cylindrical linear motor

Abstract

To provide a tubular linear motor in which displacement of a yoke from a magnet laminate in a field can be prevented, and further, the field can be resolved.SOLUTION: In order to achieve the aforementioned object, a tubular linear motor 1 according to the present invention includes: a tubular field 6 having a magnet laminate 10 formed of a plurality of annular permanent magnets 10a, 10b that are layered, on one of the inner and outer circumferences of the magnet laminate 10, with N poles and S poles being alternately arranged in the axial direction, and a tubular yoke 8 formed of a magnetic body that is disposed on the other one of the inner and outer circumferences of the magnet laminate 10; and an armature 2 that is movable in the axial direction of the field 6 with respect to the field 6. The yoke 8 has an inner diameter that is smaller than the outer diameter of the magnet laminate 10 or has an outer diameter that is larger than the inner diameter of the magnet laminate 10, and further, has a slit 30a extending over the entire length in the axial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cylindrical linear motor. [Background technology]

[0002] A cylindrical linear motor, for example, includes a core having a number of teeth arranged in the axial direction on its outer periphery, an armature having U-phase, V-phase, and W-phase windings fitted in slots between the teeth, and a field magnet facing the armature, which has a laminated magnet body formed by stacking a number of annular permanent magnets so that south and north poles are arranged alternately in the axial direction.

[0003] In a cylindrical linear motor configured in this manner, by applying current appropriately to the U-phase, V-phase, and W-phase windings of the armature, attractive and repulsive forces in the axial direction are generated between the permanent magnets in the field and the armature, driving the armature or field as a mover.

[0004] In such cylindrical linear motors, a yoke made of a magnetic cylinder may be provided on the outer periphery of the laminated magnet body in order to efficiently direct the magnetic field lines of the permanent magnets in the field toward the armature (see, for example, Patent Document 1).

[0005] Such a yoke is not particularly fixed at either end, but is merely attracted to the outer periphery of the permanent magnet by the magnetic force of the permanent magnet. Therefore, when the cylindrical linear motor is driven, it may be attracted by the magnetic force of the armature, which moves axially relative to the field magnet, and may become displaced axially relative to the permanent magnet.

[0006] On the other hand, although not a yoke, a structure has been proposed for holding a laminated magnet body housed in a cylindrical pipe, in which both ends of the cylindrical pipe are crimped from the outer periphery to cause elastic deformation, and crimped portions are provided on the inner periphery of both ends of the cylindrical pipe, and both ends of the laminated magnet body are clamped by these crimped portions (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-68624 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-73864 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, in order to prevent the permanent magnets in the yoke from shifting, it is conceivable to adopt the structure of Patent Document 2, in which both ends of the yoke are crimped from the outer periphery to elastically deform them, thereby forming crimped portions that clamp both ends of the laminated magnet body.

[0009] In this way, the yoke can be prevented from shifting axially relative to the laminated magnet body even when it receives an attractive force from the armature side. However, if both ends of the yoke are crimped to make it one piece with the laminated magnet body, it becomes impossible to disassemble the field magnet, which creates a new problem in that maintenance of the cylindrical linear motor becomes impossible.

[0010] SUMMARY OF THE INVENTION An object of the present invention is to provide a cylindrical linear motor that can prevent the yoke from shifting relative to the laminated magnet body in the field and that allows the field to be disassembled. [Means for solving the problem]

[0011] In order to achieve the above object, the cylindrical linear motor of the present invention comprises a laminated magnet body formed of a plurality of annular permanent magnets laminated on one of the inner periphery or the outer periphery so that N poles and S poles are alternately arranged in the axial direction, a cylindrical field magnet having a cylindrical yoke formed of a magnetic body arranged on the other of the inner periphery or the outer periphery of the laminated magnet body, and an armature that is movable in the axial direction of the field magnet relative to the field magnet, and the yoke is When the magnet laminate is inserted inside, the inner diameter is smaller than the outer diameter of the magnet laminate, and when the magnet laminate is inserted inside, the outer diameter is larger than the inner diameter of the magnet laminate; Has slits along the entire axial length When the yoke is viewed in the axial direction, the direction in which the slits are formed is inclined at an angle relative to the radial direction of the yoke so that the laminated magnet body is not exposed in the radial direction.

[0012] In a cylindrical linear motor configured in this manner, the yoke has a slit, so it can be easily attached to the laminated magnet body by expanding or contracting its diameter. After the yoke is attached to the laminated magnet body, the yoke fits into the laminated magnet body while applying a tensioning force due to its own restoring force, so it is firmly fixed to the laminated magnet body. Therefore, with a cylindrical linear motor configured as described above, when the armature moves axially relative to the field magnet, the yoke is not attracted by the magnetic force of the armature and does not shift axially relative to the laminated magnet body. Furthermore, because the yoke has a slit, it can be easily expanded or contracted to remove it from the laminated magnet body.

[0013] The yoke may also have a pair of notches on either side of the slit that allow a tool to be inserted. With a cylindrical linear motor configured in this way, the diameter of the yoke can be easily expanded by hooking a tool into the notches, facilitating the process of fixing the yoke to the laminated magnet body.

[0014] Furthermore, the direction of the slits formed in the yoke is inclined relative to the radial direction when viewed from the axial direction of the yoke. do. In this way, in a cylindrical linear motor in which the slits are formed in a direction inclined relative to the radial direction, the provision of the slits reduces the number of magnetic field lines that pass only through the slits and leak to the outside without passing through the yoke, thereby allowing a stronger magnetic field to act on the armature and improving thrust.

[0015] Furthermore, the shape of the slits provided in the yoke may be wavy when viewed from the radial direction of the yoke. In this way, with a cylindrical linear motor with wavy slits, the shape of the circumferential end of the yoke can be made uneven without providing notches in the yoke, and the diameter of the yoke can be easily expanded by hooking a tool on the concave portions, making it easy to fix the yoke to the laminated magnet body. Furthermore, the yoke may be formed by stacking a plurality of yoke segments. A cylindrical linear motor configured in this manner facilitates the work of attaching the yoke to the laminated magnet body. [Effects of the Invention]

[0016] The cylindrical linear motor of the present invention can prevent the yoke from shifting relative to the laminated magnet body in the field magnet, and also allows the field magnet to be resolved. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a longitudinal sectional view of a cylindrical linear motor according to an embodiment of the present invention; [Figure 2] 1A is a plan view of a yoke of a cylindrical linear motor according to an embodiment as viewed from an axial direction, and FIG. 1B is a side view of the yoke of a cylindrical linear motor according to an embodiment as viewed from a radial direction. [Figure 3] FIG. 2 is a partially enlarged vertical cross-sectional view of a field magnet of a cylindrical linear motor according to an embodiment. [Figure 4] FIG. 10 is an enlarged cross-sectional view of a field magnet in which a yoke according to a first modified example is attached to the outer periphery of a laminated magnet body. [Figure 5] FIG. 10 is a side view of a yoke according to a second modified example, as viewed from the radial direction. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described below based on the embodiments shown in the drawings. As shown in Fig. 1, a cylindrical linear motor 1 in one embodiment is configured with a laminated magnet body 10 formed of multiple annular permanent magnets 10a, 10b that are laminated on the inner periphery so that N poles and S poles are arranged alternately in the axial direction, a cylindrical field magnet 6 having a cylindrical yoke 8 formed of a magnetic material and arranged on the outer periphery of the laminated magnet body 10, and an armature 2 that is movable in the axial direction of the field magnet 6 relative to the field magnet 6.

[0019] Below, we will explain in detail each part of the cylindrical linear motor 1. The armature 2 is composed of a core 3 and a winding 5. The core 3 is composed of a cylindrical core body 3a and a plurality of annular teeth 3b provided at intervals in the axial direction on the outer periphery of the core body 3a.

[0020] As described above, the core 3 is cylindrical, and as shown in Fig. 1, it has ten teeth 3b arranged at equal intervals in the axial direction on the outer periphery of the core body 3a, and slots 4, which are gaps into which windings 5 ​​are attached, are formed between the teeth 3b. In this embodiment, a total of nine slots 4, which are gaps, are provided between adjacent teeth 3b in Fig. 1. The windings 5 ​​are wound around and attached to these slots 4. The windings 5 ​​are made up of three-phase windings: a U-phase winding, a V-phase winding, and a W-phase winding.

[0021] Each tooth 3b is annular and, except for the teeth 3b located at both ends of the core 3, is an isosceles trapezoid in the axial direction, with the outer circumferential end being narrower than the inner circumferential end, and both axial side surfaces are tapered at equal angles relative to the outer circumferential end. As shown in Fig. 1, the terminal teeth 3b have a cross-sectional shape in which the other teeth 3b are cut in half along a plane perpendicular to the axis of the core 3. The cross-sectional shape of the teeth 3b may be a shape other than an isosceles trapezoid, such as a rectangle.

[0022] The armature 2 is attached to the outer periphery of the tip of a rod 11, which is an output shaft and is made of a non-magnetic material. The rod 11 includes a cylindrical first rod 20 and a cylindrical second rod 21, which has a core 3 attached to its outer periphery and is screwed onto the inner periphery of the first rod 20.

[0023] The first rod 20 is cylindrical and includes a rod body 22 having screw portions 22a and 22b on the outer periphery at the left end in FIG. 1 and on the inner periphery at the right end in FIG. 1, respectively, and a rod cap 23 having a bracket 23a for attaching the cylindrical linear motor 1 to equipment and screwed onto the screw portion 22a at the left end in FIG. 1 of the rod body 22 to close the left end of the rod body 22.

[0024] An annular slider 25 is fitted to the outer periphery of the right end of the rod main body 22 in FIG. 1. The slider 25 includes a sliding contact portion 25a that slides against the inner periphery of a cylindrical portion 9b (described later), a small-diameter portion 25b that is provided on the base end side of the rod 11, which is to the left of the sliding contact portion 25a in FIG. 1, and has an outer diameter smaller than that of the sliding contact portion 25a, an annular groove 25c that is provided circumferentially on the outer periphery of the small-diameter portion 25b, and a flange 25d that is provided on the inner periphery of the right end in FIG. 1. A rubber seal ring 26 serving as an elastic body is fitted in the annular groove 25c of the slider 25. The inner diameter of the flange 25d is equal to or larger than the inner diameter of the rod main body 22 but smaller than the outer diameter of the rod main body 22. When the slider 25 is fitted to the rod main body 22, the flange 25d abuts against the right end surface of the rod main body 22 in FIG. 1.

[0025] The second rod 21 includes a cylindrical core retaining tube 21a on whose outer periphery the core 3 is attached, and an annular slider 21b provided on the outer periphery of the tip of the core retaining tube 21a, which is the right end in FIG. 1. A threaded portion 21c is provided on the outer periphery of the base end of the core retaining tube 21a, which is the left end in FIG. 1. The base end of the core retaining tube 21a is provided on the inner periphery thereof, with a large inner diameter portion 21d having a larger inner diameter than other portions. When the base end of the core retaining tube 21a is inserted into the inner periphery of the rod main body 22 of the first rod 20 at the right end in FIG. 1 and the threaded portion 21c is screwed into the threaded portion 22b, the first rod 20 and the second rod 21 are connected. In this manner, in this embodiment, the rod 11 is cylindrical and is composed of the first rod 20 and the second rod 21.

[0026] Furthermore, the core 3 is fitted onto the outer periphery of the core holding cylinder 21a of the second rod 21. The outer diameter of the core holding cylinder 21a is smaller than the outer diameter of the rod main body 22 of the first rod 20. Therefore, when the second rod 21, on which the armature 2 is mounted, is connected to the first rod 20, on which the slider 25 is mounted, in the manner described above, the armature 2 and the slider 25 are sandwiched and fixed between the right end of the first rod 20 in FIG. 1 and the slider 21b of the second rod 21. When the armature 2 is mounted on the rod 11 in this manner, the core 3 is fixed to the rod 11 in a manner sandwiched between the slider 21b and the slider 25. Note that, although the armature 2 is configured to have only a single core 3 in this embodiment, it may be configured to have multiple cores 3 to improve thrust, etc.

[0027] Next, the rod 11 is provided with a cover 17 that covers the outer periphery of the rod 11 and forms a gap G. Specifically, the cover 17 is cylindrical, and is attached to the rod 11 with one end fitted onto the outer periphery of an annular cover end 18 provided on the outer periphery of the rod 11 and the other end fitted onto the outer periphery of the small diameter portion 25b of the slider 25.

[0028] Lead wires L that connect the windings 5 ​​of each phase attached to the core 3 to an external drive circuit (not shown) are housed in the gap G between the cover 17 and the rod 11, and the wiring work between the windings 5 ​​and the lead wires L can be performed with the cover 17 removed, making the assembly work of the cylindrical linear motor 1 easier.

[0029] On the other hand, in this embodiment, the stator is configured to include a field 6 made up of a cylindrical laminated magnet body 10 and a yoke 8 made of a cylindrical magnetic material that is press-fitted onto the outer periphery of the laminated magnet body 10, a cylindrical inner tube 9 made of a non-magnetic material that is inserted into the inner periphery of the laminated magnet body 10, and a cylindrical barrel 7 made of a non-magnetic material into which the inner tube 9 and field 6 are inserted.

[0030] The barrel 7 is made of a non-magnetic material and has a threaded portion 7a provided on the inner periphery of the open end on the left side in FIG. 1 and a threaded portion 7b provided on the outer periphery of the open end on the right side in FIG. 1. A bottom cap 12 is screwed onto the outer periphery of the open end on the right side in FIG. 1 of the barrel 7, closing the open end on the right side in FIG. 1. The bottom cap 12 is cylindrical with a bottom 12a and a tubular portion 12b, and is attached to the barrel 7 by screwing the tubular portion 12b onto the outer periphery of the barrel 7. A bracket 12c is provided on the tubular portion 12b of the bottom cap 12, allowing the cylindrical linear motor 1 to be attached to a device. The bottom 12a of the bottom cap 12 faces the right end of the field magnet 6 in FIG. 1.

[0031] The inner tube 9 is made of a non-magnetic material and is configured to include an annular head portion 9a that is attached by screwing to the open end at the left end in Fig. 1 of the barrel 7, and a tubular portion 9b that is thinner in thickness than the head portion 9a and extends from the inner periphery of the right end in Fig. 1 of the head portion 9a and is inserted into the inner periphery of the field magnet 6. Therefore, the right end in Fig. 1 of the head portion 9a of the inner tube 9 faces the left end in Fig. 1 of the field magnet 6 that is arranged on the outer periphery of the tubular portion 9b.

[0032] The inner tube 9 also has a curved surface 9c at the boundary between the right end of the head portion 9a in Figure 1 and the cylindrical portion 9b, so that even if an axial force acts only on the head portion 9a, stress does not concentrate at the boundary between the head portion 9a and the cylindrical portion 9b. To avoid such stress concentration, a tapered surface may be provided at the boundary between the head portion 9a and the cylindrical portion 9b.

[0033] The field 6 is configured with a laminated magnet body 10 formed of a plurality of annular permanent magnets 10a serving as main magnetic poles and a plurality of annular permanent magnets 10b serving as sub-magnetic poles, which are alternately stacked in the axial direction and inserted, and a cylindrical yoke 8 that fits onto the outer periphery of the laminated magnet body 10 and is fixed to the outer periphery of the laminated magnet body 10.

[0034] The laminated magnet body 10 is composed of multiple annular permanent magnets 10a that serve as main poles and multiple annular permanent magnets 10b that serve as sub-pole poles, stacked alternately in the axial direction. The permanent magnets 10a and 10b are stacked with an adhesive between them to prevent them from scattering. Note that the triangular marks on the main pole permanent magnets 10a and sub-pole permanent magnets 10b in FIG. 1 indicate the magnetization direction, with the main pole permanent magnets 10a being magnetized radially and the sub-pole permanent magnets 10b being magnetized axially. The main pole permanent magnets 10a and sub-pole permanent magnets 10b are arranged in a Halbach array, with south and north poles alternating in the axial direction on the inner periphery of the field magnet 6.

[0035] Furthermore, in the cylindrical linear motor 1 of this embodiment, the axial length of the permanent magnet 10a of the main magnetic pole is longer than the axial length of the permanent magnet 10b of the sub-pole. In this way, if the axial length of the permanent magnet 10a of the main magnetic pole is increased, the magnetic resistance between the permanent magnet 10a of the main magnetic pole and the core 3 can be reduced, and the magnetic field acting on the core 3 can be increased, thereby improving the thrust of the cylindrical linear motor 1. In this embodiment, the axial length of the permanent magnet 10a of the main magnetic pole is longer than the axial length of the permanent magnet 10b of the sub-pole, but this is not limiting and the axial lengths of the two can be set as desired by design.

[0036] Furthermore, in the cylindrical linear motor 1 of the present invention, a yoke 8 is provided around the permanent magnets 10a and 10b. Without the yoke 8, shortening the axial length of the permanent magnets 10b of the sub-pole increases the magnetic resistance outside the permanent magnets 10a of the main pole at the axial center, reducing the field magnetic flux. This reduces the degree of improvement in thrust of the cylindrical linear motor 1 when the axial length of the permanent magnets 10a of the main pole is increased. In contrast, providing a yoke 8 around the permanent magnets 10a and 10b ensures a magnetic path with low magnetic resistance, thereby suppressing the increase in magnetic resistance caused by shortening the axial length of the permanent magnets 10b of the sub-pole. Therefore, making the axial length of the permanent magnets 10a of the main pole longer than that of the permanent magnets 10b of the sub-pole and providing a cylindrical yoke 8 around the permanent magnets 10a and 10b can significantly improve the thrust of the cylindrical linear motor 1. The thickness of the yoke 8 may be set to a thickness suitable for suppressing an increase in the external magnetic resistance of the permanent magnet 10a of the main magnetic pole.

[0037] As shown in FIG. 1, the yoke 8 is formed by stacking multiple yoke segments 30. As shown in FIG. 2, each yoke segment 30 is cylindrical and has a slit 30a formed along its entire axial length, forming a C-shape when viewed axially. Each yoke segment 30 also has a pair of notches 30b, 30b on either side of the slit 30a at its circumferential end. The inner diameter of the yoke segment 30 is smaller than the outer diameter of the laminated magnet body 10. Because the yoke segments 30 have the slits 30a, the diameter of the yoke segments 30 can be easily expanded by hooking the tips of pliers (not shown) on the notches 30b, 30b and opening the pliers. In this way, using a tool such as pliers, the inner diameter of the yoke segments 30 is expanded so that it is larger than the outer diameter of the laminated magnet body 10, and the laminated magnet body 10 is inserted into the yoke segments 30. When the expanded diameter of the yoke segments 30 is released, the yoke segments 30 exert a restoring force to return to their original diameter, applying a tensioning force to the outer periphery of the laminated magnet body 10 while fitting. In this way, the yoke segments 30 are fitted to the outer periphery of the laminated magnet body 10 while applying a tensioning force, and are therefore firmly fixed to the outer periphery of the laminated magnet body 10.

[0038] As described above, the yoke segments 30 are sequentially attached to the outer periphery of the laminated magnet body 10 and stacked on the outer periphery of the laminated magnet body 10 to form the yoke 8 that covers the outer periphery of the laminated magnet body 10. Each yoke segment 30 has a slit 30a, so that the yoke 8 as a whole also has slits 30a along its entire axial length. The axial length of the yoke 8 is set to be equal to or longer than the axial length of the laminated magnet body 10, but is set to a length that prevents the permanent magnets 10a, 10b from unnecessarily applying magnetic fields outside the stroke range of the core 3, thereby preventing a decrease in thrust. The axial length of the yoke 8 may also be set to be equal to the entire length of the laminated magnet body 10. If the axial length of the yoke 8 is longer than the entire length of the laminated magnet body 10, the magnetic field lines at the ends of the laminated magnet body 10 will not leak into the atmosphere, preventing a decrease in thrust of the cylindrical linear motor 1. In this way, to make the axial length of the yoke 8 longer than the axial length of the laminated magnet body 10, the axial length of the yoke 8 should be made longer than the maximum axial length that the laminated magnet body 10 can have due to processing errors of the permanent magnets 10a, 10b.

[0039] The axial length of the yoke segments 30 other than those at both axial ends of the yoke 8 is set to twice the length of the magnetic pole pitch P of the field 6. The yoke segments 30 at both axial ends of the yoke 8 may be set so that the total length of the yoke 8 is equal to or greater than the total length of the field 6 when all of the yoke segments 30 are stacked.

[0040] 3, the magnetic pole pitch P of the field magnet 6 extends from the center of the permanent magnet 10a of the main pole to the center of the permanent magnet 10a of the adjacent main pole, sandwiching the permanent magnet 10b of the sub-pole. The path of the magnetic field lines forms a loop, passing from the permanent magnet 10a of the main pole through the armature 2 to the permanent magnet 10a of the adjacent main pole, in the range from the center of the permanent magnet 10a of the main pole to the center of the permanent magnet 10a of the adjacent main pole, sandwiching the permanent magnet 10b of the sub-pole.

[0041] Therefore, if the axial length of the yoke segments 30 is set to an integer multiple of the magnetic pole pitch P and at least the axial end portions 30c of the yoke segments 30 are positioned on the outer periphery of the permanent magnets 10a of the main poles, the magnetic field lines of the laminated magnet body 10 will cross multiple yoke segments 30, but leakage of the magnetic field lines to the outside can be suppressed while suppressing an increase in the magnetic resistance of the yoke 8.

[0042] Because the yoke 8 is formed by stacking a plurality of yoke segments 30 in this way, it is extremely easy to attach the yoke segments 30, which are much shorter than the overall length of the yoke 8, one by one around the outer periphery of the laminated magnet body 10, compared to when the yoke 8 is a single piece and not composed of yoke segments 30. Therefore, the work of attaching the yoke 8 to the outer periphery of the laminated magnet body 10 is easy, which greatly simplifies the assembly of the cylindrical linear motor 1. Note that the laminated magnet body 10 in the cylindrical linear motor 1 is formed by laminating and adhering the permanent magnets 10a, 10b, but it is also possible to divide the laminated magnet body 10 in the axial direction according to the overall axial length of the yoke segments 30 to manufacture laminated magnet segments in which several permanent magnets 10a, 10b are stacked, and then manufacture a plurality of split field assemblies in which yoke segments are attached to the outer peripheries of the laminated magnet segments, and then stack the split field assemblies to manufacture the field 6.

[0043] Furthermore, if the axial length of the yoke segments 30 is ideally an integer multiple of the magnetic pole pitch P and the yoke segments 30 are attached to the outer periphery of the laminated magnet body 10 so that both ends of the yoke segments 30 are positioned at the center of the permanent magnets 10a of the main pole in the laminated magnet body 10, the magnetic field lines will not cross the gaps between the multiple yoke segments 30, minimizing the magnetic resistance of the yoke 8 and suppressing leakage of the magnetic field lines to the outside. As mentioned above, in the case of permanent magnets 10a, 10b in the Halbach array, the path of the magnetic field lines runs from the center of the permanent magnet 10a of the main pole to the center of the permanent magnet 10a of the adjacent main pole, across the permanent magnet 10b of the sub-pole, passing through the armature 2 and forming a loop. Therefore, in the cylindrical linear motor 1 of this embodiment, the yoke segments 30 abut on each other at the outer periphery of the axial center of the permanent magnets 10a of the main magnetic pole, so that the magnetic field lines of the field magnet 6 do not cross the gap between the yoke segments 30, and consideration is given to preventing a decrease in the thrust of the cylindrical linear motor 1 even when the yoke 8 is formed from multiple yoke segments 30. In this way, even when the yoke 8 is formed by stacking multiple cylindrical yoke segments 30, the magnetic field strength toward the inner periphery of the field magnet 6 is comparable to that of a yoke made of a single cylindrical body. In other words, by aligning the abutment surfaces of the yoke segments 30 with the axial center of the permanent magnets 10a of the main magnetic pole, good assembly of the cylindrical linear motor 1 and prevention of a decrease in thrust can both be achieved.

[0044] Note that the axial length of the yoke segments 30 is preferably an integer multiple of the magnetic pole pitch P, but even if the length is set to a length other than an integer multiple of the magnetic pole pitch P, the yoke 8 can be provided with a magnetic circuit with low magnetic resistance and the effect of increasing the field flux acting on the armature 2 can be achieved, so it is also possible to set the axial length of the yoke segments 30 to a length other than an integer multiple of the magnetic pole pitch P. Also, in this embodiment, the laminated magnet body 10 is composed of permanent magnets 10a, 10b stacked in a Halbach array, but it may also be configured by sequentially stacking an annular permanent magnet that is radially magnetized and has an N pole on its inner periphery and an annular permanent magnet that is radially magnetized and has an S pole on its inner periphery.

[0045] 3, in the cylindrical linear motor 1 of this embodiment, chamfered portions C are provided on the edges of the inner circumference at both axial ends of the yoke segments 30. By providing chamfered portions C on the inner circumference at both axial ends of the yoke segments 30 in this manner, when the yoke segments 30 are fitted onto the outer peripheries of the permanent magnets 10a, 10b, the permanent magnets 10a, 10b slide along the chamfered portions C and are guided into the yoke segments 30, making the assembly of the cylindrical linear motor 1 even easier.

[0046] The armature 2 is inserted inside the field magnet 6 so as to be movable in the axial direction, and the field magnet 6 applies a magnetic field to the core 3. Note that the field magnet 6 only needs to apply a magnetic field within the movable range of the core 3, so the installation range of the permanent magnets 10a, 10b can be determined according to the movable range of the core 3. Therefore, it is not necessary to install the permanent magnets 10a, 10b in the range of the annular gap between the barrel 7 and the cylindrical portion 9b that does not face the core 3.

[0047] An annular head-side spacer 40, the field magnet 6, and an annular end-side spacer 41 are housed between the outer periphery of the cylindrical portion 9b and the inner periphery of the barrel 7. The head-side spacer 40 is cylindrical and has a shape in which the outer diameter on the anti-field magnet side, which is the left side in FIG. 1, is larger than the outer diameter on the field magnet side, which is the right side in FIG. 1, and is equipped with a large-diameter portion 40a and a small-diameter portion 40b, with the left end of the large-diameter portion 40a in FIG. 1 abutting against the right end face in FIG. 1 of the head portion 9a of the inner tube 9, and the right end of the small-diameter portion 40b in FIG. 1 abutting against the left end of the field magnet 6.

[0048] The end-side spacer 41 is cylindrical and has a shape in which the outer diameter on the anti-field side, which is the right side in FIG. 1, is larger than the outer diameter on the field side, which is the left side in FIG. 1, and is provided with a large-diameter portion 41 a and a small-diameter portion 41 b, with the right end of the large-diameter portion 41 a in FIG. 1 abutting against the left end surface of the bottom 12 a of the bottom cap 12 in FIG. 1, and the left end of the small-diameter portion 41 b in FIG. 1 abutting against the right end 6 b of the field 6.

[0049] 1, an annular head spacer 40, field magnet 6, and an annular end spacer 41 are fitted onto the outer periphery of the cylindrical portion 9b, and after the head portion 9a of the inner tube 9 is screwed into the barrel 7, a bottom cap 12 is attached to the right end of the barrel 7 in FIG. 1. This causes the head spacer 40, laminated magnet body 10, and end spacer 41 to be sandwiched between the head portion 9a of the inner tube 9 and the bottom portion 12a of the bottom cap 12, and the laminated magnet body 10 is fixed to the inner periphery of the barrel 7. Note that the yoke 8 attached to the outer periphery of the laminated magnet body 10 is not sandwiched axially between the head portion 9a and the bottom cap 12, but is fitted onto the outer periphery of the laminated magnet body 10 with tension applied to it, and is therefore firmly fixed to the outer periphery of the laminated magnet body 10.

[0050] In addition, an annular sealing member 28 is provided on the inner circumference of the head portion 9a, which is in sliding contact with the outer circumference of the cover 17 that covers the outer circumference of the first rod 20, preventing dust, water, etc. from entering the cylindrical linear motor 1.

[0051] A rod 11 with an armature 2 attached thereto is inserted into the inner tube 9 so as to be movable in the axial direction, and sliders 21b and 25 are in sliding contact with the inner periphery of the cylindrical portion 9b to guide the movement of the armature 2 in the axial direction.

[0052] The cylindrical portion 9b forms a gap between the outer periphery of the core 3 and the inner periphery of each permanent magnet 10a, 10b, and also plays a role in guiding the axial movement of the core 3 in cooperation with the sliders 21b, 25. In this embodiment, the armature 2 is configured to have only a single core 3, but if the armature has multiple cores 3, sliders that come into sliding contact with the inner periphery of the cylindrical portion 9b may be provided not only at both axial ends of the armature 2 but also between the cores 3, 3.

[0053] Furthermore, a guide rod 16 is attached to the inner periphery of the bottom 12a of the bottom cap 12. The guide rod 16 has a base end 16a fixed to the inner periphery of the bottom 12a, and a guide portion 16b extending from the base end 16a toward the rod 11 and slidably inserted into the rod 11, and is always in sliding contact with the inner periphery of the rod 11 even when the cylindrical linear motor 1 extends or retracts. More specifically, the guide portion 16b of the guide rod 16 is slidably inserted toward the tip side of the large inner diameter portion 21d of the second rod 21.

[0054] In this way, in the cylindrical linear motor 1 of this embodiment, the guide rod 16 is in sliding contact with the inner circumference of the rod 11, and the sliders 21b, 25 are in sliding contact with the cylindrical portion 9b, so the armature 2 can move smoothly in the axial direction together with the rod 11 without becoming eccentric relative to the field 6, but the guide rod 16 may be eliminated.

[0055] Furthermore, in the cylindrical linear motor 1 configured in this manner, the cylindrical portion 9b, which guides the axial movement of the armature 2 and prevents the armature 2 from becoming eccentric relative to the field magnet 6, is integrally structured with the head portion 9a, so distortion is less likely to occur in the cylindrical portion 9b and the head portion 9a, and the sliders 21b and 25 can slide smoothly on the inner circumference of the cylindrical portion 9b, allowing it to expand and contract smoothly.

[0056] The cylindrical linear motor 1 is driven by a controller that detects the position of the rod 11 relative to the field 6 using a stroke sensor (not shown), grasps the electrical angle of the core 3 relative to the field 6, switches the energized phase, and controls the amount of current in each winding 5 using PWM control to control the thrust and the movement direction of the armature 2 in the cylindrical linear motor 1. Note that the control method of the controller described above is one example and is not limited to this. Furthermore, when an external force acts to relatively displace the armature 2 and the field 6 in the axial direction, a thrust that suppresses the relative displacement is generated by energizing the windings 5 ​​or by induced electromotive force generated in the windings 5, allowing the cylindrical linear motor 1 to damp the vibration and movement of the equipment caused by the external force, and also enabling energy regeneration to generate electric power from the external force.

[0057] As described above, the cylindrical linear motor 1 of the present invention comprises a laminated magnet body 10 formed of a plurality of annular permanent magnets 10a, 10b stacked on the inner periphery so that N poles and S poles are arranged alternately in the axial direction, a cylindrical field magnet 6 having a cylindrical yoke 8 formed of a magnetic material arranged on the outer periphery of the laminated magnet body 10, and an armature 2 that is movable in the axial direction of the field magnet 6 relative to the field magnet 6, and the yoke 8 has an inner diameter smaller than the outer diameter of the laminated magnet body 10 and has a slit 30a over its entire axial length.

[0058] In the cylindrical linear motor 1 configured in this manner, the yoke 8 has slits 30a, so that the diameter of the yoke 8 can be expanded and easily attached to the laminated magnet body 10, and after the yoke 8 is attached to the laminated magnet body 10, the yoke 8 fits while applying a tension to the laminated magnet body 10 due to its own restoring force, so that the yoke 8 is firmly fixed to the laminated magnet body 10. Therefore, with the cylindrical linear motor 1 configured in this manner, the yoke 8 is firmly fixed to the laminated magnet body 10, so that when the armature 2 moves axially relative to the field magnet 6, the yoke 8 is not attracted by the magnetic force of the armature 2 and does not shift axially relative to the laminated magnet body 10. Furthermore, because the yoke 8 has slits 30a, the diameter of the yoke 8 can be easily expanded and removed from the laminated magnet body 10, so that the field magnet 6 can be disassembled during maintenance of the cylindrical linear motor 1, and the yoke 8 can also be easily attached to the laminated magnet body 10.

[0059] Therefore, according to the cylindrical linear motor 1 of this embodiment, it is possible to prevent the yoke 8 from shifting relative to the laminated magnet body 10 in the field magnet 6, and it is also possible to disassemble the field magnet 6. Furthermore, since the field magnet 6 can be disassembled, maintenance of the cylindrical linear motor 1 is possible.

[0060] If the yoke 8 is a single component rather than including multiple yoke segments 30, the yoke 8 may have only one slit along its entire axial length. However, if the yoke 8 is formed by stacking multiple cylindrical yoke segments 30, this has the advantage of facilitating the process of attaching the yoke 8 to the laminated magnet body 10. Furthermore, since the slit 30a is formed along the entire axial length of the yoke segments 30, even if the yoke 8 is formed by stacking the yoke segments 30, the slit 30a is provided along the entire axial length of the yoke 8 as a whole. Therefore, when the yoke 8 is formed by stacking multiple yoke segments 30, the slits 30a provided in each yoke segment 30 do not need to be continuously connected to each other in the axial direction between adjacent yoke segments 30.

[0061] Furthermore, in the cylindrical linear motor 1 of this embodiment, the yoke 8 is provided with a pair of notches 30b, 30b on both sides of the slit 30a, through which a tool can be inserted. With the cylindrical linear motor 1 configured in this manner, the diameter of the yoke 8 can be easily expanded by hooking a tool on the notches 30b, 30b, facilitating the work of fixing the yoke 8 to the laminated magnet body 10. Note that the notches 30b, 30b are provided at the circumferential ends of the yoke segment 30 and open to the slit 30a, but they may also be holes that penetrate the solid portion of the yoke segment 30 separated from the slit 30a. Furthermore, the shape of the notches 30b, 30b is not limited to the shape shown in the figure, as long as it allows for the insertion of a tool and is useful for expanding the diameter of the yoke 8.

[0062] Furthermore, as shown in Fig. 4, the direction in which the slits 30a formed in the yoke 8 are formed may be inclined at an angle θ with respect to the radial direction (the direction indicated by line d in Fig. 4) when viewed from the axial direction of the yoke 8. Because the magnet body 10 is cylindrical, the magnetic field lines on the outer periphery of the magnet body laminate 10 will radiate outward in the radial direction. However, because the slits 30a are formed in a direction inclined with respect to the radial direction, they will not pass through the solid portion of the yoke 8 and will instead pass radially through the slits 30a and be less likely to head outward from the yoke 8, as shown in Fig. 4. If the inclination angle θ of the slits 30a with respect to the radial direction of the yoke 8 becomes large, the magnet body laminate 10 will no longer be exposed when viewed radially from the outer periphery of the yoke 8, and the magnetic field lines will always pass through the solid portion of the yoke 8. In this way, according to the cylindrical linear motor 1 in which the slits 30a are formed in a direction inclined relative to the radial direction, the provision of the slits 30a reduces the number of magnetic field lines that pass only through the slits 30a and do not pass through the yoke 8 but leak to the outside, thereby allowing a stronger magnetic field to act on the armature 2 and improving thrust.

[0063] Furthermore, the shape of the slits 30d provided in the yoke 8 may be wave-shaped when viewed from the radial direction of the yoke 8, as shown in Fig. 5. In this way, if the slits 30d are wave-shaped, the shape of the circumferential end of the yoke 8 is uneven even without providing the notches 30b, 30b in the yoke 8, and the diameter of the yoke 8 can be easily expanded by hooking a tool on the concave portions, facilitating the work of fixing the yoke 8 to the laminated magnet body 10. Note that the shape of the slits 30d can be various shapes, such as a sinusoidal wave with curved waves, a rectangular wave with rectangular waves, a triangular wave with triangular waves, etc., as long as the shape allows the tool to be hooked on.

[0064] In the cylindrical linear motor 1 of this embodiment, the yoke 8 is fixed to the outer periphery of the laminated magnet body 10, but in the case of a cylindrical linear motor having a structure in which the field magnet 6 is inserted inside the armature 2, the yoke 8 can be fixed to the inner periphery of the laminated magnet body 10. In this case, slits 30a can be formed in the yoke 8 to make the outer diameter of the yoke 8 larger than the inner diameter of the laminated magnet body 10, and the yoke 8 can be contracted and inserted into the inner periphery of the laminated magnet body 10. After that, the contracted diameter of the yoke 8 can be released and the restoring force of the yoke 8 can be used to apply a tension to the inner periphery of the laminated magnet body 10 while fitting the yoke 8 to fix it to the inner periphery of the laminated magnet body 10.

[0065] When mounting the yoke 8 on the inner periphery of the laminated magnet body 10 in this way, it is sufficient to provide notches in the yoke 8 on both sides of the slit 30a so that a tool can be inserted into the yoke 8 to reduce the diameter. Alternatively, instead of notches, claws that protrude inward can be provided on both circumferential ends of the yoke 8 so that the diameter of the yoke 8 can be reduced by pinching the claws together with a tool, allowing it to be inserted into the laminated magnet body 10.

[0066] Even in a case where the yoke 8 is fixed within the laminated magnet body 10, if the direction in which the slits 30a are formed is inclined relative to the radial direction of the yoke 8, leakage of magnetic lines can be suppressed and a strong magnetic field can be applied to the armature 2 side, thereby improving the thrust of the cylindrical linear motor 1.

[0067] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims. [Explanation of symbols]

[0068] 1... cylindrical linear motor, 2... armature, 6... field magnet, 8... yoke, 10... laminated magnet body, 10a... main pole permanent magnet, 10b... sub pole permanent magnet 30....Yoke division body, 30a, 30d: Slit, 30b: Notch

Claims

1. a cylindrical field magnet having a laminated magnet body formed of a plurality of annular permanent magnets stacked on one of the inner periphery or the outer periphery so that N poles and S poles are alternately arranged in the axial direction, and a cylindrical yoke formed of a magnetic material and arranged on the other of the inner periphery or the outer periphery of the laminated magnet body; an armature movable in an axial direction of the field magnet relative to the field magnet, the yoke has an inner diameter smaller than the outer diameter of the magnet laminate when the magnet laminate is inserted therein, and an outer diameter larger than the inner diameter of the magnet laminate when the yoke is inserted therein, and has a slit along its entire axial length; When the yoke is viewed in the axial direction, the direction in which the slits are formed is inclined at an angle relative to the radial direction of the yoke so as not to expose the laminated magnet body in the radial direction. A cylindrical linear motor characterized by:

2. The yoke is formed by stacking a plurality of yoke segments.

2. The cylindrical linear motor according to claim 1.

Images