JP7801149B2 - cylindrical linear motor - Google Patents

Description

The present invention relates to a cylindrical linear motor.

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

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

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

Since such a yoke is not fixed at either end and is merely attracted to the outer periphery of the permanent magnet by the magnetic force of the permanent magnet, it may be attracted by the magnetic force of the armature, which moves axially relative to the field magnet when the cylindrical linear motor is in operation, and may become misaligned axially relative to the permanent magnet.

On the other hand, although not a yoke, a structure has been proposed for holding a laminated magnet body housed within a cylindrical pipe. This structure involves caulking both ends of the cylindrical pipe from the outer periphery to cause elastic deformation, providing caulked portions that protrude from the inner periphery of both ends of the cylindrical pipe, and clamping both ends of the laminated magnet body between these caulked portions (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2020-68624 JP 2017-73864 A

Therefore, in order to prevent the permanent magnets in the yoke from shifting, it is possible to adopt the structure described in Patent Document 2, in which both ends of the yoke are crimped from the outer periphery to cause elastic deformation and form crimped portions that clamp both ends of the laminated magnet body.

This prevents the yoke from shifting axially relative to the laminated magnet body even when it receives attractive force from the armature. 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, creating a new problem that makes it impossible to perform maintenance on the cylindrical linear motor.

The present invention aims to provide a cylindrical linear motor that can prevent misalignment of the yoke relative to the laminated magnet body in the field and allows the field to be disassembled.

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 stacked on one of the inner or outer periphery so that north and south poles are arranged alternately in the axial direction, a cylindrical field magnet having a cylindrical yoke formed of a magnetic material arranged on the other of the inner or 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, the yoke having an inner diameter smaller than the outer diameter of the laminated magnet body when the laminated magnet body is inserted inside, and an outer diameter larger than the inner diameter of the laminated magnet body when inserted inside the laminated magnet body, the yoke having a slit over its entire axial length, and when viewed from the axial direction of the yoke, the direction in which the slit is formed is inclined at an angle to the radial direction of the yoke so that the laminated magnet body is not exposed in the radial direction.

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 engages with the laminated magnet body while applying tension 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.

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 yoke can be easily expanded by hooking a tool into the notches, making it easy to secure the yoke to the laminated magnet body.

Furthermore, the direction of the slits provided in the yoke is inclined relative to the radial direction when viewed from the axial direction of the yoke. In this way, with 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 do not pass through the yoke but leak to the outside, thereby allowing a stronger magnetic field to act on the armature and improving thrust.

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, a cylindrical linear motor with wavy slits allows the circumferential end of the yoke to have an uneven shape without having to provide notches in the yoke, and the diameter of the yoke can be easily expanded by hooking a tool on the concave portion, making it easy to fix the yoke to the laminated magnet body. Furthermore, the yoke may be formed by stacking multiple yoke segments. A cylindrical linear motor configured in this way makes it easy to attach the yoke to the laminated magnet body.

The cylindrical linear motor of the present invention prevents misalignment of the yoke relative to the laminated magnet body in the field and enables the field to be resolved.

1 is a longitudinal sectional view of a cylindrical linear motor according to an embodiment of the present invention; 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 the cylindrical linear motor according to an embodiment as viewed from a radial direction. FIG. 2 is a partially enlarged vertical cross-sectional view of a field magnet of a cylindrical linear motor according to an embodiment. 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. FIG. 10 is a side view of a yoke according to a second modified example, as viewed from the radial direction.

The present invention will be described below based on the embodiment 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 stacked on the inner periphery with N and S poles 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.

The following describes each part of the cylindrical linear motor 1 in detail. The armature 2 is composed of a core 3 and windings 5. The core 3 is composed of a cylindrical core body 3a and a plurality of annular teeth 3b arranged axially at intervals on the outer periphery of the core body 3a.

As mentioned above, the core 3 is cylindrical, and as shown in FIG. 1, it has ten teeth 3b arranged at equal axial intervals around the outer periphery of the core body 3a. 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 composed of three phases: a U-phase winding, a V-phase winding, and a W-phase winding.

Furthermore, 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 Figure 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. Note that the cross-sectional shape of the teeth 3b may be a shape other than an isosceles trapezoid, such as a rectangle.

The armature 2 is attached to the outer periphery of the tip of the rod 11, which serves as the output shaft and is made of a non-magnetic material. The rod 11 comprises 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.

The first rod 20 is cylindrical and includes a rod body 22 having threaded portions 22a and 22b on the outer periphery at the left end in FIG. 1 and 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, which is screwed onto the threaded portion 22a at the left end of the rod body 22 in FIG. 1 and closes the left end of the rod body 22.

An annular slider 25 is fitted to the outer periphery of the right end of the rod body 22 in FIG. 1. The slider 25 includes a sliding contact portion 25a that slides against the inner periphery of the tubular portion 9b (described below); a small-diameter portion 25b located on the base end of the rod 11 (to the left of the sliding contact portion 25a in FIG. 1) and having an outer diameter smaller than that of the sliding contact portion 25a; an annular groove 25c circumferentially formed on the outer periphery of the small-diameter portion 25b; and a flange 25d located 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 greater than the inner diameter of the rod body 22 but smaller than the outer diameter of the rod body 22. When the slider 25 is fitted to the rod body 22, the flange 25d abuts against the right end surface of the rod body 22 in FIG. 1.

The second rod 21 comprises a cylindrical core retaining tube 21a on whose outer periphery the core 3 is attached, and an annular slider 21b attached to 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, and a large-diameter portion 21d, whose inner diameter is larger than that of other portions, is provided on the inner periphery of the base end of the core retaining tube 21a. 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 embodiment, the rod 11 is thus cylindrical and composed of the first rod 20 and the second rod 21.

The core 3 is fitted onto the outer periphery of the core retaining tube 21a of the second rod 21. The outer diameter of the core retaining tube 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 attached, is connected to the first rod 20, on which the slider 25 is attached, in the manner described above, the armature 2 and 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 attached to the rod 11 in this manner, the core 3 is fixed to the rod 11, sandwiched between the slider 21b and the slider 25. Note that in this embodiment, the armature 2 is configured with only a single core 3; however, it may be configured with multiple cores 3 to improve thrust, etc.

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 one end is fitted onto the outer periphery of an annular cover end 18 provided on the outer periphery of the rod 11, while the other end is fitted onto the outer periphery of the small diameter portion 25b of the slider 25, thereby attaching it to the rod 11.

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. Wiring between the windings 5 and the lead wires L can be performed with the cover 17 removed, facilitating assembly of the cylindrical linear motor 1.

On the other hand, in this embodiment, the stator is configured with a field 6 consisting 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 non-magnetic inner tube 9 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.

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

The inner tube 9 is made of a non-magnetic material and comprises an annular head portion 9a that is attached by screws to the open end of the barrel 7 at its left end in FIG. 1, and a cylindrical portion 9b that is thinner than the head portion 9a and extends from the inner periphery of the right end of the head portion 9a in FIG. 1 and is inserted into the inner periphery of the field magnet 6. Therefore, the right end of the head portion 9a in FIG. 1 of the inner tube 9 faces the left end of the field magnet 6, which is located on the outer periphery of the cylindrical portion 9b.

The inner tube 9 also has a curved surface 9c at the boundary between the right end of the head portion 9a (as seen in Figure 1) and the cylindrical portion 9b, preventing stress from concentrating at the boundary between the head portion 9a and the cylindrical portion 9b even when axial force acts only on the head portion 9a. To avoid stress concentration in this way, a tapered surface may be provided at the boundary between the head portion 9a and the cylindrical portion 9b.

The field magnet 6 is composed of a laminated magnet body 10 formed of multiple annular permanent magnets 10a that serve as main magnetic poles and multiple annular permanent magnets 10b that serve as sub-magnetic poles, which are alternately stacked in the axial direction, and a cylindrical yoke 8 that fits onto and is fixed to the outer periphery of the laminated magnet body 10.

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 Figure 1 indicate the magnetization direction, with the magnetization direction of the main pole permanent magnets 10a being radial and the magnetization direction of the sub-pole permanent magnets 10b being axial. 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.

In addition, 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-magnetic pole. In this way, by increasing the axial length of the permanent magnet 10a of the main magnetic pole, 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-magnetic pole, but this is not limited to this and the axial lengths of both can be set as desired by design changes.

In addition, 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 sub-pole permanent magnet 10b increases the magnetic resistance outside the magnet at the axial center of the main pole permanent magnet 10a, reducing the field magnetic flux. This reduces the degree of thrust improvement of the cylindrical linear motor 1 when the axial length of the main pole permanent magnet 10a 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 sub-pole permanent magnet 10b. Therefore, making the axial length of the main pole permanent magnet 10a longer than the axial length of the sub-pole permanent magnet 10b 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 should be set to a thickness suitable for suppressing an increase in the external magnetic reluctance of the main pole permanent magnet 10a.

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 apply a tensioning force to the outer periphery of the laminated magnet body 10 using their own restoring force to return to their original diameter, thereby fitting together. In this way, the yoke segments 30 apply a tensioning force to the outer periphery of the laminated magnet body 10 when fitted together, so that they are firmly fixed to the outer periphery of the laminated magnet body 10.

The yoke segments 30 are sequentially attached to the outer periphery of the laminated magnet body 10 as described above 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 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 greater 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, resulting in a decrease in thrust. The axial length of the yoke 8 may also 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 can be made longer than the maximum axial length that the laminated magnet body 10 can have due to processing errors in the permanent magnets 10a and 10b.

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 should 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.

As shown in Figure 3, the magnetic pole pitch P in the field 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.

Therefore, if the axial length of the yoke segments 30 is 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 main pole permanent magnets 10a, the magnetic field lines of the laminated magnet body 10 will cross multiple yoke segments 30, but this will prevent the magnetic field lines from leaking to the outside while also preventing an increase in the magnetic resistance of the yoke 8.

Because the yoke 8 is formed by stacking multiple yoke segments 30 in this way, it is much easier to attach the yoke segments 30, which are much shorter than the overall length of the yoke 8, to the outer periphery of the laminated magnet body 10 in order, compared to when the yoke 8 is a single piece rather than composed of yoke segments 30. This facilitates the attachment of the yoke 8 to the outer periphery of the laminated magnet body 10, greatly simplifying 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. However, it is also possible to divide the laminated magnet body 10 axially to manufacture laminated magnet segments in which several permanent magnets 10a, 10b are stacked, depending on the overall axial length of the yoke segments 30, and then manufacture multiple split field assemblies by attaching yoke segments to the outer periphery of the laminated magnet segments, and then stack the split field assemblies to manufacture the field 6.

Ideally, the axial length of the yoke segments 30 should be an integer multiple of the magnetic pole pitch P. If 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 main pole permanent magnets 10a in the laminated magnet body 10, the magnetic field lines do 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 and 10b in the Halbach array, the path of the magnetic field lines runs from the center of the main pole permanent magnet 10a across the sub-pole permanent magnet 10b, passing through the armature 2 and looping in the range between the center of the adjacent main pole permanent magnet 10a. Therefore, in the cylindrical linear motor 1 of this embodiment, the yoke segments 30 abut on the outer periphery of the axial center of the permanent magnet 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 between the yoke segments 30 and the adjacent yoke segments 30 at the same position as the axial center of the permanent magnet 10a of the main magnetic pole, good assembly of the cylindrical linear motor 1 and prevention of a decrease in thrust can be achieved.

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 provide a magnetic circuit with low magnetic resistance and the field magnetic flux acting on the armature 2 can be increased, so the axial length of the yoke segments 30 can also be set to a length other than an integer multiple of the magnetic pole pitch P. In addition, 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 composed of an annular permanent magnet magnetized in the radial direction and having a north pole on its inner periphery, and an annular permanent magnet magnetized in the radial direction and having a south pole on its inner periphery, stacked in order.

Furthermore, in the cylindrical linear motor 1 of this embodiment, as shown in FIG. 3, chamfered portions C are provided on the inner peripheral edges of both axial ends of the yoke segments 30. By providing chamfered portions C on the inner peripheral edges of 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 assembly of the cylindrical linear motor 1 even easier.

The armature 2 is inserted inside the field magnet 6 so that it can move axially, and the field magnet 6 applies a magnetic field to the core 3. Since the field magnet 6 only needs to apply a magnetic field within the movable range of the core 3, 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 area of the annular gap between the barrel 7 and the cylindrical portion 9b that does not face the core 3.

Then, 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 (left side in FIG. 1) is larger than the outer diameter on the field magnet side (right side in FIG. 1). It has 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 the right end surface of the head portion 9a of the inner tube 9 in FIG. 1, and the right end of the small-diameter portion 40b in FIG. 1 abutting the left end of the field magnet 6.

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

1, the annular head spacer 40, field magnet 6, and annular end spacer 41 are fitted onto the outer periphery of the cylindrical portion 9b. After the head portion 9a of the inner tube 9 is screwed into the barrel 7, the bottom cap 12 is attached to the right end of the barrel 7 in FIG. 1. This sandwiches the head spacer 40, laminated magnet body 10, and end spacer 41 between the head portion 9a of the inner tube 9 and the bottom portion 12a of the bottom cap 12, securing the laminated magnet body 10 to the inner periphery of the barrel 7. The yoke 8 attached to the outer periphery of the laminated magnet body 10 is not axially sandwiched between the head portion 9a and the bottom cap 12, but is fitted to 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.

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

The rod 11, to which the armature 2 is attached, is inserted into the inner tube 9 so as to be freely movable in the axial direction, and the sliders 21b and 25 slide against the inner periphery of the cylindrical portion 9b, guiding the axial movement of the armature 2.

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 works with the sliders 21b, 25 to guide the axial movement of the core 3. In this embodiment, the armature 2 is configured with only a single core 3, but if there are multiple cores 3, sliders that slide against 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.

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 that is fixed to the inner periphery of the bottom 12a, and a guide portion 16b that extends from the base end 16a toward the rod 11 and is 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 further towards the tip side than the large inner diameter portion 21d of the second rod 21.

In this way, in the cylindrical linear motor 1 of this embodiment, the guide rod 16 is in sliding contact with the inner periphery of the rod 11, and the sliders 21b and 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.

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 eccentricity of the armature 2 relative to the field magnet 6, is integral with the head portion 9a. This means that distortion is less likely to occur in the cylindrical portion 9b and head portion 9a, allowing the sliders 21b and 25 to slide smoothly along the inner circumference of the cylindrical portion 9b and for smooth extension and retraction.

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), determines 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 used by the controller described above is one example and is not limited to this. Furthermore, when an external force acts to cause relative axial displacement between the armature 2 and the field 6, current is passed through the windings 5 or the induced electromotive force generated in the windings 5 to generate thrust that suppresses the relative displacement, allowing the cylindrical linear motor 1 to damp the vibration and movement of the equipment caused by the external force, and energy regeneration is also possible, generating electricity from the external force.

As described above, the cylindrical linear motor 1 of the present invention comprises a laminated magnet body 10 formed of multiple annular permanent magnets 10a, 10b stacked on the inner periphery with north and south poles arranged alternately in the axial direction, a cylindrical field magnet 6 having a cylindrical yoke 8 formed of a magnetic material and placed 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, where the yoke 8 has an inner diameter smaller than the outer diameter of the laminated magnet body 10 and has a slit 30a along its entire axial length.

In the cylindrical linear motor 1 configured in this manner, the yoke 8 has slits 30a, which allow the yoke 8 to be easily expanded and attached to the laminated magnet body 10. After the yoke 8 is attached to the laminated magnet body 10, the yoke 8 applies tension to the laminated magnet body 10 using its own restoring force while fitting, thereby firmly fixing it 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 yoke 8 can be easily expanded and removed from the laminated magnet body 10. This allows the field magnet 6 to be disassembled during maintenance of the cylindrical linear motor 1, and also makes it easy to attach the yoke 8 to the laminated magnet body 10.

Therefore, with 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, because the field magnet 6 can be disassembled, maintenance of the cylindrical linear motor 1 is possible.

If the yoke 8 is a single component and does not include multiple yoke segments 30, the yoke 8 only needs to have 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 making it easier to attach 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 of adjacent yoke segments 30 do not need to be continuously connected to each other in the axial direction.

In addition, 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, which allow a tool to be inserted. With a 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 process 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 segments 30 and open into the slit 30a, but they may also be holes that penetrate the solid portion of the yoke segments 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 a tool to be inserted and is useful for expanding the diameter of the yoke 8.

Furthermore, as shown in Figure 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 Figure 4) when viewed from the axial direction of the yoke 8. Because the laminated magnet body 10 is cylindrical, the magnetic field lines on the outer periphery of the laminated magnet body 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 be less likely to pass radially through the slits 30a and head outward from the yoke 8 without passing through the solid portion of the yoke 8, as shown in Figure 4. If the inclination angle θ of the slits 30a with respect to the radial direction of the yoke 8 becomes large, the laminated magnet body 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, with a 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, leaking to the outside, thereby applying a stronger magnetic field to the armature 2 and improving thrust.

Furthermore, the shape of the slits 30d provided in the yoke 8 may be wavy when viewed from the radial direction of the yoke 8, as shown in Figure 5. In this way, if the slits 30d are wavy, the shape of the circumferential ends of the yoke 8 becomes uneven even without providing 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, making it easier to fix 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, or a triangular wave with triangular waves, as long as the shape allows for hooking of a tool.

In the cylindrical linear motor 1 of this embodiment, the yoke 8 is fixed to the outer periphery of the laminated magnet body 10. However, in the case of a cylindrical linear motor 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, a slit 30a is 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. The yoke 8 is then contracted and inserted into the inner periphery of the laminated magnet body 10. The contracted diameter of the yoke 8 is then released, and the restoring force of the yoke 8 is used to apply a tension to the inner periphery of the laminated magnet body 10, allowing it to fit and fix the yoke 8 to the inner periphery of the laminated magnet body 10.

When attaching the yoke 8 to the inner circumference 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 to reduce the diameter of the yoke 8. Alternatively, instead of notches, claws that protrude inward can be provided on both circumferential ends of the yoke 8, and the yoke 8 can be inserted into the laminated magnet body 10 by pinching the claws together with a tool to reduce the diameter.

Even if the yoke 8 is fixed within the laminated magnet body 10, if the slits 30a are formed in a direction inclined relative to the radial direction of the yoke 8, leakage of magnetic field lines can be suppressed, allowing a strong magnetic field to act on the armature 2 side, improving the thrust of the cylindrical linear motor 1.

While the preferred embodiment of the present invention has been described in detail above, modifications, variations, and variations are possible without departing from the scope of the claims.

1... Cylindrical linear motor, 2... Armature, 6... Field magnet, 8... Yoke, 10... Laminated magnet body, 10a... Permanent magnet of main magnetic pole, 10b... Permanent magnet of sub-magnetic pole, 30... Yoke division body, 30a, 30d... Slit, 30b... Notch

Claims (2)

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;
A cylindrical linear motor characterized in that, 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. The cylindrical linear motor according to claim 1 , wherein the yoke is formed by stacking a plurality of yoke segments.