Cylinder-type linear motor

Abstract

A cylindrical linear motor (1) is provided with a cylindrical magnetic body (F) and an armature (E) disposed on the inner periphery of the magnetic body (F) and movable in the axial direction with respect to the magnetic body (F), the magnetic body (F) being provided with: a plurality of permanent magnets (3a, 3b) that are annular, are magnetized in the axial direction, and are arranged in the axial direction of the magnetic body (F) so that the magnetization directions thereof alternate; and a ring-shaped yoke (2b) formed of a soft magnetic material and interposed between the permanent magnets (3a, 3b). The cross-section of the permanent magnets (3a, 3b) cut in the axial direction has a convex shape in which the axial length on the armature side is shorter than the axial length on the opposite side of the armature.

Description

Technical Field

[0001] This invention relates to a cylindrical linear motor. Background Technology

[0002] Generally speaking, a cylindrical linear motor consists of a cylindrical magnetic body and an armature. The cylindrical magnetic body is formed by arranging multiple permanent magnets with alternating N and S poles. The armature faces the inner or outer periphery of the magnetic body and can move along the length of the magnetic body.

[0003] To increase the thrust of this cylindrical linear motor, it is necessary to increase the magnetic field exerted by the magnet on the armature. One way to increase the magnetic field is to arrange the permanent magnets in a Halebeck array so that more magnetic flux is concentrated on the armature side.

[0004] If the permanent magnets in the magnetic body are arranged as a Heilbeck array, for example as disclosed in JP2011-24379A, the third and fifth components contained in the waveform of the gap flux density distribution at a position slightly away from the armature side of the magnetic body are reduced. Since the waveform is close to a sine wave and the amplitude of the waveform is increased, the thrust of the cylindrical linear motor can be improved.

[0005] However, in cylindrical linear motors, the magnetic body must be formed into a cylindrical shape. If the permanent magnets are arranged in a Heilbeck array, high-valence permanent magnets with radial magnetization are required, which increases manufacturing costs.

[0006] In contrast, for example, as disclosed in JP6314833B, in a cylindrical linear motor using axially magnetized permanent magnets, it is only necessary to stack axially magnetized annular permanent magnets in an alternating manner along the axial direction of the magnetic body to form the magnetic body. Since low-cost axially magnetized permanent magnets can be used, manufacturing costs can be reduced.

[0007] Existing technical documents Patent documents Patent Document 1: JP2011-24379A Patent Document 2: JP6314833B2 Summary of the Invention The problem that the invention aims to solve However, a cylindrical linear motor that uses axially magnetized ring permanent magnets stacked in alternating magnetization directions along the axial direction of the magnetic body cannot concentrate the magnetic flux to the armature side. Therefore, although it is cheaper, its thrust is lower compared to a cylindrical linear motor with a magnetic body using a Helbeck array.

[0008] On the other hand, while cylindrical linear motors employing Helbeck arrays offer advantages in terms of increased thrust, they also present the problem of increased manufacturing costs. Thus, in conventional cylindrical linear motors, increasing thrust leads to higher costs, while reducing manufacturing costs results in lower thrust, making it difficult to achieve both increased thrust and reduced costs simultaneously.

[0009] The purpose of this invention is to provide a cylindrical linear motor that can simultaneously improve thrust and reduce manufacturing costs.

[0010] Problem-solving methods To achieve the above objectives, the cylindrical linear motor of the present invention comprises a cylindrical magnetic body and an armature disposed on the inner or outer periphery of the magnetic body and movable relative to the magnetic body axially. The magnetic body has: a plurality of permanent magnets, which are ring-shaped, magnetized in the axial direction and arranged in alternating magnetization directions in the axial direction of the magnetic body; and a magnetic yoke, which is ring-shaped, formed of a soft magnetic body and disposed between the permanent magnets; the cross-section of the permanent magnets cut along the axial direction is a convex shape in which the axial length on the armature side is shorter than the axial length on the opposite side of the armature.

[0011] In a cylindrical linear motor constructed in this manner, the magnetic flux of the shorter axial length portion of the permanent magnet on the armature side and the longer axial length portion on the opposite side of the armature flows to the armature side through the easily facilitated magnetic conduction of the yoke. The magnetic flux density increases within the radially opposing region of the yoke. Therefore, compared to a magnetic body constructed by stacking axially magnetized annular permanent magnets with rectangular cross-sections in alternating magnetization directions, the waveform of the gap magnetic flux density distribution around the armature is closer to a sine wave. Consequently, the amplitude of the waveform of the gap magnetic flux density distribution around the armature increases, thereby increasing the magnetic field acting on the armature housed within the inner circumference of the sleeve. Attached Figure Description

[0012] Figure 1 This is a longitudinal cross-sectional view of a cylindrical linear motor in one embodiment.

[0013] Figure 2 This is an enlarged cross-section of the magnetic body of a cylindrical linear motor according to one embodiment.

[0014] Figure 3 This is a longitudinal cross-sectional view of a cylindrical linear motor in a first variation of an embodiment.

[0015] Figure 4 This is a longitudinal cross-sectional view of a cylindrical linear motor in a second variation of one embodiment.

[0016] Implementation The present invention will now be described based on the illustrated embodiments. Figure 1As shown, in one embodiment, the cylindrical linear motor 1 is configured to include a cylindrical magnetic body F and an armature E disposed on the inner periphery of the magnetic body F and movable axially relative to the magnetic body F.

[0017] The following describes in detail each part of the cylindrical linear motor 1. In this embodiment, the magnetic body F is cylindrical and includes: a plurality of permanent magnets 3a and 3b, which are ring-shaped and magnetized in the axial direction, and are positioned along the axial direction of the magnetic body F. Figure 1 The magnets 3a and 3b are arranged in alternating directions of magnetization; and the yoke 2b is ring-shaped and formed by a soft magnetic material disposed between the permanent magnets 3a and 3b. In addition, the triangular markings on the permanent magnets 3a and 3b in each figure indicate the direction of magnetization.

[0018] Furthermore, in this embodiment, the magnetic body F includes a sleeve 2 that is cylindrical and has permanent magnets 3a and 3b mounted on its outer periphery. Figure 1 and Figure 2 As shown, the sleeve 2 is formed of a soft magnetic material and includes: a cylindrical portion 2a, which is fitted into the inner circumference of permanent magnets 3a and 3b; a plurality of annular yokes 2b, which are arranged at intervals along the circumferential direction on the outer circumference of the cylindrical portion 2a; and a plurality of annular grooves 2c, which are formed by annular gaps along the circumferential direction between the yokes 2b and 2b of the cylindrical portion 2a.

[0019] In this embodiment, the sleeve 2 is formed by machining an annular groove 2c on the outer periphery of a cylindrical soft magnetic material, and integrally and indivisibly includes a cylindrical portion 2a and a magnetic yoke 2b protruding in a flange shape on the outer periphery of the cylindrical portion 2a. Furthermore, as... Figure 2 As shown, at the bottom axial ends of the annular grooves 2c in the sleeve 2, i.e., at the outer periphery of the cylindrical portion 2a and the root of the magnetic yoke 2b on both axial sides, a rounded surface 2d is formed from the root of the magnetic yoke 2b to the outer periphery of the cylindrical portion 2a. Furthermore, in this embodiment, the axial width of each annular groove 2c is equal and longer than the axial width of the magnetic yoke 2b. Additionally, the annular grooves 2c are evenly spaced on the outer periphery of the sleeve 2. Furthermore, in this embodiment, the magnetic yoke 2b is also provided at both ends of the sleeve 2, but it is also possible to use the ends of the sleeve 2 as annular grooves 2c instead of providing magnetic yoke 2b at both ends. In addition, in this embodiment, the sleeve 2 integrally comprises the cylindrical portion 2a and the magnetic yoke 2b, but the cylindrical portion 2a and the magnetic yoke 2b may also be composed of different components.

[0020] The permanent magnets 3a and 3b are each annular, having a convex cross-section in which the axial length of the outer peripheral portions 3a2 and 3b2 (opposite to the armature) is longer than the axial length of the inner peripheral portions 3a1 and 3b1 (on the armature side). The shorter axial portion of each permanent magnet 3a and 3b, i.e., the axial center of the inner peripheral portions 3a1 and 3b1, and the longer axial portion, i.e., the axial center of the outer peripheral portions 3a2 and 3b2, are axially aligned. The cross-sectional shape of each permanent magnet 3a and 3b is linearly symmetrical about a line passing through the axial center. The radial thicknesses of the inner peripheral portions 3a1 and 3b1 and the outer peripheral portions 3a2 and 3b2 are equal in the illustration, but can be designed to be different. Furthermore, when end permanent magnets are provided on the end sides of the magnetic yoke 2b at both ends of the sleeve 2, the end permanent magnets can be set to the same shape as the permanent magnets 3a and 3b, for example. However, if it is desired to avoid the end of the magnetic body F being stepped, it can be set to a shape in which one side of the outer periphery 3a2 and 3b2 is cut off radially or the permanent magnets 3a and 3b are halved in the axial center.

[0021] Furthermore, each permanent magnet 3a and 3b is formed into a ring by combining magnet pieces of various shapes obtained by dividing a cylinder along its circumference. In this embodiment, the magnet pieces are semi-cylindrical in axial view, and cylindrical permanent magnets 3a and 3b are formed by combining the two ends of two magnet pieces facing each other in the circumferential direction. Thus, since the permanent magnets 3a and 3b are formed from magnet pieces divided in the circumferential direction, they can be easily and unobstructedly installed in the annular groove 2c provided on the outer circumference of the sleeve 2.

[0022] As described above, permanent magnets 3a and 3b are formed into a ring by combining multiple magnet pieces. However, when the cylindrical portion 2a and the yoke 2b are composed of different parts, or when the cylindrical portion 2a is not provided, permanent magnets 3a and 3b may not be formed by combining multiple magnet pieces into a cylindrical shape, but by forming a single ring-shaped magnet. The magnetic body F is assembled by alternately overlapping permanent magnets 3a and 3b with the yoke 2b. In addition, in this case, permanent magnets 3a and 3b may not be divided along the circumferential direction, or in addition to being divided along the circumferential direction, they may be formed by combining the magnet pieces that are divided into the shorter axial length portion (inner circumferential portion 3a1, 3b1) and the longer axial length portion (outer circumferential portion 3a2, 3b2) of permanent magnets 3a and 3b.

[0023] Furthermore, permanent magnets 3a and 3b are formed by combining magnet pieces that are divided in half in the circumferential direction into a cylindrical shape, but they can also be formed by dividing magnet pieces into three or more in the circumferential direction.

[0024] Furthermore, the inner circumferences of the inner peripheral portions 3a1 and 3b1 of each permanent magnet 3a and 3b are chamfered at both ends to form inclined surfaces 3a11 and 3b11. In addition, the axial length of the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b is approximately the same as but slightly shorter than the axial length of the annular groove 2c, so that the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b can be fitted into the annular groove 2c.

[0025] Furthermore, the permanent magnets 3a and 3b are magnetized along the axial direction, with one end of the axial direction becoming the N pole and the other end becoming the S pole. The S and N poles of the permanent magnets 3a and 3b are arranged opposite to each other, alternating in the annular groove 2c of the sleeve 2. In this way, the permanent magnets 3a and 3b are arranged in an alternating manner along the axial direction of the magnetic body F.

[0026] If permanent magnets 3a and 3b configured in this manner are alternately installed in the annular groove 2c of the sleeve 2, the inner circumference 3a1 of adjacent permanent magnets 3a and the inner circumference 3b1 of permanent magnet 3b sandwich the yoke 2b so that the N poles face each other and the S poles face each other. Furthermore, the outer circumference 3a2 of permanent magnet 3a and the outer circumference 3b2 of permanent magnet 3b face each other with a slight gap between their end faces. In addition, when the inner circumferences 3a1 and 3b1 are housed in the annular groove 2c of the sleeve 2, the axial lengths of the outer circumferences 3a2 and 3b2 of permanent magnets 3a and 3b can make their axial end faces just touch each other. However, if they are set to face each other with a slight gap, this gap absorbs the dimensional errors of the permanent magnets 3a and 3b. Therefore, this is advantageous in terms of facilitating the assembly of permanent magnets 3a and 3b into the sleeve 2.

[0027] In the cylindrical linear motor 1 of this embodiment, a magnetic pole is formed from the axial center of the permanent magnet 3a to the axial center of the adjacent permanent magnet 3b containing the yoke 2b. The N poles of the permanent magnets 3a and 3b with their N poles facing each other and the yoke 2b sandwiched between the N poles function as one N pole. The S poles of the permanent magnets 3a and 3b with their S poles facing each other and the yoke 2b sandwiched between the S poles function as one S pole.

[0028] In the magnetic body F constructed in this way, the axial length of the inner periphery 3a1, 3b1 of the permanent magnets 3a and 3b, which are on the armature side, is shorter than the axial length of the outer periphery 3a2, 3b2, which are on the opposite side of the armature. The magnetic flux of the inner periphery 3a1, 3b1 and the outer periphery 3a2, 3b2 flows to the armature side through the magnetic yoke 2b, which facilitates magnetic conduction. The magnetic flux density in the radially opposite range of the magnetic yoke 2b becomes higher. Therefore, compared with a magnetic body constructed by simply stacking axially magnetized annular permanent magnets with rectangular cross sections in an alternating manner of magnetization direction, the waveform of the gap magnetic flux density distribution on the outer periphery of the armature E is closer to a sine wave. The amplitude of this waveform is larger, which can increase the magnetic field acting on the armature E housed in the inner periphery of the sleeve 2.

[0029] Furthermore, at the bottom (outer periphery of cylindrical portion 2a) and corners of the sidewall (root of magnetic yoke 2b) at both axial ends of the annular groove 2c, curved surfaces 2d are formed by rounding. In the inner periphery at both axial ends of the inner periphery portions 3a1 and 3b1 within the annular groove 2c housing the permanent magnets 3a and 3b, inclined surfaces 3a11 and 3b11 formed by chamfering are provided. Therefore, as... Figure 2 As shown, when the inner peripheral portions 3a1 and 3b1 of permanent magnets 3a and 3b are installed in the annular groove 2c, the curved surface 2d of the annular groove 2c and the inner peripheral portions 3a1 and 3b1 are opposite to each other without interference, and a gap G is formed between them. The axial end faces of the inner peripheral portions 3a1 and 3b1 of permanent magnets 3a and 3b can make surface contact with the side surface of the magnetic yoke 2b.

[0030] When cutting the outer periphery of the cylindrical base material to form the annular groove 2c, it is difficult to machine the corners at both ends of the bottom of the annular groove 2c into right angles. If no treatment is done, the corners of the inner periphery portions 3a1 and 3b1 of the permanent magnets 3a and 3b will press over the corners, causing the inner periphery portions 3a1 and 3b1 of the permanent magnets 3a and 3b to float from the outer periphery of the cylindrical portion 2a, which is the bottom of the annular groove 2c, or the sidewall of the yoke 2b and the end faces of the inner periphery portions 3a1 and 3b1 of the permanent magnets 3a and 3b to not make face contact, which may cause the position of the permanent magnets 3a and 3b relative to the annular groove 2c to be unstable in each annular groove 2c.

[0031] In contrast, as described above, when a curved surface 2d is formed by rounding, and the inner peripheral edges of the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b are chamfered to form inclined surfaces 3a11 and 3b11 to avoid interference with the curved surface 2d, a gap G is formed between the corners of the two axial ends in the bottom of the annular groove 2c and the inner peripheral portions 3a1 and 3b1 of the two ends of the permanent magnets 3a and 3b. 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 magnetic yoke 2b, which serves as the sidewall of the annular groove 2c. When a gap G is formed between the corners at both axial ends of the bottom of the annular groove 2c and the inner peripheral edges at both axial ends of the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b, the sidewall of the yoke 2b can make face contact with the end faces of the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b. Therefore, stress concentration on a portion of the permanent magnets 3a and 3b due to axial load can be avoided when the armature E is driven. In addition, in the cylindrical linear motor 1 of this embodiment, the permanent magnets 3a and 3b are fixed to the annular groove 2c using adhesive. When a gap G is formed between the corners at both axial ends of the bottom of the annular groove 2c and the inner peripheral edges at both axial ends of the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b, as described above, excess adhesive overflows and is collected in the gap G. Therefore, it is possible to prevent the permanent magnets 3a and 3b from being unable to be properly positioned in the annular groove 2c due to the presence of adhesive. However, if not required, the rounding of the bottom ends of the annular groove 2c and the chamfering of the inner periphery of the inner periphery of the permanent magnets 3a and 3b at both axial ends can be omitted.

[0032] Furthermore, in order to provide a gap G at the corners of both axial ends of the annular groove 2c and the inner periphery of both axial ends of the inner periphery of the permanent magnets 3a and 3b, a groove can be formed by cutting the cylindrical portion 2a, which is the bottom of the annular groove 2c, close to the yoke 2b, all around its circumference. In this case, it is not necessary to provide a chamfer at the inner periphery of both axial ends of the inner periphery of the permanent magnets 3a and 3b. Furthermore, when a gap G is provided between the corners at both axial ends of the annular groove 2c and the inner periphery of the inner periphery of the permanent magnets 3a and 3b, the inner periphery of the inner periphery of the permanent magnets 3a and 3b, the inner periphery of the inner periphery of the permanent magnets 3a and 3b, the inner periphery of the bottom of the annular groove 2c, the corners at both axial ends of the annular groove 2c, the corners at both axial ends of the annular groove 2c, the inner periphery of the inner periphery of the permanent magnets 3a and 3b ...

[0033] The magnetic body F, constructed in this manner, is housed within a cylindrical casing 5 formed of a non-magnetic body. The casing 5 and the magnetic body F... Figure 1 The left end is closed by cover 6, and the barrel 5 and magnetic body F are... Figure 1 The right end is closed by an annular head cover 7. Furthermore, in the cylindrical linear motor 1 of this embodiment, the magnetic body F is covered by the non-magnetic body of the barrel 5, which can protect the permanent magnets 3a and 3b installed on the outer periphery of the sleeve 2 and prevent the permanent magnets 3a and 3b from flying off from the sleeve 2. Moreover, the barrel 5 can suppress the attraction of dust and other substances containing external iron by the magnetic body F.

[0034] Subsequently, the armature E is composed of a cylindrical core 8, a winding 9 mounted on the core 8, and a guide 10 that slides in contact with the inner circumferential surface of the sleeve 2, and can be freely inserted into the magnetic body F along the axial direction. That is, in this embodiment, the armature E is disposed on the inner circumferential side of the magnetic body F and can move relative to the magnetic body F in the axial direction.

[0035] In this embodiment, the core 8 is composed of a cylindrical magnetic yoke 8a, a plurality of ring-shaped teeth 8b with rectangular axial cross sections arranged at intervals along the circumferential direction on the outer periphery of the magnetic body side of the magnetic yoke 8a, and a slot 8c formed by the gap between the teeth 8b to mount the winding 9.

[0036] As described above, the magnetic yoke 8a is cylindrical, and its wall thickness ensures that its cross-sectional area is greater than or equal to the cross-sectional area of ​​the magnetic circuit in the tooth 8b. In this embodiment, as... Figure 1 and Figure 2 As shown, seven teeth 8b are arranged side by side at equal intervals along the axial direction on the outer periphery of the magnetic yoke 8a. A slot 8c, consisting of annular grooves for mounting the winding 9, is formed on the outer periphery of the magnetic body F side of the core 8 and between the teeth 8b. In addition, in this embodiment, the cross-sectional shape of the teeth 8b is rectangular, or it can be a trapezoid with the width of the base end side as the inner periphery being greater than the width of the front end side as the outer periphery to ensure a larger magnetic circuit cross-sectional area on the base end side.

[0037] In this embodiment, Figure 1 The adjacent teeth 8b are provided with a total of six slots 8c formed by annular grooves. The slots 8c are arranged along the circumference of the core 8 and are arranged side by side at equal intervals along the axial direction on the outer periphery of the core 8.

[0038] Furthermore, the winding 9 is wound and installed in the slot 8c. The winding 9 is a three-phase winding with U phase, V phase and W phase. Each phase winding 9 is installed in the six slots 8c in a manner appropriate to the magnetic pole configuration of the magnetic body F.

[0039] The armature E, constructed in this manner, is mounted on the outer periphery of the front end of the rod 11, which is formed of a non-magnetic body and serves as the output shaft, and is freely inserted into the magnetic body F together with the rod 11.

[0040] Rod 11 passes through the magnetic body F. Figure 1 The head cover 7 at the right end protrudes outward from the cylindrical linear motor 1. Additionally, in the core 8 of the rod 11... Figure 1 Annular guides 10 and 10 are installed on the left and right sides, with annular wear-resistant rings 10a having an outer circumference that slides in contact with the inner circumferential surface of the sleeve 2 in the magnetic body F.

[0041] Thus, core 8 is fixed to rod 11 by guides 10, 10 clamping it from both sides axially. Armature E has guides 10, 10, which slide freely into the inner circumferential surface of sleeve 2, and therefore will not axially offset relative to magnetic body F, allowing axial movement without interfering with magnetic body F. In this way, armature E is guided to move axially relative to magnetic body F by sleeve 2.

[0042] Furthermore, the sleeve 2, formed of a soft magnetic material, can reduce the magnetic gap between itself and the armature E, increase the magnetic field exerted by the magnetic material F on the armature E, and cooperate with the conductors 10 to guide the axial movement of the core 8. In addition, the outer diameter of the core 8 is smaller than the inner diameter of the cylindrical portion 2a of the sleeve 2, so it will not interfere with the sleeve 2, and the cylindrical linear motor 1 can extend and retract smoothly.

[0043] Furthermore, although not shown in the figure, the rod 11 is cylindrical and can supply power to the winding 9 from an external power source located outside the cylindrical linear motor 1 via an unseen wire passing through the rod 11.

[0044] Furthermore, for example, if the electrical angle of the sensing winding 9 relative to the magnetic body F is used to switch the energizing phase based on the electrical angle, and the current of each winding 9 is controlled by PWM control, then the thrust and the direction of movement of the armature E in the cylindrical linear motor 1 can be controlled. Moreover, the aforementioned control method is one example and is not limited to it. Additionally, when an external force causes relative displacement between the armature E and the magnetic body F in the axial direction, by energizing the winding 9 or by generating an induced electromotive force in the winding 9, a thrust that suppresses the relative displacement can be generated, enabling the cylindrical linear motor 1 to dampen the vibration or movement of the equipment caused by the external force, and thus regenerating the ability to generate electricity from external forces.

[0045] The cylindrical linear motor 1 of this embodiment includes a cylindrical magnetic body F and an armature E disposed on the inner periphery of the magnetic body F and movable axially relative to the magnetic body F. The magnetic body F includes: a plurality of permanent magnets 3a and 3b, which are ring-shaped, magnetized axially, and arranged in alternating magnetization directions axially in the magnetic body F; and a magnetic yoke 2b, which is ring-shaped, formed of a soft magnetic body, and disposed between the permanent magnets 3a and 3b; the cross-section of the permanent magnets 3a and 3b cut axially is a convex shape in which the axial length on the armature side is shorter than the axial length on the opposite side of the armature.

[0046] In the cylindrical linear motor 1 constructed in this manner, the axial lengths of the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b, which are on the armature side, are shorter than the axial lengths of the outer peripheral portions 3a2 and 3b2, which are on the opposite side of the armature. Not only the inner peripheral portions 3a1 and 3b1, but also the magnetic flux exiting from the axial end faces of the outer peripheral portions 3a2 and 3b2 flows easily to the armature side via the magnetic yoke 2b. The magnetic flux density in the radially opposing region with the yoke 2b is higher. Therefore, compared to a magnetic body constructed by stacking axially magnetized annular permanent magnets with rectangular cross-sections in alternating magnetization directions, the waveform of the gap magnetic flux density distribution around the armature E is closer to a sine wave. Thus, the amplitude of the waveform of the gap magnetic flux density distribution around the armature E is increased, which can increase the magnetic field acting on the armature E housed within the inner periphery of the sleeve 2.

[0047] Thus, in the cylindrical linear motor 1 of this embodiment, the magnetic field acting on the armature E can be increased while utilizing low-cost axially magnetized permanent magnets 3a and 3b, thereby achieving both increased thrust and reduced manufacturing cost.

[0048] Furthermore, in the cylindrical linear motor 1 of this embodiment, a sleeve 2 is provided, which is formed of a soft magnetic material and has a cylindrical portion 2a fitted into the armature side of permanent magnets 3a and 3b. The sleeve 2 and the cylindrical portion 2a are integrally provided with a yoke 2b. In the cylindrical linear motor 1 constructed in this manner, the permanent magnets 3a and 3b are mounted in an annular groove 2c formed between the yokes 2b and 2b on the outer periphery of the sleeve 2. Therefore, if the position and size of the annular groove 2c of the sleeve 2 are managed with high precision, even if there is a dimensional error in the axial length of the permanent magnets 3a and 3b, the dimensional error of the permanent magnets 3a and 3b will not accumulate in the axial direction of the sleeve 2, and the setting error of each permanent magnet 3a and 3b relative to the sleeve 2 falls within the axial range of the annular groove 2c. Therefore, according to the cylindrical linear motor 1 constructed in this manner, the axial offset of the setting position of the permanent magnets 3a and 3b relative to the sleeve 2 relative to the design value is reduced, thus reducing the cogging thrust during armature E drive. Furthermore, in the cylindrical linear motor 1 constructed in this manner, since the armature E has a guide 10 that slides in contact with the inner circumferential surface of the sleeve 2, the armature E will not be radially eccentric relative to the sleeve 2, and the radial relative positions of the permanent magnets 3a and 3b with the armature E are stable, thus generating stable thrust. In summary, the cylindrical linear motor 1 according to this embodiment can reduce cogging thrust and provide stable thrust.

[0049] Furthermore, in the cylindrical linear motor 1 of this embodiment, a cylindrical portion 2a of a sleeve 2 containing a soft magnetic material is disposed between the permanent magnets 3a and 3b and the armature E. Even when the core 8 is disposed very close to the sleeve 2, the conductors 10 prevent the core 8 from interfering with the sleeve 2. Therefore, the magnetic field generated by the permanent magnets 3a and 3b can act efficiently on the armature E, and the gap between the permanent magnets 3a and 3b and the core 8 can be minimized, thus enabling a larger magnetic field to act on the armature E. Therefore, the cylindrical linear motor 1 according to this embodiment can act on the armature E inside the magnetic material F with a larger magnetic field, and further reduce the radial magnetic air gap between the armature E and the magnetic material F, thereby increasing the thrust and resulting in improved mass thrust density.

[0050] Furthermore, in the cylindrical linear motor 1 of this embodiment, the sleeve 2 of the magnetic body F is slidably contacted with the conductor 10 of the armature E to guide the armature E to move axially, so there is no need to provide a separate mechanism to guide the armature E to move axially.

[0051] Furthermore, if the guide 10 is not aligned, an auxiliary magnetic body can be provided on both sides or one side of the sleeve 2. This auxiliary magnetic body is cylindrical in shape and has an annular groove with a permanent magnet mounted on its outer periphery, forming part of the magnetic body.

[0052] Furthermore, in the cylindrical linear motor 1 of this embodiment, a gap G is provided between the axial ends of the bottom of the annular groove 2c in the sleeve 2 and the inner periphery of the inner periphery of the permanent magnets 3a and 3b axially. With this configuration, since the gap G is formed between the corners of the bottom of the annular groove 2c axially and the inner periphery of the permanent magnets 3a and 3b axially, the yoke 2b, which serves as the sidewall of the annular groove 2c, can make surface contact with the axial ends of the inner periphery of the permanent magnets 3a and 3b axially, allowing the permanent magnets 3a and 3b to be positioned within the annular groove 2c using the yoke 2b. Therefore, with this configuration, the permanent magnets 3a and 3b can be positioned at a target location within the annular groove 2c, and thus the permanent magnets 3a and 3b can be positioned appropriately relative to the sleeve 2, further reducing the cogging thrust during armature E drive. Furthermore, in the cylindrical linear motor 1 constructed in this manner, since the sidewall of the yoke 2b can make face contact with the end faces of the permanent magnets 3a and 3b, stress concentration on a portion of the permanent magnets 3a and 3b due to axial load can be avoided when the armature E is driven. In addition, in the cylindrical linear motor 1 of this embodiment, when the permanent magnets 3a and 3b are fixed to the annular groove 2c using adhesive, excess adhesive overflows and is contained in the gap G, thus preventing the permanent magnets 3a and 3b from being unable to be properly positioned within the annular groove 2c due to the presence of adhesive.

[0053] Furthermore, in the cylindrical linear motor 1 of the aforementioned embodiment, the axial end faces of the outer peripheral portions 3a2 and 3b2 of the permanent magnets 3a and 3b are in contact with each other or facing each other with only a slight gap, but it can also be like... Figure 3 As shown in the first modified example of the cylindrical linear motor 1A, the cross-sectional shape of the magnetic yoke 2e cut along the axial direction in the sleeve 2 is set to be a convex shape with a protrusion on the outer periphery, and permanent magnets 3a and 3b are installed between the magnetic yokes 2e and 2e.

[0054] In the first modified cylindrical linear motor 1A, the sleeve 2 is formed of a soft magnetic material and includes: a cylindrical portion 2a fitted into the inner circumference of permanent magnets 3a and 3b; a plurality of annular yokes 2e arranged at intervals along the circumferential direction on the outer circumference of the cylindrical portion 2a; and a plurality of annular grooves 2f formed by annular gaps along the circumferential direction between the yokes 2e and 2e of the cylindrical portion 2a; and an integrally and indivisibly provided yoke 2e protruding in a flange shape on the outer circumference of the cylindrical portion 2a. Furthermore, the cylindrical portion 2a and the yoke 2e may also be composed of different components.

[0055] like Figure 3As shown, the magnetic yoke 2e is annular. The axial length of the inner circumferential portion 2e1, which is the cylindrical part, is longer, while the axial length of the outer circumferential portion 2e2, which is the opposite side of the cylindrical part, is shorter. The cross-section cut in the axial direction is a convex shape with a protrusion on the outer circumferential side. The radial thickness of the inner circumferential portion 2e1 of the magnetic yoke 2e is approximately equal to the radial thickness of the inner circumferential portions 3a1 and 3b1 of the permanent magnets 3a and 3b, and the radial thickness of the outer circumferential portion 2e2 is approximately equal to the radial thickness of the outer circumferential portions 3a2 and 3b2 of the permanent magnets 3a and 3b.

[0056] Therefore, unlike the yoke 2e, the axial length of the inner circumferential side of the annular groove 2f between the yokes 2e and 2e is shorter, while the axial length of the outer circumferential side, which is the opposite side of the cylindrical part, is longer. The cross-sectional shape cut in the axial direction matches the cross-sectional shape cut in the axial direction of the permanent magnets 3a and 3b, and the permanent magnets 3a and 3b can be accommodated inside.

[0057] Furthermore, although not illustrated in detail, similar to the sleeve 2 of the cylindrical linear motor 1 in one embodiment, rounding or grooving can be performed on the bottom of the inner circumferential side portion and the bottom of the outer circumferential side portion of the annular groove 2f in the sleeve 2, that is, on the outer circumference of the cylindrical portion 2a and at the root of the magnetic yoke 2e on both axial sides and at the corners of the step portion of the magnetic yoke 2e on both axial sides, to avoid interference with the corners of the permanent magnets 3a and 3b on both axial sides.

[0058] In this embodiment, all annular grooves 2f have the same cross-sectional shape, and the annular grooves 2f are equally spaced on the outer periphery of the sleeve 2. Therefore, the magnetic yokes 2e are also equally spaced on the outer periphery of the sleeve 2. Furthermore, in this embodiment, the end magnetic yokes 2g, 2g at both ends of the sleeve 2 are shaped by cutting the magnetic yokes 2e in half axially at the center. Alternatively, the ends of the sleeve 2 can be annular grooves, instead of end magnetic yokes 2g, 2g at both ends.

[0059] Furthermore, permanent magnets 3a and 3b are installed in the annular groove 2f between the yokes 2e and 2e of the sleeve 2 constructed in this manner, with alternating magnetization directions. Thus, the inner circumferential portion 2e1 of the yoke 2e is fitted between the inner circumferential portions 3a1 and 3b1 of the permanent magnets 3a and 3b, with the axial end faces of the inner circumferential portions 3a1 and 3b1 facing the axial end faces of the inner circumferential portion 2e1 of the yoke 2e. The outer circumferential portion 2e2 of the yoke 2e is fitted between the outer circumferential portions 3a2 and 3b2 of the permanent magnets 3a and 3b, with the axial end faces of the outer circumferential portions 3a2 and 3b2 facing the axial end faces of the outer circumferential portion 2e2 of the yoke 2e. In this way, the permanent magnets 3a and 3b are fitted throughout the entire space between the yokes 2e and 2e, and are entirely housed within the annular groove 2f between the yokes 2e and 2e when viewed axially.

[0060] Furthermore, although not shown in the figure, the inner circumferences of the inner circumferences 3a1, 3b1 and the outer circumferences 3a2, 3b2 at both ends of the axial direction of each permanent magnet 3a, 3b are chamfered. Even if the permanent magnets 3a, 3b are housed in the annular groove 2f between the magnetic yokes 2e, 2e, the permanent magnets 3a, 3b can be prevented from floating from the outer circumference of the cylindrical portion 2a.

[0061] In the same way as the cylindrical linear motor 1, the cylindrical linear motor 1A of this embodiment also forms a magnetic pole from the axial center of the permanent magnet 3a to the axial center of the adjacent permanent magnet 3b containing the yoke 2e. The N poles of the permanent magnets 3a and 3b with their N poles facing each other and the yoke 2e sandwiched between the N poles function as one N pole, and the S poles of the permanent magnets 3a and 3b with their S poles facing each other and the yoke 2e sandwiched between the S poles function as one S pole.

[0062] In the magnetic body F constructed in this way, the axial length of the inner periphery 3a1, 3b1 of the permanent magnets 3a and 3b, which are on the armature side, is shorter than the axial length of the outer periphery 3a2, 3b2, which are on the opposite side of the armature. The magnetic flux of the inner periphery 3a1, 3b1 and the outer periphery 3a2, 3b2 flows easily to the armature side through the magnetic yoke 2e. The magnetic flux density in the radially opposite range of the magnetic yoke 2e becomes higher. Therefore, compared with a magnetic body constructed by simply stacking axially magnetized annular permanent magnets with rectangular cross sections in an alternating manner of magnetization direction, the waveform of the gap magnetic flux density distribution on the outer periphery of the armature E is closer to a sine wave. The amplitude of this waveform is larger, which can increase the magnetic field acting on the armature E housed in the inner periphery of the sleeve 2. Furthermore, in the first modified cylindrical linear motor 1A, the outer peripheral portions 3a2 and 3b2, which are the longer axial portions of the permanent magnets 3a and 3b, clamp the outer peripheral side portion 2e2 of the yoke 2e. Therefore, not only the inner peripheral surface of the armature side of the outer peripheral portions 3a2 and 3b2, but also the magnetic flux exiting from the axial end face, flows to the inner peripheral side portion 2e1 of the yoke 2e. Thus, in the cylindrical linear motor 1A of this embodiment, compared with the cylindrical linear motor 1, more magnetic flux can be concentrated in the radially opposite range to the inner peripheral side portion 2e1 of the yoke 2e. The waveform of the gap magnetic flux density distribution around the armature E is closer to a sine wave, and the amplitude of this waveform is larger, which can further increase the magnetic field acting on the armature E housed in the inner periphery of the sleeve 2.

[0063] The cylindrical linear motor 1A in the first variation of this embodiment includes a cylindrical magnetic body F and an armature E disposed on the inner periphery of the magnetic body F and movable axially relative to the magnetic body F. The magnetic body F includes: a plurality of permanent magnets 3a and 3b, which are ring-shaped, magnetized in the axial direction and arranged in alternating magnetization directions in the axial direction of the magnetic body F; and a sleeve 2, which has a cylindrical portion 2a fitted into the armature side of the permanent magnets 3a and 3b and a ring-shaped yoke 2e integral with the cylindrical portion 2a and disposed between the permanent magnets 3a and 3b, which is formed of a soft magnetic body; the cross-section of the permanent magnets 3a and 3b cut in the axial direction is a convex shape in which the axial length on the armature side is shorter than the axial length on the opposite side of the armature, and the yoke 2e is disposed throughout the entire area between the inner periphery portions (parts) 3a1 and 3b1 of the permanent magnets 3a and 3b with shorter axial length on the armature side and between the outer periphery portions (parts) 3a2 and 3b2 with longer axial length on the opposite side of the armature.

[0064] According to the cylindrical linear motor 1A constructed in this manner, the axial length of the inner periphery 3a1, 3b1 of the permanent magnets 3a, 3b on the armature side is shorter than the axial length of the outer periphery 3a2, 3b2 on the opposite side of the armature. The permanent magnets 3a, 3b are installed throughout the entire structure between the yokes 2e, 2e. Therefore, the magnetic flux coming out from the armature side surface of the inner periphery 3a1, 3b1 and the end faces on both sides of the outer periphery 3a2, 3b2 flows easily to the armature side through the magnetic conduction current of the yoke 2e. The magnetic flux density in the radially opposite range of the yoke 2e becomes higher. Therefore, compared with a magnetic body constructed by stacking axially magnetized annular permanent magnets with rectangular cross sections in an alternating manner of magnetization direction, the waveform of the gap magnetic flux density distribution on the outer periphery of the armature E is closer to a sine wave. Therefore, the amplitude of the waveform of the gap magnetic flux density distribution on the outer periphery of armature E is further increased, which can further increase the magnetic field acting on the armature E housed in the inner periphery of sleeve 2.

[0065] Thus, in the cylindrical linear motor 1A of this embodiment, the magnetic field acting on the armature E can be further increased while utilizing the low-cost axially magnetized permanent magnets 3a and 3b, thereby further increasing the thrust and reducing manufacturing costs.

[0066] Furthermore, in the cylindrical linear motor 1A of this embodiment, a sleeve 2 is provided, which is formed of a soft magnetic material and has a cylindrical portion 2a fitted into the armature side of permanent magnets 3a and 3b. The sleeve 2 and the cylindrical portion 2a are integrally provided with a yoke 2e. In the cylindrical linear motor 1A configured in this way, the permanent magnets 3a and 3b are installed in an annular groove 2f formed between the yokes 2e and 2e formed on the outer periphery of the sleeve 2. Therefore, if the position and size of the annular groove 2c of the sleeve 2 are managed with high precision, even if there is a dimensional error in the axial length of the permanent magnets 3a and 3b, the dimensional error of the permanent magnets 3a and 3b will not accumulate in the axial direction of the sleeve 2, and the setting error of each permanent magnet 3a and 3b relative to the sleeve 2 falls within the axial range of the annular groove 2f. In addition, in the cylindrical linear motor 1A, since the yoke 2e is integrally arranged between the permanent magnets 3a and 3b in the axial direction, the permanent magnets 3a and 3b will not directly interfere with each other. Therefore, they are not easily affected by the dimensional errors of the permanent magnets 3a and 3b, and the permanent magnets 3a and 3b can be arranged in a more appropriate position relative to the sleeve 2.

[0067] Therefore, according to the cylindrical linear motor 1A in the first modified example constructed in this way, the axial offset of the permanent magnets 3a and 3b relative to the sleeve 2 relative to the design value can be further reduced, and thus the cogging thrust during armature E drive can be further reduced.

[0068] Furthermore, in the cylindrical linear motor 1 of the aforementioned embodiment, the axial end faces of the outer peripheral portions 3a2 and 3b2 of the permanent magnets 3a and 3b are in contact with each other or facing each other with only a slight gap, but it can also be like... Figure 4 As shown in the second modified example of the cylindrical linear motor 1B, the axial width of the yoke 2b in the sleeve 2 is increased, and a gap is actively provided between the outer periphery portions 3a2 and 3b2 of the permanent magnets 3a and 3b installed in the annular groove 2c between the yokes 2b and 2b, forming a magnetic gap 20 between the outer periphery portions 3a2 and 3b2 and on the outer periphery side of the yoke 2b.

[0069] In the magnetic body F constructed in this manner, a magnetic gap 20 is provided between the outer peripheral portions 3a2 and 3b2, which are the longer axial portions of the permanent magnets 3a and 3b. Therefore, the magnetic flux coming out from the axial ends of the outer peripheral portions 3a2 and 3b2 also flows to the magnetic yoke 2b located on the inner peripheral side, and does not easily pass through the outer peripheral side of the permanent magnets 3a and 3b, which is opposite to the armature side. Correspondingly, the magnetic flux flowing to the inner peripheral side, which is the armature side, increases, thereby increasing the magnetic field acting on the armature E housed in the inner peripheral side of the sleeve 2. In addition, in the cylindrical linear motor 1B of the second modification, a magnetic gap 20 is provided between the outer peripheral portions 3a2 and 3b2, which are the longer axial portions of the permanent magnets 3a and 3b, and on the armature side of the magnetic yoke 2b. Therefore, together with the magnetic flux coming out from the inner peripheral surface of the armature side of the outer peripheral portions 3a2 and 3b2, most of the magnetic flux coming out from the axial end faces of the outer peripheral portions 3a2 and 3b2 flows to the inner peripheral side portion 2e1 of the magnetic yoke 2b. Therefore, in the cylindrical linear motor 1B of this embodiment, compared with the cylindrical linear motor 1, more magnetic flux can be concentrated in the range opposite to the magnetic yoke 2b in the radial direction, and the waveform of the gap magnetic flux density distribution on the outer periphery of the armature E is closer to a sine wave. The amplitude of this waveform is increased, which can further increase the magnetic field acting on the armature E housed in the inner periphery of the sleeve 2.

[0070] The cylindrical linear motor 1B in the first variation of this embodiment includes a cylindrical magnetic body F and an armature E disposed on the inner periphery of the magnetic body F and movable axially relative to the magnetic body F. The magnetic body F includes: a plurality of permanent magnets 3a and 3b, which are ring-shaped, magnetized in the axial direction, and arranged in alternating magnetization directions in the axial direction of the magnetic body F; and a sleeve 2 having a cylindrical portion 2a fitted into the armature side of the permanent magnets 3a and 3b, and a ring-shaped portion integral with the cylindrical portion 2a and mounted within the permanent magnets. The yoke 2b between 3a and 3b is formed of a soft magnetic material; the cross-section of the permanent magnets 3a and 3b cut in the axial direction is a convex shape with the axial length on the armature side shorter than the axial length on the opposite side of the armature. The yoke 2b is installed between the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b with shorter axial length on the armature side. A magnetic gap 20 is provided between the outer peripheral portions 3a2 and 3b2 of the yoke 2b with longer axial length on the opposite side of the armature and on the opposite side of the armature of the permanent magnets 3a and 3b.

[0071] According to the cylindrical linear motor 1B constructed in this manner, the axial length of the inner peripheral portions 3a1 and 3b1 of the permanent magnets 3a and 3b on the armature side is shorter than the axial length of the outer peripheral portions 3a2 and 3b2 on the opposite side of the armature. A magnetic gap 20 is provided between the outer peripheral portions 3a2 and 3b2 of the permanent magnets 3a and 3b and on the opposite side of the armature of the yoke 2b. Therefore, the magnetic flux coming out from the inner peripheral surface and axial end face of the armature side of the inner peripheral portions 3a1 and 3b1 and the outer peripheral portions 3a2 and 3b2 flows easily to the armature side through the magnetic conduction current of the yoke 2b. The magnetic flux density in the radially opposite range of the yoke 2b becomes higher. Therefore, compared with a magnetic body constructed by stacking axially magnetized annular permanent magnets with rectangular cross sections in an alternating manner of magnetization direction, the waveform of the gap magnetic flux density distribution on the outer periphery of the armature E is closer to a sine wave. Therefore, the amplitude of the waveform of the gap magnetic flux density distribution on the outer periphery of armature E is further increased, which can further increase the magnetic field acting on the armature E housed in the inner periphery of sleeve 2.

[0072] Thus, in the cylindrical linear motor 1B of this embodiment, the magnetic field acting on the armature E can be further increased while utilizing the low-cost axially magnetized permanent magnets 3a and 3b, thereby further increasing the thrust and reducing manufacturing costs.

[0073] Furthermore, in this embodiment, the armature E is inserted into the inner periphery of the magnetic body F, but a cylindrical armature E can also be disposed on the outer periphery of the magnetic body F. In this way, when the armature E is disposed on the outer periphery of the magnetic body F, the axial length of the outer periphery portion of the magnetic body F, which consists of a ring-shaped, axially magnetized, and alternating magnetization directions of multiple permanent magnets arranged in the axial direction of the magnetic body F, can be set to be shorter than the axial length of the inner periphery portion.

[0074] Furthermore, in the cylindrical linear motors 1, 1A, and 1B of the embodiments, a structure is adopted in which the sleeve 2 and the cylindrical portion 2a integrally have a magnetic yoke 2b on the outer circumference of the cylindrical portion 2a. However, even if it is formed of a soft magnetic material, magnetic resistance exists. Therefore, the thinner the radial wall thickness of the cylindrical portion 2a, the stronger the magnetic field that can be exerted on the armature E. On the other hand, the thinner the wall thickness of the cylindrical portion 2a, the weaker the strength of the sleeve 2, making it difficult to use as a component to hold the magnetic body F. To address this, ribs that intersect the magnetic yoke 2b along the axial direction can be provided on the outer circumference of the cylindrical portion 2a to reduce the radial wall thickness of the cylindrical portion 2a and increase the magnetic field exerted on the armature E, while suppressing the reduction in the strength of the cylindrical portion 2a. When the armature E is positioned on the outer circumference of the magnetic body F, ribs can be provided on the outer circumference of the cylindrical portion 2a of the sleeve 2. Furthermore, the number and cross-sectional shape of the ribs can be arbitrarily set within the range that ensures the strength of the cylindrical part 2a. When ribs are provided, the permanent magnets 3a and 3b can be divided in the circumferential direction in such a way that the permanent magnets 3a and 3b can avoid the ribs.

[0075] The preferred embodiments of the present invention have been described in detail above, but modifications, variations and alterations are possible as long as they do not depart from the scope of the patent application.

[0076] Symbol Explanation 1. 1A, 1B cylindrical linear motors 2b, 2e magnetic yokes 3a, 3b Permanent magnets 3a1 and 3b1 Inner circumference (the shorter axial portion of the permanent magnet) 3a2, 3b2 Outer periphery (the longer axial portion of the permanent magnet) 20 Magnetic Gap E armature F magnetic body

Claims

1. A cylindrical linear motor, comprising: cylindrical magnetic body; as well as An armature, disposed on the inner or outer periphery of the magnetic body and movable axially relative to the magnetic body; The magnetic material includes: Multiple permanent magnets, in a ring shape, are magnetized axially and arranged in alternating magnetization directions along the axial direction of the magnetic body; as well as The magnetic yoke is ring-shaped, formed of a soft magnetic material, and is disposed between the permanent magnets; The permanent magnet has a convex cross-section cut along the axial direction, where the axial length on the armature side is shorter than the axial length on the opposite side of the armature.

2. The cylindrical linear motor according to claim 1, comprising: The sleeve is formed of a soft magnetic material and has a cylindrical portion that fits into the armature side of the permanent magnet; The sleeve and the cylindrical portion integrally have the magnetic yoke. The yoke is integrally mounted between the shorter axial length portion of the permanent magnet on the armature side and the longer axial length portion on the opposite side of the armature.

3. The cylindrical linear motor according to claim 1, comprising: The sleeve is formed of a soft magnetic material and has a cylindrical portion that fits into the armature side of the permanent magnet; The sleeve and the cylindrical portion integrally have the magnetic yoke. The magnetic yoke is mounted between the shorter axial portions of the armature side of the permanent magnet. A magnetic gap is provided between the longer axial length portions of the yoke on the opposite side of its armature and the permanent magnet on the opposite side of its armature.

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