Cylindrical linear motor

Abstract

To provide a cylindrical linear motor which can achieve both of enhancement of the thrust and a reduction in manufacturing cost.SOLUTION: A cylindrical linear motor 1 includes: a cylindrical field magnet F; and an armature E which is disposed on an inner circumference of the field magnet F and is movable in the axial direction with respect to the field magnet F. The field magnet F includes: a plurality of annular permanent magnets 3a, 3b which are magnetized in the axial direction, and which are arranged such that their magnetization directions may alternate in the axial direction of the field magnet F; an annular yoke (soft magnetic material) 2b which is interposed between the permanent magnets 3a, 3b; and a magnetic gap 4 which is located on the side, of the yoke (soft magnetic material) 2b, opposite to the armature side and is provided between the permanent magnets 3a, 3b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Generally, a cylindrical linear motor is configured with a cylindrical field magnet formed by arranging multiple permanent magnets so that north and south poles appear alternately, and an armature that faces the inner or outer periphery of the field magnet and can move in the longitudinal direction of the field magnet.

[0003] To improve the thrust of such a cylindrical linear motor, it is necessary to increase the magnetic field that the field magnet exerts on the armature. One method for increasing the magnetic field is to arrange the permanent magnets in a Halbach array, which concentrates a large amount of magnetic flux on the armature side.

[0004] When the permanent magnets in the field are arranged in a Halbach array in this way, the third and fifth order components contained in the waveform of the gap magnetic flux density distribution at a position slightly away from the surface of the field facing the armature are reduced, and the waveform becomes closer to a sine wave, increasing the amplitude of the waveform, thereby improving the thrust of the cylindrical linear motor (see, for example, Patent Document 1).

[0005] However, in a cylindrical linear motor, the field magnet must be formed in a cylindrical shape, and if the permanent magnets are arranged in a Halbach array, expensive permanent magnets with a radial magnetization direction are required, which increases manufacturing costs.

[0006] In contrast, in a cylindrical linear motor that uses permanent magnets that are magnetized in the axial direction, the field magnet can be formed by stacking ring-shaped permanent magnets that are magnetized in the axial direction so that the magnetization direction alternates in the axial direction of the field magnet, and manufacturing costs can be reduced because inexpensive permanent magnets that are magnetized in the axial direction can be used (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-24379 [Patent Document 2] Patent No. 6314833 Summary of the Invention [Problem to be solved by the invention]

[0008] However, a cylindrical linear motor in which axially magnetized ring-shaped permanent magnets are simply stacked so that the magnetization direction alternates in the axial direction of the field magnet is unable to concentrate magnetic flux on the armature side, and therefore, although inexpensive, has a lower thrust force compared to a cylindrical linear motor equipped with a field magnet that uses a Halbach array.

[0009] On the other hand, a cylindrical linear motor equipped with a field magnet that employs a Halbach array has the advantage of being able to produce a large thrust, but it has the problem of high manufacturing costs. As such, with conventional cylindrical linear motors, increasing the thrust results in high costs, and reducing the manufacturing cost results in a decrease in thrust, making it difficult to achieve both increased thrust and reduced costs.

[0010] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cylindrical linear motor that can achieve both improved thrust and reduced manufacturing costs. [Means for solving the problem]

[0011] In order to achieve the above object, the cylindrical linear motor of the present invention comprises a cylindrical field magnet, and an armature that is arranged on the inner or outer circumference of the field magnet and is movable in the axial direction relative to the field magnet, the field magnet having a ring-shaped structure and a plurality of permanent magnets that are magnetized in the axial direction and arranged so that the magnetization direction alternates in the axial direction of the field magnet, a ring-shaped soft magnetic material that is interposed between the permanent magnets, and a magnetic gap that is provided between the permanent magnets on the anti-armature side of the soft magnetic material.

[0012] In a cylindrical linear motor configured in this manner, a magnetic gap is provided between the permanent magnets on the opposite side of the armature of the soft magnetic material, so that the magnetic flux is directed toward the soft magnetic material and is less likely to pass through the opposite side of the permanent magnet. As a result, the magnetic flux directed toward the armature side increases, making it possible to increase the magnetic field acting on the armature.

[0013] The cylindrical linear motor may also include a sleeve integrally formed with a cylindrical portion disposed on the inner periphery of the permanent magnet, a plurality of yokes made of soft magnetic material disposed circumferentially around the outer periphery of the cylindrical portion at intervals in the axial direction, and an annular groove formed by annular gaps extending circumferentially between the cylindrical portion and the yoke, into which the permanent magnet fits. In a cylindrical linear motor configured in this manner, the permanent magnet is mounted in the annular groove formed between the yokes on the sleeve. Therefore, by precisely controlling the position and dimensions of the annular groove in the sleeve, even if there is a dimensional error in the axial length of the permanent magnet, the dimensional error of the permanent magnet is not accumulated in the axial direction of the sleeve, and the installation error of each permanent magnet relative to the sleeve is contained within the axial range of the annular groove. Therefore, with a cylindrical linear motor configured in this manner, axial deviation of the installation position of the permanent magnet relative to the sleeve from the design value is reduced, thereby reducing cogging thrust when the armature is driven. [Effects of the Invention]

[0014] According to the cylindrical linear motor of the present invention, it is possible to achieve both an improvement in thrust and a reduction in manufacturing costs. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a longitudinal sectional view of a cylindrical linear motor according to an embodiment of the present invention; [Figure 2] 1 is an enlarged cross section of a field magnet of a cylindrical linear motor according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described below based on the embodiments shown in the drawings. As shown in Figure 1, a cylindrical linear motor 1 in one embodiment is configured with a cylindrical field magnet F and an armature E that is arranged on the inner periphery of the field magnet F and is movable in the axial direction relative to the field magnet F.

[0017] Each component of the cylindrical linear motor 1 will be described in detail below. In this embodiment, the field F is cylindrical and annular, and is magnetized in the axial direction, and includes a plurality of permanent magnets 3a, 3b arranged so that the magnetization directions alternate on the left and right sides in FIG. 1, which is the axial direction of the field F; an annular yoke 2b as a soft magnetic body interposed between the permanent magnets 3a, 3b; and a magnetic gap 4 provided between the permanent magnets 3a, 3b on the anti-armature side of the yoke 2b. Note that the triangle marks attached to the permanent magnets 3a, 3b in each drawing indicate the magnetization directions.

[0018] In this embodiment, the field magnetic flux F includes a cylindrical sleeve 2 on whose outer periphery permanent magnets 3a and 3b are mounted. As shown in Figs. 1 and 2, the sleeve 2 is made of a soft magnetic material and includes a cylindrical portion 2a provided on the inner periphery of the permanent magnets 3a and 3b, a plurality of annular yokes 2b formed by annular gaps provided circumferentially around the outer periphery of the cylindrical portion 2a and spaced apart in the axial direction, and a plurality of annular grooves 2c formed by annular gaps along the circumferential direction between the yokes 2b of the cylindrical portion 2a. The permanent magnets 3a and 3b are fitted into the annular grooves 2c in the sleeve 2.

[0019] In this embodiment, the sleeve 2 is formed by processing the outer periphery of a single cylindrical soft magnetic material to provide an annular groove 2c. The sleeve 2 is integrally and inseparably composed of a cylindrical portion 2a and a yoke 2b that protrudes from the outer periphery of the cylindrical portion 2a in a flange-like shape. As shown in FIG. 2 , fillet processing is performed on both axial ends of the bottom of the annular groove 2c in the sleeve 2, i.e., on the outer periphery of the cylindrical portion 2a and on both axial ends of the yoke 2b, forming a curved surface 2d from the base of the yoke 2b to the outer periphery of the cylindrical portion 2a. In this embodiment, the axial width of each annular groove 2c is equal and longer than the axial width of the yoke 2b. The annular grooves 2c are provided at equal intervals on the outer periphery of the sleeve 2. Although the yokes 2b are provided at both ends of the sleeve 2 in this embodiment, it is also possible to use annular grooves 2c at the ends of both ends of the sleeve 2 and not provide yokes 2b at both ends. In addition, in this embodiment, the sleeve 2 is integrally provided with the cylindrical portion 2a and the yoke 2b, but the cylindrical portion 2a and the yoke 2b may be configured as separate parts.

[0020] Each of the permanent magnets 3a and 3b is formed into an annular shape by combining magnet pieces each having a shape obtained by dividing a cylinder into multiple pieces circumferentially. In this embodiment, the magnet pieces are semi-cylindrical when viewed axially, and the cylindrical permanent magnets 3a and 3b are formed by combining two magnet pieces with their circumferential ends facing each other. Because the permanent magnets 3a and 3b are formed from magnet pieces divided circumferentially in this manner, they can be easily and reasonably installed in the annular groove 2c provided on the outer periphery of the sleeve 2. As described above, the permanent magnets 3a and 3b are formed into an annular shape by combining multiple magnet pieces. However, if the cylindrical portion 2a and the yoke 2b are separate components, or if the cylindrical portion 2a is not provided, the permanent magnets 3a and 3b may be formed into an annular shape by combining multiple magnet pieces instead of multiple magnet pieces combined into a cylindrical shape, and the permanent magnets 3a and 3b and the yoke 2b may be stacked alternately to assemble the field magnet F. Furthermore, the permanent magnets 3a and 3b are formed by combining magnet pieces divided in half in the circumferential direction into a cylindrical shape, but may also be formed by magnet pieces divided into three or more parts in the circumferential direction.

[0021] Furthermore, the inner periphery of each of the permanent magnets 3a and 3b is chamfered at both ends to provide inclined surfaces 3a1 and 3b1. The axial width of the permanent magnets 3a and 3b is approximately the same as but slightly smaller than the axial width of the annular groove 2c, allowing the permanent magnets 3a and 3b to be fitted into the annular groove 2c.

[0022] Furthermore, the magnetization direction of the permanent magnets 3a, 3b is in the axial direction, with one axial end being the north pole and the other axial end being the south pole. The south pole and north pole of the permanent magnets 3a, 3b are arranged in opposite directions and are installed alternately in the annular groove 2c of the sleeve 2. In this way, the permanent magnets 3a, 3b are arranged so that the magnetization direction alternates in the axial direction of the field magnet F.

[0023] When the permanent magnets 3a, 3b configured in this manner are alternately mounted in the annular groove 2c of the sleeve 2, adjacent permanent magnets 3a and 3b have their north poles facing each other and their south poles facing each other across the yoke 2b. Therefore, in the cylindrical linear motor 1 of this embodiment, one magnetic pole is formed from the axial center of the permanent magnet 3a to the axial center of the adjacent permanent magnet 3b, and the north poles of the permanent magnets 3a, 3b whose north poles face each other and the yoke 2b sandwiched between the north poles function as one north pole, and the south poles of the permanent magnets 3a, 3b whose south poles face each other and the yoke 2b sandwiched between the south poles function as one south pole.

[0024] Furthermore, the radial thickness of the permanent magnets 3a and 3b is greater than the thickness of the yoke 2b, i.e., the thickness from the inner peripheral surface of the cylindrical portion 2a to the outer peripheral surface of the yoke 2b minus the thickness of the cylindrical portion 2a. Therefore, when the permanent magnets 3a and 3b are mounted in the annular groove 2c of the sleeve 2, the inner peripheral surfaces of the permanent magnets 3a and 3b abut against the outer periphery of the cylindrical portion 2a, causing the outer peripheral sides of the permanent magnets 3a and 3b to protrude outward from the annular groove 2c. More specifically, the outer peripheral sides of the permanent magnets 3a and 3b protrude radially outward beyond the outer peripheral surface of the yoke 2b of the sleeve 2, forming a magnetic gap 4, which is an annular gap, between the outer peripheral portions of the permanent magnets 3a and 3b and on the outer peripheral side of the yoke 2b. In this embodiment, the magnetic gap 4 is formed by providing a gap between the outer peripheral portions of the permanent magnets 3a and 3b in the axial direction. However, the outer periphery of the yoke 2b between the outer peripheral portions of the permanent magnets 3a and 3b may be filled with a non-magnetic material.

[0025] In the field F configured in this manner, a magnetic gap 4 is provided between the outer peripheries of the permanent magnets 3a, 3b, so that magnetic flux tends to flow toward the yoke 2b and is less likely to pass through the outer periphery of the permanent magnets 3a, 3b, which is on the anti-armature side. As a result, more magnetic flux flows toward the inner periphery, which is on the armature side, and this can increase the magnetic field acting on the armature E housed inside the sleeve 2. In addition, in this embodiment, the cylindrical portion 2a of the sleeve 2, which is made of a soft magnetic material, is disposed on the inner periphery, which is on the armature side, of the field F, so that the magnetic field lines from the north pole to the south pole pass more unevenly on the inner periphery of the sleeve 2, and this can further increase the magnetic field acting on the armature E housed inside the sleeve 2.

[0026] Furthermore, curved surfaces 2d are formed by filleting at the corners of the bottom (outer circumference of cylindrical portion 2a) and side wall (base of yoke 2b) at both axial ends of annular groove 2c, and inclined surfaces 3a1, 3b1 are provided on the inner circumference of both ends of permanent magnets 3a, 3b by chamfering. Therefore, as shown in FIG. 2, when permanent magnets 3a, 3b are installed in annular groove 2c, curved surface 2d of annular groove 2c and inclined surfaces 3a1, 3b1 of permanent magnets 3a, 3b face each other so as not to interfere with each other, forming gap G between them, and allowing surface contact between the end faces of permanent magnets 3a, 3b and the side surfaces of yoke 2b.

[0027] When the outer periphery of a cylindrical base material is cut to form annular groove 2c, it is difficult to process the corners at both axial ends of the bottom of annular groove 2c at right angles. If no measures are taken, the corners of the inner periphery of permanent magnets 3a, 3b may ride up onto these corners, causing permanent magnets 3a, 3b to float above the outer periphery of cylindrical portion 2a, which is the bottom of annular groove 2c, or preventing surface contact between the side wall of yoke 2b and the end faces of permanent magnets 3a, 3b, which may result in the position of permanent magnets 3a, 3b relative to annular groove 2c becoming inconsistent in each annular groove 2c.

[0028] In contrast, as described above, if the curved surface 2d is formed by filleting and the inner peripheries of both ends of the permanent magnets 3a and 3b are chamfered to provide inclined surfaces 3a1 and 3b1 to avoid interference with the curved surface 2d, a gap G is formed between the corners at both axial ends of the bottom of the annular groove 2c and the inner peripheries at both ends of the permanent magnets 3a and 3b, and when the permanent magnets 3a and 3b are installed in the annular groove 2c, the permanent magnets 3a and 3b can be positioned by the yoke 2b, which forms the side walls of the annular groove 2c. Forming the gap G between the corners at both axial ends of the bottom of the annular groove 2c and the inner peripheries at both ends of the permanent magnets 3a and 3b allows surface contact between the side walls of the yoke 2b and the end faces of the permanent magnets 3a and 3b, preventing stress from concentrating on parts of the permanent magnets 3a and 3b due to the axial load applied when the armature E is driven. Furthermore, in the cylindrical linear motor 1 of this embodiment, the permanent magnets 3a, 3b are fixed to the annular groove 2c using an adhesive, and when gaps G are formed at the corners at both axial ends of the bottom of the annular groove 2c and on the inner peripheries of both ends of the permanent magnets 3a, 3b as described above, excess adhesive escapes and is accommodated in the gaps G, preventing the permanent magnets 3a, 3b from being positioned in the correct position within the annular groove 2c due to the presence of adhesive. However, filleting at both ends of the bottom of the annular groove 2c and chamfering the inner peripheries of both ends of the permanent magnets 3a, 3b may be omitted if not necessary.

[0029] To provide the gaps G at the corners of the annular groove 2c in the axial direction and at the inner peripheries of the permanent magnets 3a and 3b, the cylindrical portion 2a, which is located at both axial ends of the bottom of the annular groove 2c and close to the yoke 2b, may be machined around the entire circumference to form the grooves. In this case, chamfering may not be required on the inner peripheries of the permanent magnets 3a and 3b. Furthermore, when providing the gaps G at the corners of the annular groove 2c in the axial direction and at the inner peripheries of the permanent magnets 3a and 3b, the inner peripheries of the permanent magnets 3a and 3b may be chamfered to form inclined surfaces 3a1 and 3b1 or curved surfaces. This eliminates the need for filleting at the corners of the annular groove 2c in the axial direction and allows the end faces of the permanent magnets 3a and 3b to be in surface contact with the side surfaces of the yoke 2b.

[0030] The field magnet F configured in this manner is housed in a cylindrical barrel 5 made of a non-magnetic material. The left ends of the barrel 5 and the field magnet F in FIG. 1 are closed by a cap 6, and the right ends of the barrel 5 and the field magnet F in FIG. 1 are closed by an annular head cap 7. In the cylindrical linear motor 1 of this embodiment, the field magnet F is covered by the non-magnetic barrel 5, which protects the permanent magnets 3a, 3b attached to the outer periphery of the sleeve 2 and prevents the permanent magnets 3a, 3b from scattering from the sleeve 2, and also prevents external dust containing iron from being attracted by the field magnet F.

[0031] Next, the armature E is configured to include a cylindrical core 8, a winding 9 attached to the core 8, and a guide 10 that is in sliding contact with the inner peripheral surface of the sleeve 2, and is inserted into the field F so as to be movable in the axial direction. That is, in this embodiment, the armature E is disposed on the inner peripheral side of the field F, and can move relative to the field F in the axial direction.

[0032] In this embodiment, the core 8 is configured to include a cylindrical yoke 8a, a plurality of annular teeth 8b with rectangular axial cross section arranged circumferentially and at intervals in the axial direction on the outer periphery of the yoke 8a on the field side, and slots 8c formed by gaps between the teeth 8b, 8b, into which the windings 9 are attached.

[0033] As described above, the yoke 8a is cylindrical, and has a wall thickness such that its cross-sectional area is equal to or greater than the cross-sectional area of ​​the magnetic path in the teeth 8b. In this embodiment, as shown in Figures 1 and 2, seven teeth 8b are arranged at equal intervals in the axial direction on the outer periphery of the yoke 8a, and slots 8c, which are annular grooves into which windings 9 are fitted, are formed between the teeth 8b on the outer periphery side, which is the field F side of the core 8. In this embodiment, the cross-sectional shape of the teeth 8b is rectangular, but it may also be trapezoidal, with the width at the base end, which is the inner periphery, being greater than the width at the tip end, which is the outer periphery, so that a large cross-sectional area of ​​the magnetic path can be secured on the base end side.

[0034] In this embodiment, a total of six slots 8c, each of which is annular groove, are provided between adjacent teeth 8b, 8b in Fig. 1. The slots 8c are provided along the circumferential direction of the core 8 and are arranged at equal intervals in the axial direction on the outer periphery of the core 8.

[0035] The slots 8c are fitted with windings 9 wound around them. The windings 9 are three-phase windings consisting of U-phase, V-phase, and W-phase. The windings 9 for each phase are fitted in six slots 8c so as to be arranged appropriately in accordance with the arrangement of the magnetic poles of the field F.

[0036] The armature E configured in this manner is attached to the outer periphery of the tip of a rod 11 made of a non-magnetic material and serving as an output shaft, and is inserted into the field F together with the rod 11 so as to be freely movable.

[0037] The rod 11 protrudes outside the cylindrical linear motor 1 through a head cap 7 attached to the right end of the field magnet F in FIG. 1. Annular guides 10, 10 are attached to the left and right sides of the core 8 of the rod 11 in FIG. 1. The guides 10 have annular wear rings 10a on their outer peripheries that come into sliding contact with the inner circumferential surface of the sleeve 2 in the field magnet F.

[0038] In this way, the core 8 is sandwiched between the guides 10, 10 on both sides in the axial direction and fixed to the rod 11. The armature E is provided with the guides 10, 10, and the guides 10, 10 are slidably inserted into the inner peripheral surface of the sleeve 2, so that the armature E can move in the axial direction without axial wobble or interfering with the field magnetic flux F. In this way, the armature E's axial movement relative to the field magnetic flux F is guided by the sleeve 2.

[0039] Furthermore, the sleeve 2, which is made of a soft magnetic material, reduces the magnetic gap between itself and the armature E, thereby increasing the magnetic field that the field F acts on the armature E, and works in conjunction with the guides 10, 10 to guide the axial movement of the core 8. Furthermore, the outer diameter of the core 8 is smaller than the inner diameter of the cylindrical portion 2a of the sleeve 2, so it does not interfere with the sleeve 2, allowing the cylindrical linear motor 1 to expand and contract smoothly.

[0040] Although not shown, the rod 11 is cylindrical, and power can be supplied to the windings 9 from an external power source installed outside the cylindrical linear motor 1 via an electric wire (not shown) that passes through the rod 11.

[0041] For example, by sensing the electrical angle of the windings 9 relative to the field F, switching the energization phase based on that electrical angle, and controlling the amount of current in each winding 9 by PWM control, it is possible to control the thrust and the direction of movement of the armature E in the cylindrical linear motor 1. Note that the above-described control method is one example and is not limited to this. Furthermore, when an external force acts to cause relative displacement between the armature E and the field F in the axial direction, energization of the windings 9 or induced electromotive force generated in the windings 9 can 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 also enabling energy regeneration to generate electric power from the external force.

[0042] As described above, the cylindrical linear motor 1 of this embodiment comprises a cylindrical field F and an armature E that is arranged on the inner periphery of the field F and is movable in the axial direction relative to the field F. The field F comprises a plurality of permanent magnets 3a, 3b that are annular, axially magnetized, and arranged so that the magnetization direction alternates in the axial direction of the field F, a yoke (soft magnetic material) 2b that is annular and interposed between the permanent magnets 3a, 3b, and a magnetic gap 4 that is provided on the anti-armature side of the yoke (soft magnetic material) 2b and between the permanent magnets 3a, 3b.

[0043] According to the cylindrical linear motor 1 configured in this manner, a magnetic gap 4 is provided between the permanent magnets 3a, 3b on the anti-armature side of the yoke (soft magnetic material) 2b, so that the magnetic flux is directed toward the yoke (soft magnetic material) 2b and is less likely to pass through the anti-armature side of the permanent magnets 3a, 3b, and therefore the magnetic flux directed toward the armature side increases accordingly, making it possible to increase the magnetic field acting on the armature E. In this way, the cylindrical linear motor 1 of this embodiment can increase the magnetic field acting on the armature E while using inexpensive axially magnetized permanent magnets 3a, 3b, and therefore can achieve both improved thrust and reduced manufacturing costs.

[0044] Furthermore, the cylindrical linear motor 1 of this embodiment includes a sleeve 2 made of a soft magnetic material, in which a yoke (soft magnetic material) 2b between the permanent magnets 3a, 3b is integrally formed with the cylindrical portion 2a that fits around the permanent magnets 3a, 3b. In the cylindrical linear motor 1 configured in this manner, the permanent magnets 3a, 3b are mounted in annular grooves 2c formed between the yokes (soft magnetic material) 2b on the outer periphery of the sleeve 2. Therefore, if the position and dimensions of the annular grooves 2c of the sleeve 2 are precisely controlled, even if there is a dimensional error in the axial length of the permanent magnets 3a, 3b, the dimensional error of the permanent magnets 3a, 3b is not accumulated in the axial direction of the sleeve 2, and the installation error of each permanent magnet 3a, 3b relative to the sleeve 2 is contained within the axial range of the annular grooves 2c. Therefore, with the cylindrical linear motor 1 configured in this manner, axial deviation from the design value of the installation position of the permanent magnets 3a, 3b relative to the sleeve 2 is reduced, thereby reducing the cogging thrust when the armature E is driven. Furthermore, with the cylindrical linear motor 1 configured in this manner, the armature E is provided with guides 10 that come into sliding contact with the inner peripheral surface of the sleeve 2, so the armature E does not become eccentric in the radial direction with respect to the sleeve 2, and the relative radial positions of the permanent magnets 3a, 3b and the armature E are stable, enabling the generation of a stable thrust. As described above, with the cylindrical linear motor 1 of this embodiment, it is possible to generate a stable thrust while reducing the cogging thrust.

[0045] Furthermore, in the cylindrical linear motor 1 of this embodiment, the cylindrical portion 2a of the sleeve 2 made of a soft magnetic material is disposed between the permanent magnets 3a, 3b and the armature E, and even if the core 8 is disposed very close to the sleeve 2, the guides 10, 10 prevent the core 8 from interfering with the sleeve 2, so that the magnetic field generated by the permanent magnets 3a, 3b can be made to act on the armature E efficiently and the gap between the permanent magnets 3a, 3b and the core 8 can be made extremely small, allowing a large magnetic field to act on the armature E. Therefore, according to the cylindrical linear motor 1 of this embodiment, a large magnetic field can be made to act on the armature E inside the field F, and the radial magnetic air gap between the armature E and the field F can be made even narrower, thereby increasing the thrust and, as a result, improving the mass thrust density.

[0046] Furthermore, in the cylindrical linear motor 1 of this embodiment, the guide 10 of the armature E is brought into sliding contact with the sleeve 2 of the field F to guide the axial movement of the armature E, so there is no need to provide a separate guiding mechanism to guide the axial movement of the armature E.

[0047] In addition, as long as the guide 10 is not opposed, an auxiliary field magnet may be provided on both or one axial side of the sleeve 2, which is cylindrical and made of a soft magnetic material and has an annular groove on its outer periphery in which a permanent magnet is attached, and which constitutes part of the field magnet.

[0048] Furthermore, in the cylindrical linear motor 1 of this embodiment, gaps G are formed between both axial ends of the bottom of the annular groove 2c in the sleeve 2 and the inner peripheries of both axial ends of the permanent magnets 3a and 3b. With the cylindrical linear motor 1 configured in this manner, gaps G are formed between the corners at both axial ends of the bottom of the annular groove 2c and the inner peripheries of both axial ends of the permanent magnets 3a and 3b. This allows the yoke (soft magnetic material) 2b, which forms the side wall of the annular groove 2c, to come into surface contact with the axial ends of the permanent magnets 3a and 3b, allowing the permanent magnets 3a and 3b to be positioned within the annular groove 2c using the yoke (soft magnetic material) 2b. Therefore, with the cylindrical linear motor 1 configured in this manner, the permanent magnets 3a and 3b can be positioned at targeted positions within the annular groove 2c, allowing the permanent magnets 3a and 3b to be positioned appropriately relative to the sleeve 2, further reducing the cogging thrust when the armature E is driven. Furthermore, in the cylindrical linear motor 1 configured in this manner, the side wall of the yoke 2b and the end faces of the permanent magnets 3a, 3b can be in surface contact, which prevents stress from concentrating on parts of the permanent magnets 3a, 3b due to the axial load received when the armature E is driven. Additionally, in the cylindrical linear motor 1 of this embodiment, when the permanent magnets 3a, 3b are fixed to the annular groove 2c using an adhesive, excess adhesive escapes and is accommodated in the gap G, which prevents the permanent magnets 3a, 3b from being positioned incorrectly in the annular groove 2c due to the presence of adhesive.

[0049] In this embodiment, the armature E is inserted on the inner circumferential side of the field F, but a cylindrical armature E may also be arranged on the outer circumferential side of the field F. In this way, when the armature E is arranged on the outer circumferential side of the field F, the field F may be configured to include a plurality of annular permanent magnets that are magnetized in the axial direction and arranged so that the magnetization direction alternates in the axial direction of the field F, annular soft magnetic material interposed between the permanent magnets, and a magnetic gap provided between the permanent magnets on the inner circumferential side that is the anti-armature side of the soft magnetic material.

[0050] Furthermore, in the cylindrical linear motor 1 of the embodiment, the sleeve 2 has a cylindrical portion 2a and a yoke 2b integrally attached to the outer periphery of the cylindrical portion 2a. However, because magnetic resistance exists even when the cylindrical portion 2a is made of a soft magnetic material, the thinner the radial thickness of the cylindrical portion 2a, the stronger the magnetic field that can be applied to the armature E. On the other hand, the thinner the cylindrical portion 2a, the weaker the strength of the sleeve 2, making it difficult to use the sleeve 2 as a member for holding the field F. Therefore, a rib that intersects with the yoke 2b along the axial direction may be provided on the outer periphery of the cylindrical portion 2a to reduce the radial thickness of the cylindrical portion 2a and increase the magnetic field that can be applied to the armature E, while suppressing a decrease in the strength of the cylindrical portion 2a. When the armature E is disposed on the outer periphery of the field F, a rib may be provided on the outer periphery of the cylindrical portion 2a of the sleeve 2. The number of ribs and their cross-sectional shape can be set as desired as long as the strength of the cylindrical portion 2a is ensured. When ribs are provided, the permanent magnets 3a and 3b can be divided in the circumferential direction so that the permanent magnets 3a and 3b can avoid the ribs.

[0051] 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]

[0052] 1···Cylindrical linear motor, 2b···Yoke (soft magnetic material), 3a, 3b···Permanent magnet, 4···Magnetic gap, E···Armature, F···Field magnet

Claims

1. A cylindrical field magnet, an armature disposed on an inner periphery or an outer periphery of the field magnet and movable in an axial direction relative to the field magnet; The field magnet is A plurality of permanent magnets are annular, axially magnetized, and arranged such that the magnetization directions alternate in the axial direction of the field magnet; a soft magnetic body having an annular shape and interposed between the permanent magnets; a magnetic gap provided between the permanent magnets on the opposite armature side of the soft magnetic body; A cylindrical linear motor.

2. A cylindrical portion provided on an inner periphery of the permanent magnet; a plurality of yokes made of the soft magnetic material, the yokes being arranged circumferentially around the outer periphery of the cylindrical portion and spaced apart in the axial direction; The sleeve is integrally formed with the cylindrical portion and the yoke, and the cylindrical portion and the yoke are provided with an annular gap along the circumferential direction, and the permanent magnet is fitted in the annular groove.

2. The cylindrical linear motor according to claim 1 .

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