatures on the movable unit side in such a way as to oppose the permanent magnets while leaving an electromagnetic gap, and a surface fixed to the coils on the movable element side is provided with a recessed portion to form an air gap between the surface fixed to the coils and the coils.

[0025] According to the invention, a device with a linearly moving stage is provided, which comprises a base plate, a stage which is constructed in such a way that it can move freely and linearly in one direction with respect to the base plate, and a linear motor which delivers a thrust to the stage in this direction, wherein the linear motor has a number of permanent magnets which are arranged on the base plate in such a way that a positive pole is arranged next to a negative pole in this direction, and a number of flat-shaped coils which are arranged along the arrangement direction of the permanent magnets and are fixed to the stage as armatures in such a way that they face the permanent magnets while leaving an electromagnetic gap, and the surface fixed to the coils on the stage side is provided with a recessed portion to form an air gap between the surface fixed to the coils and the coils.

[0026] The linear motor according to the invention has the advantages that the number of parts such as coils and magnets can be reduced, that a limitation of mechanical strength due to the attractive forces between magnets can be eliminated, and that a narrow or flat body can be obtained by ensuring sufficient heat radiation of the coils and eliminating the need for amplifying the magnetic field.

[0027] In addition to the advantages of the linear motor described above, the linearly moving stage device according to the invention has the advantages that the distance between the mounting portion of the coils to the point where the thrust is applied (a position of the stage) is made small and the thrust is immediately transmitted to the stage to restrict the generation of a random force, so that the control advantage becomes large. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] These and other objects and features of the invention will become more apparent from the following description of the preferred embodiments with reference to the drawings, in which: Fig. 1 is a plan view of a device with a linearly moving frame according to a first embodiment; Fig. 2 is a side view of the device with the linearly moving frame according to the first embodiment; Fig. 3 a cross section along the line XX in Fig. 1 according to the first embodiment; Fig. 4 is a plan view of a permanent magnet according to the first and second embodiments; Fig. 5 is a plan view of the device with the linearly moving frame according to the second embodiment; Fig. 6 is a side view of the device with the linearly moving frame according to the second embodiment; Fig. 7 a cross section along the line XX in Fig. 5 according to the second embodiment; Fig. 8A is a cross-sectional view of a device having a linearly moving frame according to a third embodiment; Fig. 8B is a plan view of a coil showing the locations where a cooling gas is injected; Fig. 9 shows a cross section of a device with a linearly moving frame according to a fourth embodiment; Fig. 10 is a view showing the structure of a coreless linear motor according to the prior art, viewed from a direction perpendicular to the longitudinal direction (movement direction); and Fig. 11 is a perspective view of a reinforcement member to be fixed to a movable body fixing plate and a coil to be fixed by fitting it into the reinforcement member. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] Hereinafter, a linearly moving stage apparatus according to embodiments of the invention and a linear motor for providing driving force will be explained with reference to the drawings. While the case of single-axis movement will be mainly explained, the present invention also allows the implementation of a linearly moving stage apparatus capable of two-axis movement (an XY-axis stage apparatus) by combining linearly moving stages arranged as described below. First embodiment

[0030] Fig. 1 is a plan view of an apparatus having a linearly moving stage according to a first embodiment. Fig. 2 is a side view in the direction of movement A of the frame, and Fig. 3 is a section along the line XX in Fig. 1.

[0031] The linear moving stage device 1 includes a base plate 2, a stage (unit) 3 as a moving stage, a linear guide 4 between the base plate 2 and the stage 3, and a linear motor for driving the stage 3 to move linearly in a state supported on the base plate 2 by the linear guide 4. Note that the linear motor is generally composed of, among other components, a coil, a permanent magnet, and a yoke, and its components will be explained below.

[0032] As in Fig. 1 to 3, the base plate 2 is in the form of a flat plate extending lengthwise in the moving direction A of the stage 3. The base plate 2 in the present embodiment is made of a magnetic material (magnetically conductive material) such as cold-rolled steel (SPCC) and low-carbon steel, and also serves as a yoke. Therefore, the thickness of the base plate 2 is set to a value required for its use as a yoke. The material and thickness for the base plate 2 are also determined by the need to achieve sufficient strength to support the weight of the stage 3.

[0033] A permanent magnet 6 is attached to an upper surface of the base plate 2. The permanent magnet 6 is explained further below.

[0034] The stage 3 is supported by the linear guide 4 and is linearly movable relative to the base plate 2; it has the shape of an approximately flat plate that entirely faces the base plate 2. The upper surface of the stage 3 is a surface for mounting a mounting part (not shown) to be linearly moved by the linearly moving stage device 1. The stage 3 is made of a lightweight, non-magnetic material, such as aluminum, to balance its weight.

[0035] As in Fig. 1, the length in the longitudinal direction A of the frame 3 is quite small compared with that of the base plate 2, and the extension in the width direction B, which is perpendicular to the direction of movement, is set to be approximately equal to that of the base plate 2.

[0036] It should be noted that the width of the frame 3 is not limited thereto, but is preferably almost as large as that of the base plate 2 in order to ensure a width for the upper surface for mounting a part and at the same time to keep the overall size as small as possible.

[0037] The linear guide 4 consists of two guide rails 41 fixed, for example, by screws, on both sides in the width direction of the base plate 2, and a number of slide units 42 fixed to the rear surface of the frame or table 3 opposite the base plate 2. In the case of the explained example, two slide units 42 are provided for one guide rail 41, and a total of four slide units 42 are fixed near the four corners of the rear side of the frame.

[0038] While the detailed explanation is omitted, mating parts of the guide rails 41 and the corresponding sliding units 42 are paired with each other, for example, on both side surfaces of each guide rail 41 and are shaped so that they do not easily separate from each other.

[0039] It should be noted that the associated portion of the sliding unit 42 may be formed such that it has, for example, a track ball to reduce friction with the guide rail 41.

[0040] Also, the mounting locations and the number of the sliding units 42 are not limited to those explained in the above example, but the sliding units 42 are preferably arranged symmetrically in the movement direction A and the width direction B of the frame or table 3.

[0041] At both ends in the longitudinal direction of the base plate 2 near the two ends of each of the guide rails 41, end members 21 are provided which protrude from the base plate 2. They serve to prevent the frame 3 from sliding off the guide rails 41 when the device 1 with the linearly moving frame is installed at a place of use, or the movement of the frame 3 can be stopped if the frame 3, which is guided by the guide rails 41, travels too far, for example, due to a malfunction.

[0042] Although it is not an essential feature, in the case of the illustrated example, a buffer portion 22 is provided at the upper portion of a side surface of the end member 21, which faces the center of the base plate, and the movement of the frame 3 is thereby controlled and an impact is buffered.

[0043] As in the Fig. 1 and Fig. 3, a locking plate 31 provided with a linear scale (not shown) formed on its underside is arranged on one side surface of the frame 3, and a position sensor, such as an encoder 7, is provided at a location corresponding to the linear scale. The encoder 7 is attached to a sensor locking plate 21, which in turn is attached to a side surface of the base plate 2, as shown in Fig. 3 shown.

[0044] The coding device 7 is only available as a single piece in Fig. 1 and Fig. 3, but may be provided in multiples at specific intervals. By mounting a plurality of encoders 7, in cases where the base plate length is long, a position of the rack 3 can be detected by at least one of these encoders, even if the rack is located anywhere on the base plate. Alternatively, if it is not necessary to detect the position of the rack, encoder 7, sensor locking plate 21, and scale locking plate 31 are not required.

[0045] A three-phase coil is attached to the back of the frame 3. The three-phase coil consists of three coils 5U, 5V, and 5W with a U-phase, V-phase, and W-phase, which are arranged at equal intervals along the direction of movement A of the frame 3, as shown in Fig. 1 shown.

[0046] Each of the coils is a flat (approximately rail-shaped) coil provided with turns, which is arranged in such a way that it faces a permanent magnet 6 and which is made with multiple wires by wet winding on the outer diameter of a reinforcing member 51 in the form of a thin plate of, for example, glass / epoxy resin, which also serves as a coil body, as shown in Fig. 3. In this case, wet winding refers to a winding process in which a predetermined coil shape is formed by winding wire, maintaining the coil shape by filling, for example, an epoxy resin between the wound wire, and fixing the wound wire. It should be noted that coreless wet winding or self-fusing (self-fusing and self-assembling) wire winding may also be used.

[0047] Each of the coils 5U to 5W has, as in Fig. 1, a side section 5A which coincides in its longitudinal direction with the frame movement direction A, and a section 5B which coincides in its longitudinal direction with the width direction B of the frame, which is approximately perpendicular to the permanent magnet 6, the section 5B being the part of the coil which contributes to the thrust of the linear motor.

[0048] Each of the coils 5U to 5W is fixed to the back of the frame 3 through the two side portions 5A and the corner portions at both ends thereof. For fixing, a coil fixing coating 52 in the form of a thermally conductive fixing agent is used, so that heat generated by the coils 5U to 5W is dissipated to the frame 3, which has a large heat capacity, as shown in Fig. 3. Instead of the coil fixing coating 52, a coating by baking or electrolytic deposition or a thin plastic plate can also be used.

[0049] The coil fixing coating 52 is a heat transfer insulating coating formed by an insulator for thermally and firmly fixing the coils 5U to 5W to the frame 3. For example, it is formed by a Kapton coating (polyimide film "Kapton," trademark of DuPont), a polyester coating, or a Teflon coating (fluoroplastic "Teflon," trademark of DuPont), and has sufficient insulation strength and a coating thickness of preferably about 0.1 mm or less.

[0050] The coating can be formed by firing using either epoxy or melamine plastics. A thin plastic sheet, for example, can be a fabric made of glass and epoxy resin.

[0051] The frame 3, which is thermally fixed to the coils 5U to 5W, is preferably provided with a fin to dissipate heat from the coils 5U to 5W. For example, as shown in Fig. 3, it is preferable to provide some ribs 3A between the part attached to the reel and the part attached to the slide unit 42 at the back of the frame.

[0052] If it is permissible to reduce the flatness on the top side of the frame 3 to some extent, the heat dissipation fins may also be provided at any location on the surface of the frame, for example, near the part attached to the coils.

[0053] As in Fig. 3, a recessed portion 3B is formed on the back of the frame 3 to which the coil 5W is attached. According to the example in Fig. 1, the size of the recessed portion 3B in the width direction B is approximately equal to the distance between the inner edges of the two side portions 5A of the coils, but it may be slightly smaller. Also, the size of the recessed portion 3B in the moving direction A of the frame is preferably limited so that all six linear portions 5B of the three coils 5U to 5W that are perpendicular to the moving direction A of the frame cross the recessed portion 3B. In this case, it is more preferable that the edges of the recessed portion 3B in the moving direction A of the frame be sufficiently far away from the linear portion 5B of the adjacent coil 5U or 5W, so that consequently an electromagnetic field generated by the permanent magnet 6 and the coils 5U to 5W is not disturbed by the recessed portion 3B.

[0054] In the present embodiment, by providing the recessed portion 3B, a space is formed between the coils 5U to 5W and the reinforcing member 51 and the frame 3.

[0055] The depth of the recessed portion 3B, that is, the distance in the height direction from the surface of the frame 3 attached to the coils to the surface facing the coils in the recessed portion 3B, is limited so that no eddy current is generated on the surface facing the coils in the recessed portion 3B by the electromagnetic strength by the permanent magnets 6 and the coils 5U to 5W or hardly contributes to the temperature increase of the frame 3 when heat is generated.

[0056] In other words, the depth of the recessed portion 3B is controlled such that the magnetic flux at the coil-opposite surface of the recessed portion 3B is 1000 Gauss (0.1 SI) or less when a maximum current flows to the coils 5U to 5W to obtain a maximum thrust of the rack.

[0057] The coils 5U to 5W themselves have sufficient strength because they are provided with the reinforcing part 51 and are manufactured by wet winding, as mentioned above, but for further firm fixing to the frame 3 to avoid deformation, as shown in Fig. 3, it is preferable to provide a projection 3C in the central part of the recessed portion 3B and to fix the projection 3C around the center of the reinforcing member 51. The size of the projection 3C must be controlled, and the distance from the coils 5U to 5W, particularly from the linear portion 5B, must be sufficiently secured so that the projection 3C does not interfere with the electromagnetic strength.

[0058] Fig. 4 is a top view of the permanent magnet 6.

[0059] The permanent magnet 6, in which the polarity of one part is different from that of the adjacent part, is arranged in the longitudinal direction (direction of movement A of the frame), in Fig. 4, viewed from above, magnetized, and a magnetic flux from the corresponding unit magnets 61 formed by the magnetization does not grow too much and does not shorten to an adjacent unit magnet 61 with different magnetic polarity.

[0060] Auxiliary magnets 62 for extracting the magnetic flux are provided at both ends in the longitudinal direction of the permanent magnet 6 in order to equalize the magnetic fields at the ends of the magnet with those of the other parts.

[0061] Due to the need to achieve the flattest possible body to reduce the height of the device 1 with the linearly moving frame, the permanent magnet 6 is preferably made as flat as possible. It should be noted that the thickness of the permanent magnet 6 is set to a specific value according to the required intensity of the magnetic field. The intensity of the magnetic field in this case is that at the locations where the coils 5U to 5W are arranged, maintaining the required distance from the permanent magnet 6.

[0062] In addition, the closer the distances between a negative and a positive pole adjacent to each other formed by the unit magnets 61, the more the height of the magnetic field is restricted. At this time, the height of the magnetic field is controlled to arrange the magnetic field in the perpendicular direction (normal line direction) with respect to the coils 5U to 5W, but not to restrict the surface opposite the coil (upper surface in Fig. 3) in the recessed section 3B by the electromagnetic strength through the coils 5U to 5W and the permanent magnet 6.

[0063] In addition, the distances between the positive pole and the negative pole are regulated by the unit magnets 61 to a value at which a smooth, linear thrust is achieved with respect to the predetermined distances of the coils 5U to 5W.

[0064] As explained above, the distances between the positive pole and the negative pole and the magnetic field intensity caused by the unit magnets 61 are determined by analyzing the magnetic field by considering the distance to the coils 5U to 5W and the pitches of their arrangement, so that a sufficient magnetic field intensity is obtained at the coil part even if the entire body is made flat and the recessed portion 3B of the frame 3 is not affected by an eddy current during operation.

[0065] The wiring from both ends of the corresponding turns of the coils 5U to 5W as well as the wiring from the encoder 7 are insulated from each other, pass through a cable duct 8, and are connected to a drive circuit not shown. As shown in Fig. 1, a cable support plate 32 for supporting the cable duct 8 is fixed to one end side in the width direction of the upper surface of the frame 3 by, for example, screws.

[0066] When a three-phase alternating current is supplied from the unillustrated drive circuit to the coils 5U to 5W, a Lorentz force due to magnetic induction and electric field strength acts on the coils 5U to 5W, causing the linear motor to thrust. As a result, the stage 3, which is fixed to the coils 5U to 5W, moves linearly while being supported by the linear guide 4. The position of the stage 3 is detected by the encoder 7, and the three-phase alternating current is controlled by the drive circuit when the detection result is obtained.

[0067] The linear motor and the device 1 with the linearly moving stage using the same in the present embodiment have advantages compared to the linear motor with the prior art construction as shown in the Fig. 10 and Fig. 11 is shown.

[0068] As in Fig. As shown in Fig. 3, the linear motor for achieving thrust is constructed of a single-layer coil (any of the three-phase coils 5U to 5W), a permanent magnet 6, and a base plate 2 that also serves as a yoke when viewed in the thickness direction, so that the entire body is flat. Furthermore, it is not necessary to provide two yokes on both sides of the coil (any of the three-phase coils 5U to 5W), and the coils 5U to 5W are fixed to the frame 3 via the coil fixing coating 52, so that the entire body is flat from this point of view as well.

[0069] The structure of the linear motor is also simple and the number of its parts is low.

[0070] Also, according to this structure, the frame 3 is made of non-magnetic material, so that no magnetic attraction force occurs between the frame 3, the permanent magnet 6, and the base plate 2. Therefore, the frame 3 and the base plate 2 have no limitations in their mechanical strength due to magnetic attraction forces, and accordingly, a flatter body can be formed.

[0071] Since the base plate 2 also serves as a yoke, a thickness that does not cause magnetic saturation and mechanical strength for supporting the stage 3 by the linear guide 4 are required, but it is not necessary to consider interference by a magnetic attraction force, so that the possibilities for selecting the material and thickness are wide.

[0072] According to the arrangement, a Lorentz force, which is determined by the product of the magnetic flux in the direction normal to the permanent magnet 6 and the coil current, is generated and serves as a drive for the linear movement of the frame 3.

[0073] At this time, since the coils 5U to 5W are fixed to the frame 3 via the coil fixing coating 52 with a high heat transfer coefficient, the distance from the thrust generation point (position of the coil) to the thrust application point (position of the frame) can be greatly shortened. Therefore, any force that might cause a reduction in the control function can also be greatly suppressed.

[0074] In particular, because the thrust generated at the sides of the coils 5U to 5W is directly transmitted to the frame, any force that may occur is extremely small, and the mechanical vibration is greatly suppressed, compared with those in the case of the device according to Fig. 10, in which the thrust is transmitted via the angled mounting plate 106 for the movable body, which has a low strength.

[0075] In the present embodiment, all parts are arranged symmetrically around the central axis in the width direction, as shown in Fig. 3 can be seen.

[0076] Therefore, the load is applied by the frame 3 as the thrust application point and a mounting member (not shown) on the frame 3 approximately perpendicular to the thrust generation point (position of the coil). Therefore, no force is generated in the horizontal direction (shear direction) of the frame 3 when the frame is moved.

[0077] Therefore, when comparing with the state-of-the-art linear motor used in Fig. 10, a dynamic disturbance at the time of moving the frame is only slight and consequently the control function is improved.

[0078] In the case of the prior art device described in Fig. As shown in Figure 11, most of the surfaces, except for the surface opposite the magnet, are enclosed by a non-magnetic material with low heat radiation capacity.

[0079] If the coils are enclosed by the reinforcement part made of non-magnetic material, the effectiveness decreases because the non-magnetic material has a high magnetic resistance and weakens the magnetization.

[0080] In contrast, in the present embodiment, less surface of the coils 5U to 5W is enclosed by non-magnetic material, such as a plastic.

[0081] This is because, in the present embodiment, a non-magnetic material (glass / epoxy resin) is used for the reinforcing member 51, for example, as a coil body to ensure strength, but after removing necessary parts for fixing the coils 5U to 5W, large parts of the other coil surfaces are exposed to the air.

[0082] As a result, the heat dissipation efficiency is increased, and the current flowing to the coils 5U to 5W to achieve the desired thrust can be lower than that of the prior art device. Also, because the magnetic induction generated by the coils 5U to 5W is not significantly weakened, the current flowing to the coils can be correspondingly lower.

[0083] In addition, when the heat radiation property of the coils 5U to 5W is good, it becomes unnecessary to compensate for a decreasing amount of effectiveness that decreases with the decrease in heat radiation ability and to increase the intensity of the magnetic field by increasing the thickness of the permanent magnet 6 to achieve the desired thrust; this contributes to making the body flat.

[0084] If you look at the Fig. Using the arrangement shown in Figure 10 for comparison, in which two-layer coils are superimposed to achieve thrust by the magnetic action of the upper and lower magnets, there is an advantage in that the natural frequency can be greatly increased. When the natural frequency is high, large-amplitude vibration to impair the control function is hardly generated, thus enabling smooth linear motion and improving the control function.

[0085] Also, heavy ferrous material is used only to a limited extent, and a lightweight material such as aluminum is primarily used, so that the weight of the stage 3 is significantly reduced. This, combined with the simple arrangement of the linear motor and the small number of parts, results in the control function of the linearly moving stage device being greatly improved. Second embodiment

[0086] Fig. 5 is a plan view of a linearly moving stage apparatus according to a second embodiment. Fig. 6 is a side view thereof in the direction of movement of the frame and Fig. 7 a section along the line XX of Fig. 5.

[0087] What greatly differs the linear moving stage device 1 of the second embodiment from that of the first embodiment is the shape of the base plate 20 and the heat radiation arrangement of the yoke 30 and the coils (in particular, the heat radiation plate 10 is newly provided). These points will be explained in turn below. The remaining parts are basically the same as those of the first embodiment, so the same reference numerals are assigned thereto in the drawings, and detailed explanations are omitted.

[0088] The base plate 20 in the present embodiment is made of a lightweight, non-magnetic material such as aluminum to reduce the weight of the entire body, and is formed so that the yoke 30 is embedded therein.

[0089] Because the heat radiation plate 10 for the coils is additionally provided in this embodiment, a space for its arrangement is required. To obtain the space for the arrangement of the heat radiation plate 10 and the permanent magnets 6, both end portions 20A in the width direction of the base plate are formed thick. As shown in Fig. 7, the base plate 20 has a recess in cross section.

[0090] The yoke 30 is firmly fixed by embedding in a thin section between the two ends 20A in the width direction of the base plate 20. Due to the high strength of the yoke 30, the necessary strength is achieved in this section.

[0091] The yoke 30 is formed from a single or multiple layers of a thin SPPC material and precisely pressed. The magnetic flux of the magnet can be kept small by narrowing the distances between the positive and negative poles of the magnet, allowing it to be formed flat. The yoke 30 can also be made from other low-carbon steels.

[0092] The permanent magnet 6 is attached to the yoke 30. The material, shape and magnetization of the permanent magnet 6 are the same as in the first embodiment (compare Fig. 4).

[0093] The heat radiation plate 10 is arranged between the three-phase coils 5U to 5W and the frame 3. The heat radiation plate 10 is fixed to the rear of the frame with support members 11, which also serve as spacers (hereinafter referred to as such) and which thermally block the frame 3 and the linear guide 4.

[0094] The spacer 11 has a thickness sufficient to create a space between the chassis 3 and the heat radiation plate 10, and has a size and material necessary to ensure the fastening strength; for example, it is made of a heat insulator so that it does not transfer heat from the coils 5U to 5W to the chassis 3. Since the spacer 11 has high strength, the chassis 3 and the heat radiation plate 10 are firmly fixed. As the material for the spacer 11, for example, ceramic or glass / epoxy resin is preferred.

[0095] On a surface of the heat radiation plate 10 on the permanent magnet side, the coils 5U to 5W having the same shape as in the first embodiment are firmly thermally fixed via a coil fixing coating 52 as a heat transfer-permitting adhesive.

[0096] The required size of the heat radiation plate 10 is determined according to the degree of temperature increase of the coils 5U to 5W during their repeated use. There is also a need to limit the space for supporting the heat radiation plate 10 and also to reduce the weight as much as possible, so the size, shape, and material of the heat radiation plate 10 are also determined from these perspectives.

[0097] In general, it is preferable to increase the heat capacity and surface area within the allowable range and to make the heat radiation plate 10 from a lightweight material to reduce the weight of the entire body. In the present embodiment, the heat radiation plate 10 is made of a lightweight material with relatively high thermal conductivity, such as aluminum.

[0098] In the first embodiment, a first recessed portion 3B was formed on the frame 3, but in the present case, a recessed portion 10B is formed on the heat radiation plate 10.

[0099] The relative position of the recessed portion 10B with respect to the fixing positions of the coils 5U to 5W and its size in plan view are the same as in the first embodiment, and the objective for providing the recessed portion and its height is also practically the same as in the first embodiment.

[0100] Namely, the recessed portion 10B is designed to form a gap between the coils 5U to 5W, the reinforcement member 51, and the heat radiation plate 10, and its height or depth is limited so that no eddy current is caused on the coil-opposite surface of the recessed portion 10B by the electromagnetic strength from the permanent magnet 6 and the coils 5U to 5W, or if such is generated, it contributes only slightly to increasing the temperature of the heat radiation plate 10.

[0101] In other words, the height of the recessed portion 10B is adjusted so that the superficial magnetic flux on the surface opposite to the coils in the recessed portion 10B is 1000 Gauss or less when a maximum current flows to the coils 5U to 5W to achieve the maximum thrust of the rack.

[0102] The heat radiation plate 10 is preferably provided with a rib to increase the heat radiation effect. For example, as shown in Fig. 7, it is preferable to form several fins 10A on the surface of the heat radiation plate 10 facing the frame or around the coil-mounted portion. The fin may also be provided as a single fin.

[0103] If it is important to increase the heat capacity and the surface area of ​​the heat radiation arrangement as mentioned above, the heat radiation effect can be further increased by making the heat radiation plate 10 thick.

[0104] In the present embodiment, the thermal conductivity of the heat radiation plate 10 itself is high, and an air cooling effect is achieved by the gap between the heat radiation plate 10 and the coils 5U to 5W formed by the recessed portion 10B and further by the gap between the heat radiation plate 10 and the frame 3 formed by the spacers 11, so that sufficient heat radiation is possible even if the heat radiation plate 10 is made flat.

[0105] According to the linearly movable stage apparatus of the second embodiment, the same effects as those of the first embodiment can be achieved.

[0106] That is, compared with the prior art arrangement, a flat and lightweight body can be obtained, and there are no limitations on strength because a magnetic attraction force is not applied, the distance from the thrust generation location to the thrust application location is short, thus suppressing the generation of an incident force, weight balance is favored by the symmetrical arrangement to prevent horizontal vibration, and the natural frequency is high to enable smooth linear motion in the present embodiment. Consequently, the control function is greatly improved.

[0107] Compared with the first embodiment, the present embodiment further has the following advantages.

[0108] In the first embodiment, the base plate 2 also serves as a yoke, so that restrictions apply to the thickness of the plate and its strength, while this is not the case with the base plate 20 of the second embodiment.

[0109] Therefore, in the second embodiment, the strength of the entire base plate can be controlled by changing the material and cross-sectional shape of the base plate 20. Particularly in the case of a device having a linearly moving stage, the strength of the base plate 20 must be optimized to achieve smooth movement, as explained below.

[0110] When a very heavy load is applied to the stage 3, the stage 3 may bend slightly in some cases while being movably supported on the guide rails 41. If the rigidity or rigidity of the base plate 20 side is too large, a force is applied in the horizontal direction to the linear guide 4, which disadvantageously increases frictional resistance, so that the mechanical function as a linearly moving stage device decreases and the magnitude of the current flowing to the coils 5U to 5W is increased.

[0111] If the stiffness becomes low so that the side of the base plate 20 bends to a certain extent, an increase in friction, a resulting decrease in mechanical function and an increase in current, as indicated above, can be prevented.

[0112] In the second embodiment, by changing the height of the thickness portion 20A of the base plate 20 according to the cross section of Fig. 7, the thrust generation location (the location around the coil mounting), the center of gravity of the movable body (the composite body of the frame 3, heat radiation plate 10, coils, and slide units 42), and the bearing of the linear guide 4 are arranged substantially at positions in the vertical direction on a line. This means that "the thrust generation location," "the thrust application location," and "a thrust interaction support location" are balanced in their positions. Therefore, the linearly movable frame device according to the second embodiment is a stable mechanism in terms of structural mechanics, and any force caused by imbalance among the three locations is extremely small.

[0113] From the above, it is apparent that it is possible to provide a linearly movable stage device in which the control function is greatly improved as compared with that of a linear motor having the prior art arrangement, and further structural advantages can be achieved even as compared with the first embodiment, so that the control function is correspondingly improved.

[0114] It should be noted that the application of the linear motor according to the invention to a device with a linearly moving stage has been explained above, but the linear motor according to the invention can also be applied to a device with an XY table capable of performing movement in the direction of two axes.

[0115] The XY stage device may employ a first linearly moving stage section that moves along the X-axis or the Y-axis, and the arrangement of attaching a second linearly moving stage section that moves linearly in the direction perpendicular thereto. In this case, the stage of the second linearly moving stage section becomes an XY stage for loading an object to be ultimately moved. Here, the first and second linearly moving stage sections are formed to have the above-mentioned structure, to which the present invention is applicable.

[0116] In the XY table device constructed as described above, the first and second linearly moving stage sections are formed flat, so that it is possible to manufacture an overall compact and flat device.

[0117] In the XY stage device constructed as mentioned above, a larger load is applied to the first linearly moving stage section located at a lower position. However, as the weight of the linearly moving stage sections is reduced, the load is reduced accordingly.

[0118] Also, vibration (dynamic disturbance) of respective linearly moving frame sections hardly affects the others, and the control function is great due to the number of structural advantages mentioned above: a force in the shear direction hardly occurs because a force is applied from practically directly above the point of thrust generation; the device has a symmetrical arrangement around a vertical surface passing through the axis of movement, and furthermore it is structurally stable because the center of gravity is balanced with respect to the positions.

[0119] In addition, the first and second linearly moving frame sections are flat, and there is the advantage that the natural frequency in the direction of spacing of the first linearly moving frame section can be increased much more than in the arrangement according to Fig. 10, where coils are stacked to achieve thrust through the magnetic action of upper and lower magnets. When the natural frequency is high, large-amplitude vibration that impedes the control function is hardly generated, thus enabling smooth linear motion and improving the control function. Third embodiment

[0120] In the first and second embodiments described above, the frame 3 or the heat radiation plate 10 can be provided with a channel for a gaseous or liquid coolant, such as air or water. The present embodiment provides such a channel.

[0121] The Fig. 8A is a cross-sectional view of a linear moving stage apparatus according to a third embodiment.

[0122] In this embodiment, a tube with a channel 70 is provided within the frame 3 or the heat radiation plate 10. The position and number of the channels 70 can be freely selected. In the present embodiment, two channels 70 are arranged near the part for fixing the coil 5, and one channel 70 is arranged near the center of the coil 5. Furthermore, an outlet 71 for a cooling gas for cooling by blowing the gas directly onto the coil 5 is preferably provided in the channel 70 in the center. The number per coil and the arrangement of the cooling gas outlet 71 can be freely selected, and in the present embodiment, the cooling gas can be blown onto two locations on each coil, as shown in Fig. 8B shown.

[0123] Therefore, the coolant of the central channel 70 must be a gas, but a liquid may flow in the channels 70 near the coil mounting location.

[0124] In the present embodiment, since the coolant channels 70 are arranged in the stage 30 or the heat radiation plate 10, the heat supplied from the coil 5 to the stage 30 or the heat radiation plate 10 is easily dissipated to the outside via the coolant. As a result, a temperature increase of the coil 5 is suppressed, and the control function of the linearly moving stage device is further improved compared to the first or second embodiment.

[0125] If the cooling gas outlet 71 is provided, the effect of cooling the coil 5 can be further enhanced.

[0126] It should be noted that by having a highly effective heat radiation as such, it is easily possible to omit the heat radiation plate 10, which has the advantage of resulting in improved overall strength or stiffness. Fourth embodiment

[0127] In the above first three embodiments, a part on the movable unit side near the coil 5, such as the frame 3 or the heat radiation plate 10, may be provided with a rib for supporting the reinforcement part 51 of the coil 5 and also serving to dissipate heat from the reinforcement part 51. In the present embodiment, such a rib is provided.

[0128] Fig. 9 is a cross-sectional view of a linearly moving stage device according to a fourth embodiment.

[0129] In the illustrated example, three ribs 80 are provided in the direction of the illustrated cross-section. The number and shape of the ribs can be freely selected, however, one end surface of the rib 80 must contact the reinforcing member 51 at the center of the coil 5. Preferably, although not illustrated in the drawing, a layer of, for example, the same material as that of the coil fixing coating 52 or another baked coating is provided between the end surfaces of the ribs 80 and the reinforcing member 51, thereby thermally and mechanically securing the two parts.

[0130] Furthermore, it is preferable that the number, position, and size of the fin 80 be selected so that no eddy current is generated. If the generation of eddy current can be sufficiently suppressed, stainless steel (a SUS plate) may be used as the material for the frame 3 or the heat radiation plate 10, other than, for example, aluminum.

[0131] In the present embodiment, the heat radiation effect of the coil 5 is improved and the coil 5 is also firmly fixed, so that the control function and the rigidity of the device with the linearly moving frame are improved compared to the embodiments in which the rib 80 is provided.

Claims

[1] Linear motor for imparting a thrust to a movable unit (3) capable of linearly moving freely in a direction of movement (A), comprising: a base plate (2) which has a flat shape extending longitudinally in the direction of movement (A) and which is magnetically conductive to perform the function of a stator; a frame (3) having a flat shape extending in the direction of movement (A), which is formed from magnetically non-conductive material, to face the base plate (2) and which is movable relative to the base plate (2) by a linear guide (4) arranged on the base plate (2), thus functioning as a movable unit (3); a number of permanent magnets (61) arranged on one side of the base plate (2) by arranging a positive and a negative pole in the direction of movement (A); and a number of flat-shaped ring-like coils (5, 5U, 5V, 5W) arranged along the arrangement direction of the permanent magnets (61) and fixed as armatures to one side of the frame (3) so as to face the permanent magnets (61) while leaving an electromagnetic gap; a number of reinforcing members (51) made of magnetically non-conductive material, arranged within the respective ring-like coils (5, 5U, 5V, 5W) and having a flat shape, wherein a surface of the frame (3) fixing the coils (5, 5U, 5V, 5W) is provided with a recess portion (3B) providing an air gap between the surface to which the coils (5, 5U, 5V, 5W) are fixed and the coils (5, 5U, 5V, 5W); wherein the coils (5, 5U, 5V, 5W) are connected at their two ends to the frame (3) through their two side portions (5A) around the recess portion (3B) via a thermally conductive fixing coating (52); wherein the area of the side of the frame (3) on which the recessed portion (3B) is arranged and the coils (5, 5U, 5V, 5W) are fixed is made of magnetically non-conductive material. [2] Linear motor for imparting a thrust to a movable unit (3) capable of linearly moving freely in a direction of movement (A), comprising: a base plate (2) which has a flat shape extending longitudinally in the direction of movement (A) and which is magnetically conductive to perform the function of a stator; a frame (3) having a flat shape extending in the direction of movement (A), which is formed from magnetically non-conductive material, to face the base plate (2) and which is movable relative to the base plate (2) by a linear guide (4) arranged on the base plate (2), thus functioning as a movable unit (3); a number of permanent magnets (61) arranged on one side of the base plate (2) by arranging a positive and a negative pole in the direction of movement (A); and a number of flat-shaped ring-like coils (5, 5U, 5V, 5W) arranged along the arrangement direction of the permanent magnets (61) and fixed as armatures to one side of the frame (3) so as to face the permanent magnets (61) while leaving an electromagnetic gap; a number of reinforcing members (51) made of magnetically non-conductive material, arranged within the respective ring-like coils (5, 5U, 5V, 5W) and having a flat shape, wherein a surface of the frame (3) fixing the coils (5, 5U, 5V, 5W) is provided with a recess portion (10B) providing an air gap between the surface to which the coils (5, 5U, 5V, 5W) are fixed and the coils (5, 5U, 5V, 5W); wherein an element (10) on the side of the frame (3), through which the recessed portion (10B) is provided and to which the coils (5, 5U, 5V, 5W) are attached, is made of magnetically non-conductive material; wherein the element (10) on the side of the frame (3) is a thermal radiation plate (10) made of magnetically non-conductive material, to which the coils (5, 5U, 5V, 5W) are fixed at both ends thereof through their two side portions (5A) around the recess portion (10B) via a thermally conductive fixing coating (52), wherein a cooling fin (10A) is formed on the thermal radiation plate (10), and wherein the cooling fin (10A) is provided near the center of the coils (5, 5U, 5V, 5W) in the recessed portion (10B). [3] A linear motor according to claim 1 or 2, wherein the height between the surface fixed to the coils (5, 5U, 5V, 5W) and the surface facing the coils (5, 5U, 5V, 5W) in the recessed portion (3B, 10B) is limited such that the surface magnetic flux generated on the surface facing the coils (5, 5U, 5V, 5W) by the magnetic field of the opposing permanent magnets (61) is 1000 gauss or less. [4] Linear motor according to claim 1 or 2, wherein a channel (70) with a coolant is formed in the frame (3) or in the thermal radiation plate (10) on the side of the movable unit (3) to which the coils (5) are attached. [5] A linear motor according to claim 4, wherein an outlet (71) for blowing out a gas as a coolant against the coils (5) is provided on the channel (70) with the coolant. [6] Linear motion frame comprising a linear motor according to one of claims 1 to 5, wherein the frame (3) is movable by the linear motor in the direction of movement (A).

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